Engineering Commons^™

Fabrication Of T-Gate Structures Using Double Layer E-Beam Lithography, Eric A. Lehner

Journal of the Microelectronic Engineering Conference

The fabrication of T-gate structures using a bilayer resist scheme of PMMA 495K molecular weight (4% solids) and PMMA 950K molecular weight (3~ solids) for use with electron beam exposure was investigated. The 1.18 sensitivity ratio between these resists was found to be insufficient to adequately provide the resist cavity necessary for fabrication of T-gate aluminum structures.

Local Stress Field Determination For Thin Polysilicon Films, Pirouz Maghsoudnia

Journal of the Microelectronic Engineering Conference

Local stress field determination by means of free standing structures was investigated. The process for manufacturing these structures was developed and used to study the stress in polysilicon films.. For a 1.5um polysilicon film, the stress was determined to be less than 6.77e8Dynes/cm2. For a 0.5um polysilicon films, the stress was found to be 4. O9e8Dynes/cm2.

Fabrication Of Micromechanical Devices: Pin Joints, Sliders, Springs, And Micromotors, Matthew P. Matessa

Journal of the Microelectronic Engineering Conference

Movable pin Joints, springs, sliders and Rotors have been constructed using silicon fabrication technology. The movable mechanical elements are built using sacrificial layers that are later removed to allow translation and rotation of the structures [1]. The devices obtained physical movement and the rotors of the Rotors spun with compressed air, but electrical rotation of the motors was not accomplished.

Solar Cell Design Employing A Textured Surface, Diane M. Mauersberg

Journal of the Microelectronic Engineering Conference

Planar-junction, 1 mm x 1 mm, p+/n/n+ silicon solar cells, both with and without a textured surface, were fabricated in order to study the effects of decreased surface reflectance on cell efficiency. The texturing process was performed through the use of a KOH preferential etchant and an array of 10um x 10um windows to form an oxide masking layer. Inverted pyramids etched to points with final base widths being 13.7 microns due to undercutting of the masking oxide. Completed cells, evaluated at an irradiance of 100 mW/cm2, showed greater efficiences for the textured surface, but outputs of both were limited …

Determination Of Si02 Profiles Achievable With Rie Using C2f6 And Chf3, Daniel P. Morvay

Journal of the Microelectronic Engineering Conference

A dry etch S1O2 process was optimized using the Plasmatrac 2406 RIE etcher at RIT, while maintaining selectivity to polysilicon and photoresist. The optimized process had Power of 350 Watts, Pressure of 127 mTorr, C2F6 of 60 sccm, and CHF3 of 171 sccm; This provided an oxide to poly selectivity of 5.5:1 with an oxide slope of 60°.

Bicmos Vs Cmos At Rit, Anatole Raif

Journal of the Microelectronic Engineering Conference

This project involved the performance comparison of the standard RIT N-well CMOS and a proposed BiCMOS processes. Device parameters were extracted from TMA SUPREM-3 simulations and used to create NPN, PMOS, and NMOS model cards for ~ccusim simulations. Two inverter circuits, one in CMOS and one in BiCMOS were designed to drive a 5OpF load. The BiCMOS circuit was determined to be four times faster, less temperature dependent, and considerably smaller than its CMOS counterpart. These results lead to a final conclusion favoring the development and use of BiCMOS here at RIT.

Linear Poly Gate Charge Coupled Device Imaging Arrays, Lucien Randazzese

Journal of the Microelectronic Engineering Conference

A five cask level process was used to fabricate single level, poly gated charge coupled devices intended for use as optical imagers. Three micron gate spacing was achieved with an emulsion cask through tight control of the lithography process. Testing revealed a short between the gates. It is hypothysised to result from insufficient poly gate etching or over diffusion of the gate.

Studies Of Optical Lithographic Process With The Aid Of Prolith/2, Wai-Man Wilma Shiao

Journal of the Microelectronic Engineering Conference

PROLITH/2, a tool for modelling and analyzing photolithographic processes, was used to explore two statistically designed experiments. The first was the aerial image formation and the second was resist development process. Results are presented to illustrate the software capability.

