Patent Application
20090311955
In general, the designs and methods described herein are in the field of polishing pads for chemical mechanical planarization or chemical mechanical polishing (“CMP”). More particularly, the designs and methods described herein are related to novel groove configurations and in-situ grooves for CMP pads.
In general, CMP is used to planarize individual layers (e.g., dielectric or metal layers) during integrated circuit (“IC”) fabrication on a semiconductor wafer. CMP removes undesirable topographical features of the IC on the wafer. For example, CMP removes metal deposits subsequent to damascene processes, and excess oxide from shallow trench isolation steps. Similarly, CMP may also be used to planarize inter-metal dielectrics (“IMD”), or devices with complex architecture, such as system-on-a-chip (“SoC”) designs and vertical gate structures (e.g., FinFET) with varying pattern density.
CMP utilizes a reactive liquid medium, commonly referred to as a slurry, and a polishing pad to provide chemical and mechanical control to achieve planarity. Either the liquid or the polishing pad may contain nano-size inorganic particles to enhance chemical reactivity and/or mechanical activity of the CMP process. The pad is typically made of a rigid, micro-porous polyurethane or poly (urethane-urea) material capable of performing several functions including slurry transport, distribution of applied pressure across a wafer, and removal of reacted products. During CMP, the chemical interaction of the slurry forms a chemically modified layer at the polishing surface. Simultaneously, the abrasives in the slurry mechanically interact with the chemically modified layer, resulting in material removal. The material removal rate in a CMP process is related to slurry abrasive concentration and the average coefficient of friction (f) in the pad/slurry/wafer interfacial region. The extent of normal forces, shear forces, and the average coefficient of friction during CMP typically depends on pad tribology. Recent studies indicate that pad material compliance, pad contact area, and the extent of lubricity of the system play roles during CMP processes. See, for example, A. Philiposian and S. Olsen, Jpn. J. Appl. Phys., vol. 42, pp 6371-63791; Chemical-Mechanical Planarization of Semiconductors, M. R. Oliver (Ed.), Springer Series in Material Science, vol. 69, 2004; and S. Olsen, M. S. Thesis, University of Arizona, Tucson, Ariz., 2002.
An effective CMP process not only provides a high polishing rate, but also a finished (e.g., lacking small-scale roughness) and flat (e.g., lacking in large-scale topography) substrate surface. The polishing rate, finish, and flatness are thought to be governed by the pad and slurry combination, pad/wafer relative velocity, and the applied normal force pressing the substrate against the pad.
Two commonly occurring CMP non-uniformities are edge effects and center slow effects. Edge effects occur when the substrate edge and substrate center are polished at different rates. Center slow effects occur when there is under-polishing at the center of the substrate. These non-uniform polishing effects reduce overall flatness.
Another commonly observed problem relates to slurry transport and distribution. In the past, polishing pads had perforations. These perforations, when filled, distributed slurry when the pad was compressed. See, for example, J. Levert et al., Proc. Of the International Tribology Conf, Yokohoma, 1995. This method was ineffective because there was no way to directly channel the excess slurry to where it was most needed (i.e., at the wafer surface). Currently, macro-texturing of pads is typically done through ex-situ pad surface groove design. See, for example, U.S. Pat. Nos. 5,842,910; 5,921,855; 5,690,540; and T. K. Doy et al., J. of Electrochem. Soc., vol. 151, no. 3, G196-G199, 2004. Such designs include circular grooves (e.g., concentric grooves referred to as “K-grooves”) and cross-hatched patterns (e.g., X-Y, hexagons, triangles, etc.). The groove profile may also be rectangular with “V-,” “U-,” or saw-tooth shaped cross sections.
Novel groove configurations for CMP pads and methods for producing in-situ grooves in CMP pads are described.
