应用于FRAM的集成铁电电容的研究

集成铁电电容的制备是铁电存储器的关键工艺之一。该文采用射频(RF)磁控溅射法在Pt/Ti/SiO2/Si制备Pb(Zr,Ti)O3(PZT)薄膜,上下电极Pt采用剥离技术工艺制备,刻蚀PZT薄膜,形成Pt/PZT/Pt/Ti/SiO2/Si集成电容结构,最后高温快速退火。结果表明,这种工艺条件可制备性能良好的铁电电容,符合铁电存储器对铁电电容的要求。     

退火温度对PZT薄膜电容器性能的影响

通过简单的溶胶–凝胶法和快速热处理工艺,获得了在Pt/Ti/SiO2/Si基片上生长良好的PZT薄膜。制膜工艺简单,不需要回流和高温去结晶水,即可获得(111)择优取向的PZT薄膜。PZT薄膜经快速热处理在550~650℃退火,薄膜致密和平滑,均具有良好的铁电和介电特性,其最佳退火温度为600℃。     

均匀设计法研究PZT铁电薄膜制备工艺的优化

应用射频磁控溅射工艺在Pt/Ti/SiO2/Si衬底上制备具有钙钛矿结构的PZT铁电薄膜。对影响PZT薄膜性能、形貌的工作气压、基片温度、氧/氩 氧之比、溅射功率、退火温度5个主要因素进行分析,在其允许范围和精度内设置5个水平,并根据均匀设计理论对该5因素及5水平进行均匀设计。不同温度下退火之后测定了PZT薄膜的厚度、SEM表面形貌、电容、介电损耗、电滞回线(包括矫顽场强、饱和极化强度、剩余极化强度)等。最后对响应结果进行多元二次线性回归,得出了回归方程。探讨达到最优化薄膜特性所需要的工艺条件。     

铁电存储器中Pb(Zr,Ti)O_3集成铁电电容的制备

在铁电不挥发存储器 (FERAM)技术中 ,集成铁电电容的制备是关键工艺之一。文中提出一种制备集成铁电电容的改进工艺 :采用 lift-off技术在衬底样品表面淀积铁电电容 Pt/Ti下电极 ,然后用 Sol-Gel方法制备 PZT薄膜。在 PZT薄膜未析晶前 ,先将它加工成电容图形 ,再高温退火成为 PZT铁电薄膜。最后完成铁电电容 Pt上电极。与传统工艺相比 ,改进后的工艺能保持 PZT铁电薄膜与金属上电极之间良好的接触界面。测试结果表明 ,工艺条件的变动不会影响 PZT铁电薄膜的成膜和结构 ,从而可得到性能优良的铁电电容。     

RF溅射法制备PZT铁电薄膜及其表征

采用对靶溅射法在SiO2/Si基板上沉积Pt/Ti底电极,用射频(RF)溅射法在Pt/Ti/SiO2/Si基板上制备了厚度约800 nm的PZT薄膜。XRD分析表明,Ar气氛中沉积,700℃下快速退火(RTA)20 min所得的PZT薄膜具有钙钛矿结构;SEM、AFM分析表明,该条件下所得薄膜的表面由平均粒径约219 nm的晶粒组成,较为均匀、致密。在1 kHz的测试频率下,PZT薄膜的介电常数为327.6,从电滞回线上可以得出,该PZT薄膜的矫顽场强为50 kV/cm,剩余极化强度和自发极化强度分别为10μC/cm2、13μC/cm2。     

水热—溶胶凝胶法制备PZT薄膜

采用水热—溶胶凝肢法制备了锆钛酸铅( PZT)压电陶瓷薄膜.首先利用水热法处理Si基板,使之生成SiO2/Si层,然后采用旋涂法在处理好的Si基板上涂覆摩尔比r(Zr:Ti)为52:48的PZT前驱体溶胶.研究了基板处理方式、退火温度以及涂胶层数对PZT薄膜结晶性能、表面形貌及厚度的影响.结果表明:水热处理Si基板对P...     

PbZr0.52Ti0.48O3薄膜红外椭圆偏振光谱研究

用磁控溅射法在Pt/Ti/SiO2 /Si衬底上制备了PbZr0 .52 Ti0 .4 8O3(PZT)薄膜 .XRD结果表明经过退火后的PZT薄膜呈现多晶结构 .通过红外椭圆偏振光谱仪测量了λ为 2 .5～ 12 .6 μm范围内PZT薄膜的椭偏光谱 ,采用经典色散模型拟合获得PZT薄膜的红外光学常数 ,同时拟合得到未经处理的PZT薄膜和退火后PZT薄膜的厚度分别为 45 4.2nm和 45 0 .3nm .最后通过拟合计算得到结晶PZT薄膜的静态电荷值为 |q|=1.76 9± 0 .0 2 4.这说明在磁控溅射法制备的PZT薄膜中 ,电荷的转移是不完全的 .     

