Influence of Materials and Packaging Solutions on Thermal Behaviour of Power Modules

Nowadays, designing ever more efficient power modules requires complex materials and more innovative methodologies. To significantly reduce the lead time of the devices and decrease the costs, especially during the prototyping and the testing phases, a Finite Element Analysis (FEA) can be the simplest way to deal with a matrix of parameters to be studied on a single setup. In this work, a thermal characterization is addressed to a stationary simulation using the COMSOL Multiphysics® software, coupling the Heat Transfer Module and the CFD Module. The study is applied to two types of power modules with different technologies, one with Direct Bonded Copper (DBC) substrate and the other one with Insulated Metal Substrate (IMS). An experimental phase follows in order to test the most performing module. A DBC module is composed by (bottom-up) a substrate (copper base, an alumina insulating layer, copper top layer with a specific electrical layout), soldering layers, the dice, the metallic pins, a covering insulating gel and an external protective box. The IMS modules are equal, except for the substrate made up by (bottom-up) a metal base (copper or aluminium), a polymer with ceramic fillers as insulating layer and a copper top layer with the same electrical layout of DBC. The experimental setup used to test real devices is composed by an aluminium water heatsink with a macroscopical copper plate on the top, separated by a thermal grease layer. The device is then mounted on the copper plate with a defined thermal grease layer in between. The geometry considered in the simulation reproduces accurately this experimental setup. The Heat Transfer Module is set to dissipate about 110 W per die. Air natural convection is neglected since it contributes only marginally to the exchange process. This has been assessed with a specific simulation that allows to fix the total insulating condition on the external boundaries, so that only conductive phenomena are considered at this point. The CFD Module is responsible of the water flux entering the heatsink, while the Multiphysics captures the non-isothermal behaviour of the fluid as it flows inside the heatsink. The mesh incorporates different element sizes, depending on the layers thickness. As a result, the FEA solution, provided by COMSOL Multiphysics®, is mostly in accordance with the experimental data. For DBC module, also the packaging is investigated. Different solutions, such as Vacuum Potting Gel (VPG), are applied to the standard module, analysing thermal resistance and heat dissipation. As an example, the VPG solution consists in filling a protective plastic case with a silicone dielectric gel. The layers disposition is precisely the one described in the DBC section above. The modules are imported in the software and placed upon the testing setup already in use for the previous part. The simulations return interesting insight in the thermal behaviour of the modules

Silicon and Silicon Carbide Recrystallization by Laser Annealing: A Review

Modifying material properties within a specific spatial region is a pivotal stage in the fabrication of microelectronic devices. Laser annealing emerges as a compelling technology, offering precise control over the crystalline structure of semiconductor materials and facilitating the activation of doping ions in localized regions. This obviates the necessity for annealing the entire wafer or device. The objective of this review is to comprehensively investigate laser annealing processes specifically targeting the crystallization of amorphous silicon (Si) and silicon carbide (SiC) samples. Silicon finds extensive use in diverse applications, including microelectronics and solar cells, while SiC serves as a crucial material for developing components designed to operate in challenging environments or high-power integrated devices. The review commences with an exploration of the underlying theory and fundamentals of laser annealing techniques. It then delves into an analysis of the most pertinent studies focused on the crystallization of these two semiconductor materials

Conformation-based Molecular Memories for Nanoscale MemComputing

We investigate the use of endohedral fullerenes and 6-(Ferrocenyl)hexanethiol cation as molecular non-volatile memory devices. We demonstrate stable encoding of the information in the geometry and dipole moment of these molecules. The write operation can be performed with external programming electric fields that drive the switching of the molecule conformation. The read operation can be performed by reading the dipole moment through the generated electric fields. Moreover, the dipole moment encoding enables the integration of proposed memories with molecular Field-Coupled Nanocomputing logic. The capability to realize compatible and purely molecular memory and logic devices paves the way for molecular MemComputing, with new possibilities for nanoscale computing paradigms

Design of Pyrrole-Based Gate-Controlled Molecular Junctions Optimized for Single-Molecule Aflatoxin B1 Detection

Food contamination by aflatoxins is an urgent global issue due to its high level of toxicity and the difficulties in limiting the diffusion. Unfortunately, current detection techniques, which mainly use biosensing, prevent the pervasive monitoring of aflatoxins throughout the agri-food chain. In this work, we investigate, through ab initio atomistic calculations, a pyrrole-based Molecular Field Effect Transistor (MolFET) as a single-molecule sensor for the amperometric detection of aflatoxins. In particular, we theoretically explain the gate-tuned current modulation from a chemical–physical perspective, and we support our insights through simulations. In addition, this work demonstrates that, for the case under consideration, the use of a suitable gate voltage permits a considerable enhancement in the sensor performance. The gating effect raises the current modulation due to aflatoxin from 100% to more than 103÷104 %. In particular, the current is diminished by two orders of magnitude from the μA range to the nA range due to the presence of aflatoxin B1. Our work motivates future research efforts in miniaturized FET electrical detection for future pervasive electrical measurement of aflatoxins

