Polishing apparatus that provides a window

Abstract

A polishing pad apparatus includes, a polishing pad, an optically transmissive window framed by an opening through the polishing pad, the window being part of an underlay, and the underlay having a perimeter that extends substantially beyond the perimeter of the window to form a fluid impermeable layer that isolates a rear surface of the window from obstruction by polishing fluid.

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a polishing pad apparatus that provides a window in a polishing pad.

[0004] 2. Related Art

[0005] U.S. Pat. No. 6,045,439 discloses a polishing pad apparatus including, a polishing pad mounted on a polishing platen of a polishing machine. An adhesive, such as, a pressure sensitive adhesive, adheres the polishing pad to the polishing platen. Successive layers of the polishing pad, such as, a polishing layer of the polishing pad and one or more sublayers of the polishing pad, adhere to one another by additional adhesive. The machine revolves the polishing platen and the polishing pad, and dispenses a polishing fluid onto the polishing pad. The polishing pad and the polishing fluid polish a semiconductor substrate, which removes material from the semiconductor substrate, and which provides a smooth, planar polished surface on the semiconductor substrate. Further, the polishing pad of the apparatus is adapted with a transparent window. The window is framed by an opening through the polishing pad. An optical beam is transmitted from an optical detector apparatus, through a rear of the window, to reflect from the surface of the semiconductor substrate. The optical beam monitors the surface of the semiconductor substrate, as the substrate is being polished. The optical beam is reflected, and transmits through the window for detection by the optical detector apparatus.

[0006] One of the problems associated with such a polishing pad apparatus is, that the polishing fluid seeps behind the polishing pad, and obstructs a rear surface of the window, which contributes to undesired attenuation of the optical beam. Another problem is, that the adhesion strength of the adhesive is reduced when the adhesive becomes wet by leaking polishing fluid, which weakens the adhesion of the polishing pad to the polishing platen, and which weakens the adhesion of successive layers of the polishing pad.

[0007] Several sources for fluid seepage exist. The polishing fluid will seep through a polishing pad that is designed to be wetted with the polishing fluid. Further, the polishing fluid will seep through an unsealed peripheral edge of the polishing pad. Further, the polishing fluid will seep through a leaking seam between the window and the opening. Manufacturing processes have been required to cut and fit the window to the opening, and to apply a sealant material in the seam, or alternatively, to mold both the window and the polishing pad simultaneously to join them together at the seam.

[0008] According to WO 01/23141, published PCT application PCT/US00/26652, a fluid impermeable layer is provided to span across a polishing layer and a window in an opening through the polishing layer. The fluid impermeable layer is provided with an adhesive forming a bond seal with the polishing layer and a rear surface of the window. The bond seal is a source for fluid seepage. Further, the optical beam transmits through a first interface at the bond layer and the fluid impermeable layer, and successively through a second interface at the bond layer and a rear surface of the window. Such interfaces tend to attenuate the optical beam. It would be advantageous to eliminate such interfaces.

[0009] A need exists for a polishing pad apparatus having an optically transmissive window framed by an opening through a polishing pad, which apparatus isolates a rear surface of the window from obstruction by polishing fluid.

SUMMMARY OF THE INVENTION

[0010] The invention provides a polishing pad apparatus having, a polishing pad, an optically transmissive window framed by an opening through the polishing pad, the window being part of an underlay that is unitary with the window, and the underlay having a perimeter that extends substantially beyond the perimeter of the window to form a fluid impermeable layer that isolates a rear surface of the window from obstruction by polishing fluid and from obstruction by the underlay.

[0011] Embodiments of the invention will now be described by way of example with reference to the following detailed description taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a top view of a polishing pad, reduced in size.

[0013] FIG. 1A is an isometric view of a polishing pad in the form of a continuous belt that is adapted to be mounted on a polishing platen of belt configuration.

