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Feng Zhu,
Chang Yong Kang,
Se Jong Rhee, Chang Hwan Choi,
Siddarth A. Krishnan,
Manhong Zhang,
Hyoung-Sub Kim,
Taekhwi Lee,
Injo Ok,
Gaurav Thareja,
Jack C. Lee
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ABSTRACT: Stacked Y <sub>2</sub> O <sub>3</sub>/ Hf O <sub>2</sub> gate dielectric, compared to Hf O <sub>2</sub> , shows significantly enhanced electron channel mobility at different temperatures. This mobility improvement can be attributed to reduced remote phonon scattering, which is associated with the smaller ionic polarization of Y <sub>2</sub> O <sub>3</sub> , and the suppressed Coulomb scattering due to less electron trapping in the bulk of high- κ layer and reduced metal impurities in the substrate.
Applied Physics Letters 11/2006; · 3.84 Impact Factor
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ABSTRACT: High- k hafnium oxide dielectric metal-oxide-semiconductor field-effect transistors with several physical thicknesses of silicon oxynitride interfacial layers were investigated to understand the relationship of their effects to electrical properties. Both flatband voltage and threshold voltage were negatively shifted with reduction of leakage current density as the thickness of silicon oxynitride interfacial layer increased. Charge pumping measurement revealed that the density of interface states were proportional to the physical thickness of the interfacial layer. The large amount of positive charge and interface state density for the thick interfacial layer affected the effective channel electron mobility, resulting in 20% of low-field peak mobility degradation. In addition, less stress immunity under stress was observed when silicon oxynitride interfacial layer increased.
Applied Physics Letters 05/2006; · 3.84 Impact Factor
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ABSTRACT: A novel approach of fabricating laminated TiO<sub>2</sub>/HfO<sub>2</sub> bilayer multimetal oxide dielectric has been developed for high-performance CMOS applications. Ultrathin equivalent oxide thickness (∼8 Å) has been achieved with increased effective permittivity (k∼36). Hysteresis was significantly reduced using the bilayer dielectric. Top TiO<sub>2</sub> layer was found to induce effective negative charge from the flatband voltage shift. Leakage current characteristic was slightly higher than control HfO<sub>2</sub>, and this is believed to be due to the lower band offset of TiO<sub>2</sub>. However, the interface state density of this bilayer structure was found to be similar to that of HfO<sub>2</sub> MOSCAP because the bottom layer is HfO<sub>2</sub>. These results demonstrate the feasibility of new multimetal dielectric application for future CMOS technology.
IEEE Electron Device Letters 05/2006; · 2.85 Impact Factor
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Feng Zhu,
Se Jong Rhee,
Chang Yong Kang, Chang Hwan Choi,
M.S. Akbar,
S.A. Krishnan,
Manhong Zhang,
Hyoung-Sub Kim,
Tackwhi Lee,
I. Ok,
J.C. Lee
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ABSTRACT: A stacked Y<sub>2</sub>O<sub>3</sub>/HfO<sub>2</sub> multimetal gate dielectric with improved electron mobility and charge trapping characteristics is reported. Laminated hafnium and yttrium were sputtered on silicon followed by post-deposition anneal (PDA) in N<sub>2</sub> ambient. The new dielectric shows a similar scalability to HfO<sub>2</sub> reference. Analysis on flatband voltage shift indicates positive fixed charge induced by Y<sub>2</sub>O<sub>3</sub>. Excellent transistor characteristics have been demonstrated. Stacked Y<sub>2</sub>O<sub>3</sub>/HfO<sub>2</sub>, compared to HfO<sub>2</sub> reference with similar equivalent oxide thickness (EOT), shows 49% enhancement in transconductance and 65% increase in the peak electron mobility. These improvements may be attributed to better charge trapping characteristics of the multimetal dielectric.
IEEE Electron Device Letters 01/2006; · 2.85 Impact Factor
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Se Jong Rhee,
Hyoung-Sub Kim,
Chang Yong Kang, Chang Hwan Choi,
Manhong Zhang,
Feng Zhu,
Tackhwi Lee,
Injo Ok,
M.S. Akbar,
S.A. Krishnan,
J.C. Lee
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ABSTRACT: Optimization of TiO<sub>2</sub>/HfO<sub>2</sub> bi-layer dielectric MOSFETs and their breakdown behaviors have been investigated for the first time. As the ratio of TiO<sub>2</sub> top layer increases, reduced EOT, reduced hysteresis, and improved transistor characteristics with increasing electron and hole mobility are observed. Distribution of a two-step breakdown characteristics suggest the breakdown occurs first in the HfO<sub>2</sub> bottom layer.
VLSI Technology, 2005. Digest of Technical Papers. 2005 Symposium on; 07/2005
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ABSTRACT: This Letter reports the nickel-silicide phase effects on the electrical characteristics of high-k and silicon dioxide (SiO2) metal-oxide-semiconductor devices. It was found that the silicon-deficient nickel-silicided gate electrode on the hafnium silicon oxynitride (HfSiON) led to a positive flatband voltage (Vfb) shift and a reduction in the equivalent oxide thickness (EOT). However, negligible Vfb shift and EOT decrease were observed in the case of control hafnium oxide and SiO2 structures. It was believed that Si dissociation from the HfSiON layer was the main reason for the positive Vfb shift and the EOT decrease.
