Analysis of Carrier Behavior for Amorphous Indium Gallium Zinc Oxide After Supercritical Carbon Dioxide Treatment

Abstract

Researchers have made various attempts to improve the sputtering a-IGZO films. [2] However, the structural defects induced by the sputtering process often lead to inferior performance and stability for a-IGZO devices, especially under voltage stress. [9] Poor-quality of a-IGZO film has hindered the development of commercial applications for a-IGZO thin film transistor (TFT)based electronics. [10][11][12] Many post-treatments such as annealing, [13] microwave irradiation, [14] plasma treatment, [15][16][17] and supercritical carbon dioxide fluid (SCCO 2 ) treatment [18,19] have been implemented to improve a-IGZO film quality. Compared with other methods, SCCO 2 method is more promising due to its low-temperature process, nondestructive property, ability to remove organic impurities, and restorability from bending. Earlier work [18] has studied the enhancing effect of this treatment on flexible a-IGZO devices. To gain maximum advantage of such technique, an understanding of the carrier mechanism beyond the performance enhancement is important. From oxygen vacancy (V o ) theory, two kinds of V o could exist in the a-IGZO film, namely traps and carriers. [20] The independent analysis for carrier-type V o and trap-type V o has not been verified in detail. Furthermore, the carrier transport mechanism of the post-treated a-IGZO film has not been fully understood yet. These are critical to understand the a-IGZO and realize high-performance devices and circuits based on metal oxide semiconductors.In this work, we design a-IGZO TFTs with different channel thicknesses and treat them using SCCO 2 process to investigate the detailed mechanism of the carrier behavior inside the a-IGZO layer. By comparing the performances of different devices, we analyze the carrier density and transport in a-IGZO. In addition to the traditional X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) characterization, new techniques including Technology Computer Aided Design (TCAD) simulation, layer-by-layer XPS, and sheet resistance measurement are adopted in TFTs for the first time to verify the more accurate carrier mechanism.Amorphous indium gallium zinc oxide (a-IGZO) thin-film quality can be enhanced using supercritical carbon dioxide (SCCO 2 ). How to verify specific and accurate mechanism for the carriers inside an a-IGZO layer before and after the SCCO 2 treatment is worth investigating. This work designs a-IGZO thin film transistors with different channel thicknesses (41, 28, and 19 nm), treats them using SCCO 2 , and analyzes the change in carrier behavior. The effect of the SCCO 2 on both carrier density and carrier transport is investigated using energy band information, Technology Computer Aided Design (TCAD) simulations on density of states and resistance analyses. After the treatment, the thinner channel thickness exhibits better drivability enhancement. That is because of the fewer traps and smoother carrier transportation path resulted from better M−O−M frameworks, and decreased M−OH bonds as ...

Ultra‐Flexible Monolithic 3D Complementary Metal‐Oxide‐Semiconductor Electronics

“…(The characteristics and working mechanisms of individual photonic and synaptic transistor are illustrated in Section 8, Supporting Information). The bandgap of the a‐IGZO layer is ≈3.10 eV, which was obtained by UV photoelectron spectroscopy (Figure S9a, Supporting Information) with a similar method described in a previous work [ 38 ] indicating the sensitivity to blue light of this system. The current of the a‐IGZO transistor increases with the increase in time or power of the blue light radiation (Figure S9b,c, Supporting Information), due to the increase in photo‐induced carriers.…”