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This study examined the relationship between the conducting filament resistance and reset voltage during the resistance switching of TiO2 thin films assuming a filament with a conical shape. There was a critical resistance (∼20 Ω) of the set state above and below which the filament responded differently in response to the current. Maintaining a higher set state resistance was more beneficial in achieving a more uniform reset voltage. This filament model coincides well with the localized switching behavior and the recently microscopically observed filament shape. [ABSTRACT FROM AUTHOR]

The frequency dispersion of the dielectric constant of yttrium (Y)-doped (Ba,Sr)TiO3 thin films (Y-BST) in the high-frequency domain (10 kHz–67 GHz) was investigated. In order to remove the substantial parasitic capacitances, inductances, and resistances from the measured impedance data, test samples, short-circuit standard, and open-circuit standard structures were fabricated and their frequency response was measured. Before removing parasitic components, the measured dielectric response showed a rolloff at approximately 4 GHz. However, after circuit calibration, the dielectric constant was almost constant up to 40 GHz where another rolloff was observed. However, this rolloff was due to the uncompensated small parasitic components. Therefore, the dielectric constant of the Y-BST films (170 with a film thickness of 30 nm) showed small frequency dispersion corresponding to the Curie–von Schweidler dispersion, of which the exponent is -0.0131, up to 40 GHz. Furthermore, the decrease of the capacitance was 17% in the frequency range from 10 kHz to 40 GHz. [ABSTRACT FROM AUTHOR]

This study investigated the variations in the dielectric constant with film thickness and measurement temperature of (Ba0.48Sr0.52)TiO3 thin-film capacitors with thicknesses ranging from 65 to 273 nm. The films were prepared by an on-axis rf magnetron sputtering, having Pt top and bottom electrodes. The thicker film showed a higher dielectric constant with a larger temperature dependence of the dielectric constant, and the maximum dielectric constant was observed at a higher temperature. The thickness-dependent dielectric constant at a given measurement temperature was explained by using the previously reported interfacial capacitance model, containing the intrinsic dead layer and electrode polarization. The temperature-dependent dielectric property could be explained using a modified Curie-Weiss (C-W) behavior of the film taking the nonferroelectric interfacial capacitance components into consideration. However, the C-W constant and Curie temperature of the ferroelectric layer must be modified in order to obtain a reasonable interfacial layer thickness. [ABSTRACT FROM AUTHOR]

The electrical conduction behavior of sputter-grown (Ba, Sr)TiO[sub 3](BST) thin films having IrO[sub 2] electrodes were studied under the assumption of a fully accumulated film. In the film-thickness range studied (40-80 nm), the dielectric constants and their electric field dependencies were found to be independent of the film thickness. Contrary to similar BST films grown on Pt electrodes, the leakage current density decreased with increasing film thickness at a given field. The phenomena were explained from the electric-field depression effect inside the film due to the accumulated negative space charges in the films. The leakage current conductions were controlled by the Poole-Frenkel mechanism in the low field whereas it changed to thermionic field emission in the high-field region. The dielectric constant obtained from the Poole-Frenkel fitting was approximately 300, which was in a qualitative agreement with the value obtained from the low-frequency capacitance measurement. The calculated interfacial potential-barrier height at zero volt and effective mass of electrons were 1.03 eV and 0.06m[sub 0], respectively, from the thermionic field emission fittings. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Multi-valued logic has been a significant focus of research in various fields with the advancement of information technology. One approach to realizing ternary logic is integrating of a threshold switching (TS) device with a transistor, but this method often entails a complex fabrication process. This work suggests a ternary gate-connected threshold switching thin-film transistor (TS-TFT) by serially connecting the TS device with a bottom-gate thin-film transistor (TFT). The fabrication process is simplified with a structure that shares electrodes and insulators. Different threshold voltages from TS and TFT devices produce stable multiple states. The Pt/HfO2/TiN TS device has an electronic trapping/detrapping switching mechanism that exhibits low power consumption and high reliability. With the superior electrical performance of an amorphous indium gallium zinc oxide TFT, the TS-TFT has stable endurance. Furthermore, pulse switching and ternary inverter are demonstrated from the practical point of view. [ABSTRACT FROM AUTHOR]

