Integration technique using thermal oxide select gate dielectric for select gate and apartial replacement gate for logic
View Patent ↗A thermally-grown oxygen-containing layer is formed over a control gate in an NVM region, and a high-k dielectric layer and barrier layer are formed in a logic region. A polysilicon layer is formed over the oxygen-containing layer and barrier layer and is planarized. A first masking layer is formed over the polysilicon layer and control gate defining a select gate location laterally adjacent the control gate. A second masking layer is formed defining a logic gate location. Exposed portions of the polysilicon layer are removed such that a select gate remains at the select gate location and a polysilicon portion remains at the logic gate location. A dielectric layer is formed around the select and control gates and polysilicon portion. The polysilicon portion is removed to result in an opening at the logic gate location which exposes the barrier layer.
1. A method of making a logic transistor in a logic region of a substrate and a non-volatile memory (NVM) cell in an NVM region of the substrate, comprising:
forming a control gate overlying a charge storage layer over the substrate in the NVM region;
forming a thermally-grown oxygen-containing dielectric layer on the substrate and the control gate in the NVM region and on the substrate in the logic region;
removing the thermally-grown oxygen-containing dielectric layer from the logic region;
forming a high-k gate dielectric layer over the substrate in the logic region;
forming a barrier layer over the high-k gate dielectric layer in the logic region;
forming a polysilicon layer over the thermally-grown oxygen-containing dielectric layer in the NVM region and over the barrier layer in the logic region;
planarizing the polysilicon layer;
forming a first masking layer over the polysilicon layer and control gate in the NVM region, wherein the first masking layer defines a select gate location laterally adjacent the control gate in the NVM region;
forming a second masking layer over the polysilicon layer in the logic region, wherein the second masking layer defines a logic gate location in the logic region;
using the first masking layer to remove exposed portions of the polysilicon layer in the NVM region, wherein a first portion of the polysilicon layer remains at the select gate location to form a select gate;
using the second masking layer to remove exposed portions of the polysilicon layer in the logic region, wherein a second portion of the polysilicon layer remains at the logic gate location;
forming a dielectric layer in the NVM region and the logic region, wherein the dielectric layer is formed over the select gate, the control gate, and the second portion of the polysilicon layer;
planarizing the dielectric layer to expose the second portion of the polysilicon layer; and
removing the second portion of the polysilicon layer to result in an opening at the logic gate location, wherein the opening exposes the barrier layer.
2. The method of claim 1 , wherein the step of forming the first masking layer is performed such that:
the first masking layer is directly over the control gate, and
a first edge of the first masking layer extends laterally from the control gate onto the polysilicon layer to define the select gate location laterally adjacent the control gate in the NVM region.
3. The method of claim 1 , further comprising:
forming a protection layer over the select gate and the control gate in the NVM region, wherein the protection layer exposes the logic region.
4. The method of claim 1 , further comprising:
prior to the step of forming the thermally-grown oxygen-containing dielectric layer, forming an oxide spacer on a sidewall of the control gate.
5. The method of claim 1 , wherein the first masking layer and the second masking layer are portions of a same patterned masking layer, and wherein the steps of using the first masking layer to remove exposed portions of the polysilicon layer in the NVM region and using the second masking layer to remove exposed portions of the polysilicon layer in the logic region are performed simultaneously.
6. The method of claim 1 , wherein the barrier layer comprises a work-function-setting metal.
7. The method of claim 1 , wherein the step of forming the control gate overlying the charge storage layer over the substrate in the NVM region comprises:
forming the charge storage layer over the substrate in the NVM region and the logic region;
forming a second polysilicon layer over the charge storage layer in the NVM region and the logic region; and
patterning the second polysilicon layer and the charge storage layer to form the control gate in the NVM region and to remove the second polysilicon layer and the charge storage layer from the logic region.
8. The method of claim 1 , wherein after the select gate is formed, a portion of the thermally-grown oxygen-containing dielectric layer is located between the select gate and the control gate.
