Exposure apparatus and method

A projection exposure method for exposing a substrate through a projection optical system with a pattern formed on a pattern-bearing surface of a mask, comprising:

• a first step of calculating an amount of lateral variation of a pattern image, the variation being caused by irregularities in the pattern-bearing surface of the mask;
• a second step of determining a distortion produced solely by the projection optical system;
• a third step of obtaining a total expected distortion by a summation of the distortion produced by the projection optical system and the calculated variation of the pattern image;
• and
• a fourth step of correcting the total expected distortion.

A projection exposure method for exposing a substrate through a projection optical system with a pattern image formed on a pattern-bearing surface of a mask, comprising:

• a first step of determining a distortion produced solely by the projection optical system;
• a second step of obtaining a total expected distortion by a summation of the distortion produced solely by the projection optical system and an amount of lateral variation of the pattern image, caused by a self-weight of the mask;
• and
• a third step of exposing the substrate with the pattern image while partially correcting the position at which the pattern image of the mask is formed through the projection optical system based on the total expected distortion.