Reo Usui

Highly conductive SnO2 thin films for flat-panel displays

Abstract— SnO2 is considered to be a promising alternative material for indium tin oxide (ITO), which is used for thin-film transparent electrodes in flat-panel displays (FPDs) and is facing a serious indium depletion problem. However, annealing processes in the manufacture of plasma-display panels (PDPs), which are major FPDs, cause high resistivity in SnO2 films. To obtain lower resistivity after the annealing processes, the relationship between deposition conditions and resistivity and the influences of annealing on resistivity, both theoretically and experimentally, were investigated. As a solution, a method involving the formation of a coating of SiO2 on SnO2 is proposed, and a SnO2 resistivity as low as 6.60 × 10−5 Ω-m was obtained after annealing.

Fabrication of selenized/sulfurized Cu(In,Ga)(Se,S) 2 solar cells based on high temperature process using high strain point glass substrate

A new high strain point glass substrate for selenized/sulfurized Cu(In,Ga)(Se,S)2 (CIGS) solar cells was developed. The developed glass has advantages not only higher strain point but also lighter weight and higher mechanical strength than the glass for Plasma Display Panels. CIGS solar cells were fabricated by a selenization/sulfurization 2-step process at high temperature using the developed glass and Soda Lime Glass (SLG) substrates. The SLG needed SiO2 alkali barrier layer to fabricate CIGS absorber thin film, otherwise delamination occurred. The CIGS fabricated under the high temperatures conditions had better crystal properties, which resulting in higher conversion efficiency than those fabricated at a low temperature of 520 degrees which is commonly used for CIGS solar cells fabrication taking into account the strain point of SLG. The CIGS solar cell fabricated on the developed glass substrate showed higher PV performance than on the SLG with SiO2 substrate processed on 580 degrees. As a reason of the difference, over 15μm warpage was observed in 30mm length of the SLG substrate, while less than 1μm of warpage occurred in the developed substrate. Our best cell so far is a 0.538-cm2 aperture-area efficiency 17.5% using the developed substrate adapting 580 degrees of process temperature.

P-210: Ta-Doped SnO2 Thin Films for PDP

SnO2 is considered to be a promising alternative material for indium tin oxide (ITO), which is used for transparent electrode in Flat Panel Display (FPD) and is facing a serious indium depletion problem. However, there are some problems such as high resistance, difficulty in processing, and low sintered density, which is necessary to sputtering. We investigated Ta-X doped SnO2. Doping these elements enabled sintered density to rise and its specific resistance to decrease below 1.0×10−2Ω⋅cm after dielectric firing, it is low enough to apply to plasma display panel (PDP). Furthermore, the films which we formed were easy to process by YAG laser. Therefore, it is favorable material for transparent electrode of PDP.

60.2: Research on Next‐Generation Manufacturing Method of Plasma Display Panels via Lift‐Off Process

This paper aims to develop the next-generation manufacturing method of plasma display panels (PDPs) which is superior in cost-performance and environmental damage to current methods, by introducing the lift-off process in place of the etching process. The lift-off process, which has been applied in the LSI fields, has been faced problems caused by inappropriate resist profiles, such as difficulty in resist removal and low pattern accuracy. Moreover, in PDP processes, inappropriate profiles cause more serious problems. In this paper, the inversely tapered and T-shaped resist profile is proposed, and its feasibility is experimentally proved. for proper design of the proposed profile, deposition model onto the profile is discussed, and a method based on the model is given.

65.1: High Conductivity SnO2 Thin Films for Flat Panel Displays

We examine SnO2 as a next generation material for transparent electrode using electron beam (EB) plasma deposition method at room temperature. We have found that a SiO2 layer is a very effective barrier in reducing the increase in resistance caused by annealing. Making use of this barrier, we were successful in obtaining SnO2 resistivities as low as 6.60 × 10−5 Ω ⋅ m after annealing.

Research on direct laser patterning of thin films for flat-panel display

On a microcircuit pattern, which is necessary for fabricating electrical devices such as plasma display and liquid crystal display, the wet process which utilizes lithography technology is commonly employed. The wet process, however, is not desirable because it needs a large number of process steps. Furthermore, chemical used in the process is hazardous to the environment. Therefore, a “dry process” that does not utilize the lithography is strongly desired. In this paper, to realize the dry process, a laser processing approach using a Nd:YAG laser is adopted as an alternative technology. We fabricate thin films made of SnO2 (a next generation material for transparent thin film electrodes for Flat-Panel Display (FPD)) under various conditions and examine the effectiveness of the laser processing approach via experiments with the thin films. We found that the film characteristics such as electrical resisivity, crystalline structure quality, and so on, change and that the effectiveness of the laser processing varies, depending on the conditions. In this work, we show that these results can be explained in terms of a wavelength shift in the absorption edge of the thin films for Nd:YAG laser from the viewpoint of interaction of light and electrons.On a microcircuit pattern, which is necessary for fabricating electrical devices such as plasma display and liquid crystal display, the wet process which utilizes lithography technology is commonly employed. The wet process, however, is not desirable because it needs a large number of process steps. Furthermore, chemical used in the process is hazardous to the environment. Therefore, a “dry process” that does not utilize the lithography is strongly desired. In this paper, to realize the dry process, a laser processing approach using a Nd:YAG laser is adopted as an alternative technology. We fabricate thin films made of SnO2 (a next generation material for transparent thin film electrodes for Flat-Panel Display (FPD)) under various conditions and examine the effectiveness of the laser processing approach via experiments with the thin films. We found that the film characteristics such as electrical resisivity, crystalline structure quality, and so on, change and that the effectiveness of the laser processin...

Method of Process Parameter Identification and Resist Profile Design for Thin-Film Pattern Formation

For realization of the next generation thin-film pattern formation technology by the lift-off method, the inversely-tapered resist profile with interstice has been proposed, and its fundamental effectiveness was shown. Furthermore, a method was given, for calculation of thickness distribution of the film pattern formed with the proposed resist profile, and a design method of the proposed resist profile. However, in these methods, there are some problems in identification of process parameters and definition of proper resist profile. This paper proposes a systematic method for identification of the parameters and a design method of proper resist profile.

49.3: Mechanism and Advanced Application of Rapid Laser Processing on SnO2 Thin Films for FPD Manufacture

A Nd:YAG laser processing on a SnO2-system thin films for FPD manufacturing is investigated as an alternative to photolithographic etching on ITO. Because of the difficulty in realizing a low energy process on SnO2 due to a high melting point, we experimentally found the proper deposition condition and composition of SnO2-system thin films. By considering two physical mechanisms, namely, plasmon oscillation and inverse bremsstrahlung process, we achieved satisfactory laser processing using only 2 J/cm2 of laser energy. This result leads to the possibility of high-speed electrode patterning suitable for FPD mass production.

60.3: Advanced Application of Direct Laser Process on SnO2 Thin Films for FPDs

A Nd:YAG laser process on pure and doped SnO2 thin films was investigated as a key technology for a next generation flat panel displays manufacture replacing photolithography etching process on Indium-Tin-Oxide that is currently in use. It is found that the laser process is capable of making fine micro patterns on SnO2 thin films that have high carrier concentration by as low laser energy as 6J/cm2.