In Chap. 14, a novel patterning method of oxide material named nano-rheology printing (n-RP) was introduced, which is a direct imprinting of the oxide precursor gel. It was proven that oxide gels have a viscoelastic property at some temperature range if solutions are properly designed and synthesized. We demonstrated fine oxide patterns with well-defined shape were able to be formed by thermal imprinting.
In this chapter, we report the adoption of the n-RP method as a fabrication tool of actual electronic devices. This corresponds to step 2 in Fig. 11.2 (Chap. 11 Guideline to oxide-based materials) which shows the developmental step to the printed electronics.
In Sect. 19.1, fabrication of two types of thin-film transistors (TFTs) is introduced: a FGT (ferroelectric gate-insulator transistor) and a switching TFT (normal TFT). The former TFT, which has a memory function due to ferroelectric nature of the gate insulator, was already introduced in Chap. 16, where the conventional fabrication method was used. Here, a FGT fabricated by the n-RP method is introduced. The channel lengths of both TFTs were 0.5 μm. This size has never been realized in the conventional PE (printed electronic) technologies.
In Sect. 19.2, a new TFT with improved structure and process is introduced. Because the structures of the TFTs described in Sect. 19.1 are very primitive and the used n-RP process for making them is not so robust, more complicated TFT structure and more sophisticated n-RP process are required inorder to apply the n-RP for practical devices and to ensure its process reliability, respectively.
As the imprinting method has an ability to make patterns with tens of nanometer, there would be much room to reduce the size of TFT. In fact, we demonstrated a reduced size TFT of which channel length is 200 nm in Sect. 19.3.
In Sect. 19.4, fabrication of an active-matrix backplane (AM-BP) for a display by using n-RP is introduced. We prepared a set of thermoplastic oxide gels sufficient for fabrication of the AM-BP and developed a suitable alignment system, giving a high alignment accuracy of less than 5 μm, for making the AM-BP. The operation of the transistors in the AM-BP was confirmed.
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