Ring structures in device die

1. A structure comprising:

a die comprising:

a first metal pad;

a passivation layer over the first metal pad;

a polymer layer over the passivation layer;

a metal pillar over and electrically coupled to the first metal pad; and

a metal ring coplanar with the metal pillar, wherein the polymer layer comprises a first portion coplanar with the metal pillar and the metal ring, wherein in a top view of the die, the metal ring encircles a portion of the polymer layer.

2. The structure of claim 1 further comprising a second metal pad coplanar with the first metal pad, wherein the second metal pad forms an additional metal ring adjacent to edges of the die.

3. The structure of claim 2 , wherein the metal ring comprises a bottom surface in contact with a top surface of the passivation layer, with the metal ring fully separated from the second metal pad.

4. The structure of claim 1 , wherein the metal ring is electrically floating.

5. The structure of claim 1 further comprising a seal ring overlapped by the metal ring, wherein the seal ring extends into a plurality of Inter-Metal Dielectric (IMD) layers.

6. The structure of claim 1 further comprising:

a molding material molding the die therein;

a plurality of through-vias penetrating through the molding material;

a dielectric layer with a surface contacting the molding material; and

redistribution lines in the dielectric layer and electrically coupled to the metal pillar and the plurality of through-vias, wherein the metal ring comprises a surface coplanar with the surface of the dielectric layer, and wherein an entirety of the surface of the metal ring is in contact with the dielectric layer.

7. The structure of claim 1 , wherein the polymer layer further comprises a second portion and a third portion overlapping the metal pillar and the metal ring, respectively.

8. The structure of claim 1 , wherein the metal ring comprises an inner sidewall contacting an outer sidewall of the portion of the polymer layer, and wherein the portion of the polymer layer fully encircles the metal pillar, with an inner sidewall of the region of the polymer layer contacting a sidewall of the metal pillar.

9. The structure of claim 1 further comprising an additional metal ring encircling the metal ring.

10. The structure of claim 9 , wherein an additional portion of the polymer layer is between the metal ring and the additional metal ring, and opposite sidewalls of the additional portion of the polymer layer are in contact with both the metal ring and the additional metal ring.

11. A structure comprising:

a die comprising:

a first metal pad;

a second metal pad coplanar with the first metal pad, wherein the second metal pad forms a ring encircling the first metal pad;

a passivation layer over the first metal pad and the second metal pad, with the passivation layer comprising an opening aligned to a center portion of the first metal pad;

a polymer layer over the passivation layer;

a metal pillar over and electrically coupled to the first metal pad;

a metal ring coplanar with the metal pillar, with the metal ring encircling the metal pillar, wherein the metal ring overlaps the second metal pad; and

a seal ring underlying and overlapped by the metal ring;

a molding material surrounding the die, wherein a top surface of the molding material is coplanar with a first top surface of the metal pillar and a second top surface of the metal ring;

a dielectric layer over and in contact with the molding material; and

redistribution lines in the dielectric layer and electrically coupled to the metal pillar, wherein an entirety of the metal ring is covered by the dielectric layer.

12. The structure of claim 11 , wherein no conductive feature in the dielectric layer is in contact with the metal ring.

13. The structure of claim 11 , wherein the metal ring is in contact with the second metal pad.

14. The structure of claim 11 , wherein the metal ring comprises a portion in the passivation layer, with a bottom surface of the portion of the metal ring in contact with the second metal pad.

15. The structure of claim 13 , wherein the metal ring comprises a bottom surface in contact with a top surface of the passivation layer, with the metal ring fully separated from the second metal pad by the passivation layer.

16. The structure of claim 13 , wherein the metal ring is fully insulated in dielectric materials, with all surfaces of the metal ring in contact with the dielectric materials.

17. A structure comprising:

a device die comprising a metal ring proximal peripherals of the device die, wherein the metal ring is either electrically floating or electrically grounded;

through-vias at a same level as the device die;

an encapsulating material encapsulating the device die therein; and

a polymer layer in contact with the encapsulating material, the through-via, and the metal ring.

18. The structure of claim 17 , wherein the polymer layer is over the metal ring, and an entirety top surface of the metal ring is in physical contact with the polymer layer to form an interface.

19. The structure of claim 17 , wherein the device die further comprises:

a semiconductor substrate; and

a seal ring extending from a bottom surface of the metal ring to a top surface of the semiconductor substrate.

20. The structure of claim 17 , wherein the metal ring is fully insulated by dielectric materials.