Coating processes – Centrifugal force utilized
Reexamination Certificate
1999-02-26
2001-04-17
Edwards, Laura (Department: 1734)
Coating processes
Centrifugal force utilized
C118S504000
Reexamination Certificate
active
06217936
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a spinner for use during semiconductor device fabrication and, more particularly, to an improved structure of a cup of the spinner for protecting the surface of a semiconductor that has been coated with a liquid from particles spun off of the semiconductor surface from returning to the surface.
During the fabrication of most semiconductor devices, it is necessary to coat the surface of the semiconductor wafer with different fluids, e.g. photoresist or developer. The method of coating the semiconductor wafer typically includes placing the semiconductor wafer on a chuck, fastening the semiconductor wafer to the chuck, spinning the chuck/semiconductor combination at a high speed and then spraying the fluid onto the surface of the semiconductor. The coating is spread out into a relatively even film and the excess is spun off by centrifugal force. This process is commonly known as “spinning on photoresist” or the like in the art.
In the conventional technology, a cup that includes a deflecting surface inclined downward is disposed around the spinner. The cup does not contact the semiconductor or its coating. This deflecting surface is located at the same height as the semiconductor so that most of the excess fluid from the coating, as well as any impurities in the coating, is spun off the semiconductor surface in the form of particles which then impact the cup at the deflecting surface. This surface deflects the particles downward, away from the semiconductor surface and toward a drain. The bottom of the cup typically contains holes for evacuation of any gaseous or particulate matter in the interior of the cup introduced during processing.
The problem in the conventional spinner described above is that, at the spin speeds necessary for processing, while most of the particles are spun off the semiconductor radially and deflected downward, a significant number will be lifted aerodynamically. These particles may reflect back on to the surface of the semiconductor instead of being deflected toward the drain. The particles that return to the surface of the semiconductor surface create unevenness in the thickness of the film, filaments in the film or resist balls, and are thus typically a source of defects brought about during the photolithographic process. Consequently, the present art requires a structure to eliminate the reflected particles and accordingly, the source of these defects. Because the production of semiconductor devices from a semiconductor wafer depends critically on the parameters used in the necessary photolithographic processes, any irregularity in the coating creates defects. These defects in turn result in a decrease in the yield of devices created from these semiconductor wafers.
SUMMARY OF THE INVENTION
In view of the above, the present invention comprises a semiconductor fabrication extended particle collection cup and method for protecting a rotating semiconductor surface coated with a fluid from particles that have been spun off from the surface.
Specifically, the semiconductor fabrication extended particle collection cup of the present invention comprises a particle-collecting cup extending upward substantially linearly from a base to define a perimeter. The particle-collecting cup is operative to receive the semiconductor wafer. An inclined deflecting surface extending upwardly and radially inwardly from the perimeter of the particle-collecting cup is also provided. This inclined deflecting surface has an upper edge and a lower edge in which the lower edge is integrally coupled to the perimeter of the particle-collecting cup and the upper edge defines an opening having a diameter no greater than the surface of the semiconductor wafer.
In a preferred structure according to the invention, the semiconductor fabrication extended particle collection cup further comprises a protective shield extending downward toward the semiconductor wafer. This shield has an upper edge and a lower edge in which the upper edge is integrally connected with the upper edge of the deflective surface.
In another preferred structure according to the invention, the semiconductor fabrication extended particle collection cup further comprises an inclined protective lip having an inner edge and an outer edge in which the inner edge is integrally connected with the lower edge of the protective shield. In addition, the protective lip is inclined so as to increase the radius of the protective lip as measured from the inner edge to the outer edge.
In another aspect of the invention, a method for protecting a rotating semiconductor surface coated with a fluid from particles that have been spun off from the surface is provided. This method comprises the initial step of providing a deflecting surface, a protective shield and a protective lip external to the semiconductor towards which said particles are projected. Subsequent steps comprise deflecting the particles that impact with the deflecting surface away from the semiconductor surface and shielding the semiconductor surface from at least some of the particles being projected back to said semiconductor surface.
In another preferred aspect of the invention, the method further comprises the step of determining the minimum angle of deflection for particles impinging on the inclined surface so as to return to the semiconductor surface.
In another preferred aspect of the invention, the method further comprises the step of protecting the semiconductor surface by directing the reflected particles into the enclosure formed by the deflecting surface, the protective surface, and the protective lip. The particles directed into the enclosure may then be channeled away from the semiconductor surface.
It is therefore a primary object of the present invention to prevent the excess particles spun off the surface of the semiconductor from returning to the semiconductor by use of the semiconductor fabrication extended particle collection cup.
The present invention will become more apparent from the description of the preferred embodiments set forth below with reference to the accompanying drawings.
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Advanced Micro Devices
Brinks Hofer Gilson & Lione
Edwards Laura
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