Keithley S530, User Manual

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S530 Parametric Test System Test Subroutine Library User's Manual Section 3: Test subroutine library reference
S530-907-01 Rev. A / September 2015 3-31
gamma1
This subroutine returns the value of the body effect parameter gamma obtained from two measurements of the
threshold voltage (V
T
) at different substrate bias voltages (V
BS
).
Usage
double gamma1(int d , int g , int s , int sub , double vlow , double vhigh , double vds ,
double vbs1 , double vbs2 , double phip , double ithr , double vstep , int npts , int
*kflag )
d
Input The drain pin of the device
g
Input The gate pin of the device
s
Input The source pin of the device
sub
Input The substrate pin of the device
vlow
Input Low limit of the expected threshold
vhigh
Input High limit of the expected threshold
vds
Input Drain-source voltage, in volts
vbs1
First substrate to source voltage
vbs2
Second substrate to source voltage
phip
Surface potential, in volts
ithr
Drain-source trigger current (I
DS
), in amperes
vstep
Gate-source voltage (V
GS
) step size, in volts
npts
The number of points in the sweep
kflag
Output Returned status flag:

0 = Normal completion

1 = First V
T
measurement failed

2 = second V
T
measurement failed
Returns Output Estimated body effect
Details
This subroutine estimates body effect from V
T
measured at two V
BS
values. The body effect
parameter characterizes the effect of the substrate bias on threshold voltage. The V
T
data is obtained
using the
vtext2
subroutine.
The equation used in this subroutine:

= V
T2
-V
T1
/

V
T1
+

p
-

V
T2
+

p
)
Where:


= MOSFET body effect constant

V
T1
= Threshold voltage at the first value of V
BS

V
T2
= Threshold voltage at the second value of V
BS


p
= Surface potential (twice the Fermi level)
The
npts
parameter must be greater than 5. If a value less than 5 is used, the subroutine uses 5
points by default.