Integration of Sr0.8Bi2.2Ta2O9/HfO2 ferroelectric/dielectric composite film on Si substrate for nonvolatile memory applications (original) (raw)
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Memory applications based on ferroelectric and high-permittivity dielectric thin films
Microelectronic Engineering, 1995
Several metal oxide perovskites and Bi layered perovskites are of substantial interest for integrated circuit memories. Strontium titanate, barium strontium titanate, and lead zirconate titanate based paraelectrics are of particular interest for dynamic memory applications since they have high charge storage densities, low leakage currents, and resistance against time dependent dielectric breakdown sufficient to achieve gigabit densities and beyond. The high remanent polarization of ferroelectric lead zirconate titanate and strontium bismuth tantalate hold out the promise of low-voltage, highspeed, non-volatile memories. Advances are being made in the reliability of ferroelectric memories.
Materials Science & Engineering R-reports, 2001
We present in this article a review of the status of thin film ferroelectric materials for nonvolatile memories. Key materials issues relevant to the integration of these materials on Si wafers are discussed. The effect of film microstructure and electrode defect chemistry on the ferroelectric properties relevant to a high density nonvolatile memory technology are discussed. The second part of this review focuses on approaches to integrate these capacitor structures on a filled poly-Si plug which is a critical requirement for a high density memory technology. Finally, the use of novel surface probes to study and understand broadband polarization dynamics in ferroelectric thin films is also presented. # 2001 Published by Elsevier Science B.V.
Ferroelectric thin film technology for semiconductor memory
Semiconductor science and technology, 1995
Recent advances in ferroelectric thin film technology have generated significant interest for use as capacitor dielectrics in semiconductor memories [I-31. Ferroelectric non-volatile memories (NVRAMS) have several unique features which set them apart from floating-gate non-volatile memories, including high-speed write operation (intrinsic switching times below several nanoseconds [4]), high write endurance low as 1.5 V [SI). These characteristics make ferroelectric NVRAMS excellent candidates for the non-volatile memory in portable electronic products such as RF tags, smart cards and pagers. This paper describes the operation of a ferroelectric NVRAM cell and the scaling methodology, reviews the device physics and reliability mechanisms and summarizes the challenges posed by the integration of ferroelectric capacitors with CMOS technology. The high dielectric constant (&r-300-1000) of the same class of materials used for ferroelectric NVRAMS can be exploited for high-density DRAMS. Capacitors fabricated with these materials have been shown to meet the charge storage specifications of gigabit-scale DRAMS (equivalent SiO, thickness as low as 2.3 A [q) without the extremely severe geometries and exceedingly complex processes required with conventional trench and stacked SiO,/Si,N, or Ta,O, capacitor cell technologies. Recent progress in this area is summarized. read/write cycles [SI) and low operating voltages (as
Scientific reports, 2015
We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectiveness for NVM device applications. X-ray photoelectron microscopy was used to investigate the band alignments between atomic layer deposited HfO2 and pulsed laser deposited BT-BCN films. Programming and erasing operations were explained on the basis of band-alignments. The structure offers large memory window, low leakage current, and high and low capacitance values that were easily distinguishable even after ~10(6) s, indicating strong charge storage potential. This study explains a new approach t...
Journal of Applied Physics, 1995
Thin film non-volatile memory devices are fabricated on glass substrates by evaporating KNO 3 in an ultra high vacuum system. The top and bottom gold electrodes [25 lam x 25 ~tm] are deposited by shadow masking in the same vacuum system. The KNO 3 is protected from moisture by depositing a passivation layer of SiO. Pulse switching characteristics of thes~thin film memory devices show excellent signal-to-noise ratios for nonlinear and linear behavior. The integration of these transient current vs. time curves yields large values of spontaneous polarization (Ps,~ 10 3 t.tC cm 2). Capacitance-voltage measurements made at high frequency (1 MHz) with slow ramp rates (200mVs-l-2Vs-1) indicated well-defined threshold voltages and the presence of mobile carriers.
IEEE Transactions on Electron Devices, 2001
A multilevel metal process-based highly reliable ferroelectric memory (FeRAM) has been developed. Highly reliable characteristics have been attained by two techniques. One is a newly developed ferroelectric material with mixed superlattice crystal of SrBi 2 (Ta ,Nb 1) 2 O 9 and Bi 2 (Ta ,Nb 1)O 6 , which provides an elevated remnant polarization while keeping a low coercive voltage. The other is a metal covering memory cell structure which makes the use of plasma silicon nitride (p-SiN) passivation possible without reduction of the ferroelectric thin film by a hydrogen plasma during p-SiN deposition, which results in no degradation of the characteristics of cell capacitors. The FeRAM cell capacitors with the above newly developed ferroelectric material and metal covering structure have been fabricated by using a 0.6double level metal process. The fabricated cell capacitors show highly reliable characteristics such as the ensured retention of data written at a low voltage of 2.4 V and humidity resistance for 10 y under a high temperature of 70 C, which is promising for commercialization of FeRAM and its embedded LSIs.
Applied Physics A, 2012
Metal-ferroelectric-insulator-semiconductor (MFIS) structures with BaTiO 3 (BTO) as a ferroelectric film and SrTiO 3 (STO) as an insulating buffer layer were fabricated on p-type Si(001) substrates using an ion beam sputter deposition technique. The effect of out-of-plane orientation on the electrical properties of the MFIS structures, including leakage current density and memory window behavior, were studied using the growth of the BTO ferroelectric film on Si substrate buffered by highly c-axis-oriented and randomoriented STO buffer layers. The experimental results show that the out-of-plane orientations of the BTO films were almost identical to those of the STO buffer layers. The MFIS structure with a high c-axis orientation exhibited a maximum clockwise capacitance-voltage memory window of 1.17 V with a low leakage current of 1.05 × 10 −7 A/cm 2 at an applied voltage of 4 V, which is a significant improvement compared to the MFIS structure with a random orientation. The difference in the electrical properties of the MFIS structures with both types of orientation is discussed in detail. The results obtained from this study indicate that the Au/BTO/STO/p-Si MFIS structure with high c-axis orientation has good potential for use in non-volatile memory applications.
J Appl Phys, 1995
Thin film non-volatile memory devices are fabricated on glass substrates by evaporating KNO 3 in an ultra high vacuum system. The top and bottom gold electrodes [25 lam x 25 ~tm] are deposited by shadow masking in the same vacuum system. The KNO 3 is protected from moisture by depositing a passivation layer of SiO. Pulse switching characteristics of thes~thin film memory devices show excellent signal-to-noise ratios for nonlinear and linear behavior. The integration of these transient current vs. time curves yields large values of spontaneous polarization (Ps,~ 10 3 t.tC cm 2). Capacitance-voltage measurements made at high frequency (1 MHz) with slow ramp rates (200mVs-l-2Vs-1) indicated well-defined threshold voltages and the presence of mobile carriers.
MRS Proceedings, 2001
ABSTRACTThis paper reports the microstructure and physical properties of ferroelectric capacitors formed from SrBi2Ta2O9(SBT) layers on Si with various buffer layers including jet-vapor deposited silicon nitride, zirconium oxide, hafnium oxide and thermally grown silicon oxide. Results from cross-sectional transmission electron microscopy (X-TEM), energy dispersive spectroscopy (EDS), X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and non-contact atomic force microscopy (nc-AFM) data coupled with capacitance-voltage (C-V) and current- voltage (I-V) data indicate that both the microstructure and physical properties of SBT films deposited on silicon are dependent on the buffer layer material employed.