Effect of Oxygen on Growth and Properties of Diamond Thin Film Deposited at Low Surface Temperatures

Polycrystalline diamond thin films are grown on a p-type Si (100) single crystal substrate at a low surface deposition temperature of 455 °C using a microwave plasma enhanced chemical vapor deposition process in an Ar-rich Ar/H2/CH4 plasma containing different oxygen levels from 0% to 0.75%. The surface deposition temperatures are measured and monitored by an IR thermometer capable of working in a plasma environment without any interference from the plasma emissions. The lower surface deposition temperature at high microwave power of 1300 W and higher gas pressure of 95 torr is achieved by active cooling of the substrate from the backside using a specially designed cooling stage. An enhanced growth rate from 0.19 to 0.63 μm/h is observed with varying oxygen from 0% to 0.75% in the plasma. Diamond grain size also increased from 0.69 μm for the sample with no oxygen to 1.74 μm for the sample with 0.75% oxygen. The diamond films are characterized using x-ray diffraction, environmental scanning electron microscopy field emission gun, Raman spectroscopy, and x-ray photoelectron spectroscopy. The enhanced growth rate is correlated with the enhanced atomic hydrogen to C2 ratio with increasing oxygen concentration in the plasma, which is measured by an in situ optical emission spectroscopy