POLISHING PAD WITH ENDPOINT DETECTION WINDOW

Description

FIELD OF THE INVENTION

The field of the invention is polishing pads used in chemical mechanical polishing.

BACKGROUND OF THE INVENTION

Chemical Mechanical Planarization (CMP) is a variation of a polishing process that is widely used to flatten, or planarize, the layers of construction of an integrated circuit or similar structure. Particularly, CMP is frequently used to produce planar uniform layers of a defined thickness in the manufacture build three-dimensional circuit structures by an additive stacking and planarizing process. CMP can remove excess deposited material on the substrate (e.g., wafer) surface to produce an extremely flat layer of a uniform thickness, with uniformity extending across the entire substrate (e.g., wafer) area. When the uniform thickness is across the entire wafer, it is known as global uniformity.

CMP utilizes a liquid, often called slurry, that can contain nano-sized particles. The slurry is fed onto the surface of a rotating multilayer polymer pad (sometimes referred to as polishing sheet), the pad being mounted on a rotating platen. The polishing pad includes a polishing layer and can include a subpad. Substrates (e.g., wafers) are mounted into a separate fixture, or carrier, that has a separate means of rotation, and pressed against the surface of the pad under a controlled load. This can lead to a high rate of relative motion between the substrate (e.g., wafer) and the polishing pad and a resulting high rate of shear or abrasion at both the substrate and the pad surface. The shear and the slurry particles trapped at the pad/substrate junction abrade the substrate (e.g., wafer) surface, leading to removal of material from the substrate surface. Control of removal rate and the uniformity of removal are important. Also, it is useful to use metrology to determine when the polishing has met its desired goal (e.g., film thickness, intended reveal of an underlying structure, etc.). This is referred to as endpoint detection.

Various types of film thickness metrology, together with real time control software, can be used for endpoint detection. Endpoint detection processes periodic signals, such as a collimated light wave, non-collimated light wave or an acoustic signal wave to avoid wafer yield issues from both under-polishing and over-polishing. For example, one approach for endpoint detection is an optical endpoint detection system that uses transmittance of desired wavelengths of light through the polishing pad, the light reflects from the substrate being polished, and the reflected light signal then passes back to the interferometer. This requires that at least a portion of the polishing pad be sufficiently transparent to the light source used to yield an acceptable signal to noise ratio. The metrology equipment can be located within the polishing equipment or the body of the platen that holds the pad.

For certain pad structures where optical detection is used, the pad material itself can be transparent to the desired optical wavelength and or have a design to allow effective transmittance of the signal waves. Alternatively, the pad can include alternate structures to facilitate transmittance of the waves. For example, a transparent polymer can be provided and opaque material molded around that to produce a transparent window. See e.g., U.S. Pat. No. 5,605,760. As another example, an opening through the entire pad can be provided. See, e.g., U.S. Pat. Nos. 8,961,266 and 7,497,763. A third approach is to form a pad with an aperture into which a transparent window material is inserted and held in place with an adhesive. See, e.g., U.S. Pat. No. 5,893,796. Various versions of polishing pads with windows have been proposed. See e.g., U.S. Pat. Nos. 7,621,798, 7,081,044, 7,195,539, 8,475,228, 10,569,383, U.S. 2021/0402556, U.S. 2022/0226956, U.S. 2020/164483, U.S. 2015/232549, U.S. Pat. No. 9,126,304, U.S. 2008/0207089, U.S. 2017/0120417, U.S. 2016/263721, U.S. Pat. Nos. 7,398,714, 7,435,161, U.S. 2005/064802, U.S. Pat. Nos. 9,475,168, 6,045,439, 6,716,085, 8,475,228, 7,264,536, JP5142866, and CN113478382.

Transmittance of a signal wave through a boundary between a gap (e.g., air) and a surface of the window can lead to refraction or reflection of the signal wave that can create noise or reduce the signal thereby lessening the effectiveness of using the signal wave for endpoint detection. Thus, in another approach, optical fibers can be inserted into openings in the subpad. See e.g., U.S. 2010/184357.

Transmittance of other vibrational waves such as acoustic waves can include non-porous windows. See e.g., U.S. 2023/0009737 and U.S. 2023/0009519.

