ISSN Online: 2377-424X
ISBN Print: 0-85295-345-3
International Heat Transfer Conference 10
THERMAL ANALYSIS OF X-RAY IRRADIATED THICK RESISTS TO DETERMINE INDUCED STRUCTURAL DEFORMATIONS
摘要
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.