A backing plate facilitates electrical probing of VLSI IC signals in an array of signal via pads on the back side of a printed circuit board and which correspond to an LGA of socket pads on the front side of the printed circuit board. The backing plate is constructed of electrically non conductive mechanically stiff material that already has drilled therein a hole for each signal via pad that might be probed. Polyamide is a suitable material for such a backing plate. Special symbols, legends and suitable grid identification axes can be silk screened onto the side of the backing plate that remains visible when installed. The drilled insulative backing plate can be equipped with captive threaded studs, if desired. Alternatively, it may simply have holes to receive fasteners, or have captive female threaded fasteners in lieu of holes.

Very large scale integration (VLSI) integrated circuits (IC's) such as big gate arrays or application specific IC's (ASIC's) may have a large number of signals that need to enter or leave the IC by "signal pins": several hundred to over one thousand. These IC's are commonly mounted to printed circuit boards (PCB's). The manner of mounting may include either soldering or the use of sockets.
By the term "socket" we refer to any of a variety of commercially available high density low inductance LGA sockets supplied by various manufacturers. One such socket uses an array of compressible small "fuzz buttons" or "brillo pads". (Brillo is a brand of steel wool balls or pads, used for cleaning, as in scouring pots and pans in a kitchen.) Each of these balls is a small irregularly wound and inter-twined ball of gold wire. These balls of tangled wire are stuffed through a regular array of holes in a thin sheet of insulative material. The regular array of holes matches the pin out pattern on the IC and the PCB, and registration is achieved by alignment pins (dowel pins). The balls of tangled of wire are compressed between the pads (lands) on the PCB and the corresponding pads or lands (signal pins) on the underside of the IC. Through such compression the fuzzy balls of wire become intervening series connections between the pads on the PCB and those on the IC. If such a socket is used the array of pads is referred to as a land grid array (LGA). To avoid any possibility of confusion in the description that follows, we shall henceforth refer to an "LGA of socket pads" when referring to those lands on the PCB that mate with an LGA socket. There is an industry standard describing what an LGA of socket pads is to look like. If an LGA socket is not used and the part is simply soldered to the PCB, the array is referred to as a ball grid array (BGA).
From the description above it is clear that use of a socket for an LGA requires sufficient compressive force to adequately squeeze all the fuzzy wire balls in the socket against the LGA of socket pads and against the signal pins of the IC. The force required can be significant, and for an IC having eight or nine hundred signal pins it may take four stout screws or small bolts to achieve the requisite force. A companion issue quickly arises. Even though the mother board may be a multi-layer PCB, just a few thousandths of an inch deformation within the region of the LGA can be enough to introduce connectivity problems. Even a multi-layer PCB is typically not stiff enough to sufficiently resist deformation, especially at elevated temperatures. The usual solution for dealing with this issue is to supply a suitably stiff backing plate, or bolster, on the opposite side of the PCB, and then use the screws to compress both the socket and the mother board between the backing plate and the IC. Painted 3/16" aluminum plate with attached threaded studs is a favorite choice for backing plates.
It should not be assumed that backing plates are needed for only LGA sockets of the fuzzy ball type. Other types of LGA sockets can require the use of backing plates, as well.
One last bit of background deserves attention. Consider the various many signals that go to and from the IC. The vast majority of them are traces on planes (layers) located in the interior of the PCB. To get to the LGA of socket pads on an outside surface they must travel by via's, which start out as holes drilled in the PCB. The most common manufacturing technique is for these holes to go all the way through the board and generate a corresponding pattern of signal vias and their pads on the "back side" of the PCB, away from the IC and next to the backing plate. The pads in this pattern might be the same as for LGA socket pads, or they might be the round land typically associated with an ordinary via. Either way, we shall henceforth refer to these pads on the backside of the PCB as an array or pattern of "signal via pads".
There are several reasons for having the holes for the vias under the LGA of socket pads go all the way through the PCB. Among these is that it facilitates reliable formation of the plating that forms the via. (There are blind hole processes, however. If one of these were used there would be no pattern of signal via pads on the back side of the PCB.) Another reason is that during development standard solid backing plates will sometimes have a small portion removed to allow probing of the IC's signals (as with an oscilloscope probe or probes for a logic or timing analyzer) from the back side of the PCB. These modified backing plates are generally made up on demand, and are best thought of as special tooling. Such probing could not be done if there were no signal via pads on the back side. A coat of enamel paint baked onto the aluminum is often relied upon to provide electrical insulation between the signal via pads on the backside and the conductive aluminum interior of the backing plate. Modification of the backing plate exposes the aluminum. Even if insulation is replaced, probe tips are generally sharp, and in time the possibility of an inadvertent short circuit to the baking plate (whether involving the probe tip or not) cannot be discounted. Certain such short circuits, however brief in duration, could be very damaging.
Even if a modified backing plate is available during a trouble shooting episode, it is a disagreeable task to remove the existing one and replace it with the special one. Aside from the effort, and the wear and tear on the PCB and the IC, there is the uncertainty introduced by the disturbance of disassembly and re-assembly. (Was there a bad connection that is now gone, or is there now a different bad connection, or, was it OK and now it is not?) It would be desirable if the backing plate used for production purposes in the first instance, and shipped as part of the product, were such that it facilitated probing of the IC's signals at the signal via pads, and that home made modified backing plates were thus not necessary.

Backing plate for LGA mounting of integrated circuits facilitates probing of the IC's pins


A bale opening machine is provided with a safety apparatus, by means of which there are produced safety barriers or fences parallel to lengthwise sides of a row of bales to be opened and/or substantially perpendicular to the direction of movement of the bale opening machine. The safety apparatus moves in conjunction with the bale opening machine. The safety apparatus can comprise mechanical and/or sensory protective structure. The sensory protective structure comprises one or more electro-acoustical transducers arranged in a sonic chute together with one or more reference reflectors such that transmitted acoustical signals are split into a measuring signal and a reference signal. The reference signal is reflected at one of the reference reflectors, whereas the measuring signal is reflected at a deflection reflector into the monitored area and back again by an object located in the monitored area.

