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Safety and Health Topics > Semiconductors > Gallium Arsenide > Device Fabrication: Wet Etching Device Fabrication: Wet Etching Various mixtures of wet chemical acid solutions are used in plastic baths in locally exhausted etch stations, some provided with laminar HEPA filtered supply systems which are vertically mounted. The primary acids in use are H2SO4, HF, HCl and H3PO4. As in silicon processing, H2O2 is used with H2SO4 and NH4OH to provide a caustic etch. A cyanide solution (sodium or potassium) is also used for etching aluminum. (See Silicon Device Manufacturing - Device Fabrication - Etching) Potential Hazards Acids and Caustics Acids and Caustics Potential Hazard Possible employee exposure to acids and caustics used for wet chemical etching. Typical acids may include mixtures of HF, HCl, H2SO4, H3PO4, etc., while common caustics include H2O2 and NH4OH. Cyanide solutions of NaCN and PCN are also used. Possible Solutions See the Possible Solutions: Acid and Caustic page. Additional Information OSHA Health Guidelines pages: Hydrogen Chloride Hydrogen Fluoride Hydrogen Peroxide

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