Nitrogen in silicon is of interest from the perspective of photovoltaics and wafers for integrated circuits. In the former, Si3N4 inclusions cause mechanical problems during sawing, and electrical shunting issues. In the latter, nitrogen provides device manufacturers with flexibility in controlling oxygen precipitation, which is necessary for effective internal gettering. Nitrogen also reduces the formation of voids and increases mechanical strength.
The fundamental properties of nitrogen in silicon are not well established. Experimental evidence for the species responsible for nitrogen diffusion in different temperature ranges and their diffusivity is lacking. Nitrogen's low concentration (~ 5 x 1015cm-3 or lower) means that it is difficult to use conventional techniques, such as secondary ion mass spectrometry (SIMS), to study its properties. With colleagues in Oxford (particularly Peter Wilshaw, Robert Falster and Charles Alpass), a novel dislocation locking technique was used to investigate the transport of nitrogen impurities in silicon. The results were interpretted in terms of the nitrogen species responsible for diffusion, its diffusivity and its interaction with dislocations.
- Nitrogen diffusion and interaction with dislocations in single-crystal silicon, C.R. Alpass, J.D. Murphy, R.J. Falster, P.R. Wilshaw, Journal of Applied Physics, 105 013519 (2009)
Measurements of dislocation locking by near-surface ion-implanted nitrogen in Czochralski silicon, C.R. Alpass, A. Jain, J.D. Murphy, P.R. Wilshaw, Journal of the Electrochemical Society, 156 H669 (2009)