Hoe-Sup Soh

Self-passivated copper as a gate electrode in a poly-Si thin film transistor liquid crystal display

Self-passivated copper as a gate electrode in the form of TiO/Cu/TiO/TiN/SiO2 has been obtained by annealing Cu/Ti/TiN/SiO2. The thickness of Ti in Cu/TiTiN was optimized at 150 A by forming an 80 A continuous TiO film on the outer surface of the Cu. The multilayer of SiO2/TiO/Cu/TiO/TiN/SiO2 showed stable electrical passivating properties against Cu diffusion into the top or bottom SiO2. Consequently, self-passivated copper has secured the dielectric properties of plasma enhanced chemical vapor deposition SiO2 and can be utilized as a gate electrode in low temperature poly-Si thin film transistor liquid crystal displays without sacrificing the low resistivity of Cu.

P‐33: A Measurement and Analysis Method of Image Sticking in LCD

In this paper, the evaluation method of image sticking was proposed by measuring 2-Dimension of luminance level. We used the 2D-CCD luminance meter and pattern generator for chessboard pattern. The test samples were burned in about 2 hours and the tested data were normalized by data before image sticking test. The normalized value was so sensitive for determining the image sticking level. We proposed a new parameter of ISV(image sticking value) for increasing sensitivity. It was resulted that the image sticking under ISV 1% was difficult to be detected by human eye. And the image sticking over ISV 2% was strongly detected. It was found that this test method is similar to human eye testing result. Therefore, this analysis method helps to determine the objective image sticking level.

Dry patterning of copper films using an O2 plasma and hexafluoroacetylacetone

Abstract Dry etching of copper films using O2 plasmas and H(hfac) has been investigated. A one-step process consisting of copper film oxidation with an O2 plasma and removal of surface copper oxide by reaction with H(hfac) to form volatile Cu(hfac)2 and H2O was carried out. The etching rate of Cu was in the 50–700 A/min range at the substrate temperature from 150 to 300°C and depended on the H(hfac)/O2 flow rate ratio and the plasma power. The copper film etch rate increased with increasing radio frequency (RF) power at temperatures higher than 215°C. The optimum H(hfac)/O2 flow rate ratio was 1:1, suggesting that the oxidation process and the reaction with H(hfac) should be in balance. Cu patterning using a Ti mask was performed at a flow rate ratio of 1:1 at 250°C and an isotropic etching profile with a taper slope of 30° was obtained. Cu dry patterning with a taper angle necessary for high-resolution large-area thin film transistor liquid-crystal displays was thus successfully obtained from the one-step process by manipulating the substrate temperature, RF power and flow rate ratio.

Effects of the dissolved oxygen in Ti films on Ti reactions in Cu/Ti/SiO2/Si system upon annealing

The reactions of Cu/Ti/SiO2 structures at temperatures ranging from 200 to 700 °C have been studied for various Ti thicknesses. X-ray and Rutherford backscattering spectroscopy (RBS) analyses were used to identify the reaction products resulting from Ti reactions in Cu/Ti/SiO2 systems and the oxygen composition in the unreacted Ti, and revealed a correlation between the oxygen concentration in Ti films and the sequences of the Ti reactions. The reaction products initially formed, at around 300 °C, were a series of Cu–Ti intermetallics (Cu3Ti/CuTi) at the Cu–Ti interface with the oxygen dissolved in the Ti moving from the compounds into the remaining unreacted Ti. At 500 °C, the Cu3Ti was converted into Cu-rich intermetallics, Cu4Ti, which grew at the expense of the CuTi due to the increased oxygen content in the Ti. In addition, the outdiffusion of Ti, to the Cu surface, and the Ti–SiO2 reactions caused an abrupt increase in the oxygen content in the Ti layer, which placed thermodynamic restraints on further Ti reactions. Furthermore, thinner Ti layers showed a higher increased rate of oxygen accumulation for the same consumption of Ti, which led to significantly reduced Ti consumption. The diffusion barrier properties of SiO2 for Cu metallization decreased with an increasing Ti thickness.

20.3: Quantitative Analysis of Image Sticking in LCDs

We have analyzed the phenomenon of image sticking and studied for the method of quantifying image sticking by the three different analysis methods. The three analysis methods are R_SEMU [1], Color Difference [2] and Luminance Ratio. We usually use a chessboard pattern to test the image sticking of LCD panels. A new method is NVP (Non-uniformity value of panel). NVP removes a non-uniformity luminance of a panel except the image sticking on the reference image and the image tested. The NVP increases the accuracy of the image sticking analysis. We have measured the image sticking after an image sticking test using a 2D CCD camera and then analyzed the data comparing with a reference image using R_SEMU, Color Difference and Luminance Ratio. We investigate which method is the best analysis one for the evaluation of the image sticking. We have developed an analysis software using VBA. This software can select the quantitative level of image sticking.

P‐7: The Horizontal Electrodes Structure for High Aperture Ratio IPS Mode (H‐IPS mode)

We designed a new pixel layout to improve the aperture ratio of IPS mode TFT-LCD(H-IPS). This H-IPS pixel layout design has reduced the width of side common electrode used to minimize the cross talk and light leakage which is induced by interference between data bus line and side common electrode of conventional IPS mode. The side common electrodes of a pixel can be reduced by horizontal layout of interdigital electrode pattern where conventional IPS pixel designs have vertical layout of interdigital electrodes. We realized 15 inch XGA TFT LCD of H-IPS structure which has aperture ratio as much as 1.2 times of corresponding conventional IPS pixel design.

P‐80: Impedance Matching in the Inverter Circuit of a 32‐inch LCD TV with EEFL‐BLUs

The circuit of the inverter has been analyzed with EEFL-BLU for 32″ LCD-TV. The analytic solutions of a lamp current and a lamp voltage are compared with the experimental data with respect to the impedance matching with the inductance and the reactance of lamp system.

P-80: External Electrode Fluorescent Lamps and Backlight Units for the Large Area of 32″∼42″ LCD-TVs

The commercialized EEFL-BLUs of 32″, 37″, and 42″ LCD-TVs are reported with respect to the basic characteristics of luminance and efficiency. The capacitive and resistive reactance is also presented to design the inverter for lamps and BLUs.

P-14: An Efficient Way to Drive H-IPS Mode using 2*2 Inversion Method

In case of applying 2×2 inversion driving method for H-IPS mode LCM, We can easily perceive the vertical line pattern phenomenon looking like a furrow. This phenomenon is caused directly by symmetrical coupling interference between both data bus lines of one pixel and pixel electrode and indirectly by three or four times of capacitance between data bus line and pixel electrode as compared to conventional IPS structure. To remove this phenomenon, we designed a optimum pixel layout to remove the vertical line pattern phenomenon. This H-IPS pixel layout design concept is having a asymmetry coupling interference between both data bus lines of one pixel and pixel electrode. With the optimum pixel layout, the vertical line pattern phenomenon which was happened in 20.1 inch 2×2 inversion driving UXGA TFT LCD of H-IPS structure was removed.