Effective SiNₓ :H Capping Layers on 1-nm Al₂O₃ for p⁺ Surface Passivation

Passivation of p+regions is typically achieved by Al2O3layers with thicknesses in excess of 10 nm. Given the expense of commonly used Al2O3precursors and, in some cases, the deposition time, it is desirable to minimize the layer thickness. We achieve recombination factor J0p+in the order of 22 fA/cm2with 1 nm of Al2O3capped with ~70-nm amorphous silicon nitride (SiNx :H) films on 85 Ω/□ boron diffusions. The passivation performance of ultrathin-Al2O3/SiNx:H stacks depends critically on both the alumina thickness and the SiNx:H composition. It was found that to achieve low J0p+with 1-nm-Al2O3/SiNx:H stacks, the SiNx :H hydrogen concentration ([Si-H]+[N-H]) was required to be low: less than 8×1021 cm-3. Fourier transform infrared measurements indicated that the initial hydrogen content is more appropriate to evaluate the hydrogen release process of SiNx :H layers than Si-N bond density, at least in this study. Both the Al2O3-Si interface and charge density of 1-nm-Al2O3/SiNx:H stacks can be impacted by the SiNx:H capping layer. The outstanding passivation quality of 1-nm-Al2O3/SiNx:H stacks is due to a combination of both chemical and electrostatic passivation.