AMI: A new thin film substrate technology

An advanced multilayer interconnect (AMI) technology has been developed. This technology offers high density and low cost multilayer substrates for use in build-up MCM-D/L layers and chip scale packages (CSPs). In the AMI manufacturing process, the multilayer is built up on a planarized substrate material, using nonphotosensitive benzocyclobutene (BCB) as an insulator, and micro-filled aluminum vias. Four major steps are involved in the AMI process: (1) aluminum deposition over a planarized base material; (2) selective conversion of the deposited aluminum oxide, thereby creating lines and via posts; (3) replacement of the previously formed aluminum oxide by BCB; (4) mechanical polishing of the coated BCB to expose the top surface of the aluminum via posts. Steps 1 to 4 are repeated until the required number of layers is achieved. A detailed description of the AMI process steps is given. The key processes of metal deposition, adhesion enhancement, anodization and mechanical polishing are discussed. Reliability test data, typical key features and the electrical performance of an AMI prototype are presented. Particularly noteworthy are the advantages offered by the AMI structure: low production cost and large area panel (LAP) processing capabilities; superior planarity provides higher production yield and facilitates flip chip attachment; high density interconnectivity through the use of stacked and padless via posts; outstanding thermal and electrical properties through the use of filled aluminum vias