Photoresist Research Articles

An Inductor‐Less Zero‐IF Down‐Conversion Mixer With Low Flicker Noise and High Conversion Gain

ABSTRACTThis paper presents a novel active inductor (AI) to improve the performance of a down‐conversion active mixer in terms of conversion gain (CG) and flicker noise. The proposed AI exhibits negative resistance and partially flat inductance over a wide frequency band of 0.5–4.5 GHz. The effect of inserting the AI between the source of the switching quad of a Gilbert cell mixer is theoretically analyzed. The proposed inductor‐less mixer, designed to operate at a 2.4‐GHz RF input frequency and a 10‐MHz IF output frequency, employs current reuse and self‐forward body bias (SFBB) techniques. The proposed circuit is simulated in Cadence Spectre‐RF using RF‐TSMC 0.18‐μm CMOS technology. Post‐layout simulations demonstrate that the proposed AI significantly reduces flicker noise by over 23 dB at an IF output frequency of 1 kHz and improves the CG by over 16 dB at an RF frequency of 2.4 GHz. The proposed mixer achieves a CG of 37.6 dB and a flicker noise corner frequency of 6 kHz. Additionally, it exhibits a third‐order intermodulation intercept point (IIP3) of −5.2 dBm and a double‐sideband noise figure (DSB‐NF) of 6.1 dB at the IF output frequency of 10 MHz. Operating with a 1.5‐V supply, the proposed mixer consumes 10.6 mW of power.

Exceptional Field Effect and Negative Differential Conductance in Spiro-Conjugated Single-Molecule Junctions.

The advancement of molecular electronics endeavors to build miniaturized electronic devices using molecules as the key building blocks by harnessing their internal structures and electronic orbitals. To date, linear planar conjugated or cross-conjugated molecules have been extensively employed in the fabrication of single-molecule devices, benefiting from their good conductivity and compatibility with electrode architectures. However, the development of multifunctional single-molecule devices, particularly those with unique charge transport properties, necessitates a more rigorous selection of molecular materials. Among different assortments of molecules suited for the construction of molecular circuits, Spiro-conjugated structures, specifically spirobifluorene derivatives, stand out as promising candidates due to their distinctive electronic properties. In this work, we focus on the charge transport characteristics of Spiro-conjugated molecules sandwiched between graphene nanogaps. Experiments reveal significant Coulomb blockade and distinct negative differential conductance effects. Beyond two-terminal device measurements, solid-state gate electrodes are utilized to create single-molecule transistors, successfully modulating the molecular energy levels to achieve an on/off ratio exceeding 1000. This endeavor not only offers valuable insights into the design and fabrication of future practical molecular devices, blessed with enhanced performance and functionality, but also presents a new paradigm for the investigation of fundamental physical phenomena.

Two-Dimensional Nanoarchitectonics of End-on Oligomers with Versatile Structures and Tunable Negative Differential Resistance.

Maximizing the molecular information density requires simultaneously functionalizing distinct monomers and their coupling connections. However, current synthesis generally focuses on distinct monomers rather than coupling reactions because the multistep reactions significantly escalate the synthetic complexity in an exponential increase. Here, we report the two-dimensional nanoarchitectures (2DNs) of end-on oligomers, with versatile molecular structures and negative differential resistance (NDR), synthesized by programmed and surface-initiated step electrosynthesis based on the simultaneous utilization of six reactions including cross- and homocouplings. The resulting vertically end-on oligomers, with similar values in thickness and molecular length, as crystalline 2DNs, exhibit subnanometer uniformity, ultrahigh compressive modulus of 40 GPa, and low-bias NDR at 0.13 V with an ultralow power consumption of down to 0.05 nW/μm2. This highly controlled electrosynthesis provides a unique dimension to enhance the structural diversity of molecular 2D nanomaterials for high-density and low-power consumption electronics.

A low-power quadrature voltage-controlled oscillators with LC emitter degeneration phase shift technique

This paper introduces a novel phase-shifting technique for quadrature voltage-controlled oscillators (QVCOs) utilizing an LC emitter degeneration architecture. The proposed technique enables a phase shift of up to ±90°in the transconductance of the coupling path while also generating a negative input resistance. This innovative approach avoids phase ambiguity, mitigates the trade-off between phase noise and phase error, and substantially reduces QVCO power consumption. Moreover, compared to conventional capacitance emitter degeneration methods, the LC emitter degeneration structure has a lower equivalent input capacitance, expanding the QVCO’s frequency tuning range. The designed QVCO is implemented using a 180 nm SiGe BiCMOS technology, occupying a compact area of 0.037 mm2. Post-layout simulation evaluations under various process, voltage, and temperature (PVT) conditions validate the robustness and reliability of the design. Results indicate a phase noise of 102.7 dBc/Hz at a 1 MHz offset from a 22.1 GHz carrier, a frequency tuning range of 25.2%, a phase error of 0.9°, and a power consumption of 12 mW from a 1.1 V supply, achieving a figure of merit (FoM) of 178.8 dBc/Hz.

