Determination of Mechanical Properties of Thin Film Materials Used in Oxide TFTs Toward Advanced Material Models

• Autor(a) principal: Bentes, Carolina Alves
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/156038
• topic: flexible electronics; thin films; mechanical properties; oxide TFTs; material function; finite element modelling; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

With an increasing demand for improvement and innovation in the field of microelectronics, flexible electronics, driven by applications that range from displays to medical devices, has gained much relevance in recent years. Thin film transistors (TFTs) are the main building block for flexible microelectronic systems, but a better understanding of the mechanical properties of the constituent thin film materials is necessary to design more reliable microelectronic devices to be used in mechanically harsh environments. This work aims to extract a set of mechanical properties of thin film materials used in flexible oxide TFTs and based on that, parameterize material models for Finite Elements Analysis (FEA). To acquire data for these material models, films from different materials are fabricated on silicon substrates. For assessing the impact of thickness and annealing process on the mechanical properties of the thin films, several samples of the same material are fabricated with distinct specifications. This study is divided into two workflows for extracting two distinct sets of parameters. For films composed of metals (Mo), semiconductors (IGZO) and dielectrics (Ta2O5 and Ta2O5/SiO2), the hardness and, as the main parameter, Young´s modulus, are determined by nanoindentation for describing linear elasticity. For the polymeric films (PI), timedependent parameters such as storage modulus, loss modulus and phase angle, which are necessary to describe viscoelasticity, are determined by nanoscale Dynamic Mechanical Analysis (nano-DMA). Based on these experimental results, the linear elastic and viscoelastic material models are parameterized for the Finite Element Method (FEM). Based on these FEM models, now relevant geometries could be simulated. Beyond that, following the methodology of the dissertation, further thin films used in oxide TFTs could be characterized which paves the way for the acquisition of data from other relevant materials and the obtaining of a complete description of the device for product development.