Surface nucleation of Ti silicides at elevated temperatures

Tung

, p. 1933 - 1935 (1996)

The nucleation of Ti silicide at the surfaces of Si was studied. Deposition of Ti and codeposition of TiSix at elevated temperatures on single crystal and amorphous Si led to the direct growth of silicides. The temperature and composition of the deposition and the crystallinity of the substrate were found to have a strong effect on the phases(s) of the silicide layer. A remarkably low nucleation temperature, ～500°C, for the low-resistivity C54-TiSi2 phase was observed on amorphous Si. Stoichiometric and uniform TiSi2 layers were grown with the depositions of pure Ti. On crystalline Si, uniform TiSi2 layers were also grown at ～500°C with the deposition of essentially Ti. The significant difference between silicide formation in the present scheme and that under conventional silicide processing was discussed in terms of a possible circumvention of precursor amorphous salicide phases during surface nucleation.

Mechanism of low temperature C54 TiSi2 formation bypassing C49 TiSi2: Effect of Si microstructure and Mo impurities on the Ti-Si reaction path

Kittl,Gribelyuk,Samavedam

, p. 900 - 902 (1998)

X-ray diffraction, high resolution transmission electron microscopy, and resistivity measurements were used to demonstrate a modification of the Ti/Si reaction path consisting of direct nucleation followed by diffusion limited growth of low resistivity C54 TiSi2 without nucleation of high resistivity C49 TiSi2, for the reaction of Ti with Mo doped polycrystalline or Mo doped amorphous Si by rapid thermal processing at 650 °C. We also report the mechanism of early C54 nucleation. We demonstrate that MoSi2 and an unidentified silicide phase lattice matched to C54 TiSi2, with spacings of 4.15 and 2.26 A, nucleate along the Ti/Si interface at early stages of the reaction and act as templates on which C54 TiSi2 nucleates and grows epitaxially. In contrast, the conventional phase sequence, nucleation and growth of C49 TiSi2 preceding nucleation of C54 TiSi2, was observed for the Ti/Mo doped single crystal (100) Si reaction and for all samples without Mo.

TiSi2 selective growth in a rapid thermal low pressure chemical vapor deposition system

Bouteville,Remy,Attuyt

, p. 2260 - 2263 (1992)

The aim of this work is to selectively deposit titanium disilicide films on silicon area vs. silicon oxide area through a new commercial RTLPCVD apparatus. As a preliminary study, we tested our deposition system by using the well-known polysilicon deposition process. By this way, we showed that the temperature homogeneity on a 4 in. wafer is quite satisfying, and that the growth rates are about ten times higher than those obtained by using a standard hot wall LPCVD system. Then, we studied the titanium silicide deposition from either pure titanium tetrachloride or hydrogen-diluted titanium tetrachloride. As-deposited layers are well-adherent to the substrate and crystallized according to the C 54 structure. The resistivity ranges from 15-20 μΩ-cm and the selectivity on 8 μm wide lines never fails. An anomalous substrate silicon etching is observed when pure titanium chloride is used but we show that hydrogen dilution inhibits this unwanted phenomenon. Chemical reactions are proposed to explain the silicide deposition and the unwanted formation of gaseous silicon species leading to this anomalous silicon etching when pure titanium chloride is used.

Reaction pathway of combustion synthesis of Ti5Si3 in Cu-Ti-Si system

Wang, Hui-Yuan,Lue, Si-Jie,Xiao, Wei,Liu, Guo-Jun,Wang, Jin-Guo,Jiang, Qi-Chuan

, p. 950 - 956 (2013)

