Probing semiconductor/insulator heterostructures through electron spin resonance of point defects: Interfaces, interlaye
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Probing semiconductor/insulator heterostructures through electron spin resonance of point defects: Interfaces, interlayers, and stress A. Stesmans, K. Clémer, P. Somers, and V. V. Afanas'ev Department of Physics, Semiconductor Physics Laboratory, INPAC, University of Leuven, Celestijnenlaan 200 D, Leuven, 3001, Belgium
ABSTRACT Electron spin resonance (ESR) spectroscopy has become indispensable when it comes to the characterization on atomic-scale of structural, and correlated, electrical properties of actual semiconductor/insulator heterostructures. Through probing of paramagnetic point defects such as the 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 containing these defects can be established. This is illustrated by some specific examples of ESR analysis on contemporary Si/insulator structures promising for future developments in integrated circuits. First the impact of strain on the Si/SiO2 entity will be discussed. Through ESR analysis of thermally oxidized (111)Si substrates mechanically stressed in situ during oxidation, and tensile strained (100)sSi/SiO2 structures, it will be pointed out that in-plane tensile stress in Si can significantly improve the interface quality. Next, ESR results for stacks of (100)Si/SiOx/HfO2 and (100)Si/LaAlO3 are presented, revealing the potential to attain a high quality Si/SiO2 interface for the former and an abrupt, thermally stable interface for the latter. INTRODUCTION In semiconductor industry, the metal-oxide-semiconductor field effect transistor (MOSFET) based on the Si/SiO2 entity has been the dominant device for large scale integrated circuits for decades, on account of the high quality of the native oxide of Si, SiO2, and the superior interface between Si and SiO2. The performance and reliability of these devices are heavily influenced by the quality and properties of the oxide/semiconductor interface, in particular by the presence of electrical traps located at or near the Si/SiO2 interface [1]. Therefore it may appear quite natural that assessing the nature of these traps, on atomic level, is vital for understanding and making progress. This urge becomes even more pertinent as down-scaling of the MOSFETs ever enhances the relative influence of the interface/interlayer quality on device performance [2-4]. Despite the fact that ESR can only assess defects in a paramagnetic state, in correlation with electrical measurements, the technique has proven to be the most adequate technique to asses the atomic nature and origin of occurring point defects [5-9].
The prototype example is the Si/SiO2 structure, for which 3 variants of interface defects could be identified on atomic level by ESR [5-7]. These so-called Pb-type defects, whose appearances are dependent on the particular Si substrate surface orientation, are inherently incorporated at the Si/SiO2 interface as a result of the lattice mismatch bet
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