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[0115] In table 1, the organic acids other than ascorbic acid have a carboxyl group. It is apparent from the data in Table 1 that the use of any of the organic acids having a carboxyl groups provides a low electrode potential as compared with the use of ascorbic acid having no carboxyl group (i.e., 7.55V vs. Ag/AgCl), and therefore the organic acids having a carboxylic acid are preferred. 

B. Relationship of Various Strong Acids with Electrode Potential 

[0116] Table 2 shows electrode potentials in polishing of the copper surface of the above-described sample wafer, carried out at a constant current density ( 40 mA/cm 2 ) in an electrolytic liquid, using the above-described chip-testing machine and various types of strong acids in the electrolytic liquid. A lower electrode potential in the table indicates that a higher electric current will flow and thus the processing rate will be higher, as compared to a higher electrode potential, if processing is carried out at the same level of electrode potential. A lower electrode potential is therefore preferred. 

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[0117] The data in Table 2 shows that the electric potential is higher in electrolytic polishing using the electrolytic liquid containing phosphoric acid (No. 2) than in electrolytic polishing using the electrolytic liquid containing methansul› fonic acid (No. 1) or nitric acid (No. 3). Roughening of the processed surface was observed in electrolytic polishing using the electrolytic liquid containing nitric acid (No. 3) or the electrolytic liquid containing sulfuric acid (No. 4), whereas the processed surface was found to be in an appreciably better state in electrolytic polishing using the electrolytic liquid containing methansulfonic acid (No. 1). As can be seen from the above results, methanesulfonid aid is the most preferable electrolyte of the strong acids tested. 

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C. Decrease in Electrode Potential by Combination of Organic Acid with Strong Acid 

[0118] Table 3 shows electrode potentials in electrolytic polishing of the copper surface of the above-described wafer sample, carried out using the various electrolytic liquids indicated in Table 3. As is apparent from comparison of the data between No. 1 and No. 2, the electrode potential value 2.04 [V vs. Ag/AgCl] for the electrolytic liquid containing the mixture of the organic acid, malonic acid, and the strong acid, methanesulfonic acid, is lower than the electrode potential value 4.51 [V vs. Ag/AgCl] for the electrolytic liquid solely containing malonic acid. Similar results were obtained with the use of glycolic acid as an organic acid as shown by the comparative data between No. 3 and N. 4. As will be appreciated from the results obtained, the use of an organic acid in combination with a strong acid in an elec› trolytic liquid will increase the current density and the processing rate with the same electrode potential as com› pared to the sole use of the organic acid. 

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D. Effect of Corrosion Inhibitor and/or Water-Soluble Poly› meric Compound 

[0119] Tables 4-a and 4-b show the results of measurement of the current densities of various electrolytic liquids, each based on the mixture of IM malonic acid and 1.4M meth› anesulfonic acid and containing as an additive a corrosion inhibitor and/or a water-soluble polymeric compound as indicated in the Tables 4-a and 4-b, carried out at a constant electrode potential of 2 [V vs. Ag/AgCl] using the above› described chip-testing machine, but without carrying out polishing (pressure O psi). 