In addition, since a window is typically formed of a material distinct from the polishing layer, other problems can arise. Particularly, since the modulus and stiffness of the solid polymer window material typically is higher than that of the surrounding composite pad, differential compression during the polishing process leads to deformation of the vicinity of the window. Differences in the coefficient of thermal expansion (CTE) and thermal conductivity (K) between the polishing material and the window can further exacerbate problems. Since the upper surfaces of the pad and window are frictionally heated during CMP, differences in CTE and K produce an additional transient stress and deformation. This can cause the window area to protrude above the upper surface of the pad polishing area during use. The protrusion of the window can cause scratching of the substrate being polished. In addition, a gap in the peripheral area around the protruding area acts as a trap for slurry, conditioning debris, and other foreign contaminates that can also lead to increased scratch defect rates. Furthermore, since the pad is conditioned during use, the conditioning wear rate is significantly higher in the raised area because of the increase in contact pressure. This differential thinning of the window can disturb the optical signal and, eventually, can lead to a break-through in the window, that is a catastrophic failure giving reduced pad lifetime.

CMP polishing pad windows are designed for use with specific endpoint detections systems for specific polishing equipment. For example, there is one window design used for optical endpoint detection systems and another type of window used for eddy current detection systems. This restricts usefulness of a specific pad to a specific endpoint detection system.

Thus, a need remains for an improved polishing pad with window region for use in end-point detection, particularly a pad that provides one or more of the following advantages: reducing or avoiding scratching the substrate being polished, good management of or toleration of stress on the pad during polishing while providing uniform polishing and good pad lifetime, and that is useful for more than one type of signal wave.

SUMMARY OF THE INVENTION

Disclosed herein is a polishing pad for chemical mechanical polishing. The polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer) comprises a polishing layer, a subpad layer, a top window portion, bottom window portion, and a support. The polishing layer has a polishing surface and a polishing layer interface surface opposite the polishing surface. The polishing layer comprises a polishing material. The subpad layer has a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface. The subpad layer comprises a subpad material. The top window portion comprises a top window material and has a polishing face surface preferably recessed from the polishing surface, a top window interface surface opposite the polishing face surface, and a top window peripheral surface extending from the polishing face surface to the top window interface surface. The support extends from the polishing layer toward and is adjacent to the top window peripheral surface. The support including a top support surface and a support interface surface opposite from the top support surface. The bottom window portion has a bottom window interface surface, a bottom window bottom surface and a bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface, wherein a region defined by the bottom window bottom surface, the bottom window peripheral surface and the bottom window interface surface is filled with a bottom window material. The bottom window interface surface is adjacent the top window interface surface and adjacent to at least a portion of the support interface surface. The pad includes a gap between the bottom window peripheral surface and the subpad material.

Also disclosed is a method of polishing comprising providing a substrate to be polished, providing the polishing pad as disclosed herein, providing a slurry on the polishing pad, moving the substrate relative to the polishing pad, transmitting a signal wave through the window material and detecting the signal wave reflected from the substrate back through the window and slurry to determine when polishing is complete wherein the signal wave is a light wave, an acoustic wave or both.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, that are exemplary embodiments, and wherein the like elements are numbered alike.

FIG. 1 is a cross-sectional view through the thickness of a portion of one example of polishing pad as disclosed herein.

FIG. 2 is a cross-sectional view through the thickness of a portion of one example of polishing pad as disclosed herein.

FIG. 3 is a cross-sectional view through the thickness of a portion of one example of polishing pad as disclosed herein.

FIG. 4 is a cross-sectional through the thickness of a portion of one example of polishing pad as disclosed herein.

FIG. 5 is a cross-sectional through the thickness of a portion of FIG. 1 with the addition of an encapsulating layer.

FIG. 6 is a top view of one example of a polishing pad as disclosed herein.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein is a polishing pad useful in chemical mechanical polishing. The polishing pad includes a polishing layer having a polishing surface, a subpad, and a window extending through the polishing layer and the subpad.

The window comprises two portions. A top portion comprises a first window material and is located in an opening in the polishing layer. A support extends from the polishing material to a peripheral edge of the top portion. A polishing face surface of the top portion of the window is recessed from the polishing surface of the polishing layer. The bottom portion comprises a second window material and is located in an opening in the subpad material. The bottom portion is adjacent the top portion of the window opposite the polishing side of the polishing pad. The bottom portion has a peripheral edge that is larger than the peripheral edge of the top portion. In other words, the bottom portion covers the entire bottom surface of the top portion and also covers a portion of a bottom surface of the support. There is a gap between the peripheral edge of the bottom portion and the subpad material. At least a portion of the gap underlies at least a portion of the support.

