Investigation of the TiN Gate Electrode With Tunable Work Function and Its Application for FinFET Fabrication

The titanium nitride (TiN) gate electrode with a tunable work function has successfully been deposited on the sidewalls of upstanding Si-fin channels of FinFETs by using a conventional reactive sputtering. It was found that the work function of the TiN (phi_TiN) slightly decreases with increasing nitrogen (N₂) gas flow ratio, R_N=N₂/(Ar+N₂) in the sputtering, from 17% to 100%. The experimental threshold voltage (V_th) dependence on the R_N shows that the more R_N offers the lower V_th for the TiN gate n-channel FinFETs. The composition analysis of the TiN films with different R_N showed that the more amount of nitrogen is introduced into the TiN films with increasing R_N, which suggests that the lowering of phi _TiN with increasing R_N should be related to the increase in nitrogen concentration in the TiN film. The desirable V_th shift from -0.22 to 0.22 V was experimentally confirmed by fabricating n⁺ poly-Si and TiN gate n-channel multi-FinFETs without a channel doping. The developed simple technique for the conformal TiN deposition on the sidewalls of Si-fin channels is very attractive to the TiN gate FinFET fabrication     

Four-Terminal FinFETs Fabricated Using an Etch-Back Gate Separation

A novel resist etch-back process for fabrication of separated-gate four-terminal FinFETs has been investigates. This process enabled co-fabrication of three-terminal (3T) and four-terminal (4T) FinFETs on a same chip. The fabricated 3T-FinFET shows excellent sub-threshold characteristics and drain induced barrier lowering (DIBL) value whereas the 4T-FinFET provides efficient V_th controllability. The effective V_th controllability with keeping a small sub-threshold slope has been confirmed in the synchronized double gate (DD) operation mode     

Application of fluorine doped oxide (SiOF) spacers for improving reliability in low temperature polycrystalline thin film transistors

The novel process of self-aligned fluorine doped oxide (SiOF) spacers on low temperature poly-Si (LTPS) lightly doped drain (LDD) thin film transistors (TFTs) is proposed. A fluorine doped oxide spacers were provided to generate the lower dissociation Si-F bonds adjusted to the interface of the drain which is the largest lateral electric field region for lightly doped drain structure. The stronger Si-F bonds can reduce the bonds broken by impact ionization. It is found that the output characteristics of SiOF spacers TFTs show the superior immunity to kink effect. The degradations in Vth shifting, subthreshold slope, drain current and transconductance of SiOF spacers after DC stress are improved.     

Electrical and optical studies of ZnO:Ga thin films fabricated via the sol–gel technique

The effects of dopant (Ga) concentration, post-heat treatment temperatures, and different heat treatment environments on the morphology, electrical and optical properties of ZnO films were studied. ZnO films doped with Ga are derived from non-alkoxide zinc acetate via the alcoholic route by a sol–gel dip-coating technique. Introduction of Ga, as a dopant, can reduce crystallite size, which is attributed to the increased number of nucleation centers. Grain growth was also observed at high post-heat treatment temperature. It was discovered that different post-heat treatment environments (air or reduced atmosphere) did not change the structure orientation, microstructure shapes and size. It was found that the sheet resistance, R_s could be reduced by an order of magnitude, using post-heat treatment in reduced atmosphere (4%H₂–96%N₂).     

Dy3+掺杂Bi4Si3O12晶体生长及其热释光特性

采用坩埚下降法生长了Dy³⁺掺杂浓度分别为0.1mol%、0.2mol%、0.3mol%、2mol%、3mol%和4mol%的Bi₄Si₃O₁₂(BSO)晶体。发现高浓度(2mol%以上)掺杂能够显著改变BSO晶体的析晶行为, 晶体表面析出物完全消失, 顶部呈现光滑结晶面; 低浓度(低于0.3mol%)掺杂能够显著提高晶体的光输出, 最高可达纯BSO的145%。晶体热释光谱测试结果表明: 少量Dy³⁺掺杂虽然热释光峰略有增强, 但有利于晶体光产额的提高; 高浓度掺杂则容易引起晶格畸变, 甚至产生新的缺陷, 降低晶体的光产额。     

Stabilization and operation of porous silicon photonic structures from near-ultraviolet to near-infrared using high-pressure water vapor annealing

The effects of high-pressure water vapor annealing (HWA), electrochemical oxidation, and substrate resistivity on the properties of porous silicon Bragg mirrors and photoluminescent cavities have been investigated. The photonic structures treated by HWA show very good stability upon ageing in air whereas as-formed structures exhibit significant drifts in their optical properties. Using HWA with lightly doped porous silicon, the structure transparency is enhanced sufficiently to enable the possible photonic operation in the near-ultraviolet. However, the index contrast achievable with these structures is very low in the visible and near-infrared. Useful index contrasts in this range can be achieved with either lightly doped porous silicon treated by electrochemical oxidation and HWA or heavily doped porous silicon treated by HWA.     

