Mechanical Properties of Composite SiNx/DLC Films Prepared by Filtered Cathodic Arc of Graphite Incorporated with RF Sputtering of Silicon Nitride

Composite SiNx/DLC films were deposited on Si substrate by RF magnetron sputtering of silicon nitride (Si3N4) target simultaneously with filtered cathode arc (FCA) of graphite. The RF power was fixed at 100 W whereas the arc currents of FCA were 20, 40, 60 and 80 A. The effects of arc current on the structure, surface roughness, density and mechanical properties of SiNx/DLC films were investigated. The results show that the arc current in the studied range has effect on the structure, surface roughness, density and mechanical properties of composite SiNx/DLC films. The composite SiNx/DLC films show the sp3 content between 53.5% and 66.7%, density between 2.54 and2.98 g/cm3, stress between 1.7 and 2.2 GPa, and hardness between 35 and 51 GPa. Furthermore, it was found that the density, stress and hardness correlate linearly with the sp3 content for composite SiNx/DLC films.

Nitridation Kinetics of Silicon Monocrystal and Morphology of Nitride Film

Basing on TGA (thermal gravimetric analysis) of thermal nitridation at l200, l250, l300℃, respectively, analysis of high temperature kinetics for nitridation of silicon monocrystal has been carried out. According to the theory for kinetics of reaction of vapour with solid phase a nitridation kinetic model, from which it can be shown thal the rate of nitridation reaction of silicon crystal should be controlled by three stage limiting factors, was proposed. These limiting factors are chemical reaction, chemical reaction mixed with diffusion and diffu- sion. Using this model to treat our experimental data, satisfactory correlation coefficient and apparent activation energy of nitridation of p-type (lll) silicon crystal have been obtained. The nitride film was identi' fied to be a-Si_3N_4 (Hexagonal, a=0.7758nm,c_o=0.5623nm) by X-ray diffraction analysis. Morphology of the nitride films formed in different nitridation duration was observed in both planar andcross-sectional views by SEM (scanning electron microscope).

Effect of Hydrogen Dilution on Growth of Silicon Nanocrystals Embedded in Silicon Nitride Thin Film by Plasma-Enhanced CVD

An investigation was conducted into the effect of hydrogen dilution on the microstructure and optical properties of silicon nanograins embedded in silicon nitride （Si/SiNx） thin film deposited by the helicon wave plasma-enhanced chemical vapour deposition technique. With Ar-diluted SiH4 and N2 as the reactant gas sources in the fabrication of thin film, the film was formed at a high deposition rate. There was a high density of defect at the amorphous silicon （a-Si）/SiNx interface and a relative low optical gap in the film. An addition of hydrogen into the reactant gas reduced the film deposition rate sharply. The silicon nanograins in the SiNx matrix were in a crystalline state, and the density of defects at the silicon nanocrystals （nc-Si）/SiNx interface decreased significantly and the optical gap of the films widened. These results suggested that hydrogen activated by the plasma could not only eliminate in the defects between the interface of silicon nanograins and SiNx matrix, but also helped the nanograins transform from the amorphous into crystalline state. By changing the hydrogen dilution ratio in the reactant gas sources, a tunable band gap from 1.87 eV to 3.32 eV was obtained in the Si/SiNx film.

Effect of hydrogen content on dielectric strength of the silicon nitride film deposited by ICP-CVD

The inductively coupled plasma chemical vapor deposition(ICP-CVD) deposited silicon nitride(SiN_(x)) thin film was evaluated for its application as the electrical insulating film for a capacitor device.In order to achieve highest possible dielectric strength of SiN_(x),the process parameters of ICP-CVD were carefully tuned to control hydrogen in SiN_(x) films by means of tuning N_(2)/SiH_(4) ratio and radio frequency(RF) power.Besides electrical measurements,the hydrogen content in the films was measured by dynamic secondary ion mass spectrometry(D-SIMS).Fourier transform infrared spectroscopy(FTIR) and micro Raman spectroscopy were used to characterize the SiN_(x) films by measuring Si-H and N-H bonds’ intensities.It was found that the more Si-H bonds lead to the higher dielectric strength.

