Pre-silicon and post-silicon testing of SIWA, a low-power RISC-V microcontroller

Abstract

Making chips is a complicated and costly process that requires specialized knowledge. A single product of the semiconductor industry often involves many teams of engineers who work to make the chip as flawless as possible. The VLSI design flow is usually the compass needed to navigate these tricky seas, as it provides a detailed description of what is required to successfully build a chip. With each passing year, chips have evolved ever more complex, drastically increasing research and development costs. A look into how the industry has changed is enough to understand the previous sentence. At the moment of this dissertation, there are far more companies in the semiconductor industry that specialize in specific aspects of the chip-making process than the decreasing number of Integrated-Device-Manufacturers (IDM) around the world. This trend is due to the increasing costs of chip manufacturing as designs and processes become more complex. Companies in this industry have learned to chain and intertwine their specialized business models to create chips at reduced costs. However, small design teams and academic groups still struggle to design and create their chips as the effort required and costs are still considerable for them. As part of a group of academic research in microelectronics, this doctoral dissertation was built from the experiences and challenges we faced while developing a low-power RISC-V microcontroller for implantable medical devices, SIWA. In particular, this thesis focuses on the validation of our microcontroller, and the strategies discussed in this document were developed considering a low-budget and the scarce human resources at our disposal. This thesis covers several aspects of the test process that SIWA went through over several years. In this document, the functional verification strategy to validate SIWA in the presilicon phases will be found. Then, a detailed description of the physical testing framework and how it was complemented with FPGA emulation is shown. Later, it is explained how software applications are built for SIWA and how I/O hardware emulation through software was achieved. Finally, this dissertation presents a benchmark proposal for classifying lowpower RISC-V microcontrollers used in implantable medical devices. It is worth mentioning that part of the results of this thesis were four scientific publications indexed in the Scopus database, demonstrating that the effort done in my PhD studies made a contribution to the knowledge in the field of microelectronics.