碲镉汞红外光伏探测器电学性能表征技术研究

发布时间：2018-01-11 20:30

本文关键词：碲镉汞红外光伏探测器电学性能表征技术研究　出处：《中国科学院研究生院(上海技术物理研究所)》2015年博士论文　论文类型：学位论文

【摘要】：碲镉汞半导体材料以其优良的光电特性,自问世以来就成为制备高性能红外探测器的重要材料。随着第三代碲镉汞红外探测器技术的快速发展,低成本大规模焦平面芯片的制备需要更稳定的工艺过程和更高芯片良品率,并且在航天遥感应用中,复杂的空间应用环境也对碲镉汞光伏探测器芯片的可靠性提出了更高的要求。不论是工艺过程监控、器件工艺改进还是芯片失效分析都要建立在探测器芯片各部分结构质量的准确表征的基础上,同时需要定量化的参数分析方法,从多批次的测试结果中统计分析芯片各部分性能的变化趋势,为器件工艺的持续改进、器件可靠性与稳定性的提高提供有效的评价方法与定量化的分析手段。然而通常使用的微电子集成测试结构的物理模型、实验数据分析方法是基于硅基器件特性建立的,并没有考虑碲镉汞光伏器件自身的独特性质(禁带宽度窄、载流子易简并等)。本文针对影响碲镉汞器件性能及长期可靠性的常见因素——表面漏电流、碲镉汞-钝化层界面状态及金属-碲镉汞接触,研究了栅控二极管、MIS电容器以及传输线测试结构,提出了相应的物理模型与数据分析方法,为这些测试结构在大规模碲镉汞红外探测器芯片中的应用奠定理论基础。其主要研究内容如下:1.碲镉汞栅控二极管与表面漏电机制。本文利用栅控二极管结构研究了表面势对碲镉汞光伏器件动态阻抗和暗电流的影响。提出了不同机制表面漏电的理论模型:表面积累时,用适当修正的隧穿电流模型来描述表面隧穿电流;表面强反型形成沟道时,利用传输线模型建立了表面沟道电流模型。通过选取适当的表面参数——平带电压VFB、表面缺陷密度Nst和沟道载流子迁移率μc,上述模型能够较好的描述中波碲镉汞光伏器件的优值因子R0A和暗电流与表面势的关系。实验结果表明本文所提出的表面漏电流模型能够比较好的描述和定量表征器件表面漏电特性,为进一步改进器件工艺提供了依据。2.金属-绝缘层-碲镉汞(MIS)器件电容理论与界面特性表征技术。针对碲镉汞材料的特点,建立包含导带非抛物和载流子简并效应的泊松方程,并利用数值方法得到了碲镉汞MIS器件高、低频理想C-V曲线;总结了各种影响碲镉汞MIS器件理想高低频C-V曲线的因素;讨论了碲镉汞MIS器件中高频C-V曲线的最小值与表面处理等工艺密切相关的事实,提出了一种等效高频界面陷阱电荷模型来描述这一实验现象,修正了用于提取界面态密度的理想高频C-V曲线,使得提取的界面态密度的大小和在禁带宽度内的分布更加合理。该理论和数值分析方法成功的应用于同批次MIS器件性能的监控和不同工艺对MIS器件的影响。实验测得Cd Te/Zn S双层钝化MIS器件的各项物理参数为:绝缘层固定电荷密度,绝缘层陷阱电荷密度,界面陷阱密度在能带中的最小值,等效高频界面陷阱密度。3.非线性金属-半导体接触表征技术。结合金属-半导体接触的电流输运特性,综合考虑了电流的聚集效应和金半接触的整流效应,提出了非线性传输线模型;以热电子发射为例,系统讨论了非线性传输线模型描述的电极IV特性;分析了非线性传输线模型与线性传输线模型中电流传输长度的不同,新模型中的电流传输长度Ltg与流入电流相关,能够更合理的描述电流在电极下的聚集效用,为碲镉汞焦平面芯片的设计提供了指导。利用非线性传输线模型和相应的数据分析方法研究了Au/Sn/p-Hg Cd Te接触的电学特性,得到了相关物理参量:肖特基势垒高度、理想因子n=1.45、欧姆特性接触电阻、电极下半导体薄膜电阻,电流传输长度Ltg在8~11μm之间并与流入电流有关。4.钝化层电阻率测试方法研究。利用MIS结构研究了电子束蒸发制备的Cd Te/Zn S钝化层电流-电压特性和电阻率,其中高阻抗的栅电极占总数的62.5%,电阻率在之间。另外,本文利用镜像电荷法模拟了四探针测试材料中的电势场分布,分析了有限尺寸的探针对测量精度的影响。模拟结果指出,在无限厚材料上,常用的计算方法只有在探针间距与探针直径的比值大于3的时候才能得到准确的材料电阻率(相对误差小于1%);在有限厚材料上,由近似公式引入的误差远大于探针尺寸引入的误差,在需要精确计算材料电阻率的情况下需要通过数值模拟精确分析。该研究结果为四探针法在微区钝化层电阻率测试上的应用奠定了良好的基础。
[Abstract]:HgCdTe semiconductor material with its excellent photoelectric characteristics, since it has become an important material for the preparation of high performance infrared detector. With the rapid development of the third generation HgCdTe infrared detector technology, low cost and large-scale focal plane chip preparation process needs more stable and higher chip yield, and in space remote sensing application in space, the complex application environment is the reliability of HgCdTe photovoltaic detectors chip put forward higher requirements. Whether the process monitoring, process improvement device or chip failure analysis should be established on the basis of accurate characterization of the quality of each part of the structure of the detector chip, at the same time parameters quantitative analysis method, from the test results many batches of statistical analysis on the changing trend of the chip performance, continuous improvement of device technology, improve the reliability and stability of devices Provide an analysis method and quantitative evaluation method of effective. However, microelectronic integrated test structure generally use the physical model, the experimental data analysis method is based on the characteristics of silicon based devices, and did not consider the unique properties of HgCdTe photovoltaic devices (the forbidden bandwidth is narrow, the carrier easily degenerate). Aiming at the performance impact HgCdTe device and long-term reliability of common factors -- the surface leakage current of HgCdTe passivation layer - metal interface state and HgCdTe contact, on the gated diode, MIS capacitor and transmission line test structures, this paper presents a physical model and data analysis method, which lays the theoretical foundation for the application of these test structures in a large-scale HgCdTe infrared detector in the chip. The main research contents are as follows: 1. HgCdTe gated diode and surface leakage mechanism. This paper uses gate controlled diode structure Study on the influence of the surface potential and the dark current of HgCdTe photovoltaic devices is proposed. The theoretical model of dynamic impedance of different mechanism of surface leakage: surface area tired, with appropriate modified tunneling current model to describe the surface of the tunneling current; surface strong inversion channel is formed when using the transmission line model of surface current model the channel. By choosing the proper parameters