Thermo-Mechanical Failure Criterion at the Micron Scale in Electronic Devices

Author： Yosibash Z. Adan O. Schneck R. Atlas H.

ISSN： 0376-9429

Source： International Journal of Fracture, Vol.122, Iss.1-2, 2003-07, pp. : 47-64

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Abstract

Thermo-mechanical failures may occur in the passivation layer of micro-electronic devices during the fabrication process. These are in form of cracks which initiate at keyhole corners. In order to predict and eventually prevent these cracks a failure criterion is presented, based on an average value of the elastic strain energy in the vicinity of a reentrant corner of any angle. The proposed strain energy density (SED) failure criterion is validated by a test including 24 full size wafers which have been fabricated with different parameters: the interconnects (metal lines) height, the passivation thickness, and the passivating plasma power which was shown to correlate with the mechanical properties of the passivation layer. For each wafer, a FE model has been constructed, and the SED computed. It has been clearly shown, that above the critical value of SED_cr[R=0.15μm]≍1000 [J/m³], all wafers manufactured were cracked. The SED criterion seems to correlate well with the empirical observations, and may be used as a standard tool for the mechanical design of failure free micro-electronic devices.