超临界CO2在物理发泡同轴电缆中的应用

利用自行研制的供气装置将超临界CO2注入普通N2物理发泡挤出装置,并对LDPE,HDPE,ADD的共混体系的发泡性能进行了应用研究.通过大量对比实验分析了注气量、挤出压力、温度等工艺参数与同轴电缆外观、物理性能、电气性能之间的关系.初步研究结果表明,加入超临界CO2气体可以制得泡孔密度更高、性能更优良的物理发泡同轴电缆.     

复活寿命已终止的镍电极CO2激光器的尝试

本文报导了复活寿命已终止的镍电极CO2激光器的实验结果。复活处理后的腔长为600mm的镍电极CO2激光器功率为15．5W，连续工作1500小时功率无变化；至2500小时，功率缓慢降到10W。其处理费用仅相当于新管售价的1／5—1／4。     

穿心莲内酯在超临界CO2萃取中晶体的形成与生长

用扫描电镜观察了超临界CO2结晶的穿心莲内酯颗粒微观形貌，并利用液相色谱进行纯度检测，阐述了穿心莲内酯在超临界CO2萃取中晶体在结晶板上成核、生长及分布。结果证实：超临界CO2在萃取釜中能同步萃取结晶穿心莲内酯，且在本实验条件下(压力低于25MPa)，晶体纯度在结晶板上呈梯度分布：从下到上，纯度越来越高。     

基于半导体激光吸收谱的在线CO和CO2浓度同时测量技术

优选了中心频率分别为6338.5895cm-1和6337.99cm-1的CO和CO2吸收谱线,使用一个激光器扫描经过该对谱线,在搭建的实验系统上实现了对CO和CO2的同时测量,实验结果表明,基于半导体激光吸收谱(DLAS)的CO和CO2检测下限分别为3σ=0.042%和3σ=0.022%,CO和CO2的线性相关系数分别为0.9999和0.9996,CO和CO2相互间干扰小于1%。现场测量结果表明,该技术能够较好地满足工业过程、机动车尾气和环保等的CO和CO2浓度同时测量的需要。     

用于高功率CO2激光器反射镜的研究

本文讨论了一种用于高功率CO2激光器反射镜的设计、制备、测试及冷却,比较了反镜基底材料的优劣。应用表明:这种反射镜远优于铜基底镀金的反射镜。     

半导体激光及CO2激光对灰黄霉素产生菌的诱变

以灰黄霉素产生菌GM120-43为出发菌株,采用半导体激光和CO2激光进行诱变.结果,仅在100mW低功率条件下,半导体激光诱变获得正突变菌株LD100-1,突变株LD100-1固体发酵产灰黄霉素的效价为119 766u/g,与出发菌株GM120-43相比提高了33.82%,且遗传性状稳定;用CO2激光进行诱变时,获得突变株C1448-1,其固体发酵产灰黄霉素比原始菌株提高22.58%,但是性状不稳定,在传代过程中可能发生回复突变,效价降低于出发菌株.     

高功率横流CO2激光器的新型管板式电极

提出一种更适用于焊接等场合的低阶模输出的新型管板式电极。阳极块长边沿阴极管方向,提高了放电均匀性和稳定性,增加了有效放电长度;阳极沿气流方向的长度和阴阳两极之间的距离根据输出模式确定,可充分利用激活体积,提高选模激光光电转换效率;其放电均匀稳定,可减小限流电阻值,降低外电路电功损耗。与现有管板电极相比,可提高注入到激活体积内的电功率密度,明显提高选模激光输出功率和总体效率。多模输出时直接光电转换效率可达20%;低阶模TEM11输出时光电转换效率可达15%,激光器总效率达8%。该电极结构适用于国内生产的横流CO2激光器,在不同模式输出时均能获得较高的光电转换效率,从而使其更好地应用于焊接等低阶模输出场合。     

一种用于CO2气体传感器的新型MEMS红外光源

基于CO2红外气体传感器微型化、智能化、低功耗的发展要求,创新性地提出一种中心温度为407℃的CO2检测用微电子机械系统(MEMS)红外光源芯片.采用X型悬空桥式微热板结构,内部发热区域以环形走线的钨(W)电极为加热丝,以SiO2和Si3N4双层薄膜作为机械支撑保护层,可防止钨电阻丝氧化并提高寿命.电热耦合有限元仿真分析显示,该光源芯片具有发热区温度分布均匀、热响应时间短、功耗低的优点.采用10.16 cm(4 inch)MEMS工艺完成了芯片的流片制造.测试结果表明,该光源芯片在24 ms内即可快速升温至工作温度407℃,功耗低至46 mW,工作电压为2.85V,工作电流为16.2 mA,具有热响应时间快、功耗低、集成度高的特点.     

