GeOx interfacial layer scavenging remotely induced by metal electrode in metal/HfO₂/GeOx/Ge capacitors

Abstract

The metal gate electrodes of Ni, W, and Pt have been investigated for their scavenging effect: a reduction of the GeOx interfacial layer (IL) between HfO₂ dielectric and Ge substrate in metal/HfO₂/GeOx/Ge capacitors. All the capacitors were fabricated using the same process except for the material used in the metal electrodes. Capacitance-voltage measurements, scanning transmission electron microscopy, and electron energy loss spectroscopy were conducted to confirm the scavenging of GeOx IL. Interestingly, these metals are observed to remotely scavenge the interfacial layer, reducing its thickness in the order of Ni, W, and then Pt. The capacitance equivalent thickness of these capacitors with Ni, W, and Pt electrodes are evaluated to be 2.7 nm, 3.0 nm, and 3.5 nm, and each final remnant physical thickness of GeOx IL layer is 1.1 nm 1.4 nm, and 1.9 nm, respectively. It is suggested that the scavenging effect induced by the metal electrodes is related to the concentration of oxygen vacancies generated by oxidation reaction at the metal/HfO₂ interface. Published by AIP Publishing.