Method of producing an optical sensor at wafer-level and optical sensor
A method of producing an optical sensor at wafer-level, comprising the steps of providing a wafer having a main top surface and a main back surface and arrange at or near the top surface of the wafer at least one first integrated circuit having at least one light sensitive component. Furthermore, providing in the wafer at least one through-substrate via for electrically contacting the top surface and back surface and forming a first mold structure by wafer-level molding a first mold material over the top surface of the wafer, such that the first mold structure at least partly encloses the first integrated circuit. Finally, forming a second mold structure by wafer-level molding a second mold material over the first mold structure, such that the second mold structure at least partly encloses the first mold structure.
1. A method of producing an optical sensor at wafer-level, comprising the steps of:
providing a wafer having a top surface and a back surface;
arrange at or near the top surface of the wafer at least one first integrated circuit having at least one light sensitive component;
providing in the wafer at least one through-substrate via for electrically contacting the back surface;
forming a first mold structure by wafer-level molding a first mold material over the top surface of the wafer using a first structured mold tool, such that the first mold structure at least partly encloses the light sensitive component; and
subsequently forming an at least partially opaque second mold structure by wafer-level molding an optically opaque second mold material over the first mold structure using a flat or structured second mold tool, such that the second mold structure at least partly encloses the first mold structure, wherein the second mold material is applied to the second mold tool to form the second mold structure and to leave an aperture at or near the top surface of the first mold structure, wherein the aperture is co-planar or flush with an at least partially transparent portion of the top surface of the first mold structure.
2. The method according to claim 1 , wherein the
the first mold structure is made at least partly transparent by using an optically transparent mold material as first mold material.
3. The method according to claim 1 , wherein
the first mold tool comprises at least a first mold cavity, a conical or otherwise tapered first mold cavity;
the first mold tool is placed at or near the top surface of the wafer; and
the first mold material is applied to the cavity via a gap to form the first mold structure.
4. The method according to claim 1 , wherein
the second mold tool is placed on the wafer at or near the top surface of the first mold structure.
5. The method according to claim 1 , wherein one or more additional flat or structured mold layers are applied to the wafer at or near the top surface of the second mold structure, in particular one or more diffuser layers.
6. The method according to claim 1 , wherein before or after wafer-level molding the first and second molding structure
a redistribution layer comprising at least one metal layer is arranged on the back surface of the wafer; and
the at least one through-substrate via is electrically connected with the redistribution layer.
7. The method according to claim 5 , wherein the redistribution layer is provided with an under-bump metallization layer for the attachment of one or more bumps, and/or provided before or after wafer-level molding of the first and the second molding structures.
8. The method according to claim 1 , wherein
the wafer is provided with a plurality of first integrated circuits each having a light sensitive component;
the first and second mold structure are applied to the front surface of the wafer or applied to an entirety of the front surface of the wafer; and
the wafer is singulated into individual optical sensors each comprising at least one of the first integrated circuits.
9. The method according to claim 8 , wherein the structured first mold tool comprises a plurality of cavities each of which are interconnected by channels allowing mold material to flow between the cavities during wafer-level molding.
10. The method according to claim 9 , wherein at least one runner comprising first mold material resulting from flowing through the channels between the cavities during wafer-level molding is at least partly removed, or removed by isotropic or by anisotropic etching, and/or by mechanical removal, by sawing or by dicing.
11. The method according to claim 9 , wherein the at least one runner is at least partly replaced by a thin layer distributed throughout the front surface of the wafer.
12. The method according to claim 9 , wherein a transparency of the first mold material of the at least one runner is reduced is reduced locally or along the whole runner.