ICP等离子体刻蚀系统射频偏压的实验研究

对于上下电极双射频源的电感耦合(ICP)等离子体刻蚀设备的关键工艺参数--下电极射频偏压的变化特性进行了实验与物理定性分析.实验以氧气作为反应气体,采用可满足300mm硅晶片刻蚀的ICP刻蚀设备的射频系统进行实验数据测定.结果表明,下电极射频偏压与其他工艺参数在可适用的工艺窗口中(改变上下电极功率和气体压力)不再是平常认为的简单的比例关系,而是随着条件的改变,对应的趋势比例关系会发生转折性变化,这种变化在高上电极射频、低下电极射频功率和低气压的条件下很容易发生.     

高密度RF等离子体刻蚀工艺直流自我偏压的研究

直流自我偏压作为高密度射频(RF)等离子体刻蚀工艺中的重要电学参数,反映出具有高能量的离子对待刻蚀晶片的轰击效果,后者决定了刻蚀工艺的各向异性、刻蚀速率、选择比及形貌特征等工艺结果。该文以HBr作为刻蚀气体,采用电感耦合等离子体(ICP)金属刻蚀系统针对刻蚀工艺中的直流自我偏压进行研究。研究中分别改变离子源功率、衬底偏压功率、刻蚀压力及HBr气体流量,观察直流自我偏压及其峰值的相应变化规律。实验结果表明,随着离子源功率的升高,直流自我偏压将会轻度降低;升高偏压功率则会显著提升直流自我偏压。刻蚀压力与直流自我偏压呈正比例关系,HBr气体流量的变化及待刻蚀晶片的材质对直流自我偏压无显著影响。     

用于垂直腔面发射激光器的GaAs/AlGaAs的ICP刻蚀工艺研究

采用电感耦合等离子体(ICP)刻蚀设备对应用于垂直腔面发射激光器的GaAs/AlGaAs材料进行刻蚀工艺研究。该刻蚀实验采用光刻胶作为刻蚀掩模,Cl2/BCl3作为刻蚀工艺气体,通过实验分析总结了ICP源功率、射频偏压功率和腔体压强对GaAs/AlGaAs材料和掩模刻蚀速率的影响。利用扫描电子显微镜观察不同参数条件对样品侧壁垂直度和底部平坦度的影响。最终在保证高刻蚀速率的前提下,通过调整优化各工艺参数,得到了侧壁光滑、底部平坦的圆台结构。     

纳米尺度多晶硅微结构刻蚀研究

以HBr作为刻蚀气体,采用ICP金属刻蚀系统对气体流量、刻蚀压力、离子源功率、偏压功率等工艺参数与刻蚀速率、刻蚀选择比和侧壁垂直度的对应关系进行了大量工艺实验。借助理论分析和工艺条件的优化,开发出一套可满足制备侧壁垂直度的纳米尺度多晶硅密排线结构的优化刻蚀工艺技术。实验结果表明:当采用900 W的离子源功率、11 W的偏压功率、25 cm3/min流量的HBr气体和3 mTorr(1 mTorr=0.133 3 Pa)刻蚀压力的工艺条件时,多晶硅与二氧化硅的刻蚀选择比大于100∶1;在保持离子源功率、偏压功率、气体流量不变的条件下,单纯提高反应腔工艺压力则会大幅提高上述选择比值,同时损失多晶硅和二氧化硅的刻蚀均匀性;HBr气体流量的变化在上述功率及反应腔工艺压力的工艺范围内,对多晶硅与二氧化硅的刻蚀选择比和多晶硅刻蚀的形貌特征均无显著影响。采用上述优化的刻蚀工艺条件,配合纳米电子束光刻技术成功得到多晶硅纳米尺度微结构,其最小线宽为40 nm。     

GaN电感耦合等离子体刻蚀的优化和损伤分析

通过分别改变电感耦合等离子体(ICP)刻蚀过程中的ICP功率和DC偏压,对ICP刻蚀GaN材料的工艺条件和损伤情况进行了系统的研究。刻蚀后表面的损伤和形貌通过扫描电子显微镜(SEM)、原子力显微镜(AFM)、电子能谱(EDS)、荧光光谱(PL)等技术进行表征和分析。实验结果表明,刻蚀速率随ICP功率和DC偏压的增加而增加;刻蚀损伤与DC偏压成正比,而与ICP功率的关系较为复杂。实验中观测到刻蚀后GaN样品的荧光光谱带边发射峰和黄带发射峰的强度均有明显下降,这意味着刻蚀产生的缺陷中存在非辐射复合中心,并且该非辐射复合中心的密度与DC偏压成正比。为了兼顾高刻蚀速率和低刻蚀损伤,建议使用高ICP功率(450 W)和低DC偏压(300 V)进行ICP刻蚀。     

