Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1998-10-14
2001-02-13
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S692000
Reexamination Certificate
active
06187681
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to mechanical polishing of a semiconductor substrate, and more particularly to a support pad for use in chemical-mechanical-polishing to planarize a substrate assembly.
BACKGROUND OF THE INVENTION
In the semiconductor industry, a technology known as chemical-mechanical-polishing (“CMP”) has been developed. In “CMP,” a semiconductor wafer is placed between a polishing pad and a wafer carrier. The wafer carrier is a mechanical device used to provide rotation of and downward pressure on the semiconductor wafer. In this manner, the semiconductor wafer is forcibly held and rotated against the polishing pad. As a result, material is abraded from the surface of the semiconductor wafer in contact with the polishing pad.
Slurry, a liquid chemical composition generally containing particulate, may be dispensed on the polishing pad. The slurry conventionally is chemically active to remove unwanted material from the semiconductor wafer. This chemical activity may be changed during CMP processing. The slurry particulate facilitates abrasion. Alternatively, the semiconductor wafer is polished without slurry by using a “fixed-abrasive polishing pad.” A “fixed-abrasive polishing pad” has protrusions formed on it to facilitate abrasion. The semiconductor wafer is thus held and rotated against the protrusions on the fixed-abrasive polishing pad.
Aside from removing unwanted material, CMP may be used to planarize a surface of a semiconductor wafer. A uniform planar surface is important for subsequent lithographic processing of the semiconductor wafer, mainly due to depth of focus limitations of lithographic equipment. Accordingly, to achieve a substantially uniformly planar surface, it is important to apply pressure uniformly. A problem has been a lack of uniform pressure resulting in a non-uniform planar surface (e.g., a wedge-like shape).
One approach to achieve greater pressure uniformity has been to place an underpad below the polishing pad. The underpad has more give than the polishing pad, and thus it distributes downward force from the wafer carrier more uniformly. However, conditions, such as temperature, applied force, and friction, change during CMP, and an underpad is not able to compensate for these changes.
Another approach to achieve a more uniform downward force has been to use a wafer carrier having multiple bellows located between a wafer carrier housing and a wafer carrier base, as is described in U.S. Pat. 5,681,215 to Sherwood et al. As the semiconductor wafer is held between the polishing pad and the wafer carrier base, by pressurizing bellows against the wafer carrier housing, force is directed onto the wafer carrier base, which in turn pushes down on the semiconductor wafer. As each bellows may be separately pressurized, downward force is supposedly adjustable from location to location to improve uniformity; however, Sherwood et al is a mechanically complicated approach.
Therefore, it would be desirable to have a CMP apparatus that is less mechanically complicated than Sherwood et al. but allows for rigidity adjustment unlike present day underpads. Furthermore, it would be desirable to have a CMP apparatus that is a disposable item like an underpad.
SUMMARY OF THE INVENTION
The present invention provides method and apparatus for CMP with a support pad to provide a more uniform application of force to polish a semiconductor substrate. Such a support pad is formed with a housing. The housing defines a volume in which an opencell material, disposed in the volume, is coupled to the housing to limit deformation of the volume. A fluid is disposed in the volume to affect rigidity of the support pad. The fluid may be in a gaseous and/or a liquid state and may be pressurized.
The housing may be attached to or in contact with a CMP wafer carrier, a CMP platen, and/or a CMP polishing pad. Such a CMP wafer carrier, platen, and/or pad may be used in combination with the housing in defining a volume in which an open-cell material and fluid is contained. Moreover, inlet and outlet tubes may be employed for providing the fluid in and out of the volume. Such ingress and egress of fluid may be used for thermal control. Baffling or webbing may be located within the volume to regulate fluid flow, to maintain pressurization, and/or to limit volume deformation.
A support pad in accordance with the present invention may be a sealed unit to better cope with a harsh CMP environment; such a support pad may easily be removed and replaced. Moreover, a sealed pad may be pressurized to a desired level for a CMP operation. Alternatively, one or more tubes may be employed for in situ maintenance and/or adjustment of support pad rigidity.
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Deo Duy-Vu
Micro)n Technology, Inc.
Schwegman Lundberg Woessner & Kluth P.A.
Utech Benjamin L.
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