P A P E R    T I T L E
A Design of Experiments Approach to BCB Etch Uniformity Improvements

A U T H O R  /  C R E D I T S
Wayne Bell and Heinz Nentwich
Nortel Networks, P.O. Box 3511, Station "C"
Ottawa, Ontario    Canada, K1Y-4H7
Email: wbell@nortelnetworks.ca

A B S T R A C T
Nortel Networks GaInP/GaAs HBT process , employs a bisbenzocyclobutene (BCB) intermetal dielectric, chosen for it's excellent planarization and dielectric properties. During a 3" to 4" conversion of the GaAs HBT production facility, the existing 3" etch conditions for the BCB etch using CF4/O2 in an Ar carrier gas were found to produce inadequate uniformity control on the 4" wafers. A program was initiated to improve etch uniformity using a Design of Experiments (DOE) methodology. Since there was already a strong starting point for the experiments (the etch conditions used in the 3" process), the approach was to use a response surface method (RSM) to optimize the existing 3" conditions for 4" wafers, forgoing the screening type experiments that would normally be required for a new process. As a result of the experiments, etch uniformity improved from ~14% to ~6%.