论文总字数：29863字

摘 要

MEMS器件具有体量小、能耗低、可靠性高的优点，在各行各业有着广泛的应用。其中，石油化工等传统企业，为了转型升级，期待将MEMS器件应用在实际生产当中替换传统器件，不乏有Honeywell这样的企业已经开始了相关研究。以及航空航天领域近年来的热门话题，中小卫星的研制中，因为载荷有限，MEMS器件也成为了很有潜力的选择。然而，由于这类产业应用的器件面临着严酷的高温条件，MEMS器件，尤其是应用广泛的以及其中包含多晶硅薄膜在内的各种薄膜材料，能否在这种频繁的温度变化和较高的最高温度的环境下正常工作，有待深入研究。

本文综述了MEMS在高温工况下的应用，包括航空航天领域、地质勘探领域以及燃料燃烧领域等所涉及的MEMS传感器或执行器。随后综述了已有的MEMS器件以及MEMS器件中常用的薄膜材料多晶硅的高温效应的研究进展，包括材料的蠕变、疲劳以及电学参数的变化等。

为了提供本文理论分析的依据，在第二章介绍了多晶硅薄膜的电阻率计算理论模型。从简化的多晶硅结构模型以及多晶硅薄膜实际物理特性的分析出发，简要介绍了载流子陷阱以及杂质分凝两种晶粒间界影响多晶硅导电性的模型，同时并列出了中低掺杂情况下电阻率的计算公式。由于本文主要研究重掺杂多晶硅薄膜的高温效应，故引入了对多晶硅薄膜电学性质中关于重掺杂修正的部分。以此为基础，引入本文的主要研究内容。

在研究高温效应的实验中，本文制定了相应的高温实验方案，包括样品制备以及实验流程。样品方面，采用的MEMS CAP的MUMPs流程制作多晶硅薄膜四线法电阻测量结构。使用KEITHLEY半导体参数测量仪，以达到进行高精度的多晶硅梁电阻测量的目的。为了检验多晶硅薄膜在高温环境下的可靠性，实验设置的高温环境比一般应用恶劣得多，这样可以更好地切合实际高温应用中可能面对的挑战，使得研究更具有实用性价值了200℃和300℃两种试验温度，并进行了多剂量点的测量。获得了器件电阻随加热时间变化的实验曲线。

总结实验数据并加以处理，依据之前所提到的多晶硅薄膜电学参数模型，讨论得出了一套可以自洽电阻随加温时间变化的可能的理论解释，该理论解释可以较好地反应实验结果。

本文对MEMS器件多晶硅薄膜材料的高温效应进行了实验方面的研究，为需要工作在高低温交替环境中的MEMS器件设计提供了一定参考价值。本文研究表明，多晶硅薄膜的电学性能会因为反复经历高温环境而产生明显的变化，会影响到需要利用多晶硅薄膜的MEMS器件在高温工作下的可靠性电阻进行传感或制动的器件正常工作。

关键词：MEMS，多晶硅薄膜，可靠性，高温，电阻

Abstract

Micro-Electro-Mechanical System (MEMS) is wildly applied in all trades, for the advantages of smaller volume, lower power consumption, and higher reliability. Among all the industries, some traditional businesses, such as petrochemical industry, are expecting the application of MEMS devices in practical production in order to reform and prompt. Some actual effort has been made by enterprises like Honeywell. Meanwhile, in aerospace field, MEMS devices are the highly potential choice for the topical issue which is the research and development of minisatellites as a result of their limited payload. However, harsher environment is not an exceptional option in these industries. Whether MEMS devices, as well as all the thin film materials like polycrystalline silicon, can function normally in this frequently changed high temperature condition, still awaits for thoroughly studies.

The applications of MEMS devices working as sensors or actuators in high temperature operating condition, including aerospace, borehole drilling, and combustion field, were summarized. The existing works of the high temperature effects, such as creep, fatigue, the change of electrical performance, and so forth, of MEMS devices and poly-silicon were expounds.

The theoretical model for calculating the resistivity of poly-silicon thin film was introduced in Chapter 2 to offer the basis of experiment discussion. Started form the simplified poly-silicon structure model and the real physical characteristics, this paper briefly included two wildly accepted factors influencing the conductivity of poly-silicon, which were the carrier trapping and dopant segregation. The resistivity calculation formula of poly-silicon in low or medium doping level is listed. Considering the specimens in this research is heavily doped poly-silicon thin film, the correction of poly-silicon electrical characteristics in high doping level was included. This part would led to the main experiment of this paper.

The paper offered a corresponding experiment scheme covering the preparation of specimens and experiment procedure for the research of high temperature effects of poly-silicon thin film. The specimens were the four-wired resistor made by MUMPs from MEMS CAP. Semiconductor Characteristics System was involved in this experiment to acquire highly accurate resistance of each specimen. Aiming to test the reliability of poly-silicon thin film under high temperature environment, the experiment set 2 testing temperature and conducted multi-dose-point measurement. The experiment results were displayed by the resistance changing curve with heating time.

The data of resistance were collected and processed to give a whole look at the high temperature effects on poly-silicon thin film material. According to these data, a plausible explanation was developed in this paper to explain the change of resistance.

The paper conducted the research of the high temperature effect on MEMS devices poly-silicon thin film material, provided certain reference value for the design of MEMS devices which need to work in such high temperature environment. The paper present the electrical characteristics of poly-silicon thin film can be influenced by the high temperature environment. Distinguish change may occur in this situation. Thus, it could jeopardize the reliability of MEMS devices working under such high temperature environment.

KEY WORDS: MEMS, polycrystalline silicon, reliability, high temperature, resistance

目录

摘要 III

Abstract IV

第一章 引言 1

1.1 MEMS器件的高温应用 1

1.2 MEMS器件的高温效应 4

1.3 多晶硅的高温效应 5

第二章 多晶硅导电模型 7

2.1 多晶硅简化模型与电学特性^[48] 7

2.2 载流子陷阱模型 8

2.3 杂质分凝 9

2.4 高掺杂修正 9

第三章 高温效应实验测定 11

3.1 样品制备 11

3.2 实验方案 13

3.2.1 四线法电阻测量 13

3.2.2 高温负载实验 14

第四章 MEMS器件薄膜材料的高温效应 15

4.1 多晶硅薄膜多次高温处理电阻实验结果 15

4.2 多晶硅高温效应讨论 18

第五章 总结与展望 19

致谢 20

参考文献 21

引言

MEMS器件的高温应用

在过去的几十年间，从自动化、航空航天、石油勘探等工业的发展中都见证了电子器件性能的大幅提升。微电子器件性能的提高是推动相关行业发展的重要基石之一，同时，各行各业对于集成电子电路系统的要求日益提高，在这两个因素的共同作用下，极大地推进并加速了电子器件性能的提升。其中，在工业界，尤其是涉及航空航天、石油化工、深井钻探等的方面，往往伴随着控制或传感电路工作在高温中的应用场景。而这种高温场景，往往远超传统电子器件的温度应用极限^[1]。

当环境温度过高时，用于监控或控制核心高温区域的传统高性能电路子系统必须安放在相对低温的区域，比如放置在离高温区较远的地方或者采用主动风冷或水冷进行冷却。然而，这种会给系统造成许多不利的影响，比如需要引入更长的管线、更多的连接系统和冷却系统，这些额外的开销不但增大了系统的成本和复杂度，也提高了全系统的故障率^[2]。正因如此，越来越多的研究者与工程师将目光投向了在严酷环境中仍能正常工作的微机电系统（Micro-Electro-Mechanical System, MEMS）^[3]。

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