Influence of Different Post Deposition Treatments on the Passivation Quality and Interface Properties of Thermal ALD Al2O3 Capped by PECVD SiNx

Atomic layer deposited (ALD) Al2O3 provides a high passivation quality on silicon surfaces, in particular on p- and p+-surfaces. For surface passivation of the base of p-type solar cells and the p+-emitter of n-type solar cells typically capping layers are required, e.g. SiNx. For such Al2O3/SiNx stacks the thermal stability in respect to low and high temperature solar cell processes is important. In this work we present a detailed study of the blistering behavior, the passivation as well as the interface properties (defect density Dit and effective fixed charge density Qf,eff) of thermal ALD Al2O3 layers capped by an antireflective SiNx coating as a function of the Al2O3 deposition temperature, the Al2O3 layer thickness and for different firing and annealing temperatures. The resulting surface recombination velocities are correlated with the Dit and Qf,eff, obtained with the corona-oxide-characterization-of-semiconductors (COCOS) technique.