US20220226956A1

US20220226956A1 - Method of manufacture of polishing pads having two or more endpoint detection windows

Info

Publication number: US20220226956A1
Application number: US17/150,071
Authority: US
Inventors: Mauricio E. Guzman
Original assignee: Rohm and Haas Electronic Materials CMP Holdings Inc
Current assignee: Rohm and Haas Electronic Materials CMP Holdings Inc
Priority date: 2021-01-15
Filing date: 2021-01-15
Publication date: 2022-07-21
Also published as: KR20220103638A; TW202241645A; CN114762960A; JP2022109865A

Abstract

A chemical mechanical polishing pad having two or more end point detection windows can be made by providing a structure that includes a polishing layer having a top surface defining a horizontal direction, a bottom surface, and two or more apertures extending from the top surface to the bottom surface wherein each of the two or more apertures has a transparent window located in the aperture, wherein each of the windows has a portion extending outward from the bottom surface of the polishing layer, wherein the two or more apertures are located at select distance from each other, applying a subpad material on the bottom surface and the portion of the windows extending outward from the bottom surface, and revealing the windows by removing a portion of the subpad material and wherein the two or more apertures remain at the select distance from each other.

Description

FIELD OF THE INVENTION

The field of this invention is a method of making polishing pads having more than one endpoint detection windows.

BACKGROUND

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. The process is often used as part of the manufacture when using lithography with multiple deposition steps, in order to precisely build multilayer three-dimensional structure or circuitry. The layer to be polished is typically a thin film (e.g. less than 10,000 Angstroms) that has been deposited on an underlying substrate. The objectives of CMP are to remove excess material on the substrate (e.g. wafer) surface to produce an extremely flat layer of a uniform thickness, the uniformity extending across the entire substrate (e.g. wafer) area.
CMP utilizes a liquid, often called slurry, which 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. Substrates (e.g. wafers) are mounted into a separate fixture, or carrier, which 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 in combination with 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.
Commercial CMP pads are multilayer composites. In addition to an upper polishing layer, which contacts the substrate (e.g. wafer) to be polished, one or more subpad layers are employed to adjust the compliance of the pad under pressure, particularly over the full area of the pad, to better achieve the required film uniformity across the full substrate (e.g. wafer) surface. Controlled increase in compliance can be achieve by using a subpad material of lower modulus than the upper layer and adjusting the relative thicknesses of both layers to achieve the desired result.
In order to precisely control the final thickness of the polished film (the endpoint), film measurement during polishing is widely employed. There are two main metrology approaches for endpointing. One approach for endpoint detection 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, which processes the reflectance signal to determine if the polishing has reached its desired goal (e.g., film thickness, intended reveal of an underlying structure). The metrology equipment can be located within the body of the platen that holds the pad. In some instances, the optical equipment may extend above the platen into the plane of the subpad layers of the CMP pad. Thus, a recess may be desired in the subpad where the window is placed.
This method requires the polishing pad to have at least a portion to be transparent to the wavelengths of light being used in the interferometer. In some pad designs this is achieved by providing a window material of a different composition than the upper pad layer is disposed in an aperture within the pad since many polishing layer materials are opaque. Use of such windows requires alignment of apertures in both the polishing layer and the subpad layer(s).
As integrated circuit dimensions scale down, increasingly accurate real-time film thickness measurements are critical for process control. This has led to the adoption of multiple endpoint units per platen and the use of multispectral optics to allow accurate real-time measurements of film thickness profiles via triangulation and signal processing. Further, to avoid reducing the area for polishing, it can be desirable to reduce the aperture size (window size). As a result, the manufacturing tolerances of current CMP pad windows are becoming more stringent. In addition, maintaining alignment of windows with respect to polishing layer and subpad layer apertures can be challenging. For instance, when forming the multi-layer pad (e.g. by lamination or the like) the differing materials of the polishing and subpad layers may shrink or stretch in different proportions causing misalignment such that the aperture in the subpad does not align with the window or does not align with the aperture in the polishing layer. Also, in forming separate apertures in each layer and then laminating, the pre-formed apertures may not have been in completely consistent locations to enable full alignment of more than two apertures or the aperture and windows in the layers. For example, if there are two apertures in each of the polishing layer and the subpad layer(s) if those are formed at a slightly distinct distance in each layer, then it will be impossible to have full alignment. Total misalignment—e.g., where there is no overlap of the apertures of the subpad and polishing layer or no overlap of the window with one of the apertures—would prevent any use of the window. Partial misalignment—e.g., where the subpad aperture overlaps partially with the window—can narrow the transparent region enough to make it difficult to use for end detection (for example by producing attenuation and noise during measurements that can lead to endpoint detection errors). The misalignment issues can be particularly problematic in pads with multiple windows with smaller aperture sizes. Accordingly, a pad manufacturing process capable of producing a multilayer window pad in a simplified manufacturing process with increased window location precision in all dimensions that is useful for a wide variety of top pad materials would represent a significant improvement in the art.