多孔α-Al2O3基陶瓷片状载体的制备与性能

采用干压成型法制备了多孔α-Al₂O₃基陶瓷片, 研究了烧结温度和掺杂SiO₂对其结构、形貌和性能的影响. 提高烧结温度能增加α-Al₂O₃基陶瓷片的抗压强度, 但收缩率也会随之增大。最佳烧结温度为1180℃, 收缩率小于0.5%, 抗压强度大于80 MPa。当掺杂SiO₂粉体后, 陶瓷片中的无定形SiO₂在烧结过程中晶化形成方石英, 能够促进α-Al₂O₃陶瓷片的烧结。当SiO₂含量为12wt%, 并在1180℃下烧结时, 陶瓷片的收缩率仅为1.2%, 抗压强度大于110 MPa。与α-Al₂O₃陶瓷片相比, 其孔径更小但孔径分布更宽。研究表明, α-Al₂O₃和SiO₂/Al₂O₃陶瓷片均具有良好的分子筛膜生长活性。但由于载体具有不同的物化性质, 所制备的ZSM-5分子筛膜具有不同的形貌和尺寸。     

Electrical property and defect structure of lanthanum-doped polycrystalline barium titanate

Electrical conductivity of two types of lanthanum-doped barium titanote ceramics with different dopant levels was measured at temperatures between 900 and 1250° C andP _{O 2}from 10^–5 to 1 atm. The activation energies of the conduction for the two are interpreted in terms of the formation energy of ionized oxygen vacancies even in such a highP _{O 2}region. This fact is in contrast with a well -known controlled -valency model proposed for rare- earth -doped semi-conducting perovskites. In a lightly lanthanum-doped specimen, semiconduction achieved at elevated temperatures is retained on cooling the specimen to room temperature, whereas in a heavily doped specimen, the resultant high-temperature semiconduction changed to insulation on cooling. The former behaviour on cooling is successfully explained by a metastabilization of oxygen vacancies accompanied by electrons formed at elevated temperatures.     

On the FinFET extension implant energy

The need of an ultrashallow junction technology for the extension of p-FinFETs has been investigated by integrated process and device simulations. For devices with 60 nm physical gate length, whose extensions are activated in a low thermal-budget process (spike anneal), it is found that the I/sub off/-I/sub on/ performance is invariant with respect to the extension implant energy. Nevertheless, the short-channel behavior worsens. This can be remedied by adding spacers to both sides of the gate before the extension implant, resulting in virtually identical dc characteristics and speed. Devices with gate lengths of 18 nm and below require dopant activation with negligible diffusion. Under those circumstances the short channel behavior of the FinFET is limited by the lateral straggle of the ion implant. Spacers may remedy what is otherwise poor short channel behavior due to a relatively high energy extension implant. However, this comes at the price of drastically worse drive current at a fixed off-current.     

掺钛石墨导电性及其微观结构的研究

研究了不同钛掺杂量的再结晶石墨的电阻率与微观结构。以探讨掺杂组元对材料导电性能的影响。实验结果表明,与相同工艺条件下制得的纯石墨相比,掺钛石墨具有高密、高石墨化程度以及极低的电阻率的特点,微观结构分析表明,钛对材料的石墨化过程中具有催化作用,掺杂石墨材料中钛掺杂量对材料的石墨化程度有很大影响：少量钛掺杂量即可使材料达到高的石墨化程度,过多钛掺杂量不利于其电阻率的降低,分析表明钛元素在材料中是以碳化钛形式存在,但在制备过程中,有少量钛逸失,雁而在材料表面形成孔隙,而这些对材料的性能有不利的影响。     

Image holography in CdF2:Ga crystals

The recording of an image hologram in CdF₂:Ga crystals at room temperature is reported. Writing the phase holographic pattern utilizes a unique property of Ga and In doped CdF₂ crystals, namely, the bistability of these dopants. In contrast to CdF₂:In crystals, in which there is only one bistable center, the holographic experiment reveals two different bistable centers in CdF₂:Ga. Room temperature bistability is related to Ga, while the low temperature center resembles very much the properties of In, likely a non-intentional In dopant of the CdF₂:Ga crystals. The holographic sensitivity of doped CdF₂ crystals compares favorably with sensitivity of standard photorefractive materials. The main advantage for some applications of using the novel mechanism is the inherently local nature of the light-induced refractive index changes.     

