JP2004247744A - Wiring structure and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliability wiring structure that excels in the mechanical property of a polyimide insulating layer and the property of interface adhesiveness by controlling the melting-out of copper from copper wiring to the insulating layer and by avoiding the crack of the insulating layer, and its low-cost manufacturing method. <P>SOLUTION: For the purpose of obtaining polyimide insulating film by directly applying polyimide precursor formulation to the surface of copper wiring and heat curing, polyamide acid with low acidity of carboxyl group or polyimide precursor formulation comprising basic compound is used as precursor of polyimide. Furthermore, for the purpose of preventing polyamide acid with high acidity from directly contacting copper, the exposed part of copper wiring 14 and 14a is covered with a copper diffusion inhibition layer 16 made from polyimide that is obtained by heat curing of polyamide acid with low acidity. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

Industrial applications

  The present invention relates to a wiring structure having a thin film wiring including a wiring material mainly made of copper and an insulating film mainly made of polyimide, and a method for manufacturing the same, and more particularly to a highly integrated mounting substrate and a method for manufacturing the same.

  2. Description of the Related Art In recent years, wiring structures such as a wiring board for mounting an LSI (Large Scale Integrated Circuit) and the like have been multi-layered, highly integrated, and highly sophisticated. Along with this, development of a multilayer wiring board for directly mounting an ultra-high-speed integrated circuit chip has been promoted. In many cases, the multilayer wiring board is formed with a thin-film multilayer wiring in which conductive patterns are provided in a multilayer at a high density on a ceramic substrate. Therefore, the insulating film of the thin-film multilayer wiring is required to have advanced characteristics. At present, polyimide is widely used as one of the materials for this insulating film.

  Polyimide is generally obtained by a method in which a diamine component and a tetracarboxylic dianhydride component are polymerized and reacted in a polar organic solvent to produce a polyimide precursor (polyamic acid), which is dehydrated and ring-closed by heating or the like.

A conventional method of manufacturing a thin-film wiring board is described in, for example, "IEE Transactions on Components Hybrid and Manufacturing Technology", Vol. 13, No. 2, June 1990, pp. 440-443 ( IEEE TRANSACTIONS ON COMPONENTS, HYBRIDS, AND MANUFACTURING TECHNOLOGY, VOL. 13, NO2, JUNE 1990, 440-443), and specific examples are described in JP-A-4-23390. .

  In the above prior art, a polyimide insulating film is formed by applying a polyamic acid varnish, which is a polyimide precursor, on a conductor pattern made of Cu and heat-curing. However, conventionally known polyimides include, for example, “Journal of Vacuum Science and Technology” A, Vol. 7, No. 3 (1989), pp. 1402-1412, and As described in Vol. 9, No. 6 (1991), pp. 2963-2974, when heating is performed for this dehydration ring closure while in contact with copper, copper becomes polyimide (or a polyimide precursor). There is a problem that the polyimide is decomposed at a high temperature due to the eluted copper. Therefore, in order to solve the problem that polyimide is decomposed at a high temperature due to copper eluted in the polyimide, heating at a high temperature of 300 ° C. or more is performed by using a reducing gas such as a mixed gas of argon and hydrogen. There is known a method of performing in an atmosphere of nature.

  However, this method can solve the problem that polyimide decomposes at high temperature, but cannot suppress the elution of copper into polyimide or polyimide precursor. The copper eluted into the polyimide (or the polyimide precursor) causes a decrease in the adhesiveness between the copper and the polyimide, and further increases the dielectric constant, thereby increasing the signal transmission delay time. Further, since the above-mentioned reducing gas is expensive, another problem arises that the cost of the product is increased particularly when a product in which wirings are repeatedly formed in multiple layers is manufactured.

  As a solution for solving the problem that copper is eluted into polyimide, a method of esterifying a carboxyl group of a polyimide precursor (polyamic acid) can be considered. In this case, since the esterified polyimide precursor is expensive, there is a problem that the cost of the product is increased particularly when a product in which wiring is repeatedly formed in multiple layers is manufactured. In addition, since the acid chloride as a raw material for esterification is unstable with respect to moisture, the esterification rate of the polyimide precursor is not always 100%, and a small amount of carboxyl groups remains. is there. Further, in the esterification reaction of the polyimide precursor with an acid chloride, there is a problem that hydrochloric acid is produced in an equimolar amount with a carboxyl group, and it is not easy to remove 100% of this. That is, when an esterified polyimide precursor is used, an acid component such as a carboxyl group or hydrochloric acid remains in the polyimide precursor solution, and this acid promotes the elution of metallic copper. However, there is a problem that the phenomenon of eluting into polyimide cannot be completely suppressed.

