# US 11,078,591 B2 · Process for optimizing cobalt electrofill using sacrificial oxidants > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,078,591 B2 - Document ID: US11078591B2 - Status: Granted - Kind: B2 - Application number: 16/410,420 - Filed: 2019-05-13 - Published: 2019-09-05 - Granted: 2021-08-03 - Earliest claimed: 2016-11-03 - Assignees: Lam Research Corporation - Applicants: Lam Research Corporation - Inventors: Lee J. Brogan; Natalia V. Doubina; Matthew A. Rigsby; Jonathan David Reid - Web page: https://patentgrep.com/patent/US11078591B2 ## CPC - C25D 7/123: {Semiconductors first coated with a seed layer or a conductive layer} - C25D 3/12: of nickel or cobalt - C25D 5/04: Electroplating with moving electrodes - C25D 17/001: {Apparatus specially adapted for electrolytic coating of wafers, e.g. semiconductors or solar cells} - C25D 17/06: Suspending or supporting devices for articles to be coated - C25D 21/12: Process control or regulation (controlling or regulating in general G05) - C25D 21/14: Controlled addition of electrolyte components - H10P 14/47: Electrolytic deposition, i.e. electroplating; Electroless plating - H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects} - H10W 20/0261: {characterised by the filling method or the material of the conductive fill} - H10W 20/057: {by selectively depositing, e.g. by using selective CVD or plating} - H10W 20/4437: {the principal metal being a transition metal} - H10P 74/207: {Electrical properties, e.g. testing or measuring of resistance, deep levels or capacitance-voltage characteristics} - H10W 20/023: {the interconnections being through-semiconductor vias} - C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract Embodiments herein relate to methods, apparatus, and systems for electroplating metal into recessed features using a superconformal fill mechanism that provides relatively faster plating within a feature and relatively slower plating in the field region. Moreover, within the feature, plating occurs faster toward the bottom of the feature compared to the top of the feature. The result is that the feature is filled with metal from the bottom upwards, resulting in a high quality fill without the formation of seams or voids, defects that are likely where a conformal fill mechanism is used. The superconformal fill mechanism relies on the presence of a sacrificial oxidant molecule that is used to develop a differential current efficiency within the feature compared to the field region. Various plating conditions are balanced against one another to ensure that the feature fills from the bottom upwards. No organic plating additives are necessary, though plating additives can be used to improve the process. ## Claims ### Claim 1 A method of electroplating a recessed feature on a substrate using a superconformal fill mechanism, the method comprising: (a) immersing the substrate in electrolyte, the electrolyte comprising metal ions and a sacrificial oxidant; (b) applying current to the substrate to plate metal in the recessed feature; (c) during (b), depleting a concentration of the sacrificial oxidant within the recessed feature to form a concentration differential with respect to the sacrificial oxidant, wherein the sacrificial oxidant becomes relatively less abundant within the recessed feature and relatively more abundant in a field region of the substrate; (d) during (b), developing a current efficiency differential, wherein the current efficiency is relatively higher within the recessed feature and relatively lower in the field region of the substrate; and (e) during (b), using the current efficiency differential to drive the superconformal fill mechanism that deposits metal relatively faster near a bottom of the recessed feature and relatively slower in the field region of the substrate. ### Claim 2 (depends on 1) The method of claim 1, wherein during (b), the metal ions are not mass transport limited, such that no substantial concentration differential forms with respect to the metal ions. ### Claim 3 (depends on 1) The method of claim 1, wherein the metal ions are cobalt ions and the sacrificial oxidant is hydrogen ions. ### Claim 4 (depends on 3) The method of claim 3, wherein the electrolyte comprises about 10-100 mM cobalt ions, about 0.05-0.6 M boric acid, a pH between about 2-4, and wherein a concentration of cobalt ions in the electrolyte is at least about 10 times higher than a concentration of hydrogen ions in the electrolyte. ### Claim 5 (depends on 4) The method of claim 4, wherein during (b) the substrate is rotated at a rate between about 1-100 RPM, and wherein during (b) current is applied to the substrate at a constant current density of about 4 mA/cm2 or below. ### Claim 6 (depends on 5) The method of claim 5, further comprising after (a) and before (b), performing a pre-conditioning step where no current or potential is applied to the substrate for a duration between about 0.25-30 seconds. ### Claim 7 (depends on 1) The method of claim 1, wherein the sacrificial oxidant, or a material that acts as a source for the sacrificial oxidant, is selected from the group consisting of: a peroxide, dissolved O2, dissolved O3, HNO3, a sugar acid, Cl2, Br2, and I2, and combinations thereof. ### Claim 8 (depends on 1) The method of claim 1, wherein the electrolyte is substantially free of suppressor, accelerator, and leveler. ### Claim 9 (depends on 1) The method of claim 1, wherein the electrolyte further comprises suppressor. ### Claim 10 (depends on 1) The method of claim 1, wherein during (b) a current density applied to the substrate increases from a starting current density to an ending current density, the starting current density being between about 0-4 mA/cm2 and the ending current density being between about 6-10 mA/cm2. ### Claim 11 An apparatus for electroplating metal into a recessed feature using a superconformal fill mechanism, the apparatus comprising: an electroplating chamber configured to hold electrolyte; a substrate holder configured to immerse the substrate in the electrolyte; and a controller comprising executable instructions for: (a) immersing the substrate in electrolyte, the electrolyte comprising metal ions and a sacrificial oxidant; (b) applying current to the substrate to plate metal in the recessed feature; (c) during (b), depleting a concentration of the sacrificial oxidant within the recessed feature to form a concentration differential with respect to the sacrificial oxidant, wherein the sacrificial oxidant becomes relatively less abundant within the recessed feature and relatively more abundant in a field region of the substrate; (d) during (b), developing a current efficiency differential, wherein the current efficiency is relatively higher within the recessed feature and relatively lower in the field region of the substrate; and (e) during (b), using the current efficiency differential to drive the superconformal fill mechanism that deposits metal relatively faster near a bottom of the recessed feature and relatively slower in the field region of the substrate.