Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1999-04-30
2001-06-05
Banks, Derris H. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S296000, C451S287000, C451S307000
Reexamination Certificate
active
06241583
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 first polishing sheet movable in a first linear direction, and a second polishing sheet movable in a second linear direction. The first and second polishing sheets are positioned in a parallel and coplanar arrangement to contact a surface of a substrate during polishing.
Implementations of the invention may include the following. The first and second linear directions may be parallel, and may be the same or opposite directions. The first and second polishing sheets may extend between a first roller and a second roller. A first motor may rotate the first roller and drive the first and second polishing sheets one direction, and a second motor may rotate the second roller and drive the first and second polishing sheets in another opposite direction. The first polishing sheet may extend between a first roller and a second roller, and the second polishing sheet may extend between a third roller and a fourth roller. The first and third rollers may be rotationally coupled, and the second and fourth rollers may be rotationally coupled. A first motor may rotate the first and third rollers and drive the first and second polishing sheets one direction, and a second motor may rotate the second and fourth rollers and drive the first and second polishing sheets in another direction opposite the one direction. A carrier head may position a surface of the substrate in contact with the first and second polishing sheets. The first and second polishing sheets may each have a portion extending over a top surface of a platen to polish the substrate. The platen may not rotatable, and a drive system may move the first and second polishing sheets during polishing of the substrate. The platen may be rotatable, and the first and second polishing sheets may be secured to the platen to rotate with the platen during polishing. A drive system may move the first and second polishing sheets incrementally between polishing operations. A third polishing sheet may be positioned in a substantially parallel and coplanar arrangement with the first and second polishing sheets. An optical monitoring system may direct a light beam, e.g., a laser beam, through a gap between the first and second polishing sheets to impinge the substrate during polishing.
In another aspect, the invention is directed to a chemical mechanical polishing apparatus that has a first polishing sheet movable in a first linear direction, a second polishing sheet movable in a second linear direction, and a third polishing sheet movable in a third linear direction. The first, second and third polishing sheets are positioned in a parallel and coplanar arrangement to contact a surface of a substrate during polishing.
Implementations of the invention may include the following. The first and third directions may be the same direction and the second direction may be opposite to the first direction. The first, second and third polishing sheets may each have a portion extending over a top surface of the platen to polish the substrate. The platen may not be rotatable, and a drive system may moves the first, second and third polishing sheets during polishing of the substrate. Alternately, the platen may be rotatable, and the first, second and third polishing sheets may be secured to the platen to rotate with the platen during polishing. A drive system may move the first, second and third polishing sheets incrementally between polishing operations.
In another aspect, the invention is directed to a chemical mechanical polishing apparatus that has a first polishing sheet extending between a first roller and a second roller, and a second polishing sheet extending between a third roller and a fourth roller. The first and second polishing sheets are positioned in a parallel and coplanar arrangement to contact a surface of a substrate during polishing.
Implementations of the invention may include the following. A first pair of motors may move the first polishing sheet relative to the substrate, and a second pair of motors may move the second polishing sheet relative to the substrate. One motor of the first pair of motors may drive the first polishing sheet in a first direction, and one motor of the second pair of motors may drive the second polishing sheet in a second direction. The first and second directions may be the same or opposite. Another motor of the first pair of motors may drive the first polishing sheet in a direction opposite the first direction, and another motor of the second pair of motors may drive th
Applied Materials Inc.
Banks Derris H.
Fish & Richardson
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