Activation behavior of BF2+ implants in RTP annealed silicon

The sheet resistance (R
_s
) initially decreases with increasing BF
₂
⁺
dose for implants exceeding the amorphization dose. This trend reverses after the implanted dose reaches a certain limit. Further dose increase results in a higher R
_s
and a deeper junction, without offering additional benefits. Fluorine gettered at implant-induced defect sites is responsible for this undesired behavior. Experimental results show that gettered fluorine and boron-fluorine bonds, formed at heavily damaged crystal sites, reduce boron activation.