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- All Subjects: Total Ionizing Dose
- Creators: Barnaby, Hugh J
Description
A modeling platform for predicting total ionizing dose (TID) and dose rate response of commercial commercial-off-the-shelf (COTS) linear bipolar circuits and technologies is introduced. Tasks associated with the modeling platform involve the development of model to predict the excess current response in a bipolar transistor given inputs of interface (NIT) and oxide defects (NOT) which are caused by ionizing radiation exposure. Existing models that attempt to predict this excess base current response are derived and discussed in detail. An improved model is proposed which modifies the existing model and incorporates the impact of charged interface trap defects on radiation-induced excess base current. The improved accuracy of the new model in predicting excess base current response in lateral PNP (LPNP) is then verified with Technology Computer Aided Design (TCAD) simulations. Finally, experimental data and compared with the improved and existing model calculations.
ContributorsTolleson, Blayne S. (Author) / Barnaby, Hugh J (Thesis advisor) / Gonzalez-Velo, Yago (Committee member) / Kitchen, Jennifer (Committee member) / Arizona State University (Publisher)
Created2017
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