Changes in Hydrogen Concentration and Defect State Density at the Poly-Si/SiOx/c-Si Interface Due to Firing

We determined the density of defect states of poly-Si/SiO_x/c-Si junctions featuring a wet chemical interfacial oxide from lifetime measurements using the MarcoPOLO model to calculate recombination and contact resistance in poly-Si/SiO_x/c-Si-junctions. In samples that did not receive any hydrogen treatment, the D_it,cSi is about 2 × 10¹² cm⁻² eV⁻¹ before firing and rises to 3–7 × 10¹² cm⁻² eV⁻¹ during firing at measured peak temperatures between 620 °C and 863 °C. To address the question of why AlO_x/SiN_y stacks in contrast to pure SiN_y layers for hydrogenation during firing provides better passivation quality, we have measured the hydrogen concentrations at the poly-Si/SiO_x/c-Si interface as a function of AlO_x layer thickness and compared these to J₀ and calculated D_it,c-Si values. We observe an increase of the hydrogen concentration at the SiO_x/c-Si interface upon firing as a function of the firing temperature that exceeds the defect concentrations at the interface several times. However, the AlO_x layer thickness appears to cause an increase in hydrogen concentration at the SiO_x/c-Si interface in these samples rather than exhibiting a hydrogen blocking property.