Tiered deposition of sub-5 nm ferroelectric Hf1-xZrxO2 films on metal and semiconductor substrates

Abstract

Using a tiered deposition approach, Hf1-xZrxO2 (HZO) films with varying atomic layer deposition (ALD) cycles from 36 to 52 cycles were grown on Ge, Ir, and TiN substrates in single runs and annealed at 500 °C. 40 ALD cycle films grown on Ir exhibit a switched polarization (Psw) of 13 μC/cm2, while those grown on Ge and TiN did not exhibit measurable Psw values until 44 and 52 ALD cycles, respectively. High-resolution cross-sectional transmission electron microscopy confirmed these results; the ferroelectric films are crystalline with defined lattice fringes, while non-ferroelectric films remain amorphous. 52 ALD cycle 1:1 HZO grown on Ge had the highest Psw of all the films fabricated at 39 μC/cm2, while the 1:1 HZO grown on TiN displayed continuous wake-up and no fatigue up to 1010 cycles with the Psw increasing from <1 μC/cm2 to 21 μC/cm2.

Epitaxial Ferroelectric La-Doped Hf0.5Zr0.5O2 Thin Films

“…This is evidenced in Figure 9d, where the endurance of the four films is plotted as a function of the switching field. A similar thickness dependence had been observed in polycrystalline HZO films, 44 reverses its direction. In the t = 6.3 nm film (red circles) E i  300 kV/cm decreases to less than 100 kV/cm after 10 10 cycles, while in the t = 4.8 nm film (black squares) the smallest E i  80 kV/cm quickly decreases to almost vanish during additional cycling.…”

Low‐Thermal‐Budget Fluorite‐Structure Ferroelectrics for Future Electronic Device Applications

“…Numerous studies conducted in several research groups in the last decade have demonstrated that fluorite‐structure ferroelectrics can be deposited using various deposition techniques such as ALD, sputtering, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and chemical solution deposition (CSD). [ 1–19,22–54 ] Among these techniques, ALD was the most intensively studied deposition technique because it can form very thin conformal and uniform ferroelectric films based on a self‐limiting mechanism by chemical reactions between metal precursors, oxygen source, and the previously deposited film (or substrate). In this regard, the only controllable parameters during the ALD process are types of metal precursor/oxygen sources, [ 27–29 ] pulse/purge time, [ 30,31 ] and deposition temperature.…”

“…Depending on the type of material, the formation of the ferroelectric phase during the annealing process (or partially during the ALD process) can be enhanced by controlling the applied stress due to the difference in the thermal expansion coefficient or increasing the concentration of oxygen vacancies at the interface by the oxygenscavenging effect. [2,4,5,[47][48][49][50][51][52] In this regard, the influence of various bottom electrodes on ferroelectric properties has been extensively studied based on the metal-ferroelectric-metal (MFM) structure. [47][48][49][50][51] According to the experimental results reported in the past decade, the use of TiN bottom electrodes could be a useful strategy to improve the ferroelectric properties of Hf 1-x B x O 2 films.…”

High polarization, endurance and retention in sub-5 nm Hf0.5Zr0.5O2 films

“…12) Hf 0.5 Zr 0.5 O 2 (HZO) films. Films thinner than 5 nm have been reported to be ferroelectric, 3,[13][14][15] which can permit their use in ferroelectric tunnel junctions, [17][18][19] but simultaneous (same sample and same poling voltage) combined high polarization, endurance and retention have not been reported for sub-5 nm films.…”