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X-Y table error mapping apparatus and method

  • US 4,972,311 A
  • Filed: 08/15/1988
  • Issued: 11/20/1990
  • Est. Priority Date: 08/15/1988
  • Status: Expired due to Term
First Claim
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1. A method of correcting for repeatable positioning errors in an X-Y table, comprising the steps of:

  • (a) mounting an accurate mask in the field of view of a pattern recognition system (PRS) of a semiconductor processing machine,said mask having a plurality of repetitive recognizable patterns thereon spaced from each other at predetermined accurate distances,(b) electronically scanning a mask pattern with said PRS to establish a reference eye point of one of said patterns,(c) mechanically moving said PRS relative to said mask a distance calculated to place said PRS over another adjacent identical pattern at a desired position,(d) electronically scanning said adjacent identical pattern to establish the actual position of said X-Y table relative to said desired position,(e) calculating X and Y deviations from said desired position,(f) repeating steps (b) to (e) to establish a plurality of X and Y deviation values for an X axis and for a Y axis of movement of said X-Y table along lines which traverse said mask,(g) storing the deviation values in a memory of a computer having an algorithm adapted to calculate the deviations at other X and Y positions of said X-Y table, and(h) mechanically moving said X-Y table relative to said PRS to predetermined X and Y positions, and(i) correcting the mechanical movement of said X-Y table by the calculated X and Y deviations stored in said memory of said computer to provide universal X-Y corrections.

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