Showing papers on "Sputtering published in 2002"

Materials science of thin films : deposition and structure

Abstract: Foreword to First Edition Preface Acknowledgments A Historical Perspective Chapter 1 A Review of Materials Science 1.1. Introduction 1.2. Structure 1.3. Defects in Solids 1.4. Bonds and Bands in Materials 1.5. Thermodynamics of Materials 1.6. Kinetics 1.7. Nucleation 1.8. An Introduction to Mechanical Behavior 1.9. Conclusion Exercises References Chapter 2 Vacuum Science and Technology 2.1. Introduction 2.2. Kinetic Theory of Gases 2.3. Gas Transport and Pumping 2.4. Vacuum Pumps 2.5. Vacuum Systems 2.6. Conclusion Exercises References Chapter 3 Thin-Film Evaporation Processes 3.1. Introduction 3.2. The Physics and Chemistry of Evaporation 3.3. Film Thickness Uniformity and Purity 3.4. Evaporation Hardware 3.5. Evaporation Processes and Applications 3.6. Conclusion Exercises References Chapter 4 Discharges, Plasmas, and Ion-Surface Interactions 4.1. Introduction 4.2. Plasmas, Discharges, and Arcs 4.3. Fundamentals of Plasma Physics 4.4. Reactions in Plasmas 4.5. Physics of Sputtering 4.6. Ion Bombardment Modification of Growing Films 4.7. Conclusion Exercises References Chapter 5 Plasma and Ion Beam Processing of Thin Films 5.1. Introduction 5.2. DC, AC, and Reactive Sputtering Processes 5.3. Magnetron Sputtering 5.4. Plasma Etching 5.5. Hybrid and Modified PVD Processes 5.6. Conclusion Exercises References Chapter 6 Chemical Vapor Deposition 6.1. Introduction 6.2. Reaction Types 6.3. Thermodynamics of CVD 6.4. Gas Transport 6.5. Film Growth Kinetics 6.6. Thermal CVD Processes 6.7. Plasma-Enhanced CVD Processes 6.8. Some CVD Materials Issues 6.9. Safety 6.10. Conclusion Exercises References Chapter 7 Substrate Surfaces and Thin-Film Nucleation 7.1. Introduction 7.2. An Atomic View of Substrate Surfaces 7.3. Thermodynamic Aspects of Nucleation 7.4. Kinetic Processes in Nucleation and Growth 7.5. Experimental Studies of Nucleation and Growth 7.6. Conclusion Exercises References Chapter 8 Epitaxy 8.1. Introduction 8.2. Manifestations of Epitaxy 8.3. Lattice Misfit and Defects in Epitaxial Films 8.4. Epitaxy of Compound Semiconductors 8.5. High-Temperature Methods for Depositing Epitaxial Semiconductor Films 8.6. Low-Temperature Methods for Depositing Epitaxial Semiconductor Films 8.7. Mechanisms and Characterization of Epitaxial Film Growth 8.8. Conclusion Exercises References Chapter 9 Film Structure 9.1. Introduction 9.2. Structural Morphology of Deposited Films and Coatings 9.3. Computational Simulations of Film Structure 9.4. Grain Growth, Texture, and Microstructure Control in Thin Films 9.5. Constrained Film Structures 9.6. Amorphous Thin Films 9.7. Conclusion Exercises References Chapter 10 Characterization of Thin Films and Surfaces 10.1. Introduction 10.2. Film Thickness 10.3. Structural Characterization of Films and Surfaces 10.4. Chemical Characterization of Surfaces and Films 10.5. Conclusion Exercises References Chapter 11 Interdiffusion, Reactions, and Transformations in Thin Films 11.1. Introduction 11.2. Fundamentals of Diffusion 11.3. Interdiffusion in Thin Metal Films 11.4. Compound Formation and Phase Transformations in Thin Films 11.5. Metal-Semiconductor Reactions 11.6. Mass Transport in Thin Films under Large Driving Forces 11.7. Conclusion Exercises References Chapter 12 Mechanical Properties of Thin Films 12.1. Introduction 12.2. Mechanical Testing and Strength of Thin Films 12.3. Analysis of Internal Stress 12.4. Techniques for Measuring Internal Stress in Films 12.5. Internal Stresses in Thin Films and Their Causes 12.6. Mechanical Relaxation Effects in Stressed Films 12.7. Adhesion 12.8. Conclusion Exercises References Index

