Abstract Aluminum Nitride Films Research Articles

Substrate Heating Effect on c-Axis Texture and Piezoelectric Properties of AlN Thin Films Deposited by Unbalanced Magnetron Sputtering

Aluminum nitride (AlN) thin films with highly preferred (002) orientations have been reactively deposited by a pulsed-closed field unbalanced magnetron sputtering system using TiN/Ti as the seed/adhesion layer with various substrate temperatures. The texture, orientation and piezoelectric properties of AlN films were characterized by means of x-ray diffraction, rocking curves and laser interferometry. A Michelson laser interferometer was designed and built to obtain the converse piezoelectric response of the deposited AlN thin films. It was found that a slight substrate temperature increase would significantly affect the (002) orientation and the piezoelectric coefficient of AlN thin films compared to the coating obtained with no intentional substrate heating, while higher temperature applications on substrate deteriorated the c-axis texture of the coatings without significant improvement in the piezoelectric response of AlN films.

Fabrication of Aluminum Nitride Films by Reactive Pulse DC Magnetron Sputtering for Vibration Energy Harvester

Aluminum nitride (AlN) film as a piezoelectric material has been used widely, particularly in vibration energy harvester due to its unique and enhanced properties such as high temperature resistance and compatibility with CMOS processes. In this work, AlN film with (002) preferred orientation was prepared on silicon wafers by pulse DC reactive magnetron sputtering (RMS), and the properties such as peak intensity, full width at half maximum (FWHM) and surface morphology were investigated by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The preferred orientation was found to be sensitive to deposition conditions such as gas flow rate, power, bottom electrodes materials and substrates temperature. The results shows that the intensity was 1.1×105 counts, the FWHM was 1.9owhen the temperature was 260°C. The film was used to fabricate the vibrated energy harvester successful and the power density reached about 3000uW/cm3 at the vibration frequency under 1g acceleration.

Deposition and characterization of AlN thin films obtained by radio frequency reactive magnetron sputtering

Aluminum nitride (AlN) thin films were deposited by reactive radio frequency magnetron sputtering from pure aluminum target, onto Si (100), ultra dense flat carbon, and quartz. Series of samples were obtained varying the Ar and N2 gaseous mixture. The characterizations performed were Fourier transform infrared (FTIR), X-ray diffraction, high resolution transmission electron microscopy, visible optical absorption, Rutherford backscattering spectrometry, and residual stress measurements by Stoney’s equation. In this paper we report on the Ar/N2 ratio needed to produce preferential (002) AlN growth. Correlations between X-ray diffraction and FTIR are made for highly oriented (002) AlN films.

Structure and electrical properties of AlN films prepared on PZT films by the DC reactive magnetron sputtering

Aluminum nitride (AlN) films were deposited by DC reactive magnetron sputtering on the (111)-orientated Lead zirconate titanate (PZT) films. The heterostructures was characterized by x-ray diffraction and atomic force microscopy. The results showed that the AlN films reasonably textured in (002) orientation and revealed good interface quality with root-mean-square values of about 7.9 nm. The scanning electron microscopy images showed that the AlN films grown on PZT layer revealed an obvious and quite uniform columnar structure, and there was a clear interface between AlN and PZT films. MIF (Metal-Insulator-Ferroelectric) structures were fabricated and electrically evaluated by C-V (capacitance-voltage) and I-V (current-voltage) measurements at high frequency (1 MHz). The results obtained from C-V curves indicated that the MIF capacitor was consistent with the traditional Al-SiO2-Si capacitor. The current-voltage curves of AlN/PZT heterostructure showed a good insulating characteristic.

Performance Optimization of AIN Films Using Self-Prepared AIN Target

Aluminum nitride (AlN) films were prepared by radio frequency (RF) sputtering technique with self-prepared AlN ceramic target. The influence of substrate type and working gas of different N2 concentration to performance of AlN films were discussed. Microstructures of the films have been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). And, the optical properties have been revealed by diffuse reflection spectrum (DRS). The optimized process to prepare AlN film of single orientation (100) was as follows: deposited on Si (100) substrate and 25% N2 concentration, 250W-300W sputtering power and 90min sputtering time, respectively.

Influence of Sputter Deposition Time on the Growth of c-Axis Oriented AlN/Si Thin Films for Microelectronic Application

Aluminum Nitride films were grown on and Si (100) substrate by D.C. reactive magnetron sputtering at room temperature. Influence of sputter deposition time on properties of the AlN films was studied. Structural optical and electrical properties of the film were investigated. XRD measurements showed the presence of hexagonal wurtzite structure. The optical reflectance spectra of the film were taken and the band gap calculated varied from 4.35 to 5.3 eV. Finally MIS capacitors were fabricated on silicon substrates and variation of dielectric parameter with deposition time was reported.

