硅衬底上异质外延生长硅化钴研究进展

综述近年国内外在CoSi2／Si异质外延生长技术领域的研究进展,在半导体衬底上异质外延具有优良导电特性的金属硅化物,从基础研究和技术发展两方面都具有重要价值。利用Co／Ti／Si多层薄膜固相反应实现CoSi2／Si异质外延,是近年取得重要进展的新方法。应用这种方法在（111）和（100）硅衬底上都可实现CoSi2外延生长,无需在超高真空下进行,与硅器件基本工艺相容性好,可形成自对准硅化物接触结构,对发展新器件制造技术有重要作用。在简要介绍分子束外延和离子合成CoSi2外延薄膜生长技术后,重点介绍和评述新型固相异质外延方法的工艺技术、机理和应用研究进展。     

Thermal treatment effects on interfacial layer formation between ZrO2 thin films and Si substrates

This paper describes the growth condition of stoichiometric ZrO₂ thin films on Si substrates and the interfacial structure of ZrO₂ and Si substrates. The ZrO₂ thin films were prepared by rf-magnetron sputtering from Zr target with mixed gas of O₂ and Ar at room temperature followed by post-annealing in O₂ ambient. The stoichiometric ZrO₂ thin films with smooth surface were grown at high oxygen partial pressure. The thick Zr-free SiO₂ layer was formed with both Zr silicide and Zr silicate at the interface between ZrO₂ and Si substrate during the post-annealing process due to rapid diffusion of oxygen atoms through the ZrO₂ thin films. After post annealing at 650-750 °C, the multi-interfacial layer shows small leakage current of less than 10⁻⁸ A/cm² that is corresponding to the high-temperature processed thermal oxidized SiO₂.     

High-quality carbon-doped β-type FeSi2 films synthesized by ion implantation

Carbon-doped β-FeSi₂ films synthesized by ion implantation is investigated with the aim to fabricate high-quality semiconducting β-FeSi₂ layer on silicon substrate. According to our TEM cross-section observations, the carbon-doped films are of better quality than the non-doped ones for their improved uniform film thickness, smooth β/Si interface and high thermal stability. In particular, annealing at 500-700 °C leads to the formation of a flat and continuous β-type silicide layer. Optical absorption measurements show that the carbon doping does not influence the band structure. We further point out that the presence of multiple and incoherent orientation relationships between β and Si, discussed within the framework of the near coincident site lattice theory, is a key factor responsible for the difficulty in obtaining high-quality epitaxial β films.     

Fe对Nb-16Si-22Ti-2Cr-2Al-2Hf合金组织与高温压缩性能影响研究

采用真空非自耗电弧炉制备了不同Fe含量的Nb-16Si-22Ti-2Cr-2Al-2Hf-xFe(x=0,1,2,3,原子分数)4种合金。采用XRD对合金相结构分析表明,制备的合金由Nbss相,Nb_3Si相及Nb_5Si_3相组成。微观组织分析发现,随着Fe元素含量的增加,促进共析反应Nb_3Si→Nbss+Nb_5Si_3的进行,合金相组成由Nbss+Nb_3Si转变为Nbss+Nb_5Si_3。Nb_3Si组织由连续变成分散的块状,体积分数减小,Nbss相由树枝晶状转变为等轴晶状,平均晶粒大小约5μm,体积分数有所增加。采用Gleeble-1500热模拟机对合金进行高温压缩实验,发现随着Fe元素含量的增加,压缩温度的升高及应变速率的降低,合金压缩开裂倾向减小,应力峰值降低,变形能力增加。Fe元素的添加令Nb-Si基超高温合金具有更好的高温塑性变形能力,对改善Nb-Si合金的热加工性能具有重要的意义。     

肖特基二极管异常击穿特性曲线的研究

本文简述了肖特基二极管的原理,结构、性能特点,分析了生产中经常出现的异常击穿特性曲线,并提出了相应的改进措施.     

