Posted by Roger Brennan (66.122.81.186) on January 12, 2006 at 10:28:51:
In Reply to: Ask for resistivity posted by ZMO on January 05, 2006 at 04:11:25:
: I want to know relation between increase resistivity (delta rho) and defect concentration(at. % or cm^3). Eg. 1 micro.Ohm.cm=? defect concentration (at% or cm^3).
We are unaware of any hard data relating defects to resistivity. Having said that, we can imagine a few cases:
1) Defects that impair the crystal quality will tend to lower the carrier mobility and, as a consequence, increase the resistivity. Case in point, an unannealed doping implant of 1E15 /cm3 or greater will definitely increase the measured resistivity in the region of the implant. (By “doping implant”, we mean the usual species like boron, phosphorus etc.) Some 20 years ago, Prometrix was suggesting an empirical method for monitoring the dose and uniformity of low dose implants exploiting the damage of the implant. The procedure went something like this: a) Implant a blank wafer with a counter-doping layer. b) Fully anneal the wafer and do a four-point probe resistivity map on it. c) Implant a lighter does to the wafer. Do not anneal. Four-point probe the wafer and note the increase in sheet resistance. d) Develop a calibration curve for your particular circumstances. We do not know if this procedure is being used today.
2) We would expect emitter/base shorts and base/collector shorts (while deadly to the impacted devices) not to have sufficient density to impact the measured resistance.
3) If excessive doping (say something greater than 1E20 cm3) is used, it is possible to lower the carrier mobility faster than one is increasing the carrier concentration --thereby increasing the resistivity.