SUMMARY OF THE INVENTION

Disclosed herein is a method of manufacturing a chemical mechanical polishing pad having two or more end point detection windows comprising providing a structure that includes a polishing layer having a top surface defining a horizontal direction, a bottom surface, and two or more apertures extending from the top surface to the bottom surface wherein each of the two or more apertures has a transparent window located in the aperture, wherein each of the windows has a portion extending outward from the bottom surface of the polishing layer, wherein the two or more apertures are located at select distance from each other, applying a subpad material on the bottom surface of the polishing layer and wherein the two or more apertures remain at the select distance from each other and the portion of the windows extending outward from the bottom surface, and revealing the windows by removing a portion of the subpad material.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1a is a top view of a pad having three windows.

FIG. 1b is a cross-section view of a portion of the pad of FIG. 1.a. showing the layers of the pad and one window.

FIG. 2 is a schematic view of a window.

FIG. 3 is a side view of a window.

FIG. 4a-4i represent a sequential series of cross section views that illustrate forming a pad and subpad with multiple windows in accordance with the method of the invention.

FIG. 5 is a cross section of a portion of a pad having a window as in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The present application is a method of forming a pad that allows for precise locating of more than one window in the pad. The method avoids the problems of misalignment of apertures in the subpad with the apertures in the polishing layer and misalignment of the windows in the apertures. Such misalignment may be caused for example by one or more of the following: by different coefficients of thermal expansion in the layers, different stretching of deformation of the layers during manufacture, imprecise location of apertures in two different layers, imprecise alignment of apertures during lamination, or the like, or a combination of two or more of those causes.
Thus, the method comprises providing a polishing layer having a top surface defining a horizontal direction, a bottom surface (also referred to herein as an interface surface), and two or more apertures extending from the top surface to the bottom surface, wherein each of the two or more apertures is located at a select distance from the other aperture(s). Located in the aperture, is a transparent window. The windows each include a portion extending outward from the bottom surface of the polishing layer. The method includes applying a subpad material on the bottom surface and the portion of the windows extending outward from the bottom surface, and then removing a portion of the subpad material to expose the windows. This method ensures alignment of the windows with the apertures in the polishing layer as each window is located in one of such apertures. This method further ensures alignment of the polishing layer aperture windows with the aperture in the subpad.
FIG. 1a is a top view of one example of a pad made by the method disclosed herein. The pad 01 has a top surface 03. Although not shown, the top surface 03 can have a surface roughness or a surface pattern such as grooves or perforations. This pad has three windows 04 located at select distances, d_s1, d_s2, and d_s3, from each other. The select distances can be the same or different. As examples of window placement and orientation: each window could be placed at the same radial distance from the center 07 of the pad or each window could be placed at a different distance from the center 07 of the pad; the windows could be equidistant from each other or the windows can be non-equidistant from each other. Most advantageously all windows are at the same radial distance from the center 07. The select distance(s) can be selected to correspond to the placement of endpoint detection sensors in a tool or platen for chemical mechanical polishing. Each window 04 can be the same size. Each window 04 can be of the same shape. Each window 04 can be of the same material. Alternatively, a first window can be of a different size, a different shape, or a different material from a second window or any third or more windows. At least two of the windows are transparent to the wavelength of radiation (e.g. light) used in the sensor. The windows can be made from a polymer or polymer blends desired so long as it has sufficient transmission at the wavelengths used by the optical metrology. It can be helpful if that window material has a hardness and 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.). Use of polyurethane materials can be helpful in pads where the polishing layer and subpad layer(s) are also polyurethanes. Advantageously, the window has transmission to as low of wavelength as possible, such as that achieve with windows manufactured with aliphatic polyurethanes or other materials having optical transparency.
