Memory device and fabrication method thereof

1. A method for fabricating a memory device, comprising:

forming a bottom electrode over a substrate;

forming an etch stop layer over and surrounding the bottom electrode;

removing at least one portion of the etch stop layer to expose the bottom electrode;

forming a stack layer over the bottom electrode and a remaining portion of the etch stop layer, the stack layer comprising a resistance switching layer; and

etching the stack layer to form a stack over the bottom electrode, the stack comprising a resistance switching element over the bottom electrode and a top electrode over the resistance switching element, wherein the etch stop layer has a higher etch resistance to the etching than that of the resistance switching element.

2. The method of claim 1 , wherein the etch resistance of the etch stop layer to the etching the stack layer is higher than that of the bottom electrode.

3. The method of claim 1 , wherein the etch resistance of the etch stop layer to the etching the stack layer is higher than that of the top electrode.

4. The method of claim 1 , further comprising

forming a spacer layer over the stack; and

etching the spacer layer to form a spacer, wherein the etch stop layer has a higher etch resistance to the etching the spacer layer than that of the spacer layer.

5. The method of claim 1 , wherein the removing the at least one portion of the etch stop layer over the bottom electrode comprises:

performing a chemical-mechanical polish (CMP) process to the etch stop layer.

6. The method of claim 1 , further comprising:

forming an interlayer dielectric layer over the stack and the etch stop layer; and

removing a portion of the interlayer dielectric layer over a logic transistor.

7. The method of claim 6 , wherein the removing the portion of the interlayer dielectric layer comprises:

etching the portion of the interlayer dielectric layer, wherein the etch stop layer has a higher etch resistance to the etching the portion of the interlayer dielectric layer than that of the interlayer dielectric layer.

8. The method of claim 1 , wherein the forming the bottom electrode comprises:

overfilling an opening in a dielectric layer with a bottom electrode layer; and

removing a portion of the bottom electrode layer to form the bottom electrode, wherein the bottom electrode is partially inside and partially outside the opening.

9. The method of claim 8 , wherein the removing the portion of the bottom electrode layer further removes a portion of the dielectric layer.

10. A method for manufacturing a memory device, the method comprising:

forming a dielectric layer over a substrate having a metallization pattern;

forming an opening in the dielectric layer to expose the metallization pattern;

overfilling the opening with a bottom electrode layer;

patterning the bottom electrode layer to form a bottom electrode;

depositing an etch stop layer over the bottom electrode and the dielectric layer, wherein depositing the etch stop layer is performed such that the etch stop layer is in contact with a top surface of the bottom electrode;

planarizing the etch stop layer until reaching the bottom electrode; and

forming a stack over the bottom electrode after planarizing the etch stop layer, the stack comprising a resistance switching element in contact with the bottom electrode and a top electrode over the resistance switching element.

11. The method of claim 10 , wherein forming the dielectric layer is performed such that the dielectric layer comprises silicon and depositing the etch stop layer is performed such that the etch stop layer comprises aluminum.

12. The method of claim 10 , wherein the forming the stack comprises:

forming a stack layer over the bottom electrode and the etch stop layer; and

etching the stack layer to form the stack over the bottom electrode, wherein the etch stop layer has a higher etch resistance to the etching the stack layer than that of the resistance switching element.

13. The method of claim 12 , wherein the etch resistance of the etch stop layer to the etching the stack layer is higher than that of the bottom electrode.

14. The method of claim 10 , further comprising

forming a spacer layer over the stack; and

etching the spacer layer to form a spacer, wherein the etch stop layer has a higher etch resistance to the etching the spacer layer than that of the spacer layer.

15. The method of claim 10 , further comprising:

forming an interlayer dielectric layer over the stack and the etch stop layer; and

etching a portion of the interlayer dielectric layer over a logic transistor, wherein the etch stop layer has a higher etch resistance to the etching the portion of the interlayer dielectric layer than that of the interlayer dielectric layer.

16. The method of claim 10 , wherein patterning the bottom electrode layer comprises:

forming an etch mask over the bottom electrode layer above the opening; and

etching a portion of the bottom electrode layer exposed by the etch mask, wherein the method further comprises removing the etch mask after patterning the bottom electrode layer.

17. A method for manufacturing a memory device, the method comprising:

forming a mask over a bottom electrode layer;

patterning the bottom electrode layer by using the mask to form a bottom electrode;

removing the mask from the bottom electrode;

forming an etch stop layer adjacent the bottom electrode after removing the mask from the bottom electrode, wherein forming the etch stop layer is performed such that the etch stop layer is in contact with a top surface of the bottom electrode;

removing a portion of the etch stop layer from the top surface of the bottom electrode;

forming a stack over the top surface of the bottom electrode, the stack comprising a resistance switching element in contact with the bottom electrode and a top electrode over the resistance switching element, wherein forming the stack is performed such that a bottom surface of the resistance switching element is above a top surface of the etch stop layer;

forming a spacer layer over the stack; and

etching the spacer layer to form a spacer, wherein the etch stop layer has a higher etch resistance to the etching the spacer layer than that of the spacer layer.

18. The method of claim 17 , wherein etching the spacer layer is performed such that the spacer is in contact with the top surface of the bottom electrode.

19. The method of claim 17 , wherein etching the spacer layer is performed such that the spacer is in contact with the top surface of the etch stop layer.

20. The method of claim 17 , wherein the top electrode has a higher etch resistance to the etching the spacer layer than that of the spacer layer.