Preparation Of X-ray Fresnel Zone Plate Based On Atomic Layer Deposition Technique

X-ray has short wavelength,high energy and strong penetrating power..X-ray microscopic imaging technology can be used for three-dimensional non-destructive detection and imaging of materials.X-ray microscopic imaging technology is used in many fields such as biomedicine,materials science,and integrated circuits.The X-ray Fresnel zone is composed of a series of concentric rings of equal area and is the core component of focusing and imaging in X-ray microscopy.According to the Rayleigh resolution formula and the X-ray diffraction focusing characteristics,the resolution of the Fresnel zone plate is determined by its outermost ring width and the diffraction efficiency depends on the aspect ratio of the zone plate.The conventional processing technique of the X-ray Fresnel zone plate is prepared by electron beam exposure and metal plating.With the deepening of scientific research,X-ray microscopic imaging is developing in the direction of high resolution,high diffraction efficiency and high energy band,and the resolution is gradually approaching 30 nm.The fabrication techniques based on electron beam exposure have approached the technical limits for nanoscale and large aspect ratio structures.At present,researchers are working on the limitations of electron beam exposure on the basis of traditional processes,and developing nano-processing innovation processes for high-resolution and high-diffraction-efficiency X-ray zone films.In this thesis,the high-precision multi-layer waveband are deposited on the surface of central filaments by ALD,Then the focused ion beam(FIB)cut into the desired thickness to achieve an ultra-large aspect ratio for arbitrary requirements.The main contents are divided into the following three parts.(1)By calculating the relationship between the structural parameters of the X-ray Fresnel zone plate and the diffraction efficiency under different material systems,the material selection rules of the X-ray zone plate are clarified,and the maximum diffraction efficiency of the zone plate under the four material systems is determined(Al2O3/HfO2?Al2O3/Ir?SiO2/HfO2?Al2O3/Ta2O5).Soft and hard X-ray band plates with energy of 500 eV and 9 keV were designed.Al2O3/HfO2 was chosen as the laminated material.The center wire diameter of the zone plate was 30 and 55 m,the number of rings was 174 and 216,the width of the outer ring were 25 and 40 nm,and the thickness of each ring was determined.(2)In this paper,the growth characteristics of Al2O3,HfO2,and Ta2O5 thin films prepared by ALD on single-sided polished silicon wafers were investigated.The central glass fibers were prepared by etching the cladding of optical fibers by hot corrosion method,and tungsten wires with small roughness were prepared by electrochemical etching polishing as the central wires of Fresnel zone plates.The 10-nm thick layers were fabricated on single-sided polished silicon wafers and filaments,which indicated that the fabrication process using SEM,AFM and ellipsometer features was not affected by the substrate materials.Then,tungsten wire and glass fiber are used as center wires to fabricate soft and hard X-ray zone plate multilayers.(3)The X-ray zone plate was fabricated by FIB cutting and polishing Al2O3/HfO2 multilayers with an energy of 9 keV and an outer ring width of 40 nm,and the imaging performance was tested.Three different characteristics of the zone plate sample holder were designed,and the diffraction efficiency of the hard X-ray zone plate was initially detected to be 7.8%.