JP2008111197A - Electroplating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroplating method by which the dissolution of a metal base body can be prevented and electroplating can be performed normally when the electroplating is applied to the surface of the metal base body comprising a metal thin film formed on the surface of a semiconductor layer through an insulating film. <P>SOLUTION: When electroplating is applied to the surface of the metal base body comprising a metal thin film formed on the surface of a semiconductor layer through an insulating film, the electroplating is performed by utilizing an induced eutectoid phenomenon in a supercritical state or a subcritical state including at least one of carbon dioxide and an inert gas, an electroplating solution in which metal powder is added and dispersed in such an amount that a portion of the metal powder is not dissolved, and a surfactant. Thereby, since the metal concentration in the electroplating solution is a saturated state or a supersaturated state, the dissolution speed of the metal base body can be reduced and a plated layer having a smooth surface can be obtained in a short time by utilizing the induced eutectoid phenomenon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electroplating method in which electroplating is performed on the surface of a metal thin film formed on the surface of a semiconductor layer via an insulating film. More particularly, the present invention provides a supercritical state even for an extremely thin metal thin film such as a metal thin film formed on the surface of a semiconductor layer through an insulating film by preventing dissolution of the metal thin film before electroplating. Alternatively, the present invention relates to an electroplating method in which a uniform film can be obtained by electroplating in a short time by using an induction eutectoid phenomenon in a subcritical state.

  Conventionally, as a method for forming fine metal wiring in a semiconductor element, after forming, for example, an aluminum thin film on a substrate by sputtering, a photoresist is applied, patterning is performed by exposure / development processing, and predetermined wiring is formed by etching. It was done to form. However, with the high integration and miniaturization of semiconductor circuit elements, it has become difficult to apply in such a wiring formation method. Therefore, grooves and holes for wiring are formed in advance, chemical vapor deposition CVD, sputtering, A so-called damascene method is performed in which aluminum or copper is embedded in grooves or holes by plating or the like, and then the surface is polished by chemical mechanical polishing (CMP). It has become. In this damascene method, a method for forming a wiring by forming a connection hole to a lower layer wiring at the time of forming the groove, and simultaneously filling the connection hole and the groove with aluminum or copper is called a dual damascene method.

In recent years, as a wiring formation process of a semiconductor device, a damascene method to which an electrolytic plating method is applied has become mainstream (see Patent Documents 1 and 2 below). Here, a method of forming a wiring of a three-dimensional mounting semiconductor device to which the damascene method disclosed as a conventional example in Patent Document 1 below is described will be described with reference to FIGS. 3A, holes 72 are formed on the surface of a substrate 70 such as a silicon substrate by lithography and etching techniques as shown in FIG. 3A, and then, on the surface of the substrate 70 as shown in FIG. 3B. For example, an insulating film 74 made of SiO ₂ is formed by CVD and the surface of the hole 72 is covered with the insulating film 74, thereby preventing electricity from leaking, and further, on the insulating film 74 as shown in FIG. 3C. A seed layer 76 as a power feeding layer for electrolytic plating is formed by, for example, CVD or sputtering.

  Then, as shown in FIG. 3D, the surface of the substrate 70 is subjected to copper plating by electrolytic plating to fill the hole 72 of the substrate 70 with copper and deposit a copper plating film 78 on the insulating film 74. 3E, the copper plating film 78 and the insulating film 74 on the substrate 70 are removed by CMP, and the surface of the copper plating film 78 filled in the holes 72 is substantially the same as the surface of the substrate 70. The embedded wiring is arranged so as to be on the same plane.

  The embedded wiring disclosed in the following Patent Document 1 can be applied to a hole 72 having a diameter W of about 5 to 20 μm and a depth D of about 50 to 70 μm. In the invention disclosed in Patent Document 1 below, in the copper plating process by electrolytic plating shown in FIG. 3D, copper overhangs near the entrance of the hole 72 as shown in FIG. In order to prevent the formation of voids, a step of etching a part of the plating film is added in the middle of the electrolytic plating process as shown in FIG. 4B, and a desired number of times as shown in FIGS. 4C and 4D. By repeating the electrolytic plating step and the plating film etching step, the groove 72 is filled with copper 78 as shown in FIG. 4E.

