High-Density Microvia Technology on Advanced Organic Substrate For Next Generation Flip-Chip Packaging

摘要

Meeting the requirements of increasing IC integration and transistor density continues to challenge those involved in package substrate and interconnect technologies. For 45nm-node IC interconnections to area array packages, an I/O pitch of 90μm is required, according to the latest ITRS and iNEMI roadmaps [1,2]. With the projected introduction of 32nm and 22nm IC nodes by 2010, a 20-50μm I/O pad pitch on the IC will necessarily require matching dimensions on the flipchip substrate. Any additional package level integration, such as embedded components, will likely escalate the interconnection demand in the substrate. Sequential build-up organic substrates have been able to meet the wiring demand since their introduction in the early 1990s. However, with the dramatic miniaturization and performance improvement sustained by semiconductor segment, there is a major need to significantly reduce the interconnection dimensions on the package substrate in a relatively short time. In addition to conductor line and space widths, the wiring pitch on the substrate is largely determined by microvia diameter, as well as its capture pad and landing pad diameter. Current state-of-the-art microvia substrates are typically achieving line and space dimensions of 15-20μm with microvia diameters in the range of 60-75μm. The forecasted substrate wiring pitch of 20- 50μm requires multiple layers of materials and high-precision processes for the necessary line/space and microvia dimensions. At this dimensional level, creating the copper interconnects necessary to maintain signal integrity requires materials and process technologies beyond those conventionally used. The build-up dielectric materials are one area where such improvements are currently directed. Equally important are the improved copper plating, photo-imaging, etching and adhesion enhancement technologies that will be required to fabricate such ultrahigh-density organic build-up substrates. This paper presents results from a collaborative research effort focused on fabrication of the next generation of multilayer build-up organic substrates for flip chip applications. Using a new epoxybased dielectric film in combination with state-of-the-art copper electroplating technology, the ability to laser ablate, metalize and fill sub-50μm diameter microvias is demonstrated. Unlike conventional solvent-based materials, this advanced dielectric is the result of the latest developments in epoxy resin-coated copper foil (RCF), using a novel and patented Advanced Dry Epoxy Powder Technology (ADEPT) process for a halogen-free system. In addition, methodologies for forming and filling such microvias, including advanced dielectric metallization and plating techniques are described.