Jeng-Hwa Liao

Resistive switching characteristics in Pr0.7Ca0.3MnO3 thin films on LaNiO3-electrodized Si substrate

The resistive switching characteristics of Pr0.7Ca0.3MnO3 (PCMO) thin films deposited on LaNiO3 (LNO)-electrodized Si substrate were investigated. Highly (100)-textured PCMO films were grown on the (100)-oriented LNO electrode. They exhibited reversible and steady bistable resistance switching behavior. The resistive switching behavior of PCMO capacitors on LNO is related to the trap-controlled space charge limited current mechanism and LNO/PCMO/LNO capacitor exhibits the strongest resistive switching effect with a resistance ratio for about two orders of magnitude.

Physical and electrical characteristics of silicon oxynitride films with various refractive indices

This study explores the relationship between both the physical and the electrical characteristics of silicon oxynitride (SiON) films and the refractive index. The single wafer rapid thermal process modules were used for low pressure chemical vapour deposition of SiON films. A series of SiON films with refractive index between 1.50 and 1.83 were fabricated. Fourier transform infrared absorption spectroscopy and x-ray photoelectron spectroscopy identified the chemical bonding configurations of different SiON films: the Si–N bonds are replaced by Si–O bonds as the refractive index of the SiON films declines. Moreover, the Si atomic ratio is kept between 35% and 40% while the oxygen atomic ratio increases and the nitrogen atomic ratio decreases as the refractive index of the SiON film declines. The electrical characteristics of different SiON-based silicon–oxide–nitride–oxide–silicon (SONOS) devices suggest that (1) the dielectric constant increases with increasing refractive index of the SiON film and (2) the charge-trap density is inversely proportional to the oxygen concentration in the SiON film. Based on these results, the SiON films with various refractive indices can provide a wider application for silicon-based devices, such as SONOS and MOS devices.

Near-interface magnetotransport in La0.75Sr0.25MnO3 epitaxial films on SrTiO3 substrate

The magnetotransport properties of La0.75Sr0.25MnO3 (LSMO) films epitaxially grown on SrTiO3 (0 0 1) substrate were studied. The Curie temperature (Tc) of LSMO films decreases from 300 to 105 K with a reduction in the film thickness to 5 nm. A clear metal–insulator transition is observed at a temperature consistent with Tc for films thicker than 10 nm. However, the 5 nm thick film displays an insulative characteristic along with a high magnetoresistence effect in a wide range of temperatures below and above Tc. A phase-separation phenomenon in the 5 nm thick film was demonstrated by thermally activated hopping transport between ferromagnetic metallic domains embedded in an insulative matrix at temperatures below Tc, but between paramagnetic metallic domains at temperatures above Tc. It was also confirmed by conductive atomic force microscopy images.

Effect of the CoFe2O4 thin film thickness on multiferroic property of (00l)-oriented Pb(Zr0.5Ti0.5)O3∕CoFe2O4∕Pb(Zr0.5Ti0.5)O3 trilayer structure

In this study, we have fabricated (00l)-oriented Pb(Zr0.5Ti0.5)O3∕CoFe2O4∕Pb(Zr0.5Ti0.5)O3 (PZT/CFO/PZT) trilayer thin films on LaNiO3 coated substrates by dual-cathode rf sputtering system. The thicknesses of top and bottom PZT thin films were fixed at 100nm but those of the CFO interlayer were 40, 80, and 120nm, respectively. The x-ray diffraction showed well-defined PZT and CFO peaks with (00l) orientation, and large grains with columnar structure were observed by field-emission scanning electron microscopy. Hard-magnetic M-H loop with a saturation magnetization of ∼235emu∕cm3 and ferroelectric hysteresis curve with saturation polarization of ∼40.1μC∕cm2 were measured at room temperature for the PZT/CFO (120 nm)/PZT trilayer thin films. Due to the low-resistance CFO interlayer in series with the PZT layers, the ferroelectric property does not significantly vary with the CFO interlayer thickness. In contrast, the possibility of the existence of nonmagnetic interfacial layer at the CFO/PZT interface caus...

A novel BE-SONOS NAND Flash using non-cut trapping layer with superb reliability

This work presents superb chip-level reliability of a BE-SONOS charge trapping NAND fabricated in both 75nm and 38nm half-pitches. Without any error correction (ECC) >100K P/E cycling endurance for SLC and >3K endurance for MLC are obtained using a novel non-cut SiN trapping layer. Key process integration strategies are discussed, including barrier and trapping layer engineering, p-well and junction doping optimization, gate-etching profile, and SSL/GSL processing. In addition to the overall good performance in programming/erasing and reliability, the non-cut SiN also demonstrated charge retention without any lateral spread - contrary to common misperception of charge migration in SiN [1,2]. We believe this is the first time the reliability and performance of a charge trapping NAND chip are demonstrated to match or surpass those for FG NAND.

