Improved Methodology for Parasitic Analysis of High-Performance Silicon Carbide Power Modules

The advent of wide bandgap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), has enabled power electronics with increasing current densities and switching frequencies. A byproduct of these improved electrical characteristics is an increase in thermal power density. Indeed, the full capability of WBG semiconductors may be underutilized if the thermal management solution cannot keep pace with the device heat generation density. Further, as many power electronics devices are integrated into a power module form factor containing a metal baseplate to allow heat spreading from high heat fluxes generated at semiconductor dies, system integrators are often sensitive to cost and weight considerations in building up systems with traditional power module designs. In this paper, a polymer baseplate with integrated microconvective cooling (PBIMC) is designed and built as a low-weight, cost-effective alternative for metal baseplates on power module devices. Microconvective cooling, featuring optimized single-phase impingement cooling and effluent fluid flow control, provides high power density heat removal from localized heat flux areas in power module packages to obviate the need for a metal heat spreader. Thermal performance of the PBIMC is tested on a thermal test vehicle representative of an IGBT power module to power densities up to 200W/cm2 and compared to an off the shelf minichannel cold plate. The PBIMC achieved equivalent per IGBT case-to-fluid areal thermal resistances of 0.15 K-cm2/W, a 69% decrease compared to the baseline cold plate. Additionally, thermal crosstalk was shown to be reduced by up to 89% when moving from the cold plate to the PBIMC, demonstrating potential advantages in utilizing thermal management techniques that do not feature heat spreading. The prototype-level polymer baseplates showed a > 80% decrease in weight compared to a traditional power module metal baseplate. The study concludes that the PBIMC shows promise as a solution for high current density power electronics in weight sensitive applications, while providing opportunities for cost savings.

Due to their superior material properties, wide bandgap (WBG) semiconductors enable the application of power electronics at higher temperature operation, higher frequencies, and higher efficiencies compared to silicon (Si). However, the commonly-used aluminum wire bonding as topside interconnection technology prevents WBG semiconductors from reaching their full potential, due to inherent parasitic inductances, large size, heat dissipation, and reliability issues of wire bonding technology. Therefore, this article presents a comprehensive review of topside interconnection technologies of WBG semiconductor power devices and modules. First, the challenges and driving factors for the interconnection of WBG semiconductor dies are discussed. Second, for each widely commercially used WBG semiconductor, i.e., silicon carbide and gallium nitride, technical details and innovative features of state-of-the-art interconnection techniques in packages are reviewed. Then, the majority of existing topside interconnection materials for WBG semiconductors are categorized and compared, followed by a discussion of their advantages, challenges, and failure modes. Based on this elaborate discussion, potential future directions of the interconnection technology development are given. It is concluded that the superior performance of WBG semiconductors can be obtained by combining novel materials with innovative designs for the topside interconnections.

Recent emergence of ultra-wide bandgap (UWBG) semiconductor-based power electronic modules provide fast switching speed, high voltage rating, and high gravimetric and volumetric power densities with high-temperature operation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(&gt;250^{\circ} \mathrm{C}\right)$</tex>. In these power module packaging, encapsulation plays a crucial role in providing protection against electrical breakdown, mechanical stress, chemical erosions, etc. Consequently, encapsulant materials with superior dielectric properties, high thermal and mechanical stability are required for UWBG-based power electronic packaging. Conventional encapsulant Silicone Gel (SG) struggles when the operating temperature rises above 200° C. Polyimide (PI), known for its outstanding operating temperature and mechanical properties, shows its potential to replace SG for high-temperature and high-power-density applications. In this study, the mechanical and thermal performance of SG and PI is compared using Finite Element Analysis (FEA). For this purpose, a numerical model of a basic power module has been developed in COMSOL Multiphysics that compares the mechanical stability of SG and PI as encapsulants. Stress and temperature distribution in the power module have been compared for both SG and PI. This study demonstrates significant improvement in the mechanical and thermal behavior of the power module when PI is used as an encapsulant. The numerical comparison conducted in this study highlights the potential of PI as a robust encapsulant for hightemperature operation in UWBG-based power electronic packaging.

Wide band gap (WBG) semiconductors, such as gallium nitride (GaN), have become popular among switching power modules. In pursuing power conversion efficiency, power module's high-speed and high-power operation leads to electromagnetic (EM) noise in a very wide frequency range, potentially interfering with nearby wireless communications [e.g., long-term evolution (LTE)]. This letter analyzes the source of EM noise from the power modules using GaN transistors in half-bridge circuits. EM noise was clearly observed in the proximity of power modules and attributed to two primary sources in the frequency range of interest up to 6 GHz: 1) the periodical switching operation of GaN transistors in the output stage and 2) the logic operation of complementary metal–oxide–semiconductor digital circuits to control gate drivers, in the lower and upper side of frequencies, respectively. Measurements analyzed the EM noise characteristics at different probing locations over the assembly of two GaN power modules as well as in different operating conditions by strategically supplying source signals. The influence of EM noise on LTE receiver performance is evaluated with wireless system-level simulation and related to the degradation of its minimum receivable input power.

