COMPOSITION FOR METAL ELECTROPLATING COMPRISING LEVELING AGENT

Abstract

A method of detecting space debris includes: generating a virtual space debris in accordance with the law of conservation of mass by applying a debris breakup model to an object of breakup origin; calculating an orbit of each virtual space debris based on a debris orbit propagation model; and generating appearance frequency distribution of a motion vector of each virtual space debris on the celestial sphere based on the orbit calculation. The above operations are executed multiple times. The method further includes setting a search range vector based on a motion vector having a high level of the appearance frequency distribution of the motion vector, and applying a stacking method to regions in images captured at time intervals during the fixed point observation, the regions being shifted along the search range vector sequentially in the order of capture, thereby detecting space debris appearing on the images.

Claims

1. A method of detecting space debris on a geocentric orbit, the space debris appearing on a plurality of images captured at time intervals during fixed point observation, the method comprising: an object identification step of identifying an object of breakup origin which is likely to have broken up on the geocentric orbit in the past; a virtual debris generation step of generating a virtual space debris piece in accordance with the law of conservation of mass by applying a debris breakup model to the object of breakup origin identified in the object identification step; an orbit calculation step of applying a debris orbit propagation model to each virtual space debris piece generated in the virtual debris generation step, thereby calculating an orbit of the virtual space debris piece during the fixed point observation; a motion vector distribution generation step of generating appearance frequency distribution of a motion vector of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of a result of the orbit calculation in the orbit calculation step; a motion vector estimation step of estimating the motion vector of the space debris piece on the images on the basis of a motion vector having a high level in the appearance frequency distribution on the basis of cumulative distribution of a plurality of appearance frequency distribution results of the motion vector obtained by performing the virtual debris generation step, the orbit calculation step, and the motion vector distribution generation step a plurality of times; and a detection step of cross-checking pieces of pixel information on respective regions in the images captured at time intervals during the fixed point observation, the regions shifted in a direction and in an amount of the estimated motion vector sequentially in the order of capture, thereby detecting space debris on the geocentric orbit appearing on the images.

2. The method of detecting space debris according to claim 1, further comprising: a search range vector setting step of setting a search range vector on the basis of the estimated motion vector, the search range vector indicating a direction of motion and an amount of motion of a search range for the space debris appearing on the images, wherein the detection step includes applying a stacking method to respective regions in the images captured at time intervals during the fixed point observation, the regions being shifted in a direction and in an amount of the set search range vector sequentially in the order of capture, thereby detecting space debris on the geocentric orbit appearing on the images.

3. The method of detecting space debris according to claim 1, wherein the orbit calculation step includes a time-based orbit calculation step of performing the orbit calculation of each virtual space debris piece generated in the virtual debris generation step for each of time points at regular time intervals in a period from start to end of the fixed point observation, and the motion vector distribution generation step generates the appearance frequency distribution of the motion vector on the basis of a result of the orbit calculation at the time points in the time-based orbit calculation step.

4. The method of detecting space debris according to claim 1, further comprising: a debris distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the orbit calculation in the orbit calculation step; and a capturing space setting step of setting a space including a region having a high level in the existence probability distribution of the virtual space debris piece on the celestial sphere during the fixed point observation as a space for capturing the images during the fixed point observation, on the basis of cumulative distribution of a plurality of existence probability distribution results obtained by performing the virtual debris generation step, the orbit calculation step, and the debris distribution generation step a plurality of times, wherein the images are obtained by capturing the set capturing space at time intervals.

5. The method of detecting space debris according to claim 4, wherein the orbit calculation step includes a time-based orbit calculation step of performing the orbit calculation of each virtual space debris piece generated in the virtual debris generation step for each of time points at regular time intervals in a period from start to end of the fixed point observation, and the debris distribution generation step includes: an existing position calculation step of calculating an existing position of each virtual space debris piece on the celestial sphere at each time point on the basis of the result of the orbit calculation at the time point in the time-based orbit calculation step; and an existence probability distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the calculation in the existing position calculation step.

