Data processing: generic control systems or specific application – Specific application – apparatus or process – Article handling
Reexamination Certificate
1999-04-16
2001-08-14
Skaggs, H. Grant (Department: 3651)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Article handling
C414S936000
Reexamination Certificate
active
06275742
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
This invention relates to a system for automatically manipulating and aligning elements such as semiconductor wafers.
In many manufacturing, processing or sorting systems, controlled robots having articulated robot arms have been used to move elements such as semiconductor wafers from one processing or storage station to another. Such robots are movable in vertical (Z), horizontal (⊖) and radial (r) directions and their manipulation must be done repetitively at high speed and with maximum precision and reliability. Also, in semiconductor processing when one or a series of wafers are moved sequentially from station to station, they must be placed at each station in the same predetermined orientation or alignment with respect to both the center of the wafer and also a point of reference or fiducial on the edge of the wafer. Thus, each wafer has a distinguishing point of reference such as a notch or a flat spot on its peripheral edge, and at each station or storage cassette to which the wafers are moved to or from the notches and the centers of all wafers must be in precise alignment.
Various prior art aligner devices have been devised that attempt to solve this problem. One such device described in U.S. Pat. No. 5,102,280 utilizes a robot arm which is manipulated to lift a wafer that is on a vacuum chuck and move it laterally until it becomes centered on the vacuum chuck. Thereafter, the wafer is rotated until a predetermined position on the edge of the wafer is located by a sensor. The sensor controls the rotating chuck so that it stops with the retained wafer in a preselected ⊖ position. The robot arm is then required to move the wafer until it is centered on the chuck before it is removed therefrom. The present invention provides an improved robot apparatus and method for aligning wafers or elements with greater precision, speed and reliability.
BRIEF SUMMARY OF THE INVENTION
In accordance with the principles of the invention a robot connected to a controller having a servo amplifier is operable at an alignment station to place wafers consecutively on a vacuum chuck. When each wafer is placed on the chuck by the robot, its center may be offset from the center axis of the chuck and its edge fiducial may be randomly positioned. As each wafer is held by the vacuum chuck, it is rotated by a motor having an encoder which is also connected to the controller. Adjacent to the chuck is an alignment device having a backlight source which is positioned to extend radially across the wafer edge. The backlight source is directed downwardly through an optical relay lens system in the device to a light sensor array preferably comprised of charge coupled device (CCD). The CCD sensor output is connected on an electronic sensing circuit on a circuit board below the optical lens system and the latter is connected to the controller. The backlight source must be far enough away from the moving wafer edge to provide uniform background lighting from the point of view of the sensing electronics. The relay lens (magnification 1:1) projects the light falling onto the wafer edge from that wafer edge plane onto the CCD sensor. Thus, when the wafer edge moves relative to the backlight due to eccentricity or to a fiducial notch the image position of the wafer edge moves on the CCD sensor. Because of the lens systems, the image position is a sharp shadow that is cast upon the CCD with much greater power. The high power permits short exposure times which, in turn, enables faster data sampling, thereby allowing the wafer to be rotated at high speed. The sensing circuit for the CCD performs the function of converting the image of the edge of the wafer falling onto the CCD to quadrature position data which is fed to the controller logic. This allows the controller to track the position of the wafer edge as a position of an axis and enables high speed communication of edge position data. The CCD sensor is a line array oriented parallel to the viewing plane, and thus the image of the wafer edge falls nearly perpendicular to the axis of the array.
The data used to find the wafer notch and wafer center is preferably processed by a controller which utilizes velocity estimation and motor feedback collection as described in U.S. Pat. Nos. 4,639,884 and 5,062,064 assigned to the assignee of this invention. Since the data from the CCD sensor circuit is transmitted to the controller using standard motor quadrature, the CCD acts like a linear encoder to the controller in that it counts up when the CCD is obscured and maintains this value until the CCD is uncovered, after which the position counts back to where it started. Thus the sensor circuit data supplied to the controller is processed in the same manner as a normal axis in the controller hardware, but the software for this axis can be configured by the user to take data, search for the notch, and calculate the wafer center when the notch has been found. The vacuum chuck is controlled as a normal motor, and the control is not linked to the CCD feedback, although the two are synchronized during operation.