Applied Physics Letters 05/2005; 86(22):222906-222906-3. · 3.84 Impact Factor
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ABSTRACT: In this letter, we present the effects of the nitrogen-incorporated interface on threshold voltage shift (ΔV<sub> th </sub>) , which was induced by charge trapping and detrapping in hafnium oxide ( Hf O <sub>2</sub>) n -metal–oxide–semiconductor field-effect transistors. Under the various gate voltage conditions, the nitrogen-incorporated interface showed a smaller ratio of interface charge density to total charge density (N<sub> it </sub>/N<sub> total </sub>) due to its thinner interface thickness and lower energy band offset. In addition, the degradations of the interface quality and the mobility under the stress condition were less severe for the nitrogen-incorporated interface devices.
Applied Physics Letters 04/2005; · 3.84 Impact Factor
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Se Jong Rhee,
Hyoung-Sub Kim,
Chang Yong Kang, Chang Hwan Choi,
M.S. Akbar,
Manhong Zhang,
Tackwhi Lee,
Injo Ok,
Feng Zhu,
S.A. Krishnan,
Jack C. Lee
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ABSTRACT: New structural approach of Gd<sub>2</sub>O<sub>3</sub> incorporated HfO<sub>2</sub> multi-metal dielectric n-MOSFETs and their electrical characteristics are investigated for the first time. Among three possible dielectric structures, top Gd<sub>2</sub>O<sub>3</sub> with bottom HfO<sub>2</sub> bi-layer dielectric shows the best EOT and leakage current characteristics. Scaling-down of this Gd<sub>2</sub>O <sub>3</sub>/HfO<sub>2</sub> dielectric result in ultra-thin regime of EOT (between 5Aring and 10Aring) with substantial reduction in leakage current compared to HfO<sub>2</sub>. Also promising MOSFET characteristics with improved output current, transconductance, and channel electron mobility for Gd<sub>2</sub>O<sub>3</sub>/HfO<sub>2</sub> are observed
Device Research Conference Digest, 2005. DRC '05. 63rd; 02/2005
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ABSTRACT: A novel approach of fabricating laminated TiO<sub>2</sub>/HfO<sub>2</sub> bi-layer multi-metal oxide dielectric was developed for high performance CMOS applications. Both layers showed negligible intermixing and no silicide formation. For the first time, ultra-thin EOT (∼8 Å) was achieved with increased effective permittivity (k ∼ 36) using the bi-layer dielectric. Leakage current characteristic was slightly higher than HfO<sub>2</sub> due to lower band offset of TiO<sub>2</sub>. However, superior thermal stability (>950°C), significantly reduced hysteresis characteristic, and comparable interface state density represent the high quality of TiO<sub>2</sub>/HfO<sub>2</sub> multi-metal oxide. Also, excellent subthreshold swing, increased transconductance, higher current drive, and -33% improved channel electron mobility compared to the control HfO<sub>2</sub> samples demonstrate the feasibility of new multi-metal oxide application for future CMOS technology.
Electron Devices Meeting, 2004. IEDM Technical Digest. IEEE International; 01/2005
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ABSTRACT: A metal–oxide–semiconductor capacitor and field effect transistor with a hafnium oxide (HfO2) dielectric have been fabricated. Various thicknesses of interfacial oxide and HfO2 film have been used. The results show that the flatband voltage changed due to the change in the physical thickness of the HfO2 film, and not that of the interfacial oxide layer. In addition, the effective channel electron mobility depends on both the amount of fixed charges and the distance from the fixed charges to the Si surface. The results also suggest that the fixed charges are rather uniformly distributed throughout the bulk of high-k layer.
Applied Physics Letters 08/2004; 85(7):1286-1288. · 3.84 Impact Factor
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ABSTRACT: Threshold voltage instability characteristics of high-k HfO<sub>2</sub> with SiON interface NMOSFETs under three different dynamic stress conditions, positive, negative, and bipolar stress, have been investigated for the first time. Frequency and duty cycle dependencies have been observed in all three conditions. In contrast to positive AC stress, negative dynamic stress showed decrease in the threshold voltage. Bipolar stress resulted in the highest threshold voltage shift, but the degradation in transconductance and subthreshold swing was actually smaller in comparison to those in negative unipolar stress. A plausible mechanism has been proposed.
Device Research Conference, 2004. 62nd DRC. Conference Digest [Includes 'Late News Papers' volume]; 07/2004
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ABSTRACT: We present the threshold voltage instability characteristics of high-k HfO<sub>2</sub> NMOSFET dielectric with SiON interface layer under dynamic stress. Compared to DC stress, reduced threshold voltage shift was observed at higher frequency and lower duty cycle in AC unipolar stress. Similarly, the degradation of maximum transconductance was also reduced with AC stress conditions. However, the degradation in subthreshold swing was found to be negligible and fairly independent of stress frequencies and duty cycles in AC unipolar stress. The traps in bulk of HfO<sub>2</sub> dielectric, which is proportional to its physical thickness, is believed as the primary factor for larger threshold voltage shift as the thickness of HfO<sub>2</sub> increases. Compared to the result under DC constant voltage stress, AC unipolar stress allows higher 10-year lifetime operating voltage.
Reliability Physics Symposium Proceedings, 2004. 42nd Annual. 2004 IEEE International; 05/2004
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ABSTRACT: This letter presents the effects of surface preparation for hafnium-based dielectrics on the bulk carrier generation rates and the carrier mobility. Different surface preparations result in different interfacial layers. Nitrogen-incorporated layers effectively block impurity penetration from hafnium oxide, and lead to the increase of bulk carrier generation lifetime. However, nitrogen-incorporated interface layers increase interface state density and degrade channel mobility, even though bulk carrier generation lifetime is increased. Thus, mobility degradation is preliminarily caused by fixed charge and interface states of the high-k dielectrics. © 2004 American Institute of Physics.
Applied Physics Letters 03/2004; 84(12):2148-2150. · 3.84 Impact Factor
