Method of forming stacked metal oxide layers
This disclosure provides a method of fabricating a semiconductor stack and associated device, such as a capacitor or DRAM cell. In such a device, a high-K zirconia-based layer may be used as the primary dielectric together with a relatively inexpensive metal electrode based on titanium nitride. To prevent corruption of the electrode during device formation, a thin barrier layer can be used seal the electrode prior to the use of a high temperature process and a (high-concentration or dosage) ozone reagent (i.e., to create a high-K zirconia-based layer). In some embodiments, the barrier layer can also be zirconia-based, for example, a thin layer of doped or un-doped amorphous zirconia. Fabrication of a device in this manner facilitates formation of a device with dielectric constant of greater than 40 based on zirconia and titanium nitride, and generally helps produce less costly, increasingly dense DRAM cells and other semiconductor structures.
1. A method of fabricating a semiconductor assembly, the method comprising:
depositing a first metal oxide layer above an electrode,
wherein the electrode comprises a metal nitride material, and
wherein the first metal oxide layer comprises zirconium oxide,
wherein the first metal oxide layer is deposited using a first oxygen reagent and a first metal precursor at a temperature of less than or equal to 220° C.; and
depositing a second metal oxide layer above the first metal oxide layer,
wherein the second metal oxide layer comprises zirconium oxide,
wherein the second metal oxide layer is deposited using a second oxygen reagent and a second metal precursor at a temperature between about 250° C. and about 300° C.,
wherein the first metal precursor comprises a low temperature Zr alkylamido-based precursor,
wherein the second metal precursor comprises a high temperature Zr alkylamido cyclopentadienyl, and
wherein the second oxygen reagent is different from the first oxygen reagent.
2. The method of claim 1 , wherein the first metal oxide layer consists substantially of an amorphous zirconia-based oxide and the second metal oxide layer consists substantially of a crystalline zirconia-based oxide.
3. The method of claim 1 , wherein the first metal oxide layer has a median thickness of between 0.5 and 2.0 nm.
4. The method of claim 1 , wherein the second metal oxide layer consists substantially of a crystalline zirconia-based oxide.
5. The method of claim 1 , wherein the depositing of each of the first metal oxide layer and the second metal oxide layer are atomic layer deposition processes.
6. The method of claim 1 , wherein the second oxygen reagent comprises ozone.
7. The method of claim 1 , wherein the first metal oxide layer is in contact with the metal nitride material, and wherein the second metal oxide layer is in contact with the first metal oxide layer.
8. The method of claim 7 , where the second metal oxide layer consists substantially of doped or undoped crystalline zirconium oxide.
9. The method of claim 1 , wherein the first oxygen reagent comprises one of water, oxygen gas, or molecular oxygen.
10. The method of claim 1 , wherein the first metal oxide layer is deposited without substantial conversion of titanium nitride into titanium oxynitride.
11. The method of claim 1 , wherein the first metal precursor decomposes at a lower temperature than the second metal precursor.
12. The method of claim 1 , wherein the second oxygen reagent is more reactive than the first oxygen reagent.