JP2012209323A - Wiring board and manufacturing method of wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for securing adhesion strength between a wiring pattern formed on a base substrate such as a resin substrate or an inorganic material substrate or the like free from unsaturated double bonds and the base substrate without performing roughening treatment for the base substrate.SOLUTION: A manufacturing method of a wiring board comprises, in this oder: a step of forming an insulating film 2 on a base material 1 in a sol-gel method which uses a precursor solution adjusted within a range of pH 3 to 5; a step of forming an organic layer 3 using a silane coupling agent; a step of absorbing an ionized metal catalyst on a surface of the organic layer; a step of reducing the metal catalyst and forming an electroless plating layer using the reduced metal as a nucleus; a step of heating the electroless plating layer or the like in a nitrogen atmosphere at a prescribed temperature and for a prescribed time; a step of forming an electric plating layer 4a using an electroless plating layer 4b as a power supply layer; a step of forming a prescribed wiring pattern by patterning the electric plating layer using a photolithography method; and a step of removing an exposed electroless plating layer.

Description

  The present invention relates to a technique for increasing the adhesion strength between a wiring pattern and a base substrate without using a roughening treatment of the base substrate.

  Copper plating is used as a technique for forming printed wiring boards and LSI wirings mounted on electronic devices. Conventionally, a method of patterning aluminum using a vacuum technique such as sputtering or CVD has been used as a conductor circuit in an LSI. As the wiring material, copper is desirable in view of conductivity, but it is difficult to pattern copper by the conventional vacuum technique. However, with the recent increase in functionality of electronic equipment, a circuit having a fine structure is required, and it has become difficult to cope with the electrical conductivity of aluminum. From such a background, wiring formation technology using copper plating plays an important role in today's semiconductor industry.

  One of the major problems in wiring formation technology is the problem of wiring adhesion strength. For example, in a printed wiring board, in order to obtain adhesion between the wiring and the insulating resin, the adhesion strength is increased by a mechanical anchor effect that roughens the resin surface. As a result, the final product can be finished without the wiring being peeled off from the base substrate. The wiring formation process uses a subtractive method or a semi-additive method, but as for the close contact of the wire, the contact by the anchor effect is still often used.

  The subtractive method is the following process. A copper layer is formed on the entire surface of the base substrate by laminating copper foil or electrolytic copper plating on the surface on which the wiring layer is to be formed. Photoresist is coated on the copper film by a spin coater, roll coater, screen printing, laminator or the like. Next, the photoresist is exposed and developed through a photomask having a predetermined pattern, and a photoresist layer is formed in a portion to be left as a wiring. Next, an unnecessary portion where the copper layer is exposed is etched. As the etching solution, a ferric chloride solution or a copper chloride solution is mainly used. Thereafter, the photoresist is peeled off to obtain a desired wiring pattern.

  The semi-additive process is the following process. A power feeding layer is formed on the entire surface of the base substrate on which the wiring layer is formed by electroless plating or sputtering. The thickness of the power feeding layer is 2 μm or less. A photoresist is applied to the power feeding layer thus formed by a spin coater, roll coater, screen printing, laminator or the like. The photoresist is exposed and developed through a photomask having a predetermined pattern, and a photoresist layer is left in an unnecessary portion of the wiring. Next, electrolytic copper plating is performed on the opening using the power feeding layer as an electrode. As the electrolytic copper plating solution, a copper sulfate plating solution is mainly used. After forming a copper plating layer having a thickness of 2 μm to 20 μm, the photoresist is peeled off, and then the power feeding layer is removed by quick etching to obtain a wiring pattern.

  However, when a copper plating layer is formed by performing a mechanical roughening process (including the case where an anchor process is performed in order to obtain a necessary adhesion) on the base substrate for improving adhesion, At this time, etching may not be completed and copper may remain on the anchoring surface, which may cause a short circuit between the wirings. In mechanical roughening treatment, the insulating layer required when forming wiring on the substrate (substrate) is destroyed when mechanical roughening treatment is performed, or mechanical roughening treatment is performed. In this case, the thickness of the insulating layer becomes non-uniform, and the insulating layer may be destroyed when etching is performed. In the high-frequency region, signal delay problems have been pointed out due to the skin effect caused by the roughness of the copper wiring surface. However, if the etching time is increased, the wiring will be thinned and the standard will not be satisfied. If the roughness of the base substrate surface is reduced, the adhesion of the wiring will be weakened, causing problems such as peeling or falling of the wiring. To do.

