8
Compact Models for Integrated Circuit Design
In early 1990s, the proprietary compact model, HSPICE Level 28, was
released from Meta-Software to address the shortcomings of BSIM1 [41,42];
where ‘H’ in HSPICE abbreviates the initial of the family name, “Hailey’
of the developers of the industrial SPICE circuit CAD and founders of the
company Meta-Software. The widespread use of Meta-Software’s circuit
CAD tool, HSPICE, served as the vehicle for the Level 28 model, helping
Level 28 to become the most widely used MOSFET model in the semiconductor industry. The HSPICE Level 28 model is based on BSIM, without
many of BSIM’s intrinsic shortcomings; it also has accurate capabilities
for modeling both the analog and digital circuits in contrast to BSIM that
has been mainly developed for modeling digital circuits.
In 1994, BSIM3 [43] was developed to account for the shortcomings of BSIM2.
The device theory has been developed over a number of years [43–46]. The
model explicitly takes into account the effects of many device sizes and process variables for good model scalability and predictability. The short channel
and narrow width effects as well as high field effects are well modeled. The
first released version of BSIM3, BSIM3v2 [43], offered better model accuracy
and scalability than the previous BSIM models but it still suffers from discontinuity problems such as negative conductance and glitches in the g m /I ds
versus V g plot at the boundary between weak inversion and strong inversion;
where g m is the device transconductance. In the meantime, the need for a good
open MOSFET model had been widely recognized by the semiconductor
companies. To eliminate all the kinks and glitches in BSIM3v2, BSIM3v3 with
a single-equation approach along with the enhanced modeling of small size
and other physical effects [44–47] was developed. The BSIM3v3.0 model has
been extensively verified and selected as the first industry standard compact
MOSFET model in 1996 by Compact Modeling Council (CMC) [48]. The convergence performance of BSIM3v3.0 was enhanced in BSIM3v3.1 [45]. Version
BSIM3v3.2 [47] introduced a new charge/capacitance model that accounts for
the QM effect, and improves V th model, substrate current model, NQS model,
and others and was released in 1998 and 2005 [49–51].
During 1990s, Philips Laboratories started developing MOS Model 9 [52,53]
and released the model in 1994 [54], making it widely available in mainstream
circuit CAD tools. The basic features of MOS 9 include very clean and simple
model equations, use of well-behaved hyperbolic expressions as smoothing
functions for good behavior in circuit simulation, and less number of model
parameters. The smoothing functions in MOS 9 serve continuous and smooth
equations across the various transition points (such as V dsat ) of MOSFET operation and allow the realization of a single-model equation (e.g., I ds equation)
valid in all regions of device operation. Finally, MOS 9 includes some of the
features of HSPICE Level 28, thus accommodating proper model binning.
Unlike BSIM3, MOS 9 retains the existing approach in describing the geometry dependence of the model characteristics. While the basic method of the
existing modeling know-how is used, the method is extensively modified to
improve the circuit simulation results.
Compact Models for Integrated Circuit Design
In early 1990s, the proprietary compact model, HSPICE Level 28, was
released from Meta-Software to address the shortcomings of BSIM1 [41,42];
where ‘H’ in HSPICE abbreviates the initial of the family name, “Hailey’
of the developers of the industrial SPICE circuit CAD and founders of the
company Meta-Software. The widespread use of Meta-Software’s circuit
CAD tool, HSPICE, served as the vehicle for the Level 28 model, helping
Level 28 to become the most widely used MOSFET model in the semiconductor industry. The HSPICE Level 28 model is based on BSIM, without
many of BSIM’s intrinsic shortcomings; it also has accurate capabilities
for modeling both the analog and digital circuits in contrast to BSIM that
has been mainly developed for modeling digital circuits.
In 1994, BSIM3 [43] was developed to account for the shortcomings of BSIM2.
The device theory has been developed over a number of years [43–46]. The
model explicitly takes into account the effects of many device sizes and process variables for good model scalability and predictability. The short channel
and narrow width effects as well as high field effects are well modeled. The
first released version of BSIM3, BSIM3v2 [43], offered better model accuracy
and scalability than the previous BSIM models but it still suffers from discontinuity problems such as negative conductance and glitches in the g m /I ds
versus V g plot at the boundary between weak inversion and strong inversion;
where g m is the device transconductance. In the meantime, the need for a good
open MOSFET model had been widely recognized by the semiconductor
companies. To eliminate all the kinks and glitches in BSIM3v2, BSIM3v3 with
a single-equation approach along with the enhanced modeling of small size
and other physical effects [44–47] was developed. The BSIM3v3.0 model has
been extensively verified and selected as the first industry standard compact
MOSFET model in 1996 by Compact Modeling Council (CMC) [48]. The convergence performance of BSIM3v3.0 was enhanced in BSIM3v3.1 [45]. Version
BSIM3v3.2 [47] introduced a new charge/capacitance model that accounts for
the QM effect, and improves V th model, substrate current model, NQS model,
and others and was released in 1998 and 2005 [49–51].
During 1990s, Philips Laboratories started developing MOS Model 9 [52,53]
and released the model in 1994 [54], making it widely available in mainstream
circuit CAD tools. The basic features of MOS 9 include very clean and simple
model equations, use of well-behaved hyperbolic expressions as smoothing
functions for good behavior in circuit simulation, and less number of model
parameters. The smoothing functions in MOS 9 serve continuous and smooth
equations across the various transition points (such as V dsat ) of MOSFET operation and allow the realization of a single-model equation (e.g., I ds equation)
valid in all regions of device operation. Finally, MOS 9 includes some of the
features of HSPICE Level 28, thus accommodating proper model binning.
Unlike BSIM3, MOS 9 retains the existing approach in describing the geometry dependence of the model characteristics. While the basic method of the
existing modeling know-how is used, the method is extensively modified to
improve the circuit simulation results.