In:
MRS Proceedings, Springer Science and Business Media LLC, Vol. 996 ( 2007)
Abstract:
In this paper, various approaches to extend scalability of Hafnium-based dielectrics are reported. Among the three crystal phases of HfO 2 (monoclinic, cubic and tetragonal), the tetragonal phase has been reported to have the highest dielectric constant. Tetragonal phase stabilization by crystallizing the thin HfO 2 using a metal capping layer and by adding zirconium is demonstrated. The microstructure, morphology, optical properties and impurities of Hf x Zr 1-x O 2 dielectrics (for 0 〈 x 〈 1) are discussed. Subtle but important modification to high-k / Si interface characteristics resulting from addition of Zr into HfO 2 is reported. To further boost the dielectric constant of hafnium-based dielectrics, incorporation of TiO 2 , which has been reported to have high dielectric constant, is explored. Hf x Zr 1-x O 2 /TiO 2 bilayer films were fabricated. 30 Å TiO 2 films were deposited on a 5, 8, 12 or 15 Å Hf x Zr 1-x O 2 underlayer to determine the minimum thickness needed to maintain good thermal stability with Si substrate. CV and IV results indicated that 12-15 Å is the optimal thickness range for the Hf x Zr 1-x O 2 underlayer. A dielectric constant as high as 150 for TiO 2 layer is extracted from TiO 2 thickness series deposited on12 Å Hf x Zr 1-x O 2 underlayer. In addition to increasing the k-value of Hafnium-based dielectrics, it is important that the threshold voltage of these high-k devices is low. Here we report the use of thin Al 2 O 3 capping layers to modulate PMOS threshold voltages. About 100 mV reduction in threshold voltage is achieved by capping HfO 2 with a 5Å Al 2 O 3 film. Finally, dielectric scaling by modifying the Si/high-k interfacial layer is attempted. Nitrogen incorporation into Hf x Zr 1-x O 2 is shown to be a simple and effective method to lower the capacitance equivalent thickness (CET) of Hafnium-based dielectrics.
Type of Medium:
Online Resource
ISSN:
0272-9172
,
1946-4274
DOI:
10.1557/PROC-0996-H03-01
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2007
Permalink