Deposited Boron Nitride Films Research Articles

Effects of nitrogen gas ratio on magnetron sputtering deposited boron nitride films

Transformation from h-BN (boron nitride) to fullerene-like e-BN with increasing N2 ratios (fN2, 20–33%) has been found in a radio frequency magnetron sputtering deposition by using Fourier transform infrared spectroscopy (FTIR). X-ray photoelectron spectroscopy (XPS) examination suggests that the stoichiometric e-BN molecule contains equal numbers of sp3 and sp2 bonds at fN2=33%. The surface morphology and corresponding roughness of as-deposited BN films were evaluated by Atomic force microscopy (AFM).

Effect of stored elastic energy on phase content of ion assisted deposited boron nitride films

Boron nitride films with a different amount of the cubic phase up to 40% have been prepared by radio frequency plasma assisted pulsed laser deposition. By a theoretical analysis of the film formation, which focuses on the stored elastic energy of the film, the cubic boron nitride (cBN) volume fraction experimentally observed has been modelled successfully. The comparison with the experiment shows that the change of the stored elastic energy with the cBN volume fraction determines the final cBN content in the film. The model presented predicts a window for cBN film formation depending on initial film stress. This can explain the often found tight range of process parameters for cBN film synthesis.

A New Method to Prepare Boron Nitride Thin Films

We report a new method to prepare boron nitride (BN)thin films on Si (100) substrates in anAr–N2-BCl3-H2 gas system by magnetron arc enhancedplasma chemical vapour deposition. Fourier transform infraredspectroscopy (FTIR) and x-ray diffraction (XRD) are used tocharacterize the films. The FTIR spectra show that the deposited boronnitride films experienced a transition from pure h-BN phase to acubic-containing phase with the variation of arc current ranging from10 A to 18 A. The BN film with 42% c-BN was obtained without substratebias voltage. In the gas system of Ar–N2–BCl3–H2,h-BN can be preferentially etched by chlorine. The chemical etchingeffect of chlorine allows the formation of c-BN without substrate biasvoltage, which may develop a new perspective for the deposition of highquality c-BN film with low stress.

Plasma deposition of low dielectric constant (k=2.2∼2.4) Boron Nitride on methylsilsesquioxane-based nanoporous films

The growth of low dielectric constant (k) Boron Nitride (BN) film on silicon as wel1 as methylsilsesquioxane-based nanoporous films (LKD-5109) using plasma-discharged borazine was investigated. BN films were grown using microwave plasma (2.45GHz) or radio-frequency (rf) atom beam deposition (13.56MHz) on LKD-5109 in order to evaluate the compatibility of the two plasma processes with the physical integrity of the nanoporous films. Capacitance–voltage measurements were used to characterize the dielectric constants of the films on silicon and BN-integrated LKD (keff≈2.4). The composition and phases of the films were studied using cross-section transmission electron microscopy and electron-energy-loss spectroscopy. Although the microwave plasma process could produce BCxN films with a k value of 2.2, the process was not compatible with the nanoporous LKD substrate due to the ion-induced damage of the films. We found that only the rf atom beam deposition process, which was characterized by low-energy neutral fluxes, maintained the dielectric property of the BN-integrated LKD stack at an overall value of 2.4. In addition, the deposited BN films can act as an effective copper diffusion barrier on the LKD and can be lithographically processed to form trench patterns.

Magnetic field assisted increase of growth rate and reduction of particulate incorporation in pulsed laser deposited boron nitride films

The deflection of the ions ablated from an h-BN target in inhomogeneous magnetic fields was investigated, aimed finally at the reduction of the number of particulates in pulsed laser deposited c-BN films. As a large fraction of the ablated species are ions at the high laser pulse energy densities used, the film growth rates can be significantly increased on substrates that are mounted above and sideways of the ablation area by using appropriate magnetic fields. Consequently, fewer laser pulses are needed for the deposition of films with the same thickness and the area density of particulate can be decreased.

Deposited well-crystallized cubic boron nitride films by pulsed plasma enhanced chemical vapor deposition at room temperature

The crystallized cubic boron nitride (c-BN) films have been grown on silicon (100) wafer substrate successfully at room temperature by using a pulsed plasma enhanced chemical vapor deposition technique. Infrared absorption spectra and x-ray diffraction indicate that deposited boron nitride films mainly consist of c-BN phase. The scanning electron microscopy images exhibit regular grain shapes. The mean grain size is about 500 nm. The ratio of c-BN phase to h-BN phase in the deposited thin films mainly depends on the discharging voltages that producing the pulsed plasma.

Microstructure and mechanical properties of pulsed laser deposited boron nitride films

Abstract Boron nitride films were prepared by pulsed laser ablation from a boron nitride target using a KrF-excimer laser, where the growing films were deposited in nitrogen atmosphere or bombarded by a nitrogen/argon ion beam. Films deposited without or at weak ion bombardment (such films will be called l-BN in this paper) are hexagonal with amorphous to turbostratic microstructure (l-BN) and show high adhesive strength to silicon and stainless steel substrates. By using them as intermediate layers, the adhesion of pure cubic boron nitride films (c-BN) can significantly be improved. l-BN films and l-BN/h-BN/c-BN layer systems have been investigated by in-situ ellipsometry, infrared spectroscopy and cross-section and plan-view high-resolution transmission electron microscopy, including diffraction. The mechanical properties, i.e. stress and hardness, of these films and layer systems are presented. l-BN films deposited at higher laser energy densities have compressive stresses as high as 11.5 GPa. Films deposited at lower laser energy densities have stresses in the range of 4.7 to 1.3 GPa and a Vickers hardness in the range of 18.6 to 7.5 GPa depending on substrate temperature and ion bombardment. The compressive stresses of 400 nm thick adherent c-BN films were estimated to be 4.5 GPa.

