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Recent progress on the self-aligned, selective-emitter silicon solar cell

Description: We developed a self-aligned emitter etchback technique that requires only a single emitter diffusion and no alignments to form self-aligned, patterned-emitter profiles. Standard commercial, screen-printed gridlines mask a plasma-etchback of the emitter. A subsequent PECVD-nitride deposition provides good surface and bulk passivation and an antireflection coating. We succeeded in finding a set of parameters which resulted in good emitter uniformity and improved cell performance. We used full-size multicrystalline silicon (mc-Si) cells processed in a commercial production line and performed a statistically designed, multiparameter experiment to optimize the use of a hydrogenation treatment to increase performance. Our initial results found a statistically significant improvement of half an absolute percentage point in cell efficiency when the self-aligned emitter etchback was combined with a 3-step PECVD-nitride surface passivation and hydrogenation treatment. 12 refs., 4 figs., 3 tabs.
Date: October 1, 1997
Creator: Ruby, D.S.; Yang, P. & Roy, M.
Partner: UNT Libraries Government Documents Department

Patterned functional arrays by selective de-wetting

Description: Using a micro-Contact Printing ({mu}-CP) technique, substrates are prepared with patterns of hydrophilic, hydroxyl-terminated SAMS and hydrophobic methyl-terminated SAMS. Beginning with a homogeneous solution of silica, surfactant, ethanol, water, and functional silane, preferential ethanol evaporation during dip-coating, causes water enrichment and selective de-wetting of the hydrophobic SAMS. Correspondingly, film deposition occurs exclusively on the patterned hydrophilic SAMS. In addition, by co-condensation of tetrafunctional silanes (Si(OR){sub 4}) with tri-functional organosilanes ((RO){sub 3}Si(CH{sub 2}){sub 3}NH{sub 2}), the authors have selectively derived the silica framework with functional amine NH{sub 2} groups. A pH sensitive, micro-fluidic system was formed by further conjugation reactions with pH sensitive dye molecules.
Date: May 11, 2000
Partner: UNT Libraries Government Documents Department

Characterization of DuPont 1900 series resistors applied to DuPont 5704 dielectric on alumina substrates

Description: Existing thick film hybrid microcircuit (HMC) production utilizing integral thick film resistors requires that thick film resistors be deposited via screen printing directly on the base alumina substrate material. This requirement, when coupled with circuits of moderate to high density and associated layer buildup prior to resistor application, results in printing on surfaces with significant topography surrounding the resistor, compared to required as-printed resistor thicknesses. Due to the technological requirement to print resistors after most other thick film processing has been completed, resistor printing is seldom performed on a flat surface. The surface topography of the substrate surrounding the resistor area prohibits the printing process from maintaining a relatively uniform printed resistor thickness across the substrate. Although resistors are, in most cases, adjusted to final electrical values by physically modifying the length-to-width ratio through laser trimming, the resistors must be within certain resistance ranges. This variation in thickness translates into potential scrap product through extreme variation in as-fired resistor electrical values and/or product incapable of being laser trimmed due to excessive resistor thickness. The development of a thick film resistor application process compatible with existing conductor and dielectric materials and enabling more planarization of the print surface was needed to enhance production yields on products of moderate complexity.
Date: June 1, 1997
Creator: Barner, G.E.
Partner: UNT Libraries Government Documents Department

Design and construction of planar mm-wave accelerating cavity structures

Description: Feasibility studies on the planar millimeter-wave cavity structures have been made. The structures could be used for linear accelerators, free electron lasers, mm-wave amplifiers, or mm-wave undulators. The cavity structures are intended to be manufactured by using DXL (deep x-ray lithography) microfabrication technology. The frequency of operation can be about 30GHz to 300GHz. For most applications, a complete structure consists of two identical planar half structures put together face-to-face. Construction and properties of constant gradient structures that have been investigated so far will be discussed. These cavity structures have been designed for 120GHz 2{pi}/3-mode operation.
Date: 1995-10~
Creator: Kang, Y. W.; Kustom, R. L.; Nassiri, A.; Song, J. J. & Feineman, A. D.
Partner: UNT Libraries Government Documents Department

