Improved Electrical Properties of ALD $\hbox{Hf}_{x} \hbox{Zr}_{1 - x}\hbox{O}_{2}$ Dielectrics Deposited on Ultrathin PVD Zr Underlayer

The impact of ultrathin metal underlayer on physical and electrical properties of Hf
_x
Zr
<sub>1-

x</sub>
O
₂
(x=~0.4) after high-temperature processing was investigated. An ~5-Aring Zr, ~5-Aring Hf, ~10-Aring Hf metal layer was sputter deposited prior to Hf
_x
Zr
<sub>1-

x</sub>
O
₂
growth. Cross-sectional transmission electron microscopy and secondary ions mass spectrometry analysis confirmed no Zr or Hf silicide formation between the high-
k
film and Si substrate even after 1000degC processing. No significant increase in equivalent oxide thickness or gate leakage current is observed on devices with metal underlayer. Furthermore, devices with a 5-Aring-thick Zr underlayer exhibited lower threshold voltage, higher mobility, and improved charge trapping characteristics.