The pad structure can provide one or more of the following advantages: avoid scratching of the substrate being polished by the top portion of the polishing window, facilitating alignment of the top and bottom window portions, tolerance of deviations in alignment of the top and bottom window portions, alleviates compressive and shear stresses generated during the polishing process. For example, having a bottom window portion with a larger peripheral edge than the top window portion can facilitate alignment of the window portions in the openings and provide more tolerance of deviations in alignment of these portions from a center point. As another example, the recess, the support, and the gap (preferably where the gap underlies at least a portion of the support), allows for more flexibility and stress release without impacting the surface of the pad during polishing. This increased flexibility may also extend lifetime of the pad and reduce polishing defects. As yet another example, the flexibility and the recess of the top portion of the window can avoid protrusion of the window material above the top polishing surface that can lead to defects or scratching. For example, a recessed top window surface avoids or prevents direct pressure transmission between the window and the substrate (e.g., silicon wafer). Furthermore, such a recess can avoid problems created by differences in conditioning wear rate between the polishing layer material and the first window material.

Referring to FIGS. 1-6, the pad 1 includes a polishing layer 10 having a polishing surface 11, a subpad layer 20, a top window portion 30, a bottom window portion 40, and a support 60. While FIG. 6 shows a polishing surface 11 without microtexture or macrotexture, the polishing surface can include macrotexture such as grooving or perforations, and microtexture. The groves can be, for example, concentric circular, radial, concentric circular plus radial or any other groove configuration. FIG. 6 shows a pad 1 that includes three window regions 2. Other pad configurations not shown can have one window region, two window regions, four window regions, or more than four window regions. FIG. 6 shows a circular window in the window region 2. However other shapes such as ovals, rectangles (optionally with curved corners) and the like can be used. FIGS. 1-5 show cross sections through the thickness of the pad in a window region 2 for various exemplary structures.

The polishing layer 20 has a polishing surface 11 and a polishing layer interface surface 13 opposite the polishing surface 11. The polishing layer 10 includes a polishing material 14, such as a porous or non-porous polymer.

The subpad layer 20 has a subpad interface surface 23 adjacent to the polishing layer interface surface 13 and a bottom surface 21 opposite the subpad interface surface. The subpad layer 20 comprises a subpad material 24.

The top window portion 30 is located in an opening in the polishing layer 10. The top window portion comprises a top window material 34. The top window portion 30 has a polishing face surface 31 recessed from the polishing surface 11, a top window interface surface 33 opposite the polishing face surface, and a top window peripheral surface 32 extending from the polishing face surface 31 to the top window interface surface 33.

The support 60 extends from the polishing layer 10 to the top window peripheral surface 32. The support 60 includes a top support surface 61 and a support interface surface 63 opposite from the top support surface 61. The support 60 and the bottom window portion 40 have partial vertical alignment since the bottom window portion 40 has a peripheral edge 42 dimension larger than the peripheral edge dimension of the top portion 30. For example, a portion of the support interface surface 63 and the bottom window interface surface 43 can be in direct contact or an adhesive or tie layer, such as a pressure sensitive adhesive (not shown) may physically connect a portion of the bottom window interface surface 43 and a portion of the support interface surface 63. Where the support abuts the top window material, the top support surface 61 can be substantially coplanar with the polishing face surface 31 of the window. The support interface surface 63 can be substantially coplanar with the polishing layer interface surface. The support interface surface 63 can overlie at least a portion of the gap 45. This structure provides enhanced flexibility and stress relief.

The support 60 can be integral with the polishing material 14. The support 60 can be the same composition as the polishing material 14. Alternatively, the support 60 can comprise a different material from the polishing material 14. The support 60 can be a separate element attached to the polishing layer 10. The top window portion 30, the support 60 and the polishing layer 10 can form a seal preventing passage of slurry or particulates from the polishing side of the pad to the other side of the pad. An adhesive can be used between the top window portion 30 and the support 60. If the support 60 is a separate element attached to the polishing layer 10 an adhesive can be used to facilitate that attachment.

FIGS. 1-5 show a sidewall surface 15 of polishing material 14 extending from the polishing surface 11 to the top support surface 61 as a vertical surface forming a right angle with the top support surface 61. In alternatives not shown in the Figures, this sidewall surface 15 could be at an angle other than a right angle forming a slope from the polishing surface 11 to the top support surface 61, or the sidewall surface 15 could be a curved surface. A top window recess 3 is defined by the sidewall surface 15, the top support surface 61, and the polishing face surface 31 of the top window portion 30. In particular, the top window recess is defined by the volume between the sidewall surfaces 15 under the plane of the polishing surface 11 and above the polishing face surface 31 and top support surface 61.

Pads similar to those shown in FIGS. 1-5 including the gap 45, but without the top window recess 3 would have less flexibility and ability to withstand the forces during polishing. In addition, such pads would be more likely to cause scratching of the substrate being polished by the top window portion as it is typically of a material harder than the polishing layer.

