探索人工干预诱导二次形核技术制备纳米金刚石膜

围绕纳米金刚石膜生长的二次形核理论,利用直流热阴极PCVD技术,在微晶金刚石膜连续生长模式常用的一些生长条件下,通过改变工作气压,改变生长温度,同时采取人工干预间歇生长模式进行金刚石膜生长实验,探索纳米级金刚石膜制备的新途径.实验表明:在金刚石膜生成的过程中,降低工作气压或生长温度,可使等离子体激励能量减弱,导致二次形核基团比例增加,成为人工干预二次形核的内在诱因;通过调节激励电压,使等离子体能量状况改变,有利于二次形核行为的引导,成为人工干预二次形核的外在诱因,在此内外因素共同作用下,可以实现二次形核现象的有效诱导,制备出纳米金刚石膜.人工干预诱导二次形核技术制备纳米金刚石膜的实现,使纳米金刚石膜制作方法得到了扩展,也拓宽了直流热阴极PCVD技术的应用范围.     

人工干预二次形核研究

采用直流热阴极PCVD技术,在CH4-H2气氛常规制备微米晶金刚石膜的参数条件下,通过人工干预实现二次形核,制备纳米晶金刚石膜.金刚石膜周期性生长过程分为沉积阶段和干预阶段,沉积阶段时间为20 min,干预阶段将沉积温度降低到600℃,时间为1 min,然后恢复到生长温度,一个生长周期为21 min,总的沉积时间为6h.实验分为高、低气压和高、低温度的四种组合,并与连续生长模式进行了对比.采用拉曼光谱仪、SEM对样品进行了分析,除高气压和高温度条件外,其它三组实验的金刚石膜的1332 cm-1拉曼峰展宽明显、金刚石膜晶粒小于100 nm,样品都具有纳米晶特征.结果表明直流热阴极PCVD技术的人工干预方法,可以导致金刚石膜生长过程的二次形核行为发生,制备出纳米金刚石膜.     

直流热阴极PCVD法间歇生长模式间歇周期的研究

采用直流热阴极PCVD方法间歇生长模式,在CH4-H2气氛常规制备微米晶金刚石膜的参数条件下,利用人工干预二次形核工艺,研究了间歇周期变化对制备纳米晶金刚石膜的影响.人工干预二次形核是指通过生长温度的周期性改变而诱发二次形核行为,从而实现金刚石膜的纳米晶生长.金刚石膜周期性生长过程分为沉积阶段和干预阶段,沉积阶段主要完成金刚石膜的生长,干预阶段将沉积温度降低到600℃,然后恢复到生长温度,即完成一个生长周期.间歇周期研究主要是考察在不同间歇时间里人工干预诱导二次形核的效果,间歇时间设定为1 min、5 min、10 min、15min、20 min,生长时间设为20 min,总的沉积时间为6 h.采用拉曼光谱仪、SEM和XRD对样品进行了分析,结果表明直流热阴极PCVD方法间歇生长模式,间歇周期的变化,对二次形核的发生有诱导作用,适当选择间歇周期,有利于二次形核基团的生成.     

杆状氧化铍表面金刚石薄膜的生长

利用一种新型线形微波等离子体源以甲烷和氢气为反应气体在135 mm×1 mm×0.5 mm杆状氧化铍表面沉积金刚石膜。研究了氧化铍基底预处理对金刚石形核密度和膜的连续性,以及基底温度对金刚石质量的影响。通过扫描电镜、拉曼光谱对沉积的金刚石膜表面形貌以及质量进行表征。实验结果表明:600#砂纸与金刚石粉混合预处理可以大大提高氧化铍表面金刚石的形核密度,得到连续性较好的金刚石薄膜;同时,基底温度不仅影响着金刚石膜的表面形貌,也影响着金刚石膜的质量。基底温度较低时,金刚石膜在沉积过程中二次形核增强,非金刚石相含量较高;提高沉积温度后,等离子体中H原子浓度增加,有利于金刚石质量的提高。     

