Induced Resistance Change Research Articles

Mapping and statistical analysis of filaments locations in amorphous HfO2 ReRAM cells

Two optical inspection techniques, Photon Emission Microscopy (PEM) and Optical Beam Induced Resistance Change (OBIRCH) laser stimulation, are used to study the forming and to map the locations of filaments in amorphous HfO2 Resistive Random-Access Memory (ReRAM) cells. The low voltage sensitivity of OBIRCH is used to investigate filament pre-forming while the high frame rate of a Silicon Intensified Charge-Coupled Device (SI-CCD) is used to dynamically study the filament after the initial forming. A Spatial Clustering Model (SCM) is developed to explain the non-Poisson spatial distribution of individual filaments measured from multiple cells of the same size.

Inkjet-printed electrical interconnects for high resolution integrated circuit diagnostics

As semiconductors continue to shrink in size and become more three-dimensional in shape, the size of defects that can induce a failure also reduces, pushing the need for better fault isolation. The resolving capability of microscopes used in failure analysis (FA) is frequently limited by how close the microscope can be brought to the circuit under test. Accessibility is often restricted by the presence of probe needles or wire bonds that are needed to power up the device during the measurement. Here, I describe a robust, rapid and cost-effective method to overcome the contacting bottleneck by re-routing the probe pads with a low-profile redistribution layer, realized by conductive inkjet printing. I demonstrate that the method enables analytical FA with high spatial resolution on a backside power delivery network structure in combination with the optical beam induced resistance change (OBIRCH) technique. Electrical and structural characterization of the printing process are also reported.

A comparative study of H2 sensing performance of stoichiometric polymorphs of titanium carbide MXenes loaded with Pd nanodots.

Although titanium-based MXenes have been widely reported for gas sensing, the effect of crystal stoichiometric variations on the sensing properties has been rarely reported. Herein, stoichiometric polymorphs of titanium carbide MXenes (i.e., Ti3C2Tx and Ti2CTx) loaded with Pd nanodots (NDs) prepared by photochemical reduction were investigated for room-temperature H2 sensing. Interestingly, we found that Pd/Ti2CTx exhibited greatly enhanced sensitivity to H2, along with faster response and recovery rates compared to Pd/Ti3C2Tx. The H2 adsorption induced resistance change in Pd/Ti2CTx was higher than that of Pd/Ti3C2Tx due to the more effective charge transfer at the heterointerface of Pd/Ti2CTx, which was confirmed by shifts of binding energies and theoretical calculation results. We hope this work could be helpful to design more high-performance MXene-based gas sensors.

`Failure analysis of short-circuit failure of metal-oxide-metal capacitor

Metal-oxide-metal (MOM) capacitors are used widely in semiconductor integrated circuits. This study describes a method for failure analysis of MOM capacitor short-circuit. We present two case examples to highlight the significance of this method. Various techniques are described, such as thermal emission microscopy (ThEM), beam induced resistance change (OBIRCH), photoemission microscopy (PEM), focused ion beam (FIB), and passive voltage comparison (PVC). ThEM could be an effective alternative, albeit with low magnification. OBIRCH could help verify the defect location in the MOM structure, albeit with a large region of interest (ROI). The application of PEM based on an InGaAs detector can reduce the ROI and yield satisfactory fault isolation results. PVC can indicate the metal bridge phenomenon and help guide FIB cross-sectional analysis. To summarize, our observations indicate that PEM and PVC are effective alternatives for the failure analysis of MOM short-circuit failure.

Electrically‐Driven Oxygen Vacancy Aggregation and Displacement in YBa2Cu3O7−δ Films

AbstractCombining direct visualization of current‐induced oxygen migration through optical microscopy and finite element modeling of driven oxygen diffusion, it is possible to estimate the average activation energy of oxygen motion in the crystallographic ab‐plane of c‐axis oriented polycrystalline YBa2Cu3O7−δ films. Experiments and modeling are compared side‐by‐side for the case of constant current electromigration as well as for a train of current pulses of varying amplitude. The simulations reproduce the induced resistance changes after electromigration and confirm a high degree of spatial inhomogeneity in the stoichiometry. Assuming a temperature and oxygen concentration dependent resistivity, the authors are able to capture the change of superconducting critical temperature, normal state resistance, and the development of multistep transitions as a function of the electromigration history. The simulations are further applied to scrutinize the influence of activation energy, disorder in oxygen content, and initial oxygen concentration on the electromigration process. These results shed new light on the non‐local modifications produced by the electromigration process on oxide conductors.

