A1N Films Research Articles

Influence of technological regimes of plasma chemical deposition on texture formation in aluminum nitride films

Textured polycrystalline aluminum nitride films were grown by magnetron sputtering of an aluminum target in a mixture of argon and nitrogen, followed by the formation of a film on sitall substrates. The influence of the pressure of the working gases, the power dissipated on the target, and the ratio of the Ar / N2 gas fluxes on the texture of the aluminum nitride films are investigated. The phase composition and degree of crystallinity of the obtained films were determined using scanning electron microscopy and X-ray diffraction. The results of studies of the phase composition and parameters of the crystal structure of aluminum nitride films are presented: the size of the coherent scattering regions, the predominant orientation of the crystallites in the growing film, and the degree of crystallinity. It is noted that the films are predominantly oriented along the (111) and (002) planes. The degree of crystallinity of the A1N films varied from 10 to 30% depending on the conditions of the deposition process. The relative microdeformation of the lattice (Δd/d), depending on the parameters, ranged from 1.7·10−3 to 6.9·10−3. The size of the crystallites is affected by the microdeformation of the lattice, with its increase by 4 times, the size of the crystallites decreased by 3.6 times from 29 to 8 nm.

712 AlCrN/AlN複合表面改質によるAl合金製摺動部品の高機能化(OS7-(3),OS7 オーガナイズドセッション《精密/微細加工と評価》)

In recent years, Aluminum alloy has been widely used because of their lightweight and easy adaptability for recycling. However, aluminum alloy has poor wear resistance. Therefore, it is necessary to improve this property to use aluminum alloys for machine parts. Aluminum chromium nitride (AlCrN) coating and Aluminum nitride (AlN) coating, which is high hardness and excellent wear resistance was performed. In this study presents an investigation of the influence of the tribological of hardness control AlCrN and A1N films on A7075 alloy substrates using Unbalanced Magnetron Sputtering (UBMS). A7075 alloy coated AlCrN films and AlN films indicated excellent tribological properties.

Two-dimensional analysis of spurious modes in aluminum nitride film resonators

In this paper, a hybrid method, which combines the traditional concept of guided waves and the finite element method (FEM), is proposed to analyze the spurious modes of aluminum nitride (AIN) film with electrodes. First, the guided wave modes in the plated area are obtained by 1-D FEM. Second, a mode-match method is used to satisfy the boundary conditions. The vibration of the film resonator is a superposition of all of the guided modes. With respect to an A1N film resonator, which is a thickness-stretch mode resonator, we have identified three families of spurious modes: extension, thickness-stretch, and thickness-shear. The spectrum of spurious modes is calculated and the influence of the spurious modes is discussed.

Effect of periods on wear performance of TiN/AlN superlattice films

In this study, the TiN/AlN superlattice films were prepared using a newly developed high-rate reactive sputtering set-up, which featured an unbalanced and a balanced magnetron sputtering system. The former was employed to deposit the A1N film, and the latter the TiN film. The aim of this study was to obtain, through controlling the deposition conditions, a group of TiN/AlN superlattice films with various periods, and then to investigate the influence of periods on their fundamental properties and wear behavior. The results revealed that the TiN/AlN superlattice films with periods ranging from 2.4 to 67.6 nm were obtained. At periods ≦ 3.6 nm, the films had extremely high hardness, excellent adhesion and wear performance, as compared with the traditional single-layer TiN film.

Piezoelectric Aluminum Nitride Films Deposited by Triode Sputtering for Surface Acoustic Wave Devices

Aluminum nitride (A1N) thin films have been widely used in various applications due to their excellent properties such as chemical stability, electrical isolation, high acoustic wave velocity and large electromechanical coupling coefficient. For surface acoustic wave(SAW) applications, structures having A1N films on high acoustic velocity substrates such as diamond or sapphire offer much interest in forming high frequency SAW devices with phase velocities greater than 10000m/s. In this study, A1N films have been deposited on (001) sapphire and (100) silicon substrates by triode sputtering at low temperature in argon-nitrogen gas mixture. The crystal orientation, stoechiometry, optical acoustic and electrical properties were investigated. Dense AIN layers with very high electrical resistivity were obtained at high deposition rates. SAW filters were formed by development of interdigital transducers on the A1N/Silicon and A1N/Sapphire structures. The phase velocity was measured by a network analyzer as a function of A1N film thickness and substrate type.

