Measurements Of Test Structures Research Articles

Edge-TCT evaluation of high voltage-CMOS test structures with unprecedented breakdown voltage for high radiation tolerance

This paper presents the edge Transient Current Technique (eTCT) measurements of passive test-structures on the UKRI-MPW0 pixel chip, a 280 µm thick proof-of-concept High Voltage-CMOS (HV-CMOS) device designed and fabricated in the LFoundry 150 nm technology node with a nominal substrate resistivity of 1.9 kΩ cm. Samples were irradiated up to 1 × 1016 1 MeV neq cm−2 with neutrons to observe the change in depletion depth and effective doping concentration with irradiation. A depletion depth of the sensor was found to be ≈50 µm at ≈−400 V at 1 × 1016 1 MeV neq cm−2. A stable damage introduction rate (g c ) was also calculated to be 0.011 ± 0.002 cm−1.

Aluminum Acceptor Ionization Energies in 4H-SiC for Low Dose, Ultra-High Energy (> 1MeV) Implants

MeV level aluminum implants into 4H-SiC were performed as part of superjunction diode fabrication. Measurement of resistance test structures produced resistivities well above expected values with large decreases at elevated temperatures. Capacitance-voltage measurements indicate a high activation rate of the implanted aluminum. Temperature dependent Hall measurements produce reasonable hole mobilities with acceptor ionization energies of approximately 330meV, well above the 200meV expected for low concentration aluminum doping in 4H-SiC.

A novel cooperative design with optimized flow field on bipolar plates and hybrid wettability gas diffusion layer for proton exchange membrane unitized regenerative fuel cell

Proton exchange membrane unitized regenerative fuel cell (PEM-URFC), as a novel electrochemical device which combines fuel cell (FC) and water electrolyzer (WE), is gradually being recognized as promising power source with reduction of size and cost. Unsatisfying mass transfer ability under the two adverse modes is the main factor hindering the commercialization of URFC, which calls for a bifunctional cell structure. In this study, a novel cooperative design with interdigitated flow field on bipolar plate (BPP) and a hydrophilic-hydrophobic alternative gas diffusion layer (GDL) is proposed to compose a new means of mass transfer under both working modes. Cells made up with different combinations of BPPs and GDLs are tested to confirm the usefulness of the new design. The cell with the optimized structure shows great progress in performance. The current density increases by 11.5% under FC mode and 4.8% under WE mode. EIS test and GDL's structure measurement are also carried out to further explain the working principle of the positive effect made by the new system on the cell. It is also found that the novel design of the URFC in this study has great adaptability to various operating conditions based on the stability test.

CMOS Pixel Potentials Extraction Method From Test Structures Based on EKV Model

Knowing exactly potentials' distribution in pixels is a key to ensure that electron retention and transport enable a good pixel operation. Moreover, it is also a key parameter for control of charge storage capability or full-well capacity, strongly driven by potential barriers. In this article, a new method is presented to characterize potentials within pixels from test structure measurements. The proposed method enables to extract potential under a gate, pinning potential of photodiodes or memories, and any potential along the charge path. It is based on the use of the Enz-Krummenacher-Vittoz (EKV) model together with measurements on adequate test structures. Thanks to the so-called “ Y function series resistance correction,” the method can even be applied to test structures including devices in series as in real pixel. The method proposed here is assessed using Sentaurus technology computer-aided design (TCAD) simulation results. Such potentials extracted on the test structure can be used for process and pixel developments, device monitoring, reliability studies, and TCAD calibration.

Silicon Test Structures Design for Sub-THz and THz Measurements

In this article, we present on-wafer thru-reflect-line (TRL)-calibrated measurements of silicon test structures fabricated using STMicroelectronics' B55 technology up to 500 GHz. The structures are fabricated in two subsequent runs, and the respective structure in each run has a different design. The improvements in the test structures layout design are presented on the terminal capacitances of “open-M1,” which is an important test structure for the deembedding of the transistor accesses. The improvements are examined using high-frequency structure simulator (HFSS) electromagnetic (EM) simulations, including the RF probe models and the neighboring structures.

