X-ray reflectivity study on TiN/Ti/Si structures before and after annealing

X-ray reflectivity was employed as a powerful tool for studying the surface and interface roughness and thickness, as well as density, of TiN/Ti/Si layers. X-ray reflectivity of the as-deposited samples, with nominal thickness of 17.5 nm of Ti and 3.0 nm of TiN, shows uniform oscillations. When the samples are annealed at 710°C, residual strongly attenuated oscillations are still observed, while the 850°C-annealed sample does not show oscillations, indicating high surface and interface roughness of the formed nitride and silicide layers. It is demonstrated that increased interface roughness, even for a layer with a larger average electron density difference, reduces the oscillations in the reflectivity curve very rapidly. For comparison, cross sectional transmission electron microscopy was employed to find the thickness of the surface and interface layers in silicide structures, which are in good agreement with the X-ray reflectivity results. The work was also supported by tapping mode atomic force microscopy observations, where we have observed nearly flat structures for the as-deposited sample surface and needle-like protrusions for the annealed samples. The surface roughness of the top TiN layer was used to obtain simulated X-ray reflectivity spectra in good agreement with the experimental results. Preliminarily, the crystallography of the layers in the samples was determined by the grazing angle X-ray diffraction technique, to acquire knowledge on the Ti and Si compounds formed in the samples after the annealing.     

Phase formation at rapid thermal annealing of Al/Ti/Ni ohmic contacts on 4H-SiC

Ohmic contacts to the top p-type layers of 4H-SiC p⁺–n–n⁺ epitaxial structures having an acceptor concentration lower than 1×10¹⁹ cm⁻³ were fabricated by the rapid thermal anneal of multilayer Al/Ti/Pt/Ni metal composition. The rapid thermal anneal of multilayer A1/Ti/Pt/Ni metal composition led to the formation of duplex cermet composition containing Ni₂Si and TiC phases. The decomposition of the SiC under the contact was found to be down to a depth of about 100 nm. The contacts exhibited a contact resistivity R_c of 9×10⁻⁵ Ω cm⁻² at 21°C, decreasing to 3.1×10⁻⁵ Ω cm⁻² at 186°C. It was found that thermionic emission through the barrier having a height of 0.097 eV is the predominant current transport mechanism in the fabricated contacts.     

Limitation of Ti/TiN diffusion barrier layers in silicon technology

The usefulness of Ti/TiN and TiSi₂/TiN bilayers as low resistive contacts and diffusion barriers between doped silicon and aluminium has been examined. The Ti layer was magnetron sputtered and the TiN layers were deposited by reactive magnetron sputtering in an argon/nitrogen mixture. After Ti/TiN deposition part of the samples were annealed in a vacuum furnace to form a TiSi₂/TiN structure. The films were characterized by Rutherford backscattering spectrometry (RBS), X-ray diffractometry (XRD) and resistivity measurements. The integrity of the final metallization systems, with aluminium as top level, for annealing temperatures in the range 400–600°C was evaluated by RBS and electrical measurements on fully processed test vehicles containing structures for contact resistivity measurements and shallow implanted gated diodes. A significant discrepancy has been observed between recorded RBS data and electrical measurements. No reaction was detected by RBS at temperatures below 525°C although a significant degradation of the electrical performance was readily observed at lower annealing temperatures, e.g. an increase in contact resistance and large reverse leakage currents. It is concluded that RBS, commonly used in the study of diffusion barrier properties, gives optimistic information on the upper limit of the metallurgical stability of the barrier layers, whereas other factors such as step coverage, compositional variation and mechanical stress are of predominant significance when actual device metallization is concerned.     

Electrical degradation of n-Si/PtSi/(TiW)/Al Schottky contacts induced by thermal treatments

Degradation of n-Si/PtSi/(TiW)/Al Schottky contacts was observed for thermal treatments at 500–550°C. The barrier height decreases from 0.86 to about 0.60 V and then rises to 0.70 V. A striking correlation between metallurgical interdiffusion, growth of intermetallic compounds and electrical degradation is reported.     

Features of CoSi<Subscript>2</Subscript> phase formation by two-stage rapid thermal annealing of Ti/Co/Ti/Si(100) structures

A method of cobalt disilicide (CoSi₂) layer formation proceeding from a Ti(8 nm)/Co(10 nm)/Ti(5 nm)/Si(100) (substrate) structure prepared by magnetron sputtering is described. The initial structure was subjected to two-stage rapid thermal annealing (RTA) in nitrogen, and the samples after each stage were studied by the time-of-flight secondary-ion mass spectrometry, Auger electron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The RTA-1 stage (550°C, 45 s) resulted in the formation of a sacrificial surface layer of TiN _x O _y , which gettered residual impurities (O, C, N) from inner interfaces of the initial structure. After the chemical removal of this TiN _x O _y layer, the enrichment with cobalt at the RTA-2 stage (830°C, 25 s) led to the formation of a low-resistance CoSi₂ phase.     

