Metal-dielectric optical filter, sensor device, and fabrication method
An optical filter, a sensor device including the optical filter, and a method of fabricating the optical filter are provided. The optical filter includes one or more dielectric layers and one or more metal layers stacked in alternation. The metal layers are intrinsically protected by the dielectric layers. In particular, the metal layers have tapered edges that are protectively covered by one or more of the dielectric layers.
1. A method comprising:
forming, in a photoresist layer and using a development time of 80 seconds to 100 seconds, an overhang by patterning the photoresist layer in a manner that uncovers a region; and
lifting the photoresist layer in a manner that provides a clean lift-off the photoresist layer without breaking a coating that covers the overhang.
2. The method of claim 1 , wherein the overhang is greater than 4 μm.
3. The method of claim 1 , wherein the overhang is about 6 μm.
4. The method of claim 1 , wherein the photoresist layer includes a bottom release layer.
5. The method of claim 4 , wherein a thickness of the bottom release layer is greater than 2 μm.
6. The method of claim 4 , wherein a thickness of the coating is about 30% of a thickness of the bottom release layer.
7. The method of claim 4 , wherein a thickness of the bottom release layer is about 2.6 μm.
8. The method of claim 1 , wherein the photoresist layer includes a top photosensitive layer.
9. The method of claim 8 , wherein a thickness of the top photosensitive layer is about 2 μm.
10. The method of claim 1 , wherein a thickness of the coating is about 500 nm.
11. The method of claim 1 , wherein one or more sides of an optical filter under the overhang are sloped at an angle of about 5 degrees.
12. A method comprising:
forming, in a photoresist layer, an overhang of about 6 μm; and
lifting the photoresist layer in a manner that provides a clean lift-off the photoresist layer without breaking a coating that covers the overhang.
13. The method of claim 12 , wherein the overhang is formed using a development time of 80 seconds to 100 seconds.
14. The method of claim 12 ,
wherein the photoresist layer includes a bottom release layer,
wherein a thickness of the bottom release layer is greater than about 2 μm, and
wherein the overhang is greater than about 4 μm.
15. The method of claim 12 ,
wherein the photoresist layer includes a bottom release layer, and
wherein a thickness of the coating is about 30% of a thickness of the bottom release layer.
16. The method of claim 12 ,
wherein the photoresist layer includes a bottom release layer and a top photosensitive layer,
wherein a thickness of the bottom release layer is about 2.6 μm,
wherein a thickness of the top photosensitive layer is about 2 μm, and
wherein a thickness of the coating is about 500 nm.
17. An optical filter, comprising:
an overhang of about 6 μm; and
a coating that covers the overhang,
a thickness of the coating being configured to ensure a clean lift-off a photoresist layer without breaking the coating.
18. The optical filter of claim 17 , further comprising:
one or more metal layers; and
a top dielectric layer that extends over and protectively covers one or more portions of the one or more metal layers.
19. The optical filter of claim 18 , wherein the one or more portions of the one or more metal layers are tapered edges of the one or more metal layers.
20. The optical filter of claim 17 , wherein one or more sides of the optical filter under the overhang are sloped at an angle of about 5 degrees.