The bottom window portion 40 is located in an opening in the subpad layer 20. The bottom window portion 40 comprises a bottom window interface surface 43, a bottom window bottom surface 41 and a bottom window peripheral surface 42 that extends from the bottom window interface surface 43 to the bottom window bottom surface 41. A bottom window material 44 fills the region defined by the bottom window bottom surface 41, the bottom window peripheral surface 42, and the bottom window interface surface 43. The bottom window interface surface 43 and the top window interface surface 33 can be in direct contact or an adhesive or tie layer, such as pressure sensitive adhesive (not shown) may physically connect bottom window interface surface 43 and the top window interface surface 33. A gap (or void space) 45 separates the bottom window peripheral surface 42 and the subpad material 24.

In FIGS. 1 and 2, the gap 45 is adjacent to and under the support 60 and is not adjacent to or under the polishing material 14. In FIG. 3 a portion of the gap 45 is adjacent to (e.g., under) the support 60 while a portion of the gap is adjacent to (e.g., under) the polishing material 14. In FIG. 4, the gap 45 is adjacent to and under the polishing material 14.

FIG. 5 shows an example that includes an optional encapsulating layer 52 underlying the bottom window portion 40 and the gap 45. The optional encapsulating layer improves the transmission of acoustic signals. In other alternatives not shown, the encapsulating layer 52 could underlie only the bottom window portion 40, or the encapsulating layer 52 could underlie the bottom window portion 40, the gap 45, and the subpad layer 20. The encapsulating layer 52 can be used as an additional feature with any of the embodiments shown in FIGS. 1-4. The encapsulating layer 52 can be a non-adhesive film. The encapsulating layer can comprise a polymer film, such as for example a polyester film.

The encapsulating layer 52 can optionally have a layer of adhesive (not shown) on the bottom surface 21 to facilitate adhesion of the pad 1 to the platen (not shown). The encapsulating layer can provide one or more of the following benefits: facilitate insertion of the window into the pad with proper alignment; provide an even surface on the bottom of the pad; prevent any adhesive between the side edges of the window and the polishing layer 1, the subpad 20, or both, from leaking out; assist in holding the top and bottom window portions 30 and 40, respectively, in place; prevent any leakage of slurry to the bottom side of the polishing pad 1. In another alternative, an encapsulating layer could also be added to the bottom window surface 41 as shown in FIG. 1 or 2. Furthermore, the encapsulating layer can be added both to the bottom window surface and the bottom surface of the subpad.

Referring to FIG. 1, support 60 allows for simplified alignment when manufacturing the top and bottom window portions, 30 and 40, respectively. In particular, the window portions 30 and 40 may be first joined together, then placed within and secured to support interface surface 63 of support 60. Adhesives, such as epoxy resins and hot melt adhesives are ideal for securing the window in place. The top window recess 3 isolates the window 30 below the polishing surface 11. In particular, this reduces stresses and eliminates scratches that can occur from the top window portion 30 rubbing against a wafer.

Referring to FIGS. 1 and 2, the FIG. 2 design has two main features different than FIG. 1. First, gap 45 provides less spacing between the bottom window portion 40 and subpad 20. This reduced spacing improves alignment of the window for simplified manufacturing. Thus, the smaller the spacing, the better the alignment. But maintaining some spacing allows for better compression of the subpad 20. Second, a portion of support 60 is secured to subpad 20. Securing the support to subpad 20 concentrates more stress on the support 60 during polishing. Advantageously, support 60 is constructed from the same material as polishing layer 10 to match deformation characteristics and eliminate material mismatch stresses that can be accentuated during polishing.

Referring to FIGS. 2 and 3, FIG. 3 is similar to FIG. 2, but the gap 45 extends under the polishing layer 10. This design increases the flexibility of support 60 during polishing. Furthermore, it reduces compressive forces on support 60. Finally it provides additional space for the expansion of bottom window portion 40 and subpad 20 adjacent to the bottom window portion during polishing.

Referring to FIGS. 1 and 4, FIG. 4 is similar to FIG. 1, except the gap 45 is only under the polishing layer 10. This design increases the rigidity of the polishing layer 10 adjacent to top window recess 3 and sidewall surface 15. This increased rigidity can reduce polishing rate reduction from excessive compression of the polishing layer.

Referring to Fig.

The overall thickness of the polishing pad (e.g., polishing layer plus subpad) is preferably no greater than 4 mm. For example, the overall thickness of the polishing pad can be from 1 up to 4 mm, from 1.5 up to 4 mm, from 1.7 up to 3.5 mm, or from 2 up to 3 mm. The polishing layer can have a thickness of from 0.5 up to 3, from 0.7 up to 2.5, from 1.2 up to 2.2, or from 1 to 2 mm. The subpad can have a thickness of from 0.5 up to 3, from 0.7 up to 2.5, from 1 to 2 mm.