The influences of low-dielectric interfacial layers on the dielectric properties of Pt/(Ba,Sr)TiO[sub 3]/Pt capacitors were investigated before and after postannealing. The interfacial layer is believed to be the intrinsic dead layer (low-dielectric layer) due to the termination of chemical bonds of the (Ba,Sr)TiO[sub 3] (BST) material at the interfaces. The dielectric constant of the capacitor decreases with decreasing BST film thickness owing to the low dielectric constant of the dead layer. The dead-layer capacitance varies with processes such as film deposition temperature, and postannealing. Higher deposition temperatures result in a larger dead-layer capacitance and a higher bulk dielectric constant. Although annealing under a N[sub 2] atmosphere is less effective in reducing the dead-layer effect than under an O[sub 2] atmosphere, it is more effective in increasing the bulk dielectric constant. Therefore, a N[sub 2], rather than an O[sub 2] atmosphere, results in a larger increase in the overall dielectric constant. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The electric-field-induced rejuvenation behavior of the degraded ferroelectric properties of integrated Pt/SrBi[sub 2]Ti[sub 2]O[sub 9]/Pt capacitors was investigated. Integration processes, especially plasma-enhanced chemical vapor deposition of the passivation layers, generate hydrogen ions and electrons which act as domain pinning centers and a source of a negative internal electric field. Domain pinning was found to reduce the remanent polarization (P[sub r]) and internal field that induces an imprint to the positive bias direction. Alternating current cyclings with peak voltages of +/-6 V rejuvenated the degraded ferroelectric performance of the capacitors. Cycling with a negative bias was more effective in fixing the damage than was a positive bias. Baking at 125 °C again degraded the rejuvenated ferroelectric performance. The degree of re-degradation was also dependent on the polarity of the rejuvenating bias. The polarity-dependent behavior of rejuvenation was explained on the basis of a negative-internal-field model due to preferential capture of electrons from the plasma at the top electrodes. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this study, the influence of the HfOxNy interfacial layer (IL), interposed between the atomic layer deposited ferroelectric (FE) Hf0.5Zr0.5O2 thin film and TiN top electrode, on the FE properties of such a film was examined. The HfOxNy IL decreased the relative proportion of the non-FE monoclinic phase, possibly due to the N-doping effect. Furthermore, the oxidation of the TiN top electrode was also suppressed by the sacrificial oxidation of the HfOxNy IL during the rapid thermal process. As a result, the double remanent polarization of a Hf0.5Zr0.5O2 thin film could be enhanced from 40.2 to 48.2 μC/cm2 by the positive-up-negative-down test, and its degradation by fatigue during the endurance test can also be decreased. This result demonstrates the significance of interfacial engineering to optimize the FE properties of Hf0.5Zr0.5O2 films. [ABSTRACT FROM AUTHOR]

Based on the first-principles calculations, the authors study defect-defect interactions between cation vacancies in rutile TiO2 and monoclinic HfO2. It is found that vacancies are greatly stabilized at small separations because of a large reconstruction of nearby oxygen atoms that have two broken bonds. As a result, O–O bonds resembling O2 or O3 molecules are formed near the divacancy site. The defect levels originated from antibonding states of O p orbitals are identified within the energy gap, which can affect leakage currents and the density of trapped charges of oxides substantially. [ABSTRACT FROM AUTHOR]

The resistance switching mechanism of TiO2 films under voltage sweep mode was investigated. From the observed soft set of Pt/TiO2/Pt sample and from the polarity-dependant switching behavior of Ir(O)/TiO2/Pt sample, local rupture and recovery of conducting filaments near the anode interface wer identified as the switching mechanism. This is consistent with the authors’ recent observation [K. Kim et al., Electrchem. Solid-State Lett. 9, G343 (2006)] of the resistance switching property of Al2O3/TiO2 multilayers, where switching was controlled by the layer close to the anode. It appears that most parts of the filaments are preserved during switching and only a small portion of the film near the anode contributes to switching. [ABSTRACT FROM AUTHOR]

