By Topic

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

Issue 1 • Date Jan 1995

Filter Results

Displaying Results 1 - 25 of 28
  • Extremely low specific contact resistivities for p‐type GaSb, grown by molecular beam epitaxy

    Page(s): 1 - 3
    Save to Project icon | PDF file iconPDF (77 KB)  

    We have investigated different metal contacts (Cr/Au, Ti/Pt/Au, and Au) on p‐type GaSb, grown by the molecular beam epitaxy. For Au contacts, specific contact resistivities in the range of 1.4×10-8–7.8×10-8 Ω cm2 have been obtained. These are the lowest values ever reported for p‐type GaSb. A simple procedure for surface preparation is also reported. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sequential tunneling through n‐type GaAs/AlGaAs multi‐quantum‐well structures with Schottky and ohmic contacts

    Page(s): 4 - 9
    Save to Project icon | PDF file iconPDF (159 KB)  

    The sequential tunneling of electrons through n‐type GaAs/AlGaAs multiple‐quantum‐well (MQW) structures with Schottky and ohmic contacts is reported. Two series of tunnelings corresponding to those between the ground state and the first and second excited states were observed in low‐temperature current–voltage (I–V) characteristics in 200‐Å‐period and 240‐Å‐period MQWs. The oscillations in the conductance (G) and steplike features in the I–V characteristics were found to be persistent up to 200 K. Unlike previous investigations using structures with nominally undoped MQW regions, S‐shaped steplike features in the I–V characteristics corresponding to the negative differential resistance (NDR) effect, were observed at low temperature in our MQW structures with Schottky contacts and uniformly doped n‐type MQW regions. The electron tunneling process through the MQW structures is discussed in terms of the creation and propagation of high electric field domains as a function of the applied bias. © 1995 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Passivation of GaAs surfaces and AlGaAs/GaAs heterojunction bipolar transistors using sulfide solutions and SiNx overlayer

    Page(s): 10 - 14
    Save to Project icon | PDF file iconPDF (138 KB)  

    Stable passivation of GaAs surfaces and AlGaAs/GaAs heterojunction bipolar transistors has been achieved using sulfide solutions and SiNx overlayers. The SiNx layers are deposited at ∼200 °C using electron cyclotron resonance plasma‐enhanced chemical vapor deposition technique. The capacitance–voltage measurements indicate a substantial reduction in the density of electronic defects at the SiNx/S–GaAs interface as a result of annealing in N2 ambient. The base current of a 36×36 μm2 AlGaAs/GaAs heterojunction bipolar transistor is reduced by approximately two orders of magnitude in the low collector current regime by using sulfide treatment, SiNx deposition, and anneal. Both the Al/SiNx/S–GaAs capacitors and transistors are stable for several months with no noticeable degradation in their electrical characteristics. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparison of H+ and He+ implant isolation of GaAs‐based heterojunction bipolar transistors

    Page(s): 15 - 18
    Save to Project icon | PDF file iconPDF (165 KB)  

    The use of multiple energy He+ implantation for producing electrical isolation between neighboring GaAs/AlGaAs or GaAs/InGaP heterojunction bipolar transistors is found to alleviate the problem of time‐dependent current gain behavior found in H+ isolated devices. This latter phenomenon is ascribed to rapid diffusion of atomic hydrogen into the active base region during the anneal required to maximize the resistance of the implanted areas, and the subsequent reactivation of passivated C acceptors in the base. Replacement of H+ with He+ ions in the implant scheme produces similar high resistance isolation regions (≳108 Ω/cm) without the presence of hydrogen passivation effects. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Focused‐ion‐beam implantation of Ga in elemental and compound semiconductors

    Page(s): 19 - 26
    Save to Project icon | PDF file iconPDF (510 KB)  

