Sputtered Zn-Sn-O based thin-film transistors: Optimization and circuit simulation

• Autor(a) principal: Lima, Diogo Luís Araújo de
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/74922
• topic: Zinc tin oxide; thin film transistors; RF sputtering; low temperature; building blocks simulation; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

The development of amorphous oxide semiconductors (AOS) has been accelerated with their application in thin-film transistors (TFTs) for transparent and flexible displays. Among the many AOS available, zinc tin oxide (ZTO) represents a promising material due to its enhanced chemical and physical properties and the abundance of its elements in nature results in low price, compared to IGZO, and favours its widespread use in mass technology production. In this work, ZTO thin films deposited by sputtering under different oxygen, hydrogen and RF power conditions were investigated. The study focus on their morphology, structure and optical behaviour and on their implementation as active channel layers in TFTs. Great device performance was obtained when deposited at a power of 160 W, in a 10% of oxygen partial pressure and 1% of hydrogen, at a 2.3 mTorr pressure. After an annealing temperature of 180 oC, mobility of 9.1 cm2 V-1s-1, subthreshold slope of 0.29 Vdec-1 and turn-on voltage of -2.0 V were achieved, using a sputtered multilayer dielectric based on Ta2O5-SiO2. The measured output and transfer a-ZTO TFT characteristics were modeled in an artificial neural network (ANNs) empirical model with very good accuracy. The model was used in the Cadence Spectre to simulate three logic gates at DC and transient analysis: inverter, NAND and NOR, with logic levels preserved up to 10 kHz.