| 초록 |
Developments of Flexible or stretchable electronics can be realized in the near future, considering recent results and interests. Core technology is involved with the guarantee of driving device thin film transistors (TFTs). When fabricating flexible and imperceptible devices, high electrical properties and stability of oxide TFT at low process temperature is a critical issue because high performance and stability are generally achieved at a process temperature above 300 °C. However, flexible and/or imperceptible organic substrates cannot endure at the high temperature due to low thermal stability of them. High performance and stability of an oxide TFT are related to two key points: i) how many stable metal-oxygen bondings can be obtained, ii) how effectively we control the defects such as oxygen vacancies, hydroxides, etc. in the oxide channel. Conventional annealing process in dry ambient (O2 or air) has been generally adopted as a reproducible optimum process to simultaneously obtain high performance and high stability. However, high annealing temperature above 300 °C is still a problem in fabricating flexible and imperceptible devices (i.e. low thermal stability of flexible and/or imperceptible organic substrates). Since typical oxidizer gas is oxygen or water vapor, most studies have utilized air or oxygen rich ambient, and some reports have used wet oxidation. Interestingly, these oxide materials grown at low temperatures are susceptible to environment status such as humidity and temperature, so that these materials have received a strong interest in the semiconductor gas sensors. We found that these oxides are very reactive for some oxidation gases such as NO2 and CO2, and choose these gases as new oxidizer gas for oxidation process at the relatively low temperatures. The proposed oxidation process revealed the maximum temperature of 150 °C exhibiting quite good electrical properties and stability. Moreover, we successfully employed this approach to fabricate ultrathin a-IGZO TFTs on a flexible polymer with the thickness of a few microns. |
