Pyroelectric aluminum nitride MEMS infrared sensor with selective wavelength infrared absorber

Patent metadata

Field	Value
Publication number	US-9335217-B2
Application number	US-201414448877-A
Country	US
Kind code	B2
Filing date	Jul 31, 2014
Priority date	Aug 1, 2013
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A MEMS sensor for detecting electromagnetic waves in a particular frequency range is provided. In a preferred embodiment, the MEMS sensor comprises a bottom substrate layer; a first electrode layer over the substrate layer; a pyroelectric layer over the first electrode layer; and a second electrode layer over the pyroelectric layer; wherein a top electrode layer is patterned with a periodic structure that has a periodicity less than or equal to target infrared wavelength.

First claim

What is claimed is:

1. A MEMS sensor comprising:
a substrate layer;
a first electrode layer adjacent the substrate layer;
a pyroelectric layer adjacent the first electrode layer; and
a second electrode layer adjacent the pyroelectric layer,
wherein the second electrode layer is patterned with a periodic structure that has a periodicity less than or equal to 8 μm.

2. The sensor of claim 1 , wherein the patterned periodic structure comprises a hole array structure.

3. The sensor of claim 1 , wherein the patterned periodic structure comprises a stripe structure.

4. The sensor of claim 1 , wherein the periodic structure has a periodicity less than or equal to a target infrared wavelength according to the equation P≦λ where P is periodicity and λ is target infrared wavelength.

5. The sensor of claim 1 , wherein the sensor is comprised of at least two sensor elements and each of the two sensor elements has a periodic structure patterned with different periodicities.

6. The sensors of claims 1 through 5 , wherein the pyroelectric layer comprises a material selected from the group consisting of PZT, ZnO, PVDF, AlN, and c-axis oriented AlN.

7. The sensor of claim 1 , wherein the first electrode layer has a thickness ranging from about 10 nm to about 1000 nm.

8. The sensor of claim 1 , wherein the first electrode layer comprises Molybdenum.

9. The sensor of claim 1 , wherein the pyroelectric layer comprises AlN.

10. The sensor of claim 1 , wherein the pyroelectric layer has a thickness according to the equation 2×t×n λ ≦λ where t is the pyroelectric film thickness, λ is the target infrared wavelength, and n λ is the index of the pyroelectric material at the target infrared wavelength.

11. The sensor of claim 1 , wherein the second electrode has a thickness ranging from about 10 nm to about 1000 nm.

12. The sensor of claim 1 , wherein the second electrode comprises Molybdenum.

13. The sensor of claim 3 , wherein the patterned periodic structure is a hole array and the diameter of a hole in the hole array is provided according to the equation r≧P×0.5 where r is the hole diameter and P is the periodicity of the patterned periodic structure.

14. The sensor of claim 1 , wherein the periodic structure comprises a stripe structure having a line/spacing (L/S) of about 1.

15. The sensor of claim 1 , wherein the second electrode layer is a top layer of the sensor.

16. The sensor of claim 1 , further comprising a second pyroelectric layer adjacent to the substrate layer.

17. The sensor of claim 1 , wherein the periodic structure has a periodicity less than or equal to 105% of a target infrared wavelength according to the equation P≦1.05*λ where P is periodicity and λ is target infrared wavelength.

18. A MEMS sensor element comprising:
a substrate layer;
a first electrode layer adjacent the substrate layer;
a pyroelectric layer adjacent the first electrode layer; and
a second electrode layer adjacent the pyroelectric layer,
wherein the second electrode layer is patterned with a periodic structure that has a periodicity less than or equal to a target infrared wavelength.

19. A method of making a MEMS sensor element, the method comprising:
forming a first electrode layer on a substrate;
forming a pyroelectric layer adjacent the electrode layer;
forming a second electrode layer adjacent the pyroelectric layer; and,
patterning the second electrode layer of the MEMS sensor to have a patterned periodic structure with a periodicity less than or equal to a target infrared wavelength.

Assignees

• Univ California

Inventors

• Pisano Albert
• Horsley David
• Yamamoto Kansho

Classifications

• G01J5/34

  using capacitors, e.g. pyroelectric capacitors · CPC title

• H10F39/184

  Infrared image sensors · CPC title

• H10F39/011

  Manufacture or treatment of image sensors covered by group H10F39/12 · CPC title

• B81B3/0045

  Improve properties related to angular swinging, e.g. control resonance frequency · CPC title

• G01J5/0853 Primary

  having infrared absorbers other than the usual absorber layers deposited on infrared detectors like bolometers, wherein the heat propagation between the absorber and the detecting element occurs within a solid · CPC title