Cyclic Deposition/Etching Process to Etch a Bowing-Free SiO2 Contact Hole

High aspect ratio SiO 2 contact holes were etched using a cyclic process, which consisted of alternating etching and deposition steps using C 4 F 6 /CH 2 F 2 /O 2 /Ar and C 4 F 6 /CH 2 F 2 /Ar plasmas, respectively, to minimize the sidewall bowing of the hole. A CF x -film deposition step was added to recover the eroded slope of the mask and to deposit an additional passivation film on the sidewall. The introduction of the deposition step also improved the etch selectivity of SiO 2 toward the amorphous carbon layer mask and the open ratio of the contact hole, which was defined as the ratio of the hole diameter at the bottom to that at the top of the hole. By regulating the durations of the deposition and etching steps in the cyclic process, the degree of bowing, which was 9 nm when using a continuous-etching process, was reduced to 1 nm during the etching of a 2.3 μm deep SiO 2 contact hole with a diameter of 118 nm.