Laser reflectance interferometry for in situ determination of silicon etchrate in various solutions

The etch rate of crystalline silicon in liquid solutions has been measured in situ by laser reflectance interferometry. A simple method has been devel oped which allows accurate real-time observation of the etch rate as a func tion of etching parameters and sample characteristics. The method is demons trated by measurements on (100)single crystal silicon samples etched in tet ramethylammonium hydroxide solutions. Etch rates in the range of 0.05-1 mu m/min have been measured. Some examples of the optical power reflected from silicon samples during etching are presented and the parameters which may influence the accuracy of the etch rate measurements are discussed. Interpr etation of the interference pattern of the reflected power can be complicat ed due to sample thickness variations and surface roughness. To investigate the impact of surface topography on the detected optical power. three simu lation models have been developed. (C) 1999 The Electrochemical Society. S0 013-4651(98)04-062-2. All rights reserved.