钒注入4H-SiC半绝缘特性的研究

研究了2100keV高能量钒注入4H-SiC制备半绝缘层的方法和特性,注入层的浓度分布用蒙特卡罗分析软件TRIM进行模拟.采用一种台面结构进行I-V测试,发现钒注入层的电阻率与4H-SiC层的初始导电类型有很大关系.常温下,钒注入p型和n型4H-SiC的电阻率分别为1.6×1010和7.6×106Ω·cm.测量了不同退火温度下的电阻率,发现高温退火有利于钒的替位激活和提高电阻率,由于钒扩散的影响1700℃退火使得电阻率略有下降.测量了n型SiC钒注入层在20～140℃时的电阻率,计算出钒受主能级在4H-SiC中的激活能为0.78eV.     

钒注入制备半绝缘SiC的退火效应

对钒离子注入P型和n型4H-SiC制备半绝缘层的方法和特性进行了研究.注入层电阻率随退火温度的升高而增加,经过1 650℃退火后,钒注入p型和n型SiC的电阻率分别为1.6×1010Ω·cm和7.6×106Ω·cm.借助原子力显微镜对样品表面形貌进行分析,发现碳保护膜可以有效减小高温退火产生的表面粗糙,抑制沟槽的形成.二次离子质谱分析结果表明退火没有导致明显的钒在SiC中的再扩散.即使经过1 650℃高温退火,也没有发现钒离子向SiC表面外扩散的现象.     

4H-SiC钒离子注入层的特性

研究了钒注入4H-SiC形成半绝缘层的方法和特性,注入层的离子浓度分布由蒙特卡罗分析软件TRIM模拟提取.采用一种台面结构进行I-V测试.钒注入层的电阻率与4H-SiC层的初始导电类型关系很大,常温下钒注入p型和n型SiC的电阻率分别为1.2×109～1.6×1010 Ω·cm和2.0×106～7.6×106 Ω·cm.     

4H-SiC钒离子注入层的特性

研究了钒注入4H-SiC形成半绝缘层的方法和特性,注入层的离子浓度分布由蒙特卡罗分析软件TRIM模拟提取.采用一种台面结构进行I-V测试.钒注入层的电阻率与4H-SiC层的初始导电类型关系很大,常温下钒注入p型和n型SiC的电阻率分别为1.2×109～1.6×1010 Ω·cm和2.0×106～7.6×106 Ω·cm.     

4H-SiC钒离子注入层的特性

研究了钒注入4H-SiC形成半绝缘层的方法和特性，注入层的离子浓度分布由蒙特卡罗分析软件TRIM模拟提取. 采用一种台面结构进行I-V测试. 钒注入层的电阻率与4H-SiC层的初始导电类型关系很大，常温下钒注入p型和n型SiC的电阻率分别为1.2E9～1.6E10Ω·cm和2.0E6～7.6E6Ω·cm.     

退火对掺钒半绝缘4H-SiC晶片质量影响的研究

通过物理气相传输(PVT)法成功地生长出直径大于7.62 cm的掺钒半绝缘4H-SiC晶体。抛光后的掺钒半绝缘4H-SiC晶片在真空且温度1 600℃～2 000℃条件下进行退火处理,利用高分辨X-ray衍射仪、显微拉曼光谱仪、非接触电阻率测试仪和应力仪对退火前后的晶片进行了测试与分析,研究了退火工艺对掺钒半绝缘4H-SiC晶片应力的影响,并且得到了合适的退火工艺。结果表明:合适的退火处理有利于进一步提高晶片的质量。     

高能量钒注入n型4H-SiC的欧姆接触形成

借助二次离子质谱法分析了注入的钒离子在碳化硅中的分布.即使经过1650℃的高温退火,钒在碳化硅中的再扩散也不显著.退火并没有导致明显的钒向碳化硅表面扩散形成堆积的现象,由于缺少钒的补偿作用,表面薄层的自由载流子浓度保持不变.采用线性传输线模型测量了钒注入n型4H-SiC上的Ni基接触电阻,在1050℃下,在氮、氢混合气体中退火10min,形成的最低比接触电阻为4.4×10-3Ω·cm2.金属化退火后的XRD分析结果表明,镍、碳化硅界面处形成了Ni2Si和石墨相.观测到的石墨相是由于退火导致C原子外扩散并堆积形成,同时在碳化硅表面形成C空位.C空位可以提高有效载流子浓度,降低势垒高度并减小耗尽层宽度,对最终形成欧姆接触起到了关键作用.     

4H-SiCN离子注入层的特性

研究了在4H-SiC p型外延层上用N离子注入制备n型层的方法及其特性,注入层的浓度分布用蒙特卡罗分析软件TRIM进行了模拟.为了测试注入层的特性,制备了横向肖特基二极管和TLM (transfer length method)结构.测得的N激活浓度为3.0×1016cm-3,计算出激活率为0.02.注入层方块电阻为30kΩ/□,电阻率为0.72Ω*cm,并计算出电子迁移率为300cm2/(V*s).     

4H-SiCN离子注入层的特性

研究了在4H-SiC p型外延层上用N离子注入制备n型层的方法及其特性,注入层的浓度分布用蒙特卡罗分析软件TRIM进行了模拟.为了测试注入层的特性,制备了横向肖特基二极管和TLM (transfer length method)结构.测得的N激活浓度为3.0×1016cm-3,计算出激活率为0.02.注入层方块电阻为30kΩ/□,电阻率为0.72Ω*cm,并计算出电子迁移率为300cm2/(V*s).     

高能量钒注入n型4H-SiC的欧姆接触形成

借助二次离子质谱法分析了注入的钒离子在碳化硅中的分布.即使经过1650℃的高温退火,钒在碳化硅中的再扩散也不显著.退火并没有导致明显的钒向碳化硅表面扩散形成堆积的现象,由于缺少钒的补偿作用,表面薄层的自由载流子浓度保持不变.采用线性传输线模型测量了钒注入n型4H-SiC上的Ni基接触电阻,在1050℃下,在氮、氢混合气体中退火10min,形成的最低比接触电阻为4.4×10-3Ω·cm2.金属化退火后的XRD分析结果表明,镍、碳化硅界面处形成了Ni2Si和石墨相.观测到的石墨相是由于退火导致C原子外扩散并堆积形成,同时在碳化硅表面形成C空位.C空位可以提高有效载流子浓度,降低势垒高度并减小耗尽层宽度,对最终形成欧姆接触起到了关键作用.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.