Cool Interconnect: A 1024-bit Wide Bus for Chip-to-Chip Communications in 3-D Integrated Circuits

In this paper, we present “Cool Interconnect,” a 1024-bit wide bus that we have developed to provide a standardized method of interconnecting chips in 3-D integrated circuits (3DICs). This wide bus chip-to-chip interconnect can be used to realize low-power high-performance multicore systems to meet the increasing demand for advanced electronics to enable autonomous vehicles and Internet of Things devices. The bus has been implemented using a $40\times 40$ fine-pitch array of through-silicon vias and bump joints. In addition, we have developed a testing methodology based on the boundary scan method to confirm the electrical performance of wide bus chip-to-chip interconnect in 3DICs. Cool Interconnect test chips were designed, fabricated, and flip-chip stacked. Joint Test Action Group (JTAG) and electrical connection tests were used to confirm the successful operation of the test chips, including the chip-to-chip interconnect.