Pattern deformation and pattern position shift caused by lens aberration of the exposure tool sis a serious problem. To analyze the effect of lens aberration, lens aberration data are needed. We have therefore developed a new technique to evaluate lens aberration by using an attenuated phase- shifting mask. We firstly measured exposure energy ratio when side-lobe of an octagonal pattern on an attenuated phase-shifting mask was printed at each of the pattern side by sign scanning electron microscope. This ratio is then compared with the ratio of simulated light intensities, and we obtained aberration values, COMA and trefoil errors. To cut down measurements time and improve measurement repeatability, we inspected the wafers to detect formation of side-lobe patterns by using wafer pattern defect inspection system. As a result, automatic measurement time decreased to 20 minutes for 11 by 11 points measurement in one shot. The light intensity simulation show that pattern delineation characteristics are affected by trefoil errors more than by COMA. We can apply this new measurement technique to select a better lens system that will not suffer so much the effect of COMA and trefoil error on pattern delineation.

Date Published: 5 July 2000
PDF: 9 pages
Proc. SPIE 4000, Optical Microlithography XIII, (5 July 2000); doi: 10.1117/12.388964

Published in SPIE Proceedings Vol. 4000:
Optical Microlithography XIII
Christopher J. Progler, Editor(s)