Method for forming light absorbing aluminum nitride films by ion beam deposition

• US 5,393,574 A
• Filed: 11/02/1993
• Issued: 02/28/1995
• Est. Priority Date: 08/28/1992
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Sulzbach, Frank C.
• Primary Examiner(s): King, Roy V.
• Application Number:
  US08/144,367
• Time in Patent Office: 483 Days
• Field of Search: 427/530, 427/528, 427/523, 427/255.7, 427/419.1, 427/164, 427/165, 427/166, 428/310.5
• US Class Current: 427/530
• CPC Class Codes: C23C 14/0617 AIII BV compounds, where A is Al, Ga, In or Tl and B is N, P, As, Sb or Bi
• CPC Class Codes: C23C 14/0641 Nitrides C23C14/0617 takes precedence
• CPC Class Codes: C23C 14/48 Ion implantation
• CPC Class Codes: F24S 70/225 for spectrally selective absorption
• CPC Class Codes: F24S 70/25 Coatings made of metallic material
• CPC Class Codes: F24S 70/30 Auxiliary coatings, e.g. anti-reflective coatings
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence
• CPC Class Codes: Y02E 10/40 Solar thermal energy, e.g. solar towers
• CPC Class Codes: Y10T 428/12479 Porous [e.g., foamed, spongy, cracked, etc.]
• CPC Class Codes: Y10T 428/12528 Semiconductor component
• CPC Class Codes: Y10T 428/12951 Fe-base component
• CPC Class Codes: Y10T 428/249956 Void-containing component is inorganic
• CPC Class Codes: Y10T 428/249961 With gradual property change within a component
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A light absorbing, low reflectance coating and method of fabricating the coating provided by electron beam evaporation of aluminum onto substrates bombarded with nitrogen ions to produce a randomly textured coating which traps light in a labyrinth. The coating is electrically insulating except for the first few tens of atoms which remain metallic. Absorptance exceeds 90% in the 0.4 to 16 μm region. The coating is flexible and can be deposited on a polymer base.

Claims

1. A method of fabricating a light absorbing film having an absorptance of about 95% in the 8 to 14 μ

m region, comprising the steps of;

(a) providing an evacuated chamber;

(b) placing a substrate in said chamber;

(c) providing and depositing on said substrate vaporized elemental aluminum in said chamber; and

(d) bombarding said vaporized elemental aluminum with nitrogen in progressively increasing amounts up to stoichiometry to deposit elemental aluminum on said substrate with aluminum nitride over said elemental aluminum having the formula Al_x N_y, where the atomic ratio of y;

x is progressively increased.

2. The method of claim 1 further including the step of evacuating said chamber to a pressure of about 10^-6 Torr prior to step (b).

3. The method of claim 1 further including the step of forming a semi-transparent dielectric layer over said aluminum nitride.

4. The method of claim 2 further including the step of forming a semi-transparent dielectric layer over said aluminum nitride.

5. The method of claim 1 wherein said substrate is one of globular or specular elements with size of about 0.5 micrometers in diameter.

6. The method of claim 2 wherein said substrate is one of globular or specular elements with size of about 0.5 micrometers in diameter.

7. The method of claim 3 wherein said substrate is one of globular or specular elements with size of about 0.5 micrometers in diameter.

8. The method of claim 4 wherein said substrate is one of globular or specular elements with size of about 0.5 micrometers in diameter.

9. The method of claim 1 wherein said step of bombarding includes bombarding said aluminum with nitrogen ions having a current density of from about 10 to about 300 μ

amperes/cm² and an acceleration voltage of from about 10 to about 1000 eV to form the deposited aluminum nitride.

10. The method of claim 9 wherein said deposited aluminum nitride is spongy and has an average density of about 1 gm/cc.

11. The method of claim 2 wherein said step of bombarding includes bombarding said aluminum with nitrogen ions having a current density of from about 10 to about 300 μ

amperes/cm² and an acceleration voltage of from about 10 to about 1000 eV to form the deposited aluminum nitride.

12. The method of claim 11 wherein said deposited aluminum nitride is spongy and has an average density of about 1 gm/cc.

13. The method of claim 3 wherein said step of bombarding includes bombarding said aluminum with nitrogen ions having a current density of from about 10 to about 300 μ

amperes/cm² and an acceleration voltage of from about 10 to about 1000 eV to form the deposited aluminum nitride.

14. The method of claim 13 wherein said deposited aluminum nitride is spongy and has an average density of about 1 gm/cc.

15. The method of claim 4 wherein said step of bombarding includes bombarding said aluminum with nitrogen ions having a current density of from about 10 to about 300 μ

amperes/cm² and an acceleration voltage of from about 10 to about 1000 eV to form the deposited aluminum nitride.

16. The method of claim 15 wherein said deposited aluminum nitride is spongy and has an average density of about 1 gm/cc.

17. The method of claim 5 wherein said step of bombarding includes bombarding said aluminum with nitrogen ions having a current density of from about 10 to about 300 μ

amperes/cm² and an acceleration voltage of from about 10 to about 1000 eV to form the deposited aluminum nitride.

18. The method of claim 17 wherein said deposited aluminum nitride is spongy and has an average density of about 1 gm/cc.

19. The method of claim 8 wherein said step of bombarding includes bombarding said aluminum with nitrogen ions having a current density of from about 10 to about 300 μ

amperes/cm² and an acceleration voltage of from about 10 to about 1000 eV to form the deposited aluminum nitride.

20. The method of claim 19 wherein said deposited aluminum nitride is spongy and has an average density of about 1 gm/cc.