Co-sputtering yttrium into hafnium oxide thin films to produce ferroelectric properties

Abstract

Thin film capacitors were fabricated by sputtering TiN-Y doped HfO2-TiN stacks on silicon substrates. Yttrium was incorporated into the HfO2 layers by simultaneously sputtering from Y2O3 and HfO2 sources. Electric polarization and relative permittivity measurements yield distinct ferroelectric properties as a result of low yttrium dopant concentrations in the range of 0.9-1.9 mol. %. Grazing incidence x-ray diffraction measurements show the formation of an orthorhombic phase in this range. Compared to atomic layer deposition films, the highest remanent polarization and the highest relative permittivity were obtained at significantly lower doping concentrations in these sputtered films

Ferroelectricity in Rare-Earth Modified Hafnia Thin Films Deposited by Sequential Pulsed Laser Deposition

“…On the other hand, in some of the reports, ferroelectric nature in doped-HfO 2 films was attributed to the influence of "wake-up" effect. [11][12][13] In this paper, we report on the ferroelectric properties of rare earth doped Sm:HfO 2 (SHO) and Gd:HfO 2 (GHO) thin films fabricated by the sequential pulsed laser deposition (SPLD) technique. [14][15][16] The deposition was performed by periodic depositions from HfO 2 and Sm 2 O 3 /Gd 2 O 3 ceramic targets.…”

“…5,6,12 The dopant incorporation into monoclinic HfO 2 matrix results in a transformation to tetragonal/cubic phase with the appearance of an intermediate metastable orthorhombic (Pca2 1 ) phase. On the other hand, in some of the reports, ferroelectric nature in doped-HfO 2 films was attributed to the influence of "wake-up" effect.…”

The origin of ferroelectricity in Hf1−xZrxO2: A computational investigation and a surface energy model

“…The discovery of the ferroelectric properties arised from the development of nanoscale thin films 7 for use in memory technology, where crystalline doped films of high quality were developed. After the observation of a remanent polarization and hysteresis in 10 nm thick films of 3 % Si doped HfO2 films 1 in a TiN-HfO2-TiN stack, the effect was additionaly found in Al-and Y-doped films 8,9 grown on TiN as well. More suitable dopants have been discovered since 10 .…”

Polarization switching behavior of Hf–Zr–O ferroelectric ultrathin films studied through coercive field characteristics

“…12,[21][22][23] It is widely recognized that the ferroelectricity in HfO 2 is attainable in a particular range of dopant concentrations, and its spontaneous polarization is induced by the displacement of oxygen ions in the noncenter symmetric orthorhombic phase crystal. 1,4,5) The ferroelectricity of HfO 2 films is maximized in ultrathin films of around 10 nm thickness.…”

“…Since the first report of ferroelectricity in Si-doped HfO 2 crystalline films, ferroelectric HfO 2 films have been reported using many types of dopants, such as Si, 1-6) Zr, [6][7][8][9][10] Y, [4][5][6][11][12][13] Al, [4][5][6]14) Gd, 4,15,16) Sr, 5,17) La, 18,19) Sc, 6) Ge, 6) and N. 6,20) Nondoped HfO 2 films also show ferroelectricity when an appropriate amount of oxygen deficiency is introduced. 12,[21][22][23] It is widely recognized that the ferroelectricity in HfO 2 is attainable in a particular range of dopant concentrations, and its spontaneous polarization is induced by the displacement of oxygen ions in the noncenter symmetric orthorhombic phase crystal.…”