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Newest version of UC Berkeley computer model, used widely by semiconductor industry, will help with design of future speedy electronics
24 Mar 2000

By Robert Sanders, Public Affairs

BERKELEY -- When it comes to computer chip design, the world is turning increasingly to the University of California, Berkeley, for expertise.

In the past three years, more and more chip manufacturers have adopted a computer model created at UC Berkeley to design and simulate the operation of new integrated circuits - computer chips - before going to the expense of fabricating them. Called BSIM, for Berkeley Short-channel IGFET Model, it can model the operation of single transistors or millions linked in an integrated circuit, like a computer processor.

Now, to pave the way for future advanced electronics, the UC Berkeley researchers have developed a new version of the computer model, BSIM4. Released today (Friday, March 24), it is provided free to the semiconductor industry.

"It paves the way for engineers to design computer chips with blinding speed, and wireless electronics that communicate at higher frequencies," said Chenming Hu, the lead developer of the model and TSMC Distinguished Professor of Microelectronics at UC Berkeley.

"If you have a hundred, a thousand or a million transistors to simulate in a circuit design, you want a very efficient and accurate transistor model," said Ralph K. Cavin, vice-president for research operations at the Semiconductor Research Corporation, a non-profit industry-supported consortium that funds some $30 million in research at 65 universities each year. "BSIM has shown itself to be such a model."

"It has become the de facto industry standard," added Lawrence Arledge, a Texas Instruments engineer on loan to SRC as program manager for integrated circuits and systems and the computer-aided design testing program.

BSIM4 is likely to be adopted as the design standard by all of the companies that have adopted the previous version, BSIM3, plus many others. Significantly, BSIM3 has been adopted as a standard model by the world's three largest foundries - companies that fabricate chips for design firms. This means that most of the electronic circuits in the world will be designed using this computer model.

"When the foundries adopt a standard model, it's like laying down the law - four hundred design companies will design chips using the Berkeley model," Hu said.

"BSIM is the lingua franca between design houses and the foundry," Cavin said. "It's how they talk with one another; they express themselves in BSIM models."

BSIM3 was recommended three years ago by the Compact Model Council, an organization that standardizes compact models across the semiconductor industry, after it evaluated various CMOS circuit models. By then already broadly adopted, BSIM3 has since taken off. The council members include Intel, IBM, Motorola, TI, AMD, Hitachi, Philips and some 15 other large companies.

"The semiconductor industry depends heavily on simulation using BSIM3v3, and we believe that BSIM4 will have a similar acceptance," said Britt Brooks, chair of the Compact Model Council. "The phase - in time may not be as quick as BSIM3v3, since BSIM3v3 still works well for many leading edge designs today. However, we believe that BSIM4 will allow leading edge design simulation for the next two to three technology generations."

Brooks noted that UC Berkeley contacted the council before embarking on development of BSIM4, allowing major semiconductor manufacturers to suggest areas that needed research.

"Because the leading semiconductor companies have been directly involved with the project, we believe that many of the previous problems encountered with model development and adoption have been solved," Brooks said.

Cavin said that the new version represents a significant improvement over BSIM3.

"The new version has several new features, including for the first time the ability to design wireless products and the capability to deal with circuits miniaturized beyond 0.1 microns," Hu said. "BSIM4 can design higher frequency, larger chips with more functions, and ultimately deliver cheaper products to the consumer."

BSIM is essentially a four-page-long mathematical equation that simulates the operation of a transistor. The new model, BSIM4, introduces original physics models of transistor operation in the time scale of one percent of a trillionth of a second. In such a short time, light travels a mere thousandth of an inch. BSIM4 also introduces a new model for the noise in transistors that has puzzled engineers for decades. With this accurate noise model, circuits can be designed to provide clearer transmissions via cellular phones, for example.

BSIM4 was developed by Hu, research engineer Weidong Liu and graduate students Xiaodong Jin and Mark Cao.


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