The effect of the carbon residue on the reliability of HfO2 thin films was investigated. HfO2 films were deposited on Si wafers by atomic layer deposition at a wafer temperature of 250 °C using Hf[N(CH3)2]4 and O3 oxidant with two different densities (160 and 390 g/m3). The films deposited at the higher O3 density contained a lower concentration of carbon impurities. The leakage current density was lower and the time-dependent dielectric breakdown was improved in the higher O3 density films. First principles calculations confirmed that trap sites were generated in the band gap of HfO2 when carbon was interstitially or substitutionally present. [ABSTRACT FROM AUTHOR]

The effects of the isoelectronic Al doping of epitaxial GaN films grown by metalorganic chemical vapor deposition on a (0001) Al2O3 single crystal substrate were investigated. It was found that the threading screw and edge dislocation densities of the GaN film decreased to less than half of that of the undoped GaN film up to Al doping concentration of 0.45%. The in-plane and out-of-plane strains were simultaneously reduced with the decrease in dislocation density as a result of the solution hardening effect. Accordingly, the electron mobility of the 0.45% Al-doped GaN film (524 cm2/Vs) was greatly improved compared to that of the undoped GaN film (178 cm2/Vs). However, the threading dislocation densities and strains were increased at a 0.64% Al concentration, and the electron mobility decreased accordingly. Therefore, the improvement in the electron mobility by Al doping up to 0.45% is the result of a decrease in the threading dislocation density and not a decrease in the number of point defects (Ga-site vacancy) as suggested earlier [Lee et al., Appl. Phys. Lett. 83, 917 (2003)]. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrate an electrostatic force microscopy based on a quartz tuning fork with 50 nm spatial resolution and 1 pN force sensitivity. We use a tuning fork with a spring constant of 1300 N/m and a Q factor of 3000. A sharpened nickel tip is attached to a prong of the tuning fork as well as electrically connected to the electrode of the prong. By applying a dc bias to the tip, ferroelectric domain patterns are recorded and read out on piezoelectric thin film. [ABSTRACT FROM AUTHOR]

Ferroelectric Hf0.5Zr0.5O2 (HZO) films were grown by the atomic layer deposition (ALD) technique on an ALD or physical-vapor-deposited (PVD, sputtering) TiN bottom electrode (BE). The PVD TiN film showed small grains with flat surface morphology, mainly consisting of the (111) crystallographic plane. In contrast, the ALD TiN film exhibited a larger diameter and faceted grain shapes, with the (200) crystallographic surface planes. The 10-nm-thick HZO film on the ALD TiN BE showed a lower internal field, enhanced endurance (>1 × 1010 cycle at 2.5 MV/cm), and decreased leakage current than identical HZO films on the PVD TiN BE. Lower interfacial oxidation of the ALD TiN BE as a result of the smaller grain boundary area of the ALD TiN induced a lower defect density in the HZO film. The higher work function of the ALD TiN film also contributed to the lowering of the leakage current. [ABSTRACT FROM AUTHOR]

The electronic structure of an amorphous SnO (a-SnO) thin film was examined by using spectroscopic methods including tender and soft x-ray absorption spectroscopies (XAS) and spectroscopic ellipsometry (SE). XAS at the Sn L1−, L3−, and O K-edges revealed that in a-SnO, the Sn 5px/y orbital states, which comprise the conduction band minimum (CBM), are broadened significantly compared to the case of crystalline SnO, whereas the hybridized Sn 5spz-O 2p states above the CBM are persistent. A lowering of the 5px/y states at the CBM by −0.4 eV and a reduction of the indirect bandgap were also observed. These orbital-dependent evolutions upon amorphization were caused by weakened interlayer couplings in the disordered quasi-2-dimensional semiconductor. However, the functionality of a-SnO as a p-type semiconductor would not be degraded significantly because the isotropic Sn 5s orbital states dominate in the valence band states. [ABSTRACT FROM AUTHOR]

The influence of La content on the ferroelectric properties of HfO2-ZrO2 thin films was examined for integrated electrostatic supercapacitor applications. A transition from ferroelectric to antiferroelectric-like behavior, accompanied by a significant increase of energy storage density value and efficiency, was observed with the increasing La concentration in La-doped HfO2-ZrO2-based capacitor structures, where the processing temperature remained below 400 °C. The combination of high energy storage density value (≈50 J/cm3) with high efficiency (70%) was obtained for the film with the highest La content (2.0 mol. %). The 2.0 mol. % La-doped HfO2-ZrO2-based capacitor structures were field cycled up to 109 times and were found to provide >40 J/cm3 energy storage density along with up to 80% efficiency. Moreover, the high thermal stability of such capacitors was confirmed. The founded property combination makes the La-doped HfO2-ZrO2 thin films suitable for integrated energy storage and pulse-power devices. [ABSTRACT FROM AUTHOR]

