374 Matching Results

Search Results

Advanced search parameters have been applied.

The effect of surface roughness on the performance of a 23 degree conical diffuser at subsonic Mach numbers

Description: Report of an investigation to determine the effect of surface roughness on the performance of a 23 degree conical diffusers with 2:1 ratio of exit to inlet area and a constant-area tail pipe. Information about the pressure survey results, including total-pressure-loss coefficient, diffuser effectiveness, and boundary-layer profiles is provided.
Date: January 16, 1952
Creator: Persh, Jerome
Partner: UNT Libraries Government Documents Department

Assessing out-of-band flare effects at the wafer level for EUV lithography

Description: To accurately estimate the flare contribution from the out-of-band (OOB), the integration of a DUV source into the SEMATECH Berkeley 0.3-NA Micro-field Exposure tool is proposed, enabling precisely controlled exposures along with the EUV patterning of resists in vacuum. First measurements evaluating the impact of bandwidth selected exposures with a table-top set-up and subsequent EUV patterning show significant impact on line-edge roughness and process performance. We outline a simulation-based method for computing the effective flare from resist sensitive wavelengths as a function of mask pattern types and sizes. This simulation method is benchmarked against measured OOB flare measurements and the results obtained are in agreement.
Date: January 25, 2010
Creator: George, Simi; Naulleau, Patrick; Kemp, Charles; Denham, Paul & Rekawa, Senajith
Partner: UNT Libraries Government Documents Department

Mask roughness and its implications for LER at the 22- and 16-nm nodes

Description: Line-edge roughness (LER) remains the most significant challenge facing the development of extreme ultraviolet (EUV) resist. The mask, however, has been found to be a significant contributor to image-plane LER. This has long been expected based on modeling and has more recently been demonstrated experimentally. Problems arise from both mask-absorber LER as well as mask multilayer roughness leading to random phase variations in the reflected beam and consequently speckle. Understanding the implications this has on mask requirements for the 22-nm half pitch node and below is crucial. Modeling results indicate a replicated surface roughness (RSR) specification of 50 pm and a ruthenium capping layer roughness specification of 440 pm. Moreover, modeling indicates that it is crucial to achieve the current ITRS specifications for mask absorber LER which is significantly smaller than current capabilities.
Date: February 16, 2010
Creator: Naulleau, Patrick; George, Simi A. & McClinton, Brittany M.
Partner: UNT Libraries Government Documents Department

Simplified models for mask roughness induced LER

Description: The ITRS requires < 1.2nm line-edge roughness (LER) for the 22nm half-pitch node. Currently, we can consistently achieve only about 3nm LER. Further progress requires understanding the principle causes of LER. Much work has already been done on how both the resist and LER on the mask effect the final printed LER. What is poorly understood, however, is the extent to which system-level effects such as mask surface roughness, illumination conditions, and defocus couple to speckle at the image plane, and factor into LER limits. Presently, mask-roughness induced LER is studied via full 2D aerial image modeling and subsequent analysis of the resulting image. This method is time consuming and cumbersome. It is, therefore, the goal of this research to develop a useful 'rule-of-thumb' analytic model for mask roughness induced LER to expedite learning and understanding.
Date: February 21, 2011
Creator: McClinton, Brittany & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department

Some effects of leading-edge roughness on the aileron effectiveness and drag of a thin rectangular wing employing a full-span plain aileron at Mach numbers from 0.6 to 1.5

Description: Report presenting an investigation of the effects of adding leading-edge roughness to the surfaces of an unswept, untapered, 6-percent-thick, circular-arc-airfoil wing equipped with a full-span, 0.2-chord, plain, trailing-edge aileron. Results regarding the rolling-effectiveness data, addition of roughness on a wing, and variation of drag coefficient are provided.
Date: November 4, 1953
Creator: English, Roland D.
Partner: UNT Libraries Government Documents Department

Effects of a typical nacelle on the characteristics of a thick low-drag airfoil critically affected by leading-edge roughness