The reaction pathway of combustion synthesis (CS) of Ti5Si 3 in Cu-Ti-Si system was explored through a delicate microstructure and phase analysis on the resultant products during differential thermal analysis (DTA). The formation of Cu-Si eutectic liquids plays a key role in the reaction pathway, which provides easy route for reactant transfer and accelerates the occurrence of complete reaction. Cu initially reacted with Si to form Cu3Si by a solid-state diffusion reaction, which further reacted with Cu to form Cu-Si liquids at the eutectic point of ~802°C; then Ti was dissolved into the surrounding Cu-Si liquids and led to the formation of Cu-Ti-Si ternary liquids; finally, Ti5Si3 was precipitated out of the saturated liquids by a solution-reaction-precipitation mechanism. The reaction pathway in CS of titanium silicide (Ti5Si3) could be described briefly as: Cu(s) + Ti(s) + Si (s)→Cu3Si(s) + Ti(s) + Si (s)→(Cu-Si)(l) + Ti(s)→(Cu-Ti-Si) (l)→Cu(l) + Ti5Si3(s).

Phase equilibria in the Dy-Ti-Si system at 1200 K

Morozkin

, p. 155 - 157 (2002)

Phase equilibria in the Dy-Ti-Si system were investigated by X-ray powder diffraction, local X-ray spectral analysis, metallographic analysis and the isothermal cross-section at 1200 K was obtained. The CeFeSi-type (space group P4/nmm, No. 129) DyTiSi compound has been confirmed. The new Sc2Re3Si4-type (space group P41212, No. 92) compound Dy2Ti3Si4 [a=0.6977(1) nm, c=1.2814(2) nm] was found. It is obvious that the AlB2-type (space group P6/mmm, No. 191) compound DyTi0.3Si1.7 [a=0.3824(1) nm, c=0.4119(1) nm] belongs to an extended region of the AlB2-type DySi1.56-based solid solution.

Peshev, P.,Khristov, M.

, p. 361 - 368 (1986)

Self-assembly of TiSi nanowires on TiSi2 thin films by APCVD

Ren, Zhaodi,Hao, Peng,Du, Jun,Han, Gaorong,Weng, Wenjian,Ma, Ning,Du, Piyi

, p. 7519 - 7524 (2011)

Titanium silicide thin films and nanowires (NWs) were prepared on a glass substrate using the APCVD method. Gaseous SiH4 and TiCl4 were used as precursors for Si and Ti, respectively. TiSi2 thin films were precipitated on

Transport limitations and Schottky barrier height in titanium silicide nanowires grown on the Si(111) surface

Soubiron,Stiufiuc,Patout,Deresmes,Grandidier,Stivenard,Koeble,Maier

, (2007)

The authors have performed electrical measurements at variable temperatures on self-assembled titanium silicide nanowires (NWs) grown on a Si(111) surface. The authors find a metallic I (V) characteristic for the NWs at a temperature of 77 K, whereas scanning tunneling spectroscopic measurements obtained at temperatures below 25 K yield a rectifying behavior. This behavior indicates that the NWs are electronically decoupled from the Si surface on a voltage range of several hundreds of meV at low temperatures. From these measurements, the authors precisely determine the Schottky barrier height between the NWs and the Si surface.

Yang, Jeng-Rern,Lue, Juh-Tzeng,Wu, In-Chin

, p. 395 - 400 (1988)

Preparation of Ti3SiC2 by electron-beam-ignited solid-state reaction

Goesmann, Fred,Wenzel, Roland,Schmid-Fetzer, Rainer

, p. 3025 - 3028 (1998)

This paper describes a novel way to prepare the ternary phase Ti3SiC2 in a single-step procedure that we call electron-beam-ignited solid-state reaction (EBI-SSR). The preparation route is discussed by means of an isothermal section of the Ti-Si-C phase diagram. Properties such as the Vickers hardness and the electrical resistivity of the resulting samples are presented. Our property data compare well to those that have been published. The main advantages of this preparation method are the controllability of process parameters such as heating rates, temperatures, and times, as well as the short duration of the overall sample preparation. However, a disadvantage is the presence of second phases (typically in amounts of 8%) that must be reduced via further optimization of the process.

Effect of amorphous silicon capping on titanium during TiSi2 formation by RTA

Kang, S. W.,Park, S. C.,Chun, S.

