Chemical and Structural Properties of a TaN/HfO[sub 2] Gate Stack Processed Using Atomic Vapor Deposition

Abstract

In this work, we investigate the crystalline structure and the chemical properties of a “metal/high k ” gate stack with TaN as the gate electrode and HfO2 as the dielectric. Both TaN and HfO2 were deposited using atomic vapor deposition. We show that a 3 nm thick layer of HfO2 is crystallized when it is integrated, whereas it is amorphous as deposited. Increasing the TaN thickness increases the amount of the TaN crystalline face-centered cubic phase. Concerning the gate-stack chemistry, oxygen and nitrogen diffusion between the layers is shown. This occurs during the gate electrode deposition for all TaN thicknesses. We show that the gate stacks, including thick TaN layers, are not chemically stable under the spike annealing used for dopant activation because oxygen and nitrogen diffusion is increased by this thermal treatment. Gate stacks with a thinner TaN layer are much more stable under annealing because they are already partially oxidized before annealing.

A study of nitrogen behavior in the formation of Ta/TaN and Ti/TaN alloyed metal electrodes on SiO2 and HfO2 dielectrics

“…This result is in agreement with a previous study of ALD-TaN deposited on HfO 2 and annealed at high temperature. 16 Reaction (4) acting at the TaN/SiO 2 interface also seems possible between TaN and the IL in the TaN/HfO 2 /IL stack through the HfO 2 layer, which can be viewed as a solid electrolyte promoting O and N exchanges. The XPS spectra in Figure 3 also display a clear chemical shift of Si 0 in Ta/HfO 2 (DE 2 ¼ À0.4 6 0.3 eV) towards lower binding energy after anneal.…”