(a) A predeposition process is carried out for 15 minutes on an n-type silicon wafer with a bulk doping concentration of 1017 atoms /cm3 at 950C using diborane gas. Determine the pn junction depth given that the surface solubility of boron at 950C is 3.81020 atoms /cm3, the intrinsic diffusivity (Do) is 0.76 cm2/s, and the Arrhenius activation energy (Ea) is 3.46eV. (b) A drive-in process is subsequently performed on this sample after the deposition process. In order to produce a p-n junction 1.28m below the wafer surface, estimate the required Dt, the product of the diffusion coefficient and time. Based on your result, determine the time required if the drive-in temperature is 1250C