Surface passivation of crystalline silicon by plasma-enhanced chemical vapor deposition double layers of silicon-rich silicon oxynitride and silicon nitride

Abstract

Excellent surface passivation of crystalline silicon (c-Si) is desired for a number of c-Si based applications ranging from microelectronics to photovoltaics. A plasma-enhanced chemical vapor deposition double layer of amorphous silicon-rich oxynitride and amorphous silicon nitride (SiNx) can provide a nearly perfect passivation after subsequent rapid thermal process (RTP) and light soaking. The resulting effective minority carriers’ lifetime (τeff) is close to the modeled maximum on p-type as well as on n-type c-Si. Restrictions on the RTP of passivated surfaces, typical of other common passivation schemes (e.g., amorphous Si), are relieved by this double layer. Harsher thermal treatments can be adopted while still obtaining salient passivation. Furthermore, characterization of the same, such as, surface photovoltage, capacitance voltage, and electron paramagnetic resonance, enables the reproducibility and the understanding of the passivation scheme under test. It is shown that the strong quality of surface passivation is ensured by a mechanism that emits electrons from shallow donor states in the passivation layer system and therefore creates a positive field effect.