Gaussian process regression for virtual metrology of microchip quality and the resulting strategic sampling scheme

Manufacturing of integrated circuits involves many sequential processes, often ex- ecuted to nanoscale tolerances, and the yield depends on the often unmeasured quality of intermediate steps. In the high-throughput industry of fabricating microelectronics on semi-conducting wafers, scheduling measurements of product quality before the electrical test of the complete IC can be expensive. We therefore seek to predict metrics of product quality based on sensor readings describing the environment within the relevant tool during the processing of each wafer, or to apply the concept of virtual metrology (VM) to monitor these intermediate steps. We model the data using Gaussian process regression (GPR), adapted to simultaneously learn the nonlinear dynamics that govern the quality characteristic, as well as their operating space, expressed by a linear embedding of the sensor traces’ features. Such Bayesian models predict a distribution for the target metric, such as a critical dimension, so one may assess the model’s credibility through its predictive uncertainty. Assuming measurements of the quality characteristic of interest are budgeted, we seek to hasten convergence of the GPR model to a credible form through an active sampling scheme, whereby the predictive uncertainty informs which wafer’s quality to measure next. We evaluate this convergence when predicting and updating online, as if in a factory, using a large dataset for plasma-enhanced chemical vapor deposition (PECVD), with measured thicknesses for ~32,000 wafers. By approximately optimizing the information extracted from this seemingly repetitive data describing a tightly controlled process, GPR achieves ~10% greater accuracy on average than a baseline linear model based on partial least squares (PLS). In a derivative study, we seek to discern the degree of drift in the process over the several months the data spans. We express this drift by how unusual the relevant features, as embedded by the GPR model, appear as the in- puts compensate for degrading conditions. This method detects the onset of consistently unusual behavior that extends to a bimodal thickness fault, anticipating its flagging by as much as two days.Mechanical Engineerin

Codeword Stabilized Quantum Codes for Asymmetric Channels

We discuss a method to adapt the codeword stabilized (CWS) quantum code framework to the problem of finding asymmetric quantum codes. We focus on the corresponding Pauli error models for amplitude damping noise and phase damping noise. In particular, we look at codes for Pauli error models that correct one or two amplitude damping errors. Applying local Clifford operations on graph states, we are able to exhaustively search for all possible codes up to length $9$. With a similar method, we also look at codes for the Pauli error model that detect a single amplitude error and detect multiple phase damping errors. Many new codes with good parameters are found, including nonadditive codes and degenerate codes.Comment: 5 page

Concatenated Codes for Amplitude Damping

We discuss a method to construct quantum codes correcting amplitude damping errors via code concatenation. The inner codes are chosen as asymmetric Calderbank-Shor-Steane (CSS) codes. By concatenating with outer codes correcting symmetric errors, many new codes with good parameters are found, which are better than the amplitude damping codes obtained by any previously known construction.Comment: 5 page

Getting to UI Biology Department\u27s Distinguished Faculty

This was a project meant to encompass the works of retired faculty in the Department of Biology at the University of Iowa through profile story writing and then an event for each professor to talk at. This project was designed to showcase some of the works of retired professors in an attempt to allure people by reading the profile stories of people with extraordinary backgrounds. I wanted people to understand how the Department of Biology came to be what it is today and inform them that things weren\u27t like they are today. To understand the history and progression behind something is to truly understand it. Not only that, I planned an event to give the individuals that read the profile stories an opportunity to meet and speak with the professors. Therefore, a meet-and-greet event was planned further away from when the profile stories were published so that students could first read the profile stories and have an idea of who these professors were. The purpose of this event was to make these retired professors and professors in general more approachable since there is sometimes a barrier of intimidation that comes into play when students may have to confront professors

Modeling the Torque of Ferrite Nano-Particles as a Ferrofluid Suspended in Liquid to Determine the Electromagnetic Response to Angular Displacement

