Low Temperature Phosphorus Doping in Silicon Using Catalytically Generated Radicals

In this paper, we report the possibility of forming a phosphorus (P)-doped layer on silicon (Si) at low temperatures. Using the radicals catalytically generated from phosphine (PH₃), a thin n-type layer is formed on a crystalline Si (c-Si) wafer at 150 °C. The secondary ion mass spectrometry (SIMS) profile of doped P atoms indicates that P atoms exist in the vicinity of the c-Si surface, and the depth at which P atom concentration decreases to 1/10 of the surface concentration is less than 12 nm for 300 s of radical treatment. The sheet carrier density on radical-treated c-Si wafers measured using the Hall effect shows that P atoms act as donors without annealing. The sheet carrier concentration of the P-doped layer is increased by adding hydrogen (H₂) to the PH₃ source gas. The effect of adding H₂ to PH₃ suggests that the surface reaction of atomic H plays an important role in the doping process.