  Even if the invention disclosed in Patent Document 1 as described above is applied, it is difficult to bury copper without voids in narrow grooves or holes of about 0.20 μm or less. In the invention disclosed in Document 2, the composition of the plating solution is adjusted to adjust the metal deposition rate on the bottom side and the inlet side of the groove or hole.

JP 2003-96596 A (claims, paragraphs [0003] to [0010], [0011], FIG. 4, FIG. 6, FIG. 8) JP 2005-259959 A (claims, paragraphs [0011], [0013], [0029], FIG. 1 and FIG. 2) JP 2003-321798 A (paragraphs [0001] to [0009]) Japanese Patent Laying-Open No. 2005-154816 (claim 15, paragraphs [0023] to [0036], FIG. 1) Japanese Patent Laid-Open No. 7-268696 (Claims, paragraphs [0021] to [0022], FIGS. 1 and 2)

  As described above, in the damascene method or dual damascene method, a seed layer as a power feeding layer for electrolytic plating, that is, a metal substrate made of an extremely thin metal thin film is formed on the surface of the insulating film by a CVD method or a sputtering method. The same kind of metal is electroplated on the surface of a metal substrate. However, according to our experiment, when this metal substrate is immersed in an electroplating solution and the same type of metal electroplating is performed, the metal substrate is dissolved even if the metal substrate is a thick plate. Many smooth plating surfaces were not obtained, resulting in poor plating. Such a phenomenon is prominent particularly in the case of an electroplating method using a supercritical fluid or a subcritical fluid in which the dissolution rate of the metal substrate is high (see Patent Documents 3 and 4).

  The inventors have repeated various experiments on the assumption that the above-mentioned plating defects can be suppressed if the dissolution of the metal substrate in the electroplating solution is suppressed. As a result, the metal powder to be plated in the electroplating solution in advance is added in a larger amount than the amount (solubility) in which the metal to be plated does not dissolve, and the metal powder is plated by stirring, etc. When electroplating is performed using a supercritical fluid or subcritical fluid while the body is dispersed in the electroplating solution, a metal thin film formed on the surface of the semiconductor layer via an insulating film is placed in the electroplating solution. It has been found that, even when immersed, the metal thin film is difficult to dissolve in the electroplating solution, so that normal electroplating is performed and a uniform film can be obtained in a short time using the inductive eutectoid phenomenon. Has been completed.

  That is, the present invention prevents the dissolution of the metal substrate before electroplating, particularly the metal thin film formed on the surface of the semiconductor layer via the insulating film by preventing the dissolution of the metal substrate before electroplating. An object of the present invention is to provide an electroplating method in which a uniform film can be obtained by electroplating in a short time using an inductive eutectoid phenomenon in a supercritical state or a subcritical state even in an extremely thin metal substrate. .

  In addition, Patent Document 5 discloses a method in which granular or powdery nickel is directly added to the dissolution tank for the purpose of adjusting the nickel concentration in the nickel-based plating solution. There is no description about, and it is clear that the obtained nickel-based plating solution is separately supplied to an electroplating tank and electroplating is performed.

  In order to achieve the above object, the electroplating method of the present invention is a method of electroplating on the surface of a metal substrate composed of a metal thin film formed on the surface of a semiconductor layer via an insulating film. At least one of them includes an electroplating solution in which a metal powder is added and dispersed in an amount that does not dissolve the metal powder and a surfactant, and electroplating is performed using an inductive eutectoid phenomenon in a supercritical state or a subcritical state. It is characterized by performing. In addition, the induction eutectoid phenomenon in this specification means the phenomenon in which a part of metal powder is simultaneously taken in into a plating film at the time of electroplating.

