Abstract: A new infrared measurement method for determining the duration of the startup of GaAs wet etching is proposed.The basis of this method is that the temperature variation of an etchant film is induced by the absorption or release of chemical heat during the startup of the reaction.The startup time can be determined by the real-time collection of infrared thermal images over the course of the temperature variation.Theoretical analysis and experimental results show that 2mm-wide linear liquid film is suitable for monitoring because it contains the information of temperature and space change.Thus the center of the liquid film can be set as a characteristic observation point.More accurate experimental data can be obtained because of the high sensitivity of temperature change of the extremely thin linear film made by sliding droplets as well as the avoidance of the influence of film weight on the startup time by using upright GaAs substrate.The startup time of the reaction between GaAs substrate and H2SO4∶H2O2∶H2O (＝5∶1∶50) is about 0.2s,as obtained from the grey-scale variation of a certain cross section of the linear liquid film.The proposed method will stimulate the research of quick etching technology and absorption capability between solids and liquids.

Key words: GaAs, etching, infrared radiation, real-time monitoring, liquid droplets