Thermal Oxidation of Phosphorus‐Doped Polycrystalline Silicon in Wet Oxygen

Oxidation characteristics of heavily phosphorus‐doped polycrystalline silicon films and single crystal silicon substrates are investigated in a wet oxygen ambient over the temperature range 700°–850°C based on the linear‐parabolic rate law. Polysilicon, undoped or uniformly doped with phosphorus of by diffusion drive‐in or ion implantation, is studied in comparison with lightly doped or heavily doped (100), (110), and (111) faces of silicon substrates. Phosphorus concentrations greater than cause a significant increase in oxidation rates. Above , however, oxidation rates tend to become saturated. A very rapid oxidation in the initial stage of oxidation is observed. This initial oxide does not fit the linear‐parabolic rate law. The resistivity of the phosphorus‐doped polysilicon is minimized at for a phosphorus concentration of around . The initial resistivity remains almost constant after reduction of the polysilicon thickness by oxidation. In addition, no evidence of enhanced oxidation along the grain boundaries is observed.