FIELD OF THE INVENTION
The present invention relates to a method and apparatus for accelerated wear testing of aggressive diamonds on diamond conditioner discs in CMP and an apparatus for carrying out the same.
DESCRIPTION OF THE PRIOR ART
Diamond conditioner discs have been used in CMP processes to great effect to maintain the roughness of polyurethane polishing pads. These discs have been produced and marketed by several vendors to standards of reliable quality and effectiveness. Generally, diamond conditioner discs are evaluated based on, among other things, the total number of diamonds present on the surface of the disc and the number of diamonds remaining after certain specified periods of use or environmental testing. However, the effectiveness of the diamond conditioner disc actually depends not upon the total number of diamonds present on the surface of the disc but upon the number of active diamonds present.
Active diamonds are the diamonds that actually contact and abrade the surface of the CMP pad during CMP processing. The diamonds on more topographically prominent areas of the surface of the diamond conditioner disc and, where diamonds are collected together on the surface of the disc, diamonds that protrude further from the disc surface than others will, from a simple geometric standpoint, be more available to contact a surface such as that of a CMP pad brought into contact with the diamond conditioner disc.
The number of active diamonds present in any given situation depends upon the total number of diamonds on the diamond conditioner disc, their grouping, the surface characteristics of the diamond conditioner disc including the topography and the load on the diamond conditioner disc. Although simple microscopic examination of diamond conditioner disc sectors and estimation based on the geometric patterns of initial diamond placement and surface area have long provided a method to determine an approximate total number of diamonds on the surface of a diamond conditioner disc, to date there has been no simple, reliable, cost effective method to measure the number of active diamonds.
Among active diamonds are certain diamonds that by size, shape and position are significantly more active than other active diamonds and are referred to as aggressive diamonds. These diamonds are responsible for a significant and disproportionate portion of the cutting of the polyurethane CMP polishing disc and additionally are under the highest degree of stress and suffer the most rapid degradation from use. U.S. patent application Ser. No. 12/359,772, incorporated herein by reference, discloses a method for identifying and characterizing aggressive diamonds as distinct from regular active diamonds. The degradation of aggressive diamonds, far more than is true with other active diamonds, is responsible for the decline in performance of the diamond conditioner disc with use. The process by which these diamonds are lost or rendered less aggressive or even non-aggressive by dislocation or the like is called “pulling”. The process by which these diamonds are lost or rendered less aggressive or even non-aggressive by breakage of the diamond itself or the like is called “fracturing”.
The number of aggressive diamonds that are pulled or fractured and the conditions causing, surrounding or resulting from their being pulled or fractured are of considerable interest not only to diamond conditioner disc manufacturers but users as well.
Although it is certainly possible to simply use a diamond conditioner disc with a CMP polishing pad in CMP conditioning for as long as is necessary to observe wear on the aggressive diamonds and their eventual pulling and fracturing, and from time to time occasionally remove and check the diamond conditioner disc to observe the progress of the pulling and fracturing of aggressive diamonds using the method described in U.S. patent Ser. No. 12/359,722, such a test, though useful, would consume an inordinate amount of time and expensive resources. Unless the CMP polisher were dedicated solely to one type of operation as the diamond conditioner disc was tested, which would be extremely inconvenient for users of CMP polishers, or even were used simply for the purpose of testing the diamond conditioner disc under constant conditions, which in itself would also be a considerable expense, the justification for which would be difficult, there would be a considerable variation in test conditions over time due to operation under different CMP conditions. It is not realistic for most users to operate a CMP polishing device with its consumption of expensive pads, slurry and operator time, not to mention the fact that the CMP device cannot then be used in efficient CMP production. To date, no effective method or apparatus have been disclosed for accelerated wear testing of aggressive diamonds on diamond conditioner discs in CMP and manufacturers and users have been limited essentially to very occasional records of actual failure or decline in usefulness of the diamond conditioner disc to observe the wear of the diamond conditioner disc by pulling or fracturing of aggressive diamonds present on the diamond conditioner disc surface.
