Testing Silicon Wafer: Predictions & V-I Characteristics

[salthepal]

Hi,
my labmates and I are trying to fabricate a functional organic semiconductor; however we are having problems indicative of surace leakage between the gate and drain, or oxide breakdown (Fowler-Nordheim or otherwise).

So now we're trying to test our silicon wafer without the organic semiconductor to see if the oxide behaves as a good indulator or not. Does anybody know an equation to help predict the voltage at which breakdown would occur, or to plot V-I characteristics for the oxide ?

Thanks !

 

[Pythagorean]

this question may be more quickly answered in the electrical engineering forum below this one in the engineering section.

 

[Gokul43201]

Hi,
my labmates and I are trying to fabricate a functional organic semiconductor; however we are having problems indicative of surace leakage between the gate and drain, or oxide breakdown (Fowler-Nordheim or otherwise).

So now we're trying to test our silicon wafer without the organic semiconductor to see if the oxide behaves as a good indulator or not. Does anybody know an equation to help predict the voltage at which breakdown would occur, or to plot V-I characteristics for the oxide ?

Thanks !

I haven't a clue, but I have neighbors who might have a pretty good idea. Or you could email them yourself: Art Epstein

 

[luckycharms]

Hi,
my labmates and I are trying to fabricate a functional organic semiconductor; however we are having problems indicative of surace leakage between the gate and drain, or oxide breakdown (Fowler-Nordheim or otherwise).

So now we're trying to test our silicon wafer without the organic semiconductor to see if the oxide behaves as a good indulator or not. Does anybody know an equation to help predict the voltage at which breakdown would occur, or to plot V-I characteristics for the oxide ?

Thanks !

Electric field breakdown strength (Ebd) is a material quality that you can find referenced fairly easily, but for oxide it depends on the deposition method. For example, CVD deposited oxide has a different breakdown strength than thermally grown oxide. Generally, it ranges somewhere from E(bd)~8-11 MV/cm. So if you know your oxide thickness, you can easily estimate the breakdown voltage. If you don't know the thickness, you can estimate it from an oxide color chart or measure it with an ellipsometer.

Oxide breakdown, at least for gate oxides, is often the result of the creation and accumulation of trap defects which eventually form a conductive path through the oxide. The oxide failure is catastrophic and irreversible.

There are two ways commonly used to characterize oxide breakdown. One is time-zero dielectric breakdown (TZDB) where you fairly rapidly ramp the voltage and note the voltage where the oxide fails, i.e. the current is roughly zero while the oxide is insulating until it takes off when it breaks down.

The other is time dependent dielectric breakdown (TDDB), where you apply a constant current and measure the time until the oxide breaks down. Here the voltage will be constant until it abruptly goes to zero when the oxide breaks down. Multiplying the current by the time gives you Qbd, the charge-to-breakdown. Ebd and Qbd give you a fairly good idea of the quality of your oxide if you compare to published values.

A few other tests you can do are high and low-frequency tests of the capacitors. These can tell you things like the interface trap density, the flatband voltage, and the oxide thickness.