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 3 ? 1019 atoms/m3. The drive-in diffusion treatment is to be carried out at 1050째C for a period of 4.0 h, which gives a junction depth xj of 3.0 ?m. Compute the predeposition diffusion time at 950째C if the surface concentration is maintained at a constant level of 2 ? 1025 atoms/m3. For the diffusion of Al in Si, values of Qd and D0 are 3.41eV and 1.38 ? 10-4 m2/s, respectively.`