摘要:

This article provides an in‐depth study of the photoluminescence (PL) and photoluminescence excitation (PLE) from Al0.48In0.52As grown by molecular beam epitaxy that exhibits linewidths of ∼17 meV, comparable with the best reported to date. When the sample temperature is increased from 2 K the emission energy exhibits an inverted S‐shape dependence and this is normally associated with exciton localization. It is suggested that this anomalous temperature dependence occurs because the emission is a convolution of more than one transition from 35 K to 65 K. The 2 K emission intensity quenches with an activation energy of 17.5±2.5 meV. A similar difference in energy of 17–20 meV is also observed between the PL and PLE spectrum and this has been explained by alloy fluctuations and a localization of the exciton. It is suggested that due to the close proximity of the Γ–Xcrossover that non‐Γ contributions to the donor binding energy cannot be dismissed. The large luminescence linewidth observed in Al0.48In0.52As compared to other ternary alloys cannot be attributed to alloy scattering alone. If non‐Γ contributions to the donor binding energy are present excitons will be more localized sensing any local fluctuations in the alloy composition. However, we have demonstrated the difficulties in proving any direct correspondence between the luminescence linewidth and clustered regions. The emission from Al0.48In0.52As may not be excitonic as it could also be attributed to a neutral donor to free hole transition (D°,h). Band‐edge emission is not observed in the luminescence spectrum until the sample temperature reaches ∼100 K.

ISSN:0734-211X    

DOI:10.1116/1.587343

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

ZnO films were deposited on a GaAs ridge structure using radio‐frequency (rf)‐magnetron sputtering. A SiO2thin buffer layer was introduced to alleviate a thermal mismatching problem between the ZnO film and the GaAs substrate. Deposition parameters such as rf power, distance, and gas composition/pressure were optimized to obtain highlyc‐axis oriented and highly resistive ZnO films. Postdeposition anneal treatment at 430 °C for 5–10 min was found to enhancec‐axis orientation of the ZnO films dramatically and to reduce intrinsic stress significantly. Stress on the cleaved facet of the waveguide was imaged with a spatially resolved and polarization‐resolved photoluminescence technique. The results showed that the GaAs mesa is stressed up to 1×109dyn/cm2(10−3strain) due to residual stress from the ZnO/SiO2/GaAs structure.

ISSN:0734-211X    

DOI:10.1116/1.587295

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The dry etching characteristics of InP and GaAs using CH4/H2plasmas produced by two different electron cyclotron resonance (ECR) source configurations were examined in terms of surface morphology, stoichiometry, etch rate and anisotropy and finally the etch uniformity on 3‘φ wafers. Both the multipolar resonant cavity ECR source and the more conventional high‐profile magnetic mirror configuration produce high ion densities (∼7×1011cm−3at 1000 W) in 1 mTorr CH4/H2/Ar discharges, although the mirror source has slightly faster etch rates for both InP and GaAs. The etching becomes more anisotropic as the rf power to the chuck position is increased, and the rates fall for substrate temperatures below −10 °C, although the stoichiometry of the near‐surface region of InP is slightly better under these conditions. The optimized etch uniformity is ≤±2% for both sources and in general is better for high rf and microwave powers. Manual tuning of the multipolar source is simpler than for the mirror source and it is a little more stable during operation, with fewer of the mode jumps observed for the mirror configuration.

ISSN:0734-211X    

DOI:10.1116/1.587296

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The effect of plasma induced damage on device yields becomes increasingly crucial as gate oxide thicknesses approach the 50–70 Å range for quarter micron design rules. To quantify plasma induced damage for new low pressure, high density plasma sources, inductively coupled carrier lifetime and photoluminescence are measured. Also, UV‐visible spectroscopic ellipsometry is used to closely examine the wafer surface both during and after plasma exposure. This study is part of an ongoing research program that compares the etching performance of two commercially available, advanced plasma sources: a Lucas Labs helicon and a Wavemat multipole electron cyclotron resonance source. Forn‐type andp‐type, nominally 100 μs lifetime wafers, plasma exposure in both sources under optimum polysilicon overetch conditions results in a degradation of carrier lifetimes of less than 5% for unprotected versus oxide protected crystalline silicon. For wafers with an initial carrier lifetime of 400 μs, exposure to plasmas in both sources leads to a decrease in carrier lifetimes to approximately 345 μs. The decrease in carrier lifetime, although measurable, is at least an order of magnitude smaller than measured in conventional reactive ion etching (RIE) processes.To simulate an RIE etching process, rf‐bias power is applied without source power so that both sources behave like highly asymmetric, parallel plate RIE reactors with the wafer platen acting as a driven electrode and the source wall acting as a grounded electrode. Under these conditions carrier lifetimes below 45 μs were measured in both sources with wafers that had initial lifetimes of 400 μs. Photoluminescence measurements indicate incorporation of hydrogen into the etched material, but no formation of interstitial defects associated with plasma induced damage. For samples exposed to a plasma at 25 and 50 W rf‐bias, hydrogen produced from HBr dissociation readily incorporates into the sample. Exposure to a plasma at 200 W applied rf‐bias results in a decrease in carrier lifetime and an increase in hydrogen incorporation. Under high rf‐bias conditions, hydrogen incorporation is probably aided by ion surface damage. Ultraviolet‐visible ellipsometry does not detect any morphological damage induced in silicon wafers, but as with carrier lifetime and photoluminescence measurements, significant damage is detected after exposure to rf‐bias power without applied source power. Ellipsometry also detects a difference between real‐time and post process spectra after HBr and Cl2plasma exposure corresponding to the desorption of a film approximately 12 Å thick. This is not observed after Ar plasma exposure. Instead, the roughened surface remains stable which shows that the differences observed during and after plasma exposure for HBr and Cl2are indeed the result of a chemically reacting layer.

