Premature Electrical Breakdown Research Articles

TCAD Analysis of Leakage Current and Breakdown Voltage in Small Pitch 3D Pixel Sensors.

Small-pitch 3D pixel sensors have been developed to equip the innermost layers of the ATLAS and CMS tracker upgrades at the High Luminosity LHC. They feature 50 × 50 and 25 × 100 μm2 geometries and are fabricated on p-type Si-Si Direct Wafer Bonded substrates of 150 μm active thickness with a single-sided process. Due to the short inter-electrode distance, charge trapping effects are strongly mitigated, making these sensors extremely radiation hard. Results from beam test measurements of 3D pixel modules irradiated at large fluences (1016neq/cm2) indeed demonstrated high efficiency at maximum bias voltages of the order of 150 V. However, the downscaled sensor structure also lends itself to high electric fields as the bias voltage is increased, meaning that premature electrical breakdown due to impact ionization is a concern. In this study, TCAD simulations incorporating advanced surface and bulk damage models are used to investigate the leakage current and breakdown behavior of these sensors. Simulations are compared with measured characteristics of 3D diodes irradiated with neutrons at fluences up to 1.5 × 1016neq/cm2. The dependence of the breakdown voltage on geometrical parameters (e.g., the n+ column radius and the gap between the n+ column tip and the highly doped p++ handle wafer) is also discussed for optimization purposes.

The Effects of Moisture in Metal Oxide on the Mechanical and Electric Properties of Dielectric Elastomer Composites

Dielectric elastomer (DE) technology are used in several applications for example generator, sensor and actuator. One of the major factors that limits the DE performance is premature electrical breakdown. Compositing is the example that have been reported to increase the breakdown strength. In this study polydimethylsiloxane (PDMS) film will be incorporated with two different fillers which are titanium dioxide (TiO2) and zinc oxide (ZnO). Both metal oxides will be calcined up to 300°C before they are added to the PDMS elastomer as fillers. The results show that the calcined TiO2 and ZnO that incorporated in PDMS films show significant increase of breakdown strengths. Meanwhile, the calcined TiO2 PDMS film give higher breakdown strength as comparison to the calcined ZnO counterpart.

Electrical characterization of AMS aH18 HV-CMOS after neutrons and protons irradiation

In view of the tracking detector application to the ATLAS High Luminosity LHC (HL-LHC) upgrade, we have developed a new generation of High Voltage CMOS (HV-CMOS) monolithic pixel-sensor prototypes featuring the AMS aH18 (180 nm) commercial CMOS technology. By fully integrating both analog and digital readout-circuitry on the same particle-detecting substrate, current challenges of hybrid sensor technologies, i.e., larger readout input-capacitance, lower production-yield, and higher production and integration cost, can be downscaled. The large electrode design using high-resistivity substrates actively helps to mitigate the charge-trapping effects, making these chips radiation hard. The surface and bulk damage induced in high irradiation environment change the effective doping concentration of the device, which modulates high electric fields as the reverse-bias voltage increases. This effect can cause high leakage current and premature electrical breakdown, driven by impact ionization. In order to assess the characteristics of heavily irradiated samples, we have carried out dedicated campaigns on ATLASPix1 chips that included irradiations of neutrons and protons, made at different facilities. Here, we report on the electrical characterization of the irradiated samples at different ambient conditions, also in comparison to their pre-irradiation properties. Results demonstrate that hadron irradiated devices can be safely operated at a voltage high enough to allow for high efficiency, up to the fluence of 2× 1015 neq/cm2, beyond the radiation levels (TID and NIEL) expected in the outermost pixel layers of the new ATLAS tracker for HL-LHC.

Electrical characterization of FBK small-pitch 3D sensors after γ-ray, neutron and proton irradiations

In view of applications in the tracking detectors at the High Luminosity LHC (HL-LHC), we have developed a new generation of 3D pixel sensors featuring small-pitch (50 × 50 or 25 × 100 μ m2) and thin active layer (∼ 100 μ m). Owing to the very short inter-electrode distance (∼ 30 μ m), charge trapping effects can be strongly mitigated, making these sensors extremely radiation hard. However, the downscaled sensor structure also lends itself to high electric fields as the bias voltage is increased, motivating investigation of leakage current increase in order to prevent premature electrical breakdown due to impact ionization. In order to assess the characteristics of heavily irradiated samples, using 3D diodes as test devices, we have carried out a dedicated campaign that included several irradiations (γ -rays, neutrons, and protons) at different facilities. In this paper, we report on the electrical characterization of a subset of the irradiated samples, also in comparison to their pre-irradiation properties. Results demonstrate that hadron irradiated devices can be safely operated at a voltage high enough to allow for full depletion (hence high efficiency) also at the maximum fluence foreseen at the HL-LHC.