Texture of atomic layer deposited ruthenium

Ruthenium films were grown by plasma enhanced atomic layer deposition (ALD) on Si(1 0 0) and ALD TiN. X-ray diffraction (XRD) showed that the as-deposited films on Si(1 0 0) were polycrystalline, on TiN they were (0 0 2) oriented. After annealing at 800 °C for 60 s, all Ru films were strongly (0 0 2) textured and very smooth. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) demonstrated that the lateral grain size of the annealed films was several 100 nm, which was large compared to the 10 nm thickness of the films. No ruthenium silicide was formed by annealing the ALD Ru films on Si(1 0 0). Comparison with sputter deposited films learned that this occurred because the ammonia plasma created a SiO_xN_y reaction barrier layer prior to film growth.     

Microstructure and oxidation behaviour of Fe–Cr–silicide coating on a niobium alloy

The cyclic oxidation performance of a Fe–Cr-modified silicide coating on Nb-alloy C-103 was evaluated in air at temperatures between 1100 and 1500°C and the microstructural changes examined. The coating was oxidation resistant and the duration of protection increased from 60 minutes at 1100°C to 255 minutes at 1500°C. The formation of the surface glassy silica layer and its ability to heal the cracks in the coating enhanced the oxidation performance at high temperatures. The outer NbSi₂ layer served as a reservoir of Si and sustained the formation of the protective silica scale. Spallation of the silica scale and the concomitant depletion of the NbSi₂ layer towards the regeneration of the silica scale limit the oxidation life of the coating.     

Ni/Si,Pt/Si,Ir/Si系的As离子注入和退火

本文用RBS,AES,TEM和X射线衍射等实验方法,分析比较了Ni/Si,Pt/Si,Ir/Si系统在室温下As离子混合和热退火的行为.得出在Ni/Si系统中,硅混合量Q_(s1)与剂量Φ的平方根成正比,形成Ni_2Si相.在Pt/Si系中,硅混合量也与剂量的平方根成正比,先后形成Pt_3Si和Pt_2Si相.对Ir/Si系,Q_(s1)与Φ则是线性关系:Q_(s1)=aΦ+b,未测到化学相.实验表明:离子束混合能大大增强金属和硅化物的化学反应.在离子混合和退火形成硅化物的过程中,注入杂质As的分布有显著变化.     

Evolution behavior of rare-earth yttria modified silicide oxidation-resistant coating at 1700 oC

Yttria-modified silicide (MoSi₂-Y₂O₃) oxidation-resistant coatings with multiple Y₂O₃ contents were prepared using supersonic atmospheric plasma spraying, and the oxidation resistance was investigated at 1700 °C with static atmosphere. Experimental results indicated that the sprayed MoSi₂-Y₂O₃ coating possessed good compactness, which adhered well to the SiC transition layer. Meanwhile, the Y₂O₃ addition greatly enhanced the bonding strength of the coating, and extended its service life at 1700 °C. Wherein the MoSi₂-20 wt.%Y₂O₃ coating exhibited the highest adhesive strength and best oxidation resistance with the lowest mass loss among all the coatings. In practice, the Y₂O₃ changed the microstructures of formed oxide glass scale during oxidation, and then modified the oxidation resistance of the coating. The action mechanism of Y₂O₃ on the oxidation behavior of MoSi₂-Y₂O₃ coating was analyzed.     

Nickel silicide encroachment formation and characterization

The stability of nickel-based silicides integrated in CMOS circuits has been studied. The evolution of transistor electrical failures is then reported, linked to Ni abnormal migration through different process steps. We have found in our studies that Ni encroachment is not only due to NiSi₂ clusters formation but also to NiSi precipitates formation. Silicon substrate doping, surface preparation, nickel film thickness and the thermal treatments were identified to modify occurrences of this randomly localized phenomenon. Ni-rich phase initial formation is preferable to prevent Ni encroachment even though other upstream process steps for CMOS integration are also key for Ni migration control.