Optical properties and residual stress in aluminum nitride films prepared by alternating-current dual reactive magnetron sputtering

Aluminum nitride films were deposited by alternating-current dual reactive magnetron sputtering. The influence of different nitrogen flow and working pressures at a sputtering power of 5 kW on the refractive index, extinction coefficient, crystalline structure, residual stress, and surface roughness of aluminum nitride films was discussed. The aluminum nitride film would have high refractive index, low extinction coefficient and small residual stress at suitable nitrogen flow rate and low working pressure.

CMOS-compatible light-emitting devices based on thin aluminum nitride film containing Al nanocrystals

Aluminum nitride (AlN) films have attractive physical properties, such as wide bandgap (6.2 eV), high thermal conductivity (320 W/mK), and good match of both thermal expansion coefficient and lattice constant to those of Si substrate . Based on these properties, AlN films can be applied in surface acoustic wave (SAW) devices, memories devices, and optoelectronic devices. It has been reported in our recent studies that amorphous AlN thin films containing aluminum nanocrystals (nc-Al) deposited on Si substrate by radio-frequency (rf) magnetron sputtering possess memory effect and exhibit interesting current conduction behaviors.

Low temperature growth of c-axis oriented AlN films on γ-LiAlO2 by radio frequency magnetron sputtering

Aluminum nitride (AlN) films were prepared on gamma-LiAlO2 substrates by radio frequency (rf) magnetron sputtering. The influence of substrate temperature (T-s) and nitrogen (N-2) concentration on film growth was investigated. The X-ray diffraction (XRD) results reveal that highly c-axis oriented AlN films can be obtained in the temperature range from room temperature (RT) to 300 degrees C. A smoother surface and a crystalline quality decrease with increasing N-2 concentration have been observed by XRD and atomic force microscopy (AFM) for the films deposited at lower substrate temperature. On the contrary, the degradation of the surface smoothness and the higher crystalline quality can be observed for the films deposited at a higher substrate temperature with N-2-rich ambient. The growth mechanism which leads to different crystalline quality of the films is discussed. (C) 2008 Elsevier B.V. All rights reserved.

Cracking of Aluminum Nitride Film on Stainless Steel Substrate at Elevated Temperature

Aluminum nitride (AlN) thin films formed on the heat-resistant alloy substrates were heated to 1100K. Cracking was observed in the AlN film formed on the stainless steel substrate (SUS430), while no crack was seen in that on the nickel-base superalloy substrate (IN750X). The electrical impedance measurements, X-ray diffraction analysis and finite element method calculation have been conducted to discuss the relationship between the cracking and the stress introduced into the AlN films. The AlN film cracking would be significantly affected by grain refinement of AlN.

PREFERENTIAL ORIENTATION GROWTH OF AlN THIN FILMS ON Si (111) SUBSTRATES BY LP-MOCVD

Aluminum nitride ( AlN ) thin films were deposited on Si (111) substrates by low pressure metalorganic chemical vapor deposition system. The effects of the V/III ratios on the film structure and surface morphology were systematically studied. The chemical states and vibration modes of AlN films were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectrometer. The optical absorption property of the AlN films, characterized by ultraviolet-visible-near infrared spectrophotometer, exhibited a sharp absorption near the wavelength of 206 nm. The AlN (002) preferential orientation growth was obtained at the V/III ratio of 10,000 and the preferential growth mechanism is presented in this paper according to the thermodynamics and kinetics process of the AlN growth.

Influences of laser energy density and annealing on structure properties of AIN films prepared by pulsed laser deposition

Aluminum nitride (AlN) films with h crystalline orientation are fabricated on p-Si (100) substrates at room temperature by pulsed laser deposition. The effects of laser energy density and annealing on the quality of the films are studied by x-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The crystalline quality of AlN films is improved considerably by increasing the laser energy density while there is increased number of farraginous particles on the surface. The annealing treatment at 600°C produces a recrystallization process in the film, characterized by the improvement of the original crystallinity, the appearance of new crystalline orientations, and the increase of the crystallites. The surface becomes rougher due to the increase of the grain size during annealing.

Growth of AlN Films by Hot-Wall CVD and Sublimation Techniques: Effect of Growth Cell Pressure

Aluminum nitride (AlN) films were grown on off-axis, Si-terminated 4H-SiC substrates by hot-wall CVD and sublimation techniques. The films were investigated by Infrared reflectance, Optical microscopy, Energy Dispersive X-ray analysis and Cathodoluminescence in a Scanning Electron Microscope with respect to their thickness, morphological, compositional and luminescence properties, in order to examine the influence of the growth cell pressure in either of the two deposition methods. Good quality thick AlN films were obtained by hot-wall CVD at temperature of 1200degreesC and reduced pressure of 100 mbar as reflected in the near stoichiometric N/Al ratio in these layers and in the appearance of the characteristic AlN near band edge emission. The AlN sublimation grown films at temperature of 2100degreesC suffered from island growth irrespective of the background pressure. The supersaturation conditions that affect strongly the growth mode became more favorable when the temperature was reduced to 1900degreesC.

