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Powderblasting is a flexible, cost-effective and accurate technique for making fluidic channels and interconnections. Because of using a lithographic mask, position and channel size accuracy is within 10 µm. There are no limits to the shape of the holes and trenches.
Design
First of all, the design of the
channels and holes is transferred onto the glass by means of photolithography: a
photoresist film is laminated on the glass and the mask with the design is
positioned above the film. The film is then illuminated with UV light through
the mask. Illuminated areas willl be removed from the glass during
development.
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Powder blasting Process
The wafer is now powderblasted. During the exposure of the wafer to the powder the areas not covered by film are etched, while the covered areas deflect the powder. The etch rate and depth can be controlled by controlling the time and particle speed.
With sophisticated powderblasting equipment the glass substrate with the developed film can be processed. By processing by lithography and powderblasting, the complexity of the design is irrelevant (when the design meets the tolerances) and only one mask is needed when processing more substrates.
Shape and roughness
Shaped wells can be
round or rectangular. The sides of the wells will not be 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.
After the powderblasting process, 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 needed.