An apparatus for automatically and periodically measuring a patient's blood glucose level wherein the patient has a catheter in a blood vessel and is receiving infusion fluid through the catheter. A testing unit is provided which has a main infusion channel and, in a preferred embodiment, the testing unit includes a side channel. The side channel has a restrictive cross-sectional area compared with the main infusion channel. A glucose test chamber is formed in the side channel. First and second valves are placed adjacent the test chamber in the side channel to isolate a blood sample for testing. The isolation of the sample provides more accurate blood glucose measurements than those provided by systems of the prior art. A second embodiment of the invention has an isolatable test chamber placed in the main infusion line and no side channel is utilized.

This invention relates to blood glucose testing in critically ill patients. The need for a convenient and easily applied method of glucose monitoring in the Intensive Care Unit became evident after the landmark study of Van den Berghe and colleagues published in the Nov. 8, 2001, issue of The New England Journal of Medicine.
This paper demonstrated an overall reduction in ICU patient mortality of 34% when blood glucose was kept in the 80 to 110 mg per deciliter range. Samples were taken from an arterial line at 1 to 4-hour intervals and sent to the hospital lab for analysis. In the intensive therapy group, an insulin infusion was started if blood glucose exceeded 110 mg per deciliter and was adjusted to maintain normal blood glucose levels. A virtual flood of articles have since appeared and confirm improved outcomes in the treatment of various critical conditions including infection, stroke, in patients undergoing coronary bypass surgery, and in the treatment of myocardial infarction in both diabetic and non-diabetic patients. One study showed greatly improved outcomes when diabetics were monitored and treated intensively with insulin in the hospital for three days prior to undergoing coronary bypass surgery.
Intensive treatment with insulin requires knowledge of patient blood sugar levels which presently involves obtaining either an arterial or a venous blood sample or pricking the patient's finger to obtain a capillary blood sample. Blood samples are placed on a strip and read using a home-type glucose meter. All of these methods require considerable nurse or technician time. In the U.S. at present only 20 to 30% of patients in the ICU have arterial lines. Many patients, especially non-diabetics, find repeated finger sticks objectionable. Furthermore, intermittent blood samples may not be done often enough to give an accurate picture of blood sugar levels.
Optimally, patients in critical care situations should have blood glucose levels monitored several times each hour so that insulin can be given appropriately to keep blood sugar readings in the narrow range of 80-110 mg/deciliter. Presently there is no system available that accurately and conveniently measures blood sugar without taking frequent blood samples from a patient. The present invention is able to do so by withdrawing blood from a central venous line, an arterial line or a catheter in a peripheral vein. The catheterized blood vessel in any of these locations is normally used for infusion of fluids with electrolytes or various medications. The present invention also allows these lines to monitor a patient's blood sugar as often as every three minutes so that a care giver can adjust insulin dosage as required.
Attempts have been made in the past to automatically monitor blood analytes from a patient's IV line. Generally these systems have used reversal of the direction of flow in an infusion line so that blood could be pulled out of the patient's circulation at intervals, analyzed, and then re-infused back into the patient. Examples of such device are described in U.S. Pat. No. 3,910,256 to Clark, U.S. Pat. No. 4,573,968 to Parker and U.S. Pat. Nos. 5,165,406, 5,758,643 and 5,947,911 to Wong and associates.
The devices described in the above patents measure blood analytes with sensors inside the main infusion line and no attempt has been made to isolate or compartmentalize blood samples during testing. This technique, while successful for monitoring blood gases, has not yet met with success in testing for blood glucose. The present invention, by novel means, allows practical and accurate monitoring of blood sugar from a reversible infusion line.
State of the art blood glucose measuring systems generally employ the enzymes glucose oxidase or glucose dehydrogenase. In the chemical reaction which occurs using either of these two enzymes, glucose is consumed and the electrons generated are drawn off and measured. Plotting current flow against time produces a curve which is distinctive for each glucose value, i.e., any given concentration level of blood glucose.
Accuracy depends crucially on maintaining a constant diffusion gradient over the glucose sensor. In the ideal case the concentration of glucose varies in a regular and linear way from the body's reservoir of blood glucose to the area just over the sensor where concentration drops to a minimum (close to zero) because it is being consumed in the chemical reaction. The major cause of inaccuracy in electrochemical glucose measurement is disturbance of the diffusion gradient. The problem is relatively small in single use disposable strips because a portion of a blood drop is allowed to rest undisturbed in a small channel during the test, having been drawn up into the channel by capillary attraction. In a flow-through system the problem of leaving the diffusion gradient undisturbed is a major one because of the much larger volume of fluid involved, which is essentially all the fluid in the infusion line from the patient to the bedside monitor.
A disturbance anywhere in this large reservoir of fluid is immediately transmitted to the test area and causes disturbance of the diffusion gradient over the sensing electrode. Invariably, the effect is to bring more glucose to the region of the electrode, causing an increase in the glucose signal and an overestimation of blood glucose.
A number of causes can contribute to disruption of the diffusion gradient in a flow through system. Any fluid movement, even a flow rate as low as 150 micro liters/minute, can cause a mixing effect which disturbs the diffusion gradient and gives an overestimation of blood glucose. Eddies in the fluid line can occur because of the intermittent "push" of a peristaltic pump. Such eddies can last several seconds after pumping has stopped.
Adjustment of blood temperature to ambient temperature can cause micro fluidic deviations which will disturb the diffusion gradient. Heat transfer issues are minimized by keeping the amount of fluid small in comparison to the total mass of the device. The device can be subjected to temperature controls but under practical conditions small volumes are required to prevent temperature differences from causing significant measurement errors. The diffusion gradient over the sensor can also be disturbed in an open-flow system by movement of the arm or chest, or changes in the relative position of the test chamber and the heart. Additionally, impacts to the tubing or glucose test area can cause measurement inaccuracies if the fluid in the test area is not protected in a small, well defined space.
For complete isolation, small valves, which may be inflatable balloons, can be located adjacent the test chamber. Besides protecting the diffusion gradient, isolation of the test sample prevents movement of glucose molecules into or out of the test area and allows consistent measurement of the current produced during the reaction at any given glucose level.
In the present invention, the test chamber for testing blood glucose can either be part of the main infusion line inside the testing unit, or it can be located in a side channel in the testing unit in continuity with the main channel. In the latter version, a valve, which may be an inflatable balloon, directs blood or fluid into the side channel at the time of testing. For reasons to be enumerated, the side channel version is considered the preferred embodiment of the invention.
The system to be described uses a bedside monitor with a digital readout and alarms and contains two peristaltic pumps, one of which normally infuses fluid through the blood vessel catheter. During glucose testing the pump assists in moving blood samples into and out of the test chamber. The second peristaltic pump automatically calibrates the sensor at intervals with a premixed calibration fluid.
The disposable, single patient use testing unit is approximately 2¼″×1½″×¾″ and is attached to the patient's chest for use with a central line or to an extremity for use with a catheter in a peripheral vessel. The distal end of the testing unit has an integral Luer fitting which connects to the patient's blood vessel catheter. The proximal end of the testing unit has the exit sites for the fluid, air, and electric lines that connect to a bedside monitor located a few meters from the patient.
The disposable testing unit portion of the invention is made of a semi-transparent plastic. It contains a channel for infusion fluid in continuity with (i.e. in fluid communication with) the infusion line and with the blood vessel catheter. A glucose sensing electrode is located in the test chamber area of the testing unit. Chambers for inflatable balloons, which serve as valves, are molded into the plastic parts along with grooves for the air lines and the electric cable. After insertion of the various components during manufacturing, the top and bottom halves are welded together to form a leak proof disposable testing unit. While inflatable balloons are considered the preferred embodiment for reasons of economy and ease of insertion, mechanical valves can also be used for this application.
The sensor of the present invention can be automatically calibrated at selected intervals using a small bag of premixed calibration fluid which is supplied with each disposable testing unit. The calibration fluid is carried inside the monitor and made to flow through the test chamber at intervals by a second peristaltic pump. After calibration is complete the test chamber is cleared by a brief flow of infusion fluid through the sampling area.
