高迁移率二硫化钼场效应晶体管的研究

发布时间：2018-04-10 13:32

本文选题：二硫化钼 + 化学气相沉积　；参考：《天津理工大学》2017年硕士论文

【摘要】：随着集成电路工艺步入22nm工艺节点,传统硅基MOSFET的短沟道效应引起的器件性能衰减越来越明显,因此寻找新的半导体材料势在必行。二维过度金属硫化物因其独特的物理特性以及超薄二维结构而受到广泛关注。二硫化钼(MoS_2)作为二维过渡金属硫化物中的一员,由于较宽的带隙(1.2-1.8eV)使得其适合作为场效应晶体管的沟道材料,形成高开关比、低功耗器件,在与传统半导体工艺兼容的基础上有效地抑制了尺寸缩小而引起的短沟道效应。大面积、层数可控的二硫化钼生长及MoS_2场效应晶体管的性能优化是其走向应用的基本要求。然而,目前关于MoS_2场效应晶体管的研究大多都采用机械剥离样品,然而机械剥离法的局限性使得其很难走向应用,同时许多课题组发现,由于单层MoS_2对于环境的敏感性导致了较低的器件迁移率(10-2-10cm2V~(-1)s~(-1));同时MoS_2与金属电极形成金半接触引起的较大接触电阻以及MoS_2沟道的缺陷同样限制了MoS_2基场效应晶体管的性能。基于以上分析,我们进行了大尺寸、层数可控CVD-MoS_2生长工艺优化以及MoS_2基场效应晶体管性能优化的研究。本文的主要研究内容有:优化CVD-MoS_2薄膜的生长工艺,获得大尺寸、层数可控的MoS_2;采用传统微纳加工工艺在合成的MoS_2薄膜上构建MoS_2基背栅场效应晶体管,其中研究以不同层数MoS_2作为沟道时,器件的性能变化;通过化学改性,降低MoS_2与金属电极的接触电阻以及MoS_2沟道的缺陷,提高器件的迁移率及开关比等电学性能。CVD-MoS_2薄膜生长工艺优化:研究温度的变化和氢气流量的变化对于二硫化钼尺寸及层数的影响,并通过工艺条件优化合成了较大尺寸(40-60μm)的单双层MoS_2三角(六角),以及一些三层(10-15μm)及四层(5μm)MoS_2薄膜;并且通过XPS、拉曼光谱及TEM等手段对二硫化钼薄膜的层数、均匀性及结晶度进行了全面的表征。通过传统微纳加工工艺(包括紫外光刻、刻蚀、电子束曝光及PVD镀膜等工艺)在上述合成的1-3层MoS_2薄膜上构建背栅场效应晶体管器件,并通过测试比较了不同层数的二硫化钼作为沟道时,器件的性能的变化,并研究引起性能变化的原因。在上述器件构建的基础上,通过化学改性改变MoS_2薄膜的晶格结构或降低MoS_2沟道中的晶格缺陷,以提高器件的迁移率。一方面,采用正丁基锂将与源漏金属电极接触部分的半导体相2H-MoS_2转变为金属相1T-MoS_2,从而极大地降低了器件的接触电阻,器件的迁移率提高及on-current都提高了约2倍;另一方面,通过MPS溶液低温退火法修复了MoS_2沟道中的硫空位,减少了MoS_2沟道的缺陷,并结合1T-MoS_2接触,最终得到了约50.23cm2V~(-1)s~(-1)的迁移率及8×10~6的器件开关比。
[Abstract]:With the integrated circuit process stepping into the 22nm process node, the performance attenuation caused by the short channel effect of traditional silicon based MOSFET becomes more and more obvious, so it is imperative to search for new semiconductor materials.Due to its unique physical properties and ultrathin two-dimensional structure, two-dimensional excessive metal sulphides have attracted wide attention.Molybdenum disulfide (MoS _ 2) as a member of the two-dimensional transition metal sulphide, due to its wide bandgap of 1.2-1.8 EV), it is suitable as a channel material for FET to form high-switching ratio, low-power devices,On the basis of compatibility with traditional semiconductor process, the short channel effect caused by size reduction is effectively suppressed.The growth of molybdenum disulfide with large area and controllable layers and the performance optimization of MoS_2 field effect transistor are the basic requirements for its future application.However, at present, most of the researches on MoS_2 field effect transistors use mechanical stripping samples. However, the mechanical stripping method is difficult to be applied because of its limitations. At the same time, many research groups have found that,Because of the environmental sensitivity of monolayer MoS_2, the lower device mobility (10-2-10cm2V) and the larger contact resistance caused by gold semi-contact between MoS_2 and metal electrode, as well as the defect of MoS_2 channel, also limit the performance of MoS_2 based FET.Based on the above analysis, we studied the growth process optimization of large size, multilayer controllable CVD-MoS_2 and the performance optimization of MoS_2 based field effect transistors.The main research contents of this paper are as follows: optimizing the growth process of CVD-MoS_2 thin film to obtain the large size and controllable number of layers of Mos\\\The performance changes of MoS_2 with different layers are studied, and the contact resistance between MoS_2 and metal electrode and the defect of MoS_2 channel are reduced by chemical modification.Optimization of the growth process of CVD-MoS _ 2 thin Film by improving the Mobility and switching ratio of the device: the effects of temperature and hydrogen flow rate on the size and number of layers of molybdenum disulfide are studied.Single and double layer MoS_2 triangles (hexagonal, some trilayers 10-15 渭 m) and four layers of 5 渭 m)MoS_2 thin films with large size of 40 ~ 60 渭 m were synthesized by optimizing the process conditions, and the number of layers of molybdenum disulfide thin films was determined by means of TEM, Raman spectroscopy and TEM.The homogeneity and crystallinity were characterized.The backgate FET devices were fabricated on 1-3 layers of MoS_2 thin films by traditional micro and nano fabrication processes (including UV lithography, etching, electron beam exposure and PVD coating).The properties of the devices with different layers of molybdenum disulfide as the channel are compared and the causes of the performance changes are studied.On the basis of the above devices, the lattice structure of MoS_2 films is changed by chemical modification or the lattice defects in the MoS_2 channels are reduced, so as to improve the mobility of the devices.On the one hand, the semiconductor phase 2H-MoS_2 in contact with the source and drain metal electrode is transformed into metal phase 1T-MoS2 by using positive Ding Ji lithium, thus greatly reducing the contact resistance of the device, the mobility of the device and the on-current of the device are increased by about 2 times, on the other hand,
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN386

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