MODELING OF CVD OF SILICON DIOXIDE USING TEOS AND OZONE IN A SINGLE-WAFER REACTOR

A new mathematical model has been developed to investigate the chemical vapor deposition of SiO2 films using tetraethoxysilane (TEOS) and ozone in a cold-wall vertical single-wafer reactor which simulates experiments we have done in the commercial Applied Materials 5000. Mixed convection, thermal diffusion, radiant heat transfer to and from the susceptor, conjugated solid-phase conduction and gas-phase convection, and realistic gas-phase and surface reaction kinetics are included in the model. The partial differential equations in three-dimensional axisymmetric form are solved numerically using a control-volume-based finite difference method. The predictions from the model compare favorably with our experimental data at 30 to 90 Torr, and the data of others at 760 Torr. Film growth rate, uniformity, density (as determined by etch rate), and temperature distribution in the wafer were studied over a wide range of operating conditions including temperature, pressure, flow rate, O-2/TEOS ratio, showerhead-wafer spacing, and showerhead size. Optimization studies indicate that process pressures >200 Torr, high total flow rates, high O-3/TEOS ratios, and high temperatures may give the best combination of film growth rate, uniformity, and density for 5 in. wafers.