Adhesion promoter apparatus and method

1. A method comprising:

forming a plateau region and a trench region over a substrate, wherein the trench region comprises a slope and a flat bottom;

depositing a reflecting layer over the flat bottom and a portion of the slope;

depositing a first adhesion promoter layer over the reflecting layer;

applying a first curing process to the first adhesion promoter layer, wherein, after the first curing process finishes, the reflecting layer and the first adhesion promoter layer form a first bonding interface;

depositing a bottom cladding layer over the first adhesion promoter layer;

applying a second curing process to the bottom cladding layer to form a second bonding interface layer;

depositing a core layer over the bottom cladding layer; and

depositing a top cladding layer over the core layer.

2. The method of claim 1 , further comprising:

after performing the first curing process and the second curing process, forming a chemical structure comprising an oxidized material on a surface of the reflecting layer, a first dielectric material of the first adhesion promoter layer and a second dielectric material of the bottom cladding layer.

3. The method of claim 1 , further comprising:

prior to the step of depositing the core layer over the bottom cladding layer, depositing a second adhesion promoter layer over and in contact with the bottom cladding layer; and

prior to the step of depositing the top cladding layer over the core layer, depositing a third adhesion promoter layer over and in contact with the core layer.

4. The method of claim 3 , wherein:

the first adhesion promoter layer, the second adhesion promoter layer and the third adhesion promoter layer are formed of a same material.

5. The method of claim 1 , wherein:

the slope and the flat bottom form an angle of about 45 degrees.

6. The method of claim 1 , further comprising:

depositing a dielectric layer over the plateau region;

forming a redistribution layer over the dielectric layer;

depositing a passivation layer over the redistribution layer;

patterning the passivation layer to expose at least a portion of the redistribution layer;

depositing a metal layer over the passivation layer, wherein the metal layer and the reflection layer are formed of a same material;

forming a bonding stack in an opening of the passivation layer, wherein a top surface of the bonding stack is higher than a top surface of the passivation layer;

attaching an external device over the bonding stack; and

forming an underfill layer between the substrate and the external device.

7. The method of claim 1 , further comprising:

removing residues from the first adhesion promoter layer through a thermal process, wherein a temperature of the thermal process is about 100 degrees.

8. The method of claim 1 , wherein:

the core layer is formed of a photo sensitive polymer.

9. A method comprising:

forming a plateau region and a trench region over a substrate, wherein the trench region comprises a slope and a flat bottom;

depositing a reflecting layer over the flat bottom and a portion of the slope;

depositing a first adhesion promoter layer over the reflecting layer;

applying a first thermal process to the first adhesion promoter layer;

depositing a bottom cladding layer over the first adhesion promoter layer;

forming a chemical structure comprising an oxidized material on the reflecting layer, a first dielectric material of the first adhesion promoter layer and a second dielectric material of the bottom cladding layer;

depositing a core layer over the bottom cladding layer; and

depositing a top cladding layer over the core layer.

10. The method of claim 9 , further comprising:

depositing a second adhesion promoter layer over and in contact with the bottom cladding layer; and

depositing a third adhesion promoter layer over and in contact with the core layer.

11. The method of claim 10 , wherein:

the first adhesion promoter layer, the second adhesion promoter layer and the third adhesion promoter layer are formed of aminopropyltriethoxysilance (APTES).

12. The method of claim 9 , further comprising:

depositing a dielectric layer over the plateau region;

forming a redistribution layer over the dielectric layer;

depositing a passivation layer over the redistribution layer;

forming on opening in the passivation layer; and

depositing a metal layer over passivation layer, wherein a center portion of the metal layer is lower than an edge portion of the metal layer.

13. The method of claim 12 , further comprising:

forming a bonding stack over the metal layer, wherein a bottom of the bonding stack is in contact with the center portion of the metal layer;

attaching an external device over the bonding stack; and

forming an underfill layer between the substrate and the external device.

14. The method of claim 9 , wherein:

the slope and the flat bottom form an angle of about 45 degrees.

15. A method comprising:

providing a substrate having a plateau region and a trench region, wherein the trench region comprises a slope and a flat bottom, and wherein the slope and the flat bottom form an angle of about 45 degrees;

depositing a reflecting layer over the flat bottom and a portion of the slope;

depositing a first adhesion promoter layer over the reflecting layer;

applying a first thermal process to the first adhesion promoter layer;

depositing a bottom cladding layer over the first adhesion promoter layer;

depositing a core layer over the bottom cladding layer; and

depositing a top cladding layer over the core layer.

16. The method of claim 15 , further comprising:

depositing a second adhesion promoter layer over the bottom cladding layer; and

applying a second thermal process to the second adhesion promoter layer.

17. The method of claim 15 , further comprising:

depositing a third adhesion promoter layer over the core layer; and

applying a third thermal process to the third adhesion promoter layer.

18. The method of claim 15 , further comprising:

after the step of depositing a bottom cladding layer over the first adhesion promoter layer, forming a chemical structure comprising an oxidized material on the reflecting layer, a first dielectric material of the first adhesion promoter layer and a second dielectric material of the bottom cladding layer.

19. The method of claim 15 , further comprising:

depositing a dielectric layer over a top surface of the plateau region;

forming a redistribution layer over the dielectric layer;

depositing a passivation layer over the redistribution layer;

forming a bonding stack in an opening of the passivation layer;

attaching an external device over the bonding stack; and

forming an underfill layer between the substrate and the external device.

20. The method of claim 15 , wherein:

the bottom cladding layer, the core layer and the top cladding layer are formed of a photo sensitive polymer.