Impact of Negative Gate Bias and Inductive Load on the Single-Pulse Avalanche Capability of 1200-V SiC Trench MOSFETs

In this study, the single-pulse avalanche capability of two types of 1.2-kV silicon carbide (SiC) trench MOSFETs was investigated through unclamped inductive switching (UIS) testing and numerical TCAD simulation. It was found that the UIS failure mechanisms differed in the two MOSFETs. In the asymmetric trench MOSFET, the failure was caused by high temperature, which can damage the SiC layer during the UIS transient, whereas in the double-trench MOSFET, the failure was caused by a high electric field concentration at the trench gate bottom oxide, and the physical damage was confirmed by optical beam induced resistance change (OBIRCH) and scanning electron microscopy (SEM) cross-sectional analysis. In addition, the UIS-based local damage phenomenon was investigated with varying inductance. Nonuniform contact resistance may have been a cause of the avalanche current concentration.

A flexible dual parameter sensor with hierarchical porous structure for fully decoupled pressure–temperature sensing

• Fabrication of a flexible dual parameter sensor by graphene coated TPU/CNFs sponge. • The sensor has fully decoupled pressure and temperature sensing capabilities. • Excellent pressing durability (>120000 cycles) and temperature detection limit (0.05 K). • Integrated into a robot arm for intelligent human–machine interaction (HMI). Flexible pressure–temperature dual parameter sensors that mimic the function of human skin show potential applications in wearable devices and intelligent robots. Simultaneous sensing of pressure and temperature has been realized by obtaining separated signals utilizing independent piezoresistive and thermoelectric sensing mechanisms, respectively. However, temperature variations induced resistance change poses a negative influence on the pressure sensing accuracy. In this study, a flexible pressure–temperature dual parameter sensor with hierarchical porous structure is presented. The conductivity is realized by inserting graphene into a multilayer structured thermoplastic polyurethane/carbon nanofibers (TPU/CNFs) sponge. The hierarchical porous structured TPU/CNFs sponge with graphene coating endows the sensor with a high pressure sensitivity of 0.14 kPa −1 (0–60 kPa) and a high temperature sensitivity of 30.8 μV/K. Moreover, in the dual parameter mode, the sensor demonstrates neglectable mutual interference between pressure and temperature signals due to lowered temperature-induced resistance change by surface coating of graphene. We show that the sensor can be integrated inside the mask to monitor real-time human respiration. It is also used as the sensing part of a robot arm for high temperature alarm and automatic evacuation. The excellent performance of the sensor ensures its promising application in healthcare monitoring, prosthesis and human–machine interaction (HMI) systems.

Reliability and failure analysis in power GaN-HEMTs during S-band pulsed-RF operating

This paper reports a reliability study on two technologies of AlGaN/GaN high-electron mobility transistors (AlGaN/GaN HEMTs) (Device “A” and Device “B”). A failure analysis study is conducted on devices stressed under real operating conditions for radar applications. The devices underwent pulsed-RF long ageing tests and after 11,000 h show a degradation in RF and DC performances (Drop of drain current and RF output power, pinch-off shift, decrease of the maximum of transconductance, lateral translation of transconductance, and increase of gate-lag and drain-lag). Hot electron effects are supposed to be the origin of the observed degradations and trapping phenomena within the passivation or GaN layers. Photon emission microscopy (PEM), Optical Beam Induced Resistance Change (OBIRCH), Electron Beam Induced Current (EBIC) measurements concur with this hypothesis. The three techniques reveal a non-uniform response and an inhomogeneous distribution along the gate fingers, in addition to the presence of some localized spots localized on the gate edge either on the drain side or on the source side. Spectral PEM analysis of these spots identifies a native defect that could be related to crystallographic defects such as dislocations or impurities. Atom probe tomography (APT) analysis on the two technologies of AlGaN/GaN HEMTs supports this hypothesis. APT results show the presence of some chemical impurities like carbon and oxygen. These impurities are in relatively significant concentrations in device “A” which could explain the high level of gate-lag and drain-lag in this device compared to device “B”.

