Tae-Kyung Kim

High-Performance Low-Temperature Poly-Silicon Thin Film Transistors Fabricated by New Metal-Induced Lateral Crystallization Process

Effect of crystalline defects in metal-induced lateral crystallization (MILC) thin film transistors (TFTs) was studied and a new MILC method was proposed to improve the electrical properties of poly-Si TFTs. Defects at channel, which were formed by Ni in conventional MILC method, could be successfully removed by means of asymmetric Ni-deposition. Since the crystalline defects were removed at the channel, field-effect electron mobility increased by a large value up to 120 cm2/Vs, while the leakage current was reduced. Electrical properties of the TFTs fabricated by the new MILC method were dependent on which side of the channel was deposited with Ni.

Versatile polychromatic dynamic testbed for optical disks

A dynamic testbed for the evaluation of optical disks has been designed and constructed. The system is achromatic within the wavelength range 440-690 nm, allowing any light source in this range to be utilized for read-write-erase experiments. In addition, the system accepts disks with substrate thicknesses ranging from 0 to 1.7 mm. The polarization handling capabilities of the testbed are such that, with the turn of a knob, one can generate either linearly polarized or circularly polarized light at the disk surface. This feature permits the testing of both magneto-optical and phase-change disks, in addition to compact disks and digital versatile disks, without any modifications to the system. A leaky polarizing beam splitter (LPBS) has been specially designed and built for this tester. The LPBS allows continuous adjustment of the ratio between p- and s-polarized components of the reflected beam that reach the detectors. This feature is especially useful for magneto-optical disks, where one can achieve an optimum signal-to-noise ratio by adjusting the relative amounts of the two components of polarization at the detection module. Focus-error detection is based on the astigmatic method, and the primary track-error detection scheme is the push-pull method, although other focusing and tracking schemes may also be implemented. The rf data signal and the focusing and tracking servo signals are all derived from the same detectors, thus allowing the optical power returning from the disk to be used in its entirety for these multiple purposes. The detection channel consists of two high-speed quad detectors mounted on the two arms of a differential detection module. By combining the various outputs of these detectors it is possible to generate the astigmatic focus-error signal, the push-pull track-error signal, the differential magneto-optical readout signal, the conventional sum signal for phase-change disk readout, and the differential edge-signal for mark-edge detection on various types of optical media.

The Loss Kinetics of Substitutional Carbon in Si1-xCx Regrown by Solid Phase Epitaxy

Epitaxial layers of Si1-xCx (x=0.016) were synthesized using ion implantation and solid phase epitaxy (SPE), and the loss kinetics of substitutional carbon was investigated. As annealing temperature and time increase, more carbon atoms were found to diffuse from substitutional to interstitial sites. The activation energy for the loss of substitutional carbon into interstitial sites was obtained over the temperature range, 700–1040°C, using both high-resolution X-ray diffraction (HR-XRD) and Fourier transform infrared spectroscopy (FTIR). Both methods yielded similar activation energies (~3 eV) for the loss kinetics. In addition, SPE layers regrown by rapid thermal annealing (RTA) were shown to have better crystalline quality than those regrown by furnace annealing.

Scanning Rapid Thermal Annealing Process for Poly Silicon Thin Film Transistor

Polycrystalline silicon (poly-Si) thin-film transistors (TFTs) were fabricated on transparent glass substrates using lamp-scan rapid thermal annealing. Scan-radiation-annealed silicon islands were crystallized by metal-induced lateral crystallization (MILC). The activation energy of Ni-MILC was calculated to be 1.56 eV. In order to enhance the MILC rate, we deposited a capping SiO2 layer over the self-aligned TFT, which was found to increase the MILC rate several times. Thus fabricated TFTs exhibited different electrical characteristics depending on the annealing conditions.

New method of the readout signal generation to reduce the adjacent track crosstalk

To realize more than 15GB data capacity using blue laser diode, suppression of the adjacent track crosstalk may be one of the key technology. Several methods have been proposed for the adjacent track crosstalk cancellation using 2 beams or 3 beams. Kasazumi et.al. have proposed one method with coaxial dual beams. Although they can reduce the adjacent track crosstalk, it is not easy to get enough optical power from the objective lens for recording. In this paper, we propose new method of the readout signal generation to reduce the adjacent track crosstalk.