Metal Oxide Semiconductor Research Articles

Efficient quantum-dot adder optimisation and analysis for future circuits

ABSTRACT In recent years, the rapid scaling of transistors has necessitated the exploration of advanced alternatives to Complementary metal oxide semiconductor(CMOS) technology for future progress. Quantum-dot cellular automata(QCA) technology has emerged as a promising solution, offering highly dense, high-speed, and low-power circuits. Among the critical digital building blocks, adder circuits play a crucial role in arithmetic and logic units. Consequently, optimising these circuits in terms of area, delay, and quantum cost is essential for the development of efficient designs. This paper presents effective multi-layer n-bit ripple carry adder(RCA) circuits, utilising full adder(FA) circuit. The outputs are generated in distinct layers and verified using the QCADesigner-Ev2.2 tool with bi-stable and coherence vector energy setups, employing Euler and Runge-Kutta methods.Additionally, the proposed designs are evaluated for various design metrics at three different scale factors(1,0.8889,and 0.7778), corresponding to cell sizes of 18 × 18 nm , 16 × 16 nm , and 14 × 14 nm respectively. The temperature’s impact on the average output polarisation of the FA is explored. The research demonstrates an n-bit-RCA surpassing existing designs with cost optimisations of 89.5%, 86%, and 90.3% for 4-bit,8-bit and 16-bit circuits, respectively. The paper also provides a thorough energy dissipation analysis for the proposed adder design.

Asynchronous interface circuit for nonlinear connectivity in multicore spiking neural networks

AbstractTo expand the scale of spiking neural networks (SNNs), an interface circuit that supports multiple SNN cores is essential. This circuit should be designed using an asynchronous approach to leverage characteristics of SNNs similar to those of the human brain. However, the absence of a global clock presents timing issues during implementation. Hence, we propose an intermediate latching template to establish asynchronous nonlinear connectivity with multipipeline processing between multiple SNN cores. We design arbitration and distribution blocks in the interface circuit based on the proposed template and fabricate an interface circuit that supports four SNN cores using a full‐custom approach in a 28‐nm CMOS (complementary metal–oxide–semiconductor) FDSOI (fully depleted silicon on insulator) process. The proposed template can enhance throughput in the interface circuit by up to 53% compared with the conventional asynchronous template. The interface circuit transmits spikes while consuming 1.7 and 3.7 pJ of power, supporting 606 and 59 Mevent/s in intrachip and interchip communications, respectively.

Nanofibrous metal oxide semiconductor for sensory face masks

Sensory face masks are designed to integrate sensors that monitor health metrics, such as breathing rate and body temperature, thereby providing continuous physiological data. However, current sensing materials are predominantly in film form. In this study, we report on the use of fibrous amorphous indium gallium zinc oxide, which offers an enlarged surface area to facilitate gas diffusion and transport into charge-carrying sites. A detailed morphological analysis and an electrical investigation of this fibrous network were conducted. By integrating this material with a wireless, miniaturised flexible circuit and mounting it on a face mask, we successfully monitored different human respiratory states in real time. This wearable face mask demonstrates the potential for promising applications in health monitoring.

Anchoring Ni atomic clusters on yolk-shell In2O3 microspheres for highly sensitive, ultra-rapid responding/recovering ppb-level NO2 detections

Highly sensitive, sophisticated and rapidly responding/recovering NO2 sensors are of a pressing demand across various modern applications. However, traditional metal oxide semiconductors (MOSs), such as In2O3, often grapple with issues such as diminished sensitivity and tardy responding/recovering. To address these challenges, we present a novel, simultaneous enhancement strategy centered around Ni atomic clusters (NiAC) integrated into In2O3 yolk-shell microspheres. This innovative structural and compositional design not only enhances NO2 adsorption thermodynamics but also improves kinetics reacting rate. The optimized heterostructured NiAC-In2O3 exhibits exceptional NO2 sensing performances with high response (454.62 to 10 ppm NO2), instantaneous responding/recovering dynamics (1/3 s), and an impressively ultra-low detection limit (1 ppb) at 200 ℃. Reaction kinetics calculation, finite element method (FEM) simulations and further validation through In-situ diffuse reflection infrared Fourier transform spectroscopy (In-situ DRIFTS) and temperature-programmed desorption (TPD) analyses confirms the accelerated NO2 adsorption/desorption dynamics, enhanced NO2 dissociation and trace-concentration NO2 molecule capturing capability attributed to NiAC. Considering these merits, The fabricated NiAC-In2O3 ensures high-precise, instantaneous, ppb-level NO2 detections.

