Composition for metal electroplating comprising leveling agent

Abstract

A composition comprising a source of metal ions and at least one additive comprising a polyalkyleneimine backbone, said polyalkyleneimine backbone having a molecular weight Mw of from 300 g/mol to 1000000 g/mol, wherein the N hydrogen atoms in the backbone are substituted by a polyoxyalkylene radical and wherein the average number of oxyalkylene units in said polyoxyalkylene radical is from 1.5 to 10 per N—H unit.

Claims

1. A composition, comprising: a metal ion source; an acidic electrolyte; and an additive comprising a polyalkyleneimine backbone, wherein the polyalkyleneimine backbone has a weight average molecular weight M.sub.w of from 300 g/mol to 1,000,000 g/mol, a hydrogen atom bonded to a nitrogen atom in the backbone is substituted by a polyoxyalkylene radical, and an average number of oxyalkylene units in the polyoxyalkylene radical is from 1.5 to 10 per N—H unit.

2. The composition of claim 1, wherein the average number of oxyalkylene units in the polyoxyalkylene radical is from 2 to 8 per N—H unit.

3. The composition of claim 1, wherein the additive is a polyalkyleneimine of formula L1: ##STR00007## or a derivative thereof obtained by a process comprising protonating or quaternizing the polyalkyleneimine, R is a linear C.sub.2-C.sub.6 alkanediyl, a branched C.sub.3-C.sub.6 alkanediyl, or a mixture thereof, A.sup.1 is a continuation of the polyalkyleneimine backbone by branching, A.sup.2 is alkyl, alkenyl, alkynyl, alkaryl, or a mixture thereof, E.sup.1 is a polyoxyalkylene unit of formula —(R.sup.1O).sub.pR.sup.2, each R.sup.1 is independently ethanediyl, 1,2-propanediyl, (2-hydroxymethyl)ethanediyl, 1,2-butanediyl, 2,3-butanediyl, 2-methyl-1,2-propanediyl (isobutylene), 1-pentanediyl, 2,3-pentanediyl, 2-methyl-1,2-butanediyl, 3-methyl-1,2-butanediyl, 2,3-hexanediyl,3,4-hexanediyl, 2-methyl-1,2-pentanediyl, 2-ethyl-1,2-butanediyl, 3-methyl-1,2-pentanediyl, 1,2-decanediyl, 4-methyl-1,2-pentanediyl, (2-phenyl)ethanediyl, or a mixture thereof, each R.sup.2 is independently hydrogen, alkyl, alkenyl, alkynyl, alkaryl, aryl, or a mixture thereof, p is from 1.5 to 10, q, n, m, and o are non-negative integers and q+n+m+o is from 10 to 24,000.

4. The composition of claim 3, wherein R is ethanediyl or a combination of ethanediyl and 1,2-propanediyl.

5. The composition of claim 3, wherein R.sup.1 is ethanediyl or a combination of ethanediyl and 1,2-propanediyl.

6. The composition of claim 3, wherein R.sup.2 is hydrogen.

7. The composition of claim 3, wherein p is from 2 to 5.

8. The composition of claim 3, wherein q+n+m+o is from 15 to 10000.

9. The composition of claim 3, wherein q+n+m+o is from 25 to 65.

10. The composition of claim 3, wherein o is 0.

11. The composition of claim 1, wherein the metal ion source comprises a copper ion.

12. The composition of claim 1, further comprising an accelerating agent.

13. The composition of claim 1, further comprising a suppressing agent.

14. A process for depositing a metal layer on a substrate, the process comprising: contacting a metal plating bath comprising the composition of claim 1 with the substrate, and applying a current density to the substrate for a time sufficient to deposit the metal layer onto the substrate.

15. A process for depositing a metal layer on a substrate, the process comprising: contacting a metal plating bath comprising: a metal ion source; an acidic electrolyte; and an additive comprising a polyalkyleneimine backbone, wherein the polyalkyleneimine backbone has a weight average molecular weight M.sub.w of from 300 g/mol to 1,000,000 g/mol, a hydrogen atom bonded to a nitrogen atom in the backbone is substituted by a polyoxyalkylene radical, and an average number of oxyalkylene units in the polyoxyalkylene radical is from 1.5 to 10 per N—H unit with the substrate, and applying a current density to the substrate for a time sufficient to deposit the metal layer onto the substrate, wherein the substrate comprises a micrometer or submicrometer sized feature and applying the current density to deposit the metal layer comprises depositing to fill the micrometer or submicrometer sized feature.

