Metal additive micro-manufacturing to achieve enhanced air-bridge geometry for coplanar waveguide mm-wave GaN-on-SiC integrated circuits

Collier, Arthur, Eblabla, Abdalla ORCID: https://orcid.org/0000-0002-5991-892X, Sampson, Wesley ORCID: https://orcid.org/0000-0001-7670-0036, Yadollahifarsi, Elham, Hepp, Edgar, Conte, Ricardo and Elgaid, Khaled ORCID: https://orcid.org/0000-0003-3265-1097 2025. Metal additive micro-manufacturing to achieve enhanced air-bridge geometry for coplanar waveguide mm-wave GaN-on-SiC integrated circuits. Presented at: CS MANTECH, New Orleans, US, 18-21st May 2025.

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Abstract

This paper presents a novel cavity coplanar waveguide (CCPW) structure based on GaN-on-SiC technology for high-power microwave applications. The CCPW structure was fabricated using an emerging monolithic microwave integrated circuit (MMIC)-compatible localised electrodeposition metal additive micro-manufacturing (μAM) process, achieving an air-bridge height of 50 μm. Electromagnetic (EM) simulations revealed that introducing a cavity above the CPW improves impedance matching at mm-wave frequencies while providing a robust ground-return path. S-parameter measurements show that the CCPW provides a 6.5 dB improvement in reflection coefficient at 110 GHz compared to a standard coplanar waveguide (CPW) structure. Furthermore, both simulations and measurements indicate a broadband reflection coefficient trough suggesting the potential for broadband impedance matching in MMIC applications. To further analyse RF parasitics, a high-frequency equivalent circuit model was developed, demonstrating significant performance improvements of the CCPW compared to a printed air-bridge.

Item Type:	Conference or Workshop Item (Paper)
Status:	Unpublished
Schools:	Schools > Engineering
Date of First Compliant Deposit:	19 June 2025
Date of Acceptance:	21 December 2024
Last Modified:	19 Jun 2025 14:11
URI:	https://orca.cardiff.ac.uk/id/eprint/179190

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