Basic issues associated with four potential EUV resist schemes

Description: Four of the better developed resist schemes that are outgrowths of DUV (248 and 193 nm) resist development are considered as candidates for EUV. They are as follows: trilayer, a thin imaging layer on top of a refractor masking/pattern transfer layer on top of a planarizing and processing layer (PPL); solution developed, organometallic bilayer where the imaging and masking layer have been combined into one material on top of a PPL; and finally silylated resists. They are examined in a very general form without regard to the specifics of chemistry of the variations within each group, but rather to what is common to each group and how that affects their effectiveness as candidates for a near term EUV resist. In particular they are examined with respect to sensitivity, potential resolution, optical density, etching selectivity during pattern transfer, and any issues associated with pattern fidelity such as swelling.
Date: June 1, 1996
Creator: Wheeler, D.R.; Kubiak, G.; Ray-Chaudhuri, A. & Henderson, C.
Partner: UNT Libraries Government Documents Department

Rule-based inspection of printed green ceramic tape

Description: A template-based vision system for the 100% inspection of printed flaws on green ceramic tape has been developed. Design goals included a requirement for the detection of flaws as small as two thousandths of an inch on parts up to 8 by 8 inches in size. The inspection engine is a Datacube, Inc., MV200 pipeline processor. As each part is inspected, four 2K by 2K pixel quadrant images are stitched together to construct a single 4K by 4K pixel image with the aid of multiple fiducials located in each quadrant. The part fiducial locations, mask image, and punched-hole position data are generated, beforehand, from CAD designs using a defect map editor (DME), a preprocessing software package developed for the PC. The DME also generates a part ``defect map``. Each unique structure in the printed pattern is defined as an object. Objects are grouped into user-defined categories such as die pads, contact fingers, traces, and electrolysis buses. The map is used during the runtime inspection to associate each detected defect with an object group and a particular defect specification for that group. Repeat defects are optionally tracked for up to three consecutive parts.
Date: January 1, 1998
Creator: Patek, D.R.; Goddard, J.S.; Karnowski, T.; Lamond, D. & Hawkins, T.A.
Partner: UNT Libraries Government Documents Department

Aminodisilanes as silylating agents for dry-developed positive-tone resists for extreme ultraviolet (13.5) microlithography

Description: We recently described a near-surface imaging scheme that employs disilanes and a bilayer resist scheme which together dramatically improve silicon contrast. A relatively thin 0.25 to 0.1 {mu}m imaging layer of a chemically amplified photo-crosslinking resist (Shipley XP-8844 or XP-9472) is spin coated on top of a thicker (0.25-0.5 {mu}m) layer of hard-baked resist (such as Shipley MP-1807). This bilayer scheme improves silicon contrast and provides additional advantages such as providing a planarizing layer and a processing layer.
Date: February 1, 1996
Creator: Wheeler, D.; Kubiak, G.; Henderson, C. & Ray-Chadhuri, A.
Partner: UNT Libraries Government Documents Department

New photolithography stepping machine

Description: A joint development project to design a new photolithography steeping machine capable of 150 nanometer overlay accuracy was completed by Ultratech Stepper and the Lawrence Livermore National Laboratory. The principal result of the project is a next-generation product that will strengthen the US position in step-and-repeat photolithography. The significant challenges addressed and solved in the project are the subject of this report. Design methods and new devices that have broader application to precision machine design are presented in greater detail while project specific information serves primarily as background and motivation.
Date: March 8, 1995
Creator: Hale, L.; Klingmann, J. & Markle, D.
Partner: UNT Libraries Government Documents Department