The area of the glucose sensor in the present invention is approximately 25 square millimeters, considerably larger than that of a typical disposable strip. The height of the test chamber's is from 0.3 to 0.5 mm, giving a fluid volume in the chamber of 8 to 12 micro liters. The large electrode described herein is thought advantageous in this specific application because of the large amount of current produced during a test. Current from a 25 sq. millimeter sensor will be measured in micro amps rather than the nano amps of some single use strips. A large current flow is advantageous for optimum resolution of the signal.
In the present invention, the openings into the test chamber are at least 300 microns in height, which duplicate the height of the test chamber. Blood is quite viscous and this minimum height is necessary to allow adequate blood flow in and out of the test chamber. Positive pressure is still required to bring blood or fluid into the test chamber and for the same reason pressure is needed to clear the site once the test has been performed. The present invention is capable of exerting adequate pressure to draw in the sample or flush it from the test chamber.
In the descriptions and drawings to follow, two embodiments of the invention are shown. The first embodiment has its test chamber located directly in the main infusion line. The second embodiment has the test chamber located in a side channel, in continuity with the main channel. Several advantages accrue to the side channel version. Firstly, an unrestricted main channel (used together with a restricted side channel) allows for the rapid flow of fluid through the device most of the time. Secondly, a constant flow of fluid through the test chamber (if no side channel is used) could disperse the reagents necessary for repeated testing of blood glucose. This problem is avoided, in the preferred embodiment, since infusion fluid usually flows through the main channel. Thirdly, in the non-side channel version, a large volume of blood must be forced through the test chamber so that an undiluted sample is adjacent the sensor. Damage to red cells can occur when forcing a large quantity of blood through a very small opening. By contrast, in the side channel version blood can be easily withdrawn from the patient through the unobstructed main channel until a pure sample is opposite the test site. At that time only a very small quantity of blood need be directed into the side channel for testing.
It should be emphasized that a controllable valve in the main channel is an essential aspect of the side channel version of the invention. Without controlled blockage of the main channel, blood and fluids would always take the path of least resistance through the main channel and never enter the side channel.
In the following description of the present invention, the one or more valves inside the device are comprised of inflatable balloons. It is to be understood that mechanical valves of various types could also be used in this application. Inflatable balloons are considered the preferred embodiment for reasons of economy and for ease of insertion during assembly.
In the examples to follow, traditional monitoring in an open-flow system is compared to testing with the preferred embodiment of the present invention. Monitoring blood sugar in a conventional flow-through system is possible if there is no disturbance of the diffusion gradient over the sensing electrode. In reality, such disturbances occur constantly for the several reasons mentioned. In a flow-through system in which blood or fluid is propelled by a peristaltic pump, the cog-wheel effect is very evident and causes confusing variations to the glucose diffusion gradient. Additionally, a peristaltic flow-through system is subject to all the additional artifacts contributed by impacts to the infusion bag, the tubing and the sensor itself. Clearly a sensor which isolates the test fluid and keeps it completely at rest is best able to maintain a stable diffusion gradient and give the most accurate estimation of blood glucose.
No references in the prior art have been found to methods of isolating small extra corporal samples for testing. Therasense U.S. Pat. No. 6,120,676 states that a sensor for blood glucose can be used in a flowing sample stream which is made to flow through a sampling chamber. No method is described of sample isolation although the authors state that the sample can be made to flow at a slow rate. In claim 32 of the same patent the authors mention holding the sample stationary in a sampling chamber but the latter is on a disposable strip and not in a reversible infusion line where the sensor must test repeatedly over a period of days.
An advantage of the present invention is to put blood in contact with the sensor only briefly during each test. Following the test, the test chamber in the testing unit is flushed with clear fluid which reduces protein and fibrin deposition on the sensing membrane. For example, if a glucose test takes 20 seconds and readings are done every five minutes, then blood will be in contact with the sensor only about 3% of the total elapsed time.
A primary object of the invention is to provide a system for repeated monitoring of blood glucose from an ordinary infusion line with an accuracy approaching that of a clinical lab.
A further object of the invention is to attain such accuracy by isolation of the test sample during a test.
A further object of the invention is a system usable with equal ease in either a peripheral vein or a central venous line.
A further object of the invention is to provide a small disposable testing unit which is attachable to either the chest for proximity to a central line or to an extremity for use with a peripheral vein.
A further object of the invention is to provide a system which is automatically and periodically self-calibrating.
Other objects and advantages of the invention will become apparent from the following description and drawings.

Method and apparatus for testing blood glucose in a reversible infusion line


The present automatic clearance adjuster mechanism maintains a predetermined maximum brake clearance regardless of the wear condition of the brake. The brake includes a longitudinally extending rod mounted to the brake housing external to the piston element. The present automatic clearance adjuster mechanism includes a sleeve element disposed about the rod, and a biasing element disposed for releasably holding the sleeve element against the rod for preventing movement thereof along the rod to limit the retraction of the piston element to a predetermined distance relative to the sleeve element. The present mechanism also includes a release element disposed to release the biasing element when the piston element is moved in a first or extend direction to allow the sleeve element to be moved by the piston element to an advanced position along the rod and allow the biasing element to hold the sleeve element against the rod in the advanced position when the movement in the extend direction is stopped or the piston element is moved in the opposite direction, the sleeve element when held against the rod in the advanced position limiting the retraction of the piston element to a predetermined distance relative to the advanced position.

This invention relates generally to a brake clearance adjuster for a vehicle such as a work machine, off-highway truck, or the like, and more particularly, to a brake clearance adjuster for automatically maintaining a predetermined maximum brake clearance regardless of the wear condition of the brake.
Currently, a wide variety of devices for adjusting the clearance or slack between rotors and frictional elements of brake mechanisms are well known. Reference, for instance, Kovac U.S. Pat. No. 2,568,858, issued Sep. 25, 1951; Frayer et al. U.S. Pat. No. 2,900,052 issued Aug. 18, 1959 to the Goodyear Tire and Rubber Company; Crossman U.S. Pat. No. 3,554,336 issued Jan. 12, 1971 to the Goodyear Tire and Rubber Company; Cunningham U.S. Pat. No. 3,517,785 issued Jun. 30, 1970 to the Bendix Corporation; Kimata U.S. Pat. No. 3,575,268 issued Apr. 20, 1971 to Isuzu Motors Limited; Davidson U.S. Pat. No. 4,478,316 issued Oct. 23, 1984; Nowosielski U.S. Pat. No. 5,497,859 issued Mar. 12, 1996; and Naedler et al. U.S. Pat. No. 5,607,033 issued Mar. 4, 1997 to Mark+2 Technologies, Inc.
However, the known clearance adjuster devices suffer from various shortcomings and limitations, for instance, complexity and cost disadvantages. In particular, numerous of the known devices are located within the piston element of the brake mechanism so as to add substantial complexity and cost to the piston element. This also makes access to the adjuster mechanism difficult for performing maintenance and service. Additionally, several of the known adjuster devices bear or transmit at least a portion of the braking force, increasing the design requirements thereof. Further, several of the known devices only allow relatively large increments of advancement of the piston element as the frictional elements of the brake wear compared to the amount of clearance or slack provided, such that the maximum allowed slack is substantially greater when the brakes are worn compared to when new.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
According to one aspect of the invention, an automatic clearance adjuster mechanism which maintains a predetermined maximum brake clearance for a brake for retarding rotation of a rotatable member about a longitudinal axis is disclosed. The brake includes a brake housing having a fluid receiving chamber and a piston element disposed partially within the fluid receiving chamber. The piston element is movable by pressurized fluid in the chamber longitudinally in a first or extend direction outwardly with respect to the fluid receiving chamber for applying a pressure for retarding the rotation of the rotatable member, and in an opposite retract direction to provide clearance for freer rotation of the rotatable member. The brake also includes a longitudinally extending rod mounted to the brake housing external to the piston element. The present automatic clearance adjuster mechanism includes a sleeve element disposed about the rod, and a biasing element disposed for releasably holding the sleeve element against the rod for preventing movement thereof along the rod to limit the retraction of the piston element to a predetermined distance relative to the sleeve element. The present mechanism also includes a release element disposed to release the biasing element when the piston element is moved in the first or extend direction to allow the sleeve element to be moved by the piston element to an advanced position along the rod and allow the biasing element to hold the sleeve element against the rod in the advanced position when the movement in the extend direction is stopped or the piston element is moved in the opposite direction, the sleeve element when held against the rod in the advanced position limiting the retraction of the piston element to a predetermined distance relative to the advanced position.
