Liu Fei, Sneck Asko, Eskelinen Patrik, Halonen Olli, Gillan Liam, Leppäniemi Jaakko
VTT Technical Research Centre of Finland Ltd, Espoo 02150, Finland.
ACS Appl Mater Interfaces. 2025 Jun 11;17(23):34150-34160. doi: 10.1021/acsami.5c03321. Epub 2025 Jun 3.
Zinc oxide (ZnO) is a benign and earth-abundant semiconductor material that has been applied in thin-film transistors (TFTs) for decades and can be used in biodegradable, transient, and biocompatible devices. Printing as an alternative fabrication method to conventional TFT manufacturing methods can deliver some benefits, such as simultaneous film deposition and patterning, good scalability, low cost, and material-saving features. However, the high annealing temperature needed for ink-to-metal oxide conversion and film densification, compounded by the poor patterning resolution of conventional printing methods, still limits the use of printing in the fabrication of flexible metal oxide TFTs. Atomic layer deposition (ALD) has recently emerged as a promising fabrication method for high-performance metal oxide TFTs that can offer more conformal film growth, precise film thickness, and higher film quality at low temperatures compared to sputtering, spin coating, or printing. Although ALD-based ZnO TFTs patterned with photolithography exhibit good electrical properties, they cannot be readily scaled to a high-throughput fabrication. Very little attention has been paid so far to the combination of low-temperature ALD growth with printing to obtain more scalable manufacturing of high-performance thin-film electronics. To overcome this challenge, we propose high-resolution reverse-offset printing (ROP) of a simple polymer resist to pattern an ALD-grown ZnO film at few μm resolution to fabricate TFTs. In this work, we report high-performance ZnO TFTs that are ALD-grown at a low temperature of 150 °C and ROP-patterned with promising stability and uniformity, a high field-effect mobility (μ) of ∼16.6 cm (Vs), an almost zero turn-on voltage () of ∼-0.49 V, a high current on-off ratio (/) of >10, a low operation voltage () of ≤5 V, and a negligible hysteresis () of ∼0.13 V. The combination of ALD and the ROP-patterning process could be developed further to fabricate fully flexible high-resolution metal oxide TFT-based circuits in the future.
氧化锌（ZnO）是一种性质温和且储量丰富的半导体材料，几十年来一直应用于薄膜晶体管（TFT）中，可用于制造可生物降解、瞬态和生物相容的器件。与传统TFT制造方法相比，印刷作为一种替代制造方法具有一些优势，例如可同时进行薄膜沉积和图案化、良好的可扩展性、低成本以及节省材料的特点。然而，油墨到金属氧化物转化和薄膜致密化所需的高退火温度，再加上传统印刷方法较差的图案化分辨率，仍然限制了印刷在柔性金属氧化物TFT制造中的应用。原子层沉积（ALD）最近已成为一种有前景的高性能金属氧化物TFT制造方法，与溅射、旋涂或印刷相比，它可以在低温下提供更均匀的薄膜生长、精确的薄膜厚度和更高的薄膜质量。尽管基于光刻图案化的ALD ZnO TFT表现出良好的电学性能，但它们不易扩展到高通量制造。到目前为止，很少有人关注低温ALD生长与印刷相结合以实现高性能薄膜电子产品更具可扩展性的制造。为了克服这一挑战，我们提出了一种简单聚合物抗蚀剂的高分辨率反向偏移印刷（ROP），以在几微米分辨率下对ALD生长的ZnO薄膜进行图案化，从而制造TFT。在这项工作中，我们报道了在150℃低温下通过ALD生长并经ROP图案化的高性能ZnO TFT，其具有良好的稳定性和均匀性，场效应迁移率（μ）高达约16.6 cm²/（V·s），开启电压（Vth）几乎为零，约为 -0.49 V，电流开/关比（Ion/Ioff）大于10，工作电压（Vdd）低至≤5 V，滞后现象（Vh）可忽略不计，约为0.13 V。ALD和ROP图案化工艺的结合未来可能会进一步发展，以制造出完全柔性的基于高分辨率金属氧化物TFT的电路。
