Patterning amorphous fluoropolymer films by reactive ion milling

Amorphous fluoropolymer films have low dielectric constants and high chemical resistance and, so, have potential to be used as the insulator for high speed interconnects and as protection layers. Many applications would require high resolution patterning of the fluoropolymer film. We have found that these films are easily etched by reactive ion beam etching using an O₂/Ar gas mixture. High etching rates of 600 nm/min with a 0.2 mA/cm^-2,500 eV ion beam were obtained. This technique allows good selectivity with typical underlayers such as Si, Au, and photoresist. We have also found that a short Arion milling of the fluoropolymer surface allows good wettability of the film by photoresist.     

Praseodymium Silicate as a High‐k Dielectric Candidate: An Insight into the Pr2O3‐Film/Si‐Substrate Interface Fabricated Through a Metal–Organic Chemical Vapor Deposition Process

Praseodymium‐containing thin films have been deposited on Si(001) substrates by metal–organic chemical vapor deposition (MOCVD) from the Pr(tmhd)₃ (H‐tmhd = 2,2,6,6‐tetramethyl‐3,5‐heptanedione) precursor. The structural, compositional, and morphological film characterization has been investigated using X‐ray diffraction (XRD), angle‐resolved X‐ray photoelectron spectroscopy (AR‐XPS), and transmission electron microscopy (TEM). Detailed studies of the deposition parameters indicate that the MOCVD process is governed by a kinetic regime and that some reactive phenomena occur at the film/substrate interface, forming a praseodymium silicate layer. A possible explanation for interfacial interaction has been proposed, taking into account the diffusion of Si from the substrate towards the bulk and that of oxygen from the film surface toward the substrate/film interface. Finally, the electrical characterization of the praseodymium silicate layer has been carried out in order to evaluate its potential implementation as an alternative dielectric. Its dielectric constant has been evaluated to be ～ 8.     

Interactions between ferroelectric BaTiO3 and Si

Ferroelectric BaTiO₃ thin films were deposited on single crystal Si substrates by radio-frequency magnetron sputtering. Bilayer structures of BaTiO₃ thin films, either amorphous on polycrystalline (A/P) or polycrystalline on microcrystalline (P/M), were utilized to reduce the leakage current and to enhance the dielectric constant of the films compared to single polycrystalline and amorphous layer structures, respectively. Relatively lower charge density, determined by the capacitance-voltage measurement on the capacitors with a configuration of Au/ BaTiO/p-Si/Al, was detected for the BaTiO₃ thin film with a structure of P/M. The current-voltage characteristics of the Al/SiO₂(~1.8 nm)/p-Si/Al diodes fabricated on the Si after removing BaTiO₃ layers gave direct evidence of the preservation of the Si surface crystal by using a P/M instead of a A/P structure. This was further confirmed by the Auger electron spectroscopy analysis on the samples.     

Effects of differential etching and masking resist preparation on the quality of the reactive-ion-etched aluminum and aluminum alloys

The conventional method used for aluminum (Al) and aluminum alloy (Al + Si, Al + Si + Cu) delineation in integrated circuits is mainly by wet chemical etching. Because of its isotropic characteristic, wet chemical etching becomes inadequate for patterning Al metal lines with linewidths narrower than about 4 Μm. In this work, Al and Al alloys (Al + 2% Si; Al + 1% Si + 1% Cu) were reactively etched in SiCl₄ plasma using patterned photoresist as the etch-mask. Resist patterns were generated either by conventional processing methods or by tri-level resist techniques which included hard-baking (200°C, ≤ 30 min), and two consecutive reactive ion etchings in CF₄ and 0₂ plasmas. Masking resists prepared by the tri-level resist technique retained their integrity during exposure to a SiCl₄ plasma, and significantly improved resolution and fidelity of pattern transfer from resist to underlying Al or Al alloy film. The substrate surface of the reactively etched Al + Si + Cu sample was considerably rougher than that of the Al or Al + Si sample due to the high concentration of Cu accumulated at the metal/substrate region during RIE process.     