Users of diamond conditioner discs need to know that they are receiving the same quality of product from diamond conditioner disc manufacturers from the standpoint of process effectiveness on a consistent basis and such a test would allow users to better observe the pulling and fracturing of aggressive diamonds present on the diamond conditioner disc surface determine specifications for what they require. Users may also want to know how well their discs are faring under certain operating conditions and a reproducible and efficient method of determining the pulling and fracturing of aggressive diamonds on the diamond conditioner disc will provide them with useful information in that regard. Finally, from a research and development standpoint, the results of such a test would provide makers of diamond conditioner discs with more useful information about how to improve existing manufacturing processes for diamond conditioner discs or in the development of new CMP and related processes.
The inventors of the present invention sought to provide an accurate and efficient method and apparatus of accelerating the pulling and fracturing of diamond conditioner discs in CMP to provide users and manufacturers with the necessary information to improve the utilization of and modify and improve, where appropriate, the manufacture of diamond conditioner discs for CMP.
SUMMARY OF THE INVENTION
The inventors of the present invention have, after considerable and determined research into the problem of accomplishing reproducible and economically feasible accelerated wear of diamond conditioner discs for CMP, invented a method and apparatus for the accelerated pulling and fracturing of aggressive diamonds on a CMP diamond conditioner disc and determining the conditions of that pulling or fracturing wherein aggressive active diamonds of known position are pulled or fractured by contacting the diamond conditioner disc to a disc of a hard material or a disc containing discrete structures of hard material relative to which the diamond disc is moved at a determinable and reproducible rate for a determinable and reproducible period of time and the number and position of the pulled or fractured aggressive diamonds are determined following the completion of said contact. More particularly they discovered a method and apparatus for determining the number of diamonds that will be pulled from or fractured in a CMP diamond conditioner disc and determining the conditions of that pulling or fracturing wherein the hard material used in the disc is aluminum, the aluminum is placed in the matrix of the disc, the matrix of the disc is polyurethane and the disc contains hard material structures embedded securely in the surface of the disc, water is applied between the disc and the diamond conditioner disc at a flow of between 0 and 100 ml per minute, the diameter of the disc is not particularly limited but preferably is between 500 and 1000 mm, the disc is rotated at between 0 and 400 RPM and the diamond conditioner disc is rotated at between 0 and 150 RPM and oscillates at a rate of between 0 and 20 cycles per minute.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view from above of a disc with elongated hard material structures placed at even angular intervals around the disc.
FIG. 2 is a cross sectional view of three possible applications of the protruding or depressed hard material structures placed at even angular intervals around the disc.
FIG. 3 is a view from above of a disc with hard material studs placed at even angular intervals around the disc at an equal distance from the center of the disc.
FIG. 4 is a cross sectional view of the hard material studs placed at even angular intervals around the disc.
FIG. 5 is a view from above of a disc with hard material blades placed at even angular intervals around the disc.
FIG. 6 is a view from above of a polycarbonate disc with aluminum pegs or studs paced halfway between the center and the edge of the disc at evenly spaced positions around the center of the disc.
FIG. 7 is SEM microscopic views of aggressive diamonds from Example 1.
FIG. 8 is a view from above of an aluminum disc with radial depressed structures such as trenches or grooves placed at evenly spaced angles around the disc.
FIG. 9 is SEM microscopic views of aggressive diamonds from Example 2
Unless otherwise indicated, in the Figures, like numbers denote the same elements throughout the Figures.
