Affect of Anneal Temperature on All-Copper Flip-Chip Connections Formed via Electroless Copper Deposition

Fabrication and Thermo-Mechanical Characterization of Fine Pitch All-Copper Interconnect

“…The phenomenon of seam-consumption during annealing is due to grain-growth and void (trapped hydrogen) diffusion to the surface. Copper recrystallization has been shown to occur, especially at temperatures above 100 • C. 10 The fracture strength of thermocycled samples have been tabulated (Table I). In all cases, failure was observed at either the interface between the pillar and the substrate or in the bonding region.…”

“…4 It was also reported 4 that electroless bonding was achieved for two copper surfaces using a standard alkaline electroless copper bath containing a minimal amount of organic additives. 10 In this paper, we demonstrate the ability to successfully fabricate fine-pitch copper pillars, 25 μm and 15 μm in diameter. Both chip-to-chip and chip-to-substrate connections have been fabricated.…”

“…[2][3][4]10 This novel all-copper bonding method can be used for I/O connections at first-level package.…”

“…In previous studies, we have demonstrated a novel method for bonding two copper pillars by forming an all-copper fillet via electroless deposition and annealing. [2][3][4]10 This novel all-copper bonding method can be used for I/O connections at first-level package.…”

“…The electrical performance and strength of 200 to 250 μm wide copper pillars was assessed. 3,10 Copper bonding shear strength of >165 MPa has been reported after a 180 • C anneal. 4 It was also reported 4 that electroless bonding was achieved for two copper surfaces using a standard alkaline electroless copper bath containing a minimal amount of organic additives.…”