| AVS 57th International Symposium & Exhibition | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM+SS-WeA |
| Session: | High-k Dielectrics for III-V Electronics |
| Presenter: | F.L. Lie, University of Arizona |
| Authors: | F.L. Lie, University of Arizona B. Imangholi, University of Arizona W. Rachmady, Intel Corp. A.J. Muscat, University of Arizona |
| Correspondent: | Click to Email |
Identification of the source of interfacial defects between high-k films and III-V substrates is crucial for developing passivation methods. Efforts have been made to isolate defects based on a specific chemical moiety at an interface. A study reported that doubly-O coordinated Ga and displaced As formed when GaAs is exposed to oxygen, induces mid-gap states1. Another study suggested that high activity interface defects originate from structural disorder instead of specific chemical moieties2. This project aims to understand the nature of Al2O3/InGaAs interface defects by relating composition to electrical performance. The modification of InGaAs(100) surfaces due to surface cleaning, Al2O3 deposition, and post deposition annealing (PDA) was investigated using capacitance-voltage (CV) curves, large AC signal conductance (LSC), and x-ray photoelectron spectroscopy (XPS). Al2O3 films were deposited by atomic layer deposition (ALD) using trimethylaluminum (TMA) and water precursors on native oxide covered and aqueous HF etched InGaAs(100) surfaces. XPS analysis on a native oxide sample revealed ~8Å oxide (52% As, 29% Ga, and 21% In) and a monolayer excess of As on an As-terminated substrate. TMA reacted on this surface during ALD, thinning the oxide to ~4.2 Å (45% As, 29% Ga, and 27% In). Aqueous HF treatment removed the native oxide and produced an As-rich surface, which re-oxidized in air. Surfaces consisted of ~4.2 Å oxide (91% As) and 1.5 monolayer excess As on an As-terminated surface. ALD Al2O3 on the liquid-cleaned surface produced a chemically sharp Al2O3/InGaAs interface with less than a monolayer of As oxide. CV and LSC measurements were performed on Au/Ni/10 nm Al2O3/InGaAs stacks. The deep-level surface recombination velocity (SRV) values extracted represent the net effect of interface defects, which includes the defect density and capture cross section. The similar SRV values obtained for native oxide (34+6 cm/s) and aqueous HF (29+13 cm/s) prepared surfaces suggest that the presence or absence of oxides was not the only determining factor. PDA in forming gas and NH3 ambients significantly improved the electrical quality, as reflected in SRV values of 1 to 5 cm/s for both surfaces. XPS analysis showed increased excess As and Ga2O3 at the interface of both surfaces, likely due to thermally or H-induced reactions between interfacial As oxide and Ga atoms in the substrate. These results suggest that high activity defects in III-V’s could be associated with interfacial dangling bonds and are amenable to standard passivation methods used in Si technology.
1Hale M. J. et al, J. Chem. Phys. 119(13), 2003
2Caymax M. et al, Microelectron. Eng. 86, 2009