Metal bumps and method forming same
A method of forming an integrated circuit structure includes forming a patterned passivation layer over a metal pad, with a top surface of the metal pad revealed through a first opening in the patterned passivation layer, and applying a polymer layer over the patterned passivation layer. The polymer layer is substantially free from N-Methyl-2-pyrrolidone (NMP), and comprises aliphatic amide as a solvent. The method further includes performing a light-exposure process on the polymer layer, performing a development process on the polymer layer to form a second opening in the polymer layer, wherein the top surface of the metal pad is revealed to the second opening, baking the polymer, and forming a conductive region having a via portion extending into the second opening.
1. A method of forming an integrated circuit structure, the method comprising:
forming a patterned passivation layer over a metal pad, with a top surface of the metal pad revealed through a first opening in the patterned passivation layer;
applying a polymer layer over the patterned passivation layer, wherein the polymer layer is free from N-Methyl-2-pyrrolidone (NMP), and wherein the polymer layer comprises aliphatic amide as a solvent;
performing a light-exposure process on the polymer layer;
performing a development process on the polymer layer to form a second opening in the polymer layer, wherein the top surface of the metal pad is revealed to the second opening;
baking the polymer layer; and
forming a conductive region comprising a via portion extending into the second opening.
2. The method of claim 1 , wherein the polymer layer comprises alkoxy decane.
3. The method of claim 1 , wherein the baking process is performed at a temperature in a range between about 120° C. and about 210° C.
4. The method of claim 1 , wherein the via portion comprises:
a straight sidewall;
a straight bottom surface; and
a round corner comprising a top end connecting to the straight sidewall, and a bottom end connecting to the straight bottom surface, wherein the round corner has an R-angle smaller than about 4 μm, wherein the R-angle is a diameter of a respective circle to which the round corner fits.
5. The method of claim 4 , wherein the straight sidewall has a tilt angle in a range between about 45 degrees and about 90 degrees.
6. The method of claim 4 , wherein the straight sidewall has a tilt angle in a range between about 70 degrees and about 80 degrees.
7. The method of claim 1 , wherein after the baking process, the polymer layer has a thickness greater than about 5 μm.
8. A method of forming an integrated circuit structure, the method comprising:
applying a polymer layer over a metal pad;
patterning the polymer layer to form an opening in the polymer layer, wherein a top surface of the metal pad is revealed to the opening, and the polymer layer comprises:
a straight sidewall facing the opening; and
a round corner surface comprising a top end connecting to the straight sidewall, and a bottom end joining to the top surface of the metal pad, wherein the round corner surface has an R-angle smaller than about 4 μm, and wherein the R-angle is a diameter of a respective circle to which the round corner surface fits; and
forming a conductive region comprising:
a via portion extending into the opening; and
a bump portion over the polymer layer.
9. The method of claim 8 , wherein the polymer layer, when applied, comprises aliphatic amide as a solvent.
10. The method of claim 8 , wherein the polymer layer, when applied, is free from N-Methyl-2-pyrrolidone (NMP).
11. The method of claim 8 , wherein the polymer layer comprises silicon alkoxide.
12. The method of claim 8 further comprising baking the polymer layer after the polymer layer is patterned, and the baking is performed at a temperature in a range between about 120° C. and about 210° C.
13. A method of forming an integrated circuit structure, the method comprising:
applying a polymer layer over and contacting a metal pad, wherein the polymer layer comprises aliphatic amide as a solvent, and alkoxy decane dissolved in the solvent;
patterning the polymer layer to form an opening in the polymer layer, wherein a top surface of the metal pad is revealed to the opening;
baking the polymer layer; and
forming a conductive region comprising a via portion extending into the opening.
14. The method of claim 13 , wherein the polymer layer is free from N-Methyl-2-pyrrolidone (NMP).
15. The method of claim 14 , wherein the polymer layer is free from NMP at a time the polymer layer is applied.
16. The method of claim 13 , wherein the via portion comprises:
a straight sidewall;
a straight bottom surface; and
a round corner comprising a top end connecting to the straight sidewall, and a bottom end connecting to the straight bottom surface, wherein the round corner has an R-angle smaller than about 4 μm, wherein the R-angle is a diameter of a respective circle to which the round corner fits.
17. The method of claim 16 , wherein the straight sidewall has a tilt angle in a range between about 45 degrees and about 90 degrees.
18. The method of claim 13 , wherein after the polymer layer is baked, the polymer layer has a thickness greater than about 5 μm.