超短沟道二硫化钼场效应晶体管的制备及其电学性质研究

发布时间：2018-06-10 12:14

本文选题：二硫化钼 + 石墨烯　；参考：《中国科学院大学(中国科学院物理研究所)》2017年博士论文

【摘要】：将晶体管的尺寸不断缩小一直都是半导体芯片行业的发展方向。然而,传统硅基晶体管经过多年的小型化,器件尺寸已经逐渐接近物理极限,在这种情况下,短沟道效应将会严重抑制器件的性能。因此,人们试图寻找新型的沟道材料替代传统硅基半导体,以求延续晶体管尺寸不断缩小的趋势。近年来,以层状二硫化钼为代表的二维半导体的出现,为解决这一问题提供了很好的思路。单层二硫化钼是一种具有2.2 eV直接带隙的单原子层厚度的二维半导体,具有优异的电子学以及光电子学性能。更重要的是,单层二硫化钼对短沟道效应超强的免疫力,这使得它成为极具潜力的未来电子学备选沟道材料。基于此,本文探索了以单层石墨烯为接触电极的超短沟道二硫化钼场效应晶体管,具体包括:1.石墨烯-二硫化钼异质结的构造。我们发展了一种简单高效的二维晶体转移方法,并以此构筑具有干净接触界面的二维材料异质结。我们将适量的聚碳酸丙烯酯(PC)溶液滴在支撑待转移二维晶体样品(比如单层二硫化钼)的衬底上,并将之高温固化成膜,然后利用它为载体。当这层PC膜被揭起时,由于其较强的粘附性,待转移样品会离开原来衬底并附着在PC膜底。接着利用我们自行搭建的转移设备,在光学显微镜下对准,将PC膜底部的待转移样品精确转移到另一块目标二维晶体(比如单层石墨烯)上构筑具有干净接触界面的二维材料异质结。2.石墨烯电极超短沟道二硫化钼场效应晶体管的构筑及其电学性能测量与分析。利用我们课题组之前发展的石墨烯氢等离子体各向异性刻蚀技术,可以将石墨烯的晶界精确可控地展宽至几个纳米的尺度。我们以纳米级展宽晶界两边的单层石墨烯为电极,构筑了超短沟道单层二硫化钼晶体管。该晶体管的沟道长度等同于石墨烯晶界展宽后的宽度,也就是说,以单层石墨烯为接触电极的超短沟道二硫化钼场效应晶体管的沟道长度可以减小至几个纳米。我们分别对沟道长度为8nm和3.8nm的二硫化钼场效应晶体管进行了电学特性测量。这些器件呈现出线性的输出特性曲线,表现出欧姆接触的行为,体现了石墨烯在超短沟道二硫化钼器件中作电极的优越性。对于8nm沟道长度,器件仍然表现出了很好的开关性能,其开关比可达1.5×106,其场效应迁移率可达28cm2V-1s-1,这些可以与长沟道二硫化钼器件相比拟的性能说明器件在此沟道长度时没有发生短沟道效应;对于3.8nm沟道长度,器件开关比为5×105,相比于8nm器件有所降低,这虽然是一种轻度的短沟道效应,但是对于高性能场效应晶体管而言,仍在可接受的范围。也就是说,二硫化钼场效应晶体管可以在突破5nm极限的同时保持优异的电学性能。本研究结果也体现了二硫化钼在未来超短沟道器件应用中的极大潜力。
[Abstract]:Reducing the size of transistors is always the development direction of semiconductor chip industry. However, due to the miniaturization of traditional silicon based transistors for many years, the device size is gradually approaching the physical limit. In this case, the short channel effect will seriously inhibit the performance of the devices. Therefore, people try to find new channel materials instead of traditional silicon-based semiconductors, in order to continue the shrinking trend of transistor size. In recent years, the appearance of two-dimensional semiconductor represented by layered molybdenum disulfide provides a good way to solve this problem. Monolayer molybdenum disulfide is a two-dimensional semiconductor with a direct band gap of 2.2 EV. It has excellent electronic and optoelectronic properties. More importantly, monolayer molybdenum disulfide has a strong immunity to short channel effect, which makes it a promising candidate for future electronics. Based on this, an ultrashort channel molybdenum disulfide field effect transistor with single-layer graphene as contact electrode has been investigated, including: 1. Structure of graphene-molybdenum disulfide heterojunction. We have developed a simple and efficient two-dimensional crystal transfer method and constructed two-dimensional heterojunction with clean contact interface. We drop a proper amount of polypropylene carbonate (PCO) solution on the substrate supporting the two-dimensional crystal sample (such as monolayer molybdenum disulfide) and solidify it into film at high temperature and then use it as the carrier. When this layer of PC film is lifted, due to its strong adhesion, the sample to be transferred will leave the original substrate and adhere to the substrate of PC film. And then, using our own transfer equipment, we aim at it under an optical microscope, The sample to be transferred from the bottom of the PC film is accurately transferred to another target two-dimensional crystal (such as single-layer graphene) to construct a two-dimensional heterojunction with clean contact interface. The Fabrication and Electrical Properties Measurement and Analysis of Graphene electrode Ultra-short Channel Molybdenum disulfide Field effect Transistor. Using the graphene hydrogen plasma anisotropic etching technique developed before our research group, the grain boundary of graphene can be extended to several nanometers accurately and controllably. A monolayer molybdenum disulfide transistor with ultrashort channel was fabricated using graphene monolayer on both sides of grain boundary as electrode. The channel length of the transistor is equal to the width of graphene grain boundary, that is, the channel length of ultrashort molybdenum disulfide field effect transistor with single graphene as contact electrode can be reduced to several nanometers. The electrical properties of molybdenum disulfide field effect transistors with channel length of 8nm and 3.8nm have been measured respectively. These devices show linear output characteristic curves and ohmic contact behavior, which shows the superiority of graphene as electrode in ultrashort channel molybdenum disulfide devices. For the 8nm channel length, the device still shows good switching performance. The switching ratio can reach 1.5 脳 106, and the field effect mobility can reach 28cm2V-1s-1.These properties can be compared with those of long channel molybdenum disulfide devices, which indicate that there is no short channel effect at this channel length; for 3.8nm channel length, The switching ratio of the device is 5 脳 10 5, which is lower than that of the 8nm device. Although it is a mild short channel effect, it is still in the acceptable range for the high performance field effect transistor. In other words, molybdenum disulfide field effect transistors can break the 5nm limit while maintaining excellent electrical properties. The results also show the great potential of molybdenum disulfide in the application of ultrashort channel devices in the future.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN386

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