  In the electroplating method, the present invention is characterized in that the metal powder is the same type of metal as at least one of a metal substrate and a metal coating obtained by electroplating.

  In the electroplating method, the present invention is characterized in that an average particle size of the metal powder is 1 nm or more and 100 μm or less.

  In the electroplating method, the present invention is characterized in that a voltage at which the metal substrate does not dissolve is applied before the metal substrate is immersed in the electroplating solution.

  In the electroplating method, the present invention is characterized in that the voltage at which the metal substrate does not melt is a voltage applied during predetermined electroplating.

  By adopting the method as described above, the present invention has the following excellent effects. That is, according to the electroplating method of the present invention, the electroplating is performed in a state where the metal powder is added and dispersed in an electroplating solution in an amount that does not dissolve the metal powder. The metal concentration in the liquid is saturated or supersaturated.

  Therefore, according to the electroplating method of the present invention, even when the metal substrate is an extremely thin metal thin film such as a metal substrate formed on the surface of the semiconductor layer via an insulating film, dissolution of the metal substrate can be suppressed. Therefore, the electroplating can be normally performed, and the present invention can be effectively applied particularly to the formation of fine wiring of a highly integrated and miniaturized semiconductor circuit element such as a damascene method or a dual damascene method. In addition, according to the electroplating method of the present invention, a uniform film can be obtained by short-time electroplating utilizing the inductive eutectoid phenomenon.

  In addition, according to the electroplating method of the present invention, since electroplating is performed in a supercritical state or a subcritical state containing at least one of carbon dioxide and inert gas, the electroplating solution and a surfactant, the electroplating solution The metal substrate is contacted in an emulsion state. For this reason, the electroplating solution quickly penetrates into minute holes and grooves, so that even a complex-shaped metal substrate is used for forming fine wiring of highly integrated and miniaturized semiconductor circuit elements. Also, electroplating can be performed effectively.

  In addition, according to the electroplating method of the present invention, since the average particle size of the metal powder is as fine as 1 nm to 100 μm, even if the electroplating proceeds and the metal ions are consumed, the metal to the electrolyte solution Since the dissolution rate of the powder is fast, metal ions can be efficiently supplied into the electrolytic solution. In addition, although metal powder melt | dissolves in order to supplement the metal ion consumed by electroplating, since the melt | dissolution rate of metal powder will become slow when the average particle diameter of metal powder exceeds 100 micrometers, it is unpreferable. Moreover, according to the electroplating method of the present invention, the smaller the particle size of the metal powder, the easier it is to electroplate in the fine structure, but the metal powder of less than 1 nm can be easily obtained. Therefore, the particle size of the metal powder is preferably 1 nm or more.

  In addition, according to the present invention, since a voltage that does not dissolve the metal substrate is applied before the metal substrate is immersed in the electroplating solution, the metal substrate is dissolved even if the metal substrate is immersed in the electroplating solution. Therefore, since the voltage necessary for electroplating can be applied after the metal substrate is sufficiently stable after being immersed in the electroplating solution, it is particularly suitable for forming fine wiring.

  In addition, according to the present invention, since a predetermined voltage applied during electroplating is applied before the metal substrate is immersed in the electroplating solution, the metal substrate is immediately immersed in the electroplating solution. Electroplating is performed on the surface. Therefore, according to the present invention, a predetermined electroplating layer can be obtained in a short time. The voltage applied to the metal substrate includes a voltage within a range where the metal substrate is dissolved, a voltage within a range where the metal substrate is not dissolved but electroplating does not proceed, and a voltage within a range where electroplating proceeds normally. Are both well known to those skilled in the art. The voltage range within which electroplating proceeds normally varies depending on the composition, concentration, temperature, etc. of the electroplating solution, but can be easily found experimentally.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to various experimental examples and drawings, but the various experimental examples described below are intended to limit the present invention to those described herein. However, the present invention can be equally applied to various modifications without departing from the technical idea shown in the claims. FIG. 1 is a schematic view of an electroplating apparatus used in each experimental example, and FIG. 2 is a diagram showing a relationship between the amount of copper dissolved from the electrolytic copper sample and the elapsed time.

