Probing defects at interfaces and interlayers of low-dimensional Si/insulator (HfO2; LaAlO3) structures by electron spin resonance

Abstract

Electron spin resonance (ESR) spectroscopy enables to assess on atomic scale the nature and structural aspects of interfaces and interlayers in semiconductor/insulator hetero structures. This has been applied to (1 0 0)/insulator entities with nm-thin amorphous layers of HfO2 and LaAlO3 of high dielectric constant (>12) grown on clean (1 0 0)Si by atomic layer chemical vapor deposition and molecular beam deposition, respectively. Through analysis and monitoring of the occurring embedded paramagnetic point defects, including Pb-type defects, E′, and EX, as a function of VUV irradiation and post-deposition heat treatment, basic information as to the nature, quality, and thermal stability of the interface and interfacial regions has been attained. On the basis of the analysis of Pb-type defects (Pb0, Pb1), archetypal for the Si/SiO2 interface, the (1 0 0)Si/LaAlO3 stack is found to be truly abrupt, i.e., no evidence for an Si/SiO2(x)-type transition in contrast with the Si/HfO2 entity, where the interface is found to be Si/SiO2(x) type in the as-grown state. Analysis as a function of post-deposition heating indicates the Si/LaAlO3 interface to remain stable and abrupt up to Tan∼800 °C, above which an Si/SiO2-type interface develops, while that in Si/HfO2 evolves to one of closely standard Si/SiO2 quality, with an SiO2 interlayer of good quality. The differences in behavior of the studied Si/insulator stacks are discussed in a comparative analysis. © 2007 Elsevier B.V. All rights reserved.