Masao Mikami

Epitaxial Growth of PbTiO3 on MgAl2O4/Si Substrates

Lead titanate (PbTiO3) thin films are successfully sputter-deposited onto (100)MgAl2O4/(100)Si substrates at 480–550°C sputtering temperatures. It is confirmed, from X-ray and electron diffraction analyses, that the PbTiO3 films grow epitaxially on MgAl2O4 films. The crystal properties of PbTiO3 films depend on those of MgAl2O4 films strongly. The PbTiO3 films are composed of c-axis and a-axis oriented domains. The ratio of the c-axis oriented domain to the a-axis oriented domain is controllable by the cooling rate of the substrate. The dielectric constant of the PbTiO3 film is estimated to be about 100, based on C-V measurements with a metal-insulator-semiconductor structure.

Crystalline correlation of epitaxial Si films with underlying spinel films in Si/(MgO Al2O3) spinel/Si structure

Using epitaxial magnesia spinel (MgO Al2O3) films on (100) Si, heteroepitaxial Si films (0.6–3 μm) on these substrates are obtained by a conventional chemical vapor deposition method. The crystallinity of both epitaxial Si and spinel films was investigated by x‐ray diffraction techniques. Silicon film quality becomes more perfect on thinner spinel films with smoother surfaces in the range of more than ∼0.1 μm, in spite of the spinel crystal perfection becoming inferior with decreasing film thickness. These results are discussed in terms of the spinel surface roughness effect on Si nuclei coalescence.

Properties of carbon films by dc plasma deposition

Perfectly smooth transparent carbon films deposit onto room‐temperature silicon wafers in a dc plasma of methane (CH4) and hydrogen (H2). Transmission electron microscope analysis reveals that the films consist primarily of amorphous carbon (a‐C). The nearest neighbor C–C bond length of a‐C formed at low discharge current densities or low working pressures approaches that of diamond. Electrical resistivity, calculated using V‐I curves for the Al‐C‐Si structure, is more than 1013 Ω cm. A face‐centered‐cubic phase with a lattice constant of 4.96 A and diamond, both of which form at relatively high pressures, consist of crystallites having a diameter of about 100 A.

Epitaxial growth of yttrium iron garnet by chemical vapor deposition

Abstract Yttrium ion garnet (YIG) epitaxial films are grown on (111)GGG substrates by chemical vapor deposition, using a newly designed horizontal reactor with rectangular cross section. The YIG flim growth rate decreases exponentially with increasing distance along the holder for nontilted substrate holder. The exponential position dependence is decreased by tilting the holder. Thickness uniformly is within ±4% in the ∽ 150 mm long and 50 mm wide reactor area for a tilted with ∽ 3° tilting angle. Growth rate is largely dependent upon the input concentrations of YCl 3 (g) and only slightly dependent upon the concentration of FeCl 2 (g), but is mostly independent of the concentration of O 2 and HCl and the growth temperature. The range of the optimum YIG growth conditions, under which defect-free YIG film does grow, is considerably wide. A simple model for YIG epitaxial growth by CVD is proposed to account for the dependence of the growth rate on the growth conditions.

New gettering using misfit dislocations in homoepitaxial wafers with heavily boron‐doped silicon substrates

The gettering mechanism due to misfit dislocations in P/P+ epitaxial wafers is clarified for copper‐diffused epitaxial wafers. The epilayer thickness of the sample is 2.2 μm and the substrate resistivity of the sample is 0.0015–0.002 Ω cm. It is dipped in a Cu(NO3 )2 ‐HF solution and annealed at 900 °C for 30 min. The in‐depth Cu profile obtained by secondary‐ion mass spectroscopy shows a distinctive peak at the P+ ‐substrate side in the vicinity of the epi/sub interface. This peak coincides with that of dislocation density for their location in depth. Furthermore, from energy dispersive spectroscopy observation the diffused copper is found to be effectively gettered at misfit dislocations as copper silicide from moire fringe.

Y3Fe5O12 epitaxial growth by CVD and its characterization

A remarkable improvement of the chemical vapor deposition technique for Y3Fe5O12 (YIG) epitaxial growth is attained. The improved reactor markedly extends the YIG film thickness uniformity range. The YCl3-FeCl2-O2-N2 gas system, in which N2 is the carrier gas, makes it easy to suppress defects and to grow good quality YIG films. The film thickness distribution is less than ±4% for four 3 inch diameter wafers which are grown at the same time. The formation of defects, such as Fe2O3 and YIG film surface roughness, depends on the source material transport ratio R=YCl3/FeCl2. In the range of 0.35<R (mol ratio)<0.7, a defect-free smooth YIG film is grown reproducibly. The guided-wave optical loss of He-Ne laser light at 1.15 μm wavelength is 2.8 dB/cm for a YIG film grown at R=0.53. This value is reduced down to 1.0 dB/cm by annealing the film in an oxiding ambient. The source of the optical loss is attributed to Fe2+-Fe3+ ion pairs in the point-defect structure model of {Y3+3}[Fe3+2−yFe2+ y−xY3+x](Fe3+3) O12−(y−x)2VO(y−x)2, in which VO is an oxygen vacancy.

Characteristics of MOSFET prepared on Si/MgO.Al 2 O 3 /SiO 2 /Si structure

A new silicon on insulator (SOI) wafer with epitaxial-Si/ epitaxial-MgO.Al<inf>2</inf>O<inf>3</inf>(0.1 µm)/SiO<inf>2</inf>(0.5 µm)/

Characteristics of MOSFET Prepared on Si/MgO /spl dot/ Al/sub 2/O/sub 3//SiO/sub 2//Si Structure

A new silicon on insulator (SOI) wafer with epitaxial-Si/ epitaxial-MgO/spl dot/Al/sub 2/O/sub 3/ (0.1 /spl mu/m)/SiO/sub 2/(0.5 /spl mu/m)/

Characteristics of MOS FET prepared on Si/MgO.Al 2 O 3 /SiO 2 /Si structure

A new SOI (silicon on insulator) wafer with epitaxial-Si/epitaxial-MgO.Al<inf>2</inf>O<inf>3</inf>(0.1 µm)/SiO<inf>2</inf>(0.5 µm)/Si7 (

Characterization of surface layer in Si/MgO·Al2O3/SiO2/Si by ultra-violet reflection spectroscopy

Abstract By means of ultra-violet (UV) light with very small penetration depth, the dependence of surface crystallinity on the epitaxial Si film thickness in the (100)Si/MgO·Al 2 O 3 /SiO 2 /bulk-Si structure has been investigated. Since the reflected intensity of UV light is drastically reduced by surface roughness, it was found that the surface haze consisting of crystal defects revealed by Secco etching can be quantitatively measured. As a result, the surface crystallinity of silicon films in this structure depends strongly on the film thickness below 3 μm.