Ferroelectric characteristic of group IV elements added SrBi2Ta2O9 thin films

The SrBi₂Ta₂O₉ (SBT) thin film added IV group elements was fabricated on the Pt/Ti/SiO₂/Si substrate by the metal–organic decomposition (MOD) method, the Pt electrode was deposited on the SBT thin film by the DC spattering method. The electric properties of the ferroelectric capacitor were measured. The remanent polarization and the relative dielectric constant of the SBT thin film have decreased, according to the amount of IV group elements addition. The IV group elements added SBT thin film with low relative dielectric constant and low remanent polarization is suitable for the application of the ferroelectric gate FET type memory.     

10%TMAH硅湿法腐蚀技术的研究

研究了浓度为10%的四甲基氢氧化铵(TMAH)溶液,在不同量的Si粉掺杂下,对铝膜及硅衬底的腐蚀及其pH值的变化。测试了在满足铝膜极低的腐蚀速率(<1nm/min)时,不同温度下该腐蚀液对硅(100)、(111)和(110)晶面及SiO2介质膜的腐蚀速率。还介绍了添加剂—过硫酸铵(APODS)和吡嗪的加入对腐蚀表面形貌及腐蚀速率的影响。研究结果表明,存在着一个临界的硅粉添加量,超过此量后铝膜的腐蚀速率急剧降低。90℃时,在10%TMAH溶液中加入1 5mol/L硅粉、3 0g/LAPODS和2g/L吡嗪可以实现铝膜不被腐蚀,同时硅(100)面约有1μm/min的腐蚀速率,腐蚀表面平整。腐蚀后的铝膜表面同硅铝丝键合良好,实现了腐蚀工艺同CMOS工艺的完全兼容。     

Composition,structure and electrical properties of DC reactive magnetron sputtered Al2O3 thin films

Thin films of alumina (Al₂O₃) were deposited over Si 〈1 0 0〉 substrates at room temperature at an oxygen gas pressure of 0.03 Pa and sputtering power of 60 W using DC reactive magnetron sputtering. The composition of the as-deposited film was analyzed by X-ray photoelectron spectroscopy and the O/Al atomic ratio was found to be 1.72. The films were then annealed in vacuum to 350, 550 and 750 °C and X-ray diffraction results revealed that both as-deposited and post deposition annealed films were amorphous. The surface morphology and topography of the films was studied using scanning electron microscopy and atomic force microscopy, respectively. A progressive decrease in the root mean square (RMS) roughness of the films from 1.53 nm to 0.7 nm was observed with increase in the annealing temperature. Al–Al₂O₃–Al thin film capacitors were then fabricated on p-type Si 〈1 0 0〉 substrate to study the effect of temperature and frequency on the dielectric property of the films and the results are discussed.     

Effects of Annealing Temperature on the Electric Properties of 0.94(Na0.5Bi0.5)TiO3–0.06BaTiO3 Ferroelectric Thin Film

0.94(Na_0.5Bi_0.5)TiO₃–0.06BaTiO₃ (NBT–BT6) ferroelectric thin films have been fabricated on Pt–Ti–SiO₂–Si(100) substrate by metal–organic decomposition. The effects of annealing temperature (650–800°C) on the microstructure, and the piezoelectric, ferroelectric, and dielectric properties of the thin films were studied in detail. The residual stress was evaluated by the orientation average method to clarify its dependence on annealing temperature and grain size, and it was correlated with the electric properties to understand the mechanism of piezoelectric enhancement. Among the thin films, NBT–BT6 thin film annealed at 750°C has the largest effective piezoelectric coefficient, 95.1 pm/V, remnant polarization, 49.7 μC/cm², spontaneous polarization, 105.2 μC/cm², and dielectric constant, 504, and the lowest dielectric loss, 0.05, and tensile residual stress, 24.5 MPa. For the NBT–BT6 thin film annealed at 750°C, a wide temperature range, 183–210°C, around the phase transition temperature (T _m) was observed in the dielectric temperature plots, and the diffusion coefficients (γ) were quantitatively assessed as 1.6, 1.78, and 1.6. Piezoelectric performance is discussed on the basis of the dispersion phase transition and residual stress.     

