Sylvie Lepilliet

What are the limiting parameters of deep-submicron MOSFETs for high frequency applications?

Parameters limiting the improvement of high frequency characteristics for deep submicron MOSFETs with the downscaling process of the channel gate length are analyzed experimentally and analytically. It is demonstrated that for MOSFETs with optimized source, drain and gate access, the degradation of the maximum oscillation frequency is mainly related to the increase of the parasitic feedback gate-to-drain capacitance and output conductance with the physical channel length reduction. Optimization of these internal parameters is needed to further improve the high frequency performance of ultra deep submicron MOSFETs.

Flexible Gigahertz Transistors Derived from Solution-Based Single-Layer Graphene

Flexible electronics mostly relies on organic semiconductors but the limited carrier velocity in polymers and molecular films prevents their use at frequencies above a few megahertz. Conversely, the high potential of graphene for high-frequency electronics on rigid substrates was recently demonstrated. We conducted the first study of solution-based graphene transistors at gigahertz frequencies, and we show that solution-based single-layer graphene ideally combines the required properties to achieve high speed flexible electronics on plastic substrates. Our graphene flexible transistors have current gain cutoff frequencies of 2.2 GHz and power gain cutoff frequencies of 550 MHz. Radio frequency measurements directly performed on bent samples show remarkable mechanical stability of these devices and demonstrate the advantages of solution-based graphene field-effect transistors over other types of flexible transistors based on organic materials.

230-GHz self-aligned SiGeC HBT for optical and millimeter-wave applications

This paper describes a 230-GHz self-aligned SiGeC heterojunction bipolar transistor developed for a 90-nm BiCMOS technology. The technical choices such as the selective epitaxial growth of the base and the use of an arsenic-doped monocrystalline emitter are presented and discussed with respect to BiCMOS performance objectives and integration constraints. DC and high-frequency device performances at room and cryogenic temperatures are given. HICUM model agreement with the measurements is also discussed. Finally, building blocks with state-of-the-art performances for a CMOS compatible technology are presented: A ring oscillator with a minimum stage delay of 4.4 ps and a 40-GHz low-noise amplifier with a noise figure of 3.9 dB and an associated gain of 9.2 dB were fabricated.

Milliwatt-level output power in the sub-terahertz range generated by photomixing in a GaAs photoconductor

It is shown from accurate on-wafer measurement that continuous wave output powers of 1.2 mW at 50 GHz and 0.35 mW at 305 GHz can be generated by photomixing in a low temperature grown GaAs photoconductor using a metallic mirror Fabry-Perot cavity. The output power is improved by a factor of about 100 as compared to the previous works on GaAs photomixers. A satisfactory agreement between the theory and the experiment is obtained in considering both the contribution of the holes and the electrons to the total photocurrent.

Gigahertz characterization of a single carbon nanotube

Carbon nanotubes are intrinsically high impedance objects. The high frequency (HF) characterization of these nano-objects is crucial for applications such as interconnects in future integrated circuits, but still represents a daunting challenge. This letter presents HF characterization of an individual metallic single walled carbon nanotube up to 7 GHz. The equivalent circuit values are directly extracted from these HF measurements without numerical procedure, thus proving that the intrinsic transport parameters of a single carbon nanotube can be determined up to gigahertz frequencies.

Metamorphic In/sub 0.4/Al/sub 0.6/As/In/sub 0.4/Ga/sub 0.6/As HEMTs on GaAs substrate

New In/sub 0.4/Al/sub 0.6/As/In/sub 0.4/Ga/sub 0.6/As metamorphic (MM) high electron mobility transistors (HEMTs) have been successfully fabricated on GaAs substrate with T-shaped gate lengths varying from 0.1 to 0.25 /spl mu/m. The Schottky characteristics are a forward turn-on voltage of 0.7 V and a gate breakdown voltage of -10.5 V. These new MM-HEMTs exhibit typical drain currents of 600 mA/mm and extrinsic transconductance superior to 720 mS/mm. An extrinsic current cutoff frequency f/sub T/ of 195 GHz is achieved with the 0.1-/spl mu/m gate length device. These results are the first reported for In/sub 0.4/Al/sub 0.6/As/In/sub 0.4/Ga/sub 0.6/As MM-HEMTs on GaAs substrate.

