Thermoelastic deformations of masks for deep X-ray lithography

Influence of developer temperature and resist material on the structure quality in deep x-ray lithography

“…3. A significant weight loss is observed at dose values above 0.26 kJ/cm 3 weight loss even after developing times of more than 26 days. Therefore this dose value is defined in this article as the minimum dose necessary to observe a significant resist attack.…”

“…2 Structure displacements of 0.2 m were observed at DCI/LURE using x-ray masks fabricated on top of a 500 m thick Be membrane due to thermal heat load. 3 Fluorescence radiation produced within a Ti mask membrane may lead to a rounding at the top layer of the resist of thickness up to 200 m. 4 These defects and structure limits become visible after the development of irradiated resist samples. As a consequence, the influence of irradiation conditions and the developing process cannot be separated.…”

“…Usually, poly͑methylmethacrylate͒ is used as the resist layer. We have measured the molecular weight and developing rates of crosslinked and noncrosslinked PMMA foils at different GG developer temperatures for dose values between 0.1 and 8 kJ/cm 3 . The determined developing rates cover a region of 7 orders of magnitude: With decreasing temperature the contrast of the resist-developer system and the limit of the developing dose are increased.…”

Metrology study of structural transfer accuracy in fabrication of high-aspect-ratio microelectromechanical systems: From optical mask to polished electroplated parts

“…Among these are: diffraction effects at the absorber edges, dose deposition by secondary electron and radiation processes, divergence of synchrotron radiation, elastic and inelastic photon scattering, and heat load on mask 8 and thermoplastic deformation of the mask during irradiation. 11 They demonstrated that the lateral degradation of those effects in the energy range usually considered for deep x-ray lithography ͑2-8 keV͒ in a medium size microstructure gives maximum contributions in the submicrometer range. Thus, this physics' approach failed to account for micrometer-scale degradation of the developed patterns as observed by a few groups.…”

Calculation and experimental determination of the structure transfer accuracy in deep x-ray lithography

“…Finite-element calculations showed that the deviations from the ideal shadow print can be kept below 0.2 µm (for 500 µm thick resist layers and 1.6 W cm −2 radiation power) if beryllium or diamond are used as mask membrane materials. The thermoelastic deformations were investigated earlier [3] and will not be addressed here.…”