Processes for reducing leakage and improving adhesion

1. A method comprising:

forming a metal seed layer on a dielectric layer;

forming a patterned plating mask over the metal seed layer, wherein an opening in the patterned plating mask is over a first portion of the dielectric layer, and the patterned plating mask overlaps a second portion of the dielectric layer;

plating a metal post in the opening;

removing the patterned plating mask to expose portions of the metal seed layer;

etching the exposed portions of the metal seed layer to reveal the second portion of the dielectric layer;

oxidizing the metal post; and

encapsulating the metal post in an encapsulant.

2. The method of claim 1 , wherein the oxidizing is performed using process gases comprising oxygen (O 2 ) and an additional gas, wherein the additional gas is selected from the group consisting of Ar, nitrogen (N 2 ), a combination thereof.

3. The method of claim 2 , wherein the oxidizing is performed with plasma being generated from the process gases.

4. The method of claim 2 , wherein the oxidizing is performed with a bias power applied.

5. The method of claim 1 further comprising, after the oxidizing, etching metal-containing particles left on the dielectric layer.

6. The method of claim 1 , wherein the oxidizing generates a metal oxide layer on surfaces of the metal post, and the encapsulating the metal post is performed after the oxidizing.

7. The method of claim 6 , wherein the metal oxide layer physically separates the metal post from the encapsulant.

8. The method of claim 1 further comprising:

forming an Under-Bump Metallurgy (UBM) overlying and electrically coupling to the metal post;

oxidizing the UBM; and

performing an etching process on the oxidized UBM.

9. The method of claim 1 , wherein the metal seed layer comprises a first layer and a second layer over the first layer, and the oxidizing is performed after the second layer is etched.

10. A method comprising:

forming a metal post over a carrier, wherein the forming the metal post comprises:

forming a metal seed layer over a dielectric layer overlying the carrier;

forming a patterned plating mask over the metal seed layer, wherein an opening in the patterned plating mask is over a first portion of the dielectric layer, and the patterned plating mask overlaps a second portion of the dielectric layer;

plating the metal post in the opening;

removing the patterned plating mask to expose portions of the metal seed layer; and

etching the exposed portions of the metal seed layer to reveal the second portion of the dielectric layer;

performing a first oxidation process using an oxygen-containing gas to oxidize a surface layer of the metal post, wherein a metal oxide layer is formed at surfaces of the metal post;

placing a device die over the carrier;

encapsulating the metal post and the device die in an encapsulant, wherein the metal oxide layer is in contact with the encapsulant;

performing a planarization process on the encapsulant, the metal post, and the device die; and

forming a redistribution structure over and electrically connecting to the metal post and the device die.

11. The method of claim 10 , wherein the planarization process is performed until a portion of the metal oxide layer on top of the metal post is removed to reveal the metal post.

12. The method of claim 10 , wherein the first oxidation process is performed using plasma.

13. The method of claim 10 , wherein the first oxidation process is performed with a bias power applied.

14. The method of claim 10 further comprising, before the first oxidation process:

performing a second oxidation process to form an additional metal oxide layer on the metal post; and

removing the additional metal oxide layer.

15. The method of claim 14 , wherein the second oxidation process is performed with plasma.

16. The method of claim 14 , wherein the first oxidation process is performed with a first bias power applied, and the second oxidation process is performed with a second bias power applied, and wherein the first bias power is lower than the second bias power.

17. A method comprising:

forming a metal post over a carrier, wherein the forming the metal post comprises:

forming a metal seed layer over a dielectric layer overlying the carrier;

forming a patterned plating mask over the metal seed layer, wherein an opening in the patterned plating mask is over a first portion of the dielectric layer, and the patterned plating mask overlaps a second portion of the dielectric layer;

plating the metal post in the opening;

removing the patterned plating mask to expose portions of the metal seed layer; and

etching the exposed portions of the metal seed layer to reveal the second portion of the dielectric layer;

removing a first metal oxide layer on the metal post to reveal a metal of the metal post;

after the first metal oxide layer is removed, oxidizing the metal post to form a second metal oxide layer on surfaces of the metal post;

encapsulating the metal post and a device die in an encapsulant;

planarizing the encapsulant, the metal post, and the device die until the metal post is removed, wherein a portion of the second metal oxide layer is left between the metal post and the encapsulant; and

forming a redistribution structure over and electrically connecting to the metal post.

18. The method of claim 17 further comprising, before the removing the first metal oxide layer, performing a plasma oxidation process to generate the first metal oxide layer on the surfaces of the metal post.

19. The method of claim 18 , wherein the plasma oxidation process is performed with a first bias power applied, and the second metal oxide layer is formed with a second bias power applied, and the first bias power is higher than the second bias power.

20. The method of claim 17 , wherein the portion of the second metal oxide layer physically contacts both of the metal post and the encapsulant.