[0014] FIG. 2 is a fragmentary, enlarged side view of a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, with parts of the apparatus broken away to disclose, a polishing pad having an opening, an underlay having a window, the underlay being adapted for mounting on a polishing platen of a polishing machine, and further wherein, the underlay is part of the polishing platen, and the polishing pad is removable from the underlay for replacement by another, duplicate polishing pad

[0015] FIG. 2A is a view similar to FIG. 2, and disclosing a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, with parts of the apparatus broken away to disclose, a polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and an underlay having a window, the underlay being adapted for mounting on a polishing platen of a polishing machine, and further wherein, the underlay is a part of the polishing platen, and the sublayer and a remainder of the polishing pad are removable from the underlay for replacement by another polishing pad.

[0016] FIG. 2B is a fragmentary, enlarged side view of an underlay of a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, adapted for mounting on a polishing platen, with parts of the apparatus broken away to disclose, a window of solid structure.

[0017] FIG. 2C is a view similar to FIG. 2B, and disclosing an underlay of a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, adapted for mounting on a polishing platen, with parts of the apparatus broken away to disclose, a window substantially coplanar with the thickness of the underlay.

[0018] FIG. 3 is a fragmentary, enlarged side view of a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, with parts of the apparatus broken away to disclose, a polishing pad, an underlay having a window, the underlay being adapted for mounting on a polishing platen of a polishing machine, and further wherein, the underlay is part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

[0019] FIG. 3A is a view similar to FIG. 3, and disclosing a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, with parts of the apparatus broken away to disclose, a polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and an underlay having a window, the underlay being adapted for mounting on a polishing platen of a polishing machine, and further wherein, the underlay is a part of the polishing pad, and, the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

[0020] FIG. 3B is a view similar to FIG. 3, and disclosing a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, with parts of the apparatus broken away to disclose, a polishing pad having a sublayer that is part of the polishing pad, and an underlay having a window, the underlay being adapted for mounting on a polishing platen of a polishing machine, and further wherein, the underlay is a part of the polishing pad, and a protruding lip on the underlay provides a seal at an edge of the sublayer.

[0021] FIG. 3C is a view similar to FIG. 3, and disclosing a polishing pad apparatus, for example, as disclosed by FIG. 1 or by FIG. 1A, with parts of the apparatus broken away to disclose an underlay adapted for mounting on a polishing platen, and further wherein, the underlay has a window that is substantially coplanar with the thickness of a remainder of the underlay.

[0022] FIG. 4 is a fragmentary enlarged side view of an underlay having a window that is fabricated as a hollow structure.

[0023] FIG. 4A is a fragmentary enlarged side view of an underlay having a window that is fabricated as a solid structure.

[0024] FIG. 4B is a fragmentary enlarged side view of an underlay having a window, and further disclosing the window as a nonprojecting structure that is coplanar with the thickness of a remainder of the underlay.

[0025] FIG. 4C is a fragmentary enlarged side view of an underlay having a window, and further disclosing underlay having a projecting lip that forms a seal.

DETAILED DESCRIPTION

[0026] Each of FIGS. 1 and 1A, discloses a polishing pad 2 having at least a top layer 4 for polishing a semiconductor substrate, an opening 5 through the top layer 4, and an optically transmissive window 6 framed by the opening 5. The size of the opening 5 is limited, to occupy a small portion of the top layer 4, which minimizes any difference in the entirety of the polishing activity provided by the polishing layer 4. Each polishing pad 2 has a perimeter 2a, with the polishing pad 2 of belt configuration having a perimeter 2a along each of the continuous edges of the belt configuration.

[0027] Each of FIGS. 2, 2A, 2B, 2C, 3, 3A, 3B and 3C discloses a corresponding embodiment of a polishing pad apparatus 1 that includes, a polishing pad 2 adapted to be mounted on a polishing platen 3 of a known polishing machine. The known polishing machine performs a known polishing operation, according to which, the polishing pad 2 is revolved by the known polishing machine. The polishing pad is accompanied by a polishing fluid to polish a semiconductor substrate that is held by the known polishing machine. The semiconductor substrate includes, and is not limited to, for example, a wafer of silicon, a magnetic storage disk, an optical storage disk, and a semiconductor wafer patterned with conducting circuit interconnects.

