Method for fabricating non-volatile storage with individually controllable shield plates between storage elements
A method for fabricating non-volatile storage having individually controllable shield plates between storage elements. The shield plates are formed by depositing a conductive material such as doped polysilicon between storage elements and their associated word lines, and providing contacts for the shield plates. The shield plates reduce electromagnetic coupling between floating gates of the storage elements, and can be used to optimize programming, read and erase operations. In one approach, the shield plates provide a field induced conductivity between storage elements in a NAND string during a sense operation so that source/drain implants are not needed in the substrate. In some control schemes, alternating high and low voltages are applied to the shield plates. In other control schemes, a common voltage is applied to the shield plates.
1. A method for fabricating non-volatile storage, comprising:
forming a plurality of strings of series-connected non-volatile storage elements on a substrate;
forming a plurality of word lines in communication with the plurality of non-volatile storage elements; and
forming a plurality of shield plates, each shield plate extends across each string of the plurality of strings, between different adjacent non-volatile storage elements which are associated with adjacent word lines, each shield plate is electrically conductive and independently controllable.
2. The method of claim 1 , further comprising:
providing at least one control circuit for coupling a voltage independently to each shield plate.
3. The method of claim 1 , wherein:
each non-volatile storage element comprises a floating gate, and each shield plate comprises a conductive material which extends at least in part between floating gates of the different adjacent non-volatile storage elements between which the shield plate extends.
4. The method of claim 1 , wherein:
the strings of series-connected non-volatile storage elements are NAND strings, and the plurality of shield plates extend transversely to the NAND strings.
5. A method for fabricating non-volatile storage, comprising:
forming a plurality of non-volatile storage elements on a substrate, the non-volatile storage elements are arranged in a plurality of sets;
forming a plurality of control lines, each control line is in communication with an associated set of non-volatile storage elements; and
forming a plurality of shields, each shield extends between different adjacent sets of non-volatile storage elements, each shield is independently controllable for reducing electromagnetic coupling between the adjacent sets of non-volatile storage elements between which the shield extends.
6. The method of claim 5 , further comprising:
providing at least one control circuit for coupling a voltage independently to each shield.
7. The method of claim 5 , wherein:
each non-volatile storage element comprises a floating gate, and each shield comprises a conductive material which extends at least in part between floating gates of the different adjacent sets of non-volatile storage elements between which the shield extends.
8. The method of claim 5 , wherein:
the plurality of non-volatile storage elements are arranged in NAND strings, the plurality of shields extend transversely to the NAND strings, and each shield extends across each NAND string.
9. The method of claim 5 , further comprising:
forming a first plurality of electrical contacts carried by the substrate laterally of a region of the substrate on which the plurality of non-volatile storage elements are formed, each electrical contact of the first plurality of electrical contacts is associated with a corresponding shield for coupling a voltage thereto.
10. The method of claim 9 , further comprising:
forming a second plurality of electrical contacts carried by the substrate laterally of the region, each electrical contact of the second plurality of electrical contacts is associated with a corresponding word line for coupling a voltage thereto.
11. The method of claim 10 , wherein:
the first and second plurality of electrical contacts are carried by the substrate on a common side of the region.
12. The method of claim 1 , wherein:
each non-volatile storage element comprises a floating gate, each word line extends above one respective floating gate in each string and acts as a control gate for the one respective floating gate in each string.
13. The method of claim 1 , wherein:
the plurality of shield plates are formed by polysilicon deposition.
14. The method of claim 5 , wherein:
each non-volatile storage element comprises a floating gate, and each control line extends above respective floating gates in each set and acts as a control gate for the respective floating gates in each set.
15. The method of claim 5 , wherein:
the plurality of shields are formed by polysilicon deposition.