Optical enhancement of integrated circuit photodetectors

1. A semiconductor integrated circuit structure comprising:

a light sensitive device integral with a semiconductor substrate, wherein the semiconductor substrate is silicon;

a first dielectric disposed directly on top of the semiconductor substrate, the first dielectric formed from a silicon-rich oxynitride having an index of refraction adjustable by changing the relative atomic percentages of silicon, oxygen and nitrogen.

2. The semiconductor integrated circuit structure of claim 1 ,

wherein a second dielectric is disposed over the first dielectric.

3. The semiconductor integrated circuit structure of claim 1 ,

wherein the index of refraction of the silicon-rich oxynitride is adjustable in the range of 1.70 to 1.85.

4. The semiconductor integrated circuit structure of claim 2 ,

wherein relative atomic percentages of silicon, oxygen and nitrogen in the silicon-rich oxynitride are adjusted such that the silicon-rich oxynitride has a preselected index of refraction at a preselected light frequency, and

a thickness of the first dielectric is within twenty-five percent of a length of a quarter wavelength of light at the preselected frequency in the first dielectric.

5. The semiconductor integrated circuit structure of claim 4 ,

wherein the preselected index of refraction of the silicon-rich oxynitride is within twenty-five percent of a square root of an index of refraction of the semiconductor substrate multiplied by an index of refraction of the second dielectric.

6. The semiconductor integrated circuit structure of claim 2 ,

wherein the second dielectric is formed from silicon dioxide.

7. The semiconductor integrated circuit structure of claim 1 ,

wherein the silicon-rich oxynitride is formed from silicon oxynitride.

8. The semiconductor integrated circuit structure of claim 1 ,

wherein the light sensitive device comprises a first semiconductor and a second semiconductor, both semiconductors integral within the semiconductor substrate, and

the first and second semiconductors are doped such that a photodiode is formed at a junction between the first and second semiconductors.

9. The semiconductor integrated circuit structure of claim 1 , further comprising:

a second light sensitive device integral with the semiconductor substrate; and

a cover dielectric disposed over the second light sensitive device,

wherein a portion of the first dielectric is disposed over the cover dielectric and a thickness of the portion of the first dielectric disposed over the cover dielectric is different from a thickness of a portion of the first dielectric not disposed over the cover dielectric.

10. The semiconductor integrated circuit structure of claim 9 ,

wherein the portion of the first dielectric disposed over the cover dielectric forms an embedded convex microlens.

11. A semiconductor integrated circuit structure comprising:

a p-type silicon substrate having a top surface;

an n-type well disposed in the p-type silicon substrate;

a recessed portion disposed in the n-type well, the recessed portion recessed from the top surface of the p-type silicon substrate;

a cover dielectric disposed in the recessed portion; and

a lens-formation dielectric disposed directly on top of the cover dielectric, the lens-formation dielectric formed from a silicon-rich oxynitride having an index of refraction adjustable by changing relative atomic percentages of silicon, oxygen and nitrogen.

12. The semiconductor integrated circuit structure of claim 11 ,

wherein the index of refraction of the silicon-rich oxynitride is adjustable in the range of 1.70 to 1.85.

13. The semiconductor integrated circuit structure of claim 11 ,

wherein the cover dielectric is formed from a field oxide.

14. The semiconductor integrated circuit structure of claim 11 ,

wherein the cover-dielectric is formed from a field oxide.