Charging of your cavities is possible in this situation.
Your ion mill should have a tungsten filament that is heated to
thermionically emit electrons,
which combine with the ions moving toward your target so as to neutralize
the ions but not decelerate them.
Check that this neutralizing  filament has not burned out.
If it is intact, try turning up its voltage/current to heat it hotter to
emit more electrons for more neutalization.
    --Kirt Williams

----- Original Message -----
From: "Ronen Almog" 
To: 
Sent: Thursday, July 08, 2004 12:06 PM
Subject: [mems-talk] SiN membrane - etching with ion milling


> Dear all,
> I am trying to etch SiN membranes from the back side with ion milling .
> The membranes are 100micron X 100micron made of 100nm LPCVD SiN on 500
> micron Si wafer.
> The membranes were fabricated using a standard KOH Si etching.
> I noticed that the etch rate of the membranes (from the back side) is
> almost 100 times smaller than the conventional etch rate of SiN with the
> same conditions.
> I would like to etch it faster. I suspect it is some kind of a charging
> problem which is slowing the etching.
> I tried to connect a ground electrode to both sides of the sample, but
> this didn't help.
> Has anybody experienced this problem or have an idea what to do?
> Thanks,
> Ronen
>
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