According to a preferred aspect of the invention, the sleeve element includes a split sleeve, the biasing element includes at least one retainer ring disposed around the split sleeve, and the release element comprises cooperatively engageable serrated portions on the split sleeve and on the rod which allow movement of the split sleeve along the rod in the first or extend direction.
According to another preferred aspect of the present invention, the sleeve element includes a split sleeve having a longitudinally tapered outer surface, and the biasing element includes a bushing disposed around the split sleeve and having a longitudinally tapered inner surface positioned for slidable engagement with the tapered outer surface for compressing the split sleeve to hold the split sleeve around the rod when the piston element is retracted, and a compression spring disposed for retracting the piston element and urging the tapered surfaces into the slidable engagement.


A method of electrostatically coating a substrate including the steps of applying a surface treatment composition to the substrate to induce conductivity, applying a charge to the substrate after applying the surface treatment and electrostatically applying a coating to the substrate, and articles made therefrom. The surface treatment composition includes a halogen, halogen salt, or halogen complex.

The present invention relates to an improved method of electrostatically coating substrates which are made of polymers, polymer composites, or other electrically non-conductive materials.
The use of electrostatic powder coating techniques to paint electrically conductive substrates, such as metals, is well known and successfully employed. Using this method, a powder coating material is statically charged or ionized to a positive polarity or negative polarity, and then sprayed or blown onto a grounded, conductive article to which it adheres. The electrostatic attraction between the paint and the grounded article results in a more efficient painting process with less wasted material, and a thicker, more consistent paint coverage, particularly on articles that have a complex shape. Once coated, the article is then baked. In electrostatic painting, a powder coating material is statically charged and applied using standard powder coating equipment. With electrically conductive substrates, a static electric potential is generated between the paint and the substrate to be painted resulting in an attraction of the paint to the object.
When articles fabricated from metals are painted, the metal, which is inherently conductive, is easily grounded and efficiently painted.
However, in recent years, there has been an emphasis on the use of polymeric materials in the manufacture of articles, particularly in applications requiring reductions in weight and improved corrosion resistance, such as automotive applications. However, polymers typically used in such processes are insufficiently conductive to efficiently obtain satisfactory paint thickness and coverage when the article is electrostatically painted.
On poor electrical conductors such as polymeric materials, the conventional electrostatic coating techniques are not as successful because an electric charge potential must exist between both the substrate and the paint. If an object has poor electrical conductivity, it cannot be efficiently electrostatically charged and cannot, therefore, be efficiently electrostatically painted. Furthermore, on non-conductive surfaces, low humidity levels can have a negative impact on the quality of the bond of the powder coating to the surface.
Even so, electrostatic painting techniques are still desirable for use due to the benefits, especially for large scale commercial operations, including less loss of paint than with the use of other painting techniques such as spraying a liquid paint, and the quality of the coating is quite good because the method allows for a uniform distribution of paint without the entire surface being easily accessible. Materials having little or no conductivity such as plastics, may first be coated with a conductive primer or xe2x80x9cprepxe2x80x9d coating, and then electrostatically painted.
Some specific examples of methods of applying an electrostatic charge to surface having little or no conductivity include the addition of conductive fillers to polymers, for instance, application of a conductive primer such as a quaternary amine, However, the conductivity from these treatments, as well as the physical and/or surface characteristics may be less than desirable for certain applications.
The use of conductive primer compositions to prime the article in order to increase its conductivity is also known. However, depending on the particular primer employed, the cured primer may have adhesion, surface smoothness, hydrolytic stability, and durability characteristics, which are less than desirable for a particular application. Additionally, such primers compositions may contain volatile organic solvents, the emission of which during the priming process may be undesirable, as well as environmentally unfriendly. Further, each of the treatments described above can be expensive.
The present invention relates to an improved surface treatment for inducing conductivity in a substrate which has little or no conductivity which includes at least one halogen or halogen complex.
The present invention further relates to a method of treating a substantially non-conductive surface to improve the adhesion of an electrostatic powder coating to the surface. The method involves application of a surface treatment composition which includes a halogen, halogen complex, or hypohalite to the surface of a substrate. In some embodiments, the surface treatment composition includes iodine or iodine complex. In other embodiments, the surface treatment composition includes sodium hypochlorite, or bleach.
More specifically, the present invention relates to a method of electrostatically coating substrates having poor electrical conductivity including the steps of priming the substrate by applying a surface treatment composition which includes at least one halogen, halogen complex, or hypohalite induce conductivity in an otherwise substantially nonconductive material, applying a charge to the surface treated substrate, and electrostatically coating the substrate. In some particular embodiments, the halide is iodine. In some embodiments, the substrate comprises at least one polymeric material.
The present invention further relates to articles electrostatically coated according to the present invention. In some embodiments, the articles comprise at least one polymeric material.
The process of the present invention finds utility for use on any article that may be electrostatically coated or painted. For example, articles for the automotive industry, appliances, equipment parts and machine components, furniture, articles for outdoor activities including hunting, fishing and camping, and so forth. The process of the invention finds a preferred application in connection with the coating of radiators, car bodies and automotive accessories, machine components, compressors, shelving units, office furniture and comparable industrial products.
Examples of articles useful for outdoor activities include, but are not limited fishing rods, fishing lures, archery bows, cookware, and so forth.
The method of the present invention is economical, and has minimal impact on the environment.
The present invention relates to an improved method of electrostatically coating substrates which have little or no electrical conductivity including, for example, polymeric substrates and polymer composite substrates, wood and wood products, and to an improved surface treatment composition for use therein.
The composition of the present invention suitable for use as surface treatment is desirably a liquid composition including at least one halogen, halogen complex, a halide salt, hypohalite, hypohalate, perhalate, and so forth, or mixture thereof, and a liquid carrier or solvent. Examples of suitable carriers include, but are not limited to, water, alcohol such as ethanol, isopropanol and methanol, acetone, ethers such as diethyl ether, toluene, p-xylene, benzene, carbon disulfide, chloroform, carbon tetrachloride, glycerol, alkaline iodide solutions, and so forth, and mixtures thereof. Some carriers are more preferable than others due to the varying levels of toxicity or environmental concern, with water being a preferred solvent. Water in combination with another carrier, such as an alcohol, is also suitably used.
Any of the halogens find utility herein including iodine, bromine, chlorine, and fluorine. Iodine and chlorine are more suitable for use, with iodine being most suitable.
xe2x80x9cHalophorsxe2x80x9d including bromophors, chlorophors, iodophors, fluorophors, and so forth, also find utility herein. As used herein, the term xe2x80x9chalophorxe2x80x9d is used to refer to complexes of halogens with solubilizers or carriers which are typically polymers such as polyvinyl pyrrolidone or polyethylene glycol, or certain types of surface active agents including those that have detergent properties. Complexes of halogens are readily known.
The hypohalites include hypochlorite, hypoiodite, hypobromite, hypofluorite, hypoastatite, and mixtures thereof. Hypochlorite is suitably employed due to the fact that it is readily available and economical. The corresponding cation may be an alkali or an alkaline earth metal. Sodium and potassium are suitably employed as cations.
Certain other metal salts may also find utility herein as well including the metal halides, perhalates, hypohalates, and so forth. Some salts may exhibit a tendency to produce a graininess in the result powder coating, thereby resulting in a lower quality powder coating.
In order to eliminate or minimize many of the difficulties involved with using atomic halogens including poor solubility in solvents, complexes of halogens with various materials may be employed. These halogen containing complexes are often referred to as xe2x80x9chalophorsxe2x80x9d and include bromophors, chlorophors, fluorophors and iodophors. The complexes are often prepared either with surfactants including nonionic, anionic, cationic and amphoteric surfactants, or with polymers.
The polymers or surface active agents may act to solubilize the halogen, as described above. Complexes formed using these materials and the halogens are readily known. Suitably, either iodophors or chlorophors are utilized herein. Most suitable for use in the present invention, are the iodophors.
Surfactants useful in forming halophors are known to those of skill in the art. The following discussion includes exemplary surfactants but is not intended to be any limitation on the types of surfactants that may be utilized in the formation of halophors useful herein.
Anionic surface-active agents are less popular in forming halogen complexes because they may not have the stability required for many applications. It may therefore be desirable to use them in combination with another surfactant. A suitable class of anionic surfactants useful in forming halophors
A suitable class of cationic surfactants useful in forming halophors are quaternary ammonium compounds.
