JP2016176099A - Plating method and intermediate for plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress elution of an organic substance into a plating solution during plating and to elongate a service life of the plating solution.SOLUTION: A plating method is provided, which includes: a seed layer formation step of forming a seed layer 12 on a surface of a treatment target substrate (substance to be treated) 11; a resist layer formation step of forming a resist layer 13 having an opening 13h so as to cover the seed layer 12 with a resist except for a plating target surface 12a and to form a plating pattern 15; a protection film formation step of forming metal protection films 14A, 14B covering the plating target surface 12a and a surface 13a of the resist layer 13 to form an intermediate 21 for plating; a plating step of forming a plating pattern 15 in the opening 13h of the resist layer 13 by applying electricity using the seed layer 12 as an electrode; a resist stripping step of removing the resist layer 13 and the metal protection film 14B deposited on the resist layer 13; and an etching step of removing the seed layer 12 in a part covered with the resist layer 13.SELECTED DRAWING: Figure 2

Description

  INDUSTRIAL APPLICABILITY The present invention is used in a plating method and a method for plating a plated surface of a workpiece to be used for forming a wiring pattern such as a semiconductor component or a mounting substrate, or a fine pattern such as a solder bump or a metal pillar. The present invention relates to an intermediate for plating.

  An electrolytic plating method is widely used as a method for performing a plating process on a surface to be plated of a workpiece. When plating the surface to be plated by the electrolytic plating method, a seed layer (conducting film) made of a conductive material is previously formed on the surface of the object to be processed, and this seed layer is patterned with a photoresist. A resist pattern is formed by exposing the surface to be plated of the seed layer. And the to-be-processed object (henceforth a plating intermediate body) in which this resist pattern was formed was immersed in a plating solution, and the surface of the seed layer exposed between the resist patterns using the seed layer as an electrode ( By depositing metal on the surface to be plated, a plating film (plating pattern) is formed.

  By the way, the plating solution used in such an electrolytic plating method is repeatedly used until a predetermined amount of electrolysis is reached. On the other hand, the plating intermediate coated with the organic resist is immersed in the plating solution successively one after another, so that the resist components of each plating intermediate are gradually eluted into the plating solution. As the number of treatments increases, the amount of elution increases, so that the elution component has an adverse effect on the plating properties of the plating intermediate and plating cannot be performed normally. In this case, it is necessary to replace the plating solution with a new one, and the problem is that the bath life is shortened by the dissolution of the resist component in the plating solution.

  In this regard, Patent Document 1 describes the composition of the resist coating itself in order to prevent the resist coating from dissolving in the acidic solution (plating solution) when forming the plating layer on the object to be processed (resin product). It has been proposed that a main component is a mixture of a vinyl chloride-vinyl acetate copolymer and an acrylic-styrene copolymer. In addition, Patent Document 1 describes that since the vinyl chloride-vinyl acetate copolymer has excellent chemical resistance, it does not elute even when the resist coating is exposed to an acidic solution during plating. .

JP-A-8-48933

  However, as described in Patent Document 1, even when an acid-resistant resist paint is used, as long as the resist paint is organic, elution into the plating solution has occurred, and further improvement is desired. It is rare.

  The present invention has been made in view of such circumstances, and suppresses the elution of organic substances into the plating solution during the plating process, and can improve the life of the plating solution and a plating intermediate. The purpose is to provide.

  The plating treatment method of the present invention includes a seed layer forming step of forming a seed layer on the surface of an object to be processed, and a portion other than the surface to be plated on the seed layer is covered with a resist and a plating pattern is formed. A resist layer forming step of forming a resist layer having an opening, a protective film forming step of forming a metal protective film covering the surface to be plated and the surface of the resist layer to form an intermediate for plating, and A plating formation step of forming a plating pattern by depositing a metal in the opening of the resist layer by immersing a plating intermediate in a plating solution and energizing the seed layer as an electrode; and the resist layer and A resist stripping process that removes the metal protective film laminated on the resist layer, and a portion of the seed layer that is covered with the resist layer is removed. And a etching process that.

By forming and covering a metal protective film on the surface of the resist layer, it is possible to minimize the portion where the plating solution and the resist come into contact in the plating forming step. Thereby, elution of the resist component (organic substance) to the plating solution during the plating treatment can be suppressed, and the life of the plating solution can be extended.
In the protective film forming step, the metal protective film is formed not only on the surface of the resist layer but also on the surface to be plated in the opening of the resist layer. The metal protective film on the surface to be plated has a height difference corresponding to the thickness of the resist layer and is in an insulated state. Therefore, in the plating process, the metal protective film on the surface to be plated is energized through the seed layer, but the metal protective film on the surface of the resist layer is not energized. Can be deposited to form a plating pattern (plating film). As described above, the metal protective film is formed by a method such as sputtering or ion plating, so that it is not necessary to separately coat the resist layer surface and the surface to be plated, and can be easily formed. Therefore, even a refined plating pattern can be easily formed by the plating method of the present invention.

