Improved Electrical Properties of ALD Hfx Zr1 − xO2 Dielectrics Deposited on Ultrathin PVD Zr Underlayer

The impact of ultrathin metal underlayer on physical and electrical properties of Hf _x Zr_{1- x} O₂(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_{1- x} O₂ 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.