Impact of Various Pulse-Bases on Charge Boost in Ferroelectric Capacitors

To fully understand the electrical characteristics of ferroelectric field-effect transistor (especially, sub-60-mV/decade switching characteristics at 300 K), it is necessary to quantitatively figure out the physics of the negative capacitance in ferroelectric material. In this work, metal-ferroelectric-metal (MFM) and metal-insulator-ferroelectric-metal (MIFM) capacitors were fabricated with Hf_0.5Zr_0.5O₂ (HZO) and HfO₂/HZO, respectively. For various bases of the input voltage pulse across the capacitors, the charge released during the falling edge of the pulse (Q_D)was measured. In reality, for the given bases of the input voltage pulse, the charge (Q_D) boost in the ferroelectric capacitors was experimentally observed without intentionally applying imprint, as done in the prior work. It turned out that, even though the MIFM capacitor’s capacitance is lower than a fixed-value capacitor’s capacitance, Q_D of the MIFM capacitor was comparable to Q_D of the fixed-value capacitor. This clearly indicates that the charge (Q_D) was boosted by the negative capacitance in the ferroelectric material.