  On the other hand, as another method for preventing elution of copper into polyimide, there is known a method in which an exposed portion of copper is coated with another metal that does not elute in polyimide, and then polyimide is formed. However, in this case, there is a problem that the cost of the product is increased because the number of steps for forming another metal other than copper is increased. Further, when nickel, aluminum, or the like is used for coating copper, the metal coated with copper interdiffuses with copper during heating, which causes an increase in the resistance value of the entire wiring. Furthermore, when copper diffuses to the surface of the coated metal, there is a problem that copper is eluted into the polyimide as a result.

In view of these problems, the present inventors have developed a polyimide or its precursor without using an esterified polyimide precursor and without using an expensive reducing gas during heat curing of the polyimide precursor. In order to suppress the elution of copper, that is, a production method for suppressing the reaction between copper and the polyimide precursor, and to provide a wiring structure free of copper elution, as a result of intensive studies, This has led to the invention.

  As described above, when copper is used as a part of the wiring and the insulating film directly in contact with the copper is a polyimide formed by heating from the polyimide precursor, the interface between the copper and the polyimide precursor is formed. In order to suppress the above reaction and to form a via wiring for connection with the upper metal layer, it is essential to reduce the stress of the insulating film in manufacturing the wiring structure.

  Therefore, in the present invention, using a polyimide precursor having a low acidity of the carboxyl group, using a polyimide precursor composition in which the acidity of the system is suppressed by a basic compound, when heating and curing the polyimide precursor, The reaction between copper and the polyimide precursor is suppressed by limiting the oxygen concentration in the atmosphere and / or reducing the thickness of the polyimide film.

  By the way, when a thin-film multilayer wiring layer of a wiring board such as a multi-chip module is formed using copper as a wiring and polyimide as an insulating film, in addition to the above-described problems, planarization of the insulating film is required. If the polishing is performed by mechanical means for the purpose, cracks may be generated in the polyimide insulating film.

  Therefore, in the present invention, it is preferable that the insulating film be a composite film including the first insulating film and the second insulating film.

  Here, as the first insulating film formed directly on the copper wiring, an organic polymer film in which reactivity with copper is suppressed (a diffusion blocking layer that blocks diffusion of copper) is used. According to this configuration, after the exposed portion of the copper is covered with the diffusion blocking layer, the second insulating layer is formed on the surface of the diffusion blocking layer. Therefore, polyamic acid having high acidity is used for forming the second insulating layer. Even if used, the diffusion of copper is prevented because the polyamic acid does not directly contact the copper. In addition, in the present invention, since the exposed portion of copper is covered with the organic polymer compound, there is no problem such as mutual diffusion between the coating material and copper, unlike the case where copper is covered with another metal that does not elute into polyimide.

  It is desirable to use a low thermal expansion polyimide film as the second insulating film formed on the surface of the first insulating film. In this way, since the film stress can be reduced, the interfacial adhesion between copper and the polyimide is excellent while maintaining the mechanical properties of the polyimide, and the cracks do not occur, and the entire wiring board has high reliability. A wiring structure is obtained.

  The present invention was used to solve the following two problems of the present invention: (1) suppression of the reaction between copper and a polyimide precursor, and (2) prevention of cracks generated in a polyimide film at the time of manufacturing a wiring structure. The operation of the means will be described.

(1) Suppression of Reaction between Copper and Polyimide Precursor First, the operation of the method for achieving suppression of the reaction between copper and the polyimide precursor will be described in detail.

It is considered that the elution of copper into the polyimide or the polyimide precursor occurs due to the reaction between copper and the polyimide precursor. The reaction between copper and the polyimide precursor is an ionization reaction of metallic copper by an acid dissociated from a carboxylic acid present in the polyimide precursor, that is, an oxidation-reduction reaction represented by any of the following reaction formulas 1 and 2. Can be considered as

  The standard potential E of these oxidation-reduction reactions is E = -0.68 V in the case of the reaction represented by the reaction formula 1, and E = + 1.78 V in the case of the reaction represented by the reaction formula 2. The standard potential E represents a difference between the potentials on the left and right sides when the Cu on the left side and the Cu ion on the right side have the same activity in the so-called Nernst equation. In general, this value is positive. In the case of, the reaction spontaneously proceeds to the right, and in the case of negative, the reaction hardly proceeds to the right.

  The reaction of the reaction formula 1 has a negative standard potential and does not proceed spontaneously. In the reaction of the reaction formula 2, the standard potential is positive and the reaction proceeds spontaneously. Therefore, the reaction between copper and polyimide is not a form of reaction formula 1 of ionization of copper by an acid and the accompanying hydrogen generation reaction, but a water formation reaction (reaction formula 2) involving three of acid, copper and oxygen. It is believed that there is.

