By Topic

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

Issue 1 • Date Jan 2008

Filter Results

Displaying Results 1 - 25 of 88
  • Issue Cover

    Page(s): c1
    Save to Project icon | PDF file iconPDF (55 KB)  
    Freely Available from IEEE
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (130 KB)  
    Freely Available from IEEE
  • Recent advance in protection technology for extreme ultraviolet lithography masks under low-pressure condition

    Page(s): L1 - L6
    Save to Project icon | PDF file iconPDF (338 KB)  

    Extreme ultraviolet lithography (EUVL) is considered a leading lithography technology for the next generation of semiconductor devices. Various noncontact approaches for protection of the EUVL masks from particle contamination have to be used due to the lack of any usable common membrane pellicles during all handling steps. In this article, protection schemes for EUVL masks from nanoparticle contamination are given and proper experimental verifications are followed. The experimental investigations for the proposed protection schemes are examined with (i) maintaining the critical surfaces upside down to avoid gravitational settling of particles onto the mask; (ii) use of a cover plate to reduce the volume from where particles might reach the surface; (iii) application of a thermal and/or electrical gradient to expose particles to a repelling thermophoretic and/or electrophoretic force. The proposed schemes showed excellent effects on protection of critical surfaces under low-pressure condition. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Boron nanobelts grown under intensive ion bombardment

    Page(s): L7 - L9
    Save to Project icon | PDF file iconPDF (226 KB)  

    High-quality α-tetragonal crystalline boron nanobelts with [001] growth axis were synthesized using a novel method combining e-beam evaporation and plasma ion bombardment techniques. Intensive ion bombardment of the growing boron nanobelts at a high substrate temperature (∼1200 °C) was found to be effective in increasing the atomic density, reducing the crystal disorder, and improving the yield of the nanobelts. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Flexible polymeric rib waveguide with self-align couplers system

    Page(s): L13 - L18
    Save to Project icon | PDF file iconPDF (512 KB)  

    The authors report a polymeric based rib waveguide with U shape self-align fiber couplers system using a simple micromolding process with SU8 as a molding material and polydimethysiloxane as a waveguide material. The material is used for its good optical transparency, low surface tension, biocompatibility, and durability. Furthermore, the material is highly formable. This unique fabrication molding technique provides a means of keeping the material and manufacturing costs to a minimum. The self-align fiber couplers system also proves a fast and simple means of light coupling. The flexible nature of the waveguide material makes this process ideal for a potential wearable optical sensor. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reducing imaging defects in high-resolution photolithography

    Page(s): L19 - L22
    Save to Project icon | PDF file iconPDF (327 KB)  

    Photoresist defects can occur in large, seemingly noncritical features in high-resolution photolithography although it is capable of resolving features of much smaller dimensions. Both optical illumination and wafer topography may contribute to the formation of resist defects in large features. This letter examines optical simulations to uncover the specific nature of these resist defects and proposes local correction methods to improve the photolithographic process. For example, adding a back-etched phase feature in the center of a large isolated trench feature reduces the illumination-responsible resist scumming effect, and optimizing the multilayered film stack can eliminate the resist defect when printing a large contact feature on the structured wafer substrate. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Undercut structure fabricated by complementary-structure micropatterning technique for the passive-matrix display of organic light-emitting diodes

    Page(s): 1 - 5
    Save to Project icon | PDF file iconPDF (443 KB)  

    This paper reports a new patterning method, the complementary-structure micropatterning (CSMP) technique, to fabricate the undercut structures for the passive-matrix display of organic light-emitting diodes (OLEDs). First, the polyvinylpyrrolidone (PVP) stripe patterns with a trapeziform cross-section were formed by micromolding in capillaries. Then the photoresist was spin coated on the substrate with the patterned PVP stripes and developed in water. The PVP was dissolved and lifted off from the substrate with the photoresist deposited on it, resulting in the undercut structures of the remaining photoresist. The undercut structures with different configurations were obtained by adjusting the photoresist thickness. The undercut structures were further used as separators in the patterning of the passive-matrix display of OLEDs. No visible performance difference was observed compared with OLEDs patterned by the traditional method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fabrication and performance of nanoscale ultrasmooth programed defects for extreme ultraviolet lithography

