等离子体辅助电子束蒸发低温制备SiO2纳光子薄膜

SiO2纳光子薄膜在光伏领域、纳光子和微电子学领域里有着广泛的应用.采用等离子体辅助电子束蒸发方法在低温条件下制备SiO2/Si纳光子薄膜样品,通过椭圆偏振光谱分析法研究薄膜光学性质随3种工艺条件(生长速率、衬底温度和射频等离子辅助功率)的变化规律,获得了薄膜的机械、化学和光学性能优于传统方法的纳光子薄膜工艺制备条件.     

Fabrication of low-loss thin film microstrip line on low-resistivity silicon for RF applications

A detail fabricating process and characterization of thin film microstrip line (TFML) on low K polyimide, used for interconnects in radio frequency integrated circuits (RFICs) technology, is reported in this study. By incorporating a spin-on dielectric polyimide and sputtering of aluminum, the TFML is fabricated on low-cost low-resistivity silicon (LRS) substrate (ρ?10 Ω cm). The TFML with a thickness of 20 μm polyimide dielectric layer presents attenuation losses of 0.385 dB/mm at 25 GHz and 0.438 dB/mm at 50 GHz. Effective dielectric constant and attenuation of TFML on polyimide are carefully investigated and discussed.     

Effect of epilayer characteristics and processing conditions on the thermally oxidized SiO2/SiC interface

The optimization of the SiO₂/SiC interface is critical for the development of SiC MOS devices. We investigate the effects of several variables spanning both epilayer attributes and processing conditions relative to our control oxidation process. Varying the shallow vicinal angle of the wafer does not affect the interface. There is a definite degradation of the interface as the epilayer doping density is increased. Sacrificial oxidation appears to reduce the number of border traps in the final oxide. Fluorine annealing has no effect on the interface quality. A low temperature (950°C) re-oxidation, which follows a bulk oxide growth at 1150°C, reduces D _it to the mid-10¹⁰ cm⁻²eV⁻¹ range near midgap and Q_f to a reacord low 5×10¹¹ cm⁻².     

High-quality oxide formed by evaporation of SiO nanopowder: Application to MOSFETs on plastic substrates and GaN epilayers

Although good gate oxide of SiO₂ is usually formed by high-temperature thermal oxidation, lowering the temperature for formation of SiO₂ is mandatory for future Si VLSIs, in particular, for flexible ICs, the demand for which has been increasing every year. Vacuum evaporation of SiO powder is an ideal technique not only to form oxide at low temperature but also to form an abrupt interface with the substrate. The latter feature of evaporation is suitable to form thin gate oxide for Si MOSFETs and gate oxide on compound semiconductors. High-quality SiO₂ on compound semiconductors helps development of MOSFETs made of compound semiconductors, which were longed for to be commercially available. The evaporation is not much used to form SiO₂ for MOSFETs in spite of its many advantages, because quality of SiO₂ formed by evaporation of SiO is too poor to be used as gate oxide. Unlike the commercial SiO powder, the newly developed SiO nanopowder, made by thermal CVD using SiH₄ and O₂, consists of spherical particles with sizes less than 50 nm. It does not contain any Si nanocrystals but small molecular Si networks. Such molecular Si networks are easily thermally or optically decomposed. This makes the deposited oxide more free from Si nanocrystals, which usually degrade the insulating property of the oxide. The SiO₂ thin films formed by evaporation of the SiO nanopowder have demonstrated great potential for application to MOSFETs on plastic substrates and GaN epilayers.     

Etching characteristics of SiO2 in CHF3 gas plasma

The etching characteristics of SiO₂} have been investigated in the CHF₃} gas plasma using the planar type reactor with the 400 kHz rf power. The etch rate of SiO₂}, the SiO₂} /Si and SiO₂}/resist etch rate ratios, and the deterioration of photoresist films are studied with a variety of etching parameters. The etching characteristics depend strongly on the coupling mode. With the cathode coupling mode, the values of 300å/min and of larger than 100 are obtained for the etch rate of SiO₂} and the SiO₂}/Si etch rate ratio, respectively. Only 8 is given for the SiO₂} /Si etch rate ratio with the anode one. The deterioration of photoresist films less occurs with the cathode coupling mode than with the anode one. The dependences of the etching characteristics on the rf current, gas pressure, gas flow rate, and the electrode separations are also studied some in detail with the cathode coupling mode. Possible explanations for some of the experimental results are discussed.     