Near Bandedge Cathodoluminescence Studies of AlN Films: Dependence on MBE Growth Conditions

Aluminum nitride films were grown by molecular beam epitaxy on sapphire (0001) substrates. In some samples, alternating GaN/AlN thin layers were incorporated prior to the deposition of the main AlN layer in an effort to possibly reduce defects. The cathodoluminescence spectra show a sharp bandedge peak, which we tentatively assign to the optical recombination of a donor bound exciton (D 0 ,X), sometimes accompanied by weak one- and two-longitudinal optical phonon replicas. There is also a broad band with maxima in the range 3200-3700 A. A large value for the ratio (D 0 ,X)/(broad band) tends to be associated with a narrow (D 0 ,X) linewidth.

Changes in optical transmittance and surface morphology of AlN thin films exposed to atmosphere

Aluminum nitride (AlN) thin films have been prepared by the ion-beam assisted deposition (IBAD) method, and the influence of exposure to different atmosphere on optical transmittance and surface morphology has been studied. AlN films have been prepared with the nitrogen ion beam energy of 0.1, 0.2, or 1.5 keV. Synthesized films have been exposed to the following conditions: (i) laboratory air (RT and 40–60% RH), (ii) saturated humidity air (RT and 80–90% RH), and (iii) elevated temperature air (100 °C and 10–20% RH). Optical transmission spectrum in the wavelength region from 190 to 2200 nm has been measured by a UV-visible spectrometer every week. Surface morphology of the films has been observed with an optical microscope (OM), and phase identification has been performed by thin film x-ray diffraction (TFXRD). The optical transmittance has not changed drastically after exposure both to the laboratory air and the saturated humidity air for 60 weeks and after exposure to the elevated temperature air for 48 weeks. Observations by OM showed that round-shaped substances were formed on the film surfaces after exposure to the atmosphere, and the size of the substances on the film surface exposed to saturated humidity air is much larger than those on the surface exposed to other atmosphere. The results of TFXRD revealed that the AlN diffraction peaks have gradually decreased with exposure time, but any new phase due to reaction products has not been detected for the samples exposed to the laboratory air, the saturated humidity air, or the elevated temperature air. From the present results, it is concluded that the IBAD AlN films can be applied in low humidity air without losing high transparency up to 60 weeks, and the films prepared with 1.5 keV ion beam show better durability than the films prepared with 0.1 or 0.2 keV ion beam for exposure to the saturated humidity air.

Epitaxial growth of aluminum nitride thin films on (111) si by ecr dual ion beam sputtering

Aluminum nitride (AIN) thin films grown on silicon substrates are very promising materials for GHz-band bulk and surface acoustic wave (SAW) devices with monolithic circuits because of their high acoustic velocity and piezoelectricity, as well as their passivation and insulating properties. Epitaxial growth techniques for AIN films with high crystallinity and a smooth surface are very important for these applications.

Columnar microstructures of preferred oriented Aluminum Nitride films prepared by reactive sputtering

Aluminum nitride (AIN) thin films have drawn much attention as piezoelectric materials for generation and detection of surface acoustic wave (SAW) owing to high ultrasonic velocity and fairly large piezoelectric coupling factors. Since the piezoelectric properties are strongly dependent upon the c-axis orientation of AIN films, it is important to control the crystallographic orientation with deposition parameters. Though many reports have been presented, the mechanism of crystallographic orientation change with deposition parameters still remains unknown and the microstructure analysis of AIN films have been scarcely carried out. In this paper, we present the effect of sputtering pressure on thecrystallographic orientation and the microstruclure of the deposited AIN films, using X-ray diffraction (XRD) and transmission electron microscopy (TEM) study.AIN films have been deposited on Si (100) wafers by reactive RF magnetron sputtering in Ar-N2 gas mixture without substrate heating. The base pressure of vacuum chamber was below 1.5X10-6 Torr, RF power was 200 W and the ratio of gas flow rate (Ar:N2) was 3:1. Processing pressures ranged from 5 to 12 mTorr. Crystal structure of as-deposited films examined with XRD (Rigaku, D/MAX-RC, 12 kW) and microstructure analyses were carried out using crosssectional and plan-view TEM (JEOL 4000FX, 400 kV).