Image sensor and method forming the same
A method forming an image sensor includes: providing a substrate including a plurality of sensing portions; forming a color filter layer on the substrate; forming a micro-lens material layer on the color filter layer; and forming a hard mask pattern on the micro-lens material layer, wherein the hard mask pattern has a first gap and a second gap larger than the first gap. The method includes reflowing the hard mask pattern into a plurality of dome shapes; transferring the plurality of dome shapes into the micro-lens material layer to form a plurality of micro-lenses; and forming a top film conformally on the plurality of micro-lenses.
1. A method forming an image sensor, comprising:
providing a substrate comprising a plurality of sensing portions;
forming a color filter layer on the substrate;
forming a micro-lens material layer on the color filter layer;
forming a hard mask pattern on the micro-lens material layer, wherein the hard mask pattern has a first gap and a second gap larger than the first gap;
reflowing the hard mask pattern into a plurality of dome shapes;
transferring the plurality of dome shapes into the micro-lens material layer to form a plurality of micro-lenses; and
forming a top film conformally on the plurality of micro-lenses.
2. The method of claim 1 , wherein the substrate further comprises a plurality of deep trench isolation (DTI) structures separating the plurality of sensing portions.
3. The method of claim 2 , wherein forming the plurality of deep trench isolation structures defines a size of an autofocus sensor unit.
4. The method of claim 3 , wherein two or more of the autofocus sensor unit constitute a group of autofocus sensor units.
5. The method of claim 4 , before the forming of the color filter layer on the substrate, further comprises forming a partition grid structure within the color filter layer, wherein the partition grid structure surrounds the group of autofocus sensor units.
6. The method of claim 5 , before the forming of the partition grid structure, further comprises forming a light shielding structure embedded within the partition grid structure.
7. The method of claim 5 , wherein forming the hard mask pattern comprises forming the first gap within the partition grid structure.
8. The method of claim 5 , wherein forming the hard mask pattern comprises forming the second gap directly above the partition grid structure.
9. The method of claim 3 , wherein the first gap is in a range between about 10% and about 20% of the size of the autofocus sensor unit.
10. The method of claim 3 , wherein the second gap is in a range between about 30% and about 40% of the size of the autofocus sensor unit.
11. The method of claim 1 , wherein the forming of the plurality of micro-lenses are only through a top portion of the micro-lens material layer.
12. The method of claim 1 , wherein a refractive index of the top film is lower than a refractive index of the micro-lenses.