DETAILED DESCRIPTION OF THE INVENTION
The inventors of the present invention have discovered and developed a method for accelerated pulling and fracturing of aggressive diamonds on a CMP diamond conditioner disc wherein aggressive diamonds of known position are pulled or fractured by contacting the diamond conditioner disc to a plate or sheet of a hard material or a plate or sheet containing discrete structures of hard material relative to which the diamond disc is in motion at a determinable and reproducible rate for a determinable and reproducible period of time and the number and position of the pulled or fractured aggressive diamonds are determined following the completion of said contact. They have further discovered and developed an apparatus for accelerated pulling and fracturing of aggressive diamonds on a CMP diamond conditioner disc wherein aggressive active diamonds of known position are pulled or fractured by comprising a plate or sheet of a hard material or a plate or sheet containing discrete structures of hard material relative to which the diamond conditioner disc is in motion at a determinable and reproducible rate for a determinable and reproducible period of time and the number and position of the pulled or fractured aggressive diamonds are determined following the completion of said contact.
The method and apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available methods and apparatus for accelerated wear testing of diamond conditioner discs. Thus, it is an overall objective of the present invention to provide a method and apparatus for accelerated wear testing of CMP diamond conditioner discs that remedy the shortcomings of the prior art. All dimensions for parts in the present invention follow are based on a diamond conditioner disc size of about 4″ in diameter and may be altered as needed in proportion to changes in the size of the discs used. The specific dimensions given herein are in no way limiting but are by way of example to demonstrate an effective embodiment of the invention.
The basic principle involved in diamond failure on diamond conditioner discs in CMP is that aggressive diamonds, to a far greater degree than mere active diamonds or inactive diamonds, are subjected to continuous and prolonged force, primarily in a lateral direction parallel to the face of the diamond conditioner disc as the diamond conditioner disc rotates and moves back and forth over the CMP polishing pad surface. Eventually the bond holding the diamond to the diamond conditioning disc surface, having endured this stress over a long period of time, or having endured periods of force of too great an intensity, gives way releasing the diamond from the surface, or in some cases the bond holds but diamond itself wears, that is to say, it fractures. In principle what then happens is that with the aggressive diamond in question no longer impacting the surface or at least no longer impacting it to the same degree, a few other diamonds, to some extent other aggressive diamonds but to a great extent mere active diamonds or formerly inactive diamonds, those that did not contact the polishing pad at all, are able in the absence of the aggressive diamond that has failed and been “pulled” to engage in greater contact with the polyurethane polishing pad. This does not inevitably result in a maintenance of cutting effectiveness however. As the initial aggressive diamonds are lost the diamonds that replace them can be more numerous and less aggressive resulting in a diminution of the cutting effectiveness of the diamond conditioner disc over time. It should be noted that in certain less frequent configurations of aggressive diamonds the loss of the leading one or two aggressive diamonds could render a sufficient number of previously active diamonds aggressive as to temporarily increase cutting rate. Determination of such effects and the extent to which they exist is another useful feature of the present invention. The exact timing that a diamond will fail is unpredictable and depends upon how well the diamond is bonded, how sound its crystalline structure is and the particular forces it is subjected to during operation.
Statistically, it is possible to understand that aggressive diamonds bonded to a diamond conditioner disc by a certain method and utilized under certain conditions can probably last an approximately determinable length of time or more properly that the disc can maintain cutting and abrasive effectiveness for the said approximately determinable length of time. One of the chief difficulties encountered in considering this problem is that to leave a diamond conditioner disc on a CMP polisher for the length of time necessary to see significant wear or pulling of diamonds from diamond conditioner discs and in addition to do so for the several discs invariably needed to obtain meaningful data would result in an enormous amount of expense, equipment time and labor and would greatly limit the productive use of any equipment dedicated to CMP.
The inventors of the present invention considered that if the diamonds could be subjected to the same or similar forces as those experienced by aggressive diamonds on diamond conditioner discs but coupled with a much sharper impact and at the same time much less resilience from the impacting material than is normally the case with the polyurethane CMP pad, the length of time needed to effect pulling and fracturing of the aggressive diamonds could be vastly reduced and with it the expense and inconvenience of carrying out the test. Although the environment of such a test would not be precisely the same as that of abrasion of a CMP pad operating under normal CMP conditions, from the standpoint of applying lateral stress on the diamond conditioner disc bond parallel to the surface of the diamond conditioner disc until the bond fails or placing lateral stress parallel to the surface of the diamond conditioner disc on the diamond itself until structural flaws in the diamond cause it to fracture, the processes are largely analogous and it can be expected that broadly diamonds that fail relatively quickly under one operation will likewise generally fail relatively quickly under the other and that the mechanisms of such failure, for example failure of the bond as opposed to the crystal itself, will be consistent as well.
