A Gold Free Aluminum Metalized GaAs PHEMT With Copper Based Air Bridges and Backside

Abstract

This paper presents the results of electrical performance studies of the newly developed GaAs pHEMT transistors with Al-based metallization of the ohmic and barrier contacts, and fully copper metallization of interconnects, air bridges, and backside. The transistors exhibited a source-drain saturation current of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dss</sub> =280 mA/mm and a maximum transconductance of g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> =450 mS/mm at U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> =1.5 V. The current cut off frequency for transistors with 600 μm total gate width was 80 GHz at U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> =1.5 V and U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> =-0.35 V, and the power gain limiting frequency was 100 GHz. Output power at 1 dB gain compression with matched input and output load an impedance was P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1db</sub> =26 dBm or 670 mW/mm at an efficiency level of about 28% and the transistor gain G=11 dB. Measurements were performed at U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> =8 V, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> =1/3 of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dss</sub> at 12 GHz. The obtained results demonstrate the promise of Al and Cu metallization in the low cost manufacture of microwave transistors and monolithic integrated circuits based on them.