Sub-Wavelength Texturing for Solar Cells Using Interferometric Lithography

Abstract

We have employed Interferometric Lithography (IL) for sub-wavelength surface texturing on large area silicon substrates. Low defect density Reactive Ion Etching (RIE) processes have been developed to transfer the pattern into the silicon using SF 6 plasma. Reflection measurements on the sub-wavelength textured surface have been carried out and show a substantial reduction from ~30% to below 4% over the spectrum range from 400nm to 1200nm. IL is a mask-less lithography technique which is used to define periodic patterns. The theoretical limit of the pitch size of the structure is half of the wavelength of the light source. Hence, the sub-wavelength patterns can be achieved easily. Moreover, sub-wavelength texturing requires short RIE processes; most of the plasma-induced damage on the silicon surface can be avoided.