Membranes contaminated
Last week during the deposition step, Chris and I discovered that part of the Cu “power cup” (piece that is bonded to target to make thermal contact with sputter gun) had eroded and coated the inside of the target shield with copper.
Later EDX and TEM characterization showed that there was indeed contamination in the films. The wafers most affected were SC 257, 258, 263-265.
We believe that the combination of using the more conductive Al shields at high powers allowed the plasma to “spill over” onto the Cu powercup. This is most likely why recent membranes have been wrinkling.
We have since cleaned the chamber, replaced the AJA powercup targets with Lesker non-powercup targets, and removed all the Al shields.