用于微机电系统的SiO2/Si3N4驻极体的制备及电荷稳定性

驻极体微型发电机是近期提出的微电子机械系统开发中的一个新领域,驻极体电荷稳定性则是影响驻极体微型发电机性能的关键.用等离子体增强化学气相沉积(PECVD)方法制备SiO2/ Si3N4双层膜,采用电晕充电和热极化方法对材料进行注极形成驻极体,探讨了器件加工工艺及存储环境对双层膜驻极体电荷稳定性的影响.结果表明,电晕充电后SiO2/ Si3N4双层膜的电荷存储稳定性明显优于SiO2单层膜;传统的电晕注极方法仅适用于大面积驻极体的制备,但对微米量级的材料表面不适用;微器件制备的工艺流程对驻极体电荷稳定性有显著影响,但存储环境对热极化驻极体电荷稳定性的影响很小.     

P(VDF/CTFE)共聚物薄膜的驻极体行为

通过不同条件下的正负电晕充电,等温表面电位衰减测量,热刺激放电（TSD）电流谱分析和热脉冲技术,首次研究了偏氟乙烯（VDF）和三氟氯乙烯（CTFE）共聚物P（VDF／CTFE）的驻极体性质,结果指出：共聚物驻极体的空间电荷热稳定性明显优于PVDF;TSD谱分析说明这种材料驻极体也是极性驻极体,即体内同时包含有偶极和空间电荷。本文还对样品的正负电晕充电后的电荷储存稳定性做了对比;研究了材料的能阱分布,确定了样品在不同温度电晕充电时平均电荷重迁移规律。     

聚丙烯驻极体在充电期间和充电后电荷在体内的输运

通过正负常温和高温电晕充电和常溫充电后不同温度下热老化后的热刺激放电(TSD)电流谱的测量,研究了聚丙烯(PP)突出的驻极性能及其电荷的贮存稳定性问题。利用热脉冲技术确定不同温度下注极后电荷重心的迁移规律,分析了脱阱电荷在体内的输运模式,显示出脱阱电荷在聚丙烯驻极体内的输运具有快捕获效应.     

聚丙烯驻极体的恒流源电晕充电

本文讨论了聚丙烯驻极体恒流电晕充电期间电荷的建立。分析了恒流电晕充电后,聚丙烯驻极体的开路TSD(Thermally Stimulatod Dischar-ge)电流谱及充电后注入样品电荷的平均电荷重心的迁移规律和恒压电晕充电相比较,揭示了恒流充电能将更多的电荷注入聚丙烯体内。因此,恒流电晕充电能明显地改善聚丙烯驻极体的电荷贮存稳定性。     

P(VDF-TFE-HFP)/PTFE双层膜的驻极体特性

通过栅控恒压电晕充电,等温表面电位衰减测量．电荷TSD(charge TSD)和热刺激放电(Thermally Stimulated Discharge．TSD)电流谱分析,首次研究了以聚四氟乙烯(PTFE)为基的偏氟、四氟乙烯和六氟丙烯三元共聚物P(VDF—TFE—HFP)构成的双层膜的驻极体性质。TSD电流谱分析说明这种复合驻极体材料是极性驻极体,即体内同时包含有空间电荷和有序取向的偶极电荷。实验结果还指出：通过对双层膜系的PTFE面充电形成的驻极体的空间电荷热稳定性明显优于传统的铁电聚合物驻极体PVDF。适当提高充电温度和充电后的等温老化储存可以改善电荷稳定性,由于该三元共聚物的高弹性柔量(顺度)和双层膜拥有的优良电荷储存能力,其压电活性高于PVDF．     

聚酰亚胺驻极体的平均电荷重心迁移及电荷的贮存

本文利用开路 TSD 电流谱讨论了电晕充电期间热处理对聚酰亚胺薄膜驻极体电荷贮存稳定性的影响,分析了恒压电晕充电期间电荷的建立过程,研究了延长注极时间及在不同温度下电晕充电的聚酰亚胺薄膜沉积电荷平均深度向背电极的迁移规律。     

