Three-dimensional direct-write EEPROM arrays and fabrication methods
First Claim
1. A direct-write EEPROM memory array formed in a semiconductor substrate, said memory array comprising:
- a plurality of substantially parallel elongated trenches adjacently formed in the semiconductor substrate;
a plurality of vertical direct-write EEPROM cells disposed within said plurality of elongated trenches, multiple EEPROM cells being disposed within each of said plurality of elongated trenches, each of said multiple EEPROM cells disposed in each of said plurality of elongated trenches being paired with another of said EEPROM cells disposed in the same elongated trench such that EEPROM cell pairs are disposed in said plurality of elongated trenches, wherein said multiple EEPROM cells in each of said plurality of elongated trenches include a continuous polysilicon structure that functions as a recall gate for said multiple EEPROM cells in said trench, and each EEPROM cell includes an isolated polysilicon structure which functions as a floating gate for the cell;
a plurality of discrete control gates disposed within said plurality of elongated trenches, each control gate being shared by one of said EEPROM cell-pairs; and
an electrically continuous diffusion structure associated with at least one elongated trench of said plurality of elongated trenches, said electrically continuous diffusion structure comprising either a source node or a drain node for each of at least two EEPROM cells of said multiple EEPROM cells disposed in said at least one elongated trench of said plurality of elongated trenches.
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Abstract
A three-dimensional memory cell, suitable for electrically erasable programmable read only memories (EEPROMS), which has direct-write cell capability is disclosed. The memory cell is utilized in the fabrication of non-volatile, direct-write EEPROM arrays with high integration density. A typical EEPROM array includes a plurality of elongated shallow trenches formed in a semiconductor substrate. Multiple direct-write EEPROM cells are disposed within each elongated trench such that each EEPROM cell shares a recall gate and a program gate with another cell in the same trench. Preferably, a silicon rich dielectric (such as silicon rich oxide) disposed between each floating gate and its associated programming and recall gates. Both common source diffusion and isolated source diffusion embodiments are disclosed. Further, various fabrication methods for the direct-write EEPROM arrays presented are described.
273 Citations
9 Claims
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1. A direct-write EEPROM memory array formed in a semiconductor substrate, said memory array comprising:
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a plurality of substantially parallel elongated trenches adjacently formed in the semiconductor substrate; a plurality of vertical direct-write EEPROM cells disposed within said plurality of elongated trenches, multiple EEPROM cells being disposed within each of said plurality of elongated trenches, each of said multiple EEPROM cells disposed in each of said plurality of elongated trenches being paired with another of said EEPROM cells disposed in the same elongated trench such that EEPROM cell pairs are disposed in said plurality of elongated trenches, wherein said multiple EEPROM cells in each of said plurality of elongated trenches include a continuous polysilicon structure that functions as a recall gate for said multiple EEPROM cells in said trench, and each EEPROM cell includes an isolated polysilicon structure which functions as a floating gate for the cell; a plurality of discrete control gates disposed within said plurality of elongated trenches, each control gate being shared by one of said EEPROM cell-pairs; and an electrically continuous diffusion structure associated with at least one elongated trench of said plurality of elongated trenches, said electrically continuous diffusion structure comprising either a source node or a drain node for each of at least two EEPROM cells of said multiple EEPROM cells disposed in said at least one elongated trench of said plurality of elongated trenches. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification