Polyimide profile control

1. A method, comprising:

depositing, on a substrate, a photoresist comprising polyimide;

performing a first anneal at a first temperature;

exposing the photoresist to a radiation source through a photomask comprising a pattern associated with a shape of a polyimide opening;

performing a second anneal at a second temperature;

removing a portion of the photoresist to form the polyimide opening;

performing a third anneal at a third temperature; and

cleaning the polyimide opening by ashing.

2. The method of claim 1 , further comprising:

adjusting a dosage of a cross-linker in the photoresist.

3. The method of claim 1 , wherein exposing the photoresist comprises exposing the photoresist using a numerical aperture (NA) between about 0.5 and about 0.7.

4. The method of claim 1 , wherein the second temperature is between about 100° C. and about 120° C., and wherein performing the second anneal at the second temperature comprises performing the second anneal between about 80 seconds and about 100 seconds.

5. The method of claim 1 , wherein removing the portion of the photoresist comprises developing the photoresist with cyclopentanone (C 5 H 8 O).

6. The method of claim 1 , further comprising:

measuring a critical dimension (CD) of the polyimide opening.

7. The method of claim 1 , wherein depositing the photoresist comprises spin coating the photoresist on the substrate.

8. The method of claim 1 , further comprising:

depositing a dielectric layer, wherein a metal-insulator-metal (MIM) structure is disposed within the dielectric layer; and

depositing a redistribution layer (RDL), wherein a bottom surface of the RDL is in contact with a top metallization (TME), and the polyimide opening is situated on a top surface of the RDL.

9. The method of claim 1 , further comprising:

depositing an under bump metallization (UBM) in the polyimide opening.

10. The method of claim 9 , further comprising:

electroplating a copper (Cu) bump on the UBM; and

forming a solder on the Cu bump.

11. A method, comprising:

forming a layer of polyimide photoresist on a substrate;

forming a polyimide opening in the layer of polyimide photoresist to expose a portion of the substrate; and

adjusting an angle of a sidewall of the polyimide opening to form a slanted profile of the polyimide opening, wherein adjusting the angle of the sidewall of the polyimide opening comprises adjusting a dosage of a cross-linker in the layer of polyimide photoresist.

12. The method of claim 11 , wherein adjusting the angle of the sidewall of the polyimide opening comprises annealing the layer of polyimide photoresist at a temperature between about 200° C. and about 400° C. for a time between about 2 hours and about 8 hours.

13. The method of claim 11 , wherein forming the polyimide opening comprises exposing a portion of the layer of polyimide photoresist to a radiation source through a photomask.

14. The method of claim 11 , wherein adjusting the angle of the sidewall of the polyimide opening comprises exposing the portion of the layer of polyimide photoresist using a numerical aperture between about 0.2 and about 1.

15. The method of claim 11 , wherein forming the layer of polyimide photoresist comprises controlling a mixing ratio between a polyimide and a solvent.

16. A method, comprising:

depositing a polyimide photoresist on a substrate, wherein the substrate comprises a conductive layer;

forming a polyimide opening in the polyimide photoresist to expose the conductive layer;

forming a slanted profile of the polyimide opening;

forming a metallic layer on a sidewall of the polyimide opening and the conductive layer;

forming a metal bump to fill the polyimide opening; and

forming a solder on the metal bump.

17. The method of claim 16 , wherein forming the polyimide opening comprises:

performing a first annealing process on the polyimide photoresist;

exposing a portion of the polyimide photoresist to a radiation source through a photomask comprising a pattern associated with the conductive layer;

performing a second annealing process on the polyimide photoresist; and

removing the portion of the polyimide photoresist.

18. The method of claim 16 , wherein forming the slanted profile of the polyimide opening comprises controlling a thickness of the polyimide photoresist to be between about 8 μm and about 12 μm.

19. The method of claim 16 , wherein depositing the polyimide photoresist comprises controlling a mixing ratio of a polyimide in the polyimide photoresist.

20. The method of claim 16 , wherein depositing the polyimide photoresist comprises adjusting a dosage of a cross-linker in the polyimide photoresist.