Susumu Horita

Heteroepitaxial Growth of Yttria-Stabilized Zirconia Film on Silicon by Reactive Sputtering

Heteroepitaxial yttria-stabilized zirconia (YSZ) film is difficult to grow on Si by reactive sputtering with Ar+O2 gas, since the bare Si surface is easily oxidized by plasma radiation. In order to overcome this difficulty, the substrate is subjected to weak oxidation and subsequent deposition of a very thin metallic Zr1-x Yx film prior to deposition of the YSZ film. It was found that the crystalline quality of the YSZ film on Si was further improved by repeating the cycle of weak oxidation and very thin metallic film deposition prior to deposition of the YSZ film. Rutherford backscattering spectrometry indicated a high-quality crystal with a channeling minimum yield of 7.4% for the YSZ film produced by this repetitive method in reactive sputtering.

Recrystallization of Silicon-on-Insulator Structures by Sinusoidally-Scanned Electron Beams

This paper describes the recrystallization by an electron beam of Si films deposited on SiO2/Si structures. To achieve pseudo-line-shaped heating, a spot beam was scanned along a line at frequencies of up to 10 kHz. It is predicted theoretically that the temperature profile along the line can be controlled by the scanning waveform and that a concave molten zone edge is obtained wih a sinusoidal scan. It was found experimentally that the recrystallization conditions required for forming a large single-crystal area with a flat surface are rather restricted in the sinusoidal-scan method, since the Si films are broken up or deformed by the temperature gradient along the line. It was also found that overlapping scans of the pseudo-line-shaped beam are effective in increasing the single-crystal area. A nearly single-crystalline Si film of 300×200 µm2 was produced on an SiO2/Si structure by overlapping scans.

Structural and electrical properties of yttria-stabilized zirconia films with controlled Y content heteroepitaxially grown on Si by reactive sputtering

Abstract Yttria-stabilized zirconia (YSZ) films with controlled Y content were heteroepitaxially grown on (100) Si substrates by dc magnetron sputtering using Y and Zr metallic targets. Y content was controlled by in-situ position control of high-density-plasma region. It is found that the deposited films of the thickness of 100 nm with the Y content between 2.3 and 19.7 at.% have the (100) cubic YSZ structure directly on (100) Si, while that with the Y content of 1.2 at.% has the (100) monoclinic (ZrO 2 ) 1− x (Y 2 O 3 ) x structure on (100) Si with a (100) cubic YSZ intermediate layer. The monoclinic structure is found to be changed from the cubic structure during the cooling process after the deposition. On the other hand, the films of the thickness of 10 nm with the Y content between 1.2 and 19.7 at.% have the (100) YSZ cubic structure on (100) Si regardless of the Y content. Both the hysteresis width in capacitance–voltage ( C – V ) characteristics due to the ion drift and the leakage current are small for the film of the thickness of 100 nm with the Y content of 1.2 at.% compared with those with the Y content between 2.3 and 19.7 at.%. On the other hand, the opposite properties are observed for the films of 10 nm thickness.

Material Properties of Heteroepitaxial Ir and Pb(ZrxTi1-x)O3 Films on (100)(ZrO2)1-x(Y2O3)x/(100)Si Structure Prepared by Sputtering

We investigated the crystalline quality and electrical properties of heteroepitaxial Ir and Pb(ZrxTi1-x)O3 films deposited by sputtering on an epitaxial (100)(ZrO2)1-x(Y2O3)x film/(100)Si substrate structure. The Ir(100) and Ir(111) orientations were enhanced and reduced, respectively, by decreasing the deposition rate. The scan pattern of X-ray diffraction showed that the (100) oriented film was the heteroepitaxial film on the epitaxial (100)YSZ film with a cube on cube relationship. On this epitaxial (100)Ir film, a heteroepitaxial (001)PZT film was obtained by reactive sputtering. The P–E hysteresis loop of the 200-nm-thick epitaxial PZT film showed a well-saturated square shape at the ac amplitude of 3 V, and the remanent polarization 2Pr and the coercive field 2Ec were 83 µC/cm2 and 131 kV/cm, respectively. The leakage current was about 1×10-7 A/cm2 at ±5 V.

Alignment of grain boundary in a Si film crystallized by a linearly polarized laser beam on a glass substrate

We performed crystallization of an amorphous Si film deposited on a Pyrex glass substrate using a Nd:YAG pulse-laser beam with linear polarization. It was found that, in the crystallized film, the grain boundaries were aligned with a period of about 550 nm or the wavelength of the laser beam. Meanwhile, in the Si film crystallized by circularly polarized beam that passed through the λ/4 plate, the grain boundaries were randomly generated. This means that linear polarization of the laser beam is essential to align grain boundaries periodically or to produce a periodic temperature distribution in the irradiated Si film.

