基于差分反射光谱的真空环境有机薄膜生长在线监测方法

有机薄膜器件是微电子和光电子领域的重点研究方向。薄膜制备过程的在线监测作为研究成膜机理和优化工艺参数最直接的测量手段，对薄膜器件的高质量制备具有重要意义。为实现真空环境有机薄膜制备过程的实时在线监测，提出了一种基于差分反射光谱术的高精度测量方法。采用离轴抛物面反射镜、光学平板和光纤等基本光学元器件构建紧凑型光路系统，运用差分算法分析光谱信号，具有较高的测量性能。测试了不同实验环境下光谱信号的波动，得出在控温条件下，系统的长时间测量重复性优于2‰。还研究了并五苯分子通过分子束外延制膜法在Au基底成膜初始阶段的生长过程。通过与膜厚仪和原子力显微镜测试结果比对，光谱信号精确反映出超薄膜在生长中引起的细微光学演变，其测量精度优于亚单分子层。实验结果表明，该差分反射光谱测量系统具有宽光谱(300～820 nm)、高稳定性(重复性优于2×10-3)、高测量精度(亚单分子层)等特点，并有效地抑制了光路装配误差、光学器件缺陷和环境干扰等对光信号的影响，作为一种高精度表面表征方法，适合于薄膜制备过程的实时在线监测。

Differential Reflectance Spectroscopy for In-Situ Monitoring of Organic Thin Films Growth in Vacuum Environment

For realizing the real-time monitoring of organic thin film preparation process in vacuum environment, the present paper proposes a high precision measurement approach based on differential reflectance spectroscopy (DRS). An optical system was constructed with off the shelf optical components, such as off-axis parabolic mirror, optical flat and optical fiber. A differential algorithm was employed to analyze the spectral signals. Based on the homebuilt setup, instability induced by variation of temperature was investigated. It was concluded that with the good control of temperature and air flow, the measurement repeatability of this system is better than 2‰ for a long-term period. Furthermore, an initial stage of organic thin film growth of pentacene molecules on the surface of Au was studied. As compared with the data of film thickness gauge and atomic force microscope, DR spectra accurately recorded the fine optical evolution with sub-monolayer resolution, which is related to the growth of the thin film. As a result, the DR optical system exhibits characteristics of broad spectrum (range from 300 to 820 nm), high stability (repeatability better than 2×10-3), and high precision (sub-monolayer resolution) after efforts were done to decrease the influences on the spectral quality produced by misalignments of the optical components, the defects of the optics, and the disturbances of the environmental conditions. It is indicated that the proposed DR method is suitable for real-time online monitoring of thin film growth with high precision.