Takao Terabayashi

Excimer ablation lithography (EAL) for TFT-LCD

The excimer ablation lithography (EAL) is a process of direct patterning and removal of a resist polymer film by photo-decomposition ablation. Comparing to the conventional photolithography, EAL does not need the development process and realizes a non-vacuum dry removal of resist. The main equipment for the new processes is a kind of aligner- exposure for the resist patterning and the removal, which reduce the cost of the clean room and the equipments considerably. This is very attractive for TFT-LCD manufacturing, as it is required to reduce the cost severely. The large area patterning and high throughput are essential for TFT-LCD applications. To prove the feasibility, we fabricated an experimental equipment for ablation patterning. It is equipped with the high precision 300 X 300 mm X-Y stages and a N.A. 0.1 image lens which enable to explore the problems inherent to TFT panel of a real size. In addition, two substantial technologies were developed. One is a dielectric multilayer mask on 8 inch quartz substrate with precision enough for TFT patterns. The other is high ablation rate resist polymer. With these technologies, A4 size TFT laser was fabricated by step and scan method. The results show that EAL is in a good prospect for a new TFT manufacturing technology.

Beam Defocus Effect in Electron Beam Machining of Green Ceramic Sheet

Abstract Diameter increase in machining of alumina green sheet with an electron beam is discussed in this paper. High speed machining experiments with a deflection coil have been performed. The following are clarified. The diameter increase is due to the beam defocus effect, produced by organic binding material. The beam defocus effect depends on the time interval of pulses, but it does not strongly depend on the distance between holes. The dynamic focal control is very effective to diameter increase. The effect of dynamic focal control is considerably influenced by the time constant of the control pattern.

Correlation between power density fluctuation and grain size distribution of laser-annealed polycrystalline silicon

The grain size of polycrystalline silicon by the excimer laser annealing (ELA) is primarily determined by the fluence, and the distribution uniformity is strongly influenced by the intensity fluctuation. Instead of the conventional CCD profile, a resist film is used to monitor the light intensity distributions over whole illumination area in submicron resolution. The high resolution measurements show speckle patterns with 0.1-0.15 spacing with maximum 10mJ/cm2 variation. The fluctuation does not influence the grain size variation in the lateral growth region over 1-2 micrometers area, however, the undulation of intensity about 10mJ/cm2 over 10 micrometers distance produces an appreciable changes in the grain sizes. Such a local temperature distribution corresponds to the envelop obtained by averaging small area, and is maintained during crystallization process.

Pattern precision of excimer ablation lithography (EAL)

Differences between EAL and the conventional photolithography are mainly with respect to the resist materials and the mask. The mask consists of dielectric multilayer reflector, and the thickness and the structure are completely different from Cr masks. This paper is aimed to clarify the influences of dielectric mask to the image qualities, and presents a rigorous simulation of the diffraction by the dielectric mask and preliminary experimental results. These results show that for low N.A. imaging system, there are not substantial differences between the dielectric mask and the metal mask concerning the resolution power, however further investigations are required for the interpretation of rather wide resist edge corresponding to a straight edge of the large opening mask.

Press Formability of Face-Centred Cubic Metals at Cryogenic Temperatures

The increase in the ductility of F.C.C. metals at cryogenic temperatures is due to the strain propagation facilitated by the increase in the work-hardening rate. In order to apply these characteristics to practical forming processes, the influence of cryogenic temperatures on the formability of copper and aluminium sheets in stretching, deep drawing and hole flanging was studied.