Method of forming spaced-apart charge trapping stacks
View Patent ↗Methods are provided for fabricating memory devices. A method comprises fabricating charge-trapping stacks overlying a silicon substrate and forming bit line regions in the substrate between the charge trapping stacks. Insulating elements are formed overlying the bit line regions between the stacks. The charge-trapping stacks are etched to form two complementary charge storage nodes and to expose portions of the silicon substrate. Silicon is grown on the exposed silicon substrate by selective epitaxial growth and is oxidized. A control gate layer is formed overlying the complementary charge storage nodes and the oxidized epitaxially-grown silicon.
1. A semiconductor memory device comprising:
a silicon substrate;
a first insulating element and a second insulating element disposed on the silicon substrate;
a first bit line region disposed in the silicon substrate underlying the first insulating element and a second bit line region disposed in the silicon substrate underlying the second insulating element;
a first charge storage node disposed along a sidewall of the first insulating element and a second charge storage node disposed along a sidewall of the second insulating element; wherein a third charge storage node and a fourth charge storage node are disposed along other sidewalls of the first and second insulating elements, respectively, and wherein the first, second, third, and fourth charge storage nodes are each disposed along a portion less than the full height of each respective insulating element sidewall;
oxidized epitaxially grown silicon disposed on the silicon substrate between the first charge storage node and the second charge storage node, wherein edges of the first and second charge storage nodes contact opposite edges of the oxidized epitaxially grown silicon, wherein a height of the oxidized epitaxially grown silicon isles than a height of the charge storage nodes disposed along respective insulating element sidewalls, wherein the epitaxially grown silicon is substantially all oxidized, and wherein a portion of the silicon substrate underlying the oxidized epitaxially grown silicon is oxidized; and
a control gate layer contiguously overlying the charge storage nodes, the first and second insulating elements, and the oxidized epitaxially grown silicon.
2. The semiconductor memory device of claim 1 , wherein the first charge storage node and the second charge storage node each comprise a layer of silicon-rich silicon nitride.
3. The semiconductor memory device of claim 1 , wherein the first charge storage node and the second charge storage node each comprise a layer of one of silicon nitride and polycrystalline silicon.
4. The semiconductor memory device of claim 1 , wherein the first charge storage node and the second charge storage node each comprise a layer of a combination of at least two of silicon nitride, silicon-rich silicon nitride, and polycrystalline silicon.
5. The semiconductor memory device of claim 1 , wherein the oxidized epitaxially grown silicon is between approximately 2 nm to approximately 15 nm thick.
6. The semiconductor memory device of claim 1 , wherein the first and second insulating elements each comprise high density silicon oxide.
7. A semiconductor memory device comprising:
a silicon substrate;
a first insulating element and a second insulating element disposed on the silicon substrate;
a first impurity-doped bit line region disposed in the silicon substrate underlying the first insulating element and a second impurity-doped bit line region disposed in the silicon substrate underlying the second insulating element;
a first multi-layer charge-trapping stack along a sidewall of the first insulating element and a second multi-layer charge-trapping stack disposed along a sidewall of the second insulating element; wherein a third multi-layer charge-trapping stack and a fourth multi-layer charge-trapping stack are disposed along other sidewalls of the first and second insulating elements, respectively, and wherein the first, second, third, and fourth multi-layer charge-trapping stack are each disposed along a portion less than the full height of each respective insulating element sidewall;
oxidized epitaxially grown silicon disposed on the silicon substrate between the first multi-layer charge-trapping stack and a second multi-layer charge-trapping stack, wherein edges of the first and second multi-layer charge-trapping stacks contact opposite edges of the oxidized epitaxially grown silicon, wherein the epitaxially grown silicon is substantially all oxidized, and wherein a portion of the silicon substrate underlying the oxidized epitaxially grown silicon is at least partially oxidized; and
a control gate layer contiguously overlying the multi-layer charge-trapping stacks, the first and second insulating elements, and the oxidized epitaxially grown silicon.
8. The semiconductor memory device of claim 7 , wherein the portion of the silicon substrate underlying the epitaxially grown silicon is fully oxidized.
9. The semiconductor memory device of claim 7 , wherein the first and second impurity-doped bit line regions are implanted with one of arsenic ions and phosphorous ions.
10. The semiconductor memory device of claim 7 , wherein the first and second multi-layer charge-trapping stacks comprise:
a first insulating layer overlying the silicon substrate;
a charge trapping layer overlying the first insulating layer; and
a second insulating layer overlying the charge trapping layer.
11. The semiconductor memory device of claim 10 , wherein the charge trapping layer comprises a layer of one of silicon nitride, silicon-rich silicon nitride, and polycrystalline silicon.
12. The semiconductor memory device of claim 10 , wherein the charge trapping layer comprises a layer comprising a combination of at least two of silicon nitride, silicon-rich silicon nitride, and polycrystalline silicon.
13. The semiconductor memory device of claim 7 , wherein the oxidized epitaxially grown silicon is between approximately 2 nm to approximately 15 nm thick.