Variation of the layer thickness to study the electrical property of PECVD Al2O3 / c-Si interface

Abstract

This paper focusses in particular on the influence of the layer thickness on the passivation quality, the charge density and the interface defects of PECVD Al2O3 passivation layers on c-Si surfaces. The surface recombination velocity and the interface defect density are observed to increase by decreasing the layer thickness. However, the density of negative charges remains almost constant with values around 3 1012 cm-2. An optimal passivation quality is obtained for thicknesses of 15 nm and higher. A linear relation between surface recombination velocity and Dit was established, allowing the estimation of the electron capture cross section (σn ∼ 10-13 cm-2). Additionally, we measured the capture cross section of holes and electrons using DLTS measurement. The results are found to be very similar to reported values for silicon dioxide. This supports the idea that the chemical passivation of crystalline silicon by Al2O3 is performed by the interstitial SiO2 layer.