Showing papers on "Atomic layer deposition published in 1997"

Substrate dependence on the optical properties of Al2O3 films grown by atomic layer deposition

Abstract: The atomic layer deposition technique has been applied to the growth of Al2O3 thin films on the substrates of Si(100), 100-nm-thick SiO2 covered Si(100) [SiO2/Si(100)], and 90-nm-thick TiN covered SiO2/Si(100). The growth rate of Al2O3 films was 0.19 nm/cycle and identical for all substrates employed under the surface controlled process. However, the optical properties of Al2O3 films were significantly affected by different substrates. The average interband-oscillator energy and refractive index parameter were determined to be 3.330 eV and 2.992×10−14 eV m2 for Al2O3 film grown on Si(100), while those for the film grown on SiO2/Si(100) were 4.492 eV and 2.074×10−14 eV m2, respectively.

Volatile Metal β‐Diketonates: ALE and CVD precursors for electroluminescent device thin films

Abstract: The use of volatile β-diketonate chelates as precursors for the deposition of thin films for electroluminescent devices is reviewed. Alternating current thin film electroluminescent (ACTFEL) devices consist of an emitting layer sandwiched between two dielectric layers, together with conducting and buffer layers. Besides various physical deposition techniques, the commonly applied methods for preparing thin films are chemical vapor deposition (CVD) and its particular variant atomic layer epitaxy (ALE). Alkaline earth β-diketonates are used as precursors for deposition of the semiconducting alkaline earth sulfide and thiogallate films that provide the matrix in emissive layers, while β-diketonates of lanthanides and a few other metals (Mn, Na, K) are precursors for dopants and codopants producing colors. β-Diketonate precursors can also be used for the preparation of dielectric alkaline earth titanate and oxide layers. Current research on thin film electroluminescent materials is focused on improving the blue color produced by cerium doping of alkaline earth sulfide and thiogallate matrices. The synthesis and properties of β-diketonate chelates and the growth and characterization of the thin films obtained with them are presented and discussed. This review of precursors for TFEL materials is also relevant for other materials, including oxide superconductors.

Dependence of atomic layer-deposited Al2O3 films characteristics on growth temperature and Al precursors of Al(CH3)3 and AlCl3

Abstract: The materials characteristics of Al2O3 films grown on a Si (100) substrate by traveling wave reactor atomic layer deposition were investigated in the growth temperature ranging from 250 to 500 °C. The Al2O3 films grown using Al(CH3)3 trimethylaluminum (TMA) and H2O as precursors were characterized and also compared with the films grown using AlCl3 and H2O. Both samples grown with different precursors revealed identical chemical binding state of oxidized Al and very flat surface morphology. In the study of impurity incorporation, the films grown using TMA showed the C and H count rates of secondary ion mass spectrometry (SIMS) approximately six and 10 times higher than those of the film grown using AlCl3, respectively. For the Al2O3 films grown using TMA, the results showed that the impurity contents and the growth rate of the films decreased and the refractive index increased with the growth temperature. The content of impurities could be also lowered by increasing the N2 purge time after TMA pulse. Howev...

Process for passivating semiconductor laser structures with severe steps in surface topography

Abstract: The specification describes a process for passivating semiconductor laser structures with severe steps in the surface topography. The technique involves atomic layer deposition to produce the passivating layer which has exceptional coverage and uniformity, even in the case of trench features with trench aspect ratios as large as 5. In addition, the passivation produced by this process has excellent environmental stability, and affords protection against air born contaminant induced degradation.

Titanium oxide/aluminum oxide multilayer reflectors for "water-window" wavelengths

Abstract: Twenty bilayers of titanium oxide and aluminum oxide with the layer-pair thickness of 443 nm on a silicon substrate were fabricated for novel multilayer reflectors at water-window wavelengths by an atomic layer deposition method of controlled growth with sequential surface chemical reactions The high reflectance of over 30% at a wavelength of 2734 nm and an incident angle of 718° from the normal incidence was demonstrated experimentally The full width at half-maximum of the reflectances at 2734 nm was 00381 nm, which corresponds to Δλ/λ=14%

Advanced Materials Processing by Adsorption Control

Abstract: Precise control and knowledge of surface structures are essential inorder to meet the requirements of today's and future materials. One possiblegrowth technique capable of meeting the requirements is atomic layer epitaxy(ALE). ALE is based on sequentially applied saturated gas-solid reactions,which provide the means for adsorption controlled material deposition atatomic layer level. In this paper the potentiality of the use of porousmaterials in a detailed study of adsorption controlled growth is discussed.At the same time the study promotes the application of adsorption controlledmaterials processing for advanced catalysts manufacturing.