Improved oxidation procedures for reduced SiO2/SiC defects

A significant reduction in the effective oxide charge and interface state densities in oxides grown on p-type 6H-SiC has been obtained by lowering the oxidation temperature of SiC to 1050°C. Further improvements are obtained by following the oxidation with an even lower temperature re-oxidation anneal. This anneal dramatically improves the electrical properties of the Si/SiC interface, and substantially lowers the interface state density. The net oxide charge density on p-type 6H-SiC is also lowered significantly, but remains quite high, at 1.0 × 10¹² cm^-2. The interface state densities of 1.0 × 10¹¹ cnr⁻²/eV are approaching acceptable MOS device levels. The breakdown fields of the oxides are also substantially improved by both the lower oxidation temperature and re-oxidation anneal. Using a low temperature oxidation followed by a re-oxidation anneal for MOSFETs results in a room temperature mobility of 72 cm²/V-s, the highest channel mobility reported for SiC MOSFETs to date.     

A photo-oxidation generated low-k dielectric film deposited by reactive evaporation of SiO

A non-stoichiometric silicon oxide film has been deposited by evaporating SiO as a source material in Ar and O₂ mixed gas. The film is composed of SiO and SiO₂, and has a porous structure. The SiO₂ results from some part of SiO reacting with O₂ and its amount depends on the pressure in the chamber. The residual SiO in the film can be photo-oxidized into SiO₂ by ultraviolet radiation with a Hg lamp. The dielectric constant of the film after photo-oxidation is 1.89±0.04 (at frequency of 1 MHz), which shows that this porous structure film is promising for potential application as a low-k dielectric.     

Evaluation of plasma damage in ultra-low-k materials with cap film using “extracted k-value” method

An “extracted k-value” method has been developed for evaluating postdevice-process damage in ultra-low-k materials inside a multi-layer structure. It is found that an in-depth analysis with using X-ray reflectivity (XRR) is very effective for recognizing the nature of the damage. With these methods, it is investigated that the damage generated in porous methylsilsesquioxane (MSQ) during cap-film deposition and the effect of subsequent process for the improvement.     

Improvement on low-temperature deposited HfO2 film and interfacial layer by high-pressure oxygen treatment

In this study, high-pressure oxygen (O₂ and O₂ + UV light) technologies were employed to effectively improve the properties of low-temperature-deposited metal oxide dielectric films and interfacial layer. In this work, 13 nm HfO₂ thin films were deposited by sputtering method at room temperature. Then, the oxygen treatments with a high-pressure of 1500 psi at 150 °C were performed to replace the conventional high temperature annealing. According to the XPS analyses, integration area of the absorption peaks of O-Hf and O-Hf-Si bonding energies apparently raise and the quantity of oxygen in deposited thin films also increases from XPS measurement. In addition, the leakage current density of standard HfO₂ film after O₂ and O₂ + UV light treatments can be improved from 3.12 × 10⁻⁶ A/cm² to 6.27 × 10⁻⁷ and 1.3 × 10⁻⁸ A/cm² at |Vg| = 3 V. The proposed low-temperature and high pressure O₂ or O₂ + UV light treatment for improving high-k dielectric films is applicable for the future flexible electronics.     

Plasma enhanced chemical vapor deposition of SiO2 films at low temperatures using SiCl4 and O2

Silicon dioxide films have been deposited by Plasma-Enhanced Chemical Vapor Deposition (PECVD) technique using SiCl₄ and O₂ as reactive materials. Infra-red transmittance, Auger electron spectroscopy analysis, ellipsometry, electrical, and chemical etch measurements have been used to characterize these films. It is possible to obtain good quality oxides at a substrate temperature of 200° C using a low flow of reactant gases. High flow of reactant gases results in highly non-homogeneous porous films. The best oxide films obtained show destructive breakdown at electrical fields above 4 MV/cm and a fixed charge density of the order of 2.6 × 10¹¹ charges/cm².     

