CHARACTERIZATION OF DEFECTS IN VERY HIGH DEEP-ETCH X-RAY-LITHOGRAPHY MICROSTRUCTURES

In deep X-ray lithography synchrotron radiation is applied to pattern several hundred micrometer thick resist layers. This technique has bee n used to obtain micro structures with an aspect ratio up to 100 and d imensions in the micrometer range. The structures are characterised by straight walls and a typical sidewall roughness of approximately 50 n m. To be able to fabricate n-coherent structures with any lateral shap e and to have the possibility to use these resist microstructures in a n additional electroforming process the resist is usually mounted on a ceramic or metallic substrate. Due to the different thermal expansion coefficients of the resist material and the substrate a developing te mperature of 37 degrees C produces cracks in the resist structures dep ending on the microstructure design. These defects are not observed if the developing temperature is reduced to 20 degrees C. Better structu re quality is obtained using the GG-developer instead of MIBK/IPA, but the developing rate is decreased. Measurements of the developing rate of PMMA in GG-developer at different temperatures show that the contr ast of the developer-resist system is increased at 20 degrees C compar ed to 37 degrees C.