Boron diffusion layer formation using Ge cryogenic implantation with low-temperature microwave annealing

Abstract

It is shown that a low-sheet-resistance p-type diffusion layer with a small diffusion depth can be fabricated efficiently by cryogenic boron and germanium implantation combined with low-temperature (400 °C) microwave annealing. Compared with the conventional annealing at 1000 °C, a much smaller diffusion depth is obtained at the same sheet resistance. The low sheet resistance at 400 °C is due to microwave absorption in the surface amorphous layer, which is formed by cryogenic germanium implantation. However, the pn junction leakage was worse than that in conventional annealing, because crystal defects remain near the amorphous/crystal interface after microwave annealing. It is found that the pn junction leakage is improved greatly by cryogenic germanium implantation. These results show that a suitable combination of cryogenic implantation and microwave annealing is very promising for p-type diffusion layer technology.

Reduction in number of crystal defects in a p+Si diffusion layer by germanium and boron cryogenic implantation combined with sub-melt laser spike annealing

“…This result is not dependent on annealing conditions, and it is shown that LT implantation is extremely effective for the suppression of EOR defect generation. 15,16) Reduction in the number of crystal defects will contribute to the suppression of not only pn junction leakage current but also dark-current white defects in CMOS image sensors. On the other hand, the diffusion layer formed by LT implantation with LSA shows higher resistance than that formed by RT implantation.…”

“…On the other hand, in this study, F contaminants in LT implantation are not a problem in furnace annealing, RTA, and MWA. 15,16) From this, there is a possibility of improvement through process integration. For example, a future work is to perform additional lowtemperature annealing to maintain the amorphous state before LSA 42) and annealing in which F is separated without the diffusion of B after LSA.…”

“…Owing to the smoother surface, the Si=SiO 2 interface state density after surface oxidation can be reduced compared with that in the case of RT implantation. 16) In this work, we have examined the combination of cryogenic implantation and laser spike annealing (LSA) as a low-thermal-budget process. In p + Si diffusion layer formation, a low-thermal-budget annealing process is strongly required to suppress B diffusion.…”