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We investigated the post-deposition heating (PDH) effect on OH content in SiOx films deposited by atmospheric-pressure CVD using a deposition source of silicone oil (SO) with O3 and TCE vapor at a temperature Td of 180 °C–250 °C. The PDH is performed in situ for 5 min in the deposition chamber just after film deposition without any supply of SO, where the heating temperature is the same as Td. The OH content in the films deposited normally decreases with increasing Td. In contrast, those with PDH decrease with deceasing Td from 220 °C, and, at Td = 190 °C, a minimum OH content can be obtained. This means that lower OH content remains at a lower deposition temperature. The PDH effect on OH reduction can be explained by easily reconstructible structure of SiOx films deposited at low temperature. Furthermore, we discuss the mechanism of the PDH effect from other points of view.

We investigated the dependences of the deposition rate and residual OH content of SiO_2 films on the concentration of trichloroethylene (TCE), which was added during deposition at low temperatures of 160-260 °C with the reactant gases of silicone oil (SO) and O_3. The deposition rate depends on the TCE concentration and is minimum at a concentration of ~0.4 mol/m^3 at 200 °C. The result can be explained by surface and gas-phase reactions. Experimentally, we also revealed that the thickness profile is strongly affected by gas-phase reaction, in which the TCE vapor was blown directly onto the substrate surface, where it mixed with SO and O_3. Furthermore, it was found that adding TCE vapor reduces residual OH content in the SiO_2 film deposited at 200 °C because TCE enhances the dehydration reaction.

A low-temperature silcon oxide film was deposited at 160 to 220 °C using an atmospheric pressure CVD system with silicone oil vapor and ozone gases. It was found that the deposition rate is markedly increased by adding trichloroethylene (TCE) vapor, which is generated by bubbling TCE solution with N_2 gas flow. The increase is more than 3 times that observed without TCE, and any contamination due to TCE is hardly observed in the deposited Si oxide films from Fourier transform infrared spectra., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/15344

A low-temperature silcon oxide film was deposited at 160 to 220 °C using an atmospheric pressure CVD system with silicone oil vapor and ozone gases. It was found that the deposition rate is markedly increased by adding trichloroethylene (TCE) vapor, which is generated by bubbling TCE solution with N_2 gas flow. The increase is more than 3 times that observed without TCE, and any contamination due to TCE is hardly observed in the deposited Si oxide films from Fourier transform infrared spectra.

Amorphous Si thin films on yttria-stabilized zirconia (YSZ) layers were crystallized widely in solid phase by the two-step method with a pulsed laser, moving the sample stage. The crystalline quality, impurity diffusion, and electrical properties of the crystallized Si films were investigated. It was found that the crystallinity of the Si thin films was improved and their surface was smooth without an incubation layer at the interface, indicating the uniform crystallinity of Si on YSZ. The diffusion of Zr and Y into the Si thin films was as small as or smaller than the order of 1017 atoms/cm3. We evaluated the electrical properties of carrier concentration and Hall mobility of the Si thin films with/without YSZ layers by using the resistivity and AC Hall effect measurements. The temperature and doping concentration dependences were measured for both undoped and P-doped films. It was found that both the undoped and P-doped Si/YSZ/glass films showed higher mobilities and carrier concentrations (and therefore higher conductivities), which indicate a smaller number of defects, than the Si/glass films. This suggested that the Si film crystallized on the YSZ layer is more suitable for application to electronic devices than the Si film on glass.

Crystalline quality of pulse-laser annealed micocrystalline silicon (poly-Si) films on yttria-stabilized zirconia [(ZrO_2)_<1-x>(Y_2O_3)_x: YSZ] crystallization-induction (CI) layers is further improved by a new two-step irradiation method, in which amorphous silicon (a-Si) films are irradiated using two kinds of energy density. Firstly, they were irradiated at a low energy density for a short time to generate nuclei, following by irradiation at a high energy density to complete crystallization. Crystalline fraction and grain size of the Si film crystallized by the two-step method were found to be larger while its FWHM was smaller than those by the conventional one. Moreover, grain size of the Si/YSZ/glass was more uniform than that of the Si/glass. This indicates not only effectiveness of the YSZ CI layer but also usefulness of the two-step method on improving Si film quality., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/12612

Crystalline quality of pulse-laser annealed micocrystalline silicon (poly-Si) films on yttria-stabilized zirconia [(ZrO_2)_<1-x>(Y_2O_3)_x: YSZ] crystallization-induction (CI) layers is further improved by a new two-step irradiation method, in which amorphous silicon (a-Si) films are irradiated using two kinds of energy density. Firstly, they were irradiated at a low energy density for a short time to generate nuclei, following by irradiation at a high energy density to complete crystallization. Crystalline fraction and grain size of the Si film crystallized by the two-step method were found to be larger while its FWHM was smaller than those by the conventional one. Moreover, grain size of the Si/YSZ/glass was more uniform than that of the Si/glass. This indicates not only effectiveness of the YSZ CI layer but also usefulness of the two-step method on improving Si film quality.