Thus, the Nernst equation for the above reaction will be considered again in detail. The standard potential E in the above-mentioned reaction formula 2 is such that when the Cu on the left side and the Cu ion on the right side have the same activity, that is, approximately Ｃｕ of the Cu on the left side reacts to become Cu ions. In this case, the potential difference between the left side and the right side was represented. In order to discuss the reaction more quantitatively, the following equation 1 (“Atlas of Electrochemical Equilibria in Aqueous solutions” (1966, Pergamon Press Ltd., published by Pergamon Press Ltd.) considering the partial pressure of oxygen, hydrogen ion concentration and activity of Cu ion is considered. ) On pages 386 and 541).

E = 1.78-0.12pH + 0.03log (pO2)
−0.06 log [Cu2 +] Formula 1
The left side E of this equation represents the difference between the potentials before and after the reaction of the reaction formula 2, that is, the difference between the potential energies, and the right side shows the oxygen concentration and the hydrogen ion concentration, respectively, the oxygen partial pressure (pO2) and hydrogen It appears in the form of an ion index (pH). When the value of E becomes smaller, the reaction becomes difficult to proceed.

  Here, consider the case where the polyimide is esterified as an example. In this case, if the esterification rate is 100%, the pH is considered to be approximately neutral, but E = 0 at pH = 7. In other words, it can be seen that even if the polyimide precursor is esterified, there is still room for the reaction of the formula (2) to proceed.

On the other hand, looking at the concentration of oxygen, pO2 takes a numerical value of 1 or less.
It is considered that the term including O2 becomes negative as a whole, and the numerical value of E decreases as the oxygen concentration decreases, and the reaction of the formula (2) becomes difficult to proceed.

  From the above considerations, two methods of suppressing the reaction between copper and the polyimide precursor include reducing the acidity of the system (increasing the pH) and reducing the oxygen concentration of the system.

  These estimates are derived from the difference in potential energy before and after the reaction in an equilibrium manner, and are not considered in terms of reaction kinetics. The actual effect needs to be verified by experiment only because is related to the ideal state. Therefore, as shown in the examples described later, the present inventors have verified this through many experiments, and in fact, any of the above has a dramatic effect in suppressing the reaction between copper and the polyimide precursor. The present invention has been found, and the present invention has been achieved.

  Of the above two means for suppressing the reaction, the present invention employs means for reducing the acidity of the system. In the present invention, a polyimide precursor having a repeating unit represented by the following general formula (Formula 1) is used as the low acidity polyimide precursor.

(Wherein R1 is

And R2 is a divalent organic group containing an aromatic ring. )
In the present specification, the “polyimide precursor” refers to at least one of a polyamic acid, an acid dianhydride, and a diamine. In addition, the precursor of the polyimide having the repeating unit represented by the general formula (Chemical Formula 1) includes a polyamic acid of the following General Formula (Chemical Formula 15), an acid dianhydride of the following General Formula (Chemical Formula 16), and the following general formula And at least one of the diamines of formula (17). Note that R1 and R2 in (Chemical Formula 15) to (Chemical Formula 17) are the same as those in the above-described general formula (Chemical Formula 1).

Among the precursors of the polyimide of the general formula (1), the polyamic acid of the general formula (15) is an acid having a carboxyl group. The acidity of the polyamic acid of the general formula (Formula 15) depends on the degree of dissociation of hydrogen ions from its carboxyl group. The degree of the dissociation depends on the structure of R1 and is determined by what other substituents are bonded to the aromatic ring to which one carboxyl group is bonded. This is known as the empirical rule called Hammett's rule. Table 1 shows the σ values indicating the degree of dissociation of hydrogen ions according to the Hammett's rule, which were calculated and calculated for some R1.

The abbreviations used in Table 1 are as follows.

PMDA: pyromellitic dianhydride BTDA: 3,4,3 ', 4'-benzophenonetetracarboxylic dianhydride BPDA: 3,3', 4,4'-biphenyltetracarboxylic dianhydride TPDA: p- Terphenyl-3,3 ", 4,4" -tetracarboxylic dianhydride m-TPDA: m-terphenyl-3,3 ", 4,4" -tetracarboxylic dianhydride ODPA: 3,3 ' , 4,4'-Oxydiphthalic dianhydride As is clear from Table 1, generally used PMDA and BTDA have a positive σ value and a large acidity. On the other hand, in BPDA, ODPA, and TPDA, the σ value is 0 or less, and the acidity is small. This indicates that when R1 is (Chemical Formula 2), the acidity of the polyimide precursor is low, and the elution of copper can be suppressed.

