MULTIFUNCTIONAL ENDPOINT DETECTION WINDOW

Abstract

A polishing pad having a window extending through the polishing pad from the polishing surface to a backside surface of the pad. The window includes a top window material separated from a polishing material, a bottom window wherein the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing. A seal between the subpad material and the top window material and/or bottom window material or a seal between the polishing layer and the bottom window material prevents particles or liquid used in the chemical mechanical polishing from passing from above the polishing layer to below the subpad layer. The pad can be used for polishing with either optical or vibrational end-point detection.

Claims

1. A polishing pad for chemical mechanical polishing comprising: a polishing layer having a polishing surface, a polishing layer interface surface opposite the polishing surface, and a polishing window region surface extending from the polishing surface to the polishing interface surface, the polishing layer comprising a polishing material, a subpad layer having a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface, and a bottom window regions interface surface extending from the bottom surface to the polishing layer interface surface, the subpad layer comprising a subpad material, a window extending through the polishing pad from the polishing surface to a backside surface of the pad, the window comprising: a top window material having a polishing face surface, a top window peripheral surface, and a top window interface surface, the top window peripheral surface being adjacent to the top window regions surface and separated from the top window region surface such that the top window peripheral surface does not have direct contact with the window region surface, and a bottom window material having a bottom window interface surface bonded to the top window interface surface a bottom window peripheral surface, a bottom window bottom surface wherein the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing, wherein a seal is formed (a) between subpad material and the top window material, the bottom window material, or a combination of the top window material and the bottom window material form a seal with the subpad material or (b) between the bottom window material and the polishing material to prevent particles or liquid used in the chemical mechanical polishing from passing from above the polishing layer to below the subpad layer, and wherein the pad includes a path in the window region for transmitting columnated or non-columnated light through the thickness of the pad and wherein vibrational signals can be transmitted through the top window material and the bottom window material enabling acoustic end-point detection.

2. The polishing pad of claim 1 wherein the top window polishing face surface is recessed below the polishing surface.

3. The polishing pad of claim 1 having a void located inward from the bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface.

4. The polishing pad of claim 1 having a void located between the bottom window peripheral surface and the subpad layer window region surface.

5. The polishing pad of claim 4 having a void located between the bottom window peripheral surface and the subpad layer window region surface.

6. The polishing pad of claim 1 including an encapsulating layer adjacent to the bottom window bottom surface.

7. The polishing pad of claim 6 wherein the encapsulating material extends across a void located between the bottom window peripheral surface and the subpad layer window region surface, across a void located inward from the bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface 41, or both, wherein the encapsulating material is transparent.

8. The polishing pad of claim 1 having an adhesive between the top window material and the bottom window material.

9. The polishing pad of claim 1 wherein the top window interface surface is in direct contact with the bottom window interface surface.

10. A method of polishing comprising: providing a substrate to be polished; providing the polishing pad as in claim 1; providing a slurry on the polishing pad; polishing by moving the substrate relative to the polishing pad; and monitoring polishing by (a) transmitting a light wave through the top window material and the void and detecting the light wave reflected from the substrate, (b) transmitting a vibrational signal through the top window material, the polishing layer material or both and through the bottom window material, or both (a) and (b).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike.

[0014] FIG. 1 is a top view of an example of a chemical mechanical polishing pad including a window.

[0015] FIG. 2A-B are cross-sectional views through the thickness of a portion of chemical mechanical polishing pad around a window region showing examples of a pad structure including a two component window as disclosed herein.

[0016] FIG. 3A-D are cross-sectional views through the thickness of a portion of chemical mechanical polishing pad around a window region showing examples of a pad structure including a two component window as disclosed herein.

[0017] FIG. 4A-C are cross-sectional views through the thickness of a portion of chemical mechanical polishing pad around a window region showing examples of a pad structure including a two component window as disclosed herein.

[0018] FIG. 5 is a cross-sectional view parallel to the bottom surface through the subpad and bottom window portion of a polishing pad showing an example of an arrangement of the bottom window material as in FIG. 4B.

[0019] FIG. 6 is a cross-sectional view parallel to the bottom surface through the subpad and bottom window portion of a polishing pad showing an example of an arrangement of the bottom window material as in FIG. 4B.

