Yi-He Tsai

High-Performance Schottky Contact Quantum-Well Germanium Channel pMOSFET With Low Thermal Budget Process

We present a high-performance Si/Ge/Si p-channel metal-oxide-semiconductor field-effect transistor (pMOSFET) with a NiSiGe Schottky junction source/drain (S/D) formed through microwave-activated annealing. A Schottky contact S/D is preferable, because the lower process temperature is beneficial for eliminating Ge diffusion. The fabricated NiSiGe Schottky junction exhibited a high effective barrier height (ΦBn) of 0.69 eV for electrons, resulting in a high junction current ratio of more than 105 at the applied voltage of |Va| = 1 V. Our quantum-well pMOSFET exhibited a high ION/IOFF ratio of ~107 (IS) and a moderate subthreshold swing of 166 mV/decade.

Experimental Realization of a Ternary-Phase Alloy Through Microwave-Activated Annealing for Ge Schottky pMOSFETs

This paper presents a high-performance Ge p-channel MOSFET (pMOSFET) with NiGePt as a ternary-phase alloy of Schottky source/drain (S/D) formed through low-temperature microwave-activated annealing (MWA). We fabricated a NiGePt alloy contact with uniform crystallinity through structural engineering and MWA. We clarified the phenomena of thermal reaction and diffusion for forming ternary-phase alloys using MWA properties such as thermal dynamics and ionic transportation. The ternary-phase NiGePt alloy is crucial for improving the off-leakage current of the junction. A lower process temperature is beneficial for eliminating surface roughness and reducing alloy agglomeration of the Schottky contact S/D. Consequently, the fabricated NiGePt/n-Ge Schottky junction exhibited a high effective barrier height (ΦBn) of 0.59 eV, resulting in a high junction current ratio of more than 105 at an applied voltage of |Va| = 1 V. In addition, we exploited the advantages of low-temperature microwave annealing to fabricate the pMOSFET, which includes a GeO2 passivation layer and a Schottky S/D. Our ternary Schottky Ge pMOSFET (L = 4μm) exhibited high ION/IOFF ratios of approximately 3.7 × 103 (ID) and 1.3 × 105 (IS) and a moderate subthreshold swing of 126 mV/dec.

Improving Thermal Stability and Interface State Density of High-

We propose a new HfGeO_x interfacial layer (IL) for the high-κ gate-stacks on p-type germanium substrate with improved thermal stability as compared with that of conventional GeO_x IL. We inserted an additional HfO2 layer after the formation of GeO_x in the HfO₂/Al₂O₃/GeO_x/Ge gate-stack by using plasma-enhanced atomic layer deposition. Through the use of post-deposition annealing and post-metal annealing, the new system exhibited greater thermal immunity and was stable up to 600 °C. We speculate that the improvement originates from the formation of HfGeO_x through the combination of HfO₂ and GeO_x, according to the thermodynamic data. By incorporating Hf into interfacial layer, the fabricated high-κ gate-stack with an equivalent oxide thickness of 1.2 nm, a low interface states density (D_it) of approximately 3.3×10¹¹ eV^-1 cm^-2, and an impressive gate leakage current of approximately 2.2 × 10^-6 A/cm² at V_FB -1V.

\kappa

In this paper, we demonstrated the shallow NiSiGe Schottky junction on the SiGe P-channel by using low-temperature microwave annealing. The NiSiGe/n-Si Schottky junction was formed for the Si-capped/SiGe multi-layer structure on an n-Si substrate (Si/Si0.57Ge0.43/Si) through microwave annealing (MWA) ranging from 200 to 470 °C for 150 s in N2 ambient. MWA has the advantage of being diffusion-less during activation, having a low-temperature process, have a lower junction leakage current, and having low sheet resistance (Rs) and contact resistivity. In our study, a 20 nm NiSiGe Schottky junction was formed by TEM and XRD analysis at MWA 390 °C. The NiSiGe/n-Si Schottky junction exhibits the highest forward/reverse current (ION/IOFF) ratio of ~3 × 105. The low temperature MWA is a very promising thermal process technology for NiSiGe Schottky junction manufacturing.

Stacks by Incorporating Hf into an Interfacial Layer on p-Germanium

In this paper, a method that entails using microwave thermal oxidation to form a high-quality gate dielectric on Ge through surface passivation at considerably low temperatures (<400 °C) is presented. Formation of the GeOx layer was confirmed by x-ray photoelectron spectroscopy. To reduce the bulk trap density and interface trap density (Dit), microwave thermal oxidation was employed for postdeposition microwave thermal oxidation after the deposition of Al2O3 through atomic layer deposition. Tiny frequency dispersion in capacitance measurement and a low Dit value of 5.9 × 1011 cm−2 eV−1 near the midgap confirmed a desirable passivation effect, which was favorable in mitigating the formation of dangling bonds on the Ge surface. A small hysteresis in capacitance was also observed, suggesting that the bulk dielectric was of high quality. On the basis of these characteristics, microwave-activated GeOx is a promising passivation layer material for aggressively scaled Ge-related metal oxide semiconductor devices.In this paper, a method that entails using microwave thermal oxidation to form a high-quality gate dielectric on Ge through surface passivation at considerably low temperatures (<400 °C) is presented. Formation of the GeOx layer was confirmed by x-ray photoelectron spectroscopy. To reduce the bulk trap density and interface trap density (Dit), microwave thermal oxidation was employed for postdeposition microwave thermal oxidation after the deposition of Al2O3 through atomic layer deposition. Tiny frequency dispersion in capacitance measurement and a low Dit value of 5.9 × 1011 cm−2 eV−1 near the midgap confirmed a desirable passivation effect, which was favorable in mitigating the formation of dangling bonds on the Ge surface. A small hysteresis in capacitance was also observed, suggesting that the bulk dielectric was of high quality. On the basis of these characteristics, microwave-activated GeOx is a promising passivation layer material for aggressively scaled Ge-related metal oxide semiconductor devices.

Microwave Annealing for NiSiGe Schottky Junction on SiGe P-Channel

In this work, we investigated the influence of retrograde-well implantation on hetero-structure body-tied germanium (Ge) FinFET [1]. Using structural engineering, the retrograde well was fabricated prior to Ge epitaxy, which could avoid the activated temperature of dopant in Si substrate. With optimizing the implant condition, the p-Ge/n-Si hetero-structure junction exhibited high I_ON/I_OFF ratio and lower junction leakage (4 × 10^-3 μA/cm²). Furthermore, we also make a comparison of planar and mesa junction structures, mesa junction exhibited lower junction leakage (6× 10^-6 μA/cm²) as compared with the planar one mentioned before, which could be attributed to improvement in peripheral leakage due to dislocation within Ge and Si. Comparing the difference between retrograde-well and implant-free Ge FinFETs, the drain induced barrier lowering (DIBL) was considerably improved by 50 %. Our retrograde-well Ge FinFET exhibited a high I_ON/I_OFF ratio ~ 8×10³ (I_S) than the conventional Ge FinFET (I_ON/I_OFF ~2×10³).