薄膜生长的宽光谱监控技术及其应用研究

【作者】 蔡清元；

【导师】 郑玉祥；

【作者基本信息】 复旦大学 ， 光学， 2011， 博士

【摘要】 高性能的光学薄膜器件的制备需要有先进的薄膜制备技术、监控技术及检测技术作支撑。作为一种非常重要的薄膜生长监控技术,光学监控技术正从单波长监控方式向多波长和宽光谱监控方式发展。以提高薄膜生长监控精度及薄膜生长工艺为目标,本论文针对宽光谱监控技术进行了研究,同时也研究了生长速率、薄膜厚度、温度等参数对薄膜的光学常数的影响。主要内容包括：1、研制了用于电子束蒸发薄膜生长设备的一套宽光谱监控系统,解决了系统研制过程中的各种软硬件问题。对传统的宽光谱监控数据处理方法进行了改进,大大减少了计算量。提出软硬两种处理方法去除衬底干涉噪声,并分别采用K9玻璃衬底和双面抛光硅片衬底制备了窄带滤波片,均实现了良好的带通特性。利用宽光谱监控系统的在位误差补偿功能,所制备的薄膜的最终光谱与理论模拟光谱符合得很好,验证了所研发的红外宽光谱监控系统具有满意的监控效果。2、研究了SiO2薄膜光学常数随生长厚度变化的趋势,及这种趋势与生长速率的关系。利用电子束蒸发方法在硅片衬底上制备系列SiO2薄膜样品,厚度范围为～1m到600nm。采用变角度椭圆偏振光谱仪对薄膜样品进行测量,每个样品获得200多组椭偏参数。选用适当的模型进行拟合得到了SiO2薄膜的折射率色散关系及厚度值。实验结果表明快速生长和慢速生长的SiO2超薄膜的折射率随厚度变化趋势不同,慢速生长的薄膜更容易形成致密膜层。3、基于单振子的洛伦兹色散模型,分析了材料的光学常数随温度变化的关系。采用自制的温度可变的椭偏测量样品室对样品进行变温,从而实现了在不同温度下对样品进行椭偏参数的测量,并进一步获得不同温度条件下样品光学常数的色散曲线。作为例子,对硅片和金膜进行了变温椭偏测量。测量结果显示,材料光学常数随温度发生了变化,能隙左右的光学常数随温度变化的趋势不同,与包含温度因素的洛伦兹色散模型的理论分析相符合。实验表明,变温椭偏适合用于确定一些固体材料(例如半导体)的能隙位置。更多还原

【Abstract】 The manufacturing of the optical thin film devices with high performance depends on the development of the advanced film deposition, monitoring and measurement techniques. As one type of the important monitoring techniques for film deposition, optical monitoring methods have always attracted much attention. In place of conventional single wavelength monitoring, multi-wavelength monitoring and broadband optical monitoring have been developed. With the purpose of improving the effect of the monitoring methods for film deposition and the quality of the deposition technique, the work focused on developing a broadband optical monitoring system and studying the effect of the deposition rate、film thickness、temperature etc. on the optical constants of the deposited films. The main work is shown as follows:1. A broadband monitoring system was set up with solving encountered software and hardware problem and applied to an electron beam evaporation system for film deposition. The conventional data processing was improved and the computational amount was obviously reduced. Both hardware-based and software-based methods were proposed to filter the interferential effect caused by the substrate. The noise-filtering methods were applied to the real deposition of narrow band filters using both K9 glass and silicon as substrates, and with in-situ error compensation process based on BOM technique, several narrow band filters with good performance, which is in accordance with the theoretical design, were finally obtained. The results demonstrated the validity of this broad band monitoring method on film deposition.2. The thickness dependence of the optical constants of SiO2 films at different deposition rates was studied. All samples of SiO2 films with thickness ranging from～1 nm to 600 nm were deposited on Si substrates by EBE method, and then measured with variable-angle spectroscopic ellipsometry(VASE). More than 200 sets of ellipsometric parameters were obtained for each sample. The optical constants and thicknesses of SiO2 films have been obtained with fitting the measured data using appropriate model. The results showed that the evolution of optical constants of SiO2 films with thickness differs for the samples deposited at higher rates and the samples at lower rates, and it is favorable to deposit films at low rate for getting denser film.3. The temperature dependence of optical constants of solid materials was analyzed using the single-oscillator-based Lorentz dispersion model. The spectroscopic ellipsometer was applied to the measurement of the samples at different temperature and a self-built sample box with temperature variable was used to keep sample at a certain temperature during measurement. The dispersion curves of samples for various temperatures were obtained. At present, the temperature dependence of optical constants for Si and Au samples were studied using the spectroscopic ellipsometry (SE) with temperature variable. The results showed that, the optical constants of materials change with temperature, and the trend of variation with temperature for the optical constants below the gap and above the gap is different, which is in accordance with the theoretical analysis using the Lorentz dispersion model with considering temperature effect. The SE with temperature variable can be applied to determination of the energy gap for some solid materials such as semiconductors.更多还原