Research On Large Grating Flatness And Pitch Deviation Measurement Technology

Microstructure grating size is more widely used in microns or submicrometer range and caliber reaches hundreds of millimeters or even large meter-size plane diffraction grating, a new generation of lithography machines and other ultraprecision test equipment, inertial confinement fusion and other large scientific and engineering, it plays a vital role in and technology in the field of modern science and advanced military technology science. Diffracted wave front is an important performance index of the diffraction grating, Diffracted wave front is determined by the quality of the microstructure grating quality, Wherein the overall flatness of the grating and the dispersion of the grating period are the main causes of the diffracted wave front distortion and they are the decisive factor of diffracted wave front quality. The measurement and evaluation of the overall flatness of the grating period and the grating dispersion have important research and application value."research on large grating flatness and pitch deviation measurement technology " is to study the influence of the grating overall flatness and the degree of non-ideal grating period on the wave-front, from the perspective of the wave-front aberration. Taking the large size flat grating as the research object, it is based on the principles of equal thickness interference and the zero order diffracted light and the first-order diffracted light of the microns period grating are respectively interfered with the standard plate. The subject evaluates the non-ideal degree of the grating period and the flatness of large-size plane grating, and strives to provide a method and means for evaluation of the large-size flat grating quality. The main contents of the subject are as follows:First, for the aim to obtain the grating flatness, based on the basic principles of the equal thickness interference, the zero order diffracted light of the microns periodic planar grating interferes with the standard plate.For the aim to obtain the grating flatness and periodic dispersion, the ? first-order diffracted light interferes with the standard plate respectively,and design the overall measurement program.In order to achieve large grating flatness and period dispersion measurements, the interference measurements stitching from a small-sized to large-sized sub-aperture is implemented by the stitching method. The subject studies the stitching method and the homogenizing error method,verifies the stitching algorithm with the program, splices the ideal interference data, verifies the validity and effectiveness of the program.The subject builds a experimental measurement device of the large grating flatness and period dispersion,designs the plane grating clamping device, and measured the 8μm pitch plane grating. Under conditions of a single aperture,the peak-to-valley values of the local flatness is 76.6nm, The peak-to-valley values of the local X-directional pitch deviations is 533.1nm. For the stitching of four sub-aperture, The peak-to-valley values of the 100 mm × 100 mm plane grating flatness is 117.1nm, The peak-to-valley values of X-directional pitch deviations is 579.2nm. The subject provides a technical approach to evaluate the surface quality of large-size type plane grating.