Package structure with dummy die

1. A package structure, comprising:

a substrate;

a device die formed over the substrate, wherein the device die comprises a device substrate and a conductive pad over the device substrate, and the device substrate has a first height;

a dummy die formed over the substrate and adjacent to the device die, wherein the dummy die comprises a dummy substrate, and the dummy substrate has a second height, the second height is smaller than the first height; and

a package layer formed between the device die and the dummy die.

2. The package structure as claimed in claim 1 , further comprising:

a buffer layer formed on the dummy die, wherein a top surface of the buffer layer is lower than a top surface of the device die.

3. The package structure as claimed in claim 1 , further comprising:

a through via formed adjacent to the device die, wherein the through via has a third height, the third height is higher than the first height.

4. The package structure as claimed in claim 1 , further comprising:

a redistribution structure formed over the package layer, wherein the redistribution structure is electrically connected to the device die.

5. The package structure as claimed in claim 1 , wherein a height ratio of the second height to the first height is in a range from about 65% to about 85%.

6. The package structure as claimed in claim 1 , wherein a coefficient of thermal expansion (CTE) of the dummy die is substantially identical to a coefficient of thermal expansion (CTE) of the device die.

7. The package structure as claimed in claim 1 , further comprising:

a through via formed adjacent to the device die; and

a second package structure formed on the device die, wherein the second package structure is electrically connected to the through via.

8. A package structure, comprising:

a substrate;

a first device die formed over the substrate, wherein the first device die comprises a first device substrate and a conductive pad over the first device substrate, and the first device substrate has a first height;

a first dummy die formed over the substrate and adjacent to the first device die, wherein the first dummy die comprises a first dummy substrate, and the first dummy substrate has a second height, the second height is smaller than the first height;

a first package layer surrounding the first device die and the first dummy die, wherein a top surface of the first dummy die is covered by the first package layer; and

a redistribution structure formed over the first package layer, wherein the redistribution structure is electrically connected to the first device die.

9. The package structure as claimed in claim 8 , further comprising:

a through via formed adjacent to the first device die, wherein a top surface of the through via is leveled with a top surface of the first device die.

10. The package structure as claimed in claim 9 , further comprising:

a second package structure formed on the device die, wherein the second package structure is electrically connected to the through via.

11. The package structure as claimed in claim 8 , further comprising:

an under bump metallurgy (UBM) layer formed on the redistribution structure; and

an electrical connector formed on the UBM layer.

12. The package structure as claimed in claim 8 , wherein the first device die has a first height, the first dummy die has a second height, and a height ratio of the second height to the first height is in a range from about 65% to about 85%.

13. The package structure as claimed in claim 8 , wherein a coefficient of thermal expansion (CTE) of the first dummy die is the same as a coefficient of thermal expansion (CTE) of the first device die.

14. The package structure as claimed in claim 8 , further comprising:

a second device die formed over the package layer; and

a second dummy die formed adjacent to the second device die.

15. The package structure as claimed in claim 14 , further comprising:

a second package layer formed between the second device die and the second dummy die, wherein a top surface of the second dummy die is covered by the second package layer.

16. A package structure, comprising:

a first package structure, comprising:

a first device die formed over a substrate;

a first dummy die formed over the substrate;

a first package layer surrounding the first device die and the first dummy die, wherein the first dummy die is covered by the first package layer; and

a redistribution structure formed over the first package layer, wherein the redistribution structure is electrically connected to the first device die; and

a second package structure, comprising:

a second dummy die formed over the redistribution structure; and

a second package layer surrounding the second dummy die, wherein the second dummy die is covered by the second package layer.

17. The package structure as claimed in claim 16 , further comprising:

a through via formed adjacent to the first device die, wherein the through via is electrically connected to the redistribution structure.

18. The package structure as claimed in claim 16 , wherein the first device die has a first height, the first dummy die has a second height, and the second height is smaller than the first height.

19. The package structure as claimed in claim 16 , further comprising:

a buffer layer formed on the first dummy die, wherein the buffer layer is formed between the first dummy die and the first package layer.

20. The package structure as claimed in claim 16 , further comprising:

a third package structure formed below the first package structure, wherein the first package structure is formed between the second package structure and the third package structure.