Polysilicon Emitter Bipolar Transistors, Todd C. Sieger

Journal of the Microelectronic Engineering Conference

Polysilicon emitter vertical NPN transistors were fabricated in an attempt to create devices with very high current gains and high forward Early voltages. TMA SUPREM-3 simulations were used to optimize the process to obtain emitter junction depths of 0.05 and 0.08um. Final emitter junction depths of 0.1um, or less, were measured. High current gains were not achieved, due to high base doping.

Characterization, Optimization, And Qualification Of Shipley 812 Photoresist For Wafertrac Processing, David H. Taylor

Journal of the Microelectronic Engineering Conference

Wafertrac processing was used to optimize the photolithographic process of Shipley 812 positive photoresist. For two, three, four, and five micron lines, it was found that optimum conditions are 30-40 seconds development time in MF-3 19 and about 72 mj/cm2 exposure dose. These optimum conditions maximize the control over the size of the image being replicated into the resist from the mask. Hardbaking of the resist resulted in a 300-400 micron thickness loss as well as a rounding of the resist profile. Contrast varied from 1.42 to 1.76 with the highest contrast being in the optimum development time range of …

Bipolar Device Fabrication Using Rit's Cmos Technology To Develop A Bicmos Process, Luigi Ternullo Jr

Journal of the Microelectronic Engineering Conference

An NPN bipolar transistor process was designed and fabricated for incorporation with RIT’s N well CMOS technology to develop BiCMOS devices. The only additions to the CMOS process were the base masking step, base implant, and drive. Base dose was varied to achieve current gains of 50, 100, and 200 using SUPREM-3. Unfortunately, do to an incomplete etch of the collector region, a rework had to be performed, whose added temperature steps pushed the emitter through the base.

Affects Of Carbon Dioxide And Helium On Reactive Ion Etching Of Silicon Dioxide, Eric E. Thompson

Journal of the Microelectronic Engineering Conference

A study of the etch characteristics of a thermally grown silicon dioxide etch in RITEs 2406 PLASMATRAC RIE was performed for a C2F6 / CHF3 / C02 gas mixture. Correlations between the amount of CHF3 and C02 introduced and Si02 etch rates and selectivity to polysilicon were investigated using a statistical experimental design. Si02 etch rates as high as 1018 A/mm were achieved with a corresponding selectivity to polysilicon of 2.84:1. At a gas flow of 60 sccm C2F6, 171 sccm CHF3, 48 sccm C02, 255 watts & 150 mtorr, an optimized etch for selectivity was found to give an …

Ferroelectric Thin Film Research At Rit, John P. Verostek

Journal of the Microelectronic Engineering Conference

At RIT, a sol-gel method is being used to synthesize lead zirconate titanate (PZT). Techniques available to characterize these films include scanning electron microscopy ellipsometry, energy dispersive analysis using X-rays (EDAX), and X-ray diffraction (XRD) to determine crystallinity. After heating above the Curie temperature, XRD indicated that a perovskite structure, known to be ferroelectric, was obtained for a PZT film.

Characterization Of Chemically Amplified Advanced Negative Resist For G Line Application, Shu Tsai Wang

Journal of the Microelectronic Engineering Conference

Chemically Amplified Advanced Negative Resist for G line application was evaluated under three different Post Exposure Bake temperatures. The photospeed increased from 22mj/cm*2 to lOmj/cm*2 as the post exposure bake temperature was increased from 120C to 140C. A contrast of approximately 2.0 was obtained for all three treatments, as opposed to the expected value of 4.0. The Optical evaluation of line and space. patterns suggested the 120C post exposure bake temperature will give wider exposure process latitude than 130C or 140C temperatures. The resist exhibited high sensitivity below 3Omj/cm*2 with wide exposure process latitude around 2Omj/cm*2.

