Problem when Measure I-V curve with 4200, triax-cable

Hi everyone,

I’m Senior of Department of Electronics and Display engineering, Hoseo university.

I’m measuring the I-V curve of TFT fabricated by our fab, using 4200A-SCS.

The leakege current of TFT when TFT turns off doesn’t lower than 0.xxpA. It seems like limited by SMU’s.

I have two SMUs.
SMU1 is connected with PA.
SMU2 is connected with nothing.

In the manual, using PA give more measurement resolution if i undersatnd well.

I tested n-channel MOSFET(VNO104) and TFT for find the limit.
There are graphs.

Gate : SMU1(PA FORCE) or SMU2(FORCE)
Drain : SMU2(FORCE) or SMU1(PA FORCE)
Source : GND unit(FORCE)

If i use SMU1 to measure Ids, it can measure almost fA but that looks very strange. Like stairs.

If i use SMU2, it is higer than SMU1.
But the graph is linear and fine to see.

I’m looking for find the solution for this problem.
How can i solve this?



Thank you
From Janghoo Lee.

To have more insight, under the Advanced settings of the Terminal Settings, place a check box on the Status Reporting for each SMU.
This will put a new column in the sheet.  When you hover or dwell the mouse cursor on that column of data, the tool tip window will decode the status info.
In particular, knowing which current measure range is in use could be helpful.

What settings for current measure range do you use?  Limited auto?

The level of current is quite small, so more settling time might help too.  Try adding some Sweep Delay.
Or try using smaller dV/dt step sizes on the gate voltage sweep (more points).

If you have the 8101-PIV and the 1GΩ sample resistor, you could compare the current measure of the two SMU.
Use two terminal device and force a small voltage with one SMU while other forces 0V and measures the arriving current.

In Clarius, under the Tools icon in the ribbon, run the SMU Auto Calibration to see if this helps.

When was last time system went to calibration lab/service center?

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