Single crystalline In–Ga–Zn oxide films grown from c-axis aligned crystalline materials and their transistor characteristics

Abstract

In this study, we analyzed the crystallinity of c-axis aligned crystalline In–Ga–Zn oxide (CAAC-IGZO) and single crystalline (sc) IGZO films. CAAC-IGZO films were formed on (111)-oriented yttria-stabilized-zirconia substrates by magnetron sputtering using a target. Sc-IGZO films were obtained by annealing CAAC-IGZO films at 1200 °C. The proportion of Zn in the composition changed during growth of the films, and as a result, sc-InGaO3(ZnO)3 films were obtained. By using CAAC-IGZO films as the starting material, sc-IGZO films were formed even without a ZnO layer. This is presumably because the CAAC-IGZO film originally exhibits c-axis orientation. In addition, the characteristics of transistors fabricated using sc-IGZO and CAAC-IGZO films were compared, and no significant difference in current drivability, i.e., field-effect mobility, was observed between the different transistors. In this sense, CAAC-IGZO films that require no high temperature annealing are favorable for industrialization.

Crystalline IGZO ceramics (crystalline oxide semiconductor)–based devices for artificial intelligence

“…Dr. Noboru Kimizuka, who first synthesized single‐crystalline IGZO, indicated that the crystal morphology of CAAC and nanocrystal (nc) should be classified as an intermediate state that is neither an amorphous structure nor a crystal structure. Similarly, Dr. Yoshio Waseda mentioned that CAAC and nc should be put in the category of a novel boundary region …”

“…18,19 CAAC-IGZO is a crystalline phase that has a structure in the boundary region between an amorphous structure and a crystal structure, including single crystal and polycrystal. [20][21][22][23][24][25] Dr. Noboru Kimizuka, who first synthesized single-crystalline IGZO, 1,2,26 indicated that the crystal morphology of CAAC 21 and nanocrystal (nc) [22][23][24] should be classified as an intermediate state that is neither an amorphous structure nor a crystal structure. Similarly, Dr. Yoshio Waseda mentioned that CAAC and nc should be put in the category of a novel boundary region.…”

“…A CAAC-IGZO film does not have clear grain boundaries, and our study revealed little difference in mobility between a single-crystalline IGZO FET and an OSFET. 26 In addition, the CAAC-IGZO can be formed easily by sputtering at low costs; thus, it is highly suitable for mass production. Figure 4 shows the crystal structure of InGaZnO 4 .…”

P‐13: The Relationship Between Crystallinity and Device Characteristics of In‐Sn‐Zn‐Oxide

“…In addition, because of the durability of the CAAC-IGZO to etching gas, it is possible to adopt a channel-etch process [6]. Furthermore, the CAAC-IGZO can be formed on a glass substrate at a relatively low temperature, under 500 ºC, unlike the case of single crystal IGZO [7][8] requiring high temperature, 1200 ºC or higher. Now using these CAAC-IGZO FETs as a backplane, LCD panels have been mass produced [9].…”

Reflective liquid crystal display without flicker for reducing eye strain

“…Indium‐gallium‐zinc oxide (IGZO) can be given as one of the OS . The formation of a CAAC‐OS thin film over a glass substrate requires annealing at less than or equal to 500 °C . We succeeded in forming a channel‐etched OS field‐effect transistor (FET) that uses a CAAC‐IGZO for an active layer and has improved characteristics and improved reliability by lowering the defect levels …”