Phase transformation in ALD hafnia based layers for silicon-on-ferroelectric devices

The Hf
0.5
Zr
0.5
O
2
layers were prepared by atomic layer deposition on Si (100) substrate and subsequently annealed or and used for SOI fabrication. The presence and evolution of ferroelectric Pca21 phase was studied by GIXRD. The piezoelectric response of the films was measured by PFM after different annealing conditions. The SOF wafers with High-K BOX were made by DeleCut® process and studied by pseudo-MOSFET technique. The GIXRD study shows transformation of amorphous Hf
0.5
Zr
0.5
O
2
film to nonpolar monoclinic phase P2
1
/C and orthorhombic polar phase Pca21. It was found that the piezoelectric response of the films increases with annealing temperature up to 900 °C, and then decreases. This behavior has some discrepancy with the X-ray diffraction data and hysteresis measurements, and can be explained by a change in the crystal texture in the films. The study experimentally shows the approach to stabilizing ferroelectric phases of HZO.