Fabrication Of High Groove Density Freestanding X-ray Blazed Transmission Gratings

As a kind of important X-ray dispersive element, X-ray transmission gratings are widely used in plasma diagnosis and astrophysics. To effectively disperse the high energy band of X-ray and improve the spectral resolving power of transmission grating spectrometer, we need high groove density and high diffraction efficiency X-ray transmission gratings. New freestanding blazed transmission gratings, which can solve the low diffraction efficiency problem of traditional gold freestanding transmission gratings, has become a research focus.The aim of this thesis is to explore and master the whole techniques for fabrication of high groove density X-ray freestanding blazed transmission gratings. It will be a necessary technology storage for fabrication of high quality X-ray transmission gratings in the applications of laser inertial confinement fusion and astronomical observation in our country. The achievements are as follows.1. We systematically researched the methods of Lloyd-mirror interference lithography and nanoimprint lithography for fabricating5000I/mm grating pattern. The high quality photoresist grating is successfully fabricated using Lloyd-mirror interference lithography by improving stability of interference fringe, analyzing the contrast of interference fringe and controlling the exposure and developing condition. The high conformity PMMA grating pattern is successfully fabricated by introducing a flexible mold and combining the UV cured nanoimprint with thermal nanoimprint.2. Methods for aligning grating lines generated by Lloyd-mirror interference lithography or nanoimprint lithography to the vertical{111} planes of<110> oriented silicon wafers were developed. The alignment process for Lloyd-minor interference lithography consists of four steps:(1) locating the vertical{111} plane direction using a pre-etch technique with a fan-shape pattern,(2) fabricating reference grating parallel with the located spoke closest to the vertical {111} plane,(3) optimizing configuration of Lloyd-mirror interferometer,(4) aligning reference grating lines to interference fringes. And the alignment process for nanoimprint lithography consists of three steps:(1) locating the vertical{111} plane direction using a pre-etch technique with a fan-shape pattern,(2) fabricating reference grating parallel with the located spoke closest to the vertical{111} plane,(3) aligning reference grating lines to mold grating lines. The alignment errors are±0.033°and±0.067°respectively which are of high precision.3. Anisotropic wet etch technique was researched. An anisotropic wet etch model was established. The nonuniform etching problem was solved. And the etching conditions which can match fabrication process tolerance have been setted.4. Other techniques for fabrication of high groove density freestanding blazed transmission grating were systematically researched, including fabricating alignment pattern, units of grating sample, freestanding structure and SiN mask, removing the back substrate, and supercritical point drying of high aspect ratio silicon grating.5.3000l/mm and5000l/mm freestanding blazed transmission grating have been successfully fabricated. The3000l/mm grating consists of four windows with size of5mm×5mm. The grating bar thickness is of5μm, and the bar width is of65nm in the top and80nm in the bottom. The5000l/mm grating also consists of four windows with size of5mm×5mm. The grating bar thickness is of1.6μm, and the average bar width is of40nm.