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单晶硅球间微量密度差异测量是阿伏伽德罗常数量子基准定义的重要研究内容,也是半导体产业中高纯度单晶硅制备工艺质量控制的主要方法.为了改善现有非接触相移干涉法测量装置复杂和静力称重法测量不确定度低的特点,根据单晶硅密度精密测量需要,实现了一种基于静力悬浮原理的单晶硅球密度相对参比测量方法.通过改变静压力和温度进行三溴丙烷和二溴乙烷混合液体密度的微量调节,分别使两个待测单晶硅球在液体中悬浮,根据悬浮状态时的液体温度和悬浮高度计算出待测单晶硅球密度差值.通过双循环水浴和PID温度控制系统实现±100μK的恒温液体测量环境.通过图像识别和迭代拟合算法实现单晶硅球悬浮高度的测量.使用PID静压力控制系统实现单晶硅球的稳定悬浮控制,同时减少Joule-Thomson效应引起的液体温度改变.利用静力悬浮模型中的温度变化和静压力变化线性关系准确测量出标准液体的压缩系数.试验结果表明,这种测量方法可以避免液体液面张力的影响,测量相对标准不确定度达到2.1×10(-7),能够实现单晶硅球密度差值的精密测量.
The measurement of the difference between the single crystal spheres is an important research content of the definition of the Avogadroe constant quantum basis and also the main method for the quality control of the high purity single crystal silicon in the semiconductor industry.In order to improve the existing non-contact phase shift interferometry According to the requirement of precision measurement of single crystal silicon density, a method of relative density measurement of single crystal silicon ball based on the principle of static levitation is achieved.Through changing static Pressure and temperature of tribromopropane and dibromoethane mixed liquid density of the micro-regulation, respectively, so that the two monocrystalline silicon balls to be suspended in the liquid suspension, according to the suspension state of the liquid temperature and suspension height calculated single crystal to be tested The difference of the density of the silicon ball.Through the double circulation water bath and the PID temperature control system to realize the constant temperature liquid measurement environment of ± 100μK, the single crystal silicon ball float height measurement is realized through the image identification and the iterative fitting algorithm.Using the PID static pressure control system to realize the single Crystal silicon ball steady suspension control, while reducing the Joule-Thomson effect caused by liquid temperature changes using the static suspension model temperature changes and The linear relationship between pressure and pressure accurately measured the compression coefficient of the standard liquid.The experimental results show that the measurement method can avoid the influence of the liquid surface tension and the relative standard uncertainty of measurement reaches 2.1 × 10 (-7) Precision measurement of ball density difference.