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Showing papers in "Journal of Vacuum Science & Technology B in 1994"


Journal ArticleDOI
TL;DR: In this article, a technique was developed for highly efficient postionization of sputtered metal atoms from a magnetron cathode, based on conventional magnetron sputtering with the addition of a high density, inductively coupled rf (RFI) plasma in the region between the sputtering cathode and the sample.
Abstract: A technique has been developed for highly efficient postionization of sputtered metal atoms from a magnetron cathode. The process is based on conventional magnetron sputtering with the addition of a high density, inductively coupled rf (RFI) plasma in the region between the sputtering cathode and the sample. Metal atoms sputtered from the cathode due to inert gas ion bombardment transit the rf plasma and can be ionized. The metal ions can then be accelerated to the sample by means of a low voltage dc bias, such that the metal ions arrive at the sample at normal incidence and at a specified energy. The ionization fraction, measured with a gridded mass‐sensitive energy analyzer is low at 5 mTorr and can reach 85% at 30 mTorr. Optical emission measurements show scaling of the relative ionization to higher discharge powers. The addition of large fluxes of metal atoms tends to cool the Ar RFI plasma, although this effect depends on the chamber pressure and probably the pressure response of the electron tempera...

376 citations


Journal ArticleDOI
TL;DR: In this article, a two-dimensional hybrid model consisting of electromagnetic, electron Monte Carlo, and hydrodynamic modules was developed to investigate inductively coupled plasma sources for high plasma density (1011-1012 cm−3), low pressure (a few to 10-20 mTorr) etching of semiconductor materials.
Abstract: Inductively coupled plasma sources are being developed to address the need for high plasma density (1011–1012 cm−3), low pressure (a few to 10–20 mTorr) etching of semiconductor materials. One such device uses a flat spiral coil of rectangular cross section to generate radio‐frequency (rf) electric fields in a cylindrical plasma chamber, and capacitive rf biasing on the substrate to independently control ion energies incident on the wafer. To investigate these devices we have developed a two‐dimensional hybrid model consisting of electromagnetic, electron Monte Carlo, and hydrodynamic modules; and an off line plasma chemistry Monte Carlo simulation. The results from the model for plasma densities, plasma potentials, and ion fluxes for Ar, O2, Ar/CF4/O2 gas mixtures will be presented.

315 citations


Journal ArticleDOI
TL;DR: The digital micromirror device (DMD) as discussed by the authors is a monolithic, micromechanical spatial light modulator that is used to implement the first truly digital projection display systems.
Abstract: The digital micromirror device (DMD) is a monolithic, micromechanical spatial light modulator. The DMD has been used to implement the first truly digital projection display systems. In these systems, discrete, tilting mirror elements are fabricated from sputter deposited aluminum directly on top of arrays of complementary metal–oxide semiconductor memory cells. The mirrors are switched between two stable tilted states according to whether a ‘‘1’’ or a ‘‘0’’ is stored in the underlying memory location. An optical system illuminates the DMD and projects its image in such a way that the image of each mirror, which represents a single pixel in the projected image, is at full brightness when the mirror is tilted in the ‘‘1’’ state and full darkness when the mirror is tilted in the ‘‘0’’ state. The refresh rate of the memory and the response rate of the mirrors are high enough so that hundreds of memory frames can be displayed during one video frame, and so that each pixel can be on or off in a binary fashion for a portion of the video frame proportional to that pixel’s individual intensity. The digital‐to‐analog conversion of this intensity occurs in the eye/brain of the viewer. The mirrors are typically square, 16 μm on a side, and placed on 17 μm centers. Each mirror tilts 10° from horizontal in each of its two addressed states, so that the ‘‘1’’ state and ‘‘0’’ state are 20° apart. Arrays of mirrors ranging from resolutions of 768×576 mirrors up to 2048×1152 mirrors have been fabricated.The article will describe the fabrication process for the DMD, the optical system used to project the DMD image, and the electronic method of addressing the device. Prototype projection systems will be described and preliminary performance measurements will be presented.

