Plasma-enhanced chemical vapor deposition and characterization of high-permittivity hafnium and zirconium silicate films

Kato, Hiromitsu; Nango, T.; Miyagawa, Takeshi; Katagiri, Takeshi; Seol, Kwang Soo; Ohki, Yoshimichi

doi:10.1063/1.1487911

Cited by 135 publications

(79 citation statements)

References 26 publications

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“…The lack of Hf-Si bonding is expected because deleterious Hf-Si bonding will be energetically unfavorable compared to Si-O bonds at the interface. With the increase in the atom ratio of Si/ ͑Hf+ Si͒ in the precursor solution, it can be clearly seen that the two peaks of Hf 4f electrons show a slight shift toward higher BE side, which is in good agreement with the observation of Kato et al 18 A similar shift in photoemission BE with composition of Hf silicate has also been suggested by Opila et al 19 In all cases, the BE of the Hf 4f is greater for the silicate than for the pure HfO 2 , reaching a shift of 1.2 eV for sample S4. According to the conclusion of Opila et al, 19 the BE shift can be due to the relatively less electron-donating nature of the second-nearest-neighbor silicon relative to hafnium.…”

Section: A Xps Characterizationsupporting

confidence: 80%

Composition dependence of electronic structure and optical properties of Hf1−xSixOy gate dielectrics

Zhang

Guo

et al. 2008

Journal of Applied Physics

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Composition-dependent electronic structure and optical properties of Hf 1−x Si x O y ͑0.1Յ x Յ 0.6͒ gate dielectrics on Si at 450°C grown by UV-photo-induced chemical vapor deposition ͑UV-CVD͒ have been investigated via x-ray photoemission spectroscopy and spectroscopy ellipsometry ͑SE͒. By means of the chemical shifts in the Hf 4f, Si 2p, and O 1s spectra, the Hf-O-Si bondings in the as-deposited films have been confirmed. Analyses of composition-dependent band alignment of Hf 1−x Si x O y / Si gate stacks have shown that the valence band ͑VB͒ offset ͑⌬E v ͒ demonstrates little change; however, the values of conduction band offset ͑⌬E c ͒ increase with the increase in the silicon atomic composition, resulting from the increase in the separation between oxygen 2p orbital VB state and antibonding d states intermixed of Hf and Si. Analysis by SE, based on the Tauc-Lorentz model, has indicated that decreases in the optical dielectric constant and increase in band gap have been observed as a function of silicon contents. Changes in the complex dielectric functions and band gap E g related to the silicon concentration in the films are discussed systematically. From the band offset and band gap viewpoint, these results suggest that Hf 1−x Si x O y films provide sufficient tunneling barriers for electrons and holes, making them promising candidates as alternative gate dielectrics.

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Section: A Xps Characterizationsupporting

confidence: 80%

Composition dependence of electronic structure and optical properties of Hf1−xSixOy gate dielectrics

Zhang

Guo

et al. 2008

Journal of Applied Physics

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“…When the composition of the IL becomes more Hf rich, the BE peak shifts to lower values because of the replacement of a Si atom by a Hf atom, which is more electropositive. 8,9 Therefore, from Fig. 2 it can be concluded that in the course of the deposition the RTO starting surface becomes more Hf rich and hence is transformed from a SiO 2 into a Hf-silicate layer, as was suggested by Fig.…”

Section: Resultsmentioning

confidence: 89%

Composition and Growth Kinetics of the Interfacial Layer for MOCVD HfO[sub 2] Layers on Si Substrates

