Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/4414—Electrochemical vapour deposition [EVD]
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
  • C25D3/14—Electroplating: Baths therefor from solutions of nickel or cobalt from baths containing acetylenic or heterocyclic compounds
  • C25D3/18—Heterocyclic compounds
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/04—Coating on selected surface areas, e.g. using masks
  • C23C16/045—Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/06—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material
  • C23C16/08—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material from metal halides
  • C23C16/14—Deposition of only one other metal element
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/02—Electroplating of selected surface areas
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D7/00—Electroplating characterised by the article coated
  • C25D7/12—Semiconductors
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D7/00—Electroplating characterised by the article coated
  • C25D7/12—Semiconductors
  • C25D7/123—Semiconductors first coated with a seed layer or a conductive layer

Definitions

• the present invention concerns electrodeposition of cobalt on a conductive surface. More precisely, it concerns an electrolyte and a method for cobalt electrodeposition that can be used to fabricate electrical interconnects in integrated circuits.
• Semiconductor devices comprise different levels of integration and two categories of conductive metallic interconnects: trenches a few tens of nanometers wide, which run on the surface of the device and which connect the electronic components, and through vias which connect the different levels and whose diameter is around several hundred nanometers.
• Fabrication of interconnects comprises etching cavities on the substrate, followed by depositing a metallic seed layer on the surface of the cavities to allow a subsequent step of filling the cavities electrochemically with a conductive metal.
• the filling of cavities can follow two mechanisms depending on the composition of the electrolyte used: a bottom-up filling or a conformal filling.
• the filling method by a bottom-up mechanism is opposed to a filling method in which the cobalt deposit grows at the same rate at the bottom and on the walls of the hollow patterns.
• electrolytes of the prior art comprise several additives including a suppressor and an accelerator.
• a suppressor limits the deposition of cobalt at the upper level of the cavities, on their walls as well as on the flat surface of the substrate onto which the cavities open, while the accelerator diffuses at the bottom of the cavities to promote the deposition of cobalt.
• the presence of an accelerator is even more necessary for cavities of narrow width and large depth since it makes it possible to increase the rate of cobalt deposition at the bottom of the cavities.
• Electrodeposition baths designed for bottom-up filling have several disadvantages that ultimately limit the smooth operation of the electronic devices manufactured and which make them too expensive to manufacture. They actually generate cobalt interconnects contaminated by the organic additives made necessary to limit the formation of holes in the cobalt during filling. Moreover, the filling speeds obtained with these chemicals are too slow and not compatible with industrial-scale production.
• the electrolyte contains numerous additives including a suppressor and an accelerator with complementary functions to ensure bottom-up filling.
• Alpha-hydroxy carboxylic acids have certainly already been used in electrochemical methods for cobalt deposition such as, for example, in application WO 2019/179897, but these methods follow a conformal filling mechanism at the end of which holes persist in the metal in the absence of annealing of the deposit.
• the invention concerns a method for creating cobalt interconnects by bottom-up filling of cavities that uses an electrolyte of pH comprised between 1.8 and 4.0, comprising cobalt II, chloride ions, an alpha-hydroxy carboxylic acid and a additive chosen from among polyethyleneimines and benzotriazole.
• the invention concerns an electrolyte for the electrodeposition of cobalt in the form of an aqueous solution comprising from 1 to 5 g/L of cobalt II ions, from 1 to 10 g/L of chloride ions, a strong acid in a sufficient quantity to obtain a pH comprised between 1.8 and 4.0, and organic additives including at least one first additive chosen from alpha-hydroxy carboxylic acids and mixtures thereof and at least one second additive chosen from polyethyleneimines and benzotriazole.
• the electrolyte of the invention allows obtaining continuous cobalt deposits of high purity whose duration of production can be less than that of the prior art.
• the filling kinetics of conventional methods must be slower to prevent the formation of holes, and the method must comprise an annealing step when holes are formed.
• the method can comprise two separate steps of cobalt electrodeposition: a step of performing the filling of cavities at a fairly slow speed, and a second step of electrodeposition using a second electrolyte comprising cobalt ions for depositing the so-called "overburden layer" on the entire substrate surface.
• the method of the invention advantageously makes it possible to perform the filling of cavities and deposition of the overburden layer in a single electrodeposition step. It also makes it possible to avoid annealing the cobalt deposit before performing the polishing step combining chemical and mechanical attack of the overburden layer.
• cobalt deposits produced in the context of the invention have the advantage of forming interconnects having a very low amount of impurities, preferably less than 1000 atomic ppm.
• Electrode means the liquid containing precursors of a metal coating used in an electrodeposition method.
