Fused-Salt Electrodeposition of Thin-Layer Silicon

Electrodeposition has been employed to produce crystalline silicon layers 5-50 ..mu..m thick on heavily doped p-type (111) Czochralski Si and polished silver. Growth was also demonstrated for the first time on metallurgical-grade Si. A 50/50 mixture of KF and LiF was used as the ; solvent and K2SiF6 was the solute. The chemicals were used as received; and were only~99% pure. Nonetheless, filmswere obtained with relatively low impurity levels, demonstrating the self-purification effects of electrodeposition. Films were grown at temperatures ranging from 750deg to 850 deg C, and the best film quality and deposition rates were obtained at 850 deg C. The film quality was also improved when a dissolving Si anode was used to replenish the Si concentration in the solution. Deposition ratesonto (111) Si were higher than those previously reported and were achieved with the use of very low resistivity Si electrodes. The films in this report were deposited at current densities between 10 and 150 mA/cm2 and as-grown layers were n-type.