公开(公告)号：DE2424313A1

公开(公告)日：1975-01-02

申请号：DE2424313

申请日：1974-05-18

Applicant: IBM

Inventor： GILL CHARLES DANA ,  RYAN PHILIP MEADE

IPC: H01J37/305 ,  G06F17/15 ,  G06F17/17 ,  G06F17/18 ,  H01J37/304 ,  H01L21/00 ,  H01L21/027 ,  G01R25/00 ,  H01L21/82

Abstract: In semiconductor manufacture, very accurate patterns must be formed in the photoresist on the surface of the semiconductor material. Chips are formed on a semiconductor wafer utilizing a beam of charged particles to expose the photoresist material on the surface of the semiconductor. If the plurality of chips, is to have the same characteristics and pattern, it is necessary that the electrons or beam of charged particles be moved such that any point within the field to which the beam is applied is always reached by the same history. This requires that patterns produced by an electron beam be properly registered with respect to previously generated patterns. This registration is accomplished by scanning previously placed registration marks on the chip with a beam of electrons and monitoring the reflected or back-scattered electrons to determine where the beam crosses said registration marks. The method disclosed herein is a system of processing the signals encountered during beam contact with the registration marks on the chip usually at the four corners thereof, whereby the location of the marks is accurately determined. This is accomplished by first improving the signal to noise ratio of the detected signal followed by a rapid cross-correlation between the averaged signal and another signal having certain specific and especially desirable characteristics. The final step utilizes a least squares curve fitting procedure tuned up to extract the essential parameter, that is the center of the cross-correlation, with a minimum of on-line computation.