Description: Report presenting testing to study the effects of a typical nacelle on the characteristics of a thick low-drag airfoil that was shown to be subject to separation difficulties due to leading edge roughness. This testing confirmed the results of previous tests which indicated that the airfoil was unconservative with respect to separation difficulties. Results regarding the internal-flow measurements and corresponding drag increments, external drag, leading-edge roughness and nacelle combination, and section lift comparisons are provided.
Date: April 1943
Creator: Ellis, Macon C., Jr.
Partner: UNT Libraries Government Documents Department

Flight measurements of the effects of surface condition on the supersonic drag of fin-stabilized parabolic bodies of revolution

Description: Report presenting testing of rocket-powered models at supersonic speeds to determine some of the surface conditions on the zero-lift drag of fin-stabilized parabolic bodies of revolution. Two types of models and three types of surface roughness were tested. Results regarding mean-drag coefficients, side-pressure coefficients, and total-drag coefficients are provided.
Date: May 2, 1952
Creator: Jackson, H. Herbert
Partner: UNT Libraries Government Documents Department

Experimental and model-based study of the robustness of line-edgeroughness metric extraction in the presence of noise

Description: As critical dimensions shrink, line edge and width roughness (LER and LWR) become of increasing concern. Crucial to the goal of reducing LER is its accurate characterization. LER has traditionally been represented as a single rms value. More recently the use of power spectral density (PSD), height-height correlation (HHCF), and {sigma} versus length plots has been proposed in order to extract the additional spatial descriptors of correlation length and roughness exponent. Here we perform a modeling-based noise-sensitivity study on the extraction of spatial descriptors from line-edge data as well as an experimental study of the robustness of these various descriptors using a large dataset of recent extreme-ultraviolet exposure data. The results show that in the presence of noise and in the large dataset limit, the PSD method provides higher accuracy in the extraction of the roughness exponent, whereas the HHCF method provides higher accuracy for the correlation length. On the other hand, when considering precision, the HHCF method is superior for both metrics.
Date: June 1, 2007
Creator: Naulleau, Patrick P. & Cain, Jason P.
Partner: UNT Libraries Government Documents Department

Non-Classical Smoothening of Nano-Scale Surface Corrugations

Description: We report the first experimental observation of non-classical morphological equilibration of a corrugated crystalline surface. Periodic rippled structures with wavelengths of 290-550 nm were made on Si(OO1) by sputter rippling and then annealed at 650 - 750 &deg;C. In contrast to the classical exponential decay with time, the ripple amplitude, A<sub>{lambda}</sub>(t), followed an inverse linear decay, A<sub>{lambda}</sub>(t)= A<sub>{lambda}</sub>(0)/(1 +k<sub>{lambda}</sub>t), agreeing with a prediction of Ozdemir and Zangwill. We measure the activation energy for surface relaxation to be 1.6&plusmn;0.2 eV, consistent with an interpretation that dimers mediate transport.
Date: May 20, 1999
Creator: Aziz, Michael J.; Chason, Eric; Erlebacher, Jonah; Floro, Jerrold A. & Sinclair, Michael B.
Partner: UNT Libraries Government Documents Department

Spin-on-glass coatings for the generation of super-polishedsubstrates for extreme ultraviolet optics

Description: Substrates intended for use as extreme ultraviolet (EUV) optics have extremely stringent requirements in terms of finish. These requirements can dramatically increase the cost and fabrication time, especially when non-conventional shapes, such as toroids, are required. Here we present a spin-on-glass resist process capable of generating super-polished parts from inexpensive substrates. The method has been used to render diamond-turned substrates compatible for use as EUV optics. Toroidal diamond-turned optics with starting rms roughness in the 3.3 to 3.7 nm range have been smoothed to the 0.4 to 0.6 nm range. EUV reflectometry characterization of these optics has demonstrated reflectivities of approximately 63%.
Date: January 1, 2005
Creator: Salmassi, Farhad; Naulleau, Patrick P. & Gullikson, Eric M.
Partner: UNT Libraries Government Documents Department

Extreme ultraviolet mask substrate surface roughness effects on lithography patterning

