Wafer level package (WLP) and method for forming the same

1. A method comprising:

attaching a semiconductor device structure to a substrate, the semiconductor device structure comprising a chip structure, a conductive pad over the chip structure, a passivation layer over the conductive pad and the chip structure, a first protection layer over the passivation layer, and a post-passivation interconnect (PPI) pad extending through the first protection layer and the passivation layer, the PPI pad being electrically connected to the conductive pad;

forming an insulating layer surrounding the chip structure, the passivation layer, and the first protection layer;

forming a second protection layer over the insulating layer, the first protection layer, and the PPI pad;

etching the second protection layer to form first openings exposing top surfaces of the PPI pad;

forming a PPI structure in the first openings, the PPI structure being electrically connected to the PPI pad; and

forming a first moisture-resistant layer over the second protection layer and the PPI structure, the first moisture-resistant layer comprising a different material than the first protection layer and the second protection layer.

2. The method of claim 1 , further comprising planarizing the insulating layer, the first protection layer, and the PPI pad such that topmost surfaces of the insulating layer, the first protection layer, and the PPI pad are level with one another.

3. The method of claim 1 , wherein sidewalls of the chip structure, the passivation layer, and the first protection layer are aligned with one another.

4. The method of claim 1 , wherein the chip structure is attached to the substrate with an adhesion layer.

5. The method of claim 1 , further comprising:

etching the first moisture-resistant layer to form a second opening;

forming an under bump metallurgy (UBM) layer in the second opening, the UBM layer being electrically connected to the PPI structure; and

forming a conductive structure on the UBM layer.

6. The method of claim 1 , further comprising forming a conductive pillar structure, the conductive pillar structure extending through the insulating layer, the conductive pillar structure contacting the substrate, wherein a topmost surface of the conductive pillar structure is level with top surfaces of the insulating layer, the first protection layer, and the PPI pad.

7. The method of claim 1 , wherein the first moisture-resistant layer comprises a first sublayer formed over the PPI structure and the second protection layer, wherein a conductive layer is formed extending through the first sublayer to electrically contact the PPI structure, and wherein the first moisture-resistant layer further comprises a second sublayer formed over the first sublayer and the conductive layer, the first sublayer comprising a different material than the second sublayer.

8. A semiconductor device comprising:

a semiconductor die;

a conductive pad over the semiconductor die;

a first protection layer over the conductive pad and the semiconductor die;

an insulating layer surrounding the semiconductor die and the first protection layer;

a second protection layer over the insulating layer and the first protection layer;

a post-passivation interconnect (PPI) structure over and extending into the second protection layer;

a first moisture-resistant layer over the second protection layer, the first moisture-resistant layer comprising a different material from the first protection layer and the second protection layer; and

an under bump metallurgy (UBM) layer extending into the first moisture-resistant layer, at least a portion of the UBM layer extending over an uppermost surface of the first moisture-resistant layer.

9. The semiconductor device of claim 8 , further comprising a passivation layer over the semiconductor die and the conductive pad, wherein sidewalls of the passivation layer are aligned with sidewalls of the semiconductor die and the first protection layer.

10. The semiconductor device of claim 9 , wherein the passivation layer and the first moisture-resistant layer are made of the same material.

11. The semiconductor device of claim 8 , further comprising a PPI pad extending through the first protection layer, the PPI pad electrically connecting the PPI structure to the conductive pad.

12. The semiconductor device of claim 11 , wherein upper surfaces of the insulating layer, the first protection layer, and the PPI pad are level.

13. The semiconductor device of claim 8 , further comprising a second moisture-resistant layer over the first moisture-resistant layer, the UBM layer extending through the second moisture-resistant layer, wherein upper surfaces of the UBM layer are free of the second moisture-resistant layer.

14. The semiconductor device of claim 13 , wherein the second moisture-resistant layer and the UBM layer have the same thickness.

15. A semiconductor device comprising:

a semiconductor die comprising a front side and a back side;

a conductive pad over the front side of the semiconductor die;

a first protection layer over the conductive pad and the front side of the semiconductor die;

a second protection layer over the first protection layer;

a wiring structure at least partially embedded in the second protection layer;

a first moisture-resistant layer over the wiring structure and the second protection layer, the first moisture-resistant layer and the second protection layer comprising different materials;

an under bump metallurgy (UBM) at least partially embedded in the first moisture-resistant layer; and

a backside redistribution layer (RDL) over the back side of the semiconductor die.

16. The semiconductor device of claim 15 , further comprising a first semiconductor package bonded to the UBM using a first conductive structure.

17. The semiconductor device of claim 16 , further comprising a second semiconductor package bonded to the backside RDL using a second conductive structure.

18. The semiconductor device of claim 15 , further comprising a first conductive structure bonded to the UBM, wherein a bottommost surface of the first conductive structure extends below a topmost surface of the first moisture-resistant layer.

19. The semiconductor device of claim 15 , further comprising an insulating layer surrounding the semiconductor die and the first protection layer.

20. The semiconductor device of claim 19 , further comprising a conductive pillar extending through the insulating layer, the conductive pillar being electrically connected to the wiring structure and the backside RDL.