3D NAND闪存中TiN与氧化表面F吸附作用的第一性原理研究  

First-principles study of F adsorption by TiN with its oxide surface in three-dimensional NAND flash memory

作　　者：方语萱 杨益 夏志良 霍宗亮 Fang Yu-Xuan;Yang Yi;Xia Zhi-Liang;Huo Zong-Liang(Institute of Microelectronics,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 101408,China;Yangtze Memory Technologies Co.,Ltd.,Wuhan 430071,China;Yangtze Advanced Memory Industry Innovation Center Co.,Ltd.,Wuhan 430014,China)

机构地区：[1]中国科学院微电子研究所,北京100029 [2]中国科学院大学,北京101408 [3]长江存储科技有限责任公司,武汉430071 [4]长江先进存储产业创新中心有限责任公司,武汉430014

出　　处：《物理学报》2024年第12期385-392,共8页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2023YFB4402500)资助的课题。

摘　　要：随着3D NAND技术的发展,存储阵列工艺的堆叠层数越来越高,后栅工艺中金属钨(W)栅字线(WL)层填充的工艺也面临越来越严峻的挑战.钨栅沉积工艺中的主要挑战在于氟攻击问题,钨栅填充时产生的空洞导致了含氟(F)副产物的积聚,并在后续高温制程的激发下,扩散侵蚀其周边氧化物层,致使字线漏电,严重影响器件的良率及可靠性.为改善氟攻击问题,通常在钨栅沉积之前再沉积一层薄的氮化钛作为阻挡层.然而在对栅极叠层组分分析中发现,F元素聚集在TiN薄膜表面,并且难以通过退火排出.本文采用第一性原理计算,研究了TiN薄膜表面吸附含F物种的情况,提出TiN的表面氧化能加剧对含F物种的吸附作用,仿真结果指导了栅极工艺过程的优化方向.基于第一性原理计算结果,提出氨气吹扫表面处理方法,有效改善了3D NAND中的氟攻击问题,将字线漏电率降低25%,晶圆翘曲度降低43%.Three-dimensional(3D)NAND flash memory is a key technology in the field of mainstream memory solutions,which is primarily due to its extremely low bit cost.The architecture of 3D NAND,characterized by its vertically stacked design,substantially enhances the capacity of individual chips.This advancement is completely consistent with the demands for high-capacity data storage in contemporary environments,securing its widespread adoption in diverse application scenarios.As storage density increases,the complexity of process integration increases,bringing new challenges.The word lines in 3D NAND are typically filled by using gate replacement techniques,and compared with chemical vapor deposition(CVD),atomic layer deposition(ALD)is favored for its superior step-coverage,especially for depositing tungsten(W)at the gate.However,due to the complexity of the replacement gate deposition structure,fluorine(F)residues are found in the voids of the tungsten metal gate filling structure and diffuse into the surrounding structure under subsequent process conditions,corroding other films such as silicon oxide and degrading device performance and reliability.To alleviate the problem of fluorine attack,a thin layer of titanium nitride is usually deposited as a barrier layer before deposition of tungsten gate,which blocks the fluorine in the tungsten gate and prevents its diffusion into the oxide layer.Previously,there were studies to increase the ability to stop F diffusion by varying the thickness of the F blocking layer(TiN).However,increasing the thickness of TiN will further increase the complexity of high aspect ratio etching in the 3D NAND process,which will have adverse effect on subsequent processes.To further minimize the effect of fluorine erosion,residual fluorine elements can be removed by introducing annealing in the subsequent process flow.In the actual 3D NAND process,elemental fluorine(F)is adsorbed and accumulates on the TiN surface,and is further activated by subsequent high-temperature processes,leading to sever

关 键 词：3D NAND闪存 氟攻击问题 第一性原理 

分 类 号：O469[理学—凝聚态物理] TP333[理学—电子物理学]