[0020] FIG. 7 is a cross-sectional view parallel to the bottom surface through the subpad and bottom window portion of a polishing pad showing an example of an arrangement of the bottom window material as in FIG. 3A-D.

[0021] FIG. 8A-B are cross-sectional views through the thickness of a portion of chemical mechanical polishing pad around a window region showing examples of a pad structure that includes a two component window.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Disclosed herein is a polishing pad useful in chemical mechanical polishing. The polishing pad can be used with end-point detection using a variety of types of signal waves. Particularly, the polishing pad can be used with optical detection using columnated or non-columnated light and the polishing pad can be used with vibrational detection using, for example, acoustic waves. This is accomplished by the window region including a path for transmission of light through the pad and also materials for transmitting vibrational signals (e.g., acoustic waves) through the pad.

[0023] Disclosed herein is a polishing pad for chemical mechanical polishing comprising a polishing layer, a subpad layer, and window. The polishing layer comprises a polishing material and has a polishing surface, a polishing layer interface surface opposite the polishing surface, and a polishing window region surface extending from the polishing surface to the polishing interface surface. The subpad layer comprises a subpad material and has a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface, and a bottom window regions interface surface extending from the bottom surface to the polishing layer interface surface. The window extends through the polishing pad from the polishing surface to a backside surface of the pad. The window comprises a top window material having a polishing face surface, a top window peripheral surface, and a top window interface surface, the top window peripheral surface being adjacent to the top window regions surface and separated from the top window region surface such that the top window peripheral surface does not have direct contact with the window region surface, and a bottom window material having a bottom window interface surface bonded to the top window interface surface a bottom window peripheral surface, a bottom window bottom surface wherein the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing. A seal is formed (a) between subpad material and the top window material, the bottom window material, or a combination of both the top window material and the bottom window material or (b) between the bottom window material and the polishing material to prevent particles or liquid used in the chemical mechanical polishing from passing from above the polishing layer to below the subpad layer or below the window. Slurry below the subpad provides a negative impact on polishing uniformity. Slurry under the window interferes with and decreases intensity of the endpoint signal strength. The pad includes a path in the window region for transmitting columnated or non-columnated light through the thickness of the pad. Vibrational signals can be transmitted through the top window material and the bottom window material enabling acoustic end-point detection.

[0024] The multifunctional window of the invention allows polishing methods comprising providing a substrate to be polished, providing the polishing pad as described herein, providing a slurry on the polishing pad, polishing by moving the substrate relative to the polishing pad, monitoring polishing by (a) transmitting a light wave through the top window material and the void and detecting the light wave reflected from the substrate, (b) transmitting a vibrational signal through the top window material, the polishing layer material or both and through the bottom window material, or both (a) and (b).

[0025] Referring to FIG. 1, the polishing pad 1 includes a polishing surface 11 and can include grooves 12. A window region 100 is found in the pad 1. As shown in FIG. 1 the window region is circular. However, other shapes such as ovals, rectangles (including rectangular shapes with curved corners), and the like could be used.

[0026] As shown, for example, in FIGS. 2A-2B, 3A-3D, 4A-4C, and 8A-B, showing cross-sections through the thickness of the pad 1 in the area around the window region 100, the pad 1 includes a polishing layer 10 comprising a polishing material 14 having a polishing surface 11, a polishing layer interface surface 13, and a polishing window-region surface 16 extending from the polishing surface 11 to the polishing layer interface surface 13. The pad 1 also include a subpad layer 20 comprising a subpad material 24 and having a subpad bottom surface 21 and a subpad interface surface 23 and a subpad layer window region surface 25 extending from the subpad bottom surface 21 to the subpad interface surface 23. The subpad interface surface 23 can be in direct contact with the polishing layer interface surface 13 or an adhesive or tie layer (not shown) could be used to connect the polishing layer 10 to the subpad layer 20.