1. Field of the Invention
The present invention is in the field of textile equipment, and, more particularly, concerns a safety apparatus for a traveling unit or device of a textile machine and a method of operating such textile machine.
In a particularly advantageous environment of use of the present invention, such relates to bale opener or opening apparatus provided with safety apparatus or equipment for minimizing risks that foreign objects, meaning not only inanimate objects but also human beings, such as especially the hands or other parts of machine operating personnel, will come into contact with rapidly rotating or moving components of the textile machine. Still further, the invention is especially, although not exclusively concerned, with safety or protective apparatuses or devices constructed and arranged to prevent entry of objects into the zone occupied by opening rollers of opening members of cotton bale openers or bale opening machines and to sensing systems for detecting in advance objects moving toward such zones, so that the opening rollers or the bale opening machines may be stopped before damage is done. The present invention is capable of specifically providing protection in zones laterally below, frontally below and directly below the opening member of a bale opener or bale opening machine.
2. Discussion of the Background and Material Information
Textile fiber raw material and, in particular, raw cotton is usually delivered in bale form. In a fiber processing operation prior to spinning, the raw cotton material must be brought into the form of loose flocks and in this state the material is subsequently cleaned and the individual fibers are stretched and rendered parallel to one another in a carding process.
Bale opening machines, which open such bales, typically contain a machine frame equipped with traveling wheels which is moved back and forth upon essentially straight rails along a limited bale opening path. At one side of the machine frame there is mounted the opening member in a direction extending transversely with respect to the essentially straight rails such that the opening member can be elevationally displaced. The bales to be opened are arranged in rows substantially parallel to the essentially straight rails and the opening member is moved back and forth over the top surface of the erected bale row in order to remove the fiber material in the form of fiber flocks.
The opening member possesses one or more drivable opening rollers arranged such that their rotational axes are disposed horizontal and substantially perpendicular to the direction of movement of the bale opening machine. These opening rollers are encased in a casing or housing which is open towards the top and laterally enclosed at all sides, however open towards the bottom. During opening of the bales this downwardly directed or lower opening of the casing or housing is essentially closed off by the top surface of the bales, so that the opening rollers present no danger to the machine operators or other objects. Nonetheless, danger zones or areas exist around the vicinity of the bale opening machine, especially when processing irregular bale rows. Under these circumstances, the opening rollers constitute a real danger during their rotation and when the lower opening of the housing is not completely shielded. A machine operator or other individual and also an inanimate object can enter from below or at an inclination from below through the lower opening and inadvertently contact the opening rollers, resulting in the occurrence of an accident.
More specifically, loosening of the bale-like raw material and the successive delivery thereof to the cleaning and carding means are generally performed through the layerwise opening up of the bales using the bale opening machine containing, as stated, one or more of such rapidly rotating opening rollers equipped, for instance, with tearing pins. As also previously explained, such bale opening machines or bale openers are, for example, provided with the opening member which is passed from above over the row of the raw textile bales. By moving the opening member backwards and forwards over the bale row with simultaneous lowering thereof, the raw fiber material is removed layer-by-layer by the opening roller or rollers, as the case may be. The thus obtained fiber flocks are supplied to a subsequent processing means as a flock stream by a ventilator or fan.
The exposed parts of the rapidly rotating opening roller or rollers can constitute a hazard for the machine operator, particularly if the operator does not exercise sufficient care when working on or around the bale opening machine. This danger occurs if the area of the bale opening machine which is open towards the bottom of the opening roller or roller is not completely and directly located over and in contact with the bale to be processed. For example, this is the case when the opening member has reached the end of the bale row, if a bale row with bales of unequal height are processed, or if the dimensions of the bales do not completely shield the opening roller or rollers.
As is known in this art, danger zones or areas either can be fenced off by mechanical barriers, so that access thereto is not possible and/or at locations where such access or entry is possible, there can be used monitoring or surveillance barriers which produce an alarm in the event of unwanted access or entry. Upon giving of such alarm the danger event is, for example, shutdown. Specifically, in the case of a bale opening machine the bale opening rollers are typically stopped, thereby eliminating any danger therefrom.
Furthermore, according to the prior art, the inherent danger of rotating bale opening rollers, in those cases where they are not screened off or shielded, is counteracted in basically two different ways: the first technique employs a stationary barrier or fence around the entire row of bales, in other words, there is fenced off the entire region or space through which the potentially dangerous bale opening roller or rollers travel, or else there can be employed a barrier or guard which essentially co-travels with the potentially dangerous bale opening roller or rollers and surrounds the immediate vicinity of such bale opening roller or rollers.
A stationary barrier or fence which encircles the entire region through which the bale opening member moves has been disclosed, for instance, in the German Patent No. 3,032,584, published Mar. 11, 1982. Here, a light barrier is provided around the row of bales. Upon interruption of the light barrier the opening rollers are stopped. A drawback of this or any similar arrangement resides in the large size of the fenced off area, and thus, the freedom of movement of the operating personnel is exceedingly limited. Although measures are taken for keeping the protected area as small as possible (switching between two monitoring areas), in general an excessively large monitoring area is covered, which can lead to unnecessary work interruptions. There is also a risk that the light beam monitoring the danger area can be stepped over by personnel, or passage under the same is possible. In addition, personnel located in the monitoring area prior to switching on of the means are not detected. The system is also based on a precise arrangement of the mirrors or reflectors and is consequently fault-prone (deformation/shifting of the reflectors). Also, there exists a relatively great probability of sounding a false alarm, since intrusion past the barrier or fence constitutes an actual danger in only a limited number of instances, and thus, for instance, the textile machine is unnecessarily shutdown too often. A further drawback of such prior art apparatuses is that large foreign bodies, even humans, located at the region of the row of bales, cannot be detected prior to turning on the safety barrier.
In order to prevent such drawbacks, there have been disclosed safety equipment which use mechanical and/or sensor means for fencing off or shielding only the immediate vicinity of the potentially dangerous opening rollers. Here, the barrier or fence moves in conjunction with the machine frame and the opening roller. Such type safety equipment has been disclosed, for example, in the commonly assigned European Published Patent Application No. 90810018.3, published Jul. 25, 1990 under European Published Patent No. 379,465. The therein disclosed safety equipment seals off by mechanical and/or sensor means all locations where the danger region beneath the opening member is not obturated by the floor, by mechanical components or the bales, resulting in complete closing off of such region. However, since fencing off of this dangerous region by the floor and the bales is dependent to a great extent upon the configuration of the row of bales, the additional barriers, especially the sensors, must be coordinated to the shape of the row of bales, and this bale row shape, in the case of irregular bales in the bale row, continually changes during movement of the bale opening machine. Even though such disclosed prior art safety equipment affords a considerable degree of operational safety along with maximum degree of mobility of the operating personnel, still such safety equipment is quite complicated in design and expensive in construction, since it must be controlled as a function of the actual shape of the row of bales which is momentarily being opened. Without such a control, bales or parts of bales would be construed as an unauthorized intrusion into the monitored area. Hence, complicated control mechanisms are required, which not only renders the machine construction more complex, but, in turn, results in new safety risks.
Reverting now again more specifically to the potentially encountered risks at such bale opening machines, these may be basically classified as follows: Firstly, there exists the risk of the bales being too narrow, that is to say, bales not extending over the full width of the opening member. In this case there is a so-to-speak projection of the opening roller beyond the textile fiber bales to be worked. There is also a risk in the lateral regions of the opening member, that is to say, on the sides in the advance direction of the opening member. Difficulties are encountered in fitting protective means to such bale openers. Particularly in the case of mechanical protective means the problem arises that they do not engage with the bales or may collide with other mechanical means.
Problems also occur with sensory protective means, because, for example, modifications of the bale profile or bales are detected as penetrating objects. Thus, in the case of the known sensory protection concepts, either the bale opener (including the complete bale row) is monitored as an entity, or the sensors only detect limited areas over the bales, so that once again only an incomplete protection is provided.
Another protective device is known from German Published Patent Application No. 3,733,972. A live electric conductor is passed around the opening member and generates an electromagnetic field. The field change brought about by an approaching person is established by a control device, which then operates a limit switch. However, as the arrangement possibilities of the conductor are limited, this device can only cover a limited area, which is fundamentally restricted to a zone above and to the side of the opening for the opening rollers. It is particularly disadvantageous that a person penetrating from below into the danger area may not even be detected, or the measuring field must be extended to such an extent that once again zones around the opening member are also detected, which leads to unnecessary interruptions. It does not solve the problem that bales are detected by the sensor if the field is extended. Thus, from the constructional side, only a limited area over the bales can be monitored, which means that protection remains incomplete. The self-monitoring question is also unsolved.
In addition, mechanical protective flaps or covers for opening rollers are known. These are located within the opening member casing or housing. With more recent constructions of opening members equipped with several, for example, two opening rollers, such a means cannot be realized for space reasons.
It has been found that the actual danger area for a bale opener is relatively small and essentially only consists of the zone or area below the opening member or opening rollers. Therefore the monitoring zone should correspond to this danger zone or area, particularly if corresponding safety or protective means are located outside the opening member casing or housing. Account is not taken of this by the known means.

Safety apparatus for a traveling unit of a textile machine and method of operating the textile machine

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Provided is a method in which an excavation surface is scanned, the excavation surface shape is determined based on scanned excavation surface, an excavating path is identified from a mining excavation equipment, a volume of a material excavated by the mining excavation equipment is actively calculated based at least on the excavation surface shape and the excavating path of the mining excavating equipment, and a weight of the material excavated by the mining excavating equipment is actively calculated based on at least one density factor.

1. Field
Aspects of the present invention relate to heavy equipment for surface mine field loading operations such as human-operated and/or autonomous mining shovels, draglines, and the like, and more particularly to systems used on such equipment to actively measure the net weight of excavated material in each load.
2. Description of Related Art
In large scale surface mining operations, excavating equipment of immense proportions is used to excavate and load material. Excavation is usually performed by mining shovels with a bucket capacity of dozens of tons per scoop.
Measurement systems have been developed to determine the net weight of material in the mining shovel bucket as it is transferred to the truck. However, upon determining that the net weight of the load exceeds required weight, the excavation equipment may be forced to dump the excavated material, causing the increase of an excavation cycle time, creating a safety hazard and, thus, higher overall labor and maintenance costs.

Methods and systems for active load weight for mining excavating equipment


A fishing rod holder assembly for transporting at least one fishing rod upon an existing luggage carrier having at least two cross bars. The fishing rod holder assembly comprises a tubular housing member having a reel slot at one end, with a handle slot disposed in alignment with the reel slot on the opposing side of the tubular housing, and a clamping bar for releasably and adjustably securing the tubular housing member to a selected cross bar of the existing luggage carrier. A resilient support member has a vertical slot positioned in axial alignment with the tubular housing member. The resilient support member has a mounting bracket and a clamping bar for releasably and adjustably securing the resilient support member to another cross bar of the existing luggage carrier. The tubular housing member and the resilient support member may be mounted to the existing luggage carrier without the need for hand or power tools. Multiple fishing rod holder assemblies may be releasably and adjustably mounted to an existing luggage carrier to suit the needs of the user.

Most fishing sportsmen must transport their fishing rods to distant fishing areas, such as rivers, streams or ocean, to pursue their sport. Typically this involves transporting the fishing rod and reel by vehicle. Many fishermen have more than one fishing rod and reel, which are difficult to transport, and a family or group of fisherman may need to transport a plurality of fishing rods to the fishing site.
Some fishing rods are collapsible, but the time and effort required to disassemble and reassemble the fishing rod takes valuable time away from fishing. It is difficult to transport fishing rods of six feet or more in length within most vehicles.
Therefore what is needed, is a fast, convenient way to transport fishing rod and reels by vehicle, such as a car, truck, or other vehicle. Many vehicles are equipped with luggage carriers which are mounted upon the roof of the vehicle. The present invention is directed to a fishing rod carrier which is easily mounted to a vehicle's existing luggage carrier. One or more of these fishing rod holders may be mounted to the luggage carrier in order to carry as many fishing rods as needed during transport to and from the fishing site.
U.S. Pat. No. 4,871,099 issuing to Earl M. Bogar, Jr. on Oct. 3, 1989 discloses a plurality of fishing rod holders having a plurality of vertically extending tubular rods supported by a plurality of horizontally spaced supports, to support fishing rods on a boat.
U.S. Design Pat. No. 349,751, issuing to Dennis J. Ruff on Aug. 16, 1994 discloses a fishing pole holder having a resilient slot for receiving a rod tip portion within the slot.


