Split-gate memory cells having select-gate sidewall metal silicide regions and related manufacturing methods
Split-gate non-volatile memory (NVM) cells having select-gate sidewall metal silicide regions are disclosed along with related manufacturing methods. Spacer etch processing steps are used to expose sidewall portions of select gates. Metal silicide regions are then formed within these sidewall portions of the select gates. Further, metal silicide regions can also be formed in top portions of the select gates. Further, the select gates can also be formed with one or more notches. By expanding the size of the metal silicide region to include the sidewall portion of the select gate, the select gate wordline (e.g., polysilicon) resistance is reduced for split-gate NVM arrays, the electrical contact to the select gate is improved, and performance of the select-gate NVN cell is improved.
1. A method for forming a split-gate non-volatile memory (NVM) cell having a select-gate sidewall metal silicide region, comprising:
forming a split-gate stack including a select gate, a control gate, a charge storage layer, and a first spacer positioned adjacent the select gate;
etching the first spacer to expose a sidewall portion of the select gate; and
forming a metal silicide region within the exposed sidewall portion of the select gate;
wherein the metal silicide region within the sidewall portion of the select gate extends at least 30 percent or more of a height of the select gate.
2. The method of claim 1 , wherein the split-gate stack further includes a second spacer positioned adjacent the control gate, wherein the etching step further comprises etching the second spacer to expose a top portion of the select gate, and wherein the forming step further comprises forming a metal silicide region within the top portion of the select gate.
3. The method of claim 1 , wherein the first spacer extends into a notch underneath the select gate.
4. The method of claim 1 , wherein the forming a metal silicide step comprises a self-aligned silicide process.
5. The method of claim 1 , the etching step comprises an isotropic etch.
6. The method of claim 1 , wherein the charge storage layer comprises at least one of a discrete charge storage layer or a continuous charge storage layer.
7. The method of claim 1 , wherein the forming a metal silicide step also forms a metal silicide region within the top portion of the control gate.
8. The method of claim 1 , wherein the forming step further comprises forming a metal silicide region within a sidewall portion of the control gate.
9. The method of claim 1 , wherein the split-gate stack further includes a second spacer positioned adjacent the control gate, wherein the forming step further comprises etching the second spacer without exposing a top portion of the select gate, and wherein the forming step comprises forming the metal silicide region within the exposed sidewall portion of the select gate without forming a metal silicide region in the top portion of the select gate.
10. A split-gate non-volatile memory (NVM) cell having a select-gate sidewall metal silicide region, comprising:
a select gate;
a control gate;
a charge storage layer positioned at least in part between the select gate and the control gate;
a first spacer positioned adjacent the select gate; and
a metal silicide region formed within a sidewall portion of the select gate;
wherein the metal silicide region within the sidewall portion of the select gate extends at least 30 percent or more of a height of the select gate.
11. The split-gate NVM cell of claim 10 , further comprising a second spacer positioned adjacent the control gate, and wherein a metal silicide region is also formed within a top portion of the select gate.
12. The split-gate NVM cell of 10 , wherein the first spacer extends into a notch underneath the select gate.
13. The split-gate NVM cell of claim 10 , wherein the charge storage layer comprises at least one of a discrete charge storage layer or a continuous charge storage layer.
14. The split-gate NVM cell of claim 10 , further comprising a metal silicide region formed in a top portion of the control gate and in a sidewall portion of the control gate.
15. The NVM cell of claim 10 , further comprising a second spacer positioned adjacent the control gate and over a top portion of the select gate, and wherein a metal silicide region is not formed within the top portion of the select gate.
16. A non-volatile memory (NVM) system having NVM cells with select-gate sidewall metal silicide regions, comprising:
an array of split-gate non-volatile memory (NVM) cells, each split-gate NVM cell comprising:
a select gate;
a control gate;
a charge storage layer positioned at least in part between the select gate and the control gate;
a first spacer positioned adjacent the select gate; and
at least one metal silicide region formed within a sidewall portion of the select gate, the metal silicide region within the sidewall portion of the select gate extending at least 30 percent or more of a height of the select gate;
wordline driver circuitry coupled to the plurality of split-gate NVM cells; and
column driver circuitry coupled to the plurality of split-gate NVM cells;
wherein the array of split-gate NVM cells, the wordline driver circuitry, and the column driver circuitry are integrated within a single integrated circuit.
17. The NVM system of claim 16 , wherein each split-gate NVM cell further comprises a second spacer positioned adjacent the control gate, and wherein for each split-gate NVM cell, a metal silicide region is also formed within a top portion of the select gate.
18. The NVM system of claim 16 , wherein for each split-gate NVM cell, the first spacer extends into a notch underneath the select gate.
19. The NVM system of claim 16 , wherein for each split-gate NVM cell, the charge storage layer comprises at least one of a discrete charge storage layer or a continuous charge storage layer.
20. The NVM system of claim 16 , wherein each split-gate NVM cell further comprises a metal silicide region formed within a top portion and a sidewall portion of the control gate.
21. The NVM system of claim 16 , wherein each split-gate NVM cell further comprises a second spacer positioned adjacent the control gate and over a top portion of the select gate, and wherein for each split-gate NVM cell, a metal silicide region is not formed within the top portion of the select gate.