  Since R2 described above is not directly bonded to the aromatic ring of R1, it hardly affects the acidity of the polyimide precursor. Since the Hammett's rule is an empirical rule in an aqueous solution, when it is directly applied to an organic solvent system such as the polyimide precursor solution of the present invention, it is necessary to verify the actual effect by experiments. As will be shown in the examples below, the present inventors have found that the precursor of the compound represented by the formula (I) of the present invention can be used not only in an aqueous solution but also in an organic solvent system targeted by the present invention. It was verified that it was effective in suppressing copper diffusion.

  By the way, the basic compound used in the present invention has the effect of neutralizing the carboxyl group in the polyimide precursor, lowering the acidity of the entire solution containing the polyimide precursor, and thus increasing the pH. . As a result, the presence of the basic compound acts in the direction of reducing the potential of the reaction on the left side of the above formula 1 and suppressing the reaction. In addition, the basic compound added in an excessive amount by neutralizing the carboxyl group further increases the pH of the system, and the effect of suppressing the reaction with copper is further increased. Therefore, the polyimide precursor composition used for forming the insulating layer preferably contains 1 equivalent or more of the basic compound with respect to 1 equivalent of the contained polyimide precursor. That is, the polyimide precursor composition preferably contains a basic compound in an amount such that the number of reaction points is equal to or greater than the total number of carboxyl groups contained in the entire polyimide precursor.

  The present invention also provides a method for manufacturing the above-described wiring structure. In the polyimide baking step, it is desirable that the oxygen concentration in the atmosphere be 0.5% or less. In a method of manufacturing a wiring structure, the effect of oxygen in the process of eluting copper into a polyimide precursor is extremely large. By reducing the oxygen concentration, elution of copper into the polyimide precursor can be suppressed. In particular, the region of the oxygen concentration where the deterrent effect is large is 0.5% or less, and when this concentration is exceeded, the amount of copper eluted rapidly increases. As this means, a nitrogen gas generated from ordinary liquid nitrogen can be used as an atmosphere for baking after the application of the polyimide precursor, and an atmosphere having a low oxygen concentration of 100 ppm or less can be easily achieved. Reducing the oxygen concentration and reducing the acidity of the solution containing the above-mentioned polyimide precursor are additive in terms of the effect of suppressing the elution of copper. Therefore, by reducing the oxygen concentration of the atmosphere when the copper and the polyimide precursor come into contact with each other as much as possible, and further reducing the acidity of the polyimide precursor (or its composition) to be used, the elution amount of copper is minimized. It can be suppressed.

  Therefore, in the present invention, when the polyimide precursor is cured by heating, it is desirable that the oxygen concentration in the atmosphere be 0.5% by volume or less. This is because if the oxygen concentration in the system is reduced to 0.5% by volume or less, the elution of copper can be further inhibited.

  Next, the effect of the presence of the solvent will be considered. The reaction between Cu and the polyimide varnish is promoted by the presence of a solvent. This is because the dispersion of copper ions is promoted by the solvent, and the progress of imidization is hindered during the presence of the solvent because the rise in temperature in the system is suppressed.

  However, since the evaporation of the solvent from the polyimide varnish occurs on the film surface which is the contact surface with the atmosphere, the solvent remains at the interface between the Cu conductor layer and the polyimide varnish for a longer time than the film surface. Therefore, it is considered effective to vaporize the solvent as soon as possible during thermal curing to prevent the reaction. However, it is difficult to shorten the evaporation time of the solvent by rapidly increasing the thermosetting temperature because it causes film swelling and the like. If the heat curing temperature is extremely high, the film surface will be rapidly cured, which may hinder the distillation of the internal solvent. Therefore, there is a limit to increasing the thermosetting temperature.

  Therefore, the inventors of the present invention have focused on the thickness of the polyimide film and have studied. Since a thick polyimide varnish film must be formed in order to obtain a thick polyimide film, the existence time of the solvent in the film becomes long. Therefore, as the formed film thickness of the polyimide is larger, the reaction between Cu and the polyimide is more likely to occur, and the diffusion amount of Cu into the polyimide film is increased.

  According to experiments performed by the inventors, it was confirmed that when the thickness of the formed polyimide film was set to 6.5 μm or more, a region where Cu was present at a high concentration was formed in the polyimide layer near the interface with the Cu layer. Was. FIG. 9 is a graph obtained by observing the diffusion state of Cu elements in the polyimide layer when the ceramic insulating layer, the copper layer, and the polyimide insulating layer are laminated in this order with respect to the formed film thickness d. It is. The polyimide film was formed by applying a varnish of a polyamic acid obtained by polymerizing pyromellitic dianhydride and 4,4′-diaminodiphenyl ether on the copper layer surface, followed by heating and imidization. Was.

