摘要
在现代社会中，无论是军用还是民用领域，红外探测器都有越来越重要的地位。热电堆红外探测器作为非制冷型红外探测器的一种，自20世纪80年代MEMS（微机械系统）工艺技术的引进，陆续出现了IC兼容的微机械硅基红外探测器类型，相较传统方法制作的热电堆器件具有低成本、低功耗、小型化等特点，受到国内外研究人员越来越多的关注。但是近年来的研究在设计与工艺兼容方面始终存在一些弊端，因此本文针对结构和工艺兼容进行一系列创新，通过大量的工艺制备实验，完整的得出一种制备简单、与CMOS兼容性强的新型热电堆红外探测器工艺流程。
本文的主要研究重点有：
（1）理论设计方面，针对成本和IC兼容性方面进行了几点创新，包括有：突破单层硅片干法刻蚀对尺寸的限制和SOI衬底价钱昂贵，不易于成批制造的缺点，采用了氧化层上的多晶硅（Si-SiO_2-POLY）作为衬底；两层热偶条采用叠放的方式，有效节省结构空间，中间采用LPCVD制作氧化硅作为热电隔离。通过热平衡分析设计的结构模型，从热偶条长度、宽度、厚度、对数和吸收区边长几个方面的优化对比。
（2）工艺方面，针对本设计的探测器结构，分析在制备过程中的工艺步骤。对这些工艺过程进行实验对比，实验包括有：多晶硅高深宽比凹槽（大于2μm）的刻蚀实验中侧壁形貌和尺寸控制与刻蚀条件的关系；使用氧化硅进行深槽填充时填充程度和填充后表面平整度的测试实验；关于在高深宽比结构内形成所需尺寸结构的条件研究和XeF_2干法释放的条件实验等。并对实验结果进行分析说明。
（3）另外，本文采用卤素气体对非晶硅进行刻蚀出现的针状结构（“黑硅”）作为探测器的表面吸收层。通过不同刻蚀条件得到表面黑化程度不同的样片；并对样片的红外吸收率进行测试。
本文通过对各项工艺制备条件的对比，得到了不同实验中多组样片结果，进行了wafer表面或者掰片后侧壁的电镜测试。通过对测试结果进行分析，最终验证了设计中各项创新点在实际工艺制备中的可行性。在克服所有工艺难题的基础上，整合本设计的工艺制备步骤，成功的得出具有腐蚀自停止、以厚多晶硅作衬底释放结构的热电堆红外探测器的制备流程。
In present society, the IR(infrared radiation) detector plays a more and more importantrole in both military and civil domain. With the introduction of MEMS(Micro-Electro-Mechanical Systems) process to IR technology in 1980’s , the thermopileinfrared detector, as a kind of uncooled IR detector, has directed to some IC compatible typesbased on silicon which have caused lots of attentions for the advantages of low cost, lowenergy consumption and miniaturization comparing with the conventional device. However,there are a lot of disadvantages in the design and IC compatibility of resent research. In thedissertation, some innovations on structure and IC compatibility are put forward to integratethe detector. Accordding to lots of process experiments, a new thermopile infrared detectorwhich is fabricated simplily and CMOS compatible is obtained.
The design has some research spots more excellent than conventional thermopile IRdetector:
(1) In the theory and design, there are some innovation spots for the cost and IC compatibility,including: To break the Silicon substrate’limitation to release and save the price of SOI, anew substrate structure which has the polysilicon on the SiO2layer (Si-SiO_2-POLY) ispresent; The two materials of thermocouple are terrace and insulated by LPCVD siliconoxide so that the place is saved. The stationary heat model is built to analyze the device.Establish the detector’s size and influences of absorbing area。
(2) In the process, analyses the MEMS process in the detector’s structure designed and dosome experiments make sure the design is IC compatible, including: when dry etching ofpolysilicon quirk(GT 2μm),the relationship between the factor of etching and the patternand size of sidewall; after filling the quirk with silicon oxide, the condition of surface test; structure formation in the deep and narrow hole and the XeF_2dry etching condition etc.Besides, analyse and explain the experimental results.
(3) In addition, the thesis presents a needle-like array ofα-Si which appears in halogen gasdry etching as the absorbing material on the surface. According to change the etchingcondition, a series of sample wafers are achieved. Testing and checking the IRabsorptivity of these samples under different wavelength light source.
Accordding to comparing the process fabrication condition, several groups of samplesare obtained in different experiments, the whole wafer’s surface or sidewall pattern after breakoff the wafer are tested by SEM. After analyse the test results, the feasibility of theinnovation spots in the design in the process fabrication is proved. Based on it, the completefabrication process is integrated to make a whole fabrication flow of the thermopile infrareddetector which has self-stopping in etching polysilicon to release the device.
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