Room-temperature solution-processed high-k gate dielectrics for large area electronics applications

One of the key challenges to manufacture low cost circuits (e.g. RFID tags) and backplanes on flexible substrates lies in the realization of a reliable gate-dielectric with a high specific capacitance required for low voltage, high current drive. Flexible substrates necessitate deposition techniques with process temperatures lower than 150 °C, making the production of high quality gate dielectric materials more difficult. Here we show a promising integration scheme for thin film circuits using anodization. Aluminium oxide can be fabricated at low cost by anodization of aluminium at room temperature, giving rise to an ultra-thin, smooth, and dense gate dielectric. Starting from a blank Al film deposited on an arbitrary substrate, we anodize part of the metal to Al2O3Al2O3 and pattern the Al/Al2O3Al/Al2O3 stack into appropriate islands in a single patterning step. Overetch of the Al gate allows the further processing of source-drain contacts without side leakage between source and gate at the edge of the gate islands. The process also allows for defined connections between source metal and gate metal as needed in circuits. With this process, we show pentacene and Ga–In–Zn–O TFTs and pentacene circuits (inverters and 19 stage ring oscillators) with channel-length down to 3 μm, operating at voltages as low as 2 V. They allow us to assess the possibility to use anodized Al2O3Al2O3 as gate dielectric for TFTs in circuits.

Graphical abstractUsing anodization integrated within a promising circuit fabrication scheme, we demonstrate low cost high-k gate dielectrics for organic TFTs and circuits (inverters and 19 stage ring oscillators) which can operate at voltages as low as 2V with channel-length down to 3 μm.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► High-k gate dielectric (Al2O3, k = 9) made by anodization is dense, thin and conformal to the gate layer. ► New process flow using overetch enables patterning of gate and anodized gate dielectric for circuit application. ► We show pentacene and Ga–In–Zn–O TFTs and pentacene circuits (inverters and 19 stage ring oscillators) with channel-length down to 3 μm, operating at voltages as low as 2V.