c轴择优取向AlN薄膜的制备研究

采用MOCVD法在蓝宝石(0001)单晶衬底上生长AlN压电薄膜。用XRD和原子力显微(AFM)技术表征薄膜的微观结构。研究了衬底温度、TMA和NH3流量、反应室气压对AlN薄膜织构特性的影响,并对薄膜生长的工艺参数进行了相应优化。结果表明:在优化条件下制备的AlN薄膜高度c轴择优取向,(0002)峰摇摆曲线半高宽仅为0.10°,且薄膜表面平整,椭圆偏振法测出其折射率为2.0～2.4。     

金刚石基底上制备(002)AlN薄膜的研究

首先采用微波等离子体化学气相沉积(MPCVD)方法,在O2/H2/CH4混合气体气氛下利用大功率微波在(100)Si片上生长出了异质外延金刚石膜,X-射线衍射(XRD)、拉曼光谱和场发射扫描电子显微镜(FESEM)对薄膜的表征分析结果表明,制备的金刚石膜具有很高的金刚石相纯度,且晶粒排列紧密;继而采用射频磁控反应溅射法,在抛光的金刚石基底上成功制备了高C轴择优取向的氮化铝(AlN)薄膜,研究了不同的溅射气压、靶基距对AlN薄膜制备的影响,XRD检测结果表明,溅射气压低,靶基距短,有利于AlN(002)面择优取向,相反则更有利于AlN薄膜的(103)面和(102)面择优取向;研究了AlN薄膜在以N终止的金刚石基底和纯净金刚石基底两种表面状态上的生长机制,结果发现,以N终止的金刚石基底非常有利于AlN(002)面择优取向生长;从Al-N化学键的形成以及溅射粒子平均自由程的角度,探讨了其对AlN薄膜择优取向的影响。     

AlN薄膜体声波谐振器性能分析

采用体硅微细加工工艺制备了背空腔型AlN薄膜体声波谐振器。研究了压电层、上电极及支撑层厚度对谐振器性能的影响。测试结果表明,谐振器所用AlN压电薄膜具有(002)择优取向,器件频率特性良好。当上电极、压电层、底电极和支持层的厚度分别为110,2600,110,200nm时,谐振频率为1.759GHz,机电耦合系数3.75%,品质因数79.5。结合Mason等效电路模型模拟分析与实验结果,分析了各层厚度对频率特性的影响机理。     

将电压基准输出噪声降低一半的电路

将一个IC电压基准产生的低频(1／f)噪声降低一半可能是很困难的。从理论上说，在基准的输出端加接一个低通滤波器就可减小噪声。事实上，一个抑制10Hz以下噪声的低通RC滤波器需要很大的串联电阻值和并联电容值。令人遗憾的是，一只大阻值串联电阻器会产生阻值误差和热噪声，而一只并联电容器的泄漏电阻会形成一条难以预测的、不稳定的分流通道。     

如何减少CATV信号的传输故障

在有线电视线路中 ,许多故障是由接头松动、氧化、进水等引起的 ,如果发生在干线、支干线就会造成大片用户看不好电视 ,因此在ＣＡＴＶ线路施工中保证接头的安装质量至关重要。在施工中 ,有些施工人员认为做Ｆ接头很简单而不认真对待。有人做Ｆ头时将电缆的金属网剪掉 ,有的不加金属箍 ,这都会使接头松动 ,造成接地不良 ,在用户电视上表现为 :高频信号勉强可收看 ,低频信号电平严重降低 ,雪花大且有网纹 ,甚至收看不到信号。还有人安装分支器不加防雨盒 ,使其暴露在外 ,一旦下雨、下雪进水就造成信号短路 ,而且日久锈蚀电路板使分支器损坏。…     

The influence of the AlN film texture on the wet chemical etching

The influence of the aluminum nitride (AlN) film texture on the chemical etching in KOH solution was invested. The AlN films with the different texture and crystal quality were prepared by sputtering. It is found that the chemical etching behaviors, including the etch rate, the activation energy, the surface morphology and the anisotropy, are strongly dependent on the film texture. There is a faster etching in the case of mixed (1 0 0) and (0 0 2) texture and a lower rate in the case of only (0 0 2) texture. The etch rate also decreases with the crystal quality. The sample with the only (0 0 2) texture forms discontinuous column structure after etching and exhibits lower porosity compared to that of the mixed (1 0 0) and (0 0 2) texture. Due to the strong anisotropy of the AlN wurtzite structure, the morphology of the film deposited at 700 °C shows the homogeneous pyramid shape after etching. The cross-section micrographs of etching patterns indicate that the anisotropy of the chemical etching is improved with the improving of the crystal quality.     

