Meaning of 1ms in CoolSiC MOSFET Vth test condition

[SANGTAEHAN]

Hello,

I'd appreciate if you can advise whether 1ms is the pulse width of Vgs=20V bias(case1 of the below) or time delay(gap) between Vgs=20V bias and Vth measurement(case2)?

I believe it's the case1, but I'd like to make sure.

Thanks

[Abhilash_P]

Hi,

  Thank you for posting on the Infineon community.

The 2nd case is the right representation of the test condition. 

To measure gate threshold voltage of a MOSFET, at first, short Gate pin and Drain pin, and then, with a given  ID=1mA, and monitor the voltage difference between Gate-Source. One significant characteristics of VGS(TH) is its negative temperature coefficient. If power system has to be operated at a certain minus degree, to avoid unpredicted being turned on, VGS(TH) needs to be taken into consideration.

This can be verified from test conditions that is mentioned with the gate threshold graph. 

The test is performed at 1ms delay time and 20us pulse time. 

Regards,
Abhilash P

[SANGTAEHAN]

Hi Abhilash,

Thank you for the reply!

May I take this as an official confirmation of Infineon or your personal knowledge at this moment? 

I am asking this because I recieved different replies through other communication channels since I posted the question. 

Need your kind understanding and reply again.

Thanks

[Abhilash_P · Accepted solution]

Hi,

   After going through the following application note, the correct explanation for measuring the gate threshold voltage is as given below,

"The threshold voltage VGS(th) is the gate-source voltage needed for current to start flowing through the channel of the device at a specific drain to source current. The left side of Figure 3 shows the threshold voltage versus temperature at IDS=10 mA. This threshold voltage VGS(th) is measured by first applying one 1 ms pulse-gate voltage at a VGS=+20 V as a precondition, then the threshold-voltage value of VGS(th) is read at VGS=VDS by forcing current IDS=10 mA . From the results, the typical threshold voltage VGS(th) equals 4.5 V at 25°C and IDS=10 mA, which provides good noise immunity against parasitic turn-on, meaning ease of use for the device."

From this explanation it is clear that 1st depiction is the correct way of understanding the Vth measurement. 

Please ignore my explanation in the previous response. 

You can refer the following paper for more details,

"Thomas Aichinger et al.: Threshold voltage peculiarities and bias temperature instabilities of SiC
MOSFETs. 80 (2018) 68–78, Journal of Microelectronics Reliability."

Regards,
Abhilash P

[SANGTAEHAN]

Hi Abhilash,

Acknowledged. Really appreciate your help. 

I should have read the app note.

Have a good day!

[喜马拉雅之雪]

Hi SANGTAEHAN：

Thanks for your comments.

Case1 is right for test.

As Coulomb scattering, Vth have a little change in first pulse. So set the test function for best engineer reference.

Thanks