A number of embodiments of crankcase ventilating systems for gas powered internal combustion engines employed in heat pumps. The crankcase ventilating system includes an oil vapor separator for separating and condensing oil from the crankcase ventilating gases and returning water vapor and the crankcase ventilating gases to the engine induction system for further combustion and purification. A number of various arrangements for controlling the temperature of the oil vapor separator are disclosed and an embodiment is disclosed that employs a pair of oil vapor separators acting in series.

This invention relates to a gas heat pump air conditioner and more particularly to an improved powering internal combustion engine and crankcase ventilating system for such an engine.
As is well known, internal combustion engines are employed for providing, power in a variety of applications. One proposed application for internal combustion engines is to employ them as a powering source for driving a compressor of a gas heat pump. In such applications, the internal combustion engine itself is powered by a gaseous fuel. Internal combustion engines have great utility in such applications because of their efficiency.
However in an application of this type for internal combustion engines, the engine may be called upon to run for long periods of time without servicing. When this is done, it is extremely important to insure that the crankcase and lubricating system for the engine is adequately ventilated, that contaminates are removed from the lubricating oil and that in doing so the oil itself does not become further contaminated.
That is, it is well known to provide a system wherein there is a flow of ventilating gas through the crankcase and lubricating system of the engine. Such ventilating systems have been found to substantially reduce the deterioration of the lubricant. However, for emission control it is desirable to insure that the crankcase ventilating gases are not discharged directly to the atmosphere. The reason for this is that they may contain a fairly high percentage of unwanted constituents, such as hydrocarbons resulting from blowby during engine operation.
It has, therefore, been the practice to return the crankcase ventilating gases to the engine induction system so that any unburned hydrocarbons can be further oxidized and consumed in the combustion chamber without being discharged directly to the atmosphere.
FIG. 1 is a cross sectional view of a conventional type of prior art internal combustion engine having a conventional type of crankcase lubricating system of the type aforedescribed. In this figure, the conventional engine is identified generally by the reference numeral 21 and is shown in a cross sectional view taken through its single cylinder. The engine 21 includes a cylinder block 22 in which a cylinder bore 23 is formed. A piston 24 reciprocates in this cylinder bore 23 and is connected by means of a piston pin 25 to the upper or small end of a connecting rod 26.
The connecting rod 26 has its lower or big end 27 journaled on a throw 28 of a crankshaft that is rotatably journaled within a crankcase chamber 29. The crankcase chamber 29 is formed by a skirt 31 of the cylinder block 22 and a oil pan 32 that is affixed to the skirt 31 in any suitable manner. A lubricant, such as oil is contained at a level shown by the dot/dash line 33 in the oil pan 32 for lubrication of the engine 21 through any suitable and well known type of lubricating system.
A cylinder head assembly, indicated generally by the reference numeral 34 is affixed to the cylinder block 22 in a known manner and has a lower recess 35 which defines, in part, the combustion chamber of the engine 21 along with the head of the piston 24 and cylinder bore 23. An intake charge is delivered to the combustion chamber 35 through an intake port 36 having an intake valve (not shown) that controls the communication of the intake port 36 with the combustion chamber 35. In a like manner, an exhaust passage 37 connects the combustion chamber 35 with the atmosphere through an exhaust system (not shown). An exhaust valve (not shown) controls the communication of the combustion chamber 35 with the exhaust passage 37. The intake and exhaust valves and their operating system have not been shown because they are well known in the art and the descriptive matter relates to the crankcase ventilation system, which is the area where the invention resides.
An air charge for the intake passage 36 is drawn from the atmosphere through an air inlet device, indicated generally by the reference numeral 38 which has an inlet opening 39. The air inlet device 38 has a discharge opening 41 with a filter element 42 being disposed between the inlet opening 39 and the outlet opening 41 for filtering the atmospheric air that is drawn for the induction system. A manifold and induction system 43 connects the air inlet device outlet 41 with the intake passage 36 of the cylinder head. A throttle valve assembly 44 is provided in the induction system 43 for controlling the speed of the engine 21 in a well known manner. A source of gaseous fuel is supplied to the engine at an appropriate position in the induction system 43.
As has been noted, it is desirable to provide a source of ventilating air for the lubricating system and particularly so as to ventilate the crankcase chamber 29. These ventilating gases in the conventional prior art type of construction are derived from the atmosphere but are generated by the blowby gases flowing past the piston 24 in the manner as shown by the dot/dash arrows in the figure. These gases then pass across the upper surface of the lubricant 33 and through an internal separator 45 formed in the skirt portion 31 of the cylinder block 22 so as to entrap larger lubricant particles and cause them to be delivered back to the crankcase chamber 29. These lubricating gases that had a coarse separation accomplished then pass through a vertically extending passage 46 formed at one side of the cylinder bore 23 and exit through a discharge fitting 47.
A flexible conduit 48 connects this discharge fitting 47 with the air intake device 38 downstream of the filter element 42. A further filter element 49 is provided in the air inlet device 38 for filtering the crankcase ventilating gases before they pass through the air inlet device outlet 41 for flow back into the engine through the induction system 43. The separator 49 will tend to remove larger particles of liquid such as lubricant and/or water vapor. As is well known, water vapor is generated by the combustion process in the engine and hence there will be a fairly large amount of water vapor in the crankcase ventilation gases.
Since the filter 49 is provided in the air inlet device 38, the air inlet device 38 and filter element 49 will operate at a considerably lower temperature than the temperature of the ventilating gases. As a result, water vapor tends to condense out into the filter element 49 and can flow back through the conduit 48 to the crankcase chamber 33 to cause dilution of the lubricant therein and other problems. In addition, there is the problem that condensation can actually form directly in the filter element 49 and may clog the filter element 49. Hence, the prior art constructions as described have these disadvantages each of which will reduce the quality of the lubricant in the crankcase chamber during long periods between servicing.
It is, therefore, a principal object of this invention to provide an improved lubricating and crankcase ventilating system for an internal combustion engine.
It is a further object of this invention to provide an improved crankcase ventilating system for an internal combustion engine that will provide extremely long service intervals for changing of the lubricant in the engine.
It is a further object of this invention to provide an improved lubricating and crankcase ventilating system for an internal combustion engine wherein water vapor can be easily extracted from the lubricant and the gases that flow through the crankcase chamber while oil will be condensed and reconveyed to the crankcase chamber.
It is a yet further object of this invention to provide an improved crankcase ventilating system for the gas powered internal combustion engine of a heat pump.

Oil vapor separator system for the engine of a gas heat pump air conditioner


Low dielectric materials and films comprising same have been identified for improved performance when used as interlevel dielectrics in integrated circuits as well as methods for making same. In one aspect of the present invention, an organosilicate glass film is exposed to an ultraviolet light source wherein the film after exposure has an at least 10% or greater improvement in its mechanical properties (i.e., material hardness and elastic modulus) compared to the as-deposited film.