Material properties of a ZrNx film on silicon prepared by ion‐assisted deposition method

The resistivity, chemical composition, and crystalline quality of ZrNx films deposited on Si(100) substrates by an ion‐assisted deposition (IAD) method were investigated as a function of deposition parameters. By this method, metallic Zr is deposited by electron‐beam evaporation while simultaneously bombarding the film with nitrogen ions having energies of 400–700 eV. It was found that the crystalline quality of the film was improved by increasing the substrate temperature Ts to 820 °C and decreasing the ion energy. When Ts was 850 °C, zirconium silicide was formed easily near the interface between the film and the Si substrate. At Ts=820 °C, the chemical composition ratio of the film was hardly influenced by the arrival rate ratio N/Zr, Ra, in the range of 1.5 to 3.0 and the deposited ZrN film was almost stoichiometric. However, when Ra was more than 1.9, the film quality was degraded by radiation damage due to excess nitrogen ions in the growing film. When Ra was less than 1.5, the surface of the film w...

Characterization of silicon‐on‐insulator films recrystallized by an obliquely scanned pseudoline electron beam

Comprehensive and systematic studies on the growth characteristics of SOI (silicon‐on‐insulator) films recrystallized by an obliquely scanned pseudoline electron beam are presented. The obliquely scanned pseudoline beam was produced by scanning a spot electron beam along a line faster than the thermal response time of the substrate and it was moved as a whole to a different direction from the normal direction of the line. In the experiment of laterally seeded epitaxial growth of SOI films, the pseudoline beam was always scanned along the seed stripes, while the direction of the seed stripes to the Si substrate and an oblique angle between the scanning direction and the normal direction of the line were changed. It was found that the sub‐boundary‐free area in the SOI film was enhanced either by increasing the oblique angle or by rotating the seed direction from a 〈110〉 to 〈100〉 axis of the substrate. It was also found that the directions of sub‐boundaries hardly depended on the oblique angle but they were ...

Epitaxial Pt Films with Different Orientations Grown on (100)Si Substrates by RF Magnetron Sputtering

Epitaxial Pt films with (111) and (100) orientations were grown on Y2O3-stabilized ZrO2 (YSZ)-covered (100)Si substrates by RF sputtering. (111)Pt films were epitaxially grown on (100)YSZ∥(100)Si substrates at 580 and 680°C, but competitive crystal orientations of (111) and (100) at 780°C. In contrast, a (100)-oriented epitaxial Pt film was grown at 550°C on a (100)YSZ∥(100)Si substrate with a (100)-oriented epitaxial (100)Ir buffer layer. This orientational control of epitaxial Pt films enables the epitaxial growth of perovskite layers with different orientations on thermally and chemically stable Pt bottom electrodes grown on (100)Si substrates.

Characterization of Pb(ZrxTi1-x)O3 Thin Film on Silicon Substrate with Heteroepitaxial Yttria-Stabilized Zirconia (YSZ) Buffer Layer

A c-axis highly oriented Pb(Zrx Ti1-x )O3 (PZT) film on Si(100) with a heteroepitaxial yttria-stabilized zirconia (YSZ) buffer layer was obtained by reactive magnetron sputtering. A 10-nm-thick YSZ buffer layer prevented the PZT film from reacting with the Si substrate at the substrate temperature of 650° C, leading to the production of a planar oriented PZT film. Polarization-voltage hysteresis measurements showed that the PZT/YSZ/Si structure had ferroelectric properties. Current-voltage and capacitance-voltage measurements indicated that this structure had crystalline defects which generated large absorption current with short relaxation time constants.

Interface control of Pb(ZrxTi1 − x)O3 thin film on silicon substrate with heteroepitaxial YSZ buffer layer

The interface between a PZT film and an Si(100) substrate was controlled by using a heteroepitaxial YSZ buffer layer. A 10 nm thick YSZ buffer layer was able to prevent the PZT film from reacting with the Si substrate at the substrate temperature of 650°C and produced the highly c-axis-oriented perovskite PZT film. The polarization-voltage hysteresis measurement showed that the PZT/YSZ/Si structure had ferroelectric properties although the leakage current was relatively large. From the results of the capacitance-voltage and the current-voltage characteristics, it was speculated that this structure had the crystalline defects or carrier traps which generated large absorption current with short relaxation time constants.