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ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

THERMAL ANALYSIS OF X-RAY IRRADIATED THICK RESISTS TO DETERMINE INDUCED STRUCTURAL DEFORMATIONS

Get access (open in a dialog) DOI: 10.1615/IHTC10.690
pages 313-318

Sinopsis

PMMA (polymethylmethacrylate) and other photoresists (resist for short) used in patterning HARMEMS (High Aspect Ratio MicroElectroMechanical Systems) structures are poor conductors of heat compared to the supporting silicon substrate. Structures built to date have been exposed with synchrotron sources that require hours to obtain the typical minimum doses of 2-4 kJ/cm3 in the resist. Thus, there has been little differential heating above the ambient temperature from the x-ray interaction; however, the time for these exposures may be a barrier to the rapid expansion of the HARMENS field and ultimately of commercialization. Other new synchrotron sources have much higher fluxes and will result in exposure times of minutes, rather than hours. With the higher flux, heating of the resist may become a limiting factor in the fabrication process since thermal expansion can lead to distortion of the exposed area compared to the unexposed adjacent resist. Additionally, stresses between the resist and the substrate will intensify due to differential heat conduction and anticipated temperatures leading to PMMA - substrate bonding problems. X-ray irradiated resists have been modeled analytically and computationally with a 2D finite element code in order to analyze the potential temperature rise and deformation. The temperature increase for 100 micron thick resists exposed by the high flux source is on the order of lO°C while the maximum displacement is on the order of .1μm.