Three-dimensional integrated circuit structures and method of forming the same

1. A method of forming a three-dimensional integrated circuit structure, comprising:

providing a first die comprising a first device;

bonding a second die comprising a second device to the first die; and

bonding a device-free die to the first die, wherein the device-free die is electrically connected to the first die and the second die,

wherein the first die has first metal bonding features embedded in a first bonding dielectric layer, the device-free die has a second metal bonding feature embedded in a second bonding dielectric layer, the second metal bonding feature is connected to one of the first metal bonding features, and the second bonding dielectric layer is bonded to the first bonding dielectric layer, and

wherein from a top view, opposing edges of the device-free die are closer to opposing edges of the first die than are opposing edges of the second die, and an entire boundary of the device-free die and an entire boundary of the second die are both within a boundary of the first die.

2. The method of claim 1 , wherein the first metal bonding features comprise bonding pads and bonding vias connected to each other.

3. The method of claim 1 , wherein the second metal bonding features comprise bonding pads and bonding vias connected to each other.

4. The method of claim 1 , wherein the first die has a first top area A 1 , the second die has a second top area A 2 , the device-free die has a third top area A 3 , and a ratio of (A 2 +A 3 ) to A 1 is 0.4 or more.

5. The method of claim 1 , wherein a semiconductor substrate of the second die is thinner than a semiconductor substrate of the device-free die.

6. The method of claim 1 , wherein an interconnect structure of the second die is thicker than an interconnect structure of the device-free die.

7. The method of claim 1 , further comprising forming a dielectric encapsulation over the first die and around the second die and the device-free die.

8. The method of claim 7 , further comprising forming through dielectric vias through the dielectric encapsulation and aside the second die.

9. A method of forming a three-dimensional integrated circuit structure, comprising:

providing a first die;

bonding a second die to the first die by connecting a second bonding metal feature of the second die to one of first bonding metal features of the first die and connecting a second bonding dielectric layer of the second die to a first bonding dielectric layer of the first die;

bonding a dummy die to the first die by connecting a third bonding metal feature of the dummy die to another of the first bonding metal features of the first die and connecting a third bonding dielectric layer of the dummy die to the first bonding dielectric layer of the first die, wherein from a top view, opposing edges of the dummy die are closer to opposing edges of the first die than are opposing edges of the second die, and an entire boundary of the dummy die and an entire boundary of the second die are both within a boundary of the first die;

forming a dielectric encapsulation over the first die and around the second die and the dummy die;

forming through dielectric vias through the dielectric encapsulation and bonded to another of the first bonding metal features of the first die, wherein a height of the through dielectric vias is substantially the same as each of a height of the second die and the dummy die; and

forming a redistribution layer structure over the second die and the dummy die, the redistribution layer structure electrically connected to the through dielectric vias, the second die and the dummy die.

10. The method of claim 9 , wherein the second die is a device-containing die and the dummy die is a device-free die.

11. The method of claim 9 , wherein the second die comprises first through substrate vias, and the dummy die comprises second through substrate vias.

12. The method of claim 11 , wherein a height of the first through substrate vias is less than a height of the second through substrate vias.

13. The method of claim 11 , wherein a dimension of the through dielectric vias is different from a dimension of the first through substrate vias or the second through substrate vias.

14. The method of claim 9 , wherein the first die has a first top area A 1 , the second die has a second top area A 2 , the dummy die has a third top area A 3 , and a ratio of (A 2 +A 3 ) to A 1 is 0.4 or more.

15. A method of forming a three-dimensional integrated circuit structure, comprising:

providing a first device die that comprises a first semiconductor substrate and a first bonding structure;

providing a second device die that comprises a second semiconductor substrate, first through substrate vias and a second bonding structure, and bonding the second device die to the first device die by the second bonding structure and the first bonding structure;

providing a dummy die that comprises a third semiconductor substrate, second through substrate vias and a third bonding structure, and bonding the dummy die to the first device die by the third bonding structure and the first bonding structure; and

forming a redistribution layer structure over the second device die and the dummy die, wherein at least two of the first through substrate vias and at least two of the second through substrate vias are in contact with a same metal feature of the redistribution layer structure, and a height of the first through substrate vias is less than a height of the second through substrate vias,

wherein from a top view, opposing edges of the dummy die are closer to opposing edges of the first device die than are opposing edges of the second device die, and an entire boundary of the dummy die and an entire boundary of the second device die are both within a boundary of the first device die.

16. The method of claim 15 , wherein the first bonding structure of the first device die has first metal bonding features, the second bonding structure of the second device die has second metal bonding features, and the third bonding structure of the dummy die has third metal bonding features, and

wherein the second metal bonding features are bonded to some of the first metal bonding features, the third metal bonding features are bonded to some of the first metal bonding features, and a number of the third metal bonding features of the dummy die is greater than a number of the second metal bonding features of the second device die.

17. The method of claim 15 , wherein the second device die further comprises a second interconnect structure between the second semiconductor substrate and the second bonding structure, the dummy die further comprises a third interconnect structure between the third semiconductor substrate and the third bonding structure, and the third interconnect structure is thinner than the second interconnect structure.

18. The method of claim 15 , further comprising forming through dielectric vias over the first device die and aside the second device die.

19. The method of claim 15 , wherein the second bonding structure and the third bonding structure are at substantially a same level.

20. The method of claim 15 , further comprising, before forming the redistribution layer structure, polishing the second semiconductor substrate and the third semiconductor substrate until portions of the first through substrate vias and the second through substrate vias are exposed.