zapping gates

Can you provide more information on test setup and proedure?

Well, I connected a power supply between gate and source and turned it up until the gate blew out... is there another way? Gate was + on the n-channel fet, - on the p-gadget, which ensured that Vd-s was zero.

So, a failure mode that we thought was possible, isn't. Gotta look somewhere else.

John

**************************** is there another way? ****************************

YES. It is called "testing" and involves defining what are you testing and how you control the test parameters so _some_ cosistent info can be gathered. Usually you define those things so another tester can repeat your findings. As reported it is technical gossip;^)

Having fun

Stanislaw Slack user from Ulladulla.

What else would you want to know? The colors of the test leads? What we had for lunch?

I seriously doubt that the gate breakdown voltage of power fets is terribly repeatable, and I'm not really interested in testing a couple hundred $10 fets to destruction and crunching the resulting statistics to be sure. So if you have any comparable data, I'd love to see it.

I thought it was interesting that both fets died at just about 4x their rated abs-max gate voltage.

Excuse me, I'm just an engineer.

John

I thought it was interesting that both fets died at just about 4x

Ramp rate, temperature...

Though I'm deeply ignorant of semiconductor physics, I would expect the electric field across the junction, and the failure threshold to vary significantly if it's 1v/s, or 1v/ns.

You are excused. Now excuse me, but I am just an (electronic) engineer (ret.) with over

25 years in aerospace industry most of them in testing department. So I read your post and try to make sense of what is written.

Have fun

Stanislaw Slack user from Ulladulla.

[snip]

Why is that surprising? The gate oxide is just a very-carefully-controlled thickness of silicon dioxide (aka glass).

You are excused ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

If it's very-carefully-controlled, why do they guardband it 4:1?

Maybe because it goes down at high drain voltages?

John

Rate, as already noted, was a guy turning a knob on a power supply. And if you read my other posts, I've already suggested the typical temperatures in San Francisco this time of year.

1 v/ns is a little fast for my personal wrist. It might be hard to read the meter at that rate, too.

John

Well, one of us seems to have some doubt about how to measure the gate breakdown voltage of a mosfet. Interesting.

John

Hot electrons ;-)

I just checked a process spec... TOX +3%/-5%

Plus there are some rate effects.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

What kind of power supply?

John, since you ask : the histogram, do a hundred and plot the histogram.

:-)

Naa. Thanks anyway, I take your measurements as a hint that the gate voltage could perhaps survive more than the 15V.

Rene

--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

I think it was grey.

John

With vents ?:-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

message

How noisy was the knob? How steady was the guy turning the knob?

I don't quite know how this thread went bad. To me, it was a very interesting post.

Since I've never done anything like this, I was just curious about how one detects blowout.

Does the current jump up dramatically? Does the part make an audible pop? I'm sure you had the current limiting set up on the PS, so maybe the Voltage just drops off suddenly as the current limit kicks in?

--Mac

The gate goes from being an essentially perfect insulator (well, gigohms) to a smallish value resistor, as the stored charge in the gate region becomes enough to break down the gate dielectric. The energies are small enough that you won't usually get any audible sign.

OK. a) Destructive or non-destructive test. b) Proper control of dv/dt and definition what di/dt is defined as breakdown. c) Manufacturer definitions of error levels on number(s) given in specs sheet. And so on and on.

All this is done so there is "No Entry!" sign for Mr.Murphy and his helpers.

And it IS a branch in our industry, not cheap, but essential.

Have fun

Stanislaw Slack user in Ulladulla.