Ain Films Grown by Electric Field Induced Flux of al Cations

The properties of aluminum nitride (A1N) make it an interesting material for applications in the microelectronics industry. These properties include: a large bandgap, good thermal conductivity, high-temperature stability and chemical inertness. Additionally, thin A1N films are used as buffer layers for the growth of GaN on alumina. In the present study, thin-films of A1N have been grown on (000l)-oriented α-Al2O3 through the use of an electric field. At elevated temperatures an electric field applied across a normally insulating oxide material will typically induce a flux of ions that carry current. In the case of Al2O3, since the more mobile species are the Al3+ cations, by applying an electric-field across the material, with an appropriate electrode material, a flux of 3+ cations can be induced toward the cathode surface (negative electrode).

AIN heteroepitaxial and oriented films grown on (111), (110) and (100) natural diamond faces

Abstract CVD growth of A1N thin films on (100), (110) and (111) diamond Cα substrates was observed, and RHEED and EPMP were used to provide the evidence of growth of epitaxial (01 · 1) [11 · 3] A1N//(111) [110] Cα or oriented wurtzitic A1N on (111) diamond. Twinning in A1N films on (111) Cα, was found. In the case of the (111) substrate, it was shown that in starting from a 0.4 μm film thickness, a conversion of epitaxial growth to a growth texture with a [00 · 1] axis normal to substrate takes place. The same textures were observed on both (100) and (110) diamond faces for 0.2–0.3 μm and greater film thickness. For an A1N thickness of about 1 μm, the crystallite size near outer A1N film surface was 10–20 nm.

The effect of the III/V ratio and substrate temperature on the morphology and properties of GaN- and AlN-layers grown by molecular beam epitaxy on Si(1 1 1)

We have studied the effect of the III/V ratio and substrate temperature on the growth of GaN and A1N films on Si(1 1 1) substrates by molecular beam epitaxy, where active nitrogen was generated by a radio frequency plasma source. In the case of GaN, two distinct regimes of growth (Ga-rich and N-rich conditions) lead to different crystal morphologies and luminescence properties. Scanning electron micrographs of the cleaved edges of films grown under highly N-rich conditions reveal columnar features, while growth under Ga-excess results in compact layers. The lowtemperature photoluminescence associated with the N-rich films is dominated by intense and narrow exciton lines, with peaks having full-width at half-maximum of less than 2 meV, whereas the Ga-rich films exhibit weaker and broader emissions. For increasing substrate temperatures above 700°C, stoichiometry is reached at higher Ga/N ratios, pointing to an enhancement of Ga desorption characterized by an activation energy of 2.5 eV. A similar study of A1N films shows that the desorption of A1 in terms of growth rate is not relevant for the substrate temperature range studied (850–920°C). III/V ratios close to the stoichiometric value and substrate temperatures above 900°C lead to high-quality A1N layers on Si(l 1 1) substrates. Complete relaxation is reached, for both GaN and A1N, in films with thicknesses well below 1 μm.

Comparative study of the elastic properties of polycrystalline aluminum nitride films on silicon by Brillouin light scattering

Brillouin light scattering (BLS) has been used to investigate the elastic properties of polycrystalline AIN films, about 1 μm thick, grown by DC-reactive magnetron sputtering on Si 3N 4 coated (100)-Si substrates. Taking advantage from the detection of a number of different acoustic modes, a complete elastic characterization of the films has been achieved. The elastic constants c 11 and c 66 have been selectively determined from detection of the longitudinal and of the shear horizontal bulk modes, respectively, travelling parallel to the film surface. The three remaining elastic constants, namely c 44, c 33 and c 13, have been obtained from detection of the Rayleigh surface wave and of the longitudinal bulk wave propagating at different angles from the surface normal. The values of the elastic constants of these sputtered AIN films depend on the deposition conditions and on the microstructural properties of the films, especially oxygen contamination and quality of texture. In the case of the films with the best degree of texture and the lowest oxygen content, the values of the elastic constants are rather close to those previously determined in epitaxial A1N films grown at high temperature by MOCVD. This demonstrates that sputter deposition at relatively low temperature can be used to grow high quality A1N films on Si and is of great importance in view of the integration of these films in the technology of IC semiconductors.

