The use of Cu decoration, followed by transmission electron microscopy, was proposed for the identification of defects in thermal oxides on poly-Si films. The method used Cu decoration to reveal the location of defects in the oxide, plus sample-thinning for transmission electron microscopic observation. It was noted that the advantage of Cu decoration was that the electronic current which was required for defect detection was so small that it did not change the original oxide defect structure. The transmission electron microscopic and scanning electron microscopic observations revealed that the defects were polygonal voids which were located on the poly-Si grain boundaries. The diameter of the voids was typically 70nm. Stress-induced migration of Si atoms along grain boundaries was thought to be implicated in the formation of the voids.

M.Itsumi, H.Akiya, M.Tomita, T.Ueki, M.Yamawaki: Journal of the Electrochemical Society, 1997, 144[2], 600-4