Passivation structure with planar top surfaces

1. A method comprising:

forming a first passivation layer;

forming a metal pad over the first passivation layer;

forming a planarization layer comprising:

depositing the planarization layer over the metal pad;

performing a planarization process on the planarization layer, wherein the planarization process comprises a polishing process, so that the planarization layer comprises a planar top surface generated by the polishing process;

patterning the planarization layer to form a first opening, wherein a top surface of the metal pad is revealed through the first opening;

forming a polymer layer extending into the first opening; and

patterning the polymer layer to form a second opening, wherein the top surface of the metal pad is revealed through the second opening.

2. The method of claim 1 further comprising:

depositing a second passivation layer on the metal pad, wherein the planarization layer is deposited over the second passivation layer.

3. The method of claim 2 , wherein the planarization process is stopped when a first top surface of the second passivation layer is revealed, and when a second top surface of the second passivation layer is under the planarization layer.

4. The method of claim 3 , wherein the first top surface overlaps the metal pad.

5. The method of claim 2 , wherein the planarization process is stopped when an entirety of the second passivation layer is under the planarization layer.

6. The method of claim 1 further comprising:

depositing a second passivation layer on the metal pad, wherein the planarization layer is deposited over the second passivation layer, and the planarization layer is deposited as having the planar top surface and a non-planar bottom surface.

7. The method of claim 6 , wherein no planarization process is performed between the planarization layer is deposited and the polymer layer is dispensed.

8. The method of claim 1 further comprising:

after the forming the metal pad and before the forming the planarization layer, probing the metal pad.

9. The method of claim 1 , wherein each of the first passivation layer and the planarization layer is an inorganic layer.

10. A structure comprising:

a first passivation layer;

a metal pad over the first passivation layer;

a planarization layer with at least a portion over the metal pad, wherein the planarization layer comprises a planar top surface, and a non-planar bottom surface, wherein the planarization layer comprises an inorganic dielectric material;

a second passivation layer over the metal pad and the first passivation layer; and

a polymer layer comprising an upper portion over the planarization layer and the second passivation layer, wherein the polymer layer extends into an opening in the planarization layer and the second passivation layer to contact the metal pad.

11. The structure of claim 10 , wherein the planarization layer is over the second passivation layer, wherein the planarization layer comprises a second top surface coplanar with a first top surface of the second passivation layer, and wherein the first top surface and the second top surface are parallel to a major top surface of the first passivation layer.

12. The structure of claim 11 further comprising a conformal dielectric layer over the planarization layer, wherein the conformal dielectric layer and the planarization layer are formed of different materials.

13. The structure of claim 11 , wherein a portion of the first top surface overlaps the metal pad.

14. The structure of claim 13 , wherein a second portion of the first top surface is vertically offset from the metal pad.

15. The structure of claim 10 , wherein an entirety of the second passivation layer is under the planarization layer.

16. The structure of claim 10 , wherein the planarization layer is underlying the second passivation layer, and is in contact with the metal pad.

17. The structure of claim 10 , wherein the planarization layer comprises a first edge facing the opening, and the second passivation layer comprises a second edge facing the opening, and wherein the first edge and the second edge are vertically aligned to each other.

18. A structure comprising:

a first passivation layer;

a conductive feature comprising a conductive via extending into the first passivation layer, and a conductive pad over the first passivation layer;

a second passivation layer comprising a first portion over and in contact with the first passivation layer, and a second portion over and in contact with the conductive pad, wherein the second portion comprises a first top surface;

a planarization layer over and in contact with the first portion of the second passivation layer, wherein the planarization layer comprises a second top surface coplanar with the first top surface, and wherein the first top surface and the second top surface are parallel to a major top surface of the first passivation layer; and

a polymer layer comprising a portion over and contacting the conductive pad.

19. The structure of claim 18 , wherein an entirety of the planarization layer is vertically offset from the conductive pad.

20. The structure of claim 18 , wherein the polymer layer is in contact with both of the first top surface and the second top surface.