Enhancement-mode AlGaN/GaN high electronic mobility transistors with thin barrier

An enhancement-mode （E-mode） A1GaN/GaN high electron mobility transistor （HEMTs） was fabricated with 15-nm A1GaN barrier layer. E-mode operation was achieved by using fluorine plasma treatment and post-gate rapid thermal annealing. The thin barrier depletion-HEMTs with a threshold voltage typically around -1.7 V, which is higher than that of the 22-nm barrier depletion-mode HEMTs （-3.5 V）. Therefore, the thin barrier is emerging as an excellent candidate to realize the enhancement-mode operation. With 0.6-tim gate length, the devices treated by fluorine plasma for 150-W RF power at 150 s exhibited a threshold voltage of 1.3 V. The maximum drain current and maximum transconductance are 300 mA/mm, and 177 mS/ram, respectively. Compared with the 22-nm barrier E-mode devices, VT of the thin barrier HEMTs is much more stable under the gate step-stress,

Deposition of Thin Titania Films by Dielectric Barrier Discharge at Atmospheric Pressure

A homogeneous atmospheric pressure dielectric barrier discharge is studied. It is in argon with small admixtures of titanium tetrachloride vapour and oxygen for the deposition of thin titania films on glass substrates. A special electrode configuration was applied in order to deposit the titania film uniformly. The sustaining voltage （6 kV to 12 kV）, current density （about 3 mA/cm^2） and total optical emission spectroscopy were monitored to characterize the discharge in the gap of 2 mm. Typical deposition rates ranged from approximately 30 nm/min to 120 nm/min. The film morphology was investigated by using scanning electron microscopy （SEM） and the composition was determined with an energy dispersive x-ray spectroscopy （EDS） analysis tool attached to the SEM. The crystal structure and phase composition of the films were studied by x-ray diffraction （XRD）. Several parameters such as the discharge power, the ratio of carrier gas to the precursor gas, the deposition time on the crystallization behavior, the deposition rate and the surface morphology of the titania film were extensively studied.

Study on Al_xNi_y Alloys as Diffusion Barriers in Flexible Thin Film Solar Cells

Co-sputtered AlxNiy thin films were used as diffusion barriers between aluminum and hydrogenated microcrystalline silicon （μc-Si：H） for flexible thin film solar cells. The stoichiometric ratio of AlxNiy showed a significant effect on the structures of the films. The obtained Al3Ni2 film was amorphous, while polycrystalline films were obtained when the ratio of aluminum to nickel was 1：1 and 2：3. An auger electron spectroscope and four-point probe system were applied to test the resistance to the interdiffusion between aluminum and silicon, as well as the conductivities of the AlxNiy barriers. The data of auger depth profile showed that the content of silicon was the minimum in the aluminum layer after sputtering for 4 min using AlNi thin film as the barrier layer. Compared to other AlxNiy alloys, the AlNi thin film possessed the lowest sheet resistance.

Diffusion barrier performance of nanoscale TaN_x thin-film

TaNx nanoscale thin-films and Cu/TaNx multilayer structures were deposited on P-type Si(100) substrates by DC reactive magnetron sputtering. The characteristics of TaNx films and thermal stabilities of Cu/TaNx/Si systems annealed at various temperatures were studied by four-point probe(FPP) sheet resistance measurement, atomic force microscopy(AFM), scanning electron microscope-energy dispersive spectrum (SEM-EDS), Alpha-Step IQ Profilers and X-ray diffraction(XRD), respectively. The results show that the surfaces of deposited TaNx thin-films are smooth. With the increasing of N2 partial pressure, the deposition rate and root-mean-square(RMS) decrease, while the content of N and sheet resistance of the TaNx thin-films increase, and the diffusion barrier properties of TaNx thin-films is improved. TaN1.09 can prevent interdiffusion between Cu and Si effectively after annealing up to 650 ℃ for 60 s. The failure of TaNx is mainly attributed to the formation of Cu3Si on TaN/Si interface, which results from Cu diffusion along the grain boundaries of polycrystalline TaN.

