Microbolometer pixel and fabrication method utilizing ion implantation

• US 7,915,585 B2
• Filed: 03/31/2009
• Issued: 03/29/2011
• Est. Priority Date: 03/31/2009
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Geneczko, Jeannie
• Primary Examiner(s): Porta; David P
• Assistant Examiner(s): Kim; Kiho
• Application Number:
  US12/414,766
• Publication Number:
  US 20100243896A1
• Time in Patent Office: 728 Days
• Field of Search: 2503381 -3385
• US Class Current: 250/338.1
• CPC Class Codes: G01J 5/023 Particular leg structure or construction or shape; Nanotubes
• CPC Class Codes: G01J 5/024 Special manufacturing steps or sacrificial layers or layer structures
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01C 17/06 adapted for coating resistive material on a base
• CPC Class Codes: H01C 7/026 Vanadium oxides or oxidic compounds, e.g. VOx
• CPC Class Codes: H01L 27/14669 Infrared imagers
• CPC Class Codes: H01L 27/14692 Thin film technologies, e.g. amorphous, poly, micro- or nanocrystalline silicon
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence

Abstract

A microbolometer pixel and a reduced-step process for manufacturing it comprising the step of ion implantation of vanadium oxide whereby VO_x is converted to a low resistivity mixed phase vanadium oxide (VO_x/V₂O₃/VO/V) in the leg, metallized support post, and detector contact areas. Masking maintains high temperature coefficient of resistance (TCR) VO_x in the sensing portion of the pixel bridge region. The implanted area resistivity and TCR can be controlled by ion implantation dose and energy.

Claims

1. A method for manufacturing at least one microbolometer pixel comprising the steps of:

providing a sacrificial layer over a substrate with at least one readout integrated circuit pad wherein a post is disposed between said at least one integrated circuit pad and a dielectric layer comprising at least one via to said post;

forming at least one VO_x layer over said at least one via and said dielectric layer;

depositing a second dielectric layer on said VO_x layer;

depositing an ion implant mask layer on said dielectric layer;

patterning said mask and etching said second dielectric layer leaving a protected sensing bridge region;

implanting ions whereby VO_x of said VO_x layer is converted to mixed phase vanadium oxide (VO_x/V₂O₃/VO/V) and whereby electrical resistivity of unmasked area of said VO_x layer is decreased.

2. The method of claim 1, wherein implanted area temperature coefficient of resistance (TCR) and resistivity are controlled by at least one of ion implantation dose and ion implantation energy.

3. The method of claim 1, wherein ion implanting dose is about approximately 1×

10¹³ to 5×

10¹⁷ ions/cm² and ion implanting energy is about approximately 2.5 KeV to 40 KeV.

4. The method of claim 1, wherein implanted area includes at least one of leg, detector contact at bridge and metallized post.

5. The method of claim 1, whereby said converted area contributes to thermal detection by increasing effective sensing area of said microbolometer pixel.

6. The method of claim 1, whereby lower thermal conductivity in converted leg area increases thermal isolation, increasing sensitivity of said microbolometer pixel.

7. The method of claim 1, wherein said step of implanting comprises a plurality of masks and implants directed at select areas to further lower resistance.

8. The method of claim 1, wherein ions of said ion implantation step are ions of at least one of argon, krypton, and nitrogen.

9. The method of claim 1 wherein said step of ion implantation comprises nitrogen ions whereby low resistivity VN is formed in said mixed phase vanadium oxide (VO_x/V₂O₃/VO/V).

10. A microbolometer pixel comprising:

a substrate with at least one adjacent readout integrated circuit pad wherein a post is disposed between said at least one circuit pad and a first dielectric layer, said first dielectric layer comprising at least one via to said post;

a VO_x bridge layer disposed between said first dielectric layer and a second dielectric layer in operational contact with said post through said via;

a dielectric cap disposed on said second dielectric layer and said bridge layer; and

wherein said bridge layer comprises an implanted area defined by implantation of ions.

11. The microbolometer pixel of claim 10, wherein said implanted area includes at least one of leg, detector contact at bridge and post.

12. The microbolometer pixel of claim 10, wherein conversion thickness of said implanted area is controlled by at least one of ion implantation dose and ion implantation energy.

13. The microbolometer pixel of claim 10, wherein said implanted area resistivity and temperature coefficient of resistance (TCR) are controlled by at least one of ion implantation dose and ion implantation energy.

14. The microbolometer pixel of claim 10, wherein conversion thickness of said implanted area is controlled by said implantation of ions from about approximately 100 Angstroms to thickness of said VO_x layer.

15. The microbolometer pixel of claim 10, wherein said implanted area resistivity is about approximately 0.001 to 0.01 Ω

-cm.

16. The microbolometer pixel of claim 10 wherein said implanted area comprises VN.

17. The microbolometer pixel of claim 10 further comprising a common substrate whereon a plurality of said pixels is positioned in a focal plane array (FPA).

18. A method for manufacturing at least one microbolometer pixel comprising the steps of:

providing a substrate with at least one readout integrated circuit pad operatively connected to at least one readout integrated circuit;

depositing a sacrificial layer over said substrate;

forming at least one metal-filled post between said at least one readout integrated circuit pad and a first dielectric layer;

forming at least one via through said first dielectric layer to said at least one metal-filled post;

forming at least one VO_x layer over said first dielectric layer and filling said at least one via;

depositing a second dielectric layer on said VO_x layer;

depositing an ion implant photoresist mask layer on said second dielectric layer;

patterning said mask and etching said second dielectric layer leaving a protected microbolometer pixel bridge sensing region;

implanting ions whereby VO_x of said VO_x layer is converted to mixed phase vanadium oxide (VO_x/V₂O₃/VO/V) and electrical resistivity of desired area is decreased;

removing said mask;

depositing a capping dielectric layer over said microbolometer pixel region;

defining leg, bridge and post areas by photolithography and etch; and

removing said sacrificial layer to complete formation of said at least one microbolometer pixel.

19. The method of claim 18 wherein said substrate is a common substrate, said method further comprising:

forming a plurality of said pixels in a focal plane array (FPA) on said common substrate.

20. The method of claim 18 wherein said step of implanting ions comprises nitrogen ions whereby VN is formed in said mixed phase vanadium oxide (VO_x/V₂O₃/VO/V).