6. The method of detecting space debris according to claim 2, wherein the orbit calculation step includes a time-based orbit calculation step of performing the orbit calculation of each virtual space debris piece generated in the virtual debris generation step for each of time points at regular time intervals in a period from start to end of the fixed point observation, and the motion vector distribution generation step generates the appearance frequency distribution of the motion vector on the basis of a result of the orbit calculation at the time points in the time-based orbit calculation step.

7. The method of detecting space debris according to claim 2, further comprising: a debris distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the orbit calculation in the orbit calculation step; and a capturing space setting step of setting a space including a region having a high level in the existence probability distribution of the virtual space debris piece on the celestial sphere during the fixed point observation as a space for capturing the images during the fixed point observation, on the basis of cumulative distribution of a plurality of existence probability distribution results obtained by performing the virtual debris generation step, the orbit calculation step, and the debris distribution generation step a plurality of times, wherein the images are obtained by capturing the set capturing space at time intervals.

8. The method of detecting space debris according to claim 3, further comprising: a debris distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the orbit calculation in the orbit calculation step; and a capturing space setting step of setting a space including a region having a high level in the existence probability distribution of the virtual space debris piece on the celestial sphere during the fixed point observation as a space for capturing the images during the fixed point observation, on the basis of cumulative distribution of a plurality of existence probability distribution results obtained by performing the virtual debris generation step, the orbit calculation step, and the debris distribution generation step a plurality of times, wherein the images are obtained by capturing the set capturing space at time intervals.

9. The method of detecting space debris according to claim 6, further comprising: a debris distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the orbit calculation in the orbit calculation step; and a capturing space setting step of setting a space including a region having a high level in the existence probability distribution of the virtual space debris piece on the celestial sphere during the fixed point observation as a space for capturing the images during the fixed point observation, on the basis of cumulative distribution of a plurality of existence probability distribution results obtained by performing the virtual debris generation step, the orbit calculation step, and the debris distribution generation step a plurality of times, wherein the images are obtained by capturing the set capturing space at time intervals.

10. The method of detecting space debris according to claim 7, wherein the orbit calculation step includes a time-based orbit calculation step of performing the orbit calculation of each virtual space debris piece generated in the virtual debris generation step for each of time points at regular time intervals in a period from start to end of the fixed point observation, and the debris distribution generation step includes: an existing position calculation step of calculating an existing position of each virtual space debris piece on the celestial sphere at each time point on the basis of the result of the orbit calculation at the time point in the time-based orbit calculation step; and an existence probability distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the calculation in the existing position calculation step.

11. The method of detecting space debris according to claim 8, wherein the orbit calculation step includes a time-based orbit calculation step of performing the orbit calculation of each virtual space debris piece generated in the virtual debris generation step for each of time points at regular time intervals in a period from start to end of the fixed point observation, and the debris distribution generation step includes: an existing position calculation step of calculating an existing position of each virtual space debris piece on the celestial sphere at each time point on the basis of the result of the orbit calculation at the time point in the time-based orbit calculation step; and an existence probability distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the calculation in the existing position calculation step.

12. The method of detecting space debris according to claim 9, wherein the orbit calculation step includes a time-based orbit calculation step of performing the orbit calculation of each virtual space debris piece generated in the virtual debris generation step for each of time points at regular time intervals in a period from start to end of the fixed point observation, and the debris distribution generation step includes: an existing position calculation step of calculating an existing position of each virtual space debris piece on the celestial sphere at each time point on the basis of the result of the orbit calculation at the time point in the time-based orbit calculation step; and an existence probability distribution generation step of generating existence probability distribution of each virtual space debris piece on the celestial sphere during the fixed point observation on the basis of the result of the calculation in the existing position calculation step.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0138] The general process of copper electrodeposition on semiconductor integrated circuit substrates is described with respect to FIGS. 1A-6B without restricting the invention thereto. The figures show:

[0139] FIG. 1A A schematic view of a dielectric substrate 1 seeded with a copper layer 2a.

[0140] FIG. 1B A schematic view of a copper layer 2 deposited onto the dielectric substrate 1 by electrodeposition.

[0141] FIG. 1C A schematic view of a copper deposited onto the dielectric substrate 1 by electrodeposition after chemical mechanical planarization (CMP).

