Handling: hand and hoist-line implements – Contact lens applicator
Reexamination Certificate
2000-05-24
2001-07-31
Kramer, Dean J. (Department: 2167)
Handling: hand and hoist-line implements
Contact lens applicator
C414S941000
Reexamination Certificate
active
06267423
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the transfer of articles, such as semiconductor wafers, and more particularly to an improved end effector for handling and transferring very thin semiconductor wafers.
The use of robot arms is a well established manufacturing expedient in applications where human handling is inefficient and/or undesired. For example, in the semiconductor arts robot arms are used to handle wafers during various process steps. Such process steps include those which occur in a reaction chamber, e.g. etching, deposition, passivation, etc., where a sealed environment must be maintained to limit the likelihood of contamination and to ensure that various specific processing conditions are provided.
Current practice includes the use of an end effector (also known as a robot blade or carrier) attached to robot arms to load semiconductor wafers from a loading port into various processing ports within a multiple chamber reaction system. The robot arms are then employed to retrieve the wafer from a particular port after processing within an associated process chamber. The wafer is then shuttled by the robot arms to a next port for additional processing. When all processing within the reaction system is complete, the robot arm returns the semiconductor wafer to the loading port and a next wafer is placed into the system by the robot arm for processing. Typically, a stack of several semiconductor wafers is handled in this manner during each process run.
Currently, a conventional robot end effector is used to transfer wafers having a thickness of between about 0.020″ and 0.030″. Wafers having a normal thickness in this range are generally flat in that they typically do not exhibit more than about 0.005″ of bowing. Furthermore, such wafers have sufficient weight to preclude slipping from the end effector as it is swung or moved between process locations attached to a wafer handling chamber.
However, under some circumstances, it is desirable to have a very thin wafer in the range of 0.005″ to 0.010″. For example, very thin wafers are better heat conductors than wafers of normal thickness. The thin wafer is formed by removing all the excess silicon from the back side of a wafer of normal thickness after the devices have been placed on the front side. The wafer is preferably thinned out by a process known in the art as “backlapping”, whereby successive passes are made across the backside of the wafer with a tool until the desired thinness is achieved. Once the wafer is thinned to about 0.005″, the backside is coated with gold, which results in a thin wafer with very good heat conductive properties.
Thinning of the wafer can cause problems, however. As the wafer is thinned, the materials forming the devices on the front side of the wafer induce stress and strain on the wafer causing it to bow. In many cases, this bowing is quite extreme. For example, wafers that have been reduced to a thickness of about 0.005″ typically exhibit bowing of 0.075″, and in extreme cases exhibit bowing of 0.120″ or more. Several problems result from the use of prior art end effectors for transfer of these thin, bowed wafers. Because the thin wafers are bowed like a potato chip, the wafer does not sit flat on the end effector. Unless some mechanism is provided to hold the wafer in place, it may become displaced from the end effector during movement of the end effector because the wafer does not have sufficient contact with the end effector. The thin wafer also does not have sufficient weight to prevent it from being displaced from the end effector during end effector movement without some means for holding the wafer in place. Furthermore, as the thin wafers sit in the wafer cassette awaiting capture by the end effector, the bowing of the wafers causes the space between adjacent wafers to be significantly reduced. Use of prior art end effectors results in breakage of a number of wafers because the end effector cannot pass through the narrow space between adjacent bowed wafers in the wafer cassette.
SUMMARY OF THE INVENTION
The present invention is an end effector for an article transfer device. The end effector is preferably attached to a robot for transferring thin, bowed semiconductor wafers within a semiconductor device processing system. The end effector is configured to be inserted into a narrow space between stacked, bowed wafers in a wafer cassette. The end effector is also configured to retain the wafer within a pocket formed therein during wafer transfer.
According to one aspect of the invention, the end effector comprises support means for attaching the end effector to the article transfer device, means for receiving an article to be transferred, and means for retaining the article within the receiving means during transfer of the article. The receiving means may be configured such that only the edge portions of the article contact surfaces of the end effector. The end effector may further include means for capturing an article within the retaining means. The capturing means may further include means for permitting insertion of said end effector capturing means between a pair of closely stacked articles.
According to another aspect, the end effector includes a pocket for receiving an article to be transferred and sloped article contact surfaces surrounding the pocket. The sloped article contact surfaces may be configured to contact the edges of the article and to prevent lateral movement of the article as it is transferred.
A further aspect of the invention is an end effector comprising a rear support mechanism for attaching the end effector to the article transfer device, a pocket extending forward from a front edge of the rear support mechanism for receiving an article therein, and wafer capture shoes located at a forward end of the pocket. A lower, or non-substrate supporting surface of each of said shoes may exhibit a sloped surface for insertion of the pocket between bowed wafers. The sloped surfaces may be configured to allow the pocket to be deep enough to receive a bowed wafer.
Another aspect of the present invention is an end effector for an article transfer device comprising a rear support mechanism for attaching the end effector to the article transfer device, a thin flat blade extending from a lower forward edge of the rear support mechanism, an article capture mechanism connected to a forward edge of the thin flat blade, a pocket located above the flat blade portion of the end effector for receiving an article therein, and sloped article contact surfaces surrounding the pocket; said sloped article contact surfaces configured to contact the edges of the article and to prevent lateral movement of the article as it is transferred. According to a further aspect, a second sloped surface may be provided adjacent to the article contact surface formed in said rear support mechanism. A lower leading edge surface of the article capture mechanism may exhibit a sloped surface for insertion of the pocket between bowed wafers. The sloped surfaces may be configured to allow the pocket to be deep enough to receive a bowed wafer.
According to yet another aspect of the present invention, an end effector for an article transfer device is provided comprising a rear support mechanism for attaching the end effector to the article transfer device, a sloped article contact surface formed in an upper surface of the rear support mechanism along a forward edge thereof, a pair of elongated rods extending horizontally from a lower surface of the forward edge of the rear support mechanism, and a pair wafer capture pin caps, each located at a forward end of one of said pair of elongated rods. The sloped article contact surface may be configured to contact the edges of the article and to prevent lateral movement of the article as it is transferred.
REFERENCES:
patent: 3708851 (1973-01-01), Vladik
patent: 4951601 (1990-08-01), Maydan et al.
patent: 5061144 (1991-10-01), Akimoto et al.
patent: 5314294 (1994-05-01), Taniguchi et al.
Marohl Dan A.
Ngan Kenny King-Tai
Applied Materials Inc.
Fulbright & Jaworski L.L.P.
Kramer Dean J.
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