In order to produce microelectromechanical systems on base of gallium arsenide it is necessary to develop novel etching techniques. The conventional dip etching is not suitable to fabricate such systems reliably and with sufficiently small thickness variations. To overcome this problem we used a modified spray etching technique. A comparison between both methods is given.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.