Laades, A.; Angermann, H.; Sperlich, H.-P.; Stürzebecher, U.; Álvarez, C.; Bähr, M.; Lawerenz, A.: Wet chemical oxidation of silicon surfaces prior to the deposition of all-PECVD AlOx/a-SiNx passivation stacks for silicon solar cells. Solid State Phenomena 195 (2013), p. 310-313
10.4028/www.scientific.net/SSP.195.310
Abstract:
AlOx films contain negative charges and therefore generate an accumulation layer on p-type silicon surfaces, which is very favorable for the rear side of p-type silicon solar cells as well as the p+-emitter at the front side of n-type silicon solar cells. However, it has been reported that quality of an interfacial silicon sub-oxide layer (SiOx), which is usually observed during deposition of AlOx on Silicon, strongly impacts the silicon/AlOx interface passivation properties [1]. The present work demonstrates that a convenient way to control the interface is to form thin wet chemical oxides of high quality prior to the deposition of AlOx/a-SiNx:H stacks by the plasma enhanced chemical vapor deposition (PECVD). To evaluate quantitatively the effect of the preconditioning steps, we conducted measurements of the interface state density Dit(E) by means of the surface photovoltage technique immediately after the wet chemically preconditioned surfaces. The work has demonstrated that wet chemical oxides with low manufacturing costs can be used to improve the passivation quality of PECVD deposited AlOx/a-SiNx:H stacks. An important contribution to the high level of passivation of the SiOx/AlOx/a-SiNx:H stacks after post-deposition thermal steps is attributed to improved interface properties controlled by the Si-O-Si bonding structure and saturation of recombination centers by hydrogen.