Thin metal interfacial layers (1-nm-thick Ti and Hf) were exploited as the appropriate interfacial layer for forming an interfacial (buffer) layer between the 10-nm-thick Ta2O5 resistance switching layer and the Ta electrode to enhance the switching cycle endurance and uniformity. The thin metal interfacial layers were in-situ oxidized to TiOx (x < 2) and HfO2 layers, respectively, during the ion beam sputter deposition on the Ta2O5 layer. Compared with the devices with no interfacial layers, the switching uniformity was improved for both interfacial layers, with Ti showing the greatest improvement. The switching cycle endurance was largely degraded for the HfO2 interfacial layer, whereas the TiOx interfacial layer greatly improved in such aspects. The appropriate level of Ti-O bond energy and an excessively high Hf-O bond energy were suggested as the main reasons for such a critical difference. [ABSTRACT FROM AUTHOR]

Thin film transistors (TFTs) with In and Ga-free multicomponent Zn-Sn-Zr-O (ZTZO) channel layers were fabricated using the cosputtering approach. The incorporation of ZrO2 into the Zn-Sn-O (ZTO) films increased the contact resistance, which led to the degradation of the transport properties. In contrast, the threshold voltage shift under negative bias illumination stress (NBIS) was largely improved from -12.5 V (ZTO device) to -4.2 V (ZTZO device). This improvement was attributed to the reduction in the oxygen vacancy defects in the ZTZO film, suggesting that the photoinduced transition from VO to VO2+ was responsible for the NBIS-induced instability. [ABSTRACT FROM AUTHOR]

Negative-bias illumination stress (NBIS) of amorphous InGaZnO (IGZO) transistors can cause a large negative shift (>7.1 V) in threshold voltage, something frequently attributed to the trapping of photoinduced hole carriers. This work demonstrates that the deterioration of threshold voltage by NBIS can be strongly suppressed by high-pressure annealing under 10 atm O2 ambient. This improvement occurred through a reduction in oxygen vacancy defects in the IGZO film, indicating that a photoinduced transition from VO to VO2+ was responsible for the NBIS-induced instability. [ABSTRACT FROM AUTHOR]

The negative bias illumination temperature stress instability of amorphous Hf-In-Zn-O thin film transistors with different dimensions was evaluated. The threshold voltage (Vth) shift increased in devices with shorter channel lengths but showed almost no association with the channel width. This behavior was attributed to the diffusion and drift of the photogenerated holes at the channel/dielectric interface from regions near the drain to those near the source, which were due to the simultaneous presence of gate and drain biases. The Vth near the source, which shows the largest shift and hence has the highest local value, governs the overall Vth. [ABSTRACT FROM AUTHOR]

Ru nano-dots were embedded in a Pt/TiO2/Pt resistive switching cell to improve the uniformity of the switching parameters. The TiO2 film grown on the Ru nano-dots had a rutile structure locally whereas other parts of the TiO2 film had an anatase structure. The rutile-structured TiO2 formed conducting filaments easily and their rupture was much more uniform than the randomized ones in anatase TiO2. This largely improved the resistance uniformity at the reading voltage during the repeated resistance switching events. The improvement was also attributed to the high leakage current of the pristine sample at the reading voltage. [ABSTRACT FROM AUTHOR]

The relations between the reset current IR, room temperature filament resistance R0, and third harmonic coefficient B0 were evaluated by a conical filament model. It was found that IR∼1/R0 when the filament is either very weak, where the filament is more conical, or quite strong, where the filament is more cylindrical. The physical implication of the B0 was also understood from the materials properties. The coherence between the model expectations for the bulkier conical filaments, typically found in TiO2, and the more random-network like filaments, typically found in NiO, suggests a common switching mechanism works in both materials. [ABSTRACT FROM AUTHOR]

