Electron spin resonance signature of the oxygen vacancy in HfO<sub>2</sub>

Gillen, Roland; Robertson, John; Clark, S. J.

doi:10.1063/1.4751110

Cited by 21 publications

(8 citation statements)

References 53 publications

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“…36(a) shows the symmetric wavefunction found by LDA. If hybrid functionals such as B3LYP or SX are used instead, these methods find a more localised wavefunction and lower symmetry defect, as seen in Fig 36(b), and this is now consistent with the experimental ESR signature [233,208].…”

Section: Hfo 2 Defects: Experimental Observationssupporting

confidence: 62%

High-K materials and metal gates for CMOS applications

Robertson

Wallace

2015

Materials Science and Engineering: R: Reports

614

367

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The scaling of complementary metal oxide semiconductor (CMOS) transistors has led to the silicon dioxide layer used as a gate dielectric becoming so thin that the gate leakage current becomes too large. This led to the replacement of SiO 2 by a physically thicker layer of a higher dielectric constant or 'high-K' oxide such as hafnium oxide. Intensive research was carried out to develop these oxides into high quality electronic materials. In addition, the incorporation of Ge in the CMOS transistor structure has been employed to enable higher carrier mobility and performance. This review covers both scientific and technological issues related to the high-K gate stack-the choice of oxides, their deposition, their structural and metallurgical behaviour, atomic diffusion, interface structure, their electronic structure, band offsets, electronic defects, charge trapping and conduction mechanisms, reliability, mobility degradation and oxygen scavenging to achieve the thinnest oxide thicknesses. The high K oxides were implemented in conjunction with a replacement of polcryslliane Si gate electrodes with metal gates. The strong metallurgical interactions between the gate electrodes and the HfO 2 which resulted an unstable gate threshold voltage resulted in the use of the lower temperature 'gate last' process flow, in addition to the standard 'gate first' approach. Work function control by metal gate electrodes and by oxide dipole layers is discussed. The problems associated with high K oxides on Ge channels are also discussed. Glossary ALD atomic layer deposition CB conduction band CBO conduction band offset CMOS complimentary metal oxide semiconductor CNL charge neutrality level CV capacitance voltage CVD chemical vapour deposition DB dangling bond DOS density of states EA electron affinity ECT equivalent capacitance thickness EOT equivalent oxide thickness ESR electron spin resosnance EWF effective work function FET field effect transistor GGA generalised gradient approximation LDA local density approximation MEIS medium energy ion scattering MIGS metal induced gap states MOCVD metla organic chemical vapour deposition MOS metal oxide semiconductor MOSFET metal oxide semiconductor field effect transistor MOx arbitrary metal oxide NMOS n-type MOS PMOS p-type MOS RCS remote Coulombic scattering RPS remote phonon scattering SBH Schottky barrier height TAT trap assisted tunnelling T inv inversion thickness Vt threshold voltage (of FET) Vfb flat band voltage VB valence band VBO valence band offset WF work function

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Section: Hfo 2 Defects: Experimental Observationssupporting

confidence: 62%

High-K materials and metal gates for CMOS applications

Robertson

Wallace

2015

Materials Science and Engineering: R: Reports

614

367

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“…The assignment of the oxygen vacancy defect centers was tentative due to a lack of agreement in the g-tensor experimentally observed and the values predicted by theory for an oxygen vacancy. However, as recently pointed out and demonstrated by Gillen et al, 95 this could be a result of a not so well-known error in density functional theory calculations, where the calculated wavefunctions for a defect center are overly delocalized. For other bulk high-k dielectrics such as Al 2 O 3 , oxygen vacancy defect centers have apparently only been observed by ESR for gamma-and neutronirradiated sapphire crystals.…”

Section: Introductionmentioning

confidence: 90%

Detection of surface electronic defect states in low and high-k dielectrics using reflection electron energy loss spectroscopy