Deposition of Silicon Nitride Films by Silane Hydrazine Process

A new catalytic chemical vapor process for depositing silicon nitride films using silane hydrazine gaseous mixture is described. This system can be useful at a temperature of lower than 400 ℃. The catalytic process gives more rapid deposition rate than 10 nm/min. The atomic composition ratio, N/Si, which is evaluated by Rutherfold backscattering method is about 1.4 under a given experimental conditions more than the stoichiometric value of 1.33 in Si 3N 4. The infrared transmission spectra show a large dip at 850 cm -1 due to Si-N bonds and no clear dip due to Si-O bonds. High N-H bond density is the evidence that the deposition mechanism is limited by N-N bond breaking of the hydrazine. The H contents, evaluated from Si-H and N-H bonds in the infrared absorption spectra, and the deposition rate are measured as a function of the substrate temperature. In addition some film properties such as the resistivity and the breakdown electric field are presented.

Cutting performance of multilayer diamond coated silicon nitride inserts in machining aluminum-silicon alloy

Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with diamond coated inserts are presented. Considering the fact that high adhesive strength and fine surface morphology play an importance role in the applications of chemical vapor deposition （CVD） diamond films, multilayer technique combining the hot filament CVD （HFCVD） method is proposed, by which multilayer diamond-coating on silicon nitride inserts is obtained, microcrystalline diamond （MCD）/ nanocrystalline diamond （NCD） film. Also, the conventional monolayer NCD and MCD coated inserts are produced for comparison. The as-deposited diamond films are characterized by field emission scanning electron microscopy （FE-SEM） and Raman spectrum. All the CVD diamond coated inserts and uncoated insert endure the aluminum-silicon alloy turning to estimate their cutting performances. Among all the tested inserts, the MCD/NCD coated insert exhibits the perfect behavior as tool wear due to its very low flank wear and no diamond peeling.

Characteristics and Electrical Properties of SiNx:H Films Fabricated by Plasma-Enhanced Chemical Vapor Deposition

SiNx：H films with different N/Si ratios are synthesized by plasma-enhanced chemical vapor deposition （PECVD）. Composition and structure characteristics are detected by Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）. It indicates that Si-N bonds increase with increased NH3/SiH4 ratio. Electrical property investigations by I-V measurements show that the prepared films offer higher resistivity and less leakage current with increased N/Si ratio and exhibit entirely insulating properties when N/Si ratio reaches 0.9, which is ascribed to increased Si-N bonds achieved.

Mechanical strains in pecvd SiN_x:H films for nanophotonic application

Hydrogenated amorphous silicon nitride films（Si N x：H） are deposited at low temperature by high-frequency plasmaenhanced chemical vapor deposition（HF PECVD）. The main effort is to investigate the roles of plasma frequency and plasma power density in determining the film properties particularly in stress. Information about chemical bonds in the films is obtained by Fourier transform infrared spectroscopy（FTIR）. The stresses in the Si N x：H film are determined from substrate curvature measurements. It is shown that plasma frequency plays an important role in controlling the stresses in Si N x：H films. For silicon nitride layers grown at plasma frequency 40.68 MHz initial tensile stresses are observed to be in a range of 400 MPa-700 MPa. Measurements of the intrinsic stresses of silicon nitride films show that the stress quantity is sufficient for film applications in strained silicon photonics.

Thin Film Encapsulation at Low Temperature Using Combination of Inorganic Dyad Layers and Spray Coated Organic Layer

Organic devices have many advantages such as low material consumption and low energy requirements, but they have serious issues regarding long term stability. Hence we need to develop a barrier film which solves this problem. Initially, the organic devices were fabricated on glass and were encapsulated using glass and epoxy (as sealant). Gradually there was a need to shift on to flexible substrates which required encapsulation to be flexible as well. Therefore, the motivation of the work is to develop thin film encapsulation that can be made flexible. The low temperature PECVD grown films of SiOx and SiNxwere used as the barrier film. Alternate inorganic layers (2-dyads) provided barrier of ~10-2 g/m2 day and increasing the number of dyads to five improved the water vapor transmission rate (WVTR) only by one order of magnitude. However, introducing organic layers in this structure resulted in WVTR value of order 10-5 g/m2 day. The organic layers were deposited by spray technique.

