Origin of trap assisted tunnelling in ammonia annealed SiC trench MOSFETs. (December 2022)

• Record Type: Journal Article
• Authors: Berens, Judith; Mistry, Manesh V.; Waldhör, Dominic; Shluger, Alexander; Pobegen, Gregor; Grasser, Tibor
• Is Part Of: Microelectronics and reliability. Volume 139(2022)
• Publication Date: 2022-12
• Subjects: 4H-SiC -- MOSFET -- NO -- NH3 -- N2 -- Post oxidation annealing sep trap assisted tunnelling -- Reliability -- Gate oxide tunnelling -- Breakdown; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2022.114789
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: The interface between silicon carbide (SiC) and silicon dioxide (SiO2 ) is of considerable importance for the performance and reliability of 4H-SiC (trench) metal oxide semiconductor field effect transistors (MOSFETs) and various different post oxidation anneals (POAs) have been used to optimize its quality. Whereas nitric oxide (NO) POA leads to very reliable and well performing MOSFETs, ammonia (NH3 ) can further improve the device performance, however, at the cost of the gate oxide (GOX) reliability, e.g. leading to trap assisted tunneling (TAT). We investigate the origin of TAT and GOX leakage in differently annealed gate oxides experimentally, using 4H-SiC trench MOSFETs, and theoretically, using Density Functional Theory (DFT) simulations. Our findings reinforce the view that the NO anneal for SiC devices results in the best overall quality as devices annealed in NH3 and nitrogen N2 show higher oxide charge density and leakage currents. DFT simulations demonstrate that, contrary to what has often been assumed so far, NH3 annealing leads to the formation of additional hydrogen related defects, which open leakage paths in the oxide otherwise not present in NO treated oxides. Highlights: NO annealing (compared to NH3, N2 ) leads to better oxide quality in SiC MOS devices. NO annealing passivates defects which cause leakage currents. NH3 annealing passivates several defects in the oxide or at the SiC/SiO 2 interface. But NH3 annealing introduces H related defects, enabling trap assisted tunnelling.