Rapid prototyping of silicon structures by aid of laser and abrasive-jet machining

Rapid prototyping of silicon microstructures for fluidic devices using laser machining in water and abrsive-jet machining through mask is described. For laser machining a Q-switched 1-2 W 1 kHz pulsed Nd:YAG laser beam (1.06 mu m) and 60 mJ XeCl excimer laser beam (308 nm) were used. The laser beam was scanned along the silicon surface at speeds 0.1-2 mm/s. Using excimer laser, the silicon nitride layer was patterned for subsequent chemical etching. Nd:YAG laser was used for fabrication of cavites and channels of depth down to 200 mu m. Comparison of Nd:YAG laser machining of silicon in air and in water has been performed. A Machining in water yields more even surfaces and there is no debris. By abrasive jet (abrasive particles in air) of velocity approximately 200 m/s and abrasive feed rate 0.4 g/s, the silicon was eroded at speed of 40 mu m/min. Several masking materials were compared, whereby a styrene based glue was found to have the best abrasion resistivity. The polymer masks were spinned on the surface and patterned by excimer laser light or by knife. The described fabrication methods were used for making the fluid channels and chambers in silicon and for releasing silicon nitride and oxide films.