The local atomic structure and electronic structure of amorphous ZrO2 (a-ZrO2) thin film were examined using the Zr K- and O K-edge x-ray absorption spectroscopy and x-ray photoelectron spectroscopy. It was found that a monoclinic local structure is stabilized in several nanometers-thick a-ZrO2 films due to the structural disorder. The distinct local structure in a-ZrO2 from the ordinary tetragonal ZrO2 (t-ZrO2) films results in different electronic structure with a decrease in the band gap by 0.5 eV. The reduced band gap and dielectric constant of a-ZrO2 suggest inferior gate leakage current performances compared to the t-ZrO2 films. [ABSTRACT FROM AUTHOR]

A phase change memory cell was fabricated by stacking plasma-enhanced cyclic chemical-vapor-deposited Ge2Sb2Te5 (GST) and atomic layer deposited TiO2 thin films. Different pairs of resistance states were obtained by controlling the current flow, which can be used to achieve higher memory density by multilevel operation. The multiresistance states of the stacked cell were explained by the resistance switching phenomena of TiO2 and the thermoelectric phase change properties of GST. The phase change characteristics of GST could be altered by controlling the degree of filament formation in the TiO2 layer, which eventually changed the phase change volume in the GST. [ABSTRACT FROM AUTHOR]

This study examined the interfacial reaction of plasma-enhanced atomic layer deposited TaCxNy films with underlying SiO2 and HfO2 layers, as well as their effective work functions (EWFs). The adoption of Ar/H2 plasma as a reducing agent suppressed the interfacial reactions resulting in a lower electrical thickness. However, it increased the interface state density due to the massive Ar+ plasma damage on the dielectric films. The interfacial reactions were suppressed in TaCxNy on HfO2 compared with that on SiO2. The EWF of TaCxNy with the H2 plasma and Ar/H2 plasma on HfO2 was ∼4.9–5.2 and ∼4.6 eV, respectively. [ABSTRACT FROM AUTHOR]

A Schottky-type diode switch consisting of a Pt/(In,Sn)2O3/TiO2/Pt stack was fabricated for applications to cross-bar type resistive-switching memory arrays. The high (0.55 eV) and low potential barrier at the TiO2/Pt and TiO2/(In,Sn)2O3 junctions, respectively, constitute the rectifying properties of the stacked structure. The forward/reverse current ratio was as high as ∼1.6×104 at an applied voltage of ∼1 V. When Pt/TiO2/Pt memory was connected to this diode in series, there was an insignificant interference on the memory function from the diode under the forward bias and virtually no resistive switching under a reverse bias. [ABSTRACT FROM AUTHOR]

TaCxNy films were grown by a plasma-enhanced atomic layer deposition using Ta(N-t-C5H11)[N(CH3)2]3 as the precursor and H2 or Ar/H2 plasma as the reducing agent. The Ar/H2 plasma appeared to efficiently break the Ta–N bonds in the Ta precursor and formed more TaCx, which significantly decreased the resistivity of the films (∼255 μΩ cm) compared with the case of the H2 plasma (∼1570 μΩ cm). The Ar/H2 plasma also made the films denser and efficiently eliminated the oxygen from the films. This improved the resistance against the elemental diffusion as well as the aging characteristics of the films after exposure to air. [ABSTRACT FROM AUTHOR]

The filamentary resistance switching mechanism of a Pt/40 nm TiO2/Pt capacitor structure in voltage sweep mode was investigated. It was unambiguously found that the conducting filaments propagate from the cathode interface and that the resistance switching is induced by the rupture and recovery of the filaments in the localized region (3–10 nm thick) near the anode. The electrical conduction behavior in the high resistance state was well explained by the space charge limited current (SCLC) mechanism that occurs in the filament-free region. The various parameters extracted from the SCLC fitting supported the localized rupture and formation of filaments near the anode. [ABSTRACT FROM AUTHOR]

ZnO nanoparticles were grown on single-walled carbon nanotubes (SWNTs) by atomic layer deposition using diethylzinc (DEZ) and water. The athors discuss that, because of chemical inertness of nanotubes to DEZ and water molecules, such nanoparticles are not likely to grow on the wall of clean and perfect nanotubes. Rather, the growth of ZnO nanoparticles should be attributed to imperfection of nanotubes, such as defects and carbonaceous impurities. Lifetime of field emission from SWNTs with the ZnO nanoparticles is 2.5 times longer than that from the as-grown nanotubes. It is thought that the protection of the defects or impurities by ZnO nanoparticles mainly contributed to the improvement of the field emission lifetime from SWNTs. [ABSTRACT FROM AUTHOR]