    Small‐area [∼(50 μm)2], focused‐ion‐beam implantation of 25 keV Ga+ in Si, Ge, InP, InSb, and ZnSe was investigated by experiments and by computer simulations. Specifically, the Ga concentration was determined for implantation fluences Φ ranging from 1×1014 to 3×1017 Ga+ ions/cm2 by means of secondary‐ion mass spectrometry. In all materials the Ga peak concentration exhibits an essentially linear increase with fluence up to some 1016 cm-2; for higher values of Φ the Ga concentration tends to saturate. The saturation content of Ga at the surface c ranges from ∼2 at % for ZnSe to ∼40 at % for Si. These values appear roughly inversely correlated with the specimens’ sputtering yields and agree thus with the predictions of a model of ion retention in the presence of concurrent sputter erosion. The computer simulations with the dynamic binary‐collision‐approximation code t‐dyn produce a fluence‐dependent evolution of the Ga concentrations in the examined semiconductors which is in qualitative agreement with the experiments. Furthermore, partial sputtering yields and the most probable ranges for 25 keV Ga+ impact on the different materials have been determined both experimentally and from the simulation output. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Plasma‐induced damage of GaAs pn‐junction diodes using electron cyclotron resonance generated Cl2/Ar, BCl3/Ar, Cl2/BCl3/Ar, and SiCl4/Ar plasmas

    Page(s): 27 - 33
    Save to Project icon | PDF file iconPDF (504 KB)  

    Plasma‐induced etch damage often degrades the electrical and optical performance of III–V high‐density integrated circuits and photonic devices. We have investigated the etch‐induced damage of electron cyclotron resonance (ECR) generated plasmas on the electrical performance of mesa‐isolated GaAs pn‐junction diodes. Cl2/Ar, BCl3/Ar, Cl2/BCl3/Ar, and SiCl4/Ar ECR plasmas at ion energies ranging from 10 to 200 eV were studied. Diodes fabricated under low dc‐bias (≤100 V) etch conditions yielded low reverse‐bias currents which were comparable to wet‐chemical‐etched devices. As the dc bias was increased, the diodes showed significantly higher reverse‐bias currents indicating plasma‐induced sidewall damage of the pn‐junction. Variations in diode reverse‐bias leakage currents are reported as a function of plasma parameters and chemistries. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Resolution enhanced scanning force microscopy measurements for characterizing dry etching methods applied to titanium masked InP

    Page(s): 34 - 39
    Save to Project icon | PDF file iconPDF (951 KB)  

    Scanning force microscopy was used to investigate the morphology and the microroughness of the dry etched surfaces of titanium masks and InP substrates. The influence of different ion beam etching procedures on the surface roughness has been studied. Since the observed surface structures were on the nanometer scale, sharp microtips with an improved geometry were used in order to obtain high lateral and vertical resolution. The tips were produced by electron‐beam‐induced deposition employing a field emission scanning electron microscope. Tip convolution effects were considered and, moreover, a scan artifact at steep surfaces features was revealed. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Smooth reactive ion etching of GaAs using a hydrogen plasma pretreatment

    Page(s): 40 - 42
    Save to Project icon | PDF file iconPDF (303 KB)  

    Extremely smooth GaAs surfaces are attained after SiCl4 reactive ion etching by preparing the surface before etching with hydrogen plasma exposure to selectively remove the native surface oxides. Using this hydrogen plasma pretreatment, the surface morphology after etching is equivalent to that of the original surface since the etching proceeds uniformly through the GaAs without micromasking effects from a nonuniform surface oxide. The beneficial effects of the hydrogen plasma processing are observed in two different reactors and are found to be independent of the platen temperature during etching. Using atomic force microscopy we find an optimized hydrogen plasma process produces an etched surface morphology with an average surface roughness of 0.9–1.5 nm, as compared to the surface roughness of 0.6 nm before etching or as great as 11.8 nm after etching without the hydrogen plasma pretreatment. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Patterned, photon‐driven cryoetching of GaAs and AlGaAs

    Page(s): 43 - 54
    Save to Project icon | PDF file iconPDF (569 KB)  

    We present a high‐resolution, damage‐free etching technique for GaAs and related compound semiconductors which utilizes surface‐specific photochemistry at 193 nm to excite a physisorbed layer of Cl2 on a cryogenically cooled (∼140 K) sample. Etch rates as high as 0.25 Å/pulse (corresponding to 0.09 μm/min) have been achieved. Etching is anisotropic, and etched features of 0.2–0.3 μm linewidth have been routinely obtained. The etch rate has been characterized as a function of several ‘‘system’’ parameters including Cl2‐partial pressure, substrate‐temperature, laser repetition rate and fluence, and the addition of rare gases. A phenomenological model of this cryoetching has been developed which agrees well with the experimental data. The etch damage and contamination have been studied with Auger electron spectroscopy, photoluminescence, and Schottky‐barrier measurements. All results indicate that there is minimal if any damage induced by the cryoetching process. © 1995 American Vacuum Society   View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High growth rate of III–V compounds by free carrier gas chemical beam epitaxy

