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Design for Manufacturability (DFM) involves changes to the design and CAD tools to help increase pattern
printability and improve process control. Design for Reliability (DFR) performs the same to improve reliability
of devices from failures such as Electromigration (EM), gate-oxide break down, hot carrier injection (HCI),
Negative Bias Temperature Insatiability (NBTI) and mechanical stress effects. Electromigration (EM) occurs due
to migration or displacement of atoms as a result of the movement of electrons through a conducting medium. The
rate of migration determines the Mean Time to Failure (MTTF) which is modeled as a function of temperature
and current density. The model itself is calibrated through failure analysis (FA) of parts that are deemed to
have failed due to EM against design parameters such as linewidth. Reliability Verification (RV) of a design
involves verifying that every conducting line in a design meets certain MTTF threshold. In order to perform RV,
current density for each wire must be computed. Current itself is a function of the parasitics that are determined
through RC extraction. The standard practice is to perform the RC extraction and current density calculation
on drawn, pre-OPC layouts. If a wire fails to meet threshold for MTTF, it may be resized. Subsequently, mask
preparation steps such as OPC and PSM introduce extra features such as SRAFs, jogs,hammerheads and serifs
that change their resistance, capacitance and current density values. Hence, calibrating EM model based on
pre-OPC layouts will lead to different results compared to post-OPC layouts. In this work, we compare EM
model calibration and reliability check based on drawn layout versus predicted layout, where the drawn layout is pre-OPC layout and predicted layout is based on litho simulation of post-OPC layout. Results show significant divergence between these two approaches, making a case for methodology based on predicted layout.
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