Heterojunctions as the Weakest Link: A Fundamental Investigation of Damage Evolution in Electronic Devices

点击翻译按钮获取中文摘要

PROJECT ABSTRACTProposal Title:Heterojunctions as the Weakest Link: A Fundamental Investigation of Damage Evolution in Electronic DevicesNon-technical AbstractReliability of microelectronic devices, such as transistors, is critical to applications. Typically, this is studied by loading the transistors to failure and then analyzing the electrical characteristics of the data. Post-mortem microscopy is also performed to visualize the damage inside the device. However, care must be taken to recreate the failure events. In this research, a novel concept is introduced where the transistor is tested inside microscopes that allow near-atomic resolution mapping of defect evolution and the role of local heat and current transport. Special consideration will be given to the interfaces between various layers inside a transistor, whose important role in device reliability has been difficult to study using conventional approaches. Such high-resolution access to mechanical, electrical and thermal domains will remove the existing challenge of identifying the local weak spots in the transistor and the fundamental mechanisms behind their impact on the global or device level failure. This unique approach will be applied to the study of high-power transistors that will be used in next generation all-electric transportation, energy storage and radio-frequency communication technologies. Success of this research will lead to transistors that will reduce the size and weight of relevant equipment in these applications while increasing power and reliability. In addition to the advancements in the fundamental science of high-power transistor reliability, the project will ensure training of the graduate and undergraduate students with cutting edge and multi-disciplinary science and technology. Outreach activities will be performed to attract K-12 students, who are the workforce of the next generation.Technical AbstractThe objective of this research is to investigate the role of heterojunctions in overall device reliability for power transistors. The research is motivated by the gap between the predicted and actual reliability of high power and high frequency devices touted to enable next generation all-electric transportation, energy storage and RF communication technologies. Gallium nitride based high electron mobility transistors (HEMT) will be studied to answer two fundamental questions: (a) what is the weakest component in a transistor in terms of defect nucleation and (b) is it defect nucleation or atomic diffusion that is more viral in device degradation. This research hypothesizes that diffusion across and along interfaces could be the answers and lays out a unique in-operando microscopy based validation approach. Transmission electron and thermo-reflectance microscopy will be used in real time to map and monitor the structural and transport characteristics of the devices during the onset of degradation. The high resolution, both spatially and temporally, shifts the current paradigm of looking for failure signatures in device data from the device-level to the atomic interface level. Realtime investigation of the atomic structure and chemistry of defects and interfaces, along with an understanding of their influence on electron-phonon interactions, will eliminate the roadblock of accurately identifying the dominant mechanism and quantifying its impact. The proposed research elaborately designs non-thermal experiments after isolating the various components of mechanical stress (residual, thermo-elastic and inverse piezo-electric). The outcome of this research will provide fundamental insights on GaN HEMT failure and suggest paths towards performance and reliability improvements. It will also train graduate and undergraduate students in both class and laboratory settings. The project will also reach out to the next generation workforce, the K-12 students, to attract them toward science and technology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.