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<< Figure 2: Te etching process. >>


completely vertical, but sloped at an angle of 70 degrees (tolerance depending on specifications). The average roughness of the channels will be between 0.8 and 2.5 µm, also depending on the process chosen. Now the substrate can be bonded to another glass or silicon substrate. As the surfaces of the powderblasted substrate remain undamaged, polishing the surface is not necessary.


Etching A different technique to create channel structures in glass is HF etching. HF is a hydrofluoric acid, commonly used for cleaning metal and etching glass. For the HF etching technique special masks are used 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. This makes HF etching an economical solution for fast, flexible, high quality prototyping and volume production (up to 50,000 wafers a year).


Because wet etching of glass is an isotropic etching technique 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. Also this technique makes it possible to combine with other etching techniques such as multiple depth HF etching, 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 the final technique used in Micronit’s cleanroom to create structures on the substrates. DRIE is a unique technique to create deep, high


>> Continued on page 32 31 | commercial micro manufacturing international Vol 7 No.3


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