posted by Andrea on .
A p-n junction is to be created by diffusing boron (B) into an n-type silicon wafer with an existing carrier concentration of 1015/cm3. The location of the junction will be 6μm below the surface of the wafer. The surface concentration of boron will be maintained at 1020/cm3 while the diffusion process is occurring. Assuming the diffusivity of B in Si is 3×10−11 cm2/sec at the process temperature, how many seconds will it take? (Hint: The junction is formed at a location where the boron concentration equals the donor concentration.) Assume no change in donor concentration occurs during the diffusion (ie: no outgassing).