  FIG. 2A shows the Cu element concentration distribution in the polyimide layer 4 having a polyimide film thickness of 10 μm. The horizontal axis represents the distance from the copper / polyimide interface, and the vertical axis represents the copper concentration. As can be seen from this figure, as the distance from the copper / polyimide interface increases, the Cu element concentration decreases, and a layer with a high Cu concentration (hereinafter, referred to as a high concentration layer) appears at a small distance from the copper / polyimide interface. Exists.

  On the other hand, FIG. 2B is a graph showing the relationship between the thickness of the high concentration layer and the thickness of the polyimide layer 4. From this figure, it can be seen that when the thickness of the polyimide layer 4 is 6.5 μm, the thickness of the high-concentration layer increases rapidly, and below that, the high-concentration layer is hardly formed. From this, it can be seen that in the present example in which the formed film thickness of the polyimide layer 4 is set to 6.5 μm or less, the high concentration layer is hardly formed.

  The region where Cu is present at a high concentration is a cause of a decrease in mechanical strength of the polyimide film in the vicinity of the Cu conductor pattern, and it is necessary to eliminate the high concentration layer to prevent the mechanical strength from decreasing. Therefore, it is desirable that at least the thickness of the polyimide film formed on the wiring be 6.5 μm or less. By doing so, the vaporization time of the organic solvent can be reduced. If the existence time of the organic solvent is short, the diffusion of Cu into the polyimide film can be suppressed, and the formation of a high-concentration layer of Cu in the vicinity of the interface with Cu can be prevented. And a decrease in mechanical strength can be prevented.

(2) Prevention of cracks generated in polyimide film during production of wiring structure Next, means for preventing cracks will be described. As described above, cracks may occur in the polyimide film in the production of the wiring structure. For example, as shown in FIG. 8A, a via wiring 3 is formed to connect a wiring 2 formed in parallel with the substrate 1 to a wiring in an upper layer, and is insulated as shown in FIG. 8B. Polyimide 4 is formed as a film. Next, as shown in FIG. 8 (c), the polyimide 4 is polished to flatten the insulating film, and when the via wiring 3 is caught, a crack is generated around the via wiring 3, and the wiring is further formed thereon. However, even if an attempt is made to do so, the wiring may be broken, resulting in a failure. The reason why cracks occur is that stress is generated between the substrate and the polyimide or between the substrate and the metal based on the difference in their thermal expansion coefficients.

  This crack can be prevented by reducing the film stress acting on the polyimide film. Here, the reason why the occurrence of cracks can be prevented by reducing the film stress will be considered with reference to FIG.

  When the polyimide film 4 is polished to obtain a flat insulating film 4 in which the upper surface of the via wiring 3 is exposed as shown in FIG. 8C, cracks may be generated around the via wiring 3. This is because a stress is generated between the substrate 1 and the polyimide 3 based on the difference between their thermal expansion coefficients. This stress is not a problem before the polyimide film 4 is polished (shown in FIG. 8B) because the polyimide 4a on the via wiring 3 is connected. However, this connection is lost after polishing, so that the film stress acts as a force to tear the polyimide around the via wiring. Cracks are considered to be generated by this force. This force to tear the polyimide film 4 cannot be prevented even if the via wiring is changed from a square shape to a round shape, and it is considered that a fundamental solution is difficult unless the film stress itself is reduced.

  Therefore, in the present invention, in order to reduce the film stress, the insulating layer is formed of a first insulating film made of polyimide having low reactivity with copper and a second insulating film made of polyimide having low thermal expansion. It is desirable to have at least two layers. By forming a first insulating film on the wiring layer and further forming a second insulating film on the first insulating film to form one polyimide insulating layer as a whole, in the present invention, It is possible to reduce the thermal stress applied to the directly formed portion of the polyimide layer. Thereby, generation of cracks after polishing is suppressed.

  In order to reduce the stress acting on the polyimide film, a low thermal expansion polyimide is used in the present invention. As a result, stress can be reduced and cracks can be prevented. The stress at that time is desirably 35 MPa (megapascal) or less for the entire insulating film. In order to achieve this low stress, it is necessary that the ratio of the film thickness of the low thermal expansion polyimide to the entire insulating film is 50% or more. This is because while the film stress of the non-low thermal expansion polyimide is about 45 MPa, the film stress of the low thermal expansion polyimide is often 25 MPa or less, and it is almost additive to the film stress of the composite film obtained by laminating them. This is because sex is established.