    Page(s): 6 - 10
    Save to Project icon | PDF file iconPDF (725 KB)  

    The authors have developed processes for producing nanoscale programed substrate defects that have applications in areas such as thin film growth, extreme ultraviolet lithography, and defect inspection. Particle, line, pit, and scratch defects on the substrates between 40 and 140 nm wide, 50–90 nm high have been successfully produced using e-beam lithography and plasma etching in both silicon and hydrogensilsesquioxane films. These programed defect substrates have several advantages over those produced previously using gold nanoparticles or polystyrene latex spheres—most notably, the ability to precisely locate features and produce recessed as well as bump-type features in ultrasmooth films. These programed defects were used to develop techniques for planarization of film defects and results are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Studies of fluorocarbon film deposition and its correlation with etched trench sidewall angle by employing a gap structure using C4F8/Ar and CF4/H2 based capacitively coupled plasmas

    Page(s): 11 - 22
    Save to Project icon | PDF file iconPDF (699 KB)  

    A high-aspect ratio, small gap structure that provides a sample surface region without direct ion bombardment has been used to study surface chemistry aspects of fluorocarbon (FC) film deposition and to simulate FC film deposition on trench sidewalls during plasma-based pattern transfer. As on the sidewalls of microscopic trenches being etched, thin FC layers form by arrival of reactive neutrals on the shadowed surface portions of the small gap structure. The deposition rates, composition, and chemical bonding of FC films formed in the small gap structure were determined by ellipsometry and x-ray photoemission spectroscopy as a function of process conditions for C4F8/Ar and CF4/H2 discharges produced in a dual frequency (40.68/4 MHz) capacitively coupled plasma reactor. Actual trench features were also produced using photoresist patterned organosilicate films for the same plasma processes. Scanning electron microscopy of the trenches shows a characteristic sidewall slope angle for different process conditions. We find that plasma process conditions producing lower FC film deposition rates on the shielded surface of the gap structure yield more vertical trench sidewalls. This relationship confirms the relevance of the small gap structure approach to the examination of trench sidewall chemistry. Since the present approach produces macroscopic samples of gap-deposited FC films, it enables direct surface chemical characterization of a material that is analogous to sidewall deposited films and allows to avoid the difficulties connected with direct measurements of microscopic samples. The lack of ion bombardment for the shielded deposition increases the retention of the chemical structure of the FC film precursors for the deposited films, which promises to be us- - eful for obtaining mechanistic insights on film precursors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mobility-diffusivity relationship for semiconductor nanowires

    Page(s): 23 - 27
    Save to Project icon | PDF file iconPDF (315 KB)  

    Semiconductor nanowires are very promising for future technology. A relationship between the diffusivity DC and the mobility μC of semiconductor nanowires has been presented. Calculations have been performed to elucidate the dependence of DCC on the carrier concentration n and the temperature T. The DCC relationship appears to be general enough for application to both nondegenerate and degenerate semiconductor nanowires under an applied bias. An analytical form for this DCC relationship based on one-dimensional dispersion formula and a reasonable approximation to the Fermi-Dirac integral is suitable for investigation of electrical transport in semiconductor nanowires. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Double oxidation scheme for tunnel junction fabrication

    Page(s): 28 - 31
    Save to Project icon | PDF file iconPDF (262 KB)  

    The authors report a method to achieve AlAlOxAl tunnel junctions with high specific resistance in a controlled manner using a double oxidation technique. The technique is based on the standard method for oxidation repeated on an additional Al layer. The tunnel junctions were characterized with standard methods, such as comparison of room temperature resistance with liquid helium resistance and the authors found them to be of comparable quality to junctions fabricated with standard single oxidation. Fitting with the Simmons model suggests that both the barrier width and barrier height are consistent with those obtained in a single oxidation step. The junction specific capacitance was determined at low temperature to be 68 fFm2. These junctions, employed in low temperature measurements and applications, demonstrate expected and stable conductance characteristics. The double oxidation method is straightforward to implement in a basic setup for tunnel junction fabrication. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Turn-on field distribution of field-emitting sites in carbon nanotube film: Study with luminescent image

