公开(公告)号：EP0804713A4

公开(公告)日：1999-03-24

申请号：EP95916365

申请日：1995-04-13

Applicant: TENCOR INSTRUMENTS

Inventor： NIKOONAHAD MEHRDAD ,  RIGG PHILIP R ,  WELLS KEITH B ,  CALHOUN DAVID S

IPC: G01B11/02 ,  G01B11/30 ,  G01N21/88 ,  G01N21/94 ,  G01N21/95 ,  G01N21/956 ,  H01L21/66 ,  G01B11/00

CPC classification number: G01N21/9501 ,  G01N21/94 ,  G01N21/956

Abstract: A surface height detection and positioning device for use in a surface inspection system. A light beam (25) impinges obliquely upon the surface (22), and a position detector (38) with a mechanical window (45) defining an aperture (46) receives specularly reflected light (33) producing a plurality of electrical signals. The aperture's width (46), along a scan direction, is of sufficient size to create a train of signals from each of the plurality of signals, having a frequency equal to the scan frequency. These signals carry information responsive to the position of the reflected beam (33) impinging on the detector and the beam's intensity. To abrogate information responsive to intensity variations at the detector, an electronic circuit (100) determines the sum and the difference of the plurality of signals, producing a summed signal and a difference signal, respectively. The difference signal is divided by the summed signal, thereby producing a normalized signal which represents the height of the surface.