Fabrication of a high-aspect-ratio stainless steel shadow mask and its application to pentacene thin-film transistors

A high-aspect-ratio and high-resolution stainless steel shadow mask for organic thin-film transistors (OTFTs) has been fabricated using a new method which combines micro-electro-discharge machining (micro-EDM) and electrochemical etching (ECE). First, square holes are serially machined using micro-EDM. Then, the ECE process is used to reduce the spacing of holes, which can be reduced down to 3.6 µm. Using this method, a 95 µm thick stainless steel shadow mask can be fabricated with a wall 3.6 µm in width and 150 µm in length. The aspect ratio of the wall is about 26. Source and drain electrodes of OTFTs were successfully patterned on a pentacene active layer through the fabricated shadow mask, and the fabricated pentacene TFTs had good output characteristics.