Because nitrogen is a non-inert gas.In reactive sputtering process it is a desired gas. In fact sputtering is a physical vapor deposition method used to create thin films. The nitrogen percentage depends on the situation and the amount of argon gas used.
Nitrogen is easily available and inerts gas. The amount can be decided according to pressure. Different amount is desired as different pressure. The sputtering is different types, in reactive sputtering Oxygen can also be used. Sputtering is one of the main processes of manufacturing optical waveguides and is another way for making efficient photovoltaic solar cells.
Sputter coating. ...
Ion-beam sputtering. ...
Reactive sputtering. ...
Ion-assisted deposition. ...
High-target-utilization sputtering (HiTUS) ...
High-power impulse magnetron sputtering (HiPIMS)
Using Ti Target, doing reactive sputtering of TiN and using Argon plus Nitrogen is the more convenient and controllable to form the desired TiN. Following are Conditions
1. High Vacuum 10 to 6 mm of Hg.
2. Ti Surface should be cleaned.
3. High Purity Nitrogen required.
4. Gas flow should be varies with pressure,
To know the amount of nitrogen required, you should start studying your process: Start with hysteresis curve (constant flow rate of argon, and progressive increase of reactice nitrogen, and then progressibe decrease). Look at the literature, there numerous reference.
You have to measure the target electrical parameters (voltage and power, if you work at constant current), pressure, and eventually deposition rate. You will know "when" - in terms of N2 flow rate - start the deposition of nitride coating (look at getter effect in numerous publication).
If it a lab scale chamber (30-80L), you can work at 0.2-1Pa, a flow rate of Ar between 10-30 sccm, and 10-40 sccm of N2 (this is very rough approximation, it depends on lots of things). Going on bigger chamber, the flowrate are generally around 80-200 sccm.
Regards,
Emile
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