Method for growing crystalline optical films on Si substrates which may optionally have an extremely small optical loss in the infra-red spectrum with hydrogenation of the crystalline optical films

Patent metadata

Field	Value
Publication number	US-12116662-B2
Application number	US-202217890913-A
Country	US
Kind code	B2
Filing date	Aug 18, 2022
Priority date	May 20, 2020
Publication date	Oct 15, 2024
Grant date	Oct 15, 2024

Abstract

A process enables growing thick stoichiometric crystalline and preferably IR-transparent optical PCMO material on Si and other substrates. Sputter deposition is carried out in oxygen-free inert gas (e.g., Ar) environment, which helps to prevent decomposition of the PCMO material over the substrate. In the disclosed process, there is no need to add a seed layer prior to PCMO deposition. Moreover, no post-deposition annealing is needed in a high-temperature and high-pressure oxygen furnace, but an anneal provides certain additional benefits in terms of improved transparency at IR wavelengths. Over a long deposition time for a thick PCMO film on the high temperature (≥450° C.) substrates, the PCMO deposition is made repeated cycles of deposition of the PCMO material at the high temperature, each deposition cycle being followed by cooling the PCMO-deposited substrate to a substantially lower temperature (<50° C.). If an anneal is applied in a hydrogen environment that will cause hydrogenation of the PCMO film which yields PCMO films with an extremely small optical loss (i.e., optical extinction coefficient k<0.001) over the entire IR range.

First claim

What is claimed is:

1. A process for growing IR-transparent Phase-Change Correlated Transition Metal Oxide (PCMO) optical films on substrates, with an optical extinction coefficient k<0.001 over an infrared range of wavelengths, the process including:
pre-cleaning a substrate in a substantially oxygen-free gas environment at room temperature;
depositing a PCMO material on the pre-cleaned substrate in the substantially oxygen-free gas environment at an elevated temperature to thereby form a PCMO deposited substrate;
cooling the PCMO deposited substrate to a lower temperature in the substantially oxygen-free gas environment, the lower temperature being at least 300° C. lower than said elevated temperature; and
annealing the PCMO deposited substrate in a hydrogen environment for hydrogenation of the PCMO material at an annealing temperature less than said elevated temperature but greater than said lower temperature without presence of a catalytic transition material.

2. The process of claim 1 wherein the PCMO material is annealed in the hydrogen environment at a temperature of approximately 200° C.

3. The process of claim 1 wherein the hydrogen environment is provided by a forming gas.

4. The process of claim 1 wherein the substrate material is Si.

5. The process of claim 2 wherein the Si substrate material has a 100 crystallographic orientation.

6. The process of claim 1 wherein the depositing the PCMO material on the substrate occurs an inert gas environment.

7. The process of claim 1 wherein the pre-cleaning occurs by plasma sputtering in a RF Magnetron Sputter deposition chamber.

8. The process of claim 1 wherein PCMO material is deposited in a RF Magnetron Sputter deposition chamber at a substrate temperature substantially equal to or greater than the PCMO crystallization temperature.

9. The process of claim 1 wherein the annealing time required for the hydrogenation of the PCMO material is dependent on the particular PCMO material selected and the thickness of the PCMO material deposited on the substrate.

10. The process of claim 1 where the PCMO material is selected from the group consisting of NdNiO 3 , SmNiO 3 , PrNiO 3 , EuNiO 3 , and GdNiO 3 and combinations thereof.

11. The process of claim 10 wherein the PCMO material is NdNiO 3 , the annealing time required for the hydrogenation is a four times repeated annealing of a two-hour annealing process for a NdNiO 3 film on the substrate.

12. The process of claim 1 wherein the deposition occurs in an oxygen-free gas environment that includes hydrogen.

13. The process of claim 12 wherein the oxygen-free gas environment includes inert gas.

14. The process of claim 1 wherein PCMO material is deposited by sputtering at a substrate temperature substantially equal to or greater than the PCMO crystallization temperature.

15. The process of claim 1 wherein the forming gas comprises 10% H 2 +90% N 2 , at a 5 sccm flow rate and at 1 atm pressure.

16. The process of claim 1 , further comprising: annealing the PCMO deposited substrate in the hydrogen environment for one or more annealing cycles.

Assignees

• Hrl Lab Llc

Inventors

• Son Kyung-Ah
• Moon Jeong-Sun
• Seo Hwa Chang
• Kremer Richard M
• Quarfoth Ryan G
• Crowell Jack A
• Taboada Mariano J
• Doria Joshua M
• Welch Terry B

Classifications

• C23C14/35

  by application of a magnetic field, e.g. magnetron sputtering {(C23C14/3457 takes precedence)} · CPC title

• C23C14/541

  Heating or cooling of the substrates · CPC title

• C23C14/5846

  Reactive treatment · CPC title

• C23C14/08 Primary

  Oxides (C23C14/10 takes precedence) · CPC title