Morphological and crystallographic evolution of patterned silicon substrate etched in TMAH solutions

• Published in: Applied surface science Vol. 496; p. 143720
• Main Authors: Shen, Jian, Chen, Yuandong, Zhang, Feihu, Zhang, Dan, Gan, Yang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2019
• Subjects: Anisotropic crystallographic etching; Morphological evolution; Patterned silicon substrate; TMAH etchant; Anisotropic crystallographic etching; TMAH etchant; Morphological evolution; Patterned silicon substrate
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.143720

Wet etching of Si substrate enables fabrication of sophisticated Si microstructures for a number of applications. However, the detailed anisotropic etching behavior of Si in the alkaline TMAH solutions is still not well understood. In this study, insights into the wet etching behavior of (100) patterned silicon substrate (PSiS) with circular aperture SiO2 mask in TMAH solutions of varying concentrations (1–25 wt%) are obtained through systematically studying the morphological and crystallographic evolutions of PSiS. Etching in 1 wt% TMAH revealed the widest spectrum of morphological evolutions including the rounded apertures, inverted octahedral frustums, octahedral pyramids, and pyramids. In contrast, etching in 5–25 wt% TMAH revealed features of inverted octahedral frustums, pyramidal frustums, and pyramids. A series of crystallographic planes formed due to anisotropic crystallographic etching were indexed as—C1 {3¯40}, C2 {1¯10}, C3 {1¯11¯}, C4 {2¯11¯}, and C5 {1 14 0}, and the etching rates of which were determined to explain the morphological evolution and anisotropic etching mechanism. This work contributes to the controllable fabrication of sophisticated Si microstructures for Si-based optoelectronic devices with potentially enhanced performance. [Display omitted] •Both etching time and TMAH concentration significantly affect morphological and crystallographic evolutions of PSiS.•A series of crystallographic planes—{3¯40}, {1¯10}, {1¯11¯}, {2¯11¯}, and {1 14 0} planes—appeared.•The {3¯40} and {1 14 0} planes were exposed in the TMAH etchants for the first time.•Larger TMAH concentration favors higher etching rates of {3¯40}, {1¯10}, {1¯11¯} planes.•Smaller TMAH concentration favors higher etching rate of the bottom (100) plane.