Study On Thickness Distribution Uniformity Control Of Soft X-ray Multilayer Mirrors

AbstractSoft X-ray has very strong interaction with matters, and was greatly expected in analysis of fundamental structure of matters. With the furthermore development of ultra thin film technology, soft X-ray multilayer mirrors was applied in many fields, such as astronomy, microscope technology, EUV Lithogrphy, X-ray Laser, ICF diagnosis and so on. When multilayers are applied in imaging system, lacks of uniformity of period thickness in large field will demage the super-polished figure of optics, and decrease the quality of image. In this paper, we mainly discuss multilayer mirrors for X-ray solar telescope operating at 17.1nm wavelength. The diameter of primary mirror for telescope is 130 millimeters and secondary mirror is 66mm. Especially, we will engage in controllation of uniformity of period thickness.Centering at soft X-ray multilayer uniformity technology, we introduce general situation of multilayer, design of multilayer structure, simulation calculation, ion-beam sputtering deposition and evaluation of samples. Above all, we carry out study of improving uniformity of period thickness spatial distribution, and develop correction mask for controlling period thickness. As a result, we improve uniformity from 4.5% to 2.0%, the error of period thickness on (130nm field is controlled within 0.18nm,and the reflectivity reach 35% at center wavelength 17.1nm.