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Articles 1 - 30 of 1775

Full-Text Articles in Engineering

Production Of Dimethyl Ether (Dme) For Transportation Fuel, Anita S. Yang, Carl V. Antrassian, Julian D. Kurtzman Apr 2020

Production Of Dimethyl Ether (Dme) For Transportation Fuel, Anita S. Yang, Carl V. Antrassian, Julian D. Kurtzman

Senior Design Reports (CBE)

Dimethyl Ether (DME) is a proposed alternative to diesel fuel that is being looked into by car and truck manufacturers worldwide. The current market, based almost completely in China, is primed for growth and a U.S. based DME total plant that is economical and environmentally feasible stands to pave the way for America’s DME market, especially since states such as California have approved DME for use as vehicle fuel (Fuel Smarts). Conventionally, the DME is produced by feeding Methanol into a xed-bed gas-phase reactor over a ɣ-alumina catalyst (Dimian et al). Using this process and normal operating conditions ...


Rare Earth Element Recovery From Phosphogypsum Using A Biolixiviant, Angelica M. Padilla, Andreea-Maria Pana, Roshan A. Patel Apr 2020

Rare Earth Element Recovery From Phosphogypsum Using A Biolixiviant, Angelica M. Padilla, Andreea-Maria Pana, Roshan A. Patel

Senior Design Reports (CBE)

This project describes the process of recovering of rare earth elements (REE) from phosphogypsum (PG) waste using a novel biolixviant produced by a bacteria strain known as Glucanobacter oxydans and is inspired by novel research occurring at Idaho National Laboratories. This report details design of a plant which has the capacity to produce the biolixiviant through fermentation, use this biolixiviant to leach REE from a solid waste such as PG, and recover the REE in oxide form through crystallization, filtration, and subsequent high temperature decomposition. The plant has the capability of processing nearly 1 million MT of PG a year ...


Production Of Astaxanthin Using Modified E. Coli Cells, Christina M. Eng, Connor S. Gallagher, Maura K. Kimmel Apr 2020

Production Of Astaxanthin Using Modified E. Coli Cells, Christina M. Eng, Connor S. Gallagher, Maura K. Kimmel

Senior Design Reports (CBE)

There are several promising markets for naturally synthesized Astaxanthin, a carotenoid found in krill, shrimp, salmon, and other marine life that imparts to these creatures a pink coloring of the flesh and has demonstrated human health-promoting anti-inflammatory and antioxidant activity. Compared to Astaxanthin produced through chemical synthesis, Astaxanthin synthesized through natural fermentative processes (in yeast and algae) is esterified, imparting greater antioxidant activity as well as bioavailability and making it the preferred ingredient for nutraceutical formulations. Additionally, as consumer preferences trend toward natural production processes free from the use of petrochemical solvents which may pose hazards to health hazards, fermentative ...


Waste Co₂ To Co For Energy Storage, Vignesh C. Bhethanabotla, Joseph C. Dennis, Mavis Athene U Chen Apr 2020

Waste Co₂ To Co For Energy Storage, Vignesh C. Bhethanabotla, Joseph C. Dennis, Mavis Athene U Chen

Senior Design Reports (CBE)

In this report, we present a process design for the storage of electricity using solid oxide fuel cell (SOFC) technology to convert electrical energy to chemical fuel via the reduction of carbon dioxide. The goal of this project was to design a system that could alleviate the issues around the intermittent nature of renewable energy production, which must phase out the use of fossil fuels in the future. The overall process was developed for two storage strategies, and the economics feasibility of the design is considered and reported. The key aspect of this process is its reversible nature. Both the ...


Enzyme Production Using An Extremophilic Biocatalyst, Adithya Sriram, Sean M. Begane, Jazriel A. Ortega Apr 2020

Enzyme Production Using An Extremophilic Biocatalyst, Adithya Sriram, Sean M. Begane, Jazriel A. Ortega

Senior Design Reports (CBE)

Bio-detergents are useful in many markets because they contain enzymes that can break down proteins and in turn enhance stain removal. However, many of these enzymes deactivate at high temperatures so sterilization and stain removal must be done in two separate processes. This process produces extremozymes, enzymes derived from extremophilic microorganisms that have optimal activity and stability at harsh conditions, to be used in bio-detergents. The thermostable characteristics of this enzyme allow it to accomplish high levels of protein breakdown at temperatures conducive to sterilization. It is expected that this characteristic provides a 15% price premium over the leading incumbant ...