[Electroplating solution]
The composition of the electroplating solution for copper used in the various experimental examples described below and the configuration of the experimental system are as follows.
Electroplating solution composition Copper sulfate _{(CuSO 4 · 5H 2 O)} 70g / L
Sulfuric acid (H ₂ SO ₄ ) 180 g / L
Chloride ion (Cl ⁻ ) 50 mg / L
Nonionic surfactant 10ml / L
Hereinafter, the copper electroplating solution having the above composition is referred to as a “high throw bath”.

[Electroplating equipment]
As the electroplating apparatus 10, as shown in FIG. 1, a pressure-resistant electroplating tank 11 is used so that electroplating can be performed using a supercritical fluid or a subcritical fluid. In this pressure-resistant electroplating tank 11, carbon dioxide from a carbon dioxide cylinder 12 can be supplied to an inlet 16 provided in an upper lid 15 via a high-pressure pump unit 13 and a valve 14 as necessary. The carbon dioxide can be discharged from the outlet 17 provided in the upper lid 15 through the pressure adjustment unit 18 into the surrounding atmosphere.

  The pressure-resistant electroplating tank 11 can inject a predetermined amount of electroplating solution 19 by removing the lid 15, and a stirrer 20 as a stirring means is inserted into the pressure-resistant electroplating tank 11. The pressure-resistant electroplating tank 11 can maintain the electroplating solution 19 placed in the oven 21 and inserted therein at a predetermined constant temperature.

  Further, the metal substrate sample 22 and the counter electrode 23 are disposed from the upper part of the withstand voltage electroplating tank 11 so as to be electrically insulated, and the metal substrate sample 22 is electrically connected to the negative terminal of the DC power source 24 to provide a counter electrode. 23 is electrically connected to the + terminal of the DC power supply 24. In the following experimental examples, examples, etc., a copper thin film formed on the surface of a copper plate or TaN film was used as the metal substrate, and commercially available phosphorous copper was used as the counter electrode.

  In the electroplating apparatus 10, when an experiment is performed in a supercritical state or a subcritical state, the carbon dioxide cylinder 12, the high pressure pump unit 13, the valve 14, and the pressure adjustment unit 18 are operated to operate in the pressure resistant electroplating tank 11. Was maintained at a pressure of 8 to 10 MPa and the electroplating solution 19 was heated to 40 ° C. by operating the oven 21 to bring the pressure-resistant electroplating tank 11 into a supercritical state or a subcritical state. When the experiment is performed under the condition of 1 atm, the inside of the pressure-resistant electroplating tank 11 is opened to the atmospheric pressure by operating the carbon dioxide cylinder 12, the high-pressure pump unit 13, the valve 14 and the pressure adjusting unit 18. Various experiments were performed by heating the electroplating solution 19 to a predetermined temperature by operating the oven 21.

[Experimental Examples 1-3]
As Experimental Examples 1 to 3, the above-described high-throw bath was used, and the solubility of the metal substrate when electroplating was performed in a supercritical state was investigated. As the metal substrate sample 22, a copper thin film having a thickness of 65 nm formed on a TaN film by a sputtering method was used. The metal substrate sample 22 was placed on the upper part of the electroplating solution 19 in the pressure-resistant plating tank 11 together with the counter electrode 23 after the pickling pretreatment so as not to touch the electroplating solution 19. The amount of electroplating solution 19 used was 30 ml.