Wide bandgap semiconductors such as SiC and GaN have superb properties in breakdown strength, temperature resistance, and efficiency. Due to the widespread use of wide bandgap devices, the power density is required to be as high as possible and the key approach is to increase the working voltage and decrease the packaging size. The packaging insulation of high-voltage power modules such as SiC MOSFET should withstand high multi-physics stress and guarantee reliability. The electric field distribution is highly related to the electrical conductivity of packaging insulation since the electric stress in the packaging insulation is either constant DC voltage or unipolar square wave voltage due to the intrinsic body diode of SiC MOSFET. However, the non-linear conductivity and its coupling relationship with the electric field and temperature have not been investigated before. In this paper, a multi-physics analysis of electric field and temperature in high-voltage SiC MOSFET power modules is proposed. The non-linear electrical conductivity of packaging insulation materials (encapsulation and substrate ceramic) is measured and analyzed to derive an expression. Then a half-bridge SiC MOSFET is modeled in multi-physics software and the non-linear conductivity is considered to simulate the transient distribution of electric field and temperature in the packaging, especially at the key triple point positions. To use the multi-physics in the packaging insulation, an optimization procedure is proposed for future high-voltage power module design and fabrication.

The Sagrada Familia Church has appointed two groups of consultants to assist the translation of Gaudi's 1:10 scaled models of the nave into coherent information from which to build. One team has been undertaking the static analysis of the nave roof vault structure and the other the study of the complexities of Gaudi's composition in order to provide full-scale production templates and models for the walls. Both teams had begun using the same basic CAD package and both have had to move onto high-end and very expensive solid-modelling software normally used by mechanical engineers and vehicle designers. Both groups are collaborating together with different accents despite an improbable geographical separation. The original problem, one of intersecting ruled-surfaces accurately to reflect the geometries of the surviving fragments of the original models, has led to surprising possibilities which were not anticipated at the outset. Currently the potential of parametric variation and associative geometries are being investigated as a mirror for some of the intuitive design process and finite element analysis is being considered as a means of interactively analysing the structural implications for each study. The software being used also has a powerful ray-tracing module; rather than being simply a tool to produce eye-catching 'realistic' renderings it has proved to be invaluable in allowing the computer user to understand the spatial complexities of the components being studied. This paper discusses the merits of an architecture so demanding (despite having been designed at the beginning of this century) that it requires the most costly equipment in today's market and it will consider the proposition that in ordinary circumstances, an architecture too complex to be described using basic CAD tools is an architecture beyond our reach. The interdisciplinary nature of the diverse and powerful modules within the software referred to will be used to contest this proposition using the presence of both teams in schools of architecture as evidence.

3-level T-type neutral point clamped (NPC) topology is more popular than its 2-level counterparts in energy conversion systems due to their higher efficiency, lower harmonics (THD), and reduced voltage stress on the switches. Wide bandgap (WBG) semiconductors have become the ultimate choice for future high-performance power electronics energy conversion due to their superior material properties compared to traditional silicon power devices. As a wide-bandgap device, while SiC’s faster-switching speed improves overall efficiency by reducing switching loss, the faster voltage and current gradient (dv/dt and di/dt) generate electromagnetic interference (EMI) noise, requiring larger and complicated filter design. A stacked DBC (direct bonded copper) based T-type NPC power module has been proposed, designed, and tested where additional DBC will be acting as an EMI shield. The EMI noise propagation path has been modeled and compared to a traditional power module. A 21 dB reduction of CM (common mode) noise has been observed.

Compared with the traditional single-sided cooling (SSC) power module, owing to the decreased thermal resistance and packaging parasitics, the double-sided cooling (DSC) power module is a promising solution of the motor drive for electric vehicle (EV) implementation. However, the lack of the model to characterize the thermo-mechanical interaction mechanism in the DSC power module challenges the co-design methodology of the power module from the respective of multi-physics. In this paper, aiming at reliability improvement, to balance the tradeoff between thermal resistance and mechanical stress, a multi-objective-coordinated automated design methodology is proposed for the DSC power module. To characterize the influences of material properties and structure sizes, the mathematical models for the thermal and mechanical features of the DSC power module are proposed. These models are also examined by using the finite element analysis (FEA) tool. Besides, to promote the specifications of DSC power module, a multi-objective optimization model is proposed to coordinate thermo-mechanical metrics in multi-physics. The non-dominated sorting genetic algorithm II (NSGA-II) is implemented to automatically achieve the Pareto solutions of the proposed multi-objective optimization model with respect to thermal resistance and mechanical stress. Considering the influences of material properties, optimal structure sizes of the DSC power module are comprehensively presented. The proposed multi-objective-oriented optimization methodology provides a new routine to reshape the thermo-mechanical performance of the next-generation DSC power module toward more reliable EV implementation.

