Resist Heating Effect Research Articles

Effectiveness of Resistive Heating Compared With Passive Warming in Treating Hypothermia Associated With Minor Trauma: A Randomized Trial

Effectiveness of Resistive Heating Compared With Passive Warming in Treating Hypothermia Associated With Minor Trauma: A Randomized Trial

Effectiveness of Resistive Heating Compared With Passive Warming in Treating Hypothermia Associated With Minor Trauma: A Randomized Trial

To determine the occurrence of hypothermia in patients with minor trauma, to test the hypotheses that resistive heating during transport is effective treatment for hypothermia and that this treatment reduces patients' thermal discomfort, pain, and fear, and to evaluate the accuracy of oral temperatures obtained at the scene of injury. In December 1999 and January 2000, 100 patients with minor trauma were randomly assigned to passive warming or resistive heating. All patients were covered with a carbon-fiber resistive warming blanket and a wool blanket, but the warming blanket was activated only in those assigned to resistive heating. Core (tympanic membrane) and oral temperatures, heart rate, pain, fear, and overall satisfaction of patients were compared between the 2 groups on arrival at a hospital. Hypothermia was noted in 80 patients at the time of rescue. Mean initial core temperatures were 35.4 degrees C (95% confidence interval [CI], 35.2 degrees C - 35.6 degrees C) in the patients who received passive warming and 35.3 degrees C (95% CI, 35.1 degrees C - 35.5 degrees C) in those who received resistive heating. From the time of rescue until arrival at the hospital, mean core temperature decreased 0.4 degrees C/h (95% CI, 0.3 degrees C/h - 0.5 degrees C/h) with passive warming, whereas it increased 0.8 degrees C/h (95% CI, 0.7 degrees C/h - 0.9 degrees C/h) with resistive heating. Oral and tympanic membrane temperatures were similar. Mean heart rate decreased 23 beats/min in those assigned to resistive heating but remained unchanged in those assigned to passive warming. Patients in the resistive heating group felt warmer, had less pain and anxiety, and overall were more satisfied with their care. Oral temperatures are sufficiently accurate for field use. Hypothermia is common even in persons with minor trauma. Resistive heating during transport augments thermal comfort, increases core temperature, reduces pain and anxiety, and improves overall patient satisfaction.

Fabrication issues for the prototype National Institute of Standards and Technology SRM 2090A scanning electron microscope magnification calibration standard

A new National Institute of Standards and Technology scanning electron microscope magnification calibration standard has been fabricated and distributed in production prototype form. The SRM 2090A samples contain structures ranging in pitch from 3000 to 0.2 μm and are useful at both high- and low-accelerating voltages. The design and fabrication of the samples has incorporated many of the improvements suggested through two previous prototype series. This article discusses optimization of the lithographic techniques in the fabrication process. We used electron beam lithography for fabrication because of the 0.1 μm features required on the samples. After liftoff, unexpected linewidth differences were measured among the smallest features. These differences were reduced through modification of the electron beam writing paths. We propose that the resist heating effect caused an axial dependence among features fabricated using the original electron beam writing paths. In addition, the susceptibility of the present prototype design to electron beam proximity effects was analyzed. Proximity effects from the 9 μm range of backscattered electrons have little effect on the pitch structures of the prototype but may impact development of the prototype as a linewidth standard.

Resist heating effect in electron beam lithography

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.

Experimental investigation of the resist heating effect in a variably shaped EBL system

Quantitative investigations of the influence of electron beam shot size on resist heating and the corresponding sensitivity change were performed for a variably shaped electron beam lithography system. The possible influence of other factors was taken into account to separate the resist heating effect. Measurements were performed for a number of beam current densities. It was shown, that the multiple exposure with a delay applied between the successive shots allows to eliminate the effect caused by the heating of the resist.

Direct measurement of thermoeffect influence on resist sensitivity in EBL

Measurements of dose characteristics of PMMA were performed with various resist temperatures. The quantitative data shows sensitivity changes with the temperature increase. The model of resist heating effect is presented.

New development in the theory of MBE growth of Si: a confrontation with experiment

The current understanding of the DC resistive heating effects in annealing of Si is outlined. The hypothesis of electromigration of Si adatoms and surface vacancies is shown to provide grounds for three different mechanisms of step bunching operating in different temperature intervals. The anisotropy of the surface diffusion on (001)Si, proven by the selective nucleation effect, is essential for the formation of predominant reconstruction domains during DC annealing. The mechanisms of the reported step bunching at a single domain (001)Si surface are, however, still unclear. In the absence of DC heating one can study some features of the undisturbed processes of MBE growth of Si. The anisotropy of the crystallization (and evaporation) kinetics at the steps causes a formation of double height steps when the surface processes are controlled by the adatom incorporation in the crystal (surface diffusion is comparatively fast). That is why formation of a single domain surface (in the absence of DC heating) can be expected in a limited range of growth and evaporation conditions.

