Wet Etching Technique to Reduce Pyramidal Hillocks for Anisotropic Silicon Etching in NaOH/IPA Solution

Abstract

The various methods of silicon wet etching techniques, which utilize ultrasonic agitation to reduce pyramidal hillocks in etched patterns, were evaluated in NaOH+IPA solution. The comparison of the etching methods composed of; 1.) no agitation + sample horizontally orientated, 2.) ultrasonic agitation + sample horizontally orientated, 3.) ultrasonic agitation + sample vertically orientated, and 4.) ultrasonic with rotation agitation + sample vertically orientated. It was found that the percentages of the etched patterns presenting hillocks after etching were 100%, 79.77%, 32.67% and 2.62%, respectively. Ultrasonic coupled with rotation agitation along with the sample vertically orientated is the most powerful etching technique, offering a high yield of smooth etched surface. The difference in etch rate between without agitation and applying ultrasonic agitation was not observed in this experiment, as it was operated in a solution temperature 60-65°C and a 275nm/min etch rate was achieved. The theories that relate to each evaluated method are also discussed.