Deep X-ray mask with integrated actuator for 3D microfabrication

Abstract

We present a novel method for 3D microfabrication with LIGA process that utilizes a deep X-ray mask in which a microactuator is integrated. The integrated microactuator oscillates the X-ray absorber, which is formed on the shuttle mass of the microactuator, during the X-ray exposures to modify the absorbed dose profile in X-ray resist, typically PMMA. The 3D PMMA microstructures according to the modulated dose contour are revealed after GG development. An X-ray mask with integrated comb drive actuator is fabricated using deep reactive ion etching, absorber electroplating, and bulk micromachining with silicon-on-insulator wafer. Silicon shuttle mass (1 mm x 1 mm, 20 mum thick) as a mask blank is supported by four I turn long suspension beams and is driven by the comb electrodes. A 10 mum thick, 50 mum line and spaced gold absorber pattern is electroplated on the shuttle mass before the release step. The fundamental frequency and amplitude are around 3.6 kHz and 20 mum, respectively, for a dc bias of 100 V and an ac bias of 20 V(P-P) (peak-peak). Fabricated PMMA microstructure shows 15.4 mum deep, S-shaped cross-section in the case of 1.6 kJ cm(-3) surface dose and GG development at 35 degreesC for 40 min. (C) 2003 Elsevier B.V. All rights reserved.