The etching properties of Al 2O 3 thin films in N 2/Cl 2/BCl 3 and Ar/Cl 2/BCl 3 gas chemistry

Abstract

In this study, we used an inductively coupled plasma (ICP) source for etching Al 2O 3 thin films because of its high plasma density, low process pressure and easy control bias power. Al 2O 3 thin films were etched using Cl 2/BCl 3, N 2/Cl 2/BCl 3, and Ar/Cl 2/BCl 3 plasma. The experiments were carried out measuring the etch rates and the selectivities of Al 2O 3 to SiO 2 as a function of gas-mixing ratio, rf power, and chamber pressure. When Cl 2 50% was added to Cl 2/BCl 3 plasma, the etch rate of the Al 2O 3 films was 118 nm/min. We also investigated the effect of gas addition. In case of N 2 addition, the etch rate of the Al 2O 3 films decreased while N 2 was added into Cl 2/BCl 3 plasma. However, the etch rate increased slightly as Ar added into Cl 2/BCl 3 plasma, and then further increase of Ar decreased the etch rate. The maximum etch rate was 130 nm/min at Ar 20% in Cl 2/BCl 3 plasma, and the highest etch selectivity was 0.81 in N 2 20% in Cl 2/BCl 3 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.