PECVD制备纳米晶多晶硅薄膜

以Si(100)为衬底,采用磁控溅射和射频等离子体增强化学气相沉积系统制备了Si(100)/Al膜/非晶Si膜结构的样品。对该样品进行Al诱导真空退火以制备多晶硅薄膜,采用X射线衍射仪(XRD)和AFM分析薄膜微结构及表面形貌。实验结果表明,在经过500℃、550℃Al诱导退火后,形成了择优取向为〈111〉晶向的多晶硅薄膜。AFM给出了550℃退火后薄膜表面形貌,为100～200nm大小的圆丘状硅晶粒,密集排列在薄膜表面;并对Al诱导真空退火晶化的机理进行了分析。     

多层PT/PZT薄膜的结构特性研究

通过溶胶-凝胶(Sol-Gel)法在Pt/Ti/SiO_2/Si基底上制备了多层PT/PZT(PbTiO_3/Pb(Zr_(0.52)Ti_(0.48))O_3)薄膜,研究了不同退火时间对其纳米结构、结晶性能及相变特性的影响。利用FESEM测试了不同退火时间对薄膜纳米结构的影响,选用XRD与Raman分析了薄膜的结晶取向及相变特点。实验结果表明,随着退火时间的增加,薄膜的三方相向四方相转变,并具有(110)择优取向。退火时间为20min是PZT薄膜的最佳退火时间,此时薄膜的结晶效果良好、晶粒大小均匀、具有纯钙钛矿结构,此种结构的薄膜有望应用于MEMS器件中。     

快速热处理中退火温度对Sol-gel法制备PZT铁电薄膜性能的影响

利用Sol-Gel法在Pt/TiO2/SiO2/Si基底上用快速热处理(Rapid Thermal Processing,RTP)退火工艺制备出了致密的PZT铁电薄膜,主要研究了在退火时间为500s时退火温度对薄膜的结晶结构、表面形貌和铁电性能的影响。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和铁电测试仪对制备的薄膜进行了性能表征。研究结果表明,当退火温度为6000C时,PZT薄膜具有(111)择优取向,表面致密无裂纹,且具有较好的铁电性能(其饱和极化值约为30 C/cm2,剩余极化约为20 C/cm2,矫顽场约为150KV/cm)。在100KV/cm电场下,电流密度J在10-1A/cm2数量级,表明所制的PZT纳米薄膜质量较好,能承受较高的场强以达到饱和极化状态而不被击穿。     

混响室中混响时间测量测点位置的探讨

在分析了混响室中引起混响时间测量随机误差之后,提出将测点置于混响室角点上,这是更为合理的测量方法。     

Sensor effect in YBa2 Cu3 Oy

The high-T_c superconducting material YBa₂ Cu₃ O_y, well known as a 1–2–3 compound, shows other very interesting properties. One of them is very strong conductivity-oxygen content dependence. On the basis of our previous measurements, an investigation of dilatation synthesis, X-ray diffraction (XRD) analysis and conductivity measurements were performed. The results on quenched and slowly cooled samples show a phase transition region and an obvious interdependence between conductivity, unit cell volume and oxygen content.     

Characterization of the annealing impact on La2O3/HfO2 and HfO2/La2O3 stacks for MOS applications

The impact of various rapid thermal annealing used during the integration on the La₂O₃/HfO₂ and HfO₂/La₂O₃ stacks deposited by Atomic Layer deposition was analyzed. The consequences of lanthanum localization in such stacks on the evolution of the films during the rapid thermal annealing are investigated in term of morphology, crystalline structure, silicate formation and film homogeneity as a function of the depth. It appeared that the La₂O₃ location has an impact on the temperature of the quadratic phase formation which could be linked to the formation of SiOHfLa silicate and the resistance of the films to dissolution in HF 0.05 wt%.     

Kinetics of chemical vapor deposition of WSix films from WF6 and SiH2Cl2: Effect of added H2, SiH4, and Si2H6

This paper describes reaction kinetics of chemical vapor deposition of WSi_x films from WF₆ and SiH₂Cl₂, focusing on the effect of added H₂, SiH₄, and Si₂H₆ as an active reaction initiator. Our studies indicate that the temperature at which film formation is extinguished, T_ex, can be lowered by introducing H₂ instead of the standard Ar carrier gas. For a SiH₂Cl₂/WF₆ pressure ratio of 20, H₂ addition changed the deposition mode from selective W deposition to blanket WSi_x deposition. The added H₂ also improved the step-coverage profile for substrate temperatures below 600 °C. Measured step coverage profiles indicate that the activation energy of deposition species was 147 kJ/mol. Adding either SiH₄ or Si₂H₆ can assist the film-forming reactions to achieve acceptable Si/W atomic composition ratios. Under these conditions, the residual fluorine concentration remained at acceptably low levels that are typical of conventional WF₆/SiH₂Cl₂ CVD processes.     