Si3N4工程陶瓷基底金刚石涂层生长规律及性能

为了避免氮化硅材料因产生裂纹或延伸破裂等造成的失效,利用热丝化学气相沉积法(Hot filament chemical vapor deposition,HFCVD)在氮化硅基底上沉积具有高硬度的金刚石涂层,采用单因素影响试验,分别探究碳源浓度、腔室压力、基底温度对金刚石成膜过程的影响机制,探究微米和纳米金刚石涂层的最优生长工艺参数。利用拉曼光谱仪(Raman)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)和原子力显微镜(AFM)对不同参数制备出的金刚石的形核、表面形貌、薄膜质量、表面粗糙度等进行表征,利用洛氏硬度计分析膜基结合力。结果表明,腔室压力越大,活性物质到达基底的动能越小,不利于金刚石的成核和生长。生长速率和表面粗糙度主要受甲烷浓度的影响:甲烷浓度从1%到7%,生长速率从0.84μm/h上升到1.32μm/h;表面粗糙度Ra从53.4 nm降低到23.5 nm;甲烷浓度过高导致涂层脱落严重,膜基结合力变差;晶面形貌和金刚石含量受到基底温度的影响较为明显,随着温度升高,金刚石质量提高。综合基底温度、腔室压力对金刚石涂层的影响,确定最佳生长温度为900℃,气压为1 kPa。调节甲烷浓度1%为微米金刚石;甲烷浓度5%为纳米金刚石。研究方法可以优化在陶瓷基底上制备具有优异性能的金刚石薄膜的制备参数。

磁控反应溅射SiN_x薄膜的研究

用磁控反应溅射 (RF)的方法制备了SiNx 薄膜 分析了以硅为靶材 ,用N2 /Ar做溅射气体条件下不同的气流比率、总气压以及沉积速率对薄膜光学常数和表面结构形态的影响 ,得出较低总气压下气流比率对薄膜光学常数的影响是最关键的 ,而总气压较大的时候 ,水汽影响增大 ,气流比率的影响反而不明显 最后提出了合适的工艺条件来制备符合要求的SiNx

p-Si TFT栅绝缘层用SiNx薄膜界面特性的研究

以NH3和SiH4为反应源气体,在低温下采用射频等离子体增强化学气相沉积(RF-PECVD)法在多晶硅(p-Si)衬底上沉积了SiNx薄膜。系统地分析讨论了沉积温度、射频功率、反应源气体流量比对SiNx薄膜界面特性的影响。分析表明,沉积温度和射频功率主要是通过影响SiNx薄膜中的Si/N比和H含量影响薄膜的界面特性,而NH3/SiH4流量比则主要通过影响薄膜中的H含量影响薄膜界面特性。实验制备的SiNx薄膜层中的固定电荷密度、可动离子密度、SiNx与p-Si之间的界面态密度分别达到了1.7×1012/cm2、1.4×1012/cm2、3.5×1012/(eV.cm2),其界面特性达到了制备高质量p-SiTFT栅绝缘层的性能要求。

SiH_2Cl_2-NH_3配比对a-SiN_x∶H薄膜PL峰的影响

低压化学气相沉积制备的纳米硅镶嵌结构的a-SiNx:H薄膜,在3.75 eV的激光激发下,室温下发射1～3个高强度的可见荧光.在相同的沉积温度下(900℃),选择不同的SiH2Cl2和NH3气体配比时,所得薄膜表现出不同的荧光属性,荧光峰的峰位和数目有着显著的变化.通过TEM、IR、XPX等分析手段对其原因进行了研究分析,认为不同配比下,生成的薄膜中缺陷态的种类和密度有所不同,这影响了其PL峰个数及其各峰的相对强弱.

用PECVD制备高抗腐蚀性能SiN_x薄膜的工艺研究

研究了一种可抗高温强碱溶液腐蚀的氮化硅薄膜的等离子增强化学气相淀积(PECVD)生长工艺。通过X射线光电子能谱(XPS)、椭圆偏振仪、湿法腐蚀等手段分析了所生长薄膜的元素含量、折射率、抗腐蚀特性等性质随淀积工艺条件的改变所产生的变化。制备出的氮化硅薄膜可在高温强碱溶液(70℃、33.3%KOH溶液)中支撑12h而无明显变化,并实现自支撑全镂空薄膜。

p-Si TFT栅绝缘层用SiN薄膜的研究

以NH3和SiH4为反应源气体,采用射频等离子体增强化学气相沉积(RF-PECVD)法在多晶硅(p-Si)衬底上沉积了一系列SiN薄膜,并利用椭圆偏振测厚仪、超高电阻-微电流计、C-V测试仪对所沉积的薄膜作了相关性能测试。系统分析了沉积温度和射频功率对SiN薄膜的相对介电常数、电学性能及界面特性的影响。分析表明,沉积温度和射频功率主要是通过影响SiN薄膜中的Si/N比影响薄膜的性能,在制备高质量的p-Si TFT栅绝缘层用SiN薄膜方面具有重要的参考价值。