铜金属化中扩散阻挡层的研究进展

随着第四次工业革命的到来,集成电路尺寸的微小型化是其发展的必然结果。铜互连取代铝互连在集成电路后道工艺中取得了革命性变革,为推动集成电路产业迈向新的发展阶段注入了强劲动力。然而,随着半导体器件尺寸的减小,铜原子向硅界面的快速扩散行为严重阻碍了铜金属化的发展。该领域重要的目标是制造超薄尺寸、低电阻率和热稳定的新型铜扩散阻挡材料,以实现铜/硅界面的可靠耦合。从4个方面总结了铜金属化中扩散阻挡层的研究进展,首先讨论了铜金属化取代铝金属化面临的关键问题及其解决方案;随后,介绍了铜金属化中扩散阻挡层的制备方法,主要包括气相沉积技术、原子层沉积技术和电沉积技术等;然后着重对铜互连中扩散阻挡层的常用材料(金属基、碳材料、自组装分子层及高熵合金)进行了讨论,系统综述了不同材料的阻挡特性,理清了扩散阻挡层材料结构与扩散阻挡性能的构效关系;最后展望了亚纳米厚度的高性能扩散阻挡层的材料筛选策略,以及制备方法的选择。

Plasma-Assisted ALD of an Al_2O_3 Permeation Barrier Layer on Plastic

Atomic layer deposition （ALD） technique is used in the preparation of organic/inorganic layers, which requires uniform surfaces with their thickness down to several nanometers. For film with such thickness, the growth mode defined as the arrangement of clusters on the surface during the growth is of significance. In this work, Al2O3 thin film was deposited on various interfacial species of pre-treated polyethylene terephthalate （PET, 12 μm） by plasma assisted atomic layer deposition （PA-ALD）, where trimethyl aluminium was used as the Al precursor and O2 as the oxygen source. The interracial species, -NH3, -OH, and -COOH as well as SiCHO （derived from monomer of HMDSO plasma）, were grafted previously by plasma and chemical treatments. The growth mode of PA-ALD Al2O3 was then investigated in detail by combining results from in-situ diagnosis of spectroscopic ellipsometry （SE） and ex-situ characterization of as-deposited layers from the morphologies scanned by atomic force microscopy （AFM）. In addition, the oxygen transmission rates （OTR） of the original and treated plastic films were measured. The possible reasons for the dependence of the OTR values on the surface species were explored.

Preparation and properties of SiCN diffusion barrier layer for Cu interconnect in ULSI

SiCN thin films and Cu/SiCN/Si structures were fabricated by magnetron sputtering. And some samples underwent the rapid thermal annealing(RTA) processing. The thin-film surface morphology, crystal structure and electronic properties were characterized by atomic force microscopy(AFM), X-ray diffractometry(XRD), Fourier transform infrared transmission(FTIR) and four-point probe(FPP) analyses. The results reveal the formation of complex networks among the three elements, Si, C and N, and the existence of different chemical bonds in the SiCN films, such as Si—C, Si—N, C—N and C=N. The as-deposited SiCN thin films are amorphous in the Cu/SiCN/Si structures and have good thermal stability, and the SiCN thin films are still able to prevent the diffusion reaction between Cu and Si interface after RTA processing at 600 ℃ for 5 min.

New Organic Thin-Film Encapsulation for Organic Light Emitting Diodes

Organic Light-Emitting diodes (OLEDs) are extremely sensitive to water vapour and oxygen, which causes rapid degradation. Epoxy and cover glass with large amount of desiccant are commonly applied to encapsulate bottom emitting OLEDs which is not a viable option for flexible as well as top emitting OLEDs. This paper reports a completely organic encapsulating layer consisting of four periods of alternate stacks of two organic materials with different morphologies deposited by simple vacuum thermal evaporation technique. Standard green OLED structures with and without encapsulation were fabricated and investigated using structural, optical and electrical studies. Moreover, the encapsulation presented being organic is safe for underlying organic layers in OLEDs and is ultrathin, transparent and without any cover glass and desiccant, ensuring its application in flexible and top emitting OLEDs.

Effect of substitution group on dielectric properties of 4H-pyrano [3,2-c] quinoline derivatives thin films

The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-（3-phenoxyphenyl）-5,6-dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile（Ph-HPQ） and 2-amino-4-（2-chlorophenyl）-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3, 2-c] quinoline-3-carbonitrile（Ch-HPQ） thin films were determined in the frequency range of 0.5 k Hz–5 MHz and the temperature range of 290–443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping（CBH） mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than the Ch-HPQ.