Batch Production Of A Potent Small Molecule Active Pharmaceutical Ingredient, Isuru N. Amarasekera, Jinwan Cho, Jason Y. Li Apr 2020

Batch Production Of A Potent Small Molecule Active Pharmaceutical Ingredient, Isuru N. Amarasekera, Jinwan Cho, Jason Y. Li

Senior Design Reports (CBE)

Small molecule Active Pharmaceutical Ingredients (APIs) have become increasingly relevant in cancer treatment due to their efficacy, targeted treatment, and clinical value. Commonly manufactured in a batch pharmaceutical process, APIs must satisfy Critical Quality Attributes (CQAs) including chemical purity and physical properties. This process involves a multitude of steps, components, and equipment that are optimized to produce an API in a timely and cost-efficient manner. Here, we consider the process and facility design of a batch production of Halfaxia, a new potent anti-cancer drug from Johnson & Johnson. The process begins with a reaction of a starting material and a second ...


Renewable Ammonia, Kolbein A. Finsnes, James P. Kwon, Dakota M. Wallach Apr 2020

Renewable Ammonia, Kolbein A. Finsnes, James P. Kwon, Dakota M. Wallach

Senior Design Reports (CBE)

Ammonia is one of the most widely used chemicals that is commercially produced today given the wide need for fertilizer to sustain the world’s ever-growing populations. Given the high world demand for ammonia, which increases every day, one can see how beneficial to the environment that a zero emission large-scale ammonia plant would be. Through the use of energy from Norwegian wind farms, which produce an excess of energy during off-peak hours, our plant design seeks to turn this wasted energy into useful ammonia products at a production rate of 67.2 kmol/hr.

The design of this ammonia ...


Mixed Plastics Waste To Ethylene And Propylene Feedstocks, Promise O. Adebayo-Ige, Sarah M. Engelhardt, Matthew C. Larson Apr 2020

Mixed Plastics Waste To Ethylene And Propylene Feedstocks, Promise O. Adebayo-Ige, Sarah M. Engelhardt, Matthew C. Larson

Senior Design Reports (CBE)

Circular recycle of waste plastic holds significant environmental benefit in reducing the need for crude oil feed to produce plastic monomers and in addressing massive global accumulation of plastic waste. A two-stage cracking process is here explored for the reduction of long-chain polyethylene (PE), polypropylene (PP), and polystyrene (PS) to ethylene and propylene. The reaction yields useful byproducts, such as liquid fuel used to sustain the high energy demands of the process, and pressurized steam. A feed of 70 MT/day of PE, PP, and PS is assumed to be treated first in a rotary kiln pyrolysis reactor and secondly ...


Commercial Process For The Conversion Of Graphite To Graphite Oxide, Alexander Goodisman, Yash Jain, Dong Bien Kwon Apr 2020

Commercial Process For The Conversion Of Graphite To Graphite Oxide, Alexander Goodisman, Yash Jain, Dong Bien Kwon

Senior Design Reports (CBE)

With steel and other everyday materials reaching their limits in terms of structural integrity and chemical properties, new materials are needed to provide the next breakthroughs in construction and R&D. Graphene provides incredible strengths and elasticities along with amazing electrical and thermal conductivity. Graphene based materials, the so-called supermaterials, are often limited by the lack of availability due to cost and volume. This report discusses the first large scale production of an important precursor to graphene, graphite oxide (GrO). Based on improvements of Hummer’s method, this project analyses the potential challenges associated with dealing with large quantities of ...


Production Of Dl-Methionine From Corn Syrup Via Biosynthesis With Corynebacterium Glutamicum, Dayoung Shin, Yvonne N. Szustakiewicz, Allison P. Walter Apr 2020

Production Of Dl-Methionine From Corn Syrup Via Biosynthesis With Corynebacterium Glutamicum, Dayoung Shin, Yvonne N. Szustakiewicz, Allison P. Walter

Senior Design Reports (CBE)

DL-methionine is an important feed additive for poultry and swine diets. The amino acid is not produced by animals so it can only be obtained through diet. Methionine is important for protein growth and helps the health of livestock. Recent increase in meat consumption in Latin America and Asia, along with a growing consumer concern of animal welfare, has driven a growth in the methionine market. The methionine market is predicted to continue to grow for at least another five years (Methionine Market 2019). The proposed design is for a process that produces DL-methionine by fermentation with the bacteria, Corynebacterium ...


