Experimental Study of Novel Materials and Module for Cryogenic (4K) Superconducting Multi-Chip Modules

Niobium based superconducting electronics (SCE) are the fastest known digital logic which operate at 100GHz and greater. Nevertheless, the performance of the SCE device depends on the temperature of the SCE integrated circuits being maintained between 4.2 -- 4.25 K. Additionally, as semiconductors are slowly approaching their performance limitations the SCE devices are viewed as a viable alternative for high end computing and commercial wireless applications. However, the successful commercialization of SCE's requires the demonstration of these devices in multichip module (MCM) architecture. Thus the stringent thermal constraint and the complex MCM architecture require an innovative method for thermal management.;This research addressed the above challenges by using a nano-engineered polymer adhesive, namely, single walled carbon nanotube (SWCNT) integrated epoxy as underfill for the packaging of SCE in MCM architecture. The current research distinguished itself by (1) examining the thermal management issues across a single chip SCE-MCM and developing a thermal model based on literature and experimental analysis, (2) developing a new material, namely SWCNT-integrated epoxy whose thermal and electrical performance were analyzed as a function of SWCNT loading and (3) demonstrating the thermal and electrical performance of single chip SCE-MCM test structure and 2D SCE-MCM test structure with SWCNT-epoxy as underfill.;The thermal analysis of the single chip SCE-MCM was studied by modeling, which illustrated that cryogenic underfill with thermal conductivity of 0.04 W/mK plays a vital role in thermal management of SCE-MCMs. A SWCNT-epoxy underfill material which was thermally conductive but electrically insulating was developed and the experimental verification of the thermal model was completed by studying the thermal performance of single chip SCE MCMs with and without SWCNT-epoxy as underfill. It was determined that the heat transport between the SCE chip and SCE carrier chip in MCM architecture was enhanced by the use of SWCNT underfill. Current-Voltage characteristics of Josephson Junctions of SCE chip and carrier bonded using SWCNT underfill were measured at 4.2 K, demonstrating the electrical performance of SCE devices bonded using SWCNT underfill. Finally, 2D SC-MCM was fabricated, and the transition to superconducting state was demonstrated at 4 K with and without SWCNT underfill.