【作者】 邱克强；

【导师】 付绍军；

【作者基本信息】 中国科学技术大学 ， 同步辐射及应用， 2008， 博士

【摘要】 作为X射线波段的一种重要色散元件,金透射光栅主要用于激光惯性约束核聚变(ICF)实验中的等离子体诊断,以及X射线天体物理研究的高能透射光栅光谱仪中。使用全息光刻技术制作金透射光栅工艺复杂,尤其是制作具有高线密度的自支撑金透射光栅。因此,对其制作工艺进行系统化的研究十分必要。本课题的目的是要掌握软X射线透射光栅的制作工艺,并制作出高线密度自支撑金透射光栅。论文的主要内容包括:1.对全息光刻制作光刻胶掩模工艺进行了深入的研究。建立了曝光监测与显影监测系统,通过大量的实验与分析,能够根据监测曲线的变化趋势,较为准确地确定不同基片所需要的最佳曝光量及最佳显影时间,实现了对曝光及显影过程的控制。2.对两种光刻胶掩模图形转移工艺技术——离子束刻蚀与电镀工艺,从实验上进行了探索。尝试了消除金再沉积现象的两种常见方法——倾斜旋转刻蚀与使用薄掩模,并取得了显著的效果。对电镀沉积金的工艺,从实验上探讨了电镀液的温度、pH值以及电流密度对电镀沉积制作的金光栅质量的影响,根据对实验结果的比较与分析获得了较为合适的电镀条件。3.计算并模拟了全息曝光过程中光刻胶内的光强分布,计算与实验结果证实了来自基底的反射光将与入射光干涉,从而使光强分布出现明显的驻波效应。进一步的分析与实验结果表明,随着基底反射率的增加,驻波效应变得越来越严重,进而给全息光刻制作的光刻胶光栅掩模的槽形、占宽比带来不利影响,并减小对曝光光束光强偏差的宽容度。因此,基底的高反射率将给光栅掩模的制作带来麻烦,尤其是利用全息光刻制作具有较窄线宽的高线密度光刻胶光栅掩模。最后提出了通过在基底与光刻胶之间增加一层减反射膜(ARC)的办法吸收来自基底的反射光强度,以减弱驻波效应的办法。实验结果表明这种方法效果显著。4.设计并制作了位相型金透射光栅,光栅的周期1μm,槽深约200nm,占宽比约0.55,面积5mm×15mm。在中国科技大学国家同步辐射实验室的光谱辐射标准与计量站测量了它在5—12nm波段的各级透射衍射效率,结果表明,在7.425nm波长处,其1级衍射效率大约为16%。5.探讨了在基底与光刻胶之间增加减反膜层后,制作自支撑金透射光栅的工艺过程,并对减反膜层的制备、保护层的制作,减反膜的反应离子刻蚀、电镀掩模占宽比的控制、电镀中应注意的问题以及支撑结构的制作等工艺细节进行了较为全面的实验研究。制作出了周期290nm,面积达10×15mm的自支撑金透射光栅。自支撑结构占宽比约35%。经测量,其1级衍射效率约为4—6%。更多还原

【Abstract】 As one of important dispersive elements usually used in x-ray region, gold transmission gratings find increasing applications in plasma diagnostic in Inertial Confinement Fusion, and in High Energy Transmission Grating Spectrometer (HETGS) used in x-ray astrophysics. It is complicated to produce a gold transmission grating by holographic lithography, especially for self-standing transmission gratings with high frequency. So it is necessary to have a systematic and detailed study on the fabrication of gold transmission gratings.The main purpose of this thesis is to master the fabrication process of soft X-ray transmission gratings and to fabricate some self-standing gold gratings with high frequency. The subject matter of the thesis are as the follows:(1) In-depth study on the fabrication process of a pattern transfer mask by interferometric lithography. A monitoring apparatus for latent image during exposure and for developing diffraction gratings in a photo-resist has been set up and the relationship between the intensity of latent image and exposure dose and development has been investigated, by which the optimum exposure dose and development time of photo-resist on surface having slight variations in optical properties can be simulated.(2) Experimentally study on the ion beam milling and electroplating which usually are used to transfer the mask patterns into gold during fabrication of gold transmission gratings. It is demonstrated that redepostion is a problem during process of milling gold, but experimental results indicates it can be cleared away by inclining and rotating the sample or using thinner mask instead of thicker photoresist mask. As far as electroplating, it is known that some influence factor such as pH, temperature of solution and current density have an impact on the quality of gold deposited by electroplating. Optimum parameters have been given by comparing results which are obtained by electroplating a large number of samples.(3) The distribution of intensity of incident irradiation in photoresist during exposure has been figured out, and it is shown that the pattern in photoresist on surface with high reflectivity will suffer from standing wave as a result that the incidence irradiation interference with the reflective light from the photoresist-substrate interface. The higher the reflectivity, the worse the effection of standing wave, and it is shown that the standing wave will have a bad effects on the profile and the duty cycle of photoresist grating and decrease the tolerance of the difference between intensity of the two incident beams. So the reflectivity of substrate must be decreased for perfect photoresist patterns transfer mask, especially for mask with finer period and small and limited linewidth. The anti-reflection coating has been used to decrease intensity of reflected beam from substrate and it is proved to be a good way.(4) Some gold transmission phase grating with 1μm period, 200nm height, 0.55 duty cycle and a size of 5mm×15mm have been produced to achieve higher efficiencies than opaque gratings in the range of 5-12nm region. Efficiencies have been measured in the Spectral Radiation Standard and Metrology Experiment Station of National Synchrotron Radiation Laboratory (NSRL) and the efficiency of the +1st order is about 16%.(5) Study on the bi-level resists process in which photoresist patterns are imaged and developed in resist over an antireflection coating. It contains a durable material (i.e. durable layer), typically a metal such as chromium, needed to be shadow-evaporated to cap the resist structure to transfer the resist pattern, reactive-ion etching (RIE) the antireflection coating (ARC) and controlling of the duty cycle of plating mask, the related problem with electroplating and the fabrication of mesh-support structure. At last, a mesh-supported gold transmission grating with 290nm period and a size up to 10mm×15mm is finished. The total obstruction of support structures is about 35%. The diffraction efficiency has been measured and the efficiency of the 1st order is about 4%-6%.更多还原