By Zhihong Liu, Executive Chairman, ProPlus Design Solutions, Inc., www.proplussolutions.com
Twenty years ago, I was part of a group of top-notch researchers at the University of California, Berkeley, advised by renowned professors Dr. Chenming Hu and Dr. Ping K. Ko. It was a privilege to be among an elite team that invented the physics-based, accurate, scalable, robust and predictive MOSFET SPICE model called BSIM3.
What we didn’t anticipate was the impact of our invention on the worldwide semiconductor industry then and 20 years later. BSIM series models helped usher in the new era defined by the availability of standardized compact models that contributed to the success of the foundry-fabless business model.
The commercialization of BSIM is 20 years old as well. (See news release titled, “ProPlus Design Solutions Celebrates 20 Years of BSIMProPlus SPICE Modeling,” dated December 11, 2013) Several members of the group and I formed Berkeley Technology Associates (BTA) in 1993 to promote BSIM3 and to provide commercial-grade parameter extraction software for BSIM3 model creation. Our first product was BSIMPro that quickly became the industry’s golden model extraction tool adopted by all leading semiconductor companies.
Initially, the BSIM3 model was used for circuit simulation and CMOS technology development, and later became the first industry-standard compact model. Since then, most ICs designed have used BSIM3 and other BSIM family models, such as BSIM4 and BSIMSOI. Amazingly, the cumulative revenue is in the hundreds of billion dollars.
The advancement of BSIM models and the BSIMPro family of products was largely driven by process technology generations as the semiconductor industry aggressively pushed Moore’s Law. In the early “happy scaling” years, devices could be scaled down easily and BSIM3 was used from 0.5µm down to 0.15µm and, in some cases, down to 90nm with extensions provided by EDA vendors.
BSIM4 was introduced in 2000 for sub-130nm technologies and met the needs of high-speed analog and CMOS RF applications. With continuous geometry down-scaling in CMOS devices, compact models became more complicated as they needed to cover more physical effects, such as gate tunneling current, shallow trench isolation (STI) stress and well proximity effect (WPE).
Over the past 10 years, other varieties of industry-standard compact models have appeared, driven primarily by different system-on-chip (SoC) applications. These include models for silicon on insulator (SOI), bipolar junction transistor and hetero-junction bipolar transistor (BJT/HBT) and advanced CMOS technologies and high-voltage devices.
Early on, BSIMPro established a new methodology for model parameter extraction using GUI-based functionality for a more intuitive and efficient way to develop advanced models. A feature called Equalizer let users tune model parameters by moving their mouse to see the effects on device characteristics. Modeling engineers used the mouse to select multiple regions of device characterization data, while BSIMPro ran mathematic algorithms to achieve the best model fitting. This resulted in a quantum jump in productivity and efficiency as well as improved model quality and continues through subsequent generations of the BSIMPro family of products, including BSIMProPlus, the current version.
While the BTA name is long gone, many members of the core team continue to work together. BTA merged with an EDA company called Ultima in 2001 and formed Celestry, acquired by Cadence Design Systems in 2003. ProPlus Design Solutions spun-out of Cadence in 2006.
The BSIMPro family’s 20-year track record of success is a rarity, as the typical product lifecycle is far less than that. I look back on the past 20 years with a great deal of satisfaction. BSIM3 models had a tremendous impact on the semiconductor industry and continue to do so today. That’s cause for celebration.