17. 1 nm 极紫外滤光片的制备

Preparation of EUV Filter at 17.1 nm

为了预警空间天气,需对日地空间物理过程进行监测,极紫外(Extreme Ultraviolet, EUV)滤光片是极紫外成像仪其中的重要组成部分,用来去除太阳辐射光谱中的非工作波段的辐射。为了优化EUV滤光片在17.1 nm波长处的透过率,本文基于比尔-朗伯定律通过理论计算和软件模拟确定17.1 nm EUV滤光片的材料及厚度。首先,采用真空热蒸发的方式在熔石英基底沉积脱膜层和金属薄膜,成功制备了以镍网为支撑的EUV滤光片。经测试,滤光片在17.1 nm处的透过率约为43.81%,表面光滑平整且无明显针孔。接下来为了说明氧化层对透过率的影响,使用椭圆偏振光谱仪测量滤光膜样品,得到放置不同时间的氧化层膜厚,并测得粗糙度来优化模拟滤光片透过率。利用IMD拟合样品氧化层厚度及粗糙度,调整层厚达到与实际测量值最为接近的曲线。实验结果表明滤光片透过率的模拟值与测量值绝对误差约1%,符合良好。本文为17.1 nm EUV滤光片提供了制备方法以及优化思路,在空间探测领域有重要应用价值。

In order to forecast and warn of space weather, the disturbances of solar-terrestrial need to be monitored. Extreme Ultraviolet(EUV) filters can remove unwanted radiation, and they are an important part of the Extreme Ultraviolet Imager. In order to optimize the transmission of EUV filters at 17.1 nm, we chosen the material and thickness of EUV filters at 17.1 nm based on the Lambert-Beer law by theoretical calculation and software simulation. First, the release layer and metal thin-film were deposited by thermal evaporation, and EUV filters with nickel-mesh supported were successfully manufactured. After testing, the transmission of the filter whose surface is smooth and flat without obvious pinholes is about 43. 81% at 17.1 nm. Next, in order to illustrate the effect of the oxide layer on the transmittance, the filter sample was measured by spectroscopic ellipsometry to obtain the thickness of the oxide layer at different placement times, and the roughness was measured to optimize and simulate the transmission of the filter. The thickness of the oxide layer and the roughness of the sample were fitted by IMD, and the layer thickness was adjusted to achieve the curve closest to the actual measured value. Experimental results indicate an excellent agreement between the measured and simulated values, and the absolute error of the transmittance of the EUV filter is only 1%. This study provides preparation methods and improvement ideas for EUV filters, and has important practical significance in space exploration.