Growth of CsLiB6O10 thin films on Si substrate by pulsed laser deposition using SiO2 and CaF2 as buffer layers

CsLiB₆O₁₀ (CLBO) thin films are grown on Si (100) and (111) substrates using lower index SiO₂ and CaF₂ as buffer layers by pulsed KrF (248 nm) excimer laser ablation of stoichiometric CLBO targets over a temperature range of 425 to 725°C. A CaF₂ buffer layer is grown on Si by laser ablation while SiO₂ is prepared by standard thermal oxidation. From extended x-ray analysis, it is determined that CaF₂ is growth with preferred orientation on Si (100) at temperatures lower than 525°C while on Si (111) substrate, CaF₂ is grown epitaxially over the temperature range; this agrees well with observed reflection high energy electron diffraction patterns. X-ray 2θ-scans indicate that crystalline CLBO are grown on SiO₂/Si and CaF₂/Si (100). Analysis of reflectance spectra from CLBO/SiO₂/Si yields the absorption edge at 182 nm. Surface roughness of the CaF₂ and CLBO/CaF₂/Si film are 19 and 15 nm, respectively. This relatively rough surface caused by the ablation of wide bandgap CaF₂ and CLBO limits the application of CLBO for waveguiding measurement.     

A high-linear wide-tunable CMOS transconductor for video frequency applications

In this paper a new CMOS transconductor structure based on a g_m-boosted degenerated differential pair is presented for applications in the video frequency range. The proposed circuit combines two techniques, a switchable array of source degenerating MOS resistors and a programmable output current mirror, in order to widen the G_m tuning range while maintaining linearity. Degeneration MOS resistors are made common-mode voltage independent thanks to a simple control circuit. Post-layout simulation results from a 0.35 μm design supplied at 3.3 V show a wide tuning range (10–100 MHz), good linearity (−58.4 dB for an output signal voltage of 1.1 V_p–p) and low excess phase (<0.5° over the whole tuning range).     

A novel method to improve spatial resolution of acousto-optic deflector

In mobile atmosphere laser communication,the fastand accurate beamsteeringis one of the key techniquesfor acquisition,tracking and pointing(ATP) of laser sig-nals .Compared with the normal loop-locked trackingand pointing system composed of fast steering …     

一氧化氮退火对高温氧化SiC/SiO2界面特性的影响研究

本文研究了高温（1300℃）氧化并在一氧化氮（NO）气体中进行氧化后退火方法对4H-SiC 金属-氧化物-半导体（MOS）电容的SiC/SiO2界面特性的影响,主要通过SiC MOS的电容-电压(C-V)特性详细讨论了NO退火时间和温度与SiO2/SiC界面特性的相互关系. 结果表明在NO气体中进行氧化后退火可明显降低界面态密度,并且界面态密度随着温度和时间的增加会进一步降低。 同时,与常规1200℃及以下氧化温度相比,1300℃下热生长的氧化层具有更低的界面态密度且显著缩短了氧化时间,节约了生产成本。     

Photoluminescent properties of ZnO thin films grown on SiO2/Si(100) by metal-organic chemical vapor deposition

We report on the photoluminescent (PL) properties of ZnO thin films grown on SiO₂/Si(100) substrates using low pressure metal-organic chemical vapor deposition. The growth temperature of the films was as low as 400°C. From the PL spectra of the films at 10–300 K, strong PL peaks due to free and bound excitons were observed. The origin of the near bandedge emission peaks was investigated measuring temperature-dependent PL spectra. In addition, the Zn O films demonstrated a stimulated emission peak at room temperature. Upon illumination with an excitation density of 1 MW/cm², a strong, sharp peak was observed at 3.181 eV.     

Optical absorption studies of Si implanted SiO2

Optical absorption of Si implanted SiO₂ is characterized as a function of implant dose and energy upon annealing in N₂, H₂ and O₂ ambients. Interpretation of optical data yields information regarding the structure of defects due to excess Si. These defects are responsible for the memory effect and enhanced conductivity previously reported for Si implanted SiO₂. A correlation between E-band absorption (Si-Si ‘wrong’ bond defect) intensity and the amount of excess Si was established. Annealing of this band in O₂ is diffusion-limited with a reaction cross-section of 5.10⁻¹⁵ cm². Compressive strain-induced, oxygen diffusivity-retardation was observed. The C-band absorption (relaxed oxygen vacancy defect) observed in this study is unique in its response to heat treatment in N₂ and H₂ since it does not anneal in these ambients. C-band annealing kinetics in O₂ closely parallel those of E-band. B₂-band absorption (unrelaxed oxygen vacancy defect) produced by Si implantation is very similar in its annealing properties to the published data.     

