Aluminum atoms are to be diffused into a silicon wafer using both predeposition and drive-in heat treatments; the background concentration of Al in this silicon material is known to be 2.01019 atoms /m3. The drive-in diffusion treatment is to be carried out at 1050C for a period of 4.0h, which gives a junction depth xj of 3.0m. Compute the predeposition diffusion time at 950C if the surface concentration is maintained at a constant level of 21025 atoms /m3. For the diffusion of Al in Si, values of Qd and D0 are 3.41 eV and 1.38104m2/s, respectively. min