Multifunctional (NOx/CO/O2) Solid-State Sensors For Coal Combustion Control

Description: Solid-state sensors were developed for coal combustion control and the understanding of sensing mechanisms was advanced. Several semiconducting metal oxides (p-type and n-type) were used to fabricate sensor electrodes. The adsorption/desorption characteristics and catalytic activities of these materials were measured with Temperature Programmed Desorption (TPD) and Temperature Programmed Reaction (TPR) experiments. The sensitivity, selectivity, and response time of these sensors were measured for steps of NO, NO{sub 2}, CO, CO{sub 2}, O{sub 2}, and H{sub 2}O vapor in simple N{sub 2}-balanced and multi-component, simulated combustion-exhaust streams. The role of electrode microstructure and fabrication parameters on sensing performance was investigated. Proof for the proposed sensing mechanism, Differential Electrode Equilibria, was demonstrated by relating the sensing behavior (sensitivities and cross-sensitivities) of the various electrode materials to their gas adsorption/desorption behaviors and catalytic activities. A multifunctional sensor array consisting of three sensing electrodes and an integrated heater and temperature sensors was fabricated with tape-casting and screen-printing and its NO{sub x} sensing performance was measured. The multifunctional sensor demonstrated it was possible to measure NO{sub 2} independent of NO by locally heating one of the sensing electrodes. The sensor technology was licensed to Fuel FX International, Inc. Fuel FX has obtained investor funding and is developing prototype sensors as a first step in their commercialization strategy for this technology.
Date: December 31, 2006
Creator: Wachsman, Eric D.
Partner: UNT Libraries Government Documents Department

Electrical test structures replicated in silicon-on-insulator material

Description: Measurements of the linewidths of submicrometer features made by different metrology techniques have frequently been characterized by differences of up to 90 nm. The purpose of the work reported here is to address the special difficulties that this phenomenon presents to the certification of reference materials for the calibration of linewidth-measurement instruments. Accordingly, a new test structure has been designed, fabricated, and undergone preliminary tests. Its distinguishing characteristics are assured cross-sectional profile geometries with known side-wall slopes, surface planarity, and compositional uniformity when it is formed in mono-crystalline material at selected orientations to the crystal lattice. To allow the extraction of electrical linewidth, the structure is replicated in a silicon film of uniform conductivity which is separated from the silicon substrate by a buried oxide layer. The utilization of a Silicon-On-Insulator (SKI) substrate further allows the selective removal of substrate material from local regions below the reference features, thus facilitating measurements by optical and electron-beam transmission microscopy. The combination of planar feature surfaces having known side-wall slopes is anticipated to eliminate factors which are believed to be responsible for methods divergence in linewidth measurements, a capability which is a prerequisite for reliable certification of the linewidths of features on reference materials.
Date: February 27, 1996
Creator: Cresswell, M.W.; Ghoshtagore, R.N.; Allen, R.A.; Linholm, L.W.; Villarrubia, J.S. & Sniegowski, J.J.
Partner: UNT Libraries Government Documents Department

Self-aligned selective emitter plasma-etchback and passivation process for screen-printed silicon solar cells

Description: Plasma-enhanced chemical vapor deposition (PECVD) is a cost-effective, performance-enhancing technique that can provide surface passivation and produce an effective antireflection coating layer at the same time. To gain the full benefit from improved emitter surface passivation on cell performance, it is necessary to tailor the emitter doping profile so that the emitter is lightly doped between the gridlines, but heavily doped under them. This selectively patterned emitter doping profile has historically been obtained by using expensive photolithographic or screen-printed alignment techniques and multiple high-temperature diffusion steps. We built on a self-aligned emitter etchback technique first described by Spectrolab. We included PECVD-nitride deposition because the low- recombination emitter produced by the etchback requires good surface passivation for improved cell performance. The nitride also provides a good antireflection coating. We studied whether plasma-etching techniques can use standard screen-printed gridlines at etch masks to form self-aligned, patterned-emitter profiles on multicrystalline (MC-Si) cells from Solarex Corp. This investigation determined that reactive ion etching (RIE) is compatible with using standard, commercial, screen printed gridlines as etch masks to form self- aligned, selectively-doped emitter profiles. This process results in reduced gridline contact resistance when followed by PECVD treatments, an undamaged emitter surface easily passivated by plasma-nitride, and a less heavily doped emitter between gridlines for reduced emitter recombination. This allows for heavier doping beneath the gridlines for even lower contact resistance, reduced contact recombination, and better bulk defect gettering. Our results found improvement of half a percentage point in cell efficiency when the self-aligned emitter etchback was combined with the PECVD-nitride surface passivation treatment.
Date: August 1, 1996
Creator: Ruby, D.S.; Fleddermann, C.B.; Roy, M. & Narayanan
Partner: UNT Libraries Government Documents Department