The present invention relates generally to the formation of dielectric films. More specifically, the invention relates to dielectric materials and films comprising same having a low dielectric constant and enhanced mechanical properties and methods for making same.
There is a continuing desire in the microelectronics industry to increase the circuit density in multilevel integrated circuit devices such as memory and logic chips to improve the operating speed and reduce power consumption. In order to continue to reduce the size of devices on integrated circuits, the requirements for preventing capacitive crosstalk between the different levels of metallization becomes increasingly important. These requirements can be summarized by the expression "RC", whereby "R" is the resistance of the conductive line and "C" is the capacitance of the insulating dielectric interlayer. Capacitance "C" is inversely proportional to line spacing and proportional to the dielectric constant (k) of the interlayer dielectric (ILD). Such low dielectric materials are desirable for use, for example, as premetal dielectric layers or interlevel dielectric layers.
A number of processes have been used for preparing low dielectric constant films. Chemical vapor deposition (CVD) and spin-on dielectric (SOD) processes are typically used to prepare thin films of insulating layers. Other hybrid processes are also known such as CVD of liquid polymer precursors and transport polymerization CVD. A wide variety of low K materials deposited by these techniques have been generally classified in categories such as purely inorganic materials, ceramic materials, silica-based materials, purely organic materials, or inorganic-organic hybrids. Likewise, a variety of processes have been used for curing these materials to decompose and/or remove volatile components and substantially crosslink the films such as heating, treating the materials with plasmas, electron beams, or UV radiation.
The industry has attempted to produce silica-based materials with lower dielectric constants by incorporating organics or other materials within the silicate lattice. Undoped silica glass (SiO2), referred to herein as "USG", exhibits a dielectric constant of approximately 4.0. However, the dielectric constant of silica glass can be lowered to a value ranging from 2.7 to 3.5 by incorporating terminal groups such as fluorine or methyl into the silicate lattice. These materials are typically deposited as dense films and integrated within the IC device using process steps similar to those for forming USG films.
An alternative approach to reducing the dielectric constant of a material may be to introduce porosity, i.e., reducing the density of the material. A dielectric film when made porous may exhibit lower dielectric constants compared to a relatively denser film. Porosity has been introduced in low dielectric materials through a variety of different means. For example, porosity may be introduced by decomposing part of the film resulting in a film having pores and a lower density. Additional fabrication steps may be required for producing porous films that ultimately add both time and energy to the fabrication process. Minimizing the time and energy required for fabrication of these films is desirable; thus discovering materials that can be processed easily, or alternative processes that minimize processing time, is highly advantageous.
The dielectric constant (K) of a material generally cannot be reduced without a subsequent reduction in the mechanical properties, i.e., elastic modulus (Young's modulus), hardness, toughness, of the material. Mechanical strength is needed for subsequent processing steps such as etching, CMP ("Chemical Mechanical Planarization"), and depositing additional layers such as diffusion barriers for copper, copper metal ("Cu"), and cap layers on the product. Mechanical integrity, or stiffness, compressive, and shear strengths, may be particularly important to survive CMP. It has been found that the ability to survive CMP may be correlated with the elastic modulus of the material, along with other factors including polishing parameters such as the down force and platen speed. See, for example, Wang et al., "Advanced processing: CMP of CU/low-K and Cu/ultralow-K layers", Solid State Technology, September, 2001; Lin et al., "Low-k Dielectrics Characterization for Damascene Integration", International Interconnect Technology Conference, Burlingame, Calif., June, 2001. These mechanical properties are also important in the packaging of the final product. Because of the trade-off in mechanical properties, it may be impractical to use certain porous low dielectric compositions.
Besides mechanical properties, an additional concern in the production of a low dielectric film may be the overall thermal budget for manufacture of the IC device. The method used extensively in the literature for cross-linking a low dielectric film and/or introducing porosity into a film is thermal annealing. In the annealing step, or a curing step, the film is typically heated to decompose and/or remove volatile components and substantially cross-link the film. Unfortunately, due to thermal budget concerns, various components of IC devices such as Cu metal lines can only be subjected to processing temperatures for short time periods before their performance deteriorates due to undesirable diffusion processes. Additional heating and cooling steps also can significantly increase the overall manufacturing time for the device, thereby lowering the throughput.
An alternative to the thermal anneal or curing step is the use of ultraviolet light in combination with an oxygen-containing atmosphere to create pores within the material and lower the dielectric constant. The references, Hozumi, A. et al. "Low Temperature Elimination of Organic Components from Mesostructured Organic-inorganic Composite Films Using Vacuum Ultraviolet Light", Chem. Mater. 2000 Vol. 12, pp. 3842–47 ("Hozumi I") and Hozumi, A et al., "Micropatiterned Silica Films with Ordered Nanopores Fabricated through Photocalcination", NanoLetters 2001 1(8), pp. 395–399 ("Hozumi II"), describe removing a cetyltrimethylammonium chloride (CTAC) pore-former from a tetraethoxysilane (TEOS) film using ultraviolet ("VUV") light (172 nm) in the presence of oxygen. The reference, Ouyang, M., "Conversion of Some Siloxane Polymers to Silicon Oxide by UV/Ozone Photochemical Processes", Chem. Mater. 2000,12(6), pp.1591–96, describes using UV light ranging from 185 to 254 nm to generate ozone in situ to oxidize carbon side groups within poly(siloxane) films and form a SiO2 film. The reference, Clark, T., et al., "A New Preparation of UV-Ozone Treatment in the Preparation of Substrate-Supported Mesoporous Thin Films", Chem. Mater. 2000, 12(12), pp. 3879–3884, describes using UV light with a wavelength below 245.4 nm to produce ozone and atomic oxygen to remove organic species within a TEOS film. These techniques, unfortunately, may damage the resultant film by chemically modifying the bonds that remain within the material.
U.S. Pat. No. 4,603,168 describes cross-linking an alkenyl-organopolysiloxane or organohydrosiloxane film by exposure to UV light or electron beam radiation in the presence of heat. The film further includes a dopant such as a photosensitizer like benzophenone or a platinum catalyst that is present in small concentrations to initiate and catalyze the cross-linking. Likewise, the reference Guo, et al., "Highly Active Visible-light Photocatalysts for Curing Ceramic Precursor", Chem. Mater. 1998, 10(2), pp. 531–36, describes using a platinum bis(beta-diketonate) catalyst to cross-link oligo(methylsilylene)methylene and tetravinylsinlane using UV/visible light. The presence of metal catalysts and chromophores would be unsuitable in dielectric films.
U.S. Pat. No. 6,284,500 describes using UV light in the from 230 to350 nm wavelength range to photoinitiate cross-linking within an organic polymer film formed by CVD or an organosilsiquoxane formed by spin-on deposition and improve the adhesion and mechanical properties of the film. A thermal annealing step may be used to stabilize the cross-linked film.
U.S. Pat. Nos. 5,970,384 and 6,168,980 describe exposing a PVD or CVD deposited oxide gate layer to UV light in the presence of N2O, NH3, or N2H4 at temperatures between 300 and 700° C. The methods described in both the '384 and '980 patents reduce the C and H impurities within the oxide gate layer and introduce nitrogen near the boundary of the material with the silicon substrate.
Besides UV exposure, a further method to process low dielectric films without effecting the thermal budget of the manufacturing of the device may be by exposure to electron beam ("e-beam") radiation. The electron beam radiation step may be in addition to, or in lieu, of a thermal cure step. It is believed that the e-beam exposure may improve the mechanical properties of the film by removing most or all of the organic species from the film. For example, U.S. Pat. No. 6,042,994 describes a process wherein a nanoporous dielectric coated substrate is treated with a large area electron beam exposure system. The '994 patent contends based upon FTIR data that the e-beam cure has removed most of the organic species from the film. WO 97/00535 teaches a process for curing a dielectric material such as a spin-on-glass (SOG) having about 10–25% organic groups by exposure to e-beam irradiation. Using FTIR analysis, the WO 97/00535 application reports that there are no longer CH groups attached to the backbone of SOG starting compounds after curing with e-beam radiation.
Accordingly, there is a need in the art to provide improved dielectric materials having low dielectric constant and sufficient mechanical strength and a method and mixture for making same. Due to thermal budget concerns, there is an additional need for a low temperature treatment for the production low dielectric constant materials for integrated circuits.
All references cited herein are incorporated herein by reference in their entirety.

This patent is subject to a terminal disclaimer.

Mechanical enhancement of dense and porous organosilicate materials by UV exposure


A vehicle control device includes an actuation unit that actuates an anomaly control switch that acknowledges execution of safety control, which improves safety during driving of a vehicle, upon detection of an occupant in an anomalous state from a monitoring result of a state of the occupant of the vehicle. The actuation unit causes the anomaly control switch to be actuated to allow the occupant to recognize a control content of the safety control. The vehicle control device further includes an operation acknowledgement unit that acknowledges operation of the anomaly control switch and a controller that executes the safety control when the operation acknowledgement unit acknowledges the operation of the anomaly control switch.

A typical driver anomaly management system automatically stops a vehicle when the driver cannot continue driving appropriately due to physical condition deterioration or the like while driving the vehicle (Patent Document 1).
Patent Document 1 describes an example of a driver anomaly management system that detects the physical condition of the driver based on the brain waves and heart rate of the driver and executes safety control (such as automatic stop control), which improves safety during the driving of the vehicle, if determining that the driver is in a state inappropriate for continuing driving.
If it is erroneously determined that the driver cannot appropriately continue driving even though the driver can continue driving appropriately, unnecessary safety control may be executed. Thus, even if the driver anomaly management system determines that the driver cannot continue driving appropriately, the driver anomaly management system does not start executing the safety control until the driver performs an operation permitting the execution of the safety control.
Patent Document 1: Japanese Patent No. 5527411

KABUSHIKI KAISHA TOKAI RIKA DENKI SEISAKUSHO


The invention provides a cryptographic system and method with a key escrow feature that uses a method for verifiably splitting users' private encryption keys into components and for sending those components to trusted agents chosen by the particular users, and provides a system that uses modern public key certificate management, enforced by a chip device that also self-certifies. In a preferred embodiment of this invention, the chip encrypts or decrypts only if certain conditions are met, namely, (1) if a valid "sender certificate" and a valid "recipient certificate" are input, where "valid" means that the particular user's private decryption key is provably escrowed with a specified number of escrow agents and that the master escrow center is registered and certified by the chip manufacturer, and (2) if a valid Message Control Header is generated by the sender and validated by the recipient, thereby giving authorized investigators sufficient information with which to request and obtain the escrowed keys.

