Lian Cong Liu, Tsung Ju Yeh, Yeh-Sheng Lin, Yu Chin Huang, Chien Wen Kuo, Wen Liang Huang, Chia Hung Lin, Chun Chi Yu, Ray Hsu, I-Yuan Wan, Jeff Lin, Kwang-Hwyi Im, Hae Jin Lim, Hyun Jeon, Yasuhiro Suzuki, Cheng Bai Xu
In this paper, we summarize our development efforts for a top-coatless 193nm immersion positive tone development (PTD) contact hole (C/H) resist with improved litho and defect performances for logic application specifically with an advance node. The ultimate performance goal was to improve the depth of focus (DoF) margin, mask error enhancement factor (MEEF), critical dimension uniformity (CDU), contact edge roughness (CER), and defect performance. Also, the through pitch CD difference was supposed to be comparable to the previous control resist. Effects of polymer and PAG properties have been evaluated for this purpose. The material properties focused in the evaluation study were polymer activation energy (Ea), polymer solubility differentiated by polymerization process types, and diffusion length (DL) and acidity (pKa) of photoacid generator (PAG). Additionally, the impact of post exposure bake (PEB) temperature was investigated for process condition optimization. As a result of this study, a new resist formulation to satisfy all litho and defect performance was developed and production yield was further improved.
A combination of simulation, resist modification and process optimization were used to develop production worthy dry 193nm lithography processes, suitable for the metal trench layers of 65nm node logic devices. The important performance characteristics of a back-end metal trench layer are through-pitch proximity bias, lithographic latitude and ultimate resolution. Simulation results suggested that a moderate annular illumination setting balances proximity bias against resolution at the forbidden pitch, yielding a good overall through-pitch common process window. Resist material optimization through resin, PAG (photo-acid generator) and base quencher modification improves proximity bias and results in excellent lithographic performances of good LER (line edge roughness), low MEF (Mask Error Factor) and wider process latitude. To investigate extendibility to 45nm node applications, the immersion compatibility of the optimized resist with several top coats are reported.
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