Application of the evolutionary kinetic Monte Carlo method for the simulation of anisotropic wet etching of sapphire

Abstract

In this paper, the simple, rejection-based kinetic Monte Carlo simulation method is applied for the approximate simulation of the etch rates and three-dimensional etch structures during anisotropic wet etching of sapphire. Based on the analysis of the composition of the atomic structure of sapphire, a model of the simplified atomic structure of sapphire is proposed, which reduces the difficulty of classifying types of surface atoms on the different crystallographic planes. This enables adopting a previously proposed six-index classification method (to differentiate effectively between the various surface atoms of sapphire) and a previously proposed removal probability function (RPF) (to link the removal probability of the surface atom with the configuration of its neighbors). By reducing errors between simulated rates and experimental rates of 11 typical crystallographic planes in the <−1 1 0 0> and <1 1 −2 0> crystallographic zones continuously with an evolutionary algorithm, reasonable values of nine energy parameters of the RPF are obtained. The simulated results describe approximately the experimental counterparts.

Analysis of Wet-Etched Structures on R-Plane Substrates of Sapphire in the Etchant of Sulfuric Acid and Phosphoric Acid

“…The etching solution is a mixture of the concentrated H 2 SO 4 (98 wt%) and concentrated H 3 PO 4 (87 wt%), the volume ratio of the etchant is 3:1, and the etching temperature is 236 °C. The procedure of gaining the etching rates of sapphire through the wet etching experiment on the sapphire hemisphere is as follows: [24][25][26]29 (1) Use a coordinate measuring device to measure the original data of the coordinate points on the surface of the sapphire hemisphere every two degrees, and the measuring range is (3) Re-measure the coordinate points on the surface of the wetetched hemisphere, following the first step. (4) The measurement data of the sapphire hemisphere before and after etching is organize and calculated, and the distribution of etching rates of sapphire in the experimental etchant (236 °C, three parts H 2 SO 4 and one part H 3 PO 4 in terms of volume) is obtained.…”

Analysis of Etch Profiles on C-Plane Wafers in Wet Etching of Sapphire Based on Undercutting Rate Distributions in Mixture of H2SO4 and H3PO4 at 236 °C

“…The specific process of obtaining etch rates by wet etching experiments of sapphire hemispheres is as follows 19,20,23,24 :…”

“…Wet etching of C-plane wafers.-In this paper, 2 inch C-plane wafers are used for wet etching experiments. The specific process of wet etching experiments of C-plane wafers is as follows: 19,20 (1) A SiO 2 film is deposited on the surface of C-plane wafers by plasma enhanced chemical vapor deposition (PECVD) and patterned by photolithography. The thickness of the SiO 2 film is 240 nm.…”

“…Due to the complicated anisotropy of etch rates of sapphire, a large number of sidewall planes will form in the etching process of sapphire substrates, which greatly increases the difficulty of analyzing etch profiles of sapphire. 19,20 For the previous wet etching of quartz, the maximum positive curvature (MPC) recognition method was used to analyze the formation of etch profiles on Z-cut, AT-cut and BT-cut successfully. 21,22 The maximum positive curvature (MPC) recognition method is proposed based on the Wulff-Jaccodine (WJ) method.…”

Fabrication of microstructures in the bulk and on the surface of sapphire by anisotropic selective wet etching of laser-affected volumes

“…A variety of unique microstructures can be made with ODE having specific geometric characteristics such as sharp corners or flat surfaces. Some of the main applications of anisotropic etching are surface-texturing of sapphire [38][39][40][41][42][43][44][45][46][47], micro/nanostructuring of crystalline silicon [34,48], or processing of crystalline quartz [49]. Anisotropic etching is also used for highlighting surface or subsurface defects of a single crystal material [50], or to understand the crystallographic structure and symmetry.…”