Control Of Film Composition Research Articles

Fabrication and Composition Control of NiTi Shape Memory Thin Films for Microactuators

AbstractMicroactuators fabricated with NiTi thin films take advantage of the shape memory effect's large energy density (∼5-10 joules/cm3) and high strain recovery (∼8%). Microelectromechanical Systems (MEMS) designed with these actuators can serve as biosensors, micro-fluidic pumps or optical switches. However, the fundamental mechanical properties of these shape memory NiTi films have not been fully characterized with micro-scale test structures. Equiatomic NiTi thin films were deposited by co-sputtering NiTi and Ti targets with the intension of fabricating such test structures. Dual cathodes allowed direct control of the film composition by adjusting the Ti cathode power. Energy Dispersive Spectroscopy (EDS) quantified the film composition relative to pure standards. A thin (∼50 nm) chromium film on a pure silicon substrate created excellent film adhesion. Oxidized Si wafers did not bond with the Cr and NiTi films. This deposition method enabled control of film composition and the necessary adhesion.

A Study of Cd SnO Thin Film Deposited at Low Temperature using Reactive Magnetron Sputtering

Transparent conductive oxide coatings will underpin the development of the next generation of photovoltaic solar cells, flat panel displays, and optoelectronic components. As alternative, the cheaper coating material Cd SnO (TCO) can be used instead of indium tin oxide. The optical and electrical properties of CTO coatings are, though, notoriously sensitive to process parameters and depend on control of film composition, structure, crystallinity, defect density, surface roughness, and dopant concentration. The paper presents results of experimental study of magnetron deposition process. Transparency and electrical conductivity of deposited films most depends on magnetron discharge voltage, work gas O2 + Ar composition and substrate potential (bias). The minimum of sheet resistance was obtained at particular voltage, and this voltage depends on work gas composition. Transparency depends on discharge voltage to a lesser degree and drops only in short wave edge at larger discharge voltage. The area of optimal technological parameters where quality layers with proper characteristics for conductive electrodes can be formed was determined by analysis of experimental results. Ill. 7, bibl. 5 (in English; summaries in Lithuanian, English and Russian).

Low energy plasma enhanced chemical vapor deposition

We present a state-of-the-art growth technique, introduced recently for SiGe heteroepitaxy. At present, its most important application is the fast fabrication of high-quality relaxed SiGe buffer layers. The process is based on chemical vapor deposition (CVD), enhanced by a high intensity, low energy plasma, which is why we call it ‘low energy plasma enhanced CVD’ (LEPECVD). The key features of the process are a wide range of epitaxial growth rates (<1 Å s −1 up to at least 10 nm s −1), independent of the substrate temperature in the range of 500–750 °C and easy control of film composition, governed solely by the mixture of the precursor gases (SiH 4 and GeH 4). Possible applications of LEPECVD include electronic devices, such as modulation doped SiGe FETs (SiGe-MODFETs) or strained-layer SiGe MOSFETs, all based on relaxed buffer layers and targeting the fast-growing RF device market. Another field of applications is high-performance SiGe solar cells. For economic production, all these devices rely on fast, high-quality epitaxy, which is the strength of LEPECVD. The process, developed on the experimental system for 4-inch wafers, is now being transferred to a 300-mm single wafer reactor for production.

Metalorganic chemical vapor deposition of very thin Pb(Zr,Ti)O3 thin films at low temperatures for high-density ferroelectric memory applications

The metalorganic chemical vapor deposition of very thin (&lt;50 nm) Pb(Zr,Ti)O3 (PZT) thin films was performed for high density (&gt;32 mega bit) ferroelectric memory devices. The growth temperatures were set between 450 and 530 °C to obtain a smooth surface morphology and prevent damage to the underlying reaction barrier layer. The average grain size of a 50-nm-thick film on a Pt electrode was about 34 nm with a size distribution (σ2) of 11 nm. These values are much smaller than the sol-gel-derived PZT films (55 and 25 nm, respectively). Very thin films with a thickness of approximately 30 nm were prepared at wafer temperatures ranging from 500 to 525 °C. Even with the very small thickness, the films showed good ferroelectric properties with a typical remanent polarization from 10 to 15 μC/cm2 and an extremely low coercive voltage of 0.3 V. However, the leakage current density was rather high resulting in nonsaturating polarization versus voltage curves. Even though good ferroelectric properties were obtained, the formation of PtxPby alloys on top of the Pt electrode was consistently observed. This precludes the reliable control of film composition and electrical performance. The adoption of an Ir electrode successfully eliminated intermetallic alloy formation and resulted in better and reproducible process control. A 50-nm-thick PZT film on an Ir/IrO2/SiO2/Si substrate also showed a reasonable ferroelectric performance.

