The use of selectively silylated resists to facilitate top surface imaging offers the potential for nanoscale lithography using both deep ultra violet (DUV) illumination and electron beam techniques. In this process, an exposure-generated crosslinking prevents silicon incorporation from silylating agents. In the non-crosslinked regions, a silylation agent reacts with OH groups in the resist to form silicon-oxygen bonds. During subsequent dry development in an oxygen plasma, the incorporated silicon attracts oxygen to form silicon dioxide, protecting the resist underneath. The adjacent un-silylated resist erodes (develops) anisotropically 25–100 times faster than the silylation-protected resist. The key to this process is the chemical formation of a silylated region at the top of the resist. A challenge associated with the silylation process, however, is lateral swelling of the silylated layer, which can lead to difficult dimensional control. The amount of swelling depends on the amount of incorporated silicon. Therefore, the uniformity and repeatability of the silylation process must be controlled. This paper will describe how spectroscopic ellipsometry has been used to characterize and monitor the resist silylation process in a non-destructive manner. The simultaneous characterization of the thicknesses and optical properties of a series of silylated resists will be presented. Optical metrology of the thickness of the silylated resists will be correlated with SEM cross-sectional analyses, and process uniformity will be quantified using 49-site wafer maps.

Physically meaningful near-surface force fields are used to calculate simulated scanning force microscope cantilever deflection data. The simulated data is used to evaluate the ability of a few models to calculate forces from cantilever deflections. The conventional simple harmonic oscillator model is shown to be significantly inaccurate in converting deflections to forces. A bending beam model is developed which accurately converts deflections to forces. This model is shown to be necessary for accurate assignment of physical meaning to the calculated forces under high force gradient conditions.

The Near-field Scanning Optical Microscope (NSOM) is an innovative new form of surface microscopy, which can be used to obtain local spectroscopic information about surfaces, enabling the characterization of nanometer-sized regions. The most important component of this instrument is the scanning probe tip. In this paper, we discuss the production of a novel fiber optic probe that can be used in local spectroscopy with an NSOM, but also for simultaneous imaging of topography and chemical forces. The probe consists of a bent, tapered silicon dioxide optical fiber. We have determined the rates of selective wet chemical etching of germanium dioxide doped pure silica optical fibers and used this information to optimize the probe etching process. A systematic approach for the development and testing of such probes is presented. The performance of the optical probes was characterized using surfaces prepared by the technique of microcontact printing. Phase and friction images of these surfaces were obtained using both standard atomic force microscopy tips and the optical fiber probe. The new optical probe was capable of distinguishing between different chemical regions on the patterned surface.

The formation and dynamics of Pt-Si liquid droplets on Si (001) substrates have been investigated by Photo-electron Emission Microscopy (PEEM). After ambient deposition of a 10nm Pt film, a uniform PtSi layer was transformed into an island structure at ∼ 800°C. The PtSi islands of micrometer size began to melt and were transformed into molten Pt-Si alloy islands below the melting point of PtSi. At ∼1100°C surface migration of the micro-droplets was observed. The moving droplets coalesced with nearby islands and grew in size. The motion was related to the temperature difference across the substrate, and droplet migration was observed from the cold to the hot regions of the surface. The migration velocity was measured as a function of temperature and droplet size. The driving force for migration is related to material diffusion, equilibrium at the solid-liquid interfaces, and surface energetics.

Our current study focuses on an analysis of the ballistic electron emission microscopy (BEEM) spectra of Au/(AIGa)As heterostructures to estimate quantitatively the effect of the carrier scattering in the metal, at the metal-semiconductor (m-s) interface and in the semiconductor on the multivalley carrier transport. The second derivative (SD)-BEEM spectra, representing the heterostructure transmission coefficient, show explicit partitioning of the contribution of different transport channels (Γ, L and X conduction valleys). Our analysis of SD-BEEM spectra by the developed theoretical model indicates that about 85–92% of the BEEM electrons are scattered at the nonepitaxial Au/GaAs interface. We also show that initial electron distribution among the conduction bands of the semiconductor, specified by the m-s interface scattering, is modified by the further hot-electron transport inside the semiconductor.

InxGa1-xN alloys are investigated by combining density-functional theory (DFT) calculations and all extended valence force field model (VFF). Based on a large nuniber of ordered InxGa1-xN supercells we determined the accuracy of various valence force field models with respect to ab initio DFT calculations. To get the correct energy difference between the stable wurtzite and the inetastable zincblende phase the inclusion of the ion-ion-interaction within the VFF’ model was necessary. As a direct consequence the inequivalent bonds of the wurtzite structure including the non-ideal c/a ratio and internal u parameter are described correctly. The wurtzite phase is found to be stable against the zincblende phase for all concentrations. The calculated elastic constants and their dependency on In alloy composition enables the determination of the local concentration by simultaneous measurement of the local lattice constants a and c.