This invention relates to cryptographic communications systems. More particularly, this invention relates to the secure generation, certification, storage and distribution of cryptographic keys used in cryptographic communications systems. Still more particularly, this invention relates to a system of cryptographic key escrow and public-key certificate management enforced by a self-certifying chip device.
The development and proliferation of sophisticated computer technology and distributed data processing systems has led to a rapid increase in the transfer of information in digital form. This information is used in financial and banking matters, electronic mail, electronic data interchange and other data processing systems. Transmission of this information over unsecured or unprotected communication channels risks exposing the transmitted information to electronic eavesdropping or alteration. Cryptographic communications systems preserve the privacy of these transmissions by preventing the monitoring by unauthorized parties of messages transmitted over an insecure channel. Cryptographic communications systems also ensure the integrity of these transmissions by preventing the alteration by unauthorized parties of information in messages transmitted over an insecure channel. The cryptographic communications systems can further ensure the integrity and authenticity of the transmission by providing for recognizable, unforgeable and document-dependent digitized signatures that can prevent denial by the sender of his own message.
Cryptographic systems involve the encoding or encrypting of digital data transmissions, including digitized voice or video transmissions, to render them incomprehensible by all but the intended recipient. A plaintext message consisting of digitized sounds, letters and/or numbers is encoded numerically and then encrypted using a complex mathematical algorithm that transforms the encoded message based on a given set of numbers or digits, also known as a cipher key. The cipher key is a sequence of data bits that may either be randomly chosen or have special mathematical properties, depending on the algorithm or cryptosystem used. Sophisticated cryptographic algorithms implemented on computers can transform and manipulate numbers that are hundreds or thousands of bits in length and can resist any known method of unauthorized decryption. There are two basic classes of cryptographic algorithms: symmetric key algorithms and asymmetric key algorithms.
Symmetric key algorithms use an identical cipher key for both encrypting by the sender of the communication and decrypting by the receiver of the communication. Symmetric key cryptosystems are built on the mutual trust of the two parties sharing the cipher key to use the cryptosystem to protect against distrusted third parties. The best known symmetric key algorithm is the National Data Encryption Standard (DES) algorithm first published by the National Institute of Standards and Technology. See Federal Register, Mar. 17, 1975, Vol. 40, No. 52 and Aug. 1, 1975, Vol. 40, No. 149. The sender cryptographic device uses the DES algorithm to encrypt the message when loaded with the cipher key (a DES cipher key is 56 bits long) for that session of communication (the session key). The recipient cryptographic device uses an inverse of the DES algorithm to decrypt the encrypted message when loaded with the same cipher key as was used for encryption. However, the adequacy of symmetric key cryptosystems in general has been questioned because of the need for the sender and the recipient to exchange the cipher key over a secure channel to which no unauthorized third party has access, in advance of the desired communications between the sender and recipient. This process of first securely exchanging cipher keys and only then encrypting the communication is often slow and cumbersome, and is thus unworkable in situations requiring spontaneous or unsolicited communications, or in situations requiring communications between parties unfamiliar with each other. Moreover, interception of the cipher key by an unauthorized third party will enable that party to eavesdrop on both ends of the encrypted conversation.
The second class of cryptographic algorithms, asymmetric key algorithms, uses different cipher keys for encrypting and decrypting. In a cryptosystem using an asymmetric key algorithm, the user makes the encryption key public and keeps the decryption key private, and it is not feasible to derive the private decryption key from the public encryption key. Thus, anyone who knows the public key of a particular user could encipher a message to that user, whereas only the user who is the owner of the private key corresponding to that public key could decipher the message. This public/private key system was first proposed in Diffie and Hellman, "New Directions in Cryptography," IEEE Transactions on Information Theory, November 1976, and in U.S. Pat. No. 4,200,770 (Hellman et al.), both of which are hereby incorporated by reference.
An early type of asymmetric key algorithm allows secure communication over an insecure channel by interactive creation by the communicating parties of a cipher key for that session of communication. Using the asymmetric key algorithm, two interacting users simultaneously and independently generate a secure cipher key that cannot be deduced by an eavesdropper and that is to be used symmetrically to encode that session of communications between the users. This interactive method of generating a secure cipher key was described by Diffie and Hellman in their 1976 paper. Under this prior art method, known as the Interactive Diffie-Hellman scheme, shown in FIG. 2, each of the two users A,B randomly chooses a secret number 21,22 and then computes an intermediate number 23,24 using two publicly-known numbers and the secret number 21,22 chosen by that user. Each user next transmits the intermediate number 23,24 to the other user and then computes the secret (symmetric) cipher key 25 using his own secret number 21,22 and the intermediate number 24,23 just received from the other user. The interactively generated cipher key 25 is then used symmetrically by both users as a DES or other symmetric cipher key to encrypt and decrypt that session of communications over an otherwise insecure channel in the manner of symmetric key algorithm communications. This interactive process requires only a few seconds of real time, and all digital communications, including digitized sound or video transmissions, in a particular session can be encrypted merely by pushing a button at the outset of a session to initiate the interactive key exchange process. Because all the numbers chosen in the Interactive Diffie-Hellman key generation scheme are very large, the computations are infeasible to invert and the secret cipher key cannot be computed by an eavesdropper, thus preserving the privacy of the communication. Because the computations are infeasible to invert, each user knows that any communication received using this algorithm was not altered and could have been sent only by the other user, thus preserving the integrity and authenticity of the communication. This interactive key exchange method, however, requires the parties to interact in real time in order to create the cipher key and may not be useful for unsolicited communications or unfamiliar parties. In particular, the Interactive Diffie-Hellman key exchange scheme does not work for store-and-forward electronic-mail style messaging or for long-term storage of documents in an electronic data storage system, because the recipient is not on-line to negotiate the session key.
A modified, non-interactive form of the Diffie-Hellman scheme, known as Certified Diffie-Hellman, can be used when the communicating parties are not on-line together. The initial, certification step of the Certified Diffie-Hellman session key generation scheme is shown in FIG. 3. One user, the recipient-to-be, randomly chooses a secret number 31 (his private key) and then computes an intermediate number 33 using two publicly-known numbers 32 and the secret number 31 chosen by that user. That user then sends proof of identification along with the intermediate number and the two public numbers, which numbers together form his public key 34, to a certifying authority that then issues a public key certificate 35 digitally signed 36 by the issuing certifying authority binding the user's identity to the user's Diffie-Hellman public key information 34. The public key 34 publicized by that user remains the same until he decides to rekey and choose another private key 31. Messaging using the Certified Diffie-Hellman method is shown in FIG. 4. In order to transmit a message to that user, a sending user first obtains the receiving user's certificate 35 and verifies the certifying authority's signature 36. The sender next computes the session key 42 for that communication session using the recipient's intermediate number 33 (from the recipient's certificate) and the sender's own secret number 41 (his private key), which he chooses at random. The sender then encrypts a message 43 using the session key 42 and places his own intermediate number 40 unencrypted at the head of the communication. Upon receiving the communication, the recipient computes the session key 42 using the sender's unencrypted intermediate number 40 and his own secret number 31 (or private key), and then uses the session key 42 to decrypt the message 43. As with the Interactive Diffie-Hellman scheme, the session key generated in the Certified Diffie-Hellman scheme is then used by both parties to encrypt and decrypt communications during that session over an otherwise insecure channel using a conventional symmetric algorithm, such as DES. The Certified Diffie-Hellman scheme, however, requires that a trusted entity or a certifying authority sign the receiving user's public key certificate so that a sending user can trust that the information contained within is correct. In addition, the private key randomly chosen by the sender, with which he computes both the session key and the intermediate number for that communication, must not be identical to the private key that is connected to the sender's own public key certificate; in order to avoid others learning his permanent private key numbers (corresponding to the public key numbers that have been certified), the sender should keep them distinct from any ephemeral private keys or intermediate numbers that are generated only for specific messages.
Another asymmetric key algorithm, named the RSA algorithm after the inventors Rivest, Shamir and Adleman, is described in U.S. Pat. No. 4,405,829 (Rivest et al.), which is hereby incorporated by reference, and involves the difficulty of factoring a number that is the product of two large prime numbers. As with the Interactive Diffie-Hellman scheme, the RSA algorithm is relatively straightforward to compute but practically infeasible to invert. Thus, it is not feasible to derive the private key from the public key and, in this way, the privacy of the communication is preserved. Once a message is encrypted with the public key using the RSA algorithm, only the private key can decrypt it, and vice versa. As with the Certified Diffie-Hellman scheme, the RSA algorithm requires a trusted entity to certify and publicize the users' public keys. In contrast to both Diffie-Hellman schemes, however, the RSA algorithm does not itself generate a "session key" to be used symmetrically by the parties. Instead, the public encryption key for a particular user directly encrypts communications to that user and that user's private decryption key decrypts those communications encrypted with the user's public key. In this way, the RSA algorithm is a pure asymmetric key algorithm.
