Theoretical and experimental investigation of ultrathin oxynitrides and the role of nitrogen at the Si–SiO2 interface

Abstract

Articles you may be interested inComparison of ultrathin Si O 2 ∕ Si ( 100 ) and Si O 2 ∕ Si ( 111 ) interfaces from soft x-ray photoelectron spectroscopy J.Photoemission and ab initio theoretical study of interface and film formation during epitaxial growth and annealing of praseodymium oxide on Si (001) We investigate microscopic properties of ultrathin oxynitride gate dielectrics using a combination of first principles electronic structure methods and the attenuated total reflection ͑ATR͒ infrared spectroscopy. We use a theoretical structural model based on the Si-SiO 2 interface. The quantum molecular dynamics simulations suggest that N accumulates at the interface. We have generated samples with the nitrogen concentrations from 1.69ϫ10 14 to 6.78ϫ10 14 cm Ϫ2 . The analysis of nitrogen containing cells indicates a significant structural improvement of the oxide layer and the strain reduction at the interface. We have performed a calculation of the vibrational density of states. The experimental infrared ATR data is in qualitative agreement with the calculation. The valence band offset is estimated with two different theoretical methods. Calculations reveal a close agreement between a reference energy level based method and a direct estimate based on the density of states analysis. For the highest nitrogen concentration considered we find a 0.3 eV increase of the valence band offset due to nitrogen at the interface. The leakage current is studied using the Landauer theory to model the conductance through the gate dielectric.

Density Functional Theory Modeling of (001)Si–Oxynitride Interfaces

“…7 Theoretical work has also been reported in conjunction with experiments. Demkov et al 8 use density functional quantum molecular dynamics simulation and report the (energetically favorable) accumulation of nitrogen at the SiO 2 /Si interface (in agreement with experiment), as well as the beneficial influence of nitrogen on the transport properties, by increasing the valence-band offset with high nitrogen concentration. Regarding nitrogen bonding, it is reported that the majority of the bonds at the interface are Si-N with threefold coordinated nitrogen atoms and that no N-O bonds are identified experimentally.…”

Effects of aluminum incorporation on band alignment at theSiO2∕HfO2interface

“…To analyze the valence band offset at the Al-doped SiO 2 / HfO 2 , we use two techniques, the average potential method 18,19 and the density of states analysis. 20 Two methods agree with each other within 0.2 eV. While the average potential method provides a unique value for the band discontinuity, the site projected partial density of states analysis gives more detailed information about the valence band maximum, including band bending.…”

Comparison of density functional theory methods as applied to compound semiconductor-oxide interfaces: Slab versus cluster models

“…1 Density functional theory ͑DFT͒ has been proven to reliably predict geometric structure, relative energies and the density of states in the band-gap region of oxidesemiconductor interfaces. [2][3][4][5][6][7][8] DFT can be reliably used to screen potential semiconductor-oxide combinations if the atomic structure of the interface is known. An atomistic understanding of the mechanism for Fermi-level pinning is necessary to further understand the phenomenon and to aid in the discovery of new stable III/V-dielectric interfaces.…”