Characteristics and Applications of CAAC-IGZO FET with Gate Length of 13nm

A field-effect transistor (FET) using CAAC-IGZO, a crystalline oxide semiconductor having a c-axis alignment, is considered for application to various circuits. In particular, its extremely low off-state leakage current[1,2] enables design of non-volatile memory and analog memory devices[3], allowing AI tasks to be run in non-von-Neumann architectures. Furthermore, CAAC-IGZO FET can be applied to use cases other than memory, such as RF applications. CAAC-IGZO FET can be integrated in the back-end-of-line processes of CMOS technologies[4], and allows higher power supply voltages than conventional CMOS devices[4]. This may contribute to reduced chip area, which can create smaller packages, which are demanded for IoT endpoints. As there are not many applications that currently use scaled CAAC-IGZO FET, CAAC-IGZO FET is not yet applied to quasi-millimeter-wave applications. In addition, circuit design for high-frequency applications of CAAC-IGZO FETs will require extraction of FET characteristics that will be utilized in this application. Compact models are available for large IGZO FETs [5], but not for scaled CAAC-IGZO FETs. For this work, we have prototyped and evaluated scaled CAAC-IGZO FETs (Fig. 1(a)) that are suitable for high-frequency applications in addition to memory applications. From network measurements, it was found that the CAAC-IGZO FET exhibits a cutoff frequency of 60 GHz (Fig. 1(b)) and a maximum oscillation frequency of 16 GHz, which is promising for quasi-millimeter-wave designs. In addition, we have designed equivalent circuits of the scaled CAAC-IGZO FET using linear devices. This circuit shows not only the characteristics of the scaled CAAC-IGZO FET, but also the potential for circuit designs with the device. This work compiles the characteristics of the scaled CAAC-IGZO FET, and proposes a novel circuit application for the device. Fig. 1 (a) L-direction cross section of the scaled CAAC-IGZO FET. (b) Network measurment result of the scaled CAAC-IGZO FET References [1] N. Kimizuka and S. Yamazaki, “Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO FUNDAMENTALS,” WILEY, 2017. [2] S. Yamazaki and M. Fujita, “Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO Application to LSI,” WILEY, 2017. [3] Y. Kurokawa et al., JJAP, vol. 59, pp. (SGGB03-1)-(SGGB03-11), 2020. [4] H. Kunitake et al., J-EDS, vol. 7, pp.495-502, 2019. [5] L. J. Giacoletto et al., JSSC, vol. 4, issue 2, pp.80-83, 1969. Figure 1