Generally, CMP pads are described as having groove configurations comprising primary grooves and secondary grooves, wherein said primary grooves are radial in nature and said secondary grooves transect sectors as defined, in part, by the primary grooves. In addition to these primary features, the CMP pads further comprise an optional terminal groove, which, in some instances, is coincident with the outermost secondary groove, and a groove pattern center that is optionally coincident with the CMP pad center. The CMP pads described herein may be circular CMP pads or they may be constructed as CMP belts. Groove configurations described for circular CMP pads can be easily translated to CMP belts as described in further detail below. The CMP pads may be made from polyurethane or poly (urethane-urea), and the grooves produced therein may be made by a method from the group consisting of molding (e.g., compression, vacuum molding, etc.), laser writing, water jet cutting, 3-D printing, thermoforming, vacuum forming, micro-contact printing, hot stamping, and mixtures thereof.
In general, the methods for producing in-situ grooves comprise the steps of patterning a mold, adding CMP pad material to the mold, and allowing the CMP pad to solidify. In some variations, the mold is made from a silicone elastomer or a metal such as aluminum.
In some variations, the mold is metallic. For example, the mold may be made from a material selected from the group consisting of aluminum, steel, ultramold material, and mixtures thereof. In some variations, the mold is patterned, in addition to the patterning of the silicone lining (i.e., a combination of patterning is used). In some variations, the CMP pad material comprises a thermoplastic material. In other variations, the CMP pad material comprises a thermoset material. In some variations, the CMP pad material is polyurethane or poly (urethane-urea).
Described herein are pads having novel groove designs and methods for in-situ CMP grooving. Grooves in CMP pads are thought to prevent hydroplaning of the wafer being polished across the surface of the pad; to help provide distribution of the slurry across the pad surface; to help ensure that sufficient slurry reaches the interior of the wafer; to help control localized stiffness and compliance of the pad in order to control polishing uniformity and minimize edge effects; and to provide channels for the removal of polishing debris from the pad surface in order to reduce defectivity.
The CMP pads described herein have novel groove configurations comprising primary (“primary”) grooves and secondary (“secondary”) grooves. In addition to these features, the CMP pads further comprise an optional terminal groove, which, in some embodiments, is coincident with the outermost secondary groove. In other embodiments, the terminal groove is not a secondary groove. For instance, the terminal groove may be circular groove encompassing the entire groove pattern and sharing the same center as the CMP pad. The CMP pads, as described in further detail below, may also have a groove pattern center that is coincident with the CMP pad center. In some embodiments, the groove pattern center is off-center in relation to the CMP pad center. The pads described herein are described in the context of circular pads; however, the invention is not limited to circular pads. As it is known in the art, CMP pads can also be constructed as belts. As such, the center of a circular CMP pad (a point) is also a reference to the center of a CMP belt (a lengthwise line). The outer edge of a circular CMP pad is also a reference to the edge (or edges) of a CMP belt. If a primary groove is described as radiating from the center of a circular CMP pad to the outer edge of said circular pad, then that primary groove also extends from the center of a CMP belt to the edge of said CMP belt. If a secondary groove is described as transecting a sector of a circular CMP pad defined by adjacent primary grooves and the outer edge of said circular pad, then that secondary groove also transects sections of a CMP belt defined by adjacent primary grooves, the center of said belt, and the edge of said belt.
The primary grooves are typically radial and may extend from, for example, the center of the CMP pad or some point near the center of said pad. In some embodiments, the intersection of the primary grooves (“groove pattern center”) coincides with the center of the CMP pad. In some embodiments, the intersection of the primary grooves does not coincide with the center of the CMP pad; i.e., the groove pattern center is off-center. Still, in other embodiments, whether on-center or off-center, the primary grooves do not intersect at all. In these embodiments, the projected intersection of the primary grooves is void of grooves or comprises an alternate groove configuration. The primary grooves terminate at, for example, the outer edge of the CMP pad or just before the outer edge of said pad. In some embodiments, the above-mentioned terminal groove is absent and the primary grooves terminate at the edge of the CMP pad. If the primary grooves terminate before the outer edge of the CMP pad, said primary grooves terminate in a terminal groove, which is, optionally the outermost secondary groove (or grooves). When the terminal groove is not the outermost secondary groove (or grooves), said terminal groove may be, for example, a circular groove having the same center as the groove pattern center, which may or may not be coincident with the center of the CMP pad. In some embodiments, the center of the terminal groove is the axis of rotation of the CMP pad and the primary grooves terminate off-center.
