Characteristics of thin film LiNbO₃ on p-Si (100)

Thin-film LiNbO₃ metal-ferroelectric-semiconductor (MFS) capacitors show improved characteristics, such as low interface trap density, low interaction with the Si substrate, and a large remanent polarization. This paper reports on ferroelectric LiNbO₃ thin films grown directly on p-type Si (100) substrates for ferroelectric random access memories (FRAM) applications by using a 13.56 MHz RF magnetron-sputtering system. Rapid thermal anneal (RTA) treatment was performed for as-deposited films in an oxygen atmosphere at various temperatures. We learned from X-ray diffraction that the 600 °C, 60-sec RTA annealed films changed from amorphous to polycrystalline LiNbO₃ which exhibited (012), (015), (022), and (023) orientations. Low-temperature film growth and post RTA treatments improved the leakage current of films. The leakage current density of films decreased from 10^-5 to 10^-7 A/cm² after RTA treatment. The breakdown electric field of the films was higher than 500 kV/cm. The capacitance-voltage (C-V) curves showed a clockwise hysteresis, which represents ferroelectric switching characteristics. The calculated dielectric constant of thin film LiNbO₃ was 27.5, which is close to the bulk value.