    Page(s): 55 - 58
    Save to Project icon | PDF file iconPDF (79 KB)  

    We present in this article a simple and economic gas line designed for low vapor pressure metalorganic sources introduced into a chemical beam epitaxy chamber without carrier gas. This gas line was tested with triethylgallium and trimethylindium for the growth of GaAs and InP layers. The high conductance of the line allowed minimizing the heating of the source and reaching growth rate as high as 12 μm/h for GaAs. The lower InP growth rate was attributed to the higher viscosity of trimethylindium compared to triethylgallium. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Novel phosphorus and antimony sources for use in metalorganic molecular beam epitaxy

    Page(s): 59 - 63
    Save to Project icon | PDF file iconPDF (269 KB)  

    Trisdimethylaminoarsenic and phenylarsine have proven to be useful replacements for AsH3 for growth of GaAs and AlGaAs by metalorganic molecular beam epitaxy. This paper will discuss the P analogs, namely, trisdimethylaminophosphorus (DMAP) and phenylphosphine (PhPH2), as well as trisdimethylaminoantimony (DMASb). All of these sources decomposed readily at the growth surface without precracking. InP surfaces were maintained with each source over a wide range, 375–525 °C, as were GaAs substrates over the range of 375–600 °C. Using DMAP, GaP was grown at rates up to 200 Å/min with slightly less carbon contamination than obtained with similar flows of PH3. When trimethylindium (TMI) or elemental In was introduced, however, neither the DMAP nor the PhPH2 readily decomposed, thus leaving In droplets on the surface. InP was successfully grown by thermally cracking these compounds prior to injection to the chamber. The dependence of cracking efficiency and impurity uptake on cracker temperature will also be presented. DMASb was found to produce just the opposite effect of DMAP, apparently preventing the adsorption of triethylgallium, tri‐isobutylgallium, or trimethylaminealane on the surface for sufficient time to allow decomposition and hence growth to occur. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evaluation of the performance and operating characteristics of a solid phosphorus source valved cracking cell for molecular beam epitaxy growth of III–V compounds

    Page(s): 64 - 68
    Save to Project icon | PDF file iconPDF (125 KB)  

    We studied the performance of a new type of valved cracking cell which contains a separate condensing reservoir and is intended for molecular beam epitaxy of phosphide compounds. The cell was designed to operate with a white phosphorus source, derived in situ by sublimation and subsequent condensation of red phosphorus vapor. The parameters investigated were stability of the beam flux, switching transients, and growth chamber recovery time. The data show that a properly constructed valved cell, which incorporates a valve where shut‐off and metering are independently controllable, provides for a rapidly switched, stable beam flux with a minimum chamber recovery time. An in situ generated white phosphorus source was found to reduce the P4 burst accompanying the use of a red phosphorus source by over 300%. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization of the Si/GaAs(110) interface by soft x‐ray surface x‐ray absorption fine structure

    Page(s): 69 - 76
    Save to Project icon | PDF file iconPDF (188 KB)  

    Surface x‐ray absorption fine structure experiments have been carried out on the system Si/GaAs(110) at coverages ranging from 0.8 to around 2 monolayers (ML) and at room temperature. Polarized experiments have allowed us to propose a model for the silicon adsorption site that has the initial silicon atoms sitting just above the middle of the As–As and Ga–Ga bond along the [001] direction. Above one monolayer, silicon atoms begin to be ordered with a siliconlike structure. At thicker coverages (above 3 ML) the silicon layer is amorphous, which permits a determination of the thickness probed by x‐ray absorption using the total electron yield technique. © 1995 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • X‐ray photoelectron spectroscopy and atomic force microscopy surface study of GaAs(100) cleaning procedures

    Page(s): 77 - 82
    Save to Project icon | PDF file iconPDF (295 KB)  

    The chemical composition of GaAs(100) surfaces after HCl/H2O wet etching sequences has been examined with x‐ray photoelectron spectroscopy (XPS). XPS measurements show that oxides and chlorides are removed from the GaAs surface by the HCl solution etching in 10–20 min and subsequent H2O rinse in several seconds. The surface of the GaAs substrate thus prepared has been examined with atomic force microscopy. The surface flatness is so improved by the HCl/H2O treatment that the surface undulation remains within a ±1 monolayer fluctuation over a 1×1 μm surface area. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Problems relevant to the use of optical pyrometers for substrate temperature measurements and controls in molecular beam epitaxy

