Abrading – Flexible-member tool – per se
Reexamination Certificate
1999-08-03
2001-10-09
Hail, III, Joseph J. (Department: 3723)
Abrading
Flexible-member tool, per se
C451S539000
Reexamination Certificate
active
06299519
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
(Not Applicable)
STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(Not Applicable)
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates generally to the field of semiconductor manufacturing. More particularly, the invention relates to devices and methods for removing polishing pads from the polishing platens of chemical mechanical planarization (CMP) machines.
2. Description of the Related Art
CMP is an abrasive process used to polish silicon wafers during semiconductor manufacturing. Polishing planarizes, or flattens, the surface of the wafer to very precise tolerances. A planarized wafer surface is essential for maintaining the precise photolithographic depth of focus required for integrated circuit chip fabrication.
CMP is typically performed using a machine having a platen, a polishing pad, a backing film, and a wafer carrier. The polishing pad resides on the platen, and a semiconductor wafer is pressed against the polishing pad. Backing film separates the wafer from the wafer carrier, which is used to hold the wafer in place during the CMP process. Once a wafer is mounted on a CMP device, a slurry consisting of liquid and small suspended particles, such as a colloidal silica suspended in a KOH solution, is applied at the interface of the pad and the wafer. The slurry uses mechanical and chemical processes to planarize the wafer.
During the CMP process, the polishing platen rotates. The wafer and the wafer carrier also rotate independent of the platen, causing the wafer to move through the slurry in a rotary fashion. As slurry flows over a wafer's surface, the suspended particles in the slurry mechanically abrade the surface and the liquid in the slurry chemically etches the abraded area. The pressure from the wafer carrier against the polishing pad provides the driving force for the process. In this manner, CMP removes materials from the high spots on the wafer while removing negligible amounts of material from the low spots on the wafer, resulting in a flattened, or planarized, wafer.
A critical component of the CMP process is the polishing pad. Polishing pads are typically made of polyurethane, and contain grooves or small perforations punched into the pads to help transport the slurry and facilitate polishing. The surface of the polishing pad contains asperites typically 1 to 10 micrometers in size that help transport and hold the slurry. With use, these asperites become flattened, resulting in a state called “glazing.” A glazed pad reduces the efficiency of the CMP process because the pad cannot hold much polishing slurry, nor can it apply appropriate pressure to a wafer. Although a glazed pad can be rejuvenated, eventually all pads need to be replaced. Typically, pads require replacement after polishing just 1500 wafers, meaning that a pad's lifespan is approximately 50 hours at a polishing rate of 30 wafers per hour.
Conventionally, polishing pads are removed from platens manually, whereby an individual tears the pad off of the platen. This conventional method is unsatisfactory, however, because polishing pads are affixed to platens using a strong adhesive. Moreover, the conventional method cannot be performed by workers lacking the necessary physical strength to remove a polishing pad. The task can cause injury not only because of the force that is necessary to remove a polishing pad from a platen, but also because the task is ergonomically difficult. On average, approximately one hour is required to remove an old pad and replace it with a new one. Given this downtime, there is a great need for a device and an improved method for removing polishing pads from platens.
SUMMARY OF THE INVENTION
The invention provides an improved method of removing a polishing pad from a platen during a CMP process by providing a pad having at least one protuberance portion extending from a main portion of the pad. This protuberance portion can be used to hold the pad, and to gain leverage for removing the pad manually or with the assistance of a mechanical device. If the protuberance portion has at least one aperture or other engagement structure, leverage can also be gained by inserting a tool into the aperture or by connecting a tool to the engagement structure.
It is an object of the invention to facilitate the removal of a polishing pad from a platen by providing a polishing pad having at least one protuberance extending from the main portion of the pad, so that the polishing pad can be held and removed manually or with the assistance of a mechanical device by engaging the protuberance portion. It is a further object of the invention to provide an aperture or other engagement structure in the protuberance portion of the polishing pad in order to provide extra leverage during the polishing pad removal process. It is still another object of the invention to make the process of removing polishing pads from a platen more time efficient, thereby improving CMP processing times.
A polishing pad, according to the invention, comprises a main portion and at least one protuberance portion extending from the main portion. This protuberance portion can elevate above the main portion or extend beyond the edge of the main portion. The main portion and the protuberance portion can be formed integrally or attached to each other. The protuberance portion can have structure for engaging a removal tool, and this engagement structure may comprise at least one aperture.
A polishing pad removal system, in accordance with the invention, comprises an engagement structure for engaging a polishing pad and a pulling structure for pulling the engagement structure, thereby separating the polishing pad from the platen. The engagement structure can be a removal roller adapted to hold the polishing pad, and the pulling structure can be a, rotating device. The pulling structure and the engagement structure can be one device so that it is unnecessary to attach the engagement structure to the pulling device.
The polishing pad can have a main portion and a protuberance portion that engages a removal roller. Rotation of the removal roller by the rotating device causes the pad to separate from the platen. The removal roller can have a slot, and the at least one protuberance portion can be inserted into the slot prior to operating the rotating device. A chain can actuate the removal roller so that pulling the chain across the removal roller rotates the removal roller. The engagement structure can comprise a fastener having a plurality of holding devices and a plurality of split connectors that engage the holding devices. If the engagement structure is a removal roller, rotation of the removal roller can cause the split connectors to rotate the holding devices. Rotation of the removal roller can also pull together the holding devices so that they can hold the polishing pad.
According to the invention, a method of removing a polishing pad from a platen comprises the steps of providing a polishing pad having a main portion and at least one protuberance portion, attaching the protuberance portion to an engagement structure, the engagement structure being attached to a pulling structure, and activating the pulling structure, whereby the polishing pad is separated from the platen.
REFERENCES:
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patent: 3932967 (1976-01-01), Hanes
patent: 4274232 (1981-06-01), Wylde
patent: 5170595 (1992-12-01), Wiand
patent: 5377455 (1995-01-01), Lanzer
patent: 5836810 (1998-11-01), Asum
patent: 42 41 890 A1 (1993-06-01), None
patent: 1321931 A (1973-07-01), None
Easter William G.
Maze, III John A.
Micelli Frank
Agere Systems Guardian Corp.
Hail III Joseph J.
Thomas David B.
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