Low-temperature diffusion of implanted sodium in silicon

Abstract

We have studied the low-temperature diffusion of sodium atoms implanted (at primary ion energy E = 300 keV to total doses within Φ = 5 × 10¹⁴–3 × 10¹⁵ cm^–2) in single-crystalline silicon grown by the method of float-zone melting (fz-Si) with low oxygen concentration N _O and by the Czochralski method in the presence of magnetic field (mCz-n-Si and mCz-p-Si) with N _O ≈ 5 × 10¹⁷ cm^–3. The diffusion was studied at annealing temperatures within T _ann = 500–420°C for periods of time t _ann = 72–1000 h. It is established that the temperature dependence of the diffusion coefficient D(10³/T) of sodium in fz-Si in a broad range of T _ann = 900–420°C obeys the Arrhenius law with E _fz = 1.28 eV and D ₀ = 1.4 × 10^–2 cm²/s. The same parameters are valid for the implanted sodium diffusion in mCz-Si in the interval of T _ann = 900–700°C. However, at lower temperatures, the values of D in mCz-Si are lower than to those in fz-Si, which is related to the formation of more complicated Na–O _n (n > 1) complexes in the former case. Estimation of the diffusion activation energy of these complexes yields ΔE ≈ 2.3 eV.