High-power Integrated Circuit Research Articles

High heat transfer plant-inspired neural network structure controlled by variable magnetic field

Efficient heat dissipation and thermal protection present urgent challenges in high-power integrated circuits (ICs). Although applying a coating of highly thermally conductive materials on the surface of ICs is anticipated to mitigate heat concentration issues, ensuring thermal protection for adjacent devices continues to pose a challenge. Inspired by the microstructure of unidirectional nutrient transport in plant roots, this study utilizes magnetic liquid metal droplets to develop a high thermal conductivity network capable of adaptively manipulating the heat transfer path. This approach aims to tackle the challenges of heat concentration, disordered thermal dissipation, and thermal protection for high-power ICs, thereby enhancing thermal management efficiency. By controlling the distribution of the magnetic field, this study orchestrates the structure of the thermal conduction network to ensure rapid and orderly heat dissipation of ICs while simultaneously validating the network's thermal protection performance. The temperature in the IC thermal concentration zone reaches thermal equilibrium at 399.1 K when the ambient temperature is at 295 K. As the ambient temperature rises to 333 K, the temperature in the IC heat concentration zone stabilizes at approximately 400 K. Simultaneously, the temperature at a specific point in the thermal path of the network registers at 341 K, with the temperatures of the devices flanking this point at 314 K. The magnetron thermal conduction network, inspired by the root structure of bionic plants, not only boosts the thermal management efficiency of ICs but also shows promising application prospects in aerospace, electronics, and other related industries.

An adjustable Ar ion-beam activation strategy to achieve hydrophilic bonding of Si and diamond by deposited AlN interlayer

As a III-nitride, AlN exhibits high thermal conductivity, excellent insulation, and low thermal expansion. Therefore, AlN is an alternative to the insulating layer in conventional Si-on-insulator (SOI) systems to solve the problem of severe self-heating effects caused by the poor thermal conductivity of buried oxide (BOX, SiO2) layers. This is particularly true for high-power integrated circuit and micro-electro-mechanical system fabrication. However, heat transfer also depends on the bottom Si substrate. With the highest thermal conductivity (≥2000 W/mK) among bulk materials, diamond is a highly attractive option to replace conventional Si substrates. Herein, we describe a low-temperature vacuum-free hydrophilic bonding method based on a thin AlN interlayer to prepare a single-crystal Si layer on a polycrystalline diamond. Through suitable Ar ion-beam activation, the surface nanomorphology and chemical state can be simultaneously modified. Increasing the real contact area and removing the surface heavy oxygen layer are critical factors for achieving complete bonding. Moreover, the relatively mild deposition and bonding conditions of AlN make it compatible with the complex CMOS transistor process and could enable the more flexible integration of diamond into 3D chip packages in the future.

High Thermal Conductivity of Submicrometer Aluminum Nitride Thin Films Sputter-Deposited at Low Temperature.

Aluminum nitride (AlN) is one of the few electrically insulating materials with excellent thermal conductivity, but high-quality films typically require exceedingly hot deposition temperatures (>1000 °C). For thermal management applications in dense or high-power integrated circuits, it is important to deposit heat spreaders at low temperatures (<500 °C), without affecting the underlying electronics. Here, we demonstrate 100 nm to 1.7 μm thick AlN films achieved by low-temperature (<100 °C) sputtering, correlating their thermal properties with their grain size and interfacial quality, which we analyze by X-ray diffraction, transmission X-ray microscopy, as well as Raman and Auger spectroscopy. Controlling the deposition conditions through the partial pressure of reactive N2, we achieve an ∼3× variation in thermal conductivity (∼36-104 W m-1 K-1) of ∼600 nm films, with the upper range representing one of the highest values for such film thicknesses at room temperature, especially at deposition temperatures below 100 °C. Defect densities are also estimated from the thermal conductivity measurements, providing insight into the thermal engineering of AlN that can be optimized for application-specific heat spreading or thermal confinement.

