Patent ID: 7643126

Claim:
A method of setting a focus condition at the time of exposure in a photolithography process of forming a resist pattern on a substrate, comprising the steps of: exposing a film on the substrate to light using a mask having a first pattern transmitting only zero-order light of a light source and then developing the film to reduce a first portion of the resist pattern of the film on the substrate in the photolithography process in which a certain focus condition has been already set; exposing the film on the substrate to light using the mask having a second pattern transmitting zero-order light and higher order light of the light source and then developing the film to reduce a second portion of the resist pattern of the film on the substrate in the photolithography process in which the certain focus condition has been already set; measuring film thicknesses of the first portion and the second portion; reading information of a previously obtained correlation between film thicknesses of the first and second portions and line widths of the resist pattern from a storage unit in which said information of the previously obtained correlation is stored; converting the measured film thickness of the first portion and the measured film thickness of the second portion into line widths of the resist pattern by said information of the previously obtained correlation stored in said storage unit; subtracting the converted line width of the second portion from the converted line width of the first portion; and setting a new focus condition based on a line width difference resulting from the subtraction.