Inductive Coupled Plasma Etching of High Aspect Ratio Silicon Carbide Microchannels for Localized Cooling

Dowling, Karen M.; Suria, Ateeq J.; Won, Yoonjin; Shankar, Ashwin; Lee, Hyoungsoon; Asheghi, Mehdi; Goodson, Kenneth E.; Senesky, Debbie G.

doi:10.1115/ipack2015-48409

Cited by 8 publications

(13 citation statements)

References 17 publications

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“…Thus, the dominant temperature rise is from SiC fins, and a more efficient operating condition associated with higher heat transfer coefficients should be considered to decrease the thermal resistance of SiC fins and to minimize the junction temperature (see Ref. [13] for more details on temperature changes in different heat transfer coefficients and channel geometries).…”

Section: Conduction Simulation Results and Discussionmentioning

confidence: 99%

“…A 1.5 lm-thick GaN layer is located underneath the gates, and a 10 lm-thick SiC layer is attached to improve heat spreading from the gate to the SiC substrate. Eightyfive microchannels are directly fabricated into the SiC substrate and each channel has a 9:1 aspect ratio (10 lm width Â 90 lm height), which is feasible using an inductive coupled plasma etching technique [13]. Methanol is used as the working fluid due to its superior thermal conductivity and latent heat of evaporation.…”

Section: Flow Boiling Heat Transfer and Flow Regimesmentioning

confidence: 99%

“…Here, we examine the cooling limits of a microcooler module that can dissipate heat fluxes exceeding 30 kW/cm 2 at the device footprint. The current microcooler design includes multiple microchannels directly fabricated on a SiC substrate to minimize the thermal resistance from the hotspot to coolant [13]. A U-bend shaped 3D manifold inlet/outlet is adopted for a path for coolant to flow in order to enhance the heat transfer coefficient at the walls of the microchannel while maintaining a low pumping power.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Modeling of Extreme Heat Flux Microchannel Coolers for GaN-on-SiC Semiconductor Devices

Lee

Agonafer

Won

et al. 2016

Journal of Electronic Packaging

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Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) dissipate high power densities which generate hotspots and cause thermomechanical problems. Here, we propose and simulate GaN-based HEMT technologies that can remove power densities exceeding 30 kW/cm 2 at relatively low mass flow rate and pressure drop. Thermal performance of the microcooler module is investigated by modeling both single-and two-phase flow conditions. A reduced-order modeling approach, based on an extensive literature review, is used to predict the appropriate range of heat transfer coefficients associated with the flow regimes for the flow conditions. Finite element simulations are performed to investigate the temperature distribution from GaN to parallel microchannels of the microcooler. Single-and two-phase conjugate computational fluid dynamics (CFD) simulations provide a lower bound of the total flow resistance in the microcooler as well as overall thermal resistance from GaN HEMT to working fluid. A parametric study is performed to optimize the thermal performance of the microcooler. The modeling results provide detailed flow conditions for the microcooler in order to investigate the required range of heat transfer coefficients for removal of heat fluxes up to 30 kW/cm 2 and a junction temperature maintained below 250 C. The detailed modeling results include local temperature and velocity fields in the microcooler module, which can help in identifying the approximate locations of the maximum velocity and recirculation regions that are susceptible to dryout conditions.

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Section: Conduction Simulation Results and Discussionmentioning

confidence: 99%

Section: Flow Boiling Heat Transfer and Flow Regimesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal Modeling of Extreme Heat Flux Microchannel Coolers for GaN-on-SiC Semiconductor Devices

Lee

Agonafer

Won

et al. 2016

Journal of Electronic Packaging

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“…A 1.5 μm-thick GaN layer is located underneath of the gates and a 10 μm-thick SiC layer is attached to improve the heat spreading. The following structure is 90 μm-deep SiC channels by assuming that 90 μm-deep channel etching is feasible with 9:1 aspect ratio by using inductive coupled plasma etching technique [5]. COMSOL Multiphysics is used to examine each thermal resistance and temperature rise between the junction and the fin walls by solving for the temperature field as the solution to the steady state heat conduction equation below.…”

Section: Geometry Description For Solid Conduction Simulationmentioning

confidence: 99%

Computational Modeling of Extreme Heat Flux Microcooler for GaN-Based HEMT

Lee

Won

Houshmand

et al. 2015

Volume 2: Advanced Electronics and Photonics, Packaging Materials and Processing; Advanced Electronics and Photonics: Packaging

