Improvement in Joint Reliability of SiC Power Devices by a Diffusion Barrier Between Au-Ge Solder and Cu/Ni(P)-Metalized Ceramic Substrates

Abstract

The long-term joint reliability of SiC power devices bonded on a ceramic substrate metalized with copper (Cu) and electroless nickel-phosphorus [Ni(P)] using a gold-germanium (Au-Ge) eutectic solder was investigated at 330°C in air. Rapid growth of Ni-Ge intermetallic compounds (IMCs) at the solder/Ni(P) interface and subsequent oxidation of the conductive Cu layer at the IMCs/Cu interface led to a dramatic decrease in bond strength and an increase in the electrical resistance of the joint. To improve the joint reliability, a 250-nm-thick tungsten (W) diffusion barrier (DB) was prepared on the surface of the substrate using a sputtering process. SiC Schottky barrier diode (SBD) power devices were then die-bonded to the W-DB-modified substrate with the Au-Ge eutectic solder using a vacuum reflow system. The bonded samples were aged at 330°C in air. After 1600 h, the joint strength was two times higher than that on the W-DB-free substrate, and no change was observed in the electrical resistance.

Experimental investigation and thermodynamic modeling of the Au–Ge–Ni system

“…[10]. Among various Au-based alloys, Au-Ge-based alloys are very attractive as possible high temperature Pb-free solders because of their good wettability and high bonding strength with the substrate materials (e.g., Cu and Ni) [11,12]. In order to better understand the interaction mechanism of the Au-Ge solders with the normally used substrate Ni to facilitate solder design and processing optimization, phase equilibria and thermodynamic properties of the Au-Ge-Ni system are indispensable.…”

高温領域まで拡張した高信頼SiCダイアタッチメント

“…12 An X-ray transmission image of a Au-Ge die attachment on CICSiN substrate having anchor (dark line) structure.…”

Wetting Behavior of Ternary Au-Ge-X (X = Sb, Sn) Alloys on Cu and Ni

“…Au-Ge-based alloys have recently become of interest as potential lead-free solders for hightemperature applications. [1][2][3][4] The Au-Ge phase diagram shows the existence of a simple eutectic at 634 K. 5 Besides, Au-Ge-based alloys also possess many interesting properties which are required for high-temperature solders: better thermal conductivity than currently used high-lead-content solders, 6 good corrosion and oxidation resistance in the presence of high humidity at elevated temperatures, tendency for glass forming 7 which eases production of thin foils that are much more convenient to be applied than paste in many applications, low natural radius of curvature for use in miniaturization industry, and excellent biocompatibility and workability for environmental and health considerations.…”