Method for forming a split-gate device
Forming a semiconductor device in an NVM region and in a logic region using a semiconductor substrate includes forming a dielectric layer and forming a first gate material layer over the dielectric layer. In the logic region, a high-k dielectric and a barrier layer are formed. A second gate material layer is formed over the barrier and the first material layer. Patterning results in gate-region fill material over the NVM region and a logic stack comprising a portion of the second gate material layer and a portion of the barrier layer in the logic region. An opening in the gate-region fill material leaves a select gate formed from a portion of the gate-region fill material adjacent to the opening. A control gate is formed in the opening over a charge storage layer. The portion of the second gate material layer is replaced with a metallic logic gate.
1. A method of forming a semiconductor device in an NVM (non-volatile memory) region and in a logic region using a semiconductor substrate, comprising:
forming a dielectric layer over the substrate in the NVM region and the logic region;
forming a first gate material layer over the dielectric layer in the NVM region and the logic region;
removing the dielectric layer and the first gate material layer from the logic region;
forming, in the logic region, a high-k dielectric over the substrate and a barrier layer over the high-k dielectric;
forming a second gate material layer over the barrier layer in the logic region and the first gate material layer in the NVM region;
patterning the first gate material layer and the second gate material layer over the NVM region to form a gate-region fill material over the NVM region;
patterning the second gate material layer and the barrier layer over the logic region to leave a logic stack comprising a portion of the second gate material layer and a portion of the barrier layer aligned to the portion of the second gate material layer over the logic region;
forming an interlayer dielectric around the logic stack and around the gate-region fill material; and
forming a control gate opening in the gate-region fill material to leave a select gate formed from a remaining portion of the gate-region fill material adjacent to the opening, wherein the opening has an exposed surface;
forming a charge storage layer over the exposed surface;
forming a control gate in the control gate opening over the charge storage layer; and
replacing the portion of the second gate material layer with a metallic logic gate.
2. The method of claim 1 , wherein the forming the control gate comprises:
depositing a polysilicon layer and planarizing the polysilicon layer.
3. The method of claim 1 , wherein the forming the control gate comprises depositing a layer comprising metal.
4. The method of claim 1 , wherein the removing the control gate opening further comprises etching through the dielectric layer.
5. The method of claim 4 , wherein the removing the control gate opening further comprises etching into the substrate.
6. The method of claim 1 , wherein the forming the first gate material layer comprises depositing a first polysilicon layer and the forming the second gate material layer comprises forming a second polysilicon layer, wherein the second polysilicon layer is thicker than the first polysilicon layer.
7. The method of claim 6 , wherein the forming, in the logic region, a high-k dielectric over the substrate and a barrier layer over the high-k dielectric is further characterized by the barrier layer being substantially the same thickness as the first gate material layer.
8. The method of claim 1 , further comprising:
forming, prior to forming the interlayer dielectric, a first sidewall spacer around the logic stack and a second sidewall spacer around the gate-region fill material.
9. The method of claim 8 , further comprising:
forming, prior to forming the interlayer dielectric, first source/drain regions in the substrate adjacent the logic stack and second source/drain regions in the substrate adjacent to the gate-region fill material.
10. The method of claim 8 , further comprising:
planarizing the interlayer dielectric to expose a top surface of the logic stack and a top surface of the gate-region fill material.
11. The method of claim 8 , wherein:
the forming the first gate material layer comprises forming a first layer of polysilicon; and
the forming the second gate material layer comprises forming a second layer of polysilicon.
12. The method of claim 8 , wherein the forming a dielectric layer over the substrate comprises one of a group consisting of forming thermal oxide and forming oxynitride.
13. A method of forming a semiconductor device in an NVM (non-volatile memory) region and in a logic region using a semiconductor substrate, comprising:
forming a first layer stack over the substrate in the NVM region, wherein the first layer stack comprises a dielectric layer over the substrate and a first polysilicon layer over the dielectric layer;
forming a second layer stack over the substrate in the logic region, wherein the second layer stack comprises a high-k layer over the substrate and a barrier layer over the high-k layer;
forming a second polysilicon layer over the first polysilicon layer and over the barrier layer;
patterning the second polysilicon layer and the first polysilicon layer in the NVM region to leave a first gate fill material in the NVM region;
patterning the second polysilicon layer and the barrier layer in the logic region to leave a second gate fill material in the logic region;
replacing a portion of the first gate fill material with a charge storage layer and a control gate over the charge storage layer and leaving a portion of the first gate fill material as a select gate; and
replacing the second polysilicon layer of the second gate fill material with a metallic logic gate.
14. The method of claim 13 , wherein the replacing a portion of the first gate fill material is further characterized by:
forming an opening in the first gate fill material;
coating the opening with the charge storage layer; and
forming the control gate over the charge storage layer in the opening.
15. The method of claim 14 , wherein the replacing is further characterized by the charge storage layer comprising nanocrystals.
16. The method of claim 13 , wherein the height above the substrate of the barrier layer is substantially the same as the height of the first polysilicon layer above the substrate.
17. The method of claim 13 , prior to the replacing the portion of the first gate fill material, further comprising:
forming a first sidewall spacer around the first gate fill material;
forming a second sidewall spacer around the second gate fill material; and
forming an interlayer dielectric around the first sidewall spacer and the second sidewall spacer.
18. A method of forming a semiconductor device in an NVM (non-volatile memory) region and in a logic region using a semiconductor substrate, comprising:
forming a first stack having a first polysilicon layer spanning a channel length of a split gate NVM cell and a second polysilicon layer on the first polysilicon layer and aligned to the first polysilicon layer;
forming a second stack in the logic region having a barrier of a logic gate dimension and an overlying polysilicon portion aligned to the barrier;
replacing a portion of the first stack with a layer of nanocrystals surrounded by a dielectric and a control gate over the layer of nanocrystals, wherein a select gate is remaining in the first and second polysilicon layers adjacent to the control gate after the replacing the portion of the second stack; and
replacing the polysilicon portion of the second stack with a metallic logic gate.
19. The method of claim 18 , further comprising:
forming a first sidewall spacer around the first stack;
forming a second sidewall spacer around the second stack; and
forming an interlayer dielectric around the first sidewall spacer and the second sidewall spacer.
20. The method of claim 18 , wherein the forming the first stack and the forming the second stack are further characterized by the overlying polysilicon layer and the second polysilicon layer being formed from the same deposited polysilicon layer.