Angular dependences of Si<inf>3</inf>N<inf>4</inf> etch rates and SiO<inf>2</inf>-to-Si<inf>3</inf>N<inf>4</inf> etch selectivity in C<inf>4</inf>F<inf>6</inf>/Ar/O<inf>2</inf>/CH<inf>2</inf>F<inf>2</inf> plasmas

Abstract

Summary form only given, as follows. Si 3 N 4 films are usually used as a protecting layer of a poly silicon gate during the etching of a contact hole. An increase in the etch rates of Si 3 N 4 at its curved surface lowers the etch selectivity of SiO 2 with respect to Si 3 N 4 [1, 2], resulting in device failure. Therefore, it is important to control the angular dependence of Si 3 N 4 etch rates and SiO 2 -to-Si 3 N 4 etch selectivity. In this work, the angular dependences of the Si 3 N 4 etch rate and SiO 2 -to-Si 3 N 4 etch selectivity in a C 4 F 6 /Ar/O 2 /CH 2 F 2 plasma were investigated using a speciallydesigned Faraday cage system. The Faraday cage allowed one to control the ion-incident angles. Etching was conducted by varying the ratio of CH 2 F 2 flow rate to study a role of steadystate fluorocarbon films formed on the surface of the Si 3 N 4 substrate during etching.