Journal of Semiconductors, Volume. 44, Issue 12, 124101(2023)
Multiple SiGe/Si layers epitaxy and SiGe selective etching for vertically stacked DRAM
Figures & Tables(8)
Fig. 1. (Color online) (a) Si/SiGe epitaxy; (b) SiGe full release; (c) high-k and top electrode deposition.
Fig. 2. (Color online) (a) Process flow. Schematic diagram of (b) hard mask growth, (c) anisotropic vertical etching of SiGe/Si MLs, and (d) isotropic selective lateral etching of SiGe.
Fig. 3. (Color online) TEM images of ML structures with SiGe layers of (a) 20 nm, (b) 40 nm and (c) 60 nm. SIMS profile of (d) Ge concentration and (e) the thickness of SiGe layers in three 15-period Si/SiGe ML structures.
Fig. 4. (a) Rocking curves (RCs) of ML structures with different SiGe layer thicknesses. RSM images of ML structures with (b) 20 nm SiGe layers, (c) 40 nm SiGe layers and (d) 60 nm SiGe layers. β1 ≈ 6.7°, β2 ≈ 10°.
Fig. 5. (Color online) TEM images of ML structures with (a) 20 nm SiGe layers, (b) 40 nm SiGe layers and (c) 60 nm SiGe layers. HRTEM cross-sectional images of ML structures with (d) 20 nm SiGe layers, (e) 40 nm SiGe layers and (f) 60 nm SiGe layers.
Fig. 6. SEM cross-sectional images of (a) 25 s dry etch, (b) 25 s continuous wet etch and (c) 40 cycles of ALE for the ML structure with 40 nm SiGe layers.
Fig. 7. (Color online) (a) Rocking curves of SiGe (20 nm)/Si ML structures at different steps of processing. RSMs in the vicinity of the asymmetric (113) Bragg reflection acquired on SiGe (20 nm)/Si ML structures: (b) as-grown, (c) after vertical anisotropy etching and (d) after lateral isotropic SiGe selectivity dry etching α1 ≈ 3°, α2 ≈ 4°.
Table 1. Selective etches of SiGe to Si.
View tableView in ArticleTable 1. Selective etches of SiGe to Si.
Method Solution Advantages Problem Thermal etching HCl[ 38 −40 ]ClF3[ 41 ]High selectivity React in chemical vapor deposition (CVD) tool The etching accuracy is limited Different etch rates for different crystal orientations Dry etching CF4/N2/O2[ 27 ]CF4/O2/He[ 20 ]NF3/O2/N2[ 42 ]Easy to use in large wafer size Isotropic Fast The etching accuracy is limited Continuous wet etching HF/HNO3/CH3COOH[ 25 ]HF/HNO3/CH3COOH/H2O[ 31 ]Excellent selectivity High etch rate Uniform etch rate in MLs etching Etch rate depends strongly on the Ge content Residues block the tunnel in MLs etching HF/H2O2/CH3COOH[ 43 −45 ]HF/H2O2/CH3COOH/H2O[ 46 ]High etch rate Nanoscale etching of SiGe to Si Not suitable for small size Long aging time Wet ALE H2O2/BOEs[ 47 ]HNO3/BOEs[ 48 ]Controllable etch rate Atomically smooth surfaces Long circle time Multistep processes Surface tension and capillary effect
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Zhenzhen Kong, Hongxiao Lin, Hailing Wang, Yanpeng Song, Junjie Li, Xiaomeng Liu, Anyan Du, Yuanhao Miao, Yiwen Zhang, Yuhui Ren, Chen Li, Jiahan Yu, Jinbiao Liu, Jingxiong Liu, Qinzhu Zhang, Jianfeng Gao, Huihui Li, Xiangsheng Wang, Junfeng Li, Henry H. Radamson, Chao Zhao, Tianchun Ye, Guilei Wang. Multiple SiGe/Si layers epitaxy and SiGe selective etching for vertically stacked DRAM[J]. Journal of Semiconductors, 2023, 44(12): 124101
Paper Information
Category: Articles
Received: Jul. 7, 2023
Accepted: --
Published Online: Mar. 13, 2024
The Author Email: Wang Guilei (GLWang)
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