Low Pressure Chemical Vapor Deposition of Semiconducting Boron Carbide Thin Films on Silicon

Boron carbide thin films were grown on the (100) plane of n-type silicon in a low pressure chemical vapor deposition (CVD) system from the thermal decomposition of boron trichloride and methane reactant gases with hydrogen as a carrier gas. Boron trichloride to methane molar ratio was 5, while the boron trichloride to hydrogen molar ratio was 3.5. Thin film deposition was carried out at 900 degrees Celsius at 25 Torr. The thin films were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy Dispersive X-Ray Spectroscopy (EDS), Laser Induced Breakdown Spectroscopy (LIBS), and current-voltage characteristics. The crystallography of the boron carbide films were determined to be largely amorphous with some polycrystalline regions. One sample was analyzed via LIBS to have a boron to carbon ratio of approximately 2. The current-voltage characteristics of another sample were Ohmic in behavior with a resistance of 300 kiliOhms. These Ohmic characteristics were hypothesized to be caused by boron carbide deposition on both sides of the silicon wafer, which created a p-n-p heterostructure. The orientation of the silicon substrate during growth caused boron carbide deposition to occur on both sides of the wafers.