Title :
Reduction of shorts between word lines on charge-trapping flash cell in a self-aligned double patterning technology
Author :
Lee, Hong-Ji ; Wei, Kuo-Liang ; Lian, Nan-Tzu ; Yang, Tahone ; Chen, Kuang-Chao ; Lu, Chih-Yuan
Author_Institution :
Technol. Dev. Center, Macronix Int. Co., Ltd., Hsinchu, Taiwan
Abstract :
This paper presents a unique gate structure for reducing shorts between word lines on charge-trapping flash cell memory. In the early stage of developing sub-45 nm half-pitch word line by a self-aligned double patterning (SADP) technology, the cell array suffered from abnormal intrinsic word line-to-word line shorts, ca. 96.3% of the bridge rate on the 72 Mb cell memory, due to the formation of polysilicon residues called stringers. The increase of polysilicon over-etching to eliminate stringers involves a trade-off between the removal efficiency of stringers and the feature size maintenance. Hence, a novel bottle-shaped gate profile was tailor-made and studied. As a result, the bridge rates are dramatically suppressed to 0%~10% on the low-density flash cells and ca. 22% in average on the high-density 512 Mb flash cell memory. The novel bottle-shaped gate structure is successfully implemented in advanced charge-trapping flash memory development.
Keywords :
etching; flash memories; bottle-shaped gate profile; cell array; charge-trapping flash cell memory; low-density flash cells; polysilicon over-etching; polysilicon residues; self-aligned double patterning technology; stringers; unique gate structure; word lines; Arrays; Bridges; Etching; Films; Flash memory; Logic gates; Resists;
Conference_Titel :
Advanced Semiconductor Manufacturing Conference (ASMC), 2010 IEEE/SEMI
Conference_Location :
San Francisco, CA
Print_ISBN :
978-1-4244-6517-0
DOI :
10.1109/ASMC.2010.5551427