Influence of Oxygen Composition and Carbon Impurity on Electronic Reliability of HfO2 Thin Films

Abstract

Highly reliable gate stack systems using a high-k dielectric thin film such as a hafnium dioxide film are indispensable for the development of ULSI (Ultra-Large-Scale Integration) devices. In this study, the degradation mechanisms of the electronic reliability of hafnium dioxide dielectric film caused by point defects such as oxygen vacancies and carbon interstitials was investigated by using quantum chemical molecular dynamics method. The magnitude of the band gap of the HfO 2-x , which is hafnium dioxide with oxygen vacancies, decreased drastically from 5.7 eV to about 1.0 eV due to the generation of donor states within the band gap of hafnium dioxide. When a carbon atom as the impurity was introduced in HfO 2 film, carbon impurity states (donor and acceptor) formed in the band gap of hafnium dioxide. The band gap calculated from the energy difference between the donor and acceptor decreases to 1.6 eV. The estimated changes of the magnitude of the band gap due to the point defects were validated by experiments using synchrotron radiation photoemission spectroscopy. We conclude therefore, it is very important to minimize point defects in the hafnium dioxide dielectric film in order to ensure the electronic performance and reliability of MOS transistors.

A Comparative Study on the Ferroelectric Performances in Atomic Layer Deposited Hf0.5Zr0.5O2 Thin Films Using Tetrakis(ethylmethylamino) and Tetrakis(dimethylamino) Precursors

“…Thus, the difference in ε r value might be determined by the relative fractions of the tetragonal and orthorhombic phases or the defect concentration, which is expected to decrease the average dielectric constant with local lattice distortions. The ε r value of the tetragonal phase (35)(36)(37)(38)(39)(40) was higher than that of the orthorhombic phase (25)(26)(27)(28)(29)(30). Thus, the high ε r value of TEMA HZO capacitor indicates that it has a higher tetragonal phase fraction compared to the TDMA HZO capacitors.…”

“…However, they reported that the increase in C concentration did not result in the decrease of the free energy difference between the orthorhombic and monoclinic phase [34]. In Kuenneth et al's work, the substitutional C defects were considered, although the C impurities are generally known as interstitial defects in HfO 2 [33,35]. Therefore, the theoretical calculations did not clearly reveal that the C impurities could decrease [12]), HZO is presented the free energy difference between the tetragonal and orthorhombic phases.…”

Hf-Based High-κ Dielectrics: A Review

“…These defects can adversely affect the performance of devices. Also, they can create an electric field which can change band offsets and disrupt its dielectric properties [49].…”

“…. Initial structures of (a) HfO2 with one oxygen vacancy and (b) HfO2 with one interstitial for quantum chemical molecular dynamics simulation [49].…”