Effect Of Silicide Research Articles

Correction: Effect of Silicide and α2 Phase on the Creep Behavior of TC25G Alloy at High Temperature

Correction: Effect of Silicide and α2 Phase on the Creep Behavior of TC25G Alloy at High Temperature

Influence of silicide and texture on the room temperature deformation size effect of Ti65 alloy sheets/foils and its constitutive model modification

In micro-scaled plastic deformation process such as micro-forming, material size effect is challenging to investigate and reveal using traditional material models. Since high-temperature titanium alloys have become the critical materials of micro-parts depending on outstanding mechanical properties, studying the effect of texture and silicide precipitate on size effect in microtensile deformation of a high-temperature titanium alloy is of great significance because the size effect of highly alloyed titanium alloys has been less studied. In the present study, various heating treatments were performed to regulate grain size and texture and obtain silicide precipitate. The room temperature tensile tests were carried out to investigate the effect of the texture and silicide precipitate on the size effect of plastic deformation behaviour. It is revealed that silicide precipitation in the heat-treated specimens can lead to a more obvious “smaller is weaker” phenomenon and the specimens with transverse textures show a better strength–ductility match. In addition, considering solution strengthening, grain boundary strengthening and precipitation strengthening, the material constitutive model is modified by the effect of silicide and texture on the size effect, allowing for an accurate description of the tensile deformation characteristics at the microscopic scale. The results of the physical experiments and the hybrid constitutive model provide a basis for understanding and further exploration of the microscale plastic deformation behaviour of high-temperature titanium alloys.

Effect of Silicide on Dynamic Recrystallization in Near Alpha Titanium Alloy

Dynamic recrystallization in Ti-1100 was investigated. Ti-1100 is one of near α titanium alloys and contains Si for improving high temperature mechanical properties. Ti-1100 exhibits martensitic transformation by quenching into iced brine after solid solution treatment. Hereafter specimens subjected to quenching into iced brine and to cooling in air after solid solution treatment are called IBQ specimen and AC specimen, respectively. After tensile test at high temperature, IBQ specimen exhibits morphological change from lath structure to equiaxed structure, but AC specimen does not. It is indicated that dynamic recrystallization occurs during the tensile test of IBQ specimen. Effect of silicide on the dynamic recrystallization was investigated using two specimens: one included more silicide precipitates and the other less. The former specimen shows smaller recrystallized grains than the latter. It is indicated that the specimen including more silicides exhibits smaller recrystallized grains.

Effect of silicide coatings on the mechanical properties of alloy 5VMTs

The paper examines the effect of silicide coatings and testing media on the strength and plasticity of alloy 5VMTs between 25 and 1100°C. It is established that uncoated samples tested in argon have higher strength and plasticity over the entire temperature range of interest than coated samples tested in argon and air. The major cause of decrease in the mechanical properties of coated samples is the silicide layer whose properties depend on testing temperature.

Effect of silicidation on silicon-based thin film resistors in SiGe integrated circuits

The resistance variation of the silicon–germanium (SiGe) thin film resistor caused by the fabrication process of SiGe integrated circuits (ICs) was investigated. The SiGe resistor and the Si resistor were made of the thin films identical with the p-type SiGe base layer and the n-type Si emitter layer of the SiGe hetero-junction bipolar transistor, respectively. The range of the resistance value of the SiGe resistor was much larger than that of the Si resistor, and an abnormally high resistance of the SiGe resistor was often observed. Ti–B precipitates and Ti(Si1−xGex)2 protrusions were created as the result of the Ti silicidation of the p-type SiGe layer, whereas no precipitates and protrusions were generated in the case of the n-type Si layer. It was confirmed by scanning electron microscopy that the nonuniform resistance of the SiGe resistor was induced by the removal of the protrusions and underlying field oxides in the contact window. Resistance uniformity of the SiGe resistor was much improved by increasing the contact size. The simulation result of the detrimental influence of the resistance change on ICs indicated that the fabrication process and the structure of the thin film resistor should be optimized for enhancing IC reliability.

Influence of silicide coatings on the mechanical properties of the NT-50 alloy

We have investigated the effect of silicide coatings on the ultimate strength of NT-50 alloy over the temperature range −196...+1100 °C. From 196 to 800 °C the ultimate strength of silicidated specimens was lower than that of the initial and annealed alloy whereas from 900 °C it was slightly higher. We have also examined the effect of silicide coatings on the relative elongation of NT-50 alloy samples. Over the temperature range −196...+1100 °C, the relative elongation of specimens annealed in a vacuum of 6.7 · 10−3 Pa at 1250 °C for 4 h was found to be lower than that of the silicidated specimens. This is attributed to the dissolution of the residual gases (O2, N2, H2, CO, and CO2) under vacuum annealing.

Selective Silicidation of Co Using Silane or Disilane for Anti-Oxidation Barrier Layer in Cu Metallization

Aiming to realize a conductive passivation layer for copper interconnection, the solid-gas reactions of cobalt films with silane and with disilane to form cobalt silicides are experimentally investigated. X-ray photoelectron spectroscopy revealed that cobalt silicides layers of up to 6 nm thickness can be selectively formed in the reaction at 473–673 K within 5 min without detectable silicon deposition on silicon dioxide, a common inter-metal dielectric layer. Rapid thermal oxidation experiments revealed that the silicided cobalt layers had better anti-oxidation performance than untreated cobalt layers, and the effect of silicidation was to suppress copper out-diffusion through the cobalt layers. Because cobalt-based alloys can be selectively electroless-plated on copper, selective silicidation of cobalt layers will be easily incorporated into device processing.