16. The process of claim 15, wherein the micrometer or submicrometer-sized feature has a size from 1 to 1000 nm, an aspect ratio of 4 or more, or both.

17. The composition of claim 7, wherein p is from 2 to 3.

18. The composition of claim 8, wherein q+n+m+o is from 20 to 5000.

19. The composition of claim 3, wherein q+n+m+o is from 1000 to 1800.

20. The process of claim 14, wherein the additive is a polyalkyleneimine of formula L1: ##STR00008## or a derivative thereof obtained by a process comprising protonating or quaternzing the polyalkyleneimine, each R is independently a linear C.sub.2-C.sub.6 alkanediyl, a branched C.sub.3-C.sub.6 alkanediyl, or a mixture thereof, A.sup.1 is a continuation of the polyalkyleneimine backbone by branching, each A.sup.2 is independently alkyl, alkenyl, alkynyl, alkaryl, or a mixture thereof, E.sup.1 is a polyoxyalkylene unit of formula —(R.sup.1O).sub.pR.sup.2, each R.sup.1 is independently ethanediyl, 1,2-propanediyl, (2-hydroxymethyl)ethanediyl, 1,2-butanediyl, 2,3-butanediyl, 2-methyl-1,2-propanediyl (isobutylene), 1-pentanediyl, 2,3-pentanediyl, 2-methyl-1,2-butanediyl, 3-methyl-1,2-butanediyl, 2,3-hexanediyl, 3,4-hexanediyl, 2-methyl-1,2-pentanediyl, 2-ethyl-1,2-butanediyl, 3-methyl-1,2-pentanediyl, 1,2-decanediyl, 4-methyl-1,2-pentanediyl and (2-phenyl)ethanediyl, or a mixture thereof, each R.sup.2 is independently hydrogen, alkyl, alkenyl, alkynyl, alkaryl, aryl, or a mixture thereof, p is from 1.5 to 10, q, n, m, o are non-negative integers and a sum q+n+m+o is from 10 to 24,000.

21. The composition of claim 1, wherein said acidic electrolyte is at least one acidic electrolyte selected from the group consisting of sulfuric acid, acetic acid, fluoroboric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, trifluoromethane sulfonic acid, phenyl sulfonic acid, toluenesulfonic acid, sulfamic acid, hydrochloric acid and phosphoric acid.

22. The composition of claim 1, wherein said acidic electrolyte is present in an amount of 1 to 300 g/L.

23. The composition according to claim 1, wherein said polyalkyleneimine backbone has a weight average molecular weight Mw of from 600 g/mol to 1,000,000 g/mol.

24. The composition according to claim 1, wherein said polyalkyleneimine backbone has a weight average molecular weight Mw of from 1,000 g/mol to 1,000,000 g/mol.

25. The composition according to claim 3, where o is 0.

26. The process according to claim 20, where o is 0.

27. The composition according to claim 3, where A.sup.2 is an alkyl which is methyl.

28. The process according to claim 20, where A.sup.2 is an alkyl which is methyl.

Description

(1) The general process of copper electrodeposition on semiconductor integrated circuit substrates is described with respect to FIGS. 1 and 2 without restricting the invention thereto.

(2) FIG. 1a shows a dielectric substrate 1 seeded with a copper layer 2a. With reference to FIG. 1b a copper layer 2′ is deposited onto the dielectric substrate 1 by electrodeposition. The trenches 2c of the substrate 1 are filled and an overplating of copper 2b, also referred to as “overburden”, is generated on top of the whole structured substrate. During the process, after optional annealing, the overburden of copper 2b is removed by chemical mechanical planarization (CMP), as depicted in FIG. 1c.

(3) The effect of a leveling agent is generally described with respect to FIGS. 2a and 2b. Without a leveling agent the deposition leads to a high ratio a/b>>1, the so called mounding. In contrast, the aim is to reduce the ratio a/b to a value, which is as close as possible to 1.

