A recording/reproducing apparatus by which optimum playback pictures can be produced eve in case of parallel recording/reproduction. A storage unit 123 transiently stores video signals obtained from an overwrite type disc-shaped recording medium 102. A signal processing unit 122 decodes video signals stored in the storage unit 123. A holding unit 124 holds video signals decoded by the signal decoding unit 122. A control unit 101 performs control of the entire apparatus and also performs control for address management and data transfer of the disc-shaped recording medium 102 so that, if the apparatus is set to a mode of performing a playback operation while the recording operation is going on, the storage means 123 stores plural fields of the video signals and the holding unit 124 interpolates the video signals.

This invention relates to a recording/reproducing apparatus for recording and reproducing video signals and speech signals on or from an optical disc or a magnetic disc as a overwrite type disc-shaped recording medium.
Recently, in a recording/reproducing apparatus for recording and reproducing video signals and speech signals on or from an optical disc or a magnetic disc as a overwrite type disc-shaped recording medium, a technique of perpetually recording live broadcast of, for example, a television program at all times in order to retrogressively view a sole scene which has been overlooked and which it is desired to re-view by the viewer.
Such a recording/reproducing apparatus includes, as shown in FIG. 1, an analog/digital (A/D) converter 311 for digitizing picture signals entering an input terminal I3a, and a synchronization separating circuit 310 for extracting vertical synchronization signal of the picture signal entering the input terminal I3a. The recording/reproducing apparatus also includes a compression circuit 312 for encoding picture data from an A/D converter 311 in synchronism with vertical synchronization signal from the synchronization separating circuit 310 and a first-in first-out buffer (FIFO) 313 for storing the picture data from the A/D converter 311. The FIFO buffer is referred to herein as a buffer for video recording. The recording/reproducing apparatus also includes an A/D converter 331 for digitizing speech signals entering an input terminal I3c and a compression circuit 332 for encoding speech data from the A/D converter 331 in synchronism with a vertical synchronization signal from the synchronization separating circuit 310. The recording/reproducing apparatus also includes a FIFO buffer 333 for storing speech data from the compression circuit 332. The FIFO buffer 333 is referred to herein as a buffer for speech recording. The recording/reproducing apparatus further includes a disc drive 303 for recording video data from speech data from the FIFO 313 for storing the picture data and the speech data from the FIFO buffer 333 for storing speech data on a overwrite type disc 302 in accordance with a pre-set format and for reproducing the speech data and the video data recorded on the disc 302.
The input terminals I3a and I3c are connected to, for example, a tuner, not shown, configured for receiving live broadcast.
The recording/reproducing apparatus 300 also includes a FIFO buffer for storing speech data obtained by the disc drive 303 and an expansion circuit 342 for decoding the speech data from the FIFO buffer 343 in synchronism with the vertical synchronization signals from the synchronization separation signal 310. The FIFO buffer 343 is referred to herein as a buffer for speech reproduction. The recording/reproducing apparatus 300 also includes digital analog (D/A) converter 341 for converting speech data from the expansion circuit 342 into analog data for outputting at an output terminal I3d, and a FIFO buffer 323 for storing video data obtained from the disc drive 303. The FIFO buffer 323 is referred to herein as a buffer for video reproduction. The recording/reproducing apparatus 300 further includes an expansion circuit 322 for decoding video data from the expansion circuit 322 and a D/A converter 321 for converting the video data from the expansion circuit 322 into analog data for outputting at an output terminal I3b. The speech data stored in the FIFO buffer for speech reproduction 343 is also supplied to the disc drive 303.
The output terminals I3b and I3d are connected to a monitor not shown, configured for displaying and outputting a picture derived from the video signals supplied thereto via output terminal I3b and for outputting the speech derived from the speech signals supplied thereto from a speaker, not shown, via output terminal I3d.
The recording/reproducing apparatus 300 also includes a system controller 301 for controlling an output of the buffer for video recording 313 to the disc drive 303, an output of the buffer for speech recording 333 to the disc drive 303, an output of the buffer for speech reproduction 343 to the disc drive 303 and an output of the disc drive 303 to the buffer for speech reproduction 343 and to the buffer for video reproduction 323. The system controller 301 is configured for performing control processing based on a vertical synchronization signal from the synchronization separation circuit 310, a full flag Ffu from the buffer 313 for video recording, an empty flag Fem from buffer 323 for video reproduction and a transfer permission flag Fok from the disc drive 303.
There is provided on the output side of the D/A converter 321 a switch 320 to which are supplied video signals from the input terminal I3a and video signals from the D/A converter 321. There is also provided on the output side of the D/A converter 341 a switch 340 to which are supplied speech signals from the input terminal I3c and speech signals from the D/A converter 341. Under switching control by the system controller 301, not shown, the switches 320, 340 are changed over to the input terminal I3a and to the input terminal I3c during the recording operation, respectively, and to the D/A converters 321, 341 during the playback operation, respectively.
There is also provided on the input side of the buffer for speech reproduction a switch 344 to which are supplied speech data from the compression circuit 332 and speech data derived from the disc drive 303. Under switching control by the system controller 301, not shown, the switch 344 is changed over to the side of the compression circuit 332 and to the side of the disc drive 303 during the recording operation and during the reproducing operation, respectively.
The above-described recording/reproducing apparatus uses a one-shoat playback system of temporarily interrupting the recording operation and a parallel recording/reproducing system of performing the payback operation while continuing the recording operation, in order to permit the user to regressively view the scene he or she has just viewed for a moment.
Referring to FIG. 2, if video signals and speech signals VA0, VA1, VA2, . . . from a tuner receiving the live broadcast, referred to herein as input signals, are supplied to the recording/reproducing apparatus 300, and the playback mode by the one-shot playback system, referred to herein as one-shot playback mode, is set directly after the end of inputting of the input signal VA5 by the key input by the user, the recording/reproducing apparatus 300 momentarily discontinues the recording operation at the same time as the one-shot playback mode is set. At this time, the input signals VA0 to VA5 have been recorded on the disc 302. The recording/reproducing apparatus 300 then reproduces the previously recorded input signals VA2 to VA5 from the disc 302. Subsequently, the recording/reproducing apparatus 300 starts the recording operation for the currently inputted input signals VA10, VA11, . . .
Thus, until the recording/reproducing apparatus 300 is set to the one-shot playback mode, a live picture corresponding to the input signals VA0 to VA5 from the tuner, not shown, for receiving the live broadcast, is displayed on the monitor, not shown. Once the recording/reproducing apparatus 300 is set to the one-shot playback mode, the playback picture corresponding to the input signals VA2 to VA5 is displayed on the monitor. The recording/reproducing apparatus 300 does not perform the recording operation for the input signals VA6 to VA9 entered during the period the playback picture is displayed on the monitor. After the end of display of the playback picture corresponding to the input signals VA2 to VA5, a live picture corresponding to the currently inputted input signals VA10, VA11, . . . is displayed.
On the other hand, if the playback mode by the parallel recording/reproducing system, referred to herein as the parallel recording/reproducing mode, is set for the recording/reproducing apparatus 300 directly after the end of inputting of the input signals VA5, by the key input by the user, the recording/reproducing apparatus 300 reproduces the previously recorded input signals VA2, VA3, VA4, . . . from the disc 302, at the same time as it continues the recording operation.
Thus, until the recording/reproducing apparatus 300 is set to the parallel recording/reproducing mode, a live picture corresponding to the input signals VA0 to VA5 from the tuner, not shown, designed for receiving the love broadcast, is displayed on a monitor, not shown. Once the recording/reproducing apparatus 300 is set to the parallel recording/reproducing mode, the playback picture corresponding to the input signals VA2, VA3, VA4, . . . is displayed on the monitor. Under this condition, the recording/reproducing apparatus 300 performs the recording operation for the currently entered input signals VA6, VA7, VA8, . . .
For performing the above-described one-shot playback mode operation and parallel recording/reproducing mode operation, the recording/reproducing apparatus 300 performs full-field playback operation and frame-skip playback operation during the one-shot playback mode operation and parallel recording/reproducing mode operation, respectively, using a first format comprised of blocks of plural fields constituted by the speech and the video not thinned out on the time axis and a second format comprised of plural blocks constituted by the speech not thinned out on the time axis and video thinned out on the time axis.
For example, if the recording/reproducing apparatus 300 manages picture data and speech data for 8 vertical synchronization periods (V), a format 300a for one block of the first format includes speech data A1 for 1 V, a video data V1 for 1 V, speech data A2 for 1 V, . . . video data V2 for 1 V, . . . speech data A8 for 1 V and video data V8 for 1 V, recorded in succession to the speech data A for 8 V, as shown in FIG. 4A. On the other hand, a format 300b for one block of the second format includes video data V 1 for 1 V in succession to the speech data A for 8 V.
If the recording/reproducing apparatus 300 is not set to the one-shot playback mode, to the parallel recording/reproducing mode nor to the usual playback mode, referred to herein as the usual mode, the recording/reproducing apparatus 300 necessarily records on the disc 302 the video data and the speech data from the tuner, not shown, designed for receiving the live broadcast, in accordance with the format 300a.
FIGS. 5 and 6 are timing charts for input/output data for the buffers 313, 323, 333 and 343. In FIGS. 5 and 6, each division of video data V-6, V-5, V-4, . . . and each division of the speech data A-6, A-5, A-4, . . . denotes one-field time of video signals.
Referring to FIGS. 1, 4A, 4B and 6, the operation for each set mode of the recording/reproducing apparatus 300 is explained in detail.
First, in the usual mode of the recording/reproducing apparatus 300, the switch 344 is changed over to the side of the compression circuit 332, under switching control by the system controller 301.
The video signals of V1, entering the input terminal I3a during the V1 period, is digitized by the A/D converter 311 and encoded by the compression circuit 312.
Simultaneously, the speech signal A1 entering the input terminal I3c is digitized by the A/D converter 331 and encoded by the compression circuit 332.
The video data V1, obtained on encoding by the compression circuit 312, is stored in the video recording buffer 313. If video data for 1 V, that is V1 video data, is stored in the video recording buffer 313, the full-flag Ffu is set to xe2x80x981xe2x80x99 and routed to the system controller 301.