The halogens, and in particular iodine may form complexes with nonionic surfactants. Useful synthetic nonionic surfactants are often the condensation products of an organic aliphatic or alkyl aromatic hydrophobic compound and hydrophilic ethylene oxide groups. Practically any hydrophobic compound having a carboxy, hydroxy, amido, or amino group with a free hydrogen attached to the nitrogen can be condensed with ethylene oxide or with the polyhydration product thereof, polyethylene glycol, to form a water-soluble nonionic surfactant.
Examples of nonionic surfactants useful in forming halophors are known to those of skill in the art and include, but are not limited to, primary and secondary aliphatic alcohol ethoxylates, alkylphenol ethoxylates and ethylene oxide/propylene oxide condensates on primary alkanols, condensates of ethylene oxide with sorbitan fatty acid esters, condensates of ethylene oxide and aliphatic ethers or glycols, and so forth.
Examples of ethylene oxide/propylene oxide condensates useful herein include those having about 50% to about 70% ethylene oxide and nonylphenoxypoly (ethyleneoxy) ethanol and octylphenoxypoly (ethyleneoxy) ethanol.
Nonionic surfactants useful in forming halophors, in particular iodophors, are discussed in U.S. Pat. No. 5,707,955 incorporated by reference herein in its entirety.
Bromophors and iodophors are discussed in U.S. Pat. No. 4,894,241 incorporated by reference herein in its entirety.
Nonionic surfactants, anionic and cationic surfactants for use in halophor formation are described in U.S. Pat. No. 4,206,204 incorporated by reference herein in its entirety.
Probably the most commonly used halophors, in particular, the iodophors, include the halogen complexed with nonionic surfactants, glycol ether, and polyvinylpyrrolidone (1-ethenyl-2-pyrrolidone homopolymer compound). While these are commonly used complexes of halogens, other compounds as described above may be used in the formation of the complexes as well. The titratable halogen, such as the titratable iodine, in such complexes is typically between about 0.5 and 1.5% halogen. It is surmised that a certain amount of halide may also be present in the compositions.
Specific examples of useful iodophors of nonionic surfactants include, but are not limited to polyethoxylated nonylphenol iodine complex and polyethoxylated fatty alcohol iodine complex. In one embodiment, a blend of these two iodophors is utilized.
Surfactants which may find utility in forming halophors are discussed in McCutcheon""s Detergents and Emulsifiers, 1999, North American Edition, MC Publishing Co. incorporated by reference herein in its entirety.
There are a vast amount of surfactants that may be utilized in the formation of halophors known to those of skill in the art, and a vast amount of references as well. The list above is by no means intended as an exclusive list of surfactants that may find utility herein. Halophors may be readily substituted without departing from the scope of the present invention.
Varying the concentration of the halogen or halogen complex in the liquid carrier will result in different conductivities as well. However, the concentration of halide or halide containing compound may be anywhere from about 0.001 wt-% to about 100 wt-%, suitably about 0.01 wt-% to about 20 wt-% halogen or halogen complex, more suitably about 0.1 to about 10 wt-%, and most suitably about 0.1 wt-% to about 5 wt-% halogen or halogen complex.
The composition may be applied to a substrate or article using any method known in the art including, but not limited to, dipping, spraying, brushing, and so forth.
In some embodiments of the present invention, a mixture of an iodine complex in a solvent is employed. A solution of about 12.5 wt-% iodine complex is further diluted with water at a ratio of about 13:1 providing a solution of about 1 wt-% complexed iodine. In this embodiment, titratable iodine is about 1 wt-%. After dilution, titratable iodine is less than about 0.1 wt-%. While denatured alcohol was found to be a suitable carrier in this embodiment, water was found to be superior.
The concentration of iodine may be anywhere from 0.001 wt-% iodine or iodine complex to about 100 wt-% iodine or complexed iodine, suitably about 0.1 wt-% to about 10 wt-%, and most suitably between about 0.1 wt-% to about 5 wt-% iodine or complexed iodine. In one particular embodiment, a solution of 12 wt-% iodine in water is employed.
The electrostatic charge may be applied to the surface after treatment with the surface treatment solution using any powder coating equipment known in the art such as that made by Nordsen and by Wagner including, for example, a Nordsen 2001 powder coating system or a Wagner EPG 2007 powder coating system. Suitably, a negative charge is applied to the treated surface. An opposite charge may also be applied to the coating composition used in the electrostatic coating process.
As used herein, the term xe2x80x9ccoatingxe2x80x9d may refer to any composition which may be electrostatically applied in such a manner, including those compositions which include pigments or dyes, and thus includes those compositions which are employed for electrostatically painting a substrate or article. The present invention is not limited, however, to compositions employed for an electrostatic painting process which compositions include pigments or dyes.
One particular advantage of using the method of the present invention is that the substrates or articles may be electrostatically coated either while xe2x80x9cwetxe2x80x9d, or after drying, or at any point in between. This allows electrostatic coating of the substrate or article immediately after surface treatment. In other words, the present invention in not sensitive to the presence of moisture. This is a surprising result.
The surface treatment composition of the present invention may be used with any electrostatic coating or painting techniques known in the art.
Electrostatic coating of both liquids and powders may be employed in the method. If a liquid coating is employed, any suitable water-based and/or organic-based composition may be employed.
A typical electrostatic coating process involves charging or ionizing a coating and then spraying the coating on a grounded, conductive article. Using the method of the present invention, sufficient conductivity is imparted to the article or substrate by using the surface treatment of the present invention prior to electrostatic coating. The electrostatic attraction between the coating and the grounded article results in a more efficient coating process with less wasted material such as a paint composition, and thicker and more consistent coverage, particularly when the article has a complex shape.
Useful powder coating compositions may include polyester resins, epoxy resins, epoxy-polyester resins, epoxy functional polyacrylate resins, and so forth. Such compositions are available form Spraylat Corp., BASF Corp., and so forth. Examples of such materials are described in U.S. Pat. Nos. 6,254,751, 6,133,344, both of which are incorporated by reference herein in their entirety. The composition may also include optional ingredients such as other film formers, binders, crosslinking agents, flow aids, catalysts, devolatilization auxiliaries, dyes, pigments, and so forth.
In the case of paints, a dye or pigment is of course required if it is desirable to impart color to a substrate or article. The present invention is not limited to any particular coating employed in electrostatic deposition and the above examples are for purpose of illustration only.
Powder coatings are typically prepared by mixing the components in a high shear mixer or extruder at a temperature which is above the softening temperature of the film-forming polymer but below the crosslinking temperature and then bringing the resulting extrudate to a particle size of from about 40 to 70 xcexcm by means of a milling process.
After electrostatic coating, the substrate or article may be placed in an oven at an appropriate heat cure temperature. Typical temperatures for use with a powder coating are in the range of about 150xc2x0 C. to 200xc2x0 C., but of course depend on the type of coating used. A commonly used temperature is about 350xc2x0 F. (about 175xc2x0 C.). The amount of time required for curing varies, but is typically less than 1 hour.
The present invention finds utility for electrostatically coating any substrates or articles made of materials which have little or no conductivity. In particle, the present invention finds utility for electrostatically coating articles manufactured from polymers, polymer composites, wood and wood products or any other low conductivity surfaces. Wood products generally refer to such materials as fiberboard, particle board, and so forth. Such articles may be made by any method known for forming articles including, but not limited to, molding, thermoforming, extruding, machining and so forth.
Polymeric materials suitable for use include those materials referred to in the art as thermoplastic, elastomeric, thermosetting, and so forth.
Examples of useful thermoplastic materials include, but are not limited to, thermoplastic polyolefin such as polyethylene and polypropylene including high and low density versions, grafted (e.g. maleated) polyethylene and polypropylene, atactic polypropylene, polyvinyl chloride, polymethylmethacrylates, polyvinyl acetate, saturated polyesters, polystyrene, polyacrylates and polymethacrylates, thermoplastic (i.e. saturated) polyurethanes, polycarbonates, thermoplastic polyesters, polyamides, nylons, polyacetals, polysulfones, ethylene-carbon monoxide copolymers, substantially linear interpolymers of ethylene and at least one alpha-olefin such as ethylene-propene, ethylene-butene, ethylene-hexene, ethylene-octene copolymers, and so forth, to mention only a few. The present invention also contemplates the use of any other copolymers and terpolymers of such polymeric materials.
