Micronit applies wet etching (HF etching) techniques to create channel structures in glass and silicon. HF is a hydrofluoric acid, commonly used for cleaning metal and etching glass. For the HF etching technique we use masks which make the absolute positioning of the structures accurate within one micrometer. By using a mask, the amount of channels, reservoirs, mixing and reaction chambers is irrelevant for the costs of the process.
Wet etching of glass is an isotropic etching technique. This means that the width of the channels is more than twice the depth of it, and that the corners are rounded. The bottom of the channel stays smooth and optically transparent.
HF etching is an economical solution for fast, flexible, high quality prototyping and volume production (up to 50,000 wafers a year).
A lot of combinations with (other) etching techniques are possible, like double-sided HF etching or one-side powderblasting, one-side HF etching. Besides, it is possible to integrate electrodes in the chips, or to use silicon layers.
Deep Reactive Ion Etching (DRIE or plasma etching) is a unique technique to create deep, high density and high aspect ratio structures in glass (fused silica) and silicon substrates. Micronit is one of the few companies able to use the DRIE method in glass substrates.
Etching with steep side walls (anisotropic etching) as well as with rounded walls (isotropic etching) in substrates is possible, with depths varying between 1 µm cavities and complete wafer-through holes.
Capabilities of Micronit in DRIE etching are as follows (based on a silicon substrate):
- Aspect ratio 1:15;
- Wafer-through etching;
- Variable inclination of the channel walls;
- DRIE on SOI wafers