Copper deposition in wafer level packaging of integrated circuits

1. A process for forming a copper feature over a semiconductor substrate in wafer level packaging for interconnecting an electronic circuit of a semiconductor device with a circuit external to the device, wherein the semiconductor assembly comprises a base structure bearing an under bump structure, the under bump structure comprising an under bump pad or under bump metal; the process comprising:

supplying current to an aqueous electrodeposition composition in contact with a cathode comprising the under bump structure on the semiconductor assembly, said aqueous electrodeposition composition comprising:

a) a source of copper ions,

b) an acid,

c) a suppressor, and

d) a leveler, wherein the leveler comprises a quaternized poly(epihalohydrin), the quaternized poly(epihalohydrin compound comprising n repeating units corresponding to structure 1N and p repeating units corresponding to structure 1P:

wherein Q has a structure corresponding to that which is obtained by reacting a pendent methylene halide group of poly(epihalohydrin) with a tertiary amine selected from the group consisting of: (i) an N-substituted and optionally further substituted heteroalicyclic amine wherein the N-substituent is selected from the group consisting of substituted or unsubstituted alkyl, alicyclic, aralkyl, aryl, and heterocyclic and (ii) a substituted or unsubstituted nitrogen-containing heteroaryl compound; and

wherein n is an integer between 3 and 35, p is an integer greater than 0 and up to 25; X is a halo substituent; and X − is a monovalent anion; and

e) an accelerator;

wherein current is supplied in an electrolytic circuit comprising a direct current power source, the aqueous electrodeposition composition, the under bump pad or under bump metal in electrical communication with the negative terminal of said power source and in contact with the electrodeposition composition, and an anode in electrical communication with the positive terminal of the power source and in contact with said electrodeposition composition;

wherein the current supplied in the electrolytic circuit is maintained at an average current density of at least 12 A/dm 2 ; and

wherein a copper bump or pillar is electrodeposited on the under bump structure.

2. The process as set forth in claim 1 , wherein the base structure comprises a concavity having sidewalls and a floor and the location of the under bump structure is within said concavity,

wherein lateral growth of the bump or pillar during electrodeposition is constrained by the sidewall(s) of the concavity; and

wherein the sidewalls are not conductive.

3. The process as set forth in claim 1 , wherein growth of the distal end of the bump or pillar is not laterally constrained during electrodeposition.

4. The process as set forth in claim 1 , wherein the under bump pad or under bump metal comprises a seminal conductive layer which functions as a cathode for initiating the electrodeposition of copper from the aqueous electrodeposition composition, and

wherein the seminal conductive layer comprises a copper seed layer.

5. The process as set forth in claim 1 , wherein the rate of growth of the bumps or pillars in the vertical direction from the under bump metal or pad is at least about 2.5 μm/min.

6. The process as set forth in claim 1 , wherein the diameter of the bump or pillar is between about 1 and about 30 μm, and

wherein the height of the bump or pillar is at least about 2 μm.

7. The process as set forth in claim 1 , wherein Q is selected from the group consisting of:

wherein: (i) structure IIB is an N-substituted heterocyclic moiety; (ii) structure IIC is a heterocyclic moiety; (iii) R d is selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alicyclic, substituted or unsubstituted aryl, and substituted or unsubstituted heterocyclic; and (iv) each of R e , R f , R g , R h and R j is independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aralkyl, substituted or unsubstituted alicyclic, and substituted or unsubstituted aryl, and substituted or unsubstituted heterocyclic.

8. The process as set forth in claim 7 , wherein Q has the structure which may be obtained from reacting a pendent methylene chloride group of poly(epihalohydrin) with:

a) a quaternizing agent selected from the group consisting of 3-hydroxypropyldimethylamine, n-butyldimethylamine, di(3-hydroxypropyl)methylamine, 2,3-dihydroxypropyldimethylamine, 3-hydroxypropyldiethylamine, 2-hydroxypropyldimethylamine, 4-hydroxybutyldimethylamine, 2-hydroxyethyldimethylamine, n-propyldimethylamine, 2-hydroxyethoxyethyldimethylamine, di(2-hydroxyethyl)methylamine, benzyldimethylamine and 4-hydroxybenzyldimethylamine, 4-methylpyridine, 3-ethylpyridine, 4-propylpyridine, 4-tertbutylpyridine, 4-cyanopyridine, 4-isopropylpyridine, 4-methoxypyridine, 3,4-lutidine, 3-methoxypyridine, and 4-pyridinemethanol; or

b) a tertiary amine selected from the group consisting of N-methylmorpholine, 1-methylimidazole, 1-benzylimidazole, 4-ethylpyridine, 2-imidazoline, and 3-imidazoline, 2-dimethylamino-1-ethanol, 1-methylimidazole, and an N,N-dimethylalkanolamine.

9. The process as set forth in claim 1 , wherein the aqueous electrodeposition composition contains between about 20 and about 100 g/L copper ions, between about 70 and about 280 g/l of an acid selected from the group consisting of sulfuric acid and an alkane sulfonic acid, between about 30 and about 80 ppm chloride ions, between about 1 and about 5-50 mg/L of said leveler, and between about 100 and about 1000 ppm of said suppressor.

10. The process as set forth in claim 1 , wherein the aqueous electrodeposition composition further comprises an accelerator; wherein the accelerator comprises an organic sulfur compound.

11. The process as set forth in claim 10 , wherein the organic sulfur compound has the following general structure (5):

wherein M is selected from the group consisting of alkali metal ions and charge balancing cations.

12. The process as set forth in claim 1 , wherein the suppressor comprises a compound selected from the group consisting of:

a) an alkoxylated amine;

b) a polyether compound comprising a combination of propylene oxide (PO) repeat units and ethylene oxide (EO) repeat units present in a PO:EO ratio between about 1:9 and about 9:1 and bonded to a nitrogen-containing species; and

c) a polyalkylene glycol having a terminal sulfonic acid moiety and a terminal aromatic moiety formed by condensing a substituted phenol with a terminal hydroxyl of said polyalkylene glycol.

13. The process as set forth in claim 1 , wherein the distal end of a copper pillar produced by the process is domed, and

wherein the deviation from within feature uniformity of the copper pillar is not greater than 10%.

14. The process as set forth in claim 1 , wherein the distal end of a copper pillar produced by the process is dished, and

wherein the deviation from within feature uniformity of the copper pillar is not greater than about 10%.

15. The process as set forth in claim 1 , wherein a copper bump or pillar produced by the process has an aspect ratio of at least about 1:1.