Baek In-Hwan, Pyeon Jung Joon, Han Seong Ho, Lee Ga-Yeon, Choi Byung Joon, Han Jeong Hwan, Chung Taek-Mo, Hwang Cheol Seong, Kim Seong Keun
Center for Electronic Materials , Korea Institute of Science and Technology , Seoul 02792 , South Korea.
Department of Materials Science and Engineering and Inter-University Semiconductor Research Center , Seoul National University , Seoul 08826 , South Korea.
ACS Appl Mater Interfaces. 2019 Apr 24;11(16):14892-14901. doi: 10.1021/acsami.9b03331. Epub 2019 Apr 15.
A new deposition technique is required to grow the active oxide semiconductor layer for emerging oxide electronics beyond the conventional sputtering technique. Atomic layer deposition (ALD) has the benefits of versatile composition control, low defect density in films, and conformal growth over a complex structure, which can hardly be obtained with sputtering. This study demonstrates the feasibility of growing amorphous In-Zn-Sn-O (a-IZTO) through ALD for oxide thin-film transistor (TFT) applications. In the ALD of the a-IZTO film, the growth behavior indicates that there exists a growth correlation between the precursor molecules and the film surface where the ALD reaction occurs. This provides a detailed understanding of the ALD process that is required for precise composition control. The a-IZTO film with In/Zn/Sn = 10:70:20 was chosen for high-performance TFTs, among other compositions, regarding the field-effect mobility (μ), turn-on voltage ( V), and subthreshold swing (SS) voltage. The optimized TFT device with the a-IZTO film thickness of 8 nm revealed a high performance with a μ of 22 cm V s, V of 0.8 V, and SS of 0.15 V dec after annealing at 400 °C for 30 min. Furthermore, an emerging device such as a vertical channel TFT was demonstrated. Thus, the a-IZTO ALD process could offer promising opportunities for a variety of emerging oxide electronics beyond planar TFTs.
对于新兴的氧化物电子学而言，除了传统的溅射技术外，还需要一种新的沉积技术来生长有源氧化物半导体层。原子层沉积（ALD）具有成分控制灵活、薄膜缺陷密度低以及能在复杂结构上实现保形生长等优点，而这些优点是溅射技术难以获得的。本研究证明了通过ALD生长非晶铟锌锡氧化物（a-IZTO）用于氧化物薄膜晶体管（TFT）应用的可行性。在a-IZTO薄膜的ALD过程中，生长行为表明前驱体分子与发生ALD反应的薄膜表面之间存在生长相关性。这为精确控制成分所需的ALD过程提供了详细的理解。在其他成分中，就场效应迁移率（μ）、开启电压（V）和亚阈值摆幅（SS）电压而言，具有In/Zn/Sn = 10:70:20的a-IZTO薄膜被选用于高性能TFT。优化后的a-IZTO薄膜厚度为8 nm的TFT器件在400°C下退火30分钟后，表现出高性能，μ为22 cm² V⁻¹ s⁻¹，V为0.8 V，SS为0.15 V dec⁻¹。此外，还展示了一种新兴器件，如垂直沟道TFT。因此，a-IZTO的ALD工艺可为平面TFT之外的各种新兴氧化物电子学提供有前景的机会。
