Process Design Kit and High-Temperature Digital ASICs in Silicon Carbide
Abstract: Electronics such as microprocessors are highly demanded to monitor or control a process or operation in temperature critical (300 ºC to 600 °C) applications. State-of-the-art silicon-based integrated circuits (ICs) have been improved significantly throughout the years but mainly for a low-temperature ambient. At a temperature higher than 300 ºC silicon-on-insulator (SOI) or bulk silicon-based electronics cannot operate reliably. Therefore the wide bandgap (WBG) semiconductor materials such as silicon carbide (SiC) come into play.In recent years, many types of SiC-based devices and low complex ICs have been reported and are operational at a high temperature (HT). The main goal of the thesis is to explore and demonstrate the feasibility of SiC-based circuits that are complex, dense and monolithically integrated for high-temperature applications such as a central-processing-unit (CPU).This thesis work demonstrates a Process Design Kit (PDK) for the SiC-based large scale integrated (LSI) circuits implementation. It consists of discrete devices, gate and module library, and SiC ICs verification programs. The thesis work reports the PDK results over the full temperature range of 25 to 500 °C with a power supply of 10 V to 20 V.The thesis work demonstrates a 4-bit CPU architecture designed for a proposed instruction set. Manual place and route with around 10,000 devices and area of 150 mm2 were carried out using the PDK standard cell library. The CPU and integral parts have been implemented at the transistor level using the PDK gate/module library and simulated from 25 to 500 °C. The CPU has been fabricated in the in-house low-power SiC bipolar process and measured at a high temperature.The thesis work also reports reference analog and mixed-signal ICs. A 555-timer consisting of both digital and analog circuits has been designed, integrated and characterized up to 500 °C. Flash and SAR ADCs have been implemented using the PDK for HT applications. A 256-pixel image-sensor design and layout were also carried out using the PDK.This thesis work is an important step and has laid the foundation of SiC-based LSI circuits realization for extreme environment applications.
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