Fluorine effect on boron diffusion: chemical or damage?

It is known that boron transient enhanced diffusion (TED) is influenced by the existence of fluorine. This paper further investigates this phenomenon by separating the damage effect of fluorine from the chemical effect of fluorine. To accomplish this goal, a ²⁰Ne ⁺ implant with equivalent energy and dose was selected to simulate the fluorine damage (F has an amu of 19). Three types of samples were investigated. First was a 5 keV BF₂ implant. The second sample created the same damage profile but the B and F implants were separated using a 1.94 keV 2e15 F⁺ followed by 1.2 keV 1e15 B⁺ implant. The third sample used a 2 keV 1.8e15 Ne⁺ implant to create the amorphous layer followed by a 1.2 keV 1e15 B⁺ implant. All three implant sets were then subjected to the same rapid thermal annealing conditions (RTA) between 950°C and 1050°C for 10 sec in a controlled 300 ppm O₂ in N₂ ambient. It was found that F⁺ plus B⁺ resulted in the least amount of B diffusion with ΔXj=20 Å at 950°C and 100 Å at 1050°C, BF₂⁺ and Ne⁺ plus B⁺ implants showed ΔXj>100 Å for all temperatures. Damage behavior was also studied by using transmission electron microscopy (TEM). The defect structure of F+B implant is similar to that of Ne+B implant and different from the BF₂ implant. Results indicate that the chemical effect of fluorine on boron diffusion dominates over the implant damage effect