Michael Schnee

Fabrication and Characterization of Enhancement-Mode High-

In this paper, we investigate the enhancement-mode (E-mode) LaLuO3 (LLO)-AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs) fabricated using fluorine (F) plasma ion implantation with a gate-dielectric-first planar process. The E-mode MIS-HEMTs exhibit a threshold voltage (VTH) of 0.6 V, a peak transconductance of ~ 193 mS/mm, a small hysteresis of 0.04 V in linear region characterized by a pulse-mode current-voltage measurement, and significantly suppressed current collapse under high-drain-bias switching conditions. X-ray photoelectron spectroscopy and secondary ion mass spectrometry analyses manifest that the negatively charged F ions penetrating into the (Al)GaN barrier layer serve as the primary VTH modulation mechanism, whereas the F ions in the fluorinated LLO film form chemical bonds with La/Lu atoms and become charge-neutral. The suppressed current collapse is verified as an advantageous byproduct of the F plasma ion implantation that also fluorinated the SiNx sidewalls in the vicinity of the gate electrode, and therefore, suppress electron injection to the gate-drain access region.

\kappa~{\rm LaLuO}_{3}

The integration of lanthanum lutetium oxide (LaLuO₃) with a n value of 30 is, for the first time, demonstrated on strained and unstrained SOI n/p-MOSFETs as a gate dielectric with a full replacement gate process. The LaLuO₃/Si interface showed a very thin silicate/SiO₂ interlayer with a D_it level of 4.5 × 10¹¹ (eV · cm²)^-1. Fully depleted n/p-MOSFETs with LaLuO₃/TiN gate stacks indicated very good performance with steep subthreshold slopes of ~70 mV/dec and high I_on/I_off ratios. In addition, strained SOI shows enhanced electron mobilities with a factor of 1.7 compared to SOI. Both electron and hole mobilities for LaLuO₃ on SOI are similar to the mobilities in reported Hf-based high-κ devices.

-AlGaN/GaN MIS-HEMTs

We report the study of high-dielectric-constant (high-κ) dielectric LaLuO3 (LLO) thin film that is grown on AlGaN/GaN heterostructure by molecular beam deposition (MBD). The physical properties of LLO on AlGaN/GaN heterostrucure have been investigated with atomic force microscopy, x-ray photoelectron spectroscopy, and TEM. It is revealed that the MBD-grown 16 nm-thick LLO film is polycrystalline with a thin (∼2 nm) amorphous transition layer at the LLO/GaN interface. The bandgap of LLO is derived as 5.3 ± 0.04 eV from O1s energy loss spectrum. Capacitance-voltage (C-V) characteristics of a Ni-Au/LLO/III-nitride metal-insulator-semiconductor diode exhibit small frequency dispersion (<2%) and reveal a high effective dielectric constant of ∼28 for the LLO film. The LLO layer is shown to be effective in suppressing the reverse and forward leakage current in the MIS diode. In particular, the MIS diode forward current is reduced by 7 orders of magnitude at a forward bias of 1 V compared to a conventional Ni-Au/...

Integration of

The miniaturization of metal-oxide-semiconductor field effect transistors (MOSFETs) is approaching fundamental limits. Novel materials and innovative device structures are needed in order to continue the evolution of complementary metal-oxide-semiconductor (CMOS) technology. High-k dielectrics combined with semiconductors with superior transport properties than Si is an attractive alternative for future CMOS applications. For instance, the use of germanium as a high-mobility channel material is very promising due to intrinsic higher carrier mobilities than Si [1]. However, one of the issues that still remains is the challenge to achieve a high quality interface between Ge and a high-k gate dielectric. Although different methods have been employed for surface passivation prior to the high-k deposition (e.g. thermally grown GeO2 [2]), their use may impede further equivalent oxide thickness (EOT) scaling to values 1nm. Therefore, the search for alternative high-k oxides that could offer stable interfaces with a low density of electrically active defects has become a topic of major interest. Ternary rare earth oxides such as the scandates (LaScO3 or GdScO3) and LaLuO3, were proven to be promising high-k dielectric candidates on silicon. Thin films of these materials keep their amorphous structure up to 1000°C, as measured by X-ray diffraction (not shown). In addition, as summarized in table 1, they offer large optical band gaps (>5 eV) and band offsets to silicon (2-2.5 eV), and have dielectric constants (k) between 23 up to 32 [3]. The integration of these oxides with high mobility substrates such as Ge, SiGe, and strained Si (sSi) also shows great potential [4,5]. Figure 1 illustrates capacitance-voltage (C-V) measurements for a ~4.5 nm thick amorphous LaLuO3 film deposited directly on n-type Ge(100) substrates without any surface passivation layer. C-V curves free of humps and irregularities could be obtained. When comparing curves measured at different frequencies, one can see a dispersion of less than 5% on the accumulation side and a small flatband voltage shift of about 0.2 V between 10 kHz and 1 MHz. Most importantly, an EOT below 1 nm could be achieved with leakage current densities kept below 10 A/cm and Dit levels in the range of 1 to 5x10 eVcm. These and other similar results obtained for scandate films on Ge (not shown) will be discussed taking into account the physico-chemical scenario at the oxide/Ge interface as studied by X-ray photoelectron spectroscopy, transmission electron microscopy and time-of-flight secondary ion mass spectrometry. It will be shown that the formation of a germanate-like interface between the oxide and Ge results in an improvement of the electrical properties.

