JP4310974B2 - Wiring board manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a wiring board in which electrical wiring is formed on an insulating layer, and more particularly to a method for manufacturing a wiring board used for a semiconductor element mounting interposer and a printed wiring board.
[0002]
[Prior art]
In recent years, in semiconductor elements such as semiconductor large-scale integrated circuits (LSIs), the degree of integration of transistors has increased, and the operation speed has reached 2 GHz as the clock frequency, and the number of input / output terminals has exceeded 2000. Has reached.
[0003]
In response to the demand for an increase in the number of input / output terminals of a semiconductor element, the microfabrication technology of the semiconductor element has progressed year by year, but the current situation is that the miniaturization technique of the interposer or the printed wiring board has not caught up.
[0004]
As the number of input / output terminals of a semiconductor element increases, a method for connecting to an interposer requires a flip chip connection in a lattice arrangement.
[0005]
When the connection terminals of the interposer are arranged in a grid, it is necessary to pass the wiring between terminals outside the grid when routing the wiring from the terminals inside the grid to the outside. If fine wiring cannot be formed, it will not be possible to cope with an increase in the number of input / output terminals. As one means, it is conceivable to reduce the terminal diameter. However, there is a limit in reducing the terminal diameter due to limitations of the resolution and alignment accuracy of the solder resist. For this reason, a miniaturization technique for passing more wiring between terminals is required.
[0006]
On the other hand, the demand for high-density mounting of mounted components such as an interposer is also increasing in printed wiring boards. BGA (Ball Grid Array) type and CSP (Chip Size Package) type interposers in which solder balls are arranged in a grid form are in the direction of narrowing the pitch of solder balls in accordance with the demand for miniaturization of the interposer size. Accordingly, there is an increasing demand for miniaturization technology for wiring around the connection pad on the printed wiring board.
[0007]
Currently, a subtractive method of forming a pattern by etching is generally used for wiring formation. The etching resist used for this is mainly an alkali development type photoresist that is developed with an alkaline aqueous solution. Compared with solvent development type, alkali development type resists do not require explosion-proof measures and are very easy to handle, but have high hydrophilicity, and as shown in FIG. However, there is a problem that a flat width on the upper surface of the wiring cannot be secured and a fine pattern cannot be formed. In other words, the upper width (dimension A) of the wiring pattern shown in FIG. 2B has a cross-sectional shape that is extremely smaller than the lower width (dimension B) of the wiring pattern. This makes it difficult to reduce the wiring pitch.
[0008]
A semi-additive construction method may be used for miniaturization of wiring. In this method, an electroplating power supply layer is formed on the insulating layer, a photoresist pattern is formed, a plating pattern is formed in the pattern opening in the plating solution, the photoresist pattern is removed, and then the etching solution is used. The power supply layer is removed to form a wiring pattern. However, in this method, the pattern width cannot be controlled by the etching solution unless the power feeding layer is formed thin, and the electroless plating or sputtering film forming method is generally used to form a thin power feeding layer. However, both methods have a problem that the adhesion of the wiring cannot be taken. Furthermore, there is a problem that the process becomes longer and the cost becomes higher than the subtractive method.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the problems of the related art, and it is an object of the present invention to provide a method of manufacturing a wiring board capable of forming fine wiring by a subtractive construction method.
[0010]
[Means for Solving the Problems]
In order to achieve the above object in the present invention, in the invention of claim 1, in the method of manufacturing a wiring board, a resist pattern is formed on the conductor layer on the insulating layer, and wiring is formed by wet etching.
The resist pattern is formed using an acrylic resin-based photoresist, and after pattern formation, an alcohol or an organic acid ammonium salt that blocks carboxylic acid is incorporated into the film of the resist pattern, whereby the patterned resist is formed. A method for manufacturing a wiring board is characterized in that the surface free energy is adjusted .
[0012]
According to a second aspect of the present invention, there is provided the method for manufacturing a wiring board according to the first aspect, wherein the conductor layer is made of copper or a copper alloy.
[0013]
According to a third aspect of the present invention, there is provided the method for manufacturing a wiring board according to the first or second aspect, wherein the oxidant solution for dissolving the conductor layer is an aqueous solution.
[0014]
According to a fourth aspect of the present invention, in the method for manufacturing a wiring board according to any one of the first to third aspects, the oxidant solution is a ferric chloride or cupric chloride solution. is there.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The wiring board of the present invention will be described with reference to FIG. Using a substrate (FIG. 1A) formed on the conductor layer 1 on the insulating substrate 2, a photoresist film 3 is formed on the conductor layer. (FIG. 1 (b)).
[0016]
Exposure and development are performed using a photomask having a predetermined pattern to form a photoresist pattern 4 (FIG. 1C), and post-baking is performed. Since the photoresist used here is soluble in an alkaline aqueous solution, many hydrophilic components still remain in the crosslinking by exposure or post-baking.
[0017]
In the present invention, the surface free energy of the film post-baked after forming the photoresist pattern is 0.1 <γp <5.0 mN / m,
Or
0.1 <γh <10.0 mN / m
If it is what is. Here, γp represents a dipole interaction component of surface free energy, and γh represents a hydrogen bond component.
[0018]
