Boomerang is a 3GeV synchrotron radiation accelerator, currently being constructed in the State of Victoria, Australia. The outline design of two beamlines, suitable for the fabrication of MEMS devices using the LIGA process, is presented, along with an estimate of the exposure doses throughout the resist. The most commonly used resist is PMMA, which requires a minimum dose of about 4500 J/cm³ for accurate microstructure definition. Exposure with such a dose, in resist thicknesses of several hundred microns, can take hours. Fortunately, SU-8 resist is becoming more widely used as the minimum dosage required is about 35 J/cm³, leading to exposure times of only a few minutes. Although Boomerang will shorten exposure times due to its higher irradiance at the substrate, the full benefits may not be realizable due to excessive resist heating. Heating effects have been simulated and suggest that helium cooling will be essential if the glass transition temperature of the resist (100°C for PMMA, 50°C for SU-8) and thermal distortion of the mask are to be avoided. The parameters chosen in this study of the future performance of Boomerang have been inserted into a cost model. The model shows that Boomerang exposure can become competitive with other exposure methods, particularly where large quantities of devices with deep structures are required.

Date Published: 2 April 2004
PDF: 11 pages
Proc. SPIE 5276, Device and Process Technologies for MEMS, Microelectronics, and Photonics III, (2 April 2004); doi: 10.1117/12.532759

Published in SPIE Proceedings Vol. 5276:
Device and Process Technologies for MEMS, Microelectronics, and Photonics III
Jung-Chih Chiao; Alex J. Hariz; David N. Jamieson; Giacinta Parish; Vijay K. Varadan, Editor(s)