Hydrogen in undoped and heavily in situ phosphorus doped silicon films deposited using disilane and phosphine

Abstract

The kinetics of hydrogen incorporation in amorphous silicon films were studied. The layers were deposited by low pressure chemical vapor deposition using disilane (Si2H6) and phosphine (PH3). The hydrogen concentration, determined by nuclear resonant reaction analysis, increased with decreasing substrate temperature. In accordance with the reported reduction of hydrogen adsorption in the presence of surface phosphorus, the addition of phosphine to disilane was observed to reduce the hydrogen film concentration. The results are discussed in terms of hydrogen adsorption/ desorption kinetics. The activation energy for hydrogen desorption in an undoped film was 1.8±0.2 eV, in good agreement with previously reported values obtained by surface analysis and desorption studies. When phosphine was added, an increase in activation energy was observed.