  In this state, the temperature of the electroplating solution in the pressure-resistant electroplating tank 11 is heated to 40 ° C., and the electroplating solution 19 is not stirred by the stirrer 20, and the carbon dioxide cylinder 12, the high-pressure pump unit 13, the valve 14, and the pressure By operating the adjustment unit 18, the pressure in the pressure-resistant electroplating tank 11 was increased to 10 MPa. And the electroplating liquid 19 was stirred with the stirrer 20 simultaneously with the pressure in the pressure-resistant electroplating tank 11 becoming 10 MPa.

  Then, since the critical pressure of carbon dioxide when the temperature of the electroplating solution 19 is 40 ° C. is about 7.38 MPa, the inside of the pressure-resistant electroplating tank 11 is substantially in a supercritical state under the above temperature and pressure conditions. The electroplating solution 19 is substantially in an emulsion state due to the surfactant contained in the electroplating solution 19 in the subcritical state. The inside is filled and the metal substrate sample 22 and the counter electrode 23 are in sufficient contact.

And
Experimental Example 1: An electroplating voltage was applied between the metal substrate sample 22 and the counter electrode 23 from the DC power source 24 five minutes after the pressure in the pressure-resistant electroplating tank 11 reached 10 MPa.
Experimental example 2: A voltage for electroplating was applied between the metal substrate sample 22 and the counter electrode 23 from the DC power source 24 at the same time when the pressure in the pressure-resistant electroplating tank 11 became 10 MPa.
Experimental Example 3: Simultaneously with the start of pressure increase in the pressure-resistant electroplating tank 11, a voltage for electroplating is applied from the DC power source 24 between the metal substrate sample 22 and the counter electrode 23.
The plating state of the surface of the metal substrate sample 22 under these three conditions was investigated.

The results were as described in Table 1 below.

  That is, in the case of the condition of Experimental Example 1, since the metal substrate sample 22 made of a copper thin film was completely dissolved before applying the plating voltage, a copper plating film could not be obtained. In the case of the condition of Experimental Example 2, a considerable portion of the metal base sample 22 made of a copper thin film was dissolved, but the remaining portion was electroplated. Moreover, in the case of the conditions of Experimental Example 3, a plating film was obtained, but it was not uniform and was mottled.

  From the above, in order to electroplate copper on a metal substrate made of copper in a critical state or a subcritical state, when a commonly used high-throw bath is used, an electroplating solution and a metal substrate made of a copper thin film This means that a good electroplated film cannot be obtained because the reaction during

[Experimental Example 4]
Therefore, as Experimental Example 4, the plating state under a pressure condition that was not in a critical state was investigated using the high-throw bath. That is, 40 ml of a high-throw bath was injected as an electroplating solution into the pressure-resistant electroplating bath 11, and the temperature of the electroplating solution 19 in the pressure-resistant electroplating bath 11 was heated to 40 ° C. Next, a metal substrate sample 22 composed of a copper thin film similar to the above was used, and the metal substrate sample 22 composed of this copper thin film was disposed so as to be immersed in the electroplating solution 19.

  In this state, by operating the carbon dioxide cylinder 12, the high pressure pump unit 13, the valve 14, and the pressure adjustment unit 18 without stirring the electroplating solution 19 with the stirrer 20, the pressure in the withstand pressure electroplating tank 11 is increased. Pressurization was performed to 5 MPa. At the same time as the pressure in the pressure-resistant electroplating tank 11 became 5 MPa, the electroplating solution 19 was stirred with the stirrer 20 and a voltage for electroplating was applied from the DC power source 24 to the metal substrate sample 22 and the counter electrode 23.

  Since this pressurized state of 5 MPa does not reach the critical condition at 40 ° C., the high-throw bath exists in a liquid state. Even in this case, most of the metal substrate made of the copper thin film was dissolved before the DC voltage was applied, and an electroplated film was obtained only on a part thereof.