, (1990)

Thin film reactions of the Ti/(100)Si structure and the amorphous-Si/Ti/(1 00)Si structure were performed by rapid thermal annealing (RTA) in argon at 500-800°C. Auger depth profiling shows that the as-deposited titanium film of the Ti/(1 00)Si structure and the as-deposited amorphous silicon (a-Si) film of the a-Si/Ti/(1 00)Si structure exhibit a roughly exponential oxygen distribution decreasing from the surface when exposed to air. electron spectroscopy for chemical analysis (ESCA) shows that the oxygen in the a-Si film forms SiO2 and the oxygen in the titanium film forms titanium oxide. For the Ti/(1 00)Si structure, the oxygen tends to be redistributed uniformly throughout the titanium film near the onset of silicide formation during RTA. As silicide formation progresses, the redistributed oxygen is snowplowed back toward the surface owing to the oxygen solubility difference between Ti and TiSi2. Consequently, the oxygen concentration in the unreacted titanium layer increases and retards the silicide growth even though there remains an unreacted titanium layer. The oxygen redistribution in the titanium film correlates well with the rapid increases in sheet resistance near the onset of silicide formation. When a-Si is sputter-deposited sequentially on the titanium film without breaking the vacuum, the oxygen in a-Si is not redistributed during RTA. Thus there is no rapid increase in sheet resistance, and the saturated sheet resistance is lower than that of Ti/(1 00)Si structure.

Growth of Ti and TiSi2 films on Si(111) by low energy Ti+ beam deposition

Lee,Ada,Lee,Kulik,Rabalais

, p. 159 - 170 (2000)

The deposition of titanium and titanium disilicide thin films on Si(111) by low-energy (10-500 eV) Ti+ beams in the temperature range 25-700°C has been investigated by in-situ Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) as well as ex-situ depth profile X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and transmission electron diffraction (TED). Small XPS chemical shifts in the Si2p and Ti2p peaks and changes in the AES line shapes originating from elemental silicon and titanium and the titanium disilicide compound have been resolved. The XPS shifts were used for resolution of the silicide layer in the depth profiles. This interfacial silicide layer is formed even at 25°C, and its characteristics are dependent on both Ti+ energy and Si temperature. The RHEED and TED results confirm the growth of a polycrystalline Ti film for T≤500°C, the C49-TiSi2 phase for T～600°C, the C54-TiSi2 phase for T～700°C or above, and the existence of synergistic effects between the substrate temperature and Ti+ kinetic energy on the crystalline quality of the films. The AFM images exhibit a broad range of morphologies as a function of growth conditions. The effects of energetic ions and temperature in Ti and TiSi2 film deposition are discussed accordingly.

d'Heurle, F.,Irene, E. A.,Ting, C. Y.

, p. 361 - 363 (1983)

Plasma enhanced chemical vapor deposition of blanket TiSi2 on oxide patterned wafers

Lee,Reif

, p. 1159 - 1165 (1992)

We investigated the effects of deposition variables on the growth of stable TiSi2 films and the silicon consumption from the substrate during the deposition of TiSi2 in a cold wall plasma enhanced chemical vapor deposition system. Low resistivity silicide films were deposited at temperatures ranging from 590 to 775°C and a SiH4/TiCl4 flow rate from 6/2 to 10/6 (sccm). The as-deposited films did not require any postannealing to lower the resistivity. It was observed that, depending on deposition conditions, substrate silicon consumption occurred during silicide deposition. However, a high SiH4 flow rate and low deposition temperature effectively suppressed silicon consumption. The deposition of a conformal blanket TiSi2 film with no silicon consumption at 590°C and SiH4/TiCl4 of 8/4 (sccm) confirmed the effects of temperature and gas flow ratio on silicon consumption. A kinetic model of silicon consumption is proposed to provide a description of the effects of silane gas flow rate on silicon consumption.

