Novel Electrical and Fluidic Microbumps for Silicon Interposer and 3-D ICs

Fine-pitch electrical microbumps (25-μm diameter and 50-μm pitch) and annular-shaped fluidic microbumps (150-μm inner diameter and 210-μm outer diameter) are presented to enable high-bandwidth die-to-die signaling, embedded microfluidic cooling and power delivery for silicon interposer and 3-D integrated electronic systems. Electrical and fluidic testing demonstrates good bonding of the electrical and fluidic microbumps; the average resistance of a single electrical microbump is 13.5 mQ. The bonded fluidic microbumps are successfully tested up to 100 kPa without any leakage. Moreover, the power supply noise (PSN) of 3-D chip stacks is analyzed using a compact physical model. Based on the model, increasing the number of power/ground pads is effective in suppressing PSN, motivating the need for fine-pitch electrical microbumps. Impact of the number of dice in a stack, die thickness, and the area of on-die decoupling capacitors on PSN is also investigated.