Fabrication of Titanium Dioxide Thin Films by DBD-CVD Under Atmosphere

Titanium dioxide films were firstly deposited on glass substrate by DBD-CVD （dielectric barrier discharge enhanced chemical vapor deposition） technique. The structure of the films was investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）. TiO2 films deposited under atmosphere pressure show preferred orientation, and exhibit columnar-like structure, while TiO2 films deposited under low gas pressure show no preferred orientation. The columnar-like structure with preferred orientation exhibits higher photocatalytic efficiency, since the columnar structure has larger surface area. However, it contributes little to the improvement of hydrophilicity. DBD-CVD is an alternative method to prepare photocatalytic TiO2 for its well-controllable property.

用于柔性电子器件的有机/无机薄膜封装技术研究进展

有机/无机薄膜封装技术被广泛用于有机发光二极管(OLED)、量子点显示及有机光伏等领域,是一种新型的柔性封装技术。综述近年来有机/无机薄膜封装技术的发展趋势,首先概述了传统硬质盖板封装方式与薄膜封装方式的发展及其优缺点。其次,系统地总结了有机/无机薄膜的制备方法,如原子层沉积、等离子体化学气相沉积等,详细阐述了不同制备方法的原理及其应用。再次,讨论了薄膜的微观缺陷、内应力,以及材料界面工程对有机/无机薄膜封装性能的影响,分析总结了有机/无机封装薄膜制备的技术要点,如采用基底表面预处理、引入中性层、调节层间应力等方式获得优质的封装薄膜。最后,探究了有机/无机封装薄膜的内在阻隔机理,提出气体在有机/无机薄膜中的传输方式以努森扩散为主,并总结了提高薄膜封装的策略,即延长气体扩散路径、“主动”引入阻隔基团及薄膜表面改性。提出了未来薄膜封装技术面临的问题,拟为柔性电子器件封装技术的发展提供一定参考。

石菖蒲抗血管性痴呆的药理机制研究进展

血管性痴呆是我国乃至全世界最主要的痴呆类型之一,其发病机制复杂,临床治疗尚无特效药,严重影响人类生活及健康。研究发现石菖蒲是中医治疗血管性痴呆最高频的核心中药,具有开窍豁痰、醒神益智、化湿开胃的功效,防治血管性痴呆具有确切优势。石菖蒲的化学成分复杂,其主要有效成分α-细辛醚、β-细辛醚因其广泛的药理活性成为研究热点。石菖蒲及其活性成分可在调节血脑屏障通透性,促进药物通过血脑屏障;清除自由基与提高抗氧化物质以抗氧化应激;调节炎症因子以抗炎;清除β-淀粉样蛋白以调节神经可塑性;调节神经递质以保护胆碱能神经;减少细胞凋亡保护海马神经元等方面发挥抗血管性痴呆的作用。本文对石菖蒲抗血管性痴呆的药理机制进行综述,为石菖蒲的运用提供理论依据及循证支持。

薄板坯连铸机保护浇注新技术的开发与应用

针对目前薄板坯连铸机保护浇注在生产遇到的瓶颈问题,对钢包的钢水通道实现气幕阻隔,并对中间包包盖进行了改造,同时通过中间包机构弹簧压力调整进一步提升板间密封效果,使钢水在浇注过程中完全与空气隔绝,C、D类夹杂物零级比例达到90%,夹杂物总量控制在0.5级以下,保护浇注新技术实施效果明显。

背界面纳米光子结构提高透明导电氧化物基超薄Cu(In, Ga)Se_(2)太阳能电池电学性能的理论探究

透明导电氧化物(TCO)基超薄Cu(In, Ga)Se_(2)(CIGSe)太阳能电池具有建筑光伏一体化的潜力,然而由于背肖特基结的存在,其增大背复合速率S_b在提高空穴传输的同时也增加了光生电子背复合,从而抑制了其性能的提高。本文使用1D-SCAPS软件对背界面纳米光子结构(NPs)如何提高电池的性能进行理论探究,结果表明,背界面NPs的引入产生了复杂的电学效应。一方面,NPs本身不吸收光能,从而降低了背界面附近的有效光吸收体积,导致背界面光生载流子浓度降低,光生电子的背复合显著降低;另一方面,NPs的引入增加了吸收层厚度,导致空间电荷区(SCR)远离背界面,降低了其对光生电子的收集效率,增加了背复合。在高背复合速率(S_(b)=1.0×10^(7)cm·s^(-1))下,光生载流子浓度降低产生的背复合降低大于SCR移动产生的背复合增加,因此总体的背复合降低。与此同时,背复合的降低还缓解了高S_b时的光生电子损耗,从而解除了随S_b增大而增加的背复合对电池性能的抑制。这些发现为设计和优化TCO基超薄CIGSe太阳能电池提供了参考。

