The thesis project is based on the research of alternative materials for the development of electronic components, which could gradually replace the conventional materials currently used. The research is focused on polymeric materials since only this class of material offers manifold properties such as low temperature processing, flexibility, transparency and good mechanical properties. Concerning the materials making up transistors, most of the research has always been interested in developing and improving the organic semiconductor materials making these latter effectively competitive with the conventional ones. While, this project will concern the development of the dielectric materials, which act as insulating layer in Thin Film Transistors (TFTs). The material of interest is a partially fluorinated polymer known as SOLVENE® T, with chemical formula P(VDF-TrFE-CTFE), provided by Solvay Specialty Polymers Italy S.p.a. (abbr. SSP). Besides the great chemical stability typical of fluorinated materials, this polymer shows high dielectric constant (above 25), and interesting mechanical properties which allow to depose it as film of hundreds of nanometres as well as to realize free-standing films with thickness in the order of tens microns. The aim of the thesis work is to improve the electrical insulating properties of the dielectric SOLVENE® T P(VDF-TrFE-CTFE) in terms of leakage current. The idea was born thanks to the collaboration with Holst Centre, an innovation centre powered by Imec & TNO located in Eindhoven NL, where the application of SSP P(VDF-TrFE-CTFE) in Thin-Film-Transistors as pure and as blended with 2% w/w of PMMA showed interesting performance and, more precisely, the blend showed higher insulating properties. Solvay Specialty Polymers Italy S.p.a. has a broad range of polymers in its portfolio and the approach for the development of new dielectric-insulating material has led to blend the SSP SOLVENE® T terpolymer with very low content of another polymer (via dissolution) in order to do not affect the dielectric properties of the pristine material. The chosen polymers were SSP rubbers, copolymers and terpolymers of VDF, for their similarity with SOLVENE® T materials as easiness in dissolving and formulating in common solvent for SOLVENE® T materials. As comparative examples blends with PMMA (by Altuglass®) have been realized. Micrometric free-standing film capacitors have been built, using the different blends as dielectric medium, and then characterized is terms of dielectric constant and leakage current. Moreover, the influence on electric performance of the pure P(VDF-TrFE-CTFE) by polymer molecular weight, residual surfactant content and added Acrylic Acid content has been investigated in thin film capacitors. The idea of blending SSP rubbers in order to reduce the leakage current through the material has, as basis, the possibility to self-produce all the elements needed to provide the best solution possible and being free from any royalties and compensation for using someone else company product.
Il progetto di tesi si basa sullo sviluppo di materiali alternativi per lo sviluppo dei dispositivi elettronici che potranno gradualmente sostituire i materiali convenzionali attualmente impiegati dalle industrie del settore. La ricerca è focalizzata sui polimeri poiché solo questa classe di materiali offre molteplici proprietà come processabilità a basse temperature, flessibilità, trasparenza e ottime proprietà meccaniche. Riguardo i materiali componenti i transistor, grande parte della comunità scientifica si è interessata nello sviluppo e miglioramento dei materiali organici semiconduttori rendendo quest’ultimi effettivamente competitivi coi materiali convenzionali. Questo progetto sarà focalizzato sullo sviluppo del materiale dielettrico utilizzato come strato isolante nei Thin Film Transistors (TFTs). Il materiale studiato è un polimero parzialmente fluorurato commercializzato come SOLVENE® T e di composizione chimica P(VDF-TrFE-CTFE), fornito da Solvay Specialty Polymers Italy S.p.a. (abbrev. SSP). Oltre alla alta stabilità chimica, tipica dei materiali fluorurati, il polimero mostra elevata costante dielettrica (maggiore di 25) e ottime proprietà meccaniche che permettono sia la deposizione di questo in film di centinaia di nanometri che la realizzazione di pellicole free-standing con spessori di decine di micron. L’obbiettivo della ricerca è il miglioramento delle proprietà elettriche isolanti del P(VDF-TrFE-CTFE) in termini di perdita elettrica, o leakage current. L’idea è nata da una collaborazione con Holst Centre, un centro di ricerca di Imec & TNO a Eindhoven NL, dove il polimero SSP, testato in TFTs come polimero puro e come blend al 2% w/w di PMMA, ha mostrato interessanti performance, ed in particolare il blend a registrato proprietà