US20090088051A1

US20090088051A1 - Leader and trailer for linear polishing sheet

Info

Publication number: US20090088051A1
Application number: US12/239,572
Authority: US
Inventors: Gregory E. Menk; Peter McReynolds; Benjamin A. Bonner; Erik S. Rondum; Gopalakrishna B. Prabhu
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2007-09-27
Filing date: 2008-09-26
Publication date: 2009-04-02

Abstract

A polishing article includes an elongated substantially rectangular central portion and a substantially rectangular edge portion. The central portion includes a polishing layer with a polishing surface. The central portion has a width, a length greater than the width and defining a longitudinal axis, and an edge. The edge portion extends from the edge of the central portion, the edge portion is thinner than the central portion, and the polishing layer does not extend onto the edge portion.

Description

RELATED APPLICATIONS

This application claims the benefit of priority from Provisional Application No. 60/975,775, filed Sep. 27, 2007, which provisional application is incorporated by reference herein in its entirety.

BACKGROUND

The present invention relates to apparatus and methods for chemical mechanical polishing a substrate.
An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive or insulative layers on a silicon wafer. One fabrication step involves depositing a filler layer over a patterned stop layer, and planarizing the filler layer until the stop layer is exposed. For example, trenches or holes in an insulative layer may be filled with a conductive layer. After planarization, the portions of the conductive layer remaining between the raised pattern of the insulative layer form vias, plugs and lines that provide conductive paths between thin film circuits on the substrate. Planarization can also be used to provide a planar surface for photolithography.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The carrier head places the exposed surface of the substrate against a polishing pad and provides a controllable load, i.e., pressure, on the substrate. A polishing liquid, such as an abrasive slurry, is supplied to the surface of the polishing pad.
In one type of polishing system, the polishing pad is a linear sheet that is incrementally advanced across a platen.

SUMMARY

In one aspect, a polishing article includes an elongated substantially rectangular central portion and a substantially rectangular edge portion. The central portion includes a polishing layer with a polishing surface. The central portion has a width, a length greater than the width defining a longitudinal axis, and an edge. The edge portion extends from the edge of the central portion, the edge portion is thinner than the central portion, and the polishing layer does not extend onto the edge portion.
Implementations of the polishing article may include one or more of the following features. The edge may be a first edge and the central portion may have a second edge on an opposite side of the central portion from the first edge. The edge portion may be a first edge portion extending from the first edge, and a second substantially rectangular edge portion may extend from the second edge of the central portion. The first and second edge portion may be thinner than the central portion and the polishing layer may not extend onto the first and second edge portions. The first edge and the second edge may extend perpendicular to the longitudinal axis of the central portion. The first edge portion and the second edge portion may have a same width as the polishing layer.
The polishing layer and central portion may be coextensive. The edge may extend perpendicular to the longitudinal axis of the central portion and the edge portion may extend longitudinally from the edge. Latitudinal edges of the edge portion may be aligned with latitudinal edges of the central portion. The edge portion may have the same width as the polishing layer.
The polishing article may include a backing layer. The backing layer may span the polishing layer and extend past the edge of the central portion to provide the edge portion. The backing layer may be coextensive with the polishing layer. The edge portion may comprise a separate sheet secured to the central portion, the polishing layer or the backing layer. The edge portion may be secured to the backing layer with an adhesive tape. The central portion may consist of the polishing layer and the polishing layer may consist of a single layer. The edge portion may be transparent. The edge portion may be more flexible than the polishing layer. The polishing layer may include a porous polyurethane. The edge portion may include polyethylene terephthalate. A bottom surface of the edge portion may be coplanar with a bottom surface of the central portion. The central portion may have a length between about twenty and thirty feet, and the edge portion may have a length of about six feet. The edge portion may be secured to the polishing layer by a tape. The polishing layer may be adhesively bonded to the support sheet.
In another aspect, a polishing sheet assembly includes an elongate, planar, substantially rectangular, polishing layer having a polishing surface, the polishing layer having two distal ends, and a continuous support sheet spanning and secured to the polishing layer, the support sheet having two distal ends, at least one distal end of the support sheet extending beyond an associated distal end of the polishing layer for attachment to a roller.
In another aspect, a polishing sheet assembly includes an elongate, planar, substantially rectangular polishing layer, the polishing layer having two distal ends, a continuous support sheet spanning and secured to the polishing layer, the support sheet coterminous with the polishing layer, and an attachment sheet abutting and secured to the support sheet at one of the distal ends for attachment to a roller.
In another aspect, a polishing sheet assembly includes an elongate, planar, substantially rectangular polishing layer, said polishing layer having two distal ends, and an attachment sheet abutting and secured to one of the distal ends of the polishing sheet for attachment to a roller.
Advantages of the invention may include the following. The polishing article can be fabricated using less polishing layer material, and thus at lower cost. The polishing article can be easier to load on the roller. The leader and trailer can be wound more tightly on the roller, thus reducing volume occupied by the polishing article.
Other features and advantages will be apparent from the following description, including the drawings and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic exploded perspective view of a chemical mechanical polishing (CMP) apparatus.