The secondary grooves typically transect sectors bounded, in part, by primary grooves. As follows, different groove configurations further describe said sectors. In general, a CMP pad “sector” is analogous to the pie- or wedge-shaped section of a circle enclosed by two radii and an arc; however, the exact shape of a CMP pad sector depends on elements such as the primary grooves, the groove pattern center (i.e., the point or projected point at which the primary grooves intersect), the terminal groove, and/or CMP pad edge. In a non-limiting example, the intersection of linear primary grooves and segments of the CMP pad circumference create pie-shaped CMP pad sectors. In another non-limiting example, CMP pad sectors are created from segments of the CMP pad circumference and the intersection of primary grooves that are linear toward the CMP pad center and logarithmic toward the CMP pad edge. In yet another non-limiting example, the intersection of sinusoidal primary grooves and segments of the terminal groove create CMP pad sectors.
Primary, secondary, and terminal grooves may be straight, curved, or in any combinations thereof. Curved grooves include, but are not limited to, logarithmic, sinusoidal, and non-sinusoidal grooves. Sinusoidal grooves may be based on simple waveforms or more complex waveforms (e.g., damped waves, waves resulting from superposition, etc.). Likewise, non-sinusoidal grooves may be based on simple waveforms of more complex waveforms. Examples of non-sinusoidal waveforms include, but are not limited to, square waves, triangle waves, sawtooth waves. Non-sinusoidal grooves are not necessarily based on periodic waveforms; however, grooves that are based on periodic waveforms (sinusoidal or non-sinusoidal) may have any period or fraction or multiple thereof. Combination grooves may include, for instance, primary grooves that are linear at an inner portion of the CMP pad and sinusoidal or logarithmic at an outer portion of the CMP pad.
Primary, secondary, and terminal grooves may be from about 4 to about 100 mils deep at any given point on said grooves. In some embodiments, the grooves are about 10 to about 50 mils deep at any given point on said grooves. The grooves may be of uniform depth, variable depth, or any combinations thereof. In some embodiments, the grooves are all of uniform depth. For example, the primary grooves and secondary grooves may all have the same depth. In some embodiments, the primary grooves may have a certain uniform depth and the secondary grooves may have a different uniform depth. For example, the primary grooves may be uniformly deeper than the secondary grooves. In another example, the primary grooves may be uniformly shallower than the secondary grooves. In some embodiments, groove depth increases with increasing distance from the center of the CMP pad. In some embodiments, groove depth decreases with increasing distance from the center of the CMP pad. In some embodiments, the depth of the primary grooves varies with increasing distance from the center of the CMP pad while the depth of the secondary grooves remains uniform. In some embodiments, the depth of the secondary grooves varies with increasing distance from the center of the CMP pad while the depth of the primary grooves remains uniform. In some embodiments, grooves of uniform depth alternate with grooves of variable depth. In a non-limiting example, primary grooves of uniform depth may alternate with primary grooves of variable depth, while secondary grooves are of uniform depth.
Primary, secondary, and terminal grooves may be from about 2 to about 100 mils wide at any given point on said grooves. In some embodiments, the grooves are about 15 to about 50 mils wide at any given point on said grooves. The grooves may be of uniform width, variable width, or any combinations thereof. In some embodiments, the grooves are all of uniform width. For example, the primary grooves and secondary grooves may all have the same width. In some embodiments, the primary grooves may have a certain uniform width and the secondary grooves may have a different uniform width. For example, the primary grooves may be uniformly wider than the secondary grooves. In another example, the primary grooves may be uniformly narrower than the secondary grooves. In some embodiments, groove width increases with increasing distance from the center of the CMP pad. In some embodiments, groove width decreases with increasing distance from the center of the CMP pad. In some embodiments, the width of the primary grooves varies with increasing distance from the center of the CMP pad while the width of the secondary grooves remains uniform. In some embodiments, the width of the secondary grooves varies with increasing distance from the center of the CMP pad while the width of the primary grooves remains uniform. In some embodiments, grooves of uniform width alternate with grooves of variable width. In a non-limiting example, primary grooves of uniform width may alternate with primary grooves of variable width, while secondary grooves are of uniform width.
