Fabrication of micronozzles using low-temperature wafer-level bonding with SU-8

Abstract

This paper describes a method for fabricating micronozzles using low-temperature wafer-level adhesive bonding with SU-8. The influence of different parameters on the bonding of structured wafers has been investigated. The surface energies of bonded wafers are measured to be in the range of 0.42-0.56 J m −2 , which are comparable to those of some directly bonded wafers. Converging-diverging nozzle structures with throat widths as small as 3.6 µm are formed in an SU-8 film bonded with another SU-8 intermediate layer to produce sealed micronozzles. A novel interconnection technique is developed to interface and test the micronozzles with a macroscopic fluid delivery system to demonstrate the feasibility of the fabrication process. Leakage test results show that this low-temperature wafer bonding process is a viable MEMS fabrication technique for microfluidic applications.

Microfluidic channel fabrication by PDMS-interface bonding

“…Benzocyclobutene (BCB) [3] and Teflonlike amorphous fluorocarbon polymer [4] are used as the 0964-1726/06/010112+05$30.00 © 2006 IOP Publishing Ltd Printed in the UK S112 adhesive layers to bond different materials such as silicon and glass. However, their required bonding temperature is still over 100 • C. SU-8 is another polymer that requires a bonding temperature of ∼95 • C [5]. For glass and silicon substrate bonding, bonding temperatures over 100 • C are still acceptable; but for polymer substrates, this would greatly affect the bonding performance.…”

Characterisation of the fabrication process of freestanding SU-8 microstructures integrated in printing circuit board in microelectromechanical systems

“…These experimental tests provided an average surface energy µγ of 1.334 J/m 2 with a standard deviation σγ of 0.136 J/m 2 , according to the described fabrication conditions. This value is larger than the surface energy of SU-8-to-PDMS [12] and the SiO2-SU-8-pyrex bonded wafers [13], 0.047 J/m 2 and 0.5 J/m 2 respectively, and comparable to Silicon-to-Pyrex glass bonding surface energy, 1.3 J/m 2 [14].…”

Fabrication of miniaturized fluidic devices using SU-8 based lithography and low temperature wafer bonding

“…Due to these differences the corresponding structures are not entirely in close contact. Consequently some voids remain after bonding [10], which decreases the yield of the bonding process. Our bonding experiments showed a yield of approximately 30%, i.e.…”

“…One can say that it behaves like thermally curing epoxy adhesive. A layer of unexposed SU-8 can be used as an adhesive layer for waferbonding [10]. If SU-8 is used for building fluid structures and-in unexposed form-for waferbonding, the unexposed SU-8 has to be patterned.…”