Stabilization of ferroelectric phase in tungsten capped Hf0.8Zr0.2O2

We report on the stabilization of the ferroelectric phase in Hf0.8Zr0.2O2 with a tungsten capping layer. Ferroelectricity is obtained in both metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) capacitors with highly-doped Si serving as the bottom electrode in the MIS structure. Ferroelectricity is confirmed from both the electrical polarization-voltage (P-V) measurement and X-Ray Diffraction analysis that shows the presence of an orthorhombic phase. High-resolution Transmission Electron Microscopy and Energy Dispersive X-ray spectroscopy show minimal diffusion of W into the underlying Hf0.8Zr0.2O2 after the crystallization anneal. This is in contrast to significant Ti and N diffusion observed in ferroelectric HfxZr1-xO2 commonly capped with TiN.