Investigating Thick-Film Sintering Technology with Silicon Nitride Substrates for Interconnection

To meet the growing demands of ultra-high-density interconnects (UHDI) and 3D integration, high-performance integrated circuits (ICs) have evolved to impose increasingly stringent demands for ceramic substrates with superior thermal conductivity, electrical insulation, and mechanical robustness. Silicon nitride (Si₃N₄), with its exceptional thermal conductivity, mechanical robustness, and thermal shock resistance, has emerged as a promising alternative to conventional alumina (Al₂O₃) and aluminum nitride (AlN) substrates. Thick-film technology, widely employed in fabricating metal interconnects, resistive networks, and dielectric layers, enables complex electrical interconnections and functional integration on ceramic substrates. However, current thick-film paste sintering processes have been primarily optimized for Al₂O₃ and AlN substrates, encountering substantial challenges when adapted to Si₃N₄ due to its inherently low surface energy and high chemical inertness.This study investigates the feasibility of applying conventional thick-film sintering processes to Si₃N₄ substrates. To evaluate the compatibility of Si₃N₄ with thick-film sintering, resistor, conductor, and dielectric pastes were formulated and subjected to sintering, followed by microstructural characterization. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS) analyses revealed significant challenges, including paste agglomeration, poor wetting and spreading behavior, and excessive porosity formation. The underlying causes of remaining problems in the sintering process of thick film pastes for Si3N4 are analyzed. The findings pave the way for future efforts to optimize paste formulations and sintering conditions for enhanced reliability in ICs applications.