[0028] When the polishing pad 2 is revolved, the opening 5 passes over an optical beam of a known optical detector. The window 6 is adapted to align directly with an opening 3a through the polishing platen 3. An optical beam of the known optical detector transmits through the opening 3a, and through the window 6 to reflect from a surface of a semiconductor substrate being polished by the polishing pad 2. Reflection of the optical beam transmits the optical beam in a reverse direction through the window 6 and through the opening 3a for monitoring by the known optical detector. Further details are disclosed by U.S. Pat. No. 6,045,439, incorporated by reference herein.

[0029] Further, each corresponding embodiment includes a polishing pad 2 having a top layer 4 that projects beyond the window 6. During a polishing operation, the top layer 4 polishes a semiconductor substrate, and is known as a polishing layer of the polishing pad 2. The window 6, being recessed, avoids contact with the semiconductor substrate, as the top layer 4 contacts the semiconductor substrate during the polishing operation.

[0030] Prior to the invention, polishing fluid would seep behind the top layer 4, to obstruct a rear surface 6a of the window 6, which contributed to attenuation of an optical beam. Several sources for fluid seepage continue to exist. The polishing fluid would seep through the top layer 4, when the top layer 4 is designed to be wetted with the polishing fluid. Further, the polishing fluid would seep through an unsealed peripheral edge 2a of the polishing pad 2. When the polishing pad 2 included a sublayer 7, as disclosed by FIGS. 2A, 3A and 3B, beneath the polishing layer 4, fluid would seep through an unsealed edge 7b of the sublayer 7. Prior to the invention, manufacturing processes have been required to cut and fit the window 6 to the opening 5, and to apply a sealant material in a seam 5a that is between the window 6 and the opening 5. Alternatively, manufacturing processes have been required to mold both the window 6 and the polishing pad 2 simultaneously to join them together at the seam 5a. However, polishing fluid would seep through leaks that would develop in the sealed seam 5a.

[0031] Each embodiment of the invention provides a polishing pad apparatus 1 having an optically transmissive window 6 framed by an opening 5 through a polishing pad 2, which apparatus 1 isolates the rear surface 6a of the window 6 from obstruction by polishing fluid. The window 6 is part of an underlay 8. The underlay 8 is unitary with a perimeter 6b of the window 6. The unitary underlay 8 and window 6 eliminate the need for an adhesive bond seal between the underlay 8 and the window 6, which bond seal would be a source for fluid seepage. Further, because the underlay 8 joins the perimeter 6b of the window 6, the rear surface of the window 6 is free of an interface with the underlay 8. Further, the rear surface of the window 6 is without a bond seal between the rear surface of the window and the underlay 6, which would contribute to attenuation of an optical beam. The underlay 8 has a perimeter 8a that extends substantially beyond the perimeter 6b of the window 6 to encompass a large area within its perimeter 8a. In an embodiment, the perimeter 8a extends to the perimeter 2a of the pad 2 disclosed by FIG. 1. In another embodiment, the perimeter 8a extends to at least one perimeter 8a of the pad 2 of belt configuration disclosed by FIG. 1A. In another embodiment, the perimeter 8a extends to each perimeter 8a of the pad 2 of belt configuration disclosed by FIG. 1A.

[0032] The underlay 8 is fabricated and combined with the polishing pad apparatus 1 in a manner to form a fluid impermeable layer that isolates the rear surface 6a of the window 6 from obstruction by polishing fluid that would otherwise seep behind the polishing pad 2. An adhesive layer 10 or an adhesive layer 12 attaches to the underlayer 8. Another adhesive layer 9 attaches to a rear surface of the underlayer 8. Either one or more than one of the adhesive layers 9, 10 and 12 against the underlayer 8 provides a corresponding seal extending substantially beyond the perimeter 6b of the window, which isolates the rear surface 6a of the window 6 from obstruction by the polishing fluid. When the underlay 8 is fabricated from an hydrophobic material, such a material by itself repels polishing fluid, and isolates the rear surface 6a of the window 6 from obstruction by the polishing fluid.