The A1 speech data obtained on encoding by the compression circuit 342 is stored in the speech recording buffer 343.
Based on the full flag Ffu (=xe2x80x981xe2x80x99) from the video recording buffer 313, the system controller 301 reads out from the speech recording buffer 333 the speech data A-6 to A0 stored therein after encoding by the compression circuit 332. The system controller 301 routes to the disc drive 303 the command and the address for recording data of the disc 302 and the speech data A-6 to A0 read out from the speech recording buffer 333.
Based on the address and the command from the system controller 301, the disc drive 303 records the speech data A-6 to A0 from the system controller 301 on the disc 302.
When the speech data A-6 to A0 has been recorded on the disc 302 by the disc drive 303, the system controller 301 reads out the A1 speech data stored in the speech recording buffer 343 and routes the read-out speech data to the disc drive 303.
The disc drive 303 records the A1 speech data from the system controller 301 in an address of the disc 302 next following the A0 speech data.
The system controller 301 then reads out the V1 video data stored in the video recording buffer 313 and routes the read-out video data to the disc drive 303.
The disc drive 303 records the V1 video data from the system controller 301 in an address of the disc 302 next following the A1 speech data.
If the V1 video data is read out by the system controller 301, the video recording buffer 313 sets the full flag Ffu to xe2x80x980xe2x80x99 which is routed to the system controller 301. If the 1V video data, that is video data for V2, is stored during the next V2 period, the video recording buffer again sets the full flag Ffu to xe2x80x981xe2x80x99 which is routed to the system controller 301.
Thus the system controller 301 reads out the A2 speech data stored in the speech recording buffer 343 after encoding by the compression circuit 332 during the V2 period and routes the read out data to the disc drive 303. The system controller 301 then reads out the V2 video data stored in the video recording buffer 313 from the video recording buffer 313 to route the read-out video data to the disc drive 303.
The disc drive 303 then records out the A2 speech data from the system controller 301 in an address next following the V1 video data of the disc 302 and subsequently records the V2 video data in an address next following the A2 speech data on the disc 302.
By the repetition of the above-described sequence of operations, block data comprised of the A-6 to A0 speech data, A1 video data, V1 speech data, . . . A8 speech data and V8 video data are recorded on the disc 302, in accordance with the format 300a, so that plural block data are recorded in succession.
If, by the key input by the user, the recording/reproducing apparatus 300 is set to the parallel recording/reproducing mode, the switch 344 is changed over to the side of the disc drive 303 under switching control by the system controller 301.
The system controller 301 routes to the disc drive 303 the command and the address in which is recorded an optional block data selected from the block data continuously recorded on the disc 302 as described above in accordance with the format 300a.
By the address and the command from the system controller 301, the disc drive 303 reproduces video data and the speech data in the optional block data from the disc 302.
That is, in FIG. 5, the system controller 301 routes to the disc drive 303 the playback command and the address of the disc 302 in which are recorded the A-6 to A1 speech data. Thus the disc drive 303 reproduces the A-6 to A1 speech data from the disc 302.
The system controller 301 writes the A-6 to A1 speech data obtained from the disc drive 303 via switch 344 on the speech reproducing buffer 343 in synchronism with the vertical synchronization signals from the synchronization separation circuit 310.
The disc drive 303 then reproduces V1 video data from an address next following the A1 speech data of the disc 302.
After resetting the write address of the video reproducing buffer 323, the system controller 301 writes the V1 video data obtained by the disc drive 303 in the video reproducing buffer 323.
The expansion circuit 322 resets the reading of the video reproducing buffer 323 in synchronism with the vertical synchronization signals from the synchronization separation circuit 310 for reading out the V1 video data stored in the video reproducing buffer 323 eight times on end and for sequentially decoding the read-out video data to route the decoded video data to the switch 320.
At this time, the expansion circuit 342 decodes the A-6 to A1 speech data stored in the speech reproducing buffer 343, in synchronism with the vertical synchronization signals from the synchronization separation circuit 310, for outputting the decoded speech data via switch 340 and output terminal I3d to the speaker.
Thus, a playback picture corresponding to the V1 video signals is displayed for eight fields on the monitor, while the speech corresponding to the speech signals A-6 to A1 are outputted via speaker, not shown.
If the video data for 8 V and the speech data are reproduced as described above, the recording/reproducing apparatus 300 performs the recording in accordance with the format 300b.
That is, the system controller 301 reads out A2 to A9 speech data encoded by the compression circuit 332 and stored in the speech recording buffer 333 during the V2 to V9 period. The system controller 301 routes to the disc drive 303 the command and the address next following the V8 video data of the disc 302 and the A2 to A9 speech data read out from the video recording buffer 333.
Based on the address and the command from the system controller 301, the disc drive 303 records the A2 to A9 speech data from the system controller 301 in an address next following the V8 video data of the disc 302.
The system controller 301 then reads out V9 video data from the system controller 301 in an address next following the A9 speech data on the disc 302.
Thus, the A2 to A9 speech data and the V9 video data are recorded on the disc 302 in accordance with the format 300b.
The system controller 301 then routes to the disc drive 303, in synchronism with the vertical synchronization signals from the synchronization separation circuit 310, at a timing of the start of the eighth playback of the V1 video data, an address by which the 8V speech data of from A2 to A9 have been recorded on the disc 302. This enables the disc drive 303 to reproduce the A2 to A9 speech data from the disc 302.
The system controller 301 then causes the A2 to A9 speech data from the disc drive 303 to be written via switch 344 in the speech reproducing buffer 343.
The disc drive 303 then reproduces the V9 video data from an address next following the A9 speech data of the disc 302.
After resetting the write address of the video reproducing buffer 323, the system controller 301 causes the V9 video data reproduced from the disc drive 303 to be written in the video reproducing buffer 323.
After read-setting the video reproducing buffer 323 in synchronism with the vertical synchronization signals from the synchronization separation circuit 310, the expansion circuit 322 reads out the V9 video data stored in the video reproducing buffer 323 eight times on end and sequentially decodes the read-out data to output the decoded data to a monitor, not shown, via D/A converter 321, switch 320 and output terminal I3b.
The expansion circuit 342 sequentially decodes, in synchronism with the vertical synchronization signals from the synchronization separation circuit 310, the A2 to A9 speech data stored in the speech reproducing buffer 343, and outputs the decoded data via D/A converter 341, switch 340 and output terminal I3d to the speaker.
This, a playback picture corresponding to the V9 video signals are displayed for 8 fields on the monitor, while the speech corresponding to the A2 to A9 speech signals is outputted by a speaker, not shown.
The above playback operation is repeated until xe2x80x98stopxe2x80x99 of the parallel recording/reproduction is commanded by the key input by the user.
In the recording/reproducing apparatus 300, block data conforming to the formats 300a or 300b are continuously recorded on the disc 302 and reproduction is performed beginning from a specified one of the plural block data recorded continuously on the disc 302 which is in accord with the format 300a. Thus it is supervised by the system controller 303 whether the reproduced block has been recorded in accordance with the format 300a or in accordance with the format 300b.
With the above-described conventional recording/reproducing apparatus, such as the above-described conventional recording/reproducing apparatus 300, the number of fields of video data of the format 300b is one, that is the number of frames during the parallel recording/reproducing mode is one for the number of fields in a block of the format 300a, as shown in FIG. 4B. Thus, if 8 V video data and speech data are managed, the playback operation is xe2x85x9 frame-skip operation during the parallel recording/reproduction, resulting in an unnatural picture obtained by the recording/reproducing apparatus.
If, for overcoming this problem, the number of reproduced frames is simply increased in carrying out the parallel recording/reproduction, it becomes necessary for the recording/reproducing apparatus to access the recording point and the playback point on the disc alternately a number of times equal to the increased number of the playback frames. Thus, much time is consumed in the seek operation for the disc such that the recording and reproduction cannot be completed within a pre-set time.
Moreover, with the above-described recording/reproducing apparatus, since the compression and expansion need to be performed on the video signals at all times for the parallel recording/reproducing mode, it is necessary to provide a compression circuit separately from the expansion circuit. Since these circuits are costly, the recording/reproducing apparatus cannot be reduced in production cost.
It is therefore an object of the present invention to provide a recording/reproducing apparatus in which a satisfactory playback picture can be obtained for the parallel recording/reproducing mode.
It is another object of the present invention to provide a recording/reproducing apparatus in which production cost can be reduced.
The present invention provides a recording/reproducing apparatus in which video signals and speech signals are recorded in synchronism with each other on an overwrite type disc-shaped recording medium based on a selected setting of the processing mode, and in which the video and the speech are reproduced in synchronism with each other from the recording medium having the video signals and the speech signals recorded thereon. The apparatus includes storage means for storing the video signals obtained from the recording medium, decoding means for decoding the video signals stored in the storage means, holding means for holding the video signals decoded by the decoding means and control means for controlling the address management and data transfer for the recording medium and for controlling the overall operation of the apparatus. In the processing mode in which the recording and the reproduction are carried out alternately so that reproduction is performed while the recording is going on, the storage means stores plural fields of the video signals and the holding means performs interpolation of video signals.
In the recording/reproducing apparatus according to the present invention, the signal processing means has the expansion function of decoding the video signals stored in the storage means, and the compression function of encoding the video signals recorded on the recording medium. In the processing mode in which the recording and the reproduction are carried out alternately so that reproduction is performed while the recording is going on, the control means switches the operating timing of the entire apparatus and switches between the expansion function and the compression function of the signal processing means so that the recording operation and the reproducing operation will be carried out alternately.