Development Of A Deep Trench Rie Etch For Capacitor And Isolation Technologies, Joseph W. Wiseman

Journal of the Microelectronic Engineering Conference

A silicon trench 2um deep was etched in a PlasmaTherm 2406 RIE tool using an SF6/C02 chemistry with an oxide mask. The single crystal silicon etch rate was 1100A/min, with a high selectivity to oxide. A trench slope approximately 50 degrees was obtained, with no undercut of the oxide mask.

Design And Fabrication Of A Lateral Bipolar Pnp Transistor Compatible With Rit's Double Diffused Process, James A. Will Ii

Journal of the Microelectronic Engineering Conference

A chip was designed containing lateral bipolar PNP devices with base widths ranging from four to ten microns. Vertical NPN devices were included in the designs. The transistors were fabricated using a double diffused process employing solid sources. Two different boron collector/emitter predepositions were performed in order to study the effects of the p-type diffusion sheet resistance on both lateral PNP and vertical NPN devices. Testing of the lateral PNP devices shows very small Early voltages for the five and six micron designs, while the four micron design exhibits punchthrough.

Low Temperature Deposition Of Si02 Films By Ecr, Merle D. Yoder Jr

Journal of the Microelectronic Engineering Conference

SiO films of high quality have been deposited by Electron Cyclotron Resonance (ECR) at temperatures less than 400 ° C. Chemistries of 02 and 25 % SiHqin Ar were used. Deposition rates of about 220 A/minute were obtained, studying films of typical thicknesses of 1100 A. Characteristics of the films studied include refractive index of 1.467 — 1.477, dielectric strengths of 5.0 — 9.0 MV/cm, dielectric constants of 3.8 — 4.2, and buffered HF etch rates of 19 - 21 A/second. These characteristics were shown to degrade around a deposition temperature of 200 °C, with temperatures on either side of …

Fabrication Of Chromeless Phase-Shifting Mask Using Spin On Glass, Kuen C. Yue

Journal of the Microelectronic Engineering Conference

This project investigated the concept of a chromeless phase-shifting mask. An optical simulator, SPLAT, was used to predict the aerial image formed for various chromeless phaseshifting patterns. Allied Signal 311 spin on glass was patterned on a quartz plate and imaged using a GCA MANN4800, lOX, NA=O.28, G-line stepper to demonstrate the concept. Simulations showed and experimental results confirmed that a dark field could be produced with checkerboard patterns below 0.4Lambda/NA. Using 25% solid KT1820 resist coated at a thickness of 5000A, 0.6um lines and spaces were resolved.

Flash Eeprom Fabrication, Keith E. Zawadzki

Journal of the Microelectronic Engineering Conference

Rochester Institute of Technology's (RIT's) first flash EEPROM cell was designed, fabricated and tested at its Microelectronic Engineering Fabrication Facilities. The RIT flash memory cell was modeled after Intel's flash memory cell was modeled after Intel's flash EEPROM cell and realized a channel length = 8um and channel width = 32um. The fabrication technology required critical process development steps including a high quality 100A tunnel oxide, 100 A polySi oxide and a 200A reactive sputter-deposited silicon nitride film. The cell successfully demonstrated 10 program and erase cycles and a programmed charge state for 130 hours before unacceptable charge loss occurred.

Peripheral Nerve Bridges For Central Nervous System Regeneration, Silvio Varon, Theo Hagg, H. Lee Vahlsing, Marston Manthorpe

Cells and Materials

A neuronotrophic hypothesis for the adult central nervous system (CNS) has been increasingly supported by in vivo studies of Nerve Growth Factor (NGF) impacts on adult rat CNS cholinergic neurons. We have extended these investigations to NGF effects on cholinergic axonal regeneration in an adult rat septo-hippocampal model. A fimbriafornix lesion deprives the dorsal hippocampal formation (HF) of its cholinergic afferents and provides a cavity into which sciatic nerve segments can be implanted to serve as regeneration bridges from septum to HF. Septa! cholinergic fibers enter and course through fresh cell-containing nerve bridges to attain a maximal number by the …

Primary Bone Formation In Porous Hydroxyapatite Ceramic: A Light And Scanning Electron Microscopic Study, M. Okumura, H. Ohgushi, S. Tamai, E. C. Shors

