Precise patterning of organic semiconductors by reactive ion etching

Abstract Minimizing the off-state current is mandatory for the development of low power consumption circuits based on organic thin-film transistors (OTFTs). Small OTFTs which are required for compact circuits suffer from parasitic current pathways through the semiconductor and hence precise patterning of the semiconductor film is essential. Since state-of-the-art patterning techniques such as oxygen based reactive ion etching usually severely damage the organic transistors, usually OTFTs with a large channel width W are discussed in the literature in order to circumvent this problem. Here we demonstrate that precise patterning of organic semiconductor films for OTFT using reactive ion etching is possible without compromising the transistor performance. If adequate etching conditions and appropriate masks are chosen, oxygen radicals do not affect the organic transistor because lateral diffusion as well as vertical bombardment of ions through the etching mask do not occur. With the method presented here, we show small footprint OTFTs with W / L  = 25 μm/10 μm and leakage current levels as low as 10 fA/μm which enable organic transistors to be used for demanding electronic applications such as high resolution active-matrix displays or photo detector arrays.