Localization of Electrical Defects in Hybrid Bonding Interconnect Structures by Scanning Photocapacitance Microscopy

We report a scanning photocapacitance microscopy technique for the localization of open electrical defects in hybrid bonding wafer-to-wafer (W2W) interconnect structures for 3-D system integration. Whereas the well-known optical beam induced resistance change (OBIRCH) method is effective for the localization of resistive opens and shorts, it cannot be applied on full electrical opens. Our approach uses a focused laser beam to stimulate the photocapacitance of the W2W interconnect, and by measuring its response, we can verify the electrical continuity of the structure. We show how illuminating the interconnects with the light of a suitable wavelength leads to an increase of the depletion capacitance due to carrier generation in the silicon substrate. Our measurement instrument uses a commercially available sigma-delta ( $\Sigma -\Delta$ ) capacitance-to-digital converter (CDC) chip with a capacitance sensing resolution down to 4 aF. We demonstrate this methodology on large open-failed W2W interconnect chains with sub-micrometer hybrid-bonded interconnect pad dimensions and confirm our results by optical and transmission electron microscopy (TEM).

The Use of Artificial Intelligence‐Based Optical Remote Sensing and Positioning Technology in Microelectronic Processing Technology

The purpose is to make defect detection in microelectronic processing technology fast, accurate, reliable, and efficient. A new optical remote sensing‐optical beam induced resistance change (ORS‐OBIRCH) target recognition and location defect detection method is proposed based on an artificial intelligence algorithm, optical remote sensing (ORS), and optical beam induced resistance change (OBIRCH) location technology using deep convolutional neural network. This method integrates the characteristics of high resolution and rich details of the image obtained by ORS technology and combines the advantages of photosensitive temperature characteristics in OBIRCH positioning technology. It can be adopted to identify, capture, and locate the defects of microdevices in the process of microelectronic processing. Simulation results show that this method can quickly reduce the detection range and locate defects accurately and efficiently. The experimental results reveal that the ORS‐OBIRCH target recognition defect location detection method can complete the dynamic synchronization of the IC detection system and obtain high‐quality images by changing the laser beam irradiation cycle. Moreover, it can analyze and process the detection results to quickly, accurately, and efficiently locate the defect location. Unlike the traditional detection methods, the success rate of detection has been greatly improved, which is about 95.8%, an increase of nearly 40%; the detection time has been reduced by more than half, from 5.5 days to 1.9 days, and the improvement rate has reached more than 65%. In a word, this method has good practical application value in the field of microelectronic processing.

Peculiar failure mechanisms in GaN power transistors

Commercial GaN power amplifiers for RF applications, made of a pair of discrete transistors for operation in Doherty configuration, failed during the HAST tests. Failure Analysis pointed out a layout-specific issue related to thermal expansion at the level of the field plates. Anyway, the search for initial degradation stages using Optical Beam Induced Resistance Change and Photon Emission Microscopy revealed a subtle second mechanism, involving Ga interdiffusion into the gate metal lines, coming from hollow pipes in GaN. Both mechanisms are discussed.

Interfacial charge and strain effects on lanthanum doped barium stannate thin film under ferroelectric gating

Interfacial charge and strain are two coupling effects in semiconductor/ferroelectric epitaxial heterostructures, which are pivotal for use in tailoring functionalities in devices. In this work, La0.04Ba0.96SnO3/0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 heterostructures with varying film thicknesses were prepared in order to understand both charge and strain's contributions to the electric-field induced resistance change. The relative resistance change to the lattice strain remains almost unchanged in those thicker films, while increases a little bit in those thinner films. This slight increase is related to the substrate constraint near the interface and follows Freund's strain relaxation model during the dynamic strain induced by the piezoelectric switch. A depletion layer model was also established to simulate the electroresistance variation from the interfacial charge effect. The depletion layer involves an equilibrium between capture and release of electrons by the acceptor-like defects near the interface region. The resistance change vs electric field evolves from a butterfly-like shape to a square-like when decreasing the film thickness, due to the joint effect of strain and interfacial polarization screening charge. This study provides an insight into understanding heteroepitaxial coupling and exploring their potential applications in oxide electronic devices.

