Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
1997-12-12
2001-02-06
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C427S240000, C430S327000, C430S331000, C252S364000
Reexamination Certificate
active
06184156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a process and system for removing extraneous resist material on a semiconductor wafer which results from the dispensing of the resist material onto the semiconductor wafer. The present invention is more particularly related to the removing of extraneous resist material on a semiconductor wafer which is formed when a wet edgebead operation is performed on the semiconductor wafer to remove “edgebeads,” the extraneous resist material which is formed during the wet edgebead operation.
2. Background of the Related Art
Photolithography, the process of exposing resist coated semiconductor wafers to develop patterns in the resist material, is currently performed or implemented with a photoresist type material. A photoresist type material is a solution of polymers bonded to photoactive compounds. The photoactive compounds are exposed to light according to a predetermined pattern, and developed forming patterns in the resist material. The developed patterns are used in the forming of devices in the semiconductor wafer.
Photoresist material is typically deposited on the semiconductor water as a sticky material which when dried becomes brittle. Accordingly, the photoresist material has a tendency to flake and create small particles which can infiltrate and destroy devices embedded or formed in the semiconductor wafer. Since the resist material may significantly affect the operation of a semiconductor chip, a great deal of attention has been given to ways of preventing the resist material from creating these small particles or flakes which can destroy the devices in the semiconductor wafer. For example, it is generally understood that when the semiconductor wafer is coated with the resist material, small balls or beads of photoresist remain stuck to the edges of the wafer. These beads are typically called “edgebeads.” The edgebeads can flake and create various defects in the semiconductor wafer as described above. Thus, the edgebeads can significantly reduce the yield of properly operating semiconductor wafers, increasing cost of manufacture.
To combat problems resulting from the normal edgebeads formed during the coating of the semiconductor wafer with resist material, many manufacturers incorporate a “wet edgebead operation” which is used to remove the edgebeads from a semiconductor wafer. The wet edgebead operation consists of dispensing solvent at the wafer edge to dissolve the edgebeads from the upper edge, back and side of the wafer. By performing the wet edgebead operation, the edgebeads can be removed to some extent, thereby reducing or minimizing the flaking of resist material and the formation of defects in the semiconductor wafer.
Even though the wet edgebead operation has been previously performed, semiconductor wafers have still encountered significant device failures. Accordingly, it is desirable to determine the cause of the semiconductor failures. Once the cause of the semiconductor failures is determined, it is also desirable to formulate a solution to correct the semiconductor failures.
It is further desirable that any solution or process used to correct the semiconductor failures be implemented in a continuous process, and also be incorporated in or used with the existing process of depositing resist material onto the semiconductor wafer.
SUMMARY OF THE INVENTION
It is a feature and advantage of the present invention to provide a practical solution to correcting the problem of semiconductor wafer failure. As part of this solution, it is a feature and advantage of the present invention to provide a solution which can be incorporated into the existing process of depositing the resist material on the semiconductor wafer in an efficient manner.
The present invention is based, in part, on identification of the problem which has resulted in significant semiconductor wafer failures due to the formation of secondary edgebeads which are formed when edgebeads are removed using the wet edgebead operation. Residual resist defects are generally produced at the secondary edgebead sites after the semiconductor wafer is coated with the resist material and after the resist material is exposed and developed for the formation of device regions. We have discovered that the residual resist defects are formed because the standard edge exposure and developing techniques used on the resist layer are unable to completely remove extraneous secondary edgebead material which is generated by the wet edgebead operation.
The present invention, by creating standard processing wet edgebead removal steps to remove the secondary edgebeads, provides a processing technique and system which is able to efficiently and significantly reduce the thickness of the extraneous or residual resist material which results from or is not removed by the wet edgebead operation. Since the present invention is able to reduce the thickness of residual resist material which is formed or remains after the wet edgebead operation using the techniques which are disclosed below, the standard edge exposure and developing steps are effective in removing substantially all of the remaining extraneous resist material which remains after the resist layer is deposited on the semiconductor wafer and after the standard wet edgebead operation is performed.
To achieve these and other features and advantages of the present invention, a method of depositing resist material onto a semiconductor wafer is provided. The method includes the steps of depositing the resist material onto the semiconductor wafer, and performing a wet edgebead operation to remove edgebeads formed at the edge of the semiconductor wafer during the depositing step. In addition, the method includes the step of performing a secondary edgebead flattening operation to remove secondary edgebeads formed during the performing step.
The present invention also provides a method of preparing a semiconductor wafer for etching. The method includes the steps of depositing resist material onto the semiconductor wafer and performing a wet edgebead operation to remove edgebeads formed at an edge of the semiconductor wafer during the depositing step. The method further provides the performing of a secondary edgebead removal operation to remove secondary edgebeads formed during the performing step and exposing the resist material deposited onto the semiconductor wafer to light in accordance with a predetermined pattern. Finally, the method includes the developing the resist material deposited onto the semiconductor wafer for device implantation in accordance with the pattern exposed in the exposing step.
The present invention also includes a method of flattening resist mounds formed during a wet edgebead operation. The wet edgebead operation is used to remove edgebeads formed when a resist material is deposited on a semiconductor wafer. The method includes the step of introducing solvent to the semiconductor wafer at the area containing the resist mounds to soften the resist mounds, and spinning the semiconductor wafer at a speed sufficient to flatten the resist mounds.
The present invention further includes a system for flattening resist mounds formed during a wet edgebead operation. The wet edgebead operation is used to remove edgebeads formed when a resist material is deposited on a semiconductor wafer. The system includes a device which introduces solvent to the semiconductor wafer at the area containing the resist mounds to soften the resist mounds, and a device which spins the semiconductor wafer at a speed sufficient to flatten the resist mounds.
These, together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, with reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like elements throughout.
REFERENCES:
patent: 4732785 (1988-03-01), Brewer
patent: 4886728 (1989-12-01), Salamy et al.
patent: 5151219 (1992-09-01), Sal
Advanced Micro Devices , Inc.
Rocchegiani Renzo N.
Smith Matthew
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