Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal–oxide–semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward success...

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High-κ gate dielectrics: Current status and materials properties considerations

A molecule containing a nitroamine redox center (2'-amino-4-ethynylphenyl-4'-ethynylphenyl-5'-nitro-1-benzenethiol) was used in the active self-assembled monolayer in an electronic device. Current-voltage measurements of the device exhibited negative differential resistance and an on-off peak-to-valley ratio in excess of 1000:1.

https://science.sciencemag.org/content/sci/286/5444/1550.full.pdf

Large On-Off Ratios and Negative Differential Resistance in a Molecular Electronic Device.

Hafnium and zirconium silicate (HfSixOy and ZrSixOy, respectively) gate dielectric films with metal contents ranging from ∼3 to 30 at. % Hf, or 2 to 27 at. % Zr (±1 at. % for Hf and Zr, respectively, within a given film), have been investigated, and films with ∼2–8 at. % Hf or Zr exhibit excellent electrical properties and high thermal stability in direct contact with Si. Capacitance–voltage measurements show an equivalent oxide thickness tox of about 18 A (21 A) for a 50 A HfSixOy (50 A ZrSixOy) film deposited directly on a Si substrate. Current–voltage measurements show for the same films a leakage current of less than 2×10−6 A/cm2 at 1.0 V bias. Hysteresis in these films is measured to be less than 10 mV, the breakdown field is measured to be EBD∼10 MV/cm, and the midgap interface state density is estimated to be Dit∼1–5×1011 cm−2 eV−1. Au electrodes produce excellent electrical properties, while Al electrodes produce very good electrical results, but also react with the silicates, creating a lower e l...

Hafnium and zirconium silicates for advanced gate dielectrics

Electron tunneling through self-assembled monolayers (SAM's) of alkanethiols is investigated using nanometer-scale devices. Temperature-dependent current-voltage measurements are performed on alkanethiol SAM's to distinguish between different conduction mechanisms. Temperature-independent electron transport is observed, proving that tunneling is the dominant conduction mechanism of alkanethiols, as well as exhibiting an exponential dependence of tunneling current on the molecule length with a decay coefficient \ensuremath{\beta}. From the bias dependence of \ensuremath{\beta}, a barrier height ${\ensuremath{\Phi}}_{B}$ of $1.39\ifmmode\pm\else\textpm\fi{}0.01\mathrm{eV}$ and a zero-field decay coefficient ${\ensuremath{\beta}}_{0}$ of $0.79\ifmmode\pm\else\textpm\fi{}0.01{\AA{}}^{\ensuremath{-}1}$ are determined for alkanethiols.

Mechanism of electron conduction in self-assembled alkanethiol monolayer devices

Hafnium silicate (HfSixOy) gate dielectric films with ∼6 at. % Hf exhibit significantly improved leakage properties over SiO2 in the ultrathin regime while remaining thermally stable in direct contact with Si. Capacitance–voltage measurements show an equivalent oxide thickness (tox) of less than 18 A for a 50 A HfSixOy film deposited directly on a Si substrate, with no significant dispersion of the capacitance for frequencies ranging from 10 kHz to 1 MHz. Current–voltage measurements show for the same film a leakage current of 1.2×10−6 A/cm2 at 1 V bias. Hysteresis in these films is measured to be less than 20 mV, the breakdown field is measured to be EBD∼10 MV/cm, and the midgap interface state density is Dit∼1011 cm−2 eV−1. Cross-sectional transmission electron microscopy shows no signs of reaction or crystallization in HfSixOy films on Si after being annealed at 800 °C for 30 min.