[0033] Each of FIGS. 2, 2A, 2B and 2C discloses a corresponding embodiment of a polishing pad apparatus 1 wherein, the underlay 8 is part of the polishing platen 3. The polishing platen 3 is circular for mounting the circular polishing pad 2 disclosed by FIG. 1, or the polishing platen 3 is of belt configuration for mounting the polishing pad 2 of belt configuration disclosed by FIG. 1A. The underlay 8 has an adhesive layer 9 on a rear surface of the underlay 8. The adhesive layer 9 has an opening 9a adapted to be in alignment with an opening 3a through the polishing platen 3. For example, the adhesive layer 9 is an adhesive tape with adhesive on opposite sides of the tape.

[0034] As disclosed by FIG. 2, a rear surface of the polishing pad 2 has an adhesive layer 10 with an opening 10a adapted to be in alignment with the opening 5. A rear surface of the adhesive layer 10 is covered by a removable covering film 11 that initially adheres to and covers the adhesive layer 10, and is peeled from the adhesive layer 10, as depicted by the arrow, which exposes the adhesive layer 10 for attachment removably to the underlay 8.

[0035] The adhesive layer 10 is provided with hollow air transmitting pathways, which pathways allow escape of air that would tend to be entrapped under the adhesive layer 10. The adhesive layer 10, as well as other adhesive layers described herein, have such air transmitting pathways as further disclosed in detail by U.S. patent application Ser. No. 09/660,798 incorporated by reference herein. Each of the other adhesive layers 9 and 12, is provided with corresponding, hollow air transmitting pathways.

[0036] When the polishing pad 2 becomes worn out from polishing, the pad 2 and the adhesive layer 10 are removable from the underlay 8 for replacement by another, duplicate polishing pad 2 The underlay 8 remains as part of the polishing platen 3, and is easily cleaned in preparation for assembly of a replacement pad 2.

[0037] The underlay 8 itself is removable, together with the adhesive layer 9, for replacement by a duplicate underlay 8. The polishing pad 2 is expected to be replaced more frequently than the underlay 8. The adhesive layer 10 is advantageously soluble in a solvent that assists in removal and cleaning of the adhesive layer 10 from the underlay 8. The adhesive layer 9 is advantageously insoluble in such a solvent, which promotes retention of the underlay 8 on the polishing platen 3.

[0038] The embodiment disclosed by FIG. 2A further includes, the polishing pad 2 having the top layer 4 assembled over and on a sublayer 7. The sublayer 7 has an opening 7a in alignment with the opening 5. Together, the opening 7a and the opening 5 combine to provide a composite opening through the polishing pad 2. The adhesive layer 10 attaches the top layer 4 to the sublayer 7. A rear surface of the sublayer 7 has an adhesive layer 12 with an opening 12a in alignment with the opening 5. The adhesive layer 12 is covered by the removable covering film 11 that is peeled from the adhesive layer 12, as depicted by the arrow, which exposes the adhesive layer 12 for attachment removably to the underlay 8. The window 6 has a projecting height sufficient to project into both the opening 7a the opening 5. A seal 7b is provided at a peripheral edge of the sublayer 7. The seal 7b includes, but is not limited to, for example, a heat seal, a pressure embossed seal, and a waterproof coating. The seal 7b resists seepage of polishing fluid into the peripheral edge 7b that is a part of the peripheral edge 2a of the polishing pad 2. Further details of the seal 7b are disclosed by U.S. patent application Ser. No. 09/635,877, incorporated herein by reference.