  The adhesion mechanism includes chemical adhesion and physical adhesion, and the anchor effect is classified as physical adhesion. Chemical adhesion generally refers to the bond strength due to a chemical reaction. In order to improve the chemical adhesion, there are a method of chemically forming irregularities on the surface and a method of removing a substance that inhibits adhesion.

  Various methods have been proposed for chemical adhesion and is generally called primer treatment. A typical example is a method using a silane coupling agent such as an imidazole silane compound. If sufficient adhesion strength can be obtained by chemical adhesion, anchor treatment that causes copper residue can be eliminated.

  Patent Document 1 describes that the adhesion strength between an insulating resin layer and a conductor wiring layer is improved by using a silane coupling agent. In this patent document 1, a silane coupling agent treatment is performed on the copper foil surface of the inner layer, and a resin having an unsaturated double bond such as an uncured epoxy resin is coated on the copper foil treated with the silane coupling agent. The adhesive strength is exhibited by thermosetting.

  Thus, the copper foil and the silane coupling agent can be easily coupled. However, conversely, it does not exhibit a silane coupling effect on resin surfaces and silicon substrates without unsaturated double bonds, and sufficient adhesion strength cannot be obtained even if a conductor wiring layer is formed after this. was there. However, for glass having a silanol group, the silane coupling agent may exhibit a certain effect.

Japanese Patent No. 3505135

  The present invention has been made in order to solve the above-mentioned problems, and is formed on a base substrate such as a resin substrate or an inorganic material substrate having no unsaturated double bond without being subjected to a roughening treatment. The present invention provides a means for ensuring adhesion strength between a wiring pattern to be performed and a base substrate, thereby providing a wiring board having high reliability.

In order to achieve the above object, the invention according to claim 1 includes an organic layer comprising a silicon dioxide insulating film having a density of 2.2 g / cm ³ or less formed by a sol-gel method on a substrate and a silane coupling agent. And a patterned electroless copper plating layer and a patterned electrolytic copper plating layer in this order.

  As invention of Claim 2, on the base material, the process of forming an insulating film by the sol-gel method using the precursor solution adjusted in the range of pH 3-5, and an organic layer using a silane coupling agent A step of adsorbing an ionized metal catalyst on the surface of the organic layer, a step of forming an electroless plating layer using the reduced metal as a core, and an electroless plating layer in a nitrogen atmosphere. And the like, a step of heating at a predetermined temperature for a predetermined time, a step of forming an electroplating layer using the electroless plating layer as a power feeding layer, and patterning the electroplating layer using a photolithography method to form a predetermined wiring pattern A method of manufacturing a wiring board comprising: a step of forming and a step of removing an exposed electroless plating layer in this order.

  The invention according to claim 3 is the method for manufacturing a wiring board according to claim 2, wherein the base material is a base material having no unsaturated double bond.

The invention according to claim 4 is that the precursor solution is a silicon dioxide film precursor solution containing silicon as a main component, and the formed insulating film has a density of 2.2 g / cm ³ or less. The method of manufacturing a wiring board according to claim 2 or claim 3, wherein

  The invention according to claim 5 is the method for manufacturing a wiring board according to any one of claims 2 to 4, wherein the metal ions are palladium ions.

  The invention according to claim 6 is the method for manufacturing a wiring board according to any one of claims 2 to 5, wherein the electroless plating layer and the electrolytic plating layer are copper layers. Is.

  According to the above invention, when an insulating layer having a predetermined density is previously formed on the base substrate by the sol-gel method, the silane coupling is directly applied to the base substrate more than when the base substrate is roughened. It is possible to form a metal plating layer having stronger adhesion strength on the base substrate than when the agent treatment is performed. In addition, a metal plating layer having the same adhesion strength can be formed on the surface of a resin substrate having no unsaturated double bond. Therefore, when the metal plating layer is patterned by a conventional method, a wiring board having a wiring pattern with strong adhesion strength can be obtained.

  Hereinafter, a mechanism for increasing the adhesion strength of the upper wiring pattern by the interaction between the layers formed on the base substrate will be briefly described.