ICP腔体压力对直流偏压的影响

基于GaAs器件干法刻蚀工艺,介绍感应耦合等离子(ICP)的刻蚀原理,以Cl2和BCl3为刻蚀气体,研究分析了在GaAs表面刻蚀工艺中不同的腔体压力下设备直流偏压的变化情况.发现在各种不同的功率下都存在一个特定的腔体压力,当低于该腔体压力时直流偏压会随腔体压力的增大而增加,当高于该腔体压力后直流偏压会随着腔体压力的增加而缓慢减小.讨论了产生这种现象的原因,揭示了其中的物理机理,以该方法作为参考,通过一组对比实验在工艺中得到验证,给出了GaAs刻蚀的工艺条件,为刻蚀工艺条件的优化提供了一个参考.     

硅基微型超级电容器三维微电极结构制备

为增大硅基微型超级电容器电极结构表面积,以提高电极的电荷存储能力,采用感应耦合离子刻蚀(ICP)技术制备了超级电容器三维微电极结构,研究了刻蚀、钝化气体流量和射频功率及电极电压等工艺参数对所制电极结构的影响。要取得较理想的结果,须根据刻蚀的一般规律和所用设备的具体特点,结合实际要求来确定工艺参数。在掩膜宽度为25μm时,所制三维电极结构表面规则平整,比二维电极结构表面积增大8.38倍。     

ICP刻蚀参数对SOI脊形波导侧壁粗糙度的影响

研究了以C4F8/SF6/O2为刻蚀气体,利用ICP刻蚀技术制作SOI脊形光波导过程中,刻蚀参数与侧壁粗糙度的关系.实验结果表明偏压、气体比例、压强是影响侧壁粗糙度的关键参数,在低偏压、低C4F8/SF6比和较高压强下更容易获得低粗糙度的侧壁.通过优化刻蚀参数,获得了侧壁粗糙度和传输损耗相对较低的SOI脊形波导     

垂直腔面发射激光器中GaAs/AlGaAs的选择性刻蚀技术研究

在氧化物限制型垂直腔面发射激光器制备中,刻蚀GaAs/AlGaAs时因异质型材料常出现选择性内蚀现象,这会直接影响后续的氧化工艺及电极钝化的效果。针对因选择性内蚀而出现的"镂空"现象,对湿法刻蚀工艺和干法刻蚀工艺进行详细研究,研究结果表明通过调整刻蚀液体积配比和感应耦合等离子体(ICP)刻蚀下电极射频功率可有效消除"镂空"现象。湿法刻蚀中,当刻蚀液H_3PO_4-H_2O_2-H_2O各物质体积配比为1\:1\:10时,得到了陡直度较好且光滑的侧壁。ICP干法刻蚀时,通过改变下电极RF功率可调整腔室内的化学刻蚀和物理刻蚀的动态平衡,在下电极射频功率为100 W时,"镂空"现象基本消失,且侧壁陡直度大于80°。     

GaN/SiO_2刻蚀选择比的研究

在干法刻蚀GaN时使用SiO2作为掩蔽物,为了在较快的GaN刻蚀速率下获得良好的GaN/SiO2刻蚀选择比,使用电感耦合等离子刻蚀机(ICP),运用Cl2和Ar作为刻蚀气体,改变ICP功率、直流自偏压、气体总流量、气体组分等工艺条件,并讨论了这些因素对GaN/SiO2刻蚀选择比以及对GaN刻蚀速率的影响。实验结果获得了GaN在刻蚀速率为165nm/min时的GaN/SiO2选择比为8∶1。设备验收时GaN刻蚀速率为70nm/min,GaN/SiO2选择比为3.5∶1,可以应用于实际生产。     

RF MEMS switch integrated on printed circuit board with metallic membrane first sequence and transferring

This letter reports, for the first time, on RF MEMS switches integrated on flexible printed circuit boards (i.e., FR-4) using transfer technology. The devices were first processed on Si-substrate using a modified MEMS sequence and subsequently transferred onto an FR-4 substrate by thermal compressive bonding, mechanical grinding, and wet removal of silicon. The switches were demonstrated with flat metal membrane (top electrode), precisely controlled gap between the membrane and bottom electrode, low insertion loss (/spl les/ 0.15 dB at 20 GHz), and high isolation (/spl sim/ 21 dB at 20 GHz). This technology shows the potential to monolithically integrate RF MEMS components with other RF devices on organic substrate for RF system implementation.     