The depth of the recess (e.g., the vertical different between the height of the polishing surface 11 and the polishing face surface 31) can be, for example, from 0.05, from 0.1, from 0.2, or from 0.3 mm up to 1.1, up to 1, up to 0.8, up to 0.6 mm, or up to 0.4 mm.

The length of the support 60 (i.e., the distance from the polishing layer 10 to the top window peripheral surface 32) can be, for example, from 0.1, from 0.3, from 0.5, from 1, from 2, from 3, or from 4 mm, up to 20, up to 15, up to 10, or up to 5 mm. The thickness of the support 60 can be, for example, from 0.4 to 2.5 mm. The thickness of the support 60 where it abuts the top window portion 30 can be the same thickness as the top window portion 30. The thickness of the support can be the same over the entire length of the support or the thickness may be slightly larger toward the polishing layer. The top window portion 30 can have a thickness of, for example, 0.4 to 2.5 mm and a cross-section dimension perpendicular to that thickness of from 2, from 3, from 4, from 5, or from 6 up to 30, up to 25, up to 20, or up to 15 mm. The bottom window portion 40 can have a thickness of from 0.5 up to 3, from 0.7 up to 2.5, from 1 to 2 mm, and preferably has a thickness within 0.1 mm of the thickness of the subpad layer 20. The bottom window portion 40 can have a cross-section dimension perpendicular to its thickness greater than the cross-section of the top window portion, such that at a portion of the bottom window interface surface 43 is adjacent (i.e., in contact with directly or via a tie or adhesive layer) with the support interface surface 63. For example, the cross-section dimension of the bottom window portion 40 perpendicular to its thickness can be from 5%, from 10%, from 15%, from 20%, from 30%, from 40%, or from 50% up to 200%, up to 150%, or up to 100% greater than the cross-section dimension of the top window portion 30. The gap 45 from the bottom window portion 40 to the subpad material can be from 0.1, from 0.2, from 0.3, from 0.4, from 0.5, from 1, from 2, from 3, from 4, or from 5 mm up to 40, up to 30, up to 20, up to 10, up to 9, up to 8, up to 7 or up to 6 mm.

The top window material can be a material conventionally used in such windows in polishing pads. This is desirable as the conditioning rates of such conventionally used materials may have already been designed to work well with that of the surrounding polishing material. The top portion can be relatively rigid (as compared to the elastomeric bottom portion of the window) such that the top portion in the plane of or parallel to the top polish surface does not substantially deform during polishing.

The top window material can be a polymer or polymer blend. For optical detection systems the top window material should have sufficient transmission at the wavelengths of light used by the optical metrology. It can be helpful if that window material has a hardness or thermal expansion coefficient similar to that of the material used in the polishing layer. Examples of top window materials include polyurethanes, acrylic polymers, cyclic olefin co-polymers (e.g., TOPAS 8007, etc.).

The top window portion is advantageously made from an aliphatic polyisocyanate-containing material (“prepolymer”). The prepolymer is a reaction product of an aliphatic polyisocyanate (e.g., diisocyanate) and a hydroxyl-containing material. The prepolymer is then cured with a curing agent. Preferred aliphatic polyisocyanates include, but are not limited to, methylene bis 4,4′ cyclohexyl isocyanate, cyclohexyl diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, tetramethylene-1,4-diisocyanate, 1,6-hexamethylene-diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, methyl cyclohexylene diisocyanate, triisocyanate of hexamethylene diisocyanate, triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate, uretdione of hexamethylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and mixtures thereof. The preferred aliphatic polyisocyanate has less than 10 wt. % unreacted isocyanate groups.

Advantageously, the curing agent is a polydiamine. Preferred polydiamines include, but are not limited to, diethyl toluene diamine (“DETDA”), 3,5-dimethylthio-2,4-toluenediamine and isomers thereof, 3,5-diethyltoluene-2,4-diamine and isomers thereof, such as 3,5-diethyltoluene-2,6-diamine, 4,4′-bis-(sec-butylamino)-diphenylmethane, 1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline), 4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”), polytetramethyleneoxide-di-p-aminobenzoate, N,N′-dialkyldiamino diphenyl methane, p,p′-methylene dianiline (“MDA”), m-phenylenediamine (“MPDA”), methylene-bis 2-chloroaniline (“MBOCA”), 4,4′-methylene-bis-(2-chloroaniline) (“MOCA”), 4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”), 4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”), 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane, 2,2′,3,3′-tetrachloro diamino diphenylmethane, trimethylene glycol di-p-aminobenzoate, and mixtures thereof. Preferably, the curing agent of the present invention includes 3, 5-dimethylthio-2,4-toluenediamine and isomers thereof. Suitable polyamine curatives include both primary and secondary amines.

