Codeposition on diamond film surface during reactive ion etching in SF6 and O-2 plasmas

The surface of polycrystalline diamond films during reactive ion etching in electron cyclotron resonance SF6 and O-2 plasmas has been examined by scan ning electron microscopy, Raman spectroscopy, and x-ray photoelectron spect roscopy. A SF6 plasma required a high voltage in negative substrate biasing in order to achieve an equivalent etching rate to an O-2 plasma. This was ascribed to the codeposition effects and the low mean energy of ions upon i mpact in a SF6 plasma. The elemental composition of the amorphous layer for med at the etched film surface in the two plasmas was almost equivalent and mainly composed of carbon and oxygen, except a low concentration (less tha n or equal to 1%) of sulfur and fluorine in the case of a SF6 plasma. The s ignificant codeposition on diamond surface was the most likely the result o f plasma-wall interactions induced by the fragments from SF6, and highly re sponsible for suppressing the ratio of lateral to vertical etching rate lea ding to anisotropic etching in a SF6 plasma, in contrast with the little or no codeposition leading to isotropic etching in an O-2 plasma. The results give the substantial implications for the etching process in practical SF6 /O-2 plasmas utilized in device fabrication. (C) 2000 American Vacuum Socie ty. [S0734-2101(00)03706-4].