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This study explores an extreme heat flux limit of microcooler for GaN-based HEMTs (high electron mobile transistors) which have local power densities exceeding 30 kW/cm2 using both solid conduction simulation and single-phase/two-phase conjugate simulations. Solid conduction simulation models are developed for full geometry of the microcooler to account for the overall thermal resistances from GaN HEMT to working fluid. This allows investigating the temperature distribution of the suggested microcooler. Parametric studies are also performed to investigate the impact of geometries and heat transfer coefficients on the junction temperature. The solid conduction simulation results using COMSOL Multiphysics agree well with single-cell ANSYS Fluent simulation results. Separately, fluid-solid conjugate CFD (Computational Fluid Dynamics) simulation models provide the detailed flow information in the microchannel using a single-channel geometry with symmetry boundary conditions. Single-phase CFD simulations obtain the lower bound of total pressure drop and heat transfer coefficient at the microchannel walls for a mass velocity range of G = 6000–24000 kg/m2-s. The local temperatures and velocity distributions are reported that can help with identifying the locations of the maximum velocity and recirculation regions that are susceptible to dryouts. Two additional alternative tapered inlet designs are proposed to alleviate the significant pressure loss at the entrance of the SiC channel. The impact of the tapered inlet designs on pressure drops and heat transfer coefficients is also investigated. Two-phase simulations in microchannel are conducted using Volume-of-Fluid (VOF) method embedded in ANSYS Fluent to investigate two-phase flow patterns, flow boiling, and temperature distributions within the GaN HEMT device and SiC etched mircochannels. A user-defined function (UDF) accounts for the phase change process due to boiling at the microchannel walls. The results show that the time relaxation factor, ri has a strongly influence on both numerical convergence and flow solutions.

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“…To alleviate the problem of hotspots, silicon carbide (SiC) heat spreaders have been used due to their high thermal conductivity of 370 W/m.K at 20 o C [4]. However, since the thermal conductivity of SiC decreases significantly as temperature increases [5], the use of SiC alone is not practical for hot spot mitigation. For high heat fluxes ( > 100 W/cm 2 ) single-phase liquid cooling and flow boiling in microfluidic systems can provide the required cooling [6].…”

Section: Introductionmentioning

confidence: 99%

Thermal management of GaN HEMT devices using serpentine minichannel heat sinks

Al-Neama

Kapur

Summers

et al. 2018

Applied Thermal Engineering

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An experimental and numerical investigation of water-cooled serpentine rectangular minichannel heat sinks (MCHS) has been performed to assess their suitability for the thermal management of gallium nitride (GaN) high-electron-mobility transistors (HEMTs) devices. A Finite Element-based conjugate heat transfer model is developed, validated experimentally and used to determine the optimal minichannel width and number of minichannels for a case with a uniform heat flux of 100 W/cm 2. The optimisation process uses a 30 point Optimal Latin Hypercubes Design of Experiments, generated from a permutation genetic algorithm, and accurate metamodels built using a Moving Least Square approach. A Pareto front is then constructed to enable the compromises available between designs with a low pressure drop and those with low thermal resistance to be explored and an appropriate minichannel width and number of minichannels to be chosen. These parameters are then used within conjugate heat transfer models of a serpentine MCHS with silicon, silicon carbide, diamond and graphene heat spreaders placed above a GaN HEMT heating source of area 4.8 × 0.8 mm 2 , generating 1823 W/cm 2. A nanocrystalline diamond (NCD) layer with thickness of 2 µm is mounted on the top surface of the GaN HEMT to function as a heat spreader to mitigate the hot spots. The effect of volumetric flow rate and heat spreader thickness on the chip temperature has been investigated numerically and each of these has been shown to be influential. For example, at a volumetric flow rate of 0.10 l/min, the maximum chip temperature can be reduced from 124.7 o C to 96.7 o C by employing a 25 µm thick graphene heat spreader attached to the serpentine MCHS together with a NCD layer compared with a serpentine MCHS without these heat spreaders.

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Inductive Coupled Plasma Etching of High Aspect Ratio Silicon Carbide Microchannels for Localized Cooling

Cited by 8 publications

References 17 publications

Thermal Modeling of Extreme Heat Flux Microchannel Coolers for GaN-on-SiC Semiconductor Devices

Thermal Modeling of Extreme Heat Flux Microchannel Coolers for GaN-on-SiC Semiconductor Devices

Computational Modeling of Extreme Heat Flux Microcooler for GaN-Based HEMT

Thermal management of GaN HEMT devices using serpentine minichannel heat sinks

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