Microbolometer systems and methods
Microbolometer systems and methods are provided herein. For example, an infrared imaging device includes a microbolometer array. The microbolometer array includes a plurality of microbolometers. Each microbolometer includes a microbolometer bridge that includes a first portion and a second portion. The first portion includes a resistive layer configured to capture infrared radiation. The second portion includes a second portion having a plurality of perforations defined therein.
1. An infrared imaging device comprising:
a readout integrated circuit (ROIC) substrate comprising a plurality of contacts and a surface, wherein the surface defines a plane; and
a microbolometer array comprising a plurality of microbolometers, wherein each microbolometer comprises:
a microbolometer bridge comprising:
a first portion comprising:
a first dielectric layer;
a resistive layer disposed on the first dielectric layer and configured to capture infrared radiation; and
a second dielectric layer disposed on the resistive layer; and
a second portion having a plurality of perforations defined therein and being separate from and surrounding the first portion; and
a leg structure coupled to the microbolometer bridge and to one of the plurality of contacts and extending between the microbolometer bridge and the one of the plurality of contacts at least in a first direction substantially parallel to the plane, wherein the leg structure comprises a cross-section having a first section, a second section substantially parallel to the first section, and a third section joining the first section and the second section, wherein the first section and the second section extend along the first direction and a second direction substantially parallel to the plane, and wherein the cross-section is an s-shaped cross-section or a z-shaped cross-section maintained as the leg structure extends along a substantial length of the leg structure to form an s-shape or a z-shape when viewed in a direction along the length of the leg structure.
2. The infrared imaging device of claim 1 , wherein the first portion further comprises:
an absorber layer disposed on the second dielectric layer; and
a third dielectric layer disposed on the absorber layer.
3. The infrared imaging device of claim 1 , wherein the first portion further comprises an absorber layer, wherein the first dielectric layer is disposed on the absorber layer, and wherein no portion of the resistive layer is in the second portion.
4. The infrared imaging device of claim 1 , wherein the third section is substantially perpendicular to the first and second sections, wherein the first portion is a sensing portion of the microbolometer bridge, wherein the second portion is a non-sensing portion of the microbolometer bridge, and wherein no portion of the resistive layer is in the leg structure.
5. A method of forming the infrared imaging device of claim 4 , the method comprising:
forming a bridge structure;
forming the leg structure; and
forming the plurality of perforations in the bridge structure to obtain the microbolometer bridge.
6. The infrared imaging device of claim 1 , wherein the third section is at an angle relative to the first and second sections, and wherein the microbolometer bridge, the leg structure, and the perforations are along a common plane.
7. The infrared imaging device of claim 1 , wherein:
the third section joins the first section and the second section in a third direction that is substantially perpendicular to the plane.
8. The infrared imaging device of claim 1 , wherein the leg structure comprises:
a first segment associated with the first section and having a first dimension that extends in the first direction that is substantially parallel to the plane and a second dimension that extends in a third direction that is substantially perpendicular to the plane, wherein the first dimension is greater than the second dimension;
a second segment associated with the second section; and
a third segment associated with the third section and adjacent to the first segment and the second segment, the third segment having a third dimension that extends in the first direction and a fourth dimension that extends in the third direction, wherein the third dimension is less than the fourth dimension.
9. The infrared imaging device of claim 8 , wherein:
each of the first segment, the second segment, and the third segment comprises a respective portion of a first metal layer, a respective portion of a first layer, and a respective portion of a second layer,
the first layer is formed on a first sidewall of the first metal layer and a first side of the first metal layer,
the second layer is formed on a second sidewall of the first metal layer and a second side of the first metal layer,
the first sidewall is opposite the second sidewall,
the first side is opposite the second side, and
the cross-section of the leg structure comprises a stack in a direction along the plane formed of the portion of the first layer, the portion of the first metal layer, and the portion of the second layer and maintained as the leg structure extends along the substantial length of the leg structure to form the stack when viewed in the direction along the length of the leg structure.
10. The infrared imaging device of claim 9 , wherein a portion of the first layer and a portion of the second layer are separated by a gap, and wherein the portion of the first layer faces the portion of the second layer.
11. The infrared imaging device of claim 1 , wherein the first portion further comprises:
a first metal layer disposed between the first dielectric layer and the resistive layer;
wherein the leg structure is in contact with the second dielectric layer.
12. The infrared imaging device of claim 11 , wherein the first portion further comprises:
a second metal layer disposed on the second dielectric layer; and
a third dielectric layer disposed on the second metal layer.
13. The infrared imaging device of claim 1 , wherein the first portion further comprises:
a metal layer disposed on the second dielectric layer; and
a third dielectric layer disposed on the metal layer,
wherein the leg structure is in contact with the third dielectric layer.
14. A method of forming an infrared imaging device, the method comprising:
forming a bridge on a sacrificial layer, wherein the bridge comprises:
a first portion comprising a resistive layer configured to capture infrared radiation; and
a second portion having a plurality of perforations formed therein;
forming an opening in the sacrificial layer;
disposing a contact metal layer on sidewalls of the opening;
forming a leg structure that couples to the bridge and the contact metal layer; and
removing the sacrificial layer to suspend the bridge and the leg structure above a substrate of the infrared imaging device, wherein the contact metal layer is coupled to the substrate.
15. The method of claim 14 , wherein the forming the bridge comprises:
disposing a first dielectric layer on a cap layer;
disposing the resistive layer on the first dielectric layer;
disposing a set of dielectric layers on the resistive layer;
disposing a second metal layer on the set of dielectric layers; and
disposing a second dielectric layer on the second metal layer,
wherein the leg structure comprises a cross-section having a first section, a second section substantially parallel to the first section, and a third section joining the first section and the second section.
16. The method of claim 15 , wherein the forming the bridge further comprises: etching through a portion of the cap layer, a portion of the first dielectric layer, a portion of each dielectric layer of the set of dielectric layers, a portion of the second metal layer, and a portion of the second dielectric layer to define the plurality of perforations.
17. The method of claim 14 , wherein the forming the bridge comprises:
disposing a second metal layer on a cap layer;
disposing a first set of dielectric layers on the second metal layer;
disposing the resistive layer on the first set of dielectric layers;
disposing a second set of dielectric layers on the resistive layer; and
etching through a portion of the cap layer, a portion of the second metal layer, a portion of each dielectric layer of the first set of dielectric layers, and a portion of each dielectric layer of the second set of dielectric layers to define the plurality of perforations.
18. The infrared imaging device of claim 1 , wherein the first portion further comprises at least one of:
a first absorber layer disposed between the first dielectric layer and the resistive layer; and/or
a second absorber layer disposed between the resistive layer and the second dielectric layer.
19. The infrared imaging device of claim 1 , wherein the cross-section of the leg structure comprises a stack in a direction along the plane formed of a first layer and a metal layer and maintained as the leg structure extends along the substantial length of the leg structure to form the stack when viewed in the direction along the length of the leg structure.
20. The infrared imaging device of claim 8 , wherein the second segment has a fifth dimension that extends in the first direction and a sixth dimension that extends in the third direction, and wherein the fifth dimension is greater than the sixth dimension.