Thickness profiles of thin films caused by secondary reactions in flow-type atomic layer deposition reactors

Abstract: The secondary reaction of HCl with the growing metal oxide surface during atomic layer deposition from a metal chloride and water is investigated using model calculations. HCl released during chemisorption of a metal chloride occupies adsorption sites for the metal chloride which results in a decrease in the film thickness in the gas-flow direction. The calculation model based on the continuity equation and kinetic equations for the surface coverage is described. The dependences of the thickness profile on the reactivity of HCl and on the adsorption of the metal chloride are analysed.

Method for the selective deposition of bismuth based ferroelectric thin films by chemical vapor deposition

Abstract: A method is described for the selective deposition of bismuth based ferroelectric films by selective chemical vapor deposition on a substrate. Selectivity in the deposition process is attained by selection of substrate-precursor combinations which assure high bismuth deposition efficiency in certain areas and low bismuth deposition efficiency in other areas in combination with specific process parameters.

A Proposed Atomic-Layer-Deposition of Germanium on Si Surface

Abstract: A novel method has been proposed for monolayer deposition of Ge on the clean Si surface. The method is based on alternating and repeated exposures of the surface to germanium tetrachloride and atomic hydrogen. The former results in self-limiting adsorption of precursors on the Si surface, and the latter in extraction of surface-terminating Cl from the precursor-adsorbed Si surface. It has been confirmed experimentally that Ge can be deposited uniformly at one-monolayer thickness on the Si(100) surface using this metod.

Influence of substrate annealing on the epitaxial growth of BaTiO3 thin films by metal-organic chemical vapor deposition

Abstract: BaTiO3 thin films were deposited by metal-organic chemical vapor deposition at 840 °C on two differently treated (100) MgO single crystal substrates. One MgO substrate was only mechanically polished and the other substrate was polished and then annealed at 1100 °C for 4 h in oxygen. Observation by transmission electron microscopy showed that the BaTiO3 thin film deposited on the unannealed substrate was fine-grained and that the whole film was epitaxial (100) in nature. In contrast, the film deposited on the annealed substrate consisted of large, (100)-oriented, epitaxial grains within which were distributed (110)-oriented grains with random in-plane orientations. These differences in BaTiO3 films deposited on differently treated substrates are discussed with reference to the surface structure of the MgO substrate and nucleation kinetics of BaTiO3 thin films on MgO.

Atomic-layer-deposited TiO2 dielectric coatings

Abstract: The possibilities of the in situ real-time Brewster-angle interferometric reflectance probe to follow cycle-dependent film-quality changes during the atomic layer deposition (ALD) are investigated. Experiments are centered around the growth of amorphous TiO 2 thin films on fused quartz substrates in a traveling-wave reactor using TiCl 4 and H 2 O as reactants. It is concluded that ALD has prospects for the preparation of microstructurally homogeneous low- optical-loss TiO 2 films in case the precise thickness control is needed. The main problem is the microporosity of the films and as a result their moderate refractive index.

