Abstract

more complex applications that more closely mimic the behavior and size scale of biology. To these ends, bioelectronic devices must demonstrate several critical features: be manufacturable via a repeatable fabrication processes; exhibit resistance to mechanical deformation; and demonstrate electrical reliability.Technologies based on TFTs allowed the microfabrication of large-area applications such as flat-panel displays, which were difficult to develop on flexible substrates due to their high temperature processing requirements and were difficult to develop on silicon due to the cost associated with using such a large area of silicon. After Nomura et al. presented TFTs based on indium-gallium-zinc-oxide (IGZO) semiconductors, these became the key component for the fabrication of system-on-glass applications. [9] The electrical performance of IGZO TFTs exhibited high-mobility values (>10 cm 2 V −1 s −1 ) compared with organic semiconductors (<0.1 cm 2 V −1 s −1 ) or amorphous silicon (≈1 cm 2 V −1 s −1 ). [9][10][11] More recently, IGZO has been reported with mobility values of 29 cm 2 V −1 s −1 by Jeon et al. to develop a voltage compensation circuit. [12] A transparent circuit based on IGZO TFTs with mobility of 70 cm 2 V −1 s −1 was presented by Liu et al. with frequency response on the order of megahertz. [13] In addition, Liu et al. incorporated silver nanowires into IGZO to achieve a mobility of 174 cm 2 V −1 s −1 , [14] but with limits on processing and scalability. Due to their relative low processing temperature requirements (compared with silicon technologies) and high-mobility, semiconductor devices made from IGZO allow for the development of emerging technologies such as flexible and wearable electronics: active-matrix phosphorescent organic light emitting diodes displays by O'Brien et al., [15] an amplifier by Münzenrieder et al., [16] and a full color organic light-emitting diodes (OLED)-based display [4] among others.There is a tradeoff among the various processing temperatures used during TFT fabrication, which affects electrical performance and the thermal compatibility with flexible substrates. Important performance characteristics of the electronic components include field effect mobility (μ FE ), threshold voltage (V TH ), changes in V TH (ΔV TH ), and subthreshold swing (SS). The use of elevated temperature during device processing can help improve the quality of amorphous IGZO, as well as its interface with a dielectric. According to Nomura, Flexible electronics are attracting great interest in healthcare, where devices such as thin-film transistors (TFTs) on polymer substrates facilitate biomedical applications requiring complex circuits in soft packages. Consequently, a repeatable process to fabricate reliable, stable electronic components on flexible substrates is required. Here, thermoset thiol-ene/acrylate shape memory polymer (SMP) substrates house indium-gallium-zinc-oxide (IGZO) TFTs and logic circuits: resulting devices exhibit stable behavior after thermal annealing at 250 °C. Fabr...

The effect of annealing atmosphere on indium-gallium-zinc-oxide (IGZO) thin film transistors (TFTs) fabricated on a deformable softening polymer substrate is presented in this work. Different annealing conditions-ambient, oxygen, vacuum and forming gas-are employed in the fabrication of IGZO TFTs and the changes in electrical characteristics are examined. Fabricated devices exhibit shape memory properties due to thiol-ene/acrylate substrates allowing the softening of bioelectronics to demonstrate modulus changes in aqueous conditions at body temperature. Gold (Au) is used as the contact metal for the gate, drain and source for its good adherence and malleability required for this polymer. It is found that annealing treatments at 250 °C can improve the field effect mobility of the TFTs from 10 −2 up to 30 cm 2 V −1 s −1 . These improvements are attributed to the reduction of oxygen concentration in the active film of the TFTs. The contact resistance is also reduced by the annealing treatments from approximately 1 MΩ to 20 kΩ, indicating improvement in physical contact at the IGZO-Au interface. In addition, the contributions of contact resistance and channel resistance to other electrical parameters are analyzed. This study will pave the way for the development and optimization of high-performance bioelectronic devices on smart polymers.

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