French

King

2013

J. Mater. Res.

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The continuation of Moore's law requires new materials at both extremes of the dielectric permittivity spectrum and an increased understanding of the fundamental mechanisms limiting their electrical reliability. To address the latter, reflection electron energy loss spectroscopy has been utilized to measure the band gap of various oxide-based low and high dielectric constant (k) materials of interest to the semiconductor industry. In situ Ar 1 sputtering has been additionally utilized to simulate process-induced defect states that are believed to contribute to electrical leakage, time-dependent dielectric breakdown, charge trapping, and other fixed-charge reliability issues in nano-electronic devices. It is observed that Ar 1 sputtering predominantly generates surface oxygen vacancy defects in the upper portion of the band gap for both low and high-k dielectric materials. These results are in agreement with numerous theoretical investigations of defects in low and high-k dielectric materials and models for mechanisms that limit their reliability.

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“…Yet, recent work has demonstrated two kinds of deep electron traps in HfO2 films which would not implicate O vacancies [9]. Pertinently, as properly outlined by Xiong et al [10] and consolidated later [3,4,[11][12][13][14], theoretical work has conclude that the O vacancy in HfO2 has five possible charge states and can also act as hole trap [3,4,[10][11][12][13][14]; An optimized scheme of the localization of the corresponding energy levels in the HfO2 band gap has been presented by Ramo et al, [3,4] and has been addressed in various other works as well [10,11,14]. Yet, different from their commonplace "culprit" status, oxygen vacancies have also been allotted benign influences as being at the origin of more intriguing physical effects in hafnia.…”

Section: Introductionmentioning

confidence: 99%

Defect correlated with positive charge trapping in functional HfO2 layers on (100)Si revealed by electron spin resonance: Evidence for oxygen vacancy?

Stesmans

Afanasʼev

2017

Microelectronic Engineering

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We report on the results of low-temperature K-and Q-band electron spin resonance (ESR) measurements on three types of device-grade HfO2 films deposited on p-(100)Si by chemical vapor deposition (CVD) using different precursors. The study has been carried out in combination with ex situ contactless charge injection, complemented with various post-growth irradiation treatments, with the intent to assess the presence and atomic nature of occurring charge trapping centers. In HfO2 layers grown by atomic layer (AL) and metal-organic (MO) CVD, this reveals the reproducible appearance of a paramagnetic center, termed H5, in firm correlation with alternate positive/negative charge injection, i.e., distinct signal intensity increase/decrease, respectively. Simulation of the observed powder pattern for both K-and Q-band consistently points to a defect of orthorhombic symmetry characterized by g1=1.880±0.006, g2=1.900±0.006, g3=1.981±0.0015. Analysis based on the inferred spectroscopic ESR characteristics in comparison with previous theoretical work leads to the suggestion that the observed center may concern an O-vacancy defect, closest perhaps to the 4-fold 1+charged O-vacancy (VO4 +). The revealed defect may account, at least partly, for the previously reported distinct propensity of positive charge trapping in Si/hafnia structures grown by ALCVD and MOCVD.

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Electron spin resonance signature of the oxygen vacancy in HfO₂

Cited by 21 publications

References 53 publications

High-K materials and metal gates for CMOS applications

High-K materials and metal gates for CMOS applications

Detection of surface electronic defect states in low and high-k dielectrics using reflection electron energy loss spectroscopy

Defect correlated with positive charge trapping in functional HfO2 layers on (100)Si revealed by electron spin resonance: Evidence for oxygen vacancy?

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Electron spin resonance signature of the oxygen vacancy in HfO2

Cited by 21 publications

References 53 publications

High-K materials and metal gates for CMOS applications

High-K materials and metal gates for CMOS applications

Detection of surface electronic defect states in low and high-k dielectrics using reflection electron energy loss spectroscopy

Defect correlated with positive charge trapping in functional HfO2 layers on (100)Si revealed by electron spin resonance: Evidence for oxygen vacancy?

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Electron spin resonance signature of the oxygen vacancy in HfO₂