SiC功率器件离子注入和退火设备及工艺验证

针对SiC功率器件工艺制程中离子注入和激活退火的技术难题,利用爱发科公司自行设计并开发的高温离子注入设备(ULVAC,IH-860DSIC)、碳膜溅射设备(ULVAC,SME-200)和高温激活退火设备(ULVAC,PFS-6000-25)。通过计算模拟、AFM对比结果、Hall电阻测定和RHEED图像分析等表征手段,研究了高温高能多步注入、碳膜覆盖技术和退火温度分别对SiC器件的物理特性、表面特性及电学特性的影响。结果表明,采用500℃Al离子注入浓度为5×1018cm-3、20 nm厚碳膜溅射技术和1 700~2 000℃激活退火技术,能够实现具有良好表面特性和电学特性的p型SiC掺杂工艺。设备的稳定性已在多条SiC生产线上用于制造SiCSBD器件和SiC-MOSFET器件完成工艺验证。     

退火工艺对Al离子注入的4H-SiC表面形貌的影响

通过应用多次Al离子注入和CVD中的高温退火技术,在SiC片表面形成了p型层。p型层中各深度下Al的浓度均为110¹⁹cm^-3,层厚为550nm。本文应用三种不同的退火工艺对注入后的SiC进行退火。通过测量和比较表面粗糙度,发现通过石墨层覆盖来保护表面的退火工艺可以很好的阻止SiC表面在高温退火下的粗化,粗糙度保持在3.8nm。通过其他两种(在氩气保护下、在SiC保护片的覆盖下)退火工艺退火所得到的表面有明显的台阶,粗糙度分别为12.2nm和6.6nm。     

快速退火对ZnTe外延层性能及In电极的影响

研究了在GaAs(001)衬底上外延生长的本征ZnTe薄膜样品在氮气氛中450～550℃下的快速退火行为。对于1 min退火的样品,随着退火温度的升高,ZnTe(004)峰双晶X射线(DCXRD)摇摆曲线的半高宽(FWHM)逐渐下降;样品表面粗糙度均方根值(RMS)由退火前的5.3 nm下降至4.7 nm左右。对于450℃退火5 min的样品,其晶体质量与550℃退火1 min的样品相当,但RMS值下降到4.26 nm。ZnTe薄膜表面的In电极之间在未退火时呈高阻状态,在适当条件下退火后In电极之间可以导通,且随着退火温度的降低,所需的退火时间将延长。但550℃退火时In电极的外观形貌发生改变且不能导通。     

退火温度对SiC薄膜结构和光学特性的影响

采用磁控溅射技术在p-Si基片上制备出SiC薄膜。将样品放在管式退火炉中通N2保护,分别在400℃,600℃,800℃和1 000℃进行退火处理,研究了退火温度对薄膜结构以及光致发光特性(PL)的影响。发现随着退火温度的升高,薄膜的结晶程度变好,SiC在800℃开始有晶相出现,Si—C峰也在向高波数的方向移动,这主要是由于膜中的Si1-xCx的化学计量发生变化。PL谱中的三个峰:322 nm起源于薄膜中的中性氧空缺,370 nm起源于SiC发光,412 nm起源于薄膜中的C簇。     

调制型Au/Sn薄膜微观形貌及合金化工艺

采用Au和Sn单质金属靶,通过直流磁控溅射法制备调制型Au/Sn薄膜(薄膜层数为3~21),经快速退火后,实现单质多层薄膜的合金化。主要研究了Au/Sn薄膜微观形貌和合金化工艺控制。结果表明,当固定薄膜总厚度为2μm时,320℃下退火10min后,膜层表面粗糙度与薄膜层数呈反比。薄膜层数较少(n=3)、调制周期厚度较大时,由于Au与Sn间扩散不完全,合金化不充分,造成薄膜表面起伏较大,其均值粗糙度最高达到188.5nm。随着薄膜层数不断增加,调制周期厚度减小到纳米级,薄膜也更加致密、平整,n=21时,320℃下退火10min后均值粗糙度仅为29.7nm。优化合金化工艺过程中,采用了不同的优化方法,包括增加退火温度、延长保温时间、降低薄膜总厚度和调制周期,最终在膜层厚度为700nm、退火温度为320℃、退火时间为10min的工艺条件下,获得了表面致密平整、合金化充分及金锡质量比约为80∶20的合金薄膜,均值粗糙度仅为23.5nm。     

