目的 为了优化单晶金刚石大批量生长的等离子体环境,开展了高功率微波等离子体环境对单晶金刚石外延生长研究.方法 利用实验室自主研发的915 MHz-MPCVD装置,在15～37 kW的高功率微波馈入的条件下,研究了在高功率微波等离子体环境中CVD单晶金刚石的均匀生长条件,利用光学显微镜及激光拉曼光谱对所生长的单晶金刚石进行了形貌质量表征,利用等离子体发射光谱对高功率微波等离子体环境进行了诊断.结果 在保持甲烷体积分数为5％时,当微波功率为15 kW时,等离子体球的尺寸较小,并不能完全覆盖直径150 mm的基片台;将微波功率从28 kW提高到37 kW,肉眼所见的等离子体尺寸变化并不明显,但等离子体的能量分布范围有一定的扩大,这意味着在一定的范围内活性基团的能量分布更均匀.在较高的微波功率下,分布于基片台不同区域的单晶金刚石片均能获得较好的层状生长台阶.随着微波功率的提高以及基片温度的增加,分布于基片台不同区域的微波电磁场强度都有所增强,提高了单晶金刚石的生长速率和质量.结论 在高功率等离子体环境中,通过大幅度的提高微波功率,可以有效地活化含碳基团,在等离子体中产生有利于单晶金刚石高质量高速生长的活性基团.在微波功率为37 kW、甲烷体积分数为5％的情况下,将基片温度控制在950℃附近,可以有效地抑制多晶杂质的生成,实现了57片单晶金刚石的批量生长.

目的 为了优化单晶金刚石大批量生长的等离子体环境,研究高功率微波等离子体环境对单晶金刚石外延生长层的影响.方法 利用实验室自主研发的915 MHz-MPCVD装置,在20～35 kW高功率微波馈入的条件下,具体研究了高功率等离子体环境中甲烷浓度、微波功率及基片温度对单晶金刚石外延生长层的影响.利用光学显微镜、激光拉曼光谱及光致发光光谱对所生长的单晶金刚石进行形貌质量表征,利用等离子体发射光谱对高功率微波等离子体环境进行诊断.结果 在馈入25 kW的微波功率时,将甲烷的体积分数从6％下降至3％,可以使单晶金刚石更易于出现层状生长结构;保持甲烷体积分数为3％,将微波功率从25 kW提高到35 kW,可以进一步优化单晶金刚石生长的层状结构,提高单晶金刚石的生长质量和生长速率;保持微波功率为35 kW,当甲烷体积分数为3％时,将基片温度从800℃提高到1210℃可以明显提高单晶金刚石的生长速率,但会易于引入非金刚石相;保持甲烷体积分数为3％,将微波功率提高到35 kW,可以在等离子体中激发更多有利于金刚石快速生长的含碳活性基团;当微波功率为35 kW、甲烷体积分数为3％、基片温度为950℃时,单晶金刚石的生长速率可达25.6μm/h,且单晶金刚石的质量及颜色较好.结论 在高功率等离子体环境中,即使在相对较低的甲烷浓度下,通过大幅度提高微波功率也可以有效活化含碳基团,在等离子体中产生有利于单晶金刚石高质量高速生长的活性基团;基片温度对单晶金刚石中的非金刚石相及颜色具有显著影响,在微波功率为35 kW、甲烷体积分数为3％的情况下,将基片温度控制在950℃附近,可以有效抑制非金刚石相的生成.

研制并测试一种新型的基于CK-619型连续波磁控管、以ATmega 16L单片机为控制核心的大功率微波电源.与以前的微波电源相比,该电源产生的微波能量主要来自于耦合的大功率微波电场所产生的高压直流电能,由此产生的高功率、高密度的等离子体形状基本可以满足通过化学气相沉积大面积高质量金刚石厚膜的实验和工业要求.通过大量时间研制成功的大功率微波电源,通过了一系列的严格测试,结果表明其完全可以满足实验室和工业对微波电源的实用要求.

对于微波电源这种比较复杂的控制系统来说,传统的PID控制器难以达到理想的控制精度和稳定性.为此,提出一种改进型BP(Back Propagation)神经网络PID控制器,使用共轭梯度算法和Fletcher-Reeves线性搜索方式,对传统PID控制器进行改进,使得对微波电源系统的控制更加精确和稳定.在Matlab/Simulink软件仿真平台进行模拟仿真,同时进行电源实时输出功率验证实验.实验结果证明了该控制算法对电源系统控制的有效性.

