Process for Etching Minimum-Size Tapered Vias in Polymer Films
Original Publication Date: 1988-Nov-01
Included in the Prior Art Database: 2005-Feb-15
A technique is shown for combining a silylated resist image and a deep ultraviolet resist underlayer to achieve a practical means for producing minimum lithographic images in a thick erodable masking layer over an organic insulator. Current via etch technology relies on reactive ion etch (RIE) of a thick reflowed resist film to achieve tapered vias. The thickness of the resist film is generally 2.5 x the thickness of the polymer thickness due to variations in polymer thickness, thinning of the resist over topological features and a rapid erosion of the resist during the dry etch process. The minimum via size that can be printed and reliably reflowed in resist of this thickness is about 3 um. This is far greater than the 1 um minimum that is achievable with state-of-the-art photo groundrules.