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

Abstract

In 2009, a crystalline oxide semiconductor with a layered structure, which we refer to as c‐axis–aligned crystalline indium‐gallium‐zinc oxide (CAAC‐IGZO), was first discovered. CAAC‐IGZO has a peculiar crystal structure in which clear grain boundaries are not observed despite high c‐axis alignment and absence of a‐b plane alignment. When compared to a Si field‐effect transistor (FET), a metal‐oxide‐semiconductor (MOS) FET, utilizing CAAC‐IGZO, presents lower off‐state current (on the order of yA [10−24 A]). These unique characteristics allow CAAC‐IGZO to realize devices with low power consumption. With the emerging era of artificial intelligence, wherein power saving becomes more significant, CAAC‐IGZO has attracted attention as a potential replacement for Si. This paper describes the characteristics and potentials of CAAC‐IGZO for the development of memory devices with unprecedented functions.

High-Performance Thin-Film Transistors with an Atomic-Layer-Deposited Indium Gallium Oxide Channel: A Cation Combinatorial Approach

“…In this regard, the IGZO with c -axis preferential orientation is an interesting material, which is known as c -axis-aligned crystalline (CAAC)-IGZO. Though the CAAC IGZO is not an amorphous phase, the thin-film transistors (TFTs) with a CAAC-IGZO channel layer exhibits the excellent threshold voltage ( V TH ) uniformity in the resulting thin-film transistors . The standard deviation (1σ) of ∼35 mV for the CAAC-IGZO with a gate length of 40 nm is comparable to that of the current Si metal–oxide–semiconductor field-effect transistor (MOSFET).…”

Recent progress of the single crystal growth of homologous (InGaO3)m(ZnO)n

“…Films with thicknesses 100–300 nm were fabricated on quartz substrates by the sputtering method. 9,10,42–44 A polycrystalline substance with In, Ga, and Zn at an atomic ratio of 1 : 1 : 1 was used as the target. The conditions for dc-magnetron sputtering were as follows: the deposition power density was 0.87 W cm −1 and the deposition pressure was 0.4 Pa with a O 2 /(Ar + O 2 ) gas flow rate of 0.33.…”

Deposition, Characterization, and Performance of Spinel InGaZnO4

“…24 Modeling anomalous X-ray scattering showed a preserved middle range order originating from the InO x planes aligned parallel to GaZnO y slabs. 25,26 The remaining periodicity along the c-axis resembles the hexagonal structure of monocrystalline IGZO.…”

“…1 In particular, the absence of mobile holes leads to extremely low off-currents (I off ) in junction-free field-effect transistors, 2 enabling long charge retention times in optical display systems as well as dynamic random-access memory (DRAM) cells. 3 Since the first applications in transparent thin-film transistors (TFTs), the performance of IGZO channels is correlated with their different morphologies: crystalline and amorphous. The amorphous phase is beneficial due to its low deposition temperature and the preservation of relatively high electron mobility compared to the crystalline material.…”

“…Oxides of the In–Ga–Zn family (IGZO) gained a lot of interest as high band gap semiconductors and are applied as channels in thin-film devices . In particular, the absence of mobile holes leads to extremely low off-currents ( I off ) in junction-free field-effect transistors, enabling long charge retention times in optical display systems as well as dynamic random-access memory (DRAM) cells . Since the first applications in transparent thin-film transistors (TFTs), the performance of IGZO channels is correlated with their different morphologies: crystalline and amorphous.…”