对微波的研究在当今这个时代已经发展的非常迅速了,而且微波技术的发展也越来越趋于成熟,如今,微波技术应用的越来越广泛,对工艺的要求也越来越高,随之微波电源也应运而生.微波电源的诞生解决了很多工业性的难题,将微波技术应用在食品的杀菌消毒,植物种子的脱水处理,液体的萃取与消毒,工业材料的制备等等.本文介绍了一种利用单片机控制的大功率微波磁控管电源,而设计制作的设备运行稳定,并具有输出功率连续可调,故障报警与处理,功率设定,以及输出功率实时显示等功能,而且进一步对微波电源的小型化做了设计构想.

目的 在实验室自制的5 kW圆柱形单模微波等离子体化学气相沉积(MPCVD)装置上,系统研究各放电参数对等离子体的影响.方法 采用模拟计算与实验调控相结合的方式,分析微波等离子体、基团的运动和分布与放电参数之间的关系.利用发射光谱诊断等离子体环境,同时,利用SEM和Raman对所沉积的金刚石膜的形貌和质量进行表征,以验证MPCVD装置的调控原则.结果 气压和温度满足Tg=8/3 P关系时,吸收功率密度可达最大.单独提高微波功率和工作气压,能很大程度地增强等离子体的电子密度及改善等离子体球的均匀性,而两者相互之间匹配升高能极大地增加等离子体的电子密度,同时激发更多Hα、Hβ、CH及C2这类适合高质量金刚石膜沉积的活性基团.得到了MPCVD装置长时间稳定运行的等离子体稳定边界,并成功制备出高质量的金刚石膜.结论 功率气压及温度相匹配可以提高吸收功率密度、等离子体密度及均匀性.在圆柱形装置稳定运行的边界条件下,能沉积得到较高质量的金刚石膜.

使用实验室自制的10 kW微波等离子体设备,研究单晶金刚石不同生长阶段的应力表现形式.通过等离子状态参数模拟和发射光谱诊断,研究不同生长阶段几种主要基团的分布和含量;通过扫描电子显微镜和拉曼光谱仪对金刚石的表面形貌和结晶质量进行表征.在整个生长阶段,单晶金刚石边缘区域的电场密度和等离子密度逐渐增强,在功率一定的情况下,中间区域的等离子密度会削弱,并且随着时间延长厚度增加,等离子体状态参数差别越明显,导致单晶金刚石生长模式发生改变,表面的层状生长改为梯度生长,边缘的多取向竞争生长失衡,取向杂乱的多晶在边缘处产生,在这种生长模式影响下,单晶金刚石的生长应力和热应力交替影响其生长状态.结果导致在生长初期,单晶金刚石应力较小且分布均匀,随着时间延长厚度增加,单晶金刚石受缺陷导致的生长应力和温差导致的热应力影响递增,产生裂纹.

在实验室自主研制的10 kW微波等离子体化学气相沉积装置上,通过改变气体的进出方式,探讨了气体流动方式对金刚石膜均匀性和质量的影响.结果表明:随着Si基片表面气体分子数增多,等离子体中的H原子和CH活性基团强度增强,扩散到基片表面中心的原子H和含碳活性基团增多,基片中心区域的金刚石膜生长速率略微有所提升,由原来的2.5μm/h提高到2.8μm/h,沉积得到的金刚石膜质量和均匀性均得到改善.

金刚石因其优异的物理化学特性,被视为下一代电力电子器件的终极材料,金刚石半导体器件的制备受到了科研工作者的广泛关注.文章对金刚石基二极管、开关器件和边缘终止效应等方面的研究成果进行了概述.着重阐述了金刚石半导体器件的电学特性,尤其是,在500℃高温条件下得到高正向电流密度,阻断能力大于10 kV,并展现出长程稳定性的肖特基势垒二极管;在金属半导体场效应晶体管与金属氧化物半导体场效应晶体管上制得阻断电压超过2 kV的开关器件.同时,针对加工技术带来的表面缺陷,详细讨论了金刚石器件的表面终止技术和缺陷对器件性能的影响,并展望了金刚石半导体在肖特基势垒二极管及场效应晶体管等领域的应用前景.

