低噪声非晶硅锗合金薄膜电学性能研究

发布时间：2018-10-07 20:57

【摘要】：非制冷红外焦平面探测器在军用和民用领域得到了广泛应用，而具有自主知识产权的小尺寸、长寿命和高性能的非制冷红外焦平面探测器，是我国高科技领域的迫切需求。其中，深入探索和研究具有优异电学性能的低噪声红外敏感薄膜，意义重大。氢化硅锗合金薄膜因具有更高的光吸收效率（锗的吸收系数比硅高出1～2个数量级）、更低的电阻率和更佳的电学性能，而在红外成像传感器领域有着良好的应用前景而备受关注。此外，采用等离子体增强化学气相沉积技术（PECVD）制备氢化硅锗合金薄膜，工艺成熟稳定，与硅半导体工艺的兼容性良好，便于工业应用。 薄膜噪声测试目前仍存在有很多不确定性因素，本文简要阐述了薄膜噪声产生的机理和物理模型，以便确定薄膜噪声的测试方案。为了能够系统地评价薄膜的噪声水平，自行搭建了一个薄膜噪声测试平台，以确保噪声测试结果的可靠性，并建立了统一的评价手段。 利用射频等离子体增强化学气相沉积（RF-PECVD）系统裂解硅烷和锗烷，并辅助以氩气稀释，制备氢化硅锗（Si1-xGex:H）合金薄膜。借助原子力显微（AFM）、X射线衍射（XRD）、拉曼光谱（Raman）和傅里叶变换红外光谱（FTIR），分析和研究不同氩稀释比例下薄膜样品的结构演变和晶化状况。研究发现，在Si1-xGex:H合金薄膜的晶化生长过程中，氩的引入及其对硅烷和锗烷的稀释发挥了重要的作用。当氩稀释比例（氩气与硅烷/锗烷混合气比例）相对较低约为4时，在非晶网络中开始出现纳米晶粒。随着氩稀释比例的增加，薄膜表面粗糙度、薄膜内纳米晶粒尺寸、晶化体积比和氢含量均有不同程度的增加。同时发现，随着氩稀释比例的提高，薄膜的电导率和电阻温度系数TCR均有微弱的提高。值得关注的是，由于氩稀释在非晶网络中引入了纳米晶化，薄膜的有序度得到提高，极大地改善了薄膜低噪声水平。 为了进一步提高薄膜的电学性能水平，，本文还研究了硼掺杂对氢化微晶硅锗薄膜的影响。测试结果表明，当硼掺杂比例为1%时，薄膜在室温下有较高的电导率（≥10~(-2)S/m）和较高的TCR（≥3%/K），薄膜噪声处于较低的水平。
[Abstract]:Uncooled infrared focal plane detectors have been widely used in military and civil fields. The uncooled infrared focal plane detectors with small size, long life and high performance, which have independent intellectual property rights, are the urgent needs in the field of high technology in China. Among them, it is of great significance to explore and study low noise infrared sensitive thin films with excellent electrical properties. Because of its higher optical absorption efficiency (the absorption coefficient of GE is 1 ~ 2 orders of magnitude higher than that of Si), the film has lower resistivity and better electrical properties. In the field of infrared imaging sensors, it has a good application prospect and has attracted much attention. In addition, SiGe alloy films prepared by plasma enhanced chemical vapor deposition (PECVD) technology are mature and stable, and have good compatibility with silicon semiconductor process, which is convenient for industrial application. There are still many uncertain factors in the measurement of thin film noise. In this paper, the mechanism and physical model of film noise are briefly described in order to determine the measurement scheme of film noise. In order to evaluate the noise level of thin films systematically, a film noise testing platform is set up to ensure the reliability of the noise test results, and a unified evaluation method is established. Silicon germanium hydride (Si1-xGex:H) alloy thin films were prepared by radiofrequency plasma enhanced chemical vapor deposition (RF-PECVD) system. The structure evolution and crystallization of films with different argon dilution ratios were studied by atomic force microscopy (AFM) X-ray diffraction (XRD), Raman spectroscopy (Raman) and Fourier transform infrared spectroscopy (FTIR),). It is found that the introduction of argon and its dilution of silane and germanium play an important role in the crystallization and growth of Si1-xGex:H alloy films. When the ratio of argon dilution (ar / silane / germanium mixture) is about 4, nanocrystalline grains begin to appear in the amorphous network. With the increase of argon dilution ratio, the surface roughness, nanocrystalline size, crystallization volume ratio and hydrogen content increase in varying degrees. It was also found that the conductivity and the resistance temperature coefficient (TCR) of the films increased slightly with the increase of the argon dilution ratio. It is worth paying attention to that the order degree of the films is improved and the low noise level of the films is greatly improved because of the introduction of nanocrystalline crystallization in the amorphous network by argon dilution. In order to further improve the electrical properties of the films, the effect of boron doping on hydrogenated microcrystalline silicon germanium films was also studied. The results show that when boron doping ratio is 1, the film has high conductivity (鈮

本文编号：2255645