Enhanced diffusion by electrical deactivation of arsenic and its implications for bipolar devices

In this paper, we present experiments designed to show enhanced diffusion of dopants due to the electrical deactivation of implanted arsenic or arsenic in-diffused from polysilicon. Results show a clear enhancement of diffusion in a nearby boron layer as well as an enhancement for the arsenic itself at an annealing temperature of 750°C. At 500°C, more typical of backend processing, no enhancement is detected in accordance with the very slow deactivation process at this temperature. Implications for bipolar devices were also investigated. Large differences in device characteristics were measured due to the enhanced diffusion. Secondary ion mass spectrometry (SIMS) analysis and simulation confirmed that enhanced diffusion of both arsenic and boron is the cause for the change in device characteristics. Evidence is also presented demonstrating that the order of the anneals is crucial, thereby rejecting the hypothesis of a full coupled diffusion effect as seen for phosphorus