This paper presents a linear model for characterizing transient behavior in power conversion circuits that use wide bandgap semiconductors. It details analytical and experimental characterization of the circuit‐level transient phenomena affecting the performance of wide bandgap (WBG) semiconductors. Specifically observed behaviors including voltage overshoot, ringing, and false turn‐on are analyzed using equivalent linear circuit models supplemented with experimental characterization. The effect that the parasitic device capacitances have on each of these transient events is also investigated. In order for WBG semiconductor devices to deliver their full performance potential of significantly enhancing next generation power electronic systems, the aforementioned transient characteristics must be eliminated. Due to the agreement between the models’ predicted results and experimental waveforms, the work presented here lays the foundation for optimizing the transient performance of power conversion circuits using WBG semiconductor devices.

Devices based on wide bandgap (WBG) semiconductors like silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga2O3) are ideal for high-power electronics in harsh environments. Among the WBG semiconductors, ultrawide bandgap (UWBG) β-phase gallium oxide (Ga2O3), EG ≈ 4.8 eV, is emerging as a replacement for the current commercially available wide bandgap (WBG) power electronics due to its generational improvements in performance and manufacturing cost [1]. Ga2O3 has a high theoretical breakdown electrical field of 8 MV/cm which in turn gives its Baliga’s figure of merit for power devices that is larger than other WBG materials. The availability of high-quality Ga2O3 substrates produced from melt-grown bulk single crystals also facilitates the development of vertical power devices.In the current stage, the vertical Schottky barrier diode (SBD) with Ga2O3 can have an improved current spreading effect when compared to power diode devices from Si, SiC, and GaN. Especially, the Ga2O3 is expected to surpass the trade-off relationship between breakdown voltage (BV) and on resistance (Ron,sp) that other materials have [2]. Nevertheless, the Ga2O3 vertical SBD still cannot achieve the theoretical breakdown electric field. One of the key topics for WBG semiconductors application is a structure for improved electrical management such as field rings, junction termination extension, and field plates to reduce the leakage current in the reverse bias state.Here, we investigate the characteristics of Ga2O3 SBDs with and without mesa structure in extreme environments at high and low temperature. Conventional and mesa Ga2O3 SBDs were fabricated on the halide vapor phase epitaxy (HVPE) grown β-Ga2O3 (001). A Sn-doped substrate with 61016 cm-3 was used for the HVPE growth. In the SBD with mesa structure, the circular mesa with a diameter of 162 μm and a depth of 500 nm was formed around anode electrodes. The Ti/Au metal stack on the back side of the substrate acted as a cathode and the anode electrode deposited Ni/Au/Pt layers. After the fabrication process, current-voltage (I-V) measurements were performed on the SBDs between -5 V and 1 V. From the results, the values of Ron,sp at 0.7 V are 46.4 Ω•cm2 and 46.2 Ω•cm2 in conventional and mesa SBDs, respectively. And additionally, the leakage current at -5 V is reduced by approximately 44.3% in the mesa structure. To obtain the Schottky barrier height (SBH) from I-V and capacitance-voltage (C-V) measurements, the C-V was observed in the range of -5 V to 0.5 V at 100 kHz. The SBH values from I-V and C-V measurements, the mesa SBDs have 1% - 5% larger SBH compared to the conventional structure, and it could be related to lower leakage current. Moreover, the depletion depths of conventional and mesa SBDs were 52.2 nm and 57.8 nm, respectively, from C-V measurements. For considering the electrical characteristics in extreme temperatures, the I-V measurements of both SBDs structure will be measured between 75 K to 525 K. From an initial low temperature measurement series, we determine a Richardson constant of 49 A/cm2 comparable to what has been reported by other groups. Furthermore, we will extend the study by performing deep-level transient spectroscopy (DLTS) to understand the defect information in Ga2O3.