(Bi0.5Na0.5)TiO3:Sm3+无铅压电陶瓷的红光发射特性

采用传统的固相反应烧结方法制备了稀土Sm³⁺掺杂的(Bi_0.5Na_0.5)TiO₃无铅压电陶瓷。系统分析了掺杂浓度、烧结温度和离子补偿对发光特性的影响。稀土Sm³⁺离子的加入实现了(Bi_0.5Na_0.5)TiO₃陶瓷的红绿光发射, 其激发光波段位于400~500 nm范围内, 与已经成熟的蓝光LED芯片的发射光谱充分匹配。当烧结温度为1100℃, Sm³⁺离子的掺杂浓度为0.015 mol时, 陶瓷样品呈现最强的发光强度。同时, 通过Li⁺、Na⁺、K⁺离子进行电荷补偿, 有效提高了陶瓷样品的发光性能, 发光强度随离子半径增大而增强。可见, Sm³⁺掺杂的(Bi_0.5Na_0.5)TiO₃材料在光电集成器件中具有很好的应用前景。     

A TaSix barrier for low resistivity and high reliability of contacts to shallow diffusion regions in silicon

It is shown that a thin TaSi_x layer underneath the aluminium-based metallization considerably improves the contacts from the metallization to shallow diffusion regions in silicon. TaSi_x with x < 2 acts as a barrier against aluminium and silicon diffusion at the contacts and thus impedes aluminium spiking as well as silicon precipitates in the contacts. Furthermore the silicon erosion induced by high currents is reduced by one order of magnitude. The contact resistance to n⁺ -Si is decreased by a factor of 3–5. Finally the TaSi_x provides a low barrier Schottky diode on lightly doped n-Si and p-Si.     

On-line monitoring of CO2 quality using doped WO3 thin film sensors

Thin films of either pure or doped tungsten oxide were grown by radiofrequency (rf) sputtering onto silicon micromachined substrates. Up to 7 different dopant materials (noble metals or metal oxides) were deposited by rf sputtering or by evaporation onto the tungsten oxide films. The responsiveness of the resulting micromachined sensors towards sulfur dioxide and hydrogen sulfide was studied. Other pollutants in CO₂ such as ethylene and methane were also tested. It was found that Au-doped tungsten oxide sensors were highly sensitive to H₂S, poorly sensitive to SO₂ and almost insensitive to hydrocarbons. On the other hand, Pt-doped tungsten oxide was highly sensitive to SO₂, poorly responsive to H₂S and nearly insensitive to hydrocarbons. By applying a principal component analysis (PCA), we show that it would be possible to selectively detect traces of H₂S and SO₂ in a CO₂ stream using doped WO₃ microsensors. These sensors could be used in a low-cost analyzer of beverage-grade CO₂.     

模拟太阳光下锗掺杂纳米TiO2对化学毒剂的降解性能

采用均匀沉淀法制备不同锗掺杂浓度的纳米二氧化钛(TiO₂); 为了研究掺杂浓度与粉体活性之间的关系, 针对化学毒剂(CWAs)模拟剂2-氯乙基乙基硫醚(2-CEES)和甲基膦酸二甲酯(DMMP)开展光催化消毒实验, 并用动力学方程拟合实验结果; 通过XRD、UV-Vis、BET、BJH、SEM和TEM等技术对样品进行表征, 分析锗掺杂对TiO₂结构及性能的影响; 综合考虑溶剂的毒性、挥发性、可燃性和溶解性等因素, 以氢氟醚(HFE)作为分散溶剂, 研究模拟太阳光下Ge-TiO₂和HFE混合体系对芥子气(HD)、梭曼(GD)和维埃克斯(VX)的消毒性能。结果表明: 适量锗掺杂不会改变纳米TiO₂的晶型结构, 可以减小晶粒尺寸, 增大比表面积, 增强光利用率, 提高消毒活性; 相较于直接使用粉体消毒, 混合体系的消毒效率明显提高; 在模拟太阳光下, 最佳锗掺杂浓度(6.24wt%)样品与HFE-458 (HCF₂CF₂CH₂OCF₂CF₂H)组成的混合体系与三种化学毒剂反应60 min的降解率分别为: HD 98.73%、GD 100%、VX 100%。     

Indium doped zinc oxide thin films obtained by electrodeposition

Indium doped ZnO thin films were obtained by co-electrodeposition (precursor and dopant) from aqueous solution. XRD analysis showed typical patterns of the hexagonal ZnO structure for both doped and undoped films. No diffraction peaks of any other structure such as In₂O₃ or In(OH)₃ were found. The incorporation of In into the ZnO film was verified by both EDS and XPS measurements. The bandgap energy of the films varied from 3.27 eV to 3.42 eV, increasing with the In concentration in the solution. This dependence was stronger for the less cathodic potentials. The incorporation of In into the film occurs as both, an In donor state in the ZnO grains and as an amorphous In₂O₃ at the grain boundaries.     

