ENHANCED DIFFUSION BY ELECTRICAL DEACTIVATION OF ARSENIC AND ITS IMPLICATIONS FOR BIPOLAR-DEVICES

In this paper, we present experiments designed to show enhanced diffus ion of dopants due to the electrical deactivation of implanted arsenic or arsenic in-diffused from polysilicon, Results show a clear enhance ment of diffusion in a nearby boron layer as well as an enhancement fo r the arsenic itself at an annealing temperature of 750 degrees C. At 500 degrees C, more typical of backend processing, no enhancement is d etected 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 e nhanced diffusion. Secondary ion mass spectrometry (SIR?IS) analysis a nd simulation confirmed that enhanced diffusion of both arsenic and bo ron 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.