Application of compact microwave ion source to low temperature growth of transition metal nitride thin films for vacuum microelectronics devices

A compact microwave ion source was applied to the low temperature growth of transition metal nitride thin films for the cathode of vacuum microelectronics devices. An ion beam assisted deposition system consisted of a compact microwave ion source and an electron beam evaporator was developed. Depositions of zirconium nitride and niobium nitride thin films were performed and the film properties were investigated. As a result, it was found that polycrystalline films of zirconium nitride and niobium nitride were prepared at the substrate temperature as low as 500 °C, which was almost 200 °C lower than the results shown in the literature. The reason for this reduction of substrate temperature might be attributed to low gas pressure during deposition, due to the use of a single aperture ion source. The control of film composition by controlling the ion-atom arrival rate ratio achieved the control of work function. It was concluded that the ion beam assisted deposition with microwave ion source provides a possible process of cathode deposition.

IR-Transparent Electrically Conductive CuAlxOy Deposited by Reactive Magnetron Co-Sputtering

AbstractThis paper reports on progress in the fabrication of IR-transparent electrically conductive copper aluminum oxide (CuAlxOy) by reactive magnetron co-sputtering from high-purity-Cu and -Al targets in an argon-oxygen-gas mixture. Recent equipment modifications have resulted in much better control of deposition parameters like forward and reflected power and, consequently, much better control of film composition. Applying the correct amount of power to each target and adjusting the oxygen-partial pressure have significantly reduced the growth of surface-oxide layers on the metal targets. Equipment and process improvements have eliminated the sputterrate inconsistencies and arcing that led to lack of composition control in our earliest films. We now have much better control of film composition and are beginning to understand the relationship between the electro-optical properties and the molecular structure of the films using Fourier transform infrared (FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), inductively coupled plasma (ICP) emission spectroscopy, high resolution electron microscopy (HREM) and electron energy loss spectroscopy (EELS). A pair of weakly intense FTIR absorption bands at 1470 and 1395cm−1 is present in films that have enhanced electrical conductivity and IR transparency. Understanding the origin of these bands could speed development of CuAlO2 as a wide-bandgap-conductive oxide since these bands are clearly associated with enhanced conductivity and carrier mobility. The best film to date transmits about 80% in the mid-wave IR and has a sheet resistance of 160Δ;/sq.

Ba1−xSrxTiO3 Thin Film Sputter-Growth Processes and Electrical Property Relationships for High Frequency Devices

AbstractPrecise control of Ba1−xSrxTiO3 (BST) film composition is critical for the production of high-quality BST thin films. Specifically, it is known that nonstoichiometry greatly affects the electrical properties of BST film capacitors. We are investigating the compositionmicrostructure- electrical property relationships of polycrystalline BST films produced by magnetron sputter-deposition using a single target with a Ba/Sr ratio of 50/50 and a (Ba+Sr)/Ti ratio of 1.0. It was determined that the (Ba+Sr)/Ti ratios of these BST films could be adjusted from 0.73 to 0.98 by changing the total (Ar+O2) process pressure, while the O2/Ar ratio did not strongly affect the metal ion composition. The crystalline quality as well as the measured dielectric constant, dielectric tunability, and electrical breakdown voltage of BST films have been found to be strongly dependent on the composition of the BST films, especially the (Ba+Sr)/Ti ratio. We discuss the impact of BST film composition control, through film deposition and process parameters, on the electrical properties of BST capacitors for high frequency devices.

Common and unique aspects of perovskite thin film CVD processes

In the past 5 years there has been a large amount of work to develop CVD technology for the deposition of the predominant perovskite oxide thin films, (Ba, Sr)TiO3, SrBi2Ta2O9 and Pb(Zr, Ti)O3. For each of these families of materials, CVD processes have matured such that state-of-the-art film properties may be achieved with this technique. Much of the progress is attributed to the use of the liquid delivery technique to transfer relatively involatile metalorganic precursors to the reactor. This paper will discuss common attributes of these thermal CVD processes, particularly the precursors, delivery methodology and reactor hardware. The paper will also highlight unique aspects that differentiate the processes, including the CVD decomposition regime, strategies for film composition control and approaches for forming the crystalline perovskite phase. Representative film properties are presented, demonstrating that these processes are becoming increasingly mature.

