Etching of high-k dielectric HfO2 films in BCl3-containing plasmas enhanced with O2 addition

Etching characteristics of high dielectric constant HfO2 films have been studied in high-density BCl3-containing plasmas without rf biasing. Emphasis was placed oil plasma conditions and etch chemistries to achieve a high selectivity over Si and SiO2 and to enhance the etch rates. The HfO2 etch rate was similar to 5 nm/min at a pressure P-0 = 10 mTorr in a BCl3 plasma, giving a selectivity of > 10 over Si and SiO2. At lower P-0 <= 6 mTorr in BCl3 the deposition of boron-chlorine compounds BxCly was observed oil all sample surfaces of HfO2, Si, and SiO2 to inhibit etching. The addition of O-2, to BCl3 was found to suppress the deposition and significantly enhance the HFO2 etch rate, which was similar to 50 nin/min at P-0 = 5 mTorr in a BCl3/30%-O-2 plasma; at higher O-2 addition >= 40%, the heavy deposition of boron-oxygen compounds BxOy Occurred oil surfaces to inhibit etching. The mechanisms underlying the phenomena observed are discussed based on plasma and surface diagnostics.