Large-area Co-silicide nanodot arrays produced by colloidal nanosphere lithography and thermal annealing

We report here the successful fabrication of large-area size-tunable periodic arrays of cobalt and Co-silicide nanodots on silicon substrates by employing the colloidal nanosphere lithography (NSL) technique and heat treatments. The growth of low-resistivity epitaxial CoSi(2) was found to be more favorable for the samples with smaller Co nanodot sizes. The sizes of the epitaxial CoSi(2) nanodots can be tuned from 50 to 100nm by varying the diameter of the colloidal spheres and annealing temperatures. The epitaxial CoSi(2) nanodots were found to grow with an epitaxial orientation with respect to the (001)Si substrates: [001]CoSi(2)//[001]Si and (200)CoSi(2)//(400)Si. From the results of planview HRTEM, XTEM, and SAED analysis, the epitaxial CoSi(2) nanodots were identified to be inverse pyramids in shape, and the average sizes of the faceted silicide nanodots were measured to decrease with annealing temperature. The observed results present the exciting prospect that with appropriate controls, the colloidal NSL technique promises to facilitate the growth of a variety of well-ordered silicide nanodots with selected shape, size, and periodicity.     

Deposition uniformities on a wafer and in a trench for tungsten silicide LPCVD in a single-wafer reactor

A transient model of a single-wafer reactor in axisymmetric, stagnation point flow is used to study the effects of operating conditions on film thickness uniformity and composition uniformity across the wafer during low pressure chemical vapor deposition of tungsten silicide. Orthogonal collocation on finite elements is used to solve the transient model equations; continuity, momentum, energy and chemical species balances. A feature scale model for simultaneous Knudsen transport and heterogeneous reactions is used to predict film thickness in infinite trenches. Boundary conditions for the feature scale model are established using the reactor scale model. The use of a combined reactor scale and feature scale model is demonstrated to select deposition conditions which provide both good interwafer uniformity and good intrafeature uniformity. Film thickness and composition uniformity on a wafer are predicted using a model for a single-wafer reactor. Significant differences in step coverage predicted using partial pressures in the feed stream and partial pressures at the wafer surface were observed. Step coverage differences between the wafer center and the wafer edge were also significant under the operating conditions used in this study. Uniformities of interwafer and intrafeature step coverages inceased as either the wafer temperature or the partial pressure ratio of dichlorosilane to tungsten silicide in the feed was decreased.     

微波热处理在钛的硅化工艺中的应用

采用微波等离子体退火方法使溅射的金属Ti膜与Si(111)衬底发生固相反应,直接生成低阻态的金属硅化物薄膜,XRD检测显示最终生成的C54相TiSi2在Si(111)衬底上有明显的织构,证明了微波等离子体退火应用于钛的硅化工艺中的可行性.     

硅钼棒电炉用电流反馈式程序控温系统的研制

叙述了电流反馈控制技术原理及其在硅钼棒电炉用程序控温系统中的应用 ,并提供了详细的系统电气原理图。通过热工和电量计算 ,确定了该温度控制系统主参数取值     

Growth of patterned thin epitaxial CoSi2-films by a titanium oxide mediated epitaxy process

A new method for fabricating thin patterned CoSi₂ layers has been studied. The silicide layers were generated by a solid phase epitaxy process, in which Co and Ti were deposited on a thin chemical oxide on Si(100) substrates. Rapid thermal annealing (RTA) of this structure leads to the formation of epitaxial CoSi₂ with a capping layer on top. Two-step annealing in a forming ambient gas produces high quality epitaxial layers with a capping layer which can be easily removed by wet chemicals. A layer structure consisting of 30 nm SiO₂ and 300 nm Si₃N₄, which is patterned using conventional optical lithography and dry etching, induces a stress field into the underlying layers near the patterning edges. This leads to a formation of separated CoSi₂ layers during the silicide formation caused by the anisotropic diffusion of the atoms in the stress field. Such layers show nearly uniform gaps of approximately 100 nm in width.     

Ni silicide formation on epitaxial Si1 − yCy/(001) layers

The formation of Ni silicides on Si_1 − yC_y (y = 0.01 and 0.018) epilayers grown on Si(001) has been investigated. The presence of C atoms was found to significantly retard the growth kinetics of NiSi and enhances the thermal stability of thin NiSi films. For Ni(11 nm)/Si_0.982C_0.018 samples, the process window of NiSi was shifted and extended to 450-700 °C. Moreover, there was an additional strain introduced into the Si_1 − yC_y epilayers during Ni silicidation. This work shows the potential of Ni silicidation on Si_1yC_y for device applications.     

Effects of Zr Content on the Microstructures and Tensile Properties of Ti-3Al-8V-6Cr-4Mo-xZr Alloys

The microstructural evolution and tensile properties of Ti-3Al-8V-6Cr-4Mo-xZr(x = 0,2,4 and 6) titanium alloys were investigated.The precipitated phases and tensile fracture morphologies were observed using scanning electron microscopy and transmission electron microscopy.Experimental results show that the presence of trace impurity Si and the addition of Zr induce the formation of(TiZr)_6Si_3 silicides.The quantity of silicides increases with Zr content increasing.The dispersed silicides refined the grain size of β Zr-containing alloys,and the grain size decreases significantly with Zr content increasing.Accompanying these microstructural changes,the strength of the alloys is enhanced gradually with the increase of Zr content,which is attributed to the combination of precipitation strengthening and grain refinement.     

TiSi_x/GaAs肖特基接触的退火特性

本文对用分层电子束蒸发法形成的TiSi_x/GaAs的肖特基接触特性进行了研究,分析了不同组分下经快速退火和常规退火后TiSi_x的电阻率,与GaAs接触界面的热稳定性,化学稳定性及所形成肖特基结的电特性.结果表明:TiSi_21/GaAs界面在975℃、12秒快速退火下表现出好的热稳定性和化学稳定性,所形成的肖特基接触具有良好的电特性,在800℃、20分钟的常规退火下,界面处有Ti的堆积和某种界面化学反应.对于快速退火工艺,TiSi_2可满足作为自对准 GaAs MESFET栅极材料所要求的界面稳定性.     

Texture of CoSi2 films on Si(111), (110) and (001) substrates

Synchrotron radiation was used to study the texture of polycrystalline CoSi₂ films that were formed by a solid-state reaction between a 30 nm Co film and Si(111), (110) and (001) substrates. All films were strongly textured, and several texture components were identified. We discuss the simultaneous occurrence of axiotaxy (i.e. alignment of lattice planes across the interface) and several different types of epitaxy in each of the films. Comparison of the different texture components observed on the three substrate orientations suggests a strong preference for the alignment of CoSi₂{110} planes in the film with Si{110} planes in the substrate, and twinning around Si[111] directions.     

Hot corrosion phenomena of Nb-Ti-Si based alloy and its silicide coating induced by different corrosive environments at 900 °C

This study aims to elucidate the hot corrosion behavior of Nb-Ti-Si based alloy and its silicide coating in different molten salts at 900?°C. The results show that both K₂SO₄ and Na₂SO₄ had detrimental effect on the corrosion performance of the alloy, but almost no effect on the coating. However, NaCl accelerated the corrosion process for both the alloy and coating, showing highest scale thickness and mass gain. The main corrosion products consist mainly of Na or K containing oxides, TiO₂ and amorphous silicate. The reactivity of the alloy and the coating in different corrosive environments is discussed.