【作者】 苏元军；

【导师】 董闯； 徐军；

【作者基本信息】 大连理工大学 ， 材料物理与化学， 2011， 博士

【摘要】 随着平板显示技术的发展和人类对太阳能利用的重视,多晶硅薄膜的研究受到越来越多的关注。与传统的非晶硅薄膜相比,多晶硅薄膜有着更高的电子迁移率和更好的光电稳定性,作为平板显示器中薄膜晶体管的沟道层和硅基薄膜太阳电池的吸收层使用都表现出更加优越和稳定的性能。目前,工业上制备多晶硅薄膜的沉积技术当中,主要以化学气相沉积(CVD)为基础的热丝化学气相沉积(HWCVD)和等离子体增强化学气相沉积(PECVD)技术为主。化学气相沉积过程当中通常要使用硅烷作为反应气体；作为一种剧毒易爆的危险气体,硅烷在工业上的使用需要辅以苛刻的安全保障系统和回收处理系统,造成多晶硅的生产成本居高不下。磁控溅射技术是一种结构简单、成本低廉的真空沉积技术。由于不需要使用硅烷,无论是生产安全性还是成本控制上,磁控溅射都比化学气相沉积有着更大的优势。然而,普通磁控溅射在沉积硅薄膜时,由于溅射过程中的反应气体离化率较低、产生的先驱沉积物活性不够,所制备出的硅薄膜都是非晶硅。我们利用电感耦合等离子体源辅助磁控溅射沉积技术成功实现的多晶硅薄膜的低温沉积(<150℃),解决了普通磁控溅射源制备多晶硅薄膜晶化率较低的问题。本文第一章中,我们详细介绍了硅基薄膜在平板显示领域和太阳电池领域的应用进展,对多晶硅薄膜与非晶硅薄膜在各个领域的性能特点进行了分类比较。第一章中我们还详细讨论了现有多晶硅薄膜沉积技术的优缺点,对磁控溅射法制备多晶硅薄膜的工艺可行性进行了分析和讨论,并介绍了本文课题的研究背景。本文第二章中,我们详细介绍了本文所使用的电感耦合等离子体源辅助磁控溅射装置,以及用于该装置等离子体诊断的Langmuir探针。通过对Langmuir探针的诊断结果分析,我们对该装置的电感耦合等离子体源的放电特性进行了详细讨论。第二章中,我们还详细介绍了本文用于多晶硅薄膜表征的拉曼散射、X射线衍射、红外光谱、可见紫外透射光谱等分析技术的基本原理和针对硅基薄膜测试的具体分析方法。本文第三章中,我们重点讨论了氢气在等离子体辅助磁控溅射过程当中对多晶硅薄膜制备的影响。在固定气压条件下,我们详细分析了氢气稀释比变化对多晶硅薄膜的微结构、硅氢键合状态、硅薄膜光学带隙的影响。在此基础上,我们在不同工作气压下进行了氢气稀释比变化的多组实验,根据这些实验数据总结了氢气分压对多晶硅薄膜晶化率的影响规律。本文第四章中,我们首先研究了不同氢气稀释比条件下辅助等离子体源的放电功率对多晶硅薄膜制备的影响。然后利用可见光发射光谱仪(OES)我们对多晶硅薄膜制备过程的反应气体中的激发态原子的变化情况进行了详细研究。通过硅薄膜的表征结果和OES的分析结果详细讨论了ICP-MS系统制备多晶硅薄膜的晶化机制,并深入分析了电感耦合等离子体源在磁控溅射制备多晶硅薄膜的过程中所起到的作用。本文第五章中,我们在不同的氢气稀释比条件下研究了沉积温度对多晶硅薄膜制备的影响,将多晶硅薄膜的沉积温度降至柔性基板所要求的150℃以内,并讨论了进一步降低沉积温度所需要具备的沉积条件。在本章中,我们还详细分析和讨论了温度对多晶硅薄膜的微结构、硅氢键合状态、光学带隙的影响及其原因。本文第六章中,我们系统介绍了多晶硅薄膜的氧化问题,并提出了使用偏压作为氧化问题的解决方案。我们详细探讨了负偏压或者离子轰击和正偏压或者说电子轰击对多晶硅薄膜制备的影响。详细分析了离子轰击所造成的多晶硅薄膜晶化率下降、孵化层增厚等问题的原因。本文最后的结论中,通过各个章节的分析和论述,我们总结出了八条有关电感耦合等离子体辅助磁控溅射技术低温沉积多晶硅薄膜的研究结论,并对磁控溅射法制备多晶硅薄膜所需要进一步解决的问题提出了展望。更多还原

