Effect of Damage Removal Treatment after Trench Etching on the Reliability of Trench MOSFET

Guaranteeing the reliability of gate oxides is one of the most important topics to realize regarding the SiC power MOSFET [1] [2]. In the case of trench MOSFET, since the gate oxides are formed on the trench sidewall, the damage and roughness on the trench sidewall can affect the lifetime of the gate oxides. Generally speaking, damage removal treatment is processed after trench dry etching in most cases. In Si processes, sacrificial oxidation, H-2 anneal and chemical dry etching (CDE) are adopted commonly. In the case of SiC processes, sacrificial oxidation, H-2 anneal, and SiH4/Ar anneal have been reported. Neverthless CDE which applied to SiC trench MOSFET has few precedents. We clarified the effect of CDE as a damage removal process. CDE has the effect of flattening the trench sidewall, and CDE makes the lifetime of gate oxides improve. CDE is an effective process for the reliability of SiC trench MOSFET.