硅氢键对波导表面光滑化影响的理论仿真

低损耗高Q值硅基纳米光波导谐振腔,是高灵敏探测器、生物传感器、光通讯器件等发展的关键。而波导表面粗糙度会造成较大的光传输损耗,是制约硅基纳米光波导谐振腔Q值提高的一个重要因素。降低硅基纳米光波导表面粗糙度已成为光波导器件发展的一个关键问题,氢退火工艺是当前改善波导表面粗糙度的一种关键技术。基于表面硅氢键流密度理论,利用Materials Studio软件模拟氢退火光滑化处理过程中硅与氢之间的反应,搜索反应过渡态,探究硅氢键、温度等因素对反应的影响。结果表明:在高温氢退火氛围下,波导表面硅原子与氢原子之间能够形成硅氢键,且温度越高,在硅氢键作用下表面硅原子迁移速率越快,表面由高能态向低能态过渡,表面光滑化效果越明显。     

Interface structure of ultrathin oxide prepared by N/sub 2/O oxidation

With X-ray photoelectron spectroscopy (XPS) measurements, we found in the N/sub 2/O-grown oxide that the nitrogen incorporation should involve the NO or N reaction with the Si-Si bond and P/sub b/ centers at the interface. Consequently, nitrogen content is very low and accumulated mainly at the interface. In addition, we found that the nitrogen atoms at the interface exist in the form of Si-N bonding and the interface oxynitride layer is a mixture of SiO/sub 2/ and Si/sub 3/N/sub 4/ clusters. This structure will result in several undesirable effects. It will give rise to the permittivity and bandgap fluctuations at the interface and hence induced gigantic surface potential fluctuation and mobility degradation in the channel of MOS devices. This bonding structure also explains the interface trap generation during the electrical stressing. The sources of trap generation are attributed to the Si-Si bonds, P/sub b/ centers, and nitride-related defects due to the over-constrained silicon atoms in the Si/sub 3/N/sub 4/ clusters at the interface.     

Deposition characteristics of Ti−Si−N films reactively sputtered from various targets in a N2/Ar gas mixture

The deposition characteristics of Ti−Si−N films obtained by using RF reactive sputtering of various targets in N₂/Ar gas mixtures have been investigated. The dependence of film growth rate and stoichiometry on both the Ti/Si ratio of the target and the N₂ flow rate were found to be due to the different intridation rates of Ti and Si, resulting in, different sputter yields of titanium and silicon nitrides. XPS results showed that an increase in nitrogen content of the Ti−Si−N films leads to the formation of amorphous Si₃N₄ bonding, which produces an in crease in resistivity. Lowering the Si content in the deposited Ti−Si−N films favors the formation of crystalline TiN, even at low N₂ flow rates, and leads to a lower resistivity. A film growth mechanism, expressed in terms of the nitrogen surface coverage on the target, was proposed.     

SAPO—5分子筛结晶过程的SEM,EDAX研究

采用不同的硅源和晶化时间合成的了一系列SAPO-5分子筛。用扫描电镜(SEM)观察不同晶化阶段分子筛的晶体及晶粒大小,用EDAX分析不同样品及同一样品中不同晶粒的元素组成.所得结果表明:当以SiO_2为硅源时,优先生成低硅含量的SAPO-5分子筛晶粒。随晶化时间加长,硅逐渐取代磷进入分子筛骨架并使分子筛晶形改变,晶粒变小。当晶化时间达72h时,产物中伴生有SAPO-34,而以Si(OEt)_4为硅源时,硅对磷的取代速度较慢、随晶化时间的增长,硅进入分子筛骨架并使其晶形变得更加规则。实验结果还暗示,SEM结合微区EDAX是分辨结晶物中无定形硅的有效手段。     

Si (100) 表面 (NH4)2S 处理及其对Al/Si肖特基势垒的影响

The effect of Si （100） surface S passivation was investigated. A thick film with a high roughness value was formed on the Si surface treated by （NH4）2S solution, which was attributed to physical adsorption of S atoms. SEM and XPS analyses reveal that Si surface atoms were chemically bonded with S atoms after Si surface treatment in NH4OH and （NH4）2S mixing solution. This induces a more ideal value for the Schottky barrier height compared with a diode treated only by HF solution, indicating that surface states originating from dangling bonds are passivated with S atoms.     