Improving the figure of very good mirrors by deposition

Description: Mid-spatial frequency errors of near perfect mirrors can be reduced by deposition through a computer generated mask without degrading the superpolish. Experimental results are presented.
Date: June 1996
Creator: Sweatt, W. C.; Weed, J. W.; Farnsworth, A. V.; Warren, M. E.; Neumann, C. C.; Goeke, R. S. et al.
Partner: UNT Libraries Government Documents Department

Expanded-mode semiconductor laser with tapered-rib adiabatic-following fiber coupler

Description: A new diode laser using a Tapered-Rib Adiabatic-Following Fiber Coupler to achieve 2D mode expansion and narrow, symmetric far-field emission without epitaxial regrowth or sharply-defined tips on tapered waveguides is presented.
Date: February 1, 1997
Creator: Vawter, G.A.; Smith, R.E.; Hou, H. & Wendt, J.R.
Partner: UNT Libraries Government Documents Department

Fabrication of mm-wave undulator cavities using deep x-ray lithography

Description: The possibility of fabricating mm-wave radio frequency cavities (100-300 GHz) using deep x-ray lithography (DXRL) is being investigated. The fabrication process includes manufacture of precision x-ray masks, exposure of positive resist by x-ray through the mask, resist development, and electroforming of the final microstructure. Highly precise, two-dimensional features can be machined onto wafers using DXRL. Major challenges are: fabrication of the wafers into three-dimensional rf structures; alignment and overlay accuracy of structures; adhesion of the PMMA on the copper substrate; and selection of a developer to obtain high resolution. Rectangular cavity geometry is best suited to this fabrication technique. A 30- or 84-cell 108-GHz mm-wave structure can serve as an electromagnetic undulator. A mm-wave undulator, which will be discussed later, may have special features compared to the conventional undulator. First harmonic undulator radiation at 5.2 KeV would be possible using the Advanced Photon Source (APS) linac system, which provides a low-emittance electron beam by using an rf thermionic gun with an energy as high as 750-MeV. More detailed rf simulation, heat extraction analysis, beam dynamics using a mm-wave structure, and measurements on lOx larger scale models can be found in these proceedings.
Date: December 31, 1995
Creator: Song, J.J.; Kang, Y.W.; Kustom, R.L.; Lai, B.; Nassiri, A.; Feinerman, A.D. et al.
Partner: UNT Libraries Government Documents Department

Dimensional variation and roughness of LIGA fabricated microstructures

Description: We have measured the dimensional variation and sidewall roughness of features on PMMA micro- components fabricated by deep x-ray lithography in order to assess the effect of dimensional variation on subsequent assembly operations. Dimensional measurements were made using a stylus profilometer with a repeatability in step height of better than 0.01 {mu}m. Roughness measurements were made with the same profilometer scanning in a direction perpendicular to the length of the parts. 22 {mu}m and 54 {mu}m features exhibited dimensional variations described by a Gaussian distribution with standard deviations of 0.202 {mu}m and 0.381 {mu}m, respectively. This corresponds to a maximum relative variation of between 0.6% and 0.9%. Sidewall roughnesses were found to be in the range of 0.02 {mu}m to 0. 03 {mu}m, an insignificant contribution to the total variation when compared to overall dimensional variation. Several potential sources of this variation are discussed, but no single cause was identified as the source of the significant dimensional variation observed here.
Date: October 1, 1996
Creator: Egert, C.M.; Wood, R. & Malek, C.K.
Partner: UNT Libraries Government Documents Department