In Situ Nitride Growth Studies by Low Energy Electron Microscopy (LEEM) and Low Energy Electron Diffraction (LEED)

Abstract Nitride films play an increasing role in modern electronics, for example silicon nitride as insulating layer in Si-based devices or GaN in blue light emitting diodes and lasers. For this reason they have been the subject of many ex situ electron microscopic studies. A much deeper understanding of the growth of these important materials can be obtained by in situ studies. Although these could be done by SEM, LEEM combined with LEED is much better suited because of its excellent surface sensitivity and diffraction contrast. We have in the past studied the high temperture nitridation of Si(l11) by ammonia (NH3)and the growth of GaN and A1N films on Si(l11) and 6H-SiC(0001) by depositing Ga and Al in the presence of NH3 and will report some of the results of this work for comparison with more recent work using atomic nitrogen instead of NH3.

Influence of AIN protective film thickness on the hardness and electrophotographic properties of organic photoconductors

The deposition of a protective film to increase the hardness of an organic photoconductor (OPC) surface is an effective method to lengthen the lifetime of the OPC. In this work, A1N protective films were deposited onto OPC samples by rf reactive magnetron sputtering with low substrate temperature. The A1N films were deposited with optimized sputtering conditions and exhibited very high transmissivity in the visible wavelength range 300-800 nm. The films caused a remarkable increase in the hardness of the OPC surface, by between 32 and 62%. The acceptance voltage, dark decay rate, photodischarge rate, difference between the residual potential and the acceptance voltage of the OPC protected by A1N film were improved. These results show A1N is a suitable protective film for OPC.

Role of interfacial-charge in the growth of GaN on α-SiC

The growth of GaN and A1N films on (0001) substrates of 6H-SiC has produced high-quality opto-electronic films. The SiC surface at the interface with GaN or A1N is either Si-terminated or C-terminated, and the Si-terminated interface is known to be the better substrate, producing higher-quality films. The polarity of the interface is important, as recognized by Sasaki and Matsuoka. We propose that the main relevant parameter for characterizing the interface and its potential for producing high-quality opto-electronic GaN or A1N films is the interfacial charge, which leads to the best films when the charge is positive and relatively large. The positive charge reduces the size of the Nions at the interface and hence improves the local lattice match. (The charges are approximately −0.45 lei and +0.55 lei on the interfacial N and Si atoms, respectively.) Therefore, while the polarity of the interface is important, the polarity's effect on the local lattice mismatch is what leads to a high-quality interface. These ideas are consistent with XPS data and are supported by electronegativity arguments, by calculations for ordinary mono-bonded GaN/SiC superlattices (with N-Si and Ga-C interfaces) and by computations for superlattices with tri-bonded interfaces. We predict that the tri-bonded N-Si interface of GaN/SiC should produce excellent GaN and AIN films.

Effect of nitrogen gas pressure on residual stress in A1N films deposited by the planar magnetron sputtering system

The crystal orientation and residual stress development in A1N films deposited on borosilicate (BLC) glass substrates were investigated by X-ray diffraction. Deposition was performed using two kinds of planar magnetron sputtering system: a conventional system (CPM system) and a special system with two facing targets (FTPM system). The nitrogen gas pressure ( P N) was varied over a suitable range for each system. The diffraction patterns of the AlN films showed that the c-axis orientation was improved when the films were deposited using the CPM system at a nitrogen gas pressure lower than 1 Pa. For the CPM system, compressive residual stress was found in films deposited at P N≤2 Pa and tensile residual stress at P N>2 Pa. For the FTPM system, tensile residual stress was found in films deposited at P N≤0.8 Pa and compressive residual stress at P N>0.8 Pa.