Frequency determination in nondestructive test of semiconductor devices with ultrasound heating

The infrared-optical beam induced resistance change (IR-OBIRCH) method is widely used to localize faults of semiconductor devices. Prior to the fault localization, the IR-OBIRCH generally requires a decapsulation of mold resin that covers the semiconductor devices. As an alternative, without the need for decapsulation, the authors propose the ultrasonic beam induced resistance change (SOBIRCH) method. This research examined a determination method of the optimal ultrasound frequency in order to improve the signal intensity of SOBIRCH even if the speed of sound and the thickness of mold resin are unknown. The resonant frequency estimated by using frequency component of signals of reflected wave agreed with the ultrasound frequency that maximized the intensity of SOBIRCH signal. The frequency dependence of SOBIRCH signal was also estimated. This research demonstrated that the proposed frequency determination method can estimate the resonant frequency on the fault observation of a practical device.

Sensitivity improvement of ultrasonic beam induced resistance change (SOBIRCH) method with ultrasound resonance inside mold resin

In some cases of the failure analysis of semiconductor devices, package state analysis without decapsulation of mold resin is required. The ultrasonic beam induced resistance change (SOBIRCH) method has been proposed as an alternative without need for the decapsulation. The sensitivity of SOBIRCH depends on the quality of the equipment of its measurement system. After a system is fixed, its sensitivity cannot be upgraded easily. However, if it is possible to improve sensitivity even after the system is fixed, it will be easier to localize faults. By means of numerical analysis, recent research suggested that ultrasound resonance inside the mold resin can improve the sensitivity of SOBIRCH significantly. Our research reported here experimentally verified the ultrasound resonance inside the mold resin improved the sensitivity of SOBIRCH by appropriate tuning of the ultrasound frequency to thinned mold resin. Additionally, this research demonstrated that a fault in a practical device could be more clearly observed by using the expected effect of ultrasound resonance in SOBIRCH observation.

Ultrasonic beam induced resistance change (SOBIRCH) method for failure analysis of semiconductor devices encapsulated by mold resin

In the process of the failure analysis for semiconductor devices, various optical methods are applied as techniques to localize faults of the semiconductor devices. Conventional optical techniques often require the decapsulation of the mold resin, since the mold resin is not optically transparent. As a new fault localization technique requiring no decapsulation, the authors are proposing the ultrasonic beam induced resistance change (SOBIRCH) method based on a heating by focused ultrasonic beam. In this report, the signal intensity of the SOBIRCH method for the capsulated samples was discussed through the experimental and the theoretical approaches. By comparing the experiment and the numerical analysis, it was suggested that a certain thickness of the thin mold resin can enhance the intensity of the SOBIRCH signal. Additionally, an expected effect of the standing wave in the thin mold resin was calculated, and a method to make use of the standing wave was proposed.

Remote Tracking of Phase Changes in Cr2AlC Thin Films by In-situ Resistivity Measurements

Resistivity changes of magnetron sputtered, amorphous Cr2AlC thin films were measured during heating in vacuum. Based on correlative X-ray diffraction, in-situ and ex-situ selected area electron diffraction measurements and differential scanning calorimetry data from literature it is evident that the resistivity changes at 552 ± 4 and 585 ± 13 °C indicate the phase transitions from amorphous to a hexagonal disordered solid solution structure and from the latter to MAX phase, respectively. We have shown that phase changes in Cr2AlC thin films can be revealed by in-situ measurements of thermally induced resistivity changes.

Theoretical and experimental investigation of piezoresistivity of brass fiber reinforced concrete

Structural health monitoring is important for the safety of lives and asset management. In this study, numerical models were developed for the piezoresistive behavior of smart concrete based on finite element (FE) method. Finite element models were calibrated with experimental data collected from compression test. The compression test was performed on smart concrete cube specimens with 75 mm dimensions. Smart concrete was made of cement CEM II 42.5 R, silica fume, fine and coarse crushed limestone aggregates, brass fibers and plasticizer. During the compression test, electrical resistance change and compressive strain measurements were conducted simultaneously. Smart concrete had a strong linear relationship between strain and electrical resistance change due to its piezoresistive function. The piezoresistivity of the smart concrete was modeled by FE method. Twenty-noded solid brick elements were used to model the smart concrete specimens in the finite element platform of Ansys. The numerical results were determined for strain induced resistivity change. The electrical resistivity of simulated smart concrete decreased with applied strain, as found in experimental investigation. The numerical findings are in good agreement with the experimental results.