The effects of thickness and operation temperature on ZnO:Al thin film CO gas sensor

Abstract: Al-doped ZnO films were deposited onto SiO 2 /Si substrates by rf magnetron sputtering system as a CO gas sensor. The dependence of the thin film thickness on CO gas sensing properties was investigated, where the film thickness was varied by controlling the deposition time. The structure of the deposited ZnO:Al films was determined by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The CO gas sensing properties were determined by in situ measurement for surface resistance of the thin film as a function of film thickness, different atmosphere, and operation temperature. It was shown that the films were flat and smooth with (0 0 0 1) preferred orientation. The grain size was increased as the film thickness was increased during deposition. Here, the CO gas sensing properties were relative to the structural characteristics where the maximum sensitivity of 61.6% was obtained at 65 nm film thickness for the operation temperature of 400 °C.

Nanostructuring surfaces by ion sputtering

Abstract: Surface etching by ion sputtering can be used to pattern surfaces. Recent studies using the high-spatial-resolution capability of the scanning tunnelling microscope revealed in fact that ion bombardment produces repetitive structures at nanometre scale, creating peculiar surface morphologies ranging from self-affine patterns to `fingerprint'-like and even regular structures, for instance waves (ripples), chequerboards or pyramids. The phenomenon is related to the interplay between ion erosion and diffusion of adatoms (vacancies), which induces surface re-organization. The paper reviews the use of sputter etching to modify `in situ' surfaces and thin films, producing substrates with well defined vertical roughness, lateral periodicity and controlled step size and orientation.

Morphology of ion-sputtered surfaces

Abstract: We derive a stochastic nonlinear continuum equation to describe the morphological evolution of amorphous surfaces eroded by ion bombardment. Starting from Sigmunds theory of sputter erosion, we calculate the coefficients appearing in the continuum equation in terms of the physical parameters characterizing the sputtering process. We analyze the morphological features predicted by the continuum theory, comparing them with the experimentally reported morphologies. We show that for short time scales, where the effect of nonlinear terms is negligible, the continuum theory predicts ripple formation. We demonstrate that in addition to relaxation by thermal surface diffusion, the sputtering process can also contribute to the smoothing mechanisms shaping the surface morphology. We explicitly calculate an effective surface diffusion constant characterizing this smoothing effect and show that it is responsible for the low temperature ripple formation observed in various experiments. At long time scales the nonlinear terms dominate the evolution of the surface morphology. The nonlinear terms lead to the stabilization of the ripple wavelength and we show that, depending on the experimental parameters, such as angle of incidence and ion energy, different morphologies can be observed: asymptotically, sputter eroded surfaces could undergo kinetic roughening, or can display novel ordered structures with rotated ripples. Finally, we discuss in detail the existing experimental support for the proposed theory and uncover novel features of the surface morphology and evolution, that could be directly tested experimentally. � 2002 Published by Elsevier Science B.V.

Current sensor, its production substrate, and its production process

Abstract: A new current sensor, its production substrate, and its production process, wherein the surface layer of the substrate is made of the thin film of low temperature coefficient of resistivity such as nickel-copper alloy, manganese-copper alloy or nickel-chromium alloy, it is tightly adhered onto the thin plates of ceramic, aluminum oxide, aluminum nitride or Beryllium dioxide (BeO) to form a new substrate by a hot-press laminating; next, by optical mask etching, the pattern of current sensor are formed on the surface of the substrate; and the flip-chip is formed on the lateral electrodes in the bottom of the current sensor unit, and the front electrodes are plated to increase the thickness; then, the pattern are modified with laser to obtain the pattern of sensor with precise and constant resistivity; after that, and the pattern of a sensor are coated with a protection layer; and the substrate is segmented, and is plated on the end face electrode 60 by sputtering; finally, a single and small chip-scaled current sensor is obtained by dicing and barrel plating.