Анализ углеродсодержащих материалов методом вторично-ионной масс-спектрометрии: содержание атомов углерода в sp-=SUP=-2-=/SUP=-- и sp-=SUP=-3-=/SUP=--гибридных состояниях

A new approach to the analysis of carbon-containing materials by the method of secondary ion mass spectrometry is studied, which allows one to determine the concentration of carbon atoms in the states of sp2 and sp3 hybridization. It is proposed to use the ratio of the intensities of cluster secondary ions C8/C7 as the main parameter of the mass spectra of secondary ions characterizing the concentration of N(sp3). From measurements of several test structures, a calibration dependence of N (sp3) on the C8/C7 ratio was obtained. The N(sp3) profiles of diamond-like carbon samples grown on diamond and silicon substrates were measured, showing an N(sp3) concentration of 0.3 to 0.6 for different growth modes and an inhomogeneous distribution of the N(sp3) concentration over the thickness of the samples.

Measurements and simulations of surface radiation damage effects on IFX and HPK test structures

Radiation damage effects at High Luminosity LHC (HL-LHC) expected fluences and total ionizing doses (TID) will impose very stringent constraints in terms of radiation resistance of silicon detectors. In this work, we address the effects of surface damage on detectors fabricated on p-type substrates by two different foundries. Starting from standard test structure measurements, the interface trap state density and the oxide charge can be extracted for each specific foundry before and after irradiation with X-rays with doses ranging from 0.05 to 100 Mrad(SiO2). These parameters are then used as inputs to the Technology-CAD simulation tools, aiming at evaluating the effects of oxide charge density and interface trap density variation with the dose on MOS capacitor capacitances and interstrip resistances. The good agreement between simulation results and measurements would support the use of the model as a predictive tool to optimize the design and the operation of novel silicon detectors in the HL-LHC scenario.

Analysis of surface radiation damage effects at HL-LHC fluences: Comparison of different technology options

Radiation damage effects at High Luminosity LHC (HL-LHC) fluences greater than 2.2×1016n∕cm2 1 MeV equivalent and total ionizing doses (TID) greater than 1 Grad will impose very stringent constraints in terms of radiation resistance of solid-state detectors. To cope with this design challenge, TCAD tools can be used to study different technology and design options, in order to optimize the performance of silicon detectors in terms of inter-electrode isolation and charge collection properties. A comprehensive modeling approach based on combined bulk and surface damage effects accounting for a limited number of measurable parameters needs therefore to be developed and validated over different technology options. In this work, we mainly focus on the effects of surface damage on detectors fabricated on p-type substrates by different providers. Actually, starting from standard test structure measurements (i.e. MOS capacitors, gated diodes), the integrated interface trap state density (NIT) and the oxide charge (QOX) can be extracted for different vendors and used as input parameter to the simulation tools. Test structures under study include MOS capacitors, gated-diodes, fabricated both at Hamamatsu Photonics (Japan) and at Infineon (Austria). Using High-Frequency (HF) and Quasi-Static (QS) C–V characteristics and current–voltage (I–V) measurements, the effective oxide charge density (NEFF), the surface generation velocity (s0) and the interface trap density (DIT) have been determined and compared for the two technologies before and after irradiation with X-rays with doses ranging from 0.05 to 20 Mrad(SiO2). A detailed simulation analysis on MOS capacitor capacitances and gated diode currents has been carried out, varying the previously mentioned parameters, with the aim to evaluate the effects of oxide charge density and interface trap density increase with the dose. The separate effects of different types of interface trap states have been considered as well, by varying one by one the total density of donor- and acceptor-type trap states, respectively. The effects of different trap energy distributions and capture cross sections have been evaluated within Synopsys Sentaurus TCAD device simulator by means of steady-state, AC and transient analyses. The good agreement obtained for both vendors would support the use of the model as a predictive tool to optimize the design and the operation of novel solid-state detectors in the HL-LHC scenario.