9. The method of claim 1 , wherein after the steps of using the first and second masking layers to remove exposed portions of the polysilicon layer in the NVM region and the logic region, the method further comprises:
forming a first source/drain region in the substrate laterally adjacent the select gate and a second source/drain region in the substrate laterally adjacent the control gate, such that the select gate and the control gate are located between the first and second source/drain regions; and
forming a third source/drain region in the substrate laterally adjacent a first sidewall of the second portion of the polysilicon layer and a fourth source/drain region in the substrate laterally adjacent a second sidewall of the second portion of the polysilicon layer.
10. The method of claim 9 , wherein after the step of using the first and second masking layers to remove exposed portions of the polysilicon layer in the NVM region and the logic region, the method further comprises:
forming a first sidewall spacer surrounding outer sidewalls of the select gate and the control gate and a second sidewall spacer surrounding the second portion of the polysilicon layer.
11. The method of claim 1 , further comprising:
prior to the step of removing the thermally-grown oxygen-containing dielectric layer from the logic region, forming a second polysilicon layer over the thermally-grown oxygen-containing dielectric layer, wherein the polysilicon layer is formed over the second polysilicon layer, and
wherein the step of removing the thermally-grown oxygen-containing dielectric layer further comprises removing the second polysilicon layer from the logic region.
12. The method of claim 11 , wherein the steps of forming the high-k gate dielectric layer and forming the barrier layer comprise:
forming the high-k gate dielectric layer over the second polysilicon layer in the NVM region and over the substrate in the logic region;
forming the barrier layer over the high-k gate dielectric layer in the NVM region and in the logic region; and
removing the high-k gate dielectric layer and the barrier layer from the NVM region.
13. The method of claim 1 , wherein the charge storage layer comprises at least one of nanocrystals or a nitride.
14. The method of claim 3 , wherein after the step of removing the second portion of the polysilicon layer to result in the opening at the logic gate location, the method further comprises:
forming a logic gate layer over the protection layer in the NVM region and within the opening on the barrier layer in the logic region; and
planarizing the logic gate layer to result in a logic gate in the logic gate location, wherein the planarizing removes the protection layer from the NVM region.
15. A method of making a logic transistor in a logic region of a substrate and a non-volatile memory (NVM) cell in an NVM region of the substrate, comprising:
forming a control gate overlying a charge storage layer over the substrate in the NVM region, wherein the control gate comprises polysilicon;
forming an oxide spacer on a sidewall of the control gate;
thermally growing an oxygen-containing dielectric layer on the substrate in the NVM region, on the control gate, and on the substrate in the logic region;
removing the oxygen-containing dielectric layer from the logic region;
forming a high-k gate dielectric layer over the substrate in the logic region;
forming a barrier layer over the high-k gate dielectric layer in the logic region;
forming a polysilicon layer over the oxygen-containing dielectric layer in the NVM region and over the barrier layer in the logic region;
planarizing the polysilicon layer, wherein the oxygen-containing dielectric layer comprises a sidewall portion located along a sidewall of the control gate;
forming a first masking layer over the polysilicon layer and control gate in the NVM region, wherein the first masking layer defines a select gate location laterally adjacent the control gate in the NVM region, wherein:
the first masking layer is directly over the control gate, and a first edge of the first masking layer extends laterally from the control gate onto the polysilicon layer to define the select gate location laterally adjacent the control gate in the NVM region;
forming a second masking layer over the polysilicon layer in the logic region, wherein the second masking layer defines a logic gate location in the logic region;
using the first masking layer to remove exposed portions of the polysilicon layer in the NVM region, wherein a first portion of the polysilicon layer remains at the select gate location to form a select gate;
using the second masking layer to remove exposed portions of the polysilicon layer in the logic region, wherein a second portion of the polysilicon layer remains at the logic gate location;
forming a dielectric layer in the NVM region and the logic region, wherein the dielectric layer is formed over the select gate, the control gate, and the second portion of the polysilicon layer;
planarizing the dielectric layer to expose the second portion of the polysilicon layer;
forming a protection layer over the select gate and the control gate in the NVM region, wherein the protection layer exposes the logic region;
removing the second portion of the polysilicon layer to result in an opening at the logic gate location, wherein the opening exposes the barrier layer;
forming a logic gate layer over the protection layer in the NVM region and within the opening on the barrier layer in the logic region; and
planarizing the logic gate layer to result in a logic gate in the logic gate location, wherein the planarizing removes the protection layer from the NVM region.