靶基距对反应溅射AlN薄膜微结构和性能的影响

采用射频(RF)磁控反应溅射法在Si基底上制备了氮化铝(AlN)薄膜,利用X射线衍射(XRD)、傅立叶红外光谱(FTIR)、扫描电子显微镜(SEM)和纳米力学测试系统研究靶基距对AlN薄膜取向性、微结构、形貌和力学性能的影响。结果表明,靶基距较大时,形成的AlN薄膜为非晶态,薄膜表面较疏松;随着靶基距的减少,AlN薄膜变为多晶态,且具有(100)择优取向;随着靶基距的进一步减少,薄膜结晶质量变好,晶粒变大,薄膜变得更致密,择优取向也由(100)逐渐向(002)转变;靶基距较小时,AlN压电薄膜与基底结合得更牢固,而压电薄膜与基底结合的紧密程度对多层膜声表面波(SAW)器件性能优劣的影响至关重要。     

How to reduce 3-D gray-scale mathematical morphology to 2-D

A planar encoding of three-dimensional (3-D) images, which is commutative with respect to set and gray-scale morphological operations, is proposed. Such an encoding indicates a way to reduce 3-D set and mathematical morphology operations to two-dimensional (2-D) ones     

制备过程中对VO_2薄膜热致相变光电性能的控制

本文利用真空还原V2 O5的方法制备出优质对VO2 薄膜 ;研究了不同真空还原时间VO2 薄膜热致相变过程中光电性能的影响 ;利用XPS、XRD对薄膜的化学状态和结晶状态进行了研究。制备的薄膜高 /低温电阻变化最大达到三个数量级 ,90 0nm处的光学透过率在相变前后改变了 40 %左右 ,热致相变性能优良。讨论了不同的真空还原时间下VO2 薄膜热滞回线的宽度、相变温度点以及高低温光透射性能。最后给出了最佳真空还原时间。     

制备过程中对VO2薄膜热致相变光电性能的控制

本文利用真空还原Ｖ２Ｏ５的方法制备出优质对ＶＯ２薄膜;研究了不同真空还原时间ＶＯ２薄膜热致相变过程中光电性能的影响;利用ＸＰＳ、ＸＲＤ对薄膜的化学状态和结晶状态进行了研究。制备的薄膜高／低 电阻变化最大达到三个数量级,９００ｎｍ处的光学透过率在相变前后改变了４０％左右,热致相变性能优良。讨论了不同的真空还原时间下ＶＯ２薄膜热滞回线的宽度、相变温度点以及高低温光透射性能。最后给出了最佳真空还原时间。     

Theoretical investigation of the electronic and structural properties of AlN thin films

Studying the electronic and structural properties of AlN thin films is an important problem because such films are widely used as a buffer layer when growing GaN-based semiconductor heterostructures on Si substrates. In this paper, we carry out a theoretical investigation of the properties of an Al-terminated AlN(0001) surface in the framework of the density functional theory. Ab initio calculations allow us to analyze the effect of the in-plane lattice strain on the energy of this surface. It is shown that compressive strain causes a decrease in the AlN(0001) surface energy, while tensile strain leads to its increase. Knowing the surface energy values allows us to evaluate the stress of the surface under investigation. In addition, the curvature of the AlN surface is calculated for various AlN film thicknesses in the case of free growth. The obtained values of the surface curvature are in close agreement with the known experimental results.     

Influence of the nitrogen fraction on AlN thin film deposited by cathodic arc ion

Thin films of aluminum nitride (AlN) have been grown, using the cathodic arc ion deposition technique. The effects of nitrogen fractions in the discharge on synthesized films growth rate, stoichiometric ratio (N/Al), crystal orientation and molecular mode of vibration have been investigated. AlN films have been studied by means of Rutherford backscattering (RBS) spectroscopy, X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM) and the four probe method. In RBS results, it has been found that growth rate and stoichiometric ratio decrease while reducing the nitrogen content in the synthesized chamber. XRD patterns indicated that films prepared in 100–85% nitrogen condition exhibit mixed phase of wurtzite+FFC, with preferential orientation along (002) corresponding to the hexagonal phase. It also demonstrated that at lower nitrogen environment, the transformation from mixed phase of wurtzite+FCC to a single phase of FCC–AlN occurs. FTIR spectroscopic analysis was employed to determine the nature of chemical bonding and vibrational phonon modes. Its spectra depicted a dominant peak around 850 cm⁻¹ corresponding to the longitudinal optical (LO) mode of vibration. A shift in the LO mode peak toward lower wavenumbers was noticed with the decrease of nitrogen fraction, illustrating the decline of nitrogen concentration in the deposited AlN films. The 75% nitrogen fraction appeared critical for AlN film properties, such as shifting of mixed (wurtzite+FCC) phase to single FCC–Al(N), a sharp drop of stoichiometric ratio and deposition rate. Measurements of resistivity recorded by the four probe method depicted a sharp decline in the corresponding growth condition.     

