Selective and Anisotropic Dry Etching of Ge over Si

Abstract

Inductively coupled plasma (ICP) etching of Ge with high selectivity over Si and anisotropic etched profiles using CF4, HBr, SF6, and Cl2 reactive gases has been studied. Because pressure and biased power should be the most important parameters to drive selectivity and etch profile, they were varied from 4 to 50 mTorr and from 0 to 50 W, respectively, so as to investigate their influence on process. Total gas flow (100 sccm) and source power (350 W) were initially held constant. Selectivity greater than 100:1 of Ge over Si was achieved using 100 % Cl2 etch gas at 50 mTorr and zero bias power but the profile of the etched features was isotropic. With the addition of N2 to the feed gas (Cl2) the profile became more anisotropic. A three steps ICP etch process was developed with a final Ge/Si etch selectivity of 5:1 and anisotropic profiles.

Design of Far-Infrared High-Efficiency Polarization-Independent Retroreflective Metasurfaces

“…Currently, our existing etching processes involve the preparation of pillar structures using CF 4 and SF 6 for Si and certain oxides. However, the Ge etching requires HBr and Cl 2 as reactive chemicals [45,46], which presents a challenge for us. Following the etching process, any remaining photoresist will be removed using oxygen plasma.…”

State of the Art and Future Perspectives in Advanced CMOS Technology

“…The etching gases are mainly CF 4 [202], CF 4 /O 2 /N 2/ CH 2 F 2 [203,204], and NF 3 /Ar/NO [205]. Conventional plasma etching is usually used for anisotropic etching [206]. However, using CF 4 /O 2/ He in traditional inductively coupled plasma (ICP) for SiGe selective etching has achieved a good etching effect.…”

Optimizing the Isotropic Etching Nature and Etch Profile of Si, Ge and Si0.8Ge0.2 by Controlling CF4 Atmosphere With Ar and O2 Additives in ICP

“…The lateral etch is evident on Ge and Si 0.8 Ge 0.2 whereas, etch selectivity is high for (Si 0.8 Ge 0.2 /Si) (Ge/Si). Etch selectivity for Si 0.8 Ge 0.2 is greater than Ge due to the presence of Si 0.8 Ge 0.2 that monopolizes the etching species and the etch rate is linked to the number of Si-Ge bonds that initiate the reactions [7]. Lateral etching depth (813 nm) and lateral etch rate (13.5 nm/min) for Si 0.8 Ge 0.2 is high (813 nm) as compared to Ge under the same process parameter.…”

“…because of not much difference in lattice constant (1% for Ge contents < 25%) [7]. Therefore, germanium offers the possibilities to differentiate it from silicon for its highly selective isotropic etching.…”