One way of accomplishing this is to use a material of significantly greater hardness than the polyurethane material from which CMP polishing pads are made. In order to cut through this material, aggressive diamonds and the bonds holding them to the diamond conditioner disc will be subjected to much greater stress than under normal CMP conditions and this induces significantly more rapid aggressive diamond and aggressive diamond bond failure. Another way of significantly increasing stress on aggressive diamonds and the bonds holding them to the diamond conditioner disc is to create or add structures to the surface the aggressive diamonds are cutting through. This has the effect of subjecting the diamond to a sudden impact which is absent from the continuous cutting that occurs during CMP operation. This significantly increases momentary stress on aggressive diamonds and the bonds holding them to the diamond conditioner disc at the time of impact. If the structures are made from a material significantly harder than the polyurethane material from which CMP polishing pads are made then the benefits of both ways are combined for a much better effect. The material used to induce failure in the aggressive diamonds and their bonds need not be in the form of a CMP polishing pad although that is one desirable and convenient form that takes advantage of the use simplify of the CMP tool to testing.
The hard material of the present invention should be in the form of a sheet or plate although the form of the sheet or plate is not particularly limited and may be disc shaped such as when it is made to resemble a CMP polishing pad or it may be rectangular or any other shape convenient to the user and which allows movement either of the diamond conditioner disc on the sheet or plate or the sheet or plate on the diamond conditioner disc, however a disc having the shape and dimensions of a CMP polishing pad and equipped so that it may be attached to a CMP polishing tool in place of a CMP polishing pad is preferred.
In one embodiment of the present invention the material of the sheet or pad is composed homogeneously of the hard material and this material is not particularly limited but may consist of any material harder than the polyurethane material used in the construction of CMP polishing pads, that is to say any material having a yield strength of greater than 75 MPa. The plate or sheet may also be composed of a composite of more than one material. One material may be significantly harder than the other. The size, relative distribution, shape and surface characteristics of the harder material embedded in the softer matrix material are not particularly limited and anything from a fine grain or grit embedded in the softer matrix material at anything from 5% to 100% composition is permitted. Larger grains or bodies may be used and the size of such grains or bodies may vary without limitation within a single embodiment. The manner of combining the materials is not limited but they may be mixed either evenly or heterogeneously, one or more materials may provide the matrix for other materials, the materials may be layered including coatings and dustings or scattering on the surface of one or more materials by one or more other harder materials, the materials may be combined as discrete structures placed in a matrix of other material, or different materials may be combined as discreet structures, such as, without limitation, bands, rectangles or concentric circles, together constituting the sheet or plate or any combination of any of these. Variation of the concentration or dispersion of one material in or on another material is also permitted and the variation may be random or patterned. The methods by which the materials may be combined are not limited by include by way of example polymerization of the matrix with hard materials as filler, copolymerization of a material containing the hard material or in which the hard material is suspended with the other material to form a polymeric alloy, mixing and pressing or melt pressing the material or materials into the desired plate or sheet form or melting, thermoset polymerization, curing and casting, rolling or by injection molding thereby creating the desired sheet or plate form.
The materials that may be used in the present invention are not particularly limited and for materials that are not hard materials any material suitable to withstand the application of the diamond conditioner disc for a reasonable period of time may be used and ceramics and plastics are preferred and plastics are more preferred and polyurethane, acrylic plastics or polycarbonates are even more preferred.