Effective cleaning process and its influence on surface roughness in anodic bonding for semiconductor device packaging

Wafer cleanliness and surface roughness play a paramount role in an anodic bonding process. Impurities and the roughness on the wafer surface result in unbonded areas which lead to fringes and Newton׳s rings. With an augment in surface roughness, lesser area will be in stroke thus making more pressure and voltage to be applied onto the wafers for better bonding. Eventually it became mandatory to choose the best cleaning process for the bonding technology that can substantially reduce the impurities and surface roughness. In this paper, we investigate the bonding of silicon/oxidized silicon on Pyrex (CORNING 7740) glass with respect to surface roughness and cleanliness of the wafers by performing three renowned cleaning processes such as degreasing, piranha, RCA 1& 2 (SC‐Standard Cleaning 1 and 2) and found that RCA compromises the best between the roughness and cleanliness. Studies were also extended to find out the effects of applied voltage and load on the bonded surface. It was observed for samples cleaned with RCA, an increase of 45% in maximum current and decrease of 75% in total bonding time with the applied load and voltage among all the cleaning techniques used. Three dimensional structures for pressure sensor application were successfully bonded by selecting the appropriate load and cleaning process. Atomic force microscopy analysis was done to investigate the surface roughness on silicon/oxidized silicon and Pyrex glass for different cleaning processes. Scanning electron microscopy and optical imaging were performed on the interface for the surface integrity of the bonded samples.     

p-Si基PTCDA的生长模式

对有机/无机光电探测器PTCDA/p-Si样品表面进行AFM测试,结果表明PTCDA呈岛状生长,各岛成圆丘状,岛的分布不均匀,PTCDA层中存在大量缺陷.原因是p-Si(100)衬底的表面原子悬挂键的作用,使硅原子横向移动满足键合需要形成台阶和其他缺陷.得出PTCDA在p-Si基底上的生长模式为:PTCDA首先在缺陷处聚集,形成许多三维岛状的PTCDA晶核,然后在PTCDA离域大π键的作用下,相邻的两层PTCDA分子存在一定程度的交叠,最终形成岛状结构.     

Surface roughness and optoelectronic properties of intrinsic and doped nc-Si:H prepared by Rf-magnetron sputtering at low temperature

The correlation between the surface roughness and optoelectronic properties of a series of intrinsic and doped nanocrystalline silicon samples deposited by rf-magnetron sputtering at low temperature has been deduced from atomic force microscopy, spectroscopic ellipsometry, optical transmission and reflection and Raman spectroscopy measurements. Atomic force microscopy observations and spectroscopic ellipsometry analysis of the surface layers reveal that the Root Mean Square (rms) surface roughness for the doped samples increases with increasing sample thickness, while for the intrinsic samples we obtain lower rms surface roughness values which are found to be independent of the film thickness. The surface roughness is related to the microstructure of crystalline grains at the layer surface as verified by analysis of the experimental pseudo-dielectric function. However optical reflectance measurements obtained show that the film thickness affects the surface roughness, but not significantly the complex refractive index.     

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.     

