Keithley 4200A-SCS Reference Manual

Model 4200A
-SCS Parameter Analyzer Reference Manual Section 4: Multi-frequency capacitance-
voltage unit
4200A-901-01 Rev. C / February 2017 4-73
Formulas and constants
This project uses one formula (no constants):
• NOISE: Calculates the standard deviation of the capacitance measurements.
NOISE = STDEV(CP_GB)
Analyze sheet
Test data is displayed in the Analyze sheet:
• Cp_GB: Measured parallel capacitance.
• Gp_GB: Measured conductance.
• DCV_GB: Forced DC bias voltage.
• F_GB: Forced test frequency.
• CVU1S: Status code for each measurement. Rows highlighted in blue indicate a fault. For details,
see Measurement status (on page 6-191
).
• NOISE: Formulator calculation result.
GB stands for gate-to-bulk.
MOS Capacitor Mobile Ion Project (moscap-mobile-ion)
Mobile ions can present a severe reliability issue in metal-oxide semiconductor (MOS) structures.
These mobile charges in MOS capacitors are mainly due to ionic impurities, such as Na+, which can
drift across the oxide and affect the device performance. One technique for determining the amount
of mobile charge in the oxide of a MOS capacitor is the bias temperature stress (BTS) method. Using
this method, the flatband voltage (Vfb) is used to determine the amount of charge. The flatband
voltage is measured both at room temperature and after the device has been at an elevated
temperature for enough time for the charges to be mobile. The difference in the flatband voltage is
related to the mobile charge as follows:
Where:
• Q
m
= mobile ion charge (C)
• V
fb
= flatband voltage (V)
• C
OX
= oxide capacitance (F)
This semi-automatic project is executed from the subsite level. The oxide thickness and flatband
voltage extracted from the data in the tests are sent to the subsite level Analyze sheet after the tests
are executed. The calculated value of the mobile ion charge and concentration can be found in the
Calc tab of the subsite Analyze sheet.
Before executing this test, you need to input the gate area of the device into the Constants area of the
Formulator for the CV-Vfb1, CV-Vfb2, and CV-Vfb3 test modules. Also, in the CV-Vfb1 test, you
must update the gate area in the formula area of the Formulator. The gate area formula to update is
called AREA_GATE and is used in the calculation of the mobile ion charge in the subsite Calc sheet.

Keithley 4200A-SCS Specifications

General

Brand	Keithley
Model	4200A-SCS
Category	Measuring Instruments
Language	English