Negative Differential Resistance Device with High Peak-to-Valley Ratio Realized by Subband Resonant Tunneling of Γ-Valley Carriers in WSe2/h-BN/WSe2 Junctions.

Resonant tunneling diodes (RTDs) are a core technology in III-V semiconductor devices. The realization of high-performance RTD using two-dimensional (2D) materials has been long awaited, but it has yet to be accomplished. To this end, we investigate a range of WSe2/h-BN/WSe2 RTD devices by varying the number of layers of source and drain WSe2. The highest peak-to-valley ratio (PVR) is demonstrated in the three-layer (3L) WSe2/h-BN/1-layer (1L) WSe2 structure. The observed PVR values of 63.6 at 2 K and 16.2 at 300 K are the highest among the 2D material-based RTDs reported to date. Our results indicate the two key conditions to achieve high PVR: (1) resonant tunneling should occur between the Γ-point bands of the source and drain electrodes, and (2) the Γ-point bands contributing to the resonant tunneling should be energetically separated from the other bands. Our results provide an important step to outperform III-V semiconductor RTDs with 2D material-based RTDs.

Graphene nanoribbon resonant tunneling diode with dual connection between contacts

In this paper, we numerically study the transport properties of a resonant tunneling diode (RTD) based on graphene nanoribbon (GNR) with an H-type antidote between the contacts. The structure may also be thought of as having two parallel (W-shape) parts connecting the contacts, each having a wider channel region sandwiched between two narrower barrier regions. The energy at which quasi-bound states occur in each part depends on the dimensional parameters of the respective portion in the structure. We study how the transmission through quasi-bound states is influenced by the edge states on the contacts and dimensional parameters such as barrier length and also by the ambient temperature. The results are compared with those of an RTD with a single part connecting the contacts. Transmission peaks at different energies are observed for an RTD with asymmetrical lower and upper parts between the contacts. This is then utilized for the creation of two negative differential resistance (NDR) peaks. For numerical computation, the non-equilibrium Green’s function formalism (NEGF) based on the nearest neighbor tight-binding model is employed.

Valleytronics and negative differential resistance in cubic boron nitride: A first-principles study

Valleytronics and negative differential resistance in cubic boron nitride: A first-principles study

VCII‐Based Immittance Simulators: Generalized Parallel Configurations

ABSTRACTIn this paper, four new generalized configurations of grounded parallel‐type immittance simulators are proposed. These circuits implement parallel resistor–inductor (RL), parallel resistor–capacitor (RC), parallel capacitor–frequency‐dependent negative resistance (CD), and capacitance multiplier configurations utilizing only two second‐generation voltage conveyors (VCII±) as active elements along with three impedances, without the need for specific matching conditions. The applicability of the proposed parallel RL and capacitance multiplier configurations as a second‐order high‐pass filter (HPF) and a first‐order low‐pass filter (LPF), respectively, is also demonstrated. These applications illustrate the versatility and utility of the proposed structures. Frequency, transient, and Monte Carlo analysis utilizing the CMOS VCII± in the SPICE simulation tool have also been performed to validate the feasibility of the presented circuits. Further validation is carried out through layout design in Cadence Virtuoso, employing 0.18‐μm CMOS technology. Both presimulation and postsimulation results are presented for a thorough assessment of the proposed circuits. Also, the claimed theory is verified by experimental results based on the VCII implementation with commercially available IC AD844.

Design of N-doped C60-σ-B-doped C60 photodetector based on resonant tunneling diode using DFT and NEGF method.

