Optical filter and sensor system

Patent metadata

Field	Value
Publication number	US-9945995-B2
Application number	US-201615099180-A
Country	US
Kind code	B2
Filing date	Apr 14, 2016
Priority date	Jul 16, 2012
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

An optical filter having a passband at least partially overlapping with a wavelength range of 800 nm to 1100 nm is provided. The optical filter includes a filter stack formed of hydrogenated silicon layers and lower-refractive index layers stacked in alternation. The hydrogenated silicon layers each have a refractive index of greater than 3 over the wavelength range of 800 nm to 1100 nm and an extinction coefficient of less than 0.0005 over the wavelength range of 800 nm to 1100 nm.

First claim

We claim:

1. A method, comprising:
forming, using a direct current (DC) sputtering technique, a plurality of hydrogenated silicon layers of an optical filter,
the plurality of hydrogenated silicon layers having a first refractive index of greater than 3 over an operating wavelength range of the optical filter of 800 nanometers (nm) to 1100 nm, and
the plurality of hydrogenated silicon layers being formed in a deposition chamber associated with a chamber pressure of less than 2 millitorr (mTorr); and

forming a plurality of lower-refractive-index layers of the optical filter,
the plurality of lower-refractive-index layers each having a second refractive index of less than 3 over the operating wavelength range of the optical filter of 800 nm to 1100 nm, and
the plurality of lower-refractive-index layers being stacked in alternation with the plurality of hydrogenated silicon layers.

2. The method of claim 1 , where the DC sputtering technique is a magnetron DC sputtering technique.

3. The method of claim 1 , where the DC sputtering technique is a pulsed DC sputtering technique.

4. The method of claim 1 , where forming the plurality of hydrogenated silicon layers comprises:
sputtering silicon to deposit the plurality of hydrogenated silicon layers onto a substrate.

5. The method of claim 4 , where sputtering the silicon comprises:
sputtering the silicon using a circular cathode with a silicon target.

6. The method of claim 5 , where a first diameter of the circular cathode is between one times (1×) a second diameter of the substrate and two times (2×) the second diameter of the substrate.

7. The method of claim 5 , where a throw distance between a first plane of the substrate and a second plane of the silicon target is between one half times (0.5×) a diameter of the substrate and two times (2×) the diameter of the substrate.

8. The method of claim 4 , where the substrate is transparent in the operating wavelength range.

9. The method of claim 1 , where the plurality of hydrogenated silicon layers are associated with an extinction coefficient of approximately 0.00055 at 800 nm.

10. The method of claim 1 , where the plurality of hydrogenated silicon layers are associated with an extinction coefficient of less than 0.0003 at 800 nm.

11. The method of claim 1 , where the plurality of hydrogenated silicon layers and the plurality of lower-refractive-index layers are a multilayer structure; and
the method further comprises:
annealing the multilayer structure at a temperature of between 250 degrees Celsius and 350 degrees Celsius.

12. The method of claim 1 , where the plurality of hydrogenated silicon layers and the plurality of lower-refractive-index layers are a multilayer structure; and
the method further comprises:
annealing the multilayer structure for a period of between 30 minutes and 90 minutes.

13. The method of claim 1 , further comprising:
providing hydrogen plasma into the deposition chamber using a plasma activation source.

14. The method of claim 1 , where the plurality of hydrogenated silicon layers and the plurality of lower-refractive-index layers are a multilayer structure; and
the method further comprises:
forming the multilayer structure on a semiconductor sensor chip using a wafer-level processing technique.

15. The method of claim 14 , where the semiconductor sensor chip includes at least one of:
a charge-coupled device (CCD) chip, or
a complementary metal oxide semiconductor (CMOS) chip.

16. The method of claim 1 , where forming the plurality of hydrogenated silicon layers comprises:
forming the plurality of hydrogenated silicon layers at a deposition rate of between 0.05 nanometers per second (nm/s) and 1.2 nm/s.

17. The method of claim 1 , where forming the plurality of hydrogenated silicon layers comprises:
forming the plurality of hydrogenated silicon layers at a deposition rate of 0.6 nanometers per second to 1.0 nanometers per second.

18. A method of fabricating an optical filter, comprising:
fabricating a plurality of hydrogenated silicon (Si:H) layers of a multilayer structure of the optical filter using a direct current (DC) sputtering technique,
the plurality of Si:H layers being fabricated in a low-pressure deposition chamber associated with a chamber pressure of 2 millitorr (mTorr), and
the plurality of Si:H layers having a first refractive index of greater than 3 over an operating wavelength range of the optical filter of 800 nanometers (nm) to 1100 nm; and

fabricating a plurality of lower-refractive-index (LI) layers,
the plurality of LI layers having a second refractive index of less than 3 over the operating wavelength range of the optical filter of 800 nm to 1100 nm, and
the plurality of LI layers being stacked in alternation with the plurality of Si:H layers.

19. The method of claim 18 , further comprising:
annealing the multilayer structure of the optical filter at a temperature of between 250 degrees Celsius and 350 degrees Celsius.

20. The method of claim 18 , where the plurality of Si:H layers are associated with an extinction coefficient of less than 0.0003 at 800 nm.

Assignees

• Viavi Solutions Inc
• Viavi Solutions Inc

Inventors

• Hendrix Karen Denise
• Bradley Jr Richard A
• Grigonis Marius
• Ockenfuss Georg J

Classifications

• G02B5/285

  comprising deposited thin solid films (G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361) · CPC title

• H04N13/254

  in combination with electromagnetic radiation sources for illuminating objects · CPC title

• G02B5/207

  comprising semiconducting materials · CPC title

• G02B5/281 Primary

  designed for the infrared light · CPC title

• C23C14/185

  by cathodic sputtering · CPC title