Evaluation of etching property in C3HXF(6−X) plasma

The etching properties of C
₃
F
₆
, C
₃
HF
₅
, C
₃
H
₂
F
₄
, and C
₃
H
₃
F
₃
were evaluated to investigate the effects of replacement of fluorine atoms to hydrogen atoms in the unsaturated fluorocarbon. Etching rates of SiO
₂
were decreased, and deposition rates of CFn films on p-Si wafer were increased with increasing the hydrogen atoms in the molecule. XPS spectra show that the contribution of strong C-C bond in the CFn film was also increased with increasing the hydrogen atoms in the molecule. Consequently, the highest selectivity for SiO
₂
/PR was obtained in C
₃
H
₂
F
₄
plasma, while the highest etching rate of SiO
₂
was obtained in C
₃
F
₆
plasma. The SiO
₂
etching was performed using patterned holes of 40 nm diameters in C
₃
H
₂
F
₄
plasma to evaluate the feasibility of C
₃
H
₂
F
₄
for the contact hole etching gas. The cross section SEM image shows that the vertical shaped holes without bowing or tapering were obtained with C
₃
H
₂
F
₄
plasma. The fine etch property of C
₃
H
₂
F
₄
was obtained as a result of the appropriate balance between fluorine atoms and hydrogen atoms in the molecule.