Photodetectors utilizing donor/acceptor (D/A) molecules have the capacity to detect light through molecular interactions between a donor and an acceptor molecule. These devices leverage electronic or optical changes within molecules when exposed to light, resulting in observable modifications. The unique properties of photodetectors with D/A molecules make them valuable tools in various fields, including molecular electronics. This paper presents the modeling and simulation of a single-molecule photodetector based on a D/A molecule configuration. The acceptor molecule used is N-doped C60 fullerene, while the donor molecule is B-doped C60 fullerene. Initially, simulations were conducted at zero bias voltage to determine the energy and states of the bipartite molecule. Subsequently, the system's Hamiltonian was computed based on these results. The self-consistent field method (SCF) and optical self-energy coefficients were employed for modeling. Finally, the current-voltage curve of the device was derived for various input light frequencies. The simulation and modeling results demonstrated that the device exhibited negative differential resistances at bias voltages of 0.33 V, 1.58 V, and - 0.93 V, depending on the input light frequency. Furthermore, the designed device demonstrated the ability to detect and absorb waves with different frequencies. The number of current peaks in the current-voltage curve varied with by altering the number of optical modes. The computational work was conducted using the software package of Atomistix ToolKit (ATK-2018.06) and MATLAB code. The calculations were based on the density functional theory (DFT) approach and the self-consistent field method, specifically the non-equilibrium Green function (NEGF). The exchange correlation function was investigated using the generalized gradient approximation (GGA) proposed by Perdew, Burke, and Ernzerhof (PBE). For the calculations, we employed the double-ζ plus polarization (DZP) basis set. Initially, the structures of N doped-C60-σ-B-doped-C60 molecule underwent optimization using the DFT approach implemented in the ATK package. This optimization process allowed us to extract the parameters of the molecule. Subsequently, we utilized the NEGF formalism in MATLAB software to model and simulate photodetector based on the optimized molecule. We calculated important features of the photodetector, such as photocurrent, and compared the performance of the photodetector using photons with energies of 2 and 3 eV.

Etch characteristics of maskless oxide/nitride/oxide/nitride (ONON) stacked structure using C4H2F6-based gas

Oxide/Nitride/Oxide/Nitride (ONON; SiO2/SiNx/SiO2/SiNx) stacked structure is widely used in the 3D vertical structure of semiconductor cells. Previously, to form a 3D cells, photoresist (PR) was patterned and repeatedly trimmed on the top of ONON after the etching of one ON layer. Due to the time-consuming process of etching layer-by-layer of ON layer, two-step etch processing using C4F8-based or C4F6-based gases composed of maskless ONON stack feature etching and followed one ON layer-by layer etching by PR trimming in the ONON stack feature are employed these days. However, the two-step etching method resulted in poor etch profiles of maskless ONON stack feature in addition to high global warming potential of C4F8 and C4F6. In this study, we investigated the etching of maskless ONON stack feature using C4H2F6-based gas having a low global warming potential and the effects of C4H2F6-based gas on the etch characteristics of maskless ONON stack feature such as etch rate, etch profile, change in critical dimensional (CD), and etch selectivity between SiO2 and SiNx have been investigated. C4H2F6-based gas showed the highest etch rates compared to C4F6 and C4F8-based gases in addition to the etch selectivity of ~ 1:1 between SiO2 and SiNx due to hydrogen included in the gas structure. In addition, the change in horizontal CD was lower in the order of C4H2F6, C4F6, and C4F8-based gases due to the more effective sidewall passivation in the order of C4F8, C4F6, and C4H2F6-based gases. The thicker carbon-based polymer layer on the sidewall also played an important role in maintaining the shape of the top edge shape of maskless ONON stack feature when etching a line feature in an environment without a mask.

Pretreatments for photoresist-patterned wafer to improve Cu pillar electrodeposition

Cu micropillars are essential components in the electronics packaging, basically connecting multiple chips. The pillars are fabricated by Cu electrodeposition that fills inside via holes formed through a photoresist (PR) layer. Unlike Damascene and TSV processes, the Cu seed layer is only opened at the bottom of via holes, while the rest of the wafer surface is covered by the PR. Therefore, additional pretreatments are required to improve the Cu electrodeposition process due to air bubbles entrapped inside PR holes, organic residues, and native oxide on Cu seed layers. This research systematically investigated the pretreatments for PR-patterned wafers. A humidifier, hot steam, and compressed water spray were assessed for surface hydration to remove air bubbles from the PR holes. Ethanol- and citric acid-based aqueous solutions were then applied to remove organic residues and native oxide from the surface of Cu seed layers. The advantages of these pretreatments were assessed by analyzing the quality of Cu electrodeposits, and the optimum methods and solutions for Cu pillar electrodeposition on the PR-patterned wafer were suggested.

