PHOSPHORUS DIRECT DOPING FROM VAPOR-PHASE INTO SILICON FOR SHALLOW JUNCTIONS

Characteristics of shallow n-type layers formed by direct doping of ph osphorus from the vapor phase are presented. Shallow doped layers can be formed with depths less than 100 nm using PH3 as a source gas and h ydrogen as a carrier gas, It is found that the phosphorus concentratio n on the surface is constant with the doping time and is determined by the flow rate of PH3, not by the solid solubility. By varying the flo w rate of PH3, the surf ace phosphorus concentration is controlled in the range of 10(18) to 10(19) cm-3. These results show that impurities with low sticking coefficients to silicon and high vapor pressure, su ch as phosphorus, can be incorporated using this process, although the doping efficiency of phosphorus is low.