温度场对金刚石薄膜质量的影响

在引进的韩国微波等离子化学气相沉积（MPCVD）设备中,利用氢气和甲烷作为气源,在单面抛光的（100）单晶硅片上研究了不同的形核温度和生长温度条件下制备出金刚石薄膜。通过Raman光谱、XRD光谱和扫描电子显微镜（SEM）对制备的金刚石膜的质量进行表征。研究结果表明,形核温度和生长温度对金刚石膜的生长均有影响。形核温度过低会增大薄膜中的非金刚石相的含量,促使二次形核增加,降低了金刚石薄膜质量。随着生长温度的升高,金刚石中非金刚石相含量越少,金刚石的质量提高,但金刚石的晶面同时也被大量刻蚀。     

衬底表面预处理对金刚石薄膜形核及长大的影响

用燃烧火焰法在 TC4 Ti 合金和单晶 Si(001)面上沉积了金刚石薄膜。对合成的膜进行了扫描电镜、激光喇曼光谱分析。结果表明,金刚石薄膜的结构和形貌强烈取决于沉积温度、O_2/C_2H_2流量比等工艺参数。研究了衬底表面预处理对金刚石薄膜形核及长大的影响,并对表面预处理影响形核的原因进行了初步探讨。     

直流热阴极PCVD法CH_4:N_2:H_2气氛下制备纳米金刚石膜

采用直流热阴极等离子体化学气相沉积(PCVD)技术,在CH4:H2中加入N2改变等离子体能量分布状态,提高二次形核比例,制备纳米金刚石膜。在CH4:H2气体中,在不同压力和温度下,改变通入N2的比例,分析直流热阴极等离子体放电下N2对金刚石膜生长的影响。采用拉曼光谱仪、扫描电镜(SEM)和X射线衍射分析仪(XRD)对样品进行了表征,结果表明,直流热阴极PCVD系统中,CH4:N2:H2气氛下,N2流量小于气体总流量的50%时,在6×103 Pa、850℃条件下,制备的金刚石膜样品的晶粒小于100nm、金刚石1332 cm-1特征峰展宽且强度较高、金刚石的XRD衍射峰强度也较高,具备纳米金刚石膜的基本特征。因此,利用直流热阴极PCVD方法,在较低温度和气压下,CH4:H2中加入少量N2,可以制备出纳米金刚石膜。     

用于X射线光刻掩模的纳米金刚石膜成核研究

介绍了金刚石膜在下一代X射线光刻掩模中应用的必要性;通过调节衬底温度,改变生长时间、控制甲烷浓度等工艺措施,实验研究了不同参数对成核密度及成核质量的影响,获得了高密度形核的样品;对形核后的预生长期进行了工艺优化,有效地控制了核岛的优势生长,总结出了一套优化的形核方案,即甲烷浓度4％,衬底温度700℃,形核时间14min;这套工艺不仅改善了自支撑金刚石薄膜窗口的光学性能,还有效地降低了膜的内应力。     

形核工艺对金刚石膜形貌和电阻率的影响

金刚石薄膜电阻率的高低是薄膜绝缘性能优劣的直观反映,也是影响辐射剂量计器件性能的重要因素.针对目前形核工艺与电阻率的关系还不十分清楚的问题.本文研究了微波等离子体形核阶段工艺参数如基片位置、微波功率、甲烷浓度的变化对金刚石薄膜的表面形貌和电阻率的影响.结果表明微波等离子体形核工艺参数对金刚石薄膜的电阻率和表面形貌有显著影响.获得的最佳成核工艺条件:基体温度960℃、甲烷浓度0.72%、压力5.3 kPa、微波功率1300 W.在此工艺条件下制得的金刚石薄膜的电阻率值达到1011 Ω·cm数量级.     

钢渗铬沉积金刚石膜的研究

用热解CVD装置研究了甲烷浓度、基底温度、室压对钢渗铬沉积金刚石膜的影响.结果表明,甲烷浓度越低,沉积得到的金刚石膜的晶形越好,甲烷浓度超过0.8%后,金刚石的形貌呈"菜花状";基体温度高时,难于在渗铬层上形成连续的金刚石膜,但基体温度高所得的晶形较好;室压越高,金刚石的形核密度越高,但随室压的升高,金刚石的形貌变差.菜花状金刚石膜是由大量二次晶核长大的微晶金刚石晶粒组成,含有较多的非金刚石碳相.     

