An accurate discrimination method of gate oxide breakdown positions by a new test structure of MOS capacitors

A new structure of MOS capacitors for discrimination of gate oxide breakdown positions is proposed. The characteristic of this test structure is that Al marks to discriminate the positions are lined up diagonally. Oxide breakdown spots determined by using the test structure are investigated by cross-sectional transmission electron microscopy (XTEM) for a 5 nm-thick gate oxide. From these observations, this test structure is found to be useful for XTEM specimen preparation to analyze degradation phenomena of thin gate oxides.