Characterizing Crystalline Polymorph Transitions in HfO2 by Extended X-Ray Absorption Fine-Structure Spectroscopy
Patrick S. Lysaght, Joseph Woicik, M A. Sahiner, B H. Lee, Raj Jammy
Detecting the spectroscopic signature of crystalline order in ultra-thin HfO2 gate dielectric films has been particularly challenging, yet essential to the explanation of atomic structure based mechanisms responsible for electrical performance. Atomic layer deposited 1.4, 1.8, and 4.0 nm thick HfO2 films on 1.0 nm SiO2 interfacial layers on Si(100) substrates have been measured by extended x-ray absorption fine-structure (EXAFS) pre- and post-anneal processing. Analysis of the second coordination shell indicates increasing atomic order with increasing anneal temperature for each film thickness. Also, increasing atomic order is evident with increasing film thickness at each anneal temperature. X-ray diffraction and high resolution transmission electron microscopy indicate the 1.4 nm HfO2 sample annealed at 1000 C is amorphous, however, Fourier transformed EXAFS spectra fit with HfO2 reference phases identify the emergence of monoclinic and tetragonal polymorphs for this film such that the fraction of higher permittivity tetragonal HfO2 increases relative to the monoclinic phase as the HfO2 film thickness decreases.
, Woicik, J.
, Sahiner, M.
, Lee, B.
and Jammy, R.
Characterizing Crystalline Polymorph Transitions in HfO<sub>2</sub> by Extended X-Ray Absorption Fine-Structure Spectroscopy, Applied Physics Letters
(Accessed September 26, 2023)