The surface free energy of the photoresist is represented by the sum of γd, which is a hydrophobic component, dipole interaction component γp, and hydrogen bond component γh. Among these, if the values of γp and γh relating to hydrophilicity are in the above range, the etching solution easily penetrates from the interface between the conductor layer and the photoresist film, and the dimension A is smaller than the dimension B, making it impossible to form fine wiring. . On the other hand, if the values of γp and γh are below the above ranges, the photoresist itself cannot be applied.
[0019]
Moreover,
0.2 <γp <1.0 mN / m,
Or
0.2 <γh <5.0 mN / m
If it is, the effect is large.
[0020]
As long as the type of resist is within the range of the values of γp and γh, a photosensitive photoresist or a printing type resist may be used. In addition, when the alkali development type photoresist pattern is in the above range of γp or γh, it can be adjusted to the range of γp or γh by increasing the post-bake temperature or increasing the baking time. It is. In particular, it is effective to use a novolac-based photoresist in which naphthoquinone diazide is blended with a novolak resin. In addition, in an acrylic resin-based photoresist using an alkali-soluble acrylic resin as a binder, it is also effective to incorporate an alcohol or an organic acid ammonium salt that blocks carboxylic acid into the film after pattern formation. On the other hand, in a water-soluble photoresist in which dichromate is blended with polyvinyl alcohol, an effect can be obtained by increasing the concentration of chromic acid used for the hardening process after pattern formation or by increasing the post-bake temperature.
[0021]
Subsequently, etching is performed with an oxidant solution capable of dissolving the conductor layer 1 to form a wiring pattern 5 (FIG. 1D), and the resist pattern 4 is peeled off to form the wiring board of the present invention (FIG. e)).
[0022]
Any conductive layer metal may be used as long as it has conductivity, but the adhesion between the conductive layer metal and the resist material also affects the penetration of the etchant at the interface. When copper or copper alloy having high adhesion to the resist material is used, the penetration of the etching solution is suppressed and fine wiring can be formed. On the other hand, when stainless steel having poor adhesion is used, the etching solution easily penetrates from the interface between the conductor layer and the resist pattern, and the wiring cross-sectional shape is deteriorated.
[0023]
The oxidizing agent solution as an etching solution is more effective in a system using a highly polar aqueous solvent. When a solvent having a low polarity is used, even if the surface energy of the resist is within the above range, the etching solution easily penetrates from the conductor layer and the resist interface as the polarity decreases. An aqueous solution using ferric chloride or cupric chloride as an oxidant has a high viscosity, and is similarly difficult to penetrate, so that a fine pattern can be formed.
[0024]
【Example】
Examples will be described below.
[0025]
An embodiment of a method for manufacturing a multilayer wiring board will be described in accordance with the flow of FIGS.
[0026]
Using a substrate obtained by laminating an electrolytic copper foil 1 having a thickness of 18 μm on a polyimide substrate 2 (FIG. 1A), 5 μm of an alkali development type acrylic resin photoresist was applied by a roll coater and dried (FIG. 1B). Exposure and development were performed using a photomask having a predetermined pattern to form a resist pattern 4 (FIG. 1C).
[0027]
Thereafter, post-baking was performed at 130 ° C. for 30 minutes, and further post-exposure was performed at ² J / cm ² . At this time, the surface free energy of the photoresist surface was determined from the contact angle of the standard solution. As a standard solution, water (γd = 29.1, γp = 1.3, γh42.4 mN / m), diiodomethyl (γd = 46.8, γp = 4.0, γh = 0 mN / m), α-bromonaphthalene (Γd = 44.4, γp = 0.2, γh = 0 mN / m), and the contact angle on the photoresist surface was measured with a contact angle measuring device manufactured by Kyowa Interface Chemical Co., Ltd. in a constant temperature room at 22 ° C. It was measured. Using the obtained contact angle θ and the γ value of the standard solution, the surface free energy of the photoresist was calculated from the following equation.
[0028]
γL (1 + COSθ) = 2 (γLd · γRd) 1/2 ↑ + 2 (γLp · γRp) 1/2 ↑ + 2 (γLh · γRh) 1/2 ↑
[0029]
Here, γL represents the surface free energy of the standard solution, and γR represents the surface free energy of the photoresist. As a result of calculation, γp was 0.8 mN / m, and γh was 3.2 mN / m.
[0030]
Using an aqueous ferric chloride solution having a Baume degree of 40 °, spray etching was performed at 50 ° C. to form a wiring pattern 5 (FIG. 1D). Finally, the resist pattern 4 was peeled off to obtain the wiring board of the present invention. When the dimension of the wiring width of 40 μm was measured, the wiring upper width (dimension A) was 38 μm, and the wiring lower width (dimension B) was 40 μm.
[0031]
【The invention's effect】
In the present invention, by reducing γp and γh related to the hydrophilic component of the surface free energy of the resist pattern, the penetration of the etching solution from the conductor layer and the resist interface can be suppressed, and a fine wiring is formed. There is an effect that can be.
[0032]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a method for manufacturing a wiring board according to the present invention.
FIG. 2 is a cross-sectional view showing a conventional wiring board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Conductor layer 2 ... Insulating layer 3 ... Resist film 4 ... Resist pattern 5 ... Wiring pattern 6 ... Etching liquid

Claims (4)

In a method for manufacturing a wiring board, a resist pattern is formed on a conductor layer on an insulating layer, and wiring is formed by wet etching.
The resist pattern is formed using an acrylic resin-based photoresist, and after pattern formation, an alcohol or an organic acid ammonium salt that blocks carboxylic acid is incorporated into the film of the resist pattern, whereby the patterned resist is formed. A method for manufacturing a wiring board, comprising adjusting surface free energy. The method for manufacturing a wiring board according to claim 1 , wherein the conductor layer is made of copper or a copper alloy. A method for manufacturing a wiring board according to claim 1 or 2, wherein the oxidizing agent solution for dissolving the conductive layer is an aqueous solution. A method for manufacturing a wiring board according to any one of claims 1 to 3, characterized in that the oxidizer solution is a ferric or cupric chloride chloride solution.

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