Low Temperature Deposition Of Thin Films Research Articles

Sustainable fabrication of organic electronics

Amorphous materials are often an unwanted result of low-temperature thin-film deposition. Yet those disordered materials can be used with great effect for applications with stringent manufacturing requirements.

Realization of high quality silicon nitride deposition at low temperatures

This work demonstrates the low temperature thin-film deposition of silicon nitride (SiNx) for III-nitride-based high electron mobility transistors using inductively coupled plasma chemical vapor deposition. It is observed that the nonlinear dependency of the deposition temperature and gas flow rates have a profound impact on the film quality. The process parameter space is scanned and the optimum film quality is achieved, which is verified with physical and electrical characterizations. The best quality film is achieved at a deposition temperature of 380 °C demonstrating near ideal stoichiometry with negligible hydrogen (<5%) and oxygen (<3%) concentrations. In addition, the optimized film is found to have zero pinholes even at a thickness of 10 nm and is uniform over a large area with an rms roughness of 0.58 nm. The deposited films are characterized by atomic force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The dielectric strength and dielectric constant of these films are determined from current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the metal-insulator-metal structure, respectively. For the best quality film, the values of dielectric strength and dielectric constant are measured to be ∼8 MV/cm and ∼7.5, respectively. A metal-insulator-semiconductor-heterostructure (metal/SiNx/AlGaN/GaN) capacitor is fabricated with the optimized recipe for interface characterization. The density of slow traps is determined from the hysteresis in the C-V curve and found to be 7.38×1010 cm−2. The frequency dependent conductance method is also used to investigate the trap density. The trap state density is found to be 1.67×1012 cm−2 eV−1 at 0.29 eV below conduction band.

Low temperature thin films for next-generation microelectronics (invited)

In this article the current methodologies for low-temperature thin film deposition in microelectronics are reviewed. The paper discusses the high temperature processes in microchip manufacturing and describes the thermal budget fitting issue. The quest for low temperature deposition techniques is motivated in the perspective of contemporary trends in microchip technology such as 3D integration and the ending miniaturization. Reduced temperature depositions tend to deliver lower quality films. This is illustrated with the relation between deposition temperature and thin dielectric film quality (dielectric strength). Existing and emerging technologies for low-temperature thin film deposition are reviewed with an emphasis on their applicability in microelectronic fabrication.

Low temperature depositions of GaN thin films by plasma-enhanced atomic layer deposition

Metalorganic chemical vapour deposition and molecular beam epitaxy have already been demonstrated to be successful techniques for obtaining high-quality epitaxial GaN layers with low impurity concentrations and pretty good electrical properties. However, high growth temperature employed in both of these methods give rise to some intrinsic defects of the thin films, such as high background-carrier concentrations. As a low-temperature thin film deposition method, plasma-enhanced atomic layer deposition (PE-ALD) has more unique advantages compared to both methods for epitaxial growth of GaN. In this paper, the polycrystalline GaN thin films were fabricated on Si (100) substrates at 150-300℃ by PE-ALD. Trimethylgallium and N2/H2 plasma gas mixture were used as the Ga and N precursors. The growth rate of the thin films was demonstrated by the spectroscopic ellipsometer. The crystal structrue and composition of the GaN thin films were characterized by X-ray diffractometer and X-ray photoelectron spectrometer (XPS). It is showed that the growth window for PE-ALD grown GaN thin films is 210-270℃, where the growth rate remains constant at 0.70 /cycle. And it is known that it is the self-limiting nature of PE-ALD that is ascribed to the plateau of the growth rate. Films grown at relatively higher temperature are polycrystalline with a hexagonal wurtzite structure, while films grown under relatively lower temperature are amorphous. The grazing incidence X-ray diffraction (GIXRD) patterns of the polycrystalline thin films reveal three main peaks located at 2=32.4, 34.6 and 36.9, which are corresponding to the (100), (002) and (101) reflections. It is showed that the Ga, N atoms would get higher energy for more effective migration to positions with lowest energy to form ordered crystalline arrange at higher growth temperature. The XPS results show that all the N elements of the as-grown thin films are in the form of NGa bond, indicating that all the N elements are formed into GaN thin films; and there is a little amount of the Ga elements that exist in GaO bond. The fact that there is no Ga2O3-related peaks in the GIXRD pattern suggests that there is small amount of amorphous Ga2O3 dispersed in the polycrystalline GaN thin films. In the future work, reducing the concentration of the C and O impurities may be achieved by increasing the time of the reaction and plasma pules in the process formula and replacing the inductively coupled plasma with the hollow cathode plasma, respectively.

