Data processing: measuring – calibrating – or testing – Measurement system – Dimensional determination
Reexamination Certificate
1999-07-28
2001-02-27
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Dimensional determination
C702S150000, C700S213000, C700S218000, C414S744500, C414S936000
Reexamination Certificate
active
06195619
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of materials processing, and more particularly, to the alignment of substrates such as semiconductor wafers on robot arms and in processing stations and, still more particularly, to the alignment of substrates, or wafers, of non-standard shape, for example, rectangular or, more broadly, right quadrilateral shaped wafers.
2. Description of the Prior Art
The production and quality control processes used by semiconductor device manufacturers and material producers often require a precise knowledge of such wafer characteristics, as wafer center and orientation, among others. Automated, high throughput assembly line like wafer checking systems are employed to obtain the desired information. The wafers must be aligned about their centers, and their flats selectively oriented in space, before being fed to the selected wafer characterization stations of a particular wafer checking system. In this regard, U.S. Pat. No. 4,457,664 to Judell et al. discloses a wafer alignment station that automatically aligns a wafer, having flats, about its centroid and orients the flats selectively in space which is suitable for use in automated production and quality control. The wafer alignment station suitably may be packaged in a module which is compatible for use with other wafer characterization stations in a high throughput material processing system.
For a number of years now, robot arms have been increasingly utilized for moving objects from one location to another. In the application of robotics to semiconductor wafer processing, a robot arm is useful for conveying a semiconductor wafer from one location to another through the use of independently controllable radial, circumferential and elevational motions. For many purposes, however, it is important that the wafer transported by the robot arm must be placed in a predetermined alignment with respect to its centroid and fiducial, if present.
According to the teaching of the inventions disclosed in U.S. Pat. Nos. 5,332,352 and 5,102,280 to Poduje et al., a robot arm is operative with an alignment station to adjust the orientation of a circular wafer or other element on the robot arm to a predetermined alignment for use by the robot arm in placing the wafer at a neighboring station in a desired orientation. According to the Poduje et al. disclosures, the robot arm includes a manipulator having independently controlled and isolated radial, circumferential and elevational motions, specifically, r, &THgr;, z. A rotating support is provided within the range of placement for a semiconductor wafer carried by the robot arm and has associated with it an edge detector which determines the location of a wafer edge as it is rotated on the rotary support. The robot arm executes r, &THgr;, z independent commands to cradle a wafer on its end effector or hand from a first location. The robot arm then places the wafer upon the rotary support where it is spun with the edge over the edge detector. The edge location is detected by electronics which determines the amount of motion of the centroid to produce alignment of the wafer on the rotary support and/or to locate the wafer fiducial in a predetermined location. The robot arm is then manipulated in a first case to move the wafer on the rotary support until alignment is secured with the fiducial relocated to a predetermined position. The wafer is again picked up by the robot arm for delivery to a further station in predetermined alignment. In a second case the robot arm is operative to pick up the wafer with the known misalignment and correct for such misalignment in delivering the wafer to a subsequent station.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.
SUMMARY OF THE INVENTION
There has been an increasing demand for aligning non-SEMI (Semiconductor Equipment and Materials International) standard wafers, such as right quadrilateral wafers for MR (Magnetic Readhead) processing. Current aligner technology cannot handle these wafers. A new design has therefore been conceived and implemented which uses only a single sensor. Further, the alignment algorithm employed is sufficiently robust as to automatically compensate for any sensor assembly tolerance. It can align a wide range of sizes of rectangular, including square, wafers. According to the invention, the wafer is rotated 360 degrees and the edge data points are collected using a suitable sensor. The data is then processed to find the corners and the fiducial, if any.
More fully, a system is provided by the invention for determining an eccentricity vector &egr; which defines the magnitude and direction of an initial placement displaced from a desired location of a centroid O of a right quadrilateral semiconductor wafer which may be clear or opaque. With an initial point of reference desirably established on its peripheral edge for detection by a sensor, the wafer is rotated about a point P and a curve defining the profile of the peripheral edge is obtained. Viewing
FIG. 9
, the eccentricity vector is computed from the sensed positions of the corners of the wafer and has a magnitude representative of the spatial dislocation of the centroid O relative to the point P and having an orientation &phgr; representative of the angle subtended by a first line connecting the point P and the centroid O relative to a second line connecting opposite corners of the wafer. As processing proceeds, the wafer is inserted into an aligner station, then repositioned from an initial position to a desired position, then advanced seriatim into a plurality of processing stations while maintaining the desired position previously attained. The aligner and the processing stations may be evacuated. The wafer may be post positioned to a new desired position by rotating the wafer until a side thereof is generally parallel to an internal wall of the aligner station, enabling an end effector of a robot arm to readily lift the wafer from its support and advance it into the processing stations while maintaining the desired position previously attained.
A primary feature, then, of the present invention is the provision of a system for aligning wafers such as semiconductor wafers being transported on robot arms to and from one or more processing stations.
Another feature of the present invention is the provision of such a system for transporting non-standard wafers, for example quadrilateral shaped wafers.
Still another feature of the present invention is the provision of such a system according to which the wafer has an initial point of reference formed on its peripheral edge and is rotated about a point P and the profile of its peripheral edge is sensed and a curve defining the profile of the peripheral edge is generated based on measurements obtained by the sensor relative to the initial point of reference and an eccentricity vector computed from the sensed positions of the corners of the wafer.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.
REFERENCES:
patent: 4457664 (1984-07-01), Judell et al.
patent: 4897015 (1990-01-01), Abbe et al.
patent: 5102280 (1992-04-01), Poduje et al.
patent: 5332352 (1994-07-01), Poduje et al.
Brooks Automation Inc.
Perman & Green LLP
Shah Kamini
LandOfFree
System for aligning rectangular wafers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for aligning rectangular wafers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for aligning rectangular wafers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2608555