FIG. 2 is a top plan view of the CMP apparatus of FIG. 1.

FIG. 3A is a top plan view, cut away, of the first polishing station of the CMP apparatus of FIG. 1.

FIG. 3B is a schematic exploded perspective view of a rectangular platen and a polishing cartridge.

FIG. 3C is a schematic perspective view of a polishing cartridge attached to a rectangular platen.

FIG. 4 is a schematic perspective view, cut away of a linear polishing sheet.

FIG. 5A is a schematic side view in cross-section of an implementation of the polishing sheet.

FIG. 5B is a schematic side view in cross-section of another implementation of the polishing sheet.

FIG. 5C is a schematic side view in cross-section of another implementation of the polishing sheet.

FIG. 6 is a schematic side view of a feed roller of the polishing cartridge.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, one or more substrates 10 will be polished by a chemical mechanical polishing apparatus 20. A description of a similar polishing apparatus may be found in U.S. Pat. No. 6,244,935, the description of which is incorporated by reference. Polishing apparatus 20 includes a machine base 22 with a table top 23 that supports a series of polishing stations, including a first polishing station 25 a, a second polishing station 25 b, and a final polishing station 25 c, and a transfer station 27.
Each polishing station includes a rotatable platen. At least one of the polishing stations, such as first station 25 a, includes a polishing cartridge 102 mounted to a rotatable, rectangular platen 100. The polishing cartridge 102 includes a linearly advanceable sheet or belt of polishing material. The remaining polishing stations, e.g., second polishing station 25 b and final polishing station 25 c, may include “standard” circular polishing pads 32 and 34, respectively, each adhesively attached to a circular platen 30. Each platen may be connected to a platen drive motor that rotates the platen.
Each polishing station 25 a, 25 b and 25 c also includes a slurry delivery port, a pad rinse system (which can be a combined slurry/rinse arm 52 that projects over the associated polishing surface) and a pad conditioner apparatus 40.
A rotatable multi-head carousel 60 is supported above the polishing stations by a center post 62 and is rotated about a carousel axis 64 by a carousel motor assembly (not shown). Carousel 60 can include four carrier head systems mounted on a carousel support plate 66 at equal angular intervals about carousel axis 64. Three of the carrier head systems receive and hold substrates, and polish them by pressing them against the polishing sheet of station 25 a and the polishing pads of stations 25 b and 25 c. One of the carrier head systems receives a substrate from and delivers a substrate to transfer station 27.
Each carrier head system includes a carrier or carrier head 80. A carrier drive shaft 78 connects a carrier head rotation motor 76 (shown by the removal of one quarter of the carousel cover) to carrier head 80 so that each carrier head can independently rotate about its own axis. In addition, each carrier head 80 independently laterally oscillates in a radial slot 72 formed in carousel support plate 66.
Referring to FIGS. 3A, 3B, and 3C, polishing cartridge 102 is detachably secured to rectangular platen 100 at polishing station 25 a. Polishing cartridge 102 includes a feed roller 130, a take-up roller 132, and a generally linear sheet 110 (which can be considered to form a polishing belt or web) of a polishing pad material. The polishing sheet (if completely unwound from the rollers) has a length significantly greater than its width. An unused or “fresh” portion 120 of the polishing sheet is wrapped around feed roller 130, and a used portion 122 of the polishing sheet is wrapped around take-up roller 132. A rectangular exposed portion 124 of the polishing sheet that is used to polish substrates extends between the used and unused portions 120, 122 over a top surface 140 of rectangular platen 100.
