IGBT forward leakage current

[min80]

Hi, 

I need to measure forward leakage current for an IGBT. 

Force 20V to VGE then measuring leakage current at the same time. 

Im using NI-4132 to source and measure at the same time. 

But the problem is the measurement actually fluctuating a lot. I suppose to get <10uA stable value, but the reading jumping from pA to nA then to uA and so on..... The reading is not stable at all. 

What am I doing wrong?

Please advice. Thanks. 

[LV_Pro]

It could be a lot of things, but how the unit is connected to the instrument is the first thing. Also, how fast are you sampling, could you be seeing noise?

[min80]

Hi, 

Measured from SMU, the force voltage ( plot 0 ) and measure current ( plot 1) as attached. 

Any idea?????? 

[johnsold]

Min80,

That is beautifully stable data!  Remember that the gate of an IGBT is a capacitor. The 10 uA currents you measure during the gate voltage transitions are charging the capacitor.  It appears that your leakage current (during the flat top of the voltage pulse) is less than 0.5 uA.  You need more sensitivity to actually measure it meaningfully.

Lynn

[LV_Pro]

I agree with Lynn, you have a clean (no visible noise) signal. If what you are expecting is a trace like like your image shows then you should not that it rises and falls with the VGE applied voltage. What is the time scale, and is the current actually going negative? How are you measuring the current (I'm not familiar with the instrument you are using)?

[K C]

Nice signals. The current you see, when you increase (or decrease) the voltage to your test setup, may be the current flowing through the capacitance of the leads, connections to IGBT and, most important, the IGBT itself.

Looking at a datasheet of an IGBT I see an input capacitance of 1000-2000pF. What is this value for your IGBT ?

When the voltage is stable at 20V the current is almost zero (I think a value of 100nA is normal). That is the leakage current that you are looking for !!

You can decrease the current by increasing the rise and fall time. However during this rise and fall there is a current flowing through the capacitance.

Hope this helps.

Kees