Microlens array fabrication by enhanced thermal reflow process: Towards efficient collection of fluorescence light from microarrays

作者：Roy E^*; Voisin B; Gravel J F; Peytavi R; Boudreau D; Veres T

来源：Microelectronic Engineering, 2009, 86(11): 2255-2261.

DOI：10.1016/j.mee.2009.04.001

• Microlens
• Reflow method
• Micro optics integration
• Microarray fluorescent detection

This paper describes two enhanced resist reflow methods for the fabrication of microlens arrays and demonstrates their use for integrated biomolecular fluorescence detection on printed microarrays. A PDMS (polydimethylsiloxane) microlens array was fabricated by a double soft lithography approach using a photoresist microlens array as master mold. Additionally, by using both a careful control of the surface wettability and thermal treatments, we demonstrate the possibility to extend the resist reflow process in order to tune the diameters of microlens array over a large range by using a unique photomask pattern.
We introduce an enhanced reflow on hydrophobic surfaces obtained by fluorosilane treatment and identify a threshold shrinkage temperature (T(shrinkage)) of 140 degrees C, above which the diameter of microlenses can be then reduced down to 40% compared with the initial pattern on the photomask. Furthermore, on hydrophilic substrates, achieved by an accurate incomplete development of the photoresist, we demonstrate a nearly perfect linear dependency (1.4 mu m/degrees C) of microlens diameter spreading up to 70% the initial diameter inside a temperature reflow window of 110-140 degrees C. For both approaches, above a freezing temperature (T(freezing)) of 170 degrees C, the microlens profile characteristics are temperature independent.
By using high numerical aperture microlens array, we provide a proof of concept for the integration and enhanced light collection of the fluorescent signals collected form a microarray of fluorescent spots thus showing the potential of the concept for biophotonic integration.

• 出版日期2009-11