Method for manufacturing thin-film lithium microbatteries

• US 6,764,525 B1
• Filed: 03/11/2003
• Issued: 07/20/2004
• Est. Priority Date: 02/08/2001
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: West, William C., Bugga, Ratnakumar V., Whitacre, Jay F.
• Primary Examiner(s): Maples, John S.
• Application Number:
  US10/390,258
• Time in Patent Office: 497 Days
• Field of Search: 296/232, 296/235
• US Class Current: 29/623.2
• CPC Class Codes: H01L 23/58 Structural electrical arrangements for semiconductor devices not otherwise provided for , e.g. in combination with batteries H01L23/49593, H01L23/49596 take precedence
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01M 10/0562 Solid materials
• CPC Class Codes: H01M 4/04 Processes of manufacture in general
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/661 Metal or alloys, e.g. alloy coatings H01M4/669 take precedence
• CPC Class Codes: H01M 6/188 Processes of manufacture
• CPC Class Codes: H01M 6/40 Printed batteries , e.g. thin film batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10T 29/4911 including sealing
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

A process for making thin-film batteries including the steps of cleaning a glass or silicon substrate having an amorphous oxide layer several microns thick; defining with a mask the layer shape when depositing cobalt as an adhesion layer and platinum as a current collector; using the same mask as the preceding step to sputter a layer of LiCoO₂ on the structure while rocking it back and forth; heating the substrate to 300° C. for 30 minutes; sputtering with a new mask that defines the necessary electrolyte area; evaporating lithium metal anodes using an appropriate shadow mask; and, packaging the cell in a dry-room environment by applying a continuous bead of epoxy around the active cell areas and resting a glass slide over the top thereof.

Claims

1. A method for manufacturing a thin-film battery comprising the steps of:

a. through a first mask, depositing a first metal as an adhesion layer on a substrate;

b. through said first mask, depositing a second metal as a current collector over said adhesion layer;

c. through said first mask, sputtering a cathode layer in an argon-oxide gas on top of said current collector while rocking said substrate in an oscillatory fashion;

d. heating said substrate in a dry environment of less than 1% humidity to an elevated temperature for a fixed period of time;

e. through a second mask, sputtering a thin film solid state electrolyte material onto said cathode layer while rocking said substrate in an oscillatory fashion, thereby forming an electrolyte layer;

f. evaporating an anode layer over said electrolyte layer; and

g. packaging and sealing the resulting structure.

2. The method as in claim 1 wherein said first metal is cobalt.

3. The method as in claim 1 wherein said second metal is platinum.

4. The method as in claim 1 wherein said cathode layer is a thin film solid state material.

5. The method as in claim 1 wherein said cathode layer is formed of LiCoO₂.

6. The method as in claim 1 wherein said electrolyte layer is formed of LiPON.

7. The method as in claim 1 wherein said step of sealing includes applying a bead of epoxy around said thin-film battery in a dry environment and placing a plate thereover.

8. The method as in claim 7 wherein said plate is glass.

9. The method as in claim 1 wherein said substrate is silicon having an insulating layer thereover.

10. The method as in claim 1 wherein said substrate is glass.

11. The method as in claim 1 wherein step d thereof said elevated temperature is 300°

C. and said fixed time is 30 minutes.

12. The method as in claim 1 wherein step c thereof said step of rocking includes rocking the substrate back and forth beneath the target with an amplitude of 5 centimeters.

13. The method as in claim 1 where step c thereof further includes the ratio of argon to oxygen gas is in the ration of 3 to 1.

14. The method as in claim 1 where step c thereof further includes the step of holding said substrate 70 millimeters away from the target.

15. The method as in claim 1 further including after step c, said substrate is maintained in a dry environment of less than 1% humidity while performing an X-ray diffraction on said deposited layers to insure that said current collector layer contains nano-crystalline LiCoO₂ grains oriented with their (104) planes parallel to the plane of said substrate.

16. The method as in claim 1 wherein step e thereof said electrolyte layer is deposited in a sputter chamber in the presence of pure N₂ holding said substrate 90 millimeters from the target using 100 Watts of power.

17. The method as in claim 1 wherein step e thereof said electrolyte is deposited to a thickness of 1 to 1.5 microns.

18. The method as in claim 1 wherein step e thereof further includes rocking said substrate back and forth beneath the target with an amplitude of 5 centimeters.

19. The method as in claim 1 further including removing with HCl acid a portion of the cathode layer not covered by the electrolyte layer to expose a portion of the current collector layer and cleaning the exposed portion of the current collector layer for ohmic contact with circuitry employing said thin-film battery.

20. A method for manufacturing a thin-film battery comprising the steps of:

a through a first mask, depositing cobalt as an adhesion layer on a substrate;

b. through said first mask, depositing platinum as a current collector layer over said adhesion layer;

c. through said first mask, sputtering LiCoO₂ as a cathode layer in a 3;

1 argon-oxide gas on top of said current collector layer while rocking said substrate under the target in an oscillatory fashion;

d. heating said substrate in a dry environment of less than 1% humidity to 300°

C. for thirty minutes;

e through a second mask, sputtering an electrolyte material of LiPON onto said cathode layer while rocking said substrate in an oscillatory fashion, thereby forming an electrolyte layer;

f. evaporating a lithium metal anodes using an appropriate shadow mask; and

,

g. packaging and sealing the resulting structure.

21. A method for manufacturing a thin-film battery comprising the steps of:

a. through a first mask, depositing a first metal as an adhesion layer on a substrate, the first metal being deposited in a first beginning element region and a second beginning element region, the first beginning element region and the second beginning element region being isolated from each other;

b. through the first mask, depositing a second metal as a current collector over the adhesion layer, the second metal forming a continuation of the first beginning element and the second beginning element;

c. through the first mask, sputtering a cathode layer in an argon-oxide gas on top of the current collector while rocking the substrate in an oscillatory fashion, the cathode layer forming a continuation of the first beginning element and the second beginning element;

d. heating the resulting structure in a dry environment of less than 1% humidity to an elevated temperature for a fixed period of time;

e. through a second mask, sputtering a thin film solid state electrolyte material onto the cathode layer above a portion of the first beginning element while rocking the substrate in an oscillatory fashion, thereby forming an electrolyte layer;

f. through a third mask, evaporating an anode layer over a portion of the electrolyte layer above the first beginning element and a portion of the cathode layer above the second beginning element; and

g. packaging and sealing an active area of the structure so that a portion of the first beginning element not covered by the electrolyte layer and a portion of the second beginning element not covered by the anode layer are not enclosed by the packaging and sealing.

22. The method as in claim 21, wherein the packaging and sealing step includes the steps of:

applying an epoxy bead around the active area of the structure; and

covering the active area of the structure with an insulating protective layer so that the epoxy bead and the insulating protective layer make a hermetic seal.

23. The method as in claim 21 further including steps of:

h. exposing a portion of the current collector layer covered by the cathode layer not enclosed by the packaging and sealing; and

i. cleaning the exposed portion of the current collector layer.

24. The method as in claim 23 wherein the exposing step includes removing with HCl acid a portion of the cathode layer not enclosed by the packaging and sealing to expose a portion of the current collector layer.

25. The method as in claim 23 wherein the cleaning step includes the step of:

applying methanol to the exposed current collector layer.

26. The method as in claim 23 further including step of:

j. melting a bead of solder onto the exposed part of the current collector layer so that an electrical lead is welded to the exposed current collector layer for making ohmic contact with external circuitry.