    Page(s): 32 - 35
    Save to Project icon | PDF file iconPDF (684 KB)  

    The turn-on field distribution of emission sites in carbon nanotube (CNT) film are measured by counting lighting dots. This provides a convenient method to characterize the field-emission uniformity of a CNT cathode. With this method, a quantitative characterization of the emission-uniformity improvement of a printed CNT film after a conditioning is obtained. The turn-on field distribution of an array of CNT dots in a pixel also can be measured with this method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Exposure latitude of deep-ultraviolet conformable contact photolithography

    Page(s): 36 - 40
    Save to Project icon | PDF file iconPDF (500 KB)  

    The authors present for the first time a study of the exposure latitude of deep-ultraviolet conformable contact photolithography in a nonevanescent regime. Exposures of grating patterns with half-pitches ranging from several hundred nanometers to 100 nm are simulated and experimentally demonstrated using an optimized trilayer resist stack. They show that a mask geometry with the absorber embedded in the glass improves image contrast, and therefore exposure latitude over a conventional chrome-on-glass mask geometry. They show that conformable contact photolithography is suitable for printing 500–100 nm half-pitch features with an exposure latitude of ±22% for ±15% linewidth tolerance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Structural and electrical investigation of laser annealed (Pb,Sr)TiO3 thin films

    Page(s): 41 - 46
    Save to Project icon | PDF file iconPDF (413 KB)  

    Material and electrical characteristics of (Pb,Sr)TiO3 (PSrT) films irradiated by various laser pulses and laser fluences are investigated in this work. Enhanced crystallinity can be obtained after excimer laser annealing (ELA). However, grain growth induced by ELA is nonuniform, and the effect is limited to the upper region of the films. As the number of laser pulses increases to 120, the film shows stronger diffraction intensities and increased oxygen content, resulting in a distinct capacitance versus electric field hysteresis loop and a larger dielectric constant than the nonirradiated one. The leakage current is found to be associated with the interface quality. The conduction mechanism of nonirradiated and irradiated PSrT films is mainly governed by Schottky emission at low electric fields, whereas the Poole-Frenkel emission occurs for films irradiated with more than 120 laser pulses or laser fluences larger than 90.5 mJ/cm2 at high electric fields. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced local oxidation of silicon using a conducting atomic force microscope in water

    Page(s): 47 - 51
    Save to Project icon | PDF file iconPDF (381 KB)  

    A new mechanism for direct-write surface scanning probe lithography is considered based on electrodynamic cavitation in a true liquid environment. Oxide layers grown on Si/SiO2/H2O and Si/SiO2/Au/H2O interfaces reached maximum heights of 130 and 690 nm, respectively. These structures represent a full order of magnitude increase in height over oxides grown in air under similar voltages and time durations, suggesting a unique reaction mechanism. Time-dependent studies indicated that oxide structures generated in water grew by discrete intervals and occasionally grew at a significant distance from the tip, effects that have not been previously reported. The possibility of electrodynamic cavitation-assisting silicon oxide growth under aqueous conditions is considered, potentially opening up opportunities for formation of nanoscale surface structures based on largely underutilized cavitation-induced (e.g., sonochemical) reactions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical properties of n-doped Ga1-xMnxN epitaxial layers grown by metal-organic chemical-vapor deposition in mid and far (5-50 μm) IR range

    Page(s): 52 - 55
    Save to Project icon | PDF file iconPDF (330 KB)  

    Optical properties of n-doped (Si) hexagonal Ga1-xMnxN films (x=0.015) grown by metal-organic chemical-vapor deposition (MOCVD) on c-plane sapphire substrates have been studied by infrared reflectance spectroscopy. The effect of free carriers on GaMnN optical phonons, namely E1(LO) and E1(TO), is explored. It is found that the frequency of E1(LO) increases with increasing free carrier concentration. The absorption coefficient (α) is calculated for the 200-2000 cm-1 range and the maximum value of α is found to be ∼105 cm-1 at a frequency of 560 cm-1. With increasing free carrier concentration, the FWHM of the absorption peak increased by 35%-40% as compared to an unintentionally doped (≪1×1016 cm-3) film. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • GaSb based midinfrared equilateral-triangle-resonator semiconductor lasers