Asymmetric trench SiC MOSFET with integrated channel accumulation diode for enhanced reverse conduction and switching characteristics

A novel asymmetric trench Silicon Carbide Metal Oxide Semiconductor Field Effect Transistor (SiC MOSFET), featuring an integrated channel accumulation diode (CAD-MOS), has been proposed and investigated through numerical simulation. This innovative design aims to mitigate switching losses and eliminate the bipolar degradation of the body diode. The current spreading layer (CSL) channel, strategically positioned in the centre of the dummy gate, offers a low-barrier reverse conduction path. This represents a substantial advancement over the traditional PN body diode, significantly reducing the reverse conduction voltage drop from 2.84 V in the PN body diode to a mere 1.39 V in the CAD-MOS. Meanwhile, the reverse recovery charge of the CAD-MOS is reduced to 0.95 μC/cm2, and the peak reverse recovery current stands at 45 A/cm2. Compared to conventional asymmetrical trench SiC MOSFET (CON-MOS), the CAD-MOS exhibits a 68.1 % reduction in reverse recovery charge and a 63.4 % decrease in peak reverse recovery current. The split-gate design also reduces the device gate to source capacitance (CGS), resulting in a 17.4 % reduction in total switching losses to 3.64 mJ/cm2. CAD-MOS also exhibits a reduced gate turn-on charge and demonstrates an enhancement in high-frequency figure of merit (HF-FOM) by 8.1 %.

ZEROES: Robust Derivative-Based Demodulation Method for Optical Camera Communication

Most of Optical Camera Communication (OCC) systems benefit from the rolling shutter mechanism of Complementary Metal-Oxide Semiconductor (CMOS) cameras to record the brightness evolution of the Light-Emitting Diode (LED) through dark and bright strips within images. While this technique enhances the maximum achievable data rate, the main difficulty lies in the demodulation of the signal extracted from images, subject to blooming effect. Thus, two main approaches were proposed to deal with this issue, using adaptive thresholds whose value evolves according to amplitude changes or detecting signal variations with the first-order derivative. As the second method is more robust, a new demodulation method based on the detection of the zeros of the first-order derivative of the extracted signal was proposed in this paper. Obtained results clearly show an improvement in the extracted signal demodulation compared to other methods, achieving a raw Bit Error Rate (BER) of 10−3 around 50 cm in a Line-Of-Sight scenario, and increasing the maximum communication distance by 43.5%, reaching 330 cm in the case of a Non-Line-Of-Sight transmission.

Ultrathin nanocapacitor assembled via atomic layer deposition

We fabricated ultrathin metal - oxide - semiconductor (MOS) nanocapacitors using atomic layer deposition. The capacitors consist of a bilayer of Al2O3 and Y2O3 with a total thickness of ~10 nm, deposited on silicon substrate. The presence of the two materials, each slab being ~5 nm thick and uniform over a large area, was confirmed with Transmission Electron Microscopy and X-ray photoelectron spectroscopy (XPS). The capacitance in accumulation varied from 1.6 nF (at 1MHz) to ~2.8 nF (at 10 kHz), which is one to two orders of magnitude higher than other nanocapacitors. This high capacitance is attributed to the synergy between the dielectric properties of ultrathin Al2O3 and Y2O3 layers. The electrical properties of the nanocapacitor are stable within a wide range of temperatures, from 25 °C to 150 °C, as indicated by capacitance-voltage (C - V). Since the thickness-to-area ratio is negligible, the nanocapacitor could be simulated as a single parallel plate capacitor in COMSOL Multiphysics, with good agreement between experimental and simulation data. As a proof-of-concept we simulated a MOSFET device with the nanocapacitor gate dielectric, whose drain current is sufficiently high for micro and nanoelectronics integrated circuits, including for applications in sensing.

