AVS2014 Session MS-ThP: Manufacturing Science and Technology Poster Session

In this study, C₆₀ /Al composite materials were prepared by a usual press sintering method. We must prevent from aggregation of C₆₀ powders in composite materials because the aggregation parts would surely cause a loss of strength of the materials. In order to distribute C₆₀ molecules around Al powders, ultrasonic vibration was applied with isopropyl alcohol as a solvent for 1 h when both powders were mixed before sintering composite materials. The powder for press sintering was prepared to dry in a furnace at about 340 K for 10 minutes. The average diameter of Al powders and the crystal grain size were about 100 nm measured by SEM and several tens of nm estimated by X-ray diffraction method, respectively. The composite materials with uniform dispersion of C₆₀ were fabricated by press sintering process under the condition of the applied pressure of 1 GPa and the temperature of 723K for 4 hour in Ar gas atmosphere. We investigated the optimal condition of the composite materials as changing composition rates from 0 to 5.0 wt.%C₆₀.

In our results, we could not find remarkable aggregated parts of C₆₀ powders mixing powders up to 1.0 wt.%C₆₀ powders by SEM observations, and the microstructures must be considered to dispersion of C₆₀ molecules around Al powders. All specimens sintered were looked like uniform bulk materials. The densities of composite materials decreased according to the increase in the composition rate of C₆₀, and decreased from 2.7×10³ kg/m³ of Al to 2.36 ×10³ kg/m³ of 1.0 wt.%C₆₀. X-ray diffraction method showed only Al crystalline structure for all composite materials and FT-IR analysis clarified the existence of C₆₀ molecules in composite materials. Vickers hardness of Al material showed drastic increase up to 300 Hv in comparison with about 60 Hv of commercial Al materials due to nanocrystallization effect. The composite material with 1.0 wt.%C₆₀ showed the maximum value of 340 Hv. The specific strength of 1.0wt.%C₆₀ was increased up to 5.4 times comparing with those of industrially Al materials. This maximum specific strength of this study clarified surprisingly enhancement of over 3 times in comparison with that of commercial Mg alloys. Therefore, dispersed C₆₀-molecules/Al-matrix composite materials with nanocrystalline powder give us dreams of development for innovative high specific strength materials.

Double patterning lithography (DPL)

technologies have become a must for 32nm

nodes below. Currently have 2 approaches for DPL:

Self-aligned double patterning(SADP) and litho

etch litho etch(LELE).In this paper, we focus on

LELE induce issue, and present an etching solution

to solve this critical VIA open issue.

In this study, striped pattern structures with linewidth of 5 μm and 10 μm on lithium niobate (LiNbO₃) substrate were fabricated by the inductively coupled plasma reactive ion etching (ICP-RIE) technique for the waveguide applications. Pure nickel (Ni) thin film of 300 nm in thickness used as the etching mask and was deposited by sputtering technique on the LiNbO₃ substrate with a 20 nm adhesion layer of nickel-chrome (Ni-Cr) alloy with a composition ratio of 80/ 20. The LiNbO₃ substrates with the Ni etching mask was etched in the boron trichloride (BCl₃)/ Argon (Ar) mixed etching gas which flow ratio was controlled at 30/ 5 SCCM and the working pressures controlled at 30 mTorr, 40 mTorr, 50 mTorr, and 60 mTorr, respectively. The ICP powers were controlled from 100 W to 600 W and the RF powers were controlled from 100 W to 500 W during 45 minutes of each ICP-RIE process.

From the experimental results, it can be found that the DC bias (-V) decreases with the working pressure, and increases with the ICP powers and the RF powers. Under suitable ICP-RIE etching parameters, the structure with 6 μm in depth and the sidewall angle of 80° was successfully prepared on the the surface of LiNbO₃ substrate, which the etch selectivity ratio was 10 and the etching rate was 70 nm/ min.

Silicon nitride (Si_xN_y) films deposited by low-pressure electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-CVD) at room temperature are proposed for nonlinear optics applications in the telecommunications C-band. Due to the high silicon nitride nonlinearity, these films recently have also been used for nonlinear optics [1]. For nonlinear applications such as the generation of frequency combs, the waveguide needs a zero dispersion point in the middle of C-band, requesting large waveguide area. Unfortunately, these thick Si_xN_y films (>400 nm) have high stress and suffer from catastrophic cracking, which reduces the device efficiency [2]. Using numerical simulations it was demonstrated that for refractive index (η) values greater than 2, the area of the waveguide with zero dispersion point at λ = 1.55 µm is greatly reduced.

By varying deposition parameters, such as gas pressure (4-6 mTorr) and Si/N ratio (0.62-1.25), Si_xN_y films with high deposition rate and high refractive index was obtained. In many cases, for larger pressure values a considerable increase in the deposition rate is observed, and for lower N₂ flow was observed a large increase of η (due to high concentration of Si). However, increasing the gas pressure, a reduction of η due the incorporation of hydrogen in the film was also observed.

A Si-rich silicon nitride layer with 730 nm of thickness, refractive index of 2, high deposition rate, low hydrogen concentration and roughness average of 0.52 nm was deposited above a Si/SiO₂ wafer during 100 minutes using ECR-CVD and applied for fabrication of nonlinear microring resonators. Due to the low temperature deposition, no thermal stress was observed in the Si_xN_y film, allowing a large thickness (obtained with only one deposition process) . The main advantage of higher Si concentration in this film is the higher values of η and the absence of losses caused by two-photon absorption, responsible for the introduction of additional losses in silicon based waveguides [3].

After experimental measurements, microring resonators having a radius of 60 µm, presented an equidistant Free Spectral Range and a Q-factor of 4x10³ was achieved, showing the high efficiency of the device. Finally, using the deposition process at low temperature and controlling the process parameters such as pressure and gas ratios, a remarkable free thermal stress silicon nitride film was obtained, overcoming the stress limitation of thick silicon nitride films.

[1] J. S. Levy et al., Nat. Photonics, vol. 4, no. 1, pp. 37–40, 2009.

[2] K. Luke et al., Opt. Express 21, 22829-22833, 2013.

[3] H. K. Tsang et al., Appl. Phys. Lett., vol. 80, no. 3, p. 416, 2002.