I was wondering if anyone has tried to modify the sputtering flux profile within their sputtering system. More specifically, has anyone tried to put some attachment on the gun/target in an attempt to create a thickness gradient along the radius of the rotating substrate? The end goal of this is to be able to sputter several samples of varying thicknesses in one deposition while keeping the substrate rotation on.
I have done so with some success, but did not quite achieve the gradient of thickness we were looking for. I got about 10-15% (nonlinear) gradation of thickness from the center to the outer radius of the substrate holder, which is approximately 9cm in diameter. I did this by covering a little less than half of the target/gun with some foil in a half-moon shape.
Some specifics about our sputtering system: 7 DC or RF powered magnetron guns in a confocal arrangement (sputtering up), 10 degree tilt of the guns, ~20cm working distance
Any ideas? Thoughts? Papers?
Thanks!
Thanks for your reply! I believe we have tried previously to change the tilt angle of the substrate on the sample holder but it had an odd effect on the film quality. Also, we want to make exchange biased films (w/ magnets on the back of the sample holder) and the tilt might affect the magnetic anisotropy.
I tried a 'half moon' aperture, got some good results but not quite a large enough change in thickness. I think I will try to look at some other shapes for the aperture, like what you are suggesting, an iris that would effectively shrink the size of the target.
Thanks again!
Thanks, a thicker iris is a good idea. I was wondering where are you placing your aperture. Is it near the target? I have been thinking of also making some sort of extension that would reach out further into the working distance but it seems like it might disrupt deposition from other guns.
The main motivation for this is just to save time (multiple samples in one depo at high temperature) while preserving film quality. These samples are polycrystalline. You are right about the rate dependence on structure/magnetic properties. I would hope the impact would not be too detrimental, but if it were I would just stick to doing the depositions the long way.
The most simple way, to my knowledge, is to increase distance between target and substrate. At a t-s distance about the diameter of the target the effect of magnets becomes small and distribution of deposition rate on angle is close to cos(theta) or even cosn(theta). Placing the substrate on the outer part of a rotating sampleholder you can get thickness gradient 50% or even more (of course, the diameter of the sampleholder should be big enough, this limits the maximal t-s distance).
Placing an aperture between target and substrate mimics point source of deposited material. If the distance from aperture to substrate is long enough, you can get cosine dependence again, and obtain high gradient far from the sample rotation center.
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