Examples of elastomeric materials include styrene-butadiene-styrene, styrene-ethylene/butylene-styrene, styrene-ethylene/propylene-styrene, styrene-isoprene-styrene, polyisoprene, ethylene-propylene diene rubbers (EPDM), chlorinated rubbers, nitrile rubbers, methylmethacrylate styrene-butadiene block copolymers, polybutadiene, and acrylonitrile-butadiene-styrene copolymers, and so forth, to mention only a few.
Thermosetting polymeric materials include, but are not limited to, unsaturated polyesters, epoxy resins, vinyl ester resins, phenolic resins, polyether, polyester and polyurea urethanes, and so forth. Such materials are commonly crosslinked with styrene, amines, vinyl toluene, hexamethylenetetraamine, and so forth.
Fillers, particulate matter, fibers, and so forth may be used in combination with the polymeric materials including, for instance, glass particles, minerals such as calcium carbonate, dolomite, clays, talc, zinc borate, perlite, vermiculite, alumina trihydrate, solid or hollow glass microspheres, and so forth. Polymer-based fibers may also be used including, for instance, nylon, polyester, polybenzoxazole, aramid, ultra high molecular weight polyethylene fibers, and so forth, to mention only a few.
All of the materials discussed above are for exemplary purposes only and are in no way intended as a limitation on the scope of the present invention. Other materials exist which may be used in accordance with the teachings of the present invention, and are known to those of skill in the art.
Other optional ingredients may be added as well including, but not limited to, thickeners, hardeners, crosslinking agents, initiators, chain extenders, mold release agents, free-radical inhibitors, catalysts, plasticizers, waxes, and so forth. Such ingredients are intended for exemplary purposes only. One of ordinary skill in the art understands that there are numerous additives that may be optionally included in making various articles not listed herein.
The ingredients may be mixed according to any standard procedures known in the art including high shear mixing, upright mixers, extruders, and so forth. The order of addition of ingredients is dependent upon which type of polymer is being used, as well as the ingredients added.
While the present invention is not limited to use on any particular article or substrate, some examples for which the present invention finds utility include, but are not limited to, automobile bodies and automotive accessories, equipment parts and machine components, radiators, compressors, household items and accessories such as furniture and shelving, siding, doors and so forth. Other examples include, but are not limited to, articles for hunting, fishing and camping such as fishing rods, fishing lures, archery bows, cookware, and so forth.
In some embodiments of the present invention, the electrostatic coating process of the present invention is used for hunting, fishing and camping equipment and accessories such as fishing rods, fishing lures, cookware, archery bows, and so forth.
One particular example of an article which may be electrostatically coated according to the present invention is an archery bow limb, such as a compound archery bow limb, made of a polymer composite of an epoxy and glass fibers. Suitably, a coating having a pigment or dye is employed. In this embodiment, the content of glass fibers may be from about 10 wt-% to about 80 wt-%, and more suitably about 50-70 wt-%.
The present invention may find utility for any article or substrate which may be electrostatically coated. The above embodiments and descriptions are in no way intended to limit the scope of the present invention. The following non-limiting examples are further illustrative of the present invention.

Method and compositions for electrostatic painting, and articles made therefrom


Chemical mechanical polishing compositions and slurries comprising a film forming agent and at least one silane compound wherein the compositions are useful for polishing substrate features such as copper, tantalum, and tantalum nitride features.

(1) Field of the Invention
This invention concerns aqueous chemical mechanical polishing compositions and slurries that are useful for polishing substrates including metal features such as copper and tantalum features. The aqueous polishing compositions comprise a film forming agent and at least one silane composition. In one method, the polishing compositions of this invention are used by applying the composition to an abrasive pad or by combining the composition with one or more abrasives to form a polishing slurry and then using the pad or slurry to polish a substrate including one or more metal features.
(2) Description of the Art
Integrated circuits are made up of millions of active devices formed in or on a silicon substrate. The active devices, which are initially isolated from one another, are interconnected to form functional circuits and components. The devices are interconnected through the use of multilevel interconnections. Interconnection structures normally have a first layer of metallization, an interconnection layer, a second level of metallization, and sometimes a third and subsequent level of metallization. Interlevel dielectrics such as doped and undoped silicon dioxide (SiO2), or low-xcexa dielectrics tantalum nitride are used to electrically isolate the different levels of metallization in a silicon substrate or well. The electrical connections between different interconnection levels are made through the use of metallized vias. U.S. Pat. No. 5,741,626, which is incorporated herein by reference, describes a method for preparing dielectric tantalum nitride layers.
In a similar manner, metal contacts are used to form electrical connections between interconnection levels and devices formed in a well. The metal vias and contacts may be filled with various metals and alloys including titanium (Ti), titanium nitride (TiN), tantalum (Ta), aluminum copper (Alxe2x80x94Cu), aluminum silicon (Alxe2x80x94Si), copper (Cu), tungsten (W), and combinations thereof. The metal vias and contacts generally employ an adhesion layer such as titanium nitride (TiN), titanium (Ti), Tantalum (Ta), Tantalum nitride (TaN) or combinations thereof to adhere the metal layer to the SiO2 substrate. At the contact level, the adhesion layer acts as a diffusion barrier to prevent the filled metal and SiO2 from reacting.
In many semiconductor manufacturing processes, metallized vias or contacts are formed by a blanket metal deposition followed by a chemical mechanical polish (CMP) step. In a typical process, via holes are etched through an interlevel dielectric (ILD) to interconnection lines or to a semiconductor substrate. Next, a thin adhesion layer such as tantalum nitride and/or tantalum is generally formed over the ILD and is directed into the etched via hole. Then, a metal film is blanket deposited over the adhesion layer and into the via hole. Deposition is continued until the via hole is filled with the blanket deposited metal. Finally, the excess metal is removed by chemical mechanical polishing, (CMP) to form metal vias. Processes for manufacturing and/or CMP of vias are disclosed in U.S. Pat. Nos. 4,671,851, 4,910,155 and 4,944,836.
In a typical chemical mechanical polishing process, the substrate is placed in direct contact with a rotating polishing pad. A carrier applies pressure against the backside of the substrate. During the polishing process, the pad and table are rotated while a downward force is maintained against the substrate back. An abrasive and chemically reactive solution, commonly referred to as a xe2x80x9cslurryxe2x80x9d is applied to the pad during polishing. The slurry initiates the polishing process by chemically reacting with the film being polished. The polishing process is facilitated by the rotational movement of the pad relative to the substrate as slurry is provided to the wafer/pad interface. Polishing is continued in this manner until the desired film on the insulator is removed. Polishing composition formulation is an important factor in the CMP step. The polishing composition should be tailored to provide effective polishing to metal layers at desired polishing rates while minimizing surface imperfections, defects and corrosion and erosion. Furthermore, the polishing composition may be used to provide controlled polishing selectivities to other thin-film materials used in current integrated circuit technology such as titanium, titanium nitride, tantalum, tantalum nitride, and the like.
There are various mechanisms disclosed in the prior art by which metal surfaces can be polished with slurries. The metal surface may be polished using a slurry in which a surface film is not formed in which case the process proceeds by mechanical removal of metal particles and their dissolution in the slurry. In such a mechanism, the chemical dissolution rate should be slow in order to avoid wet etching. A more preferred mechanism is, however, one where a thin abradable layer is continuously formed by reaction between the metal surface and one or more components in the slurry such as a complexing agent and/or a film forming layer. The thin abradable layer is then removed in a controlled manner by mechanical action. Once the mechanical polishing process has stopped a thin passive film remains on the surface and controls the wet etching process. Controlling the chemical mechanical polishing process is much easier when a CMP slurry polishes using this mechanism.
Current copper containing substrates that are polished using chemical mechanical polishing also use Ta and TaN adhesion layers. Ta and TaN are chemically very passive and mechanically very hard and thus difficult to remove by polishing. Thus, there remains a need for polishing compositions that are useful for polishing substrates including tantalum while having little detrimental effect on previously polished copper features.
In one embodiment, this invention includes aqueous chemical mechanical polishing compositions comprising a film forming agent and at least one silane compound.