185 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe the plasma formation at cathode spots, macroparticle filtering of the vacuum arc plasma by magnetic ducts, and present some examples of MPI applications.
Abstract: Plasma source ion implantation (PSII) with metal plasma results in a qualitatively different kind of surface modification than with gaseous plasma due to the condensable nature of the metal plasma, and a new, PSII‐related technique can be defined: metal plasma immersion ion implantation and deposition (MPI). Tailored, high‐quality films of any solid metal, metal alloy, or carbon (amorphous diamond) can be formed by MPI using filtered vacuum arc plasma sources, and compounds such as oxides or nitrides can be formed by adding a gas flow to the deposition. Here we describe the plasma formation at cathode spots, macroparticle filtering of the vacuum arc plasma by magnetic ducts, the underlying physics of MPI, and present some examples of MPI applications.

145 citations


Journal ArticleDOI
TL;DR: In this article, a phase diagram is constructed, showing the growth conditions under which these strained coherent uniform dots form, and photoluminescence from layers containing these dots is observed and correlated with growth conditions and with structural data obtained from TEM images.
Abstract: The two‐ (2D) to three‐dimensional (3D) growth mode transition during the initial stages of growth of highly strained InxGa1−xAs on GaAs is used to obtain quantum dot structures. Transmission electron micrographs (TEM) reveal that when the growth of InxGa1−xAs is interrupted exactly at the onset of this 2D–3D transition, dislocation‐free islands (dots) of InGaAs result. Size distribution measurements from TEM images indicate that these dots are less than 300 A in diameter and remarkably uniform. A phase diagram is constructed, showing the growth conditions under which these strained coherent uniform dots form. Photoluminescence from layers containing these dots is observed and correlated with growth conditions and with structural data obtained from TEM images. We observe that the photoluminescence emitted from the dots and an underlying reference quantum well are nearly equal, indicating a high quantum efficiency for these quantum dots.

139 citations


Journal ArticleDOI
TL;DR: In this paper, the gate voltage required to achieve a given emission current density in field-emitter arrays was reduced by scaling down the gate-to-tip and tip-tip spacing to the unprecedented levels of 0.08 and 0.32 μm, respectively.
Abstract: We have reduced the gate voltage required to achieve a given emission current density in field‐emitter arrays by scaling down the gate‐to‐tip and tip‐to‐tip spacing to the unprecedented levels of 0.08 and 0.32 μm, respectively. The submicrometer features of our arrays are patterned using interferometric lithography. Electrical tests of arrays we have fabricated have shown a record low turn‐on voltage of 8 V for cesiated molybdenum emitters. Emission current densities of 1600 A/cm2 have been obtained, which is also a record for such structures. These arrays provide large advantages for applications such as flat panel displays and microwave devices.

127 citations


Journal ArticleDOI
TL;DR: In this paper, the authors use results from a two-dimensional model to investigate design issues in transformer coupled plasmas (TCPs) for etching, and they find that designs which produce ionization predominantly at larger radii near the edge of the wafer produce more uniform ion fluxes to the substrate.
Abstract: Inductively coupled plasma (ICP) sources are being developed as reactors for high plasma density (1011–1012 cm−3), low‐pressure (<10–20 mTorr) etching of semiconductors and metals for microelectronics fabrication. Transformer coupled plasmas (TCPs) are one variant of ICP etching tools which use a flat spiral coil having a rectangular cross section powered at radio frequencies (rf) to produce a dense plasma in a cylindrical plasma chamber. Capacitive rf biasing of the substrate may also be used to independently control ion energies incident on the wafer. The uniformity of generating the plasma and the uniformity of the flux of reactants to the substrate are functions of the geometry and placement of the coil; and of the materials used in the construction of the chamber. In this article, we use results from a two‐dimensional model to investigate design issues in TCPs for etching. We parametrize the number of turns and locations of the coil; and material properties of the reactor. We find that at low pressure, designs which produce ionization predominantly at larger radii near the edge of the wafer produce more uniform ion fluxes to the substrate. This results from a ‘‘converging’’ ion flux which compensates for losses to lateral surfaces. Careful attention must be paid to metal structures in the vicinity of the coils which restrict the azimuthal electrical field. This situation results in reduced power deposition at large radii, which can be compensated by over sizing the coil or by using auxiliary solenoidal coils. The plasma and neutral transport, dominated by diffusion, treats the advective flow from the gas inlets and pump port as local sources and sinks which are rapidly volume averaged.

