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

The kinetics of hydrogen incorporation in amorphous silicon films were stud ied. The layers were deposited by low pressure chemical vapor deposition us ing disilane (Si2H6) and phosphine (PH3). The hydrogen concentration, deter mined by nuclear resonant reaction analysis, increased with decreasing subs trate temperature. In accordance with the reported reduction of hydrogen ad sorption in the presence of surface phosphorus, the addition of phosphine t o disilane was observed to reduce the hydrogen film concentration. The resu lts 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 surfac e analysis and desorption studies. When phosphine was added, an increase in activation energy was observed. (C) 1999 American Institute of Physics. [S 0021-8979(99)03516-1].