Geometrical instruments – Gauge – Center – point – distance between centers – or centerline location
Patent
1994-03-09
1995-09-26
Cuchlinski, Jr., William A.
Geometrical instruments
Gauge
Center, point, distance between centers, or centerline location
414936, 33644, G01D 2100
Patent
active
054525217
ABSTRACT:
This invention teaches an apparatus and method for detection and correction of eccentricity and angular misalignment of a wafer. The position of a wafer is determined while the wafer is stationary on a robot arm by position sensors that locate four points on the periphery of the wafer. A microprocessor selects and uses a specific combination of three of the four points to calculate the actual location of the center of the wafer. The microprocessor produces signals which are used to correct the wafer's eccentricity using two rotatable shafts, an inner shaft mounted inside an outer shaft. The outer shaft is rotated prior to arrival of the wafer, in order to position the inner shaft at a pre-determined location depending on the eccentricity to be corrected. After the wafer is placed on a turntable mounted on and rotatable by the inner shaft, the inner shaft is rotated by the requisite angle to eliminate the wafer's eccentricity in a single movement. Optionally, to correct angular misalignment of the wafer, the outer shaft is rotated by the desired angle simultaneous with the inner shaft rotation. For process shifts, both eccentricity and angular misalignment are corrected in a single movement of the wafer.
REFERENCES:
patent: 3174392 (1965-03-01), Rantsch
patent: 4457664 (1984-07-01), Judell et al.
patent: 4833790 (1989-05-01), Spencer et al.
patent: 5085558 (1992-02-01), Engelbrecht
patent: 5308222 (1994-05-01), Bacchi et al.
"Vacuum Wafer Aligner", Mar. 5, 1990, Brooks Automation.
"Non Edge-Contact Wafer Aligner Manual", Nov. 20, 1989, Brooks Automation.
Bennett G. Bradley
Cuchlinski Jr. William A.
MacPherson Alan H.
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