of the surface of the flat band voltage VFB, Nst surface defect density and channel carrier mobility of C, the model can describe the wave HgCdTe diodes better merit and scale factor R0A and dark current relationship between surface potential. Experimental results show that the proposed surface leakage current model to better describe and quantitative characterization of the device surface leakage current, provide the basis for the.2. metal insulator for the further improvement of HgCdTe device technology (MIS) device capacitance theory and interface characterization According to the characteristics of HgCdTe technology. The establishment of the Poisson equation contains a non parabolic conduction band and carrier degeneracy, and use numerical method to get MIS HgCdTe devices with high frequency, the ideal C-V curve; summarizes the various influence factors of MIS devices are ideal for low and high frequency HgCdTe C-V curve; discussed the fact the minimum value of high frequency C-V curves of HgCdTe MIS devices the surface treatment technology closely related, presents a high frequency equivalent interface trap charge model to describe this phenomenon, for the extraction of the ideal high frequency C-V curves of the interface state density correction, the extraction of the interface state density and the size of the band gap in the distribution is more reasonable. The theoretical and numerical impact monitoring the analysis method is successfully applied to the performance of the same batch of MIS devices and different processes of MIS devices. The Cd Te/Zn S double layer passivation MIS device testing The physical parameters are as follows: the insulating layer insulating layer fixed charge density, trap charge density, the interface trap density in minimum zone in the high frequency equivalent characterization techniques of interface trap density of.3. nonlinear metal semiconductor contact metal semiconductor contact. Combined with current transport properties, considered the rectifying effect of current crowding effects and gold semi contact, we propose a nonlinear transmission line model; the thermal electron emission system as an example, discusses the characteristics of IV electrode to describe the nonlinear transmission line model; analysis of the current transmission length of nonlinear transmission line model and the linear model of transmission line in different current transmission length of Ltg in the new model and the current flowing, can describe the current is more reasonable on the electrode of the aggregation effect, provides guidance for design of HgCdTe focal plane chip. By using the method of nonlinear analysis of transmission line model and the corresponding data Study on electrical characteristics of Au/Sn/p-Hg Cd contact Te, the relative physical parameters were obtained: the Schottky barrier height, ideal factor n=1.45, ohmic contact resistance, resistance of semiconductor thin film electrode, the current transmission length of Ltg between 8~11 and m and Study on test methods of.4. passivation layer resistivity. Current flowing on Cd Te/Zn evaporation preparation the electron beam S passivation layer current voltage characteristic and resistivity by using MIS structure, wherein the gate electrode of the high impedance accounted for 62.5% of the total, the resistivity between. In addition, this paper simulated the potential distribution of four probe test materials using mirror image charge method, analyzes the influence of probe finite size on the measurement accuracy of simulation. The results pointed out that in the infinite thick material, the common calculation methods only greater than in the ratio of the diameter of the probe and probe spacing of 3 times to obtain accurate resistivity (relative error Less than 1%); in finite thickness materials, by introducing the approximate formula of error is much larger than the size of probe error introduced by numerical simulation, accurate analysis requires accurate calculation of the resistivity of the materials in case of need. The results of the study for the four probe method has laid a good foundation for the application of micro resistivity test on the passivation layer.

【学位授予单位】：中国科学院研究生院(上海技术物理研究所)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN215

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