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simulating HV devices in Spectre (Read 1249 times)
vivkr
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simulating HV devices in Spectre
Nov 15th, 2005, 4:43am
 
Hi,

This is more of a simulator issue, but specific to HV. I get a message from Spectre telling me that the voltage across the gate oxide exceeds the breakdown limits. However, I probe the voltages and I can see that this is not the case, especially as I have a HV device which is capable of more than 3x-4x times the voltage that Spectre is using for it's test.

I have a safe-operating check running and it shows no problems. I suspect that there is an internal setting in the simulator which is set to around 8 V. Does anyone know how to adjust this?

Thanks
Vivek
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bernd
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Re: simulating HV devices in Spectre
Reply #1 - Nov 15th, 2005, 9:55am
 
If you get a Spectre Warning similar to these

Warning from spectre during DC analysis `dcOp'.
   Mn: Vgd has exceeded the oxide breakdown voltage of `vbox' = <someValue> V.

then vbox is a bsim3v3 operating region warning control parameter
which defines the oxide breakdown voltage.
It is 1e9*tox, where the value for tox, the gate oxide thickness, is defined in
your bsim3v3 transistor model.

Bernd
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vivkr
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Re: simulating HV devices in Spectre
Reply #2 - Nov 16th, 2005, 12:55am
 
Hi Bernd,

Thanks for the tip. I think I can see the problem. The tox parameter refers to the active gate oxide thickness on the source end which is indeed small, but on the drain side, this oxide thickness is considerably large, but this is not modelled in BSIM3 as there is only one tox parameter.

I guess I just have to get used to this warning.

Vivek
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jbdavid
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Re: simulating HV devices in Spectre
Reply #3 - Feb 3rd, 2006, 12:23am
 
Or use (or write in Verilog-A) a transitor model that is appropriate  for HV devices (bsim3v3 is appropriate for .5u down to about .13u standard CMOS transistors.. but it has no idea of a Variable thickness Oxide.. AFAIK..
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jbdavid
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