Rapid thermal nitridation of thin SiO2 films

An alternative to SiO₂ for gate dielectric applications in MIS devices is nitrided silicon dioxide. A study of this material is presented in this paper. Thin SiO₂ layers (10 nm minimum thickness) were grown on silicon substrates and subsequently nitrided in ammonia at 1 atm using a rapid thermal processing system. Nitridation times ranged from 3 sec to 60 sec at temperatures from 900 to 1200‡ C. The resulting films were then characterized using a variety of techniques including high resolution TEM, XPS, AES, SIMS, and electrical measurements (C-V). Higher temperatures and longer processing times resulted in the accumulation of nitrogen at the film surface and at the Si/SiO₂ interface. As expected, the electrical characteristics of the nitrided films were strongly influenced by the processing conditions. The morphology of the interface, as revealed by high-resolution TEM, was also altered by the nitridation process, especially for high processing temperatures (>1000° C).     

Effects of CH2F2 and H2 flow rates on process window for infinite etch selectivity of silicon nitride to ArF PR in dual-frequency CH2F2/H2/Ar capacitively coupled plasmas

The process window for the infinite etch selectivity of silicon nitride (Si₃N₄) layers to ArF photoresist (PR) and ArF PR deformation were investigated in a CH₂F₂/H₂/Ar dual-frequency superimposed capacitive coupled plasma (DFS-CCP) by varying the process parameters, such as the low frequency power (P_LF), CH₂F₂ flow rate, and H₂ flow rate. It was found that infinitely high etch selectivities of the Si₃N₄ layers to the the ArF PR on both the blanket and patterned wafers could be obtained for certain gas flow conditions. The H₂ and CH₂F₂ flow rates were found to play a critical role in determining the process window for infinite Si₃N₄/ArF PR etch selectivity, due to the change in the degree of polymerization. The preferential chemical reaction of hydrogen with the carbon in the hydrofluorocarbon (CH_xF_y) layer and the nitrogen on the Si₃N₄ surface, leading to the formation of HCN etch by-products, results in a thinner steady-state hydrofluorocarbon layer and, in turn, in continuous Si₃N₄ etching, due to enhanced SiF₄ formation, while the hydrofluorocarbon layer is deposited on the ArF photoresist surface.     

The one-step vacuum growth of high-quality CuInS2 thin film suitable for photovoltaic applications

Due to its direct energy band gap of 1.53 eV, which is well matched to the solar spectrum, the ternary compound CuInS₂ becomes a promising absorber material for high conversion efficiency solar cells. We report in this paper the preparation and characterization of improved quality CuInS₂ films for use as a high-efficiency solar cell absorber. The films were deposited by RF reactive sputter technique, in which the Cu–In alloy target, H₂S reactant gas, and soda lime glass and Si wafer substrates were used. The as-deposited films were the CuInS₂ chalcopyrite single phase with the preferred orientation of (1 1 2). Void-free films with a grain size of about 400 nm and the constituent ratio [Cu+In]/[S] and [Cu]/[Cu+In] approaching 1 and 0.5, respectively, could be attained by optimizing the process parameters, and films with outstanding electrical characteristics could thus be obtained.     

Stress in “cathodic” plasma oxides as a function of processing parameters

Stress in SiO₂ films grown via a “cathodic” plasma oxidation process has been examined as a function of growth and processing conditions. The total stress for oxides grown at 350° C in either 85% Ar/15%O₂ or 100% O₂ ambients at 700 W, 4 MHz, and a total pressure of 80 mTorr was found to be identical. It was observed that annealing these oxides for 24 hr at 700° C in an ultra-pure oxygen ambient did not have any effect on the electrical properties, but that the stress did increase slightly. Electrical properties were measured on MOS capacitors, specifically focusing on net fixed oxide charge and breakdown strength. In addition, both as-grown and annealed samples were subjected to 8.5 × 10⁶ rad(SiO₂) Al K_α ionizing radiation to simulate exposure to X-ray lithography. Notwithstanding the generation of a large areal density of net coulombic charge in the insulator, the presence of these defects did not cause a measurable change in the interfacial stress level. Surprisingly, it was found that about 16% of the wafers plastically deformed during oxide growth at 350° C and about 35% of the wafers were found to be deformed after annealing of the oxides at 700° C. Dry, thermal oxides grown at 700° C were seen to possess similar electrical properties but exhibited a higher stress than the plasma oxides.