Split gate memory device with gap spacer
View Patent ↗A method for forming a split gate device includes forming a first sidewall of a first conductive gate layer, wherein the semiconductor layer includes a tunnel region laterally adjacent the first sidewall, forming a dielectric layer along the first sidewall to provide for increased thickness of a gap spacer, forming a charge storage layer over a portion of a top surface of the first conductive layer and over the tunnel region, and forming a second conductive gate layer over the charge storage layer.
1. A method for forming a split gate device, the method comprising:
forming a first dielectric layer over a semiconductor layer;
forming a first conductive gate layer over the first dielectric layer;
forming a first sidewall of the first conductive gate layer, wherein the semiconductor layer includes a tunnel region which is laterally adjacent the first sidewall of the first conductive gate layer;
forming second dielectric layer along the first sidewall of the first conductive gate layer;
forming an oxidizable layer over the first conductive gate layer and the second dielectric layer, wherein, along the first sidewall of the first conductive gate layer, the second dielectric layer is between the first conductive gate layer and the oxidizable layer;
removing a portion of the oxidizable layer from over the tunnel region of the semiconductor layer;
oxidizing the oxidizable layer to form an oxide layer along the first sidewall of the first conductive gate layer;
forming a charge storage layer over a portion of a top surface of the first conductive gate layer and over the oxide layer, wherein the charge storage layer is located along the first sidewall of the first conductive gate layer and over the tunnel region of the semiconductor layer; and
forming a second conductive gate layer over the charge storage layer, wherein the second conductive gate layer is formed over the portion of the top surface of the first conductive gate layer, along the first sidewall of the first conductive gate layer, and over the tunnel region of the semiconductor layer.
2. The method of claim 1 , wherein the removing the portion of the oxidizable layer from over the tunnel region of the semiconductor layer comprises:
performing an anisotropic etch of the oxidizable layer using the second dielectric layer as an etch stop layer.
3. The method of claim 1 , wherein the oxidizable layer includes amorphous silicon.
4. The method of claim 1 , wherein the oxidizable layer includes silicon.
5. The method of claim 1 , wherein the forming the charge storage layer over the portion of the top surface of the first conductive gate layer and over the oxide layer comprises:
forming discrete charge storage elements over the portion of the top surface of the first conductive gate layer and over the oxide layer, wherein discrete charge storage elements are formed along the first sidewall of the first conductive gate layer and over the tunnel region of the semiconductor layer.
6. The method of claim 1 , wherein the first conductive gate layer is further characterized as a select gate layer and the second conductive gate layer is further characterized as a control gate layer.
7. The method of claim 1 wherein:
the forming the second dielectric layer includes forming the second dielectric layer over the tunnel region of the semiconductor layer;
the method further comprises removing a portion of the second dielectric layer from over the tunnel region of the semiconductor layer after the removing a portion of the oxidizable layer from over the tunnel region.
8. The method of claim 7 , wherein the removing a portion of the second dielectric layer comprises:
performing an isotropic etch to remove the first portion of the second dielectric layer which remains exposed after removing the portion of the oxidizable layer.
9. The method of claim 1 further comprising:
forming a nitride layer over the first conductive gate layer prior to the forming the first sidewall, wherein a portion of the nitride layer remains between the charge storage layer and the first conductive gate layer.
10. The method of claim 1 further comprising:
wherein oxidizing the oxidizable material further includes, forming a tunnel oxide layer over the tunnel region, wherein the tunnel oxide layer serves as a tunnel dielectric.
11. The method of claim 1 further comprising:
wherein oxidizing the oxidizable material further includes, forming a tunnel oxide layer over the tunnel region, wherein the charge storage layer is formed over the tunnel oxide layer.
12. The method of claim 11 wherein the forming the charge storage layer includes forming discrete charge storage elements on the tunnel oxide layer.
13. The method of claim 11 wherein the forming the tunnel oxide layer further includes oxidizing a portion of the semiconductor layer currently with the oxidizing the oxidizable layer.
14. The method of claim 13 , wherein the oxidizable layer includes amorphous silicon.
15. The method of claim 13 , wherein the oxidizable layer includes silicon.
16. The method of claim 13 wherein the forming the charge storage layer includes forming discrete charge storage elements on the tunnel oxide layer.
17. The method of claim 16 wherein the tunnel oxide layer serves as a tunnel dielectric.
18. The method of claim 11 , wherein the oxidizable layer includes amorphous silicon.
19. The method of claim 11 , wherein the oxidizable layer includes silicon.
20. The method of claim 11 wherein the tunnel oxide layer serves as a tunnel dielectric.