Optical navigation device, and method for manufacturing same
View Patent ↗An optical navigation sensor receives light that is produced by a light source and reflected from a surface. The optical navigation sensor has a silicon substrate having a plurality of photo-sensing regions, each of which receives a portion of the reflected light, and each of which provides a pixel of navigation information. At least one layer of material is deposited on the photo-sensing regions of the silicon substrate during a silicon wafer fabrication process. Each layer has a thickness that causes it to serve as an anti-reflection coating and reduce a percentage of light that is reflected away from the photo-sensing regions of the silicon substrate. A circuit biases each of the photo-sensing regions with a current, the current providing a given responsivity, and the current being less than a current that would be required to provide the given responsivity absent the at least one layer of material.
1. An optical navigation device, comprising:
a light source to produce light for illuminating a surface;
an optical navigation sensor to receive light reflected from the surface, the light reflected from the surface being initially produced by the light source, and the optical navigation sensor having:
a silicon substrate having a plurality of photo-sensing regions, each of which receives a portion of the light reflected from the surface, and each of which provides a pixel of navigation information;
at least one layer of material that was deposited on the photo-sensing regions of the silicon substrate during a silicon wafer fabrication process, wherein each of the at least one layer of material has a thickness that causes the layer of material to serve as an anti-reflection coating and reduce a percentage of light that is reflected away from the photo-sensing regions of the silicon substrate to less than 30%; and
a circuit to bias each of the photo-sensing regions with a current, the current providing a given responsivity, and the current being less than a current that would be required to provide the given responsivity absent the at least one layer of material.
2. The optical navigation device of claim 1 , wherein the photo-sensing regions provide the optical navigation sensor with a given resolution, the given resolution being greater than would be possible to achieve while maintaining the given responsivity in the absence of the at least one layer of material.
3. The optical navigation device of claim 1 , wherein each of the at least one layer of material is selected from the group consisting of: silicon nitride, silicon dioxide, spin-on-glass-oxynitrides, silicon-oxynitrides, and a polyimide thin films.
4. The optical navigation device of claim 1 , wherein the at least one layer of material is a single layer of silicon nitride.
5. The optical navigation device of claim 4 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the single layer of silicon nitride is about 64 nm to about 96 nm multiplied by an odd integer, and wherein the thickness of the single layer of silicon nitride provides a minimum reflection loss of less than 5%.
6. The optical navigation device of claim 4 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the single layer of silicon nitride is about 80 nm multiplied by an odd integer, and wherein the thickness of the single layer of silicon nitride provides a minimum reflection loss of about 0.08%.
7. The optical navigation device of claim 4 , wherein the light source is a VCSEL, wherein the wavelength of the light is about 840 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has an incidence angle of about 21°, wherein the thickness of the single layer of silicon nitride is about 317.1 nm, and wherein the thickness of the single layer of silicon nitride provides a minimum reflection loss of about 0.52%.
8. The optical navigation device of claim 1 , wherein the at least one layer of material is a single layer of silicon dioxide.
9. The optical navigation device of claim 8 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the single layer of silicon dioxide is about 88.8 nm to about 133.2 nm multiplied by an odd integer, and wherein the thickness of the single layer of silicon dioxide provides a minimum reflection loss of less than 12%.
10. The optical navigation device of claim 8 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the single layer of silicon nitride is about 111 nm multiplied by an odd integer, and wherein the thickness of the single layer of silicon dioxide provides a minimum reflection loss of about 8.53%.
11. The optical navigation device of claim 8 , wherein the light source is a VCSEL, wherein the wavelength of the light is about 840 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has an incidence angle of about 21°, wherein the thickness of the single layer of silicon nitride is about 445.9 nm, and wherein the thickness of the single layer of silicon dioxide provides a minimum reflection loss of about 6.82%.
12. The optical navigation device of claim 1 , wherein the at least one layer of material is formed by a first layer and a second layer, and wherein the first layer and the second layer comprise different materials from one another.
13. The optical navigation device of claim 12 , wherein the first layer is silicon dioxide, and wherein the second layer is silicon nitride.
14. The optical navigation device of claim 13 , wherein the first layer forms an interface on the photo-sensing region of the silicon substrate, and wherein the second layer forms an interface on the first layer.
15. The optical navigation device of claim 14 , wherein the first layer of silicon dioxide has a thickness and the second layer of silicon nitride has a thickness, and wherein the thicknesses of the first layer and the second layer provide a minimum reflection loss of about 0.0265%.
16. The optical navigation device of claim 15 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the first layer of silicon dioxide is about 100.1 nm, and wherein the thickness of the second layer of silicon nitride is one selected from the group consisting of about 205.9 nm, about 428.5 nm, and about 651.1 nm.
