Measuring flare in semiconductor lithography

Systems, methods, and lithography masks for measuring flare in semiconductor lithography. A layer of photosensitive material is exposed to a first test pattern and a second test pattern, the second test pattern comprising an opaque or attenuated region. The second test pattern is placed proximate features formed in a photosensitive material in a first exposure by the first test pattern, in a second exposure by the second test pattern on the same mask or a different mask. Alternatively, the second test pattern may be disposed proximate a portion of the first test pattern on a single mask using a single exposure. If flare exists in the optical system, the second test pattern causes line shortening in the features formed in the photosensitive material of the first test pattern. The line shortening can be measured to determine the effect of flare in the lithography system.