COBALT DEPOSITION IN POROUS SILICON BY CHEMICAL-VAPOR INFILTRATION AND DEPOSITION - THE EFFECTS OF PRECURSOR INSTABILITY

Cobalt has been deposited on and in porous silicon by chemical vapour infiltration and deposition using deuterated cobalt carbonyl hydride, DCo(CO)(4). This precursor is unstable, and below about 22 degrees C d ecomposes with an Initial half-life of 10 min, probably forming DCo3(C O)(9). After a time which depends on the precursor concentration, the precursor decomposes more rapidly. This reaction increases the concent ration of cobalt and the ratio of cobalt to hydrogen within the pores, At temperatures above about 22 degrees C, a similar but smaller incre ase occurs in the concentration of cobalt, and Co-2(CO)(8) is thought then to be the main decomposition product. Thermolysis preserves the i ncreased levels of metal within the pores; it is inferred that each co balt atom becomes linked to one silicon atom at the pore wall.