In situ phosphorus doping during silicon epitaxy in an ultrahigh vacuum rapid thermal chemical vapor deposition reactor

Phosphorus incorporation during selective silicon epitaxy using the phosphi ne (PH3), disilane (Si2H6). and chlorine (Cl-2) chemistry in a cold-wall ul trahigh vacuum rapid thermal chemical vapor deposition reactor was investig ated, We have studied the dependence of silicon growth rate and phosphorus incorporation on phosphine partial pressure and temperature in the range of similar to 10(-9) to 10(-6) Torr, and 650 to 800 degrees C, respectively. Even at such low partial pressures. phosphorus concentration above 10(18) c m(-3) was obtained due to the high sticking coefficient of phosphine. Phosp horus incorporation was found to be a strong function of temperature. Two p ossible incorporation mechanisms have been discussed in detail: surface ele ctronic effects created by silicon becoming extrinsic at high phosphorus co ncentrations and high phosphorus surface coverage in the form of P-P dimers . A reduction in silicon growth rate was observed due to phosphine. Doping concentration was found to be uniform in the films at low temperatures (650 -750 degrees C) accompanied with by phosphorus peaks at interfaces for grow th temperatures above 800 degrees C. A significant chamber memory effect wa s observed in the process which prohibits intrinsic silicon deposition foll owing an in situ phosphorus-doped layer. (C) 1999 The Electrochemical Socie ty. S0013-4651(99)03-049-9. All rights reserved.