The presence of cracks in LIGA microstructures can endanger the device performance. It is therefore important to avoid crack formation during processing. In order to achieve this, we have analysed crack formation and present the first results here. PMMA foils were exposed with different dose profiles in the Litho III beam line at the ANKA synchrotron. In the first experiment, foils were exposed without a mask. In the second experiment the sidewall quality was observed for different dose profile. Irradiation by X-ray produces gas in exposed areas. The gas diffusion creates conditions which provoke crack formation, due to an increase of residual stress in the interface between exposed and unexposed areas. It has been concluded that the delay time between the irradiation and the development is critical in the determination of the crack size and distribution. It has been shown that also the dose profile is an important parameter in the determination of crack formation.