A switching apparatus for an electric switch, in particular an electric circuit breaker, including a switching head with a grip section, and a switching frame connected to the switching head. In an embodiment, a bearing end of at least one spring element is mounted on the switching frame on at least one bearing device. The switching head for the bearing end of at least one spring element includes at least one positioning depression on the side of the switching head opposite to the grip section, which is embodied for a lateral positioning of the bearing end.

Switching apparatuses for an electric switch are known. They frequently comprise one or more spring elements in order to make forces available for individual switching processes within such a switching apparatus. Such spring elements are frequently embodied as coil springs, which comprise bearing ends on one or on both sides and are suited to storing and releasing force in such a switching apparatus. These bearing ends may be spring eyelets for instance.
In order to mount the spring elements on corresponding mechanical components of the switching apparatuses, bearing devices are frequently provided. In known switching apparatuses, these bearing devices are for instance fastened in a switching frame so that force can be transmitted between this switching frame and the spring element. Similarly switching heads are likewise frequently provided on such a switching frame, which can be moved by way of a grip section between different positions, in particular an on position and an off position.
In known switching apparatuses, the spring element is positioned in respect of the switching frame by corresponding geometrical embodiments on the switching frame. Fixing pins or notches are therefore provided in the material on the switching frame, which generate a positioning or an additional fixing of the spring element on the switching frame. The use of additional fixing pins increases the complexity and thus also the costs of such a switching apparatus. If a notch is provided on the switching frame for the positioning, a mechanical weakening of the switching frame thus occurs in this way so that the frame has to be additionally reinforced at other points.
The positioning of the spring element is required in order to be able to predetermine the desired force ratios inside such a switching apparatus in a precise and predefined manner. Furthermore, it is disadvantageous in known switching apparatuses for the spring length of such a spring element to be restricted. The dimensions of the overall switching apparatuses must be enlarged in known switching apparatuses if the spring element requires a longer effective spring length.


A storage device for refreshing pages of a flash memory comprises a flash memory, an ECC detector and a controller. The flash memory has a plurality of pages, and each page comprises a data area for storing data and a spare area for storing error correction code (ECC) corresponding to the data. The ECC detector is used to get the number of error bits of each page. The controller coupled to the ECC detector is used for storing data and ECC in a first page to a second page when a number of used bytes of the ECC stored in a spare area of the first page exceeds a first predetermined value. A number of used bytes of the ECC stored in a spare area of the second page is less than the first predetermined value. The second page is a blank page.

1. Field of the Invention
The present invention relates to a storage device having a flash memory and related method, and more particularly, to a storage device and related method capable of refreshing data pages of the flash memory based on error correction code.
2. Description of the Related Art
Flash Memory, a non-volatile memory, may keep the previously written stored data upon shutdown. In contrast to other storage media, e.g. hard disks, soft disks, magnetic tapes and so on, the flash memory has advantages of small volume, light weight, vibration-proof, low power consumption, and no mechanical movement delay in data access; therefore, are widely use for as storage media in consumer electronic devices, embedded systems, or portable computers.
There are two kinds of flash memory: one is an NOR flash memory and the other is an NAND flash memory. An NOR flash memory is characteristically of low driving voltage, fast access speed, high stability, and are widely applied in portable electrical devices and communication devices such as Personal Computers (PCs), mobile phones, personal digital assistances (PDAs), and set-top boxes (STBs). An NAND flash memory is specifically designed as data storage media, for example, a Secure Digital (SD) memory card, a Compact Flash (CF) card, a Memory Stick (MS) card. The NAND flash memory contains a plurality of blocks, each block having a plurality of pages and each page dividing into data area and spare area. The data area may have 2048 bytes used for storing data. The spare area may have 64 bytes used for storing error correction code (ECC) as well as other software information, such as wear-leveling or logical-to-physical block-mapping information. NAND flash memory requires ECC to ensure data integrity. ECC can be used in any device that may be susceptible to data errors.
However, the flash memory may fail to change data update-in-place, that is, prior to writing data into a non-blank page, erasing a block including the non-blank page is required. In general, erasing a block takes as much time as 10-20 times greater than writing into a page. If a size of written data is over an assigned block, the filled pages in the assigned block may have to be removed to other blocks, and then erasing the assigned block is performed.
Furthermore, flash memory blocks may fail to be accessed when in excess of one million times of erasures before the block is considered to be worn out. This is because the number of erasure times for a block is close to one million times that charge within the floating gate may be insufficient due to current leakage of realized capacitor, thereby resulting in data loss of the flash memory cell, and even a failure of access to the flash memory. In other words, if a block is erased over a limited times, that block may be unable to be accessed.
Owing to a life-cycle limitation of the flash memory, how to correctly access data before the block is worn out is an important task. A conventional way is to detect a number of written times of all pages, and then to write data into a least-used page. Nevertheless, a most-used page is not essential to be worn out in the next access time, conversely, a less-used is possibly to be worn out in the next access time. In other words, the conventional way to select a page to be written relying on the number of access time is not perfect.

Storage device for refreshing data pages of flash memory based on error correction code and method for the same


A metallic support catalyst includes a honeycomb body, an outer cylinder and a catalyst ingredient loading layer, and has a geometric surface area of 40 cm.sup.2 /g or more with respect to its unit weight. The honeycomb body is formed of a flat metallic foil and a corrugated metallic foil, which are laminated and formed as a roll so as to form a plurality of honeycomb-shaped cells in the honeycomb body. The outer cylinder holds the honeycomb body therein. The catalyst ingredient loading layer is coated on the honeycomb-shaped cells of the honeycomb body. The honeycomb body can be formed of a flat metallic foil and a corrugated metallic foil, which have a thickness of from 0.02 to 0.04 mm. The catalyst ingredient loading layer can have a weight of from 60 to 150 g/liter with respect to a unit volume of said honeycomb body.

1. Field of the Invention
The present invention relates to a metallic support catalyst, which is adapted for purifying exhaust gases emitted from internal combustion engines, and which comprises a metallic honeycomb body, and a catalyst ingredient loaded on the metallic honeycomb body.
2. Description of Related Art
As automotive exhaust gas emission control becomes strict, automobiles are equipped with an exhaust gas purifying apparatus. The following methods are available for purifying automotive exhaust gases; namely: a thermal reactor method, a lean-burn method, an engine-modification method, and a catalyst method. Many automobiles employ a catalyst method.
As for an automotive exhaust-gas-purifying catalyst, a Pt, Pd, or Rh-based catalyst is used. An automotive exhaust-gas-purifying catalyst can be classified into granular one and monolithic one in terms of shape. Monolithic catalyst is made from either ceramics or metal. Ceramics catalyst is made by the following processes; namely: ceramics is calcinated into a honeycomb-shaped support. The support is accommodated in a metallic cylinder. A .gamma.-Al.sub.2 O.sub.3 powder with a catalyst ingredient (e.g., Pt, or the like) loaded is deposited on the support. The ceramics monolithic support catalyst is susceptible to mechanical shocks, and exhibits large resistance against exhaust gases. Accordingly, metallic monolithic support catalysts have recently come to be used widely in order to reduce pressure-loss in exhaust system and enhance the heat resistance of support.
For instance, a metallic monolithic catalyst is made as follows; namely: an Fe--Cr--Al stainless steel plate is rolled into a flat foil in a thickness of a few dozens of micrometers. The Fe--Cr--Al stainless steel plate, for example, includes Cr in an amount of 20% by weight, Al in an amount of 5% by weight, and the balance of Fe and inevitable impurities. Part of the resulting flat foil is formed into a corrugated foil. The flat foil and the corrugated foil are laminated alternately, or formed as a roll so as to prepare a honeycomb body. The honeycomb body is accommodated in a metallic cylinder to make a substrate. The substrate is coated with .gamma.-Al.sub.2 O.sub.3 to form a catalyst ingredient loading layer. Then, a catalyst ingredient, such as Pt, Rh, and Pd, is deposited on the loading layer.
In the metallic monolithic catalyst or metallic support catalyst, it has been required to improve the purifying characteristic immediately after starting engine (i.e., warm-up characteristic). A variety of attempts have been made so far. For example, in order to upgrade the warm-up characteristic of metallic support catalyst, it is effective to reduce the heat capacity of metallic support. Accordingly, the cell density of honeycomb body has been reduced, or the foil, forming metallic-honeycomb body, has been perforated. However, such attempts have decreased the geometric surface area of metallic honeycomb support.
On the other hand, in order to enhance the conversion of metallic support catalyst, it is effective to increase the geometric surface area of metallic support. Accordingly, the cell density of metallic support has been increased, or the foil, forming the metallic honeycomb support, has been provided with projections or is corrugated. However, such attempts have increased the heat capacity of metallic honeycomb support, and resulted in impairing the warm-up characteristic of metallic support catalyst.
Metallic support catalysts are required to exhibit good warm-up characteristic as well as high conversion. It is understood from the foregoing description that improving the warm-up characteristic results in reducing the conversion, and that enhancing the conversion results in deteriorating the warm-up characteristic. Thus, it is difficult to satisfy both of these characteristics at the same time.


