Model 4200A-SCS Parameter Analyzer Reference Manual
Appendix D: Using a Model 82 C-V System
4200A-901-01 Rev. C / February 2017
D-57
Mobile ion monitoring with triangular voltage sweep (STVS) method
STVS is a technique developed by Keithley Instruments to monitor mobile ion charge in MOS
structures. Compared with other mobile ion monitoring techniques, such as the BTS and flatband shift
methods, it offers faster and more accurate measurement. STVS measures ionic current instead of
voltage shift. It has the ability to identify species, and it eliminates the need for temperature cycling of
the device under test (DUT). The STVS method has proven to be effective in monitoring mobile ion
charge in dielectrics to levels down to 10
9
cm
-3
.
The STVS library can perform the corresponding mobile ion charge analysis. It has a built-in
correction algorithm to eliminate the problems associated with leakage current. Many parameters,
including mobile ion charge concentration, can be extracted from this measurement.
The STVS method improves on the conventional TVS method (discussed below) by measuring both
C
Q
and C
H
and then computing mobile ion charge concentration as follows:
Where:
•
N
M
= mobile ion density (1/cm
3
)
•
V
GS
= gate-substrate voltage (V)
•
∆
V
GS
= change in gate-substrate voltage (step voltage) (V)
•
C
Q
= quasistatic capacitance measured by Model 595 (F)
•
C
H
= high-frequency capacitance measured by Model 590 (F)
•
q = electron charge (coulombs)