(4) A particular advantage of the present invention is that overplating, particularly mounding, is reduced or substantially eliminated. Such reduced overplating means less time and effort is spent in removing metal, such as copper, during subsequent chemical-mechanical planarization (CMP) processes, particularly in semiconductor manufacture. A further advantage of the present invention is that a wide range of aperture sizes may be filled within a single substrate resulting in a substantially even surface having a ratio a/b of 1.5 or less, preferably 1.2 or less, most preferably 1.1 or less. Thus, the present invention is particularly suitable to evenly filling apertures in a substrate having a variety of aperture sizes, such as from 0.01 micrometer to 100 micrometer or even larger.

(5) A further significant advantage of this leveling effect is that less material has to be removed in post-deposition operations. For example, chemical mechanical planarization (CMP) is used to reveal the underlying features. The leveled deposit of the invention corresponds to a reduction in the amount of metal which must be deposited, therefore resulting in less removal later by CMP. There is a reduction in the amount of scrapped metal and, more significantly, a reduction in the time required for the CMP operation. The material removal operation is also less severe which, coupled with the reduced duration, corresponds to a reduction in the tendency of the material removal operation to impart defects.

(6) Metal, particularly copper, is deposited in apertures according to the present invention without substantially forming voids within the metal deposit. By the term “without substantially forming voids”, it is meant that 95% of the plated apertures are void-free. It is preferred that the plated apertures are void-free.

(7) Typically, substrates are electroplated by contacting the substrate with the plating baths of the present invention. The substrate typically functions as the cathode. The plating bath contains an anode, which may be soluble or insoluble. Optionally, cathode and anode may be separated by a membrane. Potential is typically applied to the cathode. Sufficient current density is applied and plating performed for a period of time sufficient to deposit a metal layer, such as a copper layer, having a desired thickness on the substrate. Suitable current densities, include, but are not limited to, the range of 1 to 250 mA/cm.sup.2. Typically, the current density is in the range of 1 to 60 mA/cm.sup.2 when used to deposit copper in the manufacture of integrated circuits. The specific current density depends upon the substrate to be plated, the leveling agent selected and the like. Such current density choice is within the abilities of those skilled in the art. The applied current may be a direct current (DC), a pulse current (PC), a pulse reverse current (PRC) or other suitable current.

(8) In general, when the present invention is used to deposit metal on a substrate such as a wafer used in the manufacture of an integrated circuit, the plating baths are agitated during use. Any suitable agitation method may be used with the present invention and such methods are well-known in the art. Suitable agitation methods include, but are not limited to, inert gas or air sparging, work piece agitation, impingement and the like.

(9) Such methods are known to those skilled in the art. When the present invention is used to plate an integrated circuit substrate, such as a wafer, the wafer may be rotated such as from 1 to 150 RPM and the plating solution contacts the rotating wafer, such as by pumping or spraying. In the alternative, the wafer need not be rotated where the flow of the plating bath is sufficient to provide the desired metal deposit.

(10) Metal, particularly copper, is deposited in apertures according to the present invention without substantially forming voids within the metal deposit. By the term “without substantially forming voids”, it is meant that 95% of the plated apertures are void-free. It is preferred that the plated apertures are void-free.

(11) While the process of the present invention has been generally described with reference to semiconductor manufacture, it will be appreciated that the present invention may be useful in any electrolytic process where an essentially level or planar copper deposit having high reflectivity is desired, and where reduced overplating and metal filled small features that are substantially free of voids are desired. Such processes include printed wiring board manufacture. For example, the present plating baths may be useful for the plating of vias, pads or traces on a printed wiring board, as well as for bump plating on wafers. Other suitable processes include packaging and interconnect manufacture. Accordingly, suitable substrates include lead frames, interconnects, printed wiring boards, and the like.