isolanti maggiorate. Il portfolio Solvay Specialty Polymers Italy S.p.a. offre una vasta gamma di polimeri e l’approccio per lo sviluppo di nuovi materiali dielettrici-isolanti si è basato sulla formulazione di blends del terpolimero SSP SOLVENE® T con basse concentrazioni di un altro polimero (via dissoluzione) al fine di non intaccare le proprietà dielettriche del materiale puro. I materiali blendanti utilizzati sono gomme fornite da Solvay Specialty Polymers Italy S.p.a., copolimeri e terpolimeri del VDF, sono stai selezionati sulla base di affinità con i materiali SOLVENE® T in termini di facilità di dissoluzione e formulazione nei comuni solventi dei polimeri SOLVENE® T. Come esempi comparativi sono stati realizzati blends con PMMA, acquistato da Altuglass. Condensatori a pellicola di spessore micrometrici sono stati realizzati e caratterizzati in termini di costante dielettrica e perdita elettrica. Inoltre, l’effetto sulle proprietà elettriche del polimero puro P(VDF-TrFE-CTFE) da parte del peso molecolare, della quantità di tensioattivo residuo e dell’aggiunta di Acido Acrilico sono stati studiati in condensatori a pellicola sottile. L’idea di utilizzare gomme SSP come materiali blendanti al fine di ridurre la leakage current offre, di base, la possibilità di realizzare un materiale competitivo che risulta risulta essere esente da ogni royalty legata a prodotti appartenenti ad terzi.
Development of high-k materials for thin film transistors
PEDROLI, FRANCESCO
2014/2015
Abstract
The thesis project is based on the research of alternative materials for the development of electronic components, which could gradually replace the conventional materials currently used. The research is focused on polymeric materials since only this class of material offers manifold properties such as low temperature processing, flexibility, transparency and good mechanical properties. Concerning the materials making up transistors, most of the research has always been interested in developing and improving the organic semiconductor materials making these latter effectively competitive with the conventional ones. While, this project will concern the development of the dielectric materials, which act as insulating layer in Thin Film Transistors (TFTs). The material of interest is a partially fluorinated polymer known as SOLVENE® T, with chemical formula P(VDF-TrFE-CTFE), provided by Solvay Specialty Polymers Italy S.p.a. (abbr. SSP). Besides the great chemical stability typical of fluorinated materials, this polymer shows high dielectric constant (above 25), and interesting mechanical properties which allow to depose it as film of hundreds of nanometres as well as to realize free-standing films with thickness in the order of tens microns. The aim of the thesis work is to improve the electrical insulating properties of the dielectric SOLVENE® T P(VDF-TrFE-CTFE) in terms of leakage current. The idea was born thanks to the collaboration with Holst Centre, an innovation centre powered by Imec & TNO located in Eindhoven NL, where the application of SSP P(VDF-TrFE-CTFE) in Thin-Film-Transistors as pure and as blended with 2% w/w of PMMA showed interesting performance and, more precisely, the blend showed higher insulating properties. Solvay Specialty Polymers Italy S.p.a. has a broad range of polymers in its portfolio and the approach for the development of new dielectric-insulating material has led to blend the SSP SOLVENE® T terpolymer with very low content of another polymer (via dissolution) in order to do not affect the dielectric properties of the pristine material. The chosen polymers were SSP rubbers, copolymers and terpolymers of VDF, for their similarity with SOLVENE® T materials as easiness in dissolving and formulating in common solvent for SOLVENE® T materials. As comparative examples blends with PMMA (by Altuglass®) have been realized. Micrometric free-standing film capacitors have been built, using the different blends as dielectric medium, and then characterized is terms of dielectric constant and leakage current. Moreover, the influence on electric performance of the pure P(VDF-TrFE-CTFE) by polymer molecular weight, residual surfactant content and added Acrylic Acid content has been investigated in thin film capacitors. The idea of blending SSP rubbers in order to reduce the leakage current through the material has, as basis, the possibility to self-produce all the elements needed to provide the best solution possible and being free from any royalties and compensation for using someone else company product.| File | Dimensione | Formato | |
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2015_12_Pedroli.pdf
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Descrizione: Thesis text
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https://hdl.handle.net/10589/115601