[0027] The window region 100 includes a top portion comprising a top window material 30. The top window has a polishing face surface 31 and a top window interface surface 33 opposite from the polishing face surface 31, and a top window peripheral surface 32 extending from the polishing face surface 31 to the top window interface surface 33. The top window peripheral surface 32 is adjacent to the polishing window-region surface 16, but the top window peripheral surface 32 does not contact the polishing window-region surface 16. There is a gap 44 between the top window peripheral surface 32 and the polishing window-region surface 16. The window region can include a recess 15 such that the polishing face surface 31 is recessed relative to the polishing surface 11. As an alternative the polishing face surface 31 and the polishing surface 11 can be coplanar (not shown). The polishing layer 10 can have a reduced thickness in the window region 100 relative to the remainder of the polishing layer (excluding macrotexture such as grooves) as shown in FIGS. 2A-2B, 3A-3D, 4A-4C, and 8A. Alternatively, the thickness of the polishing layer 10 in the window region 100 may be the same as the thickness of the polishing layer away from the window region (excluding macrotexture such as grooves) as shown for example in FIG. 8B.

[0028] The window further includes a bottom portion comprising a bottom window material 40. The bottom window material 40 has a bottom window interface surface 43, a bottom window bottom surface 41 and a bottom window peripheral surface 42 extending from the bottom window interface surface 43 to the bottom window bottom surface 41. The bottom window interface surface 43 is adjacent the top window interface surface 33. Particularly, the bottom window interface surface 43 can be in direct contact with the top window interface surface 33. Alternatively, a tie layer or an adhesive layer (not shown) can connect the top window interface surface 33 to the bottom layer interface surface 43. The tie or adhesive layer can be, for example, a pressure sensitive adhesive. If the pad 1 is to be used with optical detection, the tie or adhesive layer preferably is transmissive to the wavelength of light used in such optional detection unless an optional gap 44 underlies the top window material 30 as shown in FIGS. 3A-3D and 4A-B, in which case light can pass through the top window material 30 and the gap 44.

[0029] The bottom window material 40 is elastomeric and reversibly compressible. The window region 100 includes a void 44 adjacent to the bottom window material 40 enabling the bottom window material to deform into the void region when the pad is under pressure during polishing. See FIG. 2B.

[0030] The void 44 can be (i) the same as the gap 44 between the polishing window-region surface 16 and the top window peripheral surface 32 as shown, for example, in FIGS. 2A-B and 3A-D; (ii) between regions of the bottom window material 40 as shown, for example, in FIG. 3A-D, FIG. 4A-B, and FIGS. 5-7; (iii) between the subpad material 24 and the bottom window material 40 as shown, for example, in FIGS. 4B-C, 5, 6, and 8A-B; or a combination of two or more of (i), (ii), and (iii), as shown in FIGS. 3A-D, 4B, 5,6, and 8A-B.

[0031] A void 44 in the subpad layer and underlying the top window material 30, such as shown in FIGS. 3A-D and 4-A-C, can facilitate transmission of light through the window region even if the bottom window material 40 is opaque or not highlight transmissive of light. In the absence of such a void underlying the top window material 30, the bottom window material 40 (and any adhesive that may optionally be used between the top window material 30 and bottom window material 40) must be transparent to light to enable transmission of light for use in optical end point detection. Thus, a pad having a window region 100 as shown, for example, in FIGS. 2A-B can include a transparent bottom window material 40 to facilitate optical end point detection. In contrast, in a pad having a window region 100 as shown, for example, in FIGS. 3A-D and 4A-C, can be used for optical end point detection with a bottom material that is transparent, partially transparent, translucent, or opaque.

[0032] The polishing pads as disclosed herein can also be used with vibrational (e.g., acoustic) end point detection. Particularly, vibrations can be transmitted through the top window material 30 and the bottom window material 40 underlying such bottom window material.

[0033] The arrangement of the bottom window material 40 and the top window material 30 relative to the polishing layer 10 and the subpad 20 are such that a seal is formed to prevent slurry and particulates above the polishing layer from leaking to the opposite side of the pad through the window region 100. For instance, a continuous bottom window material 40 together with the subpad material 24 can form a seal as shown, for example, in FIGS. 2A-B. As another instance, the bottom window material 40 can form seals with both the top window material 30 and the subpad material 24, as shown, for example, in FIGS. 3A-D. In yet another instance, the top window material 30 can form a seal with the subpad material as shown, for example, in FIGS. 4A-C. In yet another instance as shown, for example, in FIGS. 8A-B, the bottom window material 40 forms a seal with the polishing layer material 14. The seal can be formed by direct contact of the adjacent surfaces or with a tie or adhesive layer, such as hot melt adhesive or pressure sensitive adhesive between the surfaces to strengthen the seal.