InP量子点的掺杂及其光学性能

采用原位成核掺杂法合成了Li、Zn金属离子掺杂的InP量子点(分别记为Li: InP和Zn: InP), 并研究了掺杂剂对量子点的结构、尺寸和光学性能的影响。研究结果表明, Li⁺、Zn²⁺掺杂的InP量子点结晶度较高且尺寸均匀。虽然Li⁺掺杂未引起InP量子点的结构发生变化, Li⁺未进入InP晶格, 但是抑制了InP量子点的成核与长大, 使其吸收谱和荧光谱均发生大幅度的蓝移。Zn掺杂同样也抑制InP量子点的成核与长大, 并且形成InP/Zn₃P₂/ZnO复合核壳结构, 显著增强了InP量子点的荧光, 尤其是当Zn掺杂浓度(Zn/In原子比)为0.2时, InP量子点的荧光强度增加近100多倍, 这对短波长InP量子点的合成具有一定的参考价值。     

Influence of the common varistor dopants (CoO, Cr2O3 and Nb2O5) on the structural properties of SnO2 ceramics

The influence of dopants commonly used in SnO₂ varistor ceramics, such as CoO, Cr₂O₃ or Nb₂O₅, on the structural properties of SnO₂ was investigated. Several SnO₂-based ceramics containing only one of the dopants were prepared and characterized. Spectroscopic investigations [visible, near infrared (IR) and IR region] were performed to obtain information about dopants valence states inside the ceramics, as well as about their influence on electronic structure of the material. Structural properties were investigated by X-ray diffraction analysis and mechanisms of dopant incorporation were proposed. Obtained results were confirmed with results of the electrical measurements. Microstructural changes in doped ceramics were investigated by scanning electron microscopy (SEM) analysis that showed great differences in densities, grain size, and morphology of the SnO₂ ceramics depending on type of dopants and their distribution.     

Electron holographic characterization of ultra-shallow junctions in Si for nanoscale MOSFETs

This investigation attempts quantitative characterization of ultra-shallow junctions (USJs) in Si, useful for future generations of nanoscale MOSFETs as predicted by the Semiconductor Industry Association Roadmap. The USJs were fabricated using rapid thermal diffusion (RTD) from a heavily doped n-type surface source onto a heavily doped p-type substrate. The dopant profiles were analyzed using secondary ion mass spectrometry (SIMS), and were further used to calculate the metallurgical junction depth (MJD). One-dimensional (1-D) characterization of the electrical junction depth (EJD) associated with the electrically activated fraction of the incorporated dopants was performed using off-axis electron holography in a transmission electron microscope. 1-D potential profiles were derived from the unwrapped phase of the reconstructed holograms. The EJD was derived from the measured potential distribution across the p-n junction, and quantitative comparison is made with MJD derived from the SIMS profiles. The comparison between calculated electric field and total-charge distributions from the measured potential profiles and the simulated distributions using the SIMS profiles provides a quantitative estimate of the electrical activation of dopants incorporated by the RTD process, within the accuracy limits of this technique, which is discussed herein.     

Organo-lanthanide complexes as luminescent dopants in polymer waveguides fabricated by hot embossing

Lanthanide complexes, Eu(dbm)₃(Phen) and Er(dbm)₃(Phen), are employed as luminescent dopants within polymer channel waveguide devices fabricated by hot embossing. Spectroscopic properties of the complexes as dopants in the waveguide core polymer are investigated in detail. Judd–Ofelt parameters are calculated for the europium chelate and radiative properties are determined viz. potential for optical amplification. Channel waveguides fabricated by single level embossing are shown to be capable of guiding visible and infrared light emitted following optical excitation of the dopants. Multi-level polymer micro-optical benches incorporating doped channel waveguides and passive locational features for self-alignment and integration of optical fibres are fabricated in a multi-level single-step embossing process and are shown to successfully out-couple the waveguided dopant emission.