Mar. 20, 2008  10  US 2008/0067077 Al  [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.  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.  [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.  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).  TABLE 4-a  TABLE 2  TABLE 3  No. Electrolytic liquid  lM MA, 1.4M MSA  0  psi  Current density  pH  [rnA/cm 2 ]  3  11.7  2  lM MA, 1.4M MSA, 0.1% BTA  3  6.7  3  lM MA, 1.4M MSA, 1% BTA  3  5.4  4  lM MA, 1.4M MSA, 0.5% thiourea  3  8.4  5  lM MA, 1.4M MSA, 0.5% 2-methyl-8-hydroxyquinoline  3  8.3  6  lM MA, 1.4M MSA, 0.5% bismuthiol  3  3.7  7  lM MA, 1.4M MSA, 0.5% 5-methyl-lH-benzotriazole  3  3.3  8  lM MA, 1.4M MSA, 0.5% 3-amino-5-metyl-1,2,4-triazole  3  8.7  9  lM MA, 1.4M MSA, 0.2% BTA, 0.2% 2-ethylimidazole  3  5.1  10  lM MA, 1.4M MSA, 0.2% BTA, 0.2% 2-ethylimidazole, 0.6% APA, 0.7% metanol  3  4.9  11  lM MA, 1.4M MSA, 0.3% BTA, 0.6% APA, 0.7% methanol  3  4.3  12  lM MA, 1.4M MSA, 0.3% BTA, 0.6% SPA, 0.7% methanol  3  6.7  13  lM MA, 1.4M MSA, 0.3% BTA, 0.6% PVP, 0.7% methanol  3  4.9  Electrode potential  Concentration  At 40 rnA/cm 2  No. Electrolyte  [mol/1]  pH  [VvsAg/AgCl]  Methanesulfonic  0.5  1.38  acid  2  Phosphoric acid  0.81  4.24  3  Nitric acid  0.31  1.24  4  Sulfuric acid  0.26  0.95  Electrode potential  at 40 mA/cm 2  No.  Electrolyte  pH  [VvsAg/AgCl]  lM Malanie acid  3  4.51  2  lM Malanie acid, 1.2M  3  2.04  Methanesulfonic acid  3  lM Glycolic acid  4  5.47  4  lM Glycolic acid, 1.5M  4  2.56  Methanesulfonic acid 