Process compatibility of conventional and low-temperature curable organic insulation materials for 2.5D and 3D IC packaging — A user's perspective

For 2.5D and 3D IC packaging, wafer back side processing often has temperature limits substantially lower than curing temperature of conventional polyimide (PI). New low temperature curable insulation materials possess very different properties and require thorough evaluation to ensure process compatibility and product reliability. In this work, we present a set of evaluation methods that can be used to compare materials and curing processes against bench mark materials and against each other, to facilitate optimal materials selection, minimize cost, and shorten development cycle time. We also evaluated conventional PI cured in a Variable Frequency Microwave (VFM) oven, which achieved comparable properties at lower temperature compared with conventional curing.