The rectangular platen 100 can be rotated (as shown by phantom arrow “A” in FIG. 3A) to rotate the exposed portion of the polishing sheet and thereby provide relative motion between the substrate and the polishing sheet during polishing. Between polishing operations, the polishing sheet can be advanced (as shown by phantom arrow “B” in FIG. 3A) to expose an unused portion of the polishing sheet. When the polishing material advances, polishing sheet 110 unwraps from feed roller 130, moves across the top surface of the rectangular platen, and is taken up by take-up roller 132.
Referring to FIG. 4, polishing sheet 110 includes a polishing layer with a polishing surface 112, and a leader 160 and a trailer 162 that extend past the polishing layer (thus, polishing surface 112 does not extend to the ends of the polishing sheet). The leader and trailer can be formed of a material that is more flexible, and optionally less compressible, than the polishing layer. The leader 160 and trailer 162 can be attached to the feed and take-up rollers 130 and 132 by tape or a pressure sensitive adhesive on the back of the leader. A peelable liner may be placed over the tape or adhesive and removed prior to attaching the polishing sheet 110 to the rollers.
The polishing layer can be a porous polyurethane, and the leader and trailer can be a thin tear-resistant material, e.g., polyethylene terephthalate. The polishing layer can be opaque, whereas the leader and trailer can be transparent. The leader 160 and trailer 162 can be printed or embossed with information, such as a part number, material type, lot number, or polishing layer length.
Grooves can be formed in the polishing surface 112 running across the width and transverse to the direction of travel of the sheet The grooves can be about half the depth of the polishing layer, e.g., 18-20 mils deep, about one millimeter wide and spaced apart by about two to three millimeters. The backing layer 116 can be about five mils thick. The polishing layer can be between about twenty to thirty feet long, e.g., between twenty and twenty five feet long, and can be thirty inches wide. The leader and trailer 160 and 162 have same width as the polishing layer, and can be about six feet long.
Referring to FIG. 5A, in one implementation, the polishing sheet includes a backing layer 116 and a polishing layer 114 formed on the backing layer 116. In this implementation, the backing layer 116 can be a continuous sheet that spans the polishing layer 114. In the transverse direction (perpendicular to the length and direction of travel of the sheet), the wide edges 164 (along the length of the sheet) of the polishing layer 114 and backing layer 116 can be aligned so that the polishing layer and backing layer 116 have the same width. In contrast, in the longitudinal direction (parallel to the length and direction of travel of the sheet), the backing layer 116 extends past the narrow edges 166 (edges across the width of the sheet) of the polishing layer 114 to provide the leader 160 and trailer 162. In the region of the leader 160 and trailer 162, the top surface of the backing layer 116 can be the outermost surface, i.e., there are no other layers on top of the backing layer 116. As noted above, the leader 160 and trailer 162 can be printed or embossed with information, such as a part number, material type, lot number, or polishing layer length.
The polishing layer 114 can be a porous polyurethane, and the backing layer 116 can be a thin, flexible, generally incompressible, fluid-impermeable sheet, e.g., polyethylene terephthalate. The backing layer 116 can be transparent. The polyurethane layer an be 35-40 mils thick. The polishing layer 114 can be laid down as a single continuous unbroken layer. Alternatively, the polishing layer 114 can be tiled in adjacent strips, e.g., two to four feet long.
