Physical and Electrical Performance Limits of High-Speed SiGeC HBTs-Part II: Lateral Scaling

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Design, scaling and reliability of devices for high-performance mixed-signal applications

This research investigates and gains new understanding on how silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) device design couples with both performance scaling and reliability for mixed-signal applications (high-frequency and analog). In addition, this work provides methods of using this knowledge to enhance the predictive modeling of performance and reliability for these devices. The primary objective of this effort is to develop a predictive device modeling methodology and simulation framework that can be used to design new mixed-signal device technologies, and can then be used to assess the device performance and reliability concurrently. Ultimately, the goal is to highlight the need for device performance and reliability in a circuit environment, and establish best practices for practical modeling of these constraints and any resulting trade-offs. To support this objective, several specific areas were targeted to fill the existing gaps in knowledge. This includes developing a technology computer-aided-design (TCAD) based integrated simulation framework and methodology to study performance scaling and reliability in complementary SiGe HBTs; identifying factors determining the predictive nature of the simulated device figures-of-merit (FoM); studying electrothermal constraints for scaling SiGe HBTs on thick-film silicon-on-insulator (SOI) to understand its impact on the DC and RF safe-operating-area (SOA) for the device; and performing reliability studies of hot-carrier damage and annealing in npn and pnp SiGe HBT devices in an effort to gain insight into the physical mechanisms involved and to develop fundamental understanding to aid TCAD modeling of hot-carrier damage in these devices. All of these individual studies resulting from the main research tasks are harmoniously tied together by a central theme: to develop a fundamental understanding about how the device design factors influence both performance scaling and reliability. Some of the key existing challenges and knowledge gaps are addressed by analyzing and reconciling the experimental data with simulation results.Ph.D

Transport models and advanced numerical simulation of silicon-germanium heterojunction bipolar transistors

Applications in the emerging high-frequency markets for millimeter wave applications more and more use SiGe components for cost reasons. To support the technology effort, a reliable TCAD platform is required. The main issue in the simulation of scaled devices is related to the limitations of the physical models used to describe charge carrier transport. Inherent approximations in the HD formalism are discussed over different technology nodes, providing for the first time a complete survey of HD models capability and restrictions with scaling for simulation of SiGe HBTs. Moreover, a complete set of models for transport parameters of SiGe HBTs is reported, including low-field mobility, energy relaxation time, saturation velocity, high-field mobility and effective density of state. Implementation in a commercial device simulator is drawn and findings are compared with simulation results obtained using a standard set of models and with trustworthy results (i.e. MC and SHE simulation results and experimental data), validating proposed models and clarifying their reliability and accuracy over different technologies. Finally, electrical breakdown phenomena in SiGe HBTs are analyzed: a novel complete model for multiplication factor is reported and validated by experimental results; new M model provides an exhaustive accuracy over a wide range of collector voltages

An Overview of Solid-State Integrated Circuit Amplifiers in the Submillimeter-Wave and THz Regime

We present an overview of solid-state integrated circuit amplifiers approaching terahertz frequencies based on the latest device technologies which have emerged in the past several years. Highlights include the best reported data from heterojunction bipolar transistor (HBT) circuits, high electron mobility transistor (HEMT) circuits, and metamorphic HEMT (mHEMT) amplifier circuits. We discuss packaging techniques for the various technologies in waveguide modules and describe the best reported noise figures measured in these technologies. A consequence of THz transistors, namely ultra-low-noise at cryogenic temperatures, will be explored and results presented. We also present a short review of power amplifier technologies for the THz regime. Finally, we discuss emerging materials for THz amplifiers into the next decade

Towards a Universal Hot Carrier Degradation Model for SiGe HBTs Subjected to Electrical Stress

The objective of this work is to develop a generalizable understanding of the degradation mechanisms present in complementary Silicon-Germanium (SiGe) heterojunction bipolar transistors (HBTs) that can be used to not only predict the reliable lifetime of these devices but also overcome some of these aging limitations using clever device engineering. This broad motivation for understanding and improving SiGe HBT device reliability is explored through the following specific goals: 1) develop an understanding of the dominant hot carrier degradation sources across temperature (25 K – 573 K); 2) develop a broad understanding of all potentially vulnerable regions of damage within a SiGe HBT using electrically measured data, and how these degradations can be captured in a modeling framework; and 3) design optimized SiGe HBTs that can potentially overcome some of these device-level limitations in reliability across temperature. Being able to simulate the electrical degradation of a complex circuit with SiGe HBTs swinging dynamically on the output plane using a universal physics-based aging model is invaluable for any circuit designer optimizing for high performance and reliability.Ph.D

Charting the Wireless Future (part 2)

Wireless technology has already taken compound semiconductor devices into the mass market with the mobile phone. Are there similar opportunities, and mass markets, beckoning beyond 10GHz where the case for compound is even more compelling? And would the compound industry be able to cope with massively increased volumes

Operation of silicon-germanium heterojunction bipolar transistors on silicon-on-insulator in extreme environments

Recently, several SiGe HBT devices fabricated on CMOS-compatible silicon on insulator (SOI) substrates (SiGe HBTs-on-SOI) have been demonstrated, combining the well-known SiGe HBT performance with the advantages of SOI substrates. These new devices are especially interesting in the context of extreme environments - highly challenging surroundings that lie outside commercial and even military electronics specifications. However, fabricating HBTs on SOI substrates instead of traditional silicon bulk substrates requires extensive modifications to the structure of the transistors and results in significant trade-offs. The present work investigates, with measurements and TCAD simulations, the performance and reliability of SiGe heterojunction bipolar transistors fabricated on silicon on insulator substrates with respect to operation in extreme environments such as at extremely low or extremely high temperatures or in the presence of radiation (both in terms of total ionizing dose and single effect upset).Ph.D.Committee Chair: Cressler, John D.; Committee Member: Papapolymerou, John; Committee Member: Ralph, Stephen; Committee Member: Shen, Shyh-Chiang; Committee Member: Zhou, Hao Mi