Design Of Car-T Cell Manufacturing Process, Liam J. Bartie, Lauren R. Duhamel, Ruby C. Pan Apr 2020

Design Of Car-T Cell Manufacturing Process, Liam J. Bartie, Lauren R. Duhamel, Ruby C. Pan

Senior Design Reports (CBE)

CAR T-cell therapy is at the frontier of personalized immunotherapy. It is a therapy that essentially reprograms a patient’s own T-cells to attack certain blood cancers. A sample of a patient's T cells are collected from the blood, then modified to produce chimeric antigen receptors (CARs) on their surface. When these CAR T cells are reinfused into the patient, the new receptors enable them to latch onto a specific antigen on the patient's tumor cells and kill them, ideally sending the patient into remission and essentially curing their cancer. Currently, CAR T-cell therapy is FDA approved as ...


A Tendon-Driven Origami Hopper Triggered By Proprioceptive Contact Detection, Wei-Hsi Chen, Shivangi Misra, J. Diego Caporale, Daniel E. Koditschek, Shu Yang, Cynthia R. Sung Apr 2020

A Tendon-Driven Origami Hopper Triggered By Proprioceptive Contact Detection, Wei-Hsi Chen, Shivangi Misra, J. Diego Caporale, Daniel E. Koditschek, Shu Yang, Cynthia R. Sung

Departmental Papers (ESE)

We report on experiments with a laptop-sized (0.23m, 2.53kg), paper origami robot that exhibits highly dynamic and stable two degree-of-freedom (circular boom) hopping at speeds in excess of 1.5 bl/s (body-lengths per second) at a specific resistance O(1) while achieving aerial phase apex states 25% above the stance height over thousands of cycles. Three conventional brushless DC motors load energy into the folded paper springs through pulley-borne cables whose sudden loss of tension upon touchdown triggers the release of spring potential that accelerates the body back through liftoff to flight with a 20W powerstroke, whereupon ...


Case Study: Verifying The Safety Of An Autonomous Racing Car With A Neural Network Controller, Radoslav Ivanov, Taylor J. Carpenter, James Weimer, Rajeev Alur, George Pappas, Insup Lee Apr 2020

Case Study: Verifying The Safety Of An Autonomous Racing Car With A Neural Network Controller, Radoslav Ivanov, Taylor J. Carpenter, James Weimer, Rajeev Alur, George Pappas, Insup Lee

Departmental Papers (CIS)

This paper describes a verification case study on an autonomous racing car with a neural network (NN) controller. Although several verification approaches have been recently proposed, they have only been evaluated on low-dimensional systems or systems with constrained environments. To explore the limits of existing approaches, we present a challenging benchmark in which the NN takes raw LiDAR measurements as input and outputs steering for the car. We train a dozen NNs using reinforcement learning (RL) and show that the state of the art in verification can handle systems with around 40 LiDAR rays. Furthermore, we perform real experiments to ...


Thin Dry Silicon Oxide Films Grown By Thermal Oxidation, Manisha Muduli, Hiromichi Yamamoto Mar 2020

Thin Dry Silicon Oxide Films Grown By Thermal Oxidation, Manisha Muduli, Hiromichi Yamamoto

Tool Data

Dry thermal oxidation is performed at 900, 950, 1000, and 1050 C in fused silica tube furnace (Sandvik) for 10, 20, 50, 100 and 200 min. The results are analyzed by both of Deal-Grove model and the method of Gerlach, Maser, and Saad. In the analysis using the Deal-Grove model, the parabolic rate constants are obtained to be 2.1, 7.0, 17.5, and 42.4 nm^2/min at 900, 950, 1000, and 1050 C, respectively, and the linear rate constants are acquired to be 0.2, 0.4, 0.8, and 1.2 nm/min at 900 ...


Future Leader In Sustainable Enterprise — Prescilla Awino, Akudo Ejelonu Mar 2020

Future Leader In Sustainable Enterprise — Prescilla Awino, Akudo Ejelonu

wH2O: The Journal of Gender and Water

Prescilla is a trainer and a mentor of teenagers and young adolescent women. She successfully managed the Girls Leadership and Advocacy Series (GALS Kenya), a Program of Women Campaign International (WCI). WCI is a Philadelphia based non-profit organization that empowers women globally to actively participate in civil society, political leadership, economic development and peace building.