[0142] FIG. 2A A schematic view of a substrate 1 comprising a first area patterned with densely arranged parallel features and a second non-patterned area after copper electrodeposition without using a leveler.

[0143] FIG. 2B A schematic view as depicted in FIG. 2A after copper electrodeposition by using a leveler according to the invention.

[0144] FIG. 3A The SEM image of trenches comprising a copper seed having 16 to 37 nm trench width, 173 to 176 nm trench depth.

[0145] FIG. 3B The SEM image of fully filled trenches resulting from a copper electroplating according to Example 7 using a plating bath with leveler 1 as prepared in example 1 according to the present invention. The trenches are completely filled without exhibiting any defects like voids or seams thus showing that there is no interference with the gapfilling by the leveling agent.

[0146] FIG. 3C The SEM image of fully filled trenches resulting a copper electroplating according to Comparative Example 6 providing the SEM image of fully filled trenches without exhibiting any defects like voids or seams.

[0147] FIG. 4A The SEM image of trenches having 100 nm trench widths comprising a copper seed.

[0148] FIG. 4B The SEM image of fully filled trenches resulting from a copper electroplating according to Example 9 without exhibiting any defects like voids or seams while efficiently preventing bump formation over the 13 nm wide trenches.

[0149] FIG. 4C The SEM image of fully filled trenches resulting from a copper electroplating according to Example 10 without exhibiting any defects like voids or seams while still efficiently preventing bump formation over the 100 nm wide trenches.

[0150] FIG. 4D The SEM image of fully filled trenches resulting from a copper electroplating according to Comparative Example 8 revealing bump formation over the 100 nm wide trenches.

[0151] FIG. 5A the profilometry results for area (i) without using a leveling agent according to Comparative Example 11 showing a higher copper deposit over the pattererned area compared to the unpatterned area.

[0152] FIG. 5B the profilometry results for area (ii) without using a leveling agent according to Comparative Example 11 showing a higher copper deposit over the pattererned area compared to the unpatterned area.

[0153] FIG. 6A the profilometry results for area (i) using the leveling agent from example 1 according to Example 12 showing essentially no mounding over the patterned area compared to the unpatterned area.

[0154] FIG. 6B the profilometry results for area (ii) using the leveling agent from example 1 according to Example 12 showing essentially no mounding over the patterned area compared to the unpatterned area.

[0155] With reference to FIG. 1A a dielectric substrate 1 is first seeded with a copper layer 2a. With reference to FIG. 1B a copper layer 2 is then 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.

[0156] The effect of a leveling agent is generally described with respect to FIGS. 2A and 2B. The mounding may be determined by profilometry measuring the step height (distance a minus distance b) between patterned and unpatterned areas. Without a leveling agent the deposition leads to a high ratio a/b>>1. In contrast, the aim is to reduce the ratio a/b to a value, which is as close as possible to 1.

[0157] 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.

[0158] 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 more level 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.

[0159] 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.

[0160] 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.

[0161] 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. 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 200 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.

[0162] 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.

[0163] 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 copper, any other metal, or any other non-metal conducting material to initiate plating thereon. A copper 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] The following examples shall further illustrate the present invention without restricting the scope of this invention.

EXAMPLES

[0170] In table 1 the structural properties of the leveler examples 1-5 are given. The filling experiments and results are described in detail in examples 6-16.

TABLE-US-00001 TABLE 1 Leveler R.sup.2 R.sup.1 1 n-hexane-1,6-diyl H 2 n-octane-1,8-diyl H 3 propane-1,3-diyl 2-hydroxyethyl and H 4 1,3-phenyl H 5 n-hexane-1,6-diyl 2-aminoethyl and H and ethane-1,2-diyl

Example 1

[0171] Sodium dicyanamide (96% purity grade; 18.5 g), n-hexylene-1,6-diamine dihydrochloride (38.2 g) and methanol (250 ml) were placed into a 500 ml flask and the reaction mixture was stirred under reflux for 20 h. After cooling to room temperature, the resulting sodium chloride precipitate was removed by filtration and, subsequently, the solvent was distilled from the remaining product solution at 40 C. and under reduced pressure at the rotary evaporator to observe a raw material as a white solid (48.8 g). The raw material (15 g) was dissolved in hot water (400 g) and the insoluble components were removed by filtration. The remaining clear aqueous solution was heated to 100 C. and 20 mbar at the rotary evaporator to remove the solvent. Leveler 1 was received as a white solid (12 g).