Elshocht

Caymax

Gendt

et al. 2004

J. Electrochem. Soc.

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To boost MOS transistor performance, thickness of the gate dielectric is continuously scaled down. This results in an increase of gate tunneling leakage current, which at some point prevents further downscaling. Desired parameters of alternative materials to SiO 2 are a higher dielectric constant ͑high-k materials͒, stability, and compatibility with silicon. A general observation for one of the prime candidates, HfO 2 , is formation of an interfacial layer between the silicon and the high-k material that limits scalability because of its low k-value. Hence, a thorough study of the formation of this layer and its contribution to the equivalent oxide thickness is of utmost importance. We studied the composition and growth kinetics of the interfacial layer formed during the deposition of HfO 2 by metallorganic chemical vapor deposition using O 2 and tetrakis-diethylamidohafnium as precursor. We found the composition and thickness of the interfacial layer to be dependent on the deposition parameters as well as on the starting surface. The layer's composition is hafnium silicate-like and its thickness increases as a function of deposition time and temperature. It is therefore controlled by deposition of the HfO 2 layer. SiO 2 has been used for decades as the gate isolator material in complementary metal-oxide semiconductor ͑CMOS͒ technology. Downscaling of the gate dielectric to improve device performance is reaching physical limits where the gate material consists of only a few atomic layers, resulting in unacceptably high leakage currents.1 Reducing the leakage current through nitridation prolongs the lifespan of SiO 2 , 2 but according to the International Technology Roadmap for Semiconductors ͑ITRS͒, industry will from 2005 on abandon SiO 2 as a gate material and start replacing it with materials having a higher dielectric constant ͑high-k materials͒. 3 The urgent need for these new materials has resulted in extensive research on several high-k candidates, such as Al 2 O 3 , ZrO 2 , HfO 2 , ZrSiO x , HfSiO x , etc. At present, Hf-based materials are the most likely candidates.Si and SiO 2 as a gate material are chemically perfectly compatible, which was, among others, one of the reasons for choosing Si and for the success of the silicon semiconductor industry. For high-k materials possible interactions between Si ͑both substrate and polySi electrode͒ and the high-k material are an additional concern needing to be addressed. For example, these interactions can result in silicide formation at the high-k/polysilicon interface, as has been observed for ZrO 2 . 4 In addition, there is also an important difference in processing; whereas SiO 2 as gate dielectric is grown simply by oxidation of the silicon substrate, high-k materials have to be deposited. Such deposition is not straightforward and it has been found that the deposition behavior of a high-k layer can be highly dependent upon the starting surface.5 Moreover, we have observed that metallorganic chemical vapor deposition ͑MOCVD͒ of HfO 2 on various starting s...

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“…Among these possible energy loss processes, we conclude that these onsets are attributable to the electron-hole excitation because the values for the samples without nitrogen agreed with the optical band gap energies estimated previously. 18 As illustrated in Fig. 2, the band gap energies tend to decrease as C N increases and show abrupt changes between 10 and 20 at.%.…”

Section: Resultsmentioning

confidence: 95%

Dielectric properties of noncrystallineHfSiON

et al. 2006

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The dielectric properties of noncrystalline hafnium silicon oxynitride (HfSiON) films with a variety of atomic compositions were investigated. The films were deposited by reactive sputtering of Hf and Si in an O, N, and Ar mixture ambient. The bonding states, band-gap energies, atomic compositions, and crystallinities were confirmed by X-ray photoelectron spectroscopy (XPS), reflection electron energy loss spectroscopy (REELS), Rutherford backscattering spectrometry (RBS), and X-ray diffractometry (XRD), respectively. The optical (high-frequency) dielectric constants were optically determined by the square of the reflective indexes measured by ellipsometry. The static dielectric constants were electrically estimated by the capacitance of Au/HfSiON/Si (100) structures. It was observed that low N incorporation in the films led to the formation of only Si-N bonds without Hf-N bonds. An abrupt decrease in band-gap energies was observed at atomic compositions corresponding to the boundary where Hf-N bonds start to form. By combining the data for the atomic concentrations and bonding states, we found that HfSiON can be regarded as a pseudo-quaternary alloy consisting of four insulating components: SiO 2 , HfO 2 , Si 3 N 4 , and Hf 3 N 4 .The optical and static dielectric constants for the films showed a nonlinear dependence on the N concentration, whose behavior can be understood in terms of abrupt Hf-N bond formation.

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Plasma-enhanced chemical vapor deposition and characterization of high-permittivity hafnium and zirconium silicate films

Cited by 135 publications

References 26 publications

Composition dependence of electronic structure and optical properties of Hf1−xSixOy gate dielectrics

Composition dependence of electronic structure and optical properties of Hf1−xSixOy gate dielectrics

Composition and Growth Kinetics of the Interfacial Layer for MOCVD HfO[sub 2] Layers on Si Substrates

Dielectric properties of noncrystallineHfSiON

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