16. The method of claim 15 , further comprising:
prior to the step of removing the oxygen-containing dielectric layer from the logic region, forming a second polysilicon layer over the thermally-grown oxygen-containing dielectric layer, and
wherein the step of removing the oxygen-containing dielectric layer further comprises removing the second polysilicon layer from the logic region.
17. The method of claim 16 , wherein the steps of forming the high-k gate dielectric layer and forming the barrier layer comprise:
forming the high-k gate dielectric layer over the second polysilicon layer in the NVM region and over the substrate in the logic region;
forming the barrier layer over the high-k gate dielectric layer in the NVM region and in the logic region; and
removing the high-k gate dielectric layer and the barrier layer from the NVM region.
18. The method of claim 15 , wherein after the step of using the patterned masking layer to remove exposed portions of the polysilicon layer and prior to the step of forming the protection layer in the NVM region and the logic region, the method further comprises:
forming a first source/drain region in the substrate laterally adjacent the select gate and a second source/drain region in the substrate laterally adjacent the control gate, such that the select gate and the control gate are located between the first and second source/drain regions;
forming a third source/drain region in the substrate laterally adjacent a first sidewall of the second portion of the polysilicon layer and a fourth source/drain region in the substrate laterally adjacent a second sidewall of the second portion of the polysilicon layer; and
forming a first sidewall spacer surrounding outer sidewalls of the select gate and the control gate.
19. The method of claim 15 , wherein the barrier layer comprises a work-function-setting metal.
20. A method of making a logic transistor in a logic region of a substrate and a non-volatile memory (NVM) cell in an NVM region of the substrate, comprising:
forming a control gate overlying a charge storage layer over the substrate in the NVM region, wherein the control gate comprises polysilicon and the charge storage layer comprises at least one of nanocrystals or a nitride;
forming a thermally-grown oxygen-containing dielectric layer on the substrate and the control gate in the NVM region and on the substrate in the logic region;
forming a first polysilicon layer over the thermally-grown oxygen-containing dielectric layer in the NVM region and the logic region;
removing the thermally-grown oxygen-containing dielectric layer and the first polysilicon layer from the logic region;
forming a high-k gate dielectric layer over the first polysilicon layer in the NVM region and over the substrate in the logic region;
forming a barrier layer over the high-k gate dielectric layer in the NVM region and in the logic region;
removing the high-k gate dielectric layer and the barrier layer from the NVM region;
forming a second polysilicon layer over the first polysilicon layer in the NVM region and over the barrier layer in the logic region;
planarizing the second polysilicon layer, wherein the thermally-grown oxygen-containing dielectric layer comprises a sidewall portion located along a sidewall of the control gate;
forming a first masking layer over the polysilicon layer and control gate in the NVM region, wherein the first masking layer defines a select gate location laterally adjacent the control gate in the NVM region, wherein:
the first masking layer is directly over the control gate, and a first edge of the first masking layer extends laterally from the control gate onto the second polysilicon layer to define the select gate location laterally adjacent the control gate in the NVM region;
forming a second masking layer over the second polysilicon layer in the logic region, wherein the second masking layer defines a logic gate location in the logic region;
using the first masking layer to remove exposed portions of the second polysilicon layer in the NVM region, wherein a first portion of the second polysilicon layer remains at the select gate location to form a select gate;
using the second masking layer to remove exposed portions of the second polysilicon layer in the logic region, wherein a second portion of the second polysilicon layer remains at the logic gate location;
forming a dielectric layer in the NVM region and the logic region, wherein the dielectric layer is formed over the select gate, the control gate, and the second portion of the second polysilicon layer;
planarizing the dielectric layer to expose the second portion of the second polysilicon layer;
forming a protection layer over the select gate and the control gate in the NVM region, wherein the protection layer exposes the logic region;
removing the second portion of the second polysilicon layer to result in an opening at the logic gate location, wherein the opening exposes the barrier layer;
forming a logic gate layer over the protection layer in the NVM region and within the opening on the barrier layer in the logic region; and
planarizing the logic gate layer to result in a logic gate in the logic gate location, wherein the planarizing removes the protection layer from the NVM region.