Boron doped diamond deposited by microwave plasma-assisted CVD at low and high pressures

Boron doped diamond is deposited over a range of pressures and chemistries including pressures from 35–120 Torr and gas chemistries including hydrogen–methane–diborane and argon–methane–hydrogen–diborane mixtures. The diamond deposition system is a 2.45 GHz microwave resonant cavity system. Diborane (B2H6) gas chemistry has been utilized with flow rates of 2.5–100 ppm. At low pressures of 35 Torr polycrystalline films are deposited using a feed gas mixture of hydrogen and 0.5% methane. At moderate pressures of 95 Torr, diamond films are grown using 60% Ar, 39% H2 and 1% CH4. For the high pressure experiments of 120 Torr, polycrystalline films are deposited using 98% H2 and 2% CH4. The deposition rate ranges from 0.3 to 1.6 μm/h. This investigation describes the relationship of the diborane flow rate and pressure versus the resulting film morphology, electrical properties, and morphology of the deposited films. The deposition of boron-doped polycrystalline diamond is done on 5 cm diameter silicon and silicon dioxide coated substrates. The resistivity spatial variation across the wafer was ± 5% indicating a good uniformity.