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Ultrasonic-Assisted Chemical Etching (USACE) of Monocrystalline Silicon Wafer with HF-HCl-Cl2 Mixtures
A. Stapf, B. Neubert, K. Halbfaß, E. Kroke
Silicon Materials and Cells
Subtopic: Manufacturing & Production of Si Cells
Event: 37th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2CV.1.38
ISBN: 3-936338-73-6
0,00 EUR
Document(s): poster


The wet-chemical texturization of silicon wafer surfaces is very important in photovoltaic industry for the increase of light absorption. The standard texturization process for monocrystalline silicon wafer utilizes potassium hydroxide (KOH) mixtures with organic additives.1 In recent works we reported on acidic anisotropic etching mixtures based on hydrofluoric acid (HF), hydrochloric acid (HCl) and chlorine (Cl2).2 When generating high flow velocity of the etching solution, a maskless generation of random inverted pyramidal structures is observed on monocrystalline silicon surfaces.3 In this work, we introduce a new way of texturization of monocrystalline silicon wafers by ultrasonic assisted chemical etching (USACE) with HF-HCl-Cl2 mixtures (Figure 1). SEM pictures of silicon wafer surfaces etched by USACE in HF-HCl-Cl2 mixtures show a structure of small random inverted pyramids with an edge length of 0.5 – 2 μm (Figure 2). Furthermore, a rough substructure on the inside of the pyramids is generated. These structures lead to average reflections down to R (400-1100 nm)=6.3 % (Figure 3). We show the influences of various parameters on reactivity and morphology. This includes the composition of the etching solutions, variation of the ultrasonic power, temperature and orientation of the wafers in the ultrasonic field.