[0034] The pad can include an optional encapsulating layer 50 under the bottom window material 40. For example, in FIGS. 2A-B, and 3A, the encapsulating layer 50 is located only under the bottom window material 40. This approach is also shown in FIGS. 4A-C. As another example, in FIG. 3B, the encapsulating layer 50 extends across the entire window region, being located both under the bottom window material and under the void 44. A pad having a window region as in FIG. 4A-C or 8A-B could also be formed with an encapsulating layering 50 extending across the entire window region including under any void 44. FIG. 3C, shows a pad design without the optional encapsulating layer 50. Also disclosed herein (but not illustrated) are pad designs with are variations of the pad designs of FIGS. 2A-B, 4A-C. and 8A-B without an encapsulating layer. The bottom window bottom surface 41 can define a bottom surface of the pad, bottom window bottom surface 41 can be coplanar with the subpad bottom surface 21, or both. FIGS. 3D and 8A-B, show a pad designs where an optional encapsulating layer 50 extends across the entire bottom of the pad. Also disclosed herein (but not illustrated) are pad designs with are variations of the pad designs of FIGS. 2A-B, and 4A-C modified such that an encapsulating layer extends across the entire bottom of the pad instead of just under the bottom window material 40 as shown. Also disclosed herein (but not illustrated) are variations of the pad designs of FIGS. 8A-B with the encapsulating layer underlying only the bottom window material 40.

[0035] The top window portion dimension perpendicular to the thickness of the pad (e.g., the diameter or width and length or a distance from a polishing window region surface 16 to an opposing polishing window surface 16) can be larger than the bottom window portion dimension perpendicular to the thickness of the pad (e.g., the diameter or width and length or a distance from a subpad layer window region surface 25 to an opposing subpad layer window region surface 25 and comprising the bottom window material 40 and any subpad layer region void 44). (See, e.g., FIGS. 4A-C). Alternatively, such top window portion dimension perpendicular to the thickness of the pad can be the same as such bottom window portion dimension perpendicular to the thickness of the pad dimension. In yet another alternative, such top window portion dimension perpendicular to the thickness of the can be smaller dimension than the bottom window portion dimension perpendicular to the thickness of the pad. (See, e.g., FIGS. 2A-B, 3A-D, and 8A-B).

[0036] The bottom window material 40 can be a monolithic material as shown, for example, in FIGS. 2A-2D, 5, 7, and 8A-B. The monolithic window material 49 having a void (or through hole) 44 extending from the bottom window interface surface 43 to the bottom window bottom surface 41. See, e.g., FIGS. 3A-3D, 4A-B, 5, and 7. For example, as shown in FIG. 5, the bottom window material 40 could have an annular shape. However, other shapes such as ovals, rectangles, hexagons, and the like with through holes could be used. In an alternative structure, the bottom window material 24 could comprise individual columnar structures, such as rectangles as shown in FIG. 6, or arcs, wedges, cylinders, and the like.

[0037] Referring to FIGS. 8A and 8B, the void 44 improves the manufacturability of the window region 100. In particular, void 44 allows top window material 30 and bottom window material 40 to be aligned and centered within recess 15. In FIG. 8A, bottom window material is secured to polishing layer 10 and encapsulating layer 50. The encapsulating layer in turn is secured to a polishing platen (not shown).

[0038] 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 thickness of the top window material can have a thickness of, for example, from 0.3 up to 3.2, from 0.4 up to 2.7, from 0.8 up to 2.2, or 1 to 1 mm, while the thickness of the bottom window material can be from 0.3 up to 3.2, from 0.4 up to 2.7, from 0.8 up to 2.2, or 1 to 1 mm, provided that the overall thickness of the window does not exceed the overall thickness of the pad.

