The influence of texturing bath conditions on the morphology and optical properties of crystalline silicon

Abstract

Three different series of p-type (100) Crystalline Silicon (c-Si) FZ wafers of about 270 μm thickness with resistivity of 2–4 Ω-cm were textured by three different concentrations of KOH (2.5 wt.%, 3.5 wt.%, and 4.5 wt.%). For every series of textured wafers, three samples were textured, each of 1×1.5 inch2 size. The texturing process was interrupted at different duration of 20 min, 40 min, and 60 min; after which the wafers were removed from the bath and rinsed by DI water, then blow dried with nitrogen. The total bath volume was 700 ml including the initial amount of 15 ml Isopropyl alcohol (IPA). Using an automated dispenser, IPA was also added during the texturing process with a dispensing rate in the range from 0.42 ml/min to 1.3 ml/min, also DI water was added with a fixed dispensing rate of 0.82 ml/min to maintain the concentration of KOH. Additionally, for each fixed KOH concentration, two different texturing bath temperatures were applied: 70°C and 75°C. The aim of this research work is to gain a better understanding on the influence of controlled etching rate (bath composition and temperature) on the silicon surface properties; morphological and optical. Scanning Electron Microscopy (FE-SEM) was applied to study the morphological structure of the textured surface. The surface topography, bearing area ratio, and root-mean-square (RMS) surface roughness of all textured wafers were investigated using Atomic Force Microscopy (AFM). Whereas, the reflectance measurements were carried out using UV-Vis-NIR Spectrometer.