Transformations during Sintering of Small (Dcore < 2 nm) Ligand-Stabilized Gold Nanoparticles: Influence of Ligand Functionality and Core Size

Ligand-stabilized gold nanoparticles have been investigated as both discrete entities with size-dependent properties and as precursor inks for low-temperature deposition of thin films and patterns. In the first instance it is important to preserve the nanoparticle core, whereas for thin film applications it is desirable for the nanoparticles to sinter at relatively low temperatures. In each case, a detailed understanding of the factors that govern nanoparticle sintering will lead to improved nanomaterial design. An investigation of the sintering behavior of ∼1.4 and ∼0.9 nm gold nanoparticle cores, each passivated with two different ligands, by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) illustrates a clear size and ligand dependency on the sintering process. TGA reveals that free ligand volatilizes at lower temperatures than when bound to the nanoparticle core. Ligands of the same chain length with different terminal functionality show distinctly different volatilities an...

Resonant infrared pulsed laser deposition of cyclic olefin copolymer films

Barrier materials on thin-film organic optoelectronic devices inhibit the uptake of water, oxygen, or environmental contaminants, and fabricating them is a major challenge. By definition, these barrier layers must be insoluble, so the usual routes to polymer- or organic-film deposition by spin coating are not problematic. In this paper, we report comparative studies of pulsed laser deposition of cyclic olefin copolymer (COC), an excellent moisture barrier and a model system for a larger class of protective materials that are potentially useful in organic electronic devices, such as organic light-emitting diodes (OLEDs). Thin films of COC were deposited by resonant and nonresonant infrared pulsed laser ablation of solid COC targets, using a free-electron laser tuned to the 3.43 μm C–H stretch of the COC, and a high-intensity nanosecond Q-switched laser operated at 1064 nm. The ablation craters and deposited films were characterized by scanning-electron microscopy, Fourier-transform infrared spectrometry, atomic-force microscopy, high-resolution optical microscopy, and surface profilometry. Thermal-diffusion calculations were performed to determine the temperature rise induced in the film at the C–H resonant wavelength. The results show that resonant infrared pulsed laser deposition (RIR-PLD) is an effective, low-temperature thin-film deposition technique that leads to evaporation and deposition of intact molecules in homogeneous, smooth films. Nonresonant PLD, on the other hand, leads to photothermal damage, degradation of the COC polymers, and to the deposition only of particulates.

First-principles structural stability study of nonstoichiometry-related planar defects in SrTiO3 and BaTiO3

First principles (ab initio) pseudopotential total energy calculations have been made to theoretically interpret the structural stability of various planar defects appearing in the perovskite oxide compounds SrTiO3 and BaTiO3. The defects are a consequence of nonstoichiometric chemical compositions occurring during conventional high-temperature sintering or low-temperature thin-film deposition. The calculations, based on the density functional theory using wave functions expanded by a plane wave basis set, were applied to newly found defect structures in the perovskite materials and have been successfully used to interpret these structures. The results showed the applicability of first principles-based calculations to the theoretical interpretation of the stability of perovskite lattices containing defect structures, comparable to the use of the conventional empirical shell model.

Low-temperature processing of pb{(Mgl/3Nb2/3)0.9Ti0.1}O3 thin film by sol-gel-casting

This paper focuses on a new class of processing for low-temperature deposition of thin films. In this study, ferroelectric Pb{(Mg1/3Nb2/3)0.9Ti0.1}O3 thin films were successfully prepared at low-temperature of 800 °C. We proposed a new processing as a “sol-gel-casting” which includes dispersion of fine crystalline particles in the sol-gel derived precursor solutions followed by the casting and annealing at relatively low-temperatures. As a result, ferroelectric Pb{(Mg1/3Nb2/3)0.9Ti0.1}O3 thin films with a few μm thickness were successfully deposited on a silicon wafer with a platinum electrode (Pt/Ti/SiO2/Si). The dielectric properties of the resultant thin films depended on the processing conditions which controlled the microstructure of the films.

A New Low Temperature Thin Film Deposition Process: Energetic Cluster Impact (ECI)

AbstractA beam of metal cluster ions of variable size is deposited with variable kinetic energy on a substrate. Mirror-like and strongly adhering films are produced on unheated substrates for sufficiently high cluster impact energies. Numerical simulations provide the physical insight why this novel technique gives different, and sometimes superior results compared to conventional methods. Several examples are presented.

Formation of thin film dielectrics by remote plasma-enhanced chemical-vapor deposition (remote PECVD)

This paper describes the low-temperature deposition of thin films of silicon oxides, nitrides and oxynitrides by remote PECVD. The remote PECVD process differs from conventional and direct PECVD process in two ways: (a) only a subset of the process reactants and/or diluents are directly plasma excited; and (b) thin film deposition takes place on a substrate that is outside of the plasma glow region. In order to: (a) restrict the multiplicity of reaction pathways, (b) control oxide and nitride stoichiometry; and (c) minimize bonded hydrogen incorporation, the silane reactant is never directly plasma excited. In the context of the remote PECVD process, we discuss: (a) multichamber systems with in-situ process diagnostics and in-situ surface analysis; (b) different deposition protocols; (c) reaction pathways; (d) process gas-substrate reactions; (e) chemical-bonding, and the optical and vibrational properties of the deposited thin films; (e) differences between remote PECVD and thermally grown silicon oxides; and (f) remote PECVD dielectrics in device structures.