摘要:

Vapor phase pregate oxide surface preparation was studied in a high vacuum cluster tool. SiO2was etched with anhydrous vapor hydrogen fluoride and methanol vapor. The oxide etch rate can be well controlled by varying wafer temperature, chamber pressure, and gas flow rates. A standard error of 5% in oxide etch rate has been achieved. Particles generated are less than ten per 125 mm wafer at an oxide etch rate of 60 Å/min. Atomic force microscopy measurements reveal no added Si surface microroughness attributable to vapor hydrogen flouride (HF) etching. Trace metallic contaminants such as iron and chromium were reduced with UV/Cl2based processes. A combination of vapor HF etching followed by UV/Cl2metal removal is an effective pregate oxide surface preparation.

ISSN:0734-211X    

DOI:10.1116/1.588172

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

In order to improve the Schottky diode characteristics of metal‐In0.52Al0.48As, a new dry photochemical etching and sulfur passivation process has been developed. Excimer and deep UV lamps were used for photochemical etching and surface passivation, respectively. Auger electron spectroscopy measurement shows that this passivation process is as good as wet (NH4)2Sxand P2S5/(NH4)2S passivation in terms of sulfur coverage. Schottky diodes were fabricated onn‐In0.52Al0.48As by electron beam evaporation of a multilayer metal contact of the form Mo/Ti/Pt/Au (2/30/300/200 nm). The leakage current has been reduced by three orders of magnitude after applying this passivation process. X‐ray photoelectron spectroscopy measurements illustrate that these freeS* radicals are capable of replacing As–O and In–O bonds to As–S and In–S bonds. The conclusion is that the As–O and In–O bonds are the primary causes of leakage current. These bonds are dissolved after this photochemical sulfur surface passivation.

ISSN:0734-211X    

DOI:10.1116/1.588173

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

This article reports the fabrication of sub‐10‐nm Si lines bye‐beam lithography and aqueous potassium hydroxide (KOH)‐based etching. The fabrication technique provides both the high resolution and minimum linewidth fluctuation necessary for fabricating nano‐scale Si structures. Ine‐beam lithography, the combination of high‐resolution posi‐type resist and hexyl acetate developer is effective in improving the resolution and in reducing pattern fluctuation. Resist lines less than 20 nm wide with a fluctuation less than 3 nm are obtained. When these lines, aligned in the 〈112〉 direction on a (110) Si wafer, are transferred to Si by KOH etching, Si lines with a rectangular cross section are obtained and linewidth fluctuation is reduced further because (111) planes are exposed as the sidewalls. In addition, 6–9 nm wide lines can be formed by additional etching using an alcohol/KOH solution. Photoluminescence spectra are obtained for sub‐10‐nm Si lines after slight oxidation.

ISSN:0734-211X    

DOI:10.1116/1.588174

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We have observed the chemical changes in PMMA irradiated by x raysinsitu. The chemical changes are monitored by micro‐x‐ray absorption near edge structure spectra at the carbon absorption edge. The loss of the ester group (C=O) and formation of C=C bonds have been determined quantitatively from changes in the intensities of the respective π* resonant peaks as a function of dose. Samples prepared under different conditions were examined. From the dose dependence of bond formation, scission and linking, the performance of the resist can be predicted, so that the preparation strategy, dose, and development can be optimized.

ISSN:0734-211X    

DOI:10.1116/1.588175

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The widths and overall profiles of dielectric grating lines can be determined by measuring the intensity of diffracted laser light from the sample over a specified range of incident beam angles. This technique, known as 2‐Θ scatterometry, is able to accurately and precisely measure photoresist structures in the subhalf micron regime. Moreover, a 2‐Θ scatterometer is capable of making measurements in a rapid and nondestructive manner. To test this technique we measured five identically processed wafers with nominal 0.5 μm line/0.5 μm space grating patterns. Each wafer comprised gratings in a Shipley 89131 negative photoresist exposed in a matrix of incremental exposure doses and focus settings. The scatterometry results were consistent with cross‐sectional and top‐down scanning electron microscopy (SEM) measurements of the same structures. The average deviation of 11 scatterometer linewidth measurements from top‐down SEM measurements, over a broad exposure range, is 14.5 nm. In addition, the repeatability (1σ) of the 2‐Θ scatterometer is shown to be excellent: 0.5 nm for consecutive measurements and 0.8 nm for day‐to‐day measurements.