The hard materials of the present invention are not particularly limited but hard malleable materials are preferred, metals are more preferred, and these, though they are not particularly limited, include steel and aluminum. It is also possible to use less or non-malleable materials such as ceramics or crystalline materials but given the hardness of diamonds, malleable materials such as metals are more effective and are preferred. These materials when used as discrete structures with other materials may be plated coated or covered by yet other materials or treated by such methods and processes annealing, tempering, quenching, case hardening, anodizing or the like to enhance or modify their hardness.
When a simple sheet or plate of hard material is used without any discrete structures to serve as impact points the sheet or plate may, without limitation, either be a composite of harder and soft materials as described above or it may be entirely made of a hard material and such sheets or plates made entirely of a hard material are preferred and sheets and plates made entirely of aluminum or steel are more preferred.
In composite sheets or plates, as long as the hard materials are present at the surface that impacts the aggressive diamonds to be pulled or fractured by the present invention, it is not necessary that they be present throughout the entire thickness of the sheet or plate although for ease of manufacture and long wear purposes they may alternatively so be present. One method of preparing a sheet or plate with hard materials only near the surface is to place the hard material either in patterned, regular or random distribution as desired on a sheet of polymer or other matrix material and apply a thermosetting polymer to embed and hold them to the base sheet. The concentration of these hard material bodies in the lateral directions, the directions in which the diamond conditioner disc or the plate or sheet will move during practice of the present invention, need not be homogenous and the concentration of hard materials may vary from zones of heavier or lower concentrations and even to bands or regions of no embedded hard material as opposed to bands or regions of high concentration embedding of hard materials. These zones may be banded, round, have geometric shape, be of regular or irregular shape and size or may be of varying width at the surface of the sheet or plate. The hard material may be completely embedded or it may protrude slightly from the other material and if it protrudes, protrusions possessing heights of between 0 and ⅛th inch are preferred.
Where a hard material is embedded within and near or at the surface of a plate or sheet, regardless of whether other larger discrete hard material structures are present or not, the said embedded hard material is not particularly limited and steel, aluminum, ceramics, glass, quartz, corundum, diamond and other hard abrasives may be used. The shapes of these embedded hard materials may be, without limitation, spherical, cylindrical or otherwise geometric or amorphous and they may have a rough or smooth surface. The dimensions of these hard material bodies are not particularly limited provided they are not so large that they protrude more than ⅛th inch from the surface of the sheet or plate or so small that they possess negligible tribological effect compared with the matrix material.
The dimensions of the sheet are not particularly limited provided, however, that if the sheet is less than about a half inch in diameter, it is too small to be used effectively in the present invention given the general use of 4 inch diameter diamond conditioner discs in CMP processes. The sheet should not be larger than necessary to accomplish the objectives of the present invention and sheets or plates smaller than two and a half feet or so in the smallest lateral dimension are preferred. The shape of the sheet or plate is not particularly limited and rectangular or square shapes, circular discs, ovals or polygonal shapes are all preferred and circular discs are more preferred. Thickness of the sheet or plate is not particularly limited and depends upon the precise application of the method of the present invention and also on the hard materials used and, if applicable, the matrix material of the plate or sheet of the present invention. However, the sheet should not be so thin that the stress of carrying out the test deforms or destroys the sheet and a thickness of at least 1/32th inch for steel or aluminum plate is preferred and a larger thickness may be preferred for other materials. Additionally if it is intended that the sheet or plate rest either on top of a CMP polishing pad or on a platen in a CMP polishing pad of a CMP polishing tool, then the thickness should be appropriate to obtain overall contact with the diamond conditioner disc when it is attached to the CMP tool for the test.
The surface of the sheet or plate may be smooth or rough and a rough surface is preferred. The degree of roughness of the surface is not particularly limited and particularly where there are discrete structures of hard material protruding from the surface of the sheet or plate a high degree of roughness is not required or particularly desirable, but, particularly where such structures are not employed, sheet or plate surfaces with an Ra per inch of more than 100 are preferred.