In addition, other curatives such as, a diol, triol, tetraol, or hydroxy-terminated curative may be added to the aforementioned polyurethane composition. Suitable diol, triol, and tetraol groups include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, lower molecular weight polytetramethylene ether glycol, 1,3-bis(2-hydroxyethoxy) benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy}benzene, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, resorcinol-di-(beta-hydroxyethyl) ether, hydroquinone-di-(beta-hydroxyethyl) ether, and mixtures thereof. Preferred hydroxy-terminated curatives include 1,3-bis(2-hydroxyethoxy) benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy] ethoxy}benzene, 1,4-butanediol, and mixtures thereof. Both the hydroxy-terminated and amine curatives can include one or more saturated, unsaturated, aromatic, and cyclic groups. Additionally, the hydroxy-terminated and amine curatives can include one or more halogen groups. The polyurethane composition can be formed with a blend or mixture of curing agents. If desired, however, the polyurethane composition may be formed with a single curing agent.

The bottom window portion can comprise a different material from the top window portion. For example, the bottom window material can be less rigid or is more compressible than the top window material. The bottom window material can comprise an elastomeric material. As used herein, “elastomeric material” means one that deforms when under force but which returns substantially to its original form when the force is removed. The gap between at least a portion of the elastomeric material and at least a portion of the subpad material allows the elastomeric material of the bottom portion of the window to deform into the gap when the pad is under downforce (but returns substantially to its original shape when the downforce is removed). Particularly, the thickness of the bottom portion may be reduced under the downforce but the perimeter may expand in a direction perpendicular to the downforce. This compression reduces deformation forces in the polishing layer, particularly at the polishing surface. The compressibility of the bottom portion can be selected to substantially match that of the surrounding subpad material, the surrounding polishing material or both. Because the window extends to the bottom edge of the pad, reflection and refraction of the signal wave at a solid/gas or solid/vacuum interface is avoided.

The bottom window material can have an elastic modulus lower than that of the top window material. Desirably the elastomeric material can have a similar refractive index and optical transmittance to the upper window layer. A wide variety of transparent elastomers can be used, such as, for example, polyurethanes, polyolefins, polyamides, poly acrylates, styrenic block copolymers, and silicone elastomers. A preferred material family are silicone elastomers. An elastomeric material that can be easily cast or molded into appropriate shapes is desirable.

CMP pads are produced with a variety of polishing layer and subpad layer thickness and modulus values. For example, CMP pads can have a polishing layer with a tensile storage modulus of 300 to 400 MPa, while the subpad tensile storage modulus can be 5 to 30 MPa. The overall composite compressibility is highly affected by the relative layer thickness. The design of pads of the present invention allows simple methods for selecting an appropriate lower window layer material. For example, standard compressibility testing methods can be used on test samples of the pad stack and the window stack to allow rapid compressibility matching prior to any pad fabrication.

