Plasma etching of thick polynorbornene layers for electronic packaging applications

Abstract

The etch characteristics of thick (>20 μm) polynorbornene films used as insulators in chip-to-board interconnection structures were studied in O2/CHF3-based plasmas. Two polynorbornene materials were investigated in this study: one with an epoxy substituent and the other with a silicon substituent. The effects of processing parameters such as radio-frequency (rf) power, chamber pressure, flow rate, gas composition, and mask material on polymer etch rate and via sidewall angle were investigated. The etch rate increased with rf power and chamber pressure. An increase in the CHF3/O2 ratio gave a maximum etch rate at ∼10% CHF3 for the epoxy-containing polynorbornene and at ∼20% CHF3 for the Si-containing polynorbornene. The etch rate decreased with total flow rate in O2/CHF3 plasmas but did not change substantially with flow rate in O2 plasmas. The sidewall angle was strongly affected by rf power and chamber pressure.