Inertial sensing is an important part of engineering and technology, especially for determining spatial orientation. Most modern inertial sensing units rely on MicroElectroMechanical systems (MEMS) style gyroscopic sensors to determine angular acceleration. This research investigates a novel gyroscopic sensing technology that uses mechanical precision of magnetic nanoparticles, instead of MEMS, to determine inertial measurements. The only other study on this novel technology proposed a scalar set of equations for relating magnetic field and torque magnitude to the magnitude of angular displacement of the sensor. This research develops the theoretical model into a set of full vector equations, so that the magnetic field and torque can be related to both the magnitude and direction of angular displacement of the sensor. It was determined that inertial components of nanoparticle torque in the original model are negligible due to scaling laws at the nanoscale, and that the only significant contributions are due to viscous fluid drag, which changed the theoretical equations considerably. Euler rotation angles were used to derive a decomposed 3D vector that represents the torque and magnetic field of the nanoparticle response to angular displacement. Simulations verified the assumptions made in the model and overall it was concluded that, theoretically, the sensor technology could work and is viable for further applications. However, improvements should be made to the sensor design in order to improve electromagnetic immunity to exterior sources

Engineering effective fibrocartilage replacement technologies using nanostructure-driven replication of soft tissue biomechanics in thermoplastic elastomer hydrogels

2018 Spring.Includes bibliographical references.Synthesis of hydrogel networks capable of accurately replicating the biomechanical demands of musculoskeletal soft tissues continues to present a formidable materials science challenge. Current systems are hampered by combinations of limited moduli at biomechanically relevant strains, inefficiencies driven by undesirable hysteresis and permanent fatigue, and recovery dynamics too slow to accommodate rapid cycling prominent in most biomechanical loading profiles. This dissertation presents a new paradigm in hydrogel design based on prefabrication of an efficient nanoscale network architecture using the melt-state self-assembly of amphiphilic block copolymers. Rigorous characterization and preliminary mechanical testing reveal that swelling of these preformed networks produce hydrogels with physiologically relevant moduli and water compositions, negligible hysteresis, sub-second elastic recovery rates, and unprecedented resistance to fatigue over hundreds of thousands of compressive cycles. By relying only on simple thermoplastic processing to form these nanostructured networks, the synthetic complexities common to most solution-based hydrogel fabrication strategies are completely avoided. Described within this dissertation are a range of efforts, broadly focused on refining synthetic and post-synthetic processing techniques to improve the modulus, surface hydrophilicity, fatigue resistance and cytocompatibility of these thermoplastic elastomer hydrogels, with the ultimate goal of producing a material viable as a meniscal replacement

Dispute Resolution Outside of Courts: Procedural Justice and Decision Acceptance Among Users of Ombuds Services in the UK

Attitudes towards legal authorities based on theories of procedural justice have been explored extensively in the criminal and civil justice systems. This has provided considerable empirical evidence concerning the importance of trust and legitimacy in generating cooperation, compliance and decision acceptance. However, not enough attention has been paid to attitudes towards institutions of informal dispute resolution. This paper asks whether the theory of procedural justice applies to the alternative dispute resolution (ADR) context, focusing on ombuds services. What are the predictors of perceptions of procedural justice during the process of dealing with an ombuds, and what factors shape outcome acceptance? These questions are analyzed using a sample of recent ombuds users. The results indicate that outcome favorability is highly correlated with perceived procedural justice, and both predict decision acceptance

Solving the Mystery of the "Cyanide Bomb"

A man who\u27s career began as a biochemist and ended as a botanist. A man who under the instruction of a Professor Butt realized what he wanted to do for the rest of his life. This was the story of Professor Jonathan Poulton, Emeritus Faculty at the University of Iowa. He comes from an English family with a religious background and ended up in the sciences when he decided to pursue biochemistry over a dinner with a family friend. He earned his PhD at Oxford University and traveled abroad to conduct research. Poulton eventually landed himself at the University of Iowa on a frigid day but this wasn\u27t enough to deter him! Poulton became a professor of botany and conducted research on how plants stored and released cyanide from their leaves. Later in his career, his research focused on uncovering some of the genes in the Arabidopsis thaliana genome (a small flowering plant). His career was also comprised of several teaching experiences such as but not limited to Principles of Biology and Botany. If you would like to learn more about his outstanding career and unlikely story, read Professor Jonathan Poulton\u27s profile story