Process optimization of high aspect ratio sub-32nm HSQ/AR3 bi-layer resist pillar

Wei-Su Chen; Ming-Jinn Tsai

doi:10.1117/12.878591

15 April 2011 Process optimization of high aspect ratio sub-32nm HSQ/AR3 bi-layer resist pillar

Wei-Su Chen, Ming-Jinn Tsai

Proceedings Volume 7972, Advances in Resist Materials and Processing Technology XXVIII; 79722P (2011) https://doi.org/10.1117/12.878591
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

RRAM is the candidate of next generation new non-volatile memory. The etched stacking film thickness of RRAM cell pillar is not easy to reduce below 50 nm during CD scaling down since part of RRAM cell pillar height is removed during CMP polishing of dielectric passivation to expose the pillar top surface for the following metallization process. Therefore resist pillar pattern with high aspect ratio (AR) is needed to act as etch mask for defining thick RRAM cell pillar structure. Bilayer resist (BLR) process is most suitable for forming high AR pattern. Dry develop process is the key step for generating sub-32 nm high AR BLR pillar pattern. In this study optimization of dry develop process is investigated for high AR pillar with hydrogen silsesquioxane (HSQ) as upper thin imaging layer for e-beam exposure and AR3-600 as the thick underlayer for etching resistant. Experimental results are summarized below. Highest AR of ~6 for HSQ/AR3 BLR semi-dense L/S=1/2 pillar with vertical profile is obtained under optimized dry develop condition with O2, N2, Ar flow rates, chamber pressure, top and bottom power of 8, 5, 0 sccm, 1 mTorr, 200 and 100 watts respectively. AR is lower for looser pattern density. CD variation between HSQ/AR3-600 BLR pillars with different pattern density is optimized to 5.6 nm. The pillar profile is vertical in vacuum for pattern of any density but distorts more severe for denser pattern during ventilation to atmosphere. The most critical process parameters for obtaining high aspect ratio BLR pillar are O2 flow rate and top power. Sidewall profile angle of pillar is mainly dependent on chamber pressure and bottom power.

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Wei-Su Chen and Ming-Jinn Tsai "Process optimization of high aspect ratio sub-32nm HSQ/AR3 bi-layer resist pillar", Proc. SPIE 7972, Advances in Resist Materials and Processing Technology XXVIII, 79722P (15 April 2011); https://doi.org/10.1117/12.878591

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KEYWORDS

Oxygen

Etching

Argon

Critical dimension metrology

Photoresist processing

Plasma

Photomasks

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