Langmuir-Type Mechanism for In-Situ Doping in CVD Si and Si1−xGex Epitaxial Growth

In-situ doping process of B and P in CVD Si and Si 1−x Ge x (100) epitaxial growth is investigated using SiH 4 –GeH 4 –dopant gas (B 2 H 6 or PH 3 )–H 2 gas mixture. For lower dopant gas partial pressure, the in situ doping is explained quantitatively by the Langmuir-type adsorption and reaction at Si–Si, Si–Ge or Ge–Ge pair sites on the (100) surface. For higher B 2 H 6 gas partial pressure ( P B2H6 ), it is proposed that SiH 4 , GeH 4 and B 2 H 6 molecules are adsorbed and react partially at the B-occupied sites where B 2 H 6 molecules have been adsorbed on the (100) surface. For higher PH 3 gas partial pressure ( P PH3 ), it is proposed that the in situ doping and Ge incorporation are enhanced by the self-limited adsorption of PH 3 molecules and the decomposition of GeH 4 at the P-occupied sites where PH 3 molecules have been adsorbed on the (100) surface, respectively, and that the decrease of P concentration with increasing P PH3 in high P PH3 region is caused by lower segregation coefficients of P at Si–Ge and Ge–Ge pair sites than that at Si–Si pair sites according to the Henry’s law. Fairly good agreement is obtained between all the experimental data and the modified Langmuir-type mechanism for in situ doping.