A study on the fabrication of atomic layer deposited SnO2 channel layer for thin film transistor and application to multi stack channel ternary device

Abstract

With the recent emergence of the fourth industrial revolution, the internet of things (IoT) and artificial intelligence (AI) technologies are expected to be at the main keywords. Both are based on big data, so the amount of data to be processed for the upcoming fourth industry will continue to increase and the number of necessary devices will also increase accordingly. As a result, the amount of consumed electricity is also vast, and a new strategy is needed to reduce it. To handle information with ternary system instead of existing binary system can reduces the number of devices needed to deal with same information, which is a way to reduce the amount of consumed electricity. In order to realize three current levels, a ternary device that acts as a switch is needed. Among the various studies, multi stack channel ternary device was reported as a new device applicable to circuits because it is possible for large-area process, low-temperature process, and excellent performance. In the reported multi stack channel ternary device, the ternary characteristics were observed by stacking the two ZnO layers vertically and inserting an Al-based organic separation layer between them. However, in the case of ZnO ternary device, there was a problem in which the three current levels were not observed over time, which is thought to be due to the unstable ZnO in ambient. Therefore, in this study, unstable ZnO was replaced with stable n-type semiconductor to fabricate ternary device and solve time stability problem. Among various n-type semiconductors and deposition equipment, SnO2 was grown to produce ternary devices using atomic layer deposition, which is easy to control process parameters. Prior to the fabrication of ternary device, SnO2 thin film transistor (TFT), which was grown through the infiltration process, was fabricated and the results of threshold voltage 0 V, On/off ratio 104 were observed. Electrical characteristics of each layer were analyzed. Drain current of organic separation layer on the 1st SnO2 was saturated and 2nd SnO2 on organic separation layer showed the three current levels. When the time stability was evaluated, the three current states were observed up to 5 days in SnO2 ternary device. This is thought to be due to the results of dramatic changes in electrical characteristics of SnO2 TFT for 5 days. Through this study, it is expected that area of the application will be expanded as applying it to the ternary logic circuit to improve the stability of the device.