Study on optimization of annular off-axis illumination using Taguchi method for 0.35 μm dense line/space
✍ Scribed by Wen-an Loong; Jin-chi Tseng; Tzu-ching Chen; Chien-an Lung
- Book ID
- 104306337
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 281 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0167-9317
No coin nor oath required. For personal study only.
✦ Synopsis
The simulation and experiment study on optimizations of process factors under annular off-axis illumination (AOAI) using Taguchi method for design of experiment (DOE) for 0.35 ~tm dense line/space in i-line was reported in this paper. The optimized simulation results for both resolution and DOF are as follows: inner ring cri = 0.35, outer ring ~o= 0.70, NA = 0.5, negative bias on mask for line in dense line/space -0.03 ~tm (L/S = 0.320/0.380 pan), positive bias on mask for isolated line -0.03 ttm (iso. L = 0.38 ~aa), overlapped DOF (dense + isolated) -1.86 ~tm, exposure dose -278 mJ/cm 2. The experimental results are in good agreement with simulations. The optimized results by experiments with a NA of 0.57 and with AOAI are as follows: inner ring ~i = 0.35, outer ring Co = 0.70, negative bias on mask for line in dense line/space-0.015 pan (L/S=0.335/0.365 lain), positive bias on mask for isolated line-0.03 ~n (iso. L = 0.38 tam), overlapped DOF (dense + isolated) ~ 1.7 l~m, exposure time -520 ms (exact dose uncertain). Without AOAI but with the same mask bias, the overlapped DOF is -1.2 ttm by experiment. The overlapped DOF from mask patterns without any bias (L/S = 0.35/0.35 Inn; iso. L = 0.35 Ixrn) with 1/2 AOAI is -0.93 lain; and from conventional illumination without mask bias is up to-0.72 ~tm at most. The DOF, proximity effect and resolution for dense L/S are obviously improved from 1/2 AOAI exposure after optimization ff compared with conventional exposure. The Taguchi method is also proved valuable in this study.