  In the plating method of the present invention, the metal protective film is formed of the same metal species as the plating pattern, or when the plating pattern is alloy plating, the metal protective film is formed of the alloy plating. It is good to form with the most precious metal among the constituent metals.

  By forming the metal protective film with the same metal species as the plating pattern, contamination with foreign metals can be prevented. In addition, when the plating pattern is alloy plating, the metal protective film is formed of the most precious metal (metal having a low ionization tendency) in the composition of the alloy plating, so that the base layer in the composition on the metal protective film is formed. Substitutional precipitation of metals (metals with a high ionization tendency) can be prevented.

  The intermediate for plating according to the present invention covers an object to be processed on which a plating pattern is formed, a seed layer formed on the surface of the object to be processed, and a portion on the seed layer excluding the surface to be plated with a resist. And a resist layer having an opening for forming the plating pattern, and a metal protective film coated on the surface to be plated and the surface of the resist layer.

  ADVANTAGE OF THE INVENTION According to this invention, elution of the organic substance to the plating solution during plating processing can be suppressed, the lifetime of a plating solution can be aimed at, and the refined plating pattern can be formed easily.

It is a flowchart explaining the plating processing method of this invention. It is principal part sectional drawing of the to-be-processed substrate explaining the plating processing method of this invention.

Hereinafter, an embodiment of a plating method according to the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing the plating method of the present embodiment. FIG. 2 is a cross-sectional view of an essential part of a substrate to be processed (object to be processed in the present invention) for explaining each step of the plating method shown in FIG.

  As shown in FIG. 2E, the wiring board 22 manufactured by the plating method of the present embodiment has a seed layer 12 and a metal protection layer laminated on the seed layer 12 on the surface of the substrate 11 to be processed. A plating pattern 15 is formed through the film 14A. The wiring board 22 configured as described above includes a seed layer forming step (S1) for forming a seed layer 12 on the surface of the substrate 11 to be processed, as shown in the flowchart of FIG. A resist layer forming step (S2) for forming a resist layer 13 having an opening 13h for defining a plating pattern 15 on the seed layer 12, and a metal protective film 14A for covering the surface 12a to be plated and the surface 13a of the resist layer 13 , 14B to form a plating intermediate 21 (S3), and the plating intermediate 21 is immersed in a plating solution and energized with the seed layer 12 as an electrode, whereby the resist layer 13 A plating formation step (S4) for depositing a metal in the opening 13h to form the plating pattern 15; and the resist layer 13 and the resist layer 13 are laminated. And a metal protective film 14B resist separation step of removing (S5), is manufactured through the etching step (S6) of removing the seed layer 12 of the portion covered with the resist layer 13 by etching.

  To describe each step of the plating method in detail, first, in the seed layer forming step (S1), as shown in FIG. 2A, a Ti layer and a Cu layer are laminated on the surface of the substrate 11 to be processed. A seed layer 12 is formed. For example, an insulating substrate made of a silicon wafer is prepared as the substrate 11 to be processed, a Ti layer and a Cu layer are sequentially sputtered on the surface of the substrate 11 to be processed, and a seed layer consisting of two layers of a Cu layer and a Ti layer is formed. 12 is formed.

  Next, in the resist layer forming step (S2), as shown in FIG. 2 (b), the portion excluding the surface to be plated 12a on the seed layer 12 is covered with a resist and the plating pattern 15 is formed. A resist layer 13 having an opening 13h is formed. Specifically, an acrylic resin-based dry film resist is laminated on the surface of the seed layer 12, and the opening 13h is formed by mask exposure. In addition, in the case of forming the resist layer 13 by mask exposure in this way, in addition to using a dry film resist, a liquid resist can also be used, and an acrylic resin type, an epoxy resin type, a novolac resin type, Regardless of the material of the resist, such as naphthoquinonediazide, it is possible to form the resist layer 13. Moreover, these resists can be used regardless of positive type or negative type. Further, the resist layer 13 can also be formed by a method such as laser processing or screen printing.

