Compact modeling of deep submicron CMOS transistor with shallow trench isolation mechanical stress effect
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Date
2008-08
Authors
Tan, Philip Beow Yew
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Abstract
This thesis introduces a compact model, two empirical-based models and a
physical-based model of Shallow Trench Isolation (STI) mechanical stress effect on
deep submicron CMOS transistor. The compact STI x-stress model is used to capture
the stress effect in the channel length direction. This model is simpler than the BSIM4
STI stress model, but able to achieve the similar accuracy. Two new characteristics of
STI x-stress have been identified. The first characteristic is the fact that the STI xstress
effect on CMOS transistor varies for different transistor channel widths. An
empirical width dependence of STI x-stress effect model has been proposed to capture
this effect. The second new characteristic is the fact that STI x-stress effect changes
the CMOS transistor mismatch characteristics. An empirical Monte Carlo model is
proposed to capture this effect. A new hook shaped saturation drain current, Idsat curve
versus channel width has been identified. This curve cannot be modeled using the
BSIM4 STI stress model. By using a new layout method, the physical characteristics of
the curve are identified. The hook shaped Idsat curve is caused by the combined effects
of STI y-stress (stress in the channel width direction) that degrades the Idsat and the
Delta Width (OW) effect that increases the Idsat• Based on the physical characteristics, a
new physical-based STI y-stress model is proposed to capture the hook shaped Idsat
behavior. The accuracy of the models in this thesis is verified on actual silicon data
fabricated using Silterra's industry-standard 0.18 I-lm and 0.13 I-lm CMOS technologies.
These new models are incorporated into the BSIM3v3 model by using macro model
method (also known as subcircuit method). The two SPICE parameters, the zero back
bias threshold voltage parameter, PvthO and the carrier mobility parameter, Puo, are used
for developing these models. The difference in simulation time between the macro
model and the conventional model is insignificant « 5 %).
Description
Keywords
The compact STI x-stress model is used to capture , the stress effect in the channel length direction.