ISSN:0734-211X    

DOI:10.1116/1.587297

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The effects of high frequency operation on the reactive ion etching (RIE) of silylated photoresist are investigated. Using a simple parallel plate discharge model, the frequency scalings of dc bias, ion density, and sheath width are predicted to be ω−1.5, ω2, and ω−1.125, respectively. Measurements on the RIE system reveal dependencies of ω−1.48, ω1.85, and ω−1.00, respectively, in the 13.5–100 MHz range. The high frequency discharge is applied to the etching of silylated Plasmask 200G photoresist as part of the DESIRE (diffusion enhanced silylated resist) process flow. Increasing the drive frequency is shown to increase the unsilylated:silylated etch selectivity and reduce the postetch grass residues. Statistical design of experiments (SDE) is also employed to fully characterize the resist etch process. AnL934table is designed with plasma power, pressure, oxygen flow, and frequency as the controlled factors. Measured responses are etch rate, etch uniformity, selectivity, dc bias, residue size, residue density, linewidth, and etch profile angle. Main effects plots are tabulated from the design matrix revealing which factors have the greatest effect on each of the responses. Through the use of SDE, a significant reduction in postetch residues is observed for the high frequency RIE etch of Plasmask 200G resist.

ISSN:0734-211X    

DOI:10.1116/1.587298

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Resist heating effects on pattern shapes in electron beam lithography have been studied. The beam current density and dose partition dependences of the pattern shape are explained by comparison between the calculated spatial distribution of resist temperature and experimental resist pattern profiles. From direct heating of the resist using a tungsten heater during electron beam irradiation, the temperature effect on the resist sensitivity and pattern shape has been investigated. The pattern shape distortion is evaluated by a simulation considering the temperature effect.

ISSN:0734-211X    

DOI:10.1116/1.587299

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A major contribution to total overlay error can be pattern placement imprecision due to charging of the workpiece in electron beam lithography for mask manufacture. A first‐generation, worst‐case model is presented which indicates that an electron can experience quite a large placement error for a modest workpiece surface potential (100 nm/V). This model also predicts that the amount of error is proportional to the working distance. A novel method which measures the surface potential, to within 50 mV, is also presented. Results indicate that when exposed with 10 kV electrons the surface potential of 3000 Å PMMA on silicon is 1.5 V while that of 4000 Å SAL‐601 on chrome on quartz is 0.5 V. The discharging time for both samples was found to be of the same order as the write time for a typical mask.

ISSN:0734-211X    

DOI:10.1116/1.587300

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The fabrication process of a multilevel structure with a central electrode isolated from the outer gates is presented. Polymethylmethacrylate is used as the dielectric material that provides the electrical isolation. Dot gates with a diameter as small as 30 nm aligned in the middle of 0.10 μm split gates have been fabricated. The operation of the dot gates has been tested by conductance measurements through the constriction formed by the split gates.

ISSN:0734-211X    

DOI:10.1116/1.587301

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Radiation‐induced degradation in packaged bipolar junction transistors (BJT) can be efficiently removed by an anneal treatment carried out at 400 °C for 12 min in N2. The electrical characteristics of BJTs including current gain β, base currentIB, and collector currentICwere examined in the recovery of device performance. The radiation was performed by a Co‐60 (γ‐ray) source with the total doses ranging from 10 K rad to 10 M rad. The determinations of anneal temperature and anneal time were also discussed. It was shown that this anneal treatment did not degrade the radiation and hot‐carrier hardnesses of devices.

ISSN:0734-211X    

DOI:10.1116/1.587302

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The room‐temperature ion‐assisted etching of poly‐Si with molecular chlorine and 1 keV Ar+ions has been studied for a wide range of the neutral flux/ion flux ratio.Insitumeasurements of the etch rate made using quartz crystal microbalance methods are combined with modulated beam mass spectrometric studies of the etch products and the unreacted molecular chlorine reflected from the Si surface. The reaction probability for the incident chlorine is determined in two independent ways and good agreement is obtained. The products are determined to be primarily SiCl2and SiCl4with significant amounts of sputtered SiCl at low flux ratios.

ISSN:0734-211X    

DOI:10.1116/1.587303

出版商:American Vacuum Society    

年代:1994

数据来源: AIP