The effect of fluorine from BF2 source/drain extension implants on performance of PMOS transistors with thin gate oxides

Boron penetration from the gate electrode into the Si substrate presents a significant problem in advanced PMOS device fabrication, Boron penetration, which causes a degradation of many transistor parameters, is further enhan ced when BF2 is used to dope the gate electrode, It is known that pile-up o f fluorine from the BF2 gate implant at the polysilicon/gate oxide interfac e is responsible for the enhanced boron penetration. However, no reports ha ve been made that address enhanced boron penetration due to fIuorine from t he source/drain (S/D) implants, It is shown here that fluorine from the S/D extension implants is also a significant problem, degrading transistor per formance for-gate oxide thickness less than 27 Angstrom and gate lengths le ss than 0.5 mum.