Effect of TiO2 doping on crystallization, microstructure and dielectric properties of CBS glass-ceramics

He, Dongfeng,Zhong, Hao,Gao, Chong

, p. 50 - 58 (2019)

In this study, calcium borosilicate (CaO-B2O3-SiO2, CBS) glass-ceramics were fabricated using chemically pure CaO, SiO2, and B2O3 as raw materials. Differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and electrical measurements were conducted to explore the effect of titanium dioxide (TiO2) doping on crystallization, microstructure, and dielectric properties of CBS glass-ceramics. Furthermore, the influence of sintering temperature and sintering schemes on crystalline phases of CBS glass-ceramics was systematically investigated. Results showed that the increase of TiO2 content led to the reduction in sintering temperature of CBS glass-ceramics and promoted the precipitation of wollastonite crystal phase. For instance, with the increase of content of TiO2 from 0 to 3 wt%, transition temperature and crystallization temperature were reduced by 12.9 and 27.6 °C, respectively. However, excessive TiO2 affected the precipitation of wollastonite crystal phase, destroyed crystal structure, and damaged close arrangement of crystal grains. Moreover, higher TiO2 content was found to weaken dielectric properties of CBS glass-ceramics. In this study, the best molar ratio of ingredients, meeting that of ideal target material, is n(Ca): n(Si): n(B)= 1:1:0.6, with doping mass fraction of 2 wt% of TiO2. After optimal sintering procedure, dielectric constant of the best sample was found to be 1.4 (1 MHz), 1.3 (10 MHz), and dielectric loss was 3.9 × 10?3 (1 MHz) and 3.8 × 10?3 (10 MHz).

Low temperature formation of C54-TiSi2 using titanium alloys

Cabral Jr.,Clevenger,Harper,D'Heurle,Roy,Lavoie,Saenger,Miles,Mann,Nakos

, p. 3531 - 3533 (1997)

We demonstrate that the temperature at which the C49 TiSi2 phase transforms to the C54 TiSi2 phase can be lowered more than 100°C by alloying Ti with small amounts of Mo, Ta, or Nb. Titanium alloy blanket films, containing from 1 to 20 at. % Mo, Ta, or Nb were deposited onto undoped polycrystalline Si substrates. The temperature at which the C49-C54 transformation occurs during annealing at constant ramp rate was determined by in situ sheet resistance and x-ray diffraction measurements. Tantalum and niobium additions reduce the transformation temperature without causing a large increase in resistivity of the resulting C54 TiSi2 phase, while Mo additions lead to a large increase in resistivity. Titanium tantalum alloys were also used to form C54 TiSi2 on isolated regions of arsenic doped Si(100) and polycrystalline Si having linewidths ranging from 0.13 to 0.56 μm. The C54 phase transformation temperature was lowered by over 100°C for both the blanket and fine line samples. As the concentration of Mo, Ta, or Nb in the Ti alloys increase, or as the linewidth decreases, an additional diffraction peak appears in in situ x-ray diffraction which is consistent with increasing amounts of the higher resistivity C40 suicide phase.

Laser-induced direct formation of C54 TiSi2 films with fine grains on c-Si substrates

Chen,Shen,Chen,Chan,See

, p. 1727 - 1729 (1999)

In this letter, we report on the direct synthesis of C54 TiSi2 films with fine grains by pulsed-laser irradiation from Ti deposited on Si substrates, using a Q-switched Nd:YAG laser. The films were characterized using micro-Raman spectroscopy, high-resolution transmission electron microscopy, and atomic force microscopy. In comparison with the C54 TiSi2 using the conventional rapid thermal annealing (RTA) of 35 nm thick Ti/Si, which has an average grain size of about 110 nm and film thickness of 50 nm, the laser-induced C54 TiSi2 films vary from 13 to about 42 nm in thickness with different laser scanning speed and the grain size is 85 nm on average. The TiSi2/substrate Si interface is smooth on the atomic scale. Our results demonstrate the unique advantages of the laser-induced formation technique and its potential in deep submicron semiconductor technology. We propose that the C54 phase is formed by solid-state diffusion, rather than melting.