[0039] With reference to the embodiment disclosed by FIG. 2A, when the polishing pad 2 becomes worn out from polishing, the pad 2 and the adhesive layer 12 are removable from the underlay 8 for replacement by another, duplicate polishing pad 2. The underlay 8 remains as part of the polishing platen 3, and is easily cleaned in preparation for assembly of a replacement pad 2. The underlay 8 itself is removable, together with the adhesive layer 9, for replacement by a duplicate underlay 8. For this embodiment, the polishing pad 2 is expected to be replaced more frequently than the underlay 8. The adhesive layer 12 is advantageously soluble in a solvent that assists in removal and cleaning of the adhesive layer 12 from the underlay 8. The adhesive layer 9 is advantageously insoluble in such a solvent, which promotes retention of the underlay 8 on the polishing platen 3.

[0040] Each of the embodiments disclosed by FIGS. 2 and 2A includes an embodiment of an underlay 8 wherein, the window 6 is a hollow structure that projects into the opening, as well as being framed by the opening indicated by the numeral 5, or by the composite of numerals 5 and 7a. FIG. 2B discloses a portion of a polishing pad apparatus 1 having an alternative embodiment of the underlay 8 wherein, the window 6 is a solid structure that projects into the opening, as well as being framed by the opening indicated by the numeral 5, or by the composite of numerals 5 and 7a. FIG. 2C discloses a portion of a polishing pad apparatus 1 having an alternative embodiment of the underlay 8 wherein, the window 6 has a thickness that is substantially coplanar with a thickness of a remainder of the underlay 8, as well as, the window 6 being framed by the opening, as indicated by the numeral 5, or as indicated by the composite of numerals 5 and 7a. The perimeter 6b of the window 6 is indicated by a broken line through the thickness of the underlay 8.

[0041] Each of FIGS. 3, 3A, 3B and 3C discloses a corresponding embodiment wherein, the underlay 8 is part of the polishing pad 2, such that, the underlay 8 and a remainder of the polishing pad 2 are removable from the polishing platen 3 for replacement by another, duplicate polishing pad 2. The polishing pad 2 has an adhesive layer 10 with an opening 10a adapted to be in alignment with the opening 5. For each the embodiments disclosed by FIGS. 3, 3A and 3B, the adhesive layer 10 attaches the top layer 4 of the polishing pad 2 to the underlay 8. The rear surface of the underlay has attached thereto an adhesive layer 9. The adhesive layer 9 has an opening 9a adapted to be in alignment with both the opening 5 and an opening 3a through the polishing platen 3. For example, the adhesive layer 9 is an adhesive tape with adhesive on opposite sides of the tape.

[0042] Each of FIGS. 3 and 3C discloses a corresponding embodiment wherein, the adhesive layer 9 is covered by the removable covering film 11 that is peeled from the adhesive layer 9, as depicted by the arrow, which exposes the adhesive layer 9 for attachment of the underlay 8 to the polishing platen 3.

[0043] The embodiment disclosed by FIG. 3 includes the same underlay 8 with a window 6 of hollow structure, as disclosed by FIG. 2. The embodiment disclosed by FIG. 3C includes the same underlay 8 with a window 6 of substantially the same thickness as a remainder of the underlay 8, as disclosed by FIG. 2C.

[0044] Each of FIGS. 3A and 3B discloses a corresponding embodiment wherein, the polishing pad 2 has both the top layer 4 and the underlay 8 assembled on a sublayer 7. The sublayer 7 has an opening 7a through its thickness. The opening 7a is in alignment with the opening 5. Together, the opening 7a and the opening 5 combine to provide a composite opening through the polishing pad 2. The adhesive layer 9 attaches to the sublayer 7. A rear surface of the sublayer 7 has an adhesive layer 12 with an opening 12a adapted to be in alignment with the opening 5. The adhesive layer 12 is covered by the removable covering film 11 that is peeled from the adhesive layer 12, as depicted by the arrow, which exposes the adhesive layer 12 for attachment removably to the underlay 8. A seal 7b is provided at a peripheral edge of the sublayer 7. For this embodiment, the seal 7b is a unitary projecting lip on the perimeter 8a on the underlay 8. The lip extends at and over the peripheral edge of the sublayer 7. The window 6 has a projecting height sufficient to project into both the opening 7a and the opening 5.