Impact of cobalt silicidation on the low-frequency noise behavior of shallow p-n junctions

This work describes the low-frequency noise of forward biased shallow p-n junctions fabricated in epitaxial silicon substrates. Particular emphasis is on the effect of silicidation on the low-frequency noise spectral density S/sub I/. It is demonstrated that the observed 1/f noise is significantly larger in Co-silicided junctions compared with the nonsilicided ones. A detailed analysis of the current and geometry dependence of S/sub I/ leads to the conclusion that the 1/f noise is of the generation-recombination (GR) type, with the responsible GR centres homogeneously distributed over the device area. From the correlation with the forward current-voltage (I-V) characteristics, it is derived that GR fluctuations in the hole current through the n/sup +/ region cause the increased 1/f noise in the silicided devices.

The effect of silicide on ESD performance of transistors

In this paper a new model for localized breakdown in NMOSTs under ESD stress is developed, which accounts for the reduced ESD strength in silicided devices. The model explains the impact of a stabilizing drain resistance on second breakdown current for both silicided and unsilicided protections.

Formation of optically active centers in films of erbium-doped amorphous hydrated silicon

We have observed photoluminescence at 1.54 µm from a-Si:H films doped with erbium of various degrees of purity. It is shown that the additional introduction of oxygen activates the Er ions. The effect of silicides and defects in amorphous silicon a-Si:H films and in crystalline silicon c-Si is investigated.

Various effects of silicidation on shallow p/sup +/ junctions formed by BF/sub 2//sup +/ implantation into thin poly-Si films on Si substrates

Various effects of silicidation on shallow p/sup +/ n junctions formed by the scheme that implants BF/sub 2//sup +/ ions into thin poly-Si films on Si substrates are described. A post-Ni silicidation just slightly improves the preformed junctions of the annealed sample. However, as the sample is first deposited with thin Ni films after the implantation and then annealed, the resulting junctions are much better than the preformed ones. Moreover, as the sample is deposited with Ti films, the resultant junctions are just slightly better the preformed ones.

Enhancement of boron diffusion through gate oxides in metal-oxide-semiconductor devices under rapid thermal silicidation

It has recently been reported that there is anomalous enhanced diffusion of B through the gate oxide in metal-oxide-semiconductor (MOS) structures from B-implanted, p+-polycrystalline silicon gates upon annealing in the presence of H or F. This letter discusses the effects of TiSi2 formation on B penetration through the gate oxide in p+ polycrystalline silicon gate MOS devices. From secondary-ion mass spectrometry analyses, it is found that B penetration effect is enhanced by TiSi2 formation, for 950 and 1100 °C rapid thermal annealing, in spite of the fact that the F concentration in the gate oxide for samples with silicide is lower than that for samples without silicide. Furthermore, samples with a one-step TiSi2 formation process exhibit more serious B penetration effects than those with a two-step process. This indicates that the effect of silicide on B penetration is more complicated than simply acting as a sink for F. Pileup of B at the silicide/polycrystalline silicon interface, the generation of point defects such as Si vacancies and interstitials during silicide formation, and B-defect interactions must be taken into account to explain the results.

The effect of silicides on the induction and removal of defects in silicon

The effect of silicidation on the generation and removal of defects in silicon is studied in terms of dopant behaviour and shrinkage or growth of extended defects in silicon during silicide formation. A reduction in the number of interstitial-type defects is observed both for near-noble metal silicides and for refractory metal silicides, suggesting a generation of vacancies. In the case of TiSi 2, the removal of end-of-range defects was observed from electrical measurements on p + junctions, preamorphized with germanium. Complete annihilation of these defects during CoSi 2 formation failed. This might be attributed to the lower stress level of CoSi 2 on silicon compared with TiSi 2. The higher stress level of TiSi 2 on silicon can lead to generation of dislocations at film edges for silicide thicknesses exceeding 100 nm.

Effect of silicides on tensile properties and fracture of alloy Ti-6AI-5Zr-0.5Mo-0.25Si from 300 to 823 K

The tensile properties and fracture behaviour of alloy Ti-6AI-5Zr-0.5Mo-0.25Si (wt%) have been investigated over a wide range of temperature from 300 to 823 K, in the as-water-quenched (WQ) and different aged (473 to 1073 K for 24 h)conditions followingβ-solution-treatment (1323 K for 0.5 h). There is only a limited increase in strength but a drastic reduction in the ductility, at 300 K, due to ageing at ⩾ 923 K. There is strong dynamic strain-ageing (DSA) in the unaged (WQ) state from 623 to 823 K and it is essentially due to silicon in the solid solution. The degree of DSA decreases with the ageing temperature and DSA does not occur in specimens aged at 973 and 1073 K. In general, the ductility of the WQ as well as the aged material increases with test temperature, except in the range of DSA, where the ductility of WQ material is reduced. The mode of fracture of the WQ specimens remains ductile in the lower and higher ranges of test temperature, but changes to quasi-cleavage at intermediate test temperatures. The minimum in the ductility and quasi-cleavage mode of fracture at 773 K, in the WQ material, is due to strong DSA. Three different modes of fracture, namely faceted, ductile, and mixed intergranular and ductile in the lower, intermediate and higher range of test temperature, respectively, are observed also in the aged conditions (at and above 923 K) of the material. The tensile properties and fracture characteristics in the aged conditions are controlled by the silicides.

On Silicides in High Temperature Titanium Alloys

High temperature titanium alloys like IMI 685 contain small amounts of silicon (~ 0.25 wt. per cent) to improve creep resistance. Different types of silicides, namely Ti5Si3 (TiZr)5Si3(S1) and (TiZr)6 Si3 (S2), have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatment. The precipitation of silicides, their orientation relationship with the matrix in different alloys, and the beneficial influence of thermo-mechanical treatment on the distribution of silicides have been pointed out. The effect of silicides on mechanical properties and fracture of the commercial alloy IMI 685 is also indicated.