Lithography process monitoring method

A method of performing a lithography process for a semiconductor device, the method comprising:

• determining a test pattern associated with a test structure;
• forming the test pattern on a mask;
• using the mask to expose the test pattern to form a test structure having the test pattern on a semiconductor substrate, wherein the using the mask to expose the test pattern includes using an asymmetric exposure;
• and
• using a measurement of the test structure on the semiconductor substrate to determine a production lithography parameter.

A method, comprising:

• determining a test structure pattern, wherein the determining the test structure pattern includes determining a line arrangement providing symmetric diffraction such that with defocus the test structure pattern will not substantially shift in exposing the test pattern;
• performing an exposure process on a first semiconductor substrate using a mask having the test structure pattern, wherein the performing the exposure process uses an asymmetric illumination;
• and
• using the exposed test structure pattern on the first semiconductor substrate to determine a lithography parameter for symmetric illumination of a circuit pattern on a second semiconductor substrate.