Basic characteristics of metal-ferroelectric-insulator-semiconductor structure using a high-k PrOx insulator layer

Abstract

A metal-ferroelectric [ SrBi 2 Ta 2 O 9 ( SBT )] -high- k -insulator ( PrO x ) -semiconductor(Si) structure has been fabricated and evaluated as a key part of metal-ferroelectric-insulatorsemiconductor-field-effect-transistor MFIS-FET memory, aiming to improve the memory retention characteristics by increasing the dielectric constant in the insulator layer and suppressing the depolarization field in the SBT layer. A 20-nm PrO x filmgrown on Si (100) showed both a high ε of about 12 and a low leakage current density of less than 1×10 −8 A / cm 2 at 1.5 MV/cm. A 400-nm SBT film prepared on PrO x / Si shows a preferentially oriented (105) crystalline structure, grain size of about 130 nm and surface roughness of 3.2 nm. A capacitance–voltage hysteresis is confirmed on the Pt / SBT / PrO x / Si diode with a memory window of 0.3 V at a sweep voltage width of 12 V. The memory retention time was about 1×10 4 s , comparable to the conventional Pt / SBT / SiO x N y ( SiON )/ Si . The gradual change of the capacitance indicates that some memory degradation mechanism is different from that in the Pt/SBT/SiON/Si structure.