Method of forming a multilayer dielectric stack

Abstract: A multilayer dielectric stack is provided which has alternating layers of a high-k material and an interposing material. The presence of the interposing material and the thinness of the high-k material layers reduces or eliminate effects of crystallization within the high-k material, even at relatively high annealing temperatures. The high-k dielectric layers are a metal oxide of preferably zirconium or hafnium. The interposing layers are preferably amorphous aluminum oxide, aluminum nitride, or silicon nitride. Because the layers reduce the effects of crystalline structures within individual layers, the overall tunneling current is reduced. Also provided are atomic layer deposition, sputtering, and evaporation as methods of depositing desired materials for forming the above-mentioned multilayer dielectric stack.

Electrical and spectroscopic comparison of HfO2/Si interfaces on nitrided and un-nitrided Si(100)

Abstract: The interfacial chemistry of the high-k dielectric HfO2 has been investigated on nitrided and un-nitrided Si(100) using x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The samples are prepared by sputter depositing Hf metal and subsequently oxidizing it. A 600 °C densification anneal is critical to completing Hf oxidation. These spectroscopic data complement electrical testing of metal oxide semiconductor capacitors fabricated with ∼50 A HfO2 on nitrided and un-nitrided Si(100). Capacitors with interfacial nitride show reduced leakage current by a factor of 100 at a −1 V bias. Concurrently, interfacial nitride increased capacitance 12% at saturation. XPS shows that an interfacial layer composed of nonstoichiometric hafnium silicate (HfSixOy), forms at both the HfO2/Si and HfO2/SiNx interfaces. Differences in the Si 2p and O 1s XP spectra suggest more silicate forms at the un-nitrided interface. HfO2 films on un-nitrided Si show more O 1s and Si 2p photoemission intensity...

Identification of an organic coating on marine aerosol particles by TOF‐SIMS

Abstract: [1] Marine aerosol particles play an important role in atmospheric processes. It has been suggested that as marine aerosol particles form, they acquire a coating of organic surfactants. This theory has been supported only by indirect evidence. Recently, we gave new morphological indication of such organic coating without however providing molecular speciation. Here we have studied the surface of marine aerosol particles by time-of-flight secondary ion mass spectrometry (TOF-SIMS), which is very suitable for surface research due to its unique combination of surface sensitivity and the detailed molecular information obtained. Spectra from the outermost surface gave high intensity for palmitic acid and lower peaks for other fatty acids. According to TOF-SIMS images, palmitic acid was distributed on small particles, similar with the marine particles. Sputtering stripped palmitic acid and revealed the inner core of the sea-salt particles. Our results show that fatty acids are important ingredients of the outermost surface layer of the studied aerosol particles.

Control of p- and n-type conductivity in sputter deposition of undoped ZnO

Abstract: Recent theoretical studies have concluded that the low formation enthalpies of intrinsic donor defects should preclude achievement of p-type conductivity in undoped ZnO grown in thermal equilibrium with a molecular oxygen reservoir. This letter demonstrates that reactive sputtering can produce intrinsic p-type ZnO, controlled by adjusting the oxygen partial pressure in the sputtering plasma. We report the properties of p–n homojunctions fabricated in this way, and characterize transport in the films by Hall measurements. Our finding of p-type conductivity in undoped ZnO grown with dissociated oxygen is qualitatively consistent with the effect of higher chemical potential of atomic oxygen reactant on defect formation enthalpies. This parallels to some degree the recent attention to nitrogen acceptor incorporation by means of dissociating nitrogen source gases.

