Shifted micro-lenses for increased imaging device performance

1 . A method of forming an imaging device, the method comprising:

forming a plurality of image sensor elements comprising pixel units within a semiconductor substrate;

forming an isolation structure within the semiconductor substrate, wherein the isolation structure is disposed between adjacent pixel units;

depositing a grid layer over a back-side surface of the semiconductor substrate;

performing an etching process on the grid layer to form a grid structure on the semiconductor substrate, wherein the grid structure comprises a plurality of sidewalls defining a plurality of grid openings overlying corresponding pixel units, wherein the grid openings are shifted from corresponding pixel units by grid opening shift amounts;

forming a plurality of light filters in the grid openings;

depositing a dielectric layer on the grid structure and the plurality of light filters; and

forming an array of micro-lenses over the grid structure, wherein micro-lenses in the array of micro-lenses have different shapes from one another, wherein the dielectric layer is arranged between the plurality of light filters and the array of micro-lenses, wherein the dielectric layer and the array of micro-lenses respectively comprise a first material.

2 . The method of claim 1 , wherein the micro-lenses are shifted from corresponding pixel units by lens shift amounts that are different from the grid opening shift amounts.

3 . The method of claim 1 , wherein the array of micro-lenses comprises a first micro-lens and a second micro-lens adjacent to one another, wherein a height of a sidewall of the first micro-lens is different from a height of a sidewall of the second micro-lens.

4 . The method of claim 3 , wherein an area of the first micro-lens is different from an area of the second micro-lens.

5 . The method of claim 1 , wherein the array of micro-lenses comprises a plurality of first micro-lenses and a plurality of second micro-lenses, wherein the plurality of first micro-lenses are shifted inwards towards one another and the plurality of second micro-lenses are shifted outwards away from one another.

6 . The method of claim 5 , wherein a first gap is arranged at a middle region of the plurality of first micro-lenses and is defined by sidewalls of the plurality of first micro-lenses, wherein a second gap is arranged at a middle region of the plurality of second micro-lenses and is defined by sidewalls of the plurality of second micro-lenses, wherein a width of the first gap is less than a width of the second gap.

7 . The method of claim 1 , wherein forming the array of micro-lenses comprises:

depositing a micro-lens material over the grid structure and the plurality of light filters; and

selectively etching the micro-lens material.

8 . The method of claim 7 , further comprising:

forming a micro-lens template over the micro-lens material, wherein the micro-lens material is selectively etched according to the micro-lens template.

9 . The method of claim 1 , further comprising:

depositing a passivation layer on the back-side surface of the semiconductor substrate, wherein the passivation layer is arranged between the semiconductor substrate and the grid structure.

10 . A method of forming an imaging device, the method comprising:

forming a first image sensor element and a second image sensor element laterally adjacent to one another in a substrate, wherein the first and second image sensor elements respectively comprise one or more photodetectors;

etching the substrate to form a trench extending into a first surface of the substrate;

forming an isolation structure in the trench, wherein the isolation structure comprises a first pair of isolation segments on opposing sides of the one or more photodetectors of the first image sensor element and a second pair of isolation segments on opposing sides of the one or more photodetectors of the second image sensor element;

depositing a micro-lens material over the first surface of the substrate; and

selectively etching the micro-lens material to form a plurality of micro-lenses over the substrate, wherein the plurality of micro-lenses comprises a first micro-lens over the first image sensor element and a second micro-lens over the second image sensor element, wherein a center of the first micro-lens is laterally offset from a center of the first pair of isolation segments by a first lens shift distance, and wherein a center of the second micro-lens is laterally offset from a center of the second pair of isolation segments by a second lens shift distance different from the first lens shift distance.

11 . The method of claim 10 , wherein in a cross-sectional view the first micro-lens comprises a first sidewall laterally offset from a second sidewall, wherein the first sidewall is spaced laterally between the first pair of isolation segments and the second sidewall is spaced laterally between the second pair of isolation segments.

12 . The method of claim 11 , wherein a first height of the first sidewall is greater than a second height of the second sidewall.

13 . The method of claim 11 , wherein a first sidewall of the second micro-lens contacts the first sidewall of the first micro-lens.

14 . The method of claim 11 , wherein before depositing the micro-lens material the method further comprises:

depositing a grid layer over the first surface of the substrate; and

etching the grid layer to form a grid structure over the substrate, wherein the grid structure comprises a first pair of grid segments over the first image sensor element and a second pair of grid segments over the second image sensor element, wherein a center of the first pair of grid segments is laterally offset from the center of the first pair of isolation segments by a first grid shift distance that is less than the first lens shift distance.

15 . The method of claim 14 , wherein a center of the second pair of grid segments is laterally offset from the center of the second pair of isolation segments by a second grid shift distance that is substantially equal to the first grid shift distance and less than the second lens shift distance.

16 . A method of forming an imaging device, the method comprising:

receiving a semiconductor structure comprising:

a first image sensor element and a second image sensor element, wherein the first and second image sensor elements respectively comprise a plurality of pixel units in a substrate;

a grid structure over the substrate, wherein the grid structure comprises a plurality of grid openings overlying the plurality of pixel units of the first and second image sensor elements;

a plurality of light filters in the plurality of grid openings; and

an isolation structure in the substrate and around the first and second image sensor elements, wherein the isolation structure laterally encloses the pixel units of the first and second image sensor elements, wherein an outermost sidewall of the grid structure is laterally offset from an outermost sidewall of the isolation structure by a first distance; and

forming an array of micro-lenses over the plurality of light filters, wherein the array of micro-lenses comprises a plurality of first micro-lenses and a plurality of second micro-lenses, wherein the plurality of first micro-lenses are shifted inwards towards one another and the plurality of second micro-lenses are shifted outwards away from one another, wherein the plurality of first micro-lenses have convex upper surfaces and the plurality of second micro-lenses have convex upper surfaces, and wherein a sidewall of a first lens in the plurality of first micro-lenses adjacent to the outermost sidewall of the grid structure is laterally offset from the outermost sidewall of the grid structure by a second distance greater than the first distance.

17 . The method of claim 16 , wherein a second lens in the plurality of first micro-lenses contacts a third lens in the plurality of second micro-lenses.

18 . The method of claim 17 , wherein a width of the second lens is less than a width of the third lens.

19 . The method of claim 16 , wherein the first lens in the plurality of first micro-lenses overlies a first light filter in the plurality of light filters, wherein a second lens in the plurality of second micro-lenses overlies a second light filter in the plurality of light filters, wherein a center of the first lens is laterally offset from a center of the first light filter by a third distance different from a fourth distance between a center of the second lens and a center of the second light filter.

20 . The method of claim 16 , wherein a width of a segment of the grid structure between adjacent light filters in the plurality of light filters is less than the first distance.