endurance test shows the reduction in the polarization charge as the
number of pulses applied increases. For some devices, the polarization
charge may increase slightly during the initial pulse stress, before
declining with an even larger number of stresses.1 Figure 12 shows
example endurance results for QSW
. The degradation in QSW
begins at 11 million cycles. The rate of change of QSW
as well as the difference between the two parameters can assist in
understanding the degradation mechanisms in the material. The onset of
degradation is a strong function of the pulse amplitude, so different
materials and PUND voltages can provide significantly different
Click image to enlarge.
Figure 12: FRAM endurance curves show the
degradation in PSW and QSW. This data was taken by the Model 4225-PMU
with Model 4225-RPMs.
Many materials and technologies are
currently under investigation for NVM, and each has unique aspects for
the physical memory behavior. Electrical characterization is crucial to a
better understanding of the physical aspects of the underlying
technology. Regardless of the particular memory technology under
investigation, pulsing is required to exercise the switching behavior.
All candidate NVM materials require multi-level and multi-pulse
waveforms, requiring test instrumentation that can output these
complicated waveforms in a single shot, reducing characterization time
for read, write and endurance behaviors. Most importantly, pulsing with simultaneous
current and voltage measurement provides the data necessary to
understand the dynamic behavior of the switching mechanism.
1. F. Chu and T. Davenport, “The Endurance Performance of 0.5 m FRAM Products.”
About the author
J. Hulbert is a product and applications development engineer for
Keithley Instruments (Cleveland, Ohio), which is part of the Tektronix
test and measurement portfolio. He holds a bachelor’s degree in physics
from Washington State University. His career in measurement
instrumentation has overlapped a good portion of the electromagnetic
spectrum—from ionizing radiation to the far infrared.
Did you find this article of interest? Then visit the Memory Designline
where we update daily with design, technology, product, and news
articles tailored to fit your world. Too busy to go every day? Sign up
for our newsletter to get the week's best items delivered to your inbox.
Just click here
and choose the "Manage Newsletters" tab.