Multiple Exposures in Extreme Ultraviolet Lithography

An extreme ultraviolet lithography (EUVL) method, the EUVL method comprising:

• providing at least two mask areas having a same pattern, wherein at least one of the at least two mask areas includes a defect;
• forming a resist layer over a substrate;
• determining an optimized exposure dose based on an exposure dose for a pre-specified pattern on one of the at least two mask areas to achieve a pre-specified target dimension under a corresponding single exposure process;
• and
• forming a latent image in the resist layer using the at least two mask areas, wherein the forming a latent image includes:
• performing at least two exposure processes on a same area of the resist layer,
• wherein each of the at least two exposure processes uses an exposure dose that is less than the optimized exposure dose, and
• wherein a sum of the exposure dose of each of the at least two exposure processes is approximately equal to the optimized exposure dose.

A method comprising:

• providing a first mask area;
• providing a second mask area having a same pattern as the first mask area;
• forming a resist layer over a substrate;
• determining an optimized exposure dose for the resist layer;
• and
• exposing a same area of the resist layer to the first mask area with a first exposure dose and to the second mask area with a second exposure dose, wherein the first exposure dose and the second exposure dose are each less than the optimized exposure dose.