Etching of Glass Microchannels

The etch rate of Pyrex depends on the HF concentration. The lateral etch rate was found to be greater than the vertical etch rate, and the rates were reduced from 12 to 0.5 pm/min when the HF concentration decreased from 49% to 25%. 

Before photolithography, a photoresist film is usually spin-coated on glass. To improve the adhesion of photoresist on glass, it is first spin-coated with a film of hexamethyldisiazane. On the other hand, to coat photoresist on glass plates with holes, the glass should be dip-coated [103-105]. 

Scratch effects in glass etch can be reduced by pre-etching the glass in HF before deposition of the metal etch mask [108]. 

For mechanically polished glass plates, thermal annealing should be performed before etching to improve etch quality [96,102,105,109,430,529]. 

In one report, surfactant was added to yield better dimensional consistency and smoothness of channel edges [626]. In another case, glycerol was added to the HF etching bath [729]. 

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Microfluidic Lab-on-a-chip for Chemical/Biological Analysis and Discovery 2.2.1 Etching of Glass Microchannels... 

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