However, because the RSA algorithm is complex and involves exponentiation of the message by very large numbers, encrypting or decrypting a message of even moderate length using the RSA algorithm requires a great deal of time. Thus, it is much simpler, faster and efficient to use the RSA asymmetric algorithm to transport a DES cipher key for use in a symmetric algorithm. This prior art mode of operation is known as RSA key transport and is shown in FIGS. 5 and 6. For example, referring to FIG. 5, a user could generate a random DES key 51 and encrypt a message 52 with that DES key. The user would then encrypt the DES key 51 with an intended receiving user's public RSA encryption key 53 and transmit the DES-encrypted message 54 along with the RSA-encrypted DES key 55 to the receiving user. After receiving the transmission, as shown in FIG. 6, the recipient decrypts the DES key 51 using his private RSA decryption key 56 and uses that DES key 51 to decrypt the message 52. Because the DES algorithm requires much less time and expense to compute than does the RSA algorithm, the symmetric DES key is used to encrypt and decrypt the actual message, while the asymmetric RSA keys are used to encrypt and decrypt the symmetric DES key.
The RSA public/private key cryptosystem also provides for a digital "signature" that is both message dependent and signer dependent, and can be used to certify that the received message was actually sent by the sender and that it was received unaltered. RSA digital signature is based on the additional property of RSA that, in addition to allowing the user's private key to decrypt only those communications encrypted using that user's public key, permits a user's private key to encrypt messages that can be decrypted only by that user's public key. Because only the user has the private key, use of the private key to encrypt allows for proof of origin that can be verified by anyone with access to the user's public key. In practice, the sender first uses his private key to encode the message text into a signed message, which could be decrypted by anyone but could have come only from the sender. If desired, the sender may then optionally use the recipient's public encryption key to encipher the signed message to be transmitted. Upon receipt of the ciphertext, the recipient decrypts the ciphertext with his private decryption key, if necessary, and decodes the signed message with the sender's public encryption key. Because only the sender knows his unique private key, only the sender could have sent the particular "signed" message; the signature thus verifies the identity of the sender. Also, because the recipient has only the sender's public key, the sender cannot claim that the recipient or an unauthorized third party altered or fabricated his message; the signature thus prevents repudiation of the message by the sender. Furthermore, because only the sender's private key transforms the original message and only the sender knows his unique private key, neither the recipient nor an unauthorized third party could have altered the message; the signature thus certifies the integrity of the message.
The RSA algorithm also provides for another type of digital signature that uses a hashing function to create a short message digest that is unique to each document. FIGS. 7 and 8 show RSA signature creation and RSA signature verification, respectively, using a hashing function. A hashing function is another complex mathematical algorithm that is "one-way," i.e. so that it is infeasible to reconstruct the document from the hash result, and is "collision-free," i.e. so that it is infeasible to produce another document that will hash to the same digest. As shown in FIG. 7, the sender first passes the message 72 through a hashing algorithm 73 to produce the message digest 74 and then encrypts the digest with his RSA private key 75, forming a compact digital signature 76 that is attached to the message 72. After receiving the transmission of the message 72 and the message digest 76, as shown in FIG. 8, the recipient decrypts the sender's RSA encrypted message digest 76 (the digital signature) using the sender's RSA public key 77. The recipient also uses the same hashing algorithm 73 to produce a message digest 74 from the received message. The two message digests resulting from the two transformations performed by the recipient should be identical, thus verifying that the message was signed by the sender.
Another system of digital signature, called DSA for Digital Signature Algorithm, may also be used for sender verification. The DSA Algorithm was disclosed in U.S. patent application Ser. No. 07/738,431, which is hereby incorporated by reference in its entirety. The DSA Algorithm has properties that are similar to those of the RSA signature algorithm in that the sender passes the message through a hashing algorithm to produce a message digest and then encrypts or signs the message digest using his private key; the recipient verifies the encrypted digest using the sender's public key. However, unlike the RSA signature algorithm that returns the original message digest when the recipient decrypts the signature block, the DSA verification algorithm results only in a positive confirmation of the validity of the signature; communications encrypted using an intended recipient's public key cannot later be recovered by decryption with the recipient's corresponding private key. For this reason, the DSA algorithm may be used quite capably for digital signatures, but not for key transport or for direct message encryption.
In order for the public/private key system to operate efficiently, users must trust a centralized key certifying authority to be responsible for publicizing and updating a directory of public encryption keys. The key certifying authority must be trusted by all users, both senders and recipients, to distribute the correct public keys for all users so that no messages are transmitted to unintended recipients. To this end, as discussed above and elaborated below, the certifying authority would distribute each user's name and public encryption key information, and would affix its own digital signature to the distributed information in order to certify the correctness of the information. However, when more than one entity, or a hierarchy of entities, is involved in the certification process, there are several different methodologies or "trust models" for determining how a user will process the certificates. The three main models are (1) a pure hierarchical model, (2) a model using cross-certification between multiple hierarchies, and (3) a "local trust" model. These models are described in detail in the standards document American National Standard X9.30, "Public Key Cryptography Using Irreversible Algorithms for the Financial Services Industry: Part 3: Certificate Management for DSA" (American Bankers Assn., Washington, D.C., 1992), which is hereby incorporated by reference in its entirety. Although there is not yet a general consensus as to which of the above-mentioned trust models is best, it is assumed throughout this disclosure that an appropriate, generally accepted certification trust model will be established and adhered to whenever certificates issued by more than one entity are involved.
The public/private key system described above takes into account the privacy interests of the users who wish to transmit and receive communications privately. In addition, however, there are also the law enforcement and national security interests of governments to be considered. The ability of the government to monitor or eavesdrop on otherwise private electronic transmissions for law enforcement and national security purposes must be preserved so that suspected criminals, terrorists and foreign spies are not permitted to conspire beyond the reach of the law. Whereas telephone communications can be monitored through wiretapping, cryptographic algorithms make the enciphered data unable to be deciphered even by powerful code-breaking computers. The increase in the volume and percentage of digital and digitized transmissions encrypted with advanced algorithms will, therefore, serve to frustrate and thwart the lawful government electronic surveillance of these communications, especially if cryptographic devices are widely implemented in telephones, computers, facsimile machines and all other data processing equipment.
One way to enable the government or other authorized investigators to monitor communications of suspected criminals is to require all users of cryptographic communications to escrow their private decryption keys with either a private authority or the government, i.e. allow either the private authority or the government to be the trusted custodian of the users' private decryption keys. When necessary for surveillance, the government then will have access to or will be able to gain access to the private keys in order to monitor all encrypted communications. This method, however, is unworkable because it contains insufficient safeguards against abuse by the government of the private decryption keys and against possible leaking of the private decryption keys to unauthorized third parties either by theft from the government or the private authority or by corruption of government or private authority personnel.
Another method of escrowing private decryption keys to preserve both user privacy interests and law enforcement security interests is by using a system such as the method described in "Fair Public Key Cryptosystems," proposed by Silvio Micali at CRYPTO 92 in March 1993 and published by the Laboratory for Computer Science of the Massachusetts Institute of Technology on Oct. 13, 1993, and in U.S. Pat. No. 5,276,737, both of which are hereby incorporated by reference. By this method, shown in FIGS. 9-11, a user who wishes to certify his public key for encryption purposes must escrow his private key in the following manner. As shown in FIG. 9, the user first breaks his private key 91 into several "pieces" 92, each of which can be individually verified 90 to be a valid part of the complete private key 91. The private key can be reconstructed only with knowledge of all the pieces or some specified number of them. The user then sends 93 each piece to a different escrow agent or agency 94, who, as shown in FIG. 10, verifies 95 the piece as a correct part of the private key 91 using a special algorithm and communicates this verification 96 to a master escrow center. Referring to FIG. 11, after receiving verification 96,97 that each piece of the private key is correct, the master escrow center can then issue a certificate 98 for the user's public key 99, allowing it to be used in a privacy system with the assurance that, if need be and pursuant only to a warrant or court order, law enforcement agencies will be able to obtain the secret pieces of the private key from the user's chosen escrow agents, recombine them and monitor the communications of that user. By this system, users can be assured of the privacy of their encrypted transmissions, and government can be assured of its ability to gain access to encrypted transmissions upon a showing of need. Because no one entity normally ever has access to the complete private key and because the user chooses entities that he trusts, the chances of unlawful or corrupt actions are greatly reduced. Also, because a wider range of entities would be eligible as escrow agents, the chances of simultaneously compromising all the escrow agents, and thereby disrupting all trusted commerce, is even further reduced.
