ADVANCED DEEP SILICON ETCH TECHNOLOGY FOR TRENCH CAPACITOR, ISOLATION TRENCH, MEMS AND MOEMS APPLICATIONS

摘要

In this paper, we present the high aspect ratio (HAR) anisotropic silicon etch process using Applied Materials high density decoupled plasma source (DPS)~(TM). The hardware performance of DPS deep trench etcher in terms of vacuum and pumping characteristics, plasma ignition windows, ion flux distribution and temperature variations on wafer has been characterized. Process has been developed and characterized for deep silicon etch with fluorine (SF_6) based chemistry in combination of passivating gases like O_2, HBr, SiF_4, CHF_3, CH_2F_2, and C_4F_8. The effect of pressure, source power, bias power, and gas ratio on etch rate, etch rate non-uniformity, selectivity to mask, and trench profile has been studied by performing DOE and single variable experiments. A two step process scheme was demonstrated to perform HAR etch on SOI structure. A time multiplexed gas modulation (TMGM) process has been utilized to achieve high etch rate and high resist selectivity,. In TMGM process, gases were pulsed to perform isotropic etch and polymer deposition alternately. The TMGM process was also characterized and optimized to perform deep trench etch on SOI structure. With an optimized process etch rate as high as >20μm/min. and very high resist mask selectivity (>100) were achieved for through wafer silicon etch applications.