In High Aspect ratio Trenches can we get conformal deposition of metals like Cu,Al,Ti.......etc by using PVD techniques ,such as Sputtering and Aluminium.?
If I understand your question correctly, your process is not much different than growing long nano-wire using Lift-off technique. We can successfully grow 1mm long and 200 nm wide nanowire using a PPMA resist (250 nm thick), Lift-off and sputtering of Nb, Cu, and Pt.
You can get more uniform coating of the High Aspect ratio Trenches when you use a sputtering deposition and your sputtering target is large in comparison to the distance from the target to the sample. However, you will never get as uniform deposition as you can get using CVD (chemical vapor deposition) techniques.
ALD (Atomic Layer Deposition) allows you to deposit conformal coatings in high aspect ratio trenches. With sputtering, you most likely will end up with gradients in your layer thickness. As suggested by Alexei V Ermakov , you can try to obtain a more uniform deposition by varying the target-to-substrate distance, sputter gas pressure or introducing sample rotation, but I doubt that these modifications in process parameters will give you the desired results for the high aspect ratio trenches you describe. If you look for an estimation of the overall effect of these modifications in process parameters on the number of arriving particles on the walls of your trenches, you can always simulate your configuration with SiMTra (download at www.draft.ugent.be).
In my opinion those PVD techniques that you are mentioning: (Sputtering, Thermal Evaporation, Electron Beam Physical Vapor Deposition (e-beam) , does not give a good conformal deposits along all the surface,
If you are looking for a conformal deposition in more complex shapes you need to consider CVD or ALD techniques.
The drawback of those techniques in your case, is that is not common to deposit pure metals with ALD and/or CVD , as those you mentioned: Cu, Al, Ti....etc.
ALD, for example, due to issues of precursors' availability mainly, depositions of metal oxides are more common,. e.g.: Al2O3, TiO2, ZnO etc..., But I know that a few (pure) metals can be deposited too, e.g. Cr.
Although I Would n't know what the required precursors would have to be used.
Regards ! :)
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