• Continuous filling means a mass of cobalt free of voids.
• material holes or voids can be observed in a cobalt deposit between the walls of the cavities and the cobalt deposit (sidewall voids) and holes located at a distance from the walls of cavities in the form of seams. These voids can be observed and quantified by transmission or scanning electron microscopy by making cross sections of the structures.
• the continuous deposit of the invention preferably has a mean void percentage less than 10% by volume, preferably less than or equal to 5% by volume.
• the void percentage within the structures to be filled can be measured by scanning electron microscopy with a magnification between 50,000 and 350,000.
• Mean diameter or “mean width” of the cavities means the dimensions measured at the opening of the cavities to be filled.
• the cavities are, for example, in the form of cylinders or flared channels.
• Figure 1 is a transmission electron microscope slide of cavities filled according to a method of the invention of Test 1 of Example 1.
• Figure 2 is a scanning electron microscope slide of cavities filled according to a method of the invention of Test 3 of Example 1.
• Figure 3 is a scanning electron microscope slide of cavities filled according to an electrodeposition method of the prior art (Comparative Example 4).
• the invention concerns an electrolyte for the electrodeposition of cobalt characterized in that the electrolyte is an aqueous solution comprising from 1 to 5 g/L of cobalt II ions, from 1 to 10 g/L of chloride ions, a strong acid in a sufficient quantity to obtain a pH comprised between 1.8 and 4.0, and organic additives including at least one first additive chosen from alpha-hydroxy carboxylic acids and mixtures thereof and at least one second additive chosen from polyethyleneimines and benzotriazole.
• the mass concentration of cobalt II ions can range from 1 g/L to 5 g/L, for example from 2 g/L to 3 g/L. That of the chloride ions can range from 1 g/L to 10 g/L.
• Chloride ions can be introduced by dissolution in water of cobalt chloride or one of its hydrate salts, such as cobalt chloride hexahydrate.
• the electrolyte preferably comprises at most two organic additives, these additives being the first and second additive.
• All of the organic additives contained in the electrolyte are preferably sulphur free.
• the alpha-hydroxy carboxylic acid is preferably sulphur free.
• the electrolyte preferably does not contain any sulphur compound.
• the composition is preferably not obtained by dissolution of a cobalt salt such as cobalt sulfate or one of its hydrates because it generates a sulphur contamination of the cobalt deposit, which we wish to avoid.
• the total concentration of organic additives in the electrolyte is preferably comprised between 5 ppm and 50 ppm.
• the concentration of the first additive is preferably comprised between 5 and 200 ppm and the concentration of the second additive is preferably comprised between 1 and 10 ppm.
• the first additive is chosen, for example, from citric acid, tartaric acid, malic acid, mandelic acid and glyceric acid.
• the alpha-hydroxy carboxylic acid is tartaric acid.
• the second amine additive is a linear or branched poly(ethyleneimine) homopolymer or copolymer.
• the poly(ethyleneimine) is in the form of an acid, part or all of its amine functions being protonated.
• a linear poly(ethyleneimine) will be chosen, for example, having number-average molecular weight Mn comprised between 500 g/mol and 25,000 g/mol.
• a branched poly(ethyleneimine) can also be chosen having a number- average molecular weight Mn comprised between 500 g/mol and 70,000 g/L, which comprises primary amine, secondary amine and tertiary amine functions.
• the poly(ethyleneimine) can be a poly(ethyleneimine) of CAS number 25987-06-8, having, for example, a number-average molecular weight Mn comprised between 500 g/mol and 700 g/mol, and preferably a weight- average molecular weight Mw comprised between 700 g/mol and 900 g/mol.
• a poly(ethyleneimine) exists under reference 408719 sold by the Sigma- Aldrich company.
• the poly(ethyleneimine) can also be a poly(ethyleneimine) of CAS number 9002-98-6, having, for example, a number-average molecular weight Mn comprised between 500 and 700 g/mole.
• a poly(ethyleneimine) exists under reference 02371 sold by Polysciences, Inc.
• the number-average molecular weight and the weight-average molecular weight can be measured independently from one another by a conventional method known to the skilled person, such as gel permeation chromatography (GPC) or light scattering (LS).
• GPC gel permeation chromatography
• LS light scattering
• the amine is benzotriazole.
• the pH of the electrolyte is preferably comprised between 1.8 and 4.0. In a particular embodiment, the pH is comprised between 1.8 and 2.6.
• the pH of the composition can optionally be adjusted with a base or an acid known to the skilled person.
• the acid used can be hydrochloric acid.