The master escrow center, as a trusted authority certifying the authenticity of the user's public key, periodically issues a publicly-available certificate attesting or notarizing the connection between the public encryption key and its owner's identifying information. The certificate of authenticity assures the sender that transmissions to that named public key user will in fact be received and read only by the intended recipient. The certificate is usually in an internationally recognized electronic format, such as the one specified in CCITT Recommendation X.509 and issued as an international standard by the International Standards Organization (ISO). An example of a public encryption key escrow certificate format is shown in FIG. 12. The certificate contains, among other things, the name of the organization or key management center that created the certificate (the issuer) 121, the owner's public key 122, the owner's identifying information 126, a certificate serial number 123, and validity starting and ending dates 124. The issuer's digital signature 125 "seals" the certificate and prevents its alteration.
The U.S. government, however, has proposed as a government (and possible industry) standard another method to enable it to escrow private decryption keys and to monitor communications. The U.S. government has developed a microcircuit, called the "Clipper chip," that can be built into government and commercially-produced telephones and computer devices. The Clipper chip is a low-cost chip that may be used for bulk encryption and key management; the Capstone chip is a more advanced version of the Clipper chip that adds digital signature and message digest capabilities. Like other encryption systems, the Clipper chip uses a symmetric encryption algorithm, albeit a classified algorithm called Skipjack, that scrambles telephone and digital computer data communications in a manner similar to DES, but using an 80-bit key. Each Clipper chip has a unique serial number, a Clipper family key common to all Clipper chips and its own symmetric private device key that will be needed by authorized government agencies in order to decode messages encoded by a device containing the chip. When the device containing the chip is manufactured, the unique private device key will be split into two components (called "key splits") and deposited separately with two key escrow data bases or agencies that will be established within the government. Law enforcement agents can gain access to these private device keys by obtaining a warrant or other legal authorization to wiretap or monitor the communications and by presenting the warrant to the two escrow agencies.
When users of Clipper chip devices wish to communicate, they first agree on a symmetric session key with which to encrypt the communications. Any method of deriving the symmetric session key, such as Interactive Diffie-Hellman key derivation process, and any method of transporting the DES session key between users, such as RSA transport, may be used. At the start of each communication, each user sends to the other a Law Enforcement Access Field (LEAF) that contains enough information to allow law enforcement agents to wiretap or monitor the communication. The believed format of the Clipper LEAF is shown in FIG. 13 (note that because the precise details of the LEAF format, creation and verification are currently classified "secret" by the U.S. government, this discussion and FIG. 13 are both somewhat speculative). To form the LEAF, the session key is first encrypted using the private device key; then the device-key-encrypted session key, the sender device's serial number and a checksum (a verifying value) of the original unencrypted session key are together encrypted with the Clipper family key to complete the LEAF. The message is then encrypted using the chosen session key. The session-key-encrypted message and the family-key-encrypted LEAF are together transmitted to the recipient. Upon receiving the communication, the receiving user first loads the received LEAF into his Clipper chip in order to check whether the LEAF is valid and whether the session key encrypted within the LEAF matches the session key previously received. If the LEAF is valid, the Clipper chip will decrypt the message with the chosen session key that was previously received.
A law enforcement agent lawfully wiretapping or monitoring the communication, however, does not know the session key and thus must first decrypt the LEAF in order to obtain the session key. The agent intercepts the desired LEAF, decrypts it using the Clipper family key and then presents the chip serial number from the LEAF and a court-ordered warrant or other legal authorization to the two government escrow agents, receiving in return the two key splits of the wire-tapped user's private device key. The agent combines the two escrowed device key components and uses the resulting device key to decrypt the device-key-encrypted session key from the LEAF. The session key can then be used to decrypt the actual messages from the communications. The requirement that the sender and recipient each create a LEAF and validate the other's LEAF insures that law enforcement agents will have a reasonable chance at intercepting the LEAF, since each LEAF is expected to pass between the users over the same communications medium. Further, it allows law enforcement to selectively monitor only one suspected user by decrypting the LEAF generated by that user, regardless of which user originated the communication.
Unfortunately, there are many technical problems with the government's Clipper chip proposal, mostly stemming from the fact that the private keys to be escrowed are permanently embedded in the Clipper chips during manufacture. Because the private encryption key for a particular device is burned into the chip and cannot be changed, the chip and probably the entire device that contains it must be discarded if compromised. It is preferable for the user of a particular device to be able to rekey, reescrow and recertify the device at will if compromise is suspected or at regular intervals to avoid potential compromise. In addition to the inability of the user to rekey and reescrow, the user of the Clipper device has no choice of the number or the identities of the key escrow agents employed by the government to safeguard his private key. Instead, the private key splits are deposited in two escrow data bases or agencies established by the government. Users may not trust the Clipper chip devices due to the risk that the government may have complete access to any transmission or transaction through the device, access that could be abused or corrupted. Users may also desire that their keys be escrowed with more trustees than the government provides, in order that their private keys will be more secure. If the concept of key escrow is to have significance, each user must be able to choose his own trustees with whom to escrow his private keys, based upon the level of trust desired.
Also, it is believed that the government Clipper system allows users to communicate only symmetrically and in real time, and does not provide any direct support for store-and-forward electronic-mail type messaging. Prior to encrypting communications, the sender and recipient must first agree on a symmetric session key with which to encrypt the communications. Typically, this key exchange is done using the Interactive Diffie-Hellman scheme, the only key exchange method believed to be supported by the Clipper chip. Thus, unless they wish to arrange their own key management system, users are restricted to simultaneous, interactive communications, such as real-time voice or facsimile communications. In order to use store-and-forward electronic-mail type messaging, however, a user must be able to access the intended recipient's public key, such as by using a Certified Diffie-Hellman or a certified RSA key transport scheme, even if the intended recipient is not available for an interactive on-line communication. Because it is believed that the government's Clipper system does not facilitate this, store-and-forward messaging is difficult. The government's proposed standard system thus may tend to limit the communications capabilities of users to on-line interaction.
Moreover, under the government system, the users' employers have no access to the encrypted data or transmissions of their employees. Employers, on whose behalf the employees are developing, communicating or transmitting confidential or proprietary data, must retain the right to gain access to their employees' data or transmissions. Many situations could arise wherein encrypted information would be available only to the specific employees directly engaged in using the cryptographic systems and not to the management or boards of directors who are responsible for those employees and who own the corporate data resources. By encrypting data or communications, employees could develop or appropriate for themselves new programs, products and technologies or could conduct illegal activities and transactions, all without their employers' knowledge. Also, movement or reorganization of staff and changes of storage facilities could result in the loss of massive amounts of information that was important enough at the time of encryption to be encrypted. See Donn B. Parker, "Crypto and Avoidance of Business Information Anarchy" (Invited speaker presentation at First Annual AC Conference on Computer and Communication Security, Nov. 3-5, 1993, Reston, Va.), which is hereby incorporated by reference. Aside from the originator of the data or the sender of the transmissions, the Clipper chip allows only the government to have access to the transmissions. Although employers could seek a court-issued warrant in order to monitor their employees' communications, employers may wish to monitor their internal officers in a more discreet fashion than by initiating a federal investigation any time suspicion is aroused.
Furthermore, mandating a classified algorithm that is embedded in the chip and thus available only in hardware and only from government-authorized chip manufacturers injects the government into the rapidly changing and highly competitive market for communications and computer hardware. A government agency or a government-authorized manufacturer may be unable or unwilling to design and market advanced devices and products specially tailored for particular companies as would a private manufacturer. If the government authorizes only certain vendors to manufacture the chips having the classified algorithm, competition will be reduced and the technology will be prevented from being incorporated into other products. Additionally, because the details of the Skipjack algorithm have not been made public, suspicion has arisen as to whether the algorithm could be insecure, due either to an oversight by its designers or to the deliberate introduction by the government of a trap door. An important value of cryptosystem design is that the privacy and security of the encrypted messages should depend on the secrecy of the relevant key values, not on the secrecy of the system's details.
It is, therefore, desirable to provide a commercial key escrow system that uses published algorithms, operates in a manner that inspires the users' trust and confidence, and solves the problems posed by national security and law enforcement demands.
It is also desirable to provide a commercial key escrow system that uses private keys that may be changed by the user at will or at regular intervals.
It is further desirable to provide a commercial key escrow system that allows the user to choose the key escrow agents to safeguard his private key or the separate pieces of his private key.
It is still further desirable to provide a commercial key escrow system that contains safeguards against unrestricted government access, yet allows access by the employers of the users or by the countries of which the foreign users are citizens.
It is also desirable to provide a commercial key escrow system that offers an alternative to the U.S. Government's proposed Clipper chip system.