(12) Plating equipment for plating semiconductor substrates are well known. Plating equipment comprises an electroplating tank which holds Cu electrolyte and which is made of a suitable material such as plastic or other material inert to the electrolytic plating solution. The tank may be cylindrical, especially for wafer plating. A cathode is horizontally disposed at the upper part of tank and may be any type substrate such as a silicon wafer having openings such as trenches and vias. The wafer substrate is typically coated with a seed layer of Cu or other metal to initiate plating thereon. A Cu seed layer may be applied by chemical vapor deposition (CVD), physical vapor deposition (PVD), or the like. An anode is also preferably circular for wafer plating and is horizontally disposed at the lower part of tank forming a space between the anode and cathode. The anode is typically a soluble anode.

(13) These bath additives are useful in combination with membrane technology being developed by various tool manufacturers. In this system, the anode may be isolated from the organic bath additives by a membrane. The purpose of the separation of the anode and the organic bath additives is to minimize the oxidation of the organic bath additives.

(14) The cathode substrate and anode are electrically connected by wiring and, respectively, to a rectifier (power supply). The cathode substrate for direct or pulse current has a net negative charge so that Cu ions in the solution are reduced at the cathode substrate forming plated Cu metal on the cathode surface. An oxidation reaction takes place at the anode. The cathode and anode may be horizontally or vertically disposed in the tank.

(15) The present invention is useful for depositing a metal layer, particularly a copper layer, on a variety of substrates, particularly those having variously sized apertures. For example, the present invention is particularly suitable for depositing copper on integrated circuit substrates, such as semiconductor devices, with small diameter vias, trenches or other apertures. In one embodiment, semiconductor devices are plated according to the present invention. Such semiconductor devices include, but are not limited to, wafers used in the manufacture of integrated circuits.

(16) While the process of the present invention has been generally described with reference to semiconductor manufacture, it will be appreciated that the present invention may be useful in any electrolytic process where an essentially level or planar copper deposit having high reflectivity is desired. Accordingly, suitable substrates include lead frames, interconnects, printed wiring boards, and the like.

(17) All percent, ppm or comparable values refer to the weight with respect to the total weight of the respective composition except where otherwise indicated. All cited documents are incorporated herein by reference.

(18) The following examples shall further illustrate the present invention without restricting the scope of this invention.

EXAMPLES

(19) In table 1 the structural properties of the leveler examples are given. The polyalkylene-polyamine backbones of all tested levelers are in all cases polyethyleneimines from BASF. Used polyethyleneimines comprise about equal fractions of primary, secondary and tertiary amine groups. Thus, it was assumed, that one N—H unit of the polyethyleneimine backbone correlates with an average molecular weight of 43 g/mol. The molecular weights of the respective polymer backbones are given in the second column of table 1. The polyalkyleneimines according to examples 1-5 have been (poly)alkoxylated by ethylene oxide. The number of ethylene oxide units p per N—H unit of the respective polymer backbone is given in the third column. The leveler according to reference example 4 is only mono-ethoxylated (p=1). The Polyalkoxylated polyalkylenepolyamine according to example 3 has been functionalized additionally by quaternization of all nitrogen atoms using dimethyl sulfate (column 4, table 1). The last column summarizes which levelers provided defect-free filling performance (+) and which one disturbs the superfill mechanism (−). The filling experiments are described in detail in examples 12-17.

(20) TABLE-US-00001 TABLE 1 M (polyamine Example backbone) [g/mol] p Functionalization 1 2000 2 None 2 60000 2 None 3 60000 2 N-methylated 4 (comparative) 60000 1 None 5 5000 5 None

(21) The amine number was determined according to DIN 53176 by titration of a solution of the polymer in acetic acid with perchloric acid.

(22) .sup.1H NMR spectra were recorded with a 400 MHz spectrometer using the tetramethylsilane peak as internal standard.

Example 1

(23) Polyethyleneimine Lupasol PR 8515 from BASF (652 g) and water (108.2 g) were placed into a 2 l autoclave at 80 degree C. and the reactor was purged with nitrogen three times at 2 bars. Then, ethylene oxide (600 g) was added in portions at 120 degree C. over a period of 5 h. To complete the reaction, the mixture was allowed to post-react for 4 h at the same temperature and, then, it was cooled down to 40 degree C. The reaction mixture was stripped with nitrogen at 60 degree C. and, subsequently, volatile compounds were removed at 60 degree C. and 200 mbar at the rotary evaporator. A yellow viscous liquid was observed as an intermediate product (1355 g) as an aqueous solution showing a water content of 7.6% by weight according to Karl-Fischer-titration and an amine number of 8.94 mmol/g.

