S530 Parametric Test System Test Subroutine Library User's Manual
Section 3: Test subroutine library reference
S530-907-01 Rev. A / September 2015
3-61
tox
This subroutine calculates the thickness of an oxide layer from the capacitance and the area of a metal-oxide
semiconductor (MOS) capacitor.
Usage
double tox(int
hi
, int
lo
, int
sub
, double
vbias
, double
area
)
hi
Input
The HI pin of the device
lo
Input
The LO pin of the device
sub
Input
The substrate pin of the device
vbias
Input
The voltage bias on the device, in volts
area
Input
The area of the capacitor, in cm
2
Returns
Output
The calculated oxide thickness:
4.0E+21 = Preliminary leakage test fails
Details
This subroutine makes a capacitance and a conductance measurement, corrects the capacitance
measurement, and then calculates the oxide thickness. The common equation below is used to
estimate oxide thickness. The oxide thickness is returned in angstroms. The area should be specified
in cm
2
.
T
OX
=
OX
A / C
CORRECTED
Where:
OX
= 34.52
-14
farads per cm and is the oxide dielectric constant
Calculations assume that CMTR1 is a Keithley Instruments Model 9125 1 MHz capacitance meter.
Before T
OX
is calculated, voltage bias (V
BIAS
) is forced with a current limit of 1
μA, and the resulting
current is measured. If the current is within 98 % of the limit, the capacitor is considered too leaky and
the function returns a value of 4.0E+21.
This subroutine can be modified to accommodate other dielectric materials by adding the dielectric
constant into the argument list.
Example
result = tox(hi, lo, sub, vbias, area)