环境湿度对聚酰亚胺驻极体性能的影响

本文讨论了恒流电晕过程中环境湿度对聚酰亚胺驻极体表面电位建立的影响,分析了恒压充电后环境湿度对聚酰亚胺驻极体电荷储存稳定性的影响。利用热脉冲技术研究了不同湿度下电晕充电的聚酰亚胺薄膜沉积电荷平均深度向背电极的迁移规律。     

乙烯/四氟乙烯共聚物薄膜驻极体的电荷储存稳定性

研究了经栅控恒压电晕充电的乙烯／四氟乙烯共聚物（ETFE）驻极体的电荷稳定性,并将其与几种重要的驻极体材料的储电性能进行了比较。结果显示,ETFE薄膜驻极体具有优良的电荷储存稳定性,负极性ETFE的电荷稳定性明显优于正极性样品。热处理工艺能明显改善ETFE驻极体的电荷储存寿命。本文还估算出两种极性ETFE驻极体的陷阱能级的活化能,阐明脱阱电荷的输运特性。     

氟化乙丙烯共聚物薄膜驻极体电荷存储性能与电晕产生模式相关性

采用在直流稳态、高频脉冲和交变电场作用下的电晕放电对氟化乙丙烯共聚物(FEP)薄膜材料进行注极,通过等温表面电位测量和热刺激放电技术考察了FEP驻极体的电荷存储特性,依据电晕放电等离子体鞘层模型对实验结果进行了分析,研究了电晕产生模式对FEP薄膜驻极体电荷存储性能的影响。结果表明,电晕注极FEP薄膜驻极体的表面电位稳定性与电晕产生模式、电晕极性有关,但是电荷存储机制只与电晕极性有关。脉冲电晕注极时的稳定性优于稳态电晕注极,但其初始表面电位值较低。交变电场电晕注极获得的驻极体,呈现负极性。不同电晕放电模式在材料表面形成的等离子体鞘层的组成和厚度不同,是FEP驻极体性质不同的主要原因。     

Si基多孔SiO2薄膜的驻极体性能

通过控制制备工艺条件和充电参数,利用相应条件下样品的等温表面电位衰减,开路热刺激放电电流谱等。考察了利用溶胶－凝胶（sol-gel)方法制备的Si基多孔SiO2薄膜的驻极体性能,分析了各种工艺参数与蓦主极体性质之间的联系,同时利用Gauss拟合及初始上升法对薄膜驻极体的电荷阱深度进行了估算,实验结果表明,反应物中水的含量对薄膜驻极体的陷阱分布具有调节作用,估算出负电晕充电SiO2薄膜驻极体电荷的活化能为0．3 eV和1．0eV;环境湿度对电荷储存稳定性有一定的影响,降低栅压可以提高SiO2薄膜驻极体的电荷储存稳定性。     

Negative differential resistance effects in spun films of substituted phthalocyanine derivatives

Spun films of novel substituted lead phthalocyanine derivatives between aluminum and indium tin oxide electrodes exhibit large, reproducible negative differential resistance (NDR) in their current–voltage characteristics and can be electrically switched between a high conductance on state and a low conductance off state. Space charge limited conduction mechanism was identified from temperature dependent measurements to be responsible for charge transport. The NDR effect may be due to the charge storage in the structure near the electrodes.     