On-demand performance optimization of AlGaN/GaN high electron mobility transistors using stoichiometric variation of dielectric alloy AlxTayO

The current research investigates the potential advantages of optimally combining wide bandgap Al2O3 with high dielectric constant (high-κ) Ta2O5 for gate dielectric applications. Various compositions of 10 nm AlxTayO oxide films are grown on the Al0.3Ga0.7N/GaN heterostructure by co-sputtering Al and Ta metals, followed by thermal oxidation at 500 °C. The average root-mean-square roughness of the grown oxide films is ∼1.2–1.4 nm compared to 0.4 nm for as-deposited metal. X-ray photoelectron spectroscopy and transmission electron microscopyconfirm the formation and thickness of the grown oxide films. The bandgap (Eg) of the oxide films calculated from O1s electron energy loss spectra show a linear increase from 4.85 eV for pure Ta2O5 to 6.4 eV for pure Al2O3. The dielectric constant (εox) calculated from capacitance–voltage (CG−VG) measurements decreases linearly from 25.7 for Ta2O5 to 7.9 for Al2O3. The interface trap density (Dit) is estimated from the frequency dispersion of capacitance–voltage (CG−VG) characteristics. The DC and radio frequency (RF) characteristics of AlxTayO/Al0.3Ga0.7N/GaN high electron mobility transistor (HEMT) devices are measured and compared with the Schottky HEMT devices (without any gate oxide). Compared to Schottky HEMT devices, AlxTayO/Al0.3Ga0.7N/GaN HEMT devices show superior DC characteristics, which helps us achieve maximum RF output power. Furthermore, the OFF-state measurements show that the AlxTayO/Al0.3Ga0.7N/GaN HEMT devices can sustain higher source-to-drain voltages, from a minimum of 88 V on pure Ta2O5 metal-oxide-semiconductor (MOS)-HEMTs to a maximum of 138 V on pure Al2O3 MOS-HEMTs before the dielectric breakdown happens, compared to a 57 V breakdown voltage on Schottky HEMT devices. An oxide variation of AlxTayO, with Al composition ratio of 0.34, shows an exceptional ION/IOFF ratio of 4 × 1011, a gate leakage current of 8 × 10−12 A/mm, a near-ideal subthreshold slope of 63.8 mV/dec, and the unity current gain frequency (fT) of 25.6 GHz.

Large-scale fabrication of meta-axicon with circular polarization on CMOS platform

Abstract Metasurfaces, consisting of arrays of subwavelength structures, are lightweight and compact while being capable of implementing the functions of traditional bulky optical components. Furthermore, they have the potential to significantly improve complex optical systems in terms of space and cost, as they can simultaneously implement multiple functions. The wafer-scale mass production method based on the CMOS (complementary metal oxide semiconductor) process plays a crucial role in the modern semiconductor industry. This approach can also be applied to the production of metasurfaces, thereby accelerating the entry of metasurfaces into industrial applications. In this study, we demonstrated the mass production of large-area meta-axicons with a diameter of 2 mm on an 8-inch wafer using DUV (Deep Ultraviolet) photolithography. The proposed meta-axicon designed here is based on PB (Pancharatnam–Berry) phase and is engineered to simultaneously modulate the phase and polarization of light. In practice, the fabricated meta-axicon generated a circularly polarized Bessel beam with a depth of focus (DoF) of approximately 2.3 mm in the vicinity of 980 nm. We anticipate that the mass production of large-area meta-axicons on this CMOS platform can offer various advantages in optical communication, laser drilling, optical trapping, and tweezing applications.

An investigation of γ radiation detection with a CMOS imaging sensor.

In this study, a feasibility of γ radiation detection using complementary metal-oxide semiconductor (CMOS) image sensors with a neural network algorithm to extract the γ rays interacted pixels has been investigated. The responses characteristics of the CMOS imaging sensor to γ-ray is studied by placed in a γ fields produced by standard60Co or137Cs isotope sources. The supported preview frame rate of the CMOS image sensor is 25 fps, establishing the functional relationship between the gray level histograms and the dose rate through the neural network, the high energy γ-ray from60Co and137Cs source radiation dose rate in µSv/h level can be detected using the CMOS imaging sensor. The results show that the proposed method can effectively identify the number of photon particles which detected by the radiation monitoring system based on CMOS image sensor, and infer that the CMOS imaging sensor with a radiation signal extraction algorithm can be used as a dose warner for radiation protection purpose.

