Hideo Iiyori

Aluminum-based gate structure for active-matrix liquid crystal displays

This paper describes the development of an Al-based thin-film gate structure for use in large, high-resolution active-matrix liquid crystal displays (AMLCDs). Aluminum films are suitable for forming the data lines of such displays, but they are not suitable for forming the gate lines because of the hillock-induced shorts that can occur to overlying metal lines during the heating necessary for insulator deposition. Alloying with yttrium, gadolinium, and neodymium was examined with the aim of reducing hillock and whisker formation during such heating. Although Al films alloyed with 2 at.% of those metals exhibited low hillock densities (10-100 mm-2), the densities were not low enough for the fabrication of SXGA (1280 × 1024 pixels) panels. After investigation of several means to further reduce the formation of hillocks and whiskers, the most effective approach was found to be anodization of the Al-alloy gate lines, suitably patterned for anodization, followed by photoresist application and laser-cutting steps. Illustratively, by use of an anodized Al-Nd (2 at.%) thin-film gate structure, the short-circuit defect rate and contact defect rate for an 11.3-in.-diagonal experimental SVGA (800 × 600 pixels) display could be effectively reduced to zero.

Triple‐layered NdCo amorphous‐alloy films for magneto‐optical media

Magneto‐optical recording materials with high remanent Kerr rotation at a short wavelength were successfully obtained in a trilayer form. NdCo amorphous films with an in‐plane magnetization were sandwiched between TbFeCo amorphous films with strong perpendicular anisotropy and high coercivity. The thickness of the top layer of the TbFeCo film facing an incident laser beam is less than the light‐penetration depth. Triple‐layered films [Tb18Fe49Co33 (5 nm thickness)/Nd18Co82(10 nm)/Tb18Fe49Co33(200 nm)] thus obtained show a remanent Kerr rotation angle θKr = 0.37°–0.46° at wavelength λ=400–850 nm, coercivity Hc = 2 kOe, and good square loop (Mr/Ms = 1). The figure of merit √RθK, where R is reflectivity, is 0.24–0.31 at λ=400–850 nm, which is higher than that of conventional TbFeCo amorphous films (√RθK = 0.12–0.27 at λ=400–850 nm).

Annealing effects of anodized Al-based alloy for thin-film transistors

Abstract The annealing effects of anodized aluminum-based alloys were investigated. Gadolinium and neodymium were employed as respective alloy components and the surface roughness, nanostructure, leakage current and breakdown electric field of these anodized films were investigated as functions of the annealing time. The leakage current was decreased by annealing for 0.5 h at 350°C, but was increased by annealing for 1 h and was decreased again by further annealing. The breakdown electric field and surface roughness showed the same tendency as the leakage current with respect to the annealing time. In the case of the anodized aluminum–gadolinium alloy, annealing for 2 h led to a lower leakage current of 7.4 E–13 A/V, a higher breakdown electric field of 9.9 MV/cm and a lower average roughness of 4.9 nm. The leakage current was studied further by the triangular voltage sweep method. Under a negative bias, the leakage current behaved quite differently from that under a positive bias. In the latter case, it was 1 order of magnitude smaller and could be greatly reduced by annealing for 0.5 h at 350°C. In the former case, however, it was large enough after annealing for 0.5 h and remained after further annealing.

Nitrogen-added Al rare-earth alloys for thin film transistors

Abstract The effects of nitrogen addition to aluminum-rare-earth alloys were investigated. Yttrium and gadolinium were employed as respective alloy components. The electrical properties and hillock densities of alloy films were investigated, and their nanostructures were studied by cross-sectional transmission electron microscopy. Nitrogen effectively decreases the grain size, and causes the columnar structure, that is generally present in aluminum-based alloys, to disappear. Nitric aluminum-rare-earth alloys have a strong resistance to hillock formation, and formed no micro-voids even after annealing at 450°C. An N 2 flow rate of 1.3–10% in the sputtering gas gives a low hillock density of 2.0 E +1–7.7 E −1 pcs/mm 2 after annealing at 350°C in both nitric Al-rare-earth alloys. In the case of patterned nitric aluminum-yttrium alloys, an N 2 flow rate of less than 1.3% causes large side-hillocks after annealing at over 350°C. As an optimum value, an N 2 flow rate of 2.5% results in a low hillock density of 1.9 E +1 pcs/mm 2 and a low resistivity of 8.6 μΩ cm after annealing at 350°C.

Atomic structure analysis of NdFe and NdCo amorphous films

Abstract The amorphous structures of Nd 17 Fe 83 and Nd 18 Co 82 alloys with high Kerr rotation at short wavelengths were examined by means of X-ray diffraction, using dense random packing of hard sphere model analysis and polyhedron analysis. It was observed that the general local environments of NdFe and NdCo amorphous structures are very similar and that their local atomic structures are very close to those of an RETM 2 crystalline Laves phase.