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A G R E AT E R M E A S U R E O F C O N F I D E N C E C-V, I-V, and charge-pumping. From these
measurements, important device parameters
can be extracted and plotted as a function of
time to show the degradation caused by the
stresses.
Stress and C-V Measurements [5]. In this
measurement, the device under test (DUT)
usually is a MOS capacitor. A C-V sweep is
Qualifying High
performed on the DUT before and after volt-
age stress. The C-V sweep can be a full sweep
from inversion to accumulation, so that a flat
Gate Materials with
band voltage can be calculated by quantum
mechanical modeling. However, a faster and
easier way is to do the voltage sweep in a
Charge-Trapping
relatively small voltage range around an esti-
mated flat band. The flat band voltage is then
extracted from the C-V data. Either a single
Measurements sweep or bi-directional sweep can be used;
a bi-directional sweep will show any hyster-
esis effects. Flat band voltage as a function
of stress time or injected charge provides in-
Yuegang Zhao, Keithley Instruments, Inc., formation on how much charge is trapped in
the gate stack structure. The trapped charge
Chadwin D. Young and George Brown, may be characterized by an effective value
International SEMATECH assumed to be located at the insulator-silicon
interface (Qtrap), given by:
Qtrap = Cgate