(Invited) Display and LSI Applications of Oxide Semiconductor LSIs (OS LSIs) Using Crystalline In–Ga–Zn Oxide (IGZO): Applications Related to Coronavirus COVID-19 Pandemic
Authors: Onuki Tatsuya , Okamoto Yuki , Aoki Takeshi , Matsuzaki Takanori , Kozuma Munehiro , Kunitake Hitoshi , Motoyoshi Ryosuke , Kimura Hajime , Yamane Yasumasa , Sasagawa Shinya , Yamazaki Shunpei 
Published: December 2020

The coronavirus COVID-19 pandemic is becoming a global crisis in 2020. Global climate change is an indirect cause of the spread of infectious diseases [1]. The increase in greenhouse gas as a result of increased power consumption has an adverse effect on this climate change. The amount of power consumption continues to increase as human society advances, and Japan Science and Technology Agency’s report says that global and Japan’s annual power consumption concerning IT equipment in 2050 will be nearly 200 times as large as the present global and Japan’s total annual power consumption.” [2]. This means that one of the main causes of the global climate change would be the increase in the amount of power consumption through the spread of fast-growing Internet of Things (IoT) and artificial intelligence (AI) technologies.

An anwer to the question of how to reduce power consumption and defend against infectious diseases that may threaten human beings while developing the IoT and AI technologies is to reduce the power consumption of semiconductor devices intensely and reduce the power consumption concerning IT equipment to 1/1000 of the present power consumption.

A field-effect transistor (FET) fabricated using a c-axis aligned crystalline In–Ga–Zn oxide (CAAC-IGZO), which is a typical example of crystalline oxide semiconductor (OS) ceramics, exhibits an off-state current I
off in the order of yA/mm (10-
24 A/mm) at 85°C [3,4]. The FET we developed is a FinFET with a trench-gate self-aligned (TGSA) structure [5].

As shown in the figure, the upper limit of operation efficiency of AI accelerators fabricated using Si LSIs is 10 TOPS/W, whereas normally-off CPUs [6,7] and AI accelerators fabricated using CAAC-IGZO could achieve an operation efficiency of 100 TOPS/W (8 bits) or 1 POPS/W (1 bit). If this technology is adopted in all VLSI devices and supercomputers, reducing the power consumption of those devices by 1000 times will come closer to reality even in the AI/IoT era. Therefore, we believe that the use of the CAAC-IGZO technology is the only solution to the global climate change.

OS LSIs are applicable to all kinds of displays including displays for augmented reality and virtual reality, dynamic random access memories, and 3D OS NANDs (3D NANDs fabricated using IGZO). This work introduces crystalline IGZO ceramics, which would be a future key technology, and LSI and display applications of LSI of the crystalline IGZO ceramics.

References

[1] Ministry of the Environment, Government of Japan, “Global Warming and Infectious Diseases: What we know now?,” 2007 [published in Japanese].

https://www.env.go.jp/earth/ondanka/pamph_infection/full.pdf

[2] Center for Low Carbon Society Strategy, Japan Science and Technology Agency, “Impact of Progress of Information Society on Energy Consumption (Vol.1),” 2019 [published in Japanese].

https://www.jst.go.jp/lcs/pdf/fy2018-pp-15.pdf

[3] S. Yamazaki, “Challenge of crystalline IGZO ceramics to silicon LSI,” speech at Science Seminar 2018 held by Japan-Sweden Foundation at Embassy of Sweden, Alfred Nobel Auditorium on November 26, 2018.

[4] “Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO: Fundamentals,” John Wiley & Sons, 2017.

[5] H. Kunitake et al., IEDM Technical Digest, pp. 312–315, 2018.

[6] “Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO: Application to LSI”, John Wiley & Sons, 2017.

[7] T. Ishizu et al., SSC-L, vol. 2, no. 12, pp. 293–296, 2019.

Figure 1