Lithographic Process Evaluation by CD-SEM

In lithography employed in IC fabrication, focus and exposure directly determine the printed resist image. Focus and exposure settings may be optimized with a focus exposure matrix (FEM) in which one parameter is varied by column and the other parameter is varied by row. A focus exposure matrix should be measured on a highly accurate and precise metrology tool, such as a CD-SEM. This experiment was performed using a Canon FPA 2000-i1 stepper, an SSI 150 coat/develop track, and a Hitachi S-6780 CD SEM. ProData was used to graphically analyze the numerical data collected on the CD-SEM. Data collected in this experiment shows that, for the given equipment, varying exposure from 120 to 200 mJ/cm2 in 10 mJ/cm2 increments and focus from —0.5 to +1.5 microns in 0.25 micron increments gives a CD range beyond the +/-l0% needed

Electromagnetic properties of material coated surfaces

The electromagnetic properties of material coated conducting surfaces were investigated. The coating geometries consist of uniform layers over a planar surface, irregularly shaped formations near edges and randomly positioned, electrically small, irregularly shaped formations over a surface. Techniques to measure the scattered field and constitutive parameters from these geometries were studied. The significance of the scattered field from these geometries warrants further study

Model-corrected microwave imaging through periodic wall structures

A model-based imaging framework is applied to correct the target distortion seen in microwave imaging through a periodic wall structure. In addition to propagation delays caused by the wall, it is shown that the structural periodicity induces high-order space harmonics leading to other ghost artifacts in the through-wall image. To overcome these distortions, the periodic layer Greens function is incorporated into the forward model. A linear back-projection solution and a nonlinear minimization solution are applied to solve the inverse problem. The model-based back-projection image corrects the distortion and has higher resolution compared with free space due to the inclusion of multipath propagation through the periodic wall, but considerable sidelobe clutter is present. The nonlinear solution not only corrects target distortion without clutter but also reduces the solution to a sparse form. © Copyright 2012 Paul C. Chang et al

Small Scale Plasma Waves and Heating within Kelvin-Helmholtz Instabilities at Earth’s Magnetopause

The Kelvin-Helmholtz Instability (KHI) is common at the magnetopause boundary enclosing Earth’s magnetosphere. The KHI drives several secondary processes which can transport plasma from the solar wind into Earth’s magnetosphere and convert kinetic energy in the plasma to thermal energy. Previous studies have shown the KHI and its associated secondary processes play an important role in the heating of ions and could help explain the observed asymmetry between ion populations in the dawn and dusk flanks of the magnetosphere. The contribution of the KHI to heating at the electron scale, however, is not well understood. Until the launch of the Magnetosphere Multiscale (MMS) mission in 2015, measurements of electron scale processes were not available. This study uses data collected by MMS between 2015 and 2020 to identify waves and potential sources of plasma heating between the ion and electron scales

Riesz transform characterization of Hardy spaces associated with Schr\"odinger operators with compactly supported potentials

Let L=-\Delta+V be a Schr\"odinger operator on R^d, d\geq 3. We assume that V is a nonnegative, compactly supported potential that belongs to L^p(R^d), for some p>d/2. Let K_t be the semigroup generated by -L. We say that an L^1(R^d)-function f belongs to the Hardy space H_L^1 associated with L if sup_{t>0} |K_t f| belongs to L^1(R^d). We prove that f\in H_L^1 if and only if R_j f \in L^1(R^d) for j=1,...,d, where R_j= \frac{d}{dx_j} L^{-1/2} are the Riesz transforms associated with L.Comment: 6 page

CFCI3 (CFC-11): UV Absorption Spectrum Temperature Dependence Measurements and the Impact on Atmospheric Lifetime and Uncertainty

CFCl3 (CFC-11) is both an atmospheric ozone-depleting and potent greenhouse gas that is removed primarily via stratospheric UV photolysis. Uncertainty in the temperature dependence of its UV absorption spectrum is a significant contributing factor to the overall uncertainty in its global lifetime and, thus, model calculations of stratospheric ozone recovery and climate change. In this work, the CFC-11 UV absorption spectrum was measured over a range of wavelength (184.95 - 230 nm) and temperature (216 - 296 K). We report a spectrum temperature dependence that is less than currently recommended for use in atmospheric models. The impact on its atmospheric lifetime was quantified using a 2-D model and the spectrum parameterization developed in this work. The obtained global annually averaged lifetime was 58.1 +- 0.7 years (2 sigma uncertainty due solely to the spectrum uncertainty). The lifetime is slightly reduced and the uncertainty significantly reduced from that obtained using current spectrum recommendation

60 GHz indoor propagation studies for wireless communications based on a ray-tracing method

This paper demonstrates a ray-tracing method for modeling indoor propagation channels at 60 GHz. A validation of the ray-tracing model with our in-house measurement is also presented. Based on the validated model, the multipath channel parameter such as root mean square (RMS) delay spread and the fading statistics at millimeter wave frequencies are easily extracted. As such, the proposed ray-tracing method can provide vital information pertaining to the fading condition in a site-specific indoor environment