In another embodiment, this invention includes an aqueous chemical mechanical polishing compositions comprising from about 0.01 to about 0.5 wt % benzotriazole and from about 0.05 to about 1.0 wt % uriedopropyltrimethoxysilane and further optionally including from about 1.0 to about 30 wt % silica abrasive.
In yet another embodiment, this invention is a method for polishing a substrate feature. The method includes moving a substrate including at least one feature into contact with a polishing pad. Next, the substrate is moved in relationship to the polishing pad to remove a portion of the substrate feature. A liquid polishing composition is applied to the polishing pad to promote polishing wherein the liquid polishing composition comprises at least one film forming agent and at least 0.001 wt % of at least one silane compound.
The polishing compositions of the present invention have been found to be effective in polishing the metal features of an integrated circuit with few defects.
The present invention relates to chemical mechanical polishing compositions and to methods for using the compositions to polish a substrate including a metal portion at acceptable rates and with very few defects.
Before describing the details of the various preferred embodiments of this invention, some of the terms that are used herein will be defined. The term xe2x80x9cchemical mechanical polishing compositionxe2x80x9d refers to aqueous polishing compositions that do not include abrasive materials. The polishing compositions can be combined with a polishing pad with or without an abrasive to polish substrates. Alternatively, the chemical mechanical polishing compositions of this invention can be combined with a particulate abrasive to form a chemical mechanical polishing (CMP) slurry. The chemical mechanical polishing compositions and CMP slurries are useful for polishing a multiple level metallizations which may include but are not limited to semi-conductor thin-films, integrated circuit thin-films, and for any other films and surfaces where CMP processes are useful.
The terms xe2x80x9ccopperxe2x80x9d and xe2x80x9ccopper containing alloysxe2x80x9d are used interchangeably herein as it is within the understanding of one of skill in the art that the terms include but are not limited to substrates comprising layers of pure copper, copper aluminum alloys, and Ti/TiN/Cu, and Ta/TaN/Cu multi-layer substrates.
The term xe2x80x9csubstrate featurexe2x80x9d as it is used herein refers to electronic substrate features such as vias and copper interconnect lines, and to layers of materials deposited on or in the features such as dielectric layers, low-k material layers, adhesion layers, metal layers, and so forth. The polishing compositions of this invention are useful for polishing substrates to remove material layers, as well as for polishing exposed substrate features.
The chemical mechanical polishing compositions of this invention include at least one film forming agent. The film forming agent may be any compound or mixtures of compounds that are capable of chemically binding to the surface of a substrate feature to form a chemical complex wherein the chemical complex is not a metal oxide or hydroxide. The chemical complex acts as a passivation layer and inhibits the dissolution of the surface metal layer of the substrate metal feature. Useful film forming agents are nitrogen containing cyclic compounds such as imidazole, benzotriazole, benzimidazole and benzothiazole and their derivatives with hydroxy, amino, imino, carboxy, mercapto, nitro and alkyl substituted groups, as well as urea, thiourea and others. A more preferred film forming agent is benzotriazole (xe2x80x9cBTAxe2x80x9d). It is preferred that the film forming agent selected is one that is capable of forming a passivation layer on substrate copper features. The film forming agent may be present in the polishing compositions and slurries of this invention in an amount ranging from about 0.01 weight percent to about 1.0 weight percent. It is preferred that film forming agent is present in the polishing compositions and slurries of this invention in an amount ranging from about 0.01 to about 0.5 weight percent.
The polishing compositions and slurries of this invention include at least one silane compound in solution. General classes of silane compounds useful in polishing compositions on this invention include aminosilanes, uriedosilanes, alkoxysilanes, alkylsilanes, mercaptosilanes, thiocyanatosilanes, vinylsilanes, methacrylsilanes, cyanosilanes, functionalized silanes, disilanes, trisilanes and combinations thereof.
Preferred silane compositions have the formula:
Yxe2x80x94Sixe2x80x94(X1X2R)
and include dimers, trimers and oligomers thereof wherein the term xe2x80x9coligomersxe2x80x9d refers to a compound containing from 4 to 15 siloxane units. In the formulas above, Y, R, X1, and X2 may each be individually selected from hydroxy (xe2x80x94OH) or some other hydrolyzable substituent or a non-hydrolyzable substituent. More preferably, in the formula above, Y is hydroxy (xe2x80x94OH) or a hydrolyzable substituent, X1 and X2 are each independently selected from hydroxy, a hydrolyzable substituent, or a non-hydrolyzable substituent, and R is a non-hydrolyzable substituent. In a preferred embodiment the silane composition will have the formula above wherein Y is hydroxy (xe2x80x94OH) or a hydrolyzable substituent, R is a non-hydrolyzable substituent; and X1 and X2 are each individually non-hydrolyzable substituents.
Generally, xe2x80x9chydrolyzablexe2x80x9d substituents are those compounds that will form Si(OH) in an aqueous system. Such moieties include, but are not limited to alkoxide, halogens such as Cl, carboxylate, and amides. Non-hydrolyzable moieties are any compounds that do not undergo hydrolysis to form Si(OH) in an aqueous solution.
The non-hydrolyzable substituents are each independently selected from alkyl, cycloalkyl, aromatic, functionalized alkyl, functionalized aromatic, functionalized cycloalkyl, alkene, alkylsilane, one or more of which carbon atoms may be substituted with one or more atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen, silicon, and combinations thereof wherein each non-hydrolyzable substituent include from 1 to 100 carbon atoms and preferably 2 to 25 carbon atom and most preferably 2 to 10 carbon atoms.
Preferably, each non-hydrolyzable substituent is selected from the group of compounds consisting of alkyl, functionalized alkyl, and mixtures thereof having from 2 to 25 carbon atoms. More preferably each non-hydrolyzable substituent is a functionalized alkyl selected from the group consisting of alkylnitriles, alkylamides, alkylcarboxylic acids, alkyl halide, alcohol, alkyluriedo, and mixtures thereof. Most preferably, at least one of the non-hydrolyzable substituents is functionalized propyl alkyl.
Examples of useful silane compounds include, but are not limited to silanes with three hydrolyzable substituents such as glycidoxypropyltrialkoxysilane, isocyanatopropyltrialkoxysilane, ureidopropyltrialkoxysilane, mercaptopropyltrialkoxysilane, cyanoethyltrialkoxysilane, 4,5-dihydro-1-(3-trialkoxysilylpropyl)imidazole, 3-(trialkoxysilyl)-methyl ester propanoic acid, trialkoxy[3-(oxiranylalkoxy)propyl]-silane, 2-methyl, 3-(trialkoxysilyl)propyl ester 2-propenoic acid, [3-(trialkoxysilyl)propyl]urea, and mixtures thereof. Silanes with two hydrolyzable substituents including chloropropylmethyldialkoxysilane, 1,2-ethanediylbis[alkoxydimethyl]silane, dialkoxymethylphenyl silane, and mixtures thereof. And silanes with a single hydrolyzable substituent such as cyanopropyldimethylalkoxysilane, N,Nxe2x80x2-(alkoxymethylsilylene)bis[N-methyl-benzamide], chloromethyldimethylalkoxysilane, and mixtures thereof.
For purposes of this invention, the term xe2x80x9calkoxyxe2x80x9d as used in the silane names above and as used generally herein refers to the hydrolyzable group and may include xe2x80x94OR, Cl, Br, I, NRRxe2x80x2 wherein R and Rxe2x80x2 may include from 1 to 20.
The compositions and slurries of this invention will typically include from about 0.001 to 5.0 wt % silane. More preferably, the compositions of this invention will include from about 0.05 to about 1.0 wt % silane. The amount of silane in the compositions of this invention includes soluble silane that is in the polishing composition and slurry solutions as well as silanes that are associated with the surface of abrasive particles. Silane compositions including hydroxy or hydrolyazable moieties are capable of adhering to surface metal hydroxides found on many metal oxide abrasives. The term xe2x80x9csoluble silanexe2x80x9d as it is used herein refers to silanes that are present in the polishing compositions and slurries in a disassociated soluble form. The polishing compositions and slurries of this invention are liquid compositions that may include any solvents in which silanes can be solubilized or emulsified. Examples of useful solvents include polar solvents such as alcohols and water. Water is the preferred solvent of the polishing compositions and slurries of this invention. The compositions of this invention may include silanes dissolved in a solvent as well as silane/solvent emulsions.