This is directed to methods and devices suited for maintaining an opening in a wall of a body organ for an extended period. More particularly devices and methods are directed maintaining patency of channels that alter gaseous flow within a lung to improve the expiration cycle of, for instance, an individual having chronic obstructive pulmonary disease.

The American Lung Association (ALA) estimates that nearly 16 million Americans suffer from chronic obstructive pulmonary disease (COPD) which includes diseases such as chronic bronchitis, emphysema, and some types of asthma. The ALA estimated that COPD was the fourth-ranking cause of death in the U.S. The ALA estimates that about 14 million and 2 million Americans suffer from emphysema and chronic bronchitis respectively.
Those inflicted with COPD face disabilities due to the limited pulmonary functions. Usually, individuals afflicted by COPD also face loss in muscle strength and an inability to perform common daily activities. Often, those patients desiring treatment for COPD seek a physician at a point where the disease is advanced. Since the damage to the lungs is irreversible, there is little hope of recovery. Most times, the physician cannot reverse the effects of the disease but can only offer treatment and advice to halt the progression of the disease.
To understand the detrimental effects of COPD, the workings of the lungs requires a cursory discussion. The primary function of the lungs is to permit the exchange of two gasses by removing carbon dioxide from arterial blood and replacing it with oxygen. Thus, to facilitate this exchange, the lungs provide a blood gas interface. The oxygen and carbon dioxide move between the gas (air) and blood by diffusion. This diffusion is possible since the blood is delivered to one side of the blood-gas interface via small blood vessels (capillaries). The capillaries are wrapped around numerous air sacs called alveoli which function as the blood-gas interface. A typical human lung contains about 300 million alveoli.
The air is brought to the other side of this blood-gas interface by a natural respiratory airway, hereafter referred to as a natural airway or airway, consisting of branching tubes which become narrower, shorter, and more numerous as they penetrate deeper into the lung. Specifically, the airway begins with the trachea which branches into the left and right bronchi which divide into lobar, then segmental bronchi. Ultimately, the branching continues down to the terminal bronchioles which lead to the alveoli. Plates of cartilage may be found as part of the walls throughout most of the airway from the trachea to the bronchi. The cartilage plates become less prevalent as the airways branch. Eventually, in the last generations of the bronchi, the cartilage plates are found only at the branching points. The bronchi and bronchioles may be distinguished as the bronchi lie proximal to the last plate of cartilage found along the airway, while the bronchiole lies distal to the last plate of cartilage. The bronchioles are the smallest airways that do not contain alveoli. The function of the bronchi and bronchioles is to provide conducting airways that lead air to and from the gas-blood interface. However, these conducting airways do not take part in gas exchange because they do not contain alveoli. Rather, the gas exchange takes place in the alveoli which are found in the distal most end of the airways.
The mechanics of breathing include the lungs, the rib cage, the diaphragm and abdominal wall. During inspiration, inspiratory muscles contract increasing the volume of the chest cavity. As a result of the expansion of the chest cavity, the pleural pressure, the pressure within the chest cavity, becomes sub-atmospheric. Consequently, air flows into the lungs and the lungs expand. During unforced expiration, the inspiratory muscles relax and the lungs begin to recoil and reduce in size. The lungs recoil because they contain elastic fibers that allow for expansion, as the lungs inflate, and relaxation, as the lungs deflate, with each breath. This characteristic is called elastic recoil. The recoil of the lungs causes alveolar pressure to exceed atmospheric pressure causing air to flow out of the lungs and deflate the lungs. If the lungs' ability to recoil is damaged, the lungs cannot contract and reduce in size from their inflated state. As a result, the lungs cannot evacuate all of the inspired air.
In addition to elastic recoil, the lung's elastic fibers also assist in keeping small airways open during the exhalation cycle. This effect is also known as "tethering" of the airways. Tethering is desirable since small airways do not contain cartilage that would otherwise provide structural rigidity for these airways. Without tethering, and in the absence of structural rigidity, the small airways collapse during exhalation and prevent air from exiting thereby trapping air within the lung.
Emphysema is characterized by irreversible biochemical destruction of the alveolar walls that contain the elastic fibers, called elastin, described above. The destruction of the alveolar walls results in a dual problem of reduction of elastic recoil and the loss of tethering of the airways. Unfortunately for the individual suffering from emphysema, these two problems combine to result in extreme hyperinflation (air trapping) of the lung and an inability of the person to exhale. In this situation, the individual will be debilitated since the lungs are unable to perform gas exchange at a satisfactory rate.
One further aspect of alveolar wall destruction is that the airflow between neighboring air sacs, known as collateral ventilation or collateral air flow, is markedly increased as when compared to a healthy lung. While alveolar wall destruction decreases resistance to collateral ventilation, the resulting increased collateral ventilation does not benefit the individual since air is still unable to flow into and out of the lungs. Hence, because this trapped air is rich in CO2, it is of little or no benefit to the individual.
Chronic bronchitis is characterized by excessive mucus production in the bronchial tree. Usually there is a general increase in bulk (hypertrophy) of the large bronchi and chronic inflammatory changes in the small airways. Excessive amounts of mucus are found in the airways and semisolid plugs of this mucus may occlude some small bronchi. Also, the small airways are usually narrowed and show inflammatory changes.
Currently, although there is no cure for COPD, treatment includes bronchodilator drugs, and lung reduction surgery. The bronchodilator drugs relax and widen the air passages thereby reducing the residual volume and increasing gas flow permitting more oxygen to enter the lungs. Yet, bronchodilator drugs are only effective for a short period of time and require repeated application. Moreover, the bronchodilator drugs are only effective in a certain percentage of the population of those diagnosed with COPD. In some cases, patients suffering from COPD are given supplemental oxygen to assist in breathing. Unfortunately, aside from the impracticalities of needing to maintain and transport a source of oxygen for everyday activities, the oxygen is only partially functional and does not eliminate the effects of the COPD. Moreover, patients requiring a supplemental source of oxygen are usually never able to return to functioning without the oxygen.
Lung volume reduction surgery is a procedure which removes portions of the lung that are over-inflated. The portion of the lung that remains has relatively better elastic recoil, providing reduced airway obstruction. The reduced lung volume also improves the efficiency of the respiratory muscles. However, lung reduction surgery is an extremely traumatic procedure which involves opening the chest and thoracic cavity to remove a portion of the lung. As such, the procedure involves an extended recovery period. Hence, the long term benefits of this surgery are still being evaluated. In any case, it is thought that lung reduction surgery is sought in those cases of emphysema where only a portion of the lung is emphysematous as opposed to the case where the entire lung is emphysematous. In cases where the lung is only partially emphysematous, removal of a portion of emphysematous lung which was compressing healthier portions of the lung allows the healthier portions to expand, increasing the overall efficiency of the lung. If the entire lung is emphysematous, however, removal of a portion of the lung removes gas exchanging alveolar surfaces, reducing the overall efficiency of the lung. Lung volume reduction surgery is thus not a practical solution for treatment of emphysema where the entire lung is diseased. Moreover, conventional lung volume reduction surgery is an open surgical procedure which carries the risk of surgical complications and requires a significant period of time for recuperation.
Both bronchodilator drugs and lung reduction surgery fail to capitalize on the increased collateral ventilation taking place in the diseased lung. There remains a need for a medical procedure that can alleviate some of the problems caused by COPD. There is also a need for a medical procedure that alleviates some of the problems caused by COPD irrespective of whether a portion of the lung, or the entire lung is emphysematous. The production and maintenance of collateral openings through an airway wall allows air to pass directly out of the lung tissue responsible for gas exchange. These collateral openings serve to decompress hyperinflated lungs and/or facilitate an exchange of oxygen into the blood.
Methods and devices for creating and maintaining collateral channels are discussed in U.S. patent application Ser. No. 09/633,651, filed on Aug. 7, 2000; U.S. patent application Ser. Nos. 09/947,144, 09/946,706, and 09/947,126 all filed on Sep. 4, 2001; U.S. Provisional Application No. 60/317,338 filed on Sep. 4, 2001; U.S. Provisional Application No. 60/334,642 filed on Nov. 29, 2001; U.S. Provisional Application No. 60/367,436 filed on Mar. 20, 2002; and U.S. Provisional Application No. 60/374,022 filed on Apr. 19, 2002 each of which is incorporated by reference herein in its entirety.
Although creating an opening through an airway wall may overcome the shortcomings associated with bronchodilator drugs and lung volume reduction surgery, various problems can still arise. When a hole is surgically created in tissue the healing cascade is triggered. This process is characterized by an orderly sequence of events, which can be broadly classified into distinct phases. These phases proceed in a systematic fashion, with a high degree of integration, organization, and control. However, the various stages are not sharply delineated, but overlap considerably, and factors affecting one phase have a stimulatory or inhibitory effect on the overall process.
The result of this wound healing process is tissue proliferation that can occlude or otherwise close the surgically created opening. Additionally, in the event an implant is deployed in the surgically created opening to maintain the patency of the opening, the implant may become encapsulated or filled with tissue thereby occluding the channel.
Drug eluting coronary-type stents are not known to overcome the above mentioned events because these stents are often substantially cylindrical (or otherwise have a shape that conforms to the shape of a tubular blood vessel). Hence, they may slide and eject from surgically created openings in an airway wall leading to rapid closure of any channel. Additionally, the design and structure of the coronary-type stents reflect the fact that these stents operate in an environment that contains different tissues when compared to the airways not to mention an environment where there is a constant flow of blood against the stent. Moreover, the design of coronary stents also acknowledges the need to place the stent within a tubular vessel and avoid partial restenosis of the vessel after stent placement so that blood may continue to flow. In view of the above, implants suited for placement in the coronary are often designed to account for factors that may be insignificant when considering a device for the airways.
Not surprisingly, experiments in animal models found that placement of coronary drug eluting stents (i.e., paclitaxel drug eluting vascular stents and sirolimus drug eluting stents) into the airway openings did not yield positive results in maintaining the patency of the opening. The shortcomings were both in the physical structure of the stent which did not lend itself to the airways as well as the inability of those drug eluting devices to control the healing cascade caused by creation of the channel. The majority of these devices filled with tissue at an early stage and an inspection of the remainder of the implanted devices indicated imminent closure.
An understanding of the distinctions between the healing response in the coronary versus the airways may explain this outcome. For purposes of our discussion, the healing response in both the coronary and the lungs may be divided into approximately four stages as measured relative to the time of the injury: 1) acute phase; 2) sub-chronic phase; 3) chronic phase; and 4) late phase.
In the coronary, after trauma caused by the placement of a coronary stent, the healing process begins in the acute phase with thrombus and acute inflammation. During the sub-chronic phase, there is an organization of the thrombus, an acute/chronic inflammation and early neointima hyperplasia. In the following chronic phase, there is a proliferation of smooth muscle cells along with chronic inflammation and adventitial thickening. In the late stage of the healing process there is chronic inflammation, neointimal remodeling, medial hypertrophy and adventitial thickening.
Based upon the observations in a rabbit model, the healing response in the airway begins with a fibrinous clot, edema hemorrhage, and fibrin deposition. In the sub-chronic phase there is re-epithelialization, mucosal hypertrophy, squamous metaplasia, fibroplasias and fibrosis. In the chronic phase, while the epithelium is intact and there is less mucosal hypertrophy, there is still fibroplasia and fibrosis. In the late stage the respiratory epithelium is intact and there is evidence of a scar.
Accordingly, the unique requirements of the airways and collateral channels calls for specific features for any implant used in collateral channels. For example, these implants/conduits are often placed across three different tissue zones; namely the parenchyma, the newly sectioned airway wall, and the interior of the airway surface. Each different zone may have a different reaction to the presence of the implant/conduit. The parenchyma may build up a layer of scar tissue around the conduit, which may eventually eject the implant or block the air path on the parenchyma side of the conduit. The airway wall may undergo a healing response as a result of the trauma of the procedure. This healing response and associated tissue growth may restrict air-flow through the implant. Furthermore, mucus from the airways may deposit in to the conduit thereby further occluding the conduit.
In addition, placement of an implant or conduit within the collateral channel may present additional structure requirements for the devices. For example, surgeons often use radiological imaging to place coronary stents within the vasculature. In most cases, placement of coronary stents is critical so that the ends of the coronary stent straddle the vascular obstruction. In contrast, a surgeon placing an implant in collateral channels is often using a remote access device such as a bronchoscope or endoscope that allows for direct observation of the device during placement. For proper placement of the implant, and in cases where it is important to "sandwich" the airway wall, it is necessary to identify the center and/or edges of the conduit or implant prior to expansion of the device. It follows that failure to properly place the implant may result in detachment of the implant (via insufficient attachment to the airway wall), pneumothorax (if the implant is advanced too distally and breaches the pleural cavity), or deployment of the implant wholly in the lung parenchyma exterior to the airway wall. Accordingly, such devices may require a visual indicator to assist the medical practitioner during placement and to offer a measure of safety so that the device is not improperly advanced/deployed thus creating additional complications.
Accordingly, there remains a need for devices and methods that specifically address the requirements discussed herein.

