Oguz,

The problem with the AZP4620 may be related to the depth of your channels, and
the transparency of the resist.  There are two ways you could solve the problem
if this is the case:

1 - Spray coat resist onto the substrate to create a conformal layer over the
surfaces.  If you need any more details on this, check at
http://www.micromagazine.com/archive/04/03/brubaker.html.

2 - Try a more transparent resist, such as AZ9260.  This has very similar
coating capabilities to AZ4620, but is much more transparent.

Best Regards,
Chad Brubaker