Experimental Analysis of Anisotropic Surface Texturing Process of Crystalline Silicon Wafers

Abstract

The development of silicon devices, circuits, and systems in most cases relies on the wet-chemical etching of silicon wafers (SWs). To achieve deep etching and micromachining, shaping, as well as cleaning, the dissolution of silicon using liquid chemical solutions is imperative. This study reports an experimental investigation of surface texturing of silicon wafers using a mixture of aqueous potassium hydroxide (KOH) solution and isopropyl alcohol (IPA) as a complexing agent to enhance light absorption and reduce the optical reflectance in the visible spectrum. Crochralski (CZ) silicon wafers of 100 mm diameter, 2” <100>-oriented, n-type, resistivity (Ωcm) of 7-21, with polished and lapped surfaces were utilized in the experiment. The process variables investigated included temperature (60 – 90) °C, duration of etching time (30 – 60) mins and concentration of KOH and IPA of (1 - 4) mg/l for KOH and (2 – 8) mg/l for IPA. The properties of the etched and unetched silicon wafers in terms of morphology, structure, photoluminescence, and electroluminescence were investigated to determine the effects of the process parameters on the efficiency and structural properties of the textured wafers. The SEM measurements revealed the presence of localized roughening pyramidal images. This showed that the use of KOH and IPA solutions on the silicon wafers revealed pyramidal structures that can be used to control the optical reflectance of the silicon wafers due to light scattering by the localized roughening. The applied etching procedure also produced low-reflecting materials whose reflectivity increases with wavelength. This study shows that textured material has great potential in optoelectronic device manufacturing processes