Independent control of ion density and ion bombardment energy in adual RF excitation plasma

A dual RF excited discharge is described. The dual RF excitation system provides a method to control the substrate self-bias without affecting the state of the discharge. The substrate can be RF-biased utilizing an appropriate excitation frequency and power significantly less than the plasma generating RF power. The substrate self-bias dependence on various system parameters, including substrate excitation frequency, pressure, plasma generating upper electrode RF power, substrate material, and process gas compositions, is described. For a simplified model, a linear relationship between self-bias and RF power is derived using the space-charge limited assumption. The effect of substrate bias on the thermal-oxide etch rate has been studied. The results show good correlation between the ion bombardment energy, i.e., the potential difference across the substrate dark space, and the SiO ₂ etch rate. The SiO₂ etch rate in a CF₄ plasma increases linearly with the ion bombardment energy, having a threshold etch energy of ~19 V     

A computer simulation of radio-frequency ablation of theendocardium

A computer simulation of radio-frequency (RF) ablation of the endocardium is performed. The objective is to quantify some of the parameters affecting lesion growth, and to obtain theoretical data which can be used as a guide to maximize the lesions obtained with the procedure. The model under consideration consists of a block of heart tissue with the catheter electrode making contact at a right angle on one side (endocardium) and a large grounded electrode on the other side. An RF electrical current flows between the electrodes, heating the tissue. The simulations provide information on the time evolution of the tissue temperature, lesion dimension and tissue resistance. A first set of calculations is based on an applied RF voltage that maintains the maximum tissue temperature at 100°C. The results reveal that: 1) the lesions achievable by RF ablation are considerably larger than those obtained with a hot-tip catheter of the same size; 2) increasing the electrode radius enlarges the lesion because of an associated increase in contact surface area; 3) an increase in electrode length also enlarges the lesion because of the larger convective losses to the blood flow; 4) a large difference in temperature may exist between the electrode and the tissue because of the cooling effect of the blood flow; and 5) the lesions grow as long as power is applied. Other simulations in which the RF voltage is constant show that the lesions can be enlarged by lowering the applied voltage while increasing the duration. Agreement and discrepancies between the simulations and reported experimental results are identified. Finally, suggestions for improving the procedure are given     

Comparison of power deposition patterns produced by microwave andradio frequency cardiac ablation catheters

Transcatheter microwave and radio frequency (RF) electrodes are used for the ablative treatment of cardiac arrhythmias. The authors compare the power deposition patterns of microwave antennas and RF electrodes in saline phantoms of biological material. The decrease in power deposition as a function of distance away from the electrode is nearly exponential for RF and is considerably steeper than microwave antennas. These results suggest that microwave antennas are capable of heating a larger volume and thus creating a greater lesion than RF     

基于射频信号2阶零功率的链路色散测量技术

为了适应高速率大色散光纤信道对链路色散的精确补偿要求,研究并提出了一种基于射频信号2阶零功率点的信道色散测量方案。采用信号两边带的位相差来测量光纤链路中的色散值,通过在发射端加载射频信号,可以得到接收端射频信号功率大小随链路色散值的周期性变化关系,从仿真光纤链路色散随射频信号频率的变化曲线获得接收端射频信号2阶零功率点位置。结果表明,基于射频信号2阶零功率的信号测量方案色散测量误差可控制在±10ps/nm范围内。相较于1阶零功率点,基于射频信号2阶零功率点信道色散测量方案可满足高速率、长距离大色散光纤信道对色散值的精确测量需求。     

Low-voltage high-isolation DC-to-RF MEMS switch based on an S-shaped film actuator

This paper presents a new electrostatically actuated microelectromechanical series switch for switching dc to radio frequency (RF) signals. The device is based on a flexible S-shaped film moving between a top and a bottom electrode in touch-mode actuation. This concept, in contrast to most other microelectrochemical systems (MEMS) switches, allows a design with a low actuation voltage independent of the off-state gap height. This makes larger nominal switching contact areas for lower insertion loss possible, by obtaining high isolation in the off-state. The actuation voltages of the first prototype switches are 12 V to open, and 15.8 V to close the metal contact. The RF isolation with a gap distance of 14.2 /spl mu/m is better than -45 dB up to 2 GHz and -30 dB at 15 GHz despite a large nominal switching contact area of 3500 /spl mu/m/sup 2/.     

