Doped polycrystalline silicon films have often been used as a diffusion source in the formation of shallow junctions. Conventional furnace annealing of these films with high electrical activation usually results in junctions too deep for submicron devices. In this letter, we report on the results of rapid thermal annealing in the temperature range from 1000 to 1150 °C of arsenic ion‐implanted polycrystalline silicon, characterized by secondary ion mass spectroscopy, Rutherford backscattering and channeling, transmission electron microscopy, and four‐point probe measurements. We demonstrate that with rapid thermal annealing at 1150 °C for 5 s, we can achieve simultaneously a sheet resistance of 20 &OHgr;/&laplac; in the polycrystalline silicon and a diffusion profile of 50 nm into the single‐crystal silicon substrate.