Optical mismatch in double AR coated c-Si, a simple theoretical and experimental correlation

Theoretical optimization of ARC (antireflecting coating) for both, single and double ARC has been done in the order to obtain minimum reflectance on crystalline silicon surface. Experimental corroboration has been made with the deposition of a simple SiN/sub x/ (silicon nitride) and double SiN/sub x//SiO/sub 2/ (silicon nitride/silicon oxide) ARC on silicon substrates using PECVD (Plasma enhanced chemical vapor deposition) technique. Different refraction indexes were obtained by means of NH/sub 3/ flow adjustment. Reflection measurements as a function of wavelengths revealed some differences with theoretical calculations for both simple- and double-layer ARCs. We demonstrate how important is the ARC thickness for optical matching for single and double ARC. An analysis and discussions are made for a proper interpretation of the observed behavior.