Investigation of Ge nanocrytals in a metal-insulator-semiconductor structure with a HfO₂/SiO₂stack as the tunnel dielectric

Abstract

A metal-insulator-semiconductor (MIS) structure containing a HfO₂control gate, a Ge nanocrystal-embedded HfO₂dielectric and a HfO₂/SiO₂stack layer as tunnel oxide, was fabricated by an electron-beam evaporation method. High-resolution transmission electron microscopy study revealed that the HfO₂/SiO₂stack layer minimized Ge penetration, leading to the formation of Ge nanocrystals that are self-aligned between the tunnel oxide and the capping HfO₂layer. Influence of different annealing conditions on the formation and distribution of Ge nanocrystals was studied. Current–voltage (I–V) and capacitance–voltage (C–V) measurements revealed promising electrical characteristics of the MIS structure, and relatively high stored charge density of 10¹² cm⁻² was achieved.