The recent progress in the development of the lithographic processes within the LIGA technique is reported, which is based on deep-etch synchrotron radiation lithography, electroforming, and molding processes (in German: lithografie, galvanoformung, abformung). Mask blanks for high-contrast x-ray masks for 0.2 nm wavelength are fabricated from titanium and beryllium membranes produced by physical vapor deposition techniques. Absorber patterns on these masks can be produced by 50-keV electron-beam pattern generation in 3–5-μm-thick polymethylmethacrylate (PMMA) resists, because the use of beryllium strongly reduces the otherwise marked influence of electrons backscattered from the substrates on the resist profiles. To comply with the requirements of deep-etch lithography cross-linked PMMA resists and suitable multicomponent developers have been formulated. The casting resin-based resists are polymerized directly on the substrate which results in extremely low internal stresses to prevent stress corrosion of the resist structure during development.

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