On the Role of AlO_x Thickness in AlO_x/SiN_y : H Layer Stacks Regarding Light- and Elevated Temperature-Induced Degradation and Hydrogen Diffusion in c-Si

Abstract

Light- and elevated temperature-induced degradation (LeTID) is assumed to be triggered by the hydrogen content in the crystalline silicon bulk. This article investigates differently thick atomic layer-deposited aluminum oxide (AlO x ) layers acting as diffusion barrier for hydrogen originating from a hydrogen-rich silicon nitride (SiN y :H) layer. We demonstrate that the extent of LeTID can be significantly reduced by adjusting the AlO x layer thickness up to 25 nm. To directly measure the diffusing species, a deuterium-rich SiN y :D layer is deposited and the deuterium content is measured in an amorphous Si layer at the back side of the wafer via secondary ion mass spectrometry. Thus, a diffusion length of deuterium in the AlO x layer of (3.8±1.6) nm is determined at a firing temperature of (743±2)∘C . These results are not only a contribution to determine the LeTID formation dynamics, but also can be used to control LeTID in silicon wafers and solar cells.