The polishing layer 114 can be secured to the top surface of the backing layer 116 by an adhesive 170, e.g., a pressure-sensitive adhesive layer. For example, the polishing layer 114 and backing layer 116 can be fabricated separately and then adhered together. Alternatively, the polishing layer 114 can adhere to the backing layer 116 backing layer without an adhesive. For example, a liquid polishing layer precursor can be dispensed onto the backing layer 116 and cured so as to form a polishing layer 114 adhering to the backing layer 116.
Referring to FIG. 5B, in another implementation, the polishing sheet includes a backing layer 116 and a polishing layer 114 formed on the backing layer 116, but the leader 160 and trailer 162 are separate pieces 172 bonded to the backing layer 116. In this implementation, the backing layer 116 can be a continuous sheet that spans and has coextensive edges with the polishing layer 114.
The polishing layer 114 can be a porous polyurethane. The backing layer 116 can be either softer or less compressible than the polishing layer and can be transparent or opaque. For example, the backing layer can be a soft subpad such as a urethane-impregnated fibrous mat, or a generally incompressible layer such as polyethylene terephthalate. The separate pieces 172 can be thin, flexible, tear-resistant, generally incompressible, fluid-impermeable sheets, e.g., polyethylene terephthalate.
As discussed above, the polishing layer 114 can be secured to the backing layer with or without an adhesive. The leader and trailer pieces 172 can be secured to the backing layer 116 with a butt joint and a thin tape 174 on the underside of the polishing sheet.
Referring to FIG. 5C, in another implementation, the polishing sheet includes a polishing layer 114 without any backing layer, and the leader 160 and trailer 162 are separate pieces bonded to the polishing layer 114. The polishing layer 114 can be a porous polyurethane. The separate pieces 172 can be thin, flexible, tear-resistant, generally incompressible, fluid-impermeable sheets, e.g., polyethylene terephthalate. The leader and trailer pieces 172 can be bonded to the polishing layer 114 by a thin tape 174 on the underside of the polishing sheet.
In each of the above implementations, since the polishing layer does not extend to the edges of the polishing sheet, the polishing sheet can be fabricated using less polishing layer material, and thus at lower cost in comparison to a polishing sheet having the polishing layer across the entire length.
Referring to FIGS. 3B and 6, feed and take-up rollers 130 and 132 should be slightly longer than the width of polishing sheet 110. The rollers 130, 132 may be plastic or metal cylinders about 20″ long and about 2″ in diameter. The opposing end faces 134 of feed roller 130 (only the feed roller is shown in FIG. 6, but the take-up roller would be constructed similarly) can each include a recess 136 which will engage support and drive mechanisms on the platen. For example, one end face can include keyed slot into which an alignment pin will fit, and the other end face can include a keyed star pattern into which a drive gear will fit. In addition, both ends of each roller can include a circular flange 138 that projects above the surface of the roller to hold the polishing sheet in place and prevents it from sliding off either side of the roller.
Because the leader and trailer can be more flexible than the polishing layer, they can be easier to manipulate and thus easier to install on the rollers. In addition, because the leader and trailer can be more flexible than the polishing layer, the leader and trailer can be wound more tightly on the roller. This permits the diameter of the roller to be decreased, thus either reducing the volume required by the cartridge or permitting more polishing material to be stored in the cartridge.