Pad printer for electronics. Final report

Description: This is the Final report on DARPA-sponsored development Program Pad Printer for Electronics DE-FC04-95AL87486 which was initiated in February, 1995 and intended to run 24 months to February 1997. The Program has significant value to the Thick Film processing industry, an electronic manufacturing alternative for producing functional modules integrated at the multichip level. The result is highly reliable, high volumetric efficiency, subassemblies for military applications and for commercial applications in severe environments, such as automotive, portable communications, and bio-implantable devices. The program progressed quite satisfactorily through 19 months, when it encountered severe, non-technical, difficulties. Resolving these difficulties resulted in several months of delay in completing the Program, but resulted in only a trivial increase in total program cost and no increase in cost to the sponsor. The principle Objective of the Program was the development of a printing system -- machine and appropriate inks -- compatible with existing thick-film processing but offering a 5x improvement in line density. This objective has been met. The Pad Printer is capable of printing suitable inks in traces 25 g wide on 50g centers to a fired thickness of 3 {mu}; each of these parameters is roughly 1/5 the value of the current alternative, silk-screen printing. The available inks represent an assortment of conductor, dielectric, and insulator formulations and the knowledge developed permits extending this family of inks to new and diverse functional materials. An important secondary objective was maximum compatibility with existing Thick Film processing; the printer and ink systems may be substituted directly for the silk screen printers in existing processes. The Program reached or exceeded its other Technical Objectives in almost every case and, in those few instances where the objective was only partially met, work continues under private funding.
Date: May 1, 1998
Partner: UNT Libraries Government Documents Department

Self-aligned selective-emitter plasma-etchback and passivation process for screen-printed silicon solar cells

Description: We studied whether plasma-etching techniques can use screen printed gridlines as etch masks to form self-aligned, patterned-emitter profiles on multicrystalline silicon (mc-Si) cells from Solarex Our initial results found a statistically significant improvement of about half an absolute percentage point m cell efficiency when the self-aligned emitter etchback was combined with a PECVD-nitride surface passivation treatment. Some additional improvement in bulk diffusion length was observed when a hydrogen passivation treatment was used in the process. We attempted to gain additional benefits from using an extra-heavy phosphorus emitter diffusion before the gridlines were deposited. However, this required a lusher plasma-etch power to etch back the deeper diffusion and keep the etch time reasonably short. The higher power etch may have damaged the surface and the gridlines so that improvement due to surface passive and reduced gridline contact resistance was inhibited.
Date: October 1, 1996
Creator: Ruby, D.S.; Fleddermann, C.B. & Narayanan, S.
Partner: UNT Libraries Government Documents Department

High-power extreme ultraviolet source based on gas jets

Description: The authors report on the development of a high power laser plasma Extreme Ultraviolet (EUV) source for Extreme Ultraviolet Lithography. The source is based on the plasma emission of a recycled jet beam of large Xe clusters and produces no particulate debris. The source will be driven by a pulsed laser delivering 1,500 W of focused average power to the cluster jet target. To develop condensers and to optimize source performance, a low power laboratory cluster jet prototype has been used to study the spectroscopy, angular distributions, and EUV source images of the cluster jet plasma emission. In addition, methods to improve the reflectance lifetimes of nearby plasma facing condenser mirrors have been developed. The resulting source yields EUV conversion efficiencies up to 3.8% and mirror lifetimes of 10{sup 9} plasma pulses.
Date: March 1, 1998
Creator: Kubiak, G.D.; Bernardez, L.J. & Krenz, K.
Partner: UNT Libraries Government Documents Department

Deep x-ray lithography for micromechanics

Description: Extensions of the German LIGA process have brought about fabrication capability suitable for cost effective production of precision engineered components. The process attributes allow fabrication of mechanical components which are not capable of being made via conventional subtractive machining methods. Two process improvements have been responsible for this extended capability which involve the areas of thick photoresist application and planarization via precision lapping. Application of low-stress x-ray photoresist has been achieved using room temperature solvent bonding of a preformed photoresist sheet. Precision diamond lapping and polishing has provided a flexible process for the planarization of a wide variety of electroplated metals in the presence of photoresist. Exposure results from the 2.5 GeV National Synchrotron Light Source storage ring at Brookhaven National Laboratory have shown that structural heights of several millimeter and above are possible. The process capabilities are also well suited for microactuator fabrication. Linear and rotational magnetic microactuators have been constructed which use coil winding technology with LIGA fabricated coil forms. Actuator output forces of 1 milliNewton have been obtained with power dissipation on the order of milliWatts. A rotational microdynamometer system which is capable of measuring torque-speed data is also discussed.
Date: August 1995
Creator: Christenson, T. R. & Guckel, H.
Partner: UNT Libraries Government Documents Department