Numerical calculation of pulsed laser deposited film profiles

Pulsed laser deposition (PLD) is a straightforward method for production of the widest variety of materials, especially multicomponent oxides, in the form of thin film. One of the particular advantages of this technique, the possibility of control of film composition, is ensured by applying (reactive) atmospheres of pressures up to tenths of millibars.

Magnetron sputtering on large scale substrates: an overview on the state of the art

In the last 15 years sputter deposition of thin films on large area substrates has enjoyed a steady growth. On the one hand, sputtering is gaining more and more market share in applications that in earlier times have been dominated by evaporation techniques. On the other hand, completely new markets have grown, which would not have been realized without the existence of sputtering (e.g. microelectronics, flat panel displays). Some of the reasons for this development are: (1) the ability to deposit all kinds of metals including high-melting metals, binary, ternary and multicomponent alloys and compounds with precise control of film composition and structure; (2) the ability to deposit metal oxides, metal nitrides, metal carbides, etc. with precise control of the layer stoichiometry; (3) the extremely high thickness uniformity of Δ d, less than 2%, that can be realized for example For glass panes of 3.2×6 m size. In the late 1980's and the beginning of the 1990's, a handful of basically different approaches have been made in order to enhance further the performance of sputter magnetrons for large scale applications. This paper gives an overview of the state of the art of magnetron sputtering for large scale applications, covering the wellproven conventional planar magnetron, as well as those solutions that have grown in the last few years and right now are themselves on the point of being state of the art.

Manufacturing of perovskite thin films using liquid delivery MOCVD

Abstract There are numerous ternary and quaternary oxides that are attractive for use in advanced IC's. These include Ba1-xSrxTiO3 (BST), Pb1-xLax(Zr1-yTiy)1-x/4O3 (PLZT) and SrBi2Ta2O9. Although each application has unique material requirements, in most cases the deposition process must have good conformality, composition control and throughput, while minimizing the thermal budget. For these reasons, metalorganic chemical vapor deposition (MOCVD) is acknowledged as the leading candidate for manufacturing. The absence of volatile (and in some cases stable) precursors has stimulated the use of the ‘‘liquid delivery technique'’ for transport of a system of precursors in liquid solution, which are vaporized simultaneously. Film composition is easily varied by mixing component solutions which contain one or more of the metalorganic compounds. The paper will focus on the role of measurement and control of film composition in the development of a manufacturing process for perovskites and related materials. Select results for BST and PZT thin films deposited using liquid delivery CVD will be discussed.

Phase and composition control of PZT thin films

Abstract Ferroelectric PZT films were prepared by metalorganic chemical vapor deposition (MOCVD) and sputtering. Crystalline phase control and film composition control experiments were performed. In MOCVD of PZT films, the crystalline phase and film composition were easily controlled by changing the substrate temperature and the Ar carrier gas flow rates of the precursors. A change in the crystalline phase using different precursors and oxidizing gases was also discussed. In order to control the crystalline phase and obtain perovskite rhombohedral PZT thin films, a two step growth process was proposed. In contrast, in sputtering of PZT films, film composition control was more difficult to perform than when PZT films were prepared by MOCVD. The electrical properties of PZT films with different compositions were also investigated.

Ordering Transitions in Thin, Freely-Suspended Phospholipid Films

The lyotropic phase behavior of freely suspended multilayers of the phospholipid dimyristoylphosphatidylcholine (DMPC) and water, ranging in thickness from a single bilayer (∼ 50 A) to 12 bilayers, has been investigated via optical reflectivity and reflection polarization microscopy. Specifically, equilibration of the film with a vapor phase of adjustable moisture content facilitated the continuous control of film composition, and this made it possible to maintain single bilayers for periods of days. Several optical features indicate effects of reduced dimensionality on ordering transitions from the L α phase into the partially ordered, lower temperature L β' and P β' phases. These include the reversible distortion of layer steps and the formation of dendritic growth patterns at the onset of the transition. In addition, we find the ordering transitions of thin multilayers to be characterized by an increase in the optical reflectivity. On the basis of a numerical evaluation of a suitable slab model of multibilayers, we attribute this increase primarily to a lateral layer contraction, known to accompany the ordering in bulk dispersions of these materials. Comparison of the phase behavior of thin lipid films with the known phase diagram of thick films of the same system reveals a close correspondence

Electrodeposition of zinc selenide

The synthesis of polycrystalline thin films of cubic ZnSe by electrochemical plating on conducting substrates is described. The influence of deposition parameters such as electrolyte composition, deposition potential and temperature on the crystallanity and on the chemical composition of the films is discussed. Of the various plating techniques (potentiostatic, potentiodynamic pulse and galvanostatic), potentiostatic plating offers the best control of film composition. An excess of Se with respect to perfect stoichiometry cannot be avoided by adjusting electrolyte composition and deposition potential, but can be decreased by vacuum annealing.