When hard material structures are added or attached to or embedded in the sheet, these structures may, without limitation, be composed of any of the hard materials described above and steel and aluminum are preferred. The kind of hard structures that may be used in the present invention are not particularly limited but pegs, raised areas, bolts, brushes, bumps, blades, rods, ridges, wires, trenches holes and steps may all be used. Raised areas, steps, trenches, ridges, brushes and blades may be straight, curved or jagged and straight sided features are preferred. Their placement may be random or patterned and patterned placements that optimize impact when in contact with the diamond conditioner disc are preferred. The distance above the sheet or plate by which these features may protrude is not particularly limited but protrusions of between 0 and ⅛th inch are preferred. The features such as trenches and holes which are fashioned into the sheet or plate material are not particularly limited in depth but should not be so deep or such other dimensions that the plate or sheet is unable to maintain structural integrity during testing.
To accomplish the objective of the present invention, the diamond conditioner disc has to be moved over the plate or sheet in a reproducible manner at a sufficient velocity and with sufficient force holding the plate or sheet together with the diamond conditioner disc that diamonds are pulled or fractured at a rate far in excess of that observed with normal CMP processes. However, since the accelerated pulling or fracturing of diamonds is accomplished primarily through contact with the hard material, and in particular in those embodiments employing them, by impact on the hard material or other impact structures or features of the present invention such as trench or hole walls, the velocity need not be substantially different from the relative velocity during CMP polishing and though not limited is preferably between 0 and 10 feet per second and more preferably between 0 and 5 feet per second in any direction. The diamond conditioning pad may be moved against the sheet or plate or the sheet or plate may be moved against the diamond conditioner disc. The motion may be linear or curved or it may follow a random or complex pattern. The pattern of movement may be repetitive, back and forth or circular or ovoid in pattern and either the sheet or plate or the diamond conditioner disc or both may rotate.
The means of moving the sheet or plate against the diamond conditioner disc are not limited but a motor driven apparatus may be used. A motor or other motion means that oscillates the sheet or plate or the diamond conditioner disc back and forth or along any desired course across the surface of the other may be used. If the sheet or plate is in the form of a disc having the shape of or resting on the polishing pad of a CMP tool, the means of moving the sheet or plate and the diamond conditioning disc may be the motor for the rotation of the CMP polishing pad for the disc and the apparatus for rotating and oscillating the diamond conditioner disc for the diamond conditioner disc and this is the preferred method of inducing motion between the plate or sheet, in this case a disc is preferred, and the diamond conditioner disc in the best embodiment of the present invention. Generally, in the present invention and particularly in the embodiment where the plate or sheet comprises a disc attached to the platen of a CMP tool, fluid may be applied to approximate better the conditions of CMP operation and to maintain a certain degree of lubrication and temperature control. Any fluid suitable for this purpose may be used such as various oils, CMP slurrys or water and water is preferred. The amount of water applied is not particularly limited and should be suited to the particular application but in the embodiment where the sheet or plate is a disc attaché to a CMP platen the rate of water flow, though not particularly limited is between 0 and 100 ml per minute.
The amount of force maintained on the sheet or plate and the diamond conditioner disc during the method of the present invention is not particularly limited and preferably is between 0 and 20 lbs. This may be maintained by hydraulic or mechanical pressure evenly supported from behind the two surfaces or where either the diamond conditioner disc or the sheet or plate are one above the other weights may be used. In the preferred embodiment of the present invention where a disc is plated on the platen of a CMP tool, and the diamond conditioner disc is placed in the operating configuration for the said CMP tool, the load on the diamond conditioner disc may be controlled by adjusting the load on the apparatus controlling the disc.
The length of time required to pull or fracture the diamonds in the diamond conditioner disc is not specifically limited. However, even one or two minutes of operation under suitably selected conditions using the method of the present invention are equivalent in terms of pulling and fracturing aggressive diamonds on the diamond conditioner disc of tens of hours of operation with a CMP polishing pad. The length of time required for the test should not be particularly limited but between 30 seconds and 60 minutes are preferred.
