Keithley 4200-SCS, User Manual

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3-100 Return to Section Topics 4200-900-01 Rev. K / February 2017
Section 3: Common Device Characterization Tests Model 4200-SCS User’s Manual
How to perform a flash memory test on my device
Introduction
There are several projects included with the 4200-SCS FLASH package that
facilitate testing of floating gate transistors (NOR, NAND), as well as other types
of Non-volatile Memory (NVM). The package consists of two pulse cards (four
pulse channels), projects described in this section, and all required
interconnecting cables and adapters (see
Figure 3-89 ).
Depending on the desired setup, at least two SMUs are required. To illustrate the
flexibility of the 4200-SCS FLASH package
on page 3-101 Figure 3-84 and Figure
3-85 depict a typical configuration using four SMUs.
This configuration permits independent source and measure for each terminal in a
typical
4-terminal floating gate transistor.
NOTE The 4200-SCS FLASH package does not include a 4200-SCP2
(2-channel scope card). When using the Models 4205-PG2 or 4220-PGU, the scope
card can be added for manual pulse height verification. Since the Model 4225-PMU
has measure capability, a separate scope card is not necessary.
NOTE
The Reference manual, PMU-Flash-NAND project, page 16-118 uses the 4225-PMU
to test flash memory. The NVM_examples project (see Table 16-17 ) samples the
voltage and current during pulsing. For more information, see the NVM Application
Note link on the Applications page of the 4200 Complete Reference.
Theory of operation
Programming and erasing flash memory
A floating gate transistor is a modified field-effect transistor with an additional
floating gate. The floating gate transistor is the basic storage structure for data in
non-volatile memory. The floating gate (FG) stores charge, which represents data
in memory (see
Figure 3-80 ).
The control gate (CG) reads, programs, and erases the FG transistor. The
presence of charge on the gate shifts the voltage threshold, V
T
, to a higher
voltage, as shown in Figure 3-81 .