Touching microlens structure for a pixel sensor and method of fabrication
First Claim
1. A method for fabricating a microlens structure in a pixel sensor array comprising the steps of:
- a. providing a substrate including a plurality of light sensitive elements adapted to receive light incident to a respective pixel microlens;
b. forming a single photoresist material layer over said substrate;
c. applying an anti-reflective coating layer on top of said single photoresist material layer;
d. patterning said single photoresist layer using a first sub-resolution condition to form microlens structure images, said first sub-resolution condition applied in a manner sufficient to form partially connected lens portions at gaps between adjacent microlens structures;
e. developing said single photoresist layer to partially form the patterned microlens structures having partially connected lens portions at said gaps;
f. blanket applying a second sub-resolution condition to the partially formed microlens structures; and
g. thermally reflowing said partially formed microlens structures, wherein each microlens structure is webbed such that said microlens structure touches a microlens structure of an adjacent pixel in said array, wherein said thermally reflowing increases a curvature of said microlens structure to be uniform in all directions to thereby maximize collection of light incident to the microlens structure from all directions, said microlens structure of each microlens having a curvature uniformity exhibited at all pixel locations including those at a pixel array edge or corner.
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Accused Products
Abstract
A structure and method for increasing the sensitivity of pixel sensors by eliminating a gap space formed between adjacent microlens structures in a pixel sensor array. Advantageously, exposure and flowing conditions are such that adjacent microlens structures touch (are webbed) at a horizontal cross-section, yet have a round lens shape in all directions. Particularly, exposure and flowing conditions are such that each touching microlens structure is formed to have a matched uniform radius of curvature at a horizontal cross-section and at a 45 degree cross-sections. To improve quality of mircrolens structure uniformity exhibited at all pixel locations including those near a pixel array edge or corner, a top anti-reflective coating layer is applied on top of a photoresist layer prior to the exposure and flowing steps.
18 Citations
13 Claims
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1. A method for fabricating a microlens structure in a pixel sensor array comprising the steps of:
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a. providing a substrate including a plurality of light sensitive elements adapted to receive light incident to a respective pixel microlens; b. forming a single photoresist material layer over said substrate; c. applying an anti-reflective coating layer on top of said single photoresist material layer; d. patterning said single photoresist layer using a first sub-resolution condition to form microlens structure images, said first sub-resolution condition applied in a manner sufficient to form partially connected lens portions at gaps between adjacent microlens structures; e. developing said single photoresist layer to partially form the patterned microlens structures having partially connected lens portions at said gaps; f. blanket applying a second sub-resolution condition to the partially formed microlens structures; and g. thermally reflowing said partially formed microlens structures, wherein each microlens structure is webbed such that said microlens structure touches a microlens structure of an adjacent pixel in said array, wherein said thermally reflowing increases a curvature of said microlens structure to be uniform in all directions to thereby maximize collection of light incident to the microlens structure from all directions, said microlens structure of each microlens having a curvature uniformity exhibited at all pixel locations including those at a pixel array edge or corner. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of controlling dimensions of a formed microlens structure of a sensor array, said dimensions including a lens size, height and radius of curvature, said method comprising:
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applying first exposure conditions to a single photoresist layer having an anti-reflective coating layer applied thereon, said single photoresist layer patterned to partially form touching microlens structures and developing said layer after first dose exposure; blanket applying second exposure conditions to said partially formed touching microlens structures of said array; and thermally reflowing said partially formed touching microlens structures of said array at temperatures sufficient to increase curvature of said microlens structures and form adjacent microlens structures having a round lens shape in all directions. - View Dependent Claims (10, 11, 12, 13)
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Specification