Nonlinear electronic devices on single-layer CVD graphene for thermistors

In this article, we present simple, cost-effective, passive (non-gated) electronic devices based on single-layer (SL) chemical vapor deposited (CVD) graphene that show nonlinear and asymmetric current-voltage characteristics (CVCs) at ambient temperatures. Al2O3-Ti-Au contacts to graphene results in a nonlinear resistance to achieve nonlinearity in the CVC. Upon transfer to polyethylene terephthalate, the CVD-grown SL graphene shows mobility of 6200 cm2V-1S-1. We have observed both thermoelectric effect and thermoresistive sensing in the fabricated devices such as voltage and temperature concerning change in electronic power and resistance through asymmetric and nonlinear CVC. The device is stable both at low and high voltages (±200 mV to ±4 V) and temperatures (4 K - 300 K). Graphene-based thermosensing devices can be ultra-thin, cost-effective, non-toxic/organic, flexible, and high-speed for integration into future complementary metal-oxide semiconductor (CMOS) interface, and wearable self-power electronics. A strong negative temeperature coefficent of resistance is demonstrated in the realized nonlinear graphene-integrated resistors for its application in NTC thermistors.

Process optimization of preparing CMOS backplane for ultrahigh pixel density red Micro-LED display

Abstract In this paper, an AlGaInP-based red Micro-LED display measured 17.78 mm (0.7 in), with a resolution of 1920 × 1080, a light-emitting mesa size of 6 μm, a pixel pitch of 8 μm and a pixel density of 3175 PPI was designed and fabricated with a CMOS driver backplane. The metal bump preparation technology of the complementary metal-oxide semiconductor driver backplane was optimized to enhance the bonding yield and create an optimal display effect. Improper sizing of the etched window in the SiO2 insulation and passivation layer can have a detrimental impact on the metal bump preparation and subsequent bonding process. By optimizing the settings of lithography and dry etching, the appropriate size of the etched aperture in the passivation layer was achieved. The high density, small size, and large aspect ratio of the photoresist openings for the bump fabrication made it challenging to remove the photoresist following the metal evaporation. To successfully remove the photoresist, it is important to carefully choose suitable experimental conditions for the removal. Afterwards, an 8 μm AlGaInP-based red Micro-LED display was effectively integrated with complementary metal-oxide semiconductor using flip-chip bonding technology. This work may be of reference value to those who work on ultrahigh density red Micro-LEDs that is challenging but crucial for future full color micro displays.

Design of SRAM cell using an optimized D-latch in quantum-dot cellular automata (QCA) technology

A newer nanoscale technology called quantum-dot cellular automata (QCA) has been used by researchers to design digital circuits in place of the more traditional complementary metal–oxide semiconductor (CMOS) technology. This recent development in the technology change is due to the problems faced by CMOS technology in terms of power consumption and physical limitations. The advantages of QCA technology over CMOS technology are high density, low power consumption, high-speed operation, and less footprint area. This research provides a novel circuit for D-latch and static random access memory (SRAM) cells based on QCA technology. Initially, a D-latch circuit is proposed with a layout area of 0.01 μm2, a 0.5 clock cycle delay (latency), and a cell count of 18 QCA cells. Furthermore, an SRAM cell is proposed using the same D-latch circuit, which uses cell counts of 26 QCA cells and contributes to a layout area of 0.02 μm2 with a 0.75 clock cycle delay (latency). It is observed that our proposed circuits have a smaller layout area, fewer QCA cell counts, and a lower clock cycle delay (latency) than existing circuits.

Scalable on-chip multiplexing of silicon single and double quantum dots

Owing to the maturity of complementary metal oxide semiconductor (CMOS) microelectronics, qubits realized with spins in silicon quantum dots (QDs) are considered among the most promising technologies for building scalable quantum computers. For this goal, ultra-low-power on-chip cryogenic CMOS (cryo-CMOS) electronics for control, read-out, and interfacing of the qubits is an important milestone. We report on-chip interfacing of tunable electron and hole QDs by a 64-channel cryo-CMOS multiplexer with less-than-detectable static power dissipation. We analyze charge noise and measure state-of-the-art addition energies and gate lever arm parameters in the QDs. We correlate low noise in QDs and sharp turn-on characteristics in cryogenic transistors, both fabricated with the same gate stack. Finally, we demonstrate that our hybrid quantum-CMOS technology provides a route to scalable interfacing of a large number of QD devices, enabling, for example, variability analysis and QD qubit geometry optimization, which are prerequisites for building large-scale silicon-based quantum computers.