127 citations


Journal ArticleDOI
TL;DR: A range of bright, multicolor phosphor systems for field emission displays is reported in this paper, which include the standard ZnO:Zn and newer, narrow band emitting systems based on green ZnGa2O4:Mn and red CaTiO3:Pr.
Abstract: A range of bright, multicolor phosphor systems for field emission displays is reported. These include the standard ZnO:Zn and newer, narrow band emitting systems based on green ZnGa2O4:Mn and red CaTiO3:Pr. A modified, blue emitting ZnO:(Zn/Mg) and thin films of ZnGa2O4:Mn have also been prepared.

127 citations


Journal ArticleDOI
TL;DR: In this paper, a procedure for high-resolution patterning of magnetic recording films using direct write electron-beam lithography and a multistep sputter etching process was developed.
Abstract: We are investigating the feasibility of a recording medium in which each bit of information is stored in a single‐domain magnetic particle. To this end we have developed a procedure for high‐resolution patterning of magnetic recording films using direct write electron‐beam lithography and a multistep sputter etching process. We have used this procedure to define small islands of polycrystalline magnetic thin film with feature sizes down to 0.1 μm. The patterning process is suitable for many different kinds of magnetic films, including single‐crystal epitaxially grown films, and is designed to minimize physical and chemical damage to the magnetic material being patterned. Both atomic force microscopy and x‐ray photoemission spectroscopy have been used to establish that the magnetic islands patterned using this process are physically isolated from each other.

125 citations


Journal ArticleDOI
TL;DR: In this article, a two-dimensional (r,z) fluid model has been developed to study plasma transport in inductively coupled plasmas (ICP), where electron heating is treated by assuming a fixed, spatially varying power deposition profile in the electron energy balance equation.
Abstract: A two‐dimensional (r,z) fluid model has been developed to study plasma transport in inductively coupled plasmas (ICP). Electron heating is treated by assuming a fixed, spatially varying power deposition profile in the electron energy balance equation. A high aspect ratio ICP reactor geometry has been studied, with two assumed power profiles: spatially uniform and localized to within several skin depths of the radial wall. The effect of neutral gas pressure on plasma uniformity is presented for an argon discharge over the range of 1–20 mTorr. Comparisons between the fluid model and predictions from a spatially averaged global model show similar scaling of plasma density, electron temperature, and plasma potential over a wide range of pressure and power.

124 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the structure of copper-phthalocyanine monolayers on highly oriented pyrolytic graphite (HOPG) and MoS2 prepared by organic molecular beam epitaxy.
Abstract: Monolayers of copper–phthalocyanine (Cu–Pc) on highly oriented pyrolytic graphite (HOPG) and MoS2 prepared by organic molecular beam epitaxy have been investigated by scanning tunneling microscopy. On both substrates there exist well defined preparation conditions leading to ordered two‐dimensional arrays of flat lying molecules. On HOPG they form a close‐packed structure with a nearly quadratic unit cell, whereas on MoS2 we found two phases, one close‐packed and one rowlike phase. This rowlike phase can be explained by a long range interaction due to an adsorbate induced superstructure of the substrate, which also can be seen in the scanning tunneling microscopy images. In images with submolecular resolution, the molecules appear different on the two substrates. On MoS2 they look like a four‐leaved clover, on graphite they show a more detailed inner structure.