The influence of thick (1.4 nm) and thin (0.6 nm) SiO2 interfacial layers grown by an O3 predeposition treatment during atomic layer deposition of high-k HfO2 films on the thermal stability and chemical structure of the film was investigated. It was found that the HfO2/thick SiO2 stack maintained a good thermal stability up to the postdeposition annealing at 1000 °C because Hf silicate formation was accompanied by the consumption of the interfacial SiO2 layer. On the other hand, the HfO2/thin SiO2 layer stack showed an inferior stability because Hf silicate was formed by enhanced Si diffusion from the Si substrate during the same postdeposition annealing. [ABSTRACT FROM AUTHOR]

The changes in atomic-layer-deposited HfO2 films on Si and Si1-xGex (x=0.1, 0.2, and 0.3) substrates by postdeposition annealing were studied. The migration of Ge reduced the capacitance equivalent thickness while keeping the leakage current density almost invariant after annealing. High resolution x-ray photoelectron spectroscopy and secondary ion mass spectroscopy analyses confirmed that Ge atoms which had diffused into the HfO2 layer during the deposition were drawn back to the substrate by annealing which was accompanied by the decrease in the interfacial strain energy. A very low interface trap density (1.3×1010 cm-2 eV-1) was obtained when x=0.3. [ABSTRACT FROM AUTHOR]

Atomic exchanges across the interface between a HfO2 thin film and strained semiconducting Si1-xGex (x=0.1, 0.2, and 0.3) was investigated by extended x-ray absorption fine structures. Atomic layer deposition of HfO2 films on epitaxial Si1-xGex produces a Hf-silicate (Hf–O–Si bond) phase at the interface. Also O atoms diffuse into the Si1-xGex alloy to form Ge oxide in a segregated phase. This tendency becomes evident when the Ge concentration of the substrate becomes higher or when HfO2 is deposited and these samples are compared to the pure Si1-xGex substrates which have been exposed to ambient atmosphere. [ABSTRACT FROM AUTHOR]

The previously reported positive temperature coefficient of the resistivity (PTCR) observed in paraelectric BST thin films was again analyzed in terms of the non-Ohmic resistance as a result of an anode interface energy barrier induced by the high local charge density and interface energy states. The decrease in the low frequency dielectric constant, which is the dielectric constant relevant to the PTCR effect, with increasing temperature has a larger effect on the anode energy barrier than the temperature increase itself under a high bias voltage. In this case, the slope in the current-voltage curve at higher temperature decreases, which appears as the PTCR effect when the resistance is measured as a function of temperature under high voltages. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The minority carrier (electron) capture process and the interface trap density of a TiN/Al[sub 2]O[sub 3]/p-Si metal-oxide-semiconductor capacitor were examined by deep level transient spectroscopy (DLTS). It was found that the activation energies of the large peaks detected at higher temperatures with gate bias voltages of 1.8, 1.5, 1.3, and 1.1 V were 0.19, 0.24, 0.29, and 0.37 eV, respectively. These energies were related to the electron-capture process from the conduction band by interface states in the upper half of the Si band gap. The interface state passivation effect of postannealing in a hydrogen ambient was studied from the minority carrier capture process and the usual DLTS signals. The D[sub it] at an energy of 0.35 eV from the valence bandedge decreased from 1 × 10[sup 12] cm[sup -2] eV[sup -1] at the as-fabricated state to 4 × 10[sup 11] cm[sup -2] eV[sup - 1] after H[sub 2] annealing at 450 °C. It was also found that the D[sub it] at an energy of 0.3 eV from the conduction bandedge decreased to the same amount by the same annealing process. [ABSTRACT FROM AUTHOR]