H2S sensing properties of noble metal doped WO3 thin film sensor fabricated by micromachining

Abstract: The purpose of this research is to develop a semiconductor-type H2S gas sensor with silicon-based microfabrication and micromachining technology. This successful approach allows for the production of small, geometrically well-defined sensors that are reliable and mechanically robust, and is compatible with VLSI processes. Individual sensor cost is also greatly reduced because the sensors are batch fabricated. The main sensing region is covered with a 300 μm ×300 μm WO3 thin film, which is deposited by RF sputtering on silicon wafer substrate. Platinum (Pt), gold (Au) or Au-Pt noble metals was then deposited onto WO3 thin film as activator layer by sputtering. Under 1 ppm H2S and at an operating temperature of 220 °C, the individual sensitivities of the Pt and the Au-Pt doped WO3 gas sensors are 23 and 5.5, respectively. The sensor response times of Pt, Au-Pt and Au doped WO3 thin films are 30, 2 and 8 s, respectively, and the recovery times are about 30, 30 and 160 s, respectively. The results show that the Pt doped WO3 gas sensor exhibits acceptable response time, recovery time and as well as a high sensitivity.

High density plasma CVD process for gapfill into high aspect ratio features

Abstract: A method of depositing a film on a substrate disposed in a substrate processing chamber. In one embodiment the method includes depositing a first portion of the film to at partially fill a gap formed between to adjacent features formed on the substrate. The first portion of film is deposited using a high density plasma formed from a first gaseous mixture flown into the process chamber. The film deposition process is then stopped before or shortly after the entry of the gap pinches off and the film is etched to widen entry to the gap using a two step etching process that includes a first physical etch step and a subsequent chemical etch step. The physical etch step sputter etches the first portion of film by forming a plasma from a sputtering agent introduced into the processing chamber and biasing the plasma towards the substrate. After the physical etching step, the film is chemically etched by forming a plasma from a reactive etchant gas introduced into the processing chamber. After the etching sequence is complete and entry to the gap has been widened, a second portion of the film is deposited over the first portion to further fill the gap by forming a high density plasma from a second gaseous mixture flown into the process chamber.

Effect of total and oxygen partial pressures on structure of photocatalytic TiO2 films sputtered on unheated substrate

Abstract: Crystalline titanium dioxide, TiO2, photocatalytic films were deposited by reactive r.f. magnetron sputtering on glass substrates without additional external heating. A pure metallic titanium target was sputtered in a mixture of argon and oxygen. The effect of the total pressure and the oxygen partial pressure on the deposition rate, the phase composition, the crystallinity, the surface morphology and the resulting photocatalytic properties was investigated. The films were characterized by X-ray diffraction, scanning electron microscopy and scanning probe microscopy. The photocatalytic activity was evaluated by the measurement of the decomposition of methylene blue under UV irradiation. The results showed that the crystalline anatase, anatase/rutile or rutile films can be successfully deposited on unheated substrate and their formation is dependent on the total pressure and the oxygen partial pressure. A schematic phase diagram was constructed. The surface morphology is strongly influenced by the total pressure and the anatase TiO2 films with a more open surface, a higher surface roughness and a larger surface area are formed at higher total pressures. The anatase films with such surface morphology deposited in the reactive sputtering mode exhibit the best photocatalytic activity.

Growth and characterization of radio frequency magnetron sputter-deposited zinc stannate, Zn2SnO4, thin films

Abstract: Single-phase, spinel zinc stannate (Zn2SnO4) thin films were grown by rf magnetron sputtering onto glass substrates. Uniaxially oriented films with resistivities of 10−2–10−3 Ω cm, mobilities of 16–26 cm2/V s, and n-type carrier concentrations in the low 1019 cm−3 range were achieved. X-ray diffraction peak intensity studies established the films to be in the inverse spinel configuration. 119Sn Mossbauer studies identified two octahedral Sn sites, each with a unique quadrupole splitting, but with a common isomer shift consistent with Sn+4. A pronounced Burstein–Moss shift moved the optical band gap from 3.35 to as high as 3.89 eV. Density-of-states effective mass, relaxation time, mobility, Fermi energy level, and a scattering parameter were calculated from resistivity, Hall, Seebeck, and Nernst coefficient transport data. Effective-mass values increased with carrier concentration from 0.16 to 0.26 me as the Fermi energy increased from 0.2 to 0.9 eV above the conduction-band minimum. A bottom-of-the-band ...

