Investigation of reactively sputtered TaN thin-film resistors for microwave photonic applications

Electrophysical characteristics and their thermal stability of thin-film resistors based on tantalum nitride (TaN) obtained by reactive magnetron sputtering were investigated. The optimal modes of the magnetron sputtering process are determined, ensuring the Ta2N phase film composition with the value of the specific electrical resistance of 250 μm cm and high thermal stability of the parameters. On the basis of the investigations carried out, thin-film matching resistors were manufactured for use as part of an electro-optical InP-based MZ modulator

Development of a 0.15 μm GaAs pHEMT Process Design Kit for Low-Noise Applications

This work presents a process design kit (PDK) for a 0.15 μm GaAs pHEMT process for low-noise MMIC applications developed for AWR Microwave Office (MWO). A complete set of basic elements is proposed, such as TaN thin film resistors and mesa-resistors, capacitors, inductors, and transistors. The developed PDK can be used in technology transfer or education.

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.

An Approach on the Use of Co-Sputtered W-DLC Thin Films as Piezoresistive Sensing Materials

Background: Miniaturized piezoresistive sensors, particularly strain gauges, pressure sensors, and accelerometers, have been used for measurements and control applications in various fields, such as automotive, aerospace, industrial, biomedical, sports, and many more. A variety of different materials have been investigated for the development of these sensors. Among them, diamond-like carbon (DLC) thin films have emerged as one of the most promising piezoresistive sensing materials due to their excellent mechanical properties, such as high hardness and high Young’s modulus. At the same time, metal doping has been studied to enhance its electrical properties. Objective: This article explores the use of co-sputtered tungsten-doped diamond-like carbon (W-DLC) thin films as microfabricated strain gauges or piezoresistors. Methods: Different serpentine thin-film resistors were microfabricated on co-sputtered W-DLC thin films using photolithography, metallization, lift-off, and RIE (reactive ion etching) processes. In order to evaluate their piezoresistive sensing performance, gauge factor (GF) measurements were carried out at room temperature using the cantilever beam method. Results: GF values obtained in this study for co-sputtered W-DLC thin films are comparable to those reported for W-DLC films produced and characterized by other techniques, which indicates the feasibility of our approach to use them as sensing materials in piezoresistive sensors. Conclusion: W-DLC thin films produced by the co-magnetron sputtering technique can be considered as sensing materials for miniaturized piezoresistive sensors due to the following key advantages: (i) easy and well-controlled synthesis method, (ii) good piezoresistive properties exhibiting a GF higher than metals, and (iii) thin-film resistors formed by a simple microfabrication process.

Effects of deposition parameters on properties of high resistance CrSi-based thin-film resistors

Cr is a metal with lower resistivity (as compared with Si) and positive temperature coefficient of resistance (TCR value) and Si is a semiconductive material with higher resistivity and negative TCR value. For that, the commercial-grade targets of 28 wt.% Cr-72 wt.% Si, 40 wt.% Cr-60 wt.% Si and 55 wt.% Cr-45 wt.% Si were used to deposit the thin-film materials using sputtering method at the same parameters, and their physical and electrical properties were measured and compared under different deposition powers. The crystallization and the surface morphology of the CrSi-based thin-film resistors were measured using X-ray diffraction (XRD) pattern and field emission scanning electron microscopy (FESEM). In order to find the effect of deposition power on the average atomic ratio of Cr and Si, the elemental ratios were also measured as a function of deposition power for different CrSi-based targets by FESEM equipped with Energy-Dispersive X-ray spectroscopy (EDX) for elemental Cr and Si. The effects of Cr concentration and deposition power on the sheet resistances, resistivity and TCR values of the deposited CrSi-based thin-film resistors were also well measured and compared, and the reasons to cause the variations of resistivity and TCR values were also investigated and discussed.

Inkjet Printing of Highly Sensitive, Transparent, Flexible Linear Piezoresistive Strain Sensors

Flexible strain sensors are fabricated by using a simple and low-cost inkjet printing technology of graphene-PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)) conductive ink. The inkjet-printed thin-film resistors on a polyethylene terephthalate (PET) substrate exhibit an excellent optical transmittance of about 90% over a visible wavelength range from 400 to 800 nm. While an external mechanical strain is applied to thin-film resistors as strain sensors, a gauge factor (GF) of the piezoresistive (PR) strain sensors can be evaluated. To improve the GF value of the PR strain sensors, a high resistive (HR) path caused by the phase segregation of the PEDOT:PSS polymer material is, for the first time, proposed to be perpendicular to the PR strain sensing direction. The increase in the GF with the increase in the HR number of the PR strain sensors without a marked hysteresis is found. The result can be explained by the tunneling effect with varied initial tunneling distances and tunneling barriers due to the increase in the number of HR. Finally, a high GF value of approximately 165 of three HR paths is obtained with a linear output signal at the strain range from 0% to 0.33%, further achieving for the inkjet printing of highly sensitive, transparent, and flexible linear PR strain sensors.

A Review of Degradation Modeling of Key Components of Sensor Circuits Based on Physical Analysis

Nuclear power plant (NPP) accidents can cause severe effects. In order to ensure the normal operation of NPP, instrument and control system (I&C) composed of multiple sensors plays an important role in it. The sensor consists of sensitive components and functional circuits. In this paper, temperature sensor commonly used in NPP, PT100, is used as an example, and a bottom-up based physical analysis method is used to review the degradation mechanism and physical model of key components in resistance temperature detector (RTD) circuits. Resistors, capacitors, and MOSFETs are the key components of sensor circuits. Thin film resistors are the most widely used resistors due to their good performance. The transformed Arrhenius’ equation is used to describe its degradation characteristics. For the most commonly used aluminum electrolytic capacitors, the model reviewed in this paper can accurately describe the changes in equivalent series resistance (ESR), and use this as a criterion for determining capacitor failure. MOS technology is widely used in analog circuits. We have summarized three physical degradation processes, channel hot carrier (CHC), negative bias temperature instability (NBTI), and time-dependent dielectric breakdown (TDDB), that affect MOSFET performance. The physical model of the key component degradation of the sensor circuit summarized in this paper provides a basis for the subsequent establishment of a circuit-level degradation model.

Thin-Film MEMS Resistors with Enhanced Lifetime for Thermal Inkjet

In this paper, the failure mechanisms of the thermal inkjet thin-film resistors are recognized. Additionally, designs of resistors to overcome these mechanisms are suggested and tested by simulation and experiment. The resulting resistors are shown to have improved lifetimes, spanning an order of magnitude up to 2 × 109 pulses. The thermal failure mechanisms were defined according to the electric field magnitude in three critical points—the resistor center, the resistor–conductor edge, and the resistor thermal “hot spots”. Lowering the thermal gradients between these points will lead to the improved lifetime of the resistors. Using MATLAB PDE simulations, various resistors shapes, with different electric field ratios in the hot spots, were designed and manufactured on an 8″ silicon wafer. A series of lifetime experiments were conducted on the resistors, and a strong relation between the shape and the lifetime of the resistor was found. These results have immediate ramifications regarding the different printing apparatuses which function with thermal inkjet technology, allowing the commercial production of larger thermal printheads with high MTBF rate. Such heads may fit fast and large 3D printers.