This tech could have it use in EUV mask inspection, EUV Lithography research, X-Ray IC metrology.
Microfocus X-ray Grating Interferometer for Wavefront Sensing
After the discovery of synchrotron radiation on a synchrotron in 1947, the development of electronic synchrotron radiation devices has gone through three generations. Synchrotron radiation is an excellent light source with high intensity, high brightness, and high spatial, temporal, and energy resolution. It can be used to observe dynamic processes at the nm scale. The fourth-generation and free electron lasers close to the diffraction limit have greatly improved coherence, and coherent experiments can be carried out. The brightness is increased by several orders of magnitude. X-rays are electromagnetic waves with very short wavelengths. The fourth-generation synchrotron radiation light source and large scientific facilities such as X-ray free electron laser devices have the characteristics of high brightness, high coherence, and high collimation. Their beams are close to the diffraction limit and Fourier transform limit, and high spectral resolution, high spatial resolution, and high temporal resolution experiments can be carried out. The beamline system is a bridge between the light source and the experimental station. Maintaining the wavefront shape and high-fidelity transmission of the X-ray beam coherence is of great significance for conducting synchrotron radiation experiments, which poses a challenge to the manufacture and detection of high-precision optical devices. Beam quality can be affected by, for example, roughness of reflective or transmissive surfaces, large-scale form errors, misalignment of optical components, or miscalibration of adaptive elements such as bendable mirrors or crystals.
The micro-focus X-ray grating interferometer consists of a phase grating G1 as a beam splitter, an absorption grating G2 as a detector transmission mask, and an X-ray camera. After the X-rays are incident from the mirror surface, the periodic interference pattern (Talbot self-imaging) downstream of the phase grating causes a phase shift due to the wavefront distortion caused by the slope error of the mirror surface. Since the interference pattern period is small, conventional X-ray cameras cannot distinguish the phase shift signal, and the phase shift signal can be amplified by adding an analysis grating. The phase stepping technology or Fourier analysis technology can be used to analyze the fringe phase and wavefront curvature radius distribution, and then calculate the wavefront angle (phase gradient) and mirror slope error distribution. The schematic diagram of the micro-focus grating interferometer is shown in the figure below.
The micro-focus X-ray grating interferometer consists of a phase grating G1 as a beam splitter, an absorption grating G2 as a detector transmission mask, and an X-ray camera. After the X-rays are incident from the mirror surface, the periodic interference pattern (Talbot self-imaging) downstream of the phase grating causes a phase shift due to the wavefront distortion caused by the slope error of the mirror surface. Since the interference pattern period is small, conventional X-ray cameras cannot distinguish the phase shift signal, and the phase shift signal can be amplified by adding an analysis grating. The phase stepping technology or Fourier analysis technology can be used to analyze the fringe phase and wavefront curvature radius distribution, and then calculate the wavefront angle (phase gradient) and mirror slope error distribution. The schematic diagram of the micro-focus grating interferometer is shown in the figure below.
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