Use of transient enhanced diffusion to tailor boron out-diffusion

We report experimental results demonstrating the use of transient enhanced diffusion (TED) caused by silicon implant for "tuning" boron out-diffusion. The effect was measured as a function of the silicon implant dose and anne al temperature, and a range of boron junction depth movement from almost no ne up to 81 nm was observed with increasing TED at 750 degrees C. The diffu sed profiles could be approximated by using a modified solubility limit mod el to describe the enhanced boron diffusion and clustering. However, by usi ng a more sophisticated continuum model based on atomistic calculations, ex cellent agreement with the measured profiles could be obtained. In addition , the fit to the measured data yields the fraction of boron present in BI2 precursor clusters after silicon implant as a function of the silicon impla nt dose. Two possible applications of the TED "tuning" are discussed, with device simulations which show that the effect is sufficiently large to tune the base width of a bipolar device from being depleted to that suitable fo r a high performance device.