In accordance with the previously described depth and width dimensions, primary, secondary, and terminal grooves may be of uniform volume, variable volume, or any combinations thereof. In some embodiments, the grooves are all of uniform volume. For example, the primary grooves and secondary grooves may all have the same volume. In some embodiments, the primary grooves may have a certain uniform volume and the secondary grooves may have a different uniform volume. For example, the primary grooves may be uniformly more voluminous than the secondary grooves. In another example, the primary grooves may be uniformly less voluminous than the secondary grooves. In some embodiments, groove volume increases with increasing distance from the center of the CMP pad. In some embodiments, groove volume decreases with increasing distance from the center of the CMP pad. In some embodiments, the volume of the primary grooves varies with increasing distance from the center of the CMP pad while the volume of the secondary grooves remains uniform. In some embodiments, the volume of the secondary grooves varies with increasing distance from the center of the CMP pad while the volume of the primary grooves remains uniform. In some embodiments, grooves of uniform volume alternate with grooves of variable volume. In a non-limiting example, primary grooves of uniform volume may alternate with primary grooves of variable volume, while secondary grooves are of uniform volume.
Secondary grooves may have a pitch from about 30 to about 1000 mils. In some embodiments, the grooves have a pitch of about 125 mils. For a circular CMP pad, secondary groove pitch is measured along the radius of a circular CMP pad. In CMP belts, secondary groove pitch is measured from the center of the CMP belt to an edge of the CMP belt. The grooves may be of uniform pitch, variable pitch, or in any combinations thereof. In some embodiments, the grooves are all of uniform pitch. In some embodiments, groove pitch increases with increasing distance from the center of the CMP pad. In some embodiments, groove pitch decreases with increasing distance from the center of the CMP pad. In some embodiments, the pitch of the secondary grooves in one sector varies with increasing distance from the center of the CMP pad while the pitch of the secondary grooves in an adjacent sector remains uniform. In some embodiments, the pitch of the secondary grooves in one sector increases with increasing distance from the center of the CMP pad while the pitch of the secondary grooves in an adjacent sector increases at a different rate. In some embodiments, the pitch of the secondary grooves in one sector increases with increasing distance from the center of the CMP pad while the pitch of the secondary grooves in an adjacent sector decreases with increasing distance from the center of the CMP pad. In some embodiments, grooves of uniform pitch alternate with grooves of variable pitch. In a non-limiting example, the primary grooves may be linear near the CMP pad center and logarithmic toward the CMP pad edge. As such, the pitch of the secondary grooves may be uniform over the linear portion of the primary grooves and variable (e.g., decreasing) over the logarithmic portion of the primary grooves. In some embodiments, sectors of secondary grooves of uniform pitch may alternate with sectors of secondary grooves of variable pitch.
Grooves, of any sort (e.g., primary grooves, secondary grooves, terminal grooves, etc.), may be flared. From an alternative viewpoint, flared grooves may, in some instances, be interpreted as beveled or chamfered plateau regions. Grooves may be flared at any angle necessary to affect desired slurry flow, turbulence, removal rate, selectivity, and the like. Grooves may be flared along their length or just a portion thereof. In a non-limiting example, plateau region termini may be beveled or chamfered (as described below) while the remainder of the plateau region is not beveled or chamfered. In some embodiments, all grooves are flared. In a non-limiting example, both primary grooves and secondary grooves are flared, but the primary grooves are flared to a greater degree than that of the secondary grooves. In some embodiments, some grooves may be flared while adjacent grooves are not. In a non-limiting example, every other secondary groove is flared. In some instances, only primary grooves are flared. In some instances, only secondary grooves are flared.