17. The optical navigation device of claim 15 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the first layer of silicon dioxide is about 220.1 nm, and wherein the thickness of the second layer of silicon nitride is one selected from the group consisting of about 239.3 nm and about 461.9 nm.
18. The optical navigation device of claim 15 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the first layer of silicon dioxide is about 260.2 nm, and wherein the thickness of the second layer of silicon nitride is one selected from the group consisting of about 205.9 nm, about 428.5 nm, and about 651.1 nm.
19. The optical navigation device of claim 15 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the first layer of silicon dioxide is about 380.2 nm, and wherein the thickness of the second layer of silicon nitride is one selected from the group consisting of about 239.3 nm and about 461.9 nm.
20. The optical navigation device of claim 15 , wherein the light source is a light emitting diode, wherein the wavelength of the light is about 650 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has a normal incidence angle of about 0°, wherein the thickness of the first layer of silicon dioxide is about 420.3 nm, and wherein the thickness of the second layer of silicon nitride is one selected from the group consisting of about 205.9 nm, about 428.5 nm, and about 651.1 nm.
21. The optical navigation device of claim 14 , wherein the light source is a VCSEL, wherein the wavelength of the light is about 840 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has an incidence angle of about 21°, wherein the thickness of the first layer of silicon dioxide is about 1150.7 nm, wherein the thickness of the second layer of silicon nitride is about 145.5 nm, and wherein the thicknesses of the first and second layers provide a minimum reflection loss of about 0.0036%.
22. The optical navigation device of claim 14 , further comprising a silicone encapsulation material disposed on the second layer of silicon nitride, wherein the light source is a VCSEL, wherein the wavelength of the light is about 840 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has an incidence angle of about 21°, wherein the thickness of the first layer of silicon dioxide is about 920.5 nm, wherein the thickness of the second layer of silicon nitride is about 535.4 nm, and wherein the thicknesses of the first and second layers provide a minimum reflection loss of about 0.0036%.
23. The optical navigation device of claim 1 , wherein the light source is a VCSEL, wherein the wavelength of the light is about 840 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has an incidence angle of about 21°, wherein the at least one layer of material is a single layer of silicon nitride, wherein the optical navigation device further comprises a silicone encapsulation material disposed on the single layer of silicon nitride, wherein the thickness of the single layer of silicon nitride is about 322.3 nm, and wherein the thickness of the single layer of silicon nitride provides a minimum reflection loss of about 1.27%.
24. The optical navigation device of claim 1 , wherein the light source is a VCSEL, wherein the wavelength of the light is about 840 nm, wherein the light with respect to the photo-sensing region of the silicon substrate has an incidence angle of about 21°, wherein the at least one layer of material is a single layer of silicon dioxide, wherein the optical navigation device further comprises a silicone encapsulation material disposed on the single layer of silicon dioxide, wherein the thickness of the single layer of silicon dioxide is about 460.3 nm, and wherein the thickness of the single layer of silicon dioxide provides a minimum reflection loss of about 19.16%.
25. A method for manufacturing an optical navigation device, comprising:
providing a silicon wafer having a plurality of optical navigation sensors formed thereon, wherein each of the optical navigation sensors has a plurality of photo-sensing regions, and wherein each of the photo-sensing regions provides a pixel of navigation information;
depositing at least one layer of material on the photo-sensing regions of the silicon substrate during a silicon wafer fabrication process, wherein each of the at least one layer of material has a thickness that causes the layer of material to serve as an anti-reflection coating and reduce a percentage of light that is reflected away from the photo-sensing regions of the silicon substrate to less than 30%;
separating each of the optical navigation sensors from the wafer;
mounting a light source and one of the optical navigation sensors in an optical navigation device, with the light source and the one of the optical navigation sensors being positioned to enable light produced by the light source to be reflected from a surface and received by the one of the optical navigation sensors; and
coupling the one of the optical navigation sensors to a circuit to bias each of its photo-sensing regions with a current, the current providing a given responsivity, and the current being less than a current that would be required to provide the given responsivity absent the at least one layer of material.
26. The method of claim 25 , further comprising, selecting each of the at least one material from the group consisting of: silicon nitride, silicon dioxide, spin-on-glass-oxynitrides, silicon-oxynitrides, and polyimide thin films.
27. The method of claim 25 , wherein at least one of the layers of material is deposited using a mask, the mask also being used to define the photo-sensing regions of the silicon substrate.
28. The method of claim 25 , further comprising depositing a silicone encapsulant on the at least one layer of material.
29. The method of claim 25 , wherein the at least one layer of material is deposited using a standard CMOS/BICMOS deposition technique.