Formation of titanium silicides Ti5Si3 and TiSi2 by self-propagating combustion synthesis

Yeh,Chen,Hsu

, p. 90 - 95 (2007)

Preparation of titanium silicides Ti5Si3 and TiSi2 from elemental powder compacts of their corresponding stoichiometries was conducted by self-propagating high-temperature synthesis (SHS) in this study. Effects of the sample green density, preheating temperature, and starting stoichiometry on combustion characteristics, as well as on product composition were studied. Experimental evidence indicated that a self-sustained combustion front was established upon ignition and subsequently traversed the entire sample in a steady manner. After the passage of the flame front, further phase transformation taking place in the sample led to the emergence of afterburning glows. As a result of the combustion temperatures exceeding the lowest eutectic point (1330 °C) of the Ti-Si binary mixture, formation of Ti5Si3 from the stoichiometric powder compact is primarily dominated by the solid-liquid mechanism, which involves the dissolution of solid reactants and the precipitation of silicide products. Moreover, complete conversion yielding a single-phase silicide Ti5Si3 was achieved in this study. On the contrary, the interaction between reactant elements within the Ti + 2Si compacts is governed by a solid-state mechanism, due to their low reaction temperatures less than the Ti-Si eutectic point 1330 °C. The XRD analysis identifies the disilicide TiSi2 as the major composition in the final products of Ti + 2Si samples. In addition to TiSi2, however, small amounts of TiSi and Si were detected in the products obtained from the samples of Ti:Si = 1:2. It is believed that different reaction mechanisms are responsible for the significantly higher propagation velocity of the reaction front observed in the 5Ti + 3Si compacts than in the samples of Ti:Si = 1:2. Based upon the dependence of flame-front velocity on combustion temperature, the activation energies in association with formation of Ti5Si3 and TiSi2 by SHS were determined to be 205.2 and 165.4 kJ/mol, respectively.

Three-dimensional printing of Ti3SiC2-based ceramics

Nan, Beiya,Yin, Xiaowei,Zhang, Litong,Cheng, Laifei

, p. 969 - 972 (2011)

In the present work, we explored the feasibility of fabricating Ti 3SiC2-based ceramics by a near-net-shape fabrication process of three-dimensional printing (3D printing) combined with liquid silicon infiltration (LSI). The porous ceramic preform was fabricated by 3D printing TiC powder with dextrin as a binder. The heat-treated preforms contained bimodal pore structure with interagglomerate pores (da23 μm) and intraagglomerate pores (da1 μm). Upon infiltration in Ar atmosphere at 1600°-1700°C for 1 h, silicon melt infiltrated the pores and reacted with TiC to yield Ti3SiC2, TiSi2, and SiC. The effects of silicon content and infiltration temperature on the phase composition of the Ti3SiC2-based composites were also studied. After LSI at 1700°C for 1 h, the composites with an initial TiC:Si mole ratio of 3:1.2 attained a bending strength of 293 MPa, a Vickers hardness of 7.2 GPa, and an electrical resistivity of 27.8 μIA·cm, respectively.

The isothermal section of the Pr-Ti-Si ternary system at 773 K

Zhan, Yongzhong,Li, Chunhui,Liu, Jingqi,Du, Yong,Mo, Honglou

, p. 201 - 203 (2009)

The isothermal section of the Pr-Ti-Si ternary phase diagram at 773 K was investigated by powder X-ray diffraction (XRD) and differential thermal analysis (DTA). The binary compound Pr3Si4 is not observed at 773 K. There are nine bin

Co-reduction route to nanocrystalline titanium silicide by using different metal reductants

Ma, Jianhua,Gu, Yunle,Shi, Liang,Chen, Luyang,Yang, Zeheng,Qian, Yitai

, p. 250 - 253 (2004)