Strain-dependent magnetotransport properties of La0.9Sr0.1MnO3 epitaxial films on SrTiO3 and LaAlO3 substrates

The strain effect on the magnetotransport properties in La0.9Sr0.1MnO3 films epitaxially deposited on SrTiO3 (STO) and LaAlO3 (LAO) substrates, is demonstrated. Large compressive strain is formed in the films on the LAO substrate; however, that on the STO is subject to a small tensile strain. Strain relaxation of films grown on both substrates results in the formation of a spin-canted antiferromagnetic (AFM) insulative phase, causing the increase in resistivity with decreasing temperature. The characteristics of the AFM insulative phase become apparent with increasing film thickness, which leads to a clear AFM transition in the films grown on LAO and a reduction of magnetization and Curie temperature in those on STO. The magnetoresistance effect of the films is also consistent with the above results.

Ferroelectric-field-induced spin-pinning effect in Pb(Zr0.5Ti0.5)O3∕La0.9Sr0.1MnO3 bilayers

The magnetic properties of Pb(Zr0.5Ti0.5)O3∕La0.9Sr0.1MnO3 bilayers epitaxially grown on Nb-doped SrTiO3 (001) substrate were studied. Bilayers with a fixed Pb(Zr0.5Ti0.5)O3 (PZT) layer thickness of 200nm and different La1−xSrxMnO3 layer thicknesses varying from 10to40nm show a divergence between field-cooled (FC) and zero-field-cooled (ZFC) temperature-dependent magnetization measurements. Moreover, the polarization state of the PZT ferroelectric layer induces a spin-pinning effect causing a variation of the M∕M(10K) ratio in ZFC measurement and the divergent temperature (Td) between FC and ZFC processes. The magnetic hysteresis loops measured in FC and ZFC processes confirm the spin-pinning effect induced from the ferroelectric polarization field, leading to an alternation of the hysteresis loop characteristics for samples polarized with different signs of voltage.

Performance and reliability optimizations of BE-SONOS NAND Flash using SiON bandgap-tuning tunneling barrier

Bandgap-tunable SiON (oxynitride) tunnel barrier is developed to optimize the performance and reliability of BE-SONOS NAND Flash devices. The HTO O2 layer of the ONO tunnel barrier is replaced by SiON thin films with various refractive index (n) and thickness. We found that with n ≦ 1.72, SiON can provide excellent data retention comparable to conventional BE-SONOS. On the other hand, the erase speed can be greatly improved by using SiON O2 when n ≫ 1.50. We suggest that hole barrier lowering by SiON is the root cause of such erase speed improvement. Our results suggest an optimal 35Å SiON O2 layer with n = 1.63 for the best program/erase speed and data retention performance. Finally, a 75 nm BE-SONOS NAND device is fabricated to validate the performances of this concept.

Investigation of floating gate depletion effect on NAND FLASH reliability

Continuous technology scaling on NAND FLASH results in serious FG poly depletion issue due to Phosphorous out-gassing and degrades the cell reliability. Phosphorous implantation (P-IMP) into in-situ dope poly can improve poly depletion issue, but the FG bending and FG height loss were observed. In this study, we have successfully explored the methods to minimize FG bending and FG height loss issue by adding plasma oxide (PO) as screen oxide and/or changing the rotation times and temperature control of ion implantation. Finally, P-IMP on FG was validated at 36nm NAND FLASH device and shows significantly improvement on FG depletion and cell reliability.

Thermal Stability of Cobalt Silicide on Polysilicon Implanted with Germanium

The thermal stability of CoSi2 layers on P-doped polycrystalline Si was investigated. It was observed that the additional Ge+ implant is performed prior to Co sputtering can suppress the CoSi2 agglomeration behavior. The samples with Ge+ implant at 50KeV implanted energy and more than or equal to the dose of 2E15 ions/cm2 show that the agglomeration of CoSi2 film is completely suppressed during high temperature RTA annealing. The grain size by the CoSi2 formation with the Ge+ implantation is much smaller than that without Ge+ implantation during post annealing. In addition, the cobalt atom in polysilicon layer with Ge+ implantation is shallower compared to without Ge+ implantation. The thermal stability of CoSi2 is significantly improved by adding the Ge+ implantation into polysilicon.