Journal ArticleDOI
TL;DR: In this paper, the growth direction of the MnAs thin films was found to be [100] on (001) GaAs, and the epitaxial relationship was [0001] MnAs //[10] GaAs and [110] NMAs // [110 ] GaAs.
Abstract: We have successfully grown single‐crystalline ferromagnetic MnAs thin films on (001) GaAs substrates by molecular beam epitaxy. By reflection high energy electron diffraction and x‐ray measurements, the growth direction of the MnAs thin films was found to be [100] on (001) GaAs, and the epitaxial relationship was [0001] MnAs //[10] GaAs and [110] MnAs // [110] GaAs. Magnetization measurements at room temperature have revealed that the epitaxial MnAs thin films have strong magnetic anisotropy, and that the easy magnetization direction is in‐plane, along the [110] axis of the MnAs thin films which is parallel to the [110] axis of the GaAs substrate, with almost perfect square hysteresis loops, relatively high remanent magnetization, and low coercive field.

Journal ArticleDOI
TL;DR: In this article, the mismatch strain of molecular beam epitaxy (MBE) deposited InGaAs on GaAs to induce a transition from the two-dimensional growth mode to the three-dimensional (Stranski-Krastanow) growth mode is presented.
Abstract: A one step method for the production of quantum dots is presented. The method exploits the mismatch strain of molecular beam epitaxy (MBE) deposited InGaAs on GaAs to induce a transition from the two‐dimensional growth mode to the three‐dimensional (Stranski–Krastanow) growth mode. The cluster size is limited to quantum dimensions by precisely controlling the amount of InGaAs that is deposited in order to cause the growth mode transition. Very narrow lateral size distributions with standard deviations of 14% on the dot area have been obtained. Smooth MBE growth of GaAs over these clusters produces a layer of quantum dots, whose high quality and uniformity has been observed with transmission electron microscopy, atomic force microscopy, and photoluminescence (PL). The quantum dot PL intensity is enhanced compared to a reference quantum well. Resonances in photoluminescence excitation (PLE) spectra suggest that the density of states in these dots has minima close to zero between the quantum states, as expec...

Journal ArticleDOI
TL;DR: In this paper, two types of nanoscale single-domain magnetic structures were fabricated using e−beam nanolithography and were studied using magnetic force microscopy, and it was found that the magnetic properties of these structures can be controlled by engineering their size and spacing.
Abstract: Two types of nanoscale single‐domain magnetic structures were fabricated using e‐beam nanolithography and were studied using magnetic force microscopy. The first structure is the isolated and interactive arrays of Ni bars on silicon that are 35 nm thick, 1 μm long, and have widths ranging from 15 to 200 nm and spacings ranging from 200 to 600 nm. The second structure is an array of Ni pillars on silicon that have a uniform diameter of 35 nm, a height of 120 nm, and a density of 65 Gbits/in2—over two orders of magnitude greater than the state‐of‐the‐art magnetic storage density. It was found that the magnetic properties of these structures can be controlled by engineering their size and spacing. When the bar width is smaller than 150 nm, the bars become single magnetic domain. As the width of the isolated bars decreased from 200 to 55 nm, the magnetic field needed to switch the magnetization of these bars increased monotonically from 100 to 740 Oe which is the highest field reported for Ni. However, further reduction of bar width led the switching field to decrease due to thermal effect. Furthermore, it was found that as the bar spacings become smaller, the interaction between the bars will reduce the switching field. Finally, based on the artificially patterned single‐domain magnetic structures, we propose a new paradigm for ultra‐high‐density magnetic recording media: quantum magnetic disk.

Journal ArticleDOI
TL;DR: Atomic layer epitaxy (ALE) is emerging as a promising epitaxial growth technique for thickness control at the atomic level as discussed by the authors, and recent progress in ALE of III-V and Si thin films.
Abstract: Atomic layer epitaxy (ALE) is emerging as a promising epitaxial growth technique for thickness control at the atomic level. The article outlines recent progress in ALE of III–V and Si thin films. Also models describing the self‐limiting processes will be outlined.

