Nanocrystalline and microcrystalline diamond stacking structure as an insulating material deposited on large area

Abstract A stacking structure of nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) was proposed to use as an insulating layer for silicon on insulator (SOI) substrates with large wafer size, in order to improve both break down field and thermal conductivity. NCD with a thickness of about 200 nm was deposited by the surface wave microwave plasma chemical vapor deposition (CVD) on silicon (Si) substrate after seeding process and then MCD (6 µm in thickness) was deposited on the as‐grown NCD surface by hot filament CVD. It was confirmed, by scanning electron microscope observation, formation of the stacking structure of NCD and MCD. From measurements of current versus voltage characteristics, the break down field of the stacking structure was three times higher than that of MCD layer. Thermal conductivities of the self‐standing of stacking structure measured by thermo‐reflectance measurement were from 320 to 500 W mK⁻¹, which was almost the same as the thermal conductivities of the MCD layers.