Junctions are formed at the intersection of primary and secondary grooves. A 4-way junction occurs when two secondary grooves from adjacent sectors meet on a primary groove. If 4-way junctions occur along the length of primary groove, adjacent sectors are said to be “on-set” or “matched.” Analogously, a 3-way junction occurs when two secondary grooves from adjacent sectors do not meet on a primary groove. If 3-way junctions occur along the length of a primary groove, adjacent sectors are said to be “off-set” or “mismatched.” In some embodiments, some secondary grooves in a particular sector are matched with secondary grooves from an adjacent sector while other secondary grooves are mismatched. Still, in other embodiments, adjacent sectors are paired such that they match each other but are off-set when compared to an adjacent pair of sectors. The plateau regions between grooves may have unique features at junctions. In some embodiments, the plateau region termini at a junction are curved or rounded. In some embodiments, the plateau region termini at a junction are beveled or chamfered. In some embodiments, plateau region termini feature a combination of, for example, rounding and beveling. A plateau region terminus may be tailored independently of the other plateau region termini in a junction to facilitate slurry flow and transport of debris across the pad. In addition, a plateau region terminus may be adjusted to fit with the needs of the process (e.g., defects, polish rates, selectivity, and uniformity requirements, etc.).
Some areas of the CMP pad may need more slurry to be available for altering removal rates. Dam intermediates or dams may be placed in primary grooves, secondary grooves, in a terminal groove, or in any other pad location or combination of pad locations in which enhanced slurry collection is desired. Dams with random or calculated breaks may also be used to affect slurry collection in specific pad locations. In some embodiments, dams are used in every other primary groove. In some embodiments, dams are used in every other secondary groove within a sector.
The CMP pads described herein may further comprise a window for CMP systems that use optical endpoint determination. The location of the endpoint determination region or window may lie along a primary groove. Window placement along a primary groove allows for continuous slurry flow and slurry refreshment in the endpoint determination region or window. This minimizes slurry buildup and thus minimizes defect generation due to the presence of the window. The nature (e.g., depth, width, pitch, and/or other dimensions) of the grooves proximate to the window may be similar or different than the rest of the grooves in the region depending on the manner in which the window affects slurry flow. Grooves proximate to the window, for example, may be wider or shallower if those dimensions or a combination thereof facilitates slurry into and out of the endpoint determination region.
The CMP pads, in addition to any of the novel groove configurations described herein, may further comprise features such as macro-pores, macro-voids, reservoirs, dimples, studs, or islands, or combinations thereof. Typically, these features are limited to the polishing pad surface.
In addition to the novel groove configurations described above, CMP pads may also feature random grooves and/or irregular shaped features on the pad surface. These random grooves and/or irregular shaped features may be present with or without primary grooves.
Description of the CMP groove configurations described herein is intended to encompass mirror images (or reflections) of those groove configurations. As such, the CMP pad variation described in
In one variation, the CMP pad comprises features as illustrated in
In a second variation, the CMP pad comprises features as illustrated in
In a third variation, the CMP pad comprises features as illustrated in
In a fourth variation, the CMP pad comprises features as illustrated in
In a fifth variation, the CMP pad comprises features as illustrated in
In a sixth variation, the CMP pad comprises features as illustrated in
In a seventh variation, the CMP pad comprises features as illustrated in
Any of the CMP pads described above may lack secondary grooves. Alternatively, any of the CMP pads described above may have any of the secondary grooves discussed in paragraphs 18-23. For instance, in an eighth variation, the CMP pad comprises features as illustrated in
In a ninth variation, the CMP pad comprises features as illustrated in
In a tenth variation, the CMP pad comprises features as illustrated in
In an eleventh variation, the CMP pad comprises features as illustrated in
In a twelfth variation, the CMP pad comprises features as illustrated in
In a thirteenth variation, the CMP pad comprises features as illustrated in
In a fourteenth variation, the CMP pad comprises features as illustrated in
In a fifteenth variation, the CMP pad comprises features as illustrated in
In a sixteenth variation, the CMP pad comprises features as illustrated in
The embodiments shown in
These novel groove configurations may be produced by any suitable method. For example, they may be produced using the in-situ methods described below, or they may be produced using ex-situ or mechanical methods, such as laser writing or cutting, water jet cutting, 3-D printing, thermoforming and vacuum forming, micro-contact forming, hot stamping or printing, and the like. The pads may also be sized or scaled as practicable to any suitable or desirable dimension. As described herein, typically the scaling of the pads is based upon the size of the wafer to be polished.
