Defects in HfO 2 Based Dielectric Gate Stacks
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1155-C12-01
Defects in HfO2 Based Dielectric Gate Stacks Patrick M. Lenahan1, Jason T. Ryan1, Corey J. Cochrane1, and John F. Conley Jr.2 1
The Pennsylvania State University, University Park, PA 16802, U.S.A
2
Oregon State University, Corvallis, OR 97331, U.S.A
ABSTRACT We report on both conventional electron paramagnetic resonance (EPR) measurements of fully processed HfO2 based dielectric films on silicon and on electrically detected magnetic resonance (EDMR) measurements of fully processed HfO2 based MOSFETs. The magnetic resonance measurements indicate the presence of oxygen vacancy and oxygen interstitial defects within the HfO2 and oxygen deficient silicons in the interfacial layer. The EDMR results also indicate the generation of at least two defects when HfO2 based transistors are subjected to significant negative bias at modest temperature. Our results indicate generation of multiple interface/near interface defects, likely involving coupling with nearby hafnium atoms. INTRODUCTION Tremendous progress has been made towards replacing conventional (SiO2 and SiOxNy) gate dielectrics with HfO2 based materials in high performance metal-oxide-silicon (MOS) field effect transistors (MOSFETs) [1, 2]. However, there are many challenges in the integration of these materials into MOS technology. Critical issues include: trapping in HfO2 [3, 4], trapping in the interfacial layer dielectric between the silicon and the HfO2 [5, 6], silicon/dielectric interface traps [1] and various instabilities which may involve either the generation of new traps or the population of existing traps or both of these processes [7]. Magnetic resonance techniques, such as conventional electron paramagnetic resonance (EPR) or electrically detected magnetic resonance (EDMR) techniques such as spin dependent recombination (SDR), are the most powerful tools currently available to identify the structure of these trapping centers [8]. The technique is generally sensitive to paramagnetic defects. (Nearly all electrically active defects can be rendered paramagnetic.) Information about the local structure of trapping defects can be gleaned from the relationship between the magnetic field and microwave frequency at which resonance occurs. In the simplest of cases, the resonance condition is given by [8], hν = gβH,
(1)
where h is Planck’s constant, ν is the microwave frequency, β is the Bohr magneton, H is the magnetic field and g is number, typically close to 2, which depends upon the relationship between the defect’s orientation and the magnetic field vector. The g is expressed in terms of a matrix which is often called the g tensor. (This simple relationship is often altered by the presence of nearby magnetic nuclei and other factors which will not be particularly relevant for the results presented in this paper.)
HfO2 DEFECTS
ESR Intensity (Arb. Units)
At least two intrinsic defects have been observed in magnetic resonance observations of HfO2 films on silicon: oxygen vacancies and oxygen interstitials. Kang et al.[9] and Ryan et al [10
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