HfO[sub 2] thin films were deposited on SiN[sub x]-passivated Si wafers at 300 and 400 °C using an atomic-layer-deposition technique. The SiN[sub x] films were deposited by another atomic-layer-deposition process at 595 °C. The SiN[sub x] films worked well as barriers to both Si and O diffusion, resulting in a small decrease in the capacitance density even after post-annealing at temperatures up to 1000 °C, compared either to the HfO[sub 2] film deposited directly on Si or an Al[sub 2]O[sub 3]-barrier-layer/Si substrate. The decrease in the capacitance density after post-annealing, although relatively small, was due to Hf and O diffusion into the interface layer. Interestingly, post-annealing under an atmosphere containing small amount of oxygen (∼1%) decreased the capacitance density to a smaller degree. However, the interface and bulk capturing of the carrier was serious, resulting in a rather large hysteresis (∼100 mV) voltage in the capacitance–voltage measurements even after post-annealing. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Pb(Zr, Ti)O[sub 3] (PZT) thin films were deposited on Pt/Ti and Pt/IrO[sub 2] electrode stacks with various Pt thicknesses (30-200 nm) by a sol-gel process. The sputter-deposited Pt films showed a (111)-preferred texture irrespective of the thickness. However, a high-resolution x-ray diffraction study of the Pt films showed that the films were composed of three kinds of grains with slightly different lattice parameters. The grains with a bulk-like lattice parameter grew with increasing Pt thickness, which was accompanied with an improvement in the crystalline quality. Accordingly, the crystallization and ferroelectric behavior of the 100-nm-thick PZT films improved with increasing Pt film thickness. However, the PZT films on the Pt/IrO[sub 2] electrode showed a deteriorated ferroelectric performance due to the outward diffusion of the Ir (O) onto the Pt surface, which increases the depolarizing field and amount of charge injection by the formation of a conducting phase. [ABSTRACT FROM AUTHOR]

The variations in the level of ferroelectric fatigue of Sr[sub 1-χ]Bi[sub 2+y]Ta[sub 2]O[sub 9] (SBT, 220-nm-thick) thin-film capacitors with Pt electrodes as a function of the heat-treatment temperature were investigated. The ferroelectric SBT thin films were spin coated on 200-nm-thick Pt/TiO[sub 2]/SiO[sub 2]/Si and crystallized by furnace annealing at 800 °C. The post-heat-treatment temperature of the Pt/SrBi[sub 2]Ta[sub 2]O[sub 9]/Pt capacitors was varied from 800 to 950 °C. The different post-heat-treatment temperatures barely affected the remanent polarization (P[sub r]) vs. the applied voltage (V[sub a]) characteristics (saturation P[sub r] of ∼ 10 µC/cm² at a V[sub a] of 5 V). However, the samples annealed at 900 and 950 °C showed serious ferroelectric fatigue after ∼10[sup 8]-10[sup 9] switching cycles whereas the sample annealed at 800 °C showed fatigue-free behavior up to 10[sup 10] cycles. This behavior appeared to have a close relationship with the loss of oxygen from the SBT layer during high temperature annealing. [ABSTRACT FROM AUTHOR]

HfO[sub 2] thin films were deposited on Si wafers using an atomic layer deposition technique at temperatures ranging from 200 to 400 °C with HfC14 as the precursor and H[sub 2]O as the oxidant. The time-dependent interfacial-layer growth behavior was dependent on the deposition temperature. The interfacial layer grew with increasing deposition time at 200 °C. However, the film thicknesses decreased with increasing deposition time after reaching a certain maximum value at 300 and 400 °C due to the enhanced dissolution of SiO[sub χ] into the growing films at these temperatures. Post-annealing at 800 °C under a N[sub 2] atmosphere resulted in the precipitation of a Si-rich interfacial layer even for the initially interfacial layer free films. This had the effect of reducing the capacitance density of the films. [ABSTRACT FROM AUTHOR]