Barriers And Bias: Women In Water Utilities Are Breaking Them All, Swati Hegde Mar 2020

Barriers And Bias: Women In Water Utilities Are Breaking Them All, Swati Hegde

wH2O: The Journal of Gender and Water

Around the world, women are the mainstays of society, from raising children to supporting families to caring for the needy. In developing countries, they are also usually responsible for collecting and providing water for the family. In doing so, their time, health, safety, education and income are compromised. Outdated and undisputed social norms create the biases that force women to bear the responsibility to secure and distribute water, thereby creating barriers to women’s advancement in educational opportunities and significantly reducing income-earning potential. Similarly, in the developed world, outdated social norms create biases and barriers in the water industry that ...


Amigos Por Agua, Pamela J. Lazos Mar 2020

Amigos Por Agua, Pamela J. Lazos

wH2O: The Journal of Gender and Water

The role of non-profit organizations in outfitting the developing world with clean water has become more extensive as the world’s population grows, especially in places such as Nicaragua, the second poorest country in the western hemisphere. Nicaraguans suffer high rates of kidney disease, respiratory illnesses and parasites as a result of water borne diseases. NGOs such as Amigos for Christ are stepping in to fill the void in Chinandega where the local government lacks the financial wherewithal to provide a basic WASH infrastructure to its inhabitants. It is the goal of Amigos for Christ to bring water to every ...


Calibrated Prediction With Covariate Shift Via Unsupervised Domain Adaptation, Sangdon Park, Osbert Bastani, James Weimer, Insup Lee Mar 2020

Calibrated Prediction With Covariate Shift Via Unsupervised Domain Adaptation, Sangdon Park, Osbert Bastani, James Weimer, Insup Lee

Departmental Papers (CIS)

Reliable uncertainty estimates are an important tool for helping autonomous agents or human decision makers understand and leverage predictive models. However, existing approaches to estimating uncertainty largely ignore the possibility of covariate shift—i.e., where the real-world data distribution may differ from the training distribution. As a consequence, existing algorithms can overestimate certainty, possibly yielding a false sense of confidence in the predictive model. We propose an algorithm for calibrating predictions that accounts for the possibility of covariate shift, given labeled examples from the training distribution and unlabeled examples from the real-world distribution. Our algorithm uses importance weighting to ...


Examples Of Gibsonian Affordances In Legged Robotics Research Using An Empirical, Generative Framework, Sonia F. Roberts, Daniel E. Koditschek, Lisa J. Miracchi Feb 2020

Examples Of Gibsonian Affordances In Legged Robotics Research Using An Empirical, Generative Framework, Sonia F. Roberts, Daniel E. Koditschek, Lisa J. Miracchi

Departmental Papers (ESE)

Evidence from empirical literature suggests that explainable complex behaviors can be built from structured compositions of explainable component behaviors with known properties. Such component behaviors can be built to directly perceive and exploit affordances. Using six examples of recent research in legged robot locomotion, we suggest that robots can be programmed to effectively exploit affordances without developing explicit internal models of them. We use a generative framework to discuss the examples, because it helps us to separate—and thus clarify the relationship between—description of affordance exploitation from description of the internal representations used by the robot in that exploitation ...


Pac Confidence Sets For Deep Neural Networks Via Calibrated Prediction, Sangdon Park, Osbert Bastani, Nikolai Matni, Insup Lee Feb 2020

Pac Confidence Sets For Deep Neural Networks Via Calibrated Prediction, Sangdon Park, Osbert Bastani, Nikolai Matni, Insup Lee

Departmental Papers (CIS)

We propose an algorithm combining calibrated prediction and generalization bounds from learning theory to construct confidence sets for deep neural networks with PAC guarantees---i.e., the confidence set for a given input contains the true label with high probability. We demonstrate how our approach can be used to construct PAC confidence sets on ResNet for ImageNet, a visual object tracking model, and a dynamics model for the half-cheetah reinforcement learning problem.


