A Metal Interconnection Using a Direct Imaging Method for HySiF (Hybrid System in Flexible) Devices

Abstract

Organic based materials and devices for flexible electronics are recognized as a promising field and application while they also have significant disadvantages such as low charge transport, process temperature limitation, and etc. Those limitations, based on material itself, make the flexible electronic device very difficult to compete with Si-based rigid electronics that have excellent device performance and much advanced design rule. However, the rigid Si based devices are also vulnerable to any types of mechanical stress when they are in use for the flexible applications. Thus, we strongly feel the need to combine benefits from the organic based flexile devices and from the Si based rigid devices by attaching the rigid thin chips on the flexible substrates such as PI (Polyimide), PET (Polyethylene phthalate) and PDMS (Polydimethylsiloxane) which is accepted as a new or future trend for the next generation of the electronic devices. In order to achieve this new concept, thin device $(\le50 \mu ${m) showing high device performance needs to be attached on the surface of deformable substrates to construct flexible electronic device circuits and it is required to interconnect the thin Si based chip with the flexible polymer substrate. For this specific interconnection, we utilized an ElectroHydroDynamic (EHD) micro-patterning system which is not damaging the flexible substrate unlike the conventional wire bonding method that mechanically damages during the bonding process. To form narrow Ag based metal interconnections, we optimized various experimental parameters (flow rate [$\mu $l/min], applying voltage [kV], working distance [㎛], jetting velocity and acceleration [mm/s, mm/s2]) and the metal lines were sintered at 150 oC for 30 mins to remove any solvent contained in the solution based Ag ink. As a result, we expect that this work will contribute to the fabrication of 3D devices on the flexible substrate that uses the Si based thin chip interconnected by the narrow Ag based metal lines.