Analog/RF Performance of Multichannel SOI MOSFET

In this paper, for the first time, we present a detailed RF experimental and simulation study of a 3-D multichannel SOI MOSFET (MCFET). Being different from the conventional planar technology, the MCFET features a total of three self-aligned TiN/HfO2 gate stacks fabricated on top of each other, allowing current to flow through the three undoped ultrathinned silicon bodies (UTBs). In other words, the operation of the MCFET is theoretically based on two UTB double-gate SOIs and a single-gate UTB fully depleted SOI (FDSOI) at the bottom. Using on-wafer S-parameters, the RF/analog figures-of-merit of an MCFET with a gate length of 50 nm are extracted and discussed. Thanks to the enormous transconductance (gm) and very low output conductance, the RF/analog performances of MCFET-voltage gain (A VI) and early voltage (V EA) are superior compared with that of the single-gate UTB-FDSOI. However, these advantages diminish in terms of transition frequency (fT), due to the large total input gate capacitances (C GG). This inspires the introduction of spacer engineering in MCFET, aiming at improving both C GG and fT. The sensitivity of the spacer length to the RF/analog performances is experimentally analyzed, and the performance optimization is validated using ac simulation. This paper concludes that optimized MCFETs are a serious contender to the mainstream MOSFETs including FinFETs for realizing future low-power analog applications.

The indium content in metamorphic As/As HEMTs on GaAs substrate: a new structure parameter

Abstract State-of-the art metamorphic In x Al 1−x As/ In x Ga 1−x As HEMTs (MM-HEMTs) on a GaAs substrate with different indium compositions x=0.33 , 0.4 and 0.5 have been realized and characterized. The gate lengths Lg are 0.1 and 0.25 μm. These devices have been compared with lattice matched HEMTs on an InP substrate. DC-characteristics of 0.1 μm gate length MM-HEMTs show drain-to-source current Ids of the order of 550–650 mA/mm, and extrinsic transconductance of about 800 mS/mm. Schottky characteristics exhibit a gate reverse breakdown voltage varying from −14 to −7 V for x=0.33 –0.5, with an intermediate value of −10.5 V for x=0.4 . A small signal equivalent circuit of our 0.1 μm MM-HEMTs give intrinsic transconductance higher than 1100 mS/mm, with similar values of 1350 and 1450 mS/mm for x=0.5 and the lattice matched HEMT, respectively. The MM-HEMTs with a gate length of 0.25 μm present a cutoff frequency fT close to 100 GHz. To achieve the same result with pseudomorphic HEMTs on GaAs, a smaller gate length has to be realized, which requires the use of an electron beam lithography and therefore increases the device costs. For L g =0.1 μm, fT reaches 160, 195 and 180 GHz for x=0.33 , 0.4 and 0.5, respectively. These values are close to f T =210 GHz obtained for a lattice matched HEMTs on InP realized with the same technological process. The MM-HEMTs are therefore good alternatives to PM-HEMTs on GaAs and LM-HEMTs on InP in the V bands and W bands while maintaining a GaAs substrate. Moreover, metamorphic In0.4Al0.6As/In0.4Ga0.6As HEMTs exhibit a comparable microwave performance with large voltage operation than the MM-HEMT with a 0.5 indium content and the lattice matched HEMTs. These results indicate that a device with indium content x=0.4 is particularly attractive for the realization of low-noise and power circuits on the same wafer.

1.8 dB insertion loss 200 GHz CPW band pass filter integrated in HR SOI CMOS Technology

Today, measurement of 65 nm CMOS [Dambrine, G., et al., 2005] and 130 nm-based SiGe HBTs [Chevalier, p. et al., 2004] technologies demonstrate both fT (current gain cut-off frequency) and fmax (maximum oscillation frequency) higher than 200 GHz, which are clearly comparable to advanced commercially available 100nm III-V HEMT. This increase allows new millimeter wave (MMW) applications on silicon. One of the success keys is then the passive integration. In this paper, on-chip coplanar waveguides (CPWs), which have been achieved in STMicroelectronics advanced nanometric RF CMOS High Resistivity (HR) SOI (rho > 1 kOmegaldrcm) process, and characterized up to 220 GHz are reported. Moreover, for the first time passive circuits working @ 220 GHz have been achieved and characterized demonstrating state-of-the-art performances and good agreement with electric simulations using developed models.

High-Frequency and Noise Performances of 65-nm MOSFET at Liquid Nitrogen Temperature

In this paper, the high-frequency properties of MOSFETs at low-temperature operation are investigated through measurements and electrical simulations. The experimental results show that the device achieves a 335-GHz fmax and a 300-GHz ft when operating at low temperature (78 K), which constitutes, respectively, a 78% and 34% improvement compared to the room temperature performances (296 K). The minimum noise figure NFmin decreases from 1.4 dB (296 K) to 0.5 dB at 30 GHz (78 K), while the associated gain increases from 8 to 12 dB