  As described above, in the first embodiment of the present invention, a polyimide precursor having low reactivity with Cu is used as the polyimide precursor that directly contacts the Cu surface in forming the insulating layer, and the second embodiment of the present invention is used. In each of the embodiments, the polyimide precursor composition containing a basic compound is used. Therefore, in any of the embodiments, the elution of Cu is suppressed when the polyimide precursor is cured by heating. Therefore, the polyimide is excellent in thermal, electrical, and mechanical properties without deterioration of the polyimide, and excellent in the interfacial adhesion between Cu and the polyimide.

  Further, in the present invention, when forming the via wiring, the stress is reduced by forming an insulating layer of polyimide having a low thermal expansion. Accordingly, it is possible to provide a multilayer wiring structure which does not cause cracks in the polyimide film and has high reliability as a whole wiring substrate and a low-cost manufacturing method thereof.

Action

  Next, the method for suppressing the reaction between copper and the polyimide precursor in the present invention will be described in detail. In the present invention, in a wiring structure having a wiring layer and an insulating layer, at least a part of the wiring of the wiring layer is made of copper, and the insulating layer has a repeating unit represented by the following general formula (Formula 1). A wiring structure comprising a polyimide having the same is provided.

Here, R1 is

And R2 is a divalent organic group containing an aromatic ring. Since the polyamic acid, which is a precursor of this polyimide, has a low acidity, elution of copper can be suppressed by using the precursor of this polyimide. R2 is a divalent organic group containing an aromatic ring,

It is preferable to use at least one selected from Since R2 hardly affects the acidity of the polyimide precursor of the general formula (Chemical Formula 1), a group that gives good thermal and mechanical properties to the polyimide which is a thermosetting product of the polyimide precursor may be arbitrarily used. Can be. The weight average molecular weight of the polyamic acid and the polyimide used in the present invention is preferably 20,000 or more from the viewpoint of mechanical properties, and is usually about 20,000 to 100,000.

  The elution of copper can also be suppressed by including a basic compound in the polyimide precursor composition. This is because the basic compound neutralizes the carboxyl group of the polyimide precursor, thereby lowering the acidity of the entire system and, as a result, inhibiting the reaction with copper. In addition, the amount of the basic compound is desirably not less than an amount capable of substantially neutralizing the carboxyl group of the polyimide precursor, but is further increased to such an extent that the stability of the solution of the polyimide precursor is not significantly impaired. It may be added. An excessively added amount acts to further reduce the acidity of the entire system, and the effect of further suppressing the reaction with copper increases.

As this base compound, neutralizes the carboxyl group of the polyimide precursor, and does not significantly impair the stability of the polyimide precursor. Anything that does not significantly impair can be used. The basic compound is preferably at least one amine compound selected from the following (Chem. 4).

  In particular, when the basic compound is the amine compound of the above formula (4), when the polyimide is formed from the polyimide precursor by heating, finally, most of the compound is evaporated, decomposed, dissipated, and hardly remains in the polyimide. In addition, excessive addition can be performed without any problem. Therefore, the amount of the basic compound is desirably 1 equivalent or more per equivalent of the polyimide precursor. The equivalent of the polyimide is an amount obtained by calculating one valence per carboxyl group, and the equivalent of the basic compound is one equivalent to a reaction site when acid-base interaction with an acid is considered. Is calculated as a single value.

  In addition, if a polyimide precursor composition containing the polyimide precursor represented by the above-mentioned general formula (Formula 1) and the above-mentioned basic compound is used for forming the insulating film, the polyamide itself has a low acidity. By further neutralizing the carboxyl group of the acid, the acidity of the entire system can be further reduced, which is particularly effective for suppressing the elution of copper.

In addition, the mechanical strength of the polyimide film increases as the film stress of the insulating film decreases, so that the reaction between the polyimide and Cu is prevented, and at the same time, the mechanical strength of the polyimide film is reduced by reducing the film stress of the entire polyimide insulating film. It is effective in suppressing the decrease. Therefore, in the present invention, in a wiring structure having a wiring layer and an insulating layer, at least a part of the wiring of the wiring layer is made of copper, and the insulating layer is a first insulating film formed on the wiring layer. And a second insulating film formed on the first insulating film, wherein the first insulating film is formed of the polyimide precursor composition (polyimide represented by the general formula (Formula 1)) And / or a basic compound), and the second insulating film is made of a second polyimide having a smaller coefficient of thermal expansion than the first polyimide. A featured wiring structure is provided. It is preferable that the thickness of the first insulating film is thinner than the thickness of the second insulating film. As described above, by forming the insulating layer as a composite layer including an insulating film made of polyimide having low thermal expansion, the film stress of the entire insulating layer can be reduced.

