ORIGIN OF THIN-OXIDE DEFECTS AFFECTING YIELD AND RELIABILITY OF FLOATING-GATE DEVICES AND FLASH MEMORIES

Gate-oxide and inter-gate-oxide defects in floating-gate transistors a nd hash memories, the number of which has been minimized but is still not zero, have been examined extensively. Gate-oxide defects are due t o 0.1 mu m size octahedral void pits at the Si surface. They are origi nally grown-in defects in the Si crystal and appear as surface pits wh en they are truncated at the surface when wafers are sliced and polish ed. On the other hand, inter-gate oxide defects are due to polygonal-s haped voids at the poly-silicon grain boundary. These defects are prod uced as a negative crystal in the crystallization process of amorphous Si during annealing. Methods for eliminating the above defects are su ggested. (C) 1998 Elsevier Science Ltd. All rights reserved.