用于CO2排放源监测的近红外光参量振荡系统

基于CO2的近红外吸收光谱特征,提出了一种可用于CO2排放源监测的光参量振荡(OPO)和放大(OPA)系统,该系统由输入OPO的激光双种子源、OPO和OPA、带窄线宽激光种子源脉冲Nd∶YAG基频激光器、高精度和频率稳定的双通道波长计等组成,可交替输出1.572 μm的双波长激光束.系统经初步调试后,泵浦脉冲能量为326mJ时获得近25％的转换效率,脉冲能量近80mJ,满足地基差分吸收激光雷达测量对流层CO2浓度廓线的需要.     

Supercritical carbon dioxide process for releasing stuck cantilever beams

The multi-SCCO2(supercritical carbon dioxide)release and dry process based on our specialized SCCO2 semiconductor process equipment is investigated and the releasing mechanism is discussed.The experiment results show that stuck cantilever beams were held up again under SCCO2 high pressure treatment and the repeatability of this process is nearly 100%.     

Deep reactive ion etching (Deep-RIE) process for fabrication of ordered structural metal oxide thin films by the liquid phase infiltration method

Deep reactive ion etching (Deep-RIE) process was established for fabrication of highly nano-ordered metal oxide thin films such as TiO₂, ZrO₂, SnO₂ etc, by the liquid phase infiltration (LPI) method. Electron beam lithography (EBL) technique and Deep-RIE were adapted to fabricate the Si wafer coated with a positive resist ZEP520A. Etching gas of SF₆ and C₄F₈ was used for Deep-RIE process. The flow rate and repeating time were optimized in order to obtain the straight shape on the sidewalls of the trench or pillar structure. We used polymethylmethacrylate (PMMA) and acetylcellulose as a replica films. The transcribed replica films are applied to the liquid phase deposition reaction. The film structure was completely reproduced from the original shape of the designed Si wafer. The optical interference on the fabricated metal oxide thin films was also observed using absolute reflective visible spectroscopy.     

Effect of RuO2 electrode on laser-MBE prepared HfO2 gate dielectrics

In this paper, we report our recent study of the effect of RuO₂ as an alternative top electrode for pMOS devices to overcome the serious problems of polysilicon (poly-Si) gate depletion, high gate resistance and dopant penetration in the trend of down to 50 nm devices and beyond. The conductive oxide RuO₂, prepared by RF sputtering, was investigated as the gate electrode on the Laser MBE (LMBE) fabricated HfO₂ for pMOS devices. Structural, dielectric and electric properties were investigated. RuO₂/HfO₂/n-Si capacitors showed negligible flatband voltage shift (<10 mV), very strong breakdown strength (>10 MV cm⁻¹). Compared to the SiO₂ dielectric with the same EOT value, RuO₂/HfO₂/n-Si capacitors exhibited at least 4 orders of leakage current density reduction. The work function value of the RuO₂ top electrode was calculated to be about 5.0 eV by two methods, and the effective fixed oxide charge density was determined to be 3.3 × 10¹² cm⁻². All the results above indicate that RuO₂ is a promising alternative gate electrode for LMBE grown HfO₂ gate dielectrics.     

Optimization of electric properties of high-k zirconium dioxide by varying deposition and annealing conditions

ZrO₂ thin films with a smooth surface were synthesized on silicon by atomic vapor deposition™ using Zr[OC(CH₃)₃]₄ as precursor. The maximum growth rate (7 nm min⁻¹) and strongest crystalline phase were obtained at 400 °C. The increase of the deposition temperature reduced the deposition rate to 0.5 nm min⁻¹ and changed the crystalline ZrO₂ phase from cubic/tetragonal to monoclinic. These films showed no enhancement of the dominating monoclinic phase by annealing. The values of the dielectric constant (up to 32) and leakage current density (down to 1.2×10⁻⁶ A cm⁻² at 1×10⁶ V cm⁻¹) varied depending on the deposition temperature and film thickness. The midgap density of interface states was N_it=5×10¹¹ eV⁻¹ cm⁻². The leakage current and the density of interface states were lowered by the annealing to 10⁻⁷ A cm⁻² at 1×10⁶ V cm⁻¹ and to 10¹⁰ eV⁻¹ cm⁻², respectively. However, this also led to a decrease of the dielectric constant.     

Bio/chemical detection in liquid with self-sensing Pr-Oxi-Lever (piezo-resistive SiO2 cantilever) sensors

The paper presents a self-sensing microcantilever for bio/chemical detection in liquid. The developed silicon piezoresistance encapsulated SiO₂ cantilever (Pr-Oxi-Lever) is with the electric interconnection wires insulated by a SU-8 coating layer for specifically detecting bio/chemical molecules in liquid environment. Functionalized with specific sensing terminals, siloxane-based molecule layer is directly modified on the cantilever SiO₂ surface via reliable Si-O covalent bond. Instead of the previously used thiol self-assembly molecule layers that show long-term instability, the modified siloxane sensing layer secures long-term sensitivity stability and long working life. The sensors have been successfully used for detection of 2.5% aqueous tetramethylammonium hydroxide (TMAH) and avidin at 10⁻¹¹ mol/mL trace level. An interesting phenomenon of opposite surface-stress sensing signals for different-sized target-molecules is experimentally observed. A simple model is proposed for preliminary explanation of this phenomenon.     