Description: The composition and microstructure of the sensing electrode are the key parameters that influence the sensing mechanism, and hence key sensor performance parameters: sensitivity, selectivity and response time. During this reporting period we investigated the effect of microstructure and the fundamental heterogeneous gas solid interactions of our NO sensor electrode material. In order to optimize the sensor electrode microstructure, powders were prepared using four different powder synthesis routes, resulting in different particle sizes distributions and BET surface areas. Different electrode processing conditions, e.g. screen-printing slurry composition, sintering schedule, etc. were also applied. In this report we demonstrate that the microstructure of electrodes, synthesized with the same composition, has a dramatic effect on both sensitivity and response time of potentiometric NO sensors. A quartz reactor and a tube furnace were built for the catalysis experiments. The installation of a quadrupole mass spectrometer (QMS) and a multi gas controller were completed. Moreover, the system for the temperature-programmed reaction (TPR) and desorption (TPD) were completed by combining the equipment. We used this heterogeneous catalysis system to determine the adsorption characteristics of O{sub 2}, NO, CO, CO{sub 2}, and their mixtures, on the electrode material using TPD, and related the results to sensor performance.
Date: December 31, 2003
Creator: Wachsman, Eric D.
Partner: UNT Libraries Government Documents Department


Description: Technology Management, Inc has evaluated the practical fabrication advantages and potential economic impact of a multi-pass screen printing process on the costs of fabricating planar solid oxide fuel cell stacks. During this program, multiple catalyzed binder systems were considered. Preliminary screening experiments resulted in four systems being selected for further evaluation. Inks were formulated using these binders in combination with at least three fuel cell materials (anode, cathode, and seal material). Reactivity of the binder with catalyst and fuel cell materials was evaluated. Cell tests indicated that the catalyzed binders did not negatively impact cell performance. Tests were conducted demonstrating single cell performance comparable with standard cell fabrication technology. Tailored patterns were also demonstrated. Economic evaluation indicated that a significant reduction in cost could be achieved, primarily through reduced capital equipment needs.
Date: June 1, 2002
Creator: Milliken, Christopher; Ruhl, Robert & Hillman, Jennifer
Partner: UNT Libraries Government Documents Department


Description: This report summarizes the results of a four-year project, entitled, ''Low-Cost Manufacturing Of Multilayer Ceramic Fuel Cells'', jointly funded by the U.S. Department of Energy, the State of Ohio, and by project participants. The project was led by NexTech Materials, Ltd., with subcontracting support provided by University of Missouri-Rolla, Michael A. Cobb & Co., Advanced Materials Technologies, Inc., Edison Materials Technology Center, Gas Technology Institute, Northwestern University, and The Ohio State University. Oak Ridge National Laboratory, though not formally a subcontractor on the program, supported the effort with separate DOE funding. The objective of the program was to develop advanced manufacturing technologies for making solid oxide fuel cell components that are more economical and reliable for a variety of applications. The program was carried out in three phases. In the Phase I effort, several manufacturing approaches were considered and subjected to detailed assessments of manufacturability and development risk. Estimated manufacturing costs for 5-kW stacks were in the range of $139/kW to $179/kW. The risk assessment identified a number of technical issues that would need to be considered during development. Phase II development work focused on development of planar solid oxide fuel cell elements, using a number of ceramic manufacturing methods, including tape casting, colloidal-spray deposition, screen printing, spin-coating, and sintering. Several processes were successfully established for fabrication of anode-supported, thin-film electrolyte cells, with performance levels at or near the state-of-the-art. The work in Phase III involved scale-up of cell manufacturing methods, development of non-destructive evaluation methods, and comprehensive electrical and electrochemical testing of solid oxide fuel cell materials and components.
Date: June 12, 2004
Creator: Swartz, Scott; Seabaugh, Matthew; Dawson, William; Anderson, Harlan; Armstrong, Tim; Cobb, Michael et al.
Partner: UNT Libraries Government Documents Department