First Demonstration of True 4-bit Memory with Record High Multibit Retention >10<sup>3</sup>s and Read Window >10<sup>5</sup> by Hydrogen Self-Adaptive-Doping for IGZO DRAM Arrays
Gangping Yan, Yanna Luo, Jianjian Wang, Zhiyu Song, Chuqiao Niu, Shangbo Yang, Guo‐Liang Tian, Jiaxin Yao, Xueli Ma, Qingzhu Zhang, Jinjuan Xiang, Na Zhou, Guilei Wang, Gaobo Xu, Zhenhua Wu, Jinshun Bi, Chao Zhao, Jun Luo, Huaxiang Yin
Abstract
For the first time, we demonstrate a true 4-bit memory with a large operation margin, as well as record-long multibit retention with the largest read window in IGZO-based 2T0C DRAM. It is enabled by a low-cost oxygen-compensated hydrogen self-adaptive-doping (OHAD) method with a new theory of H self-adaptive-doping. Due to the controllable compensation for defects and enhanced source/drain doping by the OHAD method, the reduced channel carrier scattering and contact resistance are both achieved. The best-in-class devices exhibit the V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> modulated to +0.23 V and the I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</inf> boosted to 35 μA/μm, along with the smallest performance variation of σ(V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> ) = 25 mV and σ/μ(I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</inf> ) = 4%. It yields a record-high memory window >10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> and ultra-long retention of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> s with the largest margin, capable of the first 16-level separated current memory states for realizing a true 4-bit 2T0C DRAM cell with record-long 1000-s retention time in multibit operation.