  Note that it is preferable to use a polyimide having a repeating unit represented by the above general formula (Formula 1) as the first polyimide, and the thickness of the first insulating film is to be 6.5 μm or less. desirable. Further, the thickness of the second insulating film is desirably thicker than the first insulating film, and more desirably from 6.5 μm to 20 μm.

  Note that, as the low thermal expansion polyimide used for the second insulating film to achieve low stress, a polyimide having good adhesion to a metal layer or polyimide formed thereover is desirable.

  For example, a first example of the second polyimide has a repeating unit represented by the following general formula (Formula 5) and a repeating unit represented by the following (Formula 6) and is included in one molecule. When the sum of the number of repeating units represented by the general formula (Formula 5) and the number of repeating units represented by the general formula (Formula 6) is set to 100, the repetition represented by the general formula (Formula 5) A polyimide in which the number of units is less than 95 and the number of repeating units represented by the general formula (Formula 6) is 5 or more is given.

(Wherein, R3 is the following (Chemical Formula 7)

And at least one tetravalent organic group selected from the group consisting of

And at least one divalent organic group selected from the group consisting of

At least one divalent organic group selected from )
This polyimide is obtained by heating and curing a precursor of this polyimide. The polyamic acid of this polyimide precursor has a repeating unit represented by the following general formula (Chemical Formula 18) and a repeating unit represented by the following (Chemical Formula 19), and is contained in one molecule. When the sum of the number of repeating units represented by Formula (Formula 18) and the number of repeating units represented by Formula (Formula 19) is 100, the number of repeating units represented by Formula (Formula 18) The polyamic acid has a number of less than 95 and the number of repeating units represented by the general formula (Formula 19) is 5 or more.

  Further, the polyamic acid is obtained by mixing an acid dianhydride of the following general formula (Chemical Formula 20) and a diamine mixture composed of two kinds of diamines and curing by heating. The polyimides represented by (Chem. 5) and (Chem. 6) are obtained. Here, the diamine mixture is a mixture of less than 95% (molar ratio) of a diamine of the following general formula (Formula 21) and 5% or more (molar ratio) of a diamine of the following general formula (Formula 22). In addition, R3 to R5 in (Chem. 18) to (Chem. 22) are the same as those in the above-described general formulas (Chem. 5) and (Chem. 6).

  A second example of the second polyimide includes a repeating unit represented by the following general formula (Chemical Formula 10) and a repeating unit represented by the following (Chemical Formula 11) and contained in one molecule. When the sum of the number of repeating units represented by the formula (Formula 10) and the number of repeating units represented by the formula (Formula 11) is 100, the number of repeating units represented by the formula (Formula 10) The second polyimide has a number of 85 to 50, and the number of repeating units represented by the general formula (Formula 11) is 50 to 15.

(Wherein, R3 is the following (Chemical Formula 7)

Wherein R6 is at least one tetravalent organic group selected from

Wherein R7 is at least one divalent organic group selected from

At least one divalent organic group selected from )
This polyimide is obtained by heating and curing a precursor of this polyimide. The polyamic acid of the polyimide precursor has a repeating unit represented by the following general formula (Formula 23) and a repeating unit represented by the following (Formula 24), and is contained in one molecule. When the sum of the number of repeating units represented by Formula (Formula 23) and the number of repeating units represented by Formula (Formula 24) is 100, the number of repeating units represented by Formula (Formula 23) The polyamic acid has a number of less than 95 and the number of repeating units represented by the general formula (Formula 24) is 5 or more.

Further, the polyamic acid is obtained by mixing an acid dianhydride of the above general formula (Chemical Formula 20) and a diamine mixture composed of two kinds of diamines and curing by heating. Polyimides represented by (Chem. 10) and (Chem. 11) are obtained. Here, the diamine mixture is a mixture of less than 95% (molar ratio) of a diamine of the following general formula (Chemical Formula 25) and more than 5% (molar ratio) of a diamine of the following general formula (Chemical Formula 26). Incidentally, R3 in (Chemical Formula 20), (Chemical Formula 25) and (
R6 and R7 in Chemical formula 26) are the same as those in the above general formulas (chemical formula 10) and (chemical formula 11).

  Of the above two examples of low thermal expansion polyimides, in the first example, an organic group component having a methyl group in an aromatic ring is introduced into a polyimide molecular chain to bond to an upper layer metal or a polyimide formed in an upper layer. Secure. This is because the organic group having a methyl group in the aromatic ring can create an extremely active surface state by a treatment such as ashing with oxygen or sputtering using argon ions, and as a result, the above-mentioned adhesion is secured. can do. The ratio is required to be 5% or more in molar ratio, and a sufficient effect can be achieved. In the second example, an organic group component having an ether bond is introduced into a polyimide molecular chain to secure adhesion to a metal or polyimide formed on an upper layer. The organic group component having an ether bond is originally excellent in adhesion to the upper metal layer and the polyimide formed in the upper layer, but on the other hand, it becomes a hindrance factor for the polyimide to have low thermal expansion. Therefore, low stress and high adhesiveness described above can be achieved in a range limited to a certain ratio as described above.

