Manufacture of microfluidic glass chips by deep plasma etching, femtosecond laser ablation, and anodic bonding

Two dry subtractive techniques for the fabrication of microchannels in borosilicate glass were investigated, plasma etching and laser ablation. Inductively coupled plasma reactive ion etching was carried out in a fluorine plasma (C4F8/O-2) using an electroplated Ni mask. Depth up to 100 mu m with a profile angle of 83A degrees-88A degrees and a smooth bottom of the etched structure (Ra below 3 nm) were achieved at an etch rate of 0.9 mu m/min. An ultrashort pulse Ti:sapphire laser operating at the wavelength of 800 nm and 5 kHz repetition rate was used for micromachining. Channels of 100 mu m width and 140 mu m height with a profile angle of 80-85A degrees were obtained in 3 min using an average power of 160 mW and a pulse duration of 120 fs. A novel process for glass-glass anodic bonding using a conductive interlayer of Si/Al/Si has been developed to seal microfluidic components with good optical transparency using a relatively low temperature (350A degrees C).