Dependence of ferroelectric characteristics on the crystallinity of HfN thin film formed on Si(100) by a two-step deposition method

Abstract In this research we investigated the formation of ferroelectric HfN (Fe-HfN) thin film on a Si(100) substrate by a two-step deposition method to improve the crystallinity of Fe-HfN thin film, especially at the Fe-HfN/Si(100) interface region. A 3 nm thick initial HfN x layer was deposited on the Si(100) substrate by electron cyclotron resonance plasma reactive sputtering. The Ar/N 2 flow ratio was changed from 14/17.5 sccm to 14/21 sccm to increase the nitrogen concentration in the initial layer compared with the conventional Ar/N 2 flow ratio of 14/14 sccm. Then, a 7 nm thick HfN 1.15 layer was in situ deposited followed by deposition of the HfN 0.50 gate electrode layer. The Ar/N 2 flow ratios were 14/14 sccm and 10/0.2 sccm, respectively. Post-metallization annealing (PMA) was carried out at 400 °C/5 min for the HfN 0.50 /HfN 1.15 /HfN x /Si(100) metal–ferroelectric–semiconductor diode structure followed by deposition of the Al top electrode and gate patterning. The in situ deposited HfN 1.15 /HfN x stacked layer crystallized to a Fe-HfN layer by the PMA process. The crystallinity of the Fe-HfN layer was improved by increasing the Ar/N 2 flow ratio to 14/21 sccm for initial layer deposition without degrading the Fe-HfN/Si(100) interface property. The remnant polarization (2 P r ) increased from 2.4 μC cm −2 with a conventional Ar/N 2 flow ratio of 14/14 sccm to 3.7 μC cm −2 with 14/21 sccm for initial layer deposition. The fatigue characteristics up to 10 11 cycles were achieved without the wake-up phenomenon and a 2 P r of 95% of the initial value was maintained under program/erase pulses of ± 3 V/0.5 μs.