High-density capacitor for focal plane arrays
A photodetector structure includes a readout integrated circuit (ROIC) substrate and a dielectric layer overlaying the IC substrate. The dielectric layer defines a plurality of recesses formed in a top surface of the dielectric layer where each recess has at least one sidewall that extends from a top surface of the dielectric layer to a bottom portion of each respective recess. A capacitor structure forms a portion of the photodetector structure and includes a first electrode formed across the top surface of the dielectric layer and across the at least one sidewall of each recess of the plurality of recesses. A capacitor dielectric layer is formed across the first electrode and a second electrode is formed across the capacitor dielectric layer. A detector overlays the capacitor structure.
1. A unit cell of a focal plane array comprising:
a semiconductor layer having one or more integrated electrical components;
an electrically insulative layer overlaying the semiconductor layer and defining:
a plurality of partial vias formed in a first surface of the electrically insulative layer, wherein each partial via of the plurality of partial vias includes at least one sidewall that extends from the first surface to a bottom portion of the respective partial via; and
an interlayer connector extending through the electrically insulative layer to the semiconductor layer, wherein a first portion of the plurality of partial vias are disposed on a first side of the interlayer connector and another partial via of the plurality of partial vias is disposed on a second side of the interlayer connector:
a capacitor structure coupled to one or more of the integrated electrical components by the interlayer connector and including:
a first electrode formed across the first surface of the electrically insulative layer and disposed at a first distance from the semiconductor layer and along the at least one sidewall of each partial via of the plurality of partial vias;
a capacitor dielectric layer formed over the first electrode; and
a second electrode formed over the capacitor dielectric layer;
a topmost metal layer disposed at a second distance from the semiconductor layer, wherein the second distance is greater than the first distance;
a plurality of vias passing through the electrically insulative layer and positioned between the topmost metal layer and the capacitor structure, wherein the plurality of vias electrically connect the topmost metal layer to the second electrode; and
a detector overlying the capacitor structure.
2. The unit cell of a focal plane array of claim 1 wherein the electrically insulative layer comprises a passivation layer formed on the semiconductor layer as a part of an integrated circuit substrate.
3. The unit cell of a focal plane array of claim 1 wherein the electrically insulative layer comprises a dielectric layer that is positioned between the semiconductor layer and the detector.
4. The unit cell of a focal plane array of claim 1 wherein a first portion of the electrically insulative layer is positioned between the capacitor structure and the detector and a second portion of the electrically insulative layer is positioned between the capacitor structure and the semiconductor layer.
5. The unit cell of a focal plane array of claim 1 wherein the capacitor structure comprises a first capacitor structure and wherein a second capacitor structure is formed in a dielectric layer and is positioned between the first capacitor structure and the detector.
6. A unit cell of a focal plane array comprising:
a semiconductor layer having one or more integrated electrical components;
an electrically insulative layer overlaying the semiconductor layer and defining:
a plurality of partial vias formed in a top surface of the electrically insulative layer; and
an interlayer connector extending through the electrically insulative layer to the semiconductor layer, wherein a first portion of the plurality of partial vias are disposed on a first side of the interlayer connector and another partial via of the plurality of partial vias is disposed on a second side of the interlayer connector;
a capacitor structure coupled to one or more of the integrated electrical components by the interlayer connector and including:
a first electrode formed across the top surface of the electrically insulative layer and disposed at a first distance from the semiconductor layer and within the plurality of partial vias;
a capacitor dielectric layer formed across the first electrode; and
a second electrode formed across the capacitor dielectric layer;
an outer metal layer disposed at a second distance from the semiconductor layer, wherein the second distance is greater than the first distance;
a plurality of vias passing through the electrically insulative layer and positioned between the outer metal layer and the capacitor structure, wherein the plurality of vias electrically connect the outer metal layer to the second electrode; and
a detector overlying the capacitor structure.
7. The unit cell of a focal plane array of claim 6 wherein the electrically insulative layer comprises a passivation layer formed on the semiconductor layer.
8. The unit cell of a focal plane array of claim 6 wherein the electrically insulative layer comprises a dielectric layer that is positioned between the semiconductor layer and the detector.
9. The unit cell of a focal plane array of claim 6 wherein a first portion of the electrically insulative layer is positioned between the capacitor structure and the detector and a second portion of the electrically insulative layer is positioned between the capacitor structure and the semiconductor layer.
10. The unit cell of a focal plane array of claim 6 wherein the capacitor structure comprises a first capacitor structure and wherein a second capacitor structure is formed in a dielectric layer and is positioned between the first capacitor structure and the detector.
11. The unit cell of a focal plane array of claim 10 wherein the second capacitor structure comprises a planar capacitor.
12. A capacitor formed within a focal plane array unit cell, the capacitor comprising:
an electrically insulative layer defining:
a first plurality of vias formed in a first surface of the electrically insulative layer, wherein the electrically insulative layer is formed above a semiconductor substrate having one or more integrated electrical components;
an interlayer connector extending through the electrically insulative layer to the one or more integrated electrical components of the semiconductor substrate and connecting the capacitor to the one or more integrated electrical components, wherein a first portion of the first plurality of vias are disposed on a first side of the interlayer connector and another via of the first plurality of vias is disposed on a second side of the interlayer connector;
a first electrode formed across the first surface of the electrically insulative layer and disposed at a first distance from the semiconductor substrate and within the first plurality of vias;
a capacitor dielectric layer formed across the first electrode;
a second electrode formed across the capacitor dielectric layer; and
a second plurality of vias passing through the electrically insulative layer and positioned between a topmost metal layer formed above the semiconductor substrate at a second distance greater than the first distance and the second electrode, wherein the second plurality of vias electrically connect the topmost metal layer to the second electrode.
13. The capacitor of claim 12 wherein the electrically insulative layer comprises a passivation portion of an integrated circuit substrate.
14. The capacitor of claim 12 wherein the electrically insulative layer comprises a dielectric layer that is positioned between a readout integrated circuit device and a detector.
15. The capacitor of claim 12 wherein the first plurality of vias comprise partial vias.