Lookup NU author(s): Dr Noushin Moharrami,
Dr Adrian Oila,
Professor Steve Bull
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The thickness of the copper coatings that are used for the manufacture of conducting tracks in microelectronic devices are being aggressively scaled down and there is a need to monitor the mechanical response of metallization at a scale comparable to the material microstructure. When using indentation tests to assess the properties of thin films, the plastic zone dimensions are of a similar scale to the grain size. For the purposes of designs based on continuum mechanics approaches it is usually required that the grain size is much smaller than the deforming volume, which is not always observed in practice. Considerable differences between predicted and observed performance can be seen depending on the material tested and its grain size; the extent of oxidation of the copper after deposition is critical, as is that of its underlying silicon substrate. Whereas it is possible to make good measurements of metallization properties on stiff substrates such as silicon there are serious issues with the reliability of Young's modulus and hardness data from coatings on device quality wafers which may have been oxidized prior to use. The effects of grain size, shape and orientation on the mechanical response of metallic thin films used for semiconductor metallization on oxidized silicon are presented in this paper. The appropriate conditions for the successful use of continuum mechanics are discussed and the importance of considering the consequences of crystallographic anisotropy and oxidation on the selection of suitable design data is presented with regards to copper coatings.
Author(s): Moharrami N, Oila A, Bull SJ
Publication type: Article
Publication status: Published
Journal: Journal of Physics D: Applied Physics
Print publication date: 06/08/2014
Online publication date: 11/07/2014
Acceptance date: 12/06/2014
ISSN (print): 0022-3727
ISSN (electronic): 1361-6463
Publisher: Institute of Physics Publishing Ltd
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