A combined surface and bulk TCAD damage model for the analysis of radiation detectors operating at HL-LHC fluences

In this work we present the development and the application of a new TCAD modelling scheme to simulate the effects of radiation damage on silicon radiation detectors at the very high fluence levels expected at High Luminosity LHC (up to 2 × 1016 1MeV n/cm2). In particular, we propose a combined approach for the analysis of the surface effects (oxide charge build-up and interface trap states introduction) as well as bulk effects (deep level traps and/or recombination centers introduction). Experimental measurements have been carried out aiming at: i) extraction from simple test structures of relevant parameters to be included within the TCAD model and ii) validation of the new modelling scheme through comparison with measurements of different test structures (e.g. different technologies) before and after irradiation. The good agreements between experimental measurements and simulation findings foster the suitability of the TCAD modelling approach as a predictive tool for investigating the radiation detector behavior at different fluences and operating conditions. This would allow the design and optimization of innovative 3D and planar silicon detectors for future HL-LHC High Energy Physics experiments.

Source/Drain Series Resistance Extraction in HKMG Multifin Bulk FinFET Devices

Effective extraction of source/drain (S/D) series resistance is a challenging task owing to poor epi-growth and nonuniform distribution of current density in S/D, critical limitation of restrictive design rule, ultra thin contact film, and complicated 3-D fin-type field effect transistor (FinFET) structure. In this paper, we report a test structure for measurement of linear and nonlinear S/D series resistances. This technique enables us to evaluate each component of S/D series resistance resulting from the S/D contact, the S/D epi-growth fin, the S/D extension, and the channel gate, respectively. The S/D series resistance for fins on different layout location of the same diffusion is characterized and modeled by connection with a specified S/D contact on it. Furthermore, the S/D series resistance of each fin can be analytically calculated, respectively, by swapping the S/D bias condition. The proposed test structure and extraction technique provides a robust monitoring tool to diagnose a process weak point of the 16-nm multifin high-k/metal gate bulk FinFET devices.

Electrically Small Loop Antennas for RFID Applications

The electromagnetic properties of electrically small loop antennas for two different applications are discussed: near-field and far-field RFID systems. In the first case miniature loop antennas are designed for the near field wireless biological and medical sensing application. The magnetic field in the near-field zone is used for coupling between the loops. Using regularly placed capacitors between segments of the loop provides a homogeneous current distribution along the electrically small loop resulted in the improved magnetic coupling. In another case the loop antenna with the improved radiation characteristics is designed for far distance RFID reader antenna. The antenna consists of a combination of the noninteracting loop and dipole. Such a combination shows a cardioid-type radiation pattern and doubled antenna gain. Results of simulations and measurements of test structures of the loop antennas are presented.

Testbeam and laboratory characterization of CMS 3D pixel sensors

The pixel detector is the innermost tracking device in CMS, reconstructing interaction vertices and charged particle trajectories. The sensors located in the innermost layers of the pixel detector must be upgraded for the ten-fold increase in luminosity expected at the High-Luminosity LHC (HL-LHC). As a possible replacement for planar sensors, 3D silicon technology is under consideration due to its good performance after high radiation fluence. In this paper, we report on pre- and post- irradiation measurements of CMS 3D pixel sensors with different electrode configurations from different vendors. The effects of irradiation on electrical properties, charge collection efficiency, and position resolution are discussed. Measurements of various test structures for monitoring the fabrication process and studying the bulk and surface properties of silicon sensors, such as MOS capacitors, planar and gate-controlled diodes are also presented.

Adiabatically widened silicon microrings for improved variation tolerance.

We show that silicon microrings with adiabatically widened bends are more tolerant to dimensional variations than conventional microring designs with uniform waveguide widths. Through wafer-scale measurements of test structures fabricated in the IMEC Standard Passives process (193 nm DUV lithography, 200 mm SOI wafer), improvements in the intra-die and wafer-scale variation of the resonance wavelength are demonstrated. A 2.1× reduction in the standard deviation of the resonance wavelength across the wafer was observed.

A Self-Amplifying Four-Transistor MOSFET Mismatch Test Structure

Mismatch can be difficult to monitor in a production test environment as it can be small and, therefore, it requires precise, time-consuming, costly measurements. This paper describes a four-transistor test structure for measurement and characterization of MOS transistor mismatch that self-amplifies the effect of mismatch, thereby generating a large and easily measurable dc output voltage. Test and design aspects of the structure are detailed, and several additional applications of the new structure are described.