The methods of determining which diamonds are aggressive and observing at intervals whether aggressive diamonds have been pulled or fractured is not particularly limited and any method may be used. However, the method described by U.S. patent application Ser. No. 12/359,772 is preferred and specifically a long pull profilometry followed by scanning electron microscope (SEM) or optical microscopic observation is more preferred. A diamond that has been pulled can easily be distinguished in the scanning electron microscope (SEM) or optical microscopy test simply by its absence and a disturbed site or small depression where it was. A fractured diamond is noticeably smaller and may be of different shape than it was before when observed at later intervals by scanning electron microscope or optical microscope.
Therefore, the overall method of the present invention may be described in other words as subjecting diamond conditioner discs to tribological contact and relative motion with the above described sheet or plate under load for a suitable length of time and locating aggressive diamonds and observing the effect on them from time to time by examination using scanning electron microscope (SEM) or optical microscope and other technologies where required in accordance with the methods of U.S. patent app Ser. No. 12/359,772 and the apparatus of the present invention may be seen as the sheet or plate plus any devices used to bring the surfaces of the sheet or plate into contact with the surface of the diamond conditioner disc, induce tribological motion and apply load to the surface.
The forms that the present invention may take are not limited so long as the essential features are applied in a way suitable to achieve the desired results. Specifically, a sheet or plate as described hereinabove must be present together with a means of moving the sheet or plate relative to the diamond conditioner disc and additionally a means of holding the diamond conditioner disc to the said sheet or plate as it moves an preferably a means of monitoring and controlling such motion. However, it should be clear that the preferred embodiment employs a sheet or plate as described above in the form of a disc essentially the size or slightly smaller as the case may be than a CMP polishing pad in a form that may be attached to a CMP polisher by placing it on or in place of the platen, securing it and then operating the CMP polishing tool in the manner of a CMP operational run. It should be clear that the apparatus of the present invention in this case comprises the said disc and the CMP polisher which in combination supply all of the required parts of the apparatus of the present invention.
In this embodiment, referring to FIG. 1, either an essentially flat disc (2) of uniform or composite hard material as described above may be used or a disc with structures (4) of hard material or depressed structures fashioned within it as described above may be employed and the latter is preferred. Where a disc with structures is used these structures may either be trenches (6) or holes in the disc surface comprise of the same material as the disc itself, whether or not the disc is hard material or with surface enhancement or may comprise pegs, raised areas, bolts, brushes, bumps, ridges, blades, or wires or hard material, attached, affixed or embedded in and protruding slightly from the disc as described above. A variation on this embodiment shown in FIGS. 3 and 4 involves the placement of pegs or studs (10) in holes (12) the disc (2) created drilling and secured by adhesive or other suitable means and placing them so that they protrude (14) up to ⅛th inch from the surface of the disc (2). A third form of this embodiment involves blades (16) set in a radial pattern in cuts made in the disc (2) by a cutting tool and secured with adhesive or other suitable means at approximately equal angles to each other. As may be seen from FIG. 2, the surface features may consist of purely protruding structures, (4) depressed structures (6) such as holes or grooves or trenches or both used on the same disc (2). As the operation speed of the apparatus, though this is not limited except by the limitations of the CMP polisher in this embodiment, the normal operational speed of the CMP tool may be used and an RPM of between 0 and 400 is preferred. The diamond conditioner disc may be left stationary, may be made to rotate, may be made to oscillate or may be made to rotate and oscillate within the parameters of the CMP tool and motion equivalent to the motion of the diamond conditioner disc during CMP operation may be employed. Rotation of the diamond conditioner disc between 0 and 150 RPM is preferred and oscillation at between 0 and 20 cycles per minute is preferred. Furthermore, the load or range of loads on the diamond conditioner disc normally employed in CMP polishing may be employed and loads of between 0 and 20 lbs are preferred.
