硅基自旋注入器件及其界面特性研究

发布时间：2018-01-10 19:25

本文关键词：硅基自旋注入器件及其界面特性研究　出处：《兰州大学》2016年博士论文　论文类型：学位论文

【摘要】：发展硅基自旋电子器件是当今半导体自旋电子学应用领域的研究热点之一。本论文围绕硅基自旋注入三端器件的研制为主线,重点开展了NiFe/HfO_2/Si磁隧道结的制备及其界面特性研究,以期开发新的硅基自旋电子器件。此外,还对Ge pMOSFET器件的制备及电学特性进行了一些探索,为今后开发自旋晶体管积累经验。(一)磁性电极NiFe薄膜的制备和特性研究1.以高掺n型Si为衬底,利用磁控溅射制备了不同厚度的NiFe薄膜,并对部分样品进行了退火处理,系统研究了样品的面内和面外磁各向异性与薄膜厚度之间的关系,以及不同条件退火对磁性能的影响,结果表明为了符合硅基自旋注入对磁性电极薄膜的要求,NiFe薄膜的厚度需控制在30 nm以内,并且退火温度以250℃为佳;2.为了抑制NiFe薄膜中的Ni、Fe往Si衬底中扩散,同时也为了形成隧道结,在NiFe与Si之间插入了2 nm厚的HfO_2薄膜,并进行了退火处理,研究了样品退火前后的磁性能,并利用XPS测试和分析了NiFe薄膜的组分、化学键和扩散情况,结果显示HfO_2薄层的引入可部分抑制Ni、Fe往Si中扩散,使得Al(22 nm)/NiFe(28 nm)/HfO_2(2 nm)/Si样品经250℃退火以后其饱和磁化强度提高了约80%,有利于硅基自旋注入;3.对CoFe薄膜的制备进行了一些探索。(二)介质层HfO_2超薄薄膜的制备及界面、电学特性研究1.分别采用(E-beam)和原子层沉积(ALD)技术在高掺n型Si衬底上制备了HfO_2超薄薄膜(厚度范围0-5 nm),并利用XPS进行了深度剖析,系统研究了Si上直接生长HfO_2薄膜的组分、化学键和扩散情况,结果显示ALD生长的HfO_2薄膜粗糙度较小,约0.10 nm,厚度控制精度较高,表面层符合化学配比,可能适合用于硅基自旋注入;2.研究了不同方法制备的Metal/HfO_2/n+-Si接触随HfO_2插层厚度(E-beam0-5nm或ALD 0-2.5 nm)变化的I-V特性,优化了用于硅基自旋注入隧穿层的HfO_2薄膜的制备方案;3.研究了NiFe/HfO_2(0-2 nm)/p-Si接触的I-V特性,探讨了HfO_2插层对NiFe/Si肖特基势垒高度的调制作用和机理,为今后转向低掺杂浓度Si进行自旋注入探路。(三)硅基自旋注入三端器件的研制和性能测试及分析1.根据前两章的研究结果设计工艺流程,制备出了以NiFe/HfO_2/n+-Si磁隧道结为核心的硅基自旋注入三端器件,为了对比,采用相同的工艺参数也制备了NiFe/Al_2O_3/n+-Si三端器件,并对部分器件进行了退火处理,测试了器件的电学特性(I-V特性)和自旋注入特性(Hanle曲线);结果显示研制的NiFe/HfO_2/Si器件在低温(10K)下的阻值很大,超过2 MW,比NiFe/Al_2O_3/Si器件大了2~3个数量级;经过退火以后,NiFe/HfO_2/Si器件的阻值降到了0.2 MW,有利于Hanle曲线测试;退火后的NiFe/HfO_2/Si器件测到了Hanle曲线,提取出了自旋寿命(256ps)和自旋扩散长度(264 nm),并计算出了注入到Si中的自旋极化率,约为0.85%;2.NiFe/Al_2O_3/Si器件在退火前后都测到了Hanle曲线,并且自旋寿命和自旋扩散长度都比NiFe/HfO_2/Si器件的略大,但是自旋极化率比较低,退火前仅为0.11%,退火后提高到了0.48%。(四)肖特基源、漏Ge pMOSFET的研制1.以低掺杂浓度的n型Ge为衬底,HfO_2为栅极介质层,并以NiGe合金作为源、漏,制备了肖特基源、漏Ge pMOSFET;2.为了得到性能较好的Ge pMOSFET,对沟道Ge进行了Si钝化处理,并对有、无Si钝化层的器件都进行了电学特性测试,重点研究了样品的转移、输出特性,并探讨了Ge pMOSFET器件产生双极性的原因。
[Abstract]:The development of silicon based spintronic devices is one of the research hotspot in the field of semiconductor spintronics applications. This paper focuses on the development of silicon spin injection three terminal device as the main line, focus on the NiFe/HfO_2/Si magnetic tunnel junction and the study of the interfacial properties of prepared silicon to develop new spin electronic devices. In addition, some of the exploration of Ge pMOSFET fabrication and electrical properties, accumulate experience for the future development of the spin transistor. (a) magnetic electrode NiFe thin film preparation and characterization of 1. high doped n type Si substrate, NiFe thin films with different thickness were prepared by magnetron sputtering, and some samples were annealed the system, study the relationship between the magnetic anisotropy and the thin films of the in-plane and out of plane thickness, and the influence of different annealing conditions on the magnetic properties, results show that in order to comply with the silicon based on magnetic spin injection Electrode film, NiFe film thickness should be controlled within 30 nm, and the annealing temperature to 250 DEG C is preferred; 2. in order to suppress the NiFe film Ni, Fe to Si substrate diffusion, but also in order to form a tunnel junction, between NiFe and Si into 2 nm thick HfO_2 thin film, and the annealing treatment on the magnetic properties of the samples before and after annealing, and the use of XPS test and analysis of the NiFe thin film components, chemical bonding and diffusion, results show that the