By making the density of the insulating layer 2.2 g / cm ³ or less, which is the density of pure quartz glass, the structure becomes rough and contains many defects inside, so that it has a shape with fine irregularities on the surface. This unevenness increases the surface area, increases the number of bonding points with the upper organic layer, and improves the adhesion strength. For this reason, it is preferable that the density of an insulating layer is smaller than the density of pure quartz glass.

  In addition, since the insulating layer can be bonded to the upper organic layer by exposing silanol groups on the surface, it is desirable that the insulating layer is made of a substance containing silicon atoms and oxygen atoms.

  By using a sol-gel method as a method for forming the insulating layer, an insulating layer having fine irregularities on the surface and having silanol groups exposed on the surface can be obtained. The sol-gel method is a technique in which a sol of a precursor solution containing a metal alkoxide, alcohol, or the like is precipitated through a gel state by hydrolysis / condensation reaction. In the sol-gel method, a catalyst is required to cause hydrolysis / condensation reaction of the precursor solution, but it is preferable to use an acid catalyst as the catalyst. This is because the product is three-dimensionally bonded by hydrolysis / condensation reaction under an alkali catalyst, whereas the product is likely to bond linearly under an acid catalyst, so that a low-density insulating layer is likely to be formed. It is. Typical examples of the acid catalyst used include hydrochloric acid, sulfuric acid, and nitric acid.

Further, by forming the insulating layer by a sol-gel method using a precursor solution adjusted in the range of pH 3 to 5, the density can be adjusted and the adhesion strength can be improved at the same time. This is because the degree of condensation is reduced by making the hydrolysis / condensation reaction of the silica precursor less likely to occur, resulting in the formation of an insulating layer containing many uncondensed silanol groups on the surface. By containing a large amount of silanol groups, the number of bonding points with the upper organic layer increases, and the adhesion strength can be improved. When the pH is less than 3, an insulating layer having a high hydrolysis / condensation reaction rate and a high density is formed. When the pH exceeds 5, the reaction is difficult to proceed and it is difficult to form the insulating layer.

  The organic layer can be chemically bonded to the insulating layer by using a silane coupling agent. This is because a dehydration condensation reaction occurs between the silanol group on the insulating layer and the silane coupling agent, and a siloxane bond which is a covalent bond can be formed.

  Moreover, it is desirable that the silane coupling agent composing the organic layer has an electron donating group. This is because the electron donating group of the silane coupling agent interacts with metal ions of metals such as palladium and platinum which are electroless plating catalysts and can selectively adsorb metal ions on the organic layer. . The electron donating group of the silane coupling agent may be an amino group or a thiol group, but is not limited thereto.

  There are various metal ions adsorbed on the organic layer. For example, it is possible to adsorb palladium and platinum ionized as typical catalysts, and ionize copper as a copper plating catalyst. It can also be adsorbed.

  In addition, the metal ions adsorbed on the organic layer become a metal by performing a reduction treatment, and can be used as a catalyst. At this time, metal ions can be reduced with a reducing agent in the electroless plating solution in the next step. Moreover, when a metal ion cannot be reduced with the reducing agent in the electroless plating solution, it is necessary to reduce the metal ion in advance before the electroless plating step. For example, when palladium ions are adsorbed as a catalyst, it can be reduced if the reducing agent in the electroless plating solution is sodium hypophosphite or dimethylamine borane, but in the case of formaldehyde, it cannot be reduced. Reduction is required with borane. Reducing agents that can be used include, but are not limited to, sodium hypophosphite, dimethylamine borane, formalin, sodium borohydride, hydrazine and the like.

  For the wiring layer, various metals that can be formed by plating can be used, and examples thereof include copper, silver, gold, nickel, and platinum. It is desirable to use copper which is excellent in terms of electrical characteristics and cost.

  A power feeding layer can be formed by electroless plating using a metal catalyst obtained by adsorbing and reducing these metals on an organic layer as a nucleus.

  By heating the power feeding layer and the like formed by this electroless plating, the dehydration condensation reaction between the silanol group on the insulating layer and the silane coupling agent described above can be promoted, and the adhesion strength can be improved. . It is desirable that the heating temperature is 100 ° C. or higher because the reaction is accelerated at a high temperature. However, the temperature is desirably 200 ° C. or lower because it is necessary to be in a temperature range where the silane coupling agent does not decompose.