We give an overview of the open-boundary planar supercell stack method (OPSSM), as a means for treating 3D quantum transport in mesoscopic tunnel structures. The flexibility of the method allows us to examine a variety of physical phenomena relevant to quantum transport. In this work we focus on the effects of interface roughness and embedded nanostructures in tunnel devices. Four representative applications of OPSSM are discussed: (1) interface roughness in double barrier resonant tunneling structures, (2) self-organized InAs quantum dot insertions in GaAs/AlAs double barrier structures, (3) tunneling characteristics of ultra-thin oxides with interface roughness, and, (4) embedded quantum wire model of dielectric breakdown. These examples demonstrate scattering and localization effects under different biasing conditions.

We study an As2 molecule approaching a planar, non-reconstructed, As terminated GaAs(001) surface by using a suitable cluster and quantum mechanical ab-initio calculation methods. During our calculations the As2 molecule is always oriented perpendicularly to the surface and its bonding length may vary. We find a metastable position below the growing surface which facilitates the incorporation of the leading As atom into an interstitial position of the crystal during growth. We give a first model for this incorporation process.

We have studied qualitatively the effect of patterned substrate surface on adatom nucleation using Kinetic Monte Carlo simulations and solid-on-solid model. The inhomogeneity in the activation energies of adatom diffusion was incorporated into the simulations using two models: a) periodic variation of the adatom–substrate interaction energy as a function of the adatom lateral position and b) adding a direction dependent and periodically varying diffusion barrier energy to the adatom diffusion activation energy. The effect of the patterned surface was clearly manifested as a confinement of nucleated islands and, consequently, narrowing the island size distribution. The effect was strong in a narrow temperature range.

The kinetics of deposition of CdTe, ZnS and ZnSe films was studied. An overall microkinetically reversible kinetic scheme consisting of elementary reactions, comprehensive of gas phase and surface processes was developed. Kinetic constants of gas phase reactions were either found in the literature or determined through quantum chemistry methods. Kinetic constants of surface reactions were first guessed combining kinetic theory with quantum chemical calculations and then their values were refined to reproduce experimental data. The kinetics schemes so developed were tested through the simulation of deposition reactors. Measured growth rates and gas phase compositions were thus compared with those calculated. The major finding of this studies is that the growth of CdTe, ZnS and ZnSe can be represented adopting a surface kinetic scheme constituted essentially by the same fundamental steps.

Silicon thin films grown by CVD processes take various structures depending on the reaction conditions. In the case of low-temperature CVD, hydrogen coverage on the silicon substrate affects the growth as well. In order to analyze the effect of hydrogen coverage on elementary surface reactions, we performed molecular dynamics simulations in which gasphase radicals, H and SiH3, fell onto a hydrogen-terminated silicon surface. We prepared monohydride and dihydride Si(100) surfaces and modified their hydrogen coverage in a certain area in the range from 0.5 to 2.0 monolayers so as to describe the growing surface. As a result of our simulation, H radicals mainly caused H adsorption and H abstraction reactions and altered the hydrogen coverage of the surface. While reactions of SiH3 radicals with monohydride or dihydride surfaces rarely occurred, these radicals reacted more frequently with the modified surfaces. These results indicate that the change in the local hydrogen coverage caused by H radicals may induce subsequent surface reactions

We report the development of an atomistic scale Kinetic Monte Carlo model of silicon CVD growth. By employing a variable time step algorithm, simulations have been performed over a range of time scales, enabling direct comparison with experimental data. The validity of using the kinetic theory of gases for evaluating steady state incoming particle fluxes within the model is demonstrated by comparison with computational fluid dynamics simulations. The model is applied to study hydrogen desorption rates from Si(001) and the dependence of silicon growth rate on substrate temperature, with results found to be in good agreement with experimental data. An experimentally observed decrease of growth rate with increasing H2 partial pressure is also reproduced by the model and shown to be caused by a decrease in silane adsorption on a hydrogen-rich surface.

We have investigated crystal growth and defect formation processes during solid phase epitaxy (SPE) of Si in the [001] direction based on molecular dynamics (MD) simulations using the Tersoff potential. From the Arrhenius plot of the growth rates obtained by MD simulations, we have found that the activation energy of SPE at lower temperatures is in good agreement with the experimental value, approximately 2.7 eV, while it becomes lower at higher temperatures. This can be attributed to the difference in the amorphous/crystalline (a/c) interface structure. In the low temperature region, the a/c interface is essentially (001) and the rate-limiting step is two-dimensional nucleation on the (001) a/c interface. On the other hand, the a/c interface becomes rough due to (111) facets formation in the high temperature region and the rate-limiting step is presumably a diffusion process of Si to be trapped at the kink sites associated with these facets. Defect formation is found to be initiated by 5-membered rings created at the a/c interface. These mismatched configurations at the interface give rise to (111) stacking faults during further SPE growth.

