Hirohiko Nakano

Fabrication Of InP Sub-micron Pillars For Two-dimensional Photonic Crystals By Reactive Ion Etching

We have fabricated periodic arrays of InP pillars for two-dimensional (2D) photonic crystals by reactive ion etching (RIE) with SiCl4/Ar inductively coupled plasma (ICP) and Cl2 electron cyclotron resonance (ECR) plasma chemistry. Prior to the fabrication of the arrays, photonic band structures for electromagnetic waves are calculated theoretically, and photonic band gaps are predicted to appear in the optical wavelength region. Periodic arrays of InP micron pillars with fairly smooth etched surfaces are fabricated by ICP-RIE with SiCl4/Ar. The reflective properties of the arrays have been characterized in the optical wavelength region by Fourier-transformed infrared reflection absorption spectrometry (FTIR-RAS). FTIR-RAS spectra of the arrays exhibit characteristic features such as a blue shift with decreasing period of pillars. In ECR-RIE, we systematically investigate InP etch characteristics as functions of various etching parameters, and successfully fabricate periodic arrays of vertical submicron pillars with smooth surfaces.

Fabrication of two-dimensional InP photonic band-gap crystals by reactive ion etching with inductively coupled plasma

We fabricated two-dimensional (2D) InP photonic band-gap crystals by reactive ion etching (RIE) with a SiCl 4 /Ar inductively coupled plasma (ICP) chemistry, and characterized their reflective characteristics in the optical wavelength region by Fourier-transformed infrared reflection absorption spectrometry (FTIR-RAS). The photonic band-gap crystals consisted of a periodic array of parallel air rods of circular cross section whose intersections with a perpendicular plane form a triangular lattice in InP substrates. Prior to the fabrication of the periodic array of air rods, the photonic band structure for electromagnetic waves was calculated theoretically in the sample structure and was predicted to appear in the optical wavelength region. In RIE with the SiCl 4 /Ar ICP chemistry, we systematically investigated the InP etch rate and the etch selectivity of InP over SiO 2 as functions of various etching parameters, to fabricate deep air rods with a vertical profile. The effect of the N 2 O addition to the SiCl 4 /Ar ICP chemistry was investigated and it was revealed that the addition of a small amount of N 2 O results in an improvement in the vertical profile with a slight increase in the InP etch rate. The InP etch rate and the etch selectivity of InP over SiO 2 depended strongly on the SiCl 4 flow rate. In FTIR-RAS measurements, characteristic features were observed in the optical wavelength region, depending on the diameter of the air rods. Behaviors of the features were discussed in relation to theoretically calculated densities of states.

Stabilization of chlorofluorocarbons (CFCs) by plasma copolymerization with hydrocarbon monomers

We carried out the plasma copolymerization of CFCs (trichlorofluorocarbon) and PFC (perfluorocarbon) with C2 hydrocarbons. For the purposes of improving the recovery rate of the copolymerization process, we developed a cascade-type plasma reaction system. The reaction system was equipped with a maximum of 12 reaction tubes, each with an internal diameter of 32 mm and 390 mm in length. In the copolymerization experiments using the cascade type plasma reaction system, the CFC recovery rate reached a level of 95%, which represents a vast improvement of the 30–40% recovery rate previously achieved with parallel plate and tubular reaction systems. We found that when performing plasma copolymerization of hydrocarbons and CFCs, which contain chlorine and fluorine, the results varied, depending on the dwell time in the reactor. The level of importance of the parameters that influence the recovery rate could be ranked as follows: CFC/hydrocarbon mixing ratio>RF power>reactor pressure. When the CFC/hydrocarbon mole ratio is CFC-113: C2H4=1:1, the recovery rate reaches the maximum level where 95% of the CFCs are recovered in the form of copolymers and related substances.

Materials characterization of plasma deposited copolymer using CFC-113 with C2H4 monomer

Chlorofluorocarbons ( CFCs) with C2H4 copolymer films have highly hydrophobic surfaces and good adhesion. We confirmed that the copolymer is highly thermostable in a high-temperature environment. These properties are strongly dependent on the mixing ratio of CFC-113 and C2 hydrocarbon monomers. We report on the influence of process conditions such as monomer composition, r.f. power and pressure on polymer film deposition. The bond strength, contact angle and thermal stability of the polymer thin films at 400° C in an oxygen atmosphere were measured and electrical properties such as a dielectric constant of (e) 2.2–3.1 and breakdown voltage of 2.62–3.30 MV/cm were obtained.