Methods and devices for maintaining patency of surgically created channels in a body organ


An apparatus and method uses diffusive modulation (without generating a wave of carriers) for measuring a material property (such as any one or more of: mobility, doping, and lifetime) that is used in evaluating a semiconductor wafer. The measurements are carried out in a small area, for use on wafers having patterns for integrated circuit dice. The measurements are based on measurement of reflectance, for example as a function of carrier concentration. In one implementation, the semiconductor wafer is illuminated with two beams, one with photon energy above the bandgap energy of the semiconductor, and another with photon energy near or below the bandgap. The diameters of the two beams relative to one another are varied to extract additional information about the semiconductor material, for use in measuring, e.g. lifetime.

1. Field of the Invention
This invention relates generally to the evaluation of a wafer of semiconductor material, and in particular to the measurement of a property of the semiconductor material.
2. Description of Related Art
In the processing of a semiconductor wafer to form integrated circuits, charged atoms or molecules are directly introduced into the wafer in a process called ion implantation. Ion implantation normally causes damage to the lattice structure of the wafer, and to remove the damage, the wafer is normally annealed at an elevated temperature, typically 600xc2x0 C. to 1100xc2x0 C. Prior to annealing, material properties at the surface of the wafer may be measured, specifically by using the damage caused by ion implantation.
For example, U.S. Pat. No. 4,579,463 granted to Rosencwaig et al. (that is incorporated herein by reference in its entirety) describes a method for measuring a change in reflectance caused by a periodic change in temperature of a wafer""s surface (see column 1, lines 7-16). Specifically, the method uses xe2x80x9cthermal waves [that] are created by generating a periodic localized heating at a spot on the surface of a samplexe2x80x9d (column 3, lines 54-56) with xe2x80x9ca radiation probe beam . . . directed on a portion of the periodically heated area on the sample surface,xe2x80x9d and the method xe2x80x9cmeasure[es] the intensity variations of the reflected radiation probe beam resulting from the periodic heatingxe2x80x9d (column 3, lines 52-66).
As another example, U.S. Pat. No. 4,854,710 to Opsal et al. (also incorporated herein by reference in its entirety) describes a method wherein the density variations of a diffusing electron-hole plasma are monitored to yield information about features in a semiconductorxe2x80x9d (column 1, lines 61-63). Specifically, Opsal et al. state that xe2x80x9cchanges in the index of refraction, due to the variations in plasma density, can be detected by reflecting a probe beam off the surface of the sample within the area which has been excitedxe2x80x9d (column 2, lines 23-31) as described in xe2x80x9cPicosecond Ellipsometry of Transient Electron-Hole Plasmas in Germanium,xe2x80x9d by D. H. Auston et al., Physical Review Letters, Vol. 32, No. 20, May 20, 1974.
Opsal et al. further state (in column 5, lines 25-31 of U.S. Pat. No. 4,854,710): xe2x80x9cThe radiation probe will undergo changes in both intensity and phase. In the preferred embodiment, the changes in intensity, caused by changes in reflectivity of the sample, are monitored using a photodetector. It is possible to detect changes in phase through interferometric techniques or by monitoring the periodic angular deflections of the probe beam.xe2x80x9d
A brochure entitled xe2x80x9cTP-500: The next generation ion implant monitorxe2x80x9d dated April, 1996 published by Therma-Wave, Inc., 1250 Reliance Way, Fremont, Calif. 94539, describes a measurement device TP-500 that requires xe2x80x9cno post-implant processingxe2x80x9d (column 1, lines 6-7, page 2) and that xe2x80x9cmeasures lattice damagexe2x80x9d (column 2, line 32, page 2). The TP-500 includes xe2x80x9c[t] wo low-power lasers [that] provide a modulated reflectance signal that measures the subsurface damage to the silicon lattice created by implantation. As the dose increases, so does the damage and the strength of the TW signal. This non-contact technique has no harmful effect on production wafersxe2x80x9d (columns 1 and 2 on page 2). According to the brochure, TP-500 can also be used after annealing, specifically to xe2x80x9coptimize . . . system for annealing uniformity and assure good repeatabilityxe2x80x9d (see bottom of column 2, on page 4).
A method in accordance with this invention: (1) creates charge carriers in a concentration that changes in a cyclical manner (also called xe2x80x9cmodulationxe2x80x9d) only with respect to time, in a region (also called xe2x80x9cilluminated regionxe2x80x9d) of a semiconductor material, and preferably also (2) maintains the charge carriers at an average concentration that remains the same (or at least approximately the same e.g. varies less than 10%) before and during a measurement indicative of the number of charge carriers created in the illuminated region by act (1).
In one embodiment (also called xe2x80x9cscanning embodimentxe2x80x9d), one or more such measurements are compared each with the other, thereby to identify a sudden change in the measurements. In another embodiment (also called xe2x80x9cmeasurement embodimentxe2x80x9d), one or more measurements are compared with similar measurements on wafers (also called xe2x80x9creference wafersxe2x80x9d) processed under known conditions and having known properties, thereby to determine one or more process conditions or properties of a wafer under fabrication.
In one implementation, an attribute derived from measurements on a wafer is interpolated with respect to corresponding attributes of wafers having a known material property (or process condition), thereby to determine a corresponding property (or condition) of the wafer under measurement. An example of a process condition is the temperature (also called xe2x80x9cannealing temperaturexe2x80x9d) at which the wafer is annealed. Examples of material properties include surface concentration, mobility, junction depth, lifetime and defects that cause leakage current at the junction (when the junction is reversed biased).
The charge carriers (also called xe2x80x9cexcess carriersxe2x80x9d) being created and measured as described above are in excess of a number of charge carriers (also called xe2x80x9cbackground charge carriersxe2x80x9d) that are normally present in the semiconductor material (e.g. due to dopant atoms) even in the absence of illumination. Therefore, in the first act described above, a number of excess carriers are created in the above-discussed region (also called xe2x80x9cilluminated regionxe2x80x9d), e.g. by focusing thereon a laser beam or an electron beam. The concentration of excess carriers is modulated, both at the surface and in the bulk only as a function of time (e.g. by modulating the intensity of the just-described laser or electron beam that is also called xe2x80x9cgeneration beamxe2x80x9d).
The frequency of modulation of the concentration of excess carriers is deliberately selected to be sufficiently low to avoid modulation in space (i.e. avoid the creation of a wave of charge carriers). A carrier concentration that is devoid of a wave in space is created when at least a majority of the charge carriers (i.e. greater than 50%) move out of the illuminated region by diffusion. Such a temporal modulation under diffusive conditions (also called xe2x80x9cdiffusive modulationxe2x80x9d) is used to measure the reflectance caused by excess carriers, e.g. by detection of the intensity of a beam (also called a xe2x80x9cprobe beamxe2x80x9d) reflected by the illuminated region at the modulation frequency.
In the second act, an average concentration (e.g. root mean square average) of the excess carriers is determined from a measurement of the above-described reflectance over the time period of a modulation cycle. The average concentration is maintained the same (or approximately the same) prior to and during the measurement of reflectance. Specifically, the creation of new charge carriers (also called xe2x80x9cmeasurement-relatedxe2x80x9d carriers) in addition to the background charge carriers and the excess carriers is minimized or avoided during the reflectance measurement, thereby to maintain the total carrier concentration at or about the just-described average prior to the measurements.
An apparatus (also called xe2x80x9cprofilerxe2x80x9d) that implements the above-described method includes, in one embodiment, a source that produces a probe beam formed of photons of energy lower than the bandgap energy (the energy necessary to generate conduction electrons) of the semiconductor material. Use of such a probe beam source eliminates the measurement-related carriers and the resulting errors that are otherwise created by a prior art apparatus, e.g. in measuring the reflectance with a probe beam that has photons of energy greater than the bandgap energy of silicon (such as the Hexe2x80x94Ne laser probe beam described at column 15, line 56 of U.S. Pat. No. 4,854,710).