FIG. 1b shows a cross-section of a portion of a pad. The pad includes a polishing layer 05 and a subpad 06. The window 04 shown in FIG. 1b has a plug shape. The polishing layer 05 can comprise a polymeric material. It can optionally include pores and or particulates. 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 05 can comprise a polymer that is a polyurethane formed by reaction of one or more polyfunctional isocyanates and one or more polyols.
The subpad layer 06 can comprise one or more layers. The subpad layer(s) can comprise a material that is more compliant than the material of the polishing layer 05. The subpad layer(s) 06 can comprise a polymeric material. The subpad 06 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.
FIGS. 2 and 3 show other window shapes. The window 204 in FIG. 2 has an upper portion 204 u and a lower portion 204 l, each portion being cylindrical or oval. The upper portion 204 u has a dimension (e.g. diameter) d_uthat is smaller than the dimension (e.g. diameter), d_l, of the lower portion 204 l such that a rim 204 r is formed. The lower portion can form a flange portion. In FIG. 3 a cross section of a similar window 304 is shown that include an upper portion 304 u, a middle portion 304 m, and a lower portion 304 l. The middle portion 304 m has a dimension (e.g. a diameter) in the horizontal direction that is larger than the dimension of either the upper portion 304 u or the lower portion 304 l, thus forming an upper rim 304 ur and a lower rim 3041 r. The middle portion can form a flange portion. While FIG. 3 shows the lower portion 304 l having a dimension in the horizontal direction that is smaller than the dimension in the horizontal direction of the upper portion 304 u, those dimensions could in the alternative be approximately the same size. Generally the window dimensions in the horizontal direction are on the order of 8 to 18 mm. Generally the overall height of the window is less than the overall thickness of the pad. For example, the overall height (e.g. h_total) of the window can be 1 to 5 mm, or 1 to 4 mm, where the height of the upper and lower portions can be 1 to 2 mm and the height of a middle portion can be 0.3 to 2, 0.4 to 1, or 0.5 to 0.8 mm.
FIGS. 4a-i represent a sequential series of schematic showing an example of herein using a mold and a window as disclosed in FIG. 2. A mold 208 is provided having at least two recess 211 (one is shown). The two recesses are located at a select distance, ds, (not shown) from each other. The location of the recesses can correspond to the location of endpoint detection sensors elements in a chemical mechanical polishing tool. The recess dimension 210 and the lower portion 204 l of the window 204 are selected such that the lower portion 204 l of the window 204 fits, preferably fits precisely and snuggly without any or any significant gaps between sides of the window 204 and the sides of the recess 211. As shown, the depth 209 of the recess 211 can be the same or substantially the same as the height, hi, of the lower portion 204 l of the window 204. If a window 304 as shown in FIG. 3 is used, the recess can mate with either the lower portion 304 l or with both the lower portion 304 l, and the middle portion 304 m. If a plug type window 04 as is shown in FIG. 1b is used, the depth 209 is less than the full height of the window 04. In each instance, an upper portion of the window (e.g. 204 u or 304 u, latter not shown) protrudes above a surface 212 of the mold 208. The mold can be made from any material, for example, a metal such as steel. The mold can also be fitted with a removable collar around its outer perimeter that can shape the outer perimeter of the layer 205. The mold includes a top surface 212. As shown in FIG. 4c , a polishing material 205 is applied over the top surface 212 and, optionally, over the upper portion (e.g., 204 u as shown) of the window (e.g. 204 as shown). The polishing material can be applied by coating (e.g., spray coating), casting, molding (e.g. injection molding), additive manufacture (e.g. 3D printing), or laminating. The polishing layer material 205 can be applied in polymerized form or can be applied as a pre-polymer composition and polymerized or can be applied in a curable form and cured while in the mold 208. The polishing layer 205 as initially formed can have thickness 215 equal to, substantially equal to, or greater than the height of the upper portion of the window 204 that is extending above the surface 212. In FIG. 4c , the polishing layer 205 as initially formed has a thickness