Leakage Current Optimization and Circuit Reliability Modeling
Sub-threshold leakage currents consume a significant fraction of total circuit
power in 90 nm and 65 nm technologies. Generation of library cells for low
leakage current is important for achieving low power ASIC designs. Since a
typical ASIC library may contain thousands of cells, efficient techniques are
required. In this project, a complete automated leakage optimization flow is
presented. It includes an efficient circuit optimization engine to optimize
device channel length and width while keeping cell delay increase and cell
area change minimal. Optimization results show about 30% leakage current
reduction with only several percent active area and dynamic power increase.
The optimization flow starts with SPICE net-lists including parasitic RC
extracted from the existing library. After leakage optimization, revised cell
layouts are generated and characterized based on the optimized net-lists. In
addition, investigations indicate that the optimization process has little
impact on cell noise margins, and that new cell layout variations from
placement, routing and compaction have little effect on the results. This
efficient automated layout to layout cell leakage optimization flow is most
suitable for leakage reduction and library migration for 90nm and 65 nm ASIC
designs and beyond.
In deep sub-micron region, reliability issues that previously had little
impact on circuits are becoming increasingly important. In this project,
a simulation framework for reliability analysis of circuits in the SPICE
environment has been proposed. The framework incorporates the degradation
of physical parameters such as threshold voltage for PMOS transistors into
circuit simulation and enables the design of highly reliable circuits.
Papers are to be published at the IEEE Circuits and Devices and
ISQED'07.
- "Efficient sub-threshold leakage current optimization and
layout migration for 90nm and 65nm ASIC libraries," IEEE Circuits and
Devices, Sep./Oct. 2006. Here is the
paper.
- "A new simulation method for NBTI analysis in SPICE environment," March,
ISEQD'07.
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