Description: In extreme ultraviolet lithography exposure systems, mask substrate roughness induced scatter contributes to LER at the image plane. In this paper, the impact of mask substrate roughness on image plane speckle is explicitly evaluated. A programmed roughness mask was used to study the correlation between mask roughness metrics and wafer plane aerial image inspection. We find that the roughness measurements by top surface topography profile do not provide complete information on the scatter related speckle that leads to LER at the image plane. We suggest at wavelength characterization by imaging and/or scatter measurements into different frequencies as an alternative for a more comprehensive metrology of the mask substrate/multilayer roughness effects.
Date: June 21, 2010
Creator: George, Simi; Naulleau, Patrick; Salmassi, Farhad; Mochi, Iacopo; Gullikson, Eric; Goldberg, Kenneth et al.
Partner: UNT Libraries Government Documents Department

Mask roughness induced LER: a rule of thumb -- paper

Description: Much work has already been done on how both the resist and line-edge roughness (LER) on the mask affect the final printed LER. What is poorly understood, however, is the extent to which system-level effects such as mask surface roughness, illumination conditions, and defocus couple to speckle at the image plane, and currently factor into LER limits. Here, we propose a 'rule-of-thumb' simplified solution that provides a fast and powerful method to obtain mask roughness induced LER. We present modeling data on an older generation mask with a roughness of 230 pm as well as the ultimate target roughness of 50 pm. Moreover, we consider feature sizes of 50 nm and 22 nm, and show that as a function of correlation length, the LER peaks at the condition that the correlation length is approximately equal to the resolution of the imaging optic.
Date: March 12, 2010
Creator: McClinton, Brittany & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department

Investigation of the effects of variations in the Reynolds number between 0.4 x 10(exp 6) 3.0 x 10(exp 6) on the low-speed aerodynamic characteristics of three low-aspect-ratio symmetrical wings with rectangular plan forms

Description: Report presenting an investigation of the effect of Reynolds number and the addition of leading-edge roughness on the aerodynamic characteristics of wings with aspect ratio 1, 2, and 3, a rectangular plan form, square-cut wing tips, and NACA 0012 airfoil sections. Results regarding lift and moment, lift-curve slope, and maximum lift are provided.
Date: September 22, 1952
Creator: Jones, George W., Jr.
Partner: UNT Libraries Government Documents Department

Effect of distributed granular-type roughness on boundary-layer transition at supersonic speeds with and without surface cooling

Description: Report presenting an investigation to determine the effect of a distributed granular-type roughness on boundary-layer transition at several temperatures. The roughness was not found to introduce any disturbances of significant magnitude to influence transition. Surface cooling did not increase the value of the critical roughness Reynolds number for a distributed granular-type roughness either.
Date: March 10, 1958
Creator: Braslow, Albert L.
Partner: UNT Libraries Government Documents Department

Optimization of Superhydrophobic Surfaces to Maintain Continuous Dropwise Condensation

Description: In the past decade, the condensation on superhydrophobic surfaces has been investigated abundantly to achieve dropwise condensation. There is not a specific approach in choosing the size of the roughness of the superhydrophobic surfaces and it was mostly selected arbitrarily to investigate the behavior of condensates on these surfaces. In this research, we are optimizing the size of the roughness of the superhydrophobic surface in order to achieve dropwise condensation. By minimizing the resistances toward the transition of the tails of droplets from the cavities of the roughness to the top of the roughness, the size of the roughness is optimized. It is shown that by decreasing the size of the roughness of the superhydrophobic surface, the resistances toward the transition of the tails of droplets from Wenzel state to Cassie state decrease and consequently dropwise condensation becomes more likely.
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: May 2014
Creator: Vandadi, Aref
Partner: UNT Libraries

The Influence of Surface Roughness and Its Geometry on Dynamic Behavior of Water Droplets

