NUCLEATION AND SELECTED-AREA DEPOSITION OF DIAMOND BY BIASED HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION

This paper describes a process for uniformly enhancing the nucleation density of diamond films on silicon (Si) substrates via de-biased hot filament chemical vapor deposition (HFCVD). The Si substrate was negatively biased and the tungsten (W) filaments were positively biased relative to the grounded stainless steel reactor wall. It was found that by directly applying such a negative bias to the Si substrate in a typical HFCVD process, the enhanced diamond nucleation occurred only along the edges of the Si wafer. This resulted in an extremely nonuniform nucleation pattern. Several modifications were introduced to the design of the substrate holder, including a metal wire-mesh inserted between the filaments and the substrate, in the aim of making the impinging ion flux more uniformly distributed across the substrate surface. With such improved growth system designs, uniform enhancement of diamond nucleation across the substrate surface was realized. In addition, the use of certain metallic wire mesh sizes during biasing also enabled patterned or selective diamond deposition.