(24) The intermediate product (180 g), an aqueous solution of potassium hydroxide (concentration: 50 weight percent; 0.2 g) and water (30 ml) were homogenized in the microwave and, then, the mixture was placed into a 21 autoclave. The reaction mixture was heated at 120 degree C. and purged with a constant nitrogen stream (0.5 m.sup.3 N.sub.2/h) for 2 h. Residual water was removed at below 10 mbar for 3 h. Subsequently, the reactor was purged with nitrogen three times at 5 bars. Then, ethylene oxide (77.9 g) was added in portions at 120 degree C. over a period of 1 h. To complete the reaction, the mixture was allowed to post-react for 6 h at the same temperature and, then, it was cooled down to 40 degree C. The reaction mixture was stripped with nitrogen and, subsequently, diluted with water (150 ml). Leveler L1 was observed as a dark brown aqueous solution (366.9 g) with a water content of 32.7% by weight according to Karl-Fischer-titration. .sup.1H NMR (D20): δ=3.72 (m, 6H, —CH2O—), 2.73 (m, 6H, —CH.sub.2N—) ppm. Amine number: 4.64 mmol/g.

Example 2

(25) Water-free hydroxyethylated polyethyleneimine Lupasol SC-61 B from BASF (100.5 g) was diluted with water and homogenized in the microwave to give an aqueous solution (150 ml). Then, potassium hydroxide (concentration: 50 weight percent; 0.4 g) was added and the mixture was stirred overnight. Then the solution was placed into a 21 autoclave. The reaction mixture was heated at 120 degree C. and purged with a constant nitrogen stream (0.5 m.sup.3 N2/h) for 2 h. Subsequently, the reactor was purged with nitrogen three times at 5 bars. Then, ethylene oxide (53.6 g) was added in portions at 120 degree C. over a period of 5 h. To complete the reaction, the mixture was allowed to post-react overnight at the same temperature. Volatile compounds were removed at the rotary evaporator at 100 degree C. at 1-3 mbars. The product was observed as a brown highly viscous liquid (154.9 g). .sup.1H NMR (CDCl.sub.3): δ=3.58 (m, 6H, —CH.sub.2O—), 2.64 (m, 6H, —CH.sub.2N—) ppm. Amine number: 7.0 mmol/g.

Example 3

(26) The compound prepared by example 2 (20.0 g) and water (153 g) were placed into a 250 ml flask and dimethyl sulfate was added drop-wise into the solution at room temperature. The reaction mixture was stirred for 22 h at room temperature and heated for additional 6.5 h at 100° C. The resulting brown solution showed an amine number of 0 mmol/g, indicating complete quaternization of all amine atoms present in the polyalkoxylated polyethyleneimine starting material. The aqueous solution of the product showed a water content of 77.3%.

Comparative Example 4

(27) Hydroxyethylated polyethyleneimine Lupasol SC-61 B available from BASF.

Example 5

(28) Polyethyleneimine Lupasol G 100 from BASF (1001 g; water content: 50 weight percent) was placed into a 21 autoclave at 80 degree C. The reaction mixture was heated at 100 degree C. and purged with a constant nitrogen stream (0.25 m.sup.3 N.sub.2/h) for 3 h. Then, ethylene oxide (460.8 g) was added in portions at 120 degree C. over a period of 5 h 10 min. To complete the reaction, the mixture was allowed to post-react for 2 h at the same temperature and, then, it was cooled down to 40 degree C. The reaction mixture was stripped with nitrogen at 80 degree C. and, subsequently, volatile compounds were removed at 60 degree C. and 200 mbar at the rotary evaporator. A yellow viscous liquid was observed as an intermediate product (1360 g) as an aqueous solution, showing a water content of 31%.