  It is also possible to form a wiring layer by performing electroplating using a wiring layer formed by electroless plating as a power feeding layer. By performing electroplating, the wiring can be easily thickened in a short time. The electroplating wiring layer is preferably copper, which is excellent in terms of electrical characteristics, but is not limited thereto.

By heating the wiring layer formed by this electrolytic plating, the stress of the plating layer is relieved by the rearrangement of metal atoms constituting the wiring layer, and the adhesion strength can be improved. The higher the heating temperature, the shorter the time required for rearrangement of metal atoms. Considering that the silane coupling agent decomposes at a high temperature, the heating temperature is desirably 200 ° C. or lower.

It is a figure of the cross-sectional view of the wiring board which is one Example of this invention. It is a figure of the cross-sectional view which formed the wiring layer in order of the electroless plating and the electrolytic plating on the organic layer which is one Example of this invention. It is a figure of the cross-sectional view of the board | substrate with which the wiring pattern which is one Example of this invention was formed.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a wiring board according to an embodiment of the present invention.

  An insulating layer 2 is formed on the substrate 1. As a means for forming, a sol-gel method is used. First, the precursor sol solution adjusted in the range of pH 3 to 5 is stirred and gelled by hydrolysis / condensation reaction. This solution is deposited on the substrate, and the solvent is evaporated by drying to form a solid insulating layer. As a method for applying the sol-gel method to the base material, the precursor solution is dropped on the base material with a dropper, etc., the base material is rotated at a high speed, and the solution is attached to the whole by centrifugal force. The base material is a precursor. A dipping method in which the solution is attached by dipping in the solution and pulling up can be considered, but is not limited thereto.

  Next, the organic layer 3 is formed on the insulating layer 2 using a silane coupling agent. As a means for forming, a dipping method, a coating method, a gas phase method, and the like are conceivable, but it is desirable to carry out the dipping method in order to form an organic layer densely and uniformly.

  Then, the ionized metal catalyst is adsorbed on the organic layer 3. As a means for forming, a dipping method, a coating method, or the like can be considered. However, it is preferable to carry out the dipping method in order to adsorb the organic layer densely and uniformly.

  Further, the ionized metal catalyst adsorbed on the organic layer 3 is reduced. As a means to reduce, it reduces with the reducing agent in an electroless-plating liquid, or it is immersed and reduced in the solution containing a reducing agent before an electroless-plating process.

  A wiring layer 4 is formed on the organic layer 3 on which the reduced metal catalyst is adsorbed. As an order of formation, first, a plating layer 4 (b) serving as a power feeding layer is formed by electroless plating (see FIG. 2). After forming the plating layer 4 (b), it is heated. Heating is possible in the atmosphere, vacuum, and inert gas, respectively. However, in order to prevent the surface from being oxidized, it is desirable to heat in vacuum or in the presence of inert gas.

  Thereafter, the plating layer 4 (a) is formed on the plating layer 4 (b) by electrolytic plating (see FIG. 2). After forming the plating layer 4 (a), the wiring layer 4 is formed by heating again. In order to prevent the surface from being oxidized, it is desirable to heat in a vacuum or in the presence of an inert gas.

  In this manner, the wiring layer is formed on the substrate.

  Then, the wiring layer formed by electrolytic plating is patterned by regular photolithography to remove unnecessary wiring layers and form a wiring pattern (see FIG. 3).

Although not shown, it is also possible to produce a wiring board having a multilayer structure by repeating a similar method using a sol-gel method on the formed wiring. At this time, by forming a through hole in advance with a laser after forming the insulating layer, the wiring layer can be formed in the through hole when the wiring layer is formed by plating, and the upper and lower wiring layers can be made conductive. it can.

  An insulating layer was formed by a sol-gel method on an n-type semiconductor substrate doped with a small amount of phosphorus in silicon. The precursor solution for the sol-gel method is a mixture of tetraethoxysilane, ethanol, and water in a molar ratio of 1:10:10, adjusted to pH 4 by adding hydrochloric acid, and applied to a n-type semiconductor substrate by spin coating. Attached. Then, in order to dry a board | substrate, it heated at 80 degreeC, the residual solvent was removed, and the silicon dioxide layer used as an insulating layer was formed.