Journal ArticleDOI
TL;DR: In this article, self-assembled monolayers have been modified with focused electron beams of energy 1-50 keV and scanning tunneling microscopy (STM) based lithography with energies of ∼10 eV.
Abstract: Self‐assembled monolayers have been modified with focused electron beams of energy 1–50 keV and scanning tunneling microscopy (STM) based lithography with energies of ∼10 eV. Modifications ∼15 nm in size have been formed by STM and ∼25 nm in size by 50 keV beams. The fact that these materials work as self‐developing electron beam resists is demonstrated by both atomic force microscopy imaging and pattern transfer using conventional wet etchants. Patterns have been transferred to silicon substrates to a depth of ≳120 nm with a multistep wet etching process. The mechanism of electron beam modification has also been explored to better design future monolayer processes.

Journal ArticleDOI
TL;DR: In this paper, real space studies of the interaction of the two-dimensional electron gas provided by metal surface states with localized scatterers are presented, and the decay of the amplitude of the oscillations as a function of distance from the scatterer can be explained by a model that describes the loss of coherence as a result of the wave number (k∥) spread of the states probed by the STM.
Abstract: Real space studies of the interaction of the two‐dimensional electron gas provided by metal surface states with localized scatterers are presented. The results involve electron scattering by steps and point defects (adsorbates) at Au(111) and Ag(111) surfaces. These scattering events lead, through interference, to an oscillatory local density of states (LDOS), which is imaged in maps of (dI/dV)/(I/V). Analysis of the LDOS oscillations provides insights into the scattering phenomena involved. We show that the decay of the amplitude of the oscillations as a function of distance from the scatterer can be accounted for by a model that describes the loss of coherence as a result of the wave number (k∥) spread of the states probed by the STM. This model also explains the energy dependence of the amplitude of the oscillations and provides a basis for comparing results from different metal surfaces. Analysis of the properties of the oscillations shows that at low k∥, steps act very much like hard walls isolating ...

Journal ArticleDOI
TL;DR: A magnetron sputtering system for the deposition of Mo/Si multilayer (ML) coatings onto large-area, figured optics, as required for the imaging system in a practical, extreme-ultraviolet (EUV) lithography tool was developed in this paper.
Abstract: We have developed a magnetron sputtering system for the deposition of Mo/Si multilayer (ML) coatings onto large‐area, figured optics, as required for the imaging system in a practical, extreme‐ultraviolet (EUV) lithography tool. Coating uniformity on figured optics is adjusted by implementing contoured, shaped baffles during ML deposition. We have also developed an EUV reflectometer that is capable of measuring the reflectance versus wavelength across the surface of these optics, so that the coating uniformity can be determined with the required precision. We discuss the ML coating uniformity requirements for a practical EUV lithography tool, describe the facilities and techniques we have developed, and present some recent results wherein these facilities and techniques have been used to deposit high‐reflectance coatings onto a variety of spherical and aspherical substrates.

Journal ArticleDOI
TL;DR: The calibrated AFM (C•AFM) as mentioned in this paper uses a flexure stage driven by piezoelectric transducers for scanning, a heterodyne interferometer to measure the X and Y displacements of the sample, and a capacitance sensor for measuring the Z displacement.
Abstract: Advances in the manufacture of integrated circuits, x‐ray optics, magnetic read–write heads, optical data storage media, and razor blades require advances in ultraprecision metrology. Each of these industries is currently investigating the use of atomic force microscopy (AFM) to improve the precision and accuracy of their manufacturing process control. To facilitate the use of AFMs for manufacturing we have developed an AFM capable of making accurate dimensional measurements. We call this system the calibrated AFM (C‐AFM). The C‐AFM has been constructed as much as possible out of commercially available components. We use a flexure stage driven by piezoelectric transducers for scanning, a heterodyne interferometer to measure the X and Y displacements of the sample, a capacitance sensor to measure the Z displacement of the sample, and a commercially available AFM control system. The control system has two feedback loops which read from the X and Y interferometers, respectively, and adjust the piezoelectric ...