ISSN:0734-211X    

DOI:10.1116/1.588176

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Our earlier design procedures for constructing quadrupole columns are further expanded to include octupole corrector units and ‘‘octupole’’ deflectors with no third‐order harmonics. The additional complications are finer partitioning of the plates and increased number of voltage controllers. Two sample designs, one having only the additional octupole deflectors and one having both the deflectors and the correctors, are presented and compared to our previous quadrupole system. The additional octupole components are shown to be capable of increasing the current density from 30% to more than 300% for a four‐plate system, designed to focus and scan the electron beam over a circular area of 0.25 mm radius. The electron beam is assumed to have an initial divergence of ±2.3 mrad, an initial energy of 6 kV, a total energy spread of 1 eV, and a final acceleration of 30 keV. These systems are then slightly reoptimized for a superficial comparison with the commercially available column by Micrion Corporation. The numerical results indicate a potential for substantial improvements, demonstrating the power of this design procedure. Finally, a discussion is presented on how the individual components can interact with each other to reduce the various aberrations.

ISSN:0734-211X    

DOI:10.1116/1.588177

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Radial and azimuthal transverse chromatic aberrations, which are calculated from the electron trajectories, are much larger than those calculated from the axial magnetic field distribution and its first derivative. The generation mechanism for such large transverse chromatic aberrations is assumed to be that the electron trajectories initiated at the same object position with different beam energies travel through different paths. This assumption is roughly confirmed by studying the crossover position deviation and the magnetic vector potentials as a function of radius along theZaxis and their curvature. When the object side and image side lenses are shifted in the crossover direction by 32 and 8 mm, respectively, the azimuthal and radial transverse chromatic aberrations are 1.9 and 1.3 nm/eV for a field size of 20×0.25 mm2and a beam energy of 100 keV. The radial and azimuthal distortions in the subfield are much smaller than 10 nm, when the radial subfield size is 250 μm and the target rotation is corrected.

ISSN:0734-211X    

DOI:10.1116/1.588178

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Transmission electron microscopy (TEM) and focused ion beam sputtering have been used for investigations of microstructure and defect formation in AlGaAs/GaAs heterojunction bipolar transistors. The use of focused ion beam sputtering to prepare nearly ideal thin membranes within the active region of transistors for cross‐sectional electron microscopy is described. Results are obtained from as‐fabricated devices, devices annealed at temperatures of 400 °C, and devices for which ‘‘aging’’ is accelerated by operating at high‐bias conditions and heating in combination. We find that electrical operation leads to significant microstructural changes which are distinct from those observed in devices which are annealed. TEM images of the metal/semiconductor contact reveal ‘‘metal spiking’’ and facetted structures associated with alloy interpenetration. Characterization of the semiconductor heterojunctions reveal precipitates at the emitter‐base junction. Mechanisms for the formation of these defects under high‐biased operation are discussed.

ISSN:0734-211X    

DOI:10.1116/1.588179

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The effects of the interfacial oxide layer in Schottky barrier junctions on submicron GaAs metal–semiconductor field‐effect transistors (MESFETs) have been investigated. These effects include a shift in threshold voltage and compression in transconductance which can be explained by the current transport theory for the Schottky barrier with an interfacial layer. MESFETs were characterized by direct current measurements and oxide‐related degradation was evaluated by measuring the gate leakage current. It has been shown that a gate‐length dependent study of threshold voltage and transconductance is only possible if all the devices under consideration have identical Schottky responses. The current through a Schottky barrier appears to flow in a voltage‐dependent resistor and the voltage drop across this resistor cannot be neglected when the density of states at the metal–semiconductor interface becomes prominent because it will effectively increase the threshold voltage and reduce the device gain.

ISSN:0734-211X    

DOI:10.1116/1.588180

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We demonstrate the quantum confined Stark effect near 1.5 μm in the InGaAs/AlGaAs quantum wells grown on GaAs. This is achieved through the successful growth of very highly mismatched InGaAs/AlGaAs multiple quantum wells (MQWs) on GaAs substrates by molecular beam epitaxy. In these devices, linearly graded InGaAs buffer layers are grown beneath the MQWs to minimize threading dislocations. Furthermore, to improve the material quality and interface smoothness of the MQWs, a very low growth temperature (280 °C) is used in addition to a one monolayer deposition of GaAs and growth interruptions on both sides of quantum wells. These devices clearly exhibit the quantum confined Stark effect as measured by electroabsorption at 300 K.

ISSN:0734-211X    

DOI:10.1116/1.588181

出版商:American Vacuum Society    

年代:1995

数据来源: AIP