Excimer laser patterning of a novel resist using masked and maskless process steps

摘要

A dual layer resist configuration is employed for photopatterning high resolution conductive patterns on underlying polymeric or ceramic substrates, particularly substrates exhibiting surface roughness and non- planar design features such as channels, bosses and ridges. More particularly, a thin underlayer of ablatable photoabsorptive polymer is disposed on a metal coated substrate, after which a thicker layer of substantially transparent material is disposed over the polymer. A beam of laser energy, such as that produced by an ultraviolet excimer layer, is directed through the upper layer and is absorbed by the lower layer which is ablated and simultaneously removes the thick layer above it. This results in the ability to etch high resolution features on polymeric and other substrates, particularly copper coated polyetherimide circuit boards. The resist system is also applicable to VLSI wafers even though such wafers usually do not exhibit surface roughness on the scale generally considered herein. It is also equally applicable in various high density interconnect systems used for the direct connection of chip devices. A mask for patterning and a method for making it are also seen to be desirable because of the high laser energy densities generally desired for thorough ablation. An alternate method is also disclosed which employs two laser exposure steps with the first step being a masked operation on only an ablatable layer and with the second step being an unmasked operation on a dual layer material.