Analysis of Mechanism of Reactive Ion Etching by Real-time Spectroscopic Ellipsometry

研制了一台带有电荷耦合器件的多道椭圆偏振光谱仪，用于分析氮化硅、二氧化硅和碳化硅薄膜在O2/CF4等离子体中的干法刻蚀过程。主要研究成果如下：1.首次设计和搭建了由白光光源(氙灯)、准直器、旋转偏振器、样品台、固定分析器、光谱仪、CCD探测器和CCD控制器组成的多通道椭偏仪。2.对椭偏仪光学系统进行了一系列的标定。对椭偏仪的性能进行了全面的标定，在470~1060 nm波长范围内，一次光谱的最小采集时间为100ms，椭圆偏振参数的标准偏差小于0.1度。3.采用离子束溅射方法在硅和铂衬底上沉积了Si^3N_4、SiO_2和碳化硅薄膜。通过X射线光电子能谱(XPS)和原子吸收光谱(AESS)分析，确定了适合获得化学计量比化合物的沉积参数。4.用实时椭圆偏振光谱仪研究了氮化硅、二氧化硅和碳化硅薄膜在O2/CF4等离子体中的刻蚀过程。结果表明，随着刻蚀过程的进行，薄膜的刻蚀速率和微结构发生了快速变化。

A multichannel spectroscopic ellipsometer equipped with a CCD detector has been developed and applied to the analysis of dry etching processes of thin Si_3N_4, SiO_2 and SiC films in O_2/CF_4 plasma. The results are summarized as follows :1.A multichannel ellipsometer consisting of a white light source (Xe lamp), a collimator, a rotating polarizer, a sample stage, a fixed analyzer, a spectrometer, a CCD detector, and a CCD controller has been originally designed and constructed.2.A series of calibration was carried out to eliminate systematic errors arising from optical systems of the ellipsometer. The performance of the ellipsometer was evaluated after the complete calibration ; the minimum acquisition time of one spectrum over the wavelength range of 470 to 1060nm is 100ms, and the standard deviation in ellipsometric parameters is less than 0.1 degrees.3.Thin films of Si^3N_4, SiO^2 and SiC have been deposited on Si and Pt substrates by ion beam sputtering. The deposition parameters suited to obtain stoichiometric compounds were determined through the analysis of chemical composition by XPS and AES.4.Etching processes of Si_3N_4, SiO_2 and SiC films in O^2/CF^4 plasma were examined by real-time spectroscopic ellipsometry. It was found that the rapid changes in the etching rate and microstructure of the films occur as etching proceeds.