Polyimide profile control
A structure includes a controlled polyimide profile. A method for forming such a structure includes depositing, on a substrate, a photoresist containing polyimide and performing a first anneal at a first temperature. The method further includes exposing the photoresist to a radiation source through a photomask having a pattern associated with a shape of a polyimide opening. The method further includes performing a second anneal at a second temperature and removing a portion of the photoresist to form the polyimide opening. The method further includes performing a third anneal at a third temperature and cleaning the polyimide opening by ashing.
1. A structure, comprising:
a top metallization (TME) on a semiconductor substrate;
a first dielectric layer on the TME, wherein the first dielectric layer comprises:
a metal-insulator-metal (MIM) structure; and
a redistribution layer (RDL), wherein a bottom surface of the RDL is in contact with the TME;
a second dielectric layer on the RDL; and
a polyimide layer on the second dielectric layer, wherein a portion of the polyimide layer is on a top surface of the RDL and comprises a circular shape or an elliptical shape.
2. The structure of claim 1 , further comprising:
an under bump metallization (UBM) on the polyimide layer, wherein a portion of the UBM is on the top surface of the RDL;
a copper (Cu) bump on the UBM; and
a solder on the Cu bump.
3. The structure of claim 1 , wherein a thickness of the portion of the polyimide layer is between about 0.8 μm and about 2.7 μm.
4. The structure of claim 1 , wherein the portion of the polyimide layer comprises sidewalls with an angle between about 40° and about 90°.
5. A structure, comprising:
a redistribution layer (RDL) on a substrate;
a dielectric layer on the RDL;
a polyimide layer on the dielectric layer; and
an under bump metallization (UBM) through the polyimide layer and in contact with the RDL, wherein a top surface of the UBM is above a top surface of the polyimide layer.
6. The structure of claim 5 , wherein a portion of the polyimide layer is in contact with a side surface of the dielectric layer and a top surface of the RDL.
7. The structure of claim 5 , wherein the UBM is in contact with a slanted side surface of the polyimide layer.
8. The structure of claim 5 , wherein the polyimide layer comprises a slanted surface, and wherein the slanted surface comprises:
a first surface connected to a top surface of the polyimide layer;
a second surface connected to a bottom surface of the polyimide layer; and
a third surface connected to the first and second surfaces.
9. The structure of claim 8 , wherein:
an angle between the third surface and the bottom surface is greater than an angle between the first surface and the top surface; and
the angle between the third surface and the bottom surface is greater than an angle between the second surface and the bottom surface.
10. The structure of claim 9 , wherein the angle between the third surface and the bottom surface is between about 50° and about 80°.
11. The structure of claim 5 , wherein the polyimide layer comprises a cross-linker with a mixing ratio between about 0.8% and about 2.2%.
12. The structure of claim 5 , wherein the polyimide layer comprises a photo initiator with a mixing ratio between about 0.1% and about 2%.
13. The structure of claim 5 , wherein the polyimide layer comprises an inhibitor with a mixing ratio between about 0.8% and about 2.2%.
14. A structure, comprising:
a first dielectric layer on a substrate;
a redistribution layer (RDL) on the first dielectric layer;
a second dielectric layer on the RDL;
a polyimide layer on the second dielectric layer, wherein a bottom surface of the polyimide layer has a ring shape;
an under bump metallization (UBM) in contact with a side surface of the polyimide layer and a top surface of the RDL; and
a copper bump on the UBM.
15. The structure of claim 14 , wherein:
a bottom portion of the UBM is surrounded by a bottom portion of polyimide layer.
16. The structure of claim 15 , wherein a thickness of the ring shape is between about 0.8 μm and about 2.7 μm.
17. The structure of claim 15 , wherein the copper bump is in contact with a side surface of the UBM and a top surface of the bottom portion of the UBM.
18. The structure of claim 14 , wherein a portion of the RDL is in contact with a side surface of the first dielectric layer.
19. The structure of claim 14 , wherein the first dielectric layer comprises a titanium nitride (TiN) layer and a metal-insulator-metal (MIM) structure in contact with the TiN layer.
20. The structure of claim 19 , wherein the MIM structure comprises:
a first conductive layer and a second conductive layer; and
an insulating layer interposed between the first and second conductive layers.