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Band Alignments of High-K Dielectrics on Si and Pt

Published online by Cambridge University Press:  10 February 2011

J Robertson ,
E Riassi ,
J-P Maria  and
A I Kingon
J Robertson
Affiliation:
Engineering Dept, Cambridge University, Cambridge CB2 1PZ, UK
E Riassi
Affiliation:
Engineering Dept, Cambridge University, Cambridge CB2 1PZ, UK
J-P Maria
Affiliation:
Dept of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7919, USA.
A I Kingon
Affiliation:
Dept of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7919, USA.
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Abstract

Materials with a high dielectric constant (K) such as tantalum pentoxide (Ta2O5) and barium strontium titanate (BST) are needed for insulators in dynamic random access memory capacitors and as gate dielectrics in future silicon devices. The band offsets of these oxides must be over 1 eV for both electrons and holes, to minimise leakage currents due to Schottky emission. We have calculated the band alignments of many high K materials on Si and metals using the method of charge neutrality levels. Ta2O5 and BST have rather small conduction band offsets on Si, because the band alignments are quite asymmetric. Other wide gap materials Al2O3, Y2O3, ZrO2 and ZrSiO4 are found to have offsets of over 1.5 eV for both electrons and holes, suggesting that these are preferable dielectrics. Zirconates such as BaZrO3 have wider gaps than the titanates, but they still have rather low conduction band offsets on Si. The implications of the results for future generations of MOSFETs and DRAMS are discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 592 , 1999 , 87
Copyright
Copyright © Materials Research Society 2000

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