Electrical stability of polyimide siloxane films for interlayer dielectrics in multilevel interconnections

Electrical stability of a polyimide siloxane (PSI) film for ultra-large scale integrated circuit (ULSI) multilevel interconnections is studied. The PSI films, modified by p-aminophenyltrimethoxysilane (APTMS), are designed to have three-dimensional polymer structures through Si–O bonds. It has been revealed that the PSI films are more stable in electrical properties at higher temperatures than 150°C, as compared to the conventional polyimide (PI) films. The electrical conduction mechanism study for the PSI films has revealed that Schottky emission is dominant. Barrier height φ_B obtained from the electrical property for the PSI film was 0.460 eV in the temperatures ranging from 25–250°C. On the other hand, barrier height of 0.422 eV at lower temperatures than 150°C and activation energy of 1.09 eV at higher temperatures than 150°C were obtained for the conventional PI film. The difference in polymer structure is very sensitive to the electrical conduction at high temperature, due to sodium ion migration. The ideal band diagrams of metal-insulator-semiconductor (MIS) structures were also discussed. The optical band gaps for PSI and conventional PI films were 3.320 eV and 3.228 eV, respectively. This result suggests that the band gap of PI films can be enlarged by modification with Si–O components. The differential barrier height between the PSI and conventional PI films is 0.038 eV, and is close to the difference in half of optical band gaps (0.046 eV).     

Studies of thermally stimulated currents and surface charge in polystyrene thin films

A careful study was undertaken of the initial charge developed on the non-metallized surface and of short-circuit thermally stimulated currents (TSCs) in unilaterally metallized polystyrene (PS) films 25 microm thick. The films had been negatively charged by Townsend breakdown at a voltage of −5 kV at various temperatures ranging from 90 to 130°C. The surface charge densities observed were of the order of 10^-8 C cm^-2, corresponding to full trap densities of the order of 10¹⁴ cm⁻³. The short-circuit TSC spectra of newly charged samples show a single peak at a temperature between 98 and 102°C. The thermal activation energy associated with this peak was found to be 1.2 eV. An analysis of TSCs indicates that electrons are subject to fast retrapping in PS. The ratio of the mean charge depth to the sample thickness is found to increase from 0.069 to 0.12 with the increase in the temperature of polarization, indicating a higher charge accommodation at higher temperatures of polarization. The trap-modulated mobility values for electrons at the TSC peak temperatures are the order of 10⁻¹² cm² V⁻¹s⁻¹. Such low mobility values at peak temperatures are considered to indicate the excellent charge storage properties of PS.     

聚酰亚胺/二氧化硅复合薄膜的热物性及其影响因素

应用自行研制的亚微米/微米薄膜激光脉冲法热扩散率测定仪和差示扫描量热仪(DSC)分别测定了聚酰亚胺(PI)薄膜和PI/SiO_2复合薄膜在不同温度下的热扩散率、热导率和比热,解决了激光脉冲法测定热导试样的透光问题.研究了PI/SiO_2复合薄膜的热物性随SiO_2添加量和温度的变化关系.结果表明:随着温度的升高,PI薄膜及PI/SiO_2复合薄膜的热扩散率下降,比热和热导率线性增加.在PI薄膜中添加SiO_2颗粒可降低PI薄膜的比热,明显增强导热性能,但是不会改变PI薄膜热导率随温度升高而增大的变化规律.     

Modeling and characterization of viscoelasticity of PI/SiO2 nanocomposite films under constant and fatigue loading

In this paper, the viscoelastic behavior of PI/SiO₂ nanocomposite thin films under constant and fatigue tensile loading was studied. The cyclic hardening and viscous dissipation of PI/SiO₂ nanocomposite thin films during the fatigue process were experimentally investigated and analyzed by storage modulus, loss modulus and phase lag. The time-dependent deformation under constant and fatigue loading was simulated based on two viscoelastic models known as Burger model and Findley power law. Standard parameter analysis methodology was employed to interpret the structure–property relationship and deformation mechanisms of this kind of nanocomposites. In addition, the effects of nano-silica content, stress level and loading pattern (constant or fatigue loading) on the creep resistance of materials were discussed as well.     