Criterion to judge whether the resist heating effect will occur

A specific criterion for judging whether the resist heating effect will occur under given beam and resist conditions is proposed. The criterion is directly applicable to direct-writing variably shaped electron-beam systems and chain-scission type resists. After studying the relationship between resist temperature and pattern deformation, it is hypothesized then verified experimentally that pattern deformation occurs when temperature at the shot edge point is higher than the glass transition temperature of the resist. Experiments revealed that chemically amplified resists are more resistant to the resist heating effect than chain-scission type resists. Applying the hypothesis to resist temperature calculations, a constant figure was derived that represents the criterion for high-throughput writing systems. The figure suggests the beam and resist conditions that are required for high-throughput pattern writing without the resist heating effect.

Optimizing electron beam lithography writing strategy subject to electron optical, pattern, and resist constraints

A new model for the exposure rate of electron beam lithography is developed, accounting for electron optical, electronic, resist, and pattern statistics/quality constraints. Resist heating and beam interaction effects, as well as current density, flash size and edge resolution are included as measurable parameters that couple in rather complicated ways to determine performance for a specific task. Gaussian beam raster scan, small fixed shaped beam, and variable shaped beam vector scan machine strategies are compared using hypothetical but realistic assumptions. Address grid, minimum feature dimension, and the maximum flash area influence coverage in different ways, and pattern fracture techniques profoundly influence coverage, particularly in variable shaped beam systems. Remarkably small shapes, high current density, and high flash rates are usually favored. A constant flash area fracture is desirable because it maximizes the average beam current. The controlling resist parameter is sensitivity divided by the maximum beam current useable to achieve a given level of pattern quality. This parameter is frequently limited by heating effects. Examples of lithography guided by this model are given.

Resist heating effects in 25 and 50 kV e-beam lithography on glass masks

Electron sensitive resists have been exposed on optical masks in a variably shaped spot electron beam lithography system, EL3, at 25 and 50 kV and beam current densities up to 50 A/cm2 to evaluate the effects of resist heating during electron exposure. Resist heating effects are primarily observed in dense patterns at high electron exposure dose. For the purpose of comparison resist heating effects are quantified in terms of the development rate change that is caused by the temperature rise in the resist during electron beam exposure. From an energy density point of view the maximum temperature rise in the resist during exposure is very similar for both 25 and 50 kV exposures. The area on the mask over which the temperature rise in the resist can change resist properties is significantly larger at 50 kV: up to 20 μm at 50 kV compared to ∼5 μm at 25 kV. Using sensitive electron beam resists requiring 1–5 μC/cm2 exposure dose no resist heating effects are observed at beam current densities up to 50 A/cm2.

Resist heating effect in direct electron beam writing

A new model for the analysis of resist heating is proposed and applied to the direct electron beam writing method using a variably-shaped electron beam system and a single-layer resist. From calculations based on the present model and experiment, it was found that the resist heating effect leads to resist ablation, difference in resist sensitivity between single exposure and multiple exposures, and depth dependence and beam size dependence of resist sensitivity. It also explains the degradation of shaped beam stitching accuracy as well as pattern size error. The resist heating effect is more serious for direct writing than the estimation obtained from a conventional model. In order to realize submicron patterns below 0.5 μm with considerable high throughput, the use of a highly sensitive resist is essential for overcoming the resist heating effect.

Ionospheric heating by radio waves: Predictions for Arecibo and the satellite power station

The effect of resistive heating by radio waves on ionospheric temperatures, electron densities, and airglow emissions is examined by using numerical ionospheric structure and heat balance codes. Two cases are studied: (1) a 3‐GHz, 10‐GW microwave beam from a proposed satellite power station and (2) 1‐MW and 3‐MW beams of 15‐MHz radio waves launched by the Arecibo antenna. By intent, these two cases have similar intensities and geometries of resistive heating. The most dramatic heating effects are predicted to occur in the E region, where a thermal runaway will take place. The E region electron temperature will increase from 200°K to roughly 1000°K, and the E region electron density will increase by a factor of about 3. In the F region, where thermal conductivity plays an important role, temperature increases of 200°–500°K will appear along magnetic field lines passing through the radio wave beams. Enhanced emissions in airglow and molecular infrared lines will also occur. Radio wave heating, when combined with the diagnostic capabilities of the Arecibo incoherent scatter radar, will generate new opportunities to measure the rates of atomic physics processes and neutral atmosphere temperatures and composition at D and E region altitudes.