Evolution of Si Crystallographic Planes-Etching of Square and Circle Patterns in 25 wt % TMAH.

Milče Smiljanić,Branislav Radjenović,Vesna Jović,Žarko Lazić,Marija Radmilović-Radjenović

doi:10.3390/mi10020102

Abstract

Squares and circles are basic patterns for most mask designs of silicon microdevices. Evolution of etched Si crystallographic planes defined by square and circle patterns in the masking layer is presented and analyzed in this paper. The sides of square patterns in the masking layer are designed along predetermined <n10> crystallographic directions. Etching of a (100) silicon substrate is performed in 25 wt % tetramethylammonium hydroxide (TMAH) water solution at the temperature of 80 °C. Additionally, this paper presents three-dimensional (3D) simulations of the profile evolution during silicon etching of designed patterns based on the level-set method. We analyzed etching of designed patterns in the shape of square and circle islands. The crystallographic planes that appear during etching of 3D structures in the experiment and simulated etching profiles are determined. A good agreement between dominant crystallographic planes through experiments and simulations is obtained. The etch rates of dominant exposed crystallographic planes are also analytically calculated.

Highlights

Anisotropic wet etching of a (100) silicon substrate in 25 wt % tetramethylammonium hydroxide (TMAH) water solution is a well-known process [1,2,3,4,5,6,7,8,9,10,11]
Etching of a (100) silicon substrate is performed in 25 wt % tetramethylammonium hydroxide (TMAH) water solution at the temperature of 80 ◦C
We explore etching of square patterns that are designed along predetermined crystallographic directions (0 ≤ n < 10) and circle patterns in the masking layer on a (100) silicon

Summary

Introduction

Anisotropic wet etching of a (100) silicon substrate in 25 wt % tetramethylammonium hydroxide (TMAH) water solution is a well-known process [1,2,3,4,5,6,7,8,9,10,11]. Most of the results have been obtained through the analysis of the etching square or rectangular patterns in the masking layer with sides along crystallographic direction. During etching of these mesa structures, a severe convex corner undercutting appears. The convex corner compensation techniques for the TMAH water solutions etching are developed for the patterns with sides along crystallographic directions [12,13,14,15,16,17,18,19,20,21,22].

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