In addition to the above-described probe beam source, the profiler also includes a photosensitive element (such as a xe2x80x9cphotodiodexe2x80x9d) that is located in the path of a portion of the probe beam reflected by the illuminated region. The photosensitive element generates an electrical signal (e.g. a voltage level) that indicates the intensity of the probe beam portion reflected by the illuminated region. The intensity in turn indicates reflectance caused by the excess charge carriers (e.g. created by incidence of a generation beam).
So, in one embodiment, the intensity measurement is used by the profiler as a measure of the concentration of excess charge carriers in the illuminated region. In this embodiment, the profiler also includes a computer that is coupled to the photosensitive element to receive the electrical signal, and that is programmed to determine the value of a material property in the illuminated region from one or more such measurements.
In another embodiment, the profiler creates measurement-related carriers by use of a probe beam having photons at or slightly above the bandgap energy of the semiconductor material. Even in the presence of such measurement-related carriers, the profiler maintains the overall accuracy of a measurement of a material property (as described herein) within a predetermined limit (e.g. 10% error) by limiting the number of such measurement-related carriers to a small percentage (e.g. up to 10%) of the excess carriers.
In the just-described embodiment, a diffusive modulation of charge carriers is created by use of a generation beam that has a wavelength and power chosen so that the rate of carriers generated by this beam is sufficiently larger, e.g. one order (preferably two orders) of magnitude larger than the rate of carriers generated by the probe beam so as to make the latter negligible.
In one implementation, in addition to the above-described probe beam source, the profiler includes a source that produces a generation beam (formed of photons) having an intensity that is modulated at a sufficiently low frequency to avoid creation of a wave of charge carriers. The powers of the two beams are maintained by the profiler to be at least approximately the same. Other implementations have two beams that each have a power different from the other, and yet maintain the measurement-related carriers (created by the probe beam) at a negligible percentage (e.g. the probe beam has photons of energy higher than the bandgap energy but has a power that is half or one-fourth the power of the generation beam, assuming that the power of the reflected portion of the probe beam is detected with sufficient accuracy as described above).
Measurement of intensity of a reflected portion of the probe beam while (1) using diffusive modulation and (2) generating negligible (preferably none) percentage of measurement-related carriers is a critical aspect of one embodiment of the invention. One or more such measurements provide a measure of a process condition or a property of the semiconductor material in the illuminated region. Such measurements are performed in one embodiment after annealing to activate the dopants, thereby to obtain a measure that is more indicative of the electrical behavior of the devices being fabricated than a property that is measured prior to annealing (as described in U.S. Pat. No. 4,854,710).
The above-described intensity measurements (from which reflectance measurements are derived), and one or more properties (also called xe2x80x9cmaterial propertiesxe2x80x9d) are preferably (but not necessarily) monitored during fabrication, to control a process step (e.g. to control annealing temperature of a wafer that has been ion implanted) used in fabricating a wafer. As the material properties are measured directly on the wafer undergoing fabrication (also called xe2x80x9cpatterned waferxe2x80x9d or xe2x80x9cannealed waferxe2x80x9d depending on the stage of fabrication), a measurement as described herein increases yield, as compared to an off-line measurement of a test wafer""s properties.
During operation, the profiler (described above) performs a number of reflectance measurements, each measurement being for a different value of a parameter used either (1) in the generation of the excess carriers or (2) in the measurement of the concentration of excess carriers. In one embodiment, the profiler fits two or more such measurements to one or more straight lines or to a curved line, and compares an attribute of the fitted line (e.g. compares a first order coefficient, also called xe2x80x9cslope,xe2x80x9d of the fitted line), with corresponding attributes of corresponding lines generated from such measurements on wafers having known properties, thereby to determine a material property corresponding to the fitted line.
Moreover, a process condition (e.g. the temperature at which a patterned wafer has been annealed) can also be determined from such comparison of reflectance measurements, if the process condition affects the semiconductor material. Depending on the implementation, the comparison can be performed either manually or by a computer.
In a first implementation, the parameter varied between the measurements is the average concentration of charge carriers that is controlled by, e.g., changing the power or the diameter of the generation beam used to generate the charge carriers. Thereafter, a material property, such as mobility (or junction depth) is determined from intensity measurements by comparison of the above-described attribute with the corresponding attributes of wafers having known mobilities (or junction depths).
In one example, the wafer is undoped and mobility is determined by computing the slope of a plot of the intensity measurement against the power of the generation beam. In another example, the wafer has doped regions, and mobility is determined by comparing a slope obtained from the measurements (in the same manner as the just-described slope for the undoped wafer) with slopes of wafers having known mobilities.
In a second implementation, the varied parameter is the distance between the two beams that are used in performing an intensity measurement. In two variants of this implementation, the location of either (1) the generation beam, or (2) the probe beam, is changed relative to the wafer. The material property determined from such intensity measurements is lifetime.
In a third implementation, the parameter that is varied is the relative size of the two beams used in the intensity measurement e.g. the diameter of the probe beam is changed (while keeping the power of the probe beam the same). In this implementation as well, the material property determined from the intensity measurements is lifetime.
In another embodiment (also called xe2x80x9cpolarized embodimentxe2x80x9d), a laser beam that is linearly polarized is used as a probe beam (also called xe2x80x9cpolarized probe beamxe2x80x9d). The polarized probe beam need not have photons of energy below the bandgap energy of the semiconductor material, i.e. a beam of photons at or slightly above the bandgap energy (as described above) can be used if polarized.
On reflection from the illuminated region, a plane of polarization of the probe beam rotates through two different angles, depending on the following two reflection coefficients: one coefficient in a plane (also called xe2x80x9csurface planexe2x80x9d) of the surface of the illuminated region, and another coefficient in a plane (also called xe2x80x9cnormal planexe2x80x9d) perpendicular to the surface plane.
After reflection, a portion of the probe beam that has been reflected is interfered with another portion that was not reflected. Next, two measurements are made, specifically of the sum and difference signals generated by the interference. Thereafter, a difference (hereinafter xe2x80x9cin-phase differencexe2x80x9d) between the two measurements that is in phase with the modulation of charge carriers is determined using a phase detector. The in-phase difference signal provides a measure of the concentration of excess carriers in the illuminated region.
Thereafter, one or more of the material properties discussed above are determined by use of in-phase difference signal (instead of using the intensity measurement described above). Use of a polarized probe beam (as described herein) provides an increase in sensitivity of the measurement of material properties by about two orders of magnitude over the use of a non-polarized beam, because of the increased sensitivity of a phase detector used in the polarized embodiment (as compared to an amplitude detector that is otherwise used) to measure the power of the reflected portion of the probe beam.

Apparatus and method for evaluating a semiconductor wafer


The present invention concerns a shoe (10) including an upper (12), having lateral and medial sides, a midsole (14) joined to the upper (12), and an outsole (16) joined to the midsole (4). Shoe (10) is tightened around the wearer's foot using a lacing system (18) comprising a lace (20) and tightening mechanism (22). Lace (20) is threaded through shank (24) positioned under the arch and heel wrap (26) and attached at opposite ends to tightening mechanism (22). In an advantageous aspect of the present invention, lace (18) is tensioned to draw shank (24) upwards and towards the arch of the foot. In order to support the foot, shank (24) is comprised of a material having a strain rate lower than the upper (12).