[0045] The embodiment disclosed by FIG. 3A includes an underlay 8 having a window 6 of hollow structure, similar to that disclosed by FIG. 2. The embodiment disclosed by FIG. 3B includes an underlay 8 having a window 6 of solid structure the same as in the embodiment disclosed by FIG. 2B.

[0046] Each of FIGS. 4, 4A, 4B and 4C discloses a corresponding embodiment of the underlay 8 and the window 6 fabricated as a unitary structure. For example, the underlay 8 and the window 6 are fabricated by shaping a fluent material, and solidifying the fluent material to a solid phase that is optically transparent. The fluent material is shaped in a cavity 13 defined between two, opposed shaping dies 14, 14a of a known molding apparatus, or alternatively, a known sintering apparatus. The dies 14, 14a meet along a parting line 14b. The dies 14, 14a fabricate the fluent material into the underlay 8 as a thin layer. Further, the dies 14, 14a fabricate the window 6 in a window shaped recess 14c defined between the dies 14, 14a. Alternatively, as disclosed by FIG. 4, the window 6 is vacuum formed, by drawing a reduced atmosphere through an exhaust vent 14d provided in the shaping die 14 to communicate with the window shaped recess 14c. Following solidification of the fluent material between the dies 14, 14a, the dies 14, 14a are opened along the parting line 14b, which allows removal of the underlay 8 and unitary window 6. Alternatively, the fluent material is a melt that is shaped and solidified between the dies 14, 14a that are molding dies of a known molding apparatus. Alternatively, the fluent material is a powder mixed with a sintering binder that is shaped between the dies 14, 14a serving as sintering preforms. During a known heat sintering operation the powder binds to itself, and the binder is driven off by heat. The fluent material is solidified as a sintered material that is optically transparent in the solid phase.

[0047] FIG. 4 discloses an embodiment of the underlay 8 having the window 6 fabricated as a thin and hollow structure. The recess 14c is narrowly spaced from the opposed die 14a, which defines a relatively thin space in the cavity 13 within which the dies 14, 14a fabricate the hollow window 6.

[0048] FIG. 4A discloses an embodiment of the underlay 8 having the window 6 fabricated as a thick and solid structure. The recess 14c is substantially spaced from the opposed die 14a, defining a relatively wide space in the cavity 13 within which the dies 14, 14a fabricate the solid window 6 from the solidified fluent material.

[0049] FIG. 4B discloses an embodiment of the underlay 8 having the window 6 as a nonprojecting structure. The cavity 13 is spaced from the opposed die 14a the same distance as is a remainder of the cavity 13 within which the dies 14, 14a fabricate the window 6 from the solidified fluent material. The dies 14, 14a fabricate the window 6 with a thickness that is substantially coplanar with the remainder of the underlay 8.

[0050] FIG. 4C discloses an embodiment of the underlay 8 having a projecting lip 7b, according to FIG. 3A The following materials are suitable for being transmissive of the optical beam of the known optical detector; PET, polyethyleneterapthalate, PE, polyethylene, PP, polypropylene, PU, polyurethane and PVC, polyvinylchloride, could be used in varying thickness of thin sheets.

[0051] The invention further attains a reduced cost of production by eliminating the need for die cutting the shape of the window to interfit with the opening in the pad. The invention eliminates the disadvantage of a leaking seal between the window and the opening through the polishing layer 4 of the polishing pad 2.

Claims

1. A polishing pad apparatus comprising: a polishing pad for polishing a semiconductor substrate with a polishing fluid, an optically transmissive window framed by an opening through the polishing pad, the window being part of an underlay that is unitary with the window, and the underlay having a perimeter that extends substantially beyond the perimeter of the window to form a fluid impermeable layer that isolates a rear surface of the window from obstruction by polishing fluid and from obstruction by the underlay.

2. A polishing pad apparatus as recited in claim 1 wherein, the underlay is fabricated from a hydrophobic material.

3. A polishing pad apparatus as recited in claim 1 wherein, the window projects outwardly of a remainder of the underlay and within the opening.