NS-GAAFET Compact Modeling: Technological Challenges in Sub-3-nm Circuit Performance

NanoSheet-Gate-All-Around-FETs (NS-GAAFETs) are commonly recognized as the future technology to push the digital node scaling into the sub-3 nm range. NS-GAAFETs are expected to replace FinFETs in a few years, as they provide highly electrostatic gate control thanks to the GAA structure, with four sides of the NS channel entirely enveloped by the gate. At the same time, the NS rectangular cross-section is demonstrated to be effective in its driving strength thanks to its high saturation current, tunable through the NS width used as a design parameter. In this work, we develop a NS-GAAFET compact model and we use it to link peculiar single-device parameters to digital circuit performance. In particular, we use the well-known BSIM-CMG core solver for multigate transistors as a starting point and develop an ad hocresistive and capacitive network to model the NS-GAAFET geometrical and physical structure. Then, we employ the developed model to design and optimize a digital inverter and a five-stage ring oscillator, which we use as a performance benchmark for the NS-GAAFET technology. Through Cadence Virtuoso SPICE simulations, we investigate the digital NS-GAAFET performance for both high-performance and low-power nodes, according to the average future node present in the International Roadmap for Devices and Systems. We focus our analysis on the main different technological parameters with regard to FinFET, i.e., the inner and outer spacers. Our results highlight that in future technological nodes, the choice of alternative low-K dielectric materials for the NS spacers will assume increasing importance, being as relevant, or even more relevant, than photolithographic alignment and resolution at the sub-nm scale

Single-molecule Aflatoxin B1 Sensing via Pyrrole-based Molecular Quantum Dot

We investigate through ab-initio simulations the gold-8PyrroleDiThiol-gold (Au-8PyDT) molecular quantum dot as an amperometric single-molecule sensor for the aflatoxin B1 (AFB1) detection. We study the adsorption of AFB1 onto the Au-8PyDT and we analyze the transport characteristics for the most probable adsorption configuration. We find that a significant current modulation occurs, with around 80% of current decrease in presence of AFB1. Interestingly, the investigated sensor exhibits a voltage-dependent response, that we motivate through a transmission properties analysis. Our results, considering the synthesis simplicity of PolyPyrroles and their non-toxicity, motivate future research efforts in this direction

Electronic Transport Study of Bistable Cr@C28 Single-Molecule Device for High-Density Data Storage Applications

We investigate through ab initio calculation the endohedral monometallofullerene Cr@C28 as a candidate for data storage applications. First, we study the encapsulation energy and the electronic properties of two stable states of the Cr@C28 - namely I-Cr@C28 and II-Cr@C28. Then, we address the adsorption of C28, I-Cr@C28, and II-Cr@C28 onto a gold substrate. Finally, by emulating a Scanning Tunneling Microscope (STM) break-junction experimental setup, we analyze the STM-mediated transport characteristics for the most probable adsorption configurations. We find and discuss a significant and measurable current difference between the two stable states. This outcome enables the binary encoding of the information, making the proposed device promising as a single-molecule data storage element for future high-density integrated circuits

Tunnel Field-Effect Transistor: Impact of the Asymmetric and Symmetric Ambipolarity on Fault and Performance in Digital Circuits

Tunnel Field-Effect Transistors (TFETs) have been considered one of the most promising technologies to complement or replace CMOS for ultra-low-power applications, thanks to their subthreshold slope below the well-known limit of 60 mV/dec at room temperature holding for the MOSFET technologies. Nevertheless, TFET technology still suffers of ambipolar conduction, limiting its applicability in digital systems. In this work, we analyze through SPICE simulations, the impact of the symmetric and asymmetric ambipolarity in failure and power consumption for TFET-based complementary logic circuits. Our results clarify the circuit-level effects induced by the ambipolarity feature, demonstrating that it affects the correct functioning of logic gates and strongly impacts power consumption. We believe that our outcomes motivate further research towards technological solutions for ambipolarity suppression in TFET technology for near-future ultra-low-power application

HOXC8 (homeobox C8)

Review on HOXC8 (homeobox C8), with data on DNA, on the protein encoded, and where the gene is implicated