Synthesis and properties of Fe3C film by r.f. magnetron sputtering

Fe3C film, which is a promising new magnetic recording material, can be synthesized by r.f. magnetron sputtering. Several graphite plates were attached to an iron plate to adjust the area of a composite target for the control of film composition. The crystalline phases in a film changed from Fe-C solid solution to Fe3C with increasing substrate temperature from 350 °C and above. Sputtering at an argon pressure of 5 Pa was favourable for the formation of crystalline Fe3C film. All Fe3C films showed in-plane magnetization. The saturation magnetization of the film was around 100–120 e.m.u. g−1 regardless of the deposition conditions. The coercivity of the films increased from 1 Oe to 250 Oe with increasing substrate temperature, and the coercivity remained constant at 250 Oe at 350 °C, regardless of argon pressure.

Sputtering preparation of ferroelectric PLZT thin films and their optical applications

Preparation of epitaxial PLZT thin films on sapphire has been investigated, and excellent ferroelectric properties such as piezoelectricity and electrooptic effect with high transparency were obtained in thin films. Moreover, a preparation process was developed involving the multitarget sputtering method, and strict control of film composition and epitaxial growth with the buffer layer of graded composition were performed. Using these PLZT thin films, some optical applications, including an acoustooptic deflector and an electrooptic guided-light switch, are shown.

Photochemical vapor deposition of iron-cobalt thin films: wavelength and temperature control of film compositions [Erratum to document cited in CA114(8):72158c

ADVERTISEMENT RETURN TO ISSUEPREVArticlePhotochemical vapor deposition of iron-cobalt thin films: wavelength and temperature control of film compositions [Erratum to document cited in CA114(8):72158c]David K. Liu, Roger J. Chin, and Angela L. LaiCite this: Chem. Mater. 1991, 3, 2, 378Publication Date (Print):March 1, 1991Publication History Published online1 May 2002Published inissue 1 March 1991https://doi.org/10.1021/cm00014a032RIGHTS & PERMISSIONSArticle Views21Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (69 KB) Get e-Alerts Get e-Alerts

Photochemical vapor deposition of iron-cobalt thin films: wavelength and temperature control of film compositions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochemical vapor deposition of iron-cobalt thin films: wavelength and temperature control of film compositionsDavid K. Liu, Roger J. Chin, and Angela L. LaiCite this: Chem. Mater. 1991, 3, 1, 13–14Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://doi.org/10.1021/cm00013a006RIGHTS & PERMISSIONSArticle Views91Altmetric-Citations18LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (293 KB) Get e-Alerts Get e-Alerts

Synthesis and properties of metal clusters in polymeric matrices

A one-step plasma deposition process is described which allows the uniform dispersion of small metal clusters throughout a thin film polymer matrix. Plasma parameters and plasma gas phase diagnostics relevant to the control of film composition and structure are discussed. Chemical and structural analytical techniques such as I.R. absorption spectroscopy, E.S.C.A., Auger electron spectroscopy, X-ray fluorescence, X-ray and electron diffraction and microscopy are used to characterize the cluster containing films. Changes in cluster size and shape as a function of volume fraction and as a result of post deposition annealing are described. Optical and electrical properties are presented below and above the onset of percolation and are evaluated in terms of contemporary effective medium theories.

Excimer laser induced deposition of InP and indium-oxide films

InP and In-oxide films have been deposited on quartz, GaAs, and InP substrates by excimer laser induced photodecomposition of (CH3)3InP(CH3)3 and P(CH3)3 vapors at 193 nm. The oxide film refractive index and stoichiometry are close to In2O3. Phosphorus incorporation in the films was greatly enhanced by focusing the laser beam to promote multiple-photon dissociation processes. These conditions also lead to enhanced carbon inclusion in the films, due to formation of species such as CH and CH2 in the gas phase. However, this carbon inclusion could be suppressed by focusing the beam onto the surface at normal incidence. In the irradiated zone InP could be deposited with P(CH3)3-to-(CH3)3InP(CH3)3 ratios of only ∼1:1. The technique offers several potential advantages over conventional metalorganic chemical vapor deposition, including lower temperature, enhanced rates, safer gases, and three-dimensional film composition control. Strong atomic In emission is observed in the gas phase above the depositing film, due to a multiple photon dissociation process. Gas phase fluorescence from P, CH, and C was also observed. These emissions give insight into the photodecomposition mechanism and also serve as a monitor of metalorganic precursor concentrations.