Modulation Of Robot Orientation Via Leg-Obstacle Contact Positions, Divya Ramesh, Anmol Kathail, Daniel E. Koditschek, Feifei Qian Jan 2020

Modulation Of Robot Orientation Via Leg-Obstacle Contact Positions, Divya Ramesh, Anmol Kathail, Daniel E. Koditschek, Feifei Qian

Departmental Papers (ESE)

We study a quadrupedal robot traversing a structured (i.e., periodically spaced) obstacle field driven by an open-loop quasi-static trotting walk. Despite complex, repeated collisions and slippage between robot legs and obstacles, the robot’s horizontal plane body orientation (yaw) trajectory can converge in the absence of any body level feedback to stable steady state patterns. We classify these patterns into a series of “types” ranging from stable locked equilibria, to stable periodic oscillations, to unstable or mixed period oscillations. We observe that the stable equilibria can bifurcate to stable periodic oscillations and then to mixed period oscillations as the ...


A Programmably Compliant Origami Mechanism For Dynamically Dexterous Robots, Wei-Hsi Chen, Shivangi Mishra, Yuchong Gao, Young-Joo Lee, Daniel Koditschek, Shu Yang, Cynthia R. Sung Jan 2020

A Programmably Compliant Origami Mechanism For Dynamically Dexterous Robots, Wei-Hsi Chen, Shivangi Mishra, Yuchong Gao, Young-Joo Lee, Daniel Koditschek, Shu Yang, Cynthia R. Sung

Departmental Papers (ESE)

We present an approach to overcoming challenges in dynamical dexterity for robots through programmably compliant origami mechanisms. Our work leverages a one-parameter family of flat sheet crease patterns that folds into origami bellows, whose axial compliance can be tuned to select desired stiffness. Concentrically arranged cylinder pairs reliably manifest additive stiffness, extending the programmable range by nearly an order of magnitude and achieving bulk axial stiffness spanning 200–1500 N/m using 8 mil thick polyester-coated paper. Accordingly, we design origami energy-storing springs with a stiffness of 1035 N/m each and incorporate them into a three degree-of-freedom (DOF) tendon-driven ...


Teaching Autonomous Systems At 1/10th-Scale, Abhijeet Agnihotri, Matthew O'Kelly, Rahul Mangharam, Houssam Abbas Jan 2020

Teaching Autonomous Systems At 1/10th-Scale, Abhijeet Agnihotri, Matthew O'Kelly, Rahul Mangharam, Houssam Abbas

Real-Time and Embedded Systems Lab (mLAB)

Teaching autonomous systems is challenging because it is a rapidly advancing cross-disciplinary field that requires theory to be continually validated on physical platforms. For an autonomous vehicle (AV) to operate correctly, it needs to satisfy safety and performance properties that depend on the operational context and interaction with environmental agents, which can be difficult to anticipate and capture. This paper describes a senior undergraduate level course on the design, programming and racing of 1/10th-scale autonomous race cars. We explore AV safety and performance concepts at the limits of perception, planning, and control, in a highly interactive and competitive environment ...


Cdse Quantum Dots Synthesis Laboratory Course For High School Students, Danlin Zuo, Gyuseok Kim, David Jones Dec 2019

Cdse Quantum Dots Synthesis Laboratory Course For High School Students, Danlin Zuo, Gyuseok Kim, David Jones

Protocols and Reports

Cadmium selenide quantum dot is a fascinating subject for leading high school students to the quantum world. An 8-hour laboratory course for up to 12 high school students is proposed. The 8-hour course consist of two 4-hours sections. This laboratory course includes the quantum dot syntheses, absorption and emission characterization, and data analysis. The proposes process runs at relatively lower temperature which means safe and easy, and shows apparent experimental results.


Extended Version Of Simple Sagittal Running: Stability Of A Quadrupedal Bound, Jeff Duperret, D. E. Koditschek Dec 2019

Extended Version Of Simple Sagittal Running: Stability Of A Quadrupedal Bound, Jeff Duperret, D. E. Koditschek

Technical Reports (ESE)

This paper develops a three degree-of-freedom sagittal-plane hybrid dynamical systems model of a bounding quadruped. Simple within-stance controls yield a closed form expression for a family of hybrid limit cycles that represent bounding behavior over a range of user-selected fore-aft speeds as a function of the model's kinematic and dynamical parameters. Controls acting on the hybrid transitions are structured so as to achieve a cascade composition of in-place bounding driving the fore-aft degree of freedom thereby decoupling the linearized dynamics of an approximation to the stride map. Careful selection of the feedback channels used to implement these controls affords ...


