Spectral filter, and image sensor and electronic device including spectral filter
Provided is a spectral filter, and an image sensor and an electronic device each including the spectral filter. The spectral filter includes: at least one first filter having a central wavelength in a first wavelength region; and at least one second filter having a central wavelength in a second wavelength region. The first filter includes: a plurality of first metal reflection layers vertically spaced apart from each other; and at least one first cavity provided between the plurality of first metal reflection layers. The second filter includes: a second metal reflection layer and a Bragg reflection layer vertically spaced apart from each other; and at least one second cavity disposed between the second metal reflection layer and the Bragg reflection layer.
1. A spectral filter comprising:
a first filter having a central wavelength in a first wavelength region; and
a second filter having a central wavelength in a second wavelength region,
wherein the first filter comprises:
two first metal reflection layers vertically spaced apart from each other;
a first cavity provided between the two first metal reflection layers; and
a first dielectric layer and a second dielectric layer disposed below and above the first cavity, respectively, and
the second filter comprises:
a second metal reflection layer and a Bragg reflection layer vertically spaced apart from each other;
a second cavity disposed between the second metal reflection layer and the Bragg reflection layer; and
a third dielectric layer and a fourth dielectric layer disposed below and above the second cavity, respectively,
wherein the second metal refection layer and the Bragg reflection layer are of different materials.
2. The spectral filter of claim 1 , wherein the central wavelength in the first wavelength region is shorter than the central wavelength in the second wavelength region.
3. The spectral filter of claim 2 , wherein the two first metal reflection layers comprise Al, Ag, Au, Ti, W, or TiN, and the second metal reflection layer comprises Cu, Ag, Au, Ti, W, or TiN.
4. The spectral filter of claim 2 , wherein the second metal reflection layer further comprises poly-Si.
5. The spectral filter of claim 1 , wherein the first metal reflection layer and the second metal reflection layer have a thickness of 10 nm to 80 nm.
6. The spectral filter of claim 1 , wherein the two first metal reflection layers comprise Al, Ag, Au, Ti, W, or TiN, and the second metal reflection layer comprises Cu.
7. The spectral filter of claim 1 , wherein the first filter further comprises a first filter array comprising a plurality of first filters having different central wavelengths, and the second filter further comprises a second filter array comprising a plurality of second filters having different central wavelengths.
8. The spectral filter of claim 1 , wherein the central wavelength of the first filter is based on a thickness or an effective refractive index of the first cavity, and the central wavelength of the second filter is based on a thickness or an effective refractive index of the second cavity.
9. The spectral filter of claim 1 , wherein each of the first, the second, the third, and the fourth dielectric layers has a single-layer or a multi-layer structure.
10. The spectral filter of claim 1 , wherein a thickness or an effective refractive index of each of the first and second dielectric layers is based on the central wavelength of the first filter, and a thickness or an effective refractive index of each of the third and fourth dielectric layers is based on the central wavelength of the second filter.
11. The spectral filter of claim 1 , further comprising a plurality of microlenses provided at the first filter and the one second filter.
12. The spectral filter of claim 1 , further comprising a color filter disposed on a same plane as the first filter and the second filter.
13. The spectral filter of claim 1 , further comprising an additional filter provided at the first filter and the second filter and configured to transmit a particular wavelength band.
14. The spectral filter of claim 13 , wherein the additional filter comprises a color filter or a broadband filter.
15. The spectral filter of claim 1 , wherein a short-wavelength absorption filter is provided at a part of the first filter and the second filter, and a long-wavelength cut-off filter is provided at another part of the first filter and the second filter.
16. An image sensor comprising:
a spectral filter; and
a pixel array receiving light transmitted through the spectral filter,
wherein the spectral filter comprises:
a first filter having a central wavelength in a first wavelength region; and
a second filter having a central wavelength in a second wavelength region,
wherein the first filter comprises:
a plurality of first metal reflection layers vertically spaced apart from each other; and
a first cavity provided between the plurality of first metal reflection layers, and
the second filter comprises:
a second metal reflection layer and a Bragg reflection layer vertically spaced apart from each other; and
a second cavity disposed between the second metal reflection layer and the Bragg reflection layer
wherein the plurality of first metal reflection layers comprise Al, Ag, Au, Ti, W, or TiN, and the second metal reflection layer comprises Cu,
wherein the first filter further comprises a first dielectric layer and a second dielectric layer disposed below and above the first cavity, respectively, and the second filter further comprises a third dielectric layer and a fourth dielectric layer disposed below and above the second cavity, respectively, and
wherein the central wavelength of the first filter is based on a thickness or an effective refractive index of each of the first and the second dielectric layers, and the central wavelength of the second filter is based on a thickness or an effective refractive index of each of the third and the fourth dielectric layers.
17. The image sensor of claim 16 , wherein the pixel array comprises a plurality of pixels, and each pixel of the plurality of pixels comprising a wiring layer including a driver circuit and a photodiode disposed at the wiring layer.
18. The image sensor of claim 16 , wherein the central wavelength in the first wavelength region is shorter than the central wavelength in the second wavelength region.
19. The image sensor of claim 16 , wherein the first filter further comprises a first filter array comprising a plurality of first filters having different central wavelengths, and the second filter further comprises a second filter array comprising a plurality of second filters having different central wavelengths.
20. The image sensor of claim 16 , wherein the central wavelength of the first filter is based on a thickness or an effective refractive index of the first cavity, and the central wavelength of the second filter is based on a thickness or an effective refractive index of the second cavity.
21. The image sensor of claim 16 , wherein the spectral filter further comprises a plurality of microlenses provided at the first filter and the second filter.
22. The image sensor of claim 16 , wherein the spectral filter further comprises a color filter disposed on a same plane as the first filter and the second filter.
23. The image sensor of claim 16 , wherein the spectral filter further comprises an additional filter provided at the first filter and the second filter and configured to transmit a particular wavelength band.
24. The image sensor of claim 16 , further comprising a timing controller, a row decoder, and an output circuit.
25. An electronic device comprising the image sensor of claim 16 .
26. The electronic device of claim 25 , wherein the electronic device comprises a mobile phone, a smartphone, a tablet, a smart tablet, a digital camera, a camcorder, a notebook computer, a television, a smart television, a smart refrigerator, a security camera, a robot, or a medical camera.