Characterization of the CH4/H2/Ar high density plasma etching process for HgCdTe

High density plasma etching of mercury cadmium telluride using CH₄/H₂/Ar plasma chemistries is investigated. Mass spectrometry is used to identify and monitor etch products evolving from the surface during plasma etching. The identifiable primary etch products are elemental Hg, TeH₂, and Cd(CH₃)₂. Their relative concentrations are monitored as ion and neutral fluxes (both in intensity and composition), ion energy and substrate temperature are varied. General insights are made into surface chemistry mechanisms of the etch process. These insights are evaluated by examining etch anisotropy and damage to the remaining semiconductor material. Regions of process parameter space best suited to moderate rate, anisotropic, low damage etching of HgCdTe are identified.     

Charging effects in CdSe nanocrystals embedded in SiO2 matrix produced by rf magnetron sputtering

Charging effects in CdSe nanocrystals embedded in SiO₂ matrix fabricated by rf magnetron co-sputtering technique were electrically characterized by means of capacitance-voltage (C-V) combined with current-voltage (I-V). The presence of CdSe nanocrystals was demonstrated by X-ray diffraction technique. The average size of nanocrystals was found to be approximately 3 nm. The carriers transport in the CdSe/SiO₂ structure was shown to be a combination of Fowler-Nordheim tunnelling and Poole-Frenkel mechanisms. A memory effect was demonstrated and a retention time was measured.     

Removal of HF/CO2 post-etch residues from pattern wafers using water-in-carbon dioxide microemulsions

We have investigated different methods for removing the HF/CO₂ post-etch residues from blanket and patterned wafers of borophosphosilicate glass. The use of co-solvents, rinsing the residues with DI water followed by CO₂-based drying process, and the use of water-in-CO₂ (W/C) microemulsions were explored as possible methods to remove the etch residues. It was found that the addition of co-solvents were ineffective for quantitative removal of residues, whereas rinsing the etch residues with DI water followed by the surfactant-aided scCO₂ drying was found to be effective. To eliminate the pure water rinsing step, W/C microemulsions formed with different surfactants were directly treated with residues. While ionic surfactants such as ammonium carboxylate perfluoropolyether and sodium salt of bis (1H,1H,2H,2H-tridecafluoro-octyl)-2-sulfosuccinate did not produce stable microemulsions in the presence of HF, due to protonation effect, the reverse micelles formed with an amphiphilic block copolymeric surfactant, poly(ethylene oxide-b-perfluorooctylmethacrylate), was found to be highly efficient as clean and residue-free images were observed by microscopic analysis.     

N2 effect on GaAs etching at 150 mTorr capacitively-coupled Cl2/N2 plasma

The role of N₂ on GaAs etching at 150 mTorr capacitively-coupled Cl₂/N₂ plasma is reported. A catalytic effect of N₂ was found at 20-25% N₂ composition in the Cl₂/N₂ discharges. The peak intensities of the Cl₂/N₂ plasma were monitored with optical emission spectroscopy (OES). Both atomic Cl (725.66 nm) and atomic N (367.05 nm) were detected during the Cl₂/N₂ plasma etching. With the etch rate and OES results, we developed a simple model in order to explain the etch mechanism of GaAs in the high pressure capacitively-coupled Cl₂/N₂ plasma as a function of N₂ ratio. If the plasma chemistry condition became positive ion-deficient at low % N₂ or reactive chlorine-deficient at high % N₂ in the Cl₂/N₂ plasma, the GaAs etch rate is reduced. However, if the plasma had a more balanced ratio of Cl₂/N₂ (i.e. 20-25% N₂) in the plasma, much higher etch rates (up to 150 nm/min) than that in pure Cl₂ (50 nm/min) were produced due to synergetic effect of neutral chlorine adsorption and reaction, and positive ion bombardment. Pure Cl₂ etching produced 14 nm of RMS surface roughness of GaAs. Introduction of ?20% N₂ gas in Cl₂/N₂ discharges significantly reduced the surface roughness to 2-4 nm. SEM photos showed that the morphology of photoresist mask was strongly degraded. Etch rate of GaAs slightly increased from 10 to 40 nm/min when RIE chuck power changed from 10 to 150 W at 12 sccm Cl₂/8 sccm N₂ plasma condition. The surface roughness of GaAs etched at 12 sccm Cl₂/8 sccm N₂ plasma was 2-3 nm.