摘要:

A model for strain relaxation in linear compositionally graded epitaxial layers is derived. Equilibrium dynamics for misfit dislocation generation is used in each compositional segment of the graded layers through the film thickness. A local relaxation thicknesses in the compositionally graded layers is calculated as a function of film thickness. The calculated critical thicknesses show good correspondence with the depth of dislocation‐free regions which are observed at the top of graded layers with different grading rates. From analysis of the model, we explain the origin of dislocation structures and minimized threading dislocation density in the compositionally graded layers. The compositional grading produces a large equilibrium dislocation spacing compared to that of highly mismatched conventional stepwise growths, and thus enables misfit dislocations to glide freely without dislocation–dislocation interactions. At successive local relaxation thicknesses, lateral dislocations pile up horizontally by continuous dislocation generation and expansion. The analysis with calculated results coincides with dislocation structures observed by transmission electron microscopy in InGaAs graded layers on GaAs.

ISSN:0734-211X    

DOI:10.1116/1.589150

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Thermal desorption of oxide layers from InSb(001) substrates was studied using reflection high energy electron diffraction (RHEED), x‐ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron spectroscopy. Surfaces of as‐loaded substrates prepared using either of two common chemical etchants were composed of oxide layers containing In2O3and Sb2O5. As the substrate temperature was raised, a multistage desorption process was observed. Most of the Sb2O5was reduced during the first stage, leaving behind a thin oxide layer consisting predominantly of In2O3. In2O3was desorbed during the second stage, as the substrate temperature was raised further in the presence of an Sb flux. Indium droplets condensed on the surface before a smooth morphology ensued. We suggest that the reduction of In2O3produced In droplets which reacted with the supplied Sb flux to form InSb. Annealing produced smooth, stoichiometric surfaces that gave rise to well‐defined, Sb‐stabilized pseudo‐(1×3) RHEED patterns. InSb films grown on such substrates exhibited good structural and electrical properties.

ISSN:0734-211X    

DOI:10.1116/1.589151

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

This article shows that the thermal stability of an InGaP Schottky contact can be improved by the refractory metal WSiN. Both the electrical characteristics and interfacial reactions were estimated by theI–V(current–voltage method), scanning electron microscopy, atomic force microscopy, and Auger electron spectroscopy. The WSiN/InGaP shows excellentI–Vcharacteristics, and the Schottky barrier height is 0.85 eV after annealing at 400 °C. Over 500 °C, an interfacial reaction occurs and theI–Vcharacteristic becomes leaky. We present an interfacial reaction model that shows In atoms condense and an eutectic alloy with W is formed.

ISSN:0734-211X    

DOI:10.1116/1.589152

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

We report on novel Ir–Al/n‐GaAs Schottky contact systems based on sequentially evaporated Ir–Al multilayers which enable us to control the barrier height at the interface with annealing temperature. Auger depth profiling and Rutherford backscattering methods were applied to analyze the Ir–Al composition and the interfacial reaction stability. An increase of the barrier height with annealing temperature has been indicated for all the Schottky contact systems. Barrier heights as high as 0.95 V were measured for annealed Schottky diodes with the first aluminum or very thin iridium interfacial layer. A model of the barrier height enhancement based on a solid phase epitaxy of a graded AlxGa1−xAs layer at the interface at elevated annealing temperatures was considered to explain the electrical properties of the contacts. The model contributions to the formation of a metal/AlxGa1−xAs/GaAs heterojunction diodes with required barrier height and thermal stability are discussed.

ISSN:0734-211X    

DOI:10.1116/1.589153

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Electron beam induced deposition from W(CO)6was studied for beam energies between 2 and 20 keV and a range of exposure doses, to investigate the dependence of deposit thickness and electrical conductivity on energy and the dependence of deposit conductance on cumulative exposure dose. Larger deposited thicknesses and higher conductivities were produced at the lower beam energies and were attributed to the higher secondary electron yield at lower energies. The deposit thickness was found to scale linearly with exposure dose. The initial dependence of conductance on exposure dose (and deposit thickness) was nonlinear and was attributed to the change from a discontinuous to a continuous film, and to increased backscattering. The subsequent dependence of conductance on exposure dose was linear for deposit thicknesses which were small compared with the electron range, implying that burial precludes the further decomposition of partially decomposed W(CO)6molecules incorporated in the deposit. Transmission electron microscope examination showed that the structure of the deposits depended on the beam scanning conditions. Deposits were used to form a mask for CF4plasma etching of Si, while deposits on a doped GaAs substrate were found to form a Schottky contact with an ideality factor of 1.40, enabling the repair of a metal–semiconductor field‐effect transistor gate to be demonstrated.

