The Road to a Robust and Affordable SiC Power MOSFET Technology

This article provides a detailed study of performance and reliability issues and trade-offs in silicon carbide (SiC) power MOSFETs. The reliability issues such as threshold voltage variation across devices from the same vendor, instability of threshold voltage under positive and negative gate bias, long-term reliability of gate oxide, screening of devices with extrinsic defects by means of gate voltage, body diode degradation, and short circuit withstand time are investigated through testing of commercial devices from different vendors and two-dimensional simulations. Price roadmap and foundry models of SiC MOSFETs are discussed. Future development of mixed-mode CMOS circuits with high voltage lateral MOSFETs along with 4−6× higher power handling capability compared to silicon circuits has been described.

Mechanically driven SMR-based NEMS magnetoelectric antennas

Mechanically driven magnetoelectric (ME) antennas have been demonstrated to be one of the most effective methods to miniaturise antennas compared to state-of-the-art compact antennas. However, the nanoelectromechanical systems (NEMS) ME antennas are fragile due to their suspended thin-film heterostructure, and have very low power handling capabilities. Here we show that solidly mounted resonator (SMR)-based NEMS ME antennas on a Bragg acoustic resonator, which have a circular resonating disk of 200 μm diameters and operate at 1.75 GHz, show a high antenna gain of -18.8 dBi and 1dB compression point (P1dB) of 30.4 dBm. Compared to same-size thin-film bulk acoustic resonator (FBAR) ME antennas with a free-standing membrane, the SMR-based antennas are much more structurally stable with 23.3 dB higher power handling capability and easier fabrication steps. These SMR-based ME antennas are fabricated with processes compatible with complementary metal-oxide-semiconductor (CMOS), exhibiting dramatic size miniaturisation, high power handling, high mechanical robustness, simple fabrication processes, and much higher antenna radiation gain compared to same-size state-of-the-art antennas.

A Cascaded MEMS Amplitude Demodulator for Large Dynamic Range Application in RF Receiver

An amplitude demodulator with a large dynamic range, based on microelectromechanical systems (MEMS), is proposed in this paper. It is implemented as a cascade of a capacitive and a thermoelectric sensor. Two types of the transducer can improve the measurement range and enhance the overload capacity. This MEMS-based demodulation is realized by utilizing the square law relationship and the low-pass characteristic during the electromechanical and thermoelectric conversion. The fabrication of this device is compatible with the GaAs monolithic microwave integrated circuit (MMIC) process. Experiments show that this MEMS demodulator can realize the direct demodulation of an amplitude modulation (AM) signal with a carrier frequency of 0.35–10 GHz, and cover the power range from 0 to 23 dBm. This MEMS demodulator has the advantages of high power handling capability and zero DC power consumption.

Energy deposition and melt deformation on the ITER first wall due to disruptions and vertical displacement events

An analysis workflow has been developed to assess energy deposition and material damage for ITER vertical displacement events (VDE) and major disruptions (MD). This paper describes the use of this workflow to assess the melt damage to be expected during unmitigated current quench (CQ) phases of VDEs and MDs at different points in the ITER Research Plan. The plasma scenarios are modelled using the DINA code with variations in plasma current Ip, disruption direction (upwards or downwards), Be impurity density nBe, and diffusion coefficient χ. Magnetic field line tracing using SMITER calculates time-dependent, 3D maps of surface power density q_⊥ on the Be-armored first wall panels (FWP) throughout the CQ. MEMOS-U determines the temperature response, macroscopic melt motion, and final surface topology of each FWP. Effects of Be vapor shielding are included. Scenarios at the baseline combination of Ip and toroidal field (15 MA/5.3 T) show the most extreme melt damage, with the assumed nBe having a strong impact on the disruption duration, peak q_⊥ and total energy deposition to the first wall. The worst-cases are upward 15 MA VDEs and MDs at lower values of nBe, with q_(⊥,max)=307 MW/m^2 and maximum erosion losses of ~2mm after timespans of ~400-500 ms. All scenarios at 5 MA avoided melt damage, and only one 7.5 MA scenario yields a notable erosion depth of 0.25 mm. These results imply that disruptions during 5 MA, and some 7.5 MA, operating scenarios will be acceptable during the Pre-Fusion Power Operation phases of ITER. Preliminary analysis shows that localized melt damage for the worst-case disruption should have a limited impact on subsequent stationary power handling capability.