两层流体中水波在垂直薄板上的反射与透射

研究在两层流体中表面波模态和内波模态的波浪与半潜式刚性垂直薄板相互作用的问题.基于特征函数展开理论,建立了两种模态入射波作用下,半潜式刚性垂直薄板的反射与透射能量的计算方法,证明了对每一种模态的入射波,另一种模态波浪的反射与透射能量是相等的.对水面漂浮和座底半潜式薄板的反射与透射能量,以及作用在其上的水平波浪力进行了数值计算分析,表明在某个频率范围内,流体的分层效应对这些水动力量的影响是不可忽视的.特别地,当薄板的一端位于两层流体的内界面上时,两种模态波浪的能量转化是最大的.

分层流体中内孤立波在潜浮式竖直薄板上透射和反射

采用边缘层理论研究了两层流体系统中内孤立波在潜浮式竖直薄板上的透射和反射问题,提出了非线性演化方程的“初值”条件,分析了内孤立波与薄板非线性相互作用的效应。研究表明:流体层的密度比以及薄板伸入上下层的深度对于反射和透射波结构具有显著的影响,薄板伸入下层越深、密度差越小,则薄板阻碍孤立波透射的效率越高;透射波通常演化为单峰孤立波和迅速衰减的尾波,反射波演化为缓慢衰减的尾波列;对于具有小密度差的跃层结构,内孤立波在潜浮式竖直薄板上的透射及其演化近乎是无障碍的。

新型高阻隔陶瓷薄膜包装材料及技术

综述了高阻隔性陶瓷包装材料的应用现状、发展进程、镀膜的生产工艺,以及影响其性能的各方面因素,包括基材性能、基材预处理、镀膜技术等。

连续分层流体中垂直薄板的水动力特性

研究了在线性连续分层流体中水波与半潜式刚性垂直薄板相互作用的问题．在Boussinesq近似下,基于分离变量法,导出了具有自由面的平面前进波的色散关系,建立了半潜式刚性垂直薄板的反射与透射能量、水平波浪力的计算方法．对给定的频率,当它大于浮力频率时,流场中只有一种模态的平面前进波,当它小于浮力频率时,流场中有无数多个模态的平面前进波,并证明了对每一种模态的入射波,其它每个模态水波的反射与透射能量是相等的．对水面漂浮和座底半潜式薄板的反射与透射能量,以及作用在薄板上的水平波浪力进行了数值计算分析,表明了流体的线性连续分层效应对这些水动力的影响是不可忽视的．特别地,在入射波频率小于浮力频率时,与第1模态入射波的能量转化量及其对薄板产生的水平波浪力相比,其它模态入射波的能量转化量及其对薄板产生的水平波浪力都要大得多．

InAlN/AlN/GaN HEMT器件特性研究

通过利用MOCVD生长的高质量蓝宝石衬底InAlN/AlN/GaN异质结材料,获得了高的二维电子气面密度,其值为1.65×1013cm-2。通过该结构制备了0.15μm栅长InAlN/AlN/GaN HEMT器件,获得了相关的电学特性:最大电流密度为1.3 A/mm,峰值跨导为260 mS/mm,电流增益截止频率为65 GHz,最大振荡频率为85 GHz。对比于相应的AlGaN/AlN/GaN HEMT器件,InAlN/AlN/GaN HEMT器件由于具有高的二维电子气面密度和薄的势垒层厚度,其最大电流密度和峰值跨导特性有了很大的改善,同时频率特性也有显著提高。

应用SBFEM研究波浪与薄板的相互作用问题

应用比例边界有限元法(SBFEM)求解了频域下波浪与刚性薄板防波堤相互作用问题。求解中将整个计算区域分为薄板周围的有限子域和直到无限远处的无限子域。有限子域的比例中心设置在薄板的下端,这时薄板的两侧为侧边面,而无限子域的比例中心设置在无限子域与有限子域的交界上,同时将水底和自由水面做为平行侧边面。应用加权余量法在每个子域内推导出比例边界有限元方程,然后在有限子域与无限子域交界上匹配求解。通过与解析解的对比,证明了这种方法的精确性,而后对不同类型的薄板防波堤进行了计算,并给出了反射和透射系数的变化规律。