ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- Creators: Barnaby, Hugh J
Description
Implantable medical device technology is commonly used by doctors for disease management, aiding to improve patient quality of life. However, it is possible for these devices to be exposed to ionizing radiation during various medical therapeutic and diagnostic activities while implanted. This commands that these devices remain fully operational during, and long after, radiation exposure. Many implantable medical devices employ standard commercial complementary metal-oxide-semiconductor (CMOS) processes for integrated circuit (IC) development, which have been shown to degrade with radiation exposure. This necessitates that device manufacturers study the effects of ionizing radiation on their products, and work to mitigate those effects to maintain a high standard of reliability. Mitigation can be completed through targeted radiation hardening by design (RHBD) techniques as not to infringe on the device operational specifications. This thesis details a complete radiation analysis methodology that can be implemented to examine the effects of ionizing radiation on an IC as part of RHBD efforts. The methodology is put into practice to determine the failure mechanism in a charge pump circuit, common in many of today's implantable pacemaker designs, as a case study. Charge pump irradiation data shows a reduction of circuit output voltage with applied dose. Through testing of individual test devices, the response is identified as parasitic inter-device leakage caused by trapped oxide charge buildup in the isolation oxides. A library of compact models is generated to represent isolation oxide parasitics based on test structure data along with 2-Dimensional structure simulation results. The original charge pump schematic is then back-annotated with transistors representative of the parasitic. Inclusion of the parasitic devices in schematic allows for simulation of the entire circuit, accounting for possible parasitic devices activated by radiation exposure. By selecting a compact model for the parasitics generated at a specific dose, the compete circuit response is then simulated at the defined dose. The reduction of circuit output voltage with dose is then re-created in a radiation-enabled simulation validating the analysis methodology.
ContributorsSchlenvogt, Garrett (Author) / Barnaby, Hugh J (Thesis advisor) / Goodnick, Stephen (Committee member) / Vasileska, Dragica (Committee member) / Arizona State University (Publisher)
Created2010
Description
Linear bipolar circuits, designed with bipolar junction transistors (BJTs), are particularly vulnerable to the effects of space radiation. These circuits, which are usually commercial off-the-shelf (COTS) components, typically exhibit Enhanced Low Dose Rate Sensitivity (ELDRS), which is characterized by the enhancement of degradation when parts are exposed to radiation at low dose rates as compared to high dose rates. This phenomenon poses significant problems for the qualification of bipolar parts for use in low dose rate environments, such as most Earth orbits. ELDRS in BJTs has been well-documented in ground-based experiments; however, the effects of low dose rate irradiation on bipolar transistors manufactured in an integrated linear process had never been characterized in space - until the ELDRS experiment was launched in June 2019. The ELDRS instrument measures changes in the active collector and base currents in 24 lateral PNP (LPNP) BJTs on eight packaged die (three BJTs per die). Sixteen of the 24 BJTs are gated, while eight are standard, un-gated LPNPs. Device Under Test (DUT) and measurement variables include oxide thickness, passivation layer, packaging conditions, and gate voltage. This thesis reports the results obtained after more than 20 months of space flight in a highly elliptical Earth orbit. These results demonstrate that this category of bipolar devices is susceptible to low dose rate exposures and therefore exhibits the ELDRS effect in an actual space environment. This thesis also assess the impact of packaging variables on radiation response and examines one of the major causes behind radiation degradation, interface traps. An understanding of radiation effects in real space environments is critical for future missions that use these low-cost COTS bipolar technologies, making these results highly relevant for the satellite community.
ContributorsBenedetto, Adalin (Author) / Barnaby, Hugh J (Thesis advisor) / Goodnick, Stephen (Committee member) / Sanchez, Ivan (Committee member) / Arizona State University (Publisher)
Created2023