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.

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.

Deposition of Silicon Nitride Films by Silane Hydrazine Process

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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。

Thermal conductivity of PECVD silicon-rich silicon nitride films measured with a SiO_2/Si_xN_y bimaterial microbridge test structure

In order to balance the compressive stress of a silicon dioxide film and compose a steady MEMS structure, a silicon-rich silicon nitride film with tensile stress is deposited by plasma enhanced chemical vapor deposition process. Accurately measuring the thermal conductivity of the film is highly desirable in order to design, simulate and optimize MEMS devices. In this paper, a Si02/SixNy bimaterial microbridge structure is presented to measure the thermal conductivity of the silicon-rich silicon nitride film by single steady-state measurement. The thermal conductivity is extracted as 3.25 W/（m-K）. Low thermal conductivity indicates that the silicon-rich silicon nitride film can still be utilized as thermally insulating material in thermal sensors although its thermal conductivity is slightly larger than the values reported in literature.

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。

STRUCTURE AND BINDING STATE OF CN_x FILMS SYNTHESIZED BY FACING TARGETS SPUTTERING

CN x films were made by a facing targets sputtering ( FTS) systemon the Si(100) substrate under different N 2 partial pressure. XRD, XPS, FTIR and Raman Spectroscopy( RS) were measured to investigate the structure and the binding state of the film. The films are amorphous and the N/C increases with the N 2 partial pressure increasing and reaches 0 46 when the N 2 pressure is 100%. The N incorporated C forms N sp 2C and N sp 3C mainly and there is a small amount of C≡N.

Intermodal frequency generation in silicon-rich silicon nitride waveguides

Dispersion engineering in optical waveguides allows applications relying on the precise control of phase matching conditions to be implemented. Although extremely effective over relatively narrow band spectral regions,dispersion control becomes increasingly challenging as the bandwidth of the process of interest increases.Phase matching can also be achieved by exploiting the propagation characteristics of waves exciting different spatial modes of the same waveguide. Phase matching control in this case relies on achieving very similar propagation characteristics across two, and even more, waveguide modes over the wavelengths of interest, which may be rather far from one another. We demonstrate here that broadband(>40 nm) four-wave mixing can be achieved between pump waves and a signal located in different bands of the communications spectrum(separated by50 nm) by exploiting interband nonlinearities. Our demonstration is carried out in the silicon-rich silicon nitride material platform, which allows flexible device engineering, allowing for strong effective nonlinearity at telecommunications wavelengths without deleterious nonlinear-loss effects.

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.

Dependence of Optical Absorption in Silicon Nanostructures on Size of Silicon Nanoparticles

在 helicon 准备的电影挥动的硅氮化物(SiNx ) 嵌入的非结晶的硅 nanoparticles (Si NP ) 提高血浆的化学蒸汽免职(HWP-CVD ) 技术被学习。从散布调查的拉曼，我们决定扔的电影有在硅氮化物(nc-Si/SiNx ) 嵌入的硅 nanocrystals 的结构在某个氢冲淡数量的薄电影。光吸收系列的分析暗示 Si NP 被量尺寸效果影响并且有一个 indirect-band-gap 半导体的性质。进一步，在振荡器力量，和量监禁上考虑吝啬的 Si NP 尺寸和他们的分散的效果，我们获得分析表情为光谱整体样品的吸收度。Si NP 的 Gaussian 以及 lognormal 尺寸分发为光吸收系数计算被考虑。光吸收系列上的粒子尺寸分发的影响系统地被学习。我们在场光吸收的试穿与我们的模型一起的试验性的数据并且讨论结果。

基于MEMS芯片的磁性材料TEM表征技术

传统透射电子显微镜(TEM)以电磁场为透镜,通常情况下磁性材料不能直接在TEM下进行观测,一般使用以碳为支撑膜的双联铜网作为样品载网,但仍然有一定的破损概率。设计并实现了一种新型的基于微电子机械系统(MEMS)芯片的磁性材料TEM表征技术。该技术通过磁性TEM芯片和配套的样品杆,在TEM内形成一个密闭空间。将磁性样品上载到磁性TEM芯片上,从而实现在TEM下对磁性样品的安全观测。该芯片的核心结构是可以透射电子束的超薄氮化硅窗口,该窗口采用低压化学气相沉积(LPCVD)法制备,具有极高的机械强度,最高可以承受接近400 kPa的气压差。实验结果表明,利用该TEM表征技术可以在TEM下成功观测铁包硅和NiO两种磁性材料,分辨率可以达到原子级。

