Thermal atomic layer deposition of ternary gallium oxide thin films
The present disclosure describes a method of a thermal atomic layer deposition (ALD) process of depositing a ternary gallium oxide thin film, which includes gallium, a metal element other than gallium, and oxygen. The disclosed method starts with providing a reactive surface. Next, one or more ALD growth cycles are conducted. Each ALD growth cycle includes one or more first ALD sub-cycles and one or more second ALD sub-cycles. Herein, conducting each first ALD sub-cycles includes applying a pulse of a first metal precursor and a pulse of water sequentially, where the first metal precursor is a gallium compound. Conducting each second ALD sub-cycles includes applying a pulse of a second metal precursor and a pulse of water sequentially, where the second metal precursor includes the metal element other than gallium.
1. A method of a thermal atomic layer deposition (ALD) process of depositing a gallium aluminum oxide thin film, which is (GaxAl 1 -x) 2 O 3 , 0<x<1, the method comprising:
providing a reactive surface coated with hydroxyls;
conducting one or more ALD growth cycles, wherein each of the one or more ALD growth cycles comprises one or more first ALD sub-cycles and one or more second ALD sub-cycles, wherein:
conducting each of the one or more first ALD sub-cycles comprises:
applying a pulse of a first metal precursor to react with the hydroxyls on the reactive surface to form a first monolayer material, wherein the first metal precursor is a gallium compound comprising one or more ligands of a N,N′-diisopropylacetamidinato-group (-amd), a N,N′-diisopropylformamidinato-group (-famd), a N-butyl group (-nBu), a vinyl group (-vinyl), and a guanidinato ligand; and
applying a pulse of an oxygen source after applying the pulse of the first metal precursor to react with the first monolayer material to re-provide a reactive surface coated with hydroxyls; and
conducting each of the one or more second ALD sub-cycles comprises:
applying a pulse of a second metal precursor to react with the hydroxyls on the reactive surface to form a second monolayer material, wherein the second metal precursor is an organic aluminum precursor; and
applying a pulse of an oxygen source after applying the pulse of the second metal precursor to react with the second monolayer material to re-provide a reactive surface coated with hydroxyls.
2. The method of claim 1 wherein:
the oxygen source in each of the one or more first ALD sub-cycles is water; and
the oxygen source in each of the one or more second ALD sub-cycles is water.
3. The method of claim 1 further comprising repeating the ALD growth cycle.
4. The method of claim 1 wherein conducting each of the one or more ALD growth cycles comprises conducting one first ALD sub-cycle and conducting one second ALD sub-cycle in series.
5. The method of claim 4 wherein the first ALD sub-cycle is conducted before the second ALD sub-cycle within one ALD growth cycle.
6. The method of claim 4 wherein the first ALD sub-cycle is conducted after the second ALD sub-cycle within one ALD growth cycle.
7. The method of claim 4 further comprising repeating the ALD growth cycle.
8. The method of claim 1 wherein conducting each of the one or more ALD growth cycles comprises conducting one first ALD sub-cycle and conducting two sequential second ALD sub-cycles.
9. The method of claim 8 wherein the first ALD sub-cycle is followed by the two sequential second ALD sub-cycles within one ALD growth cycle.
10. The method of claim 9 further comprising repeating the ALD growth cycle.
11. The method of claim 2 , wherein conducting each of the one or more first ALD sub-cycles further comprises one purge step between applying the pulse of the first metal precursor and applying the pulse of water, and another purge step after applying the pulse of water.
12. The method of claim 2 , wherein conducting each of the one or more second ALD sub-cycles further comprises one purge step between applying the pulse of the second metal precursor and applying the pulse of water, and another purge step after applying the pulse of water.
13. The method of claim 1 wherein the first metal precursor has a formula of GaL1(L2) 2 , wherein:
Ga is a central gallium atom, and L1 and L2 are ligands surrounding the central gallium atom; and
each of L1 and L2 is selected from one of an (-amd), an (-famd), a (-nBu), a (-vinyl), and a N,N′-diisopropyl-N-dimethyl-guanidinato-group (-guan).
14. The method of claim 13 wherein L1 and L2 are a same ligand.
15. The method of claim 13 wherein L1 and L2 are different ligands.
16. The method of claim 13 wherein the first metal precursor is one of a group consisting of Ga(amd) 3 , [Ga (famd) 3 ] 2 , Ga(amd) 2 (Me), Ga(amd)(Me) 2 , Ga(amd)(nBu) 2 , Ga(amd)(vinyl) 2 , Ga(amd)(NMe 2 ) 2 , and Ga(guan)(NMe 2 ) 2 .
17. The method of claim 1 wherein the first metal precursor is Ga(amd) 3 , and the second metal precursor is Trimethylaluminium (TMA).
18. The method of claim 1 wherein a concentration ratio of gallium versus aluminum in the resulting gallium aluminum oxide thin film from the thermal ALD process is dependent on a pulse ratio between pulses of the first metal precursor and pulses of the second metal precursor within one ALD growth cycle.
19. The method of claim 18 wherein the concentration ratio of gallium versus aluminum in the resulting gallium aluminum oxide thin film is further dependent on sub-cycle order in one ALD growth cycle, pulsing time of each pulse of the first metal precursor, and pulsing time of each pulse of the second metal precursor.
20. The method of claim 1 wherein, in one ALD growth cycle, a number of the pulses of the first metal precursor is N, and a number of the pulses of the second metal precursor is M, wherein N and M are positive integers.
21. The method of claim 2 wherein, without conducting the one or more second ALD sub-cycles, the reaction between the first metal precursor and the oxygen source is incapable of forming any oxide film having a thickness greater than 5 Å.
22. The method of claim 1 wherein:
the oxygen source in each of the one or more first ALD sub-cycles is hydrogen peroxide; and
the oxygen source in each of the one or more second ALD sub-cycles is hydrogen peroxide.