AlN coatings with high thermal conductivity and excellent electrical properties for thermal management devices

Thermal conductive materials with low dielectric constant under high frequencies play an important role in high-power integrated circuits packaging. The application of Cu in the packaging substrates is limited due to the high dielectric constant. In this paper, the AlN coatings were deposited on the Cu substrates to maintain the high thermal conductivity and obtain excellent electrical properties for the first time. The microstructure, thermal conductivity and electrical properties of the AlN/Cu systems were adjusted by duty cycles. The results show that improving the duty cycle reduced the hcp-AlN (002) preferred orientation degree of the coatings. The growth structure of the coatings could be regulated by increasing the duty cycle, which induced the grain and particle size first increasing and then decreasing. AlN/Cu systems improved the thermal conductivity of Cu. All coatings show far higher resistivity than Cu and 0.006–0.24 low dielectric loss. The minimum dielectric constant (5.6) of the coating at 2000 kHz frequency was obtained. The AlN/Cu systems in this paper realize high thermal conductivity and excellently dielectric properties, meeting the application in high-power integrated circuit packaging.

Surface wetting to enhance thermoreflectance characterization of integrated circuits.

Thermoreflectance (TR) imaging enables non-contact thermal imaging of devices and integrated circuits (ICs) with sub-µm spatial resolution. TR coefficient of most metals and semiconductors in visible wavelengths is in the 10-5 to 10-3K-1 range, which gives a temperature resolution of 0.1-0.5 °C with a few minutes of averaging. Here, we show that surface wetting with various solvents, such as water, methanol, as well as Fluorinert, which is a commonly used coolant for high-power ICs, can enhance the TR coefficient by up to 19 times. Systematic characterizations as a function of the heating power, illumination-wavelength, liquid layer thickness, sample's tilt, and objective lens's numerical aperture are presented. TR images are distorted due to interference in the liquid layer, but this technique could be used for fast detection of small temperature variations and hot spots in ICs.

A review of passive methods in microchannel heat sink application through advanced geometric structure and nanofluids: Current advancements and challenges

AbstractMicrochannel heat sink (MCHS) is an advanced cooling technique to fulfil the cooling demand for electronic devices installed with high-power integrated circuit packages (microchips). Various microchannel designs have been innovated to improve the heat transfer performance in an MCHS. Specifically, the utilisation of nanotechnology in the form of nanofluid in an MCHS attracted the attention of researchers because of considerable enhancement of thermal conductivity in nanofluid even at a low nanoparticle concentration. However, a high-pressure drop was the main limitation as it controls the MCHS performance resulted from heat transfer augmentation. Therefore, this study aimed to critically summarise the challenges and limitations of both single and hybrid passive methods of MCHS. Furthermore, the performance of nanofluid as a coolant in the MCHS as affected by the type and concentration of nanoparticle and the type of base fluid was reviewed systematically. The review indicated that the hybrid MCHS provides a better cooling performance than MCHS with the single passive method as the former results in a higher heat transfer rate with minimal pressure drop penalty. Besides that, further heat transfer performance can be enhanced by dispersing aluminium dioxide (Al2O3) nanoparticles with a concentration of less than 2.0% (v/v) in the water-based coolant.

Ultrasonic Bonding of Ag and Ag-Alloy Ribbon—An Innovative Alternative for High Power IC Packages

With the development of automotive power electronics and high-power integrated circuits, ribbon bonding is currently in the spotlight for its superior properties to those of traditional heavy wire bonding. In this article, innovative ribbon materials made of Ag and Ag–4Pd are introduced. The ultrasonic bonding of Ag and Ag-alloy ribbons on direct bonded copper (DBC) substrates metallized with Ni/Pd/Au films was evaluated as replacements for Al and Cu ribbons. A continuous bonding interface with satisfactory pull strength can be obtained from substrates metallized with Pd and Au films due to their similar metallurgical properties and softer surface conditions. The footprint study of bond residuals after pull tests correlated with the failure codes and bond strengths of the modules. The reliability of Ag and Ag–4Pd ribbons with regard to pull strength after high-temperature storage tests (HTSTs) at 150 °C for 1000 h was slightly increased, and the bond interface remained unchanged. The results showed that Ag and Ag-alloy ribbons made specifically for power electronics are feasible and can be an attractive alternative to aluminum ribbons.

