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Lookup NU author(s): Christopher Wilson,
Dr Alton Horsfall,
Professor Anthony O'Neill
This is the final published version of an article that has been published in its final definitive form by American Institute of Physics, 2009.
For re-use rights please refer to the publisher's terms and conditions.
The stress of Cu/low-k interconnects with linewidths scaled to 50 nm was determined using precision lattice parameter measurement at an advanced light facility. Grazing incidence and theta-2 theta diffraction geometries were used to gain a direct measurement of the strain tensor, showing an increase in stress as the linewidth is reduced an order of magnitude from 500 to 50 nm. This increase in stress contrasts existing predictions of finite element simulations, which predict a decrease in stress as the line aspect ratio increases above one. Our simulations, considering the low-k stack, have shown this decrease should occur at lower aspect ratios; however, neither trend is reflected in the measured data. All of the lines showed a strong  texture suggesting their stiffness was not affected at the scaled dimensions. The narrower lines show a more bamboolike structure compared to a more polycrystalline structure in the wider lines. In the narrow lines, the grains become pinned in the linewidth reducing stress relaxation through grain growth or reorder. This leads to the observed increase in stress with linewidth scaling and the increase in stress for bamboo lines during fabrication. This work demonstrates the grain structure of interconnects has a significant effect on stress and stress evolution.
Author(s): Wilson CJ, Croes K, Zhao C, Metzger TH, Zhao L, Beyer GP, Horsfall AB, O'Neill AG, Tokei Z
Publication type: Article
Publication status: Published
Journal: Journal of Applied Physics
Date deposited: 15/09/2016
ISSN (print): 0021-8979
ISSN (electronic): 1520-8850
Publisher: American Institute of Physics
Notes: Article no. 053524
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