| AVS 58th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing Division | Tuesday Sessions |
| Session EM+TF-TuM |
| Session: | High-k Dielectrics for MOSFETs Part 1 |
| Presenter: | Nick Terlinden, Eindhoven University of Technology, Netherlands |
| Authors: | N.M. Terlinden, Eindhoven University of Technology, Netherlands G. Dingemans, Eindhoven University of Technology, Netherlands M.M. Mandoc, Eindhoven University of Technology, Netherlands M.C.M. van de Sanden, Eindhoven University of Technology, Netherlands W.M.M. Kessels, Eindhoven University of Technology, Netherlands |
| Correspondent: | Click to Email |
In this contribution, we investigate the influence of the SiO2 thickness on the density and polarity of built-in charges in SiO2/Al2O3 stacks deposited on Si(100). Such charges lead to the development of a space-charge region (SCR) in the Si at the dielectric interface, having consequences such as flat band voltage shifts in MOS devices and electric-field induced passivation in optoelectronic devices like solar cells. We have employed the nonlinear optical technique of second-harmonic generation (SHG) to probe the Si(100) SCR electric field through the effect of electric-field-induced SHG (EFISH). Using this non-intrusive and contactless technique we found previously that the built-in charge density at the SiO2/Al2O3 interface is independent of the Al2O3 thickness down to ~2 nm.1 Here we report on the influence of the interfacial SiOx layer, present between the Si(100) substrate and the atomic layer deposited (ALD) Al2O3 film, addressing the origin, density, and polarity of the charges. For this reason, we have synthesized SiO2/Al2O3 stacks with intentionally grown SiO2 interlayers having a thickness in the range ~1.4-150 nm using various deposition methods (e.g. thermal oxidation, PECVD, ALD). Spectroscopic SHG measurements were carried out with a femtosecond pulsed Ti:sapphire laser tunable in the 1.33-1.75 eV photon energy range. From the obtained spectra we found that the charge density is highly influenced when increasing the SiO2 thickness, dropping from 1013 to 1011 cm-2, with the polarity switching from negative to positive. These measurements were confirmed by C-V measurements and surface voltage measurements employing corona charging of the stacks. On the basis of the observations the mechanism and consequences of charge trapping in Si/SiO2/Al2O3 stacks will be addressed.
1 Terlinden et al., Appl. Phys. Lett. 96, 112101 (2010)