用α能损法测量薄膜厚度所需真空度的确定方法

用α能损法测量薄膜厚度及其厚度分布的均匀性是一种有效的新方法，但这种测量必须在真空室内进行，如何恰当地选择真空度对于提高测量精度和降低真空系统的建造成本都具有重要意义。通过采用SRIM软件模拟5.486 MeV α粒子在空气中的阻止本领，计算出在不同真空度时，从241Am源发出α粒子穿过不同距离达到探测器时的能量损失，得到α粒子能量损失与真空度的关系。根据这一关系，结合所建α能谱仪在测量过程中的稳定性和重复性，建立了用α粒子测量薄膜厚度所需真空度的确定方法，并用这一方法得到了在源与探测器距离为2~8 cm时，小于100 Pa的真空度能完全满足测量要求的结果。

Abstract

The alpha energy-loss method is an effective and novel way to measure film thickness and thickness uniformity. But this kind of measurement should be carried out in a vacuum chamber. How to choose the appropriate vacuum degree is of great importance for improving the measurement precision and reducing the construction cost of the vacuum system. In this paper, we simulate the process of alpha particles with a power of 5.486 MeV going through air by using the software SRIM, calculate the energy loss of α particles coming from Am-241 through different air distances between the source and the detector with different vacuum degrees and obtain the relationship between the energy loss and the vacuum degree. According to this relationship, combined with the stability and repeatability of the measurement of alpha spectrometer, we have found the method of determining the required vacuum degree in the chamber for measuring the film thickness with alpha particles. Based on the result, we get a conclusion that a vacuum degree less than 100 Pa will completely meet the requirement of sufficient accuracy when the distance between the source and the detector is 2-8 cm.

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许佳, 徐家云, 马小军, 宋佳玲, 黎刚, 张敏超, 王力. 用α能损法测量薄膜厚度所需真空度的确定方法[J]. 强激光与粒子束, 2016, 28(8): 28084002. Xu Jia, Xu Jiayun, Ma Xiaojun, Song Jialing, Li Gang, Zhang Minchao, Wang Li. A method to determine the vacuum degree while measuring the thickness of thin films using energy loss of α-particles[J]. High Power Laser and Particle Beams, 2016, 28(8): 28084002.

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