Cu returns in w319 series
After the w310 series being beautiful (few pinholes, reasonable strength, high yield), we have retreated somewhat with a return of the copper-related piholes. Here is an SEM image and EDX scan from the well wall:
Here is a pic of a pinhole on the membrane with a telltale copper silicide particle attached to the edge:
Nearly all pinholes of this size have one of these particles either bound to it or sitting on the membrane nearby – too much coincidence for these to be unrelated effects. We will continue trying to narrow down the source of this problem so we can eliminate it.
In the mean time, please be careful when inspecting membranes for use. A 2 micron pinhole can easily be overlooked or mistaken for a particle, especially if a particle is sitting inside it!!