Example 2

[0172] Sodium dicyanamide (96% purity grade; 18.6 g) and n-octylene-1,8-diamine (28.8 g) were placed into a 250 ml flask and the reaction mixture was heated to 70 C. Then, concentrated hydrochloric acid (39.4 g) was added dropwise resulting in a temperature increase to 102.5 C. A constant nitrogen stream was applied and, then, the temperature was increased to 180 C. and water was destilled off. After 30 min the heating was turned off, the distillation condenser was replaced by a reflux condenser and methanol (120 ml) was poured into the reaction mixture. After cooling to room temperature, the resulting sodium chloride precipitate was removed by filtration and, subsequently, the solvent was distilled from the remaining product solution at 40 C. and under reduced pressure at the rotary evaporator. Leveler 2 was received as a white solid (53.3 g).

Example 3

[0173] Sodium dicyanamide (96% purity grade; 37.0 g) and N-(2-hydroxyethyl)-1,3-propandiamine (49.0 g) were placed into a 250 ml flask and concentrated hydrochloric acid (79.5 g) was added dropwise resulting in a temperature increase to 95 C. Then, the reaction mixture was heated to 180 C. under a constant nitrogen stream to remove water resulting in an exothermic reaction and a temperature increase to 216 C. After 7 min, the distillation condenser was replaced by a reflux condenser and methanol (120 ml) was added. After cooling to room temperature, the resulting sodium chloride precipitate was removed by filtration and, subsequently, the solvent was distilled from the remaining product solution at 40 C. and under reduced pressure at the rotary evaporator. Leveler 3 was received as a brown solid (87.0 g).

Example 4

[0174] Sodium dicyanamide (96% purity grade; 18.6 g) and 1,3-phenylendiamine (21.6 g) were placed into a 250 ml flask and heated to 100 C. Then, concentrated hydrochloric acid (39.4 g) was added dropwise resulting in a temperature increase to 109 C. The reaction mixture was heated to 113 C. under a constant nitrogen stream for water removal. Due to the high viscosity, the distillation condenser was replaced by a reflux condenser immediately and methanol (120 ml) was added. After cooling to room temperature, the resulting sodium chloride precipitate was removed by filtration and, subsequently, the solvent was distilled from the remaining product solution at 40 C. and under reduced pressure at the rotary evaporator. Leveler 4 was received as a brown solid (41.6 g).

Example 5

[0175] Sodium dicyanamide (96% purity grade; 18.6 g), diethylentriamine (2.0 g) and n-hexylene-1,6-diamine (20.9 g) were placed into a 250 ml flask and the reaction mixture was heated to 70 C. Then, concentrated hydrochloric acid (39.4 g) was added dropwise resulting in a temperature increase to 105 C. A constant nitrogen stream was applied to remove water and, then, the temperature was increased to 180 C. At this temperature, the distillation condenser was replaced by a reflux condenser and methanol (120 ml) was poured into the reaction mixture. After cooling to room temperature, the resulting sodium chloride precipitate was removed by filtration and, subsequently, the solvent was distilled from the remaining product solution at 40 C. and under reduced pressure at the rotary evaporator. Leveler 5 was received as a brownish solid (44.1 g).

Comparative Example 6

[0176] A plating bath was prepared by combining DI water, 40 g/l copper as copper sulfate, 10 g/l sulfuric acid, 0.050 g/l chloride ion as HCl, 0.028 g/l of SPS and 2.00 ml/l of a 5.3% by weight solution in DI water of a suppressor being a EO/PO copolymer having a molecular weight of <13000 g/mole and terminal hydroxyl groups (PS151).

[0177] A copper layer was electroplated onto a wafer substrate with feature sizes shown in FIG. 3A (16 to 37 nm trench width, 173 to 176 nm trench depth) 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 6 s. The thus electroplated copper layer was cross-sectioned and investigated by SEM inspection.