Na_2(b~3Σ_g~ )→Na_2(x~3Σ_u~ )发射光谱

用XeF激光的351毫米微来激励Na_2(x~1Σ_g~ )得到c~1Π_u→2~1Σ_g~ 跃迁范围内三条受激发射谱线及b~3Σ_g~ →x~3Σ_u~ 830毫微米至900毫微米准连续发射谱。文中讨论了这两个跃迁的关联并估计了产生激光振荡的可能性。     

碳酸锰和纳米钛酸钡的添加对钛酸钡陶瓷的影响

以钛酸丁酯和乙酸钡为起始原料,采用液相法制备了纳米钛酸钡。研究了纳米钛酸钡和碳酸锰的掺杂对普通亚微米级钛酸钡的形貌及介电性能的影响。结果表明,在普通钛酸钡中加入一定量的纳米钛酸钡可以促进晶粒的生长,同时提高陶瓷的介电常数。而在普通钛酸钡中加入一定量的碳酸锰则可以抑制晶粒的生长。但同时添加碳酸锰和纳米钛酸钡,碳酸锰对晶粒生长的抑制作用将居于主导地位,并且此时钛酸钡陶瓷的介电常数温度特性曲线与单独添加锰离子时的走势基本相同,室温附近的介电常数峰将由于钛酸钡陶瓷的细晶效应而弥散。     

H2/O2 plasma on polysilicon thin-filmtransistor

It is reported for that H₂ plasma followed by O₂ plasma is more effective for passivating grain boundary states in polysilicon thin film. Polysilicon thin-film transistors (TFTs) made after H₂/O₂ plasma treatment can exhibit a turn-on threshold voltage of -0.1 V, a subthreshold swing of 0.154 V/decade, an ON/OFF current ratio I_on/I_off over 1×10⁸, and an electron mobility of 40.2 cm² /V-s     

Time-dependent-dielectric-breakdown characteristics of Hf-doped Ta2O5/SiO2 stack

The Time-Dependent-Dielectric Breakdown (TDDB) characteristics of MOS capacitors with Hf-doped Ta₂O₅ films (8 nm) have been analyzed. The devices were investigated by applying a constant voltage stress at gate injection, at room and elevated temperatures. Stress voltage and temperature dependences of hard breakdown of undoped and Hf-doped Ta₂O₅ were compared. The doped Ta₂O₅ exhibits improved TDDB characteristics in regard to the pure one. The maximum voltage projected for a 10 years lifetime at room temperature is −2.4 V. The presence of Hf into the matrix of Ta₂O₅ modifies the dielectric breakdown mechanism making it more adequate to the percolation model. The peculiarities of Weibull distribution of dielectric breakdown are discussed in terms of effect of three factors: nature of pre-existing traps and trapping phenomena; stress-induced new traps generation; interface layer degradation.     

TiO_2/SiO_2、ZrO_2/SiO_2多层介质膜光学损耗及激光损伤研究

以TiO_2/SiO_2及ZrO_2/SiO_2多层介质膜为例,测试了不同工艺条件及不同膜系结构下薄膜样品的光学损耗及激光损伤阈值,同时对实验结果作了初步的分析讨论.     

Low-frequency noise in Si0.7Ge0.3 surface channel pMOSFETs with ALD HfO2/Al2O3 gate dielectrics

Low-frequency noise was characterized in Si_0.7Ge_0.3 surface channel pMOSFETs with ALD Al₂O₃/HfO₂/Al₂O₃ stacks as gate dielectrics. The influences of surface treatment prior to ALD processing and thickness of the Al₂O₃ layer at the channel interface were investigated. The noise was of the 1/f type and could be modeled as a sum of a Hooge mobility fluctuation noise component and a number fluctuation noise component. Mobility fluctuation noise dominated the 1/f noise in strong inversion, but the number fluctuation noise component, mainly originating from traps in HfO₂, also contributed closer to threshold and in weak inversion. The number fluctuation noise component was negligibly small in a device with a 2 nm thick Al₂O₃ layer at the SiGe channel interface, which reduced the average 1/f noise by a factor of two and decreased the device-to-device variations.