TaN interface properties and electric field cycling effects on ferroelectric Si-doped HfO2 thin films

Abstract

Ferroelectric HfO2-based thin films, which can exhibit ferroelectric properties down to sub-10 nm thicknesses, are a promising candidate for emerging high density memory technologies. As the ferroelectric thickness continues to shrink, the electrode-ferroelectric interface properties play an increasingly important role. We investigate the TaN interface properties on 10 nm thick Si-doped HfO2 thin films fabricated in a TaN metal-ferroelectric-metal stack which exhibit highly asymmetric ferroelectric characteristics. To understand the asymmetric behavior of the ferroelectric characteristics of the Si-doped HfO2 thin films, the chemical interface properties of sputtered TaN bottom and top electrodes are probed with x-ray photoelectron spectroscopy. Ta-O bonds at the bottom electrode interface and a significant presence of Hf-N bonds at both electrode interfaces are identified. It is shown that the chemical heterogeneity of the bottom and top electrode interfaces gives rise to an internal electric field, which causes the as-grown ferroelectric domains to preferentially polarize to screen positively charged oxygen vacancies aggregated at the oxidized bottom electrode interface. Electric field cycling is shown to reduce the internal electric field with a concomitant increase in remanent polarization and decrease in relative permittivity. Through an analysis of pulsed transient switching currents, back-switching is observed in Si-doped HfO2 thin films with pinched hysteresis loops and is shown to be influenced by the internal electric field.

RETRACTED ARTICLE: Enhancement of the blue photoluminescence intensity for the porous silicon with HfO2 filling into microcavities

“…It is reported that the ferroelectricity of HfO 2 is related with the mechanical encapsulation of HfO 2 and the dopant insertion, which leads to the distortion of HfO 2 during crystallization and phase change10111213. The ferroelectricity in HfO 2 films originates from the existence of the metastable and non-centrosymmetric orthorhombic phase with the space group of P ca2 1  1415. If crystallization occurs under mechanical encapsulation, the formation of the monoclinic phase is inhibited10, then the orthorhombic phase that shows a distinct piezoelectric response141617181920 will obtained.…”

“…The ferroelectricity in HfO 2 films originates from the existence of the metastable and non-centrosymmetric orthorhombic phase with the space group of P ca2 1  1415. If crystallization occurs under mechanical encapsulation, the formation of the monoclinic phase is inhibited10, then the orthorhombic phase that shows a distinct piezoelectric response141617181920 will obtained. It is 600 ~ 700 °C for HfO 2 films crystallized according to previous reports21.…”

Strong photoluminescence of the porous silicon with HfO2-filled microcavities

“…It is suggested that the ferroelectricity in HfO 2 films originates from the existence of the metastable and non-centrosymmetric orthorhombic phase with the space group of Pca2 1 . 11,21 Ferroelectricity is found to exist even in thin films of less than 10 nm in thickness, which could be enhanced and modulated by various dopants such as, Si, Al, and Y. 18,[22][23][24] In this work, the pure HfO 2 located at the surface of porous Si had been removed with the lift-off process.…”

“…This phase shows a distinct piezoelectric response. [11][12][13][14][15][16] According to the previous reports, the crystallization temperature is generally at 600-700 C for HfO 2 films. 17 The monoclinic and tetragonal phases were first present, and then orthorhombic phase was shown with annealing temperature increasing.…”

Prediction of new metastable $$\hbox {HfO}_{2}$$ HfO 2 phases: toward understanding ferro- and antiferroelectric films

“…This discovery is of great interest to the semiconductor industry and has led to intensive experimental [3][4][5][6][7][8][9][10][11][12][13][14] and theoretical [9,[15][16][17][18][19][20][21][22] research, because these materials are believed to avoid the problems typical for the traditional ferroelectric materials (such as lead zirconate titanate) during integration into microelectronic devices. However, precise identification of the phase(s) in these films is problematic due to experimental limitations such as the broadness of the thin-film diffraction spectra, unknown film texture and strain fields, and possible presence of multiple phases within a single film.…”