Effect Of Annealing On The Contact Resistance Of Aluminum On A P-Type Substrate, Shrey Shah, George Patrick Watson Nov 2019

Effect Of Annealing On The Contact Resistance Of Aluminum On A P-Type Substrate, Shrey Shah, George Patrick Watson

Protocols and Reports

Aluminum contacts are widely used to form both ohmic and rectifying contacts. The process to form these contacts involves annealing, thus it is important to study the effect of annealing on the electrical properties of the contacts. Here, we present a way to measure the contact resistance of aluminum contacts formed on a p-type silicon substrate. It was found the contact resistivity decreased by an average of 18%. It was thus found that annealing at 400°C in a forming gas environment improves the electrical properties of aluminum contacts.


Fabrication Of Organic Thin Film Transistors Using Inkjet Printing Of Pedot:Pss, Sourajit Das, Akshaya Venkatakrishnan, Hiromichi Yamamoto, George Patrick Watson Nov 2019

Fabrication Of Organic Thin Film Transistors Using Inkjet Printing Of Pedot:Pss, Sourajit Das, Akshaya Venkatakrishnan, Hiromichi Yamamoto, George Patrick Watson

Protocols and Reports

An Organic Thin Film Transistors (OTFT) using poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) is fabricated using a Fuji film Dimatix Inkjet printer, and successfully shows the characteristics of field effect transistor as a result of optimization of the inkjet printing condition. The V-I characteristics of the two devices also satisfy the fundamental property of transistors that wider is the channel length, smaller is the drain current. Another significant property is observed that the higher gate voltage induces the higher drain current as it allows larger carrier concentration in the channel region.


Influence Of Flow Rate, Nozzle Speed, Pitch And The Number Of Passes On The Thickness Of S1805 Photoresist In Suss Microtec As8 Spray Coater, Rohan Sanghvi, Gyuseok Kim Oct 2019

Influence Of Flow Rate, Nozzle Speed, Pitch And The Number Of Passes On The Thickness Of S1805 Photoresist In Suss Microtec As8 Spray Coater, Rohan Sanghvi, Gyuseok Kim

Tool Data

S1805 positive photoresist has been deposited on single crystalline Si wafers using a Suss MicroTec Alta Spray. The influence of flow rate, nozzle speed, pitch and number of passes on the thickness of the photoresist was studied. Results show that the thickness of S1805 is linearly proportional to the flow rate and number of passes, and inversely proportional to the nozzle speed and pitch.


Progress Report Ii: Fabrication Of Nanopores In Silicon Nitride Membrane Using Self-Assembly Of Ps-B-Pmma: Nanopore Pattern Transfer To The Si Substrate, Kodai Watanabe, Unnati Joshi, Hiromichi Yamamoto Oct 2019

Progress Report Ii: Fabrication Of Nanopores In Silicon Nitride Membrane Using Self-Assembly Of Ps-B-Pmma: Nanopore Pattern Transfer To The Si Substrate, Kodai Watanabe, Unnati Joshi, Hiromichi Yamamoto

Protocols and Reports

The asymmetric PS(46k)-b-PMMA(21k) film was spin-coated on a neutral brush layer grafted onto a Spin-On-Glass (SOG) layer on the aluminum oxide layer on a Si substrate. An aluminum oxide layer was used as a hard mask. The PS-b-PMMA film was annealed at 190 degree C under vacuum for 3 days, so that the ~20 nm diameter nanopores in the film was successfully prepared as a result of self-assembly. The nanopores in the PS-b-PMMA film were able to be transferred to the Si substrate by CF4 etching through the SOG and aluminum oxide layers, although the etching was ...


Correction Of Pattern Size Deviations In The Fabrication Of Photomasks Made With A Laser Direct-Writer, Ningzhi Xie, George Patrick Watson Oct 2019

Correction Of Pattern Size Deviations In The Fabrication Of Photomasks Made With A Laser Direct-Writer, Ningzhi Xie, George Patrick Watson

Protocols and Reports

When using Heidelberg DWL66+ laser writer to fabricate the photomask, the pattern feature dimensions may have deviations. These deviations can be caused by the lithography process and the undercut in the metal etch process. The same deviation value of 0.8µm was found to appear in all the patterns independent of the pattern original size and local pattern density. To overcome this universal deviation, a universal bias is suggested to be applied to the original patterns during the data preparation for the lithography process. In order to ensure this pre-exposure bias method can work, both the laser direct-write exposure conditions ...