introduction of HfO_2 layer can inhibit Ni, Fe to Si diffusion, makes Al (22 nm) /NiFe (28 nm /HfO_2 (2) nm) /Si samples were annealed at 250 C after the saturation magnetization is improved by about 80% to 3. of silicon spin injection; preparation of CoFe films is explored. (two) the dielectric layer of HfO_2 thin films preparation and electrical properties of the interface, respectively, 1. (E-beam) and atomic layer deposition (ALD) in high technology N doped Si substrate were prepared on HfO_2 thin films (thickness range of 0-5 nm), and analyze the use of XPS, Si on the growth of HfO_2 thin films were systematically studied, chemical bonding and diffusion, results show that the smaller HfO_2 ALD films grown by about 0.10 nm, roughness, thickness control precision high surface layer with chemical composition, may be suitable for silicon based on spin injection; 2. different preparation methods of Metal/HfO_2/n+-Si contact with the HfO_2 layer (E-beam0-5nm or ALD 0-2.5 nm) I-V characteristic variation, scheme for preparation of silica based spin injection into the tunneling layer of HfO_2 film was optimized; 3. NiFe/HfO_2 (0-2 nm I-V) characteristics of /p-Si contact, discusses the HfO_2 intercalation of NiFe/Si Schottky barrier height modulation effects and mechanism of spin injection pathfinder for future to low doping concentration of Si. (three) three terminal devices based on silicon spin injection Development and performance test and analysis of 1. of the first two chapters according to the research results of design process, prepared by the NiFe/HfO_2/n+-Si magnetic tunnel junction silicon as the core of the spin injection of three terminal device, for comparison with the parameters of the same NiFe/Al_2O_3/n+-Si three terminal devices were prepared, and some of the devices were annealed. The electrical properties of the device test (I-V characteristics) and spin injection characteristics (Hanle curve); results show that the developed NiFe/HfO_2/Si devices at low temperature (10K) of the resistance value is very large, more than 2 MW, ratio of NiFe/Al_2O_3/Si devices for 2~ 3 orders of magnitude; after annealing, the resistance of NiFe/HfO_2/Si devices down to 0.2 MW. To test Hanle curve; NiFe/HfO_2/Si device after annealing are measured by Hanle curve, extract the spin lifetime (256ps) and spin diffusion length (264 nm), and calculated the injection into the spin polarization in Si rate, About 0.85%; 2.NiFe/Al_2O_3/Si device before and after annealing are measured by Hanle curve, and the spin lifetime and spin diffusion length than the NiFe/HfO_2/Si device is slightly larger, but the spin polarization rate is relatively low, only 0.11% before annealing, annealing is improved to 0.48%. (four) Schottky source, drain Ge pMOSFET 1. to develop n type Ge low doping concentration as substrate, HfO_2 as the gate dielectric layer, taking NiGe alloy as the source, drain, Schottky source prepared drain Ge pMOSFET; 2. Ge pMOSFET in order to get better performance of channel Ge of Si passivation, and the device, without the passivation layer are Si the electrical testing, focus on the sample transfer, output characteristics, and discusses the reasons of producing bipolar pMOSFET devices Ge.

【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN386

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