Trenched 4H-SiC with tapered sidewall formed by Cl₂/O₂ reactive ion etching

In this article, trenches with various sidewall slant angles were generated on 4H silicon carbide substrate using Cl₂/O₂-based reactive ion etching. A series of experiments was conducted to investigate the effects of chamber environmental conditions, including Cl₂/O₂ mixing ratios, radio frequency power, and process pressure. The results indicate that the chamber pressure, ion energy, redeposition of etch products/byproducts, and even the existence of photoresist are critical factors affecting the slant angle. The introduction of oxygen not only changes the etch profile but may also cause a serious problem known as the micromasking effect. A method combining photoresist and hydrofluoric acid clean was proposed to eliminate the micromasking effect while keeping the sidewall passivation.