Comparison of the Microstructure of AlN Films Grown by MOCVD and by PLD on Sapphire Substrates

ABSTRACT(0001) aluminium nitride thin films were grown epitaxially on (0001) Sapphire substrates by MOCVD at 1200° C and PLD at 800° C. Both films have the same epitaxial growth relationship: (0001)AlN//(0001)Sap, and the same in-plane relationship which shows a 30° rotation between A1N and Sapphire: [ 12 10]AlN//[0 110]Sap and [10 10]AlN //[ 2110]Sap. The full width at half maximum (FWHM) of x-ray rocking curve of the MOCVD A1N film was 0.16° and PLD A1N film was 0.2°. Films grown by both MOCVD and PLD showed high crystalline quality. HRTEM images showed that these films are single crystalline with very low density of defects.Dislocations in the film parallel to the film / substrate interface were observed in both A1N films. Atomic force microscopy images showed that the MOCVD films have flatter and larger terraces than the PLD films. The PLD technique for A1N growth needs to be improved further. But both films have a surface roughness of approximately 100nm.

The Influence of Hydrogen Addition on the Chemical Properties of Hydrogenated Aluminum Nitride Films Prepared by RF Reactive Sputtering

ABSTRACTHydrogenated aluminum nitride (A1N:H) films have been deposited on the (100) silicon wafers by the RF reactive magnetron sputtering method with H2 gas in addition to an Ar-N2 gas mixture. Stoichiometric A1N films without oxygen impurities can be prepared by adding 10 % H2 to reactive gas, which is proven by Rutherford Backscattering Spectrometry (RBS). The bonding aspects of Al, N, O and H atoms in A1N:H films have been examined by X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared (FTIR) to understand the effects of H2 addition. The chemical shift of the binding energies of A1, N and O atoms in A1N:H films from XPS analysis and the change of N-H bonding in FTIR with respect to different partial pressures of H2 gas have been confirmed. The role of H atoms is suggested to facilitate bonding with unbound N atoms in A1N:H films and hinder N-O bonding, thus, reducing oxygen concentration in A1N:H films. Also, the activation energy for the evolution of H2 gas from A1N:H film has been determined to be 0.11 eV/atom through a Kissinger-type analysis by a thermal desorption test using Gas Chromatograph(GC). This result implies that the hydrogen atom in film forms the hydrogen bond.

Formation and High Frequency CV-Measurements of Aluminum / Aluminum Nitride / 6H Silicon Carbide Structures

AbstractUndoped single crystalline aluminum nitride films were grown by metal organic chemical vapor deposition (MOCVD) at 1200 °C. The precursors used were trimethylaluminium (TMA) and ammonia (NH3) in a hydrogen carrier flow, at a pressure of 10 Torr. Silicon carbide substrates of the 4H or the 6H polytype with an epilayer on the silicon face, were used to grow the 200 nm thick A1N films. Aluminum was evaporated and subsequently patterned to form MIS capacitors for high frequency (400 kHz) capacitance voltage measurements at room temperature. It was possible to measure the structure and characterize accumulation, depletion and deep depletion. However, it was not possible to invert the low doped SiC epilayer at room temperature. From an independent optical thickness measurement the relative dielectric constant of aluminum nitride was calculated to be 8.4. The films were stressed up to 50 Volts (2.5 MV/cm) without breakdown or excessive leakage currents. These results indicate the possibility to replace silicon dioxide with aluminum nitride in SiC field effect transistors.

