Try long throw sputtering process, which means try to keep the wafer to target
distance as large as possible, to deposit Cu seed layer. This may help you to
deposit the Cu film at the bottom as well as on the sidewalls of the vias, which
means you will get a conformal deposition of Cu film in the via. The Cu film
thickness at the bottom and the sidewalls of the vias will be different. But it
does not matter as long as you have a continuous film. The dep rate in the long
throw process is much lower than the conventional sputtering.

  Best of luck.

Isibhakhomen Umolu Abhulimen  wrote:
  Sorry All,

It was a mistake, I meant PVD not PECVD. I have tried sputtering over 1.5um on
the top surface but still no Cu seed layer at the bottom of the via.

Isi