    Page(s): 56 - 61
    Save to Project icon | PDF file iconPDF (110 KB)  

    Theoretical calculations of the mode characteristics of an equilateral-triangle resonator (ETR) with a 10 μm cavity side length show that the fundamental mode, with longitudinal mode index of 25, has a wavelength of 2.185 μm and a longitudinal mode separation of 100 nm. This mode has a quality factor (∼2×105) that is much larger than the first (∼5×104) and second (∼3×104) order modes, indicating that single fundamental mode lasing should be accessible over a broad wavelength tuning range. An electrically injected ETR based on this design is fabricated from an InGaAsSb/AlGaAsSb/GaSb, graded-index separate-confinement heterostructure, laser diode wafer with a 2.1 μm emission wavelength. This device achieved single mode, continuous wave operation at 77 K with a threshold current of 0.5 mA and a single mode wavelength tuning range of 3.25 nm, which is accomplished by varying the injection current from 0.5 to 6.0 mA. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Grayscale lithography by a polymer photomask doped with laser dye

    Page(s): 62 - 66
    Save to Project icon | PDF file iconPDF (316 KB)  

    This article reports on the development of a novel grayscale photomask which operates on the basis of differential absorption of ultraviolet (UV) light in photoabsorbing material. The developed photomask is made of a patterned, moldable polymer (polydimethylsiloxane) doped with a laser dye (Coumarin 314). The doped polymer functions as photoabsorbing material. Due to the moldable nature of polydimethylsiloxane, micro- and nanostructures can be created on its surface from a complementary mold relief. By adjusting the thickness of patterns formed on the photomask, concentration of the dye in the polymer, and UV exposure dose, a multitude of unique multidimensional microstructures can be fabricated with desired geometries and dimensions. Using the developed polymer photomask with a standard UV source, three-dimensional microstructures with different heights have been formed in positive photoresist by a single UV exposure step. This method is inexpensive compared to other grayscale lithography techniques and relatively easy to implement due to its process simplicity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Improvement of the wiggling profile of spin-on carbon hard mask by H2 plasma treatment

    Page(s): 67 - 71
    Save to Project icon | PDF file iconPDF (664 KB)  

    The H2 plasma treatment for spin-on carbon (SOC) hard mask in the trilayer resist process is expected to serve as a reliable alternative to single layer resist process for 45 nm nodes and beyond. The authors have investigated this treatment with a view to suppress the deformation of SOC by oxide etching. The wiggling profile of SOC drastically improves due to the formation of a thicker diamondlike amorphous carbon structure by the H2 plasma treatment with higher-energy hydrogen ions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nonlocal reduced boron diffusivity in silicon below strained Si1-xGex surfaces

    Page(s): 72 - 75
    Save to Project icon | PDF file iconPDF (461 KB)  

    The silicon (Si) surface can be the dominant source of self-interstitials for many annealing conditions. Incorporation of germanium (Ge) and strain into the surface may be expected to perturb the equilibrium point defect concentrations at the surface (i.e., the atomic steps at which the point defects are generated and annihilated) and consequently in the bulk Si. In this work, boron (B) diffusion marker layers were epitaxially grown in Si by rapid thermal chemical vapor deposition followed by either undoped Si, 45 nm of Si0.75Ge0.25, or 5 nm of Si0.55Ge0.45 leaving a surface with three different Ge contents. The B diffusivity (DB) below the Si1-xGex surface layers was found to be as much as two times slower than that in the all-Si samples between 800 and 900 °C. The activation energy for the DB in the Si1-xGex capped samples was also observed to increase to ∼4.1 eV. This work demonstrates that a Si1-xGex surface can reduce the DB in the underlying Si during N2 annealing. Furthermore, this novel test structure helps separate the effects of strain and local Ge trapping on DB in Si1-xGex. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nanostructuring GaN using microsphere lithography

    Page(s): 76 - 79
    Save to Project icon | PDF file iconPDF (419 KB)  

