Nitrogen diffusion and interaction with dislocations in single-crystal silicon

Abstract

The results of dislocation unlocking experiments are reported. The stress required to unpin a dislocation from nitrogen impurities in nitrogen-doped float-zone silicon (NFZ-Si) and from oxygen impurities in Czochralski silicon (Cz-Si) is measured, as a function of the unlocking duration. It is found that unlocking stress drops with increasing unlocking time in all materials tested. Analysis of these results indicates that dislocation locking by nitrogen in NFZ-Si is by an atomic species, with a similar locking strength per atom to that previously deduced for oxygen atoms in Cz-Si. Other experiments measure dislocation unlocking stress at 550 °C in NFZ-Si annealed at 500–1050 °C. The results allow an effective diffusivity of nitrogen in silicon at 500–750 °C to be inferred, with an activation energy of 3.24 eV and a diffusivity prefactor of approximately 200 000 cm2 s−1. This effective diffusivity is consistent with previous measurements made at higher temperatures using secondary ion mass spectrometry. When the results are analyzed in terms of a monomer-dimer dissociative mechanism, a nitrogen monomer diffusivity with an activation energy in the range of 1.1–1.4 eV is inferred. The data also show that the saturation dislocation unlocking stress measured at 550 °C in NFZ-Si is dependent on the anneal temperature, peaking at 600–700 °C and falling toward zero at 1000 °C.

Kinetics of Bulk Lifetime Degradation in Float‐Zone Silicon: Fast Activation and Annihilation of Grown‐In Defects and the Role of Hydrogen versus Light

“…It is assumed that N is a constituent of these defects as its absence (N‐lean FZ–Si) suppresses thermally induced τ bulk ‐degradation. [ 11 ] For the transport of N in Si in the temperature window used here, activation energies of 2.8 [ 32 ] to 3.24 ± 0.25 eV [ 33 ] were reported. These values show a striking coincidence with the activation energy of the defect annihilation of 3.1 ± 1.0 eV (Arrhenius plot in Figure 4a), although that data analysis should be treated with caution as explained earlier.…”

Nitrogen substitutional defects in silicon. A quantum mechanical investigation of the structural, electronic and vibrational properties

“…[1][2][3] It was observed that nitrogen increases precipitation of oxygen by increasing the number of nucleation sites and retarding silicon self-interstitial migration. 4 N impurities can pin dislocations 5 and form electrically active defects such as the substitutional deep donor. 6 A photoluminescence zero-phonon at 1.223 eV, also known as "A,B,C", has been correlated with nitrogen content in doped silicon.…”

Elimination of strength degrading effects caused by surface microdefect: A prevention achieved by silicon nanotexturing to avoid catastrophic brittle fracture

“…This requirement has led numerous researchers to investigate various methodologies, such as crack deflection through implanting external elements into the bulk 17 or reducing defect size 15 , for strengthening silicon wafers. Dopant diffusion by oxygen 18 , nitrogen 19 20 21 , and germanium 22 has been shown to generate a greater pinning effect on dislocations, which delocalizes the stress concentration at defects and obstructs crack propagation. In a doped material, some of the original Si–Si bonds are replaced with higher-energy bonds that eventually strengthen the material 23 .…”