The effect of DC bias on the synthesis of crystalline carbon nitrides on silicon by microwave plasma enhanced chemical vapor deposition (CVD)

Crystalline carbon nitride compounds have been successfully deposited on a silicon wafer over an intermediate layer of Si3N4 formed by chemical conversion of the silicon using a microwave plasma enhanced chemical vapor deposition (MPECVD) process. Both nitrogen and methane were used as the primary precursors for the initial nitriding of silicon and the subsequent formation of crystalline carbon nitride. In the later step, a negative de bias of -150V was applied to the nitrided silicon substrate. The crystalline carbon nitride compounds were characterized by X-ray diffractometer and X-ray photoelectron spectroscopy and compared to alpha- and beta-Si3N4. It should be noted that crystalline carbon nitride has never been observed to form simply by reaction of solid carbon with nitrogen plasma Application of a negative de bias to the substrate has proved to be a prerequisite for the formation of carbon nitride in this study.