Alvin Leng Sun Loke

Analog/mixed-signal design challenges in 7-nm CMOS and beyond

The economics of CMOS scaling remain lucrative with 7-nm mobile SoCs expected to be commercialized in 2018. Driven by careful design/technology co-optimization, modest reduction in fin, gate, and interconnect pitch as well as process innovations continue to offer compelling node-to-node power, performance, area, and cost benefits to advance logic and SRAM to the next foundry node. However, analog/mixed-signal circuits do not fully realize these improvements. They become more cumbersome to design, having worse parasitic resistance and capacitance, stronger layout-dependent effects, and layout growth in some situations. Furthermore, early adopters of these cutting-edge finFET nodes must cope with the complications of design concurrent with technology development for shorter product time-to-market. We provide an overview of the key process technology elements enabling 7 nm and beyond to address analog/mixed-signal design challenges. From this insight, we offer layout guidelines aimed to reduce design vulnerability to technology and model immaturity.

Analog/Mixed-Signal Design in FinFET Technologies

Consumer demand for low-power mobile ICs has propelled CMOS scaling to arrive at the fully depleted finFET with foundry offerings already available at 16/14, 10, and 7 nm. The compact three-dimensional structure of the finFET offers superior short-channel control that achieves digital power reduction while increasing device performance for a given area. As system-on-chip technology remains driven by logic and SRAM scaling needs, designers of analog/mixed-signal subsystems must continue to adapt to new technology constraints. We attempt to summarize the challenges and technology considerations encountered when we port analog/mixed-signal designs to a finFET node. At 16/14 nm and beyond, designers also face many implications from scaling innovations leading to the finFET.