Interferometric detection in picosecond ultrasonics for nondestructive testing of submicrometric opaque multilayered samples: TiN/AlCu/TiN/Ti/Si

An experimental investigation of nanometric thin films by a picosecond ultrasonic technique is presented. A photoelastic model is used with an interferometric device, combined with ultrafast optical pump and probe setup, to measure the thicknesses of submicrometric layers made of TiN, Ti, and AlCu deposited on silicon (Si) wafers. The results are in good agreement with ellipsometry measurements showing that the picosecond ultrasonic technique can give accurate results even when the reflectance signal is very low. Additional important results are first, that the adhesion of the TiN surface film is probed by processing both the frequency and the damping of the oscillation of a resonance acoustic mode; and second, the presence of a thin buried TiN layer under an opaque AlCu film is highlighted by the interferometric setup.     

The influence of rapid thermal annealing on electrical and structural properties of Pt/Au Schottky contacts to n-type InP

The electrical and structural properties of Pt/Au Schottky contacts to n-InP have been investigated in the annealing temperature range of 200–500 °C by current–voltage (I–V), capacitance–voltage (C–V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements. The barrier height of as-deposited Pt/Au Schottky contact is found to be 0.46 eV (I–V) and 0.68 eV (C–V). For the contacts annealed at 300 °C, the barrier height is increased to 0.51 eV (I–V) 0.89 eV (C–V). Further increase in annealing temperature up to 500 °C, the barrier height has been found to decrease to 0.49 eV (I–V) 0.82 eV (C–V) from those values obtained at 300 °C. It has been found that the electrical characteristics are significantly improved for Pt/Au Schottky contacts upon annealing at 300 °C. Based on the Auger electron spectroscopy and X-ray diffraction results, the formation of Pt–In and Au–In intermetallic compounds at the interface may be the reason for the increase of barrier height after annealing at 300 °C for Pt/Au Schottky contacts. From the atomic force microscopy (AFM) results, it is evident that the surface becomes smooth with RMS roughness of 16.91 nm for the Pt/Au Schottky contacts after annealing at 500 °C compared to the 300 °C annealed sample (RMS roughness of 17.33 nm).     

Influence of rapid thermal annealing effect on electrical and structural properties of Pd/Ru Schottky contacts to n-type GaN

Pd/Ru metallization scheme is fabricated on n-GaN as a Schottky contact, and the electrical and structural properties have been investigated as a function of annealing temperature by current–voltage (I–V), capacitance–voltage (C–V), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements. As-deposited Ru/Pd/n-GaN contact yielded Schottky barrier height (SBH) of 0.67 eV (I–V) and 0.79 eV (C–V), respectively. Further, it is observed that the Schottky barrier height increases to 0.80 eV (I–V) and 0.96 eV (C–V) for the contact annealed at 300 °C. However, both I–V and C–V measurements indicate that the barrier height slightly decreased when the contacts are annealed at 400 °C and 500 °C. From the above observations, the optimum annealing temperature for Pd/Ru Schottky contact is 300 °C. Norde method is also employed to extract the barrier height of Pd/Ru Schottky contacts which are in good agreement with those obtained by the I–V technique. X-ray photoelectron spectroscopy results shows that the Ga 2p core-level shift towards the low-energy side for the contact annealed at 300 °C compared to the as-deposited contact. Based on the XPS and XRD results, the reason for the increase in SBH upon annealing at 300 °C could be attributed to the formation of gallide phases at the Ru/Pd/n-GaN interface vicinity. The AFM results showed that the overall surface morphology of the Pd/Ru Schottky contacts on n-GaN is fairly smooth. The above observations reveal that the Pd/Ru Schottky contact is attractive for high-temperature device applications.     