The polishing material of the polishing layer 10 can comprise a polymer. The polishing material 14 can be opaque at the thickness of the polishing layer 10. Pores can be provided, for example, by addition of hollow flexible polymer elements (e.g., hollow microspheres), blowing agents, frothing or supercritical carbon dioxide. Examples of polymeric materials for the polishing layer include polyurethanes, polycarbonates, polysulfones, nylons, polyethers, polyesters, polystyrenes, acrylic polymers, polymethyl methacrylates, polyvinylchlorides, polyvinyl fluorides, polyethylenes, polypropylenes, polybutadienes, polyethylene imines, polyether sulfones, polyamides, polyether imides, polyketones, epoxy resins, silicones, copolymers thereof (such as, polyether-polyester copolymers), and combinations or blends thereof. The polishing layer can comprise a polymer that is a polyurethane formed by reaction of one or more polyfunctional isocyanates and one or more polyols. For example, a polyisocyanate terminated urethane prepolymer can be used. The polyfunctional isocyanate used in the formation of the polishing layer of the chemical mechanical polishing pad of the present invention can be selected from the group consisting of an aliphatic polyfunctional isocyanate, an aromatic polyfunctional isocyanate and a mixture thereof. For example, the polyfunctional isocyanate used in the formation of the polishing layer of the chemical mechanical polishing pad of the present invention can be a diisocyanate selected from the group consisting of 2,4-toluene diisocyanate; 2,6-toluene diisocyanate; 4,4′-diphenylmethane diisocyanate; naphthalene-1,5-diisocyanate; tolidine diisocyanate; para-phenylene diisocyanate; xylylene diisocyanate; isophorone diisocyanate; hexamethylene diisocyanate; 4,4′-dicyclohexylmethane diisocyanate; cyclohexanediisocyanate; and, mixtures thereof. The polyfunctional isocyanate can be an isocyanate terminated urethane prepolymer formed by the reaction of a diisocyanate with a prepolymer polyol. The isocyanate-terminated urethane prepolymer can have 2 to 12 wt. %, 2 to 10 wt. %, 4 to 8 wt. % or 5 to 7 wt. % unreacted isocyanate (NCO) groups. The prepolymer polyol used to form the polyfunctional isocyanate terminated urethane prepolymer can be selected from the group consisting of diols, polyols, polyol diols, copolymers thereof and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of polyether polyols (e.g., poly(oxytetramethylene)glycol, poly(oxypropylene)glycol and mixtures thereof); polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and, mixtures thereof with one or more low molecular weight polyols selected from the group consisting of ethylene glycol; 1,2-propylene glycol; 1,3-propylene glycol; 1,2-butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol; 1,4-butanediol; neopentyl glycol; 1,5-pentanediol; 3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropylene glycol; and, tripropylene glycol. For example, the prepolymer polyol can be selected from the group consisting of polytetramethylene ether glycol (PTMEG); ester based polyols (such as ethylene adipates, butylene adipates); polypropylene ether glycols (PPG); polycaprolactone polyols; copolymers thereof; and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of PTMEG and PPG. When the prepolymer polyol is PTMEG, the isocyanate terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 2 to 10 wt. % (more preferably of 4 to 8 wt. %; most preferably 6 to 7 wt. %). Examples of commercially available PTMEG based isocyanate terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., such as, PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Adiprene® prepolymers (available from Chemtura, such as, LF 800A, LF 900A, LF 910A, LF 930A, LF 931A, LF 939A, LF 950A, LF 952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D and L325); Andur® prepolymers (available from Anderson Development Company, such as, 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF). When the prepolymer polyol is PPG, the isocyanate terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 3 to 9 wt. % (more preferably 4 to 8 wt. %, most preferably 5 to 6 wt. %). Examples of commercially available PPG based isocyanate terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., such as, PPT-80A, PPT-90A, PPT-95A, PPT-65D, PPT-75D); Adiprene® prepolymers (available from Chemtura, such as, LFG 963A, LFG 964A, LFG 740D); and Andur® prepolymers (available from Anderson Development Company, such as, 8000APLF, 9500APLF, 6500DPLF, 7501DPLF). The isocyanate terminated urethane prepolymer can be a low free isocyanate terminated urethane prepolymer having less than 0.1 wt. % free toluene diisocyanate (TDI) monomer content. Non-TDI based isocyanate terminated urethane prepolymers can also be used. For example, isocyanate terminated urethane prepolymers include those formed by the reaction of 4,4′-diphenylmethane diisocyanate (MDI) and polyols such as polytetramethylene glycol (PTMEG) with optional diols such as 1,4-butanediol (BDO) are acceptable. When such isocyanate terminated urethane prepolymers are used, the unreacted isocyanate (NCO) concentration is preferably, 4 to 10 wt. %, more preferably 4 to 10 wt. %, most preferably 5 to 10 wt. %). Examples of commercially available isocyanate terminated urethane prepolymers in this category include Imuthane® prepolymers (available from COIM USA, Inc. such as 27-85A, 27-90A, 27-95A); Andur® prepolymers (available from Anderson Development Company, such as, IE75AP, IE80AP, IE 85AP, IE90AP, IE95AP, IE98AP); and Vibrathane® prepolymers (available from Chemtura, such as, B625, B635, B821).

The subpad 20 can comprise a polymeric material. The subpad material 24 can be more compliant (or more elastic) than the polishing material. The subpad 20 can comprise a porous layer. Examples of polymeric materials for the subpad layer(s) include polyurethanes, polycarbonates, polysulfones, nylons, epoxy resins, polyethers, polyesters, polystyrenes, acrylic polymers, polymethyl methacrylates, polyvinylchlorides, polyvinyl fluorides, polyethylenes, polypropylenes, polybutadienes, polyethylene imines, polyether sulfones, polyamides, polyether imides, polyketones, silicones, copolymers thereof (such as, polyether-polyester copolymers), and combinations or blends thereof.

Polishing pads as disclosed herein can be prepared via a variety of processes, including insertion of a discrete window assembly into a pad having a matching opening, addition of the lower window component to a pad that already has a cast in place upper window component in the upper pad layer, or insertion of the window assembly into a net shape mold used to prepare a top pad layer blank followed by lamination of the subpad and application of the optional pressure sensitive adhesive.

For example, a plug comprising a material of a top portion on the window can be placed in a mold and polishing material molded into a block or cake around the plug. The block or cake can then be sliced into layers having the desired thickness of the polishing layer. A bottom portion of the window can be applied to a surface of the top portion of the window. For example, a pre-formed bottom portion could be adhered or a bottom portion could be cast or molded. The subpad can be laminated or cast onto a bottom surface of the polishing layer.