    The authors report on the fabrication and characterization of nanopillar arrays on GaN substrates using the technique of microsphere lithography. Self-assembled hexagonally packed silica microsphere arrays were formed on GaN wafers by spin coating and tilting. By precision control of process parameters, a monolayer can be formed over a wide region. The silica microspheres act as a hard mask for pattern transfer of the nanostructures. After dry etching, arrays of nanopillars were formed on the surface of the wafer. The ordered nanostructures can be clearly seen in the scanning electron microscopy images, while photoluminescence measurements revealed a twofold enhancement of light emission intensity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Flare-variation compensation for 32 nm line and space pattern for device manufacturing on extreme-ultraviolet lithography

    Page(s): 80 - 83
    Save to Project icon | PDF file iconPDF (522 KB)  

    One of the critical issues in extreme-ultraviolet lithography (EUVL) is flare, which degrades the contrast of aerial images and control of the critical dimension (CD) across the exposure field and is related to the density of the absorber layout. It is necessary, therefore, to determine a process window under flare-variation compensation (FVC), taking into account residual FVC error and estimated resist properties. In this article, the authors specify a process window for 32 nm line/space patterns under a FVC framework based on rigorous aerial-image simulations. FVC, by means of proper mask resizing, can provide an exposure latitude of up to 23% or more. A 0.5 nm grid can be used for mask-data preparation due to the low mask-enhancement error factor of EUVL. In addition, resist blur, estimated by convolving a Gaussian function to aerial images, has a significant impact and the standard deviation of the blur needs to the kept below 7 nm to obtain a usable process window, considering mask CD error and the process margin for flare levels of 0%–10%. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Potential of phase-shifted optical proximity correction for 65 nm T-shaped pattern in high numerical aperture lithography

    Page(s): 84 - 88
    Save to Project icon | PDF file iconPDF (492 KB)  

    Optical proximity correction (OPC) has been employed as a key enabling resolution enhancement technique required to meet image size control requirements imposed by state-of-the-art integrated circuit product programs. However, at the sub-65-nm node, the line end shortening effect for T-shaped pattern becomes pronounced and it is hard to correct using OPC due to the small gap size. Phase shift masks (PSMs) can improve lithography resolution and will be used at 65 nm node. However, phase conflicts occur when imaging a T-shaped pattern with PSM. Hence, it is becoming increasingly more challenging to print T-shaped patterns for sub-65-nm nodes. A new OPC method, phase-shifted optical proximity correction (PSOPC), has been proposed to improve the imaging fidelity for T-shaped pattern and avoid the phase conflict caused by the use of PSM. A PSOPC mask has phase-shifted segments that can simultaneously modify the intensity and phase of the incident light. PROLITH 9.0 and in-house-software microcruiser were applied to demonstrate the new approach of PSOPC. The authors’ results show that the line end shortening can be reduced to 4.6 nm and the depth of focus can be improved to over 200 nm. These results showed that PSOPC has significant potential as a new resolution enhancement technology for 65 nm T-shaped pattern lithography. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Atomic diffusion and interface electronic structure at In0.49Ga0.51P/GaAs heterojunctions

    Page(s): 89 - 95
    Save to Project icon | PDF file iconPDF (645 KB)  

    We have performed cross-sectional cathodoluminescence spectroscopy and secondary ion mass spectrometry measurements of lattice-matched, SiOx-capped In0.49Ga0.51P/GaAs double heterostructures (DHs) in order to investigate the relation between chemical interactions and localized electronic states at the epitaxial heterojunction. We measure atomic diffusion of over 100 nm resulting from anneals ranging from 650 to 850 °C. A 20 meV increase in the near-band-edge (NBE) emission energy of InGaP is observed after the highest temperature anneals. This increase is consistent with an increase in the Ga concentration of the ternary layer as a result of diffusion from neighboring GaAs layers. Additionally, we observe InGaP/GaAs interface-localized features at ∼1.49 and ∼1.37 eV. The intensity of these emissions relative to the band-edge emission of the underlying layer depends sensitively on the anneal temperature and corresponding diffusion. These results reveal a correlation between cross diffusion and defect emission at InGaP/GaAs interfaces. They clarify the nature of the cross diffusion and reactions that occur at these interfaces in SiOx-capped structures, and those may be expected to occur during interface growth or processing at elevated temperatures. It is demonstrated that these chemical effects can have a significan- - t impact on the electronic structure of lattice-matched III-V heterostructures. 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