Returning to FIGS. 3A, 3B and 3C, rectangular platen 100 includes a generally planar rectangular top surface 140 bounded by a feed edge 142, a take-up edge 144, and two parallel lateral edges 146. A groove 150 (shown in phantom in FIGS. 3A and 3C) is formed in top surface 140. The groove 150 can be a generally-rectangular pattern that extends along edges 142, 144, 146 of top surface 140. A passage through platen 100 connects groove 150 to a vacuum source. When passage is evacuated, exposed portion 124 of polishing sheet 110 is vacuum-chucked to top surface 140 of platen 100. This vacuum-chucking helps ensure that lateral forces caused by friction between the substrate and the polishing sheet during polishing do not force the polishing sheet off the platen. Optionally, a central region 148 of top surface 140 can be free from grooves to prevent potential deflection of the polishing sheet into the grooves from interfering with the polishing uniformity.
An unillustrated compressible backing pad can be placed on the top surface of the platen to cushion the impact of the substrate against the polishing sheet. In addition, platen 100 may include an unillustrated shim plate. Shim plates of differing thickness may be attached to the platen to adjust the vertical position of the top surface of the platen. The compressible backing pad can be attached to the shim plate.
In some implementations, the rectangular platen 100 also includes four retaining flanges 156 that hold feed and take-up rollers 130 and 132 at feed and take-up edges 142 and 144, respectively. Each retaining flange 156 includes a projection or detent that can engage the corresponding feature on the end of the rollers 130 or 132.
The rollers 130 and 132 can be positioned sufficiently below top surface 140 so that the polishing sheet stays in contact with the feed and take-up edges 142 and 144 of the platen when the entire polishing sheet is wound around either roller. This assists in the creation of a seal between the polishing sheet and the rectangular platen when vacuum is applied to the passage to vacuum-chuck the polishing sheet to the platen. Furthermore, feed edge 142 and take-up edge 144 of the platen are rounded to prevent abrasion of the underside of the polishing sheet as it moves across the platen.
A transparent strip 118 can be formed along the length of polishing sheet 110. The transparent strip may be positioned at the center of the sheet, and may be about 0.6 inches wide. With respect to FIGS. 5A and 5B, transparent strip 118 may be formed by removing the upper layer 114 from this region of the transparent backing layer 116. With respect to FIG. 5C, a transparent strip 118 may be formed by molding a window into the polishing layer 114. The transparent strip 118 can be aligned with an aperture or transparent window 154 in rectangular platen 100 to provide optical monitoring of the substrate surface for end point detection.
Referring again to FIGS. 3A, 3B and 3C, in operation, exposed portion 124 of polishing sheet 110 is vacuum-chucked to rectangular platen 100 by applying a vacuum to the passage. A substrate is lowered into contact with polishing sheet 110 by carrier head 80, and both platen 100 and carrier head 80 rotate to polish the exposed surface of the substrate. After polishing, the substrate is lifted off the polishing pad by the carrier head. The vacuum on passage 152 is removed. The polishing sheet is advanced to expose a fresh segment of the polishing sheet. The polishing sheet is then vacuum-chucked to the rectangular platen, and a new substrate is lowered into contact with the polishing sheet. Thus, between each polishing operation, the polishing sheet may be advanced incrementally. If the polishing station includes a cleaning apparatus the polishing sheet may be washed between each polishing operation.
The amount that the sheet may be advanced will depend on the desired polishing uniformity and the properties of the polishing sheet, but should be on the order of 0.05 to 1.0 inches, e.g., 0.4 inch, per polishing operation. Assuming that the exposed portion 124 of polishing sheet is 20 inches long and the polishing sheet advances 0.4 inches after each polishing operation, the entire exposed portion of the polishing sheet will be replaced after about fifty polishing operations.
The invention is not limited to the embodiment depicted and described. Rather, the scope of the invention is defined by the appended claims.

