Fan-out package having a main die and a dummy die, and method of forming

1. A method, comprising:

placing a functional die and a first dummy die on a first substrate, wherein the first dummy die comprises a polymer layer overlying a second substrate;

encapsulating sidewalls of the functional die and the first dummy die with a molding material;

forming a redistribution structure over the functional die and the first dummy die, the redistribution structure comprising a plurality of conductive lines and a plurality of dielectric layers, wherein the functional die is electrically connected to a first conductive line of the plurality of conductive lines, and wherein the polymer layer of the first dummy die faces the redistribution structure; and

forming a plurality of external connectors on the redistribution structure.

2. The method according to claim 1 , wherein the polymer layer of the first dummy die is physically separate from the redistribution structure, and the molding material extends between the first dummy die and the redistribution structure.

3. The method according to claim 1 , wherein the polymer layer of the first dummy die contacts the redistribution structure.

4. The method according to claim 3 , wherein a plurality of first connectors extends through the polymer layer of the first dummy die.

5. The method according to claim 4 , wherein the plurality of first connectors is electrically isolated from the plurality of conductive lines.

6. The method according to claim 4 , wherein the plurality of first connectors are electrically connected to a ground node by the plurality of conductive lines.

7. The method according to claim 1 , further comprising:

placing a second dummy die on the first substrate; and

forming a through via on the first substrate adjacent to the second dummy die.

8. A method of forming a device, comprising:

forming a first through via and a second through via;

disposing a main die and a plurality of dummy dies between the first through via and the second through via;

encapsulating sidewalls and top surfaces of the main die and the plurality of dummy dies with a molding material;

planarizing the molding material to expose the main die;

forming a redistribution structure over the main die and the plurality of dummy dies, the main die contacting the redistribution structure; and

forming a plurality of connectors on the redistribution structure.

9. The method according to claim 8 , wherein an area of the main die and the plurality of dummy dies in a plan view is a first area, an area of the device in a plan view is a second area, a ratio of the second area to the first area is 2.5 or less.

10. The method according to claim 8 , wherein an effective coefficient of thermal expansion (CTE) of the main die is the same as an effective CTE of a first dummy die of the plurality of dummy dies.

11. The method according to claim 8 , wherein a thickness of a first dummy die of the plurality of dummy dies is less than a thickness of the main die.

12. The method according to claim 8 , wherein a first dummy die of the plurality of dummy dies comprises a polymer layer overlying a substrate, the polymer layer defining a surface of the first dummy die, wherein the surface of the first dummy die defined by the polymer layer faces the redistribution structure.

13. The method according to claim 12 , wherein a plurality of metal pillars is disposed in the polymer layer of the first dummy die, and wherein the plurality of metal pillars is electrically connected to the redistribution structure.

14. The method according to claim 12 , wherein the polymer layer of the first dummy die is free of any electrical connectors.

15. A method, comprising:

forming a first package, wherein forming the first package comprises:

patterning a mask to form a plurality of openings;

plating a conductive material in the plurality of openings to form a plurality of through vias;

removing the mask;

placing at least one main die and at least one dummy die between two adjacent through vias of the plurality of through vias;

encapsulating sidewalls of the at least one main die, the at least one dummy die, and the plurality of through vias with a molding material; and

forming a redistribution structure over the at least one main die and the at least one dummy die, wherein the at least one main die contacts the redistribution structure, and wherein the plurality of through vias contacts the redistribution structure; and

attaching the first package to a second package using a plurality of connectors, wherein a first through via of the plurality of through vias contacts a first connector of the plurality of connectors.

16. The method according to claim 15 , wherein an area of the at least one main die and the at least one dummy die in a plan view is a first area, an area of the first package in a plan view is a second area, and a ratio of the second area to the first area is 2.5 or less.

17. The method according to claim 15 , wherein the at least one dummy die is free of any functional electrical circuits.

18. The method according to claim 15 , wherein the at least one dummy die comprises a first substrate, the at least one main die comprises a second substrate, and wherein the first substrate comprises a same material as the second substrate.

19. The method according to claim 15 , further comprising:

planarizing the molding material to expose the at least one main die and the at least one dummy die through the molding material.

20. The method according to claim 15 , wherein an effective coefficient of thermal expansion (CTE) of the at least one main die is the same as an effective CTW of the at least one dummy die.