The Relation between Crystalline Phase, Electronic Structure and Dielectric Properties in High-K Gate Stacks
Safak Sayan, Mark Croft, Nhan Van Nguyen, Tom Emge, James R. Ehrstein, Igor Levin, John S. Suehle, Robert A. Bartynski, Eric Garfunkel
As high permittivity dielectrics approach use in metal-oxide-semiconductor field effect transistor (MOSFET) production, an atomic level understanding of their electronic, and dielectric properties are being rigorously examined. The valence and conduction band densities of states for the HfO2/SiO2/Si and ZrO2/SiOxNy/n-Si structures are determined by soft x-ray photoemission and inverse photoemission. First principles calculations are used to help in assigning valence band maxima and conduction band minima. The energies of defect states at the band edges are determined by comparing the theoretical and experimental results. It is shown that both of these dielectric materials have high enough barriers for both electron and hole transfer. It is shown that crystal structure in ultrathin ZrO2 films has considerable effects on permittivity as well as bandgap. The films reported here are predominantly amorphous below a critical thickness (5.4nm) and transform to the tetragonal phase upon annealing. Thicker films appear tetragonal as grown. These phase changes may have a significant effect on channel mobility. Finally bandgap obtained from combined PES and IPES studies compared with the optical bandgap derived from ellipsometry measurements. The difference in the bandgap values can be attributed to the final state effects.
2005 International Conference on Characterization and Metrology for ULSI Technology
, Croft, M.
, Nguyen, N.
, Emge, T.
, Ehrstein, J.
, Levin, I.
, Suehle, J.
, Bartynski, R.
and Garfunkel, E.
The Relation between Crystalline Phase, Electronic Structure and Dielectric Properties in High-K Gate Stacks, 2005 International Conference on Characterization and Metrology for ULSI Technology, Dallas, TX, USA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=32018
(Accessed February 28, 2024)