Hi,

I'm wondering if someone can help me with this problem.

I'm using an acetic acid/water-based recipe to make PZT thin film by
sol-gel method. After spin-coating, I see particle-like dots on the film
scattered across the whole wafer. The diameters of the dots range from 3
to 40 microns, and under microscope it looks very light in color under
80x lense.

Is it possible that these dots are some kind of precipitate? Since my
sol will show transparent crystal-like precipitate after a while.

I used to work fine with this recipe, but recently it suddenly shows
this problem. I noticed this seems to conincide with the time when I
started to use new bottles of chemicals. Is this possible? If possible,
what's the cause of it and how do I fix it?
(I'm pretty sure the spin-coating environment and the wafer are ok and
not a cuase of the dots.)

Thank you for the help!

Ryan