Non-invasive soft breakdown localisation in low k dielectrics using photon emission microscopy and thermal laser stimulation

For the first time a non-invasive localisation of a soft breakdown (SBD) is shown. The localisation is completed on fully functional back end of line (BEOL) test structures. The test structures used, provided by the interuniversity microelectronics centre (imec), are metal insulator semiconductor (MIS) structures. The low k dielectric within the test structures is SiOCH type with OSG 2.0 (k = 2.0), 45% porosity and 40 nm thickness. Contacless faul isolation methods have been evaluated for detecting a SBD on these structures.We evaluated photon emission microscopy (PEM) with two different signal detectors, the Si – CCD and the InGaAs camera.A proof of concept for detecting a SBD with themal laser stimulation (TLS) is presented.Using a Si – CCD and up to 2000 s integration time, photon emission (PE) signals from a 2 μm × 2 μm test structure with a leakage current less than 1 nA are presented.With the InGaAs detector a localised SBD from a 2 μm × 2 μm test structure with a leakage current of 100 pA is shown.The detected SBDs have a resistance of 33 GΩ and 260 GΩ respectively thus the level of degradation is several orders of magnitude lower compared to a hard breakdown (HBD). Up to now it was only possible to localise defects at higher levels of degradation. Due to the high energy at these levels, original defect signatures for SBD are usually destroyed. To better control the process of degradation, a way to nearly freeze the degradation process is shown. This method was used to detect a 1 nA leakage current of a 2 μm × 2 μm structure with a resistance of 35 GΩ using optical beam induced resistance change (OBIRCH) which is a similar contactless fault isolation (CFI) method to TLS. The presented SBD localisations allow to plan accurate physical preparations for the first time.Physical analysis of PEM localised SBD and HBD have been performed and compared.Possibilities to further improve the presented SBD detection levels are discussed for OBIRCH. Limitations for PEM with Si – CCD and InGaAs detectors as a CFI for SBDs are discussed.

Ultrasonic Beam Induced Resistance Change

Abstract Researchers have developed an imaging technique that reveals wiring defects in packaged ICs without requiring decapsulation. The sensing mechanism is based on resistance changes, similar to IR-OBIRCH, but instead of an IR beam, the metal conductors in the chip are heated by ultrasonic waves. This article describes the basic principles of ultrasonic beam induced resistance change (SOBIRCH) imaging and demonstrates its effectiveness in a wide range of applications, including multilayer metal stacks.

Voltage Pulse Induced Resistance Change Response of Reram with HfO2 Dielectric layer

ReRAM is one of promising nonvolatile memories with excellent properties such as low power, high switching speed, and scalability against downsizing. Recently, ReRAM has been attracted attention as artificial neuron devices such as synapse which changes resistance according to input voltage or current signals. Recently we observed multiple resistance states in the RESET process of Ti/HfOx/Pt ReRAM devices. Then we found that the resistance of the reset state changed according to input of voltage pulses. In this study, we focused resistance change response of the SET as well as RESET processes of the Ti/HfO2/Pt ReRAM device. The size of the cross-point device area was 1×1 μm2. The HfOx layer was deposited by reactive sputtering using Ar and O2 mixture gases. Fig.1 shows the typical bipolar resistance switching characteristic. Compliance current was SET to 500 μA. We applied voltage pulse train of constant voltage with 1 μsec pulse width and 2 μsec interval. Fig.2 shows resistance changes of the device during 200 pulses at various voltages. There was an initial abrupt increase of resistance followed by gradual increase. Pulse numbers before initiating abrupt increase of resistance was smaller as the absolute voltage value was larger. Fig.2 shows voltage dependence of the r5000 (resistance after 5000 voltage pulses were applied), and r5000 was continuously changed with applied negative voltage. On the other hand, resistance change behaviors in the set process is completely different as shown in Fg.4. Resistance was high around 106 W when the applied voltage was lower than 1.1 V, ad it changed to low around 103 W when the applied voltage was higher than 1.5 V . In the voltage pulse ranges between 1.2 and 1.4 V, the resistance state indicated only two values of high and low. There were binary resistance states existed. From these experimental results, it maybe suggested that voltage pulse response of the RESET process is suitable for application to artificial synapse.