• the electrolyte may not contain a buffer compound, such as, for example, boric acid. Preferably, the electrolyte does not contain boric acid.
• the solvent Although there is no restriction in principle regarding the nature of the solvent (provided that it sufficiently solubilizes the active species of the solution and does not interfere with electrodeposition), it will preferably be water. According to one embodiment, the solvent predominantly comprises water by volume.
• the conductivity of the electrolyte is preferably comprised between 2 mS/cm and 10 mS/cm.
• the invention also concerns an electrochemical method for deposition on a substrate provided with a conductive surface comprising a flat part and cavities, by filling said cavities bottom-up, said method comprising: - a step of contacting the conductive surface with an electrolyte according to the preceding description,
• the duration is sufficient to perform the filling of the cavities and the coating of the flat part of the conductive surface by a cobalt deposit having a thickness ranging from 50 nm to 400 nm.
• the deposition method of the invention therefore comprises:
• polishing step combining chemical and mechanical attack of the cobalt deposit, without performing a prior annealing treatment of the deposit at a temperature ranging from 50°C to 500°C.
• the polarization step in the presence of the electrolyte of the invention can last as long as necessary to fill the cavities without covering the flat surface.
• the deposition method can comprise a second polarization step during which a second cobalt deposit is formed using an electrolyte other than that of the invention.
• the polarization step in the presence of the electrolyte of the invention can last as long as necessary to fill the cavities and coat the flat surface, the thickness of the cobalt deposit above the flat surface being at least 20 nm.
• the part of the cobalt deposit that coats the flat surface also called overburden layer, can have a thickness comprised between 50 nm and 400 nm. It is advantageously of constant thickness over the entire substrate surface.
• the layer is also homogenous, shiny and compact.
• the method of the invention is a so-called “bottom-up” method as opposed to the “conformal” methods of the prior art.
• the speed of cobalt deposition is higher at the bottom of the cavities than on the walls.
• the cobalt deposit obtained at the end of the polarization step advantageously has an impurity content less than 1000 atomic ppm.
• the predominant impurity is oxygen, followed by carbon and nitrogen.
• the total carbon and nitrogen content is preferably less than 300 ppm.
• the cobalt deposit obtained at the end of the electrodeposition step is advantageously continuous, in the sense that it comprises a void percentage of less than 10% by volume or by area, preferably less than or equal to 5% by volume or by area, without undergoing a heat treatment at a temperature ranging from 50°C to 500°C, preferably comprised between 150°C and 500°C.
• the void percentage in the cobalt deposit can be measured by electron microscope observation known to the skilled person, who will choose the method that seems most appropriate.
• One of these methods can be scanning electron microscopy (SEM) or transmission electron microscopy (TEM) by using a magnification comprised between 50,000 and 350,000.
• SEM scanning electron microscopy
• TEM transmission electron microscopy
• the void volume can be assessed by measuring the void area observed over one or more cross sections of the substrate comprising the filled cavities. When several areas are measured over several cross sections, the mean of these areas will be calculated to assess the void volume.
• a low content of impurities combined with a very low void percentage makes it possible to obtain a cobalt deposit whose resistivity is reduced.
• the resistivity of the cobalt deposit obtained at the end of the polarization step can be less than 30 mW.ati without undergoing a heat treatment at a temperature ranging from 50°C to 500°C.
• the cobalt deposition rate can be between 0.1 nm/s and 3.0 nm/s, preferably between 1.0 nm/s and 3.0 nm/s, and more preferably between 1 nm/s and 2.5 nm/s.
• the cavities to be filled can be fashioned according to a Damascene or Dual Damascene method known to the skilled person comprising a succession of steps comprising: - etching trenches on the upper part of a silicon wafer; - depositing an insulating dielectric layer generally consisting of silicon oxide on the etched surface; - depositing a thin layer of a barrier material used to prevent the migration of cobalt into the silicon; - optionally depositing a thin metallic layer, called the seed layer.
• the barrier layer and the seed layer generally have, independently of one another, a thickness comprised between 1 nm and 10 nm.
• the conductive surface which is in contact with the electrolyte is a surface of a metal layer comprising, for example, at least one compound chosen in the group made up of cobalt, copper, tungsten, titanium, tantalum, ruthenium, nickel, titanium nitride and tantalum nitride.
• the conductive surface of the substrate can be the surface of an assembly comprising a tantalum nitride layer of a thickness comprised between 1 nm and 6 nm, itself covered and in contact with a layer of metallic cobalt comprised between 1 nm and 10 nm, preferably between 2 nm and 5 nm, on which the cobalt will be deposited during the electrical step.