We investigated the crystallization-induction (CI) effect of yttria-stabilized zirconia (YSZ) on the solid phase crystallization of amorphous Si (a-Si) films. The incubation time τ_i for crystallization on a polycrystalline YSZ layer was shorter than that on a glass substrate. From the result of Arrhenius plots of 1/τ_i, it is suggested that the CI effect is not due to the difference in the activation energy E_i but to a higher nucleation site area density on the YSZ layer. Also, preheating the YSZ layer prior to a-Si film deposition was effective to shorten the incubation time τ_i because E_i was reduced.

The solid-phase crystallization of amorphous Si films with/without a crystallization-induction (CI) layer of yttria-stabilized zirconia (YSZ) was performed using a Nd:YAG pulse laser. We investigated the crystallinity of the Si films by Raman spectroscopy. It was found that, at the same crystalline fraction, the FWHM of the c-Si peak for Si/YSZ/glass was smaller than that for Si/glass. The result is considered owing to the CI effect of the YSZ layer. This was confirmed by scanning electron microscopy observation, which showed that the grain size of Si on YSZ layers was more uniform than that on glass substrates. On the other hand, at a lower beam energy, the crystalline quality of the Si films was found to be better although the increase in the crystallization rate with the pulse number N is smaller. On the basis of the above results, the crystallization model of an a-Si film on a YSZ layer is speculated., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/11938

The solid-phase crystallization of amorphous Si films with/without a crystallization-induction (CI) layer of yttria-stabilized zirconia (YSZ) was performed using a Nd:YAG pulse laser. We investigated the crystallinity of the Si films by Raman spectroscopy. It was found that, at the same crystalline fraction, the FWHM of the c-Si peak for Si/YSZ/glass was smaller than that for Si/glass. The result is considered owing to the CI effect of the YSZ layer. This was confirmed by scanning electron microscopy observation, which showed that the grain size of Si on YSZ layers was more uniform than that on glass substrates. On the other hand, at a lower beam energy, the crystalline quality of the Si films was found to be better although the increase in the crystallization rate with the pulse number N is smaller. On the basis of the above results, the crystallization model of an a-Si film on a YSZ layer is speculated.

Si films were deposited at low temperatures on glass substrates covered with poly-yttria-stabilized zirconia (YSZ) layers. We investigated the dependences of crystallization on the Y content and cleaning solution for the YSZ layers. Transmission electron microscopy showed that some regions of the Si film deposited at 430 °C were directly crystallized on a YSZ layer without an amorphous region, where Si lattice fringes were tightly connected to YSZ lattice fringes. The crystallization of Si films on YSZ layers occurred at deposition temperatures lower than that on glass substrates by more than 100 °C. Zr, Y, and F concentrations in the Si film were negligible, except the Zr concentration near the interface. The discussion on the crystallization mechanism gave the following suggestions on the method of obtaining a high crystalline fraction. The YSZ layer should be chemically cleaned using a solution containing HF before Si film deposition, and the content ratio Y/(Zr+Y) of YSZ should be ≳ 0.2., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/9218

Si films were deposited at low temperatures on glass substrates covered with poly-yttria-stabilized zirconia (YSZ) layers. We investigated the dependences of crystallization on the Y content and cleaning solution for the YSZ layers. Transmission electron microscopy showed that some regions of the Si film deposited at 430 °C were directly crystallized on a YSZ layer without an amorphous region, where Si lattice fringes were tightly connected to YSZ lattice fringes. The crystallization of Si films on YSZ layers occurred at deposition temperatures lower than that on glass substrates by more than 100 °C. Zr, Y, and F concentrations in the Si film were negligible, except the Zr concentration near the interface. The discussion on the crystallization mechanism gave the following suggestions on the method of obtaining a high crystalline fraction. The YSZ layer should be chemically cleaned using a solution containing HF before Si film deposition, and the content ratio Y/(Zr+Y) of YSZ should be ≳ 0.2.

