Multi-rate resist method to form organic TFT contact and contacts formed by same

摘要

A method for forming a thin film electrode for an organic thin film transistor of the invention provides a multi-layer mask on a substrate with an electrode area opening in a top layer of the mask that is undercut by openings in other layers of the mask. A thin film of metal is deposited in the electrode area on the substrate. Removing the multi-layer mask leaves a well-formed thin film electrode with naturally tapered edges. A preferred embodiment of the invention is a method for forming a thin film electrode for an organic thin film transistor. The method includes depositing a first layer of photoresist on a substrate. The photoresist of the first layer has a first etching rate. A second layer of photoresist is deposited on the first layer of photoresist. The photoresist of the second layer has a second etching rate that is lower than the first etching rate. The first and second layer of photoresist are patterned by exposure. Developing the first and second layers of photoresist provides an electrode area on the substrate. An electrode is deposited in the electrode area. Lift-off of the first and second layers is performed. The electrode that is deposited has a tailored, tapered edge. A preferred embodiment thin film electrode in an organic thin film transistor has a tapered edge with a contact angle of approximately +40±4.4°.