| Large-size diffraction gratings have very important applications in many areas of science and technology. It is limited by aperture of lens in exposure system for manufacturing large, high-quality holographic gratings by conventional single exposure. Scanning beam interference lithography system combines some features of the traditional interference lithography, laser direct writing and mechanical ruling in the manufacturing method. It is a new method of making holographic gratings in recent years. The basic working principle of the system is that by interfering two small diameter Gaussian laser beams to produce a grating image, it produces large holographic gratings by step-and-scanning the substrate on the stage. It is essentially making gratings by dynamic scanning and stepping mosaic exposure in scanning beam interference lithography system. Interference fringes are recorded to the photoresist in the form of energy integral and their pattern will directly or indirectly affects the dose contrast and printed error. Thus, it is necessary to analyze the effects of interference fringes errors on exposure dose, measure and adjust these errors. Thesis includes the following contents.Firstly, the influence of the angle between fringe direction and scanning direction on dose contrast in Scanning beam interference lithography system is analyzed. Method of fringe direction adjustment based on the metrology grating is proposed and its feasibility is theoretically analyzed. Taking advantage of grating phase shift property and beam alignment, the angle of fringes direction is adjusted to less than 20μrad. Secondly, factors affecting the interference fringes nonlinear phase error and the effects of fringes nonlinear phase errors on the scanning exposure dose are analyzed. Accurate measurement and adjustment method of fringes nonlinear phase error is given. Thirdly, effects of measure interference fringe period error on dose contract are analyzed. According to the exposure and development model of scanning beam interference lithography, variation of groove profile with measured fringe period error is given. The effect of the measured fringe period error on printed phase is analyzed and variations of printed error and lithography grating period are given. And then the tolerance of measured interference fringe period error is obtained. Fourthly, according to the characteristics of scanning beam interference lithography system, method of measuring the fringe period with a beam splitter movement is proposed. Based on Gaussian beam propagation theory, the theoretical error of this method is analyzed. Period counting and discrete Fourier transformation method is applied to calculate fringe period. In order to make it easy for two-dimension stage design, measuring period by short-stroke linear stage’s assistance is put forward and experiments are done. Experiment results show that the period measurement repeatability is 10.8 part-per-million(1σ). In this paper, measurement and adjustment of interference fringes in scanning beam interference lithography system is researched in depth. This is the basis for scanning lithography to produce Large-size holographic grating. It is important to develop the system and produce holographic gratings. |
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