| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM+PS-WeM |
| Session: | Oxides and Dielectrics for Novel Devices and Ultra-dense Memory II |
| Presenter: | D. Zeller, North Carolina State University |
| Authors: | D. Zeller, North Carolina State University G. Lucovsky, North Carolina State University J. Kim, University of Illinois at Urbana Champaign |
| Correspondent: | Click to Email |
Semiconductor conduction band edge states (CBES), and symmetries and singlet transport and/or trapping states of vacated O-atom defects are quantitatively different for nc-Si(Ge)O2 and nano-grain (ng-) TM oxides. CBES in Si(Ge)O2 and Si/Ge an zinc-blende III-V semiconductors are "s-like" with high electron mobilities. Combined with intrinsic band edge triplets in SiO2, energies of vacated O-atom singlet defect states are deeper into the band-gap. Injection into, and transport through singlet defects localized in 1 nm nc-SiO2 clusters with "crystalline-like" medium range order (MRO) extends to self-organized symmetric dihedral angles. Hopping transport through vacated O-atom sites is determined by percolation. It is l\eiminated through nc-Si(Ge)O2 interfacial transition regions by the 0.6 eV spectral extent of the intrinsic band edge triplets explaining the absence of bulk negative space-charge in devices, and after accelerated bias-controlled stress testing. CBES and vacated O-defects in X-ray absorption spectra (XAS).
Properties of nc-SiO2 dielectrics and their semiconductor interfaces are the standard against which high-k TM gate dielectrics are evaluated. CBES are "d-like" with symmetries dependent on coordination, "t2g-like" for 6-fold coordinated TiO2 and Ti2O3 and Magneli-phase alloys, and "eg-like" for 7- and 8-fold coordinated HfO2 and ZrO2. Jahn-Teller effects remove 3-fold t2g and 2-fold eg degeneracy in O K-edge XAS in thin films <2 nm in TiO2 and <3 nm-HfO2.In thicker films O-vacancy singlet states are below CBES with bias-controlled injection and transport. Combined with metal gates, and n- and p-type doping, for Si, Ge and III-V semiconductor substrates, memory and switching functionality is established. 300° CVD devices are obtained in RPD ~2 nm thick TiO2 or HfO2 onto nitrided Ge substrates with ~0.5 nm of Ge-N detected by in-line AES. 400-500°C post-deposition annealling removes Ge-N bonds at nitrided interfaces, and provides a template for deposition of nc- and ng-dielectrics. Nc-HfSiON on Si-passivated and nitrided Ge (100) and ng-TiO2 yield Dit levels of 2-5x1010 cm-2. C-V characteristics are symmetric with respect to flat-band voltages, VFB yielding fixed charge levels ~2-3x1011 cm-3. J-V characteristics yield currents at 1 V > VFB, of 3-5x10-6 A-cm-2. TiO2 capacitors on Ge have EOT values of ~ 4.5 nm, as well as low values of Dit .
[1] G. Lucovsky, et al: Many-Electron Multiplet Theory Applied to O-Vacancies in (i) Nanocrystalline HfO2 and (ii) Non-crystalline SiO2 and Si Oxynitride Alloys, Progress in Theoretical Chemistry and Physics 23 (2010) 193-211.
[2] G. Lucovsky, D. Zeller, Remote Plasma Enhanced Chemical Deposition of Non-Crystalline GeO2 on Ge and Si Substrates, Journal of Nanoscience and Technology 11 (2011) 7974-7981
[3] Y. Tanabe, S. Sugano, On the absorption spectra of complex ions, Journal of the Physical Society of Japan (1956) 11 (8) (1956) 864–877; 9(5) (1954) 9(5) 766-779.