Of the raised structures any suitable raised structure permitted under the present invention may be used but blades, brushes, ridges and pegs are preferred. These together with trenches may be located in any arrangement on the surface of the dish but for blades, brushes, and ridges a radial configuration starting from the center of the disc and going to the edges is preferred and though without limitation an equiangular configuration of these such radial features is preferred. The number of such features is not limited but between 2 to 4 features on the disc is preferred. In the case of pegs, bumps or holes, these can be provided on the disc surface in regular patterns, radial patters or at random and radial patterns with equiangular configurations are preferred. The number of such features is not limited but between 2 and 100 such features are preferred and between 2 and 12 such features are more preferred. These features may be all of one type on any one disc or they may be combined with one another in any combination. The dimensions of the features are not particularly limited but a depth of 0 to ⅛th inch is preferred and a width of 0 to ½ inch is preferred. The length can be any fraction of the length of the radius of the disc if they are radial or longer if they are curved or jagged.
These discs may be prepared by tooling features such as holes, trenches or steps into the surface of a sheet of metal, polycarbonate or polyurethane or the like that has been cut to the size of a CMP platen. In the case of pegs where a plastic disc is used holes may be drilled into the plastic sheet and the pegs bolted or fixed by adhesive and in the case of metal sheets riveted, bolted or welded or tightly fitted and hammered into holes drilled or punched in suitable dimensions for that purpose. In the case of longer features such as blades, brushes, and ridges a trench may be fashioned in the surface of the disc and the feature attached by the methods described above for pegs or studs.
The practice of the present invention is demonstrated without being limited by reference to the following practice examples:
An aluminum disc 550 mm in diameter and ⅛th inch thick was prepared from aluminum sheet by cutting and in the upper surface of the disc 4 grooves were cut ¼ inches wide and 150 mm long starting 50 mm from the center of the disc and heading out radially at right angles to each other to end 75 mm short of the edge of the disc. The grooves were cut with a cutting tool to a depth of 1/16th inch.
The disc was attached, grooves facing up, to the top of the platen of an APD 500 polishing tool using adhesive paper. The top ten aggressive diamonds determined by scratch furrow area as measured by profilometer on a Mitsubishi Materials Corporation Triple Ring Dot diamond conditioner disc (MMCTRD) were identified using the method of U.S. patent application Ser. No. 12/359,772 and observed by scanning electron microscope as shown in the before column in FIG. 7. The diamond conditioner disc was attached to the CMP tool which was then operated with the platen rotating at 50 RPM, the diamond conditioner disc rotating at 30 RPM and oscillating 10 times per minute with a down force of 6 lb for 15 minutes.
Photographs were again taken by scanning electron microscope and the results are included in FIG. 7 the after column. Three aggressive diamonds were observed to have been pulled cleanly from their bonds with the diamond conditioner disc and no aggressive diamonds from this sample were observed to have experienced significant fracturing.
A polycarbonate disc made from polycarbonate sheet and having the same dimensions as the aluminum plate in Example 1 was prepared and 4 holes halfway between the center and edge of the disc on lines at ninety degree intervals were drilled at ⅙th inch diameter as shown in FIG. 8. The depth of the holes was 3/32nds inch, the length of the studs, which were aluminum, was ⅛ inch, the studs were made fast with adhesive and allowed to protrude 1/32nd of an inch above the surface of the disc.
Except for the use of this disc, precisely the same procedure was used as in Example 1 and before and after scanning electron microscope photographs of the top ten aggressive diamonds in FIG. 9 shows 3 pulled and 4 fractured aggressive diamonds when observed by scanning electron microscope.
DETAILED DESCRIPTION OF THE DRAWINGS
In FIG. 1, 2 is the disc.
- 4 is a hard material structure,
- 6 is a trench or groove,
- 10 are pegs or studs
- 12 is the hole for pegs or studs.
- 14 is the peg's or stud's protrusion
- 16 is a blade.