    Page(s): 83 - 87
    Save to Project icon | PDF file iconPDF (123 KB)  

    In molecular beam epitaxy an optical pyrometer is frequently used to determine substrate and epilayer temperatures during the growth of semiconductors. This implies a calibration of the pyrometer and a correct analysis of its indications. In this article we discuss problems presented by this calibration. We first compare the temperatures measured on the sample holder and on several substrates (GaAs, InAs, GaSb) attached to it. Then we present examples of temperature variations recorded during the growth of AlSb and GaSb on GaSb or GaAs substrates. GaSb epilayers thicker than 0.1 μm induce a 40°–60° decrease of the measured temperature. AlSb deposition on GaSb produces temperature oscillations. We discuss these variations in terms of apparent and true temperature variations. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Monolayer resolved monitoring of AlAs growth with metalorganic molecular beam epitaxy by reflectance anisotropy spectroscopy

    Page(s): 88 - 91
    Save to Project icon | PDF file iconPDF (93 KB)  

    Metalorganic molecular beam epitaxy (MOMBE) growth is studied here for the first time in situ with reflectance anisotropy spectroscopy (RAS). Growth of AlAs on GaAs(001) and optical monitoring was performed in a standard MOMBE system. Triisopropylgallium, dimethyl‐ ethylaminoalane, and precracked arsine were used as precursors. RAS spectra obtained are similar to the ones observed under molecular beam epitaxy or metalorganic vapor phase epitaxy conditions and correspond to the GaAs(001) and AlAs(001) c(4×4) surface reconstructions. Initiating AlAs growth from an arsenic stabilized c(4×4) GaAs(001) or AlAs (001) surface, the RAS signal shows oscillations with a period corresponding to the growth of one AlAs monolayer, as verified by thickness determination on thicker layers. As opposed to growth on an AlAs surface, when growing on GaAs the growth rate was not found to be constant right from the start, but was increasing slightly until it stabilized after several monolayers had been deposited. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Scaling of Si and GaAs trench etch rates with aspect ratio, feature width, and substrate temperature

    Page(s): 92 - 104
    Save to Project icon | PDF file iconPDF (506 KB)  

    The scaling of etch rates with feature dimensions is an important issue in the fabrication of microelectronic and photonic devices. Because etch rates depend on circuit layouts and design rules, considerable effort is spent to modify processes each time changes in design are made. Knowing how etch rates scale with design parameters should accelerate the introduction of new designs into manufacturing while minimizing the cost of doing so. Recently it has been shown that etch rates for a variety of conditions scale with the depth/width or aspect ratio and not on width or depth alone. While various mechanisms might be responsible for such scaling, isolating one mechanism from another is not straight forward. Nonetheless, it is important to understand the underlying mechanisms so that differences in etch chemistry and etch reactor design can be accounted for when scaling plasma processes from one design or reactor to another. To assess the effects of etch chemistry alone, the trench etch rates of Si and GaAs are compared under constant plasma conditions. Substrate temperature is varied to further assess the relative importance of surface vs transport phenomena during the etching process. At higher temperatures, both Si and GaAs trench etch rates scale only with aspect ratio in an Ar/Cl2 electron cyclotron resonance plasma. The results are consistent with an ion‐neutral synergy model based on Langmuir adsorption kinetics where the scaling can be explained by the aspect ratio dependence of the neutral reactant transport into the trench: charging effects, ion shadowing, and Knudsen transport are not consistent with the data. At -45 °C, the etch rate no longer scales with aspect ratio alone, but now also depends on trench width. The data at this lower temperature are well described by a model incorporating the deposition of an etch inhibiting layer. While the trench etch rates for GaAs and Si scale in similar ways with aspect ratio and trenc- - h width, the dependence on feature dimensions of the Si etch rate is much stronger than that for GaAs at all substrate temperatures because the steady‐state surface coverage of Cl is smaller for Si. This results in a greater sensitivity to the incoming, aspect ratio dependent, neutral fluxes. The implications of the models on the goal of aspect ratio independent etching are also discussed. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ellipsometry study of the nucleation of Si epitaxy by electron cyclotron resonance plasma chemical vapor deposition

    Page(s): 105 - 110
    Save to Project icon | PDF file iconPDF (519 KB)  