[Experimental Example 5]
From the results of the above experimental examples 1 to 4, since the metal base made of copper has a high dissolution rate in a high-throw bath that is an electroplating solution for copper, the composition of the electroplating solution was examined. That is, sulfuric acid and chlorine ions are added to the high-throw bath described above for stabilization. Therefore, in Experimental Example 5, an experiment was performed using an electroplating solution having the following composition excluding sulfuric acid and chlorine ions for the purpose of slowing the dissolution rate of the metal substrate made of copper. The surfactant is the same as described above.
Electroplating solution composition Copper sulfate _{(CuSO 4 · 5H 2 O)} 70g / L
Sulfuric acid (H ₂ SO ₄ ) 0g / L
Chlorine ion (Cl ⁻ ) 0 mg / L
Nonionic surfactant 10ml / L

  Using the electroplating apparatus 10 shown in FIG. 1, 40 ml of the electroplating solution having the above composition was injected into the pressure-resistant electroplating bath 11, and the temperature of the electroplating solution in the pressure-resistant electroplating bath 11 was heated to 40 ° C. Next, a metal substrate sample 22 made of the same copper thin film as that used in Experimental Examples 1 to 4 was used, and the metal substrate sample 22 was disposed so as to be immersed in the electroplating solution 19. In this state, the electroplating solution 19 was stirred with the stirrer 20 under atmospheric pressure without any particular pressure, and a voltage for electroplating was applied from the DC power source 24 to the metal substrate sample 22 and the counter electrode 23.

  In Experimental Example 5, the elution of the copper thin film partially occurred from the metal substrate sample 22, but a plating film was partially obtained. Thus, it was confirmed that even if sulfuric acid or chlorine ions were excluded from the conventional electroplating solution for copper, elution of the copper thin film occurred and electroplating could not be performed normally.

[Experimental Example 6]
From the results of Experimental Examples 1 to 5, it can be seen that in order to perform copper electroplating on a metal substrate made of copper, it is necessary to slow down the dissolution rate of copper in the electroplating solution for copper. Therefore, as Experimental Example 6, the copper dissolution rate in the electroplating solution for copper was examined. First, an electrolytic copper sample of 2 cm × 2 cm × 5 mm is prepared, and 40 ml of a copper electroplating solution composed of the high-throw bath used in Experimental Examples 1 to 4 is injected into the pressure-resistant electroplating tank 11, It was immersed in the electroplating solution 19 for copper, and the dissolution rate at 1 atm 60 ° C. was examined. The amount of copper dissolved from the electrolytic copper sample was measured gravimetrically. The relationship between the amount of copper dissolved and the elapsed time is shown in FIG.

  From the results shown in FIG. 2, the copper concentration in the high-throw bath does not reach the saturation concentration even after 31 hours. When bulk copper is used, the copper concentration in the electroplating solution for copper It has been found that it takes considerable time to saturate.

  Therefore, the solubility when copper powder was added to the electroplating solution for copper used in Experimental Examples 1 to 4 was examined. When 300 g of particles passing through 300 mesh were used as copper powder and 0.3 g was added to 500 ml of the high-throw bath with stirring, an electroplating solution in which the copper powder was present in a dispersed state was obtained. Thus, it turned out that it is preferable to add copper of a powder state in order to saturate copper with respect to the electroplating solution for copper conventionally used.

[Experimental Examples 7 to 10]
Next, the solubility was examined when the same metal substrate sample as used in Experimental Examples 1 to 5 was immersed in various electroplating solutions for copper at 25 ° C. under atmospheric pressure. The following four types of experimental examples 7 to 10 were used as the electroplating solution for copper. In addition, the addition ratio of the copper powder in Experimental Examples 9 and 10 was the same as that shown in Experimental Example 6 except that 0.3 g of copper powder for 300 mesh passing grains was added to 500 ml of the high-throw bath with stirring. It is. Moreover, the surfactant used in Experimental Example 10 is the same type as that added in the high-throw bath, and is additionally added directly into the pressure-resistant electroplating tank 11.
Experimental example 7: High-throw bath Experimental example 8: High-throw bath + electrolytic copper 31 hours dissolution (of Experimental example 6)
Experimental Example 9: High throw bath + copper powder Experimental Example 10: 0.4 ml of nonionic surfactant was further added to that of Experimental Example 9.

