Potential of phase-shifted optical proximity correction for T-shaped pattern in high numerical aperture lithography
(a) Phase conflict occurs when T-shaped pattern is imaged with phase shift mask due to its perpendicular structure. (b) Polarized mask used for reducing phase conflict. The green arrows mean the polarization orientation, 180° and 0° means att-PSM region. (c) Double exposure mask. The region masked second binary mask exposure means that the region need another exposure process to eliminate unwanted patterns caused by phase conflict.
Different kinds of OPC (from left to right it was original mask, serif bar, bias, hammerhead, serif, and jog).
Exposure results for T-shaped patterns. (a) The LESE for T-shaped pattern without OPC. (b) Line conjunction occurs when the OPC segment size is increased in order to eliminate LES.
The illustration of PSOPC mask. 180° phase-shift polygons (with transmittance) and nonopaque polygons with transmittance is added around the serif instead of opaque polygons.
(a) Solutions for T-shaped pattern using PSOPC. (b) Final resist image profile and mask. The line CD was controlled under CD and the gap was .
Lithography performances for T-shaped pattern after the application of PSOPC. (a) Process window. The DOF is , which is acquired at , sidewall , and (b) pattern placement error of T-shaped pattern is under through focus range.
Process verification of PSOPC. (a) The DOF nearly has only a change when NA changes from 0.9 to 1. (b) Even sigma in and sigma out have a fluctuation, the change of DOF value is below . (c) PEB time error nearly had no influence on DOF. (d) resist thickness and BARC thickness error has less than DOF reduction.
Comparisons of main lithography performance when using OPC, PSOPC, and no OPC. When using PSOPC, the gap CD error has a over 50% reduction compared with OPC, CD error is controlled under CD, DOF has a three times improvement and the LES is reduced to .
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