  All the above-mentioned polyimide precursors can be easily obtained by stirring a necessary tetracarboxylic dianhydride component and a diamine component in a polar organic solvent to cause a polymerization reaction to generate a polyimide precursor (polyamic acid). Can be. Here, it is desirable that the amounts of the acid dianhydride and the diamine are almost stoichiometrically equivalent.

  Examples of usable polar organic solvents include 1-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, hexamethylphosphoramide, tetramethylenesulfone, p-chloropheno- , P-bromophenol and the like, and at least one or more of these can be used, but are not necessarily limited to these, and any one may be used as long as the polyimide precursor is dissolved. Can be used.

  Furthermore, in order to obtain a polyimide precursor composition containing a basic compound, after synthesizing the polyimide precursor by the above method, a basic compound may be added to the obtained reaction solution and stirred.

  The present invention also provides a method for manufacturing a wiring structure. Here, the wiring structure refers to an electronic device having a wiring and an insulating layer, and includes a semiconductor integrated circuit element, a wiring substrate, a thermal head, a magnetic head, and the like. Here, as an example, a method of manufacturing a thin film / thick film composite multilayer wiring board will be described.

  First, a conductor pattern is formed on the surface of a ceramic substrate having a wiring to form a wiring layer. A well-known method such as a photolithography method or an additive method can be used for forming the conductor pattern. It is preferable that the copper wiring layer includes a conductor layer made of a material selected from Cr, Ti, Ta, W, Nb, and TiW on at least one of the upper layer and the lower layer.

  Next, a film of the polyimide precursor composition is formed on the surface of the wiring layer. As a film forming method, a known method such as spin coating can be used. The insulating film made of polyimide is obtained by curing the film of the polyimide precursor composition by heating. The polyimide precursor composition desirably contains at least one of the polyimide precursor represented by the above general formula (Formula 1) and a basic compound. Further, in order to shorten the existence time of the solvent, the thickness of the polyimide precursor composition is desirably set to a thickness such that the thickness of the insulating film obtained by heating and curing becomes 6.5 μm or less.

  When the polyimide precursor composition film is cured by heating, an insulating film made of polyimide is obtained. In the step of heating and curing the polyimide precursor, the oxygen concentration in the atmosphere is desirably 0.5 v / v% or less, and more desirably in an oxygen-free atmosphere. Note that a step of forming a film made of polyimide having low thermal expansion on the surface of the insulating film obtained in this manner to make the insulating film a composite film may be provided.

  Further, by repeating the step of forming the conductor wiring on the surface of the insulating film and the step of further forming the insulating film on the conductor wiring in this order, a multilayer wiring board having a plurality of wiring layers can be obtained.

Next, an example of a basic manufacturing process will be described. FIG. 10 shows the basic structure of a thin film wiring board. As an example of the basic manufacturing process of a thin film wiring board,
(A) When an insulating layer 104 made of polyimide is formed on a wiring layer 102 made of a Cu conductor as shown in FIG.
(B) As shown in FIG. 10 (b), when an insulating layer 104 made of polyimide is formed on the wiring layer 102 made of Cu conductor and the via 106, and
(C) As shown in FIG. 10C, when the insulating layer 104 made of polyimide is formed on the wiring layer 103 made of a Cu conductor existing on the through hole 100 in the insulating layer 107,
And the like.

  First, the manufacturing process of the structure shown in FIG. A Cu film is formed on the insulating layer 101 using a normal sputtering method, and the Cu film is processed into a predetermined pattern shape using a known photo-etching method to form a wiring layer 102 made of Cu. I do. A polyimide precursor composition is formed on the obtained wiring layer 102 by spin coating or the like, and is cured by heating to form a polyimide layer 104. Thus, the wiring board having the structure shown in FIG. 10A is obtained.

  Next, a manufacturing process of the structure shown in FIG. On the insulating layer 101, a Cu film is formed by a normal sputtering method. A resist pattern for plating is formed on the surface of the Cu film by a known process, and a via wiring 106 made of a Cu conductor is formed by a plating method. Next, after removing the plating resist, the wiring layer 102 having the via pad 105 and the wiring 102a is formed by a known photoetching method. Next, a polyimide precursor composition is formed on the wiring layer 102 by spin coating or the like, and is cured by heating to form the polyimide layer 