ISSN:0734-211X    

DOI:10.1116/1.589154

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The properties of Ta2N and TaN compound films as a diffusion barrier between Cu and Si have been investigated by examining compositional depth profiles obtained by Auger electron spectroscopy. The use of a Ta2N barrier is effective for improving the thermal stability of the contact system by raising the silicide formation temperature as compared with the use of a Ta barrier. The contact system of Cu/TaN/Si is fairly stable due to annealing for 1 h even at 750 °C. This is interpreted by the stability of the TaN compound, which is chemically inert to Si as well as Cu at this temperature. Eliminating the grain growth of TaN due to annealing is also effective for suppressing the physical diffusion through the barrier.

ISSN:0734-211X    

DOI:10.1116/1.589155

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Collimated sputtering has been successful in providing good contact barriers for sub‐half micron contacts with aspect ratios of 3 and greater. This approach does present drawbacks, however, particularly in terms of reduced deposition rates and degraded film uniformity. The deposition rate can be less than 25% relative to uncollimated systems due to the flux collected on the collimator itself. This in turn leads to closing off of the collimator cells by depositing material, which further reduces deposition rate on the wafer and limits the life of the collimator. This article demonstrates simulation of the filling of the collimator with different system configurations and pressures using the SIMSPUD vapor transport and SIMBAD thin‐film growth simulators. The model can determine collimator filling uniformity, blanket film uniformity, angular distribution of collimated sputter flux, and lifetime of the collimator. Given the target erosion profile, system geometry, and deposition rate, collimator lifetime can be predicted. The model indicates that for a 300 mm diam source a drop in operating pressure from 0.67 to 0.27 Pa has little effect on collimator life in terms of kW h, while increasing collimator life in terms of wafers by about 50%. The increase in the number of wafers processed comes at the expense of a small loss of uniformity. A universal relationship between via hole aspect ratio and the product of collimator transmission and hole bottom fill is also demonstrated.

ISSN:0734-211X    

DOI:10.1116/1.589156

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Electromigration study of various layer‐structured aluminum conductors with three widths revealed that lifetime (defined as a 1% resistance increase) depends on two critical parameters: the grain size/conductor width ratio and the grain orientation. These two parameters work independently and monotonically. Investigation of the number and size of voids formed by electromigration showed that lifetime is proportional to the square of the number of voids. This relationship is independent of linewidth and current density.

ISSN:0734-211X    

DOI:10.1116/1.589157

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The removal of the native oxide overlayers on the surfaces of III–V semiconductors, although widely investigated, requires further examination. Specifically, the main emphasis of research has been on the oxide layer characterization and, hence, on the development of cleaning procedures. This article attempts to study the H‐atom plasma reduction of the native oxide on indium phosphide (InP) substrates, using a process parametric investigation and x‐ray photoelectron spectroscopy (XPS) analysis. Oxide‐free and stoichiometric InP surfaces are prepared by operating the plasma cleaning at the surface temperature of 270 °C, as a thermally activated process has been found. For the untreated substrate, the nature of the InP oxide changes, along the thickness, from indium phosphates (InPOx) to an indium oxide (In2O3) rich sublayer. High temperature plasma treatment is able to completely reduce the In2O3oxide, unlike the wet‐etching procedure. In addition, improved stability of the surface against reoxidation has been confirmed for plasma treated substrates.

ISSN:0734-211X    

DOI:10.1116/1.589158

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

A patterning technology for fabrication of nanometer structures in Si/SiGe heterosystems is developed. The method pursued here combines high‐resolution electron‐beam lithography with reactive‐ion‐etching pattern transfer. A modified SF6/O2dry‐etching process is optimized by varying the gas mixture to achieve the required anisotropy. Photoluminescence measurements are carried out on uniformly etched samples to determine the influence of the reactive‐ion‐etching process on the optical properties. Etch process induced surface modifications drastically alter the electrical surface potentials. They are identified by laser desorption. These modifications are partially removed by low‐temperature postannealing steps. A qualitative model is presented to explain the observed effects. With this optimized technology, SiGe wires with lateral widths from 4 μm down to 25 nm are fabricated. Photoluminescence has been detected for structures as small as 600 nm.

ISSN:0734-211X    

DOI:10.1116/1.589159

出版商:American Vacuum Society    

年代:1996

数据来源: AIP