Tetsuo Shibutami

Ruthenium Film with High Nuclear Density Deposited by MOCVD Using a Novel Liquid Precursor

Ruthenium thin films were deposited on SiO 2 /Si substrates at 260-500°C by metallorganic chemical vapor deposition (MOCVD) using a liquid precursor (2.4-dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium [Ru(DMPD)(EtCp), DMPD: 2.4-dimethylpentadienyl, EtCp: ethylcyclopentadienyl]. The deposition characteristics and the electrical properties of the deposited films were compared with those using bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp) 2 ] precursor. The Ru films from Ru(DMPD)(EtCp) were deposited more stably than those from Ru(EtCp) 2 . Both films consisted of Ru single phase for the entire deposition temperature range. Initial nucleation of Ru films from Ru(DMPD)(EtCp) was smaller in size and denser than that from Ru(EtCp) 2 . Morover the deposition process from Ru(DMPD)(EtCp) has a much shorter incubation time than that from Ru(EtCp) 2 .

Fatigue-free RuO2/Pb(Zr,Ti)O3/RuO2 capacitor prepared by metalorganic chemical vapor deposition at 395 °C

We deposited an RuO2/Pb(Zr0.40Ti0.60)O3/RuO2 capacitor by metalorganic chemical vapor deposition. RuO2 and Pb(Zr0.40Ti0.60)O3 films were prepared at 350, 395, and 445 °C from respective Ru(C7H11)(C7H9)–O2 and Pb(C11H19O2)2–Zr(O⋅t-C4H9)4–Ti(O⋅i-C3H7)4–O2 systems. Good ferroelectricity was observed for PZT films deposited at 445 °C but not at 395 °C. However, we obtained ferroelectricity with a remanent polarization above 30 μC/cm2 by inserting a 10-nm-thick sputtered-Pt layer between the PZT and RuO2 bottom electrodes, which improved the crystallinity of PZT films even those deposited at 395 °C. This capacitor had hardly any fatigue after 1×1010 switching cycles. This demonstrates the possibility of preparing fatigue-free capacitor all deposited below 400 °C for high-density ferroelectric random-access memory applications.

Seed Layer Free Conformal Ruthenium Film Deposition on Hole Substrates by MOCVD Using (2,4-Dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium

Ruthenium thin films were deposited at 260-400°C on hole substrates by metallorganic chemical vapor deposition (MOCVD) using (2,4-dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium [Ru(DMPD)(EtCp)] for the Ru source. The microstructure, conformability, crystallinity, and resistivity of the films were examined. Conformal films whose resistivity was below 30 μΩ-cm were deposited below 300°C on SiO 2 /TiAIN/Ti/SiO 2 /Si(100) hole substrates with aspect ratio of 1.7. Finally, conformal films with a step coverage of 97% were deposited on SiO 2 /Si hole substrates, even those with a high aspect ratio of 6.4, by using Ru(DMPD)(EtCp) without a seed layer.

A Novel Ruthenium Precursor for MOCVD without Seed Ruthenium Layer

The molecular structure of Ru(DMPD)(EtCp) and Ru(EtCp)2 are shown in Fig.1(a) and 1(b), respectively. Ru thin films were deposited on oxidized Si substrates without seed Ru layer by MOCVD at the deposition temperature range from 260°C to 500°C using Ru(DMPD)(EtCp) and Ru(EtCp)2 individually. The vapor of the precursor was generated by bubbling method kept at 60°C where vapor pressure of Ru(DMPD)(EtCp) and Ru(EtCp)2 were the same and showed approximately 5.3Pa. This vapor was transferred to the cold wall type CVD reactor chamber

Development of Novel Al-Doped Zinc Oxide Films Fabricated on Etched Glass and Their Application to Solar Cells

We have successfully developed novel aluminum-doped zinc oxide (AZO-X) films with a high haze ratio by the combined use of an etched glass substrate and wet-etched AZO-X films. The effects of the use of an etched glass substrate and wet-chemical etching on the properties of AZO-X films were investigated. The texture size and rms roughness of these films largely increased with glass surface roughening. Post-treatment using wet chemical etching slightly increased the texture size and rms roughness. The etched glass approach has been found to be a promising method for achieving an AZO-coated glass substrate with a high haze ratio. Using high-haze ratio AZO-X films as the front transparent conductive oxide (TCO) layers in solar cells, we improved the quantum efficiency (QE) of these solar cells particularly in the long-wavelength region. Thus, the AZO-X films deposited on etched glass have a high potential for use as front TCO layers in silicon-based thin-film solar cells.

Development of Novel Aluminum-Doped Zinc Oxide Film and Its Application to Solar Cells

We have developed novel aluminum-doped zinc oxide films (AZO-X and AZO-HX films) with a high haze value using wet-chemical etching for various times after dc magnetron sputtering, and have investigated their electrical and optical properties, durability under high-humidity condition, and surface morphology. The AZO-X and AZO-HX films showed good balance between transmittance in the near-infrared area and durability under 85 °C–85%RH condition. These novel films also had a higher haze value after wet chemical etching than normal AZO films. The crater size and haze value of the AZO-HX film increased with increasing etching time in comparison with those of the AZO-X film. The haze value of the AZO-HX film was higher than that of the AZO-X film; their values are 90% at 550 nm and 60% at 800 nm. Furthermore, the AZO-HX film was applied in amorphous silicon (a-Si) single-type solar cells as the front electrode. The short-circuit current of the solar cell using the AZO-HX film was higher than that of the solar cell using the AZO-X film. As an optimization-based result, an efficiency as high as 10.2% was obtained, showing that the new AZO-HX film is a promising material for the front electrode of a-Si solar cells.

Development of novel Al doped zinc oxide film and its application to solar cells

We have developed novel Al doped zinc oxide (AZO) films, AZO-X films, using d.c. magnetron sputtering process and have investigated their electro-optical properties and their surface morphology. AZO-X films showed a good balance between the transmittance in near-infrared area and the durability under 85°C-85%RH condition. And AZO-X film also had higher haze value after wet chemical etching than the value obtained in normal AZO film. Furthermore, AZO-X films have been applied to amorphous Si (a-Si) single-type solar cells as the front electrodes. The efficiency as high as 10.1% with high short-circuit current has been obtained, showing that this novel AZO-X is the new promising material for front electrode of a-Si solar cells.

High Sensitive Magneto-Optical Media with New Types of Protective Film

SiCN:H and SiN:H have been studied for use as protective films of magneto-optical (MO) media. These films were sputter-deposited from an Si target in atmosphere containing hydrogen. Both compounds exhibited substantially improved affinities over conventional nitride compounds used as protective films for the polycarbonate substrate of the MO media. In addition to providing superior protection and Kerr rotation enhancement, SiCN:H and SiN:H films had a distinctive advantage that the use of them as protective films reduced the write laser power of the MO media. This feature satisfies the need of higher sensitive MO media applicable to high speed driving of up to 3600 rpm.