Reliability Physics of GaN HEMT Microwave Devices: The Age of Scaling

• Published in: 2020 IEEE International Reliability Physics Symposium (IRPS) pp. 1 - 10
• Main Authors: Zanoni, Enrico, Meneghini, Matteo, Meneghesso, Gaudenzio, Rampazzo, Fabiana, Marcon, Daniele, Zhan, Veronica Gao, Chiocchetta, Francesca, Graff, Andreas, Altmann, Frank, Simon-Najasek, Michel, Poppitz, David
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.04.2020
• Subjects: GaN; HEMT; HEMT scaling; HEMTs; hot-electrons; Logic gates; metal-semiconductor interdiffusion; Metallization; microwave; millimeter-wave; Radio frequency; Reliability; Schottky barriers; Wide band gap semiconductors
• ISSN: 1938-1891
• DOI: 10.1109/IRPS45951.2020.9128358

This paper reviews failure modes and mechanisms of 0.5 μm, 0.25 μm and 0.15 μm AlGaN/GaN HEMTs for microwave and millimeter-wave applications. Early devices adopting Ni/Pt/Au metallization were found to be affected by sidewall interdiffusion of Au and O, followed by electrochemical oxidation of AlGaN, a problem which was solved by adopting a new metallization and passivation scheme providing 0.25 μm devices capable of withstanding 24h at V DS = 60V, on-state, T ch = 375°C with no failure. 4000 h long-term thermal storage tests with no bias identified a non-monotonic behaviour of gate Schottky barrier height, causing a temporary increase of gate leakage current which presented no risk for device reliability. Beside contact-related degradation mechanisms, hot electron effects become increasingly more relevant during DC life tests (inducing a 10% increase of on-resistance), rf tests (creating or re-activating deep levels, which increase current-collapse and reduce rf output power and gain). RF tests are the harshest ones for hot-electron degradation, which represents the limiting factor for GaN HEMTs having L G ≤ 0.15 μm.