(29) The intermediate product (70.7 g), an aqueous solution of potassium hydroxide (concentration: 50 weight percent; 0.2 g) and water (10 g) were placed into a 21 autoclave. The reactor was purged with nitrogen three times at 5 bars at 120 degree C. Then, the reaction mixture was purged with a constant nitrogen stream (0.5 m.sup.3 N.sub.2/h) for 1 h. Residual amounts of water were removed in vacuo (below 10 mbar) for additional 2 h. Again, the reactor was purged with nitrogen three times at 5 bars at 120 degree C. Then, ethylene oxide (106.7 g) was added in portions at 120 degree C. over a period of 10 h. To complete the reaction, the mixture was allowed to post-react overnight at the same temperature. After cooling to room temperature water was added. Volatile organic compounds were removed at the rotary evaporator. The final product was observed as a dark brown aqueous solution (141.1 g) with a water content of 32.8%. Amine number: 2.60 mmol/g. .sup.1H NMR (D20): δ=3.72 (m, 18H, —CH.sub.2O—), 2.73 (m, 6H, —CH.sub.2N—) ppm.

Comparative Example 6

(30) A copper plating bath was prepared by combining 40 g/I copper as copper sulfate, 10 g/I sulfuric acid, 0.050 g/I chloride ion as HCI, 0.100 g/I of an EO/PO copolymer suppressor, and 0.028 g/I of SPS and DI water. The EO/PO copolymer suppressor had a molecular weight of below 5000 g/mole and terminal hydroxyl groups.

(31) A copper layer was electroplated onto a structured silicon wafer purchased from SKW Associate Inc. containing grooves, so called trenches. These lines varied in width ranging from 130 nm to several microns with a depth of approximately 250 nm and a separation ranging from 130 nm to several microns. Such wafer substrates were brought into contact with the above described plating bath at 25 degrees C. and a direct current of −5 mA/cm.sup.2 for 120 s followed by −10 mA/cm.sup.2 for 60 s was applied.

(32) The thus electroplated copper layer was investigated by profilometry inspection with a Dektak 3, Veeco Instruments Inc. In the case of 130 nm feature sizes a field of wires was scanned and the height difference between the unstructured and structured area was measured.

(33) The results using a plating bath without a leveling agent are shown in FIG. 4a

Example 7

(34) The procedure of example 6 was repeated except that 1 ml/l of an aqueous stock solution containing 1% by weight of the active leveling agent of example 1 was added to the plating bath.

(35) A copper layer was electroplated onto a wafer substrate as described in example 6. The thus electroplated copper layer was investigated by profilometry as described in example 6.

(36) The results using a plating bath with a leveling agent according to the present invention are shown in FIG. 4b. The profilometry cross-sectional scan of trenches having 0.130 micrometers width with a separation of 0.130 micrometers (FIG. 4b), shows a significant reduction of the mounding compared to prior art (FIG. 4a). The measured values are depicted in table 2.

Example 8

(37) The procedure of example 6 was repeated except that 1 ml/l of an aqueous stock solution containing 1% by weight of the active leveling agent of example 2 was added to the plating bath.

(38) A copper layer was electroplated onto a wafer substrate as described in example 6. The thus electroplated copper layer was investigated by profilometry as described in example 6.

(39) The values obtained from profilometry, as depicted in table 2, show a significant reduction of the mounding compared to example 6 without a leveling agent.

Example 9

(40) The procedure of example 6 was repeated except that 1 ml/l of an aqueous stock solution containing 1% by weight of the active leveling agent of example 3 was added to the plating bath.

(41) A copper layer was electroplated onto a wafer substrate as described in example 6. The thus electroplated copper layer was investigated by profilometry as described in example 6.

(42) The values obtained from profilometry, as depicted in table 2, show a significant reduction of the mounding compared to example 6 without a leveling agent.

Example 10

(43) The procedure of example 6 was repeated except that 1 ml/l of an aqueous stock solution containing 1% by weight of the active leveling agent of example 4 was added to the plating bath.

(44) A copper layer was electroplated onto a wafer substrate as described in example 6. The thus electroplated copper layer was investigated by profilometry as described in example 6.

(45) The values obtained from profilometry, as depicted in table 2, show a significant reduction of the mounding compared to example 6 without a leveling agent.

Example 11

(46) The procedure of example 6 was repeated except that 1 ml/l of an aqueous stock solution containing 1% by weight of the active leveling agent of example 5 was added to the plating bath.