greater than the height of the upper portion of the window 204. In this instance, the polishing layer material 205 can cover the top surface of the window 204 by an excess amount 213 and the top surface of the window 204 can be exposed by a reveal step to arrive at the structure in FIG. 4d . In other instances—e.g., where injection molding is used where a top portion of a mold contacts a top surface of the window, coating with a mask over the window 204, or additive printing are used—the polishing material 205 may not be on the top surface of the window 204 such that the applying step directly forms the structure of FIG. 4d . When a reveal step is used this step can also provide desired texture or controlled surface roughness to the top surface of the polishing layer 205. The structure can be such that the windows do not protrude above the top surface of the polishing layer 205. The top surface of the windows can be coplanar with the top surface 205 t of the polishing layer 205.
After forming the polishing layer 205 (before or after any needed reveal step), the polishing layer with at least two windows in two apertures formed in the preceding steps is removed from the mold 208 exposing an interface surface 205 i and the lower portion of the windows 204. (See FIG. 4e showing the polishing layer and window removed from mold 208 and inverted). Note, that while FIG. 4 shows the method using a window with a structure as in FIG. 2 with a smaller upper portion and a larger lower portion, the method is equally applicable to a window that has a simple plug shape or to a window that has three portions as shown in FIG. 3. Note further that while FIG. 4 shows that the entire larger lower portion fits in the recess, it is also contemplated that a portion of the larger lower portion could extend above the top surface 212 of the mold. Similarly, if a window with three portions is used, the mold could have a recess for only the lowest portion 304 l (or a portion there) or a stepped recess to accept both the lowest portion 304 l and at least a portion of the middle portion 304 m.
Alternatively, the structure as shown in FIG. 4e , can be made by forming two or more apertures in a pre-formed polishing layer the apertures being formed at a select distance, ds, from each other. The location of the apertures can correspond to the positioning of endpoint detection sensors in a chemical mechanical polishing tool. A window can then be inserted into each aperture such that a portion of the window extends above the interface surface 205 i of the polishing layer. In this instance, an adhesive can be applied to at least a portion of the regions of the polishing layer contacting the window and at least a portion of the regions of the window contacting the polishing layer. Particularly, the adhesive can be applied at rim portions 204 r and 304 ur (as shown in FIG. 2 and FIG. 3, respectively) of the window and the adjacent polishing layer.
As shown in FIG. 4f , the polishing layer with windows can then have subpad 206 formed on the interface surface 205 i and the lower portion 204 u. During this process the polishing layer 205 with windows can be supported on a support 218 (not shown). The support could be a mold. This support mold could also be fitted with a removable collar around its outer perimeter, which support can be used to define the outer perimeter and the thickness of the subpad material 206. The subpad material can be applied in already polymerized form or can be polymerized or cured after application to the interface 205 i and the windows. While the subpad material 206 is shown with a planar top surface and extending above the window at an excess thickness amount 213, the top surface can alternatively generally follow the contour of the interface surface 205 i and the window portion extending from that surface such that there is a raised portion of subpad material where the window is found. This raised portion can be used to identify where to apply the reveal step to form a structure as shown in FIG. 4h with a recess area 214.
As shown in FIG. 4g , the excess subpad material 206 can be removed to reveal the window 204, by machining, grinding or etching. As shown in FIGS. 4h and 4i , (FIG. 4i is FIG. 4h inverted) the window material can be further etched back to provide a recess area 214. Alternatively, if a raised portion of subpad 206 is used to identify the location of the window, a selective etch or well machining can be done in that location to reveal the window and form the recess.
FIG. 5 shows use of a window 504 similar to that in FIG. 3 with adhesive 520 applied in certain portions (for example, the adhesive can be applied on at least one rim or flange) to hold the window in the polishing layer 505. The extended middle portion of the window 504 serves as a flange that further can hold the window in its desired location.