喷流对提高高厚径比PCB板深镀能力的研究

文章简单介绍了电极反应速度理论和流体力学理论,从理论上找到解决提高高厚径比PCB板件深镀能力的研究方法;电镀反应包括液相传质步骤、电化学步骤、新相生成步骤;流体流动主要有层流和湍流两种方式,两者的转换条件判断为雷诺数数值;通过电化学极化曲线比较了底喷,侧喷,鼓气对深镀能力贡献不同的影响,从理论上分析了底喷效果优于其它两种溶液交换方式的原因,证明底部喷流方式对于高厚径比通孔电镀是最优选择,讨论了喷流流量大小对深镀能力提高的贡献。     

一种用于台面探测器的新型电极结构

提出一种用于台面探测器的新型电极结构.该结构通过在台面底部两次制备电极而获得接力电极.同传统的引出电极结构相比,这种接力电极结构不仅简化了从台面底部引出电极的工艺,而且能够增加台面顶部空间从而更有利于其它工艺的进行以及工艺集成.在200 W超声处理5分钟后,接力电极的高度和形貌都未发生变化.从倒焊互连的剖面SEM照片可以看出台面底部的接力电极是个整体,并且该接力电极结构完全可以应用在台面探测器中.     

ANALYSIS OF DUAL FREQUENCY CONFINED CAPACITIVELY COUPLED PLASMA AT LOW POWER

Confined dual frequency hydrogen plasma discharge has been investigated with microwave interferometer method and radial profiles are taken by Abel inversion technique. Dual radio-frequency sources, operating at 27.12MHz and 1.94MHz, are coupled to each other through the plasma. 27.12MHz RF power is used to enhance plasma density and 1.94MHz power is used to enhance ion acceleration energy to the electrode. Radial density profiles has been taken for comparing the effects of low frequency source that the secondary RF source causes reduction in plasma density due to the sheath expansion. Instead radial density profile is assumed as flat by most of the models, there is about 2.5eV of potential drop occurs from centre to boundary at 40W of primary source power. It has been observed that increasing sheath width (increasing the secondary source power to primary source power) reduces the bulk plasma volume and makes potential profile flattening in y direction. While the high frequency power is dissipated by electrons in the bulk plasma; low frequency power is mostly dissipated by ions in the sheath region. Using both high and low frequency power, we may control plasma density and ion acceleration energy to the electrode simultaneously.     

Radiofrequency electromagnetic leakage fields from plastic welding machines. Measurements and reducing measures

Operators of unshielded plastic welding machines are often exposed to radiofrequency (RF) electromagnetic leakage fields that substantially exceed all present occupational standards. Measurements show that the Swedish ceiling values (SE = SH = 250 W/m2) in many cases are exceeded at distances up to 1 meter from the electrode. To reduce the stray fields to an acceptable level at the location of the operator, RF field suppression devices should be fitted to the machine. We have studied the strength and the extent of the RF leakage field under various operating conditions and also investigated different methods for reducing the leakage field. The following measurements have been performed: E- and H-field strengths as a function of distance from the electrode, and as a function of load/tuning; the time dependence of [E]2 for various combinations of tuning and welding times producing a welding seam with the same strength; isopower density curves for SE and SH = 250 W/m2 with different types of RF emission control devices fitted to the machine; the RF voltage between the electrode and the welding table and the RF voltage on the machine casing. By decreasing the RF power and increasing the welding time the field strengths at the location of the operator can be reduced to levels below the ceiling values. The RF voltage between the electrode and the welding table ranged from 800 V up to 2100 V for the different plastic material that was welded. The RF voltage on certain parts on the chassis could be as high as 200 V. In order to reduce these voltages and the stray fields the machine should be equipped with a "large capacitive shield" in cases where this is possible.