(47) A copper layer was electroplated onto a wafer substrate as described in example 6. The thus electroplated copper layer was investigated by profilometry as described in example 6.

(48) The values obtained from profilometry, as depicted in table 2, show a significant reduction of the mounding compared to example 6 without a leveling agent.

(49) For FIB/SEM investigations about the influence of the polyethyleneimines according to the present invention on the fill performance in sub 50 nanometer features as shown in FIG. 3 were used for electroplating with the different plating baths described in the following sections. Thus the used copper seeded wafer substrate exhibited feature sizes of 15.6 to 17.9 nanometer width at the trench opening, 34.6 to 36.8 nanometer width at half height of the trench, and 176.4 nanometer depth.

Comparative Example 12

(50) A plating bath was prepared by combining DI water, 40 g/I copper as copper sulfate, 10 g/I sulfuric acid, 0.050 g/I chloride ion as HCI, 0.028 g/I of SPS and 2.00 ml/l of a 5.3% by weight solution in DI water of a EO/PO copolymer suppressor having a molecular weight M.sub.w of below 13000 g/mole and terminal hydroxyl groups.

(51) A copper layer was electroplated onto a wafer substrate with feature sizes shown in FIG. 3 provided with a copper seed layer by contacting the wafer substrate with the above described plating bath at 25 degrees C. applying a direct current of −5 mA/cm.sup.2 for 3 s. The thus electroplated copper layer was cross-sectioned and investigated by SEM inspection.

(52) The result is shown in FIG. 5, providing the SEM image of the filled trenches without exhibiting any defects like voids or seams. The bottom up fill is clearly shown since the trenches are filled up to just underneath the trench opening.

Example 13

(53) The procedure of example 12 was repeated except that in addition 0.625 ml/l of a 1% by weight aqueous solution of a polyethyleneimine from example 1 was added to the plating bath.

(54) The result using a plating bath with the leveling agent as prepared in example 1 according to the present invention is shown in FIG. 6. The trenches are filled without exhibiting any defects like voids or seams thus showing that there is not any interference in the gap filling by the leveling agent.

Example 14

(55) The procedure of example 12 was repeated except that in addition 0.625 ml/l of a 1% by weight aqueous solution of a polyethyleneimine from example 2 was added to the plating bath.

(56) The result using a plating bath with the leveling agent as prepared in example 2 according to the present invention is shown in FIG. 7. The trenches are filled without exhibiting any defects like voids or seams thus showing that there is not any interference in the gap filling by the leveling agent.

Example 15

(57) The procedure of example 12 was repeated except that in addition 0.625 ml/l of a 1% by weight aqueous solution of a polyethyleneimine from example 3 was added to the plating bath.

(58) The result using a plating bath with the leveling agent as prepared in example 3 according to the present invention is shown in FIG. 8. The trenches are filled without exhibiting any defects like voids or seams thus showing that there is not any interference in the gap filling by the leveling agent.

Comparative example 16

(59) The procedure of example 12 was repeated except that in addition 0.625 ml/l of a 1% by weight aqueous solution of a polyethyleneimine from example 4 was added to the plating bath.

(60) The result using a plating bath with the leveling agent as prepared in example 4 is shown in FIG. 9. The filled trenches show void formation. This indicates that the leveler strongly interferes in the gap filling.

Example 17

(61) The procedure of example 12 was repeated except that in addition 0.625 ml/l of a 1% by weight aqueous solution of a polyethyleneimine from example 5 was added to the plating bath. The result using a plating bath with the leveling agent as prepared in example 5 according to the present invention is shown in FIG. 10. The trenches are filled without exhibiting any defects like voids or seams thus showing that there is not any interference in the gap filling by the leveling agent.

(62) TABLE-US-00002 TABLE 2 mounding filling performance Example Leveler 130 nanometer comparative 6/12 none 370 nm (FIG. 4a) + (FIG. 5)  7/13 Example 1 −28 nm (FIG. 4b) + (FIG. 6)  8/14 Example 2  39 nm + (FIG. 7)  9/15 Example 3  48 nm + (FIG. 8) comparative comparative  19 nm − (FIG. 9) 10/16 Example 4 11/17 Example 5 192 nm + (FIG. 10)