Polydimethylglutarimide (PMGI) as a sacrificial material for SU-8 surface-micromachining

Abstract

SU-8 is finding increased use as a structural polymer MEMS material due to its biocompatibility, mechanical properties and low cost. The goal of this work is to expand the use of SU-8 through the creation of SU-8-based surface-micromachining processes that use polydimethylglutarimide (PMGI) as a sacrificial layer. PMGI is a deep-UV positive resist, used mainly for bilayer lift-off processes. PMGI is a good sacrificial layer candidate, as it is spinable at a wide variety of thicknesses, is photopatternable and has a glass transition temperature greater than the processing temperatures required for SU-8. PMGI is shown to be useful as a sacrificial layer for SU-8 surface micromachining processes with one freestanding layer with patterned metal, single-layer devices with more than one thickness, and two layer devices. Two classes of devices were fabricated with the developed processes. The first class of devices are compliant mechanisms, including bent-beam actuators, thermal isolation platforms and out-of-plane grippers. The second class of devices fabricated are freely moving devices such as hinged plates and gears, which require the use of true kinematic joints, such as scissor hinges, staple hinges and pin joints.

Photopatternable Electrical Conductive Ag- SU-8 Nanocomposite for MEMS/MST

“…The ability to photopattern an electrically conducting layer provides the fabricators in the areas of microelectromechanical systems (MEMS) and microfluidics with greater flexibility and the possibility of avoiding an expensive vacuum deposition. SU-8 is an insulating near-UV negative-tone photoresist used as a structural material in both the MEMS [3][4][5][6] and microfluidic [7][8][9][10] communities. However, because SU-8 is an insulator most applications in both MEMS and microfluidics require patterned electrical leads to provide for transducers.…”

Sacrificial Layer Technique for Releasing Metallized Multilayer SU-8 Devices

“…This is ideal for single layer SU-8 whereas for multilayers it falls short, as the stresses would delaminate during the processing. PMGI is a lift of resist which is commonly used for sacrificial release in MEMS [36,37,38]. Thermally cured PMGI is not suitable for multilayer sacrificial release and needs deep-UV exposure to make it inert for SU-8 developer [38].…”

Novel Fabrication Technique of Suspended Nanowire Devices for Nanomechanical Applications

“…Here, we propose a method to fabricate suspended NW NEMS devices that features two novel process steps: inkjet printing for precise assembly of NW‐dispersed droplets and the formation of trenches filled with PMGI to improve device design flexibility . After dropping a very small amount of solution containing dispersed NWs with an inkjet printer onto a patterned substrate, we can move the NWs in the droplet to the desired position on the substrate with an In tip manipulator .…”