氮气体积流量对磁控溅射氮化硅薄膜性能的影响

磁控溅射法制备氮化硅薄膜具有工艺简单、粉尘少等优点,氮化硅薄膜在微电子机械系统(MEMS)领域中可用作腐蚀掩蔽层和力学结构层。以氮化硅为靶材、高纯氮气为反应气体,采用射频磁控溅射法在硅衬底上制备氮化硅薄膜,在射频功率150 W、偏压150 V、工作气压0.5 Pa、温度450℃、氩气体积流量60 cm3/min的条件下,随着氮气体积流量从0增加到25 cm3/min,氮化硅薄膜的沉积速率先增大后减小,薄膜的压应力从1.38 GPa逐渐减小到672.2 MPa。沉积的氮化硅薄膜在质量分数为10%的HF溶液中的腐蚀速率从20.1 nm/min减小到5.9 nm/min,在80℃、质量分数为40%的KOH溶液中的腐蚀速率从26.8 nm/min减小到1.3 nm/min。随着氮气体积流量增加,薄膜更为致密,缺陷减少,可应用于红外光源、流量传感器等MEMS器件中作为绝热层或者钝化层。

低压化学气相沉积制备低应力氮化硅膜的研究

采用低压化学气相沉积方法,通过改变工艺气体配比,在硅衬底上生长低应力氮化硅薄膜。用应力仪、椭偏仪对生成的氮化硅薄膜的应力、生长速率、均匀性、折射率及腐蚀速率等进行实验。实验结果表明:低应力氮化硅薄膜制备的关键是增大DCS和NH3的配比,配比越大,生成的氮化硅薄膜应力越小,折射率越大,耐酸腐蚀能力越强,致密性越好;但随着配比增大,生成的氮化硅薄膜均匀性变差。选择合适的工艺气体配比可在硅衬底上制备出高质量的低应力氮化硅薄膜。

紧凑型纳米薄膜铌酸锂复合波导光电子可逆逻辑门

基于纳米薄膜铌酸锂与氮化硅复合波导结构,构建了光电子可逆逻辑门,应用于神经形态光子学和量子计算。该光电子可逆逻辑门的主体由两个马赫-曾德尔调制器级联而成,结构紧凑,全长仅为4.4 mm,是普通质子交换铌酸锂调制器长度的百分之一。工作在1.55μm波长时,该马赫-曾德尔调制器仅需4.9 V电压就可以实现一次完整的功率交换,很好地与CMOS工艺相兼容。器件特性研究表明,该光电子可逆逻辑门能够实现可逆逻辑运算功能。此外,该器件在1.4~1.6μm波长范围内,插入损耗均值为0.6 dB,输出端口的最小串扰为-47 dB,消光比的最大值为41 dB;在4~6 V电压范围内,插入损耗均值为0.63 dB,输出端口的最小串扰为-26 dB,消光比的最大值为22 dB,显示出了良好的响应特性。

板式PECVD氮化硅薄膜工艺研究

本文采用微波等离子增强化学气相沉淀技术,在单晶硅衬体上高速沉积一层氮化硅薄膜。通过对比实验,系统研究了沉积压强、气体流量、微波功率、温度等工艺参数对氮化硅薄膜沉积速率、折射率的影响,分析其产生机理。通过优化氮化硅沉积的工艺参数,采用分步沉积氮化硅工艺,测试对比两者内量子效应和光谱反射率,得出分步沉积氮化硅工艺,在200~400 nm短波段,反射率更低,进一步降低了氮化硅薄膜对光的反射率。同时,在1000~1200 nm的长波段,内量子效应增强,表明提升氮化硅薄膜的钝化效果,最终实现晶硅太阳能电池效率提升0.1%,为优化生产工艺奠定了良好基础。

LPCVD氮化硅薄膜室温高强度可见光发射

在５．０ｅＶ的激光激发下，在室温下ＬＰＣＶＤ氮化硅薄膜可发射高强度可见荧光，其峰位位置分别为２．９７，２．７７，２．５５，２．３２，２．１０和１．９０ｅＶ的六个ＰＬ峰，建立了其可见荧光发射的能隙态模型，并初步讨论了其发光机制．