Nd掺杂对BiFeO3薄膜微结构和电学性能的影响

采用化学溶液方法,在LaNiO3/Si(100)衬底上生长了Nd掺杂的BiFeO3薄膜.XRD分析结果表明,随着Nd掺杂量的增加,薄膜晶格变小,Nd掺杂量为20%时,薄膜出现杂相.介电测试表明,随着Nd掺杂量的增加,介电常数和损耗减小,Nd掺杂量为2%的薄膜表现出很强的介电色散现象并出现介电损耗弛豫峰,其符合类德拜模型特征.随着Nd掺杂量增加,薄膜的漏电流减小,在低电场下,电流输运遵从SCLC模型,在高场下,电流输运遵循Poole-Frenkel模型.分析结果表明Nd掺杂对薄膜微结构和电学性能有显著影响.     

CeO_2高K栅介质薄膜的制备工艺及其电学性质

研究了 Ce O2 作为高 K (高介电常数 )栅介质薄膜的制备工艺 ,深入分析了衬底温度、淀积速率、氧分压等工艺条件和利用 N离子轰击氮化 Si衬底表面工艺对 Ce O2 薄膜的生长及其与 Si界面结构特征的影响 ,利用脉冲激光淀积方法在 Si(10 0 )衬底生长了具有 (10 0 )和 (111)取向的 Ce O2 外延薄膜 ;研究了 N离子轰击氮化 Si衬底表面处理工艺对 Pt/ Ce O2 / Si结构电学性质的影响 .研究结果显示 ,利用 N离子轰击氮化 Si表面 /界面工艺不仅影响 Ce O2 薄膜的生长结构 ,还可以改善 Ce O2 与 Si界面的电学性质     

Recent progress of (Ba,Sr)TiO<Subscript>3</Subscript> thin films for tunable microwave devices

The (Ba_1−xSr_x)TiO₃ (BST) ferroelectric thin films exhibit outstanding dielectric properties, even at high frequencies (>1 GHz), and large, electric-field dielectric tunability. This feature makes them suitable for developing a new class of tunable microwave devices. The dielectric properties and dielectric tuning property of BST thin films are closely related to the film compositions, substrate types, and post-deposition process. The successful implementation of BST films as high-frequency dielectrics in electrically tunable microwave devices requires a detailed understanding of both their processing and material properties. This paper will review the recent progress of BST thin films as active dielectrics for tunable microwave devices. The technical aspects of BST thin films, such as processing methods, post-annealing process, film compositions, film stress, oxygen defects, and interfacial structures between film and substrate, are briefly reviewed and discussed with specific samples from the recent literature. The major issues requiring additional investigations to improve the dielectric properties of BST thin films for tunable microwave applications are also discussed.     

ZnO过渡层对BiFeO_3薄膜铁电性能的影响

采用溶胶–凝胶法,在Pt(111)/Ti/SiO2/Si(100)衬底上采用逐层退火工艺制备了BFO(BiFeO3)、ZnO/BFO和ZAO(掺铝氧化锌)/BFO薄膜,研究了ZnO、ZAO过渡层对BFO薄膜晶相以及铁电、漏电和介电性能的影响。结果表明:与BFO薄膜相比,ZnO/BFO薄膜的表面更加致密、平整,结晶性更好,双剩余极化强度(2Pr)有非常大的提高,漏电和介电性能也均有改善。ZAO/BFO薄膜的铁电性能比ZnO/BFO薄膜的铁电性能差,这与ZAO的导电性强于ZnO有关。     

