Distribution of Phosphorus Atoms and Carrier Concentrations in Single-Crystal Silicon Doped by Catalytically Generated Phosphorous Radicals

A phosphorus (P)-doped ultrathin n + layer is formed on crystalline silicon (c-Si) using radicals generated by the catalytic cracking reaction of phosphine (PH 3 ) gas with a heated catalyzer. The carrier concentration and the depth distributions of P atoms are investigated by Hall effect and secondary ion mass spectrometry (SIMS), respectively. The surface of the p-type c-Si substrate is converted to n-type c-Si by this doping even at a substrate temperature of 20 °C, when the tungsten (W) catalyzer is heated at 1300 °C. SIMS measurements demonstrate that P atoms exist on the c-Si surface. However, the distributions of P atoms obtained by SIMS do not change, even for the increase in substrate temperature from 80 to 350 °C or the increase in radical exposure time from 60 to 3600 s. Although the sheet carrier concentration increased with the substrate temperature, the sheet carrier concentration increased only slightly with the radical exposure time. It is revealed that the doping mechanism does not appear to be the same as that of the thermal diffusion, but that the reaction of the P-related species with Si atoms on the surface plays a key role for this radical doping.