Degradation patterns of silicone-based dielectric elastomers in electrical fields

ABSTRACTSilicone elastomers have been heavily investigated as candidates for the flexible insulator material in dielectric elastomer transducers and are as such almost ideal candidates because of their inherent softness and compliance. However, silicone elastomers suffer from low dielectric permittivity. This shortcoming has been attempted optimized through different approaches during recent years. Material optimization with the sole purpose of increasing the dielectric permittivity may lead to the introduction of problematic phenomena such as premature electrical breakdown due to high leakage currents of the thin elastomer film. Within this work, electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers are investigated. Results showed that different types of polymer backbone chemistries lead to differences in electrical breakdown patterns, which were revealed through SEM imaging. This may pave the way towards a better understanding of electrical breakdown mechanisms of dielectric elastomers and potentially lead to materials with increased electrical breakdown strengths.

The Role of Dielectric Heating and Effects of Ambient Humidity in the Electrical Breakdown of Polymer Dielectrics

Polymer-based dielectric materials have potential applications in microelectronics, power electronics, photovoltaics, flexible electronics, MEMS, and sensing industries. The possibility of premature electrical breakdown due to high electric fields, particularly at high frequencies and in high ambient temperature and humidity conditions, has restricted its widespread adoption. In this paper, we generalize the thermochemical model of dielectric breakdown and establish dielectric heating as the primary ac degradation mechanism in polymers and develop an analytical dielectric breakdown model that satisfactorily explains measured trends in constant and ramp stress tests under both ac and dc electric fields applied to 5- $\mu\mbox{m}$ -thick PBO capacitors. We also study and quantify the effects of exposure to ambient relative humidity on the electrical breakdown lifetime of polymer dielectrics. Our study provides a fundamental physical understanding of the frequency, ambient humidity, and thickness dependencies of lifetime and breakdown strength for polymer dielectrics; the proposed breakdown model suggests far more optimistic dielectric lifetimes when accelerated test results are scaled to normal operating conditions.

Electromechanical response and failure modes of a dielectric elastomer tube actuator with boundary constraints

As a widely used configuration for dielectric elastomer (DE) actuators, DE tube actuators (or cylindrical actuators) are also found to be susceptible to electromechanical instability (EMI), which may lead to a premature electrical breakdown (EB), and inhibit the potential actuation of DE actuators. This work investigates the electromechanical response of a DE tube actuator with and without boundary constraints to demonstrate an alternative to avoid EMI while achieving large actuation. Our simulation results based on the Gent strain energy model show that the EMI of a DE tube actuator can be eliminated, and larger actuation deformation can be achieved by applying boundary constraints. As a result of these constraints, consideration is also given to the possible mechanical buckling failure that may occur. Mechanisms of possible failure modes of constrained and unconstrained DE tube actuators, such as electromechanical instability, electrical breakdown and mechanical buckling, are elucidated. This paper should provide better theoretical guidance on how to improve the actuation performance of DE actuators, thus leading to the optimal design of DE-based devices.

Investigation of dielectric behavior of thermally aged XLPE cable in the high-frequency range

The widespread use of crosslinked polyethylene (XLPE) in the wire and cable industry may be attributed mainly to its outstanding physical and chemical properties. However, it has been recognized that degradation of XLPE insulation during service, such as thermo-oxidation and water treeing, may lead to premature electrical breakdown of the XLPE insulation cables. Diagnostic measurements would considerably assist to distinguish between bad and still good cables. Estimation of the degree of aging is at present the most important task of diagnostic methods. This paper presents a study on the thermo-oxidation-induced changes in the dielectric properties of the thermally aged 3.3 kV XLPE cables in the frequency range from 70 kHz to 10 MHz.

Numerical analysis of multiple field limiting ring systems

Multiple field limiting ring systems are well established as a means of protecting high voltage, deep diffused junctions from premature electrical breakdown. However, as the depths of these diffusions decrease, the number of rings required to achieve a given percentage of the plane breakdown, increases and efficient design becomes more difficult. In this work we describe an efficient algorithm, that makes practical the design of complete interacting ring systems containing many rings. Important aspects of ring design are first explored using our model to investigate a basic three ring structure. Then theoretical predictions and experimental results are compared for a nine ring design aimed at 1000 V breakdown with a 5 μm junction depth.

Section X-ray topography applied to power device materials problems

X-ray section topographs contain much information about the position of defects inside single crystal slices of silicon. In this paper, the type of information which can be obtained without recourse to the complex dynamic diffraction theory is described. Some examples where section topographs have provided useful information concerning problems in development of power devices are given: bulk defects in silicon starting materials have been studied and shown to be a direct cause of premature electrical breakdown in high power devices. Other examples include determination of the depth of process-induced dislocations and revelation of copper decorated swirls on the crystal growth front.