Effect of dopant type on immersion plating into porous silicon layer

Metal deposition into a porous silicon (PS) layer prepared from n-type sili con by immersion plating was studied. The results were compared with those of p-type PS. Quantitative differences between p- and n-type PS were observ ed in the behaviors of the amount of metal deposition and Fourier transform infrared (FTIR) spectra. Copper deposition was saturated by 2 min immersio n in 1 M CuSO4, for p-type PS, whereas for n-type PS, the saturation was no t attained by 20 min immersion in 1 M CuSO4,. The intensities of absorption s due to SiHx, decreased much faster for p-type PS than for n-type PS in FT IR spectra. PS prepared from p-type silicon is expected to have higher reac tivity with aqueous solutions containing metal ion. This is probably due to the smaller crystallite size. However, PS samples formed on p- and n-type silicons showed the same behaviors qualitatively. Ag and Cu were found to d eposit on PS, but Ni was found not to deposit. Adsorption of chloride and b romide ions on the PS surface inhibited the copper deposition process. Meta l deposits chemically, simultaneously with the oxidation of silicon to SiO2 ,. (C) 1999 Elsevier Science B.V. All rights reserved.