The etching properties of Al2O3 thin films in N2/Cl2/BCl3 and Ar/Cl2/BCl3 gas chemistry

In this study, we used an inductively coupled plasma (ICP) source for etching Al2O3 thin films because of its high plasma density, low process pressure and easy control bias power. Al2O3 thin films were etched using Cl2/BCl3, N2/Cl2/BCl3, and Ar/Cl2/BCl3 plasma. The experiments were carried out measuring the etch rates and the selectivities of Al2O3 to SiO2 as a function of gas-mixing ratio, rf power, and chamber pressure. When Cl2 50% was added to Cl2/BCl3 plasma, the etch rate of the Al2O3 films was 118 nm/min. We also investigated the effect of gas addition. In case of N2 addition, the etch rate of the Al2O3 films decreased while N2 was added into Cl2/BCl3 plasma. However, the etch rate increased slightly as Ar added into Cl2/BCl3 plasma, and then further increase of Ar decreased the etch rate. The maximum etch rate was 130 nm/min at Ar 20% in Cl2/BCl3 plasma, and the highest etch selectivity was 0.81 in N2 20% in Cl2/BCl3 plasma. And, we obtained the results that the etch rate increases as rf power increases and chamber pressure decreases. The characteristics of the plasmas were estimated using optical emission spectroscopy (OES). The change of Cl radical density was measured by OES according as the plasma parameters change. As the rf power increases and chamber pressure decreases, we measured that the intensity of Cl radical increases.