Synthesis of ultrathin polymer dielectric layers via initiated chemical vapor deposition (iCVD) and their application to organic electronic devices

Abstract

Dielectric layer is an essential component enabling reliable operation of many electronic devices including thin film transistors (TFTs), flash memories, and capacitors in modern electronic systems. With the emergence of next-generation electronics relying on the mechanical flexibility of materials involved, the new generation of electronic devices requires insulators to work with unconventional substrates and newly emerging semiconductor materials, and polymeric layers are being intensively investigated as new dielectric layers. However, only with few exceptions, the insulating property of the polymer films and device-to-device uniformity degrade abruptly as the polymer becomes thinner. To address this issue, a vapor-phase process, initiated chemical vapor deposition (iCVD), was adopted to develop ultrathin polymer insulators. Inherited from conventional CVD processes, iCVD has a good scalability and compatibility with other high-throughput production processes. Also, the solvent-free nature and low substrate temperature of the iCVD process enables non-destructive deposition onto underlying layers and substrates, which are thermally/chemically sensitive. Furthermore, since the iCVD reactor is compatible with conventional vacuum deposition system for oxides, hybrid-type inorganic-organic bilayer dielectric layer could be also fabricated by combining the iCVD process and atomic layer deposition (ALD) process in a one chamber. In this thesis, four kinds of ultrathin iCVD polymer dielectric layers (poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3), poly(ethylene glycol dimethacrylate) (pEGDMA), poly(isobornyl acrylate) (pIBA), poly(1H, 1H, 2H, 2H-perfluorodecyl acrylate) (pPFDA)). Not only the polymers, hybrid-type dielectric layer was also developed, by designing new vacuum reactor for continuously depositing ALD and iCVD layer in a one chamber. All dielectric layers developed in this thesis could be utilized as dielectric layers for low-voltage operating, flexible organic TFTs (OTFTs). Together with the wide range of material choice, tunability and scalability of the iCVD process, its aforementioned benefits may open up a new pathway towards fabrication of low-power, high-performance soft electronic devices based on unconventional materials and form factors.