Titanium silicides were synthesized by co-reducing silicon tetrachloride and titanium tetrachloride with different metal reductants (Na, Mg, Zn and Al) in an autoclave at 650°C. The X-ray diffraction patterns indicated that the obtained titanium silicides

Reaction synthesis of TiSi2 and Ti5Si3 by ball-milling and shock loading and their photocatalytic activities

Liu, Jianjun,Bai, Yuna,Chen, Pengwan,Cui, Naifu,Yin, Hao

, p. 375 - 380 (2013)

Shock loading and high energy ball-milling are typical mechanochemical processing methods by which the chemical reaction of different substances can be initiated and the functional materials with particular physical and chemical properties were produced. In this paper, the precursors of Ti-Si powder with different stoichiometric ratios were pre-activated by ball-milling and then loaded by shock wave. The recovered samples were characterized by XRD, SEM, and DSC, and photocatalytic activity of splitting water into hydrogen was evaluated under visible light. The results indicate that shock-induced reaction of Ti-Si is easier after certainly ball-milling treatment in which the Ti 5Si3 with high thermodynamic stability was produced in the precursor mixtures of Ti:Si = 1:2 and the designed Ti5Si3 was also produced in that of Ti:Si = 5:3. The test for photocatalytic activity shows that there has a common sequence of photocatalytic activity of the treated samples with different stoichiometric ratios including the precursor mixtures of Ti:Si = 1:2 and 5:3: (ball-milling + shock loading) > shock loading > ball-milling meaning that the samples treated by both of milling and shock loading exhibit better photocatalytic activity than that of only milling or shock loading due to the greater degree of activation.

Influence of carbon on the electron stimulated desorption from titanium silicide surfaces

Montero,Román,Segovia,Galán

, p. 42 - 46 (2003)

The influence of carbon on the electron stimulated desorption from titanium silicide thin film surfaces has been studied by means of electron-stimulated-desorption (ESD) and Auger electron spectroscopy. The superficial carbon was due to exposure to air. T

Enhanced thermal stability of C49 TiSi2 in the presence of aluminum

Zhang,D'Heurle,Lavoie,Cabral Jr.,Harper

, p. 312 - 314 (1998)

The introduction of a thin layer of Al at the interface between Ti films and Si substrates enhances the formation of C49 TiSi2 and retards the transition from C49 to C54. An Al interlayer, 0.64 nm thick, reduces the time required to form C49 TiSi2 isothermally at 500°C from 14 to 7 min. The C49-C54 transformation temperature is increased from 767 to 853°C, when heating the samples at a constant ramp rate of 3 K/s. Most of the Al is found toward the interface between a Ti-rich silicide at the surface and TiSi2, rather than at the interface between TiSi2 and the Si substrate. The grain size of the C49 TiSi2 formed in the presence of Al is about five times smaller than that formed on a control sample with pure Ti, indicating that the increased density of grain boundaries in C49 TiSi2 in the presence of Al does not help the C49-C54 transformation. Therefore, the improved thermal stability of C49 TiSi2 is likely to be caused by other factors such as a reduced electron/atom ratio when replacing Si with Al in the disilicide.

Synthesis and field emission properties of TiSi2 nanowires

Xiang,Wang,Wang,Zhang,Liu,Xu,Yu

, p. 1 - 3 (2005)

TiSi2 is a high-melting compound with excellent conductivity ～several μΩ cm. TiSi2 nanowires were fabricated in large scale by a simple vapor phase deposition method. The as-synthesized TiSi2 nanowires were investigated using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman scattering. Field emission property of TiSi2 nanowires was studied and an emission current density of 5 mAcm2 was obtained and no obvious degradation was observed in a life stability experiment period for over ～40 h. The cathodoluminescence images were very bright and homogenous. The remarkable performance reveals that the TiSi2 nanowires can serve as a good candidate for commercial application in vacuum microelectronic devices, particularly flat panel displays.