elimination of surface level difference and the surface roughness of the processed surface. 

[0127] For comparison, electrolytic polishing was carried out in the same manner using the same electrolytic liquid (pH 3) but not containing ammonium polyacrylate. As a result, the processing rate, the elimination of surface level difference and the surface roughness of the processed sur› face were all found to be poor. In particular, etch pits having a diameter of several µm and a depth of several hundred nm were formed in the processed surface. It is believed from the results of this comparative test that the water-soluble poly› meric compound, ammonium polyacrylate, enhances the effect of the corrosion inhibitor and, in addition, facilitates mechanical polishing. 

G. Effect of Starting Copper (Conductive Material) Com› ponent 

[0128] Using the electrolytic polishing apparatus shown in FIGS. 2 and 3, the influence of the presence or absence of copper ( conductive material), as a starting component, in an electrolytic liquid on the polishing rate and a surface rough› ness of a processed surface was determined. A substrate (workpiece) sample, which was used in this experiment, is a copper blanket wafer. In this experiment were used elec› trolytic liquids which had been prepared by adding copper ( conductive material) in various amounts to a base liquid having a pH of3 and comprising: IM malonic acid and 1 .4M methanesulfonic acid; 0.3% of benzotriazole; 0.6% of ammoniumpolyacrylate (molecular weight: 10,000); 0.7% of methanol; 0.05% of an anionic surfactant (formaldehyde condensate of ~-naphthalenesulfonic acid); and 0.5% of abrasive particles. Electrolytic polishing was carried out under the same conditions as described above under the heading "effect of abrasive particles". 

[0129] FIG. 4 shows copper-concentration dependency of the surface roughness (Rmax) of the processed surface, and FIG. 5 shows copper-concentration dependency of the pol› ishing rate. As can be seen from FIG. 4, the surface roughness decreases with an increase in the concentration of copper in the electrolytic liquid, and the use of the electro› lytic liquid having a copper concentration of not less than 0.005% provides the surface roughness of the polished surface which is less than ‰ of the surface roughness obtained by the use of the electrolytic liquid containing no copper as a starting component. As can be seen from FIG. 5, the use of the electrolytic liquid having a copper concen› tration of not less than 0.01 % provides the polishing rate which is more than 2.5 times the polishing rate attained by the use of the electrolytic liquid containing no copper as a starting component. 

[0130] A description will now be made of a process for removing an unnecessary portion of a film of interconnect material formed on a barrier film in a substrate as a polishing object, thereby exposing the barrier film. 

[0131] The process comprises the steps of: a first step of polishing a conductive material (i) lying over interconnect portions at a lower polishing rate than that of the other conductive material (ii) lying outside the interconnect por› tions so that the conductive material (i) becomes raised with respect to the conductive material (ii); and a second step of polishing the conductive material (ii) until the barrier film becomes exposed while polishing the raised conductive 

material (i). In the two-step process, an electrolytic liquid (hereinafter referred to as second electrolytic liquid) is used throughout the process. 

[0132] FIG. 6 is a vertical sectional front view of an electrolytic polishing apparatus for carrying out this process. In FIG. 6, the same or equivalent members as the electrolytic polishing apparatus shown in FIGS. 2 and 3 are given the same reference numerals, and a duplicate description thereof will be omitted. 

[0133] Above a polishing table 50 is disposed an electro› lytic liquid supply nozzle 60 for supplying an electrolytic liquid (second electrolytic liquid) for the present barrier layer-exposing process to the upper surface of the polishing table 50 during polishing. The electrolytic liquid supply nozzle 60 is connected to an electrolytic liquid supply line 64 which extends from an electrolytic liquid storage tank 62 for temporary storage of the second electrolytic liquid, and which is provided with a not-shown electrolytic liquid supply means, such as a tube pump, a diaphragm pump or a bellows pump. Above the polishing table 50 is also disposed a pure water supply nozzle 66 for supplying rinsing or cleaning pure water to the upper surface of the polishing table 50 after polishing. 

[0134] In this embodiment, an additive component(s) of the second electrolytic liquid which easily precipitates or decomposes is stored in a separate storage container 68 from the electrolytic liquid storage tank 62, and is added to the second electrolytic liquid stored in the electrolytic storage tank 62 to adjust the liquid into a predetermined condition before supplying the liquid from the electrolytic liquid supply nozzle 60 to the upper surface of the polishing table 50. In some cases, however, it is possible not to provide the storage tank 68 and to directly supply the second electrolytic liquid, which has been prepared and stored in the electrolytic liquid storage tank 62, from the electrolytic liquid supply nozzle 60 to the upper surface of the polishing table 50. 

[0135] A film thickness detection sensor 74, e.g., com› prised of an eddy current sensor, for detecting a film thickness of a (remaining) surface conductive material, such as copper 34, of a substrate W is embedded in the polishing table 50 with the upper surface of the sensor exposed on the surface of the processing electrode 56. An output signal from the film thickness detection sensor 74 is inputted into a control section 76 via a not-shown slip ring, and a power source 72, a table drive section 78 for rotating the polishing table 50, a holder drive section 80 for rotating and vertically moving a substrate holder 52, etc. are controlled by an output signal from the control section 78. 

[0136] The film thickness detection sensor 74 also detects an end point of polishing by sensing of the film thickness of conductive material, and outputs a signal to terminate pol› ishing. In terminating polishing, it is preferred to first stop the application of a voltage and then stop the supply of the second electrolytic liquid in order not to impair the polishing performance. 

[0137] A description will now be made of the second electrolytic liquid for use in the present barrier layer-expos› ing process carried out by the electrolytic polishing appa› ratus shown in FIG. 6. 

[0138] The second electrolytic liquid contains (1) at least one organic acid or its salt, (2) at lest one strong acid having 