Diffusion and adhesion properties of Cu films on polyimide substrates

Copper thin films were prepared on polyimide (PI) substrates by physical vapor deposition (PVD) and chemical vapor deposition (CVD). Titanium nitride (TiN) diffusion barrier layers were deposited between the copper films and the PI substrates by PVD. Auger electron spectroscopy compositional depth profile showed that TiN barrier layer was very effective in preventing copper diffusion into PI substrate even after the Cu/TiN/PI samples were annealed at 300 °C for 5 h. For the as-deposited CVD-Cu/PI, CVD-Cu/TiN/PI, and as-deposited PVD-Cu/PI samples, the residual stress in Cu films was very small. Relatively larger residual stress existed in Cu films for PVD-Cu/TiN/PI samples. For PVD-Cu/TiN/PI samples, annealing can increase the peeling strength to the level observed without a diffusion barrier. The adhesion improvement of Cu films by annealing treatment can be attributed to lowering of the residual tensile stress in Cu films.     

Electrical characterisation of AlCuMo thin films prepared by DC magnetron sputtering

Thin film resistors have been manufactured to evaluate the electrical performance characteristics of AlCuMo thin films. The films were prepared on Al2O3 substrates at room temperature as a function of Mo concentration by DC magnetron sputtering and were then annealed at various temperatures in air and N2 atmospheres. The effect of annealing temperature on the electrical properties of the films was systematically investigated. Increase in Mo content produced a decrease in temperature coefficient of resistance (TCR), an increase in resistivity (r) and an improvement in long term stability (DV/V) of the films. TCR varied from negative to positive and further improvements in resistance stability of the films were also achieved through increasing annealing temperature in both air and N2 atmospheres. A temperature region is proposed where `near zero? TCR (ppm/8C) and long term stability of better than 0.2% can be realised.     

Vacuum deposited polyimide thin films

Vacuum deposition as an attractive alternative for polyimide (PI) layers formation is discussed. PI thin films can be formed by vapour co-deposition of the precursor monomers pyromellitic dianhydride and 4,4′-oxydianiline following a thermal treatment at a temperature of over 150°C. The effects of the dynamic state of the substrate, dose stoichiometry and thermal treatment on the surface morphology and imidization rate of PI films were investigated using scanning electron microscopy, thermogravimetric, differential thermal analyses and Fourier transform infrared spectroscopy and microscopy. The results showed that the solid state reaction between the precursors starts at about 175°C. The imidization finishes in the temperature interval of 342–365°C. The destruction of PI is observed at 520°C. The surface morphology of the layers depends only on the monomer ratio. The resulting vacuum deposited PI films are smooth, uniformly thick and form without shrinkage.     

Electrical transport mechanism in plasma polymerized 2, 6, diethylaniline thin films

Plasma polymerized 2, 6, diethylaniline (PPDEA) thin films were deposited at room temperature on to glass substrates by a capacitively coupled parallel plate glow discharge reactor. The surface of the PPDEA thin films has been found uniform and pinhole free from the scanning electron micrographs. The observation by electron dispersive X-ray analysis indicates the presence of carbon, nitrogen and oxygen in the PPDEA thin films. The current density-voltage characteristics of aluminum (Al)/PPDEA/Al structure of different film thicknesses have been studied at different temperatures. In the low voltage region, the conduction current obeys Ohm's law while the charge transport phenomenon appears to be Schottky type in the higher voltage region. The temperature dependence of the current density for different bias voltages was also investigated which confirms the possibility of Schottky emission in PPDEA thin films as well.     

充电前的淬火对Teflon FEP薄膜驻极体电荷贮存能力的影响EI

研究了充电前的淬火对Teflon FEP等驻极体材料电荷贮存能力的影响。淬火前的升温率、淬火期间的冷却率、淬火温度、淬火后和充电前的储存时间等热处理参数的调节,导致了TSD电流谱线峰值的变化和峰温的漂移,影响了电荷的贮存寿命。如果合理地控制淬火参数,在样品结晶度降低并不明显而平均晶粒直径显著减小时,能改善电荷贮存稳定性。利用初始上升法和峰值清洗术估算了Teflon FEP在淬火前后的活化能和试图逃逸频率。此外,还利用热传输方程和电晕、电子束充电及TSD实验从理论和实验方面研究了FEP样品在淬火期间的淬透性和样品厚度的关系。