[0039] The top window material can have a diameter (or length and width) of from 2, from 3, or from 4 up to 60, up to 50, up to 40, up to 30, up to 25, up to 20, up to 15, or up to 10 mm. The void 44 between the top window peripheral surface 32 and the polishing window region surface 16 can be from 1, from 2, from 3, from 4, from 5, from 7, from 10, from 15, or from 20 up to 40, or up to 35 mm. The distance from a bottom window peripheral surface 42 to an opposite bottom window peripheral surface 42 can be from 1.5, from 2, from 3, from 4, from 5, from 6, from 7, from 8, from 9, or from 10 up to 75, up to 70, up to 60, up to 50, up to 40, up to 30, or up to 20 mm.

[0040] Any void 44 being inward from the bottom window peripheral surface 42 necessarily has a smaller dimension that the distance from a bottom window peripheral surface 42 to an opposite bottom window peripheral surface 42, but can have a dimension in the direction parallel to the polishing surface 11 of from greater than 0, from 0.5, from 1, from 2, from 3, from 4, from 5, from 6, from 7, from 8, from 9, or from 10 up to 40, up to 38, up to 35, up to 30, up to 25, or up to 20 mm. Any void 44 from the bottom window peripheral surface 42 to the subpad layer window region surface 25 can be 0 or can be from 0.1, from 0.2 from 0.3, from 0.4, or from 0.5 up to 40, up to 35, up to 30, up to 25, up to 20, up to 15, up to 10, or up to 5 mm.

[0041] The depth of the recess 15 can be, for example, greater than 0.1, greater than 0.2, or at least 0.3 millimeters (mm) up to 1.1, up to 1, up to 0.8, up to 0.6 mm, or up to 0.4 mm. Having a thinner polishing material in a peripheral portion of the polishing layer adjacent to the top window material 30 than in the other areas of the pad 100 as shown in FIGS. 2A-2D, 3A-3D, and 4A-4D can enable flexibility during use. Similarly, a width of the peripheral portion can be adjusted to provide the desired mechanical response for the pad materials and design. The width of the peripheral region can be, for example, at least 0.05, at least 0.1, at least 0.2, or at least 0.3 millimeters (mm) up to 1.1, up to 1, up to 0.8, up to 0.6 mm, or up to 0.4 mm.

[0042] The top window material 30 can comprise a polymer or a blend of polymers. For optical detection systems the top material 30 should have sufficient transmission at the wavelengths of light used by the optical metrology. It can be helpful if that top window material 30 has a hardness or thermal expansion coefficient similar to that of the material used in the polishing layer. Examples of window materials include polyurethanes, acrylic polymers, cyclic olefin co-polymers (e.g., TOPAS 8007, etc.).

[0043] The top window material 30 can be 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.

[0044] The curing agent can be 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.

[0045] 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.

[0046] The bottom window material 40 is an elastomeric material. As used herein, elastomeric material means one that deforms when under force, but which returns substantially to the original its original form when the force is removed. The void(s) 44 allow the elastomeric material of the bottom window material 40 to deform into the void 44 when the pad is under downforce during polishing. The bottom window material 40 can return substantially to its original shape when the downforce is removed. Particularly, the thickness of the bottom window material 40 will be reduced under the downforce during polishing but a portion of the bottom window material 40 may deform into the void 44. For example, as shown in FIG. 2B, when under downforce, the bottom window material 40 may deform into the void space 44 above and adjacent to the bottom window material 40. As another example, when under down force bottom window material may deform into a void 44 that is inward from the bottom window peripheral surface 42 as shown in FIGS. 3A-D, 4A-B, and 5. As yet another example, the bottom window material 40 may deform into a void 44 that is between the bottom window peripheral surface 42 and the subpad window region surface 25 as shown in FIGS. 4B, 4C, and 5. 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.

[0047] The elastomeric material of the bottom window material 40 preferably has an elastic modulus that is lower than that of the top window material 30. 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.

[0048] The polishing layer 10 can have, for example, a tensile storage modulus of 300 to 400 MPa, while the subpad layer 20 can have, for example, a 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.

[0049] The polishing layer material 14 can comprise a polymer. The polishing material can be opaque at the thickness of the polishing layer 101. 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.

[0050] % 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).

[0051] The subpad material 24 can comprise a polymeric material. The subpad material can be more compliant (or more elastic) than the polishing material. The subpad 102 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.

