Methods for forming conductive titanium oxide thin films
The present disclosure relates to the deposition of conductive titanium oxide films by atomic layer deposition processes. Amorphous doped titanium oxide films are deposited by ALD processes comprising titanium oxide deposition cycles and dopant oxide deposition cycles and are subsequently annealed to produce a conductive crystalline anatase film. Doped titanium oxide films may also be deposited by first depositing a doped titanium nitride thin film by ALD processes comprising titanium nitride deposition cycles and dopant nitride deposition cycles and subsequently oxidizing the nitride film to form a doped titanium oxide film. The doped titanium oxide films may be used, for example, in capacitor structures.
1. A process for producing a doped titanium oxide layer on a substrate in a reaction chamber by atomic layer deposition, the process comprising:
a titanium nitride deposition cycle comprising alternately and sequentially contacting the substrate with a titanium precursor and a first nitrogen precursor;
a dopant nitride deposition cycle comprising alternately and sequentially contacting the substrate with a dopant precursor comprising a group V metal and a second nitrogen precursor,
wherein the titanium nitride deposition cycle and dopant nitride deposition cycle are repeated until a doped titanium nitride thin film of a desired thickness and composition is obtained, and wherein the doped titanium nitride thin film comprises Ti 1-x Nb x N y or Ti 1-x Ta x N y , wherein x is between 0 and 1 and y is between 1 and 2; and
oxidizing at least a portion of the doped titanium nitride thin film to form the doped titanium oxide layer, wherein the doped titanium oxide layer is conductive and is doped with the group V metal.
2. The method of claim 1 , wherein the doped titanium oxide thin film is deposited directly over and contacting a bottom electrode.
3. The method of claim 1 , further comprising depositing a high-k structure directly over and contacting the doped titanium oxide thin film.
4. The method of claim 3 , further comprising depositing a top electrode directly over and contacting the high-k structure.
5. The method of claim 3 , wherein the high-k structure comprises an ultra-high-k material having a dielectric constant value above 10.
6. The method of claim 5 , wherein the ultra-high-k material comprises Ti.
7. The method of claim 5 , wherein the ultra-high-k material comprises one or more of PbTiO 3 , PbZr x Ti 1-x O 3 , SrTiO 3 , BaTiO 3 , SrBaTiO 3 , BiTaO x and SrBiTaO x .
8. The method of claim 1 , wherein the first nitrogen precursor and the second nitrogen precursor are the same.
9. The method of claim 1 , wherein the dopant precursor comprises tantalum or niobium.
10. The method of claim 1 , further comprising annealing the Ti 1-x Nb x N y or Ti 1-x Ta x N y thin film at a temperature greater than 600° C.
11. The method of claim 1 , wherein the doped titanium oxide layer has a resistivity less than 0.01 Ω·cm.
12. The method of claim 1 , wherein the doped titanium oxide layer produced thereby has an optical transmittance of greater than 60% in the visible region.
13. The method of claim 1 , wherein the dopant precursor comprises an organic ligand.
14. A process for producing a conductive doped titanium oxide layer on a substrate in a reaction chamber, the process comprising:
a titanium nitride deposition cycle comprising:
contacting the substrate with a vapor phase titanium precursor to form no more than a single molecular layer of the titanium precursor on the substrate;
contacting the substrate with a first nitrogen precursor such that the first nitrogen precursor reacts with the titanium precursor on the substrate;
a dopant nitride deposition cycle comprising:
contacting the substrate with a vapor phase dopant reactant to form no more than a single monolayer of dopant reactant on the substrate surface, the vapor phase dopant reactant comprising a group V metal;
contacting the substrate with a second nitrogen precursor such that the second nitrogen precursor reacts with the dopant reactant on the substrate surface;
wherein the titanium nitride deposition and dopant nitride deposition cycles are repeated until a doped titanium nitride thin film is formed, and wherein the doped titanium nitride thin film comprises Ti 1-x Nb x N y or Ti 1-x Ta x N y , wherein x is from 0 to 1 and y is from 1 to 2; and
oxidizing at least a portion of the doped titanium nitride thin film to form the conductive doped titanium oxide layer.
15. The method of claim 14 , wherein alternating titanium nitride layers and dopant nitride layers are formed.
16. The method of claim 14 , wherein the titanium nitride deposition cycle is repeated from 1 to 10 times for each of the dopant nitride deposition cycles.
17. The method of claim 14 , wherein the dopant nitride deposition cycle is repeated consecutively two or more times.
18. The method of claim 14 , further comprising annealing the Ti 1-x Nb x N y or Ti 1-x Ta x N y thin film at a temperature greater than 600° C.
19. The method of claim 14 , wherein at least one of the first and second nitrogen precursors comprises nitrogen-containing plasma.
20. The method of claim 19 , wherein the nitrogen-containing plasma comprises a N 2 /H 2 -plasma or a NH 3 -plasma.
21. The method of claim 14 , wherein the titanium nitride deposition cycle and the dopant nitride deposition cycle are repeated at a ratio of 50:1 to 1:3.