Low temperature processed 0.7SrBi2Ta2O9–0.3Bi3TaTiO9 thin films fabricated on multilayer electrode-barrier structure for high-density ferroelectric memories

Abstract

Thin films of solid-solution material 0.7SrBi2Ta2O9–0.3Bi3TaTiO9 (0.7SBT–0.3BTT) were fabricated on n+-polycrystalline (n+-poly) Si substrates by a metalorganic solution deposition technique at a low processing temperature of 650 °C using a Pt–Rh/Pt–Rh–Ox electrode-barrier structure. The Pt–Rh/Pt–Rh–Ox structure was deposited using an in situ reactive radio frequency sputtering process. The electrodes had a smooth and fine-grained microstructure and were excellent diffusion barriers between the 0.7SBT–0.3BTT thin film and Si substrate. The ferroelectric (0.7SBT–0.3BTT) test capacitors using these electrode-barrier grown directly on Si showed good ferroelectric hysteresis properties, measured through n+-poly Si substrate, with 2Pr and Ec values of 11.5 μC/cm2 and 80 kV/cm, respectively, at an applied electric field of 200 kV/cm. The films exhibited good fatigue characteristics (<10% decay) under bipolar stressing up to 1011 switching cycles and the leakage current density was lower 10−7 A/cm2 at an applied electric field of 200 kV/cm. The good ferroelectric properties of 0.7SBT–0.3BTT solid-solution thin films at a low processing temperature of 650 °C and excellent electrode-diffusion barrier properties of a Pt–Rh/Pt–Rh–Ox structure are encouraging for the realization of high-density nonvolatile ferroelectric random access memories on silicon substrates.

Low temperature synthesis and ferroelectric properties of La substituted Bi4Ti3O12 thin films by sol–gel

“…Among BLSFs, SrBi 2 Ta 2 O 9 (SBT) and Bi 4 Ti 3 O 12 (BIT) have attracted a dominant attention. However, the SBT films have some serious drawbacks, such as high processing temperatures (above 800 • C) and low remanent polarization of 4-10 C/cm 2 , which is insufficient for the high-density integration of FRAM [3,5]. In the case of BIT thin films, a-axis-orientation BIT thin film has a large spontaneous polarization of 45 C/cm 2 , which is three to four times higher than that of SBT.…”

Fabrication and ferroelectric studies of (Bi, Gd)4Ti3O12 thin films grown on Pt/Ti/SiO2/Si and p-type Si substrates

“…SBT shows a superior fatigue endurance during polarization switching over 10 12 cycles, however, it has a few disadvantages, such as high process temperatures of 750-850 1C and small remanent polarization (2P r ) of 4 $16 mC/cm 2 [7][8][9]. On the other hand, BIT single crystal exhibits a large spontaneous polarization (P s ) along a-axis ($50 mC/cm 2 ), however, polycrystalline BIT thin films exhibits relatively high leakage current, poor fatigue resistance, and small remanent polarization (2P r ) of 4$8 mC/cm 2 [2,10].…”

“…Lead-free bismuth-layered perovskite ferroelectrics, such as SrBi 2 Ta 2 O 9 (SBT) and Bi 4 Ti 3 O 12 (BIT), have been extensively studied as alternative materials for memory applications [2,[7][8][9]. SBT shows a superior fatigue endurance during polarization switching over 10 12 cycles, however, it has a few disadvantages, such as high process temperatures of 750-850 1C and small remanent polarization (2P r ) of 4 $16 mC/cm 2 [7][8][9].…”

Structure of sol-gel prepared ferroelectric Bi3.4La0.6Ti3O12

“…Ferroelectrics have been extensively studied for applications on nonvolatile ferroelectric random access memories (FeRAMs) [1][2][3]. Among them, lanthanide doped Bi 4 Ti 3 O 12 (BIT) thin films have been extensively investigated, since they exhibit several advantages, such as a large remanent polarization, a good fatigue resistance, and a relatively low processing temperature [4][5][6][7][8][9].…”