Enhanced cryptographic system and method with key escrow feature


A chirped pulse amplification system employs chirped quasi-phase-matched (QPM) gratings as dispersive delay lines for stretching and/or compressing ultrashort pulses. QPM gratings with periods varying along the beam propagation direction produce simultaneous second-harmonic generation and, in general, both amplitude and phase modulation of this second harmonic output. The aperiodic QPM gratings are designed to provide stretching or compression of the output second harmonic pulse with respect to the fundamental-wavelength input pulse. The chirped QPM gratings are also used for simultaneous harmonic generation and compressing of the chirped output from a femtosecond laser oscillator. In general, the aperiodic QPM gratings can be used to efficiently produce arbitrarily shaped second-harmonic pulses.

1. Field of the Invention
The present invention relates to the use of chirped (aperiodic) quasi-phase-matched (QPM) gratings as dispersive components in ultrashort-pulse laser systems.
2. Description of the Related Art
Chirped pulse amplification (CPA) systems are well known in the field of ultrafast optics. See, for example, D. Strickland et al., Compression of Amplified Chirped Optical Pulses, Opt. Commun. Vol. 56, pp. 219 (1985). CPA techniques are used to stretch ultrashort optical pulses prior to amplification when it is necessary to reduce the unacceptably-high pulse peak powers in the amplifier material or optical components in order to avoid detrimental effects. The ultrashort pulse duration must be restored after amplification using a pulse compressor.
Pulse stretching and compression can be achieved by introducing dispersion. Group velocity dispersion (GVD) of an optical pulse arises from the difference in the group velocities for different spectral components constituting the pulse. An optical element producing this dispersion is called a dispersive delay line (DDL). A variety of dispersive delay lines are known in the prior art associated with the field of ultrashort pulse optics, where they are commonly used for ultrashort pulse stretching and compression. Optical pulses are generally considered to be ultrashort if their duration is in the range from approximately 10.sup.-15 to 10.sup.- seconds.
Conventional dispersive delay lines include: diffractive (diffraction grating based), refractive (using prisms or other refractive shapes), interferometric (using Gires-Tournois or Fabry-Perot etalons), and Bragg reflection (fiber gratings, chirped mirrors) DDLs. All of the previously known CPA systems use conventional dispersive delay lines for stretching and recompression, and all of the conventional DDLs produce dispersed output pulses at the same wavelength as the input pulses.
Diffraction gratings can provide a large amount of stretching and compression and possess a broad spectral bandwidth. However, diffractive DDLs are disadvantageous because they are typically large in size, consist of multiple components, require complicated alignment procedures and induce relatively high losses on the dispersed optical pulse. Additionally, diffractive DDLs provide a limited degree of control of the linearity of the GVD characteristics.
Refractive DDLs are advantageous because of their low loss. However, refractive DDLs provide only a small amount of stretching/compression, are relatively large in size and provide only limited control of the linearity of the dispersion characteristics.
Interferometric DDLs are compact and have low loss. However, the practical use of interferometric DDLs is very limited due to the small bandwidth and the small amount of dispersion they provide.
Advantages of Bragg reflection DDLs, such as fiber gratings, include their small size, large dispersion, large bandwidth, and arbitrary control of dispersion characteristics. The primary disadvantages of fiber gratings are the limitations on the recompressed pulse energy and insertion losses due to the reflective configuration of such DDLs. Chirped mirrors, on the other hand, have a substantially higher energy threshold for pulse distortions, but provide a very small amount of dispersion.
It is known in the prior art that unmatched, higher-order dispersion terms can arise either if the pulse stretcher and pulse compressor are different types of DDLs or if the large amount of linear GVD introduced by the material in an optical path of propagating pulses causes a dispersion mismatch between pulse stretchers and compressors of the same type. See, for example, B. E. Lemoff et al., Quintic-phase-limited, spatially uniform expansion and recompression of ultrashort optical pulses, Opt. Lett., Vol. 18, pp. 1651 (1993); S. Kane et al., Grating Compression of Third-Order Material Dispersion in the Normal Dispersion Regime: Sub-100-fs Chirped-Pulse Amplification Using a Fiber Stretcher and Grating-Pair Compressor, IEEE J. of Quantum Electron. QE-31, pp. 2052 (1995).
In general, use of DDLs for commercially viable ultrashort pulse lasers, amplifiers and pulse shapers requires improvement of certain characteristics of existing DDLs, such as compactness, manufacturability, cost, amount of loss, and ability to control the linearity of dispersion characteristics, while maintaining the key properties of large dispersion capability, large spectral bandwidth, and the capability to sustain high pulse energies. As the above description of the properties of conventional DDLs reveals, there generally exists a trade-off between the properties of any conventional DDL. Therefore, a novel device capable of providing all of the required properties in one element would be highly beneficial.
In general, solid-state mode-locked lasers operating in a chirped pulse mode are capable of obtaining higher pulse energies. An example of a solid-state laser producing increased pulse energies for chirped output is disclosed by C. Spielmann et al. in Experimental study of additive-pulse mode-locking in an ND:glass laser, IEEE J. of Quantum Electron., Vol. 27, pp. 1207 (1991).
Another example of using a dispersive delay line in an ultrafast laser system is disclosed by L. E. Nelson et al. in Efficient frequency doubling of a femtosecond fiber laser, Opt. Lett., Vol. 21, pp. 1759 (1996), where a refractive prism-based compressor is used to compress chirped pulses from a stretched-pulse additive-pulse mode-locked fiber laser prior to frequency doubling of these compressed pulses in a conventional birefringence phase-matched nonlinear crystal. Such a fiber laser can generate pulses with energies that are approximately an order of magnitude higher than those from a typical mode-locked fiber laser directly producing bandwidth-limited pulses. However, the necessary external compressor substantially increases the complexity and size of the laser system.
A dispersive delay line in an ultrafast system can be used not only for pulse stretching or compression but also for arbitrary pulse shaping, as often required for various applications in chemistry, optical communications, etc. One example of such an arrangement is disclosed by A. Weiner et al. in Programmable femtosecond pulse shaping by use of a multielement liquid-crystal phase modulator, Opt. Lett., Vol. 15, pp. 326 (1990). In such an apparatus, the pulse to be shaped is spectrally and spatially dispersed using, for example, a grating pair or a pair of prisms. The spectrum is propagated through a spacial mask which spectrally filters both the amplitude and phase of the pulse. The spectral components are then recollimated into a beam by a second grating or pair of prisms forming a reshaped optical pulse. In principle, by a proper choice of spectral mask, any required optical waveform can be generated. The main disadvantage of this method is that the apparatus is a complex system with relatively large dimensions.
Methods of quasi-phase-matching offer broad engineerability to the phasematching properties of frequency conversion devices but have, to date, almost exclusively been applied only with periodic gratings. See, for example, M. Fejer et al., Quasi-Phase-Matched Second Harmonic Generation: Tuning and Tolerances, IEEE J. of Quantum Electron. QE-28, 2631 (1992). Such use of periodic QPM has allowed interactions in wavelength ranges and use of large nonlinear coefficients not available with birefringence phasematching. While aperiodic QPM gratings were suggested by T. Suhara et al. in Theoretical Analysis of Waveguide Second-Harmonic Generation Phase Matched with Uniform and Chirped Gratings, IEEE J. of Quantum. Electron. QE-26, 1265 (1990) for the additional advantage of increasing the wavelength acceptance bandwidth in continuous-wave second harmonic generation, the important implications of the phase response of these aperiodic QPM structures to ultrashort-pulse frequency conversion have not been known or used in practice.
In U.S. patent application Ser. No. 08/824,032, Arbore et al. disclose that a quasi-phase-matched (QPM) second harmonic generator (SHG) with QPM period chirped along the crystal length, in effect, provides group velocity dispersion (GVD) at the second-harmonic wavelength. This property allows construction of unique devices for simultaneous second-harmonic generation and temporal stretching or compression of the second-harmonic output with respect to the fundamental input pulses.
The properties of this type of dispersive element provide a number of advantages over conventional dispersive delay lines. Aperiodic QPM gratings combine compact size, manufacturability and low cost, monolithic design. Further, aperiodic QPM gratings have low loss at the fundamental wavelength, and pulse energies can be scaled by scaling the beam size. Also, such QPM gratings allow nearly arbitrary control of dispersion characteristics. In addition, aperiodic QPM gratings possess the unique property of simultaneously performing SHG and pulse compression in a single device.
All of the above-mentioned articles, patents and patent applications are hereby incorporated herein by reference.

Use of aperiodic quasi-phase-matched gratings in ultrashort pulse sources


The present invention is directed towards an apparatus for guiding continuous materials. In one embodiment of the invention, the apparatus comprises first and second conveyors, each comprising a continuous conveyor belt carried by a set of pulleys including a drive pulley and an idler pulley. The conveyor belts have opposing inner surfaces that are oriented to travel substantially parallel to one another to sandwich continuous materials therebetween. The ratio of the diameters of the idler pulleys to the drive pulleys is greater than about 8:1. In another embodiment of the invention, a chopper is provided. The chopper comprises a cutting roll and a cot member defining a nip region therebetween. The cutting roll has an axis of rotation that is aligned substantially parallel to an axis of rotation of a cot member. The small turning radii permit the conveyor belts to extend within the nip region.

Continuous glass fibers are formed by extruding molten glass through a bushing and attenuating the extruded molten glass. Formation of the fibers also normally involves treating the fibers with a size to enhance the properties of the fibers in subsequent operations. The resultant fibers, after solidifying, may then be directed to another area for fabrication into desired products, or collected as a package for storage prior to further processing.
Strands are formed from a plurality of glass fibers arranged adjacent to one another. Rovings are formed from a plurality of strands. Strands and rovings are often used to further form yarns and tows. Other products, such as tapes, ribbons, scrims, webs, and veils, are also formed from glass fibers. When fiberglass packages are formed, the glass fibers, or products formed therefrom, are wound onto a tube utilizing various methods and apparatus.
Continuous materials, such as fibers or fiber products, are often cut into discrete lengths in a process involving a chopping operation. In a chopping operation, the continuous materials are conveyed along a pathway into engagement with a chopper. A chopper includes a cutting roll that rotates about an axis that is perpendicular or transverse to the path of the continuous materials. The cutting roll is comprised of a steel roll with a plurality of spaced cutting blades projecting radially outwardly from, and generally parallel to, the axis of the steel roll. The cutting blades can be oriented so that the blades cut the continuous materials longitudinally and transversely relative to the pathway of the continuous materials being cut. The cutting roll cooperates with a backup roll or cot roll to cut or chop the continuous materials as they pass through the nip between the cutting roll and the cot roll to produce segments of chopped materials having discrete lengths. The chopped materials are discharged downstream of the cutting blades.
The continuous materials are guided into the cutting blades by an apparatus, which includes a guide roll or belt. The guide roll or belt cooperates with a support plate, roll, or belt to guide and control the continuous materials through the nip between the cutting and cot rolls. This cooperative arrangement is deficient because the guide roll or belt tends to slip relative to the support plate, roll, or belt. This slippage produces friction that causes the continuous materials to slip. This causes the size in the continuous materials to break down. When the size breaks down, it causes the continuous materials to stick to the guide roll or belt. Consequently, the continuous materials wrap around the guide roll or belt.
What is needed is an apparatus for guiding continuous materials, which has a reduced tendency to cause size in the continuous materials to break down and thus become sticky.