Electron Irradiation on Metal Oxide Silicon Field Effect Transistors in Space Applications

The space environment is hostile to most semiconductor electronic devices and components used for space applications. The radiation generally encountered in space are α, β, γ, x-ray, energetic electrons, protons, neutrons and ions of various kinds. Especially the Van Allen Belts consist of high energy electrons which are in continuous motion. Satellites systems operating in Low Earth Orbits (LEO) are prone to get exposed to high energy electrons. This paper describes the effect of electron beam irradiation on MOSFETs planned for space applications. The devices selected for the study are 2N6768 n- channel MOSFETs (JANTXV) procured from ISAC, Bangalore. The decapped MOSFETS are exposed to a beam of electrons for various doses ranging from 50 Gy to 10 KGy in the electron energy range 7 – 10 MeV using the electron accelerator facility at RRCAT, Indore. Pre and post- irradiation measurements of the electrical characteristics are undertaken to investigate the electron induced device degradation and damage. The dominant mechanism of the interaction of the electrons with semiconductors is to produce atomic displacement which can have serious impact on electrical characteristics. MOS (Metal oxide semiconductor) devices are the most sensitive of all semiconductor devices to radiation showing considerable degradation even for a relatively low dose of exposure to high energy electrons. The energy dissipated by electrons in semiconductors is sufficient to displace silicon atoms and causes a shift in the threshold voltage and leakage current. The study indicates that the gate threshold voltage substantially decreases with the increase in electron dose. The leakage current increases with dose which could have an impact on the performance of the device. The transconductance of the MOS transistor is found to decrease with increase in electron dose. The observed changes in the electrical characteristics upon electron irradiation are analysed and interpreted as due to trapped charges in the SiO2 layer and at the interface. The present investigation reveals that there is a remarkable degradation in threshold voltage and the leakage current displays substantial increase when the devices are exposed to electrons. This increase in leakage current can have significant impact on device performance in a radiation environment.

Investigation on oxygen vacancy regulation mechanism of ZnO gas sensors under temperature modulation mode to distinguish alcohol homologue gases

Homologous gases are difficult to be detected due to their similar chemical properties, especially for metal oxide semiconductor gas sensors whose selectivity has always been a significant challenge. Dynamic temperature modulation method with periodically changing operating temperature was used to detect alcohol homologous gases. However, there are still problems with the deviceization of heating control circuits. In this paper, dynamic temperature modulated method which needs a simple heating circuit is used to distinguish alcohol homologous gases in combination with oxygen vacancy modulation of ZnO gas sensors. Ethyl alcohol, n-propyl alcohol, isopropyl alcohol and n-butyl alcohol were measured by ZnO gas sensors with different oxygen vacancies content ratios under rectangular wave with a voltage range of 2–6 V. It was found that the greatest difference among the response curves when the material calcined at 600°C which has the largest oxygen vacancies content ratio. Finally, the recognition of the four homologue gases measured by ZnO-600 sensor was achieved by dynamic time warping and the recognition accuracy is 99.33 %.

ITO-Based Electrically Tunable Metasurface for Active Control of Light Transmission.

In recent years, the rapid development of dynamically tunable metasurfaces has provided a new avenue for flexible control of optical properties. This paper introduces a transmission-type electrically tunable metasurface, employing a series of subwavelength-scale silicon (Si) nanoring structures with an intermediate layer of Al2O3-ITO-Al2O3. This design allows the metasurface to induce strong Mie resonance when transverse electric (TE) waves are normally incident. When a bias voltage is applied, the interaction between light and matter is enhanced due to the formation of an electron accumulation layer at the ITO-Al2O3 interface, thereby altering the resonance characteristics of the metasurface. This design not only avoids the absorption loss of metal nanostructures and has a large modulation depth, but also shows compatibility with complementary metal oxide semiconductor (CMOS) technology.