High-Frequency Electromagnetic Simulation and Optimization for GaN-HEMT Power Amplifier IC

Rapid increase in operating frequencies and power density necessitate the importance of examining electromagnetic compatibility/electromagnetic emissions (EMEs) from high-frequency and high-power integrated circuits (ICs). In this paper, a simulation method is demonstrated to study the EME using gallium nitride high electron mobility transistor power amplifier IC chip as a device under test. Simulation model is developed by collaborating a high-frequency structure simulator with a Keysight Advance Design System for simulation of three-dimensional layout of IC. The simulated EME results are verified with experimental measurement results; the hotspots obtained with higher EME as identified by a near-field scanner and simulation results are identical. With this simulation method, optimization is done using a response surface methodology to reduce the EME for the IC chip. It is found that small changes in the IC layout can make a significant difference in the EME. Simulation model developed with RSM optimization technique opens a gateway for the IC industry to investigate EME of their chip design without going through a costly and time-consuming process of fabrication for testing its EME.

Copper coin-embedded printed circuit board for heat dissipation: manufacture, thermal simulation and reliability

Purpose – The purpose of this paper is to form copper coin-embedded printed circuit board (PCB) for high heat dissipation. Design/methodology/approach – Manufacturing optimization of copper coin-embedded PCB involved in the design and treatment of copper coin, resin flush removal and flatness control. Thermal simulation was used to investigate the effect of copper coin on heat dissipation of PCB products. Lead-free reflow soldering and thrust tests were used to characterize the reliable performance of copper coin-embedded PCB. Findings – The copper coin-embedded PCB had good agreement with resin flush removal and flatness control. Thermal simulation results indicated that copper coin could significantly enhance the heat-dissipation rate by means of a direct contact with the high-power integrated circuit chip. The copper coin-embedded PCB exhibited a reliable structure capable of withstanding high-temperature reflow soldering and high thrust testing. Originality/value – The use of a copper coin-embedded PCB could lead to higher heat dissipation for the stable performance of high-power electronic components. The copper coin-embedded method could have important potential for improving the design for heat dissipation in the PCB industry.

Formation of Antithermal Shock Composite Membrane on Aluminum Alloy through Anodic Oxidation

In order to improve antithermal shock of anodic oxidation membrane on aluminum alloy for heat dissipation substrate of high-power integrated circuit, an organic/inorganic composite membrane on aluminum alloy was investigated through one-trip anodic oxidation. The microstructure, ingredient and performance of composite membrane was characterized through scanning electron microscope(SEM), Energy Dispersive Spectrometer(EDS), microscopic hardness meter, dielectric withstand test station and so on. The results indicated that the structure of composite membrane formed on aluminum alloy 6061 was multilayers piled up of bar-like pieces, which was definately different from traditional anodic oxidation membrane. The breakdown voltage and hardness were 1400V and 282 HV respectively, which were little lower than 1600V and 394HV of traditional anodic oxidation membrane. Composite membrane has a high resistivity in the order of 1014Ω×cm, which was equal to that of traditional anodic oxidation membrane. However, the antithermal shock properties of composite membrane were more excellent than traditional ones, its did not change after processing 10 cycles of heat/cool treatment. In contrast, the resistivity and configure of traditionals changed significantly. In conclusion, the composite membrane formed with one-trip anodic oxidation possessed good insulation, high antithermal shock, as well as breakdown voltage, which is potential for application as heat disspation substrate in high-power integrated circuit.