Low-Voltage and High-Reliability RF MEMS Switch with Combined Electrothermal and Electrostatic Actuation

In this paper, we report a novel laterally actuated Radio Frequency (RF) Microelectromechanical Systems (MEMS) switch, which is based on a combination of electrothermal actuation and electrostatic latching hold. The switch takes the advantages of both actuation mechanisms: large actuation force, low actuation voltage, and high reliability of the thermal actuation for initial movement; and low power consumption of the electrostatic actuation for holding the switch in position in ON state. The switch with an initial switch gap of 7 µm has an electrothermal actuation voltage of 7 V and an electrostatic holding voltage of 21 V. The switch achieves superior RF performances: the measured insertion loss is −0.73 dB at 6 GHz, whereas the isolation is −46 dB at 6 GHz. In addition, the switch shows high reliability and power handling capability: the switch can operate up to 10 million cycles without failure with 1 W power applied to its signal line.

Cu-Doped TiNxOy Thin Film Resistors DC/RF Performance and Reliability

We fabricated Cu-doped TiNxOy thin film resistors by using atomic layer deposition, optical lithography, dry etching, Ti/Cu/Ti/Au e-beam evaporation and lift-off processes. The results of the measurements of the resistance temperature dependence, non-linearity, S-parameters at 0.01–26 GHz and details of the breakdown mechanism under high-voltage stress are reported. The devices’ sheet resistance is 220 ± 8 Ω/□ (480 ± 20 µΩ*cm); intrinsic resistance temperature coefficient (TCR) is ~400 ppm/°C in the T-range of 10–300 K; and S-parameters versus frequency are flat up to 2 GHz with maximum variation of 10% at 26 GHz. The resistors can sustain power and current densities up to ~5 kW*cm−2 and ~2 MA*cm−2, above which they switch to high-resistance state with the sheet resistance equal to ~200 kΩ/□ (~0.4 Ω*cm) caused by nitrogen and copper desorption from TiNxOy film. The Cu/Ti/TiNxOy contact is prone to ageing due to gradual titanium oxidation while the TiNxOy resistor body is stable. The resistors have strong potential for applications in high-frequency integrated and hybrid circuits that require small-footprint, medium-range resistors of 0.05–10 kΩ, with small TCR and high-power handling capability.

Analysis and Design of a Fully-Integrated High-Power Differential CMOS T/R Switch and Power Amplifier Using Multi-Section Impedance Transformation Technique

In this paper, a new topology for a high-power single-pole-double-throw (SPDT) antenna switch is presented, and its loss mechanisms are fully analyzed. The differential architecture is employed in the proposed switch implementation to prevent unwanted channel formations of OFF-state Rx switch transistors by relieving the voltage swing over the Rx switch devices. In addition to that, the load impedance seen by the Tx switch is stepped down to reduce the voltage swing even more, allowing the antenna switch to handle a high-power signal without distortions. To drop the switch operating impedance, two matching networks are required at the input and the output of the Tx switch, respectively, and they are carefully implemented considering the integration issue of the front-end circuitries. From the loss analysis of the whole signal path, an optimum switch operating impedance is decided in view of a trade-off between power handling capability and insertion loss of the antenna switch. The insertion loss of the proposed design is compared to the conventional design with electromagnetic (EM) simulated transformer and inductors. The proposed antenna switch is implemented in a standard 0.18 µm CMOS process, and all switch devices adopt the deep n-well structure. The measured performance of the proposed transmitter front-end chain shows a 1 dB compression point (P1dB) of 32.1 dBm with 38.3% power-added efficiency (PAE) at 1.9 GHz.