RE.sub.x M.sub.1-x Mn.sub.y O.sub..delta. films for microbolometer-based IR focal plane arrays

• US 5,854,587 A
• Filed: 06/26/1997
• Issued: 12/29/1998
• Est. Priority Date: 06/26/1997
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Dorsey, Paul E., Chrisey, Douglas, Caulfield, John T., Horwitz, James
• Primary Examiner(s): Walberg, Teresa J.
• Assistant Examiner(s): PWU, JEFFREY C
• Application Number:
  US08/883,037
• Time in Patent Office: 551 Days
• Field of Search: 338/15, 338/17, 338/18, 338/22 R, 338/22 SD, 252/521.1, 252/520.5
• US Class Current: 338/22.0SD
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01L 31/095 comprising amorphous semiconductors

Abstract

Microbolometers can be made with a thin film composition of matter having a large temperature coefficient of resistance (TCR) as compared to the same material in the bulk form. The composition is a manganite of the formula

RE.sub.x M.sub.1-x Mn.sub.y O.sub.δ

where

RE is Y and the rare earths such as La, Ce, Pr, Nb, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof,

M is a divalent metal such as Ca, Sr, Ba, Pb, and combinations thereof,

x is less than l,

y is from about 0.75 to about 1.5, and

δ is from about 2.5 to about 4.0.

The microbolometer is made by applying a thin film of the composition on to a substrate such as SiN_x and annealing the deposited film to remove inhomogeneities and to decrease the defects so as to increase the TCR.

Claims

1. An improved microbolometer comprising:

a thin film composition of matter, the thin film comprising;

a manganite of the formula

space="preserve" listing-type="equation">RE.sub.x M.sub.1-x Mn.sub.y O.sub.δ

wherein

RE is selected from the group consisting of Y and the rare earths, and combinations thereof,

M is selected from the group consisting of divalent metals, and combinations thereof,

x is less than 1,

v is from about 0.75 to about 1.5, and

δ

is from about 2.5 to about 4.0; and

a microbridge for measuring resistance changes due to temperature changes in the thin film, comprising a substrate having a cavity disposed thereon;

wherein the thin film is deposited on the microbridge.

2. An improved microbolometer according to claim 1, wherein the deposited thin film has been annealed to remove inhomogeneities and to decrease the defects so as to increase the TCR.

3. An improved microbolometer according to claim 1, wherein the substrate is Si₃ N₄ or LaAlO₃.

4. An improved microbolometer according to claim 1, wherein a buffer layer is deposited between the substrate and the thin film.

5. An improved microbolometer according to claim 1, wherein the thin film has a thickness of less than about 1 μ

m.

6. An improved microbolometer according to claim 1, wherein the thin film has a thickness from about 0.05 to about 0.5 μ

m.

7. An improved microbolometer according to claim 1, wherein the manganite composition has a high temperature coefficient of resistance at near room temperature.

8. An improved microbolometer according to claim 7, wherein the high temperature coefficient of resistance is at least 4%.

9. An improved microbolometer according to claim 8, wherein the high temperature coefficient of resistance is at least 8%.

10. An improved microbolometer according to claim 1, wherein the manganite composition has a temperature coefficient of resistance of at least 4% at temperatures obtained by thermo-electric coolers.

11. An improved microbolometer according to claim 1, wherein the manganite composition has a temperature coefficient of resistance of at least 8% at temperatures obtained by thermo-electric coolers.

12. An improved microbolometer according to claim 1, wherein said thin film is disposed in zero applied magnetic field.