Angular dependences of Si3N4 etch rates and SiO2-to-Si3N4 etch selectivity in C4F6/Ar/O2/CH2F2 plasmas

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.