• the substrate can therefore be obtained by successive deposits of Si0 2 , tantalum nitride and cobalt.
• Cobalt can be deposited on tantalum nitride by chemical vapor deposition (CVD) or by atomic layer deposition (ALD).
• the resistivity of the assembly comprising the metal layer and the cobalt deposit can range from 7 to 10 ohm/cm. It is preferably comprised between 7.5 and 8.5 ohm/cm.
• the cavities designed to be filled with the cobalt according to the method of the invention preferably have a width at their opening (i.e., at the surface of the substrate) of less than 100 nm, preferably comprised between 10 and 50 nm.
• the depth can range from 50 to 250 nm. According to one embodiment, they have a width comprised between 30 nm and 50 nm, preferably between 35 nm and 45 nm, and a depth comprised between 125 nm and 175 nm.
• the intensity of the polarization used in the electrical step preferably ranges from 2 mA/cm 2 to 20 mA/cm 2 .
• the cobalt deposition rate is comprised between 0.1 nm/s and 3.0 nm/s when the intensity of the polarization current ranges from 8.5 mA/cm 2 to 18.5 mA/cm 2 , which is very advantageous in comparison with methods of the prior art for which a much lower rate is observed in this current range.
• the electrical polarization step of the method of the invention may comprise a single or several different polarization mode steps.
• the conductive surface can be contacted with the electrolyte either before polarization or after polarization. It is preferred that the contact with the cavities be done before energizing, so as to limit corrosion of the surface by the electrolyte.
• the electrical step can be performed by using at least one polarization mode chosen from the group made up of ramp mode, galvanostatic mode and galvano-pulsed mode.
• the electrical step comprises one or more steps of cathode polarization in ramp mode in a current range from 0 mA/cm 2 to 10 mA/cm 2 , for a duration preferably comprised between 10 s and 100 s.
• the electrical step can also comprise one or more steps of polarization in galvanostatic mode with a current ranging from 5 mA/cm 2 to 20 mA/cm 2 .
• the electrical step comprises at least one step of polarizing the cathode in ramp mode with a current preferably ranging from 0 mA/cm 2 to 10 mA/cm 2 , followed by a step in galvanostatic mode by imposing a current of 5 mA/cm 2 to 20 mA/cm 2 .
• the method of the invention can comprise a step of annealing the cobalt deposit obtained at the end of filling described previously, but it advantageously does not have this step.
• An annealing heat treatment is generally conducted at a temperature comprised between 350°C and 550°C, for example around 450°C, preferably under reducing gas such as 4%H 2 in N 2 .
• the method may comprise a preliminary step of treatment with a reducing plasma so as to reduce the native metal oxide present on the conductive surface of the substrate.
• the plasma also acts on the surface of the trenches which allows improving the quality of the interface between the seed layer and the electrodeposited cobalt. It is preferred that the electrodeposition step be performed immediately after the plasma treatment to minimize the reformation of native oxide.
• the method of the invention is especially applied in the manufacture of semiconductor devices when creating conductive metallic interconnects such as trenches running on the surface and vias connecting different levels of integration.
• Trenches are filled by electrodeposition of cobalt on a cobalt seed layer.
• the deposition is conducted using a composition containing cobalt dichloride, an alpha-hydroxy carboxylic acid and polyethyleneimine (PEI) at pH 2.2.
• PEI polyethyleneimine
• the substrate used in this example was made up of a 3.3 x 3.3 cm trench-etched silicon coupon that has been successively coated with a layer of silicon oxide, a layer of TaN 2 nm thick and a layer of metallic cobalt 3 nm thick.
• the resistivity of the substrate is approximately 600 ohms per square.
• the width of the cavities to be filled is equal to 40 nm at their opening and their depth is equal to 150 nm.
• the Co 2+ concentration is equal to 2.3 g/L obtained from COCI 2 (H 2 0) 6 .
• the tartaric acid has a concentration equal to 15 ppm.
• the PEI has a concentration equal to 5 ppm.
• the pH of the solution is adjusted to 2.2 by addition of hydrochloric acid.
• electrolytic deposition equipment composed of two parts: the cell designed to contain the electrodeposition solution equipped with a fluid recirculation system in order to control the hydrodynamics of the system and a rotating electrode equipped with a sample holder adapted to the size of the coupons used (3.3 cm x 3.3 cm).
• the electrolytic deposition cell had two electrodes:
• the reference is connected to the anode.
• Connectors allowed the electrical contact of the electrodes that were connected by electrical wires to a potentiostat providing up to 20 V or 2 A.
