Correlated diffusion of silicon and boron in thermally grown SiO2

Abstract

Si self-diffusion and B diffusion in SiO2 were simultaneously investigated in thermally grown Si28O2 co-implanted with Si30 and B. The B diffusivity increases with decreasing distance between the implanted B and Si∕SiO2 interface, in the same way as Si self-diffusivity. This result together with a numerical simulation shows that SiO molecules, which are generated at the Si∕SiO2 interface and diffusing into SiO2, enhance not only Si self-diffusion, but also B diffusion. In addition, we found that the diffusivities of both Si and B increase with higher B concentration in SiO2. The experimental results can be quantitatively explained by a numerical simulation assuming that the diffusivity of SiO, which enhances the diffusivities of Si and B, increases with higher B concentration.

Self-diffusion and impurity diffusion in silicon dioxide

“…Figure 3 shows the experimental B profiles in lowdose samples with various thicknesses after annealing at 1250°C for 6 h. In the same way as Si self-diffusion, the B diffusion shows a clear dependence on the thickness of the 28 SiO 2 layer; the shorter the distance from the Si-SiO 2 interface, the higher the B diffusivity in SiO 2 . [15,16] This tendency was also observed for the high-dose samples and other temperatures used in this study. The distance dependence of B diffusivity indicates that the SiO molecules, which are generated at the Si-SiO 2 interface and diffusing into SiO 2 , enhance not only Si self-diffusion but also B diffusion.…”

“…The profile of 30 Si in the high-dose samples shows larger diffusion than that without B. [15,16] On the other hand, the 30 Si profile of the low-dose samples (not shown in Fig. 4) showed no significant difference from that without B.…”

Simulation of correlated diffusion of Si and B in thermally grown SiO2

“…Recently, we have simultaneously observed Si selfdiffusion and B diffusion in 28 SiO 2 samples coimplanted with 30 Si and B. 11 Both Si self-diffusivity and B diffusivity increase with decreasing distance from the Si/ SiO 2 interface, which indicates that the SiO molecules from the interface govern not only Si self-diffusion but also B diffusion. In addition, both Si self-diffusivity and B diffusivity increase as B concentration increases, indicating faster SiO diffusion with higher B concentration in SiO 2 .…”

Atomic Processes at and near Silicon/Silicon Dioxide Interfaces

“…Further we have obtained a surprising result that B diffusivities has time dependent. Further, we show that the macroscopic diffusion equation analysis taking into account the existence of SiO generated at the Si/SiO 2 interface interactions have successfully reproduce the experiments [14,15].…”

“…Taking into account the effect of SiO, we can construct coupled diffusion equations that include normal thermal B diffusion and SiO assisted B diffusions [14,15]. As shown in Fig.…”