Electrical properties of hafnium silicate gate dielectrics deposited directly on silicon

We present a compact, 3-stage millimeter-wave monolithic integrated circuit (MMIC) amplifier with an operating frequency of 206–294 GHz, formed by common-source configured 35 nm L g InP mHEMTs and a multi-layer thin-film microstrip (TFM) wiring environment. The amplifier S 21 mid-band gain is 11–16 dB, 3 dB bandwidth at 294 GHz, and 82.5 mW P DC . This is the first reported InP HEMT MMIC operating in G-, H-band employing thin-film microstrip. Because the TFM ground-plane shields the signal interconnects from the substrate, well behaved device (0.1–67, 140–200, 210–310 GHz) and amplifier (206–320 GHz) measurements are presented from an unthinned, 25 mil substrate. The total size of this 3-stage amplifier is only 0.77×0.40 mm2.

A 206–294GHz 3-stage amplifier in 35nm InP mHEMT, using a thin-film microstrip environment

The radiation tolerance of high electron mobility transistors (HEMTs) based on InGaAs/InAlAs lattice matched to InP has been studied. At low fluences of 3 MeV He+ ions, the only effect is a reduction in the leakage currents. At higher fluences, the drain current decreases, the threshold voltage increases toward zero, and the transconductance decreases. These results are consistent with increased trapping in the donor layer and increased scattering in the channel layer. Radiation-induced increases in the threshold voltage occur three to nine times more slowly here than in GaAs/AlGaAs HEMTs, indicating high radiation tolerance.

Irradiation effects in InGaAs/InAlAs high electron mobility transistors

Static frequency dividers with a maximum clock frequency > 110 GHz were designed and fabricated in a narrow mesa InP/In/sub 0.53/Ga/sub 0.47/As/InP DHBT technology. Divider operation is fully static, operating from f/sub clk/ = 4 GHz to 118.70 GHz and dissipating 686.4 mW of power from a -4.2 Volt supply. The circuit employs single-buffered emitter coupled logic (ECL) and inductive peaking. The transistors have an emitter junction width of 0.5 /spl mu/m and a collector-to-emitter area ratio of 3.0. A microstrip wiring environment is employed for high interconnect density, and to minimize loss and impedance mismatch at frequencies > 100 GHz.

http://ieeexplore.ieee.org/iel5/9837/30998/01442813.pdf

Ultra high frequency static dividers in a narrow mesa InGaAs/InP DHBT technology

We summarize our work on creating substrate platforms, processes, and devices for the monolithic integration of silicon CMOS circuits with III-V optical and electronic devices. Visible LEDs and InP HBTs have been integrated on silicon materials platforms that lend themselves to process integration within silicon fabrication facilities. We also summarize research on tensile Ge, which could be a high mobility material for III-V MOS, and research on an in-situ MOCVD Al2O3/GaAs process for III-V MOS.

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Monolithic III-V/Si integration

The roadmap for silicon device technology has been drawn, extending to the year 2010, and featuring a CMOS transistor with a gate length of 0.07 μm [{xc1}]. Beyond this point, silicon heterojunctions could provide a means to further device scaling. Silicon heterojunctions could also bring new devices to the silicon substrate including light emitters and detectors, and resonant tunneling diodes (RTDs). Today SiGe/Si and SiGeC/Si heterojunctions are receiving the greatest attention, but heterojunctions now being developed to realize silicon RTDs are increasing the heterojunction options for silicon-based quantum-well and optical devices. Here we outline the fundamental device requirements for silicon optical and tunneling devices and describe progress on silicon heterojunction development towards demonstration of silicon-based RTDs. Materials now under study include, ZnS, crystalline oxides and nitrides; new processes could provide methods for forming crystalline materials over amorphous barriers.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400219751

Bobby Brar

Papers

A 206–294GHz 3-stage amplifier in 35nm InP mHEMT, using a thin-film microstrip environment

Irradiation effects in InGaAs/InAlAs high electron mobility transistors

Ultra high frequency static dividers in a narrow mesa InGaAs/InP DHBT technology

Monolithic III-V/Si integration

Beyond-The-Roadmap Technology: Silicon Heterojunctions, Optoelectronics, and Quantum Devices