The Investigation of 3D Embedded Microchannel Networks for 3D IC Cooling, Vacuum Packaging and THz Passive Device Applications

This Paper reports the design, simulation and test of 3D microchannel networks intended for the 3D IC stackup cooling, vacuum building and even THz passive device applications. Recently, the prominent advantages of 3D IC integration, including reduction in system size, interconnect delay, power dissipation and enabling hyper-integration of chips from disparate process technologies, have drive the relentless research effort worldwide. Although various low-power methodologies are exploited, rapid increasing in device packing density in 3D stacking of chips have demanded revolutionary heat removal technologies, as high performance chips projected to dissipate more than 100W/cm² and require more than 100A of supply current are frequently integrated. Besides, high data rate and bandwidth interconnects are urgently needed as an efficient data transfer backbone between the chips comprising 3D ICs. To address these limits, the authors investigated 3D microchannel networks with various layouts such as fractal tree, which is embedded into stackup structures for highly efficient cooling, and as THz (terahertz) range waveguides. The 3D microchannel networks, with water as working medium are designed and simulated with computational fluidic dynamic methodology, which reveals both the flow and temperature fields and verifies their effectiveness in 3D stackup structure cooling. The 3D microchannels are further experimentally validated on a fast microsystem prototyping platform based on laminating multiple layers of Low Temperature Cofired Ceramic plates, which is capable of quickly realizing a complex exterior or interior 3D structures, for experimental validation. A testing system is set up, consisting of resistive heating source, temperature pickup device and microfluidic metering pumping devices. The temperature rises for samples with or without 3D microchannels with different configurations under various heat flux are obtained and compared with simulated results. The testing results shows that this embedded microfluidic cooling technique may effectively realized a decrease of around 60 centigrade at a heat flux of 1W/cm² and increase with the flux, confirming the effectiveness of this 3D microchannel in cooling a stackup structure and that of the simulation and modeling. Beside the microchannel, combined with sealed pipe I/O joints may effectively act as a ventilation pumping path for the vacuum buildup, adjustment and vacuum level inspection for 3D IC vacuum packaging. In addition, the authors present the investigations of the conceptional design of waveguide and functional structures operating at terahertz frequencies, together with the simulation results which demonstrate the prosperity of this simple structure for high data rate transmission in 3D IC stackups.