Study On Water-assisted Laser Induced Plasma Etching Of Pyrex7740 Glass

Pyrex7740 glass (a borosilicate glass) has excellent properties such as good bio-compatibility, high heat resistance and electrical isolation,excellent optical performance, similar thermal coefficient of expansion(TCE) to silicon in a range of temperature and contains appropriate amount of Na+ and K+, very suitable for anodic bonding with silicon, so is more and more applied in biotechnology, RF, optical and other MEMS devices, micro-sensors and micro-electronics packaging technology. With the rapid development of MEMS (micro-electro-mechanical-system)research and application, the reliability of the packing, interconnection,geometry and dimensional accuracy of MEMS devices are becoming more and more demanding. Therefore, severe processing requirements of Pyrex7740 glass processing accuracy and surface quality are proposed.However, Pyrex7740 glass belongs to a hard and brittle material with some properties such as high hardness, low fracture toughness and the elastic limit very close to the intensity limit, which is very difficult to process by now.Aiming at much high energy density threshold is needed for direct laser etching Pyrex7740 glass and the other methods have problems such as low machining precision, chipping, small aspect ratio, impurities and low processing efficiency, etc. In this dissertation, a new method of water-assisted laser induced plasma backside etching Pyrex7740 glass is presented. Machining experiment and theoretical analysis are carried out to explore the influences of laser energy density and the number of laser processing on the average etching depth and the function of deionized water in the etching process. The results show that the average etching depth depends much on the laser energy density and the processing number. Only with the assist of deionized water can realize continuous etching, the maximum etching depth is 2.8?m when the laser energy density is 3.4 J/cm2 and in the absence of deionized water. The laser processing parameters such as laser energy density, processing speed,pulse repetition frequency, the number of laser process and so on were studied by means of the parameter control method to figure out the influence rule of water-assisted laser induced plasma etching Pyrex7740 glass processing quality. Finally, a scaled-down cross-channel microfluidic chip with a width of 77.8?m and a depth of 20.4 ?m which has no obvious damage in the edge of the micro-channel and smooth ground was fabricated successfully on the Pyrex7740 glass with suitable laser processing parameters.At the same time, the method of water-assisted laser induced plasma etching Pyrex7740 glass proposed in this dissertation, can also be applied to the microstructure etching of other optical transparent materials such as quartz glass, crystal, transparent ceramics and so on. It is expected to be widely applied in the field of MEMS devices manufacture and packaging technology.