A window assembly having a top portion and bottom portion as described herein can be placed in a mold and the polishing layer formed around the relevant portions. The subpad can then be applied by lamination.

As another example, a polishing pad as disclosed here can be made by providing a window assembly in a mold with a recess in the mold to hold at least part of the bottom portion of the window and molding the polishing layer around the portion of the window protruding into the mold cavity. This forms a polishing layer with an embedded plug where a portion of the plug protrudes beyond the polishing layer. To form the subpad portion of the pad, the subpad can be molded in a second molding step in a separate mold provided the mold includes a spacer to provide for the gap.

Where desired, a recess of the window region 113 is cut into the top surface of the pad. The polishing layer 10 can also be cut to provide the macrotexture. Cutting to form the recess can be done, for example, by milling with a CNC mill or other machining equipment configured to cut polymers.

A method of using the polishing pad as disclosed herein comprises providing a substrate to be polished, providing the polishing pad as disclosed herein, optionally providing a slurry on the polishing pad, contacting the polishing pad to the substrate and moving the substrate and the polishing pad relative to each other (e.g., in a rotational movement), and transmitting a signal wave through the window and detecting the signal wave reflected from the substrate back through the window to determine when polishing is complete. When an optical detection is used, use of a semi-transparent slurry is preferred. The method can use an optical signal wave, a vibrational (e.g., acoustical) signal wave or both optical and vibrational signal waves.

This disclosure further encompasses the following aspects.

Aspect 1: A polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer) comprising a polishing layer, a subpad layer, a top window portion, bottom window portion, and a support. The polishing layer has a polishing surface and a polishing layer interface surface opposite the polishing surface. The polishing layer comprises a polishing material. The subpad layer has a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface. The subpad layer comprises a subpad material. The top window portion comprises a top window material and has a polishing face surface preferably recessed from the polishing surface, a top window interface surface opposite the polishing face surface, and a top window peripheral surface extending from the polishing face surface to the top window interface surface. The support extends from the polishing layer toward and is adjacent to the top window peripheral surface. The support including a top support surface and a support interface surface opposite from the top support surface. The bottom window portion has a bottom window interface surface, a bottom window bottom surface and a bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface, wherein a region defined by the bottom window bottom surface, the bottom window peripheral surface and the bottom window interface surface is filled with a bottom window material. The bottom window interface surface is adjacent the top window interface surface and adjacent to at least a portion of the support interface surface. The pad includes a gap between the bottom window peripheral surface and the subpad material.

Aspect 2: The polishing pad of Aspect 1 wherein a top of the gap is defined by the support interface surface.

Aspect 3: The polishing pad of Aspect 1 wherein a top of the gap is defined by the support interface surface and by the polishing interface surface.

Aspect 4: The polishing pad of any one of the previous Aspects wherein the top support surface is coplanar with the polishing face surface of the top window portion.

Aspect 5: The polishing pad of any one of the previous Aspects wherein the bottom window material is elastomeric.

Aspect 6: The polishing pad of any one of the previous Aspects wherein the support interface surface is coplanar with the polishing layer interface surface, with the top window interface surface, or both.

Aspect 7: The polishing pad of any one of the previous Aspects wherein a seal is formed between the support and the top window material.

Aspect 8: The polishing layer of any one of the previous Aspects wherein the support is integral with the polishing layer.

Aspect 9. The polishing layer of any one of the previous Aspects wherein the top window material and the bottom window material are transmissive of radiation used for optical signals such that the polishing pad are suitable for both optical end point detection and vibrational end point detection.

Aspect 10. A method of polishing comprising providing a substrate to be polished, providing the polishing pad as in any one of the previous Aspects, providing a slurry on the polishing pad, moving the substrate relative to the polishing pad, transmitting a signal wave through the window material and detecting the signal wave reflected from the substrate back through the window and slurry to determine when polishing is complete wherein the signal wave is a light wave, an acoustic wave or both.

All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt. %, or, more specifically, 5 wt. % to 20 wt. %”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt. % to 25 wt. %,” etc.).

Moreover, stated upper and lower limits can be combined to form ranges (e.g., “at least 1 or at least 2 wt. %” and “up to 10 or 5 wt. %” can be combined as the ranges “1 to 10 wt. %”, or “1 to 5 wt. %” or “2 to 10 wt. %” or “2 to 5 wt. %”).

As used herein in describing surfaces or portions, “adjacent” means in direct contact with or next to but separated only by a tie layer or adhesive layer.

The disclosure may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The disclosure may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function or objectives of the present disclosure.

All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.