4. A polishing pad apparatus as recited in claim 1 wherein, the window projects within the opening, and a seam between the window and the opening is sealed.

5. A polishing pad apparatus as recited in claim 1 wherein, the window projects within the opening, and a seam between the window and the opening is unsealed.

6. A polishing pad apparatus as recited in claim 1, and further comprising: the underlay having a first contact adhesive that attaches the underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that removably attaches the polishing pad to the underlay.

7. A polishing pad apparatus as recited in claim 1, and further comprising: the underlay having a first contact adhesive that removably attaches the underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that permanently attaches the polishing pad to the underlay.

8. A polishing pad apparatus as recited in claim 1 wherein, the underlay is part of the polishing platen, and the polishing pad is removable from the underlay for replacement by another polishing pad.

9. A polishing pad apparatus as recited in claim 1 wherein, the underlay is part of the polishing pad, and the underlay and a remainder of the polishing pad removable from the polishing platen for replacement by another polishing pad.

10. A polishing pad apparatus as recited in claim 1, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of the polishing platen, and the sublayer and a remainder of the polishing pad are removable from the underlay for replacement by another polishing pad.

11. A polishing pad apparatus as recited in claim 1, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

12. A polishing pad apparatus as recited in claim 1, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, the underlay having a projecting lip that forms the seal at the edge of the sublayer, and further wherein, the underlay is a part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

13. A polishing pad apparatus, comprising: a polishing pad having at least a top layer for polishing a semiconductor substrate with a polishing fluid, an opening through the top layer, and an optically transmissive window framed by the opening, and further wherein, the window is part of an underlay that is unitary with the window, and the underlay extends substantially from the window and substantially beyond the perimeter of the window to form an uninterrupted and continuous, fluid impermeable layer that isolates a rear surface of the window from obstruction by the underlay and from obstruction by the polishing fluid.

14. A polishing pad apparatus as recited in claim 13 wherein, the underlay is fabricated from a hydrophobic material.

15. A polishing pad apparatus as recited in claim 13 wherein, the window projects outwardly of a remainder of the underlay and within the opening.

16. A polishing pad apparatus as recited in claim 13 wherein, the window projects within the opening, and a seam between the window and the opening is sealed.

17. A polishing pad apparatus as recited in claim 13 wherein, the window projects within the opening, and a seam between the window and the opening is unsealed.

18. A polishing pad apparatus as recited in claim 13, and further comprising: the underlay having a first contact adhesive that attaches the underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that removably attaches the polishing pad to the underlay.

19. A polishing pad apparatus as recited in claim 13, and further comprising: the underlay having a first contact adhesive that removably attaches the underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that permanently attaches the polishing pad to the underlay.

20. A polishing pad apparatus as recited in claim 13 wherein, the underlay is part of the polishing platen, and the polishing pad is removable from the underlay for replacement by another polishing pad.

21. A polishing pad apparatus as recited in claim 13 wherein, the underlay is part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

22. A polishing pad apparatus as recited in claim 13, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of the polishing platen, and the sublayer and a remainder of the polishing pad are removable from the underlay for replacement by another polishing pad.

23. A polishing pad apparatus as recited in claim 13, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

24. A polishing pad apparatus as recited in claim 13, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, the underlay having a projecting lip that forms the seal at the edge of the sublayer, and further wherein, the underlay is a part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

25. A polishing pad apparatus, comprising: a polishing pad having at least a top layer for polishing a semiconductor substrate with a polishing fluid, an opening through the top layer, and an optically transmissive window framed by the opening, and further wherein, the window is part of an underlay, a perimeter of the underlay extends substantially beyond a perimeter of the window to form a fluid impermeable layer that isolates a rear surface of the window from obstruction by the polishing fluid.

26. A polishing pad apparatus as recited in claim 25 wherein, the underlay is fabricated from a hydrophobic material.

27. A polishing pad apparatus as recited in claim 25 wherein, the window projects outwardly of a remainder of the underlay and within the opening.