A wideband high-PSR OCL LDO using a gain-relaxed OTA featuring dynamic complex zeros frequency compensation

This article proposes an Output-Capacitor-Less (OCL) Low-Dropout (LDO) regulator with an assisted positive feedback loop technique, which mimics a negative resistance, along with a single common-gate stage. Conventional techniques utilize multistage high-gain OTA to achieve a high DC loop gain. However, such an OTA suffers from high power consumption and sophisticated frequency compensation mechanisms. Instead, the use of a single-stage relatively low-gain OTA helps to extend the bandwidth. Then, the overall DC loop gain is maximized by the proposal of a novel negative resistance circuit. To further improve the PSR, a bulk-driven ripple canceling path that is insensitive to process corners is proposed making the LDO suitable for high-PSR applications. Stability is another challenge in the design of OCL LDOs due to its associated complex poles. We propose a new frequency compensation technique by introducing two complex zeros to eliminate these complex poles. Hence, the overall stability is improved. Since these complex poles location vary from light to heavy loads, the proposed zeros dynamically change accordingly. Besides, this suggested mechanism has been analyzed using the generalized time-and-transfer constants (TTCs) circuit analysis technique. Under heavy load conditions, the suggested LDO has attained phase and gain margins of 62.8° and 29 dB, respectively. Moreover, Monte Carlo simulations along with process and temperature variations have been investigated to prove the reliability of such a frequency compensation technique. The proposed LDO has been implemented in 65 nm CMOS technology node with a short pass transistor length of 100nm. The simulation results reveals that the LDO draws 299.4μA of quiescent current under light load conditions and 296.8μA under heavy load conditions (including the bandgap voltage reference). The suggested LDO functions at 1.2V supply voltage, delivers 0.93V output voltage and can handle a load current up to 10mA with load regulation of 17μV/mA, line regulation of 2.22mV/V, and PSR of −48.7dB at low frequencies. The PSR at 1MHz is at least −32.5dB which is superior to the reported recent LDOs.

Negative Sequence Impedance Emulation: A New Perspective and Control

Negative Sequence Impedance Emulation: A New Perspective and Control

Relaxation behaviour, conductive grains and resistive boundaries of bismuth-based double perovskite Bi2-xLaₓFeGaO₆

The successful synthesis of the ceramic Bi2-xLaxFeGaO6 powder ceramic sample with varying La content (x = 0.01, 0.03, 0.07, 0.10) were synthesized via the solid-state method. Analysis using X-ray diffraction at room temperature was carried out to examine its structure, revealing a crystallite size of approximately 22.07–50.84 nm. This size indicates the potential applications in microwave technology due to its small grain size, which has the capability to enhance microwave absorption properties. The dielectric constant of the material shows an increase with the frequency applied, in accordance with the behaviour anticipated by the dielectric HN model and Debye model. This model proposes that the material's dielectric response can be manipulated by modifying the applied frequency, making it a valuable tool in the material design for specific purposes. The full width at half maximum (FWHM) curve of the electrical modulus displayed variability, suggesting the existence of a non-Debye relaxation mechanism in the material. This indicates that the material could possess distinct electrical properties that might be beneficial for certain applications. The outcomes demonstrated a negative temperature coefficient resistance (NTCR), indicating a decrease in the material's resistance with increasing temperature. Such behaviour can be advantageous in situations where temperature variations require monitoring or regulation. The Cole-Cole plot illustrated that the grains exhibit conductive behaviour at lower frequencies, a crucial insight for comprehending the material's electrical properties. In conclusion, these results indicate that the ceramic Bi2-xLaxFeGaO6 for x = 0.01, 0.03, 0.07, 0.1) showcases promising attributes for various applications, particularly in microwave technology and electrical conductivity.

The novel methods of insulation detection based on Adaptive Levenberg–Marquardt algorithm and Third-Order Variable Forgetting Factor Recursive Least Squares-Decouple algorithm

Electric vehicles (EVs) are central to the future of automotive development, with high-voltage insulation performance critical for operational safety. Existing insulation detection methods face challenges such as limited scope, low accuracy, poor interference resistance, and slow response. This study introduces two insulation detection models based on the unbalanced bridge method and low-frequency signal injection, analyzing their theoretical effectiveness and confirming superior detection capability in the unbalanced bridge method. Furthermore, to address feedback voltage waveform issues in this method, an adaptive Levenberg–Marquardt (ALM) algorithm is proposed to prevent the divergence typically seen in traditional approaches. Additionally, a decoupling algorithm utilizing a Third-order Variable Forgetting Factor Recursive Least Squares (TVFF-Decouple) simplifies algorithm complexity significantly while enabling anomaly detection. Finally, AEKF and SRCKF algorithms were used for observation, identifying an optimal combination that reduces noise interference effectively. Simulations and bench tests demonstrate that the proposed methods swiftly and accurately detect positive and negative insulation resistances and equivalent Y capacitance under various conditions.