Blanket-selective deposition of cvd aluminum and reflectivity improvement using a self-aligning ultra-thin layer

Abstract: The present invention relates generally to an improved apparatus and process to provide a thin self-aligning layer prior to forming a conducting film layer there over to improve the film characteristics and deposition coverage. In one aspect of the invention, a dielectric layer (32) is formed over a conducting or semiconducting layer (36) and etched to form an aperture (38) exposing the underlying conducting or semiconducting layer (36) on the aperture floor (42). An ultra-thin nucleation layer (34) is then deposited by either vapor deposition or chemical vapor deposition onto the field (33) of the dielectric layer (32). A CVD metal layer is then deposited onto the structure (30) to achieve selective deposition on the floor (42) of the aperture (38), while preferably also forming a highly oriented blanket layer (46) on the field (33). In another aspect of the invention, a thin, self-aligning layer is formed over a barrier layer prior to deposition of a conducting film there over. It is believed that the self-aligning layer enhances the reflectivity of the films by improving the crystal structure in the resulting film and provides improved electromigration performance by providing 〈111〉 crystal orientation. The process is preferably carried out in an integrated processing system that includes both a PVD and CVD processing chamber so that once the substrate is introduced into a vacuum environment, the process occurs without the formation of oxides between the layers.

The Characterization of Al 2 O 3 Films Grown by Atomic Layer Deposition Using Al(CH 3 ) 3 and H 2 O

Abstract: The materials characteristics of Al2O3 films grown on Si (100) substrate by traveling wave reactor atomic layer deposition were investigated at the growth temperature ranging from 250 to 500°C. The Al2O3 films grown using Al(CH3)3(TMA) and H2O as precursors were characterized and also compared with the films grown using AlCl3 and H2O. In the study of impurity incorporation, the films grown using TMA showed the C and H count rates of secondary ion mass spectrometry (SIMS) approximately 7–10 times higher than those of the film grown using AlCl3. For the Al2O3 films grown using TMA, the impurity contents and the growth rate decreased and the refractive index increased as increasing the growth temperature. The effect of purge time increase on the impurity incorporation was very small compared with that of growth temperature. The refractive indices were 1.64 and 1.68 at the growth temperatures of 250 and 400°C, respectively. The rough estimation using SIMS data and refractive indices indicated that the H-content decreased from 8.6 at% to 2.9 at% as increasing the substrate temperature from 250 to 400°C. The Al2O3 film grown using AlCl3 and H2O at 500°C contained approximately 0.5% Cl and revealed the refractive index of 1.65.

Focused-ion-beam-induced insulator deposition at decreased beam current density

Abstract: Localized focused-ion-beam (FIB) induced deposition of an insulating film provides reconstructive capability in previously modified areas. The application of this technique has led to a need for an ion-induced deposited insulator material with improved dielectric integrity. This paper presents a method that increases the yield of FIB-deposited SiO/sub 2/ films per incident ion by decreasing the current density of the ion beam. Both electrical and chemical analyses are presented of films deposited with a range of beam current densities and pixel sizes. As predicted, as the current density is decreased, the deposition yield increases. An incremental decrease in the atomic percent of gallium is detected in the films deposited at lower current densities, while the atomic percent of oxygen increases slightly and the atomic percent of silicon remains approximately unchanged. No degradation or enhancement of the films electrical integrity, as measured by leakage current, is achieved by reducing the current density by as much as a factor of ten from that of a standard process for a commercial focused-ion-beam system.

Novel oxide multilayer reflectors for "water-window" wavelengths fabricated by atomic layer deposition

Abstract: In this paper, we report that we could demonstrate experimentally high reflectance (71.8/spl deg/) over 30% for soft X-ray multilayer mirrors, at 2.734 nm near the titanium L/sub 2,3/ absorption edge located at 2.729 nm, by novel metal oxide multilayers of titanium oxide and aluminum oxide fabricated by the atomic layer deposition method.

Organometallic Chemical Vapor Deposition of Group-III Nitride Thin Films using Single Source Precursors

Abstract: The OMCVD of AIN, GaN and InN thin films using the novel single source precursors (N3)2Ga[(CH2)3NMe2] (1), (N3)In[(CH2)3NMe2]2(2) and (N3)Al(CH2)3NMe2]2(3) is reported. The compounds are non-pyrophoric. Compound 2 is air stable. No additional N-sources were used for the growth of the nitrides. We achieved epitaxial (A1N, GaN) or polycrystalline (InN) growth at least 200°C below the decomposition temperature of the respective nitride. Some aspects of the reactivity of the precursors with ammonia and the resulting influence on the deposition process were investigated.