Methods of forming strontium titanate films
View Patent ↗Embodiments of the current invention include methods of forming a strontium titanate (SrTiO 3 ) film using atomic layer deposition (ALD). More particularly, the method includes forming a plurality of titanium oxide (TiO 2 ) unit films using ALD and forming a plurality of strontium oxide (SrO) unit films using ALD. The combined thickness of the TiO 2 and SrO unit films is less than approximately 5 angstroms. The TiO 2 and SrO units films are then annealed to form a strontium titanate layer.
1. A method for forming a strontium titanate film, comprising:
a. applying between 50 and 200 pre-saturation pulses without a pulse of an oxidant between the pulses of a Sr-precursor to a substrate, wherein the substrate comprises a conductive layer;
b. forming a Sr-containing and Ti-containing film on the substrate after applying the pulses by
i. forming an SrO film from one or more SrO unit films;
ii. forming a TiO 2 film from one or more TiO 2 unit films over the previously formed SrO film;
iii. forming one or more SrO unit films over the previously formed TiO 2 film if the combined total thickness of all previously formed SrO films and all previously formed TiO 2 films has not reached a desired value;
iv. forming one or more TiO 2 unit films over the previously formed SrO film if the combined total thickness of all previously formed SrO films and all previously formed TiO 2 films has not reached a desired value;
v. repeating steps iii) and iv); and
c. annealing the Sr-containing and Ti-containing film.
2. The method of claim 1 wherein the conductive layer comprises one of titanium nitride, platinum, iridium, iridium oxide, tungsten, tungsten oxide, molybdenum, molybdenum oxide, ruthenium, or ruthenium oxide.
3. The method of claim 1 wherein an oxygen containing source is one of ozone, oxygen, plasma activated oxygen, or water.
4. The method of claim 3 wherein the oxygen containing source is ozone.
5. The method of claim 1 wherein a combined total thickness of a single SrO unit film plus a single TiO 2 unit film is between 2 angstroms and 10 angstroms.
6. The method of claim 5 wherein a combined total thickness of a single SrO unit film plus a single TiO 2 unit film is between 2 angstroms and 5 angstroms.
7. The method of claim 6 wherein a combined total thickness of a single SrO unit film plus a single TiO 2 unit film is between 3 angstroms and 4 angstroms.
8. The method of claim 1 wherein the combined total thickness of the SrO film plus the TiO 2 film is between 10 nm and 20 nm.
9. The method of claim 8 wherein the combined total thickness of the SrO film plus the TiO 2 film is 15 nm.
10. The method of claim 1 wherein the ratio of the number of SrO unit films to the number of TiO 2 unit films is 3:2.
11. The method of claim 1 wherein the annealing step is performed at a temperature between 550 C and 700 C.
12. The method of claim 11 wherein the annealing step is performed at a temperature between 600 C and 650 C.
13. The method of claim 1 wherein the annealing step is performed in an atmosphere of one of nitrogen, oxygen, or inert gas.