The Surface Texturing of Monocrystalline Silicon with NH4OH and Ion Implantation for Applications in Solar Cells Compatible with CMOS Technology

This work presents the development of photovoltaic cells based on p+/n junction in Si substrates, aimed at compatibility with fabrication processes with CMOS technology. The compatible processes, which are developed in this study, are the techniques:i) Si surface texturing, with the textured surface reflection of 15% obtained by the formation of micro-pyramids (heights between 3 and 7 μm) using NH4OH (ammonium hydroxide) alkaline solution, which is free of undesirable contamination by Na+ and K+ ions, when NaOH and KOH traditional solutions are used, respectively, and ii) of the ECR-CVD (ElectronCyclotron Resonance - Chemical Vapor Deposition) deposition of SiNx (silicon nitride) anti-reflective coating (ARC), which is carried out at room temperature and can be performed after the end of cell fabrication without damage on metallic tracks and without variation of p+/n junction depth. The ARC coating characterization presented that the silicon nitride has a refractive index of 1.92 and a minimum reflectance of 1.03%, which is an excellent result for application in solar (or photovoltaic) cells. For the formation of the pn junction was used ion implantation process with 11B+, E=20 KeV, dose of 1x1015 cm2 and four rotations of 90° to get uniformity on texturized surfaces.