Direct measurement of intrinsic critical strain and internal strain in barrier films

Abstract

Resistance measurements during uniaxial tensile deformation of very thin (10 nm) conducting oxide films deposited on 150 nm SiN films on polyethylene naphthalate are discussed. It is first shown that certain characteristics of resistance versus strain curves are representative for the fracture behavior of the SiN film and not for that of the thin conducting oxide film. Subsequently, it is shown that the hysteresis in curves of resistance as a function of strain offers a way to directly measure the intrinsic critical strain of the SiN film without the need to determine internal strains from independent (curvature) measurements that rely on knowledge of moduli and geometry. The method should be applicable, in general, to measure intrinsic critical strain and residual strains of thin brittle films on polymers. Advantages and limitations of the method are discussed.

Subcritical crack growth in SiNx thin-film barriers studied by electro-mechanical two-point bending

“…(16). These values, also shown in Table I, match excellently with the values m 0 1 extracted from the sets of data in Table II.…”

“…The internal strain in this case is 0.47% 6 0.02%. Vellinga et al 16 performed tensile tests on another batch of the same barrierpolymer combination and found an internal compressive strain of 0.45% 6 0.05% in the barrier, which is very close to the value here.…”

“…Therefore, the expectation is that the internal strain in the SiN x film is not significantly influenced by the deposition of ITO layer. Last but not least, the energy release rate in the fracture of SiN x layer will not change by adding the ITO layer on top, as has been addressed in the paper from Vellinga et al 16 All in all, the 10 nm ITO layer has proved to be an effective probe to monitor the fracture failure of the SiN x layer beneath.…”

“…First, the observed critical failure strain 16 of this 10 nm ITO film is around 1.5%, which is much higher than that of the SiN x film (from 0.7% to 0.8%). Second, in the manufacturing of this polymer-SiN x -ITO structure, the highest temperature is reached during the deposition of the SiN x layer, which is the main cause of the internal strain in the structure.…”

“…However, the electrical resistance measurement restrains the observation to conductive films. To detect mechanical failure of dielectric layers, a conducting layer such as amorphous graphite, 6 ITO, 16 or ITO-Ag 17 is sputtered or deposited as an electrical probe. The influence of various electrical probes on the internal strain in the multilayers and the accuracy of the crack onset strain observation have also been investigated.…”