Microreplication in a silicon processing compatible polymer material

Abstract

Devices combining optical and micromechanical elements have become key components for many applications in recent years. In this paper, we present a novel fabrication process for the integration of polymer micro-optical elements on silicon. The fabrication process relies on a reverse-order protocol in which the diffractive lens is first hot embossed into a polymer layer spin coated onto a silicon wafer and the subsequent process steps are carried out with the lens already in place. This is possible due to an extremely stable and chemically resistant amorphous fluorocarbon polymer, Cytop™, used for lens fabrication. Cytop is a Teflon-like material which exhibits high optical transmittance, excellent adhesion to silicon and resistance to most chemicals used for silicon processing. These properties make it ideally suited for the integration of polymer optical elements with silicon micromechanical components.

Refractive lenses in silicon micromachining by reflow of amorphous fluorocarbon polymer

“…The resist pattern acts as the protective shield during the subsequent Cytop etch process, which was carried out in an inductively coupled plasma/reactive ion etch (ICP/RIE) system with the following etch conditions: 40.0 sccm O 2 , 90.0 mTorr chamber pressure, 200 W RF power and 0 W ICP power. A similar etch process is described in [22,23]. The etch rate of the Cytop polymer film was 1 µm min −1 for our etch conditions and the etch rate of the resist was approximately 0.3 µm min −1 .…”

“…In previous work, we showed that it is possible to fabricate diffractive microlenses (sawtooth Fresnel lenses) by hot embossing of the Cytop polymer [22,23]. The new process presented here results in continuous-surface profile refractive lenses using the same polymer as a lens material.…”

“…Different methods have been used to fabricate such microlenses, e.g. reflow techniques [1,2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], replication [1][2][3][20][21][22][23], local volume change of a substrate material [24], micro-jet printing [25], gray-scale lithography [1,2], direct writing with laser or electron beam [1,2] and dip-coating [26]. Continuous-surface profile refractive microlenses can be produced using any of these methods, but thermal reflow techniques are most frequently used.…”

Integrated Label-Free Protein Detection and Separation in Real Time Using Confined Surface Plasmon Resonance Imaging

“…Finally, channels were formed by selectively etching away the polymer layer. This can be accomplished via patterned reactive ion etching, sacrificial liftoff, or physical milling. , As a result, hydrophobic polymer walls 500 nm thick defined the network of channels on the hydrophilic glass surface. The device was assembled by pressing the channel substrate face down onto the sensor surface to seal the channels.…”

“…This can be accomplished via patterned reactive ion etching, sacrificial liftoff, or physical milling. 21,22 The open-faced channel substrate was pressed against the sensor substrate forming a network of channels 500 nm in height. This was then positioned onto the SPRi prism for testing.…”