Module 7
Measurement Functions
7-29
Good
Continuous Curve
No Static Damage
BAD
Broken-Lumpy Curve
Severe Static Damage
*
*
Vth Measurement
Damaged MOS FET Device?
The class exercise uses a packaged MOS FET device which is very susceptible to static damage. If
the device has been handled or moved in and out of the socket a few times, you may see a BAD
response as indicated above. Replace the device with a new one.
At the wafer level, you can have the same problems. Putting a charged probe with cables attached
down on a gate junction can weaken or destroy the device. Also, the B1500A offset cancel (zero
cancel) sends signals down to the probes. These voltages can damage a sensitive gate junction.
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