Si3N4/TiN复相陶瓷常温导电性研究

分析了以高硅铁尾矿合成的Si3N4粉和高钛渣为原料常压烧结制备的Si3N4/TiN复相陶瓷的常温导电性,并对其进行放电加工。研究结果表明,初始原料中20%(质量分数)左右的TiO2加入量是决定材料中TiN能否形成导电网络的最低TiO2加入量,此时材料的电阻率为4.25×10-2Ω.cm。烧结温度升高,材料的电阻率略有降低。随放电加工速度的增加,加工表面的粗糙度明显增加。     

Rapid thermal annealing of Ti Schottky contacts ton-GaAs

Ti Schottky contacts were formed onn-GaAs surfaces and were subjected to rapid thermal annealing (RTA) at various temperatures. Low temperature RTA (<500 °C) results in a reduction in the diode leakage currents and increase in the barrier voltage. High temperature RTA (>500 °C) results in progressive degradation of the diode parameters. The improvement in diode parameters is expected to be due to better adhesion of Ti Schottky contact resulting in a more intimate contact of the Schottky metal to the GaAs substrate.     

Effects of thermal annealing on the electrical and structural properties of Pt/Mo Schottky contacts on n-type GaN

Thermal annealing temperature effects on the electrical and structural properties of platinum/molybdenum (Pt/Mo) Schottky contacts on n-type GaN have been investigated by current–voltage (I–V), capacitance–voltage (C–V), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. As-deposited Pt/Mo/n-GaN Schottky diode exhibits barrier height of 0.75 eV (I–V) and 0.82 eV (C–V). Upon annealing at 400 and 500 °C, the barrier height slightly increased to 0.77 eV (I–V) and 0.92 eV (C–V) and 0.82 eV (I–V) and 0.97 eV (C–V), respectively. A maximum barrier height of 0.83 eV (I–V) and 0.99 eV (C–V) is obtained on the Pt/Mo contacts annealed at 600 °C. X-ray photoelectron spectroscopy results shows that the Ga 2p core-level shift towards the low-energy side for the contact annealed at 600 °C as compared to the as-deposited one. Based on the results of XPS and XRD studies, the formation of gallide phases at Pt/Mo/n-GaN interface could be the reason for the increase of Schottky barrier heights upon annealing at elevated temperatures. The atomic force microscopy (AFM) results showed that the Pt/Mo contact does not seriously suffer from thermal degradation during annealing even at 600 °C (RMS roughness of 5.41 nm). These results make Pt/Mo Schottky contacts attractive for high temperature device applications.     

Correlation between the performance and microstructure of Ti/Al/Ti/Au Ohmic contacts to p-type silicon nanowires

Understanding the electrical and microstructural aspects of contact formation at nanoscale is essential for the realization of low-resistance metallization suitable for the next generation of nanowire based devices. In this study, we present detailed electrical and microstructural characteristics of Ti/Al/Ti/Au metal contacts to p-type Si nanowires (SiNWs) annealed at various temperatures. Focused ion beam cross-sectioning techniques and scanning transmission electron microscopy (STEM) were used to determine the microstructure of the source/drain metal contacts of working SiNW field-effect transistors (FETs) annealed for 30 s in the 450-850?°C temperature range in inert atmosphere. Formation of titanium silicides is observed at the metal/semiconductor interface after the 750?°C anneal. Extensive Si out-diffusion from the nanowire after the 750?°C anneal led to Kirkendall void formation. Annealing at 850?°C led to almost complete out-diffusion of Si from the nanowire core. Devices with 550?°C annealed contacts had linear electrical characteristics; whereas the devices annealed at 750?°C had the best characteristics in terms of linearity, symmetric behavior, and yield. Devices annealed at 850?°C had poor yield, which can be directly attributed to the microstructure of the contact region observed in STEM.     

Effects of rapid thermal annealing on the morphology and electrical properties of ZnO/In films

Zinc oxide (ZnO) films were prepared by ultrasonic spray pyrolysis on indium (In) films deposited by evaporation and subsequently subjected to rapid thermal annealing (RTA) in air or vacuum. The crystallographic properties and surface morphology of the films were characterized before and after RTA by X-ray diffraction and scanning electron microscopy, respectively. The variation in resistivity of the films with RTA temperature and time was measured by the four-point probe method. Auger electron spectroscopy (AES) was carried out to determine the distribution of indium atoms in the ZnO films. The resistivity of the ZnO on In (ZnO/In) films decreased to 2×10⁻³ Ω cm by diffusion of the In. Indium diffusion into the ZnO films roughened the film surface. The results of depth profiling by AES showed a hump of In atoms around ZnO/In interface after RTA at 800 °C, which disappeared on RTA at 1000 °C. The effects of temperature, time and atmosphere during RTA on the structural and electrical properties of the ZnO/In films are discussed.     

Electromigration of interconnects of a TiN/Cu/TiN/Ti structure

Electromigration (EM) tests have been performed to assess the interconnect reliability of a TiN/Cu/TiN/Ti structure. In this paper we demonstrate the feasibility of Cu interconnects and we present the first electrical results. An energy activation close to 1·2 eV was found for the grain boundary diffusion. We explain the variation in the Black parameters with the different conditions applied for the reliability tests. Particular attention is paid to the dependence of the activation energy on current densities and width.     