周期性梯度富硅SiN_x薄膜的微结构与发光特性

采用磁控共溅射结合快速光热退火技术在单晶硅和石英衬底上制备了含硅量子点的周期性梯度富硅SiNx薄膜(梯度薄膜)和单层富硅SiNx薄膜(单层薄膜)。采用Raman光谱、掠入射X射线衍射(GIXRD)、透射电子显微镜(TEM)、傅里叶变换红外(FTIR)光谱和光致发光(PL)光谱分析了薄膜的结构特性、键合特性和发光特性。Raman光谱、GIXRD和TEM结果表明,梯度薄膜和单层薄膜中的硅量子点晶化率分别为41.7%和39.2%;梯度薄膜的硅量子点密度是单层薄膜的5.4倍。FTIR光谱结果显示两种薄膜均为富硅氮化硅薄膜,梯度薄膜的硅含量小于单层薄膜。PL光谱结果表明梯度薄膜中的辐射复合缺陷少于单层薄膜。

PECVD法SiN_x:H薄膜减反钝化特性研究

利用射频等离子体增强化学气相沉积法制备了在太阳电池中用作表面钝化和减反层的SiN_x:H薄膜。制备的折射系数分布在1.72～2.55范围内的一系列薄膜对电阻率为10Ω·cm的p型衬底硅片具有较好的钝化效果。研究给出了SiH_4/NH_3流量比和衬底温度对薄膜折射系数和钝化效果的影响规律,当衬底温度为300℃,SiH_4/NH_3流量比低于50/15时,制备的SiN_x:H薄膜具有优良的减反钝化效果。

射频等离子体增强化学气相沉积SiN_x薄膜的研究

采用射频等离子体增强化学气相沉积技术,以N2和SiH4作为反应气体,在P型硅基片上进行SiNx薄膜的沉积.使用椭偏仪对薄膜厚度和光学常量进行了测量,用傅里叶变换红外光谱仪对SiNx薄膜的化学键合结构进行了分析.研究了基片温度、射频功率以及N2和SiH4的气体流量比率等实验工艺参量对薄膜沉积速率和光学常量的影响.结果表明,射频等离子体增强化学气相沉积技术沉积的SiNx薄膜是低含氢量的SiNx薄膜,折射率在1.65～2.15之间,消光系数k在0.2～0.007之间,当SiNx薄膜为富氮时k≤0.01,最高沉积速率高达6.0nm/min,N2和SiH4气体流量比率等于10是富硅和富氮SiNx薄膜的分界点.

SiN_x薄膜的光致发光研究

用射频磁控溅射技术制备了氮化硅薄膜,室温下测试了薄膜的光致发光谱(PL)和光致发光激发谱(PLE),对薄膜材料的发光特性进行了分析.结果表明,在可见光范围内薄膜有很好的光致发光性质.在波长为381nm的光激发下,SiNx薄膜的主要发光峰位于520 nm(2.38 eV),553 nm(2.24 eV),573 nm(2.16 eV),587 nm(2.11 eV)和627 nm(1.98 eV),主要来自电子在导带与缺陷能级才以及缺陷能级与价带之间的辐射复合.

基于亚波长光栅辅助定向耦合器的集成铌酸锂偏振分束器

绝缘体上铌酸锂(LNOI)是实现高速光子集成回路(PICs)的理想平台。通过充分利用铌酸锂(LN)的优势,LNOI平台能够实现高速电光和高效非线性光学集成器件。偏振分束器(PBS)作为分离和组合两种正交偏振光模式的关键无源器件之一,在实现片上偏振复用系统并提升光通信系统数据传输容量方面发挥着至关重要的作用。近年来,基于不同结构的PBS已经被成功实现,其中,基于亚波长光栅辅助定向耦合结构的PBS表现出优异的器件性能和紧凑的器件尺寸。本文基于氮化硅-铌酸锂异质集成的间接刻蚀方案,实现了一种亚波长光栅辅助定向耦合结构的高性能PBS。仿真结果表明,当波长在1500~1600 nm时,器件的偏振消光比均大于24.49 dB。实验数据进一步证实,当波长在1500~1580 nm时,器件偏振消光比均大于18.06 dB。