Superconformal filling composition and superconformally filling a recessed feature of an article
Superconformally filling a recessed feature includes: contacting the recessed feature with superconformal filling composition that includes: Au(SO 3 ) 2 3− anions; SO 3 2− anions; and Bi 3+ cations; convectively transporting Au(SO 3 ) 2 3− and Bi 3+ to the bottom member of the recessed feature; subjecting the recessed feature to an electrical current to superconformally deposit gold from the Au(SO 3 ) 2 3− on the bottom member relative to the sidewall and the field, the electrical current providing a cathodic voltage; and increasing the electrical current subjected to the field and the recessed feature to maintain the cathodic voltage between −0.85 V and −1.00 V relative to the SSE during superconformally depositing gold on the substrate to superconformally fill the recessed feature of the article with gold as a superconformal filling of gold, the superconformal filling being void-free and seam-free.
1. A process for superconformally filling a recessed feature of an article with gold, the process comprising:
providing the article comprising:
a substrate;
a field disposed on the substrate;
the recessed feature disposed on the substrate and surrounded by the field, the recessed feature comprising:
a bottom member;
a sidewall that separates the bottom member from the field,
the recessed feature having an aspect ratio of a depth to a width from 0.5 to 100 before superconformally filling the recessed feature, the aspect ratio decreasing during superconformally filling the recessed feature; and
an overlayer disposed on the article such that the field and the recessed feature are fully metallized for contact with a superconformal filling composition;
contacting the field and the recessed feature with the superconformal filling composition in an absence of cyanide and lead, the superconformal filling composition having a near-neutral pH and comprising:
a plurality of Au(SO 3 ) 2 3− anions as a source of gold for superconformally depositing gold in the recessed feature;
a plurality of SO 3 2− anions; and
a plurality of Bi 3+ cations as a brightener and an accelerator for superconformally depositing gold in the recessed feature;
convectively transporting the Au(SO 3 ) 2 3− anions and the Bi 3+ cations to the bottom member by actively moving the substrate relative to the superconformal filling composition;
subjecting the field and the recessed feature to an electrical current to superconformally deposit gold from the Au(SO 3 ) 2 3− anions on the bottom member relative to the sidewall and the field, the electrical current providing a cathodic voltage (V SSE ) from −0.66 V to −1.00 V relative to a saturated sulfate electrode (SSE), and a first deposition ratio of a first deposition rate of gold on the bottom member relative to a second deposition rate of gold on the sidewall being from 1.5 to 10 6 ; and
increasing the electrical current subjected to the field and the recessed feature to maintain the V SSE from −0.66 V to −1.00 V relative to the SSE during superconformally depositing gold on the substrate to superconformally fill the recessed feature of the article with gold as a superconformal filling comprising gold, the superconformal filling being void-free and seam-free,
such that in a presence of the superconformal filling composition: passivation of the field and the recessed feature occurs at the V SSE greater than −0.65 V relative to the SSE, sub-conformal deposition of gold occurs at the V SSE less than −1 V relative to the SSE, and superconformal deposition of gold occurs at the V SSE from −0.66 V to −1.00 V relative to the SSE.
2. The process of claim 1 , further comprising changing the V SSE from a first potential to a more negative potential during superconformally depositing gold.
3. The process of claim 1 , further comprising catalyzing superconformal deposition of gold with underpotential deposited Bi from the Bi 3+ cations.
4. The process of claim 1 , wherein actively moving the substrate relative to the superconformal filling composition comprising rotating the substrate at a rotation rate from 25 revolutions per minute (rpm) to 2000 rpm.
5. The process of claim 4 , further comprising changing the rotation rate from a first rotation rate to a second rotation rate during superconformally depositing gold.
6. The process of claim 1 , further comprising:
maintaining the VSSE from −0.66 V to −1.00 V relative to the SSE until the recessed feature is partially filled with the aspect ratio being less than or equal to 0.5; and
thereafter changing a deposition condition to fill the recessed feature sub-conformally, conformally, or a combination comprising at least one of the foregoing non-superconformal filling regimes.
7. The process of claim 1 , wherein the V SSE is maintained from −0.66 V to −1.00 V relative to the SSE until the recessed feature is completely filled with the superconformal filling.
8. The process of claim 1 , wherein the Au(SO 3 ) 2 3− anions are present in the superconformal filling composition in an amount from 50 millimolar (mM) to 350 mM.
9. The process of claim 1 , wherein the SO 3 2− anions are present in the superconformal filling composition in an amount from 0.1 molar (M) to 1 M.
10. The process of claim 1 , wherein Bi 3+ cations are present in the superconformal filling composition in an amount from 1 micromolar (mmM) to 50 mmM.
11. The process of claim 1 , wherein contacting the field and the recessed feature with the superconformal filling composition occurs in an absence of thallium.
12. The process of claim 1 , wherein contacting the field and the recessed feature with the superconformal filling composition occurs in an absence of a suppressor.
13. The process of claim 1 , wherein the superconformal filling composition consists essentially of the Au(SO 3 ) 2 3− anions, the SO 3 2− anions, the Bi 3+ cations, and an additive in an aqueous liquid in an absence of a suppressor.
14. The process of claim 1 , wherein the near-neutral pH of the superconformal filling composition is from 6.5 to 10.
15. The process of claim 1 , wherein the superconformal filling is crystalline.
16. The process of claim 1 , wherein the superconformal filling is nonporous.
17. The process of claim 1 , wherein the superconformal filling further comprises cobalt, and the superconformal filling is a cobalt-gold alloy.
18. The process of claim 13 , wherein the cobalt-gold alloy is a single phase.
19. The process of claim 1 , wherein the superconformal filling is shiny and planar at an exposed surface of the superconformal filling on a submicron level, a brightness of the superconformal filling occurring in an absence of dendrites on the exposed surface.
20. The process of claim 1 , wherein a second deposition ratio of the first deposition rate of gold on the bottom member relative to a third deposition rate of gold on the field is from 1.5 to 10 6 .
21. The process of claim 1 , wherein superconformally filling the recessed feature is bottom-up filling.
22. The process of claim 17 , wherein the field is passivated during bottom-up filling.
23. The process of claim 1 , wherein the bottom-up filling is uniform over the entire bottom member.
24. The process of claim 1 , wherein a deposition ratio of a thickness of gold deposited on the field to a thickness of gold deposited on the bottom member is from 1:20 to 1:50.
25. The process of claim 1 , wherein depositing the gold on the field and the recessed feature automatically stops before completely filling the recessed feature with gold while the V SSE is from −0.66 V to −1.00 V relative to the SSE.
26. The process of claim 1 , wherein the recessed feature comprises a trench, a via, a contact hole, or a combination comprising at least one of the foregoing recessed features.
27. The process of claim 1 , wherein the overlayer comprises a gold seed crystal.