Application of a Femtosecond Laser in the Fabrication of Quartz Sensing Elements for MEMS Accelerometers

Abstract—A group method of manufacturing quartz sensing elements of microelectromechanical systems (MEMS) for Q-flex type accelerometers is known, it is based on sequential wet etching and reactive ion etching (RIE) in fluorinated plasma. In order to reduce the defects in final products, labor costs for their manufacture and to obtain a rectangular etching profile of through holes in the section of the sensing element, an alternative technology for forming holes was developed. The technology includes the laser-radiation pretreatment of quartz glass with ultrashort pulse duration (on the order of hundreds of femtoseconds) for the entire thickness of the substrate and the subsequent wet etching of holes. The conducted researches reveal a local increase in the etching rate of the irradiated section of quartz glass during wet etching with hydrofluoric acid or an alkaline solution. The influence of the etching-solution concentration on the etching rate and the roughness of quartz was analyzed. The technology is universal and it can be used for high-precision 3D machining of products formed from quartz glass up to 4 mm thick.