  Next, as the organic layer, a silicon dioxide film was coated using a silane coupling agent having an amino group and an alkyl group, 3- [2- (2-aminoethylamino) ethylamino] propyltrimethoxysilane. This silane coupling agent was dissolved in toluene to prepare a 10% silane coupling agent solution, and the substrate was immersed. Thereafter, the substrate was washed with methanol and pure water, and excessively attached silane coupling agent and solvent were removed.

  The substrate on which the organic layer was formed was immersed in a solution containing 0.3 g / liter of palladium chloride, and palladium ions were adsorbed on the organic layer. The substrate to which the catalyst was attached was immersed in a solution containing 0.15 mol / liter dimethylamine borane and subjected to reduction treatment.

  A copper plating layer having a thickness of 50 nm was formed by electroless copper plating using the reduced palladium as a nucleus.

  The substrate on which the copper plating layer was formed was heated at 150 ° C. for 2 hours in a nitrogen atmosphere.

  After heating, electrolytic copper plating was performed using a copper plating layer formed by electroless plating as a power feeding layer to form a wiring layer having a thickness of 10 μm.

  The substrate on which the wiring layer was formed was heated at 200 ° C. for 2 hours in a nitrogen atmosphere.

  Finally, using a regular photolithography, a wiring having a wiring width and interval of 1 mm was formed.

  When the peel strength of these wirings was measured, it showed a value of 10.2 N / cm, which has sufficient adhesion to form the wiring.

<Comparative example>
Comparative examples of the present invention are shown below.

  When the peel strength of the wiring formed by the method shown in Example 1 was measured using the insulating layer formed by adjusting the pH of the sol-gel precursor solution to pH 2, it was 3.4 N / cm. . Further, when the pH of the precursor solution was adjusted to 6, hydrolysis / condensation reaction did not proceed and an insulating layer could not be formed.

  Moreover, when the plating layer was formed by electroless plating by the method shown in Example 1 and electrolytic copper plating was performed without heating, and the peel strength of the formed wiring was measured, 5.8 N / cm Met.

  The peel strength of the wiring formed without heating the wiring layer formed by electrolytic copper plating by the method shown in Example 1 was 7.2 N / cm.

  By these, by adjusting in the range of pH 3-5 of the sol-gel method, and by heating after each process of electroless plating and electrolytic plating, the wiring board with high adhesion strength in which the density is adjusted and its wiring The formation method could be shown.

  The above-described invention can be used as a wiring formation technique or a wiring board using a plating method such as a printed wiring board or LSI.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Insulating layer 3 ... Organic layer 4 ... Wiring layer 4 (a) ... Plating layer 4 (b) formed by electroplating ... Plating layer formed by electroless plating

Claims (6)

A silicon dioxide insulating film having a density of 2.2 g / cm ³ or less formed by a sol-gel method on a substrate, an organic layer made of a silane coupling agent, a patterned electroless copper plating layer, and patterned And an electrolytic copper plating layer in this order.   A step of forming an insulating film by a sol-gel method using a precursor solution adjusted in the range of pH 3 to 5 on a substrate, a step of forming an organic layer using a silane coupling agent, and a surface of the organic layer A step of adsorbing an ionized metal catalyst, a step of reducing the metal catalyst and forming an electroless plating layer using the reduced metal as a nucleus, and an electroless plating layer in a nitrogen atmosphere at a predetermined temperature for a predetermined time A step of heating, a step of forming an electroplating layer using the electroless plating layer as a power feeding layer, a step of patterning the electroplating layer using a photolithography method to form a predetermined wiring pattern, and an exposed portion And a step of removing the electroless plating layer in this order.   The method for manufacturing a wiring board according to claim 2, wherein the base material is a base material having no unsaturated double bond. 2. The silicon dioxide film precursor solution containing silicon as a main component, and the formed insulating film is a silicon dioxide film having a density of 2.2 g / cm ³ or less. The manufacturing method of the wiring board of Claim 2 or Claim 3.   The method for manufacturing a wiring board according to claim 2, wherein the metal ions are palladium ions.   6. The method for manufacturing a wiring board according to claim 2, wherein the electroless plating layer and the electrolytic plating layer are copper layers.

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