以铝作过渡层的c轴取向Si基ZnO晶体薄膜的生长及其肖特基二极管的研制

利用直流反应磁控溅射方法在金属Al过渡层上沉积了Si基Zn O晶体薄膜,并利用X射线衍射、扫描电子显微镜和扩展电阻测试仪对Zn O薄膜的晶体质量和电学性能进行了分析.结果表明,Zn O薄膜具有高度的c轴取向,样品表明光洁、平整,薄膜与衬底之间有清晰的过渡区.在此Zn O薄膜上成功地制备了肖特基二极管的原型器件,室温下的I- V测试结果表明该Au/ Zn O/ Al肖特基二极管具有明显的整流特性     

Al薄膜对(002)ZnO/Al/Si结构基片中ZnO薄膜特性影响的实验研究

采用射频磁控溅射法沉积制备了(002)ZnO/A l/Si复合结构。研究了Al薄膜对(002) ZnO/Al/Si复合结构的声表面波器件(SAWD)基片性能影响以及当ZnO 薄膜厚度一定时的Al膜最佳厚度。采用X射线衍射(XRD)对Al和ZnO薄膜进行了结构表征 ,采用 扫描电镜(SEM)对ZnO薄膜进行表面形貌表征,并从薄膜生长机理角度进行了分析。结果 表明,加Al薄膜有利于ZnO薄膜按(002)择优取向生长,并且ZnO 薄膜的结晶性能提高;与(002)ZnO/Si结构基片相比,当Al薄膜 厚为100nm时,(002)ZnO/Al/Si结构中ZnO薄 膜的机电耦合系数提高 了65%。     

Theoretical study of mechanical properties of multi-layer ULSI interconnect dielectrics by surface acoustic wave method

The surface acoustic waves (SAWs) technique is becoming an attractive tool for accurately and nondestructively characterizing the mechanical property of the fragile low dielectric constant (low-k) thin film used in the advanced ULSI multi-layer interconnects. The dispersion features of SAWs propagating on the layered structure of low-k/SiO₂/Si substrate and low-k/Cu/Si substrate are investigated in detail. The influence of the film thickness on the dispersion curvature is provided as an instruction for an accurate and facile fitting process. Numerical results indicate that the mechanical property of low-k films is expected to determine effectively when the broadband frequency is up to 300 MHz.     

Characterization of pulsed laser deposited Ba0.6Sr0.4TiO3 on Pt-coated silicon substrates

The high dielectric constant (Ba,Sr)TiO₃ (BST) films have been widely used to realize capacitors integrated on silicon with a high value of capacitance. The multilayer Pt/Ti/SiO₂/Si is one of the most currently used bottom electrodes for the integration of BST on silicon. However, the crystal orientation and the dielectric properties of ferroelectric thin films are greatly influenced by the underlying Pt/Ti metallization, and particularly by the out-diffusion of titanium towards the platinum surface during thermal treatments. In this study, we show that the heating stage of the Pt/Ti/SiO₂/Si substrate before the BST pulsed laser deposition is of primary importance in both favoring the (1 1 1) growth of the BST material within a wide range of oxygen deposition pressure and in reducing drastically the loss tangent values of Al/BST/Pt capacitors because of the oxygen saturation of platinum. Electrical measurements indicate the existence of an interfacial layer degrading the capacitance. They support the presence of an interfacial depleted layer. The dramatic increase of the loss tangent under positive polarities applied on the platinum electrode is attributed to the ohmic contact of the BST/Al interface. Except this increase, all of the electrical properties are very promising in view to realize capacitors with high capacitance value and low dispersion.     

