Material or article handling – Process – Of emptying portable receptacle
Reexamination Certificate
1999-02-24
2001-11-20
Lillis, Eileen D. (Department: 3652)
Material or article handling
Process
Of emptying portable receptacle
C414S749400, C414S416080, C414S937000, C414S941000, C118S500000
Reexamination Certificate
active
06318957
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus and method for facilitating the handling and transport of semiconductor wafers, and more particularly to an apparatus and method for protectively supporting semiconductor wafers in a manner which permits easy transport between processing stations and between cassettes or other wafer transport/holding mechanisms with minimal risk of damage and contamination of the wafer.
BACKGROUND OF THE INVENTION
During semiconductor wafer processing, the wafers frequently move through several locations such as: a cassette, a load lock station where the atmosphere around the wafer is purged and the wafer may be etched, a pre-processing station where the wafer may be measured or cleaned, a reactor, and a post-processing station where the wafer is cooled, and the thickness of a deposition layer may be measured. The wafer obviously must be handled in order to move to each location; however, each time the wafer is contacted or jarred, particles may be generated, and the likelihood of backside scratching or contamination by such particles is increased. These wafers can be rendered useless for device fabrication by contamination, abrasion, or damage. Therefore, extreme care is required to support and transport wafers.
U.S. Pat. No. 5,046,909 by Murdoch teaches clipping the wafer onto a retaining ring so that the ring is handled during processing instead of directly handling the wafer. A robotic arm moves the wafer to be engaged with the clips. However, the clips contact both the top and bottom of the wafer, and great precision is required in order to initially engage the wafer with the clips.
U.S. Pat. No. 4,306,731 by Shaw, and U.S. Pat. No. 4,779,877, also by Shaw, teach an apparatus comprising a plate-like support provided with an aperture of a diameter larger than the wafer, and clip means for gripping the edge of the wafer. The leading edge of each clip has an arcuate portion within which the edge of the wafer is retained. However, the Shaw inventions require that the clip must first be spread before receiving the wafer to prevent edgewise abrasion. Thus, these inventions are rather complex because additional parts are needed to actuate the clip, such as a pneumatic cylinder and contact pin.
U.S. Pat. No. 4,473,455 by Dean et al. teaches spring-mounted members disposed around the periphery of an aperture in a wafer-mounting plate. However, once the wafer is retained within the wafer-mounting plate, the wafer cannot be moved with the plate because this invention is only for use of holding the wafer during a processing step.
European Pat. Application (Publication number 0 634 784 A1) by A. Tepman discloses a variable speed wafer exchange robot. However, the design is quite complicated, especially that of the wafer support assembly.
Consequently, a need exists for a simple wafer carrying device which is simple to use, has few parts, transportable through multiple locations, minimizes contact with the wafer, and reduces the potential for particle generation.
SUMMARY OF THE INVENTION
The present invention is a carrier that supports a wafer during most stages of wafer handling, and a method for using the carrier with a wafer handler which moves the carrier and wafer to multiple stations.
The wafer handler has multiple sensors which sense the location of the handler at different points of the processing cycle. A control device receives location information from the sensors and sends signals to a variable speed drive motor which changes the acceleration and speed of the handler based on this information. When the handler moves vertically to place or pick up the wafer carriers from the stations, the control device decreases the handler acceleration and speed to ensure a smooth transition and prevent the carriers from shifting or chattering which may cause particle generation, thereby contaminating the wafers. However, immediately after the handler picks up the carrier during the handler's motion upward or places the carrier down on a base plate, the handler accelerates and increases in speed in order to maximize throughput. The handler moves with the fastest speed when it is not transporting any wafer carriers.
An end effector removes the wafer from a cassette and places the wafer onto the carrier. The carrier has a plurality of support elements defining a wafer support plane, and a support structure or frame below the plane connecting the support elements. The periphery of the wafer rests upon the support elements. The wafer can then be moved by lifting the carrier rather than engaging the wafer.
In one example, a wafer handler arm is inserted beneath the carrier so that the handler does not contact the wafer. The wafer handler may be provided with a plurality of arms that lift and rotate a plurality of carriers with wafers from station to station. The wafers rest safely atop the carriers, so that the handling is absorbed by the carrier instead of the wafer.
After processing, an end effector removes the wafer from the carrier back to the cassette, leaving the carrier in the handling chamber for repeated use. The use of the carrier in an environment where the wafer must be repeatedly picked up and set down reduces the number of times the wafer is contacted. This reduces the amount of backside marking on the wafer. Additionally, the carrier has locating features which assist in centering the wafer to be properly positioned for processing.
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patent: 0 634 784 A1 (1995-01-01), None
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Copy of International Search Report corresponding to PCT/US99/15593, filed Jul. 8, 1999.
Aggarwal Ravinder K.
Carr Paul R.
Jacobson Paul T.
Kusbel James F.
Lenz Rod
ASM America Inc.
Knobbe Martens Olson & Bear LLP
Lillis Eileen D.
Tran Thuy V.
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