Abstract
A new Au-Ge die attachment system for next-generation SiC power electronics is proposed that is capable of withstanding both higher junction temperatures Tj and greater ΔTj cycle stress. In this system, a Au-Cu fine anchor structure is skillfully formed at the surface of the Cu conductor on a SiN ceramic substrate. In addition, the usual Cu conductor is replaced with a Cu/Invar/Cu (thickness ratio of 1/8/1) clad plate, comparable in coefficient of thermal expansion (CTE) to an SiC die. The anchors effectively prevent power chip delamination caused by the progress of thermochemical reactions among the Au-Ge layer, Cu conductor, plated Ni and air. The application of the CIC clad plate significantly reduces Au-Ge die attachment fatigue caused by repetitive thermal stress during thermal cycling. A storage test and a thermal cycle test were conducted for 3000 hours at Tj > 250°C and 3000 cycles at ΔTj > 290°C, respectively. It was found that the new attachment system maintained ample joint strength even after rigorous reliability testing.
