3D integration-past, present and future

This paper presents an overview of the fine pitch transfer and joining (T&J) method for 3D device integration. T&J fine pitch transfer and joining technology was originally developed for IBM high-end G5 multi-chip-module (MCM-D) to enable the enhanced wiring density needs. The method enables processing and handling of an ultra thin functional layer such as a dense wiring stack or a MEMS device on a temporary carrier, joining to connect and secure the ultra thin media to a permanent base substrate and the releasing of the temporary carrier. This method has been demonstrated in a wide range of applications, including multi-chip and single-chip modules (MCM/SCM), in chip-to-wafer and wafer-to-wafer 3DI thru-via integration (3DI) for micro-electro-mechanical systems (MEMS) and in micro-opto-electro system (MOES) for hybrid devices. The salient unit process elements of the T&J technology and the process commonality that underpins the wide range of applications made possible with T&J will be reviewed. Potential extendibility of T&J for 3D integration of microelectronic device layers will also be discussed.