Preparation of boron nitride films by multi-source plasma CVD method

Boron nitride films were deposited from BF 3 and NH 3 gases using the multi-source plasma CVD technique. This new technique controls to activate each source gas. Each kind of source gas was introduced separately through the plasma generator. After excitation of each gas, these gases were introduced to the front of the substrate. On the other hand, widely spread sheet-like plasma generated above the substrate by dc arc-plasma gun under magnetic field also excited the gas in front of the substrate, and boron nitride film was deposited on it. Also rf power was applied between the grounded chamber and the substrate electrode during the deposition. We have investigated the effect of substrate self-bias, to accelerate ions toward the growing surface, on the structure of the boron nitride films. Deposited boron nitride films were characterized by infrared (IR) absorption spectroscopy. The results of IR absorption spectroscopy indicated the structure of the deposited boron nitride films became hexagonal at lower substrate bias. As the self-bias increased, the shape of the spectra was changed and the broad absorption band near the position of cubic boron nitride formation appeared.

Properties of pulsed laser deposited boron nitride films

Pulsed laser ablation using an excimer laser of 248 nm wavelength was applied to prepare boron nitride films, where the ablation from boron nitride as well as elemental boron targets was studied. The growing films were bombarded by a nitrogen or a nitrogen/argon ion beam to obtain stoichiometric films and to investigate ion induced modifications of structure and properties. Depending on deposition parameters the refractive index of the boron nitride films in the visible wavelength range varies between 2.5 and 1.7 and the optical energy band gap between 2.0 and 4.5 eV. Most films were found to be completely sp 2-bonded and amorphous to nanocrystalline with a turbostratic microstructure. Only boron nitride films deposited from the boron target and bombarded with nitrogen/argon ions show also an absorption peak in the infrared spectrum that indicates the presence of the cubic phase.

Diffuse Reflectance Fourier Transform Infrared Spectrometry of BN Films Deposited on Steels by Remote Microwave Plasma CVD from Borazine

The diffuse reflectance Fourier transform infrared spectra of the boron nitride (BN) films deposited on steels by remote microwave plasma chemical vapour deposition (CVD) from borazine with nitrogen, hydrogen and argon were investigated in the wavenumber range of 400-4000 cm-1. It was found that the cubic BN formation depends on production of the intermediate species of cyclotriborazane ((BH2NH2)3) and its dehydrogenation. The structural bonds of cyclotriborazane are similar to that of cubic BN. Optimum conditions for deposited BN films were found to be the borazine-nitrogen mixture at the substrate temperature of 550°C. The BN films were a mixture of crystalline cubic BN accounting for the major content and hexagonal BN with relatively low hydrogen content.

Plasma deposition of cubic boron nitride films from non-toxic material at low temperatures

Abstract Boron nitride has become the focus of a considerable amount of interest because of its properties which relate closely to those of carbon. In particular, the cubic boron nitride phase has extreme hardness and very high thermal conductivity similar to the properties of diamond. The conventional methods of synthesis use the highly toxic and inflammable gas diborane (B 2 H 6 ) as the reactant material. A study has been made of the deposition of thin films of boron nitride (BN) using non-toxic material by the plasma-assisted chemical vapour deposition technique. The source material was borane-ammonia (BH 3 -NH 3 ) which is a crystalline solid at room temperature with a high vapour pressure. The BH 3 -NH 3 vapour was decomposed in a 13.56 MHz nitrogen plasma coupled either inductively or capacitively with the system. The composition of the films was assessed by measuring their IR absorption when deposited on silicon and KBr substrates. The hexagonal (graphitic) and cubic (diamond-like) allotropes can be distinguished by their characteristic absorption bands which occur at 1365 and 780 cm −1 (hexagonal) and 1070 cm −1 (cubic). We have deposited BN films consisting of a mixture of hexagonal and cubic phases; the relative content of the cubic phase was found to be directly dependent on r.f. power and substrate bias.

BN膜の形成におよぼす原子状水素の影響

Formation and deposition processes of boron nitride (BN) films are discussed. BN films were sythesized from boran-ammonia (BH3NH3) with a 4-coordinated structure by RF plasma CVD with tungsten filament heating. The deposited BN films are structurally cubic (four-coordinated) or turbostratic (three-coordinated), which strongly depends on the tungsten filament temperature, total gas pressure and RF power. That is, BH3NH3 can be changed to both cubic and turbostratic structures.The etching rate of turbostratic BN (t-BN) increases with increasing emission intensity I(Hα) in the gas plasma, where I(Hα) is the spectral intensity at the wavelength of 656 nm corresponding to the emission from the atomic hydrogen by plasma excitement and filament heating. The atomic hydrogen causes the preferential chemical ecthing of t-BN, thus contributing greatly to the growth of cBN in the films.

Radio frequency sputter deposited boron nitride films

Thin films (∼1 μm) of boron nitride were grown on water-cooled glass, silicon, and sapphire substrates by reactive sputter deposition from a BN target in Ar, Ar/N2, and N2 discharges. The effect of sputtering gas composition on film chemical and optical behavior is reported and discussed in the present paper. The following changes occurred as the gas N2 content was increased: (1) The concentration of excess boron in the films, relative to an external standard, decreased. (2) Absorption of visible and ultraviolet radiation decreased. (3) The energy band gap increased by >2 eV. Smaller band gap values were correlated with excess boron. (4) The average B–N bond strength and the ordering of B and N atoms to form B–N bonds increased. Near stoichiometric (B/N=1.1–1.4), colorless, wide band gap (5.4–5.6 eV) films were grown in gas containing from 25% to 100% N2.