Active Thermal Control of Distributed Parameter Systems Excited at Multiple Frequencies

Abstract In testing packaged high-power integrated circuits, active thermal control is useful in providing die-level temperature stability. A time-varying heat load is applied to the surface of the package to compensate for the time-varying test power sequence applied to the die. An earlier study determined the proper control heat load for a single-frequency sinusoidal variation in die power subject to a finite allowed temperature variation on the die. Actual test power sequences contain many frequencies at various phase angles, each contributing to the temperature variation of the die. In the present study, we develop a method of controlling multiple frequency test sequences subject to a finite temperature tolerance. It is shown that the total control power may be minimized assigning temperature tolerances to the highest frequencies in the test power sequence.

Simulation and characterization on properties of AlN films for SOI application

Application of SOI in high-power integrated circuit is limited by the self-heating effect, caused by the poor thermal conductivity of the buried SiO 2 layers. It is important to investigate new buried insulator with good thermal conductivity. We simulated the self-heating effects of AlN and SiO 2 thin films caused by power consumption of SOI devices with the help of ANSYS v6.1. Then prepared AlN thin films through ion beam enhanced deposition (IBED) system. The microstructure and dielectric properties were characterized through AFM, XPS, C– V, I– V and SRP. Our results show that the AlN thin films we prepared have excellent insulating properties and better thermal conductivity compared with SiO 2 films.

Determination of sp 3/sp 2 ratio in amorphous-carbon thin film synthesized by reactive filtered arc deposition

The application of a silicon on insulator device in a high-power integrated circuit is limited by the self-heating effect caused by the poor thermal conductivity of the buried SiO 2. We introduce tetrahedral amorphous-carbon thin films formed by reactive filtered arc deposition method, as an alteration. The sp 3/sp 2 components in the thin films and the surface roughness were measured by spectroscopic ellipsometry, which is a well known non-destructive and in situ characterization method. The dielectric functions of the composite materials were calculated using the Bruggeman effective medium approximation.

Tetrahedral amorphous-carbon thin films for silicon-on-insulator application

The application of a silicon-on-insulator substrate in a high-power integrated circuit is limited by the self-heating effect, caused by the poor thermal conductivity of the buried SiO2. We introduce tetrahedral amorphous-carbon thin films, formed by the filtered arc deposition method, as an alteration. We investigated the surface morphology, microstructure, and electrical properties of these films. The films deposited under a substrate bias of −200 V displayed outstanding surface topography (low surface roughness with the Rrms value under 0.5 nm) and excellent electrical property (breakdown field of 4.7 MV/cm). The film has a high content of sp3 bonds of carbon (87%) and low content of oxygen (&amp;lt;2%).

MBE growth of wide band gap Pb 1− xSr xSe on Si(1 1 1) substrate

Epitaxial wide band gap Pb 1− x Sr x Se ( x>0.9) layers have been successfully grown by molecular beam epitaxy on Si(1 1 1) and BaF 2(1 1 1) substrates. Reflection high-energy electron diffraction (RHEED) showed that layers on both substrates were single crystal and oriented to the substrate. X-ray diffraction showed that layers on Si(1 1 1) were high quality as indicated by full-width at half-maximum (FWHM) values of less than 300 arcsec. These results provide a foundation for the eventual fabrications of ultraviolet detector arrays and high power-integrated circuits on silicon substrates.

Heat Transfer Correlatins for Use in Naturally Cooled Enclosures with High-Power Integrated Circuits

Heat transfer rates were experimentally measured in an air-filled two-dimensional simplified model of a naturally cooled rectangular enclosure with a concentrated energy source representing a high-power integrated circuit (IC). The aspect ratio of the enclosure and the size and location of the source were parametrically varied. Correlations are presented such that a component temperature rise can be estimated if the energy dissipation rate is known in a specified design.