Cells and Materials

Porous hydroxyapatite ceramics combined with rat marrow cells were implanted subcutaneously in the back of syngeneic Fischer rats . Fluorochrome-labeling (calcein, tetracycline) was performed post-operatively and the ceramics were harvested 4 weeks after implantation. Undecalcified thin sections of the implants were observed under light microscopy or fluoromicroscopy and the corresponding areas were also analyzed in a scanning electron microscope connected to an electron probe microanalyzer (SEM-EPMA). Many pore areas of the ceramics showed bone and osteoid formation together with active osteoblasts. The bone formation began directly on the surface of the ceramic and proceeded in a centripetal direction towards the …

Deposition And Resorption Of Calcified Matrix In Vitro By Rat Marrow Cells, J. E. Davies, R. Chernecky, B. Lowenberg, A. Shiga

Cells and Materials

Rat bone marrow derived cells were cultured using a-Minimal Essential Medium supplemented with antibiotics, ascorbic acid and !3-glycerphosphate in the presence of 10-8M dexamethasone, on polystyrene and hydrophilic fluorocarbon substrata for periods of 2 - 4 weeks. During this time, a large yield of bone nodules was achieved and the elaborated tissue was examined by both scanning and transmission electron microscopy. The matrix produced by the cells contacting the underlying substratum was an afibrillar, globular, calcified material which formed a layer approximately 0.5μm thick. The calcium and phosphorus content of this material was confirmed by energy dispersive X-ray dot mapping …

Analysis Of Protein Adsorption On Retrieved Human Vascular Grafts Using Immunogold Labelling With Silver Enhancement, N. P. Ziats, N. S. Topham, D. A. Pankowsky, J. M. Anderson

Cells and Materials

The adsorption of proteins on biomedical materials such as vascular grafts is important in modulating thrombosis, one eventual cause of vascular graft failure. We have identified proteins expressed on the surfaces of retrieved vascular grafts to determine if certain proteins were present at the end stage of vascular failure. Scanning electron microscopic analysis of protein adsorption on the surfaces of retrieved vascular prostheses was determined using antibodies to human blood proteins fibrinogen, fibronectin, Hageman factor (factor XII) and factor VIII/von Willebrand Factor. The detection of these proteins on the blood contacting surface was evaluated by immunogold labelling with protein A-gold …

Scanning Electron Microscopic Evaluation Of The Fractured Surfaces Of Canine Calculi From Substrata With Different Surface Free Energy, H. M. W. Uyen, W. L. Jongebloed, H. J. Busscher

Cells and Materials

The strength of adhesion between dental calculus and enamel or dentin surfaces determines the ease with which the calculus can be removed by brushing or professional dental treatment. In this study, we examined the adhesion of canine calculi formed on substrata with different surface free energies (sfe) and roughness by means of scanning electron microscopy. In 4 beagle dogs fenestrated crowns were made on the upper fourth premolars. Subsequently, facings of glass (sfe = 120 mJ. m-2), bovine enamel (sfe = 85 mJ.m-2), bovine dentin (sfe = 92 mJ.m-2), polymethyl-methacrylate (PMMA, sfe = 56 mJ.m-2) and polytetrafluorethylene (PTFE, sfe = …

Polylysine Stimulation Of Ectopic Cartilage Formation, Rocky S. Tuan, Dina M. Turchi, David S. Kreitzer

Cells and Materials

Cartilage development, or chondrogenesis, is a process which involves the condensation of prechondrogenic mesenchymal cells, followed by the expression of the cartilage phenotype characterized by the biosynthesis of cartilage-specific, extracellular matrix components. We have previously shown that the cationic biopolymer, polylysine (PL), is able to stimulate chondrogenesis by embryonic limb bud mesenchymal cells in vitro. In this study, we have evaluated the chondrogenesis-stimulating activity of PL in vivo using an experimental system consisting of chick embryonic muscle explants, which were grafted onto the chorioallantoic membrane of chick embryos maintained in long-term shell-less culture. The muscle grafts were treated with PL …

A Versatile, Low Toxicity Glycol Methacrylate Embedding Medium For Use In Biological Research, And For Recovered Biomaterials Prostheses, Peter O. Gerrits, Bernhard Eppinger, Harry Van Goor, Richard W. Horobin

Cells and Materials

Methods for preparing standardized glycol methacrylate (GMA) based embedding media for use in light microscopy in a rational, precise and reproducible manner are described. The application of these procedures resulted in a versatile, low toxicity GMA embedding medium.

