Nano Imprinting을 통한 나노선 패턴 형성 및 신경모방 소자 응용

Abstract

Conventional electronic devices used to be fabricated by photolithography which is exposing the light selectively on the target with a photo-mask. Due to the limitation and obstruction of lens system and wavelength of industrial light, the culmination of Moore`s law has been arrived and the development of alternative technology has been inevitable. To overcome those limitations, various lithography systems (e-beam lithography, x-ray lithography, Focused ion beam milling) have been researched to achieve more sophisticate pattern fabrication. While those were succeed in a measure, however, in respect of high-cost equipment and relatively long-time fabrication, nanoimprint lithography (NIL), proposed by Chou, came to the fore. Using nano-patterned elastic molds and simple mechanical pressure, NIL can replicate the sophisticate patterns on the target substrate repeatedly with a relatively low price, short process time as well as high reproducibility. By utilizing this method, we investigated nanometer scale metal line electrode fabrications using silver nanoparticle ink under none-vacuum environment. In this process, methanol meniscus (capillary force effect) method is employed to remove a metallic particle residual layer. Due to direct plasma etching process injected in the substrate can damage metal lines, methanol meniscus method is more suitable for efficient device fabrications. Without unnecessary etching and low-cost solution base process, clean metal lines are prepared and utilized in subtle cross arrays of metal line formations. Furthermore, we demonstrated a Synapstor (Synapse + Transistor), 3-termanal structure based back gated thin film transistor, by using NIL method for the fabrication of channel area between source and drain. We applied NIL process in channel pattern fabrication between source and drain electrode to perform the Synapstor function with a back gate thin film transistor (BG-TFT). In2O3 doped IGZO was deposited on the elaborately replicated line patterns of PMMA which was fabricated by NIL and effectively reduced the PMMA residue by O2 plasma etching. As a result of current measurement in the condition of constant pulse (V) in manufactured 3-terminal device, it could memorize a current state by oneself without depending on the external power (V), and showed a STDP characteristic, based on the chain reaction of the Hebbian`s rule. Through this method, we displayed a multiline pattern channel base, fabrication of 3-terminal Synaptor device using non-light exposure and non-vacuum NIL process. We expected this method will be the foundation of fabricating fine patterned or Neuromorphic device, and applied in various filed such as high-integration memory device and logic device performing under ultra-low electricity.