Diffusion profiles of Al were produced under rapid thermal annealing conditions. The effect of P upon the diffusion behavior of Al was investigated by the pre-deposition of P into Al-diffused wafers, and vice versa. The dopant profiles were determined by means of secondary-ion mass spectroscopy, electrochemical, capacitance-voltage and spreading resistance methods. The profiles after Al pre-deposition at 1293K exhibited Al surface concentrations which ranged up to the solid solubility limit of about 2 x 1025/m3. It was shown that P had a marked effect upon the drive-in behavior of Al; leading to accelerated Al diffusion ahead of the P profile (due to an enhanced Al diffusion which was caused by a supersaturation of self-interstitials) and to the up-hill migration of Al in the high-concentration regime. This was explained in terms of field-assisted diffusion. A strong retardation of Al diffusion, combined with concentrations which were well above the solid-solubility limit, was observed during Al pre-deposition into P-diffused wafers.
D.Nagel, C.Frohne, R.Sittig: Applied Physics A, 1995, 60, 61-5