Delamination issues in integration of highly filled polymer-ceramic nanocomposite films on MCM-L compatible substrates

The National Electronics Manufacturing Technology roadmap indicates that a capacitance density of 50 nF/cm² will be required in 2001 for successful implementation of integral passive technology. Polymer-ceramic composites are a favorable choice for thin-film capacitors in low-temperature MCM-L technology. Improvement in dielectric properties of the material, achievement of thin and defect-free films and integration on to large area substrates form the cornerstones for this technology. The Packaging Research Center at Georgia Tech. has been actively involved in achieving improved dielectric properties by developing high solids loading and well-dispersed suspensions based on colloidal techniques. The integration of thin-film composites into the subsequent fabrication process becomes increasingly challenging with higher filler content. For example, delamination of the composite from the bottom copper layer has been consistently observed during the modification of composite surface for increasing the adhesion between the electroless copper deposit (top electrode) and composite surface. The surface modification typically involves an etch-treatment with a powerful oxidizing agent such as permanganate. This delamination was not observed in fully cured neat epoxies. The role of fillers in preventing the curing of the epoxy, the reactions between permanganate and uncured epoxy and the lack of adhesion between ceramic and bottom electrode are some of the key issues involved in this delamination problem. This is further complicated by the classic copper-epoxy de-adhesion problem originating from the copper oxide film at the copper-epoxy interface. This work presents our investigation of the origin of this delamination problem by delineating these issues and identifying the key effects. In particular, the role of epoxy curing and filler content based on the interface and epoxy characterization is addressed here. A failure mechanism is proposed from the correlation between epoxy cure and the delamination during etch treatment