Selected-area deposition of diamond films on SiN/Si surfaces with microwave plasma enhanced CVD

Selected-area deposition (SAD) of diamond films with selectivity greater than 200 was achieved on patterned SiN/Si surface, using microwave plasma CVD method. Among the important parameters that can modify the plasma characteristics, the total pressure and CH₄-to-H₂ ratio were observed to influence the selected-area deposition behaviors most significantly. The number density of diamonds grown on Si surface decreased rapidly as the total pressure reduced from 75 torr to 60 torr. The selectivity of SAD diamond films increased as the CH₄-to-H₂ ratio increased from 9:300 sccm to 15:300 sccm. These phenomena were accounted for by the decrease in proportion of ion species with CH₄-to-H₂ ratio such that the formation of sp³ bonds on Si surfaces is suppressed. Scanning electron microscopy (SEM) and Raman spectroscopy indicated that the quality of diamonds grown on SiN surface was optimized for the SAD films deposited under 2500 W microwave power with CH₄-to-H₂ = 15:300 sccm