\hbox{LaLuO}_{3} \ (\kappa \sim \hbox{30})

In this study, the authors present results on the structural, chemical, and electrical characterization of HfO2 thin layers on 300 mm Si wafers. The layers were prepared by atomic layer deposition using a liquid delivery system technology for metal organic precursors, which allows an accurate control of the Hf precursor. After optimization of the deposition process with an alkylamide precursor for Hf and ozone chemistry, the growth of the SiOx interfacial layer between the HfO2 layer and the Si substrate could be minimized using TiN as metal gate. In addition, the authors studied the effect of Al2O3 interfacial layers on the properties of metal-oxide-semiconductor capacitor resulting in a positive flat band voltage shift of up to ∼300 mV according to the layer thickness. Gate stacks with equivalent oxide thicknesses around 1.1 nm showed leakage current densities as low as 1.1×10−2 A/cm2 at VFB of 1 V. In addition, the capacitance-voltage curves for thin HfO2 layers indicated a negligible hysteresis, below...

as High-

A high-κ LaLuO₃ (LLO) thin film is successfully incorporated into AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) as the gate dielectric. The LLO-AlGaN/GaN MISHEMTs fabricated with a planar process exhibit a high I_ON/I_OFF of 10⁹, a maximum drain current of 820 mA/mm at V_GS = 3 V, a peak transconductance (G_m) of ~ 192 mS/mm, and a steep subthreshold slope (SS) of ~ 73 mV/dec.

\kappa

A high-κ LaLuO₃ (LLO) thin film is successfully incorporated into AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) as the gate dielectric. The LLO-AlGaN/GaN MISHEMTs fabricated with a planar process exhibit a high I_ON/I_OFF of 10⁹, a maximum drain current of 820 mA/mm at V_GS = 3 V, a peak transconductance (G_m) of ~ 192 mS/mm, and a steep subthreshold slope (SS) of ~ 73 mV/dec.

Dielectric on Strained and Unstrained SOI MOSFETs With a Replacement Gate Process

The chemical reactions at the higher-k LaLuO<inf>3</inf>/Ti<inf>1</inf>N<inf>X</inf>/poly-Si gate stack interfaces are studied after high temperature treatment. A Ti-rich TiN metal layer degrades the gate stack performance after high temperature annealing. The gate stack containing TiN/LaLuO<inf>3</inf> with a near stoichiometric TiN layer is stable during 1000 °C, 5s anneals. Both electrical and structural characterization methods are employed to explore the thermal stability of the gate stack. Based on these results an integration of TiN/LaLuO<inf>3</inf> in a gatefirst MOSFET process on SOI is shown.

Characterization of high-κ LaLuO3 thin film grown on AlGaN/GaN heterostructure by molecular beam deposition

In this work, enhancement-mode (E-mode) AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) with high-κ LaLuO3 (LLO) gate dielectric were fabricated by deploying the CF4 plasma treatment technique in a gate-dielectric-first planar process. CF4 plasma treatment can shift the threshold voltage from -2.3 V [for depletion-mode (D-mode) LLO MIS-HEMTs] to 0.6 V (for E-mode LLO MIS-HEMTs). Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results suggest that fluorine ions could penetrate through the polycrystalline/amorphous LLO film and be implanted into the (Al)GaN barrier layer. The primary threshold voltage (VTH) shift mechanism of the E-mode LLO MIS-HEMTs is the negatively-charged fluorine ions in (Al)GaN, while fluorine atoms form chemical bonds with La/Lu atoms in the fluorinated LLO film. The E-mode LLO MIS-HEMTs exhibit a drive drain current density of 352 mA/mm at VGS = 2.5 V and a peak transconductance (Gm) of ~193 mS/mm. Significant suppression of current collapse and low dynamic ON-resistance are obtained in the E-mode LLO MIS-HEMTs under high-drain-bias switching conditions.

Electrical and Structural Properties of Ternary Rare-Earth Oxides on Si and Higher Mobility Substrates and Their Integration as High-k Gate Dielectrics in MOSFET Devices

To obtain quantitative depth information from hard X-ray photoemission spectroscopy, the effective attenuation length (EAL) is required. In this paper, the EAL was determined for LaLuO3 for electron kinetic energies between 7 and 13 keV. As a result, the EAL is in the range of 100–150 A for the investigated photon energies. In addition, higher binding energy orbitals of La and Lu were measured and are discussed. LaLuO3 is a promising high-k dielectric for future nano-scaled MOS devices.