Minimizing disturbs in dense non volatile memory arrays
A nitride read only memory (NROM) array includes a silicon substrate having trenches therein, a plurality of polysilicon bit lines deposited in the trenches and connecting columns of memory cells, a layer of (oxide nitride oxide) ONO at least within the memory cells and a plurality of polysilicon word lines to connect rows of the memory cells. An NROM array with a virtual ground architecture includes a plurality of bit lines to connect columns of NROM memory cells, a layer of ONO at least within the memory cells and a plurality of word lines to connect rows of the NROM memory cells, wherein a distance between word lines is at least twice the width of the word lines.
1. A nitride read only memory (NROM) array comprising:
a silicon substrate having trenches therein;
oxide liners along at least a portion of the inside walls of said trenches;
a plurality of polysilicon bit lines deposited on top of said oxide liners and filling said trenches, said bit lines connecting columns of memory cells;
a charge trapping layer of ONO (oxide nitride oxide) at least on top of horizontal channels in said substrate between said bit lines at least in said memory cells; and
a plurality of polysilicon word lines to connect rows of said memory cells,
wherein said oxide liner insulates said bit lines from said silicon substrate.
2. The array according to claim 1 and wherein said polysilicon bit lines are formed of doped polysilicon.
3. The array according to claim 2 and wherein said doped polysilicon is in-situ doped polysilicon.
4. The array according to claim 1 and also comprising at least at the sides of said polysilicon bit lines above said oxide liners.
5. The array according to claim 1 and wherein a depth of said trenches is at least ½ of a lithographic feature size F.
6. A method for manufacturing bit lines of an NROM array, the method comprising:
cutting trenches in a silicon substrate for bit lines of said array, said bit lines to connect columns of memory cells of said array;
insulating said trenches by depositing an oxide lining on the walls of said trenches; and
depositing polysilicon on said oxide lining to form said bit lines;
creating a charge trapping layer of ONO (oxide nitride oxide) at least on top of horizontal channels in said substrate between said bit lines at least in said memory cells.
7. The method according to claim 6 and also comprising doping said bit lines and annealing said bit lines to create bit line junctions.