305
Modeling Process Variability in Scaled MOSFETs
Similarly, the PDF for the global component of M is expressed as
PDF
a gauss
global
global
σ
σ
(
) = (
)
( , , )
0 1 3
(8.24)
Equations 8.22 through 8.24 are used to formulate the variability-sensitive
compact model parameters to develop the final model library for HSPICE
circuit CAD. Table 8.4 shows the formulation of variability-sensitive BSIM4
model parameters determined in Section 8.5.2 in the model library. Thus, for
the variability-sensitive V TH , we have
V
V
Avt
WL
agauss
V agauss
TH
TH
TH
=
+
+
0
0
1
2
0 1 1
01 3
( , , )
( , , )
σ
(8.25)
The above procedure is used to build a BSIM4 MOSFET compact model library
for the advanced CMOS technology [5–7]. In order to show the basic functionality of the present modeling approach, all mismatches are lumped into V th
mismatch and the correlation between global model parameters is ignored.
TABLE 8.3
Typical Parameter Limits for Worst-Case BSIM4
Fixed Corner Model Generation
Compact Model Parameter
FF
SS
TOXE
Minimum
Maximum
TOXM
XL
Minimum
Maximum
XW
Maximum
Minimum
VTH0
Minimum
Maximum
U0
Maximum
Minimum
K1
Minimum
Maximum
RDSW
Minimum
Maximum
CGSL
Maximum
Minimum
CGDL
CGSO
Maximum
Minimum
CGDO
CJS
Minimum
Maximum
CJD
CJSWS
Minimum
Maximum
CJSWD
CJSWGS
Minimum
Maximum
CJSWGD
Source:
S.K. Saha, IEEE Access, 2, 104–115, 2014.
FF: fast NMOS and fast PMOS; SS: slow NMOS and slow
PMOS.