[0178] The result is shown in FIG. 3C providing the SEM image of fully filled trenches without exhibiting any defects like voids or seams.

Example 7

[0179] The procedure of example 6 was repeated except that 0.625 ml/l of a 1% by weight aqueous solution of polymeric biguanide compound leveler 1 as prepared in example 1 was added to the plating bath.

[0180] A copper layer was electroplated onto a wafer substrate as described in example 6. The thus electroplated copper layer was cross-sectioned and investigated by SEM inspection.

[0181] The result using a plating bath with leveler 1 as prepared in example 1 according to the present invention is shown in FIG. 3B. The 16 to 37 nanometer wide trenches are completely filled without exhibiting any defects like voids or seams thus showing that there is no interference with the gapfilling by the leveling agent.

Comparative Example 8

[0182] A plating bath according to comparative example 6 was prepared.

[0183] A copper layer was electroplated onto a wafer substrate with feature sizes shown in FIG. 4A (100 nm trench width) 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 27 s followed by 10 mA/cm.sup.2 for 27 s. The thus electroplated copper layer was cross-sectioned and investigated by SEM inspection.

[0184] The result is shown in FIG. 4D providing the SEM image of fully filled trenches without exhibiting any defects like voids or seams. FIG. 4D clearly reveals bump formation over the 100 nm wide trenches.

Example 9

[0185] A plating bath according to example 7 was prepared.

[0186] A copper layer was electroplated onto a wafer substrate with feature sizes shown in FIG. 4A (100 nm trench width) 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 27 s followed by 10 mA/cm.sup.2 for 27 s. The thus electroplated copper layer was cross-sectioned and investigated by SEM inspection.

[0187] The result is shown in FIG. 4B providing the SEM image of fully filled trenches without exhibiting any defects like voids or seams while efficiently preventing bump formation over the 100 nm wide trenches.

Example 10

[0188] The plating bath of example 6 was repeated except that 0.3125 ml/l of a 1% by weight aqueous solution of polymeric biguanide compound leveler 1 as prepared in example 1 was added to the plating bath.

[0189] A copper layer was electroplated onto a wafer substrate with feature sizes shown in FIG. 4A (100 nm trench width) 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 27 s followed by 10 mA/cm.sup.2 for 27 s. The thus electroplated copper layer was cross-sectioned and investigated by SEM inspection.

[0190] The result is shown in FIG. 4C providing the SEM image of fully filled trenches without exhibiting any defects like voids or seams while still efficiently preventing bump formation over the 100 nm wide trenches.

[0191] The plating experiments with substrates carrying 100 nm wide trenches as described in examples 9 to 10 (FIGS. 4B and 4C) compared to example 8 (FIG. 4A) reveal that the invention provides defect-free and particularly void-free gap filling while efficiently levelling. Even in decreased concentration of leveler 1 efficient levelling is observed (FIG. 4B versus FIG. 4C). The experiment accomplished without any levelling agent in the plating bath solution (FIG. 4D) clearly reveals bump formation over the trenches and thus indicates the levelling efficiency of the invention while providing defect-free Cu deposits.

[0192] Additionally plating experiments have been performed with substrates carrying 16 to 37 nm wide trenches (FIG. 3A) and plating bath solutions containing either leveler 1 according to the present invention (FIG. 3B) or no leveler (FIG. 3C). The SEM image shown in FIG. 3B reveals that leveler 1 provides defect-free, also meaning void-free, gap fill as also found with the substrate plated without any levelling agent in the plating bath solution (FIG. 3C).

[0193] The use of a polymeric biguanide compound according to the present invention as levelling agent thus provides excellent levelling efficiency without interfering with the bottom-up-fill causing voids.

Comparative Example 11

[0194] A copper plating bath was prepared by combining 40 g/l copper as copper sulfate, 10 g/l sulfuric acid, 0.050 g/l chloride ion as HCl, 0.100 g/l of an EO/PO copolymer suppressor, and 0.028 g/l of SPS and DI water. The EO/PO copolymer suppressor had a molecular weight of <5000 g/mole and terminal hydroxyl groups.