Synthesis of Diamond Thin Films on TC4 by Using a Scanning Linear Flame

A scanning linear flame is used to deposit diamond films over a large area, and with high quality and good continuity by employing appropriate cooling means for the substrate. It is found that the structure and morphology of the deposited films mainly depend on the substrate temperature, the ratio of 0₂ to C₂H₂ flow rate and the relative position of the substrate with respect to the flame. These factors affecting the structure and morphology of diamond films are interrelated. Moreover, the influences of surface pretreatments on nucleation and growth of diamond films are also studied. The experimental results show that the nucleation density of diamond films is enhanced by scratching the surface of the substrate with diamond grit and initially coating a mechanical pump oil layer. For the substrate surface etched with metallographic etching acid, the nucleation and growth of diamond films are very uniform. In addition, the adhesion between the film and substrate is enhanced. Nucleation is favored on the prominent features of the substrate, i.e. scratch and crystal boundary.     

微波等离子体化学气相沉积法在硅片上同时生长碳化硅和金刚石

研究了衬底温度、核化密度、衬底表而预处理等工艺参数对微波等离子体化学气相沉积法在硅片上同时生长碳化硅和金刚石的影响.采用扫描电镜、X-射线衍射、喇曼光谱和红外光谱对样品进行了表征.结果表明:从高核化密度生长的金刚石膜中探测不到碳化硅;不论对硅衬底进行抛光预处理还是未抛光预处理,从低核化密度牛长的金刚石厚膜中总能探测到碳化硅.碳化硅生长在硅衬底上未被金刚石覆盖的地方,或者是在金刚石晶核之间的空洞处.碳化硅形成和金刚石生长是同时发生的两个竞争过程.此研究结果为制备金刚石和碳化砟复合材料提供了一种新的方法.     

燃焰法沉积金刚石薄膜的实验研究

研究分析了燃焰法沉积金刚石薄膜时基片表面处理状态，燃烧气体流量比基片温度对薄膜成核密度、质量和晶体形态的影响。结果表明，在不同粒度的研磨粉研磨的基片表面上金刚石薄膜成核密度不同；燃烧气体流量配比对金刚石薄膜的质量影响很大；基片温度是影响金刚石薄膜晶体形态的一个重要因素。     

硬质合金YG8上金刚石薄膜的成核研究

利用调节基底表面碳流量的方法促进了热丝ＣＶＤ中硬质合金ＹＧ８上金刚石薄膜的成核，使成核期大为缩短，根据扫描电镜和拉曼光谱对沉积结果的分析，研究了ＹＧ８上金刚石薄膜成核的机理。     

大面积长生金刚石相关物理参量的空间分布

研究了在热丝化学气相生长金刚石的过程中,衬底温度、衬底表面附近的气体温度以及气流的质量流密度分布对金刚石膜的形核和生长的影响。模拟计算结果表明,这三个参量是空间位置的参数,在某些区域,这三个参量均匀分布。当热丝阵列面与衬底间距离超过７ｍｍ之后,这三个参量在衬底上有一个较大的均匀区域,在该区域的两侧,各参量值显著变化。在衬底中心的均匀区域,金刚石膜晶形清楚而致密;偏离该区域,这三个参量数值明显下降,形核密度和生长速度较低,三个参量均匀的区域可作为金刚石大面积均匀的形核和生长的位置。     

HFCVD金刚石膜过程的气氛模拟与分析

对热丝法化学气相沉积金刚石膜过程的气氛进行了模拟与分析。使用GRI－Mech3.0甲烷燃烧过程C／H／O／N四元体系热化学反应机理和动力学数据，模拟并分析了HFCVD金刚石膜的C／H气相化学反应，通过对反应流的简单模拟得到了衬底位置气相组成，结果与前人实验数据吻合，探讨了灯丝温度、碳源浓度和碳源种类等因素变化对衬底位置气相组成的影响。结果表明甲基是金刚石膜生长最主要的前驱基团，其作用远高于乙炔，而超平衡态原子氢的存在对金刚石膜的质量至关重要。     

