Via etching through extremely thick organic dielectrics

A process for etching vias in extremely thick (85 to 152 /spl mu/m) HD MicroSystems polyimide PI2611 was developed using commercial reactive ion etching tools. Sloped via profiles were obtained using a combination of hard masks made of aluminum and silicon dioxide thin films, combined with reactive ion etch steps in pure O/sub 2/ and O/sub 2//CF/sub 4/. The deep via profiles provided good step coverage. These vias, coated with a 3-/spl mu/m-thick copper film, produced satisfactory electrical continuity between layers of package interconnects. The process is reproducible, reliable, and, hence, practically useful for fabricating a small number of parts in spite of extended etch periods.