Other objects, advantages and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing.
REFERENCES:
patent: 3972424 (1976-08-01), Levy et al.
patent: 3986109 (1976-10-01), Poduje
patent: 4158171 (1979-06-01), Abbe et al.
patent: 4457664 (1984-07-01), Judell et al.
patent: 4646009 (1987-02-01), Mallory
patent: 4692695 (1987-09-01), Poduje
patent: 4724322 (1988-02-01), Knowles et al.
patent: 4746256 (1988-05-01), Boyle et al.
patent: 4752898 (1988-06-01), Koenig
patent: 4770600 (1988-09-01), Ishikawa
patent: 4813846 (1989-03-01), Helms
patent: 4819167 (1989-04-01), Cheng et al.
patent: 4846626 (1989-07-01), Engelbrecht
patent: 4860229 (1989-08-01), Abbe et al.
patent: 4880348 (1989-11-01), Baker et al.
patent: 4881863 (1989-11-01), Braginsky
patent: 4887904 (1989-12-01), Nakazato et al.
patent: 4892455 (1990-01-01), Hine
patent: 4895486 (1990-01-01), Baker et al.
patent: 4897015 (1990-01-01), Abbe et al.
patent: 4910453 (1990-03-01), Abbe et al.
patent: 4931962 (1990-06-01), Palleiko
patent: 4955780 (1990-09-01), Shimane et al.
patent: 4958129 (1990-09-01), Poduje et al.
patent: 4980971 (1991-01-01), Bartschat et al.
patent: 5030057 (1991-07-01), Nishi et al.
patent: 5054991 (1991-10-01), Kato
patent: 5102280 (1992-04-01), Poduje et al.
patent: 5102291 (1992-04-01), Hine
patent: 5193969 (1993-03-01), Rush et al.
patent: 5194743 (1993-03-01), Aoyama et al.
patent: 5238354 (1993-08-01), Volovich
patent: 5261776 (1993-11-01), Burck et al.
patent: 5265170 (1993-11-01), Hine et al.
patent: 5332352 (1994-07-01), Poduje et al.
patent: 5340261 (1994-08-01), Oosawa et al.
patent: 5365672 (1994-11-01), Kato
patent: 5386481 (1995-01-01), Hine et al.
patent: 5405230 (1995-04-01), Ono et al.
patent: 5452521 (1995-09-01), Niewmierzycki
patent: 5456561 (1995-10-01), Poduje et al.
patent: 5466945 (1995-11-01), Brickell et al.
patent: 5511005 (1996-04-01), Abbe et al.
patent: 5513948 (1996-05-01), Bacchi et al.
patent: 5520501 (1996-05-01), Kouno et al.
patent: 5540821 (1996-07-01), Tepman
patent: 5557267 (1996-09-01), Poduje et al.
patent: 5563798 (1996-10-01), Berken et al.
patent: 5564889 (1996-10-01), Araki
patent: 5642298 (1997-06-01), Mallory et al.
patent: 5655871 (1997-08-01), Ishii et al.
patent: 5668452 (1997-09-01), Villarreal et al.
patent: 5691907 (1997-11-01), Resler et al.
patent: 5740062 (1998-04-01), Berken et al.
patent: 5741114 (1998-04-01), Onodera
patent: 5743695 (1998-04-01), Ryu
patent: 5746565 (1998-05-01), Tepolt
patent: 5818632 (1998-10-01), Stephenson
patent: 5822213 (1998-10-01), Huynh
patent: 5831738 (1998-11-01), Hine
patent: 5851102 (1998-12-01), Okawa et al.
patent: 5870488 (1999-02-01), Rush et al.
patent: 5905850 (1999-05-01), Kaveh
patent: 5943130 (1999-08-01), Bonin et al.
patent: 5944476 (1999-08-01), Bacchi et al.
patent: 5980195 (1999-11-01), Miyashita
patent: 5990650 (1999-11-01), Brock
patent: 6078876 (2000-06-01
Gaudio Stephen A.
Sagues Paul
Wong Tim K.
Berkeley Process Control, Inc.
Jaffer David H.
Pillsbury & Winthrop LLP
Skaggs H. Grant
Tran Khoi H.
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