28. A polishing pad apparatus as recited in claim 25 wherein, the window projects within the opening, and a seam between the window and the opening is sealed.

29. A polishing pad apparatus as recited in claim 25 wherein, the window projects within the opening, and a seam between the window and the opening is unsealed.

30. A polishing pad apparatus as recited in claim 25, and further comprising: the underlay having a first contact adhesive that attaches the underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that removably attaches the polishing pad to the underlay.

31. A polishing pad apparatus as recited in claim 25, and further comprising: the underlay having a first contact adhesive that removably attaches underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that permanently attaches the polishing pad to the underlay.

32. A polishing pad apparatus as recited in claim 25 wherein, the underlay is part of the polishing platen, and the polishing pad is removable from the underlay for replacement by another polishing pad.

33. A polishing pad apparatus as recited in claim 25 wherein, the underlay is part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

34. A polishing pad apparatus as recited in claim 25, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of the polishing platen, and the sublayer and a remainder of the polishing pad are removable from the underlay for replacement by another polishing pad.

35. A polishing pad apparatus as recited in claim 25, and further comprising: the polishing pad having a sublayer, and further wherein, the underlay has a projecting lip providing a seal at the edge of the sublayer.

36. A polishing pad apparatus as recited in claim 25, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

37. A polishing pad apparatus as recited in claim 25, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, the underlay having a projecting lip that forms the seal at the edge of the sublayer, and further wherein, the underlay is a part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

38. A polishing pad apparatus, comprising: a polishing pad having at least a top layer for polishing a semiconductor substrate with a polishing fluid, an opening through the top layer, and an optically transmissive window framed by opening, and further wherein, the window is part of an underlay that is unitary with the window, the underlay having an adhesive thereon, and a perimeter of the underlay having the adhesive thereon extends substantially beyond a perimeter of the window to form an uninterrupted and continuous, fluid impermeable layer that isolates a rear surface of the window from obstruction by the polishing fluid.

39. A polishing pad apparatus as recited in claim 38 wherein, the underlay is fabricated from a hydrophobic material.

40. A polishing pad apparatus as recited in claim 38 wherein, the window projects outwardly of a remainder of the underlay and within the opening.

41. A polishing pad apparatus as recited in claim 38 wherein, the window projects within the opening, and a seam between the window and the opening is sealed.

42. A polishing pad apparatus as recited in claim 38 wherein, the window projects within the opening, and a seam between the window and the opening is unsealed.

43. A polishing pad apparatus as recited in claim 38, and further comprising: the underlay having a first contact adhesive that attaches the underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that removably attaches the polishing pad to the underlay.

44. A polishing pad apparatus as recited in claim 38, and further comprising: the underlay having a first contact adhesive that removably attaches the underlay to a polishing platen of a polishing machine, and the polishing pad having a second contact adhesive that permanently attaches the polishing pad to the underlay.

45. A polishing pad apparatus as recited in claim 38 wherein, the underlay is part of the polishing platen, and the polishing pad is removable from the underlay for replacement by another polishing pad.

46. A polishing pad apparatus as recited in claim 38 wherein, the underlay is part of the polishing pad, and the underlay and a remainder of the polishing are removable from the polishing platen for replacement by another polishing pad.

47. A polishing pad apparatus as recited in claim 38, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of the polishing platen, and the sublayer and a remainder of the polishing pad are removable from the underlay for replacement by another polishing pad.

48. A polishing pad apparatus as recited in claim 38, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, and further wherein, the underlay is a part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

49. A polishing pad apparatus as recited in claim 38, and further comprising: the polishing pad having a sublayer that is part of the polishing pad, a seal at an edge of the sublayer, the underlay having a projecting lip that forms the seal at the edge of the sublayer, and further wherein, the underlay is a part of the polishing pad, and the underlay and a remainder of the polishing pad are removable from the polishing platen for replacement by another polishing pad.

50. A polishing pad apparatus as recited in claim 38, and further comprising: the polishing pad having a sublayer, and further wherein, the underlay has a projecting lip providing a seal at the edge of the sublayer.