Non-volatile memory (NVM) and high-k and metal gate integration using gate-first methodology
View Patent ↗A method of making a semiconductor structure includes forming a select gate over a substrate in an NVM portion and a first protection layer over a logic portion. A control gate and a storage layer are formed over the substrate in the NVM portion, wherein the control and select gates have coplanar top surfaces. The charge storage layer is under the control gate, along adjacent sidewalls of the select gate and control gate, and is partially over the top surface of the select gate. A second protection layer is formed over the NVM portion and the logic portion. The second protection layer and the first protection layer are removed from the logic portion leaving a portion of the second protection layer over the control gate and the select gate. A gate structure is formed over the logic portion comprising a high k dielectric and a metal gate.
1. A method of making a semiconductor structure using a substrate having a non-volatile memory (NVM) portion and a logic portion, comprising:
forming a select gate over the substrate in the NVM portion and a first protection layer over the logic portion;
forming a control gate and a charge storage layer over the substrate in the NVM portion, wherein a top surface of the control gate is substantially coplanar with a top surface of the select gate and the charge storage layer is under the control gate, along adjacent sidewalls of the select gate and control gate, is partially over the top surface of the select gate;
forming a second protection layer over the NVM portion and the logic portion;
removing the second protection layer and the first protection layer from the logic portion leaving a portion of the second protection layer over the control gate and the select gate; and
forming a gate structure over the logic portion comprising a gate dielectric of high k material and a metal gate over the gate dielectric.
2. The method of claim 1 , wherein the forming the select gate is further characterized by the select gate comprising polysilicon.
3. The method of claim 2 , wherein the forming the control gate and the charge storage layer is further characterized by the control gate comprising polysilicon.
4. The method of claim 3 , wherein the forming the control gate and the charge storage layer is further characterized by the charge storage layer comprising nanocrystals.
5. The method of claim 1 , further comprising forming a gate dielectric prior to forming the select gate by growing thermal oxide on the substrate in the NVM portion, wherein the forming the select gate is further characterized by the select gate being directly on the gate dielectric.
6. The method of claim 1 , further comprising:
depositing a conformal layer over NVM portion and the logic portion; and
etching the conformal layer to leave a first sidewall spacer around the logic gate and second sidewall spacer around the control and select gate.
7. The method of claim 6 , further comprising performing an implant into the substrate using the first and second sidewall spacers as masks for the implant.
8. The method of claim 7 , wherein the forming the second protection layer comprises forming a first oxide layer, a nitride layer on the first oxide layer, and a second oxide layer on the nitride layer.
9. The method of claim 1 , wherein the step of forming the charge storage layer and the control gate comprises:
depositing a layer comprising nanoncrystals over the NVM portion and the logic portion;
forming a polysilicon layer over the layer comprising nanocrystals;
planarizing the polysilicon layer; and
patterning the polysilicon layer and the layer comprising nanocrystals to form the control gate from the polysilicon layer and to form the layer of nanocrystals as the charge storage layer partially over the control gate.
10. The method of claim 9 , further comprising forming an optical patterning layer over the select gate.
11. The method of claim 9 , further comprising recessing the polysilicon layer.
12. The method of claim 1 , wherein the forming the charge storage layer and the control gate comprises:
forming a sacrificial layer over the NVM portion;
planarizing the sacrificial layer;
etching an opening in the sacrificial layer adjacent to the select gate;
forming a layer comprising nanocrystals in the NVM portion including in the opening, along a sidewall of the select gate, and over the select gate;
removing the sacrificial layer to leave a space adjacent to the layer comprising nanocrystals along the sidewall of the select gate;
filling the opening with control gate material; and
etching back the control gate material to form the control gate.
13. The method of claim 12 , wherein the forming the charge storage layer and the control gate further comprises etching the layer of nanocrystals to leave the top surface of the select gate partially covered with the layer of nanocrystals.
14. A method of making a semiconductor structure using a substrate having a non-volatile memory (NVM) portion and a logic portion, comprising:
growing thermal oxide on the substrate in the NVM portion;
forming a select gate in the NVM portion on the thermal oxide;
counterdoping the substrate in the NVM portion adjacent to the select gate;
forming a control gate and a charge storage layer over the substrate in the NVM portion, wherein a top surface of the control gate is substantially coplanar with a top surface of the select gate and the charge storage layer is under the control gate, along adjacent sidewalls of the select gate and control gate, is partially over the top surface of the select gate;
forming a protective layer over the NVM portion and the logic portion;
removing the protective layer from the logic portion;
forming a gate structure in the logic portion comprising a high k dielectric as a gate dielectric and a metal gate over the gate dielectric that sets a work function;
depositing a dielectric layer over the NVM portion and the logic portion;
performing an etch of the dielectric layer to form a first sidewall spacer around the select gate and the control gate, and a second sidewall spacer around the metal gate; and
performing an implant into the substrate using the first and second sidewall spacers.
15. The method of claim 14 , wherein the forming the control gate and the charge storage layer comprises:
depositing a layer comprising nanoncrystals over the NVM portion and the logic portion;
forming a polysilicon layer over the layer comprising nanocrystals;
planarizing the polysilicon layer; and
patterning the polysilicon layer and the layer comprising nanocrystals to form the control gate from the polysilicon layer and to form the layer of nanocrystals as the charge storage layer partially over the control gate.
16. The method of claim 15 , further comprising:
planarizing the polysilicon layer; and
recessing the polysilicon layer.
17. The method of claim 14 , wherein the forming the charge storage layer and the control gate comprises:
forming a sacrificial layer over the NVM portion;
planarizing the sacrificial layer;
etching an opening in the sacrificial layer adjacent to the select gate;
forming a layer comprising nanocrystals in the NVM portion including in the opening, along a sidewall of the select gate, and over the select gate;
removing the sacrificial layer to leave a space adjacent to the layer comprising nanocrystals along the sidewall of the select gate;
filling the opening with control gate material; and
etching back the control gate material to form the control gate.
18. The method of claim 17 , wherein the forming the change storage layer and the control gate further comprises, prior to etching the opening, forming a liner in the opening.