CMOS-compatible plasmonic magnetic field sensor: An alternative approach using ultra-compact MIM configuration

This paper introduces a novel magnetic field sensor (MFS) that utilizes a metal-insulator-metal (MIM) waveguide integrated with a resonator structure and incorporates water-based Fe3O4 magnetic fluid. The sensor uses titanium nitride (TiN) as the plasmonic material which offers numerous advantages over conventional noble plasmonic materials. The sensor takes advantage of the tunable optical properties of the magnetic fluid and TiN to detect changes in the external magnetic field and quantify the magnetic field strength which has been demonstrated using the Finite Element Method (FEM). Our proposed MFS exhibits a high sensitivity of 11.97 pm/Oe, a narrow-band full-width half maximum of 93.66 nm, and a resolution of 8.36 × 10−4 Oe. The sensor is also compatible with complementary metal oxide semiconductor (CMOS) fabrication techniques, which enables chip-scale integration and low-cost production. The sensor can be used for various applications in navigation, military, space, healthcare, and beyond.

Real-time, specific, and label-free transistor-based sensing of organophosphates in liquid

Organophosphates (OP), commonly used in agriculture and as chemical warfare agents, pose significant environmental risks, necessitating real-time, low-cost OP detection methods. In particular, liquid-phase OP sensing with minimal sample volumes is crucial. While several methods allow rapid detection of low concentrations of OP vapors, they are effective only in the short term, while vapors are still being produced. Many OP compounds are semi-volatile, leading to the contamination of water, soil, and surfaces, posing a risk of secondary, long-term exposure. Detecting this contamination requires methods that can be directly applied to droplets of the affected medium. Currently, no method provides the desired combination of ultra-sensitivity, quantitative detection, rapid response, and low-cost for detecting OPs in liquid samples. This study aims to demonstrate quantitative, low-cost, real-time, specific, and label-free OP sensing in ultra-small samples using a transistor-based approach. The current work employs the 2-(4-Aminophenyl)-1,1,1,3,3,3-hexafluoro-2-propanol (aminophenyl-HFIP) functionalized meta-nano-channel field-effect chemical sensor (MNChem sensor) to monitor the organophosphate, diethyl cyanophosphonate (DCNP), in liquid samples. The silicon component of the MNChem is fabricated using a complementary metal-oxide semiconductor (CMOS) process, and the amine-based chemical functionalization of the sensing area is performed post-fabrication. The MNChem sensor provides electrostatic control over the source-drain current (IDS), allowing an optimized channel configuration that efficiently transduces localized OP recognition events into significant IDS variations. Sensing is performed using 0.5 μL buffer solution to simulate a miniature field-deployable sensor for on-site liquid analysis. We report the sensing of DCNP with a limit-of-detection of 100 fg/mL, a dynamic range of 9 orders of magnitude, and excellent linearity (≥0.97) and sensitivity. Control measurements confirm the specificity and reliability of the sensor's response, validating its applicability. This study introduces a novel method for OP detection in contaminated droplets using a low-cost disposable transistor technology.

Taguchi Method Statistical Analysis on Characterization and Optimization of 18-nm Double Gate MOSFETs

A bi-layer graphene with a multigate structure was intensified and analysed on an 18-nm Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) device to obtain an optimal performance parameter. The device has a gate structure made of Titanium Dioxide (TiO2) that serves as a high-k material and a metal gate made of Tungsten Silicide (WSix). The Silvaco TCAD Software which are ATHENA and ATLAS modules were used to enhance the fabrication process of virtual devices and to verify the electrical properties of a specific device. According to the International Technology Roadmap Semiconductor (ITRS) specifications of 0.179 V ± 12.7% for threshold voltage (VTH) and 20 nA/m for leakage current (ILEAK), the Taguchi L9 orthogonal array strategy was used to improve the device process parameters for optimum VTH and ILEAK. For the NMOS device, the process parameter of VTH Adjust Implant Dose was used as the dominant factor while Source/Drain (S/D) Implant Energy was used as the adjustment factor whereby for PMOS device, S/D Implant Energy was the dominant factor while S/D Implant Tilt was the adjustment factor in order to achieve a robust design through the Taguchi method implementation. The percentage affecting the process parameter is then applied to the results of the signal to noise ratio (SNR) of Nominal-the-best (NTB) for VTH and Smaller-the-better (STB) for ILEAK.