Description: In this study the author reports the effects of surface roughness on dynamic behavior of water droplets on different types of rough structures. First, the influence of roughness geometry on the Wenzel/ Cassie-Baxter transition of water droplets on one-tier (solid substrates with Si micropillars) surfaces is studied (Chapter 3). In order to address distinct wetting behaviors of the advancing and receding motions, the author investigates the Wenzel/ Cassie-Baxter transition of water droplets on one-tier surfaces over a wide range of contact line velocities and droplet volumes in both advancing and receding movements. The discussions are strengthened by experimental results. According to the author’s analysis, the advancing contact zone tends to follow the Cassie-Baxter behavior for a wider range of geometric ratios than the receding contact zone. Physical phenomena such as advancing contact line rolling mechanism and the pinning of the receding contact line are introduced to justify distinct transition points of the advancing and receding movements respectively. Based on the analysis provided in Chapter 3, the author experimentally investigates the contact line fluctuations and contact line friction coefficients of water droplets on smooth, one-tier, and two-tier (with carbon nanotubes (CNTs) grown on Si micropillars) surfaces in Chapters 4 and 5. Both the advancing and receding contact line fluctuations/friction coefficients have been measured, analyzed and compared on smooth, one-tier, and two-tier surfaces over a wide range of contact line velocities and droplet volumes. A comprehensive analysis is provided to explain the experimental observations.
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: December 2014
Creator: Sadeghpour, Nima.
Partner: UNT Libraries

Comparison between structural properties of bulk GaN grown under high N pressure and GaN grown by other methods

Description: In this paper defects formed in GaN grown by different methods are reviewed. Formation of particular defects are often related to the crystallographic direction in which the crystals grow. For bulk crystals the highest growth rates are observed for directions perpendicular to the c-axis. Threading dislocations and nanopipes along the c-axis are not formed in these crystals, but polarity of the growth direction plays a role concerning defects that are formed and surface roughness. For growth of homoepitaxial layers, where growth is forced to take place in the c-direction threading dislocations are formed and their density is related to the purity of constituents used for growth and to substrate surface inhomogeneities. In heteroepitaxial layers two other factors: lattice mismatch and thermal expansion mismatch are related to the formation of dislocations. Doping of crystals can also lead to formation of defects characteristic for a specific dopant. This type of defects tends to be growth method independent but can depend on growth polarity.
Date: July 31, 2002
Creator: Liliental-Weber, Z.; Jasinski, J. & Washburn, J.
Partner: UNT Libraries Government Documents Department

Wake fields and energy spread for the ERHIC ERL

Description: Wake fields in high-current ERLs can cause significant beam quality degradations. Here we summarize effects of coherent synchrotron radiation, resistive wall, accelerating cavities and wall roughness for ERL parameters of the eRHIC project. A possibility of compensation of such correlated energy spread is also presented. An emphasis in the discussion is made on the suppression of coherent synchrotron radiation due to shielding and a possible reduction of wall roughness effects for realistic surfaces.
Date: October 16, 2011
Creator: V., Fedotov A.; Kayran&#44 & D.
Partner: UNT Libraries Government Documents Department

Real-space and energy representations for the interface roughness scattering in quantum-well structures

Description: The authors show that the real space representation of the interface-roughness as a fluctuating potential in the coordinate space is equivalent to the usual energy-fluctuation representation for intrasublevel scattering in a single quantum well with a generally shaped confinement-potential profile. The coordinate picture is, however, more general and can be used for higher-order effects and multi-sublevel scattering in coupled multi-quantum-well structures.
Date: April 24, 2000
Creator: LYO,SUNGKWUN K.
Partner: UNT Libraries Government Documents Department

Solid Deuterium-Tritium Surface Roughness In A Beryllium Inertial Confinement Fusion Shell

Description: Solid deuterium-tritium (D-T) fuel layers for inertial confinement fusion experiments were formed inside of a 2 mm diameter beryllium shell and were characterized using phase-contrast enhanced x-ray imaging. The solid D-T surface roughness is found to be 0.4 {micro}m for modes 7-128 at 1.5 K below the melting temperature. The layer roughness is found to increase with decreasing temperature, in agreement with previous visible light characterization studies. However, phase-contrast enhanced x-ray imaging provides a more robust surface roughness measurement than visible light methods. The new x-ray imaging results demonstrate clearly that the surface roughness decreases with time for solid D-T layers held at 1.5 K below the melting temperature.
Date: April 19, 2006
Creator: Kozioziemski, B J; Sater, J D; Moody, J D; Montgomery, D S & Gautier, C
Partner: UNT Libraries Government Documents Department