Alteration of Ti 2p XPS spectrum for titanium oxide by low‐energy Ar ion bombardment

Abstract: Alteration of Ti 2p XPS spectra for TiO 2 single crystal was measured during Ar ion sputtering. The acceleration voltage of Ar ion bombardment ranged from 10 V to 2 kV. Components of Ti 2+ and Ti 3+ as reduced states have appeared, in addition to the Ti 4+ state, after ion bombardment at 2 kV. However, although a small amount of Ti 3+ has been observed in the case of 10 V bombardment, the Ti 2+ component has not appeared. The intensities of the reduced states (Ti 2+ and/or Ti 3+ ) that have appeared at each acceleration voltage reach constant values after a long sputtering time. This saturation shows that the surface reaches an equilibrium state between the sputtered atoms and implanted ions. Moreover, the intensities of the reduced states increase with increasing accelerating voltage of the primary ions. The alteration by 10 V ion bombardment suggests that there is a critical energy for reduction to the Ti 2+ state.

Ionized PVD with sequential deposition and etching

Abstract: An iPVD apparatus (20) is programmed to deposit material (10) into high aspect ratio submicron features (11) on semiconductor substrates (21) by cycling between deposition and etch modes within a vacuum chamber (30). The modes operate at different power and pressure parameters. Pressure of more than 50 mTorr, for example, is used for sputtering material from a target while pressure of less than a few mTorr, for example, is used to etch. Bias power on the substrate is an order of magnitude higher for etching, producing several hundred volt bias for etching, but only a few tens of volts for deposition. The alternating etching modes remove deposited material that overhangs edges of features on the substrate, removes some of the deposited material from the bottoms (15) of the features, and resputters the removed deposited material onto sidewalls (16) of the features. The substrate (21) is cooled during deposition and etching, and particularly during etching to substantially below 0°C. RF energy is coupled into the chamber (30) to form a high density plasma, with substantially higher RF power coupled during deposition than during etching. The substrate (21) is moved closer to the plasma source during etching than during deposition.

Electrical properties of reactively sputtered WO3 thin films as ozone gas sensor

Abstract: Electrical properties of the metallic oxide semiconductor, such as tungsten trioxide (WO3) thin films, deposited on SiO2/Si substrates by RF reactive magnetron sputtering system from a metallic tungsten target and argon–oxygen mixture gas have been investigated. This study is devoted to analyse the relationship between the electrical properties and the WO3 thin film deposition parameters (substrate temperature, oxygen partial pressure, annealing) and the sensitivity and stability of these WO3 gas sensors. The surface morphology evolution of these films has been investigated by atomic force spectroscopy (AFM). Two types of electrical measurements were performed: conductivity versus temperature and some tests under ozone at different temperatures. The activation energy evolution is correlated with the reactivity of surface sensors under oxygen partial pressure.

Magnetron sputtered epitaxial single-phase Ti3SiC2 thin films

Abstract: We report on the synthesis and characterization of epitaxial single-crystalline Ti3SiC2 films (Mn+1AXn-phase). Two original deposition techniques are described, (i) magnetron sputtering from Ti3SiC2 compound target and (ii) sputtering from individual titanium and silicon targets with co-evaporated C60 as carbon source. Epitaxial Ti3SiC2 films of single-crystal quality were grown at 900 °C with both techniques. Epitaxial TiC(111) deposited in situ on MgO(111) by Ti sputtering using C60 as carbon source was used to nucleate the Ti3SiC2 films. The epitaxial relationship was found to be Ti3SiC2(0001)//TiC(111)//MgO(111) with the in-plane orientation Ti3SiC2[100]//TiC[101]//MgO[101].

