Patent ID: 6449029
Filing Date: 2002-09-10
Classification: G03F,H01L

Abstract:
A photolithography apparatus comprising:a mask support system for supporting a mask having a chip pattern and imagewise-modulating incident light with the chip pattern; a projection lens system for projecting the modulated light onto a focal point; a wafer support system for adjustably and horizontally movably supporting a semiconductor wafer, the system being controlled to successively set the wafer in one of a plurality of cell positions; a position sensing system for directing at least four laser beams to the surface of the wafer at each of said cell positions, one said laser beam directed at each corner of said cell positions, and detecting the reflection of at least one said beam off the surface of the water; position analyzer circuitry for successively analyzing a signal representing the reflecting light of each said cell position and determining therefrom a plurality of vertical offset positions of the wafer at said plurality of cell positions; angle calculation circuitry for determining a plurality of tilt angles of the wafer at said cell positions from said plurality of vertical offset positions; and control circuitry controlling said wafer support system to successively set the wafer in one of said cell positions, horizontally aligning, at each cell position, the surface of the wafer according to the tilt angle determined for the cell position and vertically moving, at each cell position, the surface of the wafer to said focal point according to the vertical offset position determined for the cell position.