Large-scale molecular dynamics simulations are performed to investigate the atomiclevel stresses on InAs/GaAs mesas. The simulations are based on an interatomic-potential scheme for InAs/GaAs systems which depends on the local chemical composition. Multiresolution techniques are used to speed up the simulations. InAs/GaAs square mesas with { 101 }-type sidewalls are studied. The atomic-level pressure distribution and surface atomic stresses on the sidewalls with 12, 10, 8 and 6 monolayers of InAs overlayers have been calculated.

In this work the total energy of metallic superlattices is evaluated at semi-empirical level. The superlattice has an heterogenous composition and it has two shapes, i.e.(i) two facingA/B wires and (ii) a hut-shaped island of the element A deposited on a rigid B substrate. The elements A and B are Ag, Cu, Pd, Pt and Fe. The calculations show the existence of competing bonding contributions. In fact, a strong bond arises from charge exchanges at the A/B interface and from the bulk-like bonds of interior atoms. On the contrary, surface atoms are undercoordinated and reduce the strength of bonding. These contributions act on opposite sense on the large structures and the geometry dependence of the binding energy suggests a self-limited growth, rather than Ostwald ripening.

This article reviews technology issues in scaling conventional planar transistors to a physical gate length of 30nm that are expected to produce an effective channel length of 10 nm. Gate fabrication features direct write e-beam lithography to form a ring structure capable of exploring the practical limits of gate processing while requiring only a single level of lithography. Other processing elements include ultra-thin gate dielectric formation (∼ 0.6nm); highly selective transformer coupled plasma (TCP) etching; and low energy ion implantation. DC electrical results obtained for high performance n-MOS and p-MOS type nanotransistors made using this process are discussed as are simulations of sub-threshold currents for n-MOS transistors with physical gate lengths down to 26nm

Nanofabrication strategies developed by using electron beam (EB) are described. Ten-nm structures of organic positive and negative resist patterns have been achieved by using a commercially available EB lithography system. As one of the applications of EB nanolithography to nanodevices, an electrically variable shallow junction MOSFET (EJ-MOS) is described. As a novel approach, material-wave nanotechnology using de Broglie wave has been developed. Line and dot patterns with 100-nm periodicity were exposed on a PMMA resist by EB holography with a thermal field-emitter gun and an electron biprism. This technique allows us to produce nanoscale periodic patterns. Furthermore, the possibility of nanostructure fabrication by atomic-beam holography has been demonstrated by using a laser-trap technique and a computer-generated hologram made by EB lithography.

In this paper, electron beam (EB) lithography and direct processes are summarized for application to nanometer-scale electron devices such as single electron transistor. As decreasing line width in lithography, the delineated patterns has fluctuation of line width, which is so-called line-edge-roughness. It is kwon that such a roughness is caused by aggregates of resist molecules. Therefore to avoid the rougphness to make smooth line edge, we have to use rather low molecular weight resist materials. As one of such candidates, EB exposure characteristics of thermally oxidized SiO2 film are described. Although the sensitivity of the resist is about a few C/cm2 which is lower than conventional resists, it is possible to delineate fine line and space pattern with 15 nm pitch and 5 nm width. This technique is extended to make miniature metal/insulator/metal junctions using SiO2/Si bilayer resist system and the following metal liftoff process. Metal layer is directly deposited on SiO2 substrates in WF6 gas ambient simultaneously with EB irradiation. The resistivity of the deposited film is about 6×10/4 Ωcm depending on hydrocarbon contamination of the substrate itself. We can make the deposited lines with line-width of about 10 nm using 3 nm diameter of the incident EB. From current-voltage characteristics for single tunnel junctions with various tunnel resistances, the barrier height is estimated to be about 0.2 eV. This result indicates clearly the junction properties can be controlled at least with the accuracy of minimum deflection increment of the EB system used here. It is successfully observed that single-electron-transistor produced by EB-induced deposition exhibits Coulomb oscillation at temperature of 230 K.

A novel method to prepare nanometer-size patterns by using currently available massproduction technology is proposed. In this study, a contact pattern-mask with nanometersize slit is fabricated by combination of photolithography and anodic oxidation of metal. The slit width of the pattern-mask can be controlled in the order of nano-meters by anodic voltage during oxidation of side-wall of the metal. 10nm width trench is formed in Si substrate by using such nanometer slit-mask. It is suggested that the technique can be utilized as fabrication process of the nano-scale devices.

Scanning probe assisted nanolithography is a very attractive technique in terms of low-cost, patterning resolution and positioning accuracy. Our approach makes use of a commercial atomic force microscope and silicon probes to build simple nanostructures, such as metal electrode pairs, for application in novel quantum devices.

Sub-100 nm patterning was successfully performed using three different techniques: direct material removal, scanning probe assisted mask patterning and local oxidation.