采用MPCVD技术,研究了CO2-CH4-N2体系中N2对纳米金刚石膜生长状态及晶界处H含量的影响.利用SEM,XRD,Raman,FTIR及TEM对纳米金刚石膜的形貌、结构和质量进行研究,并利用Raman及FTIR对晶界处H的含量进行计算分析.结果 表明,N2流量的增加会在促使纳米金刚石膜的晶粒团聚体从球状逐渐转变为针状的同时减小晶粒尺寸,并使择优取向由<111>转变为<110>.随着N2流量的增加,纳米金刚石膜的质量也随之降低,但晶界处的H含量逐渐上升.具有针状晶粒团聚体的纳米金刚石膜具有明显的金刚石相和晶体石墨相.N2流量的增加不仅可以有效降低纳米金刚石膜的晶粒尺寸,改变晶粒的团聚形态及择优取向,还可以显著增加晶界处H的含量,促进石墨相的生成.

随着我国科技的不断发展,电源稳定技术广泛应用于工业、科研、国防及日常生活.同时,各行各业对电源的要求日益提升,促进了电源稳定技术的发展.开展大功率稳定微波电源研究,是对电源稳定技术的深入拓展和延伸.基于此,采用型号为CK-611的大功率磁控管进行微波电源设计,以期提供相关参考.

The resistance abilities of (100) and (111)-faceted diamond films against oxygen plasma, 100 μm as film thickness, were investigated by the microwave power chemical vapor deposition (MPCVD) technique. The results indicate that the preferred etching points of the (100)-faceted diamond films are located at the grain boundaries and the preferred etching points of the (111)-faceted diamond films are located at the crystal surfaces. After 30 minutes etching, the (100)-faceted crystal can still be obviously shown while the (111)-faceted crystal is unobvious. After 60 minutes etching, the preferential orientations of (100)-faceted and(111)-faceted diamond films both are disappeared. The FWHM value of the (100)-faceted diamond films is increased from 8.51 cm–1 to 12.48 cm–1 and the FWHM value of the(111)-faceted diamond films is increased from 8.74 cm–1 to 148.49 cm–1 when the etching time is 60 minutes. The etching rate of the (100)-faceted diamond film is 0.35 μm/min when the etching time is 40 minutes and it is increased to 1.34 μm/min when the etching time is 60 minutes. At early stage, the (100)-faceted diamond film presented better resistance ability than the (111)-faceted diamond film against the oxygen plasma etching. But the resistance abilities to the plasma etching of the (100) and the (111)-faceted diamond films are similar when the etching time is 60 minutes.

在实验室自制的10 kW微波等离子体化学气相沉积装置中,系统分析提高功率对生长金刚石膜的影响.利用等离子体发射光谱诊断分析高功率微波等离子体放电环境的特征,同时采用扫描电镜及Raman光谱对不同功率条件下获得的金刚石膜的形貌和质量进行表征.结果 表明:微波功率的提高可以获得面积更大的强场区域,为金刚石的大面积均匀成膜提供了有利条件;同时提高微波功率可以产生更高的电子密度,激发更多的活性氢原子和有利于金刚石生长的含碳基团;在气压为15 kPa,H2/CHa流量比为200∶6 mL/min的条件下,当功率由4000上升到5000 W时,金刚石膜的质量明显得到提高;当功率升高到5500 W时,金刚石质量开始下降,出现孪晶;但在升高功率的过程中,晶粒尺寸增大的趋势没有改变.因此,提高微波功率易于活性氢原子的产生并可更为充分的活化含碳大分子基团;在本实验条件下,当微波功率为5000 W时,所制备的金刚石膜可具有较高的质量.

使用新型多模MPCVD装置,通过耦合改变微波功率和沉积气压进行大面积金刚石膜均匀沉积研究.结果表明:微波功率一定时,电子密度随气压的上升先上升后下降;电子密度随气压和微波功率耦合上升而上升,其中微波功率起主导作用;当微波功率为5 kW时,等离子体能量中心随着气压上升先靠近后远离沉积基底;当微波功率为5 kW、气压为15 kPa时,在直径为75 mm的钼基片上实现了大面积金刚石膜的均匀沉积,中心和边缘区域的拉曼光谱FWHM值为4.69cm-1和4.83 cm-1.