Structure and soft magnetic properties of Fe-Co-Ni-based multicomponent thin films

Soft magnetic thin films with suitable uniaxial anisotropy and high saturation magnetization are required for high frequency applications, since the ferromagnetic resonance frequency (f_FMR) is proportional to the multiplication of the saturation magnetization and anisotropy magnetic field. In this study, multicomponents of Fe-Co-Ni-based soft magnetic thin films were deposited on the Si substrate by radio frequency (RF) magnetron sputtering with various Ar/N₂ ratios at room temperature. The composition, crystal structure, surface morphology, and magnetic domain were analyzed. Without nitrogen doping, the domain of the magnetic thin film was arranged randomly. The effect of N₂ content in the thin film on the magnetic properties was evaluated and further discussed. Magnetic properties, including saturation magnetization (M_s) and coercivity (H_c), were determined. The saturation magnetization of the undoped magnetic thin film was around 1.3 T. However, when the nitrogen was added, the magnitude of the anisotropy field could reach 30 Oe, while the saturation magnetization was around 1 T. It is expected that the derived magnetic thin film is a promising candidate for potential usage in high frequency inductors.     

Tuning of the electrical characteristics of organic bistable devices by varying the deposition rate of Alq3 thin film

Organic bistable devices with an Al/Alq₃/n-type Si structure are investigated at different deposition rates of Alq₃ thin film. We can obtain current–voltage characteristics of these devices similar to those of metal/organic semiconductor/metal structures that are widely used for organic bistable devices. The bistable effect of the Al/Alq₃/n-type Si structure is primarily caused by the interface defects at the Al/Alq₃ junction. Moreover, the electrical properties of these devices can be modified and controlled by utilizing the appropriate deposition rates of the Alq₃ thin film by thermal deposition. XPS, AFM, and GIXRD measurements are performed to characterize the properties of Alq₃ thin film and Alq₃/Al interface. This type of devices involves an extremely simple fabrication process and offers great potential in future advanced organic electronics.     

Sm2O3 gate dielectric on Si substrate

High dielectric constant (κ) materials have become a necessity for down scaling of metal-oxide-semiconductor (MOS) based devices. Rare-earth oxides have been studied as alternative dielectric material to replace SiO₂ gate for future Si-based technology due to their excellent dielectric properties and thermodynamic stability with Si. This paper reviews reasons behind the use of rare-earth oxides as alternative high-κ dielectric materials and their requirements. Of these rare-earth oxides, Sm₂O₃ is one of the potential candidates that capture the attention of researchers owing to its intrinsic properties. These properties have been reviewed in comparison with the properties of other rare-earth oxides. Various deposition methods of Sm₂O₃ thin films on Si are also described, compared, and related to their physical and electrical properties. Based on the outcome of this review, Sm₂O₃ thin film has a huge potential to be the alternative dielectric for future MOS based devices when the listed challenges are resolved.     

Cr/Cu/Al/Cr薄膜电极的防氧化性能

采用Al作为Cu导电层的主要防氧化保护层,在普通浮法玻璃上利用磁控溅射和湿法刻蚀技术制备Cr/Cu/Al/Cr复合薄膜及其电极,研究不同的热处理温度对复合薄膜及其电极的结构、表面形貌和导电性能的影响。由于有Al层作为保护层,在热处理过程中,Al先与穿过Cr保护层的氧进行反应,从而可以更有效地保护Cu膜层在较高的温度下不被氧化,所制备的薄膜在经过600℃的热处理之后仍然具有较好的导电性能。而对于Cr/Cu/Al/Cr电极,侧面裸露的金属层在热处理过程中的氧化是其导电性能逐渐下降的主要原因,退火温度超过500℃之后,电极侧面裸露部分的氧化范围不断往电极的中间扩散,导致了薄膜电极导电性能显著恶化。虽然如此,Cr/Cu/Al/Cr薄膜电极在430℃附近仍然具有较好的导电性能,电阻率为7.3×10-8Ω.m,符合FED薄膜电极的要求。以此薄膜电极构建FED显示屏,通过发光亮度均匀性的测试验证了Cr/Cu/Al/Cr电极的抗氧化性。