  40 ml of each of the above four types of copper electroplating solutions is injected into the pressure-resistant electroplating tank 11, and the metal substrate sample is immersed in these four types of copper electroplating solutions at 25 ° C. under atmospheric pressure for 3 minutes. Each surface condition after minutes, 10 minutes, 12 minutes and 15 minutes was examined. The results are summarized in Table 2. In addition, the result shown in Table 2 is represented by ◯ when the dissolution is not observed on the copper surface, Δ when the dissolution state is recognized on the copper surface, and × when the copper is completely dissolved. .

  From the results shown in Table 2, it was not possible to suppress the elution of the metal base made of copper even if the bulk electrolytic copper was previously dissolved in the high-throw bath, but the copper metal powder was in a powder state by adding the copper metal powder. In the dispersed state, it can be confirmed that the elution of the metal substrate made of copper can be suppressed, and that the elution of the metal substrate made of copper can be further suppressed by adding more surfactant. It was.

[Experimental Examples 11 to 12]
From the results shown in Table 2, using a copper plating solution in which a copper metal powder is added and the copper metal powder is dispersed in a powder state, a metal substrate made of copper is further added when a large amount of surfactant is added. As a result, it was clarified that elution of the metal substrate sample can be suppressed. Therefore, the electroplating solution of Experimental Example 10 was used and the metal substrate sample was compared with the same copper metal substrate sample as used in Experimental Examples 1 to 5 above. The change in the elution state of copper from the metal substrate when the voltage applied between the electrode and the counter electrode was changed was investigated.

  That is, in Experiment Example 11, no voltage was applied, in Experiment Example 12, a voltage of 1 V was applied, and in Experiment Example 12, a voltage of 5 V was applied. The amount of each electroplating solution used was 40 ml, and electroplating. The temperature of the liquid was 40 ° C., and all operations were performed with stirring. The voltage of 1V is theoretically a voltage at which copper plating does not proceed and copper is not dissolved.

The results are summarized in Table 3. In Table 3, the case where a normal copper plating film is formed in a visual state is indicated by ○, the case where a plating film is formed but uneven is indicated by Δ, and the case where all are dissolved is indicated by ×. It was.

  From the results shown in Table 3, copper powder was added to a high-throw bath so that the copper powder was in a floating state, and a copper plating was applied to a metal substrate made of copper using an electroplating bath to which a large amount of surfactant was added. It can be seen that it is preferable to apply a voltage (here, 5 V) necessary for electroplating before immersing the metal substrate in the electroplating solution.

[Experimental Example 14]
In Experimental Example 14, the conditions of Experimental Example 13 with the best results shown in Table 3 were adopted, and the electroplating apparatus 10 shown in FIG. 1 was used to perform electroplating under supercritical conditions. It was. As the copper electroplating solution, as in Experimental Example 13, a copper powder added to a high-throw bath so that the copper powder is in a floating state is injected into the 30 ml pressure-resistant electroplating layer 11, and An additional 0.3 ml of nonionic surfactant was added.

  Next, as the metal substrate sample 22, a 65 nm thick copper thin film formed on a 2 cm × 2 cm TaN substrate by sputtering was used. This metal substrate sample 22 was arranged so as not to touch the electroplating solution 19 on the upper part of the electroplating solution 19 in the pressure-resistant plating tank 11 together with the counter electrode 23 after the pickling pretreatment. The amount of electroplating solution 19 used was 30 ml. Subsequently, after the same metal substrate sample 22 as used in Experimental Examples 1 to 5 is subjected to the pre-washing treatment, the electroplating solution 19 is not touched on the electroplating solution 19 in the pressure-resistant plating tank 11 together with the counter electrode 23. Arranged.