Effect of ion beam energy on the synthesis of oriented aluminium nitride thin films

Polycrystalline aluminium nitride (A1N) thin films were synthesized by evaporation of aluminium and simultaneous irradiation with nitrogen ions, ion-beam assisted deposition, and the effect of the ion beam energy on the film microstructure was studied. The substrate was single-crystal Si(100), and the substrate temperature was varied from room temperature to 573 K. The kinetic energy of the nitrogen ion beam was varied from 0.05 keV to 0.5 keV. The structure of the A1N thin films was examined by X-ray diffraction (XRD). From the XRD patterns, it is found that (1) the (00•2) plane of hexagonal A1N grows preferentially with an ion beam energy of 0.05 keV (the c -axis oriented structure) independently of the substrate temperature, (2) the intensity of the lines (10•0) and (10•1) becomes stronger with increasing ion beam energy, and (3) the full width at half maximum of the (00•2) diffraction line tends to narrow with decreasing ion beam energy and increasing substrate temperature. The present results show that the ion beam energy plays an important role in the degree of preferred orientation of A1N films and c -axis oriented films can be synthesized at room temperature by controlling the ion beam energy.

Effect of ion beam energy on the synthesis of oriented aluminium nitride thin films

Polycrystalline aluminium nitride (A1N) thin films were synthesized by evaporation of aluminium and simultaneous irradiation with nitrogen ions, ion-beam assisted deposition, and the effect of the ion beam energy on the film microstructure was studied. The substrate was single-crystal Si(100), and the substrate temperature was varied from room temperature to 573 K. The kinetic energy of the nitrogen ion beam was varied from 0.05 keV to 0.5 keV. The structure of the A1N thin films was examined by X-ray diffraction (XRD). From the XRD patterns, it is found that (1) the (00•2) plane of hexagonal A1N grows preferentially with an ion beam energy of 0.05 keV (the c-axis oriented structure) independently of the substrate temperature, (2) the intensity of the lines (10•0) and (10•1) becomes stronger with increasing ion beam energy, and (3) the full width at half maximum of the (00•2) diffraction line tends to narrow with decreasing ion beam energy and increasing substrate temperature. The present results show that the ion beam energy plays an important role in the degree of preferred orientation of A1N films and c-axis oriented films can be synthesized at room temperature by controlling the ion beam energy.

Low-Temperature (< 100°C) Growth of Ain by Ion Beam Assisted Deposition+

AbstractDuring the past few years, there has been growing interest in aluminum nitride (A1N) thin films because of their excellent optical, electrical, chemical, mechanical and high-temperature properties. Ion beam assisted deposition (IBAD) was used to deposit A1N films on flat and curved substrates, including Si, SIMOX, sapphire, quartz, aluminum, stainless steel, and carbon, at temperatures substantially below 100°C. The objective was to enhance the physical and mechanical properties of A1N film by controlling the crystal size and structures.Experimental results, as obtained by Rutherford backscattering spectroscopy (RBS) show the formation of stoichiometric A1N. Plan-view/cross-sectional transmission electron microscopy (TEM), clearly demonstrated the formation of a smooth, uniform A1N film. Electron diffraction and dark field TEM studies clearly show the growth of A1N crystallites with cubic and/or hexagonal structures and dimensions of 30 to 100A. The films are transparent and have good adhesion to all substrates. In addition to excellent high temperature (up to 1050°C measured) and chemical stability (shown through a variety of acid tests), these films have demonstrated extreme hardness, greater than two times that of bulk AIN.

A New Single Source Precursor Approach to Gallium and Aluminum Nitride

ABSTRACTSingle source precursors which contain preformed gallium-nitrogen and aluminum-nitrogen bonds are being considered for the growth of gallium and aluminum nitride because of their potential for overcoming problems associated with conventional precursors. Presented is the evaluation of dimethylgallium azide, Me2GaN3(1), bisdimethylamidogallium azide, (Me2N)2GaN3(2), and bisdimethylamidoaluminum azide, (Me2N)2AlN3(3) as potential precursors for A1N and GaN film growth. The compounds were evaluated for stability, ease of transport, temperature of decomposition and quality of film deposited. Amorphous thin films of GaN with a band gap of 3.4 eV were deposited with 2 at 250 °C. Increasing the substrate temperature to 580 °C resulted in the deposition of epitaxial GaN films. Polycrystalline A1N films were grown with 3 at 600 °C.