currently i am working on AlN deposition on silicon wafer, i was using DC sputtering but due to arcing effect i switched to RF. since then i tried 3 experiments and in all three of them the silicon wafer was untouched. the odd thing i found out was the plasma intensity (when shutter was open and when it was closed) was the same. i was successful creating thin layer when i was doing on dc but i cant do it with RF. following are the parameters used for RF sputtering.
Base pressure 1 micro torr
Sputtering pressure 15 milli torr
N2 to Are ratio 50:50
forward Power - 100 W/ (10 W/s)
Temp - 200 C
Process was ran for 2-3 hrs
Silicon wafer was used as substrate.
i have attached a image of plasma generated due to RF.
please tell me what is wrong with my experiments.
From your picture, it seems that the plasma is more lightening near the substrate than near the target? It should be the contrary.
What is the voltage during sputtering?
Can you reduce the target–to-substrate distance?
I think you are in what is called the poisoning effect . With a high reactive gas flow (N2), the target is almost or completely nitrided (formation of a layer of AlN) which considerably reduces the rate sputtering of your target. The solution is to reduce the flow of N2 gas.
It seems like the substrate is the one with more plasma, rather than the target, is this correct?
You need to check 4 things here.
1. Check if you can tinker with the Ar/N2 composition ratios. Can you go with only Ar here.
2. if you want to do a reactive sputtering, then better use Ar/O2 80/20.
3. Does your machine allow you to check reflected power? I feel that there is a lot of loss of power in your system, which can be a major cause of little to no deposition.
4. Target to substrate distance can be shortened, however at-least some deposition must occur at the distance you have shown in the picture.
Do let me know if any of these works.
Regards
So your substrate holder is grounded and the target (cathode) is at - 500V ? This situation should give the plasma close to the target.
It seems from the sight of the plasma it could be the contrary (target = 0V and substrate = -500V) ?
Perhaps you can try to improve the connection of the substrate holder to the ground ?
This looks like a grounding problem of you substrate manipulator. It might not be grounded properly. Kindly check the ground connection of the substrate manipulator.
* For your information, same situation occurs during reverse sputtering from the substrate. In that case the substrate manipulator is disconnected from the ground and the RF power is applied to the substrate. This method is often used by many to clean/etch the substrate.
Seems like the grounding problem.Try changing the substrate -target distance to 8cm for these parameters.Also the high N2 /Ar ratio can cause nitrite deposition on the target, so optimize it too
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