  In this state, the temperature of the electroplating solution in the withstand voltage electroplating tank 11 is heated to 40 ° C., a voltage of 5 V is applied between the metal substrate sample 22 and the counter electrode 23, and the electroplating solution 19 is firstly applied by the stirrer 20. The pressure in the pressure-resistant electroplating tank 11 was increased to 10 MPa by operating the carbon dioxide cylinder 12, the high-pressure pump unit 13, the valve 14, and the pressure adjustment unit 18 without stirring. And the electroplating liquid 19 was stirred with the stirrer 20 simultaneously with the pressure in the pressure-resistant electroplating tank 11 becoming 10 MPa.

  This state is maintained for 3 minutes, and then the carbon dioxide in the pressure-resistant electroplating tank 11 is gradually exhausted by operating the pressure adjustment unit 18 while applying a voltage of 5 V between the metal substrate sample 22 and the counter electrode 23. The pressure was reduced to atmospheric pressure. A good copper plating film was formed on the surface of the obtained metal substrate sample 22. Therefore, it has been clarified that the operation conditions employed in Experimental Example 14 can be applied to a damascene method using a supercritical fluid or a dual damascene method.

  In the above experimental example, a copper powder having a particle size of 300 mesh was used, but this copper powder is intended to maintain the copper concentration in the electroplating solution at a substantially saturated concentration. Therefore, it is better that the particle size is small in order to increase the dissolution rate. In particular, when particles of less than 1 μm are used, the dispersion state in the electrolytic solution is good, and further, it is difficult to agglomerate, so that it is possible to easily electroplate even a substrate structure having an accuracy of less than 1 μm. At present, it is difficult to obtain a fine metal powder having an average metal particle size of less than 1 nm, but it can be realized up to an average particle size of about 1 nm.

  In each of the above experimental examples, the case where the metal base and the metal to be electroplated are both copper has been described. However, the electroplating method of the present invention has the same effect as long as the metal base and the metal to be electroplated are the same type. Play. Therefore, the metal substrate and the metal to be electroplated are equally applicable not only to copper but also to zinc, iron, nickel, cobalt, and the like.

It is the schematic of the electroplating apparatus used in each experiment example. It is a figure which shows the relationship between the copper dissolution amount from an electrolytic copper sample, and elapsed time. FIG. 3A to FIG. 3E are diagrams for sequentially explaining the wiring formation process of the conventional three-dimensional mounting semiconductor device. It is a figure explaining the void suppression process employ | adopted conventionally shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electroplating apparatus 11 Withstand pressure electroplating tank 12 Carbon dioxide cylinder 13 High pressure pump unit 14 Valve 15 Lid 16 Inlet 17 Outlet 18 Pressure adjustment unit 19 Electroplating solution 20 Stirrer 21 Oven 22 Metal substrate sample 23 Counter electrode 24 DC power supply

Claims (5)

  In the method of electroplating on the surface of a metal substrate composed of a metal thin film formed on the surface of a semiconductor layer via an insulating film, at least one of carbon dioxide and inert gas, the metal powder is more than the amount in which the metal powder does not dissolve An electroplating method comprising performing electroplating using an induced eutectoid phenomenon in a supercritical state or a subcritical state, comprising an electroplating solution and a surfactant added to and dispersed in the material.   2. The electroplating method according to claim 1, wherein the metal powder is a metal of the same kind as at least one of a metal substrate and a metal coating obtained by electroplating.   The electroplating method according to claim 1 or 2, wherein the average particle size of the metal powder is 1 nm or more and 100 µm or less.   The electroplating method according to any one of claims 1 to 3, wherein a voltage at which the metal substrate does not dissolve is applied before the metal substrate is immersed in the electroplating solution.   5. The electroplating method according to claim 4, wherein the voltage at which the metal substrate does not melt is a predetermined voltage applied during electroplating.

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