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This paper investigates the phenomenon of latent gate oxide defects in MOS ICs caused by charge device model ESD (CDM-ESD). It was observed in about 58% of the MOS memory ICs investigated here. A physical model, called the "Melt Ball Model", has been developed to explain the creation of these gate oxide defects. It predicts the formation of a low conductivity and voltage stress sensitive amorphous "filament". The results of a focused ion beam-transmission electron microscopy (FIB-TEM) investigation are presented confirming this model. Further, experimentally observed leakage current instability phenomena connected with the investigated latent defects are described in detail. The dependence of the CDM-ESD damage threshold for the creation of the observed gate oxide defects on the chip layout is described quantitatively for an n-MOS SRAM.
Date of Conference: 12-14 Sept. 1995