The effects of pressure on the deposition of diamond films is based on simulation and simulation were sys-tematically investigated in a 10 kW home-made MPCVD apparat in a certain high-power environment.The surface mor-phology of the diamond was analyzed by SEM and the crystal quality and FWHM of the diamond films were analyzed by Raman characterization.The results show that pressure has a great effect on electron density,which in turn affects the sur-face morphology of diamond-deposited films.Under the microwave power of 5 kW,17 kPa is the optimum deposition pressure,the deposition morphology is the best,and the half width is the minimum.When the pressure is lower than 17 kPa, the quality of the crystals increases with the increase of the pressure.When the pressure exceeds 17 kPa,the quality of the crystals does not increase or decrease.

The influence of total gas pressure(20~26kPa)and methane concentration(0.3%~1%)on diamond growth using mixture gas of H2/Ar/CH4source by microwave plasma chemical vapor deposition(MPCVD)was investigat-ed.For a fixed methane concentration,characterization by Raman spectroscopy,scanning electron microscopy and X-ray diffraction indicated Characterization of nano diamond quality,surface morphology,grain size. The results show that growth rate increase with pressure increasing,but quality of nano-diamond films first become better then become worse while the pressure increases.Then using higher pressure and litter methane concentration could gain highly quality nano-crystalline diamond films.

The work aims to study law of influence of CO2/CH4flow ratio on growth of diamond films and grain size. The diamond films exhibiting different structural features were prepared controllably by adjusting the CO2/CH4flow ratio and applying MPCVD technology. The diamond films were characterized and analyzed with scanning electron microscope, X-ray diffractometer and Raman spectrum, the rule of influence of CO2/CH4flow ratio on grain size of diamond films was obtained. When microwave power, deposition pressure, substrate temperature and of CH4flow was 1.2 kW, 7.0 kPa, 850 ℃ and 50 mL/min, respectively, nanocrystalline diamond films could be deposited using 20 and 25 mL/min CO2, microcrystalline diamond films could be obtained using 30 and 35 mL/min CO2, and diamond could be deposited using 67 mL/min CO2. By adjusting mi-crowave power to 0.9, 1.4, 1.8 kW, respectively while keeping the other parameters constant, grain size variation of diamond films along with the CO2/CH4flow ratio could be divide into three regions: nanocrystalline diamond film deposition region (CO2/CH4<50%), microcrystalline diamond film deposition region (CO2/CH4>60%), and grain size transition region (50%<CO2/CH4<60%). It is feasible to conclude that the decrease of CO2/CH4flow ratio is conductive to decreasing grain size of diamond films.

在实验室自制的10 kW微波等离子体化学气相沉积装置中,分析了高功率微波等离子体环境中甲烷浓度对金刚石膜生长的影响.利用等离子体发射光谱诊断分析高功率微波等离子体放电环境的特征,同时利用SEM及Raman光谱对不同沉积条件下获得的金刚石膜的形貌及质量进行表征,以确定高功率微波等离子体环境下金刚石膜生长的最优甲烷浓度范围.实验表明在保持微波功率为5000 W,CH4/H2≤1％时,金刚石膜中二次形核现象明显,晶粒尺寸较小;CH4/H2≥2.5％时,金刚石膜可获得较大的晶粒,但易于产生孪晶体;CH4/H2=1.5％～2％时,可获得晶粒完整且质量较高的金刚石膜.

In order to achieve the uniform deposition of large area diamond films with the high growth rate, the gas flow field, electron density, electron temperature, the species distribution and the quality of the diamond film were investigated by the microwave plasma chemical vapor deposition (MPCVD) method in a novel self-built overmoded MPCVD device. The gas flow field results indicate that the overmoded MPCVD presents good stability of the gas flow field even at a high gas flow rate. The optical emission spectroscopy (OES) results indicate that the intensities of all chemical radicals increase with the increase of the hydrogen flow rate. The chemical radicals can be systematically distributed along the substrate surface when the gas flow rate is within 400 cm(3)/min. The electron density and electron temperature first increase and then slightly decrease when the gas flow rate keeps increasing. The maximum values of the electron density and electron temperature are 2.3x10(19)/m(3) and 1.65 eV, respectively, when the hydrogen flow rate is 500 cm(3)/min. The uniform diamond film is deposited on the molybdenum plate of 100 mm diameter when the hydrogen flow rate is 300 cm(3)/min. The FWHM value is 4.39 cm(-1) and 4.51 cm(-1) for the center and verge place of the diamond film, respectively, and the growth rate is 5.8 mu m/h.