Patent ID: 7250235

Claim:
A focus monitor method comprising: preparing a mask comprising a first and second focus monitor patterns and an exposure monitor pattern, the first and second focus monitor patterns being used to form first and second focus monitor marks having dimensions variable depending on a defocus amount on a wafer, defocus amount dependency of the dimension of the first focus monitor mark being different from defocus amount dependency of the dimension of the second focus monitor mark, and the exposure monitor pattern being used to form exposure meters having dimensions variable depending on an effective exposure on the wafer; obtaining exposure dependency of a relationship between the dimensions of the first and second focus monitor marks and the defocus amount; forming the first and second focus monitor marks and the exposure meters on the wafer by using the mask; measuring the dimensions of the exposure meters to obtain the effective exposure; selecting a relationship, corresponding to the effective exposure, between the dimensions of the first and second focus monitor marks and the defocus amount in accordance with the obtained effective exposure and the exposure dependency of the relationship between the dimensions of the first and second focus monitor marks and the defocus amount; measuring the dimensions of the first and second focus monitor marks; and obtaining the defocus amount in accordance with the measured dimensions of the first and second focus monitor marks and the relationship, corresponding to the effective exposure, between the dimensions of the first and second focus monitor marks and the defocus amount.