Fluorine-enhanced boron diffusion induced by fluorine postimplantation in silicon

Abstract

In this article, the postimplanted fluorine effect on boron transient-enhanced diffusion (TED) and dose loss during a 750°C annealing is shown. F19 implants at 2keV, after B11 implant at an energy of 1keV,3×1014∕cm2, have been investigated in the dose range between 1×1013∕cm2 and 6×1014∕cm2 without a preamorphizing implant. Below a F-implant dose of 1×1014∕cm2, the reduction or non-enhancement of boron-TED effect is observed. In the case of a F-implant dose of 6×1014∕cm2, the enhanced boron TED (∼2.6×) in crystalline Si and the increased dose loss(∼2×) than that of a normal boron TED is shown, and this anomalous diffusivity enhancement persists for 120min at 750°C. The B+F6×1014∕cm2 consecutive implant damage is smaller than that of the BF25keV implant. In the case of the B+F6×1014∕cm2, a high content of fluorine is retained around the end-of-range (EOR) damage region within 120min. These results indicate that the fluorine retained around the EOR region may affect the enhanced boron TED in crystalline Si at 750°C. Boron-diffusion model, which describes both the native interstitial fluorine and the boron-fluorine chemical effect, explains that the suppression of boron TED with a low F-implant dose is due to the reduction of the interstitial supersaturation.