• Test 1 Three tests are conducted, called Test 1, Test 2 and Test 3, by applying different electrical methods.
• the three methods comprised two, three or five steps out of the following steps: a) "Cold input”: The electrodeposition solution is poured into the electrolytic deposition cell. The different electrodes are put in place and contacted in the electrodeposition solution without polarization. Polarization is then applied. b) In a second step, the cathode is polarized in galvanodynamic ramp mode in a current range from 0 mA to 30 mA (or 3.8 mA/cm 2 ). This step is conducted with a rotation of 65 rpm for 3 seconds.
• the cathode is polarized in galvanodynamic ramp mode in a current range of 30 mA (or 3.8 mA/cm 2 ) to 60 mA (or 7.6 mA/cm 2 ). This step is conducted with a rotation of 65 rpm for 55 seconds.
• the cathode is polarized in galvanodynamic ramp mode in a current range of 60 mA (or 7.6 mA/cm 2 ) to 130 mA (16.5 mA/cm 2 ) for example a current range of 60 mA (or 3.8 mA/cm 2 ) to 90 mA (11.4 mA/cm 2 ).
• This step is conducted with a rotation of 65 rpm for 7 seconds.
• the cathode is polarized in galvanostatic mode in a current range of 90 mA (11.4 mA/cm 2 ) to 130 mA (16.5 mA/cm 2 ) for example 90 mA (11.4 mA/cm 2 ).
• This step is conducted under a rotation of 65 rpm or 100 rpm and lasts from 40 to 150 seconds.
• the first electrical protocol comprised three steps, steps a), b) and c).
• the second electrical protocol comprised five steps, steps a) to e).
• the cathode was polarized in galvanostatic mode at 90 mA (11.4 mA/cm 2 ) with a rotation of 100 rpm for 40 seconds.
• the third electrical protocol (Test 3) comprised two steps, steps a) and e).
• the cathode was polarized in galvanostatic mode at 90 mA (11.4 mA/cm 2 ) with a rotation of 65 rpm for 133 seconds.
• Figure 2 shows a slide resulting from scanning electron microscopy (SEM) analysis of Test 3 which reveals filling with no hole defects on the walls of the trenches (sidewall voids) reflecting good nucleation of the cobalt and no holes in the structures (seam voids) reflecting optimal bottom-up filling with no annealing.
• SEM scanning electron microscopy
• Trenches identical to those of Example 1 are filled using a composition containing cobalt dichloride, an alpha-hydroxy carboxylic acid and benzotriazole at pH 2.2.
• the substrate used is strictly identical to that of Example 1.
• the Co 2+ concentration is equal to 2.3 g/L obtained from CoCI 2 (Fl 2 0) 6 .
• the tartaric acid has a concentration equal to 15 ppm.
• the benzotriazole has a concentration equal to 10 ppm.
• the pH of the solution is adjusted to 2.2 by addition of hydrochloric acid.
• the electrical method was identical to that of Test 2 of Example 1 and comprised the five steps a) to e).
• SEM scanning electron microscopy
• Trenches identical to those of Example 1 are filled using a composition containing cobalt dichloride and alpha-hydroxy carboxylic acid at pH 2.2.
• the substrate used is strictly identical to that of Example 1.
• the Co 2+ concentration is equal to 2.3 g/L obtained from COCI 2 (H 2 0) 6 .
• the tartaric acid has a concentration equal to 15 ppm.
• the pH of the solution is adjusted to 2.2 by addition of hydrochloric acid.
• the electrical method was identical to that of Test 2 of Example 1 and comprised the five steps a) to e).
• SEM scanning electron microscopy
• Comparative Example 4 Electrodeposition for structures of 40 nm wide and 150 nm deep with an electrolyte of the prior art
• An electrodeposition of cobalt in trenches identical to those of Example 1 is performed using a composition of the prior art according to the teaching of application US 2016/0273117 A1 containing cobalt sulfate, boric acid, thiourea and polyethyleneimine (PEI) at pH 4.
• the substrate used is strictly identical to that of Example 1.
• Electrodeposition solution In this solution, the Co 2+ concentration is equal to 2 g/L obtained from C0SO4.
• the boric acid has a concentration equal to 20 g/L.
• the thiourea has a concentration equal to 150 ppm.
• the PEI has a concentration equal to 10 ppm.
• the pH of the solution is adjusted to 4 by addition of sulfuric acid.
• the resistivity of the film deposited in Test 3 of Example 1 is better than that of Comparative Example 4, which is more desirable at the industrial level.
• a lower resistivity is synonymous with a better film quality with fewer impurities.

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