Kentaro Tada

Measurement of adhesive force between mold and photo-curable resin in imprint technology

Imprint lithography using photocurable resin is the most promising technique compared with other imprint lithography techniques, because it can complete a pattern transfer at room temperature. Thus, it would be able to implement practical mass-production lithography. In a previous report, however, a part of the solidified polymer was ripped away, because of strong adhesive force between the mold and solidified polymer. In order to improve this phenomenon, release coating of quartz mold and development of a photocurable resin are necessary. In this paper, we describe a measurement method of adhesive force between mold and resin using a tensile tester and, furthermore, durability of release coating material.

632.7 nm CW Operation (20?C) of AlGaInP Visible Laser Diodes Fabricated on (001) 6? off toward [110] GaAs Substrate

632.7 nm continuous wave operation was achieved at 20°C, by an AlGaInP visible laser diode (LD) with an AlGaInP quaternary active layer fabricated on a (001) GaAs substrate with a misorientation angle of 6° toward the [110] direction. The epitaxial layers for the laser structure are grown by metalorganic vapor phase epitaxy. The lasing wavelength is almost the same as that for He-Ne lasers. Lasing wavelengths for the LDs were also compared with wavelengths for those fabricated on an exact (001) orientation substrate.

Improvement of imprinted pattern uniformity using sapphire mold

Imprint lithography is an attractive technology for LSIs era below 40-nm critical dimension from the viewpoints of high-throughput and low-cost equipment. In order to avoid a pattern placement error due to thermal expansion in the conventional thermal imprint process, we have previously attempted to replicate a mold pattern onto a liquid polymer, which was solidified using ultra-violet (UV) light irradiation at room temperature. The imprint technology based on photo-induced solidification has several advantages such as elimination of heat-up and cool-down time and possibility of step and repeat process. However part of the solidified polymer film was remained on the quartz mold surface. In order to improve this problem, in this article we propose to use a sapphire plate as a mold.

Step-bunching in (AlxGa1−x)0.5In0.5P layers on misoriented (001) GaAs substrates grown by metalorganic vapor phase epitaxy

Step-bunching in metalorganic vapor phase epitaxy (MOVPE) growth for Ga 0.5 In 0.5 P and (Al 0.6 Ga 0.4 ) 0.5 In 0.5 P was studied. Crystals were grown at 660°C, at V/III ratios of 55 and 1500. Vicinal (001) substrates were used. When GaInP was grown on (001) GaAs misoriented by 6° in the [110] and in the [110] directions at V/III = 55, step-bunching was significant. When V/III was increased to 1500, however, step-bunching was largely suppressed. On the other hand, step-bunching for AlGaInP was fairly well suppressed even at low V/III of 55. Compositional modulation occurred in the AlGaInP layer, which is identified as the In/Ga-deficient and In/Ga-rich areas. The In/Ga-rich areas coincide with the traces of the bunched surface during growth

Uniform hole injection resulting in low operating current and stable high temperature cw operation in 630 nm band AlGaInP multi-quantum well laser

Summary form only given. The influence of hole injection was investigated for AlGaInP MQW lasers. By improving the uniformity of the hole injection, low operating currents were obtained for 630 nm band AlGaInP MQW lasers, with stable operation at 60/spl deg/C, for the first time.

650 nm AlGaInP visible light laser diode with dry-etched mesa stripe

CW operation of 650 nm GaInP/AlGaInP index waveguide-type visible-light laser diodes (LDs) with dry-etched mesa stripes fabricated by Cl2 reactive ion beam etching was achieved for the first time. Its threshold current of 47 mA and slope efficiency of 0.40 W/A are almost the same as those of wet-etched LDs fabricated from the same wafer (L=500 µ m). Cross-sectional scanning electron microscopy image of the buried mesa stripe shows that dry-etched LD has a symmetric mesa shape, promising a small focusing spot size and a stable mode operation, whereas the wet-etched mesa is asymmetric because of the use of a 6°-misoriented substrate for this wavelength operation. The aging test operated with a light output power of 3 mW at 50° C reveals that these LDs have an operating time of over 3000 h, indicating they have sufficient lifetime for conventional uses.

Reliability consideration for AlGaInP laser diodes by automatic power control aging simulation

We develop an automatic power control aging simulation method for AlGaInP visible light emission laser diodes and apply it to aging tests of 650 nm wavelength AlGaInP lasers. A laser degradation expression, on which the simulation is based, is derived from automatic current control tests for 680 nm lasers. The simulation results agree well with the experimental results. The simulation is then used to show laser reliability (operation lifetime) as a function of laser initial characteristics (threshold current, characteristic temperature and the maximum cw temperature).

Compact Magneto-Optical Head Module Integrated with Chip Elements using Double Holograms

A compact magnetooptical head module integrated with chip elements, which uses a polarizing grating and a holographic optical element, has been developed. The module size is W14.4 mm x D5.6 mm X H13 mm. A readout experiment for a magneto-optical disk has been carried out employing a 685 nm laser diode. Carrier-to-noise ratio of more than 45 dB has been obtained under quadruple capacity conditions compared with the first-generation ISO (International Organization for Standardization) standard. Alignment tolerance was also investigated.

3D imprint technology using SOG mold

Nanoimprint lithography (NIL) provides a major breakthrough in nanopatterning because it produces nanometer features over a large area with high throughput and low cost. There are a lot of NIL studies, however, all of them are concerned with two dimensional pattern transfers. Fine three-dimensional (3D) fabrication process is now required and studied for various applications such as photonic crystals. In this work, we found out that Spin-On-Glass (SOG) behaves a positive-type-electron-beam (EB) resist using buffered HIP (BHF) development.