Wide bandgap (WBG) and ultrawide bandgap (UWBG) semiconductors in n‐type metal–oxide–semiconductor (n‐MOS) integrated circuits (ICs) are increasingly being explored for their potential applications in the rapidly developing field of electronics. This review comprehensively examines the role of n‐MOS inverters underpinned by WBG and UWBG semiconductors and their application possibilities. It delves into various n‐MOS inverter topologies, including resistive, enhancement or diode‐load, depletion‐load, and pseudo‐complementary MOS inverter topologies. Each topology's operational principles, unique advantages, and potential performance are elucidated in detail. Finally, these topologies are simulated using the Advanced Design System software for a fair comparison between various topologies. The literature and simulation results show that the pseudo‐D topology has the best gain and improved noise margin. The review methodology involves an extensive exploration of WBG/UWBG n‐MOS inverters to advance the current understanding of WBG/UWBG n‐MOS‐based ICs.

Thermal–mechanical behavior of the bonding wire for a power module subjected to the power cycling test

While the employment of wide bandgap (WBG) devices in high-frequency and high-voltage applications brings benefits such as reduced system size and improved efficiency, it aggravates the electromagnetic interference (EMI) issue due to fast switching. High-frequency EMI noise suppression relies mainly on the filter design, where the filter's performance is strongly affected by parasitics. Through analyzing the common-mode (CM) equivalent circuit of a half-bridge power module, this letter identifies the key parasitics that dominate the performance of a common-mode filter (CMF) at high frequencies. To minimize the parasitics, the concept of integrating the CMF inside the WBG power module package is developed to improve the noise attenuation. A π-type CMF is integrated with a half-bridge GaN-based power module as a prototype to validate the concept. Experiments are conducted by measuring the CM noise spectrum received by the line impedance stabilization networks (LISNs) from the hard switching of the designed power module under 70 V and 80 kHz. Comparing the measured results of the integrated CMF to the externally added CMF, up to 50 dBμV more attenuation is achieved by the integrated CMF in the frequency range of 10 to 100 MHz, verifying the theoretical analysis and the established CM equivalent circuit.

This paper presents the development of a power electronics teaching lab to prepare students for the next generation of power electronics engineering using wide bandgap (WBG) semiconductor devices. The objectives are to expedite the transfer of theoretical knowledge to practical experience on WBG semiconductor devices, and at the same time to provide a hands-on understanding of the development of comprehensive power electronics systems. To incorporate different types of semiconductor devices, especially WBG semiconductor switches, and perform various lab experiments from an investigation of component switching characteristics to construction and operation of power converters, a plug-and-play (P&P) modular power electronics education board is developed. The P&P architecture allows easy construction of different power electronics circuits by simply inserting semiconductor daughter boards to the motherboard. To assist students’ learning experience, the lab curriculum consisting of lab manuals and supporting resources is developed. Multiple workshops have been held with ECE undergraduate and graduate students to evaluate the performance of the lab. Final assessment and student’s feedback are presented as the outcome of the development.

Wide bandgap (WBG) semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) offer higher switching speed, greater power density, and elevated operational temperature capabilities compared to silicon-based counterparts. However, conventional packaging technologies cannot fully leverage these benefits, necessitating innovative packaging strategies. This dissertation explores pressure contact technology (PCT) to enhance performance and reliability of highly integrated WBG power modules. Various interconnection approaches are evaluated for their suitability: fuzz buttons provide low parasitic inductance and flexibility for gate connections; graphene film (GF) elastomers offer compact size and high thermal conductivity; and metal sheet springs ensure robust power interconnections. A novel spring connector with low inductance (3 nH) and electrical resistance (5 mΩ) is utilized to connect substrates, enhancing heat dissipation and mechanical stability. The electro-thermal characteristics and reliability of pressure contact with molybdenum plates (PCMo) technology are compared with emerging die-attach technologies such as pressureless sintered Ag (SAg), pressure sintered Cu (PSCu), and commercial TO220 counterparts incorporating the same SiC chips. Experimental results demonstrate that PCMo introduces additional contact resistance (∼ 10 mΩ, 0.42 K/W) but exhibits superior power cycling reliability (∼ 6053 cycles) under a junction temperature from 50ºC to 200ºC due to the elimination of die-attach failures. Failure analysis identifies degradation and crack mechanisms in SAg, PSCu, and TO220 samples. Building on these insights, a 3D PCT-based half-bridge SiC module is developed using GF and fuzz buttons, achieving a low thermal resistance of 0.66 K/W, minimal parasitic inductance of 5.1 nH, and reduced voltage overshoot of 5.8%. For high-power applications, an eight-chip parallel SiC module with metal sheet springs demonstrates balanced current distribution and low inductance of 4.8 nH. The findings of this dissertation highlight the potential of PCT in improving the performance and reliability of heterogeneous integrated WBG power modules, particularly for high-power and high-temperature applications.