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Proceedings Paper

Process optimization of high aspect ratio sub-32nm HSQ/AR3 bi-layer resist pillar
Author(s): Wei-Su Chen; Ming-Jinn Tsai
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Paper 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.

Paper Details

Date Published: 16 April 2011
PDF: 11 pages
Proc. SPIE 7972, Advances in Resist Materials and Processing Technology XXVIII, 79722P (16 April 2011); doi: 10.1117/12.878591
Show Author Affiliations
Wei-Su Chen, Industrial Technology Research Institute (Taiwan)
Ming-Jinn Tsai, Industrial Technology Research Institute (Taiwan)

Published in SPIE Proceedings Vol. 7972:
Advances in Resist Materials and Processing Technology XXVIII
Robert D. Allen; Mark H. Somervell, Editor(s)

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