Journal ArticleDOI
TL;DR: In the last five years, plasma source ion implantation (PSII) research at the University of Wisconsin-Madison has encompassed work in the areas of plasma physics, diagnostics, ion-material interactions' modeling, materials science issues, and a broad spectrum of industrial applications of PSII technology.
Abstract: In the last five years, plasma source ion implantation (PSII) research at the University of Wisconsin–Madison, has encompassed work in the areas of plasma physics, diagnostics, ion‐material interactions’ modeling, materials science issues, and a broad spectrum of industrial applications of PSII technology. The third generation PSII system is presently under construction. Three methods of plasma generation, namely, electron impact method, glow discharge, and radio frequency have been successfully employed. In the following article the highlights of the above facets of PSII research activities have been presented.

Journal ArticleDOI
TL;DR: In this article, an ultrahigh vacuum (UHV) scanning tunneling microscope (STM) was used to selectively desorb the hydrogen passivation on silicon monohydride surfaces.
Abstract: Nanoscale patterning of the Si(100)‐2×1 monohydride surface has been achieved by using an ultrahigh vacuum (UHV) scanning tunneling microscope(STM) to selectively desorb the hydrogen passivation. Hydrogen passivation on silicon represents one of the simplest possible resist systems for nanolithography experiments. After preparing high quality H‐passivated surfaces in the UHV chamber, patterning is achieved by operating the STM in field emission. The field emitted electrons stimulate the desorption of molecular hydrogen, restoring clean Si(100)‐2×1 in the patterned area. This depassivation mechanism seems to be related to the electron kinetic energy for patterning at higher voltages and the electron current for low voltage patterning. The patterned linewidth varies linearly with the applied tip bias achieving a minimum of <10 A at −4.5 V. The dependence of linewidth on electron dose is also studied. For positive tip biases up to 10 V no patterning occurs. The restoration of clean Si(100)‐2×1 is suggestive of selective area chemical modifications. This possibility has been explored by exposing the patternedsurface to oxygen and ammonia. For the oxygen case, initial oxidation of the patterned area is observed. Ammonia dosing, on the other hand, repassivates the surface in a manner different from that of atomic hydrogen. In both cases the pattern resolution is retained and the surrounding H‐passivated areas remain unaffected by the dosing.

Journal ArticleDOI
TL;DR: In this article, the authors describe in situ, high data rate, accurate measurements of the chemical kinetics that occur in chemically amplified (CA) resists during the post-exposure bake and propose models for the thermal and acid-catalyzed deprotection and extracted rate coefficients using a stochastic kinetics simulator.
Abstract: Deep ultraviolet (UV) chemically amplified (CA) resists are leading candidates for semiconductor lithography manufacturing in the sub‐half‐micron regime. In this article, we describe in situ, high data rate, accurate measurements of the chemical kinetics that occur in CA resists during the post‐exposure bake. The thermal and acid‐catalyzed deprotection of two candidate deep‐UV resist materials, poly(p‐t‐butoxycarbonyloxystyrene) (PTBOCST) and poly(t‐butylmethacrylate) (PTBMA), was characterized. The thermal deprotection of PTBOCST and PTBMA showed auto‐accelerated behavior as the reaction proceeds, while the acid‐catalyzed deprotection displayed inhibition as extent of conversion increased. We propose models for the thermal and acid‐catalyzed deprotection and extracted rate coefficients using a stochastic kinetics simulator. Excellent agreement between the model and experimental data was obtained.