GMA embedding medium and resin blocks were tested utilizing a variety of physico-chemical techniques, namely: gas chromatography, determination of the maximum temperature reached during polymerization, the time taken to reach the maximum temperature, hardness testing, determination of the glass transition temperature, and measurement of the dimensional changes following section stretching and mounting at various temperatures. Data obtained from these techniques enabled a …

Fracture Toughness And Fractography Of Dental Ceramics, H. J. Mueller

Cells and Materials

Chevron-notch short-rod fracture toughness (KIv) and scanning electron microscopy analyses of leucite-, tetrasilicic fluormica-, and alumina- reinforced dental ceramics and control materials were investigated. Short-rod fracture toughness is a measure of the bulk resistance to crack propagation but not of the surface resistance to crack initiation. Results indicated significant differences in KIv among the following six groups (from lowest to highest (a) Dicor and Optec, (b) Optec, Excelco's Incisal, Macor and Excelco's Gingival, (c) Excelco's Brush-O-Paque, (d) Vitadur-N core, (e) Coming's 9606 glass-ceramic, and (t) Vita Hi Ceram. Good agreement occurred with published data for Macor and 9606. Comparisons of …

Composite Filler Characterization By Scanning Electron Microscopy, Image Analysis And Thermogravimetry, J. Vaidyanathan, T. K. Vaidyanathan

Cells and Materials

The morphological and compositional characterization of the filler particles in selected dental composites has been accomplished by a combination of backscattered electron imaging, digital imaging , energy dispersive X-ray analysis and thermogravimetry. Backscattered electron images provide excellent composition contrast between the filler and the matrix in this analysis . Qualitative energy dispersive spectroscopy was used to classify the filler composition in the composites studied. The digital imaging technique of feature analysis was utilized to quantitatively characterize the particle morphological parameters and their distributions. Several parameters were determined of which the particle area, breadth, height and Waddel diameter are emphasized. Particle …

Adhesion Of Staphylococci To Breast Prosthesis Biomaterials: An Electron Microscopic Evaluation, T. A. Fassel, J. E. Van Over, C. C. Hauser, C. E. Edmiston, J. R. Sanger

Cells and Materials

Gram-positive coagulase-negative staphylococci have been implicated in breast prosthesis infection. Staphylococcus au re us, Staphylococcus epidermidis, and Staphylococcus hominis strains were examined for adhesion and proliferation morphology to polyurethane foam and smooth silicone rubber prosthetic biomaterials. Ruthenium red, alcian blue and ruthenium red-lysine in en bloc procedures were applied to optimally visualize the polysaccharide slime. Ruthenium red processing resulted in observation of additional outer material close to the cell wall, more than seen in the absence of cationic reagent. Alcian blue preserved fibrous or netlike strands or meshworks of material. Ruthenium red-lysine preserved considerable amounts of slime covering the cocci …

A Comparative Study Of Bovine Pericardium Mineralization: A Basic And Practical Approach, Branko B. Tomazic, Chakwan Siew, Walter E. Brown

Cells and Materials

The biomineralization of bovine pericardium (BP) heart valve bioprostheses was investigated by simulation of the process under in vitro and in vivo conditions. The nature and composition of calcific deposits that formed in human heart valve bioprostheses were compared with the mineral formed on BP discs immersed in a calcifying medium or subcutaneously implanted into Sprague-Dawley rats. The early stage of experimental biomineralization in vitro took place on the surface only, while in vivo deposition appeared to be intrinsic, as documented by histological cross sections. The chemical composition of the initial mineral phase formed under in vitro conditions had a …