To achieve disturb-free writing, we proposed a new writing operation for ferroelectric-gate field-effect transistor memories with intermediate electrodes. The writing voltages V_W applied to the wordlines for Pr^+ and Pr^0 memory states are the same pulse magnitudes, which consist of V_W^ + followed by V_W^ -, whereas the bias timings of the bitline voltages differ from each other. The bitline voltage for the Pr^+ memory state is set high when V_W is set V_W^ +, and it is set to low by the time when V_W is changed to V_W^-. On the other hand, the bitline voltage for the Pr^0 memory state is set high until the whole writing pulse of (V_W^+ + V_W^-) is finished. This is verified experimentally using a discrete circuit, which showed that the new writing operation achieves disturb-free writing. The memory consists of two transistors for data writing and reading. With the obtained experimental results, we discuss the possibilities of high integration of this memory as well as low reading voltage., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/8476

Using the chemical reaction between silicone oil vapor and ozone gas at atmospheric pressure and above 200 °C, we deposited a Si oxide film. Fourier transformer infrared (FT-IR) spectra of the films were very similar to those of thermal SiO_2 films without peaks due to carbon for deposition temperatures T_s from 200 to 350 °C. Although a small peak due to the Si–OH bond appeared for T_s ≤300 °C, it was reduced with increasing T_s and almost disappeared around 350 °C. Secondary ion mass spectrometry measurements showed that the concentrations of metal and carbon impurities were at a negligible level for device performance even for T_s = 200 °C. The dielectric property of the film deposited at 350 °C was also shown to be comparable to the SiO_x film produced by a conventional low-temperature deposition method, although the estimated density of interface trap was in the order of 10^<11>/(cm^2·eV)., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/9164

Using the chemical reaction between silicone oil vapor and ozone gas at atmospheric pressure and above 200 °C, we deposited a Si oxide film. Fourier transformer infrared (FT-IR) spectra of the films were very similar to those of thermal SiO_2 films without peaks due to carbon for deposition temperatures T_s from 200 to 350 °C. Although a small peak due to the Si–OH bond appeared for T_s ≤300 °C, it was reduced with increasing T_s and almost disappeared around 350 °C. Secondary ion mass spectrometry measurements showed that the concentrations of metal and carbon impurities were at a negligible level for device performance even for T_s = 200 °C. The dielectric property of the film deposited at 350 °C was also shown to be comparable to the SiO_x film produced by a conventional low-temperature deposition method, although the estimated density of interface trap was in the order of 10^<11>/(cm^2·eV).

To achieve disturb-free writing, we proposed a new writing operation for ferroelectric-gate field-effect transistor memories with intermediate electrodes. The writing voltages V_W applied to the wordlines for Pr^+ and Pr^0 memory states are the same pulse magnitudes, which consist of V_W^ + followed by V_W^ -, whereas the bias timings of the bitline voltages differ from each other. The bitline voltage for the Pr^+ memory state is set high when V_W is set V_W^ +, and it is set to low by the time when V_W is changed to V_W^-. On the other hand, the bitline voltage for the Pr^0 memory state is set high until the whole writing pulse of (V_W^+ + V_W^-) is finished. This is verified experimentally using a discrete circuit, which showed that the new writing operation achieves disturb-free writing. The memory consists of two transistors for data writing and reading. With the obtained experimental results, we discuss the possibilities of high integration of this memory as well as low reading voltage.

As an induction layer for Si crystallization, an yttria-stabilized zirconia (YSZ) film was deposited on a glass substrate. The YSZ layer, already etched with HF and rinsed with ethanol, was heated to 430 °C. The Si film deposited on it was partially crystallized. This was confirmed by transmission electron microscope. The crystallization fraction was greater than that on a YSZ layer rinsed by deionized water. Without using YSZ layer, deposited Si film was amorphous. F atoms in HF-etching solution were adsorbed on the YSZ layer and remained even after the ethanol rinse. These remaining F may be important for crystallization.

We investigated the reading and writing of ferroelectric-gate field-effect transistor memory with an intermediate electrode (IF-FET) to achieve perfect nondestructive readouts. In the previous operation method, although the difference in output voltage ΔV_O between positive P_r^+ and negative P_r^- remanent polarization memory states was adequate for the first reading time, the nondestructive readout for the P_r^- state was seriously degraded due to the generation of nonreturning domains. In order to solve this issue, a P_r^0 memory state was used instead of the previous P_r^- memory state. The P_r}^0 state was induced by applying a pulse combined with a positive voltage V_W^+ and a negative voltage (V_W^-). V_W^+ was to reset the previously written memory states, and V_W^- was to control the amount of remanent polarization. In addition, in order to extinguish perfectly the nonreturning domains, a negative voltage V_R^- was applied for data reading, following a positive voltage V_R^+, where V_R^+ was determined for clear decoding. The appropriate heights of the writing and reading voltages were determined individually from the viewpoint of good nondestructive readout and large ΔV_O. As a result, it was verified experimentally that the reading endurance reached more than 10^8 cycles and that the retention time of IF-FET at 150 ℃ was possible to exceed ten years.