A Novel Bonding Method for Ionic Wafers

A novel method for bonding sapphire, quartz, and glass wafers with silicon using the modified surface activated bonding (SAB) method is described. In this method, the mating surfaces were cleaned and simultaneously coated with nano-adhesion Fe layers using a low energy argon ion beam. The optical images show that the entire area of the 4-in wafers of LiNbO₃/Si was bonded. Such images for other samples show particle induced voids across the interface. The average tensile strength for all of the mating pairs was much higher than 10 MPa. Prolonged irradiation reduced polarization in sapphire, quartz, and Al-silicate glasses. Fe and Ar ion-induced charge deposition result in the formation of an electric field, which was responsible for the depolarization. The lattice mismatch induced local strain was found in LiNbO₃/Si. No such strain was observed in the Al-silicate glass/Si interface probably because of annealing at 300 for 8 h. The Al-silicate glass/Si interface showed an interfacial layer of 2 nm thick. A 5-nm-thick amorphous layer was observed with the other layer across the /Si interface. The EELS spectra confirmed the presence of nano-adhesion Fe layers across the interface. These Fe layers associated with the electric field induced by ion beam irradiation for prolonged period of time, particularly in LiNbO₃/Si, might be responsible for the high bonding strength between Si/ionic wafers at low temperatures.     

Analyses for stoichiometry and for Hydrogen and Oxygen in silicon nitride films

Optical, ion, and electron probe techniques can be effectively applied to analyze for H, O, and the Si/N ratio in thin films of silicon nitride. The films studied were formed by chemical-vapor deposition or plasma deposition for application as a gate dielectric in semiconductor memory devices and for circuit encapsulation. The H concentration is measured by the multiple internal reflection technique which detects NH and SiH vibrational modes. A decrease in SiH bonding with an increase in deposition temperature is shown for chemical-vapor-deposited silicon nitride, and a very high concentration of SiH bonds is observed in plasma-deposited silicon nitride. Ion back-scattering analysis is a direct method for measuring the Si/N ratio and a related nuclear reaction analysis technique is a direct method for measuring and profiling the O content. Backscattering analysis shows a significantly larger Si/N ratio for plasma than for chemical-vapor-deposited silicon nitride. The O profile obtained by reaction analysis for a nitride/oxide/Si structure is compared to that obtained by sputter Auger electron spectroscopy, and the results show that O concentrations down to ∼0.5 at % can be measured by either technique. Auger analysis gives better depth resolution than reaction analysis but it requires a calibration standard. Auger results also show N penetration of interfacial SiO2and accumulation of N at the Si-SiO2interface.     

环境气压对脉冲激光烧蚀沉积纳米Si薄膜表面粗糙度的影响

薄膜表面粗糙度是表征薄膜质量的重要指标,为了探求环境气压对脉冲激光烧蚀沉积纳米Si薄膜表面粗糙度的影响,采用XeCl脉冲准分子激光器,分别在惰性气体氦气和氩气的不同气压环境下烧蚀沉积了纳米Si薄膜,用Tencor Instruments Alpha-Step 200台阶仪对相应薄膜的表面粗糙度进行了测量.结果表明,薄膜表面粗糙度开始随着气压的增大而逐渐增加,在达到一最大值后便随着气压的增大而减小.由不同气体环境下的结果比较可以看出,充氩气所得Si薄膜表面粗糙度比充氦气的小,最大粗糙度强烈地依赖于气体种类.对于原子质量较大的氩气而言,其最大粗糙度仅比低气压时高出11%,而对于原子质量较小的氦气来说,其最大粗糙度比低气压时高出314%.     

氢与氧及氮钝化对多孔硅光致发光的影响

对多孔硅在NH3和O2中进行后处理的结果表明,SiH(O3),SiH(SiO2）,SiH2(O2),Si(NH)2和Si3N4结构的产生是实验中多孔硅稳定性提高的原因。     

Toward two-dimensional self-organization of nanostructures using wafer bonding and nanopatterned silicon surfaces

The structure of ultrathin silicon layers obtained by molecular hydrophobic bonding is investigated. The twist and tilt angles between the two crystals are accurately controlled. The buried Si|Si interface is observed by transmission electron microscopy and by grazing incidence X-ray techniques. For low twist angle values (/spl psi/<5/spl deg/) plane view observations reveal well-defined dislocation networks. Cross-section observations give evidence that the dislocation networks are localized at the bonding interfacial plane with no threading dislocation. Grazing incidence small angle X-ray scattering measurements confirm the good quality of the bonding interface as well as the quality of the dislocation networks. Grazing incidence X-ray diffraction is also used and shows the long-range order of the periodic strain field in the silicon layer. It shows, especially, the interaction between the dislocations. X-ray reflectivity was employed and estimated that the interfacial thickness (i.e., thickness of the bonding) lower than 1 nm decreases when the twist angle increases. The nanopatterned surface is then investigated by scanning tunneling microscopy and X-ray methods. To validate these substrates for long-range order self-organization, the growth of Si and Ge quantum dots is finally achieved.     