Semiconductive-like behaviour and negative differential effect observed in self-assembled riboflavin layer on gold electrodes

Riboflavin or vitamin B2 plays significant roles in metabolic reactions and energy production, establishing it as an important research subject in biology and medicine. While there are numerous riboflavin-related publications in these fields, interrogation of its electronic properties in relation to the physiological function at the cellular level remains obscure due to technological challenges. However, progress in molecular electronics and the discovery of the semiconductor-like behaviour of biomolecules in recent times have initiated growing interest in exploring the electronic properties of these materials for potential bioelectronic device applications. In this work, we demonstrate novel semiconductor-like behaviour in riboflavin within a gold/Riboflavin/gold Schottky junction. We observed the occurrence of two negative differential resistance peaks at low voltages of 1.5 and 2.0 V, probably the first-ever report of this effect in a biomolecule. Interestingly, the proposed mechanism simulates a single Schottky junction behaviour despite the physical existence of two junctions. Solid-state parameters such as turn-on voltage, shunt resistance, and ideality factor were also calculated using Conventional and Cheung and Cheung’s methods. The results were highly characteristic to the riboflavin studied when compared to previous works on biomolecules. This opens up the possibility of developing solid-state sensors for electronically characterising biomolecules like vitamins to help advance our understanding of the electronic properties of these essential nutrients.

Large-signal stability analysis of an islanded DC microgrid with constant power loads based on mixed potential function

Abstract In DC microgrids, power electronic converters are widely used to connect loads and renewable energy sources to generate different voltages. These loads operate as constant power loads (CPL) within a closed control loop. When voltage fluctuates, these loads display negative impedance characteristics, potentially leading to system instability. Therefore, the analysis of the impact of CPL on DC microgrids during large disturbances is crucial. This paper employs mixed potential theory to study the large disturbance stability of DC microgrids under CPL. Deriving the stability criterion for the system under significant perturbations reveals the impact of load types and control parameters on system stability and provides a detailed analysis of how specific system parameters affect stability. Consequently, the stability criterion can ensure the system’s stability under large disturbances without the need for repeated calculations and simulations. Simulation results verify the correctness of this stability criterion.

Low bias charge transport in DNA.

The low-bias current-voltage technique was utilized to study charge transport in single-stranded DNA (ssDNA), assessing the method's effectiveness for future studies aimed at estimating the degree of mutation or DNA damage. In the paper, we showed that charge carrier transfer processes in ssDNA can be precisely monitored using low-bias currents. We used negative differential resistance and the Fowler-Nordheim model to differentiate the charge transport mechanisms observed in a device composed of gold electrode-thiol-ssDNA junctions. It was possible to distinguish the processes at the two junctions (Au/thiol and thiol/DNA) due to their distinct current-voltage characteristics. We observed positive charge carrier tunneling, which we attribute to oxidation and reduction processes in the nucleobases of the ssDNA. Our results suggest that even minor changes in DNA chains can be accurately detected using the described methodology.

Molecular switching by proton-coupled electron transport drives giant negative differential resistance

To develop new types of dynamic molecular devices with atomic-scale control over electronic function, new types of molecular switches are needed with time-dependent switching probabilities. We report such a molecular switch based on proton-coupled electron transfer (PCET) reaction with giant hysteric negative differential resistance (NDR) with peak-to-valley ratios of 120 ± 6.6 and memory on/off ratios of (2.4 ± 0.6) × 103. The switching dynamics probabilities are modulated by bias voltage sweep rate and can also be controlled by pH and relative humidity, confirmed by kinetic isotope effect measurements. The demonstrated dynamical and environment-specific modulation of giant NDR and memory effects provide new opportunities for bioelectronics and artificial neural networks.

Extreme Chemical Reduction on Photoresist Stripping Process by Using Sulfuric Acid Ozone Mixture in Liquid Film

Sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) mixture (SPM) has been widely used in the photoresist (PR) stripping process of semiconductor manufacturing. However, the consumption of H2SO4 and H2O2 increases environmental burden such as water pollution. To reduce SPM consumption, one of the ideas was that SPM was supplied to the wafer until liquid film was formed and stopped during stripping process instead of continuous dispensing. It was concerned that chemical species in SPM became inactive while SPM was stopped. Therefore, in this work, H2SO4 liquid film was formed on the wafer and then exposed to ozone (O3) atmosphere so that chemical species remained active. Generation of peroxydisulfate ion (S2O8 2−) by reacting hydrogen sulfate (HSO4 −) with O3 was the key to achieve PR stripping (1, 2). Results showed sulfuric acid ozone mixture (SOM) in liquid film was comparable to conventional SPM even though chemical consumption of SOM was extremely reduced.