[0195] A copper layer was electroplated onto a structured silicon wafer substrate purchased from SKW Associate Inc. containing trenches arranged as shown in FIGS. 2A and 2B. These substrates exhibited two test areas: [0196] (i) a first area comprising densely arranged parallel trenches of 130 nm widths (w, see FIG. 2A) and a depth (d) of approximately 250 nm, and [0197] (ii) a second area comprising densly arranged parallel trenches of 250 nm width and a depth of approximately 250 nm.

[0198] 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.

[0199] The thus electroplated copper layer was investigated by profilometry inspection with a Dektak 3, Veeco Instruments Inc. The height difference between the patterned area (distance a) and unpatterned area (distance b) (see FIG. 2A) was measured for both areas (i) and (ii).

[0200] FIG. 5A shows the profilometry results for area (i) without using a leveling agent, and FIG. 5B shows the results for area (ii). Both, FIGS. 5A and 5B show a higher copper deposit over the pattererned area compared to the unpatterned area. FIGS. 5A and 5B show a significant mounding. The measured values for the 0.130 micrometer and 0.250 micrometer featured area are listed in table 2.

Example 12

[0201] The procedure of example 11 was repeated except that 1 ml/l of a stock solution containing 1% (w/w) of the active leveling agent of example 1 was added to the plating bath.

[0202] A copper layer was electroplated onto a wafer substrate as described in example 11. The thus electroplated copper layer was investigated by profilometry as described in example 11.

[0203] FIG. 6A shows the profilometry results for area (i) using the leveling agent from example 1. FIG. 6B shows the results for area (ii). Both, FIGS. 6A and 6B show essentially no mounding over the patterned area compared to the unpatterned area. The measured values for the 0.130 micrometer and 0.250 micrometer featured area are listed in table 2.

Example 13

[0204] The procedure of example 11 was repeated except that 1 ml/l of a stock solution containing 1% (w/w) of the active leveling agent of example 2 was added to the plating bath.

[0205] A copper layer was electroplated onto a wafer substrate as described in example 11. The thus electroplated copper layer was investigated by profilometry as described in example 11.

[0206] The values obtained from profilometry, as listed in table 2, show an excellent reduction of the mounding compared to example 11 without any leveling agent.

Example 14

[0207] The procedure of example 11 was repeated except that 1 ml/l of a stock solution containing 1% (w/w) of the active leveling agent of example 3 was added to the plating bath.

[0208] A copper layer was electroplated onto a wafer substrate as described in example 11. The thus electroplated copper layer was investigated by profilometry as described in example 11.

[0209] The values obtained from profilometry, as listed in table 2, show a significant reduction of the mounding compared to example 11 without any leveling agent.

Example 15

[0210] The procedure of example 11 was repeated except that 1 ml/l of a stock solution containing 1% (w/w) of the active leveling agent of example 4 was added to the plating bath.

[0211] A copper layer was electroplated onto a wafer substrate as described in example 11. The thus electroplated copper layer was investigated by profilometry as described in example 11.

[0212] The values obtained from profilometry, as listed in table 2, show an excellent reduction of the mounding compared to example 11 without any leveling agent.

Example 16

[0213] The procedure of example 11 was repeated except that 1 ml/l of a stock solution containing 1% (w/w) of the active leveling agent of example 5 was added to the plating bath.

[0214] A copper layer was electroplated onto a wafer substrate as described in example 11. The thus electroplated copper layer was investigated by profilometry as described in example 11.

[0215] The values obtained from profilometry, as listed in table 2, show an excellent reduction of the mounding compared to example 11 without any leveling agent.

TABLE-US-00002 TABLE 2 mounding [a-b, see FIG. 2A] area (i) area (ii) 0.130 micrometer 0.250 micrometer Leveler featured area featured area Prior art (example 11) 370 nm 123 nm 1 (example 12) 4 nm 10 nm 2 (example 13) 61 nm 12 nm 3 (example 14) 194 nm 91 nm 4 (example 15) 96 nm 5 nm 5 (example 16) 77 nm 38 nm