There currently exist a number of mechanisms and methods for tightening a shoe or boot around a wearer's foot. A traditional method comprises threading a lace in a zigzag pattern through eyelets that run in two parallel rows attached to opposite sides of the shoe. The shoe is tightened by first tensioning opposite ends of the threaded lace to pull the two rows of eyelets towards the midline of the foot and then tying the ends in a knot to maintain the tension. A number of drawbacks are associated with this type of lacing system. First, laces do not adequately distribute the tightening force along the length of the threaded zone, due to friction between the lace and the eyelets, so that portions of the lace are slack and other portions are in tension. Consequently, the higher tensioned portions of the shoe are tighter around certain sections of the foot, particularly the ankle portions which are closer to the lace ends. This is uncomfortable and can adversely affect performance in some sports.
Another drawback associated with conventional laces is that it is often difficult to untighten or redistribute tension on the lace, as the wearer must loosen the lace from each of the many eyelets through which the laces are threaded. The lace is not easily released by simply untightening the knot. The friction between the lace and the eyelets often maintains the toe portions and sometimes much of the foot in tension even when the knot is released. Consequently, the user must often loosen the lace individually from each of the eyelets. This is especially tedious if the number of eyelets is high.
U.S. Pat. Nos. 5,934,599, 6,202,953, and 6,289,558 to Hammerslag (the "Hammerslag Patents"), which are incorporated herein by reference in their entireties, disclose a lacing system that automatically distributes lateral tightening forces along the length of the wearer's ankle and foot. More particularly, the Hammerslag Patents describe a circular tightening apparatus that is rotated to tighten stainless steel wire/strands coated with friction reducing polymers and locked in place with a ratchet and pawl lock. The polymer coated stainless steel wire is threaded through the eyelets around the ankle and is connected at both ends to the tightening apparatus. The stainless steel laces are loosened when the lock is released by lifting the pawl and pulling on the laces to loosen them, or using reverse rotation of the ratchet. This lacing system is known commercially as the BOA™ system, and the FootJoy ReelFit™ golf shoes have incorporated this lacing system. However, the footwear incorporating the lacing system disclosed in the Hammerslag Patents only supports the top of the foot and the ankle, and does not support the arches of the feet. Furthermore, the stainless steel lace disclosed therein can cause discomfort when it traverses through conventional padding in a shoe. Such shortcomings can diminish a wearer's athletic performance in sports such as golf, where it has been long recognized that proper foot support is the foundation to a powerful and consistent golf swing.
Thus, there is a need for a tightening system for footwear that does not suffer from the aforementioned drawbacks.


A heater that is capable of heating an object to a desired temperature in a short period while minimizing the temperature difference the surface of the object is provided. The heater comprising a plate having a first surface and a second surface, the first surface being a mount surface whereon an object is placed and having a resistive heating member; wherein the resistive heating member is formed in a continuous band having arc bands located on one of two concentric circles of different radii, at least one arc band located on the other circle, and linkage arc band that connects the arc band located on the one circle and the arc band located on the other circle; while the distance between the adjacent linkage arc bands is smaller than the distance between the arc band located on the one circle and the arc band located on the other circle.

1. Field of the Invention
The present invention relates mainly to a heater used in heating a wafer, a wafer heating apparatus and a method for manufacturing the heater.
2. Description of the Related Art
In a manufacturing process of semiconductor devices, a heater is used to heat a semiconductor wafer (hereinafter referred to simply as a wafer) during formation of thin semiconductor film, etching, baking of resist film and other steps.
For such heating purposes, for example, Patent Document 1, Patent Document 2 and Patent Document 3 disclose wafer heating apparatus as shown in FIG. 16.
A heater 771 comprises a plate-shaped ceramic member 772 and a metal casing 779 as major components, and is constituted by securing the plate-shaped ceramic member 772 made of a ceramic material of nitride or carbide on an opening of the bottomed metal casing 779, that is made of a metal such as aluminum, via an insulating contact member 774 made of a resin by means of bolts 780. The heater 771 uses the top surface of the plate-shaped ceramic member 772 as a heating surface 773 whereon a wafer W is to be mounted, so that the wafer W is heated by a resistive heating member 775 that is formed, for example, in concentric configuration as shown in FIG. 20, on the bottom surface of the plate-shaped ceramic member 772.
Power terminals 777 are connected by brazing to power feeder sections of the resistive heating member 775, with the power terminals 777 electrically connected to lead wires 778 that are passed through wiring holes 776 provided at a bottom 779a of the metal casing 779.
In order to form a uniform film over the entire surface of the wafer W or cause a resist film to react uniformly in heating reaction by using the heater 771, it is important to make uniform temperature distribution over the wafer. Accordingly, various measures have been employed as described below to keep the temperature difference across the wafer surface small.
One of the measures is to divide the resistive heating member 775 and independently control the temperatures of the divided sections.
Patent Document 4 discloses a heater that has a plurality of resistive heating member blocks. The resistive heating member of this heater is radially divided into four equal sections of fan-shaped block as shown in FIG. 17. A heater such as shown in FIG. 18 is also known that comprises four blocks of resistive heating member located along the periphery and a circular block of resistive heating member located at the center.
Patent Document 5 discloses a heater comprising a resistive heating member that is divided into identical rectangular regions 711 through 718 that can be controlled either independently or in groups each consisting of a plurality of regions, as shown in FIG. 19. In this heater, as shown in FIG. 19, four regions 715 through 718, among the regions 711 through 718, are located at positions that correspond to the arcs formed by dividing the peripheral portion of the wafer into four equal parts, and other four regions 711 through 714 are disposed inside of the four regions 715 through 718 in parallel thereto.
As to configuration of the resistive heating member, such a heater 500 (Patent Document 6) that comprises a plurality of resistive heatin members of which one located at the outermost position is formed in a sine curve, and heater 500 having outermost resistive heating member 750 formed in rectangular shape (Patent Document 7 and Patent Document 8) is also disclosed (FIGS. 21, 22, 23). In these heaters, a power feeder section 760 is disposed adjacent to the resistive heating member.
Patent Document 8 discloses a heater having a spiral-shaped resistive heating member.
Patent Document 9 discloses a heater where wafer W support pins (not shown) are provided on a mount surface 773 is provided so as to lift the wafer W from the mount surface 773 by a small distance, in order to achieve uniform temperature distribution over the wafer.
Patent Document 10 discloses a heater where a wall is provided along the periphery of the plate-shaped ceramic member 772 to surround the wafer W, so as to prevent the wafer W from moving laterally.
Patent Document 11 discloses a heater where a protrusion that engages with the wafer W is formed along the periphery of the plate-shaped ceramic member 772, and a multitude of projections that contact with the wafer W are formed inside of the protrusion, in order to achieve uniform temperature distribution.
Patent Document 12 discloses a heater where guide pins that locate the wafer W are provided around the plate-shaped ceramic member, thereby to achieve uniform temperature distribution over the wafer W.
Patent Document 13 discloses a heater where temperature distribution over the wafer W can be controlled by adjusting the height of support pins of the wafer W. A heater having guide pins engaged with the support pins is also disclosed.
Patent Document 14, Patent Document 15 and Patent Document 16 also disclose heater 850 made of ceramics where a coil-shaped resistive heating member 853 is embedded as shown in FIG. 24. The heater 850 consists of a plate-shaped ceramic member 851 made of a nitride ceramic material such as silicon nitride or aluminum nitride in which a coil-shaped resistive heating member 853 formed in spiral configuration is embedded, while the power feeder terminals 855 are connected to both ends of the resistive heating member 853. In order to decrease the temperature difference across the wafer surface, such measures are disclosed as increasing the density of the resistive heating member 853 in a region of 10% of the mount surface on the outside, restricting the variation in the number of windings per unit length of the coil-shaped resistive heating member 853 and 3-dimensional arrangement of the resistive heating member 853.
Patent Document 17 and Patent Document 18 also describe attempts to decrease the temperature difference across the wafer surface by connecting and embedding a resistive heating member having different coil diameter, or by providing a swelling portion at a turn-back portion of the resistive heating member.
Moreover, in a CVD film forming process, for example, such a wafer holding member is employed that supports a ceramic heater comprising a plate-shaped ceramic member by means of a cylindrical support member made of ceramics. Such a heater 850 made of ceramics is also known as one principal surface of the plate-shaped ceramic member 851 having resistive heating members 853, 854 embedded therein is used as mount surface 851a and a cylindrical support member 860 made of ceramics is joined onto the other principal surface, as shown in FIG. 25. In the heater 850, the power terminals 856, 857 are connected by brazing to the terminals of the resistive heating members 853, 854, and power terminals 856, 857 are lead through inside of the cylindrical support member 860 to the outside for connection.
In recent years, increasing number of semiconductor devices are manufactured with circuits having line width of 90 nm or 45 nm. Manufacturing such semiconductor devices requires a heater that can heat a wafer with more uniform temperature distribution.
[Patent Document 1]
Japanese Unexamined Patent Publication No. 2001-203156
[Patent Document 2]
Japanese Unexamined Patent Publication No. 2001-313249
[Patent Document 3]
Japanese Unexamined Patent Publication No. 2002-76102
[Patent Document 4]
Japanese Unexamined Patent Publication No. 11-121385
[Patent Document 5]
Japanese Unexamined Patent Publication No. 11-354528
[Patent Document 6]
Japanese Unexamined Patent Publication No. 2001-6852
[Patent Document 7]
Japanese Unexamined Patent Publication No. 2001-223257
[Patent Document 8]
Japanese Unexamined Patent Publication No. 2001-257200
[Patent Document 9]
Japanese Unexamined Patent Publication No. 10-223642
[Patent Document 10]
Japanese Unexamined Patent Publication No. 10-229114
[Patent Document 11]
Japanese Unexamined Patent Publication No. 2002-237375
[Patent Document 12]
Japanese Unexamined Patent Publication No. 2002-184683
[Patent Document 13]
Japanese Unexamined Patent Publication No. 2001-68407
[Patent Document 14]
Japanese Unexamined Patent Publication No. 4-101381
[Patent Document 15]
Japanese Unexamined Patent Publication No. 7-220862
[Patent Document 16]
Japanese Unexamined Patent Publication No. 7-65935
[Patent Document 17]
Japanese Unexamined Patent Publication No. 2004-6242
[Patent Document 18]
Japanese Unexamined Patent Publication No. 2004-111107
[Patent Document 19]
Japanese Unexamined Patent Publication No. 11-339939
[Patent Document 20]
Japanese Unexamined Patent Publication No. 2001-102157
[Patent Document 21]
Japanese Unexamined Patent Publication No. 2002-170655
There has been a demand for a heater that can heat a wafer with more uniform temperature distribution with a simpler structure, since it is difficult to achieve uniform temperature distribution with the conventional heater and it is necessary to carry out very complex and delicate control procedure to achieve a uniform temperature distribution.
In the case of the technology of chemically amplified resist that is being employed along with the trend toward smaller circuit line width of the semiconductor devices, emphasis is placed not only on the uniform temperature distribution over the wafer, but also on the temperature changes throughout the period from the time when the wafer is set in a heat treatment apparatus to the time when the heat treatment is completed and the wafer is taken out. Thus it is desired to stabilize the wafer temperature in uniform temperature distribution with about 60 seconds after placing the wafer on a heater, but the conventional heater cannot satisfy this requirement because it takes a long period of time to stabilize the temperature.
There has also been such a problem that a heater comprising a coil-shaped resistive heating member embedded therein has a tendency of the density of the heating member changing significantly between the outside and inside at a bending portion of the resistive heating member, which makes it difficult to decrease the radius of curvature. Accordingly, the methods described in Patent Document 17 and Patent Document 18 require it to connect the resistive heating members of different coil diameters within the plate-shaped ceramic member, or to form a swelling portion at a turn-back section of the resistive heating member. This results in a complex process that is not suitable for volume production, and it is very difficult to mass-produce products with stabilized quality and high level in the yield of production.
In addition, there has been such a problem that the heater having the cylindrical support member attached thereto allows heat to dissipate through the cylindrical support member, thus resulting in significant temperature difference across the wafer surface.
To counter this problem, Patent Document 19 discloses a heater having increased resistance density on the inside of the cylindrical support member 860 so as to keep the temperature difference across the wafer surface small even when the temperature is raised quickly and prevent the plate-shaped ceramic member 851 from breaking.
Patent Document 20 discloses a heater made of ceramics having a cylindrical support member attached thereto wherein temperature difference across the surface is decreased to prevent breakage, by increasing the resistance of a middle portion and an independent resistive heating member 854 is embedded at a position near the joint surface of the support member 860. Furthermore, Patent Document 21 discloses a heater having a resistive heating member embedded therein so as to heat the cylindrical support member 860.
Recently, it has been called for to decrease the time taken to raise the temperature to a very short period. However, there is a possibility that the heater made of ceramics having the coil-shaped resistive heating member breaks when heated at a high rate. Particularly, heaters made of ceramics having cylindrical support members attached thereto designed for increasing wafer size of 300 mm in diameter were often broken due to the high thermal stress generated by quick heating.

