Hong-Ying Chen

XPS analyses of TiN films on Cu substrates after annealing in the controlled atmosphere

Abstract X-ray photoelectron spectroscopy (XPS) has been used to investigate the thermal annealing of TiN films in the controlled atmosphere. The films were prepared by a cathodic arc plasma deposition technique on Cu substrates. The flowing gases used in the annealing are air, N 2 , Ar, and CO 2 /N 2 /H 2 gas mixtures, which possess extremely different nitrogen and oxygen partial pressures. Annealing the samples in air at 300, 400, and 500°C causes the gradual transformation from amorphous TiO 2 to crystalline TiO 2 on the TiN surface. Annealing in N 2 and Ar at slightly different temperatures results in various adsorbed nitrogen states. After annealing in CO 2 /N 2 /H 2 =10:81:9 and N 2 /H 2 =9 gas mixtures from 400°C to 700°C, the relative intensity of crystalline TiO 2 increases with temperature and that of titanium oxynitride decreases. The adsorbed nitrogen associated with the oxidation of TiN is discussed. The TiN oxidation chemistry under these controlled oxygen and nitrogen partial pressures is also discussed.

Phase changes of CrN films annealed at high temperature under controlled atmosphere

Abstract CrN films were deposited onto (100) Si wafers by cathodic arc plasma deposition. After that, the films were annealed between 400 and 1200°C for 2 h in air, N 2 , and N 2 /H 2 =9, which possess dramatically different P n 2 and P o 2 . XRD results showed that oxidation of CrN films occurred above 700°C in all gases but the relative amount of the resultant oxide Cr 2 O 3 decreased with rising ( P n 2 / P o 2 ) ratio in the gases for a given temperature. The driving force for oxidation of the nitride is the Gibbs free energy changes in the oxidation reaction. Meanwhile, the β-Cr 2 N phase appeared at 500°C, diminished at 700°C, and showed up again at 1100°C under all atmospheres. The reason for the presence of β-Cr 2 N at temperatures above 1100°C is that Cr 2 N is thermodynamically more stable than CrN in the high temperature range, as analyzed from thermodynamics. The phase transforming from CrN to Cr 2 N in the low temperature range is possibly due to the large stress relaxation occurring in the film during annealing, as observed in the in situ stress measurements.

Oxidation behavior of titanium nitride films

The oxidation behavior of titanium nitride (TiN) films has been investigated by using x-ray diffraction, Raman scattering spectroscopy, and field emission scanning electron microscopy. TiN films were deposited onto Si substrates by using cathodic arc plasma deposition technique. After that, the films were annealed in the air at 500–800 °C for 2 h. The x-ray diffraction spectra showed that rutile–TiO2 appeared above 600 °C. The relative intensity of TiO2 rapidly increased with temperatures. Only rutile–TiO2 was detected above 700 °C. Raman scattering spectra indicated the presence of rutile–TiO2 signals above 500 °C. Meanwhile an additional Si peak appeared at 700 °C in Raman spectra, above which only Si peak appeared. Many nano pores were found on the surface of films annealed at temperatures between 600 and 700 °C in field emission scanning electron microscopy, while the granular structure existed at 800 °C. The as-deposited TiN films had an apparent columnar structure. The thin and dense oxide overlayer...

Characterization of titanium nitride films deposited by cathodic arc plasma technique on copper substrates

Abstract TiN films were deposited directly on Cu substrates by a cathodic arc plasma deposition technique. The films were then characterized by X-ray diffraction (XRD), grazing incidence X-ray diffraction (GID), (TEM), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The preferred orientation of the film changed from (200) to (111) with increasing film thickness. Analyses of both the XRD and GID results showed that in the highly (111) textured grains, the (111) plane was approximately parallel to the film surface, while in the (200) textured grains, the (200) plane was tilted away from the film surface. Small-elongated crystallites with a large aspect ratio and textured grains were found on the TiN surface. AES, which was employed to examine the concentration depth profile, showed no apparent interdiffusion between Cu and TiN during the growth of the film. XPS results showed that amorphous TiO 2 , as well as titanium oxynitride, was present on the TiN surface. The spectra of Ti-2p, N-1s, O-1s and Cu-2p before and after the film being sputter etched through the entire film region were also discussed.

Phase transformation in chromium nitride films

The phase transformation of CrN films prepared on (100) Si substrates by cathodic arc plasma deposition was investigated at various temperatures using x-ray diffraction and stress measurements. The films were annealed in a N2/H2=9 reducing atmosphere over the temperature range of 300–1200 °C. X-ray diffraction results showed that an additional Cr2N phase appeared both at temperatures above 1100 °C and over temperatures between 500 and 650 °C. Thermodynamics can explain the formation of Cr2N at temperatures above 1100 °C but not that in the low temperature range. Nevertheless, the residual stresses in the films were determined and found to be relaxed largely over such a low temperature range. The stress states of the films were strongly correlated to the phase transformation of the films. It is concluded that the formation of Cr2N at such low temperatures is mainly due to a nonthermodynamic factor—large stress relaxation occurring in the films. More experimental proof of the stress relaxation-induced phase...

Phase transformations in copper oxide nanowiresa)

Cu nanowires were electrodeposited into the nanopores of self-ordered aluminum oxide films. CuO and Cu2O nanowires were fabricated by oxidizing Cu nanowires in air. Cu nanowires oxidized at 250°C transform only to Cu2O (grain size ∼21nm), they transform to a mixture of CuO and Cu2O above 350°C and finally to CuO with a preferred orientation of CuO (111) at 900°C.