This disclosure further encompasses the following aspects.
Aspect 1: A method of manufacturing a chemical mechanical polishing pad having two or more end point detection windows comprising providing a structure that includes a polishing layer having a top surface defining a horizontal direction, a bottom surface, and two or more apertures extending from the top surface to the bottom surface wherein each of the two or more apertures has a transparent window located in the aperture, where each of the windows has a portion extending outward from the bottom surface of the polishing layer, wherein the two or more apertures are located at select distance from each other, applying a subpad material on the bottom surface and the portion of the windows extending outward from the bottom surface, and revealing the windows by removing a portion of the subpad material.
Aspect 2. The method of Aspect 1 wherein the providing of the structure comprises providing a mold with a surface and two or more recesses in the surface each recess formed to receive a portion of one of the windows, the recesses being located at the select distance from each other, inserting the windows into the recesses such that a top portion of each the windows extends above the mold surface, forming the polishing layer on the mold surface and around a periphery of the top portion of the windows, and removing the polishing layer with the windows from the mold.
Aspect 3. The method of Aspect 2 wherein in forming the polishing layer a top surface of the windows is covered by a portion of the polishing layer and further comprising revealing the top surface of the windows by removal of a portion of the polishing layer.
Aspect 4. The method of Aspect 1 wherein the providing of the structure comprises forming the two or more apertures in the polishing layer at the select distance from each other, providing the windows for each aperture, each window having a top portion and a flange portion, wherein the top portion has an area in the horizontal direction that is smaller than an area of the flange portion in the horizontal direction such that the second portion forms a rim, applying adhesive to the bottom surface of the polishing layer adjacent the aperture, to the rim of the windows, or both, and inserting into each of the two or more the apertures one of the windows such that the polishing layer surrounds a periphery of the top portion of each of the windows in the horizontal direction.
Aspect 5. The method of Aspect 4 wherein at least a segment the flange portion of the windows forms the portion of the window that extends from the bottom surface of the polishing layer.
Aspect 6. The method of Aspect 4 wherein the flange portion of the windows is between the top portion of the windows and a bottom portion of the windows, wherein the bottom portion has an area in the horizontal direction that is smaller than the area of the flange portion in the horizontal direction, wherein the bottom portion, or the bottom portion and at least a segment of the flange portion form the portion of the windows extending outward from the bottom surface of the polishing layer and the area of the flange portion in the horizontal direction is larger than the area of the portion of the window extending outward from the bottom surface of the polishing layer.
Aspect 7. The method of any one of Aspects 1-6 wherein the subpad material is applied by coating, injection molding, printing.
Aspect 8. The method of any one of Aspects 1-7 wherein an amount of the portion of the window extending outward from the bottom surface of the polishing layer is removed during or after the removing of a portion of the subpad material to form a recessed window.
Aspect 9. The method of any one of Aspects 1-8 wherein there are three or more apertures and windows and the select distance between adjacent apertures is the same or different.
Aspect 10. The method of any one of Aspects 1-9 wherein the select distance corresponds to a distance of placement of endpoint detectors in a chemical mechanical polishing apparatus having two or more endpoint detectors.
Aspect 11: The method of any one of Aspects 1-10 wherein each of the apertures in the polishing layer and each of the windows in the pad are at a distance from a center of the polishing layer, preferably a radial distance, which is the same for each aperture and equidistant from the center.
Aspect 12: The method of any one of Aspects 1-11 wherein there are three windows that are equidistant from each other.
Aspect 13: The method of any one of Aspects 1-12 wherein the windows are of the same size.
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”).
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.
References numerals stand for the element/component as listed below:

