Effect of the duty ratio of line and space in phase‐shifting lithography
作者:
J. Miyazaki,
A. Yamaguchi,
K. Fujiwara,
N. Yoshioka,
H. Morimoto,
K. Tsukamoto,
期刊:
Journal of Vacuum Science&Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena
(AIP Available online 1995)
卷期:
Volume 13,
issue 1
页码: 137-141
ISSN:1071-1023
年代: 1995
DOI:10.1116/1.587971
出版商: American Vacuum Society
关键词: MEMORY DEVICES;INTEGRATED CIRCUITS;LITHOGRAPHY;PHOTORESISTS;PHASE SHIFT;SPATIAL RESOLUTION;DENSITY;IMAGE FORMING;MASKING
数据来源: AIP
摘要:
This article discusses the impact of the line and space duty ratio and optical coherence on image quality fori‐line projection systems used in conjunction with alternated type phase shifters on projection masks. With a negative process, it was found that the alternated phase‐shifting method improve the depth of focus (DOF) for space patterns with a width smaller than the linewidth. On the contrary, there was no effect for narrow line patterns when the space width was larger than twice the linewidth. It was also found that the DOF became larger when the coherence became higher using both the alternated and the conventional mask for line patterns with a width smaller than the space width. It is concluded that high degree of optical coherence must be chosen for the phase‐shifting method. The alternated phase‐shifting method was applied to a bit line layer of 64 Mbit DRAM, and a DOF of 1.2 μm was obtained for both memory cells and peripheral patterns in which the minimum feature size is 0.35 μm. It is suggested that a negativei‐line resist with a large focus latitude at a high degree of optical coherence will be indispensable in applying phase‐shifting lithography to device fabrication.
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