R&D: Improvement of Warpage and Leakage for 3D NAND Flash Memory

Materials Science in Semiconductor Processing has published an article written by Kun Zhang, Wenxi Zhou, School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, 430074, China, Tuo Li, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China, Sicong Wang, School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, 430074, China, Xiaomin Cheng, School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, 430074, China, Zhiliang Xia, University of Chinese Academy of Sciences, Beijing, 100049, China, and Xiangshui Miao, School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, 430074, China.

Abstract: “GLS (Gate line split) filling is a very important process in 3D NAND flash memory (3D NAND) fabrication. Filling materials in the GLS should have threefold properties, such as warpage tunability, leakage-free and low resistance. In this paper, the effects of different GLS filling materials (SiO₂, W, amorphous silicon: A-Si) on F-attack, warpage and resistance were studied. GLS filled with A-Si shows best performance on warpage and F-attack. For 3D NAND, the number of stacked layers is predicted as a function of the wafer warpage, and the wafer warpage difference between GLS filled with A-Si and W was compared. With the same number of stacking layers, the wafer warpage post GLS filled with A-Si is smaller than that filled with W. Meanwhile, A-Si is produced by the decomposition of SiH₄ by low pressure chemical vapor deposition (LPCVD) process, F-related by-product in the GLS filling material and consequent ACS (array common source) to WL (Word line) leakage by F-attack are avoided. A-Si is the best choice for GLS filling. This work provides an efficient method to solve the warpage and leakage problem in 3D NAND flash memory fabrication.“