The hydrogen/nitrogen may be supplied in the form of forming gas containing less than 7 % hydrogen.
In one preferred embodiment of the method the etchant gasses include ammonia, helium, and a forming gas preferably comprising hydrogen and nitrogen.
A forming gas is introduced into the plasma.
The water vapor is generated by introducing O2 and an H2 containing forming gas including hydrogen and at least one dilutant gas into the CMG.
The method can include applying an OH/H containing plasma, such as H2O or O2 or a forming gas, to a via which has been etched in a layer of the device.
In a disclosed example, the hydrogen-nitrogen mixture contains less than 0.1% hydrogen.
At least one fluorine-containing compound is introduced into the plasma.