Diamond deposition on copper: studies on nucleation, growth, and adhesion behaviours

This paper presents a systematic study on diamond growth on copper by microwave plasma chemical vapour deposition (MPCVD). It includes the following four main parts. 1. Effect of substrate pre-treatment on diamond nucleation. 2. Effect of deposition conditions on diamond nucleation and growth. 3.Preparation of free-standing diamond films using copper substrate. 4. Adherent diamond coating on copper using an interlayer. In the first part we show that diamond nucleation on copper is strongly affected by the substrate pre-treatment. The residues of abrasives left in the surface of the copper substrate play an important role in the diamond nucleation. In the second part we show that the diamond growth rate increases with microwave power and gas pressure. The effect of the microwave power is mainly an effect of substrate temperature. Increasing methane concentration results in a higher nucleation density and higher growth rate, but at the cost of a lower film quality. Gas flow rate has little influence on the diamond nucleation density and growth rate. In the third part we demonstrate the possibility of preparing large area free-standing diamond films using copper substrate, which has nearly no carbon affinity and usually leads to weak adhesion of the diamond films. The normally observed film cracking phenomenon is discussed and a two-step growth method is proposed for stress release. In the fourth part we show that adherent diamond coating on copper can be obtained using a titanium interlayer. Residual stress in the films is evaluated by Raman spectroscopy. It is found that with increase in the film thickness, the diamond Raman line shifts from higher wave numbers to lower, approaching 1332 cm–1. The stress variation along the depth of the film is also analysed using Airy stress theory.     

Filament-assisted growth of diamond films

Filament-assisted pyrolytic growth of diamond films on (100) Si wafers was investigated in an attempt to grow quality layers for semiconductor applications. The work was carried out in hydrogen ambient under a reduced pressure condition of about 100 torr (133, 322×10² Pa). Using isopropanol and methanol as carbon source chemicals, the growth process and film properties were characterized as functions of reactant concentration, filament and substrate temperature, reaction pressure and the total gas flow rate. Diamond films of good quality were grown under condition of low source concentration and small flow rate. However, the growth rates were generally slow. The films were polycrystalline. The filament and substrate temperatures were fairly critical to the nucleation and growth processes. The substrate surface finishing from diamond paste polishing predominated the nucleation site and grain size of the deposits.     

The oxygenated phenomena of the undoped large-grain and small-grain polycrystalline diamond films

The polycrystalline diamond films in this research were deposited using a methane/hydrogen gas mixture in a microwave plasma assisted chemical vapor deposition system. Large-grain, several μm size crystallite, diamond films and small-grain, sub-micron size crystallite, diamond films were prepared by diamond paste and diamond powder nucleation method, respectively. It is found that there is no oxygen incorporated into the diamond films during the microwave plasma chemical vapor deposition process at the synthesis temperature between 900°C and 1000°C. However, the oxygenated phenomena did appear for both of the large-grain and the small-grain polycrystalline diamond films after the films were exposed to air for a period of time. It was shown that the large-grain diamond films are oxygenated more than the small-grain diamond films as the samples were exposed to air for a period of time and also after the chemical cleaning treatment. It is indicated that the oxygenated phenomena of the diamond films come from two contributors, the diamond crystallite surfaces and the diamond grain boundaries. The reaction between the diamond grain boundaries and the air is fast and the oxidized dangling bonds are hard to remove. However, the oxidized dangling bonds on the diamond crystallite surfaces are gradually formed and are easily etched away by the hydrogen plasma.     

MPCVD法在氧化铝陶瓷上的金刚石膜沉积及其成核分析

用微波等离子体化学气相沉积（ＭＰＣＶＤ）法在氧化铝陶瓷基片上沉积了金刚石薄膜。实验表明，对基片进行适当的预处理，包括用金刚石研磨膏仔细研磨和沉积前原位沉积一层无定形碳层，可显著提高成核密度；对硅衬底和氧化铝基片上金刚石膜的成核过程进行了对比分析，并提出了提高氧化铝基片上沉积金刚石的成核的措施。