01, 201 polishing pad
03, 205 t top surface of polishing pad
04, 204, 304, 504 windows
05, 205, 505 polishing layer
06, 206, 506 subpad
204 u, 304 u upper portion of window, generally surrounded in its periphery by polishing
player
204 l, 304 l lower portion of window, generally at least part of its height is surrounded in its
periphery by subpad material. 204 l can be flange
304 m middle portion of window or flange
208 mold
209 depth of recess in mold
210 horizontal dimension of recess in mold
211 recess in mold
212 top surface of mold
205 i interface surface of polishing layer upon which subpad is formed
213 excess height of subpad material applied over window
214 recess formed on bottom side (subpad side) of window
215 excess height of polishing layer material applied over window
520 adhesive

Claims

What is claimed is:

1. A method of manufacturing a chemical mechanical polishing pad having two or more end point detection windows comprising:

providing a structure that includes a polishing layer having a top surface defining a horizontal direction, a bottom surface, and two or more apertures extending from the top surface to the bottom surface wherein each of the two or more apertures has a transparent window located in the aperture, wherein each of the windows has a portion extending outward from the bottom surface of the polishing layer, wherein the two or more apertures are located at select distance from each other,

applying a subpad material on the bottom surface and the portion of the windows extending outward from the bottom surface of the polishing layer and wherein the two or more apertures remain at the select distance from each other,

revealing the windows by removing a portion of the subpad material.

2. The method of claim 1 wherein the providing of the structure includes the following:

providing a mold with a surface and two or more recesses in the surface each recess formed to receive a portion of one of the windows, the recesses being located at the select distance from each other,

inserting the windows into the recesses such that a top portion of each the windows extends above the mold surface,

forming the polishing layer on the mold surface and around a periphery of the top portion of the windows, and

removing the polishing layer with the windows from the mold.

3. The method of claim 2 wherein in forming the polishing layer a top surface of the windows is covered by a portion of the polishing layer and further comprising revealing the top surface of the windows by removal of a portion of the polishing layer.

4. The method of claim 1 wherein the providing of the structure comprises

forming the two or more apertures in the polishing layer at the select distance from each other,

providing the windows for each aperture, each window having a top portion and a flange portion, wherein the top portion has an area in the horizontal direction that is smaller than an area of the flange portion in the horizontal direction such that the second portion forms a rim,

applying adhesive to the bottom surface of the polishing layer adjacent the aperture, to the rim of the windows, or both, and

inserting into each of the two or more the apertures one of the windows such that the polishing layer surrounds a periphery of the top portion of each of the windows in the horizontal direction.

5. The method of claim 4 wherein at least a segment the flange portion of the windows forms the portion of the window that extends from the bottom surface of the polishing layer.

6. The method of claim 4 wherein the flange portion of the windows is between the top portion of the windows and a bottom portion of the windows, wherein the bottom portion has an area in the horizontal direction that is smaller than the area of the flange portion in the horizontal direction, wherein the bottom portion, or the bottom portion and at least a segment of the flange portion form the portion of the windows extending outward from the bottom surface of the polishing layer and the area of the flange portion in the horizontal direction is larger than the area of the portion of the window extending outward from the bottom surface of the polishing layer.

7. The method of claim 1 wherein the subpad material is applied by coating, injection molding, or printing.

8. The method of claim 1 wherein an amount of the portion of the window extending outward from the bottom surface of the polishing layer is removed during or after the removing of a portion of the subpad material to form a recessed window.

9. The method of claim 1 wherein there are three or more apertures and windows and the select distance between adjacent apertures is the same or different.

10. The method of claim 1 wherein the select distance corresponds to a distance of placement of endpoint detectors in a chemical mechanical polishing apparatus having two or more endpoint detectors.