The project objective is the development and characterization of new technologies for thin film transistors (TFTs) and thin film based microsystems. The principal investigation field has been the optimization of the active layer of polycrystalline silicon films made with advanced methods, such as sequential lateral solidification excimer laser annealing (SLS ELA), and of the performance parameters of TFTs fabricated in them. Advanced polysilicon TFTs are necessary for novel large area electronics systems, yet even they now constitute a maturing technology. Novel concepts, utilizing near room temperature fabrication and deposition on almost any kind of substrate, including flexible ones, are needed to allow for new applications of “electronics on anything”. Recently our objectives have been expanded to include a novel field, namely that of devices fabricated in thin films of transition metal chalcogenides. These are materials especially suited for thin film and two-dimensional applications, as they are characterized by strong in-plane covalent bonding and weak inter-planar coupling.
The specific investigation targets being pursued are:
- Investigation of SLS ELA polysilicon TFT characteristics and of stress-induced degradation, with identification of ageing mechanisms.
- Assessment of the material properties of polycrystalline silicon thin films and of the effects of variations in crystallization technique, film thickness, device structure and fabrication process on film defects, TFT performance and reliability.
- Investigation of material and electrical properties of transition metal sulphide and oxide thin films (initial focus on MoS2 and MoOx) and of their suitability for device fabrication. Evaluation of metal contacts to them and of the compatibility of these films with various materials and processes.
- Development of a reliable TFT fabrication procedure at low or even room temperature that utilizes metal sulphide or metal oxide active area films. The procedure characteristics will be such that a great variety of substrates can be used. Such versatile devices will be far more conducive to applications like flexible, wearable or ubiquitous electronics.
Furthermore, the project aims at the development of applications in TFT-addressed displays and microsystems, in collaboration with various European research partners, utilizing such advanced TFTs. These systems would incorporate thin film sensors, display pixels and other elements. Several relevant partnerships have been formulated (e.g. for development of thin film sensor – TFT microsystem modules) and are being pursued.