    The formation and evolution of Si nuclei on the Si(100) surface at 600 and 700 °C were observed in a microwave electron cyclotron resonance plasma chemical vapor deposition system, using both real‐time in situ single wavelength and spectroscopic ellipsometry combined with high‐resolution cross‐sectional transmission electron microscopy and secondary ion mass spectroscopy. The deposited Si layers are epitaxial, and decidedly different nucleation behavior is seen at 600 and 700 °C. The experimental ellipsometry results were compared with simulations and the results show that temperature has a profound effect on the initial nucleation and growth, and the different interface structures that are observed are attributable to impurities. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Postgrowth of a Si contact layer on an air‐exposed Si1-xGex/Si single quantum well grown by gas‐source molecular beam epitaxy, for use in an electroluminescent device

    Page(s): 111 - 117
    Save to Project icon | PDF file iconPDF (382 KB)  

    A Si contact layer for an electroluminescent (EL) diode was successfully grown on a Si1-xGex/Si single quantum well (SQW) layer by ‘‘hybrid’’ Si molecular beam epitaxy (MBE). The ‘‘hybrid’’ MBE was performed by growing the Si contact layer in a solid‐source MBE chamber after transferring the sample through air from a gas‐source MBE (GSMBE) chamber in which the starting SQW layer was initially grown by using disilane (Si2H6) and germane (GeH4). The growth characteristics of the hybrid MBE were investigated by in situ monitoring of the reflection high energy electron diffraction. A (2×1) reconstruction was observed even after the sample was exposed to air for up to 15 h on a GSMBE‐prepared Si(100) surface. Evidence of the excellent quality of the EL device was provided by the sharpest emission lines, a full width at half maximum of ≊5.5 meV. The spectral features of the EL and photoluminescence were found to be almost identical, and a well‐resolved acoustic phonon replica was observed. Linear polarization for a no‐phonon replica of EL was also observed along SQW plane. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Role of ions in electron cyclotron resonance plasma‐enhanced chemical vapor deposition of silicon dioxide

    Page(s): 118 - 124
    Save to Project icon | PDF file iconPDF (147 KB)  

    Silicon dioxide films were deposited in an electron cyclotron resonance plasma onto substrates at temperatures ranging from 65 to 200 °C. In order to determine the effect of ions on the deposition, both ion flux and ion energy were investigated. The ratio of ion flux to deposition flux was found to be a significant parameter and this ‘‘flux ratio’’ was varied between 8 and 100. Mean ion energy was investigated at 10, 50, and 75 eV. The silicon dioxide films were characterized by measurement of wet etch rate, density, composition, and stress, and by infrared spectroscopy. It was found that above a flux ratio of about 20, high‐quality SiO2 was deposited whether or not the substrate was thermally floating or at 65–200 °C, indicating that the flux ratio was dominant over the temperature. Use of radio‐frequency bias to increase the mean ion energy to 50 eV or above was effective in producing high‐quality SiO2 when the flux ratio was below 20, but not as effective as using a high flux ratio. Thus high ion flux and low ion energy were found to be useful in producing SiO2 at temperatures as low as 65 °C with properties close to that of thermal silicon dioxide. The role of ions in the deposition process was found to be densification, removal of –OH (or hydrogen) and alteration of Si–O bonding. © 1995 American Vacuum Society   View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Filling dual damascene interconnect structures with AlCu and Cu using ionized magnetron deposition

    Page(s): 125 - 129
    Save to Project icon | PDF file iconPDF (1546 KB)  

    The semiconductor industry is moving toward the use of damascene processes for wiring of circuits on chips. These processes are based on the etching of vias and trenches into dielectric layers, filling these features with metal, and finally chemical–mechanical polishing, which results in a planarized, embedded feature. A two‐layer feature, typically a pad or trench with a via at the bottom which connects to some underlying contact is known as ‘‘dual damascene.’’ Ionized magnetron sputter deposition has been used to successfully fill these two‐layer features, both with AlCu and Cu metallurgies. This process uses conventional, commercial manufacturing‐scale magnetrons in combination with a dense, inductively coupled rf discharge to ionize a large fraction of the sputtered atoms. A small electrical bias on the sample then causes the metal ions to deposit at normal incidence, which results in dense fills at moderate aspect ratios (AR = 2:1) on room temperature samples. © 1995 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization of thin copper films grown via chemical vapor deposition using liquid coinjection of trimethylvinylsilane and (hexafluoroacetylacetonate) Cu (trimethylvinylsilane)