【Abstract】 Hydrogenated microcrystalline silicon (μc-Si:H) thin film is a competitive material in planar display area and solar cell industry. As a channel layer in the thin film transitor (TFT) and intrinsic layer in solar cell,μc-Si:H works with more efficient electron mobility and higher photovoltaic stability. Now in industry the most popular way to depositμc-Si:H thin films is based on chemical vapor deposition (CVD), such as hot filament chemical vapor deposition (HWCVD) and plasma enhanced chemical vapor deposition (PECVD). During HWCVD and PECVD process for the growth ofμc-Si:H, it often uses toxic and explosive silane as its precursor gas, which results in high cost in the security systems and gas recycling systems.Magnetron sputtering with simple equipment structure, easy scalability and high safty is a promising technique for the deposition ofμc-Si:H thin films. However, most sputtering sources often exhibit low ionization which results in poor crystallinity of silicon thin films deposited by magtron sputtering. To solve this issue, we developed a plasma source assistant magnetron sputtering system which employed inductively coupled plasma as plasma source for the growth of highly crystallized silicon thin films. In this thesis, we introduced exact deposition process and material characteristics ofμc-Si:H thin films by inductively coupled plasma source assistant magnetron sputtering (ICP-MS) system.In Section One, we introduced the state of the art of silicon thin film applications in planar display and solar cell industries. We illustrated different techniques for synthesis ofμc-Si:H thin films and summaried their characteristics. In the end of this section, we introduced the background of our project and pointed out the advantage of our system.In Section Two, we presented in detail our ICP-MS system. We demonstrated the plasma diagnosis by Langmuir probe and discussed the characteristics of our plasma source. In this section we also introduced the methods we employed for the analysis of silicon thin films.In Section Three, we studied the effects of H2 on the growth ofμc-Si:H thin films. First we fixed the total gas pressure and increased the hydrogen dilution ratio ([H2]/[H2+Ar]) gradually from pure Ar gas to hydrogen dilution ratio of 80%. We observed the effects of hydorgen dilution ratio on the properities of deposited Si films including microstructure, Si-H bonding configurations and optical band gap. And then we mapped crystalline properties with changing gas pressures and hydrogen dilution ratios. Finally, we summarized the effects of hydrogen partial pressure on the crystllinity of Si films.In Section Four, we studied the effects of ICP plasma source and growth mechanism ofμc-Si:H thin films in ICP-MS system. First we illustrated the results of characteristics of Si films with changing ICP powers at three different hydrogen dilution ratios. Then we used optical emission spectroscopy (OES) to study the radicals during depositon process of Si films. Finally based on results of sample analysis and OES, we discussed the effects of ICP plasma source and growth mechanism ofμc-Si:H thin films in ICP-MS system.In Section Five, we studied the effects of growth temperature from 150℃to 450℃on the growth of Si films. We showed thatμc-Si:H thin films were also formed by ICP-MS deposition even at growth temperature below 150℃. And we pointed out the precondition for low temperature or even room temperature growth ofμc-Si:H thin films in ICP-MS system.In Section Six, we focused on effects of bias voltage on the growth ofμc-Si:H thin films in ICP-MS system. At first, we demonstrated the oxidation issue of Si thin films deposited by magnetron sputtering. Then we illustrated the effects of negative bias voltages on the growth ofμc-Si:H thin films. And we pointed both the advantage and disadvantage of ion bombardment for the growth of Si films by magnetron sputtering. Finally, we studied the effects of positive bias voltages, and further explained the effects of ion on the growth onμc-Si:H thin films in ICP-MS system.In the conclusion part, we summaried results from Section Two to Section Six and also the unsolved issues need to be studied in the future work.更多还原