[0052] The optional encapsulating layer 50 can provide one or more of the following benefits: facilitate insertion of the window 103 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 103 and the polishing layer 101, the subpad 102, or both, from leaking out; assist in holding the window 103 in place; prevent any leakage of slurry to the bottom side of the polishing pad 100. The encapsulating layer can be a polymer, such as, for example, a polyester. The encapsulating layer can be a non-adhesive layer. The encapsulating layer can have a thickness of, for example, from 0.025, from 0.05, from 0.1 up to 1 mm.

[0053] 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 top window material 30 to a partially assembled pad that already has a cast in place bottom window material 40 in the subpad layer, or insertion of the window assembly into a net shape mold used to prepare a bottom layer blank followed by lamination of the polishing layer.

[0054] An optional pressure sensitive adhesive can be applied on the bottom of the pad to facilitate adhesion of the pad to the platen during polishing.

[0055] 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. According to a preferred method, during polishing both optical detection (e.g., a columnated or non-columnated light wave) and vibrational detection (e.g., acoustic waves) are used during polishing of a single substrate.

[0056] This disclosure further encompasses the following aspects.

[0057] Aspect 1: A polishing pad for chemical mechanical polishing comprising: a polishing layer having a polishing surface, a polishing layer interface surface opposite the polishing surface, and a polishing window region surface extending from the polishing surface to the polishing interface surface, the polishing layer comprising a polishing material, a subpad layer having a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface, and a bottom window regions interface surface extending from the bottom surface to the polishing layer interface surface, the subpad layer comprising a subpad material, a window extending through the polishing pad from the polishing surface to a backside surface of the pad, the window comprising: a top window material having a polishing face surface, a top window peripheral surface, and a top window interface surface, the top window peripheral surface being adjacent to the top window regions surface and separated from the top window region surface such that the top window peripheral surface does not have direct contact with the window region surface, and a bottom window material having a bottom window interface surface bonded to the top window interface surface a bottom window peripheral surface, a bottom window bottom surface wherein the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing, wherein a seal is formed (a) between subpad material and the top window material, the bottom window material, or a combination or (b) between the bottom window material and the polishing material prevent particles or liquid used in the chemical mechanical polishing from passing from above the polishing layer to below the subpad layer, and wherein the pad includes a path in the window region for transmitting columnated or non-columnated light through the thickness of the pad and wherein vibrational signals can be transmitted through the top window material and the bottom window material enabling acoustic end-point detection.

[0058] Aspect 2: The polishing pad of Aspect 1 wherein the top window polishing face surface is recessed below the polishing surface.

[0059] Aspect 3: The polishing pad of Aspect 1 or 2 having a void located inward from the bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface.

[0060] Aspect 4: The polishing pad of any of the previous Aspects having a void located between the bottom window peripheral surface and the subpad layer window region surface.

[0061] Aspect 5: The polishing pad of Aspect 4 having a void located between the bottom window peripheral surface and the subpad layer window region surface.

[0062] Aspect 6: The polishing pad of any of the previous Aspects including an encapsulating layer adjacent to the bottom window bottom surface.

[0063] Aspect 7: The polishing pad of Aspect 6 wherein the encapsulating material extends across a void located between the bottom window peripheral surface and the subpad layer window region surface, across a void located inward from the bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface 41, or both, wherein the encapsulating material is transparent.

[0064] Aspect 8: The polishing pad of any of the previous Aspects having an adhesive between the top window material and the bottom window material.

[0065] Aspect 9: The polishing pad of any of the previous Aspects wherein the top window interface surface is in direct contact with the bottom window interface surface.

[0066] Aspect 10: A method of polishing comprising providing a substrate to be polished, providing the polishing pad as in claim 1, providing a slurry on the polishing pad, polishing by moving the substrate relative to the polishing pad, monitoring polishing by (a) transmitting a light wave through the top window material and the void and detecting the light wave reflected from the substrate, (b) transmitting a vibrational signal through the top window material, the polishing layer material or both and through the bottom window material, or both (a) and (b).

[0067] 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 weight percent and up to 10 or 5 weight percent can be combined as the ranges 1 to 10 weight percent, or 1 to 5 weight percent or 2 to 10 weight percent or 2 to 5 weight percent).

[0068] 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.

[0069] 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.

[0070] 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.