Other well known polishing composition additives may be incorporated into the compositions and/or slurries of this invention. U.S. Pat. Nos. 6,136,711, and 6,083,419, the specifications of each of which are incorporated herein by reference describe several embodiments of compositions of this invention as well as polishing composition additives that can be optionally included in compositions of this invention. Non-limiting examples of useful polishing composition additives include, but are not limited to one or more oxidizing agents such as hydrogen peroxide, ammonium persulfate, and the like; complexing agents, surfactants; film forming agents such as benzotriazole; organic acids and inorganic acids; and/or salts such as sulfuric acid, phosphoric acid, phosphonic acid, nitric acid, HF acid, ammonium fluoride, ammonium salts, potassium salts, sodium salts or other cationic salts of sulfates, phosphates, phosphonates, and fluorides, acids and bases used to adjust composition pH. In essence, any ingredient that are known to be useful in chemical mechanical polishing slurries and compositions may be included in the polishing compositions and slurries of this invention.
The polishing compositions of this invention may also include an optional metal oxide abrasive selected from metal oxide abrasives including alumina, titania, zirconia, germania, silica, ceria, tantalum oxide (TaOx), mixtures thereof, and chemical admixtures thereof. The term xe2x80x9cchemical admixturexe2x80x9d refers to particles including atomically mixed or coated metal oxide abrasive mixtures. A most preferred metal oxide abrasive is silica (silicon dioxide).
The abrasive particles useful in this invention may consist of metal oxide aggregates or individual single particles. The term xe2x80x9cparticlexe2x80x9d as it is used herein refers to both aggregates of more than one primary particle and to single particles. Preferred metal oxide particles are silica and aluminum with silica being most preferred.
The metal oxide abrasives used in the present invention may be produced by any techniques known to those skilled in the art to give abrasive particles having the characteristics reported above. Metal oxide abrasives useful in this invention are derived from processes including flame processes, sol-gel processes, hydrothermal processes, plasma processes, aerogel processes, fuming processes, precipitation processes, mechanochemical milling, mining, and by any combination of these processes just so long as the abrasive includes surface metal hydroxides.
Generally, the metal oxide abrasives will be present in polishing slurries of this invention in an amount ranging from about 1 to about 30 wt %. More preferably, the abrasives will be present in the polishing slurries of this invention in an amount ranging from about 3 to about 15 wt % abrasive.
Alternatively, the polishing compositions of this invention may be used in conjunction with an abrasive containing polishing pad to polishing substrate metal features. The optional metal oxide abrasives may be produced by any techniques known to those skilled in the art such as sol-gel, hydrothermal or, plasma process, or by processes for manufacturing fumed or precipitated metal oxides. Preferably, the metal oxide is a fumed or precipitated abrasive and, more preferably it is a fumed abrasive such as fumed silica or fumed alumina with fumed silica being most preferred.
Preferably, the metal oxide abrasive is incorporated into the polishing composition as a concentrated aqueous dispersion of metal oxides, comprising from about 1% to about 45% solids, and preferably between 10% and 20% solids. The aqueous dispersion of metal oxides may be produced utilizing conventional techniques, such as slowly adding the metal oxide abrasive to an appropriate media, for example, deionized water, to form a colloidal dispersion. The dispersion is typically completed by subjecting it to high shear mixing conditions known to those skilled in the art. The pH of the slurry may be adjusted away from the isoelectric point to maximize colloidal stability.
BTA, or polishing additives included in polishing compositions may destabilize the uniform dispersion of abrasive in the slurry. In order to stabilize polishing slurries against settling, flocculation, and decomposition, a variety of optional polishing slurry additives, such as surfactants, stabilizers, or dispersing agents, can be used. If a surfactant is added to the polishing slurry, then it may be an anionic, cationic, nonionic, or amphoteric surfactant or a combination of two or more surfactants can be employed. Furthermore, it has been found that the addition of a surfactant may be useful to reduce the within-wafer-non-uniformity (WIWNU) of the wafers, thereby improving the surface of the wafer and reducing wafer defects.
In general, the amount of optional additives such as a surfactant that may be used in the polishing slurry should be sufficient to achieve effective stabilization of the slurry and will typically vary depending on the particular surfactant selected and the nature of the surface of the metal oxide abrasive. Stabilizers such as surfactants may be present in the polishing slurry in an amount ranging from about 0.001% to about 0.2% by weight, and preferably from about 0.001 to about 0.1 weight percent. Furthermore, the additive may be added directly to the slurry or treated onto the surface of the metal oxide abrasive utilizing known techniques. Examples of useful surfactants include dodecyl sulfate sodium salt, sodium lauryl sulfate, dodecyl sulfate ammonium salt, and mixtures thereof. Examples of useful surfactants include TRITON(copyright) DF-16 manufactured by Union Carbide, and SURFYNOL(copyright) manufactured by Air Products and Chemicals.
It is desirable to maintain the pH of the polishing compositions of this invention within a range of from about 3.0 to about 12.0, and preferably between from about 5.0 to about 12.0 in order to facilitate control of the CMP process. The pH of the polishing compositions of this invention may be adjusted using any known acid, base, or amine. However, the use of an acid or base that contains no metal ions, such as ammonium hydroxide and amines, or nitric, phosphoric, sulfuric, or organic acids are preferred to avoid introducing undesirable metal components into the CMP slurry of this invention.
The polishing composition of this invention may be used to polish any type of substrate feature. It is preferred that the polishing compositions of this invention are used to polish metal features since the compositions of this invention exhibit desirable low defectivity towards metal layers such as copper layer, while exhibiting a desirable adhesion layer, tantalum, tantalum nitride, or dielectric layer polishing rate. Examples of metals and dielectric materials that can be polished by the compositions of this invention include, but are not limited to, aluminum copper (Alxe2x80x94Cu), aluminum silicon (Alxe2x80x94Si), copper (Cu), tungsten (W), titanium nitride (TiN), titanium (Ti), tantalum (Ta), tantalum nitride (TaN), ultra low-k materials, silicon oxide, aluminum oxide, phosphorous, boron doped silica, or combinations thereof.
The polishing compositions and slurries of this invention may be used with any standard polishing equipment appropriate for use on the desired metal layer of the wafer. Polishing compositions of this invention are most useful for polishing substrates including either a tantalum or tantalum nitride portion and a copper alloy containing portion, both over a dielectric layer.
The polishing compositions are used to polish substrates by conventional means using conventional polishing machines. The polishing compositions of this invention may be applied directly to the substrate, they may be applied to a polishing pad, or they may be applied to both in a controlled manner during substrate polishing. It is preferred however that polishing compositions are applied to the pad which thereafter is brought into contact with the substrate surface after which the pad is moved in relationship to the substrate surface in order to achieve substrate polishing. Polishing compositions of this invention are then continuously or intermittently applied to the pad in order to maintain a sufficient amount of polishing composition at the pad/substrate surface. When the polishing end point is reached, the flow of polishing composition to the polishing pad is interrupted and excess polishing composition is washed from the substrate with deionized water or another solvent.
In one method of this invention, an abrasive free polishing composition including a soluble silanes and a film forming agent is applied to an abrasive-containing polishing pad and the wetted abrasive containing polishing pad is then used to polish substrate surface features. Alternatively, polishing slurries of this invention including soluble silanes, film forming agents and one or more abrasives may be applied to an abrasive containing polishing pad or to an abrasive-free polishing pad before and during substrate feature polishing. Examples of abrasive-containing polishing pads that can be used with the polishing compositions of this invention are disclosed in U.S. Pat. Nos. 5,849,051 and 5,849,052 the specification of which are incorporated herein by reference.
The polishing compositions of this invention are most useful in polishing metal substrate features and especially copper, titanium, titanium nitride, tantalum, and tantalum nitride features at various stages of semiconductor integrated circuit manufacture and provide effective polishing at desired polishing rates while minimizing surface imperfections and defects.


An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

PET is a medical imaging technique in which a radioactively labeled substance is administered to a patient and then traced within the patient's body by means of an instrument that detects the decay of the isotope. In PET, a chemical tracer compound having a desired biological activity or affinity for a particular organ is labeled with a radioactive isotope that decays by emitting a positron (positive electron). The emitted positron loses most of its kinetic energy after traveling only a few millimeters in living tissue. It is then highly susceptible to interaction with an electron, an event that annihilates both particles. The mass of the two particles is converted into 1.02 million electron volts (1.02 MeV) of energy, divided equally between two 511 keV photons (gamma rays). The two photons are emitted simultaneously and travel in almost exactly opposite directions. The two photons penetrate the surrounding tissue, exit the patient's body, and are absorbed and recorded by photodetectors typically arranged in a circular array.