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.     

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.     

Si(001)外延ZnSe薄膜界面原子的结合与成键

基于密度泛函理论的第一性原理计算,通过对Si(001)和氮化Si(001)表面单层Zn/Se原子结合的方式,模拟ZnSe外延薄膜的二维生长模式,从单层原子结合能、界面原子电子得失、共价结合成键的角度解释了Zn/Se原子在衬底表面的黏附性问题,阐述了薄膜生长初期界面无定形Se出现等现象,分析了氮化Si(001)表面对薄膜二维均匀生长的作用,结果显示N的引入缓和了Si衬底的非极性共价结合与ZnSe原子间的极性离子键结合之间的异质差异。     

应用于中红外波段的阵列化多孔硅一维光子晶体的制备

首先通过光刻工艺制作了阵列化岛状硅衬底,然后利用交替变换阳极腐蚀电流,通过合理地控制制备参数,适当的热氧化条件,成功地制备了禁带中心位于5μm、6μm、7μm、10μm的阵列化多孔氧化硅一维光子晶体.随后在其表面淀积一层低应力的Si3N4,通过原子力显微镜(AFM)和傅里叶红外反射谱(FTIR)测试证明,沉积Si3N4后该结构仍然具有良好的平整度和较高的反射特性.该阵列结构不但具有较好的隔热和高反射特性,而且岛状的阵列结构可使其与其他器件互联变得简单易行,必将为制备多功能、一体化器件提供有利条件.     

异丙醇在硅碱性腐蚀液中的作用

在硅单晶的碱性腐蚀过程中,往往由于碱性腐蚀液对单晶硅的腐蚀速率过快,从而增大了硅单晶片表面的粗糙度。异丙醇有着减缓腐蚀速率的功效因而降低了硅单晶片表面的粗糙度。主要讨论了异丙醇在碱性腐蚀液中的作用原理并对腐蚀实验结果做了分析。     

Effects of thermal annealing on the structural properties of sputtered W–Si–N diffusion barriers

W–Si–N thin films were deposited via rf-magnetron sputtering from a W₅Si₃ target in Ar/N₂ reactive gas mixtures over a large range of compositions, obtained by varying the partial flow of nitrogen within the reaction chamber. The samples of each set were then thermally annealed in vacuum at different temperatures up to 980 °C.Film composition was determined by Rutherford backscattering spectrometry (RBS), surface film morphology by scanning electron microscopy (SEM), micro-structure by transmission electron microscopy (TEM), vibrational properties by FT-IR absorption and Raman scattering spectroscopy, and electrical resistivity by four-point probe measurements.Independently of the deposition conditions, all the as-deposited films have an amorphous structure, while their composition varies, showing an increase of Si/W ratio from 0.1 up to 0.55 when the nitrogen concentration in the films increases from 0 to 60 at%. Thermal treatments in vacuum induce an important loss of nitrogen in the nitrogen-rich samples, especially at temperatures higher than 600 °C. Samples with high nitrogen content preserve their amorphous structure even at the highest annealing temperature, despite the chemical bonding ordering observed by means of FT-IR measurements. Raman spectroscopy of as-deposited films rich in nitrogen suggests the presence of an important amorphous silicon nitride component, but fails to detect any structural rearrangement either within the composite matrix of film or within silicon nitride component. Segregation of metallic tungsten was detected by TEM in the annealed sample with lowest nitrogen content (W₅₈Si₂₁N₂₁). Finally, the resistivity of the films increases with the N content, while the loss of nitrogen accompanies the decrease of resistivity especially of samples with high nitrogen content.