Oxide-Semiconductor Channel Transistor DRAM (OCTRAM) with 4F2 Architecture
Shosuke Fujii, Tsung Che Lu, Keiji Ikeda, Szu Yao Chang, Kei Sakamoto, Li‐Chuan Chung, Mutsumi Okajima, Jhen-Yu Tsai, Toshifumi Kuroda, Chung Peng Hao, Shinji Miyano, Peng Mei, Kimitoshi Okano, Martin Sillero, Akihiro Kajita, Chung Lin Huang, T. Fujimaki, Chiang-Lin Shih
Abstract
We successfully demonstrated the world's first 4F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> gate-all-around oxide-semiconductor channel transistor DRAM (OCTRAM). In this structure, a high-performance gate-all-around InGaZnO vertical channel transistor (InGaZnO VCT) was integrated on top of an advanced high aspect ratio capacitor. The InGaZnO VCT achieved a high ON current of over <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15\mu \mathrm{A}/\text{cell}$</tex> and ultra-low leakage below laA/cell simultaneously. This performance was maintained even after BEOL processing. A 275Mbit OCTRAM array was fabricated with WL 54nm/BL 63nm pitches and showed successful DRAM operation in the designed voltage range, making it a breakthrough technology for future high density 4F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>DRAM.