I have been trying to deposit AlN in a magnetron sputtering chamber with a pure Al target in Ar/N2 environment. After numerous attempts with varying power (RF and DC), N2 percentage, substrate heating and other relevant parameters in the system, the film persists to grow in amorphous phase.
I have changed the substrates as well from Si to Sapphire and glass etc. the results remains the same.
Kindly suggest where there could be a correction needed.
Thanks
Is the film really amorphous, polycrystalline oder fibertextured?
[Amorphous is sort of easy to detect because that would be hydrolyzed by air humidity so that it would stink link ammonia.]
How do your tried process parameters compare to this work by my colleagues?
Article Influence of growth temperature on the properties of aluminu...
Particularly for Si wafers, what did you do to remove the native oxide layer? As you can find in the paper, the etching is quite crucial.
Materials deposited in vacuum that can be amorphous, often are amorphous when made by evaporative or sputtering deposition. The substrate needs to be hot enough during deposition to allow sufficient atomic mobility to reach the equilibrium phase after the atoms land on the substrate. It also generally helps to have a crystalline substrate with structure and lattice spacing similar to your desired material to provide a template for the atomic arrangement. Sounds like Jürgen knows specifics, so use the information in his paper.
Thank you for the suggestions Dr. w.s.l. Boyer
Dear Dr. Jürgen Weippert I have been using mostly c-Al2O3 (sapphire) substrate and to remove the native oxide layer, sonication in acetone along with other usual cleaning processes were employed.
The films so obtained were indeed of amorphous nature as confirmed by XRD, Raman and FTIR Transmission etc.
The problem I believe lies in the nature of sputtering, reactive.
As I am positive to believe that not all the aluminum sputtered reacts with the N2 leading to a metal excess surface which shown to have an abnormal Refractive index behaviour as calculated by UV-Vis reflection.
some ways that could potentially enhance the reaction taking place at the substrate may solve the issue.
Kindy provide the full access of the paper you have recommended if you can
Thanks and Regards
If they are truly amorphous, that would speak for a too low temperature, if it was high enough, I would expect at least a polycrystalline film.
c-plane sapphire is generally a "good-natured" substrate which doesn't require a lot of pretreatment, so you should be fine there.
Regarding the metal excess: in reactive sputtering, there are the "poison mode" and the "metallic mode":
Article Mechanisms of target poisoning during magnetron sputtering a...
This can be overcome by decreasing the Ar/N2 ratio. Please note that working in poison mode indeed poisons your target and you require pasting (pure metal sputtering) processes in between every run.
Regarding access to Bala Sundarapandian's paper: if you have no access, you can ask via RG's request tool or contact him directly via mail; especially if you have deeper questions going beyond the published data, I don't want to "leak" information he might want to publish himself later.
I believe this discussion has provided ample information regarding the point of issues and further directions.
Thank you Dr. Jürgen Weippert
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