Self-ionized and inductively-coupled plasma for sputtering and resputtering

Abstract: A magnetron sputter reactor for sputtering deposition materials such as tantalum, tantalum nitride and copper, for example, and its method of use, in which self-ionized plasma (SIP) sputtering and inductively coupled plasma (ICP) sputtering are promoted, either together or alternately, in the same or different chambers. Also, bottom coverage may be thinned or eliminated by ICP resputtering in one chamber and SIP in another. SIP is promoted by a small magnetron having poles of unequal magnetic strength and a high power applied to the target during sputtering. ICP is provided by one or more RF coils which inductively couple RF energy into a plasma. The combined SIP-ICP layers can act as a liner or barrier or seed or nucleation layer for hole. In addition, an RF coil may be sputtered to provide protective material during ICP resputtering. In another chamber an array of auxiliary magnets positioned along sidewalls of a magnetron sputter reactor on a side towards the wafer from the target. The magnetron preferably is a small, strong one having a stronger outer pole of a first magnetic polarity surrounding a weaker outer pole of a second magnetic polarity and rotates about the central axis of the chamber. The auxiliary magnets preferably have the first magnetic polarity to draw the unbalanced magnetic field component toward the wafer. The auxiliary magnets may be either permanent magnets or electromagnets.

Phase transformation of thin sputter-deposited tungsten films at room temperature

Abstract: Thin films of W have application in semiconductor interconnect structures as diffusion barriers and potentially as seed layers for electroplating. Thin W films have been deposited by sputtering [physical vapor deposition (PVD)] at near-room temperature, using Ar as the working gas, for evaluation of the electrical and structural properties of the films in the thickness range of 3 to 150 nm. Films deposited at 45 nm or greater thickness are composed of alpha (bcc) phase (only) with an electrical resistivity of 12 μΩ cm. Films deposited at thicknesses below 5 nm are mostly beta (A15 cubic) phase as-deposited with significantly higher resistivity, which is due partly to the phase and partly to electron-surface scattering (the “size effect”). In the thickness range of 5 to 45 nm, the as-deposited films are mostly beta phase and undergo transformation to the alpha phase at room temperature in tens of hours to several days. The resistivity also declines concurrently, as much as 70%. The exact mechanism driving ...

Fully integrated on-chip electrochemical detection for capillary electrophoresis in a microfabricated device.

Abstract: Microfabricated lab-on-a-chip devices employing a fully integrated electrochemical (EC) detection system have been developed and evaluated. Both capillary electrophoresis (CE) channels and all CE/EC electrodes were incorporated directly onto glass substrates via traditional microfabrication techniques, including photolithographic patterning, wet chemical etching, DC sputtering, and thermal wafer bonding. Unlike analogous CE/EC devices previously reported, no external electrodes were required, and critical electrode characteristics, including size, shape, and placement on the microchip, were established absolutely by the photolithography process. For the model analytes dopamine and catechol, detection limits in the 4-5 microM range (approximately 200 amol injected) were obtained with the Pt EC electrodes employed here, and devices gave stable analytical performance over months of usage.

High Resolution Focused Ion Beams: FIB and its Applications: The Physics of Liquid Metal Ion Sources and Ion Optics and Their Application to Focused Ion Beam Technology

Abstract: Preface. About the Authors. Introduction. 1. Field Ionization Sources. 2. Physics of Liquid Metal Ion Sources. 3. Ion Optics for LMIS. 4. Interactions of Ions with Solids. 5. Practical Focused Ion Beam Optics and Systems. 6. Applications of Focused Ion Beams. Appendix 1. Elements of the Theory of Field Desorption and Ionization. Appendix 2. Table of Sputter Yields. Index.

Magnetic behavior of lithographically patterned particle arrays (invited)

Abstract: This article reviews recent progress in the fabrication, characterization, and analysis of large area arrays of sub-100-nm magnetic particles made by lithographic techniques. Particles are made by electrodeposition, evaporation and liftoff, or sputtering and etching, leading to a wide range of shapes, compositions, and microstructures. The remanent states, magnetic hysteresis, and uniformity of the particles and the interparticle interactions will be discussed.

Jetlike component in sputtering of LiF induced by swift heavy ions.

Abstract: Angular distributions of sputtered atoms from SiO2 and LiF single crystals were measured under the irradiation of 1 MeV/u swift heavy ions. In contrast to the almost isotropic distribution of SiO2, an additional jetlike component was observed for LiF. The total sputtering yield of SiO2 ( approximately 10(2) atoms/ion) can be reproduced by an extended inelastic thermal spike model, whereas the huge yield of LiF ( approximately 10(4) atoms/ion) needs a substantial decrease of the sublimation energy to be described by the model.