Cat-doping: Novel method for phosphorus and boron shallow doping in crystalline silicon at 80℃

摘要

Phosphorus (P) or boron (B) atoms can be doped at temperatures as low as 80 to 350℃, when crystalline silicon (c-Si) is exposed only for a few minutes to species generated by catalytic cracking reaction of phosphine (PH_3) or diborane (B_2H_6) with heated tungsten (W) catalyzer. This paper is to investigate systematically this novel doping method, "Cat-doping", in detail. The electrical properties of P or B doped layers are studied by the Van der Pauw method based on the Hall effects measurement. The profiles of P or B atoms in c-Si are observed by secondary ion mass spec-trometry mainly from back side of samples to eliminate knock-on effects. It is confirmed that the surface of p-type c-Si is converted to n-type by P Cat-doping at 80℃, and similarly, that of n-type c-Si is to p-type by B Cat-doping. The doping depth is as shallow as 5 nm or less and the electrically activated doping concentration is 10~(18) to 10~(19)cm~(-3) for both P and B doping. It is also found that the surface potential of c-Si is controlled by the shallow Cat-doping and that the surface recombination velocity of minority carriers in c-Si can be enormously lowered by this potential control.