Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-09-13
2001-10-16
Morgan, Eileen P. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S059000, C451S303000, C451S307000, C451S309000
Reexamination Certificate
active
06302767
ABSTRACT:
BACKGROUND
The present invention relates to apparatus and methods for chemical mechanical polishing a substrate, and more particularly to such apparatus and methods using a moving polishing sheet.
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.
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 exposed surface of the substrate is placed against a rotating polishing pad. The polishing pad may be either a “standard” pad or a fixed-abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. A polishing slurry, including at least one chemically-reactive agent, and abrasive particles if a standard pad is used, is supplied to the surface of the polishing pad.
An effective CMP process not only provides a high polishing rate, but also provides a substrate surface which is finished (lacks small-scale roughness) and flat (lacks large-scale topography). The polishing rate, finish and flatness are determined by the pad and slurry combination, the relative speed between the substrate and pad, and the force pressing the substrate against the pad. The polishing rate sets the time needed to polish a layer, which in turn sets the maximum throughput of the CMP apparatus.
During CMP operations, the polishing pad needs to be replaced periodically. For a fixed-abrasive pad, the substrate wears away the containment media to expose the embedded abrasive particles. Thus, the fixed-abrasive pad is gradually consumed by the polishing process. After a sufficient number of polishing runs the fixed-abrasive pad needs to be replaced. For a standard pad, the substrate thermally and mechanically damages the polishing pad and causes the pad's surface to become smoother and less abrasive. Therefore, standard pads must be periodically “conditioned” to restore a roughened texture to their surface. After a sufficient number of conditioning operations (e.g., three hundred to four hundred), the conditioning process consumes the pad or the pad is unable to be properly conditioned. The pad must then be replaced.
One problem encountered in the CMP process is difficulty in replacing the polishing pad. The polishing pad may be attached to the platen surface with an adhesive. Significant physical effort is often required to peel the polishing pad away from the platen surface. The adhesive then must be removed from the platen surface by scraping and washing with a solvent. A new polishing pad can then be adhesively attached to the clean surface of the platen. While this is happening, the platen is not available for the polishing of substrates, resulting in a decrease in polishing throughput.
SUMMARY
In one aspect, the invention is directed to a chemical mechanical polishing apparatus that has a platen, a polishing sheet extending between a first roller and a second roller, and a support sheet extending between a third roller and a fourth roller. A portion of the polishing sheet extends over a surface of the platen to polish a substrate, and a portion of the support sheet extends between the platen and the polishing sheet.
Implementations of the invention may include the following. The support sheet may move in the same direction and at approximately the same speed as the polishing sheet. A first motor may drive the first and second rollers and a second motor may drive the third and fourth rollers. The first and second motors may be synchronized to drive the rollers in the same direction at substantially the same speed. A motor may drive the polishing sheet, and wherein the intermediate support sheet may engage an underside of the polishing sheet to move therewith. There may be a passage through the platen to inject a fluid between the top surface of the platen and the support sheet to form a fluid bearing. The polishing sheet may be a continuous belt or a reel-to-reel tape, and the support sheet may be a continuous belt or reel-to-reel tape. The polishing sheet may include a fixed-abrasive polishing material.
In another aspect, the invention is a method of chemical mechanical polishing in which a substrate is brought into contact with a polishing sheet that extends between a first roller and a second roller, and the polishing sheet is moved from the first roller to the second roller. A support sheet that extends between the polishing sheet and a platen is moved in the same direction and at substantially the same speed as the polishing sheet.
Implementations of the invention may include the following. Moving the support sheet may include having a top surface of the support sheet engage a bottom surface of the polishing sheet, or driving the polishing sheet with a motor. The support sheet and the polishing sheet may be moved continuously during polishing. The substrate may rotate while in contact with the polishing sheet. The polishing sheet may includes a fixed-abrasive polishing material. The polishing sheet may be a continuous belt or a reel-to-reel tape, and the support sheet may be a continuous belt or a reel-to-reel tape.
Advantages of the invention may include the following. More substrates can be polished without replacing the polishing pad, thereby reducing downtime of the CMP apparatus and increasing throughput. A sheet of fixed-abrasive polishing material can be provided in a polishing cartridge. It is easy to remove and replace the polishing cartridge from a platen. The polishing apparatus gains the advantages associated with fixed-abrasive polishing materials. A rotating carrier head can be used to press the substrate against the polishing sheet. Lateral frictional forces on the substrate can be reduced, thereby decreasing the load of the substrate against the retaining ring and improving polishing uniformity. The rigidity of the polishing sheet against the substrate can be adjusted independent of the polishing sheet material.
Other features and advantages will be apparent from the following description, including the drawings and claims.
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Applied Materials Inc.
Fish & Richardson
Morgan Eileen P.
LandOfFree
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