    Page(s): 130 - 136
    Save to Project icon | PDF file iconPDF (544 KB)  

    We have developed a technique recently for copper chemical vapor deposition utilizing direct liquid coinjection of trimethylvinylsilane (TMVS) and the copper (I) precursor (hexafluoroacetylacetonate) Cu (TMVS). We present here an investigation of the properties of copper films deposited using this technique. The films were grown on Si3N4 substrates at temperatures in the range of 220–250 °C and characterized using several experimental techniques, with an emphasis placed on factors influencing copper film resistivity. The average as‐deposited film resistivity is 1.86 μΩ cm; this value is reduced to 1.82 μΩ cm when the effects of surface scattering are taken into account. The resistivity is essentially independent of film thickness for thicknesses between 0.2 and 3.5 μm, and is reduced by less than 0.05 μΩ cm by annealing at 400–600 °C in vacuum. The total impurity content of the films is approximately 100 parts per million. The film density is 97±2% of the bulk copper value. The average grain size increases with film thickness and falls in the range of 0.5–1.5 μm. Morphological defects are the main cause of the resistivities (after adjusting for surface scattering) being approximately 0.14 μΩ cm above the bulk copper value (1.68 μΩ cm). Comparison of thickness and resistivity measurements for rough as‐deposited films and smooth chemical‐mechanical polished films shows that the surface roughness causes surface profilometry to overestimate the thicknesses of the unpolished films by approximately 1300 Å. This effect can lead to both artificially high resistivity values and a false dependence of resistivity on film thickness if profilometry measurements for the unpolished films are not properly corrected. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of the duty ratio of line and space in phase‐shifting lithography

    Page(s): 137 - 141
    Save to Project icon | PDF file iconPDF (586 KB)  

    This article discusses the impact of the line and space duty ratio and optical coherence on image quality for i‐line projection systems used in conjunction with alternated type phase shifters on projection masks. With a negative process, it was found that the alternated phase‐shifting method improve the depth of focus (DOF) for space patterns with a width smaller than the linewidth. On the contrary, there was no effect for narrow line patterns when the space width was larger than twice the linewidth. It was also found that the DOF became larger when the coherence became higher using both the alternated and the conventional mask for line patterns with a width smaller than the space width. It is concluded that high degree of optical coherence must be chosen for the phase‐shifting method. The alternated phase‐shifting method was applied to a bit line layer of 64 Mbit DRAM, and a DOF of 1.2 μm was obtained for both memory cells and peripheral patterns in which the minimum feature size is 0.35 μm. It is suggested that a negative i‐line resist with a large focus latitude at a high degree of optical coherence will be indispensable in applying phase‐shifting lithography to device fabrication. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimization of electrostatic deflectors

    Page(s): 142 - 149
    Save to Project icon | PDF file iconPDF (213 KB)  

    Optimization of electrostatic lenses was successfully achieved by using the cubic spline method or the a priori given multielectrode approach. In this article we propose optimization of electrostatic deflectors by using the cubic spline method for the purpose of attaining the minimum beam spot size. We propose the reconstruction of the electrodes of electrostatic spline deflectors in terms of the optimized first harmonic field distribution functions. Our calculations show that geometrical deflection aberrations can be reduced by 2–3 orders of magnitude. © 1995 American Vacuum Society   View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fabrication of column‐based silicon field emitter arrays for enhanced performance and yield

    Page(s): 150 - 157
    Save to Project icon | PDF file iconPDF (645 KB)  

    In this article, simulation, fabrication, and direct current (dc) characterization data are presented for column‐based silicon field emitter array (FEA) devices, made using anisotropic or isotropic etching of silicon to form emitter tips. In the design of the fabrication process, we have attempted to minimize spatial nonuniformity of process parameters affecting the geometry of the device structure, and, where possible, counteract the nonuniformity through a proper choice of processing variables. FEA devices, with as many as 232 630 tips, on 4–10 μm centers, have been successfully fabricated. The highest electron emission current measured was over 18 mA at the gate voltage of 150 V for a 6648 tip array. © 1995 American Vacuum Society View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

The Journal of Vacuum Science and Technology B is devoted to reports of original research, review articles, and Critical Review articles.

Full Aims & Scope

Meet Our Editors

Editor
Gary E. McGuire
International Technology Center