Biological activity within an organ under investigation can be assessed by tracing the source of the radiation emitted from the patient's body to the photodetectors. The source of the radiation can be accurately estimated by linking each photodetector with several other photodetectors on the opposite side of the photodetector array and registering a signal only if two detectors sense 511 keV photons coincidentally. When a coincidence is registered, an annihilation is recorded along a line connecting the two photodetectors. In this manner, a circumferential array of photodetectors can establish the sources of all coincident pairs of photons that originate within a volume defined by straight lines joining paired detectors. A computer program reconstructs the spatial distribution of the decaying isotopes within the patient. With suitable interpretation, PET images provide a noninvasive, regional assessment of many biochemical processes associated with human organs.
The value of PET as a clinical imaging technique is in large measure dependent upon the performance of the photodetectors. The typical PET camera comprises an array of photodetectors consisting of scintillator crystals coupled to photomultiplier tubes (PMTs). When a photon strikes a detector, it produces light in one of the scintillator crystals that is then sensed by the PMT, which registers the event by passing an electronic signal to the reconstruction processing circuitry. The scintillator crystals themselves must have certain properties, among which are (1) good stopping power, (2) high light yield, and (3) fast decay time.
Stopping power is the ability to stop the 511 keV photons in as little material as possible so as to reduce the overall size of the photodetector, of which the scintillator crystals form a substantial portion. Stopping power is typically expressed as the linear attenuation coefficient (tau) having units of inverse centimeters (cm.sup.-1). After a photon beam has traveled a distance "x" in a crystal, the proportion of photons that have not been stopped by the crystal is calculated as follows: EQU fraction of unstopped photons=e.sup.(-tau * x).
Thus, after traveling a distance of 1/tau (the "absorption length"), approximately 37% of the photons will not have been stopped; 63% will have been stopped. Likewise, 63% of the remaining photons will have been stopped after traveling an additional distance of 1/tau. For PET, one wants 1/tau to be as small as possible so that the photodetector is as compact as possible.
Light yield is also an important property of scintillators. Light yield is sometimes referred to as light output or relative scintillation output, and is typically expressed as the percentage of light output from a crystal exposed to a 511 keV photon beam relative to the light output from a crystal of thallium-doped sodium iodide, NaI(Tl), exposed to a 511 keV photon beam. Accordingly, the light yield for NaI(Tl) is defined as 100.
A third important property of scintillators is decay time. Scintillation decay time, sometimes referred to as the time constant or decay constant, is a measure of the duration of the light pulse emitted by a scintillator, and is typically expressed in units of nanoseconds (nsec). As noted above, in PET, the source of biological activity within an organ under investigation is determined by tracing the source of coincident photons emitted from the patient's body to the photodetectors. When two 511 keV photons are detected at the same time by a pair of photodetectors, the source of the photons is known to lie along the linear path connecting the two photodetectors. In general, only a fraction of the detected photons are in coincidence and thus used in the reconstruction analysis. Moreover, many false coincidences are registered because the finite decay time associated with each scintillator may cause it to emit light at the same time as another scintillator when in fact the photons inducing the light were slightly out of coincidence. For example, a photon arriving at one photodetector may produce a flash of light that does not decay (i.e., "turn off") until after a later photon, not in coincidence, produces a flash of light in a detector on the side opposite the first detector. In this instance, the flashes would overlap, and the photodetectors would register them as in coincidence. Thus, scintillator materials with long decay constants have an inherent problem in detecting coincident photons.
In addition to the problem of false coincidences, the positron emitting tracer compounds themselves typically have very short half-lives. In fact, most medical facilities performing PET also operate on-site accelerators to produce the short-lived radioactively labeled tracer compounds. Because of the short half-lives of these compounds, data on the occurrence of coincident photons needs to be gathered at as high a rate as possible. As noted above, the majority of the detected photons are not in coincidence, i.e.. they are from sources outside the plane of the detector array. Consequently, if a scintillator's decay constant is short, then more of its time will be available for the detection of coincident photons.
In addition to the three important properties discussed above, scintillator crystals for PET should be easy to handle. For example, certain known scintillators are very hygroscopic, i.e., they retain moisture, making it necessary to very tightly encapsulate them to allow their use as scintillators in PET. These hygroscopic scintillators are expensive and difficult to use.
Known scintillator materials include (1) plastic scintillators, (2) thallium-doped sodium iodide (NaI(Tl)), (3) cesium fluoride (CsF), (4) bismuth germanate (Bi.sub.4 Ge.sub.3 O.sub.12, also referred to as "BGO"), and (5) barium fluoride (BaF.sub.2). Of these five scintillators, only the latter two, BGO and BaF.sub.2, are used routinely for PET.
Plastic scintillators, typically composed of polystyrene doped with a wavelength-shifting additive, are commercially available under such trade names as PILOT U and NE 111. Upon excitation with a 511 keV photon, plastic scintillators emit a light pulse having a very fast decay constant of approximately 1.5 nsec and light output proportional to the energy of the incident photon. The main disadvantage of plastic scintillators is their low density (approximately 1.1 to 1.2 g/cm.sup.3) due to the light atoms (hydrogen and carbon) that make up the molecules of the material. Because of their low density, plastic scintillators have poor stopping power, and are therefore poorly suited for use in PET.
NaI(Tl), thallium-doped sodium iodide, has the best light output of the five scintillators listed above. NaI(Tl) also has reasonably good stopping power 1/tau=3.0 cm at 511 keV). However, NaI(Tl) has a long decay constant (250 nsec), a significant disadvantage for use in PET. NaI(Tl) has an additional disadvantage: it is highly hygroscopic, making it extremely difficult to handle in that it must be tightly encapsulated in bulky cans.
CsF, cesium fluoride, has an advantage over plastic scintillators because of its relatively high density (4.61 g/cm.sup.3) and consequent stopping power. However, the light output and decay constant of CsF are inferior to those of plastic scintillators. CsF is also highly hygroscopic, well above NaI(Tl) which, as noted above, makes it expensive and difficult to handle.
BGO has the highest density (7.13 g/cm.sup.3) of the five known scintillator materials listed above. Its stopping power is the best of the five materials (1/tau=1.1 cm at 511 keV). As a result, BGO is best able to absorb 511 keV photons efficiently in small crystals. However, BGO's very long delay constant (300 nsec), longer even than NaI(Tl), is a significant disadvantage for use in PET.
The use of BaF.sub.2 as a scintillator material is described in Allemand et al. U.S. Pat. No. 4,510,394. BaF.sub.2 emits light having two components: a slow component having a decay constant of approximately 620 nsec and a fast component having a decay constant of approximately 0.6 nsec. BaF.sub.2 has a light yield of approximately 16% that of NaI(Tl) and about half the stopping power of BGO 1/tau=2.3 cm at 511 keV). Unlike CsF and NaI(Tl), BaF.sub.2 is not hygroscopic.
The fast component of BaF.sub.2 emits light in the ultraviolet region of the spectrum. Glass photomultiplier tubes are rat transparent to ultraviolet light, so a quartz photomultiplier tube must instead be used to detect the fast component of BaF.sub.2. Since quartz photomultiplier tubes are substantially more expensive than glass, one would prefer to avoid using BaF.sub.2, if possible, in favor of using a scintillator that can be detected by a glass photomultiplier tube. The fast component gives BaF.sub.2 very good timing resolution, but the slow component limits its high rate capabilities. In other words, it takes longer for BaF.sub.2 to get ready for the next event.
Of the known scintillator materials, BGO has the best stopping power, NaI(Tl) has the best light yield, and BaF.sub.2 has the best timing resolution. However, as noted above, some of these materials have significant shortcomings which hinder their performance as scintillators for PET: BGO has a very long decay constant; NaI(Tl) also has a very long decay constant and is hygroscopic. Of these materials, BaF.sub.2 has the best balance of stopping power, light output and decay constant, and does not present a problem with hygroscopy. However, the slow component of BaF.sub.2 does limit its race capabilities.