Heater, wafer heating apparatus and method for manufacturing heater


A method for power net analysis of integrated circuits is provided. A circuit simulator determines current values for integrated circuit devices at specified supply voltages. A power net simulator uses the current values to calculate characteristics of the power net. The characteristics include voltage drop, current density and ground bounce. A layout representation of the power net is shown on a computer display along with the user-specified characteristics.

The present invention relates to computer-aided design (CAD) tools for analyzing integrated circuits and, more particularly, to analyzing power Vdd and ground nets in integrated circuits for electromigration, voltage drop and ground bounce.
Aggressive development within the semiconductor industry keeps electronic products moving on a brisk course forward. With each new generation of integrated circuit (IC) chips, device geometries and supply voltages are decreasing while the clock frequencies are increasing. Typical ICs today contain more than three million transistors and include three to five layers of metal interconnects that supply power and transport signals.
Along with smaller device geometries come narrower metal lines and larger resistances. Also, as more devices are interconnected, the lines are getting longer, further increasing the interconnect resistance. The substantial voltage drops that develop across metal power nets cause the circuits to malfunction, especially when the supply voltage is reduced below 3 volts. For example, a 1 volt drop in a 3 volt system would have a much more severe impact on circuit functionality than a proportional drop in a 5 volt system. So, in deep submicrometer designs (feature sizes less than 0.5 .mu.M), voltage drop analysis is crucial. Additionally, the narrower metal lines have undesirable wear-out of metal wiring caused by electromigration.
Ground bounce is due to the inductance in the IC package pins and bonding wires and the current switching (dI/dt) in the integrated circuit. Ground bounce noise may affect circuits in various ways. For example, ground bounce noise may degrade the performance of the circuit. Additionally, ground bounce noise may cause the circuit to malfunction due false latching in receiving chips.
In deep submicron design, the circuit consumes more power which means that dI/dt is even greater than in non-submicron designs. The ground bounce problem in the past was more significant in output buffers than on-chip circuits. However, the ground bounce noise in on-chip circuits is becoming more important with today's technologies.
Numerous CAD tools exist for simulating transistor networks of ICs (e.g., SPICE). An innovative system is described in U.S. patent application Ser. No. 08/040,531, entitled "Transistor-Level Timing and Power Simulator and Power Analyzer", filed Mar. 29, 1993 by Huang et al., and U.S. patent application Ser. No. 08/231,207, entitled "Power Diagnosis for VLSI Designs", filed Apr. 21, 1994 by An-Chang Deng, which are both hereby incorporated by reference for all purposes. However, none of the prior art systems allow the user to simulate the power nets of an IC and display power net characteristics like voltage drop, current density and ground bounce. The present invention fulfills this and other needs.

Integrated circuit power net analysis through simulation


This invention relates to a steering system arrangement for a vehicle, the steering system arrangement comprising a first portion providing a steering input, and a second portion providing a steering output, the first and second portions being connected by connection means selectively releasable to permit selection of the relative positioning of the steering input and the steering output. An associated method for retro fitting the steering system arrangement to a vehicle is also disclosed.

Drivers of early model vehicles that have their original steering configuration, often experience vagueness in steering while driving. This is a result of worn component such as the original steering box and steering linkages.
Vehicles from the 1960's and 70's, often referred to as muscle cars, typically have recirculating ball steering arrangements which are known to have a "dead spot" on centre. This dead spot means that a small turn of the steering wheel does not influence the vehicle's direction of travel.
Furthermore the steering of older vehicles often display mechanical play, slow response and poor centring capabilities.
These vehicles typically did not include power assisted steering systems. This, combined with their weight results in a significant amount of effort being required to turn the steering wheel, especially at low speed.
Simply rebuilding the existing steering systems of these vehicles using new gears, bearings and linkages may reduce the mechanical play. The feel of the steering does not however compare to the performance of modern power assisted rack and pinion steering systems. As a result many owners opt to replace the original mechanical steering systems with rack and pinion powered assisted steering, which utilize a hydraulic pump to increase the ease of steering at low speed.
Conventional rack and pinion steering systems include a rack, having teeth along one side, adapted to engage a toothed end of a pinion shaft. The opposite end of the pinion shaft is connected to the steering wheel shaft by way of a universal joint.
The rack is connected to opposing front wheels by way of corresponding tie rods. This means that the circular motion of the steering wheel and pinion shafts is converted into rectilinear movement of the rack and tie rod ends. There are many advantages with modern rack and pinion steering systems, including that they eliminate the on-centre spot and offer improved steering accuracy, reduced effort, and considerably improved tracking ability.
A popular type of rack and pinion steering system is the centre takeoff systems, which enable correct geometry and an optimum level of positive and direct steering. Centre takeoff systems include a pinion and a rack having a toothed portion and a shaft portion, wherein the rack is connected to a drag link that in turn is connected to the tie rod ends. This construction is more compact than the "enddriven" design rack and pinion systems, where the tie rods connect directly to opposing ends of the rack.
Due to their many advantages, power assisted rack and pinion conversions have become a popular option for owners of cars such as the Pontiac GTO, Ford Mustang and Chevrolet Corvette. This is especially the case when cars are being converted between left and right hand drive because the owner is already required to replace or modify the steering system.
One of the problems with existing centre takeoff rack and pinion assemblies, is they typically need to be custom made for each make and model of vehicle. This is because the pinion needs to be at a different angle for different types of vehicle to take into account the particular constraints of the Y-frame, the configuration of the engine bay and placement of components therein.
Furthermore the centre takeoff rack and pinion system has to allow placement of the steering rack to provide adequate clearance for both long and short tube exhaust manifolds, or aftermarket components within the engine bay. There may also be physical constraints arising from converting a vehicle between left and right hand drive.
An object of the present invention is to ameliorate one or more of the above described difficulties, or at least provide a useful alternative to steering arrangements of the type discussed above.
Other advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, several embodiments of the present invention are disclosed.

Steering system arrangement with releasable connection means