PID调节器对制备纳米钛薄膜的重要作用

简述了IBAD(离子束辅助沉积)法制备纳米钛膜的过程中,关键工艺因素是如何将衬底温度维持在一个适当的范围,并运用PID(比例积分微分)调节器较好地实现这一要求的。     

如何防止FPC贴膜起卷

由于FPC基材轻薄柔软,在干膜贴膜后基材往往会弯曲起翘起卷,严重时卷成＂管状＂。基材变形后给曝光作业带来不少麻烦,要将基材打开压平后才能进行曝光,这样的作业方式导致作业效率非常低下。另外由于基材弹性弯曲,尖锐的基材角部划伤照相底版的几率增大,带来严重的品质隐患。本文对干膜贴膜过程进行分析,为控制FPC贴膜起卷作出了一套控制方法。     

光化学汽相淀积技术在薄膜备制中的应用

介绍了光化学汽相淀积法的原理以及ＰＶＤ－１０００设备淀积薄膜的规律，特点等，并且给出了所淀积的ＳｉＯ２膜，Ｓｉ３Ｎ４膜和ＺｎＳ膜的基本特性。     

PZT铁电薄膜的制备和应用

介绍了一种制备膜厚为数微米的均匀相和非均匀相(准周期性多层膜)铁电薄膜的有效方法,研究了PZT平面波导结构的光波导特性及准周期性多层铁电薄膜的布拉格反射特性.研究表明厚度在数微米的均匀相铁电薄膜膜层致密,棱镜耦合实验表明该铁电薄膜波导层对光波的传播有良好的限定性能.准周期铁电多层薄膜具有良好的布拉格反射特性,周期数为10以上的铁电多层膜样品在室温下具有90%以上的反射率和约40 nm的反射带宽.     

Frequency effects on the dielectric properties of AlN film deposited by radio frequency reactive magnetron sputtering

Applications insulated metal substrates (IMS) for high-density and high-power mounting are greatly extending with miniaturizing of electronic components. Recently, aluminum nitride film has been used as a potential insulator and/or passivation material in insulated metal substrate because of its high intrinsic thermal conductivity, low thermal expansion coefficient, low dielectric constant and high electric resistivity. In this investigation, AlN films were deposited on Al substrates by radio frequency (RF) reactive magnetron sputtering. The metal-interfacial insulator layer-metal (Al/AlN/Al MIM) structures were obtained with AlN layer on Al substrates. Electrical properties of the MIM structures were investigated by meaning of C-V and C-f characteristics in the frequency range of 100 Hz-500 kHz and voltage range of −4 V to 4 V. Experimental results show that the dielectric constant of this structure decreases gradually with increasing frequency. While the dielectric loss tangent was tested from low frequency to high frequency, it is found that the dielectric loss tangent decreases from 0.03375, reaches a minimum (0.00424) at approximately 65 kHz and then increases sharply. These results are in accordance with modified model of Goswami and Goswami for such structure. The dielectric dispersion is observed due to distribution of interface states as well as ionized space charge carriers such as the oxygen atoms, nitrogen vacancies and defects. The AC conductivity results show that the electrical resistance decreases as the frequency increasing due to hopping type conduction.     

Influence of substrate temperature to prepare (1 0 3) oriented AlN films

(1 0 3) Oriented AlN films is an attractive piezoelectric material for the applications on surface acoustic wave (SAW) and film bulk acoustic wave (FBAR) devices. As regards the SAW properties of the (1 0 3) oriented AlN films, the electromechanical coupling constant (K²) is larger than the (0 0 2) oriented AlN films. As regards the bulk acoustic wave (BAW) properties of (1 0 3) oriented AlN films, it can excite a quasi-shear mode (velocity = 5957 m/s, K² = 3.8%) that can be used for FBAR liquid sensor. In this research, the (1 0 3) oriented AlN films were successfully prepared on the silicon substrate by rf magnetron sputtering. Different temperatures (100 °C, 200 °C, 300 °C, and 400 °C) were used in this experiment process. The crystalline structure of films was determined by X-ray diffraction (XRD) and the surface microstructure was investigated by the atomic force microscope (AFM). The result exhibited the optimal substrate temperature is 300 °C. The optimal (1 0 3) oriented AlN films have the strongest XRD intensity, the smallest full width at half maximum (FWHM) value (0.6°), the largest grain size (15.8 nm) and the smoothest surface (Ra = 3.259 nm).     

用于光波导的高性能聚合物薄膜制备工艺研究

讨论了在硅基片上旋涂用于光波导的PS聚合物薄膜时,部分工艺参数,如溶液浓度、旋涂转速、溶剂挥发性、吸水性等对薄膜质量的影响,得到了薄膜厚度随浓度和转速变化的经验公式。分析了造成薄膜缺陷的原因,并对薄膜的性能如薄膜厚度、红外吸收特性和表面轮廓进行了测试。