Patent ID: 6444995
Filing Date: 2002-09-03
Classification: G03F

Abstract:
A focussing method for confirming two or more foci on a semiconductor wafer in an exposure apparatus, the semiconductor wafer having a stack structure and a coating of a photoresist layer, the focussing method comprising:transmitting a light to the semiconductor wafer for detecting a focus, wherein the light is transmitted at an incident angle at which an amount of light reflected from a surface of the photoresist layer is larger than an amount of light penetrating a surface of the photoresist layer; detecting the light reflected from the surface of the photoresist layer; and controlling a position of the semiconductor wafer in response to the light detected and confirming two or more foci, wherein a consistent focus is obtained in a fixed area of the semiconductor wafer; wherein the focussing method confirms three foci when the semiconductor wafer is in a paused state, two of the three foci defining a line on a surface of the wafer, a third of the three foci being offset perpendicular to a center point of that line by a predetermined distance.