Journal ArticleDOI
TL;DR: In this article, an atomic force microscope (AFM) having a tip on whose surface sensor molecules were immobilized has been developed for chemical sensing, and the AFM tip chemically modified with octadecyltrichlorosilane [CH3(CH)17SiCl3; OTS] or perfluorotrichlorosa [CF3(CF2)7C2H4SiCl 3; FS‐17] were more sensitive than the unmodified tips in detecting adhesive force on some monolayers on the silicon substrates.
Abstract: A novel atomic force microscope (AFM) having a tip on whose surface sensor molecules were immobilized has been developed for chemical sensing. The AFM tips chemically modified with octadecyltrichlorosilane [CH3(CH)17SiCl3; OTS] or perfluorotrichlorosilane [CF3(CF2)7C2H4SiCl3; FS‐17] were more sensitive than the unmodified tips in detecting adhesive force on some monolayers on the silicon substrates. Using OTS modified tip, the hydrocarbon chain length of chemically adsorbed alkyltrichlorosilanes [CH3(CH)nSiCl3, n=1,8,13,17] on the silicon substrates was discriminated in ethanol environment. The origin of the interaction between the chemically modified tips and the sample surfaces, which depend on the monolayers and environmental liquids where the interactions were measured, has been speculated to arise from the entwining of carbon chains in monolayers on the tip and the sample.

Journal ArticleDOI
TL;DR: In this article, the secondary ion mass spectrometry (SIMS) analysis of ultrathin or delta layers of impurity in a semiconductor matrix and their use in establishing the limitations of SIMS depth profiling, exploring the fundamental processes occurring during analysis, and enhancing the quantification ofSIMS data are described.
Abstract: The subject of this review is the secondary ion mass spectrometry (SIMS) analysis of ultrathin or delta layers of impurity in a semiconductor matrix and their use in establishing the limitations of SIMS depth profiling, exploring the fundamental processes occurring during analysis, and enhancing the quantification of SIMS data. Methods for extracting accurate information for the grower (concerning the material) and the analyst (concerning the SIMS instrument) are described. It is demonstrated that sets of SIMS profiles obtained over a range of analytical conditions are desirable if accurate information is required. In this context, the observation of dopant interaction occurring in codoped samples during SIMS analysis is reported for the first time. It is shown that quite large discrepancies exist between different measurements of decay length and associated parameters for the same impurity/matrix combination. These need to be explained before attempting to relate delta profile shape to primary ion beam i...

Journal ArticleDOI
TL;DR: In this paper, a high selective, highly anisotropic, notch-free and charge build-up damage-free polycrystalline silicon etching is achieved using an electron cyclotron resonance plasma modulated at a pulse time in the range of 10-20 μs.
Abstract: Highly selective, highly anisotropic, notch‐free and charge build‐up damage‐free polycrystalline silicon etching is achieved using an electron cyclotron resonance plasma modulated at a pulse time in the range of 10–20 μs. In this plasma, the selectivity ratio of the polycrystalline silicon etching rate to the SiO2 etching rate is increased significantly by the same etching rate as that attained using a continuous discharge. Additionally, vertical and notch‐free phosphorus‐doped polycrystalline silicon etching profiles and suppressing charge build‐up damage can be achieved. These results are attained by controlling the ion energy distribution through the duty ratio, maintaining a high ion current density, generating a collimated ion flux, and eliminating surface charge with the pulsed discharge.

Journal ArticleDOI
TL;DR: In this paper, a systematic examination of InAs island formation on GaAs(100) as a function of deposition conditions and thickness is presented, indicating that currently popular frameworks of compound semiconductor molecular beam epitaxical growth and island formation mechanism(s) need to be enlarged.
Abstract: Results of a systematic examination of InAs island formation on GaAs(100) as a function of deposition conditions and thickness are presented. A non‐Arrhenius dependence of the island density on substrate temperature and a decrease in the island density with increasing As4 pressure at lower substrate temperatures is observed, indicating that currently popular frameworks of compound semiconductor molecular‐beam epitaxical growth and island formation mechanism(s) need to be enlarged. Plan‐view transmission electron microscopy (TEM) and use of the behavior of Moire fringes provides the island size distribution and demarcation between coherent and incoherent islands. Photoluminescence (PL) behavior is shown to vary significantly with the growth conditions and to correlate to the attendant structural nature revealed by TEM. The issue of lateral quantum confinement (i.e., three‐dimensional islands as quantum boxes) is shown to be subtle and complex, calling for caution in interpreting PL behavior. The results su...