Characterization of irradiated test structures for the CMS tracker upgrade

The CMS collaboration is currently conducting a campaign to identify radiation-hard materials for an upgrade of the CMS tracker. This upgrade is needed to be able to cope with the higher radiation background of the future HL-LHC; additionally the performance of the current tracker will be significantly degraded at the time of the upgrade, requiring a replacement. Several different test structures (TSs) and sensors have been designed for a 6 in. wafer layout. These wafers were produced by an industrial supplier (Hamamatsu Photonics K.K.) and differ by their bulk material (Float Zone, Magnetic Czochralski and CVD-Epi), thickness (from 50μm to 320μm) and N–P type doping. These TSs consist of different microelectronic devices including diodes, resistors or MOS structures. They enable the extraction of parameters which are not accessible in a silicon detector and allow the assessment of the quality of the sensors produced on the same wafer. The TSs have been irradiated with protons and neutrons to emulate the radiation damage caused by the particle fluence inside the future CMS tracker after 10 years of operation. This contribution will present measurements of non-irradiated and irradiated test structures at different fluences. The changes of the properties of the microelectronic devices will be discussed as well as the design of the TSs.

Improved Frequency Response in a SiGe npn Device through Improved Dopant Activation

We study the impact of improved dopant activation in a BiCMOS SiGe technology, using laser annealing to improve activation, and a low temperature contact module to avoid de-activation. We present the results of simple DC test structure measurements and high frequency bipolar transistor measurements. Improved activation significantly reduces sheet resistance, particularly for polysilicon layers. Likewise, reductions in the bipolar device resistance parasitics cause an improvement in maximum power gain frequency (fMAX).

Method for characterization of Si waveguide propagation loss

A new method for measuring waveguide propagation loss in silicon nanowires is presented. This method, based on the interplay between traveling ring modes and standing wave modes due to back-scattering from edge roughness, is accurate and can be used for on wafer measurement of test structures. Examples of loss measurements and fitting are reported.

A Free and Fast Three-Dimensional/Two-Dimensional Solar Cell Simulator Featuring Conductive Boundary and Quasi-Neutrality Approximations

Details of Quokka, which is a freely available fast 3-D solar cell simulation tool, are presented. Simplifications to the full set of charge carrier transport equations, i.e., quasi-neutrality and conductive boundaries, result in a model that is computationally inexpensive without a loss of generality. Details on the freely available finite volume implementation in MATLAB are given, which shows computation times on the order of seconds to minutes for a full I-V curve sweep on a conventional personal computer. As an application example, the validity of popular analytical models of partial rear contact cells is verified under varying conditions. Consequently, it is observed that significant errors can occur if these analytical models are used to derive local recombination properties from effective lifetime measurements of test structures.

Power Integrity and Shielding Effectiveness Modeling of Grid Structured Interconnects on PCBs

In this paper, we investigate the power integrity of grid structures for power and ground distribution on printed circuit board (PCB). We propose the 2D transmission line method (TLM)-based model for efficient frequency-dependent impedance characterization and PCB-package-integrated circuit (IC) co-simulation. The model includes an equivalent circuit model of fringing capacitance and probing ports. The accuracy of the proposed grid model is verified with test structure measurements and 3D electromagnetic (EM) simulations. If the grid structures replace the plane structures in PCBs, they should provide effective shielding of the electromagnetic interference in mobile systems. An analytical model to predict the shielding effectiveness (SE) of the grid structures is proposed and verified with EM simulations.

A Correlation-Considered Variation-Aware Interconnect Parasitic Profile Extraction Method

This paper presents a novel technique of performing correlation-considered statistical interconnect parasitic parameter extraction on 40-nm process technology. Five test structures are designed for the extraction. Then, 3-D simulations are performed, and typical interconnect technology profile (ITP) file is extracted. Based on the full mapping measurements of test structures, their distribution analysis, and particularly the correlations between parasitic coupling capacitance of each metal layer, statistical parameters are extracted using principal-component-analysis method. Then, a complete flow of correlation-considered variation-aware ITP file extraction is concluded. According to the comparison between distributions of Monte Carlo simulations and measurements of output signal periods of ring oscillators, the extracted statistical ITP is proved to be accurate.