Amorphous Si films of 60 and 10 nm thick on glass substrates were irradiated by a linearly polarized Nd:YAG pulse laser with the wavelength λ=532 nm at the incident angle θ_i=0. The surface of the irradiated 60-nm-thick film had both periodic ridges perpendicular to the electric field vector E and aperiodic ridges roughly parallel to E, where the spatial period of the periodic ridges was almost λ.From the continuous 10-nm-thick film, the separate rectangular Si islands were formed with a periodic distance of λ, with the edges parallel or perpendicular to E. When θ_i was increased from normal incidence of the s-polarized beam for a 60-nm-thick film, the aperiodic ridges were reduced while the periodic ridges were still formed. For a 10-nm-thick film, the Si stripes were formed perpendicular to E, using the s-polarized beam at θ_i=12°. In order to investigate the mechanisms of the surface modifications of, in particular, aperiodic ridges, islands, and stripes, we improved the previous theoretical model of the periodic distribution of the beam energy density (periodic E-D) generated by irradiation of the linearly polarized laser beam, taking account of the multireflection effect in the Si film which is semitransparent for λ. Further, the calculated E-D was corrected with respect to the thermal diffusion in the irradiated Si film. The calculation results show that the two-dimensional E-D consists of a constant or a dc term and a sinusoidal or an ac term which contains various spatial periods. The multireflection effect strongly influences the amplitude and phase of every ac term, which means that the amplitude and phase depend on the film thickness. The thermal diffusion during the heating of the irradiated film greatly reduces the amplitudes of the acterms with periods below the thermal diffusion length. The theoretical calculation showed that, by increasing θ_i, the temperature distribution in the irradiated Si film was changed from two-dimensional toward one-dimensio

We investigated the multireflection effect on the formation of a periodic surface structure produced by a linearly polarized Nd:YAG laser beam of 532 nm on an Si film deposited on a glass substrate, as well as on heating rate in the film, compared with an excimer laser beam. From the theoretical calculation results, it was found that the formation of the periodic surface structure and heating rate strongly depended on film thickness or that they were influenced by the multireflection effect. The thickness most effective for forming the periodic surface structure and heating rate was about 60 nm. Furthermore, we attempted to verify the calculation results by carrying out an experiment in which we checked whether the periodic structure was formed on the surface of the melting-crystallized Si films. As a result, the thickness range for producing the periodic surface structure was found to be from 50 to 70 nm, which were larger than the theoretical values of 40 to 60 nm.

An operation model of a ferroelectric gate field-effect transistor memory with an intermediate electrode was proposed and analyzed. Read endurance characteristics of the memory during a consecutive reading was simulated using this model. The simulation results showed good agreement with the experimental data., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/4653

An operation model of a ferroelectric gate field-effect transistor memory with an intermediate electrode was proposed and analyzed. Read endurance characteristics of the memory during a consecutive reading was simulated using this model. The simulation results showed good agreement with the experimental data.

type:Article, We investigated influence of the beam irradiation conditions with oblique incidence on crystallization of an Si film by a linearly polarized pulse laser in order to enlarge the periodic width of grain boundary. The irradiation conditions are fluence, pulse number and film thickness. We can obtain the periodic width of about 900 nm by increasing the incident angle to 25°. The experimental results suggest that the pulse number and the film thickness should be controlled properly as well as fluence in order to produce large grain stably for the oblique incidence. The detail of these conditions was discussed., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/4009

We investigated influence of the beam irradiation conditions with oblique incidence on crystallization of an Si film by a linearly polarized pulse laser in order to enlarge the periodic width of grain boundary. The irradiation conditions are fluence, pulse number and film thickness. We can obtain the periodic width of about 900 nm by increasing the incident angle to 25°. The experimental results suggest that the pulse number and the film thickness should be controlled properly as well as fluence in order to produce large grain stably for the oblique incidence. The detail of these conditions was discussed.

We investigated the crystalline and electrical properties of heteroepitaxial lead zirconate titanate (PZT) films grown on Si covered with epitaxial (100) (ZrO_2)_<1-x>(Y_2O_3)_x (YSZ) buffer layers. The PZT films were prepared by reactive sputtering. When the substrate temperature was between 400 and 485°C, we obtained a heteroepitaxial (110) oriented monoclinic PZT (m-PZT) film which was metastable. The lattice parameters were as follows: a=b=0.379 nm, c= 0.521 nm and γ=81.3°. The m-PZT film had a larger oxygen composition ratio O/(Zr+Ti) of 3.2 to 3.8 than the perovskite phase. Although the resistivity of the as-grown m-PZT film was much lower than that of the normal perovskite phase, it was increased by two to five orders of magnitude by a step-annealing process of 300°C for 120 min, 325°C for 120 min and 350°C for 180 min in sequence. From the C?V characteristics of the step-annealed m-PZT/YSZ/Si structure, the relative dielectric constant was estimated to be about 45.