Resonance enhanced absorptive color filters having resonance cavities
View Patent ↗Resonance enhanced color filter arrays are provided for image sensors. Resonance cavities formed with color filter materials that enhance the color filtering capabilities of the color filter materials. Resonance enhanced color filter arrays may be provided for back side illumination image sensors and front side illumination image sensors. A layer of high refractive index material or metamaterial may be provided between a microlens and a color filter material to serve as a first partially reflecting interface for the resonance cavity. An optional layer of high refractive index material or metamaterial may be provided between color filter material and a substrate. In front side illumination image sensors, color filter material may be provided in a light guide structure that extends through interlayer dielectric. The color filter material in the light guide structure may form at least part of a resonance cavity for a resonance enhanced color filter array.
1. An image sensor, comprising;
an array of photodiodes in a substrate;
color filter material in a color filter array;
a microlens array; and
a metamaterial layer between the color filter material and the microlens array, wherein a resonance cavity is formed at least partly from the color filter material and a first partially-reflecting interface between the color filter material and the metamaterial layer, and wherein the color filter array is formed between the microlens array and the substrate on a first side of the substrate, wherein the image sensor further includes an additional color filter array with an additional resonance cavity on a second side of the substrate.
2. The image sensor defined in claim 1 , wherein the metamaterial comprises a bandgap metamaterial.
3. The image sensor defined in claim 1 , wherein the metamaterial comprises a plasmonic metamaterial.
4. The image sensor defined in claim 1 , wherein a portion of the resonance cavity is formed from the substrate.
5. The image sensor defined in claim 1 , wherein the resonance cavity is also formed from a second partially-reflecting interface between the color filter material and the substrate.
6. The image sensor defined in claim 1 , further comprising an additional metamaterial layer between the color filter material and the substrate, wherein the resonance cavity is also formed from a second partially-reflecting interface between the color filter material and the additional metamaterial layer.
7. The image sensor defined in claim 1 , wherein the image sensor comprises a back side illumination image sensor and wherein the second interface is interposed between the color filter material and the substrate.
8. A system, comprising:
a central processing unit;
memory;
input-output circuitry; and
an imaging device, wherein the imaging device comprises:
a pixel array in a substrate; and
a resonance enhanced color filter array, wherein the color filter array forms at least part of a resonance cavity, and wherein the resonance enhanced color filter array comprises at least one layer of metamaterial, wherein the metamaterial comprises periodic structures having a periodicity of about 100 nm to 200 nm.
9. The system defined in claim 8 , wherein the resonance enhanced color filter array comprises:
color filter material; and
a patterned 3D band gap filter in the color filter material.
10. The system defined in claim 8 , wherein the resonance enhanced color filter array comprises at least one layer of material having a refractive index of two or higher.
11. The system defined in claim 8 , wherein the resonance enhanced color filter array comprises color filter material having a thickness of less than 300 nm.