The degradation of TiN films on Cu substrates at high temperature under controlled atmosphere

Abstract This research employed TiN as a model system to study the degradation of ceramic films at high temperature under controlled atmosphere. The TiN films were prepared on Cu substrates by a cathodic arc plasma deposition technique. The degradation of TiN films on the Cu substrates at high temperature under controlled atmosphere was investigated using X-ray photoelectron spectroscopy and scanning electron microscopy/energy dispersive spectroscopy. Annealing was performed in the flowing gases including air, nitrogen, argon, and N2/H2=9 gas mixtures, which possess different nitrogen and oxygen partial pressures. The degradation of the films at high temperature results mainly in color changes associated with the presence of TiO2 and formation of thermally induced fracture of the films. The degradation diagrams at various annealing temperatures and times in the controlled atmosphere were successfully generated. The driving force of the oxidation, i.e. the Gibbs free energy change for TiN and TiO2, was discussed. The thermal stress which induced the fracture of the film was also analyzed.

Effect of metal vapor vacuum arc Cr-implanted interlayers on the microstructure of CrN film on silicon

c Abstract The effect of metal vapor vacuum arc (MEVVA) Cr-implanted interlayers on the microstructure of CrN films on the silicon wafer was investigated.Two types of the CrN-coated specimens (CrNySi and CrNyCrySi) by cathodic arc plasma deposition were prepared with and without a MEVVA Cr-implanted interlayer.The diffraction patterns of the coated specimens revealed the presence of CrN, and the (220) preferred orientation for both CrNySi and CrNyCrNySi.The CrN coating thicknesses for CrN y Si and for CrNyCrySi were 0.3 mm and 1.3 mm, respectively.Secondary ion mass spectrometry proved the high quality of the films on silicon substrates.Transmission electron microscopy micrographs and selective area diffractions revealed the presence of a large number of nano-scale Cr resulting from the interlayer of MEVVA Cr with a background of single crystal silicon spots. Furthermore, in situ stress measurement demonstrated that the presence of a Cr interlayer between CrN and Si could drastically reduce the residual stress in the CrNyCrySi assembly. 2003 Elsevier Science B.V. All rights reserved.

Stress relaxation-induced phase transformation in chromium nitride films

Chromium nitride (CrN) films have been widely used as tribological coatings and also in the electronics industry, because of their high hardness (Hv 1090) and low resistivity (640 μ -cm) [1]. Although the oxidation of CrN films has been investigated extensively, the phase transformation of CrN to Cr2N has seldom been studied [2–6]. Lai and Wu [2] stated that the Cr2N phase was generated in CrN films annealed at 1150 ◦C in N2 and vacuum (pO2 = 1.3 × 10−3 Pa) conditions. Heau et al. [3] indicated that Cr2N was present in CrN films annealed above 327 ◦C in vacuum (pO2 = 10−3 Pa). Almer et al. [4] reported that CrN transformed to Cr2N between 450 ◦C and 550 ◦C in Ar, and interpreted the phase transformation as tending toward the equilibrium CrN-Cr2N phase fraction within the nitrogen-deficient CrN phase. Hsieh et al. [5] showed that the Cr2N phase appeared in CrN films over temperatures from 500 ◦C to 800 ◦C. The authors’ previous work [6] proposed that a non-thermodynamic factor governs the phase transformation of CrN in a low temperature range. This work determines the residual stresses of the films at different temperatures and then correlates these values to phase transformation. More experimental evidence is also presented to validate the proposed mechanism of phase transformation at low temperatures. (100) p-type Si wafers (Toshiba Ceramics Co., Ltd.) were used as substrates. CrN films were deposited directly onto the substrates by cathodic arc plasma deposition. Before deposition, the chamber was pumped down to a pressure of 6.7 × 10−3 Pa. The bias and the current of the substrate were maintained at −150 V and 60 A, respectively, under a pN2 of 3 Pa during deposition. The deposition time was 30 min and the corresponding thickness of the films was about 1 μm. After deposition, the films were annealed at temperatures between 450 ◦C and 900 ◦C under a reducing atmosphere of N2/H2 = 9 for 2 h, in a gas-tight tube furnace equipped with an oxygen sensor (15% CaOdoped ZrO2) that was used to monitor and ensure a low oxygen level in the flowing gas. Changes in the crystal structure of the films after annealing, were examined by X-ray diffraction (MacScience MXP3, λCu,Kα = 0.154 nm) operated at 40 kV and 30 mA. The collection interval was 0.02 ◦ (2θ mode) and the scanning rate was 5 ◦/min. The residual stress was measured by the scanning laser curvature

Aluminum nitride films synthesized by dual ion beam sputtering

Aluminum nitride films were deposited by varying the voltages of argon ion beams from 400 to 1200 V in dual ion beam sputtering. The crystal structure, microstructure, and elemental distributions of the aluminum nitride films were analyzed by x-ray diffraction, field emission scanning electron microscopy, and secondary ion mass spectroscopy, respectively. The aluminum nitride films exhibited the 〈002〉 preferred orientation at an optimal ion beam voltage of 800 V. The orientation changed to a mixture of {100} and {002} planes above 800 V, accounting for radiation damage. The thickness of the film increases with increasing ion beam voltage, reaching a steady state value of 210 nm at an ion beam voltage of 1200 V. Under optimal condition (800 V), the c-axis orientation of the aluminum nitride 〈002〉 film was obtained with a dense and high-quality crystal structure.