In general, any suitable method of producing in-situ grooves on a CMP pad may be used. Unlike the current methods of ex-situ grooving, which are mainly mechanical in nature, the in-situ methods described herein may have several advantages. For example, the methods of in-situ grooving described herein will typically be less expensive, take less time, and require fewer manufacturing steps. In addition, the methods described herein are typically more useful in achieving the complex groove configurations. Lastly, the in-situ methods described herein are typically able to produce CMP pads having better tolerances (e.g., better groove depth, and the like).
In one variation, the methods for in-situ grooving comprise the use of a silicone lining placed inside a mold. The mold may be made of any suitable metal. For example, the mold may be metallic, made from aluminum, steel, ultramold materials (e.g., a metal/metal alloy having “ultra” smooth edges and “ultra” high tolerances for molding finer features), mixtures thereof, and the like. The mold may be any suitable dimension, and the dimension of the mold is typically dependent upon the dimension of the CMP pad to be produced. The pad dimensions, in turn, are typically dependent upon the size of the wafer to be polished. For example, illustrative dimensions for CMP pads for polishing a 4, 6, 8, or 12 inch wafer may be 12, 20.5, 24.6, or 30.5 inches respectively.
The silicone lining is typically made of a silicone elastomer, or a silicone polymer, but any suitable silicone lining may be used. The silicone lining is then typically embossed or etched with a pattern, which is complementary to the desired groove pattern or configuration. The lining is then glued or otherwise adhered to, or retained in, the mold. It should be noted that the lining may also be placed in the mold prior to it being patterned. The use of lithographic techniques to etch patterns into the silicone lining may help provide better accuracy in groove size. See, e.g., C. Dekker, Stereolithography tooling for silicone molding, Advanced Materials & Processes, vol. 161 (1), pp 59-61, January 2003; and D. Smock, Modern Plastics, vol. 75(4), pp 64-65, April 1998, which pages are hereby incorporated by reference in their entirety. For example, grooves in the micron to sub micron range may be obtained. Large dimensions in the mm range may also be obtained with relative ease. In this way, the silicone lining serves as the “molding pattern.” However, in some variations, the mold may be patterned with a complementary groove design. In this way, the mold and the lining, or the mold itself, may be used to produce the CMP pad groove designs.
Using this method, the CMP pad can be formed from a thermoplastic or a thermoset material, or the like. In the case of a thermoplastic material, a melt is typically formed and injected into the mold. In the case of a thermoset material, a reactive mixture is typically fed into the mold. The reactive mixture may be added to the mold in one step, or two steps, or more. However, irrespective of the material used, the pad is typically allowed to attain its final shape by letting the pad material cure, cool down, or otherwise set up as a solid, before being taken out of the mold. In one variation, the material is polyurethane, and polyurethane pads are produced. In another variation, the material is poly (urethane-urea), and poly (urethane-urea) pads are produced. For example, polyurethane or poly (urethane-urea) pellets may be melted and placed into the silicone lined mold. The mold is etched with the desired groove pattern as described above. The polyurethane or poly (urethane-urea) is allowed to cool, and is then taken out of the mold. The pad then has patterns corresponding to those of the mold.
In many of the following methods, a large bun of, for example, polyurethane or poly (urethane-urea), may be sliced to form pad-shaped forms in which grooves are subsequently formed.
Laser writing or cutting may be used to make the novel groove configurations described herein. Laser cutters typically consist of a downward-facing laser, which is mounted on a mechanically controlled positioning mechanism. A sheet of material, e.g., plastic, is placed under the working area of the laser mechanism. As the laser sweeps back and forth over the pad surface, the laser vaporizes the material forming a small channel or cavity at the spot in which the laser hits the surface. The resulting grooves/cuts are typically accurate and precise, and require no surface finishing. Typically, grooving of any pattern may be programmed into the laser cutting machine. More information on laser writing may be found in J. Kim et al., J. Laser Applications, vol. 15(4), pp 255-260, November 2003, which pages are hereby incorporated by reference in their entirety.
