Impact of Water Content in NMP on Ohmic Contacts in GaN HEMT Technologies

Alexander Hugger, Aleksandra Dlugolecka, Hermann Stieglauer, Raphael Ehrbrecht, Michael Hosch

2020IEEE Transactions on Semiconductor Manufacturing10 citationsDOI

Abstract

Wet chemical lift off in N-Methyl-2-pyrrolidone (NMP) is widely used in GaN HEMT Front End manufacturing. In case of a Ti-Al-Ni-Au based metal stack for ohmic contacts, the quality of the lift-off process is a strong function of the water content in the solvent NMP. In this article, it will be shown that the metal stack can be attacked during lift off in NMP when its water content is exceeding 5%. Additionally, environmental impacts on the hygroscopy of NMP are investigated. Both temperature of NMP and its contact area to air impact the evolution of its water content. Based on these investigations, the lift off sequence was slightly adapted in order to keep moisture below a certain level and avoid optical defects on ohmic contacts.

Topics & Concepts

Ohmic contactLift (data mining)Materials scienceHigh-electron-mobility transistorStack (abstract data type)Water contentOptoelectronicsMetalNanotechnologyMetallurgyElectrical engineeringEngineeringTransistorLayer (electronics)Computer scienceData miningGeotechnical engineeringVoltageProgramming languageGaN-based semiconductor devices and materialsSemiconductor materials and devicesSemiconductor materials and interfaces