| US 7,602,067 B2 | ||
| Hetero-structure variable silicon rich nitride for multiple level memory flash memory device | ||
| Yi Ma, Santa Clara, Calif. (US); and Robert Ogle, San Jose, Calif. (US) | ||
| Assigned to Spansion LLC, Sunnyvale, Calif. (US) | ||
| Filed on Dec. 17, 2007, as Appl. No. 11/957,787. | ||
| Prior Publication US 2009/0152617 A1, Jun. 18, 2009 | ||
| Int. Cl. H01L 29/40 (2006.01) | ||
| U.S. Cl. 257—760 [257/E29.309; 257/325] | 20 Claims |
| 1. A charge storage stack for a memory cell, comprising:
a first insulating layer over a semiconductor substrate;
n charge storage layers comprising silicon-rich silicon nitride over the first insulating layer, wherein numbers of the charge
storage layers increase from the bottom to the top and a k-value of an n−1th charge storage layer is higher than a k-value
of an nth charge storage layer;
n−1 dielectric layers comprising substantially stoichiometric silicon nitride between each of the n charge storage layers;
and
a second insulating layer over the nth charge storage layers,
wherein n is 2 or more and about 12 or less.
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