Water jet cutting may also be used to produce the novel groove configurations described herein. This process uses a jet of pressurized water (e.g., as high as 60,000 pounds per square inch) to make grooves in the pad. Often, the water is mixed with an abrasive like garnet, which facilitates better tolerances, and good edge finishing. In order to achieve grooving of a desired pattern, the water jet is typically pre-programmed (e.g., using a computer) to follow desired geometrical path. Additional description of water jet cutting may be found in J. P. Duarte et al., Abrasive water jet, Rivista De Metalurgica, vol. 34(2), pp 217-219, March-April 1998, which pages are hereby incorporated by reference in their entirety.
Three Dimensional printing (or 3-D printing) is another process that may be used to produce the novel groove configurations described here. In 3-D printing, parts are built in layers. A computer (CAD) model of the required part is first made and then a slicing algorithm maps the information for every layer. Every layer starts off with a thin distribution of powder spread over the surface of a powder bed. A chosen binder material then selectively joins particles where the object is to be formed. Then a piston which supports the powder bed and the part-in-progress is lowered in order for the next powder layer to be formed. After each layer, the same process is repeated followed by a final heat treatment to make the part. Since 3-D printing can exercise local control over the material composition, microstructure, and surface texture, many new (and previously inaccessible) groove geometries may be achieved with this method. More information on 3-D printing may be found in Anon et al., 3-D printing speeds prototype dev., Molding Systems, vol. 56(5), pp 40-41, 1998, which pages are hereby incorporated by reference in their entirety.
Other processes that may be used to produce the novel groove configurations described herein are thermoforming and vacuum forming. Typically, these processes only work for thermoplastic materials. In thermoforming, a flat sheet of plastic is brought in contact with a mold after heating using vacuum pressure or mechanical pressure. Thermoforming techniques typically produce pads having good tolerances, tight specifications, and sharp details in groove design. Indeed, thermoformed pads are usually comparable to, and sometimes even better in quality than, injection molded pieces, while costing much less. More information on thermoforming may be found in M. Heckele et al., Rev. on micro molding of thermoplastic polymers, J. Micromechanics and Microengineering, vol. 14(3), pp R1-R14, March 2004, which pages are hereby incorporated by reference in their entirety.
Vacuum forming molds sheet plastic into a desired shape through vacuum suction of the warmed plastic onto a mold. Vacuum forming may be used to mold a specific thicknesses of plastic, for example 5 mm. Fairly complex moldings, and hence complex groove patterns, may be achieved with vacuum molding with relative ease.
Using micro contact printing (μCP), which is a high-resolution printing technique grooves can be embossed/printed on top of a CMP pad. This is sometimes characterized as “Soft Lithography.” This method uses an elastomeric stamp to transfer a pattern onto the CMP pad. This method is a convenient, low-cost, non-photolithographic method for the formation and manufacturing of microstructures that can be used as grooves. These methods may be used to generate patterns and structures having feature sizes in the nanometer and micrometer (e.g., 0.1 to 1 micron) range.
Hot stamping can be used to generate the novel grooves designs describe here as well. In this process, a thermoplastic polymer may be hot embossed using a hard master (e.g., a piece of metal or other material that has a pattern embossed in it, can withstand elevated temperatures, and has sufficient rigidity to allow the polymer pad to become embossed when pressed into the hard master.) When the polymer is heated to a viscous state, it may be shaped under pressure. After conforming to the shape of the stamp, it may be hardened by cooling. Grooving patterns of different types may be achieved by varying the initial pattern on the master stamp. In addition, this method allows for the generation of nanostructures, which may be replicated on large surfaces using molding of thermoplastic materials (e.g., by making a stamp with a nano-relief structure). Such a nano-structure may be used to provide local grading/grooving on these materials that may be useful for several CMP processes. W. Spalte, Hot-stamping for surface-treatment of plastics, Kunsstoffe-German Plastics, vol. 76(12), pp 1196-1199, December 1986, which pages are hereby incorporated by reference in their entirety, provides more information on hot stamping.
This application claims benefit of U.S. Provisional Application No. 61/036,897 (Attorney Docket No. 30022.00), filed on Mar. 14, 2008, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61036897 | Mar 2008 | US |
