Investigation of Die Top-Side Re-Metallization for SiC-Based Double-Side Cooled Power Modules

The advancement of wide-bandgap (WBG) technology has enabled a new generation of high-density inverters for automotive applications. To fully benefit from WBG devices, like silicon carbide (SiC), there is an increased focus on double-side cooled (DSC) modules with wirebond-less interconnects. To enable wirebond-less interconnects, the die top-side must be solderable or sinterable. Additionally, the quality of die top-side metallization is critical to ensure that interconnects can conduct high currents and dissipate heat. This paper investigates the thin-film deposition process to provide key insights into the challenges of re-metallizing SiC MOSFET for sintered interconnect applications. Key challenges with the re-metallization, including iridescent discoloration, low bond strength, and high contact resistance, are identified and validated. X-ray photoelectron spectroscopy analysis of the dies identifies the presence of organic residue and oxides on the aluminum source pad, which can lead to adhesion challenges. XPS scans of the shadow mask stencils identify electrolytes (sodium and calcium) as a possible source of contamination in the re-metallization fixtures.