Analysis of ferroelectric properties of ALD-Hf0.5Zr0.5O2 thin films according to oxygen sources

초록

Ferroelectric Hf 0.5 Zr 0.5 O 2 (HZO) thin films are mostly deposited with a thickness of less than 10 nm by an atomic layer deposition (ALD) process. Since the oxygen source used in the ALD process affects the residues in the deposited HZO films, the choice of oxygen source can be one of the important factors to improve ferroelectricity. From this point of view, the ferroelectric properties of 10-nm-thick ALD-HZO films according to the oxygen source (O 3 , H 2 O, and D 2 O) were comprehensively analyzed in this study. Heavy water (deuterium water, D 2 O) was used as a tracer to pinpoint the origin of hydrogen that could be derived from unreacted metal precursors or unreacted hydroxyl groups. As a result, it was revealed that the decrease in ferroelectric polarization and increase in leakage current observed in the H 2 O- and D 2 O-based HZO capacitors compared to the O 3 -based HZO capacitor were due to the oxygen source. These results highlight the importance of using O 3 as a hydrogen -free oxygen source in the ALD process to achieve better ferroelectricity.

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