Alkaline or acidic etching agents remove the surface damage induced by the sawing process and texture the surface of the wafer. Acidic etching agents, like HF and HNO3 are used for isotropic etching. Typical alkaline etching agents are caustic soda (NaOH), caustic potash (KOH) and tetramethylammonium hydroxide (TMAH) solutions. Wafer surface texturing is important to improve the light trapping into the cell and the energy absorption capacity. The major factors of influence in this process are the current bath concentration and residence time.
Because of the consumption and discharge of etching chemicals during the texturing process, it is necessary to measure the concentration and temperature continuously. This insures consistant product quality and, if needed, more etching agents can be added. LiquiSonic® inline analyzers monitor the current texturing and etching bath concentration. This enables an automatic additional dosing through the incorporation in to existing process control systems.