Scaling the microwave plasma-assisted chemical vapor diamond deposition process to 150–200 mm substrates

The scale up of two microwave plasma assisted chemical vapor deposition processes from 75 mm to 200 mm substrates is investigated. A thermally floating 2.45 GHz reactor is scaled up by increasing its physical size by a factor of 2.7 and exciting the reactor with 915 MHz microwave energy. Two processes are investigated, 1) the deposition of ultananocrystalline diamond films (UNCD) and 2) the deposition of polycrystalline diamond films (PCD). Gas chemistries of argon/methane/hydrogen were used for UNCD deposition and hydrogen/methane was used for PCD deposition. Experimental pressures range from 40–110 Torr while microwave power input ranged from 1.9–7 kW resulting in steady state substrate temperatures from 630–950 °C. Uniform deposition was demonstrated over 150–200 mm substrates, i.e. thickness variations of 4% over 150 mm and 6% over 200 mm were achieved with deposition rates ranging from 30–460 nm/h. Low temperature deposition at 633 °C was achieved and thereby demonstrated the potential of integrating the process with temperature sensitive materials. A comparison of the power densities between the two reactors indicates that the large reactor operates at five to nine times lower discharge power densities than smaller reactors suggesting improved deposition efficiencies.