Effects of interfacial layer on characteristics of TiN/ZrO2 structures

To minimize the formation of unwanted interfacial layers, thin interfacial layer (ZrCN layer) was deposited between TiN bottom electrode and ZrO2 dielectric in TiN/ZrO2/TiN capacitor. Carbon and nitrogen were also involved in the layer because ZrCN layer was thermally deposited using TEMAZ without any reactant. Electrical characteristics of TiN/ZrO2/TiN capacitor were improved by insertion of ZrCN layer. The oxidation of TiN bottom electrode was largely inhibited at TiN/ZrCN/ZrO2 structure compared to TiN/ZrO2 structure. While the sheet resistance of TiN/ZrCN/ZrO2 structure was constantly sustained with increasing ZrO2 thickness, the large increase of sheet resistance was observed in TiN/ZrO2 structure after 6 nm ZrO2 deposition. When ZrO2 films were deposited on ZrCN layer, the deposition rate of ZrO2 also increased. It is believed that ZrCN layer acted both as a protection layer of TiN oxidation and a seed layer of ZrO2 growth.     

Rapid thermal annealing of Cu/WN x /Si structures

The thermal stability of Cu/WN _x /Si multilayer structures fabricated by using reactive d.c. magnetron sputtering was studied using rapid thermal annealing (RTA) and several analytic methods. The analytic methods included four-point resistance measurements, X-ray diffraction analysis, Rutherford backscattering spectrometry, and optical and scanning electron microscopy. The barrier performance of WN _x -layers is compared to the performance of sputtered W layers. It is shown that a 15-nm thick tungsten nitride (WN _x ) layer prevents the destructive reactions up to 700 °C for a 12-s RTA process in a nitrogen atmosphere.     

Aluminum/nickel silicide contacts on silicon

The results of a study of the interaction occurring at elevated temperatures between nickel silicide contacts on n-type 〈111〉 silicon and a thin aluminum overlayer are presented. The electrical and structural characteristics of the Al-nickel silicide interaction were investigated using Schottky barrier diodes, Auger electron spectroscopy, X-ray diffraction and scanning electron microscopy. As-grown diodes were found to consist mainly of NiSi and the NiSi-Si interface exhibited a Schottky barrier energy φ_Bn of 0.62 eV. Upon heat treatment the NiSi layer was transformed to the intermetallic NiAl₃, and the barrier energy for the resulting NiAl₃-Si interface was found to be 0.76 eV. The electrical characteristics of the NiAl₃ layer were stable up to 500°C and no evidence of aluminum penetration into the silicon substrate was found.     

The influence of TiN on cosputtered (Ti+Si) blanket film

X-ray diffraction, transmission electron microscopy and Auger spectroscopy were used to study the formation of TiSi₂ from a cosputtered (Ti+Si) film with and without TiN capping. In all cases, a metal rich silicide identified as Ti₅Si₃, was the first phase to form from the amorphous (Ti+Si) regardless if a TiN overlayer was or was not present. At temperatures of 923 K and below it only Ti₅Si₃ was observed in all specimens. C54 TiSi₂ formation is enhanced in specimens having a TiN capping and its formation occurs at lower temperatures and at a faster rate at some appropriate temperature than in specimens without TiN. The effect of tensile stress induced by the TiN layer is suggested as the reason of C54 TiSi₂ formation.     

Structural and electrical properties of Au and Ti/Au contacts to n-type GaN

Au and Ti/Au layers were deposited on n-GaN. The samples were annealed at 400, 700 and 900 °C for 10 min in vacuum. The contacts were rectifying up to 700 °C and the highest Schottky barrier height of 1.07 eV was obtained for an Au single layer by current-voltage measurements. A binary phase of Au₂Ga was identified at the interface of the n-GaN/Ti/Au contact after annealing at 900 °C. The formation of Ti₂N and TiN (twin) phases epitaxially grown on GaN was also observed in the same contact as well as some gold diffusion into the topmost region of the GaN epilayer.     

N/Ti原子比对TiN膜微结构及性能的影响综合分析

TiN硬质膜是很多现有的多组元氮化物硬质膜的基础.N/Ti原子比对TiN硬质膜具有重要影响.结合TiN硬质膜的制备工艺方法,分析了膜层中N含量变化的影响因素及控制方法,详细讨论了N/Ti原子比对TiN膜相组成、硬度、耐摩擦磨损性能、光电性能的影响关系.