Iduabo John Afa^1,, Gema López¹, Pablo Rafael Ortega Villasclaras¹

High efficiency Interdigitated back contact (IBC) solar cells help reduce the area of solar panels needed to supply sufficient amount of energy for household consumption. We believe that a properly passivated IBC cell with the aid of light trapping schemes can maintain an efficiency of 20% even with thickness under 20 μm. In this work, photolithography and etching techniques are used for deep etching of crystalline Silicon (c-Si) wafer to a thickness less than 20 μm. Tetramethylammoniumhydroxide (TMAH) wet anisotropic etching and plasma based Reactive ion etching (RIE) are used with SPR 220-7.0 and SU-8 photoresists. SiO₂ is used as making layer for TMAH etching. TMAH etch of a 4-inch c-Si wafer is done at a temperature of 80°C for 8 hours. RIE of a quarter of a 4-inch c-Si wafer is done for 3 hours using SF₆ as reactive gas. A baseline photolithography process flow for SU-8 photoresist deposition was developed. The etch rates of TMAH etch techniques fall within the range of 0.3 – 0.45 μm/min and etch rates for RIE fall within the range of 1.2 – 1.8 μm/min. The RIE shows capability of achieving smaller thickness sizes with greater advantages than the TMAH etching technique.

IBC solar cells, masked etching, photolithography, reactive-ion etch, and tMAH etching