sol-gel法制备纳米TiO_2-SiO_2宽带高增透膜

通过模拟计算设计出一种透射比为99%、包含一层TiO2薄膜和一层SiO2薄膜的宽带高增透膜。两层薄膜均由溶胶-凝胶法制得并采用提拉法成形于玻璃基片上。对增透膜样品的透射比、表面形貌、膜厚等进行了表征,考察了提拉速度、退火温度、催化条件等对其透射比、表面均匀性的影响。结果表明:增透膜的使用提高了玻璃基片的透射比;当提拉速度为9cm/min,增透膜厚约为255nm时,基片在400～800nm波段的透射比提高了7%。控制退火温度,可以使增透膜在某些波段的透射比增强。增透膜样品的表面均匀性良好,室温下膜层的均方根表面粗糙度(RMS)为1.682,平均粗糙度(RA)为1.208,在550℃的温度以下,随着退火温度升高,表面粗糙度降低。     

SiC纳米晶薄膜的制备及发光性质研究

用射频磁控溅射及后退火(800℃、1000℃和1200℃)方法,在Si(111)衬底上制备出了SiC纳米晶(nc-SiC)薄膜。傅立叶变换红外光谱(FTIR)、X射线衍射谱(XRD)及扫描电子显微镜(SEM)形貌像等研究表明,制备出的nc-SiC薄膜具有立方结构;样品经800℃、1000℃退火后,表面的纳米晶粒分别为10nm和20nm左右;而1200℃退火后,样品晶化完全。光致发光(PL)研究表明,nc-SiC薄膜室温条件下发射蓝光,发光峰峰位随退火温度的降低发生蓝移且发光峰强度变大;1000℃退火后样品的发光峰在478nm,800℃退火后发光峰在477nm,800℃退火比1000℃退火的样品发光强度高4倍。     

退火温度对纳米TiO2薄膜微结构的影响

利用XRD、IR、UV-VIS、AFM、XPS等手段,研究了退火温度对溶胶–凝胶法制备的纳米TiO2薄膜微结构和表面形貌的影响。450~600℃退火处理的薄膜呈锐钛矿和金红石型混晶结构,700℃退火后为纯金红石相;水峰的吸收峰消失在300~500℃之间,至500℃有机基团完全消失,薄膜表面主要有C,Ti,O三种元素;改变退火温度,可以使薄膜的禁带宽度在3.26~3.58eV之间变化,可以在一定范围内,获得不同折射率的TiO2纳米薄膜;薄膜的表面粗糙度(RMS)为2~3nm。     

不同温度下的表面粗糙度对4H-SiC MOSFETs迁移率的影响(英文)

在制造4H-SiC MOSFETs过程中,超过1 500℃的高温退火用来激活被注入的离子。经常在4H-SiC表面会涂上一层碳膜来进行保护,以此期待4H-SiC MOSFETs取得好的电特性。基于前期4H-SiC MOS电容的实验结果,采用计算机模拟研究了不同温度条件下的表面粗糙度对4H-SiC MOSFETs沟道迁移率的影响。结果表明,在较高的栅压下,限制沟道迁移率的主要机制是表面粗糙度散射,然而,表面粗糙度数值的大小对迁移率的影响不大。结果同时表明,迁移率的峰值会随着温度的增加而增加,然而,对于更高的温度,峰值会随着温度的继续增加而减小。     

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.     

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.     

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.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.