High work function, manufacturable top electrode
Provided are MIM DRAM capacitors and methods of forming thereof. A MIM DRAM capacitor may include an electrode layer formed from a high work function material (e.g., greater than about 5.0 eV). This layer may be used to reduce the leakage current through the capacitor. The capacitor may also include another electrode layer having a high conductivity base portion and a conductive metal oxide portion. The conductive metal oxide portion serves to promote the growth of the high k phase of the dielectric layer.
1. A method for forming a capacitor stack comprising:
forming a first electrode layer,
wherein forming the first electrode layer comprises:
forming a first layer above a substrate,
wherein the first layer comprises a conductive metal nitride,
wherein the first layer has a thickness of between 20 A and 150 A, and
forming a second layer above the first layer,
wherein the second layer comprises molybdenum oxide having a distorted rutile structure;
forming a third layer above the second layer,
wherein the third layer is a dielectric layer; and
forming a second electrode layer above the third layer,
wherein forming the second electrode layer comprises:
forming a fourth layer,
wherein the fourth layer comprises nickel oxide, and
forming a fifth layer above the fourth layer,
wherein the fifth layer comprises a conductive metal nitride.
2. The method of claim 1 , wherein the conductive nitride in the first layer comprises titanium nitride.
3. The method of claim 1 , wherein the third layer comprises one of aluminum oxide, barium-strontium-titanate (BST), hafnium oxide, hafnium silicate, niobium oxide, lead zirconium-titanate (PZT), a bilayer of silicon oxide and silicon nitride, silicon oxy-nitride, strontium-titanate (STO), tantalum oxide, titanium oxide, zirconium oxide or doped versions of the same.
4. The method of claim 3 , wherein the third layer comprises titanium oxide or a doped version of the same.
5. The method of claim 4 , wherein the third layer further comprises a dopant comprising at least one of AI, Ce, Co, Er, Ga, Gd, Ge, Hf, In, La, Lu, Mg, Mn, Nd, Pr, Sc, Si, Sn, Sr, Y, or Zr.
6. The method of claim 1 , further comprising a first annealing, wherein the first annealing is performed after the forming of the first layer and the second layer, and before the forming of the third layer.
7. The method of claim 6 , wherein the first annealing is performed in a reducing atmosphere comprising between about 0% and about 10% H 2 in N 2 at a temperature between about 300 C and about 600 C for between 1 millisecond and about 60 minutes.
8. The method of claim 1 , further comprising a second annealing, wherein the second annealing is performed after the forming of the first layer, the second layer, and the third layer, and before the forming of the fourth layer.
9. The method of claim 8 , wherein the second annealing is performed in a first oxidizing atmosphere comprising between about 0% O 2 to about 20% O 2 in N 2 and at temperatures between 400 C to 600 C for between 1 millisecond to 60 minutes.
10. The method of claim 1 , wherein the fifth layer comprises one of ruthenium, platinum, titanium nitride, tantalum nitride, titanium-aluminum-nitride, tungsten, tungsten nitride, molybdenum, molybdenum nitride, or vanadium nitride.
11. The method of claim 10 , wherein the fifth layer is titanium nitride.
12. The method of claim 1 , further comprising a third annealing, wherein the third annealing is performed after forming the first layer, the second layer, the third layer, the fourth layer, and the fifth layer in a second oxidizing atmosphere.
13. The method of claim 12 , wherein the second oxidizing atmosphere comprises between about 0% O 2 to about 20% O 2 and at temperatures between 300 C to 600 C for between 1 millisecond to 60 minutes.
14. The method of claim 1 , wherein the molybdenum oxide of the second layer has a stoichiometric formula of MoO 2 .
15. The method of claim 1 , wherein the molybdenum oxide of the second layer is operable as a template for the third layer when the third layer is formed directly on the second layer.
16. The method of claim 1 , wherein the second layer is formed using atomic layer deposition (ALD) at a temperature of between about 125° C. and 400° C.