Annealing Induced Interfacial Evolution of Titanium/Gold Metallization on Unintentionally Doped Beta-Ga2O3
Journal Article - Open Access
University of Michigan Ann Arbor United States
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Here, we study the kinetic evolution of the interface between a TiAu metal stack and bulk 010 -Ga2O3 substrate under different annealing conditions using scanning transmission electron microscopy. We observe distinct processes of interfacial reaction and interdiffusion between the metal films and at the metal-semiconductor junction. Upon rapid thermal annealing RTA, the as-deposited Ti readily reacts at the Beta-Ga2O3 interface, driven by redox favorability. After a 1-min 470C N2 RTA, the interface exhibits two segregated crystalline layers a 5 nm Ti-rich Ti-TiOx layer lattice-matched to the -Ga2O3 substrate and a 3 nm Ga-rich TiGaxlayer. A substitutional mechanism is proposed based on the similarity in ionic radii of Ti3, Ti4, and Ga3. After 15-min RTA, the Ga-rich layer is diluted within the Ti-Au matrix, while the Ti-TiOx layer does not significantly change, and there is no further observable Ga out-diffusion from the substrate. Thus, we propose that the Ti-TiOx layer acts as a diffusion barrier, even when it is no longer lattice-matched with -Ga2O3. In addition, Ti-rich nanocrystals form within the Ti-Au layer, presumably via the proceeding reactions. The observations here provide insights for contact stack evolution during operation of power electronic devices at elevated temperature.
- Electrical and Electronic Equipment