  Then, in the protective film forming step (S3), as shown in FIG. 2C, the metal protective film 14A is formed on the surface to be plated 12a exposed in the opening 13h of the resist layer 13 and the surface 13a of the resist layer 13. , 14B is formed to form the plating intermediate 21. The metal protective films 14A and 14B can be easily formed by a method such as sputtering or ion plating. However, from the viewpoint of preventing the metal protective film from adhering to the side wall in the opening 13h of the resist layer 13, straightness is achieved. It is preferable to form by high sputtering. When there is adhesion of the metal protective film to the side wall in the opening 13h, when the seed layer 12 is energized in the plating formation step (S4), the metal protective film 14A on the surface to be plated 12a, Insulating state is not maintained with the metal protective film 14B on the surface 13a of the resist layer 13, and metal is deposited on the surface 13a of the resist layer 13, so that the plating pattern 15 can be formed normally. This is because it becomes difficult. Also, in order to increase the straightness of the sputtered particles and prevent the metal protective film from adhering to the side wall in the opening 13h, it is desirable that the argon gas pressure during film formation is low, and the distance between the electrodes should be as long as possible. desirable.

  The side wall in the opening 13h of the resist layer 13 has a small area with respect to the surface 13a of the resist layer 13, so that the resist component is not eluted from the side wall even if it is not covered with the metal protective film. Contamination of the plating solution due to elution of organic substances can be minimized.

  Further, the metal protective films 14A and 14B are formed thick (50 nm or more) to such an extent that they have a sufficient protective function during the plating process time in the plating formation step (S4), and affect the coating composition of the plating pattern 15. It is desirable to form it thinly (1 μm or less) to such an extent that it does not give an effect.

  The metal protective films 14A and 14B are formed of the same metal species as the plating pattern 15. Alternatively, when the plating pattern 15 is alloy plating, the metal protective films 14A and 14B are made of alloy plating metal. Of these, the most precious metal is used. In this way, by forming the metal protective films 14A and 14B with the same metal species as the plating pattern 15, it is possible to prevent contamination from mixing different kinds of metals. When the plating pattern 15 is alloy plating, the metal protective films 14A and 14B are formed of the most precious metal (metal having a low ionization tendency) in the composition of the alloy plating, so that the metal protective films 14A and 14B are formed. Substitutional precipitation of a base metal (a metal having a high ionization tendency) in the composition can be prevented. Specifically, for example, when the plating pattern 15 is formed of Cu, the metal protective films 14A and 14B are formed of a Cu film. Further, when the plating pattern 15 is formed of a SnAg alloy, the metal protective films 14A and 14B are formed of an Ag film.

  Next, in the plating formation step (S4), a metal is deposited in the opening 13h of the resist layer 13 by energizing the seed layer 12 as an electrode while the plating intermediate 21 is immersed in the plating solution. Then, a plating pattern 15 is formed as shown in FIG. Specifically, a metal protective film exposed in the opening 13h of the resist layer 13 by immersing the plating intermediate 21 in a Cu plating solution or a SnAg plating solution and energizing the seed layer 12 as an electrode. A plating pattern 15 is formed by depositing a plating film of Cu or SnAg alloy on 14A so as to fill the opening 13h. In addition, it is desirable that the plating process is finished before the plating film in the opening 13h reaches the metal protective film 14B.

In the resist stripping step (S5), the resist layer 13 is removed, and the metal protective film 14B laminated on the resist layer 13 is removed. Specifically, the peeling process of the resist layer 13 is performed by immersing the plating intermediate 21 on which the plating pattern 15 is formed in a peeling solution.
Finally, in the etching step (S6), the portion of the seed layer 12 covered with the resist layer 13 is removed, whereby the wiring substrate 22 shown in FIG. Specifically, the substrate to be processed 11 after the resist stripping step (S5) is immersed in an etching solution made of sulfuric acid, phosphoric acid, hydrofluoric acid, hydrogen peroxide, etc. for a predetermined time to perform an etching process.

  As described above, in the plating method of the present embodiment, the plating solution and the resist are brought into contact in the plating formation step (S4) by forming and covering the metal protective film 14B on the surface 13a of the resist layer 13. It is possible to reduce the portion to be as much as possible. Thereby, elution of the resist component (organic substance) to the plating solution during the plating treatment can be suppressed, and the life of the plating solution can be extended.

