Innovation Japan 2018 New technologies of manufacturing process were proposed one after another

August 30-31, Innovation Japan 2018 were held in Tokyo Big Sight. New topics of manufacturing process in this exhibition are picked up.

First of all, as regards printable manufacturing process, National Institute for Materials Science (NIMS) appealed an original printable wiring circuit technology in the booth of New Energy and Industrial Technology Development Organization (NEDO). Fine wiring circuit can be formed without annealing process by making use of this technology, as a result, it can be applied to low thermal resistivity substrate such as plastic film, paper, flower and so on.

Pic.1 Stacking sample of printable circuit

Fig.1 Image of Nano size metal grain

Concretely, C-INK's Nano size metal ink is used in this technology. As figure 1, metal core is covered with a conductive aromatic ligand. If the ink is coated on the substrate, metal grains are connected by aromatic ligand. For this reason, relatively high conductivity is obtained without annealing process. Of course, electric conductivity is enhanced with annealing process because of increased grain size by fusion phenomenon. Specific resistance of Au is a notch above bulk Au, that of Ag without annealing process is 10^-3〜-4Ω･cm, and that of Ag with annealing process is approximate 10^-5 Ω･cm. By the way, in case of without annealing process, adhesion is ensured by irradiation of visible light.

As above, fine pattern can be formed easily by use of this ink. Concretely, first of all, a hydrophobic polymer is coated on the substrate, and then, it is exposed by irradiation of UV light, as a result, irradiated area only is changed from hydrophobic property to hydrophilic property. The next, the Nano size metal ink is coated without pattern by various coating method, for example, the spin coating method. As a result, it gathers in hydrophilic area only selectively. In short, fine pattern is formed by making use of surface treatment technology. Fine line such as 1 μm width can be formed by use of this technology. In the booth, 4-layer stacking sample was introduced for effective application.

AZO transparent film is deposited by new FTS sputtering method

Fig.2 Structure of new sputtering system and picture of target in deposition process

As concerns deposition process, Saga University proposed a new facing target sputtering (FTS) method. It's categorized into FTS method (Two sputtering targets are set up at facing, so that, high density plasma which is generated by applied voltage is confined to between targets. As a result, bombarded and rebounded atom only by Ar ion is incident into the substrate). However, as figure 2, a ring shape type target is used in this method. In short, sputtering deposition is done by confined plasma in the rotary target. As a result, high utilization ratio ( maximum 70 ％) is obtained because of uniform erosion of target, and also, uniform film is obtained easily in room temperature process.

The research group have mainly researched and developed AZO film as candidate transparent conductive film of ITO film. Transmittance is 80 % and over, and specific resistance is 10^-4Ω･cm in room temperature process. In the booth, AZO film on the PC film was exhibited.

New spray deposition method appeared on the scene for concavity and convexity plane

Pic.2 Result of PEDOT/PSS deposition on Si substrate with texture structure

Fig.3 Distribution of diameter of mist grain

On the other hand, Saitama University introduced an original aerosol spray deposition method using charged mist for substrates with texture structure. Various dispersed liquids inclusive of inorganic material and organic material are atomized by applying ultrasonic wave, and then, it is adhered and deposited on the substrate by carrying N2 career gas in room temperature and atmospheric pressure environment.

As figure 3, mist grain size can be controlled by applied frequency, and it can be decreased to minimum 20 - 30 nm. For this reason, it is effective for substrates with concavity and convexity plane, which is difficult to deposit uniformly. The research group introduced a deposited sample on silicon wafer with texture structure as an antireflection film. As picture 2, they demonstrated that it could be deposited at high uniform quality against slant plane.