Design and Fabrication of Flexible OTFT Array by using Nanocontact Printing

摘要

The high-resolution and large-area flexible OTFT array to use as a driving device for an OLED was designed and fabricated in the nanocontact printing process and organic thin films could be deposited even in a room temperature process. The gate, source, and drain electrode patterns of OTFT were fabricated through the nanocontact printing process using as a mask PDMS stamp on which an SAM used as an etching mask was inked selectively. To fabricate an OTFT array, an E-beam deposition device with a low-temperature inside a chamber was used to deposit Cr as an adhesion layer, to deposit a thin film of Au as an etching layer, and to create a conductive gate electrode through the nanocontact printing on a PEN plastic substrate. High-permittivity parylene-C was deposited at the room temperature using an exclusive deposition device to create an organic dielectric on the fabricated gate electrode and the patterned organic dielectric was etched selectively by O_2 plasma. Channel length of 1um was left on the parylene-C organic dielectric so that source and drain metal electrodes could be patterned and fabricated using the nanocontact printing process. On a contact electrode, an organic active semiconductor layer of pentacene was deposited through e-beam deposition device. The nanocontact printing process using SAM and PDMS stamp made it possible to fabricate OTFT arrays with channel lengths minimize to even sub-micron size, and reduced and optimized the procedure by 10 steps compared with photolithography. Since the process was done in room temperature, there was no pattern transformation, retraction, and shrinking problem appeared. Also, it was possible to improve electric field mobility, to decrease contact resistance, and to reduce threshold voltage by using a big dielectric and fabricate nanopatterns.