Claims

1. A polishing article, comprising:

an elongated substantially rectangular central portion having a width, a length greater than the width and defining a longitudinal axis, and an edge, the central portion including a polishing layer with a polishing surface; and

a substantially rectangular edge portion extending from the edge of the central portion, wherein the edge portion is thinner than the central portion and the polishing layer does not extend onto the edge portion.

2. The polishing article of claim 1, wherein the edge is a first edge and the central portion has a second edge on an opposite side of the central portion from the first edge, and where the edge portion is a first edge portion extending from the first edge, and the article further comprises a second substantially rectangular edge portion extending from the second edge of the central portion, wherein the first and second edge portions are thinner than the central portion and the polishing layer does not extend onto the first and second edge portions.

3. The polishing article of claim 2, wherein the first edge and the second edge extend perpendicular to the longitudinal axis of the central portion.

4. The polishing article of claim 3, wherein the first edge portion and the second edge portion have a same width as the polishing layer.

5. The polishing article of claim 1, wherein the polishing layer and central portion are coextensive.

6. The polishing article of claim 1, wherein the edge extends perpendicular to the longitudinal axis of the central portion and the edge portion extends longitudinally from the edge.

7. The polishing article of claim 6, wherein latitudinal edges of the edge portion are aligned with latitudinal edges of the central portion.

8. The polishing article of claim 7, wherein the edge portion has a same width as the polishing layer.

9. The polishing article of claim 1, further comprising a backing layer.

10. The polishing article of claim 9, wherein the backing layer spans the polishing layer and extends past the edge of the central portion to provide the edge portion.

11. The polishing article of claim 9, wherein the backing layer is coextensive with the polishing layer.

12. The polishing article of claim 11, wherein the edge portion comprises a separate sheet secured to the backing layer.

13. The polishing article of claim 12, wherein the edge portion is secured to the backing layer with an adhesive tape.

14. The polishing article of claim 1, wherein the central portion consists of the polishing layer and the polishing layer consists of a single layer.

15. The polishing article of claim 14, wherein the edge portion comprises a separate sheet secured to the central portion.

16. The polishing article of claim 1, wherein the edge portion comprises a separate sheet secured to the central portion.

17. The polishing article of claim 1, wherein the edge portion is transparent.

18. The polishing article of claim 1, wherein the edge portion is more flexible than the polishing layer.

19. The polishing article of claim 1, wherein the polishing layer comprises a porous polyurethane.

20. The polishing article of claim 1, wherein the edge portion comprises polyethylene terephthalate.

21. The polishing article of claim 1, wherein a bottom surface of the edge portion is coplanar with a bottom surface of the central portion.

22. The polishing article of claim 1, wherein the central portion has a length between about twenty and thirty feet.

23. The polishing article of claim 22, wherein the edge portion has a length of about six feet.

24. A polishing sheet assembly, comprising:

an elongate, planar, substantially rectangular, polishing layer having a polishing surface, said polishing layer having two distal ends; and

a continuous, unbroken support sheet spanning and secured to the polishing layer, said support sheet having two distal ends, at least one distal end of the support sheet extending beyond an associated distal end of the polishing layer for attachment to a roller.

25. The polishing sheet assembly of claim 24, wherein the two distal ends of the support sheet extend beyond the two distal ends of the polishing layer.

26. The polishing sheet assembly of claim 24, wherein the polishing layer is adhesively bonded to the support sheet.

27. A polishing sheet assembly, comprising:

an elongate, planar, substantially rectangular polishing layer, said polishing layer having two distal ends;

a continuous, unbroken support sheet spanning and secured to the polishing layer, the support sheet coterminous with the polishing layer; and

an attachment sheet abutting and secured to the support sheet at one of the distal ends for attachment to a roller.

28. The polishing sheet assembly of claim 27, further comprising a second attachment sheet abutting and secured to another of the distal ends of the support sheet.

29. The polishing sheet assembly of claim 27, wherein the attachment sheet is secured to the support sheet by a tape.

30. A polishing sheet assembly, comprising:

an elongate, planar, substantially rectangular polishing layer, said polishing layer having two distal ends; and

an attachment sheet abutting and secured to one of the distal ends of the polishing layer for attachment to a roller.

31. The polishing sheet assembly of claim 30, further comprising a second attachment sheet abutting and secured to another of the distal ends of the polishing layer.

32. The polishing sheet assembly of claim 30, wherein the attachment sheet is secured to the polishing layer by a tape.