  In the protective film forming step (S3), a metal protective film is formed not only on the surface 13a of the resist layer 13 but also on the surface to be plated 12a in the opening 13h of the resist layer 13. The metal protective film 14B on the surface 13a of the layer 13 and the metal protective film 14A on the surface to be plated 12a have a height difference corresponding to the thickness of the resist layer 13, and are in an insulated state. Therefore, in the plating formation step (S4), the metal protective film 14A on the surface to be plated 12a is energized through the seed layer 12, but the metal protective film 14B on the surface 13a of the resist layer 13 is not energized. The plating pattern 15 can be formed by depositing metal only in the opening 13 h of the resist layer 13. In this way, the metal protective film is formed by a method such as sputtering or ion plating, so that it is not necessary to separately coat the surface 13a of the resist layer 13 and the surface to be plated 12a, and can be easily formed. it can. Therefore, even the refined plating pattern 15 can be easily formed by the plating method of this embodiment.

In order to confirm the effect of the present invention, a plurality of plating intermediate samples (Comparative Examples 1 to 3 and Examples 1 to 3) are formed, and the plating intermediates of each sample are immersed in a plating solution for plating. Processing was performed to confirm the content of the resist component eluted in the plating solution.
As an intermediate for plating of each sample, a 6-inch diameter silicon wafer was used as a substrate to be processed, and a seed layer in which a Ti layer (1 μm) and a Cu layer (0.3 μm) were laminated was formed on the surface of the silicon wafer. . Also, after laminating an acrylic resin dry film resist with a film thickness of 50 μm on this seed layer, a bump pattern in a matrix form in which bump holes with a diameter of 75 μm are arranged at intervals of 225 μm by mask exposure (total of 90000 bump holes) And a resist layer was formed. And about Examples 1-3, after forming a resist layer, on the sputtering conditions shown in Table 1, various metal protective films shown in Table 3 are formed on each sample by sputtering, and various intermediates for plating are formed. Produced. In Comparative Examples 1 to 3, an intermediate for plating in which the surface of the resist layer was exposed was formed without forming a metal protective film.

  Each of the plating intermediates thus produced was immersed in a 10 L plating solution to form a plating film (plating pattern) in the bump hole. In this plating forming step, a paddle stirring type plating rod was used. In addition, as shown in Table 2, the plating solution generally includes a commercially available copper sulfate-based Cu plating solution (described as Cu in Table 3), an alkylsulfonic acid-based SnAg plating solution (described as SnAg in Table 3), A sulfamic acid-based Ni plating solution (described as Ni in Table 3) was used. The immersion time of each plating intermediate in the plating solution is performed for several minutes to several tens of minutes for each plating intermediate, and for each plating solution, a plurality of pieces are used until the total processing time reaches 20 hours. The plating intermediate was immersed in the plating process. Table 2 shows the plating treatment conditions.

And each plating solution after a plating process was fractionated, and the quantitative analysis of the resist component melt | dissolved in the plating solution was performed using the high performance liquid chromatography.
Table 3 shows the analysis results.

  As can be seen from the results in Table 3, in Examples 1 to 3 in which a metal protective film was formed on the surface of the resist layer, the peak area of the resist detected from the plating solution was not compared with the metal protective film formed. Compared with Examples 1 to 3, it was 1/10 or less, and by forming a metal protective film, elution of the resist component into the plating solution could be efficiently suppressed.

11 Substrate to be processed (object to be processed)
12 Seed layer 12a Surface to be plated 13 Resist layer 13a Surface 13h Openings 14A and 14B Metal protective film 15 Plating pattern 21 Plating intermediate 22 Wiring substrate

Claims (3)

A seed layer forming step of forming a seed layer on the surface of the workpiece;
A resist layer forming step of forming a resist layer having an opening for forming a plating pattern while covering a portion of the seed layer excluding the surface to be plated with a resist,
A protective film forming step of forming an intermediate for plating by forming a metal protective film covering the surface to be plated and the surface of the resist layer;
A plating formation step of forming a plating pattern by depositing a metal in the opening of the resist layer by immersing the plating intermediate in a plating solution and energizing the seed layer as an electrode;
A resist stripping step for removing the resist layer and the metal protective film laminated on the resist layer;
An etching step of removing the seed layer in a portion covered with the resist layer.   The metal protective film is formed of the same metal species as the plating pattern, or when the plating pattern is alloy plating, the metal protective film is the most precious metal among the constituent metals of the alloy plating. The plating method according to claim 1, which is formed by: An object to be processed on which a plating pattern is formed;
A seed layer formed on the surface of the workpiece;
A resist layer having an opening for forming the plating pattern while covering a portion of the seed layer excluding the surface to be plated with a resist,
An intermediate for plating, comprising: a surface to be plated and a metal protective film coated on the surface of the resist layer.

Images