The electrical conduction properties of 10-nm-thick atomic-layer deposited Al[sub 2]O[sub 3] thin films with Al bottom and Pt top electrodes were characterized for use in field emission display. The as-deposited films, grown at 300 °C, exhibited such a high electrical leakage that their electrical properties could not be measured. However, post-treatment at 300 °C under a remote O[sub 2] or H[sub 2]O plasma for 30 min improved the insulating properties of the Al[sub 2]O[sub 3] films. However, the electrical conduction mechanism, particularly in the high field (>4 MV/cm) was not Fowler–Nordheim (F–N) tunneling but was influenced by space charge limited conduction implying that there were many traps inside the dielectric film or the electrode interfaces. Postannealing of the top electrode at 300 °C in an oxygen atmosphere resulted in a F–N conduction mechanism by removing the interfacial traps. The calculated barrier height at the Al/Al[sub 2]O[sub 3] interface from the F–N fitting of the current density versus voltage curves using the electron effective mass (m[sup *]) of 0.5 m[sub 0] was approximately 2.0 eV. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Interfacial reactions between HfO[sub 2] thin films and a Si substrate during thin-film growth and postannealing under a N[sub 2] atmosphere were investigated by high-resolution transmission electron microscopy, Auger electron spectroscopy, and electrical measurements of metal-insulator-semiconductor capacitors. HfO[sub 2] thin films were deposited on HF-cleaned Si wafers by a chemical-vapor-deposition technique at a wafer temperature of 200 °C using a carbon-free precursor [Hf(NO[sub 3])[sub 4]]. The film thicknesses ranged from 1.5 to 5.6 nm. During the initial stage of film growth, the Si surface oxidized to form a Si-rich hafnium silicate film. With increasing deposition time, Hf-rich hafnium silicate films grew. Postannealing resulted in a double-layered film structure with upper and interfacial layers having dielectric constants of approximately 9.3 and 5.6, respectively. The results were compared with the results from HfO[sub 2] films grown on SiO[sub 2]-passivated Si wafers. [ABSTRACT FROM AUTHOR]

The film thickness-dependent imprinting behavior (voltage shift) of (Pb, La)(Zr, Ti)O[sub 3] capacitors was evaluated by a thermal stress process under a remanence bias. The remanent polarization (P[sub r]) was found to be almost independent of the film thickness whereas in the 50-300 nm range the relative dielectric constant (ε[sub r]) increased linearly with the square root of the film thickness. It was found that the voltage shift, which was attributed to the accumulation of charged defects near the electrode interface, also increased linearly with increasing film thickness. In addition, the charge accumulated thickness varied with the square root of the film thickness. This was established from a simple assumption that the level of charge accumulation is determined by the product of the total amount of charged defects (total film thicknessxcharged defect density) and the internal field that is generated by the P[sub r]. Therefore, the imprint is much more a bulk-related degradation phenomenon compared to the fatigue. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Voltage offset in the polarization-voltage characteristics of Pb(Zr,Ti)O[sub 3] (PZT) capacitors was evaluated by a thermal stress process. A thermally induced voltage shift occurs when heating the sample under either remanence or a saturating bias. It was found that the voltage shifts can, to a large extent, be attributed to the role of charged defects and the defect-dipole alignment throughout the films. PZT film with a high Zr/Ti ratio, i.e., rhombohedral compositions exhibited the best imprint resistance. When these films were doped wit up to 6% La, the imprint resistance was further improved. It was also found that B-site donors were more effective in minimizing the voltage shift than A-site donors. However, dopants with the same charge value as Pb, for example, Ca and Sr, did not affect the thermally induced voltage shifts of the films since they could not reduce the charged defects in the films. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The degradation behavior of integrated Pt/SrBi[sub 2]Ta[sub 2]O[sub 9]/Pt capacitors by hydrogen impregnation during the intermetal dielectric deposition and passivation is investigated. The hydrogen ions generated as a reaction byproduct from the SiH[sub 4]-based deposition processes of the dielectric films induce reduction in the remanent polarization (P[sub r]) as well as the imprint behavior of the small size capacitors (2x2 μm[sup 2]). The degree of degradation is quite dependent on the size of the individual capacitors. The smaller capacitors underwent more serious degradation implying that the hydrogen ions impregnate into the SBT layer mainly along the etched side area of the capacitors not through the top Pt electrode. Metallization adopting TiN/Al/TiN/Ti multilayer is very effective in suppressing the hydrogen impregnation. In particular, the Ti layer appears to block the hydrogen penetration. Therefore, the optimized metallization scheme, wider metal lines than the top electrode area by 1 μm, successfully protects the integrated capacitors from the hydrogen damage. 12 μC/cm2 of 2P[sub r] and 1.1 V of 2V[sub c] (coercive voltage) with an imprinting voltage of 0.16 V were obtained from the passivated 2x2 μm[sup 2] array capacitors by the optimized metallization. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]