Journal ArticleDOI
TL;DR: In this article, the structure and properties of PIII and plasma nitrided AISI 316 austenitic stainless steel were characterized in order to establish the similarities and differences between the two processes.
Abstract: Plasma immersion ion implantation (PIII), although originally developed as an alternative non‐line‐of‐sight ion implantation technique, is also capable of producing structures typical of thermochemical processing. In this work, the structure and properties of PIII and plasma nitrided AISI 316 austenitic stainless steel were characterized in order to establish the similarities and differences between PIII and plasma nitriding. A distinct difference between PIII and plasma nitriding has been identified with respect to the degree of nitrogen supersaturation of the austenite that can be achieved. It is proposed that the extent of supersaturation and the resultant microstructure are primarily controlled by the nitrogen mass transfer mechanism. For plasma nitrided stainless steel, a surface iron nitride layer is formed and limits the nitrogen content to less than 20 at. %. For PIII, where nitrogen is also directly implanted below the surface, nitrogen contents near the theoretical limit of 50 at. % can be achieved.

Journal ArticleDOI
TL;DR: In this article, the Hamaker constant of the van der Waals forces between a silicon nitride tip and a mica sample in air was measured using an atomic force microscopy image.
Abstract: An understanding of the interaction between tip and sample in atomic‐force microscopy is needed to interpret atomic‐force‐microscope (AFM) images. In contact mode, the strength of the van der Waals (vdW) force sets image resolution; in noncontact mode, local gradients in the vdW force are imaged. By immersing tip and sample in an appropriate fluid, we can decrease the vdW forces and even change their sign. Selecting a fluid that leads to a small repulsive vdW force can greatly improve image resolution and eliminates problems caused by the well‐known tip‐snapping instability. To measure the vdW interactions produced by different fluids, we have developed ways to calibrate the spring constant and sharpness of AFM tips and to measure accurately the Hamaker constant of vdW interactions. These techniques show that the AFM can be used for local force measurements with an accuracy approaching that of surface‐force apparatuses. As an example, we have observed the crossover from nonretarded to retarded vdW forces between a silicon nitride tip and a mica sample in air.

Journal ArticleDOI
TL;DR: The first high-resolution study of the optical emission from nitrogen plasmas produced by an ASTeX compact electron cyclotron resonance (ECR) microwave plasma source is reported in this article.
Abstract: The first high‐resolution study of the optical emission from nitrogen plasmas produced by an ASTeX compact electron cyclotron resonance (ECR) microwave plasma source is reported. The spectroscopic results clearly show that the ECR plasma source generates an appreciable flux of nitrogen atoms, as indicated by strong atomic emission lines in the near‐infrared spectral region, in addition to various species of molecular nitrogen.

Journal ArticleDOI
TL;DR: Using plasma immersion ion implantation (PIII), silicon has been doped with boron in a high voltage pulsed microwave multipolar bucket plasma system and a collisional dynamic sheath model has been developed to optimize the system design and predict the doping results.
Abstract: Using plasma immersion ion implantation (PIII), silicon has been doped with boron in a high voltage pulsed microwave multipolar bucket plasma system. In order to optimize the system design and predict the doping results, a collisional dynamic sheath model has been developed, which has been verified by measurements as well as simulations. Silicon devices, including diode, metal–oxide–semiconductor (MOS) capacitor, and PMOS transistor, were fabricated by PIII doping technique. B2H6 diluted in helium (1%) was used as the gas source. The reasonable contamination levels involved from PIII process were observed by the measurements of secondary ion mass spectrometry and characteristics of fabricated devices. Good quality of devices has been demonstrated including low reverse current of diode and reasonable lifetimes of the minority carrier.