Establishment of theoretical model and experimental equipment for researching on carbon contamination of EUV multi-layer mirror

Carbon contamination on extreme ultraviolet (EUV) multi-layer mirror is a seriously restrictive factor for lithography quality, chip output and life of lithography machine. In order to estimate the carbon contamination of EUV multi-layer and study the mechanism of carbon contamination deeply, an effective theoretical model of the carbon deposition on the multi-layer surface and experimental equipment for studying the carbon contamination are established. The theoretical model describes the transport of residual hydrocarbons to the irradiated area and the subsequent dissociation of the hydrocarbon by direct EUV radiation and secondary electron excitation, and indicates that the direct EUV radiation is the primary reason to dissociate the hydrocarbon, and makes the carbon deposited on the surface of multi-layer. Various carbon deposition states are simulated by the theoretical model, and some effective simulated results are obtained. Optical design scheme and structure design scheme of the experimental equipment are presented. The optical system includes two spherical multi-layer mirrors and a plane mirror multi-layer mirror. Ray trace and EUV intensity on sample are calculated, the light spot on sample is about Φ10mm and the EUV intensity is about 0.126mW/mm2. Structure of the experimental equipment includes adjusting mechanism of two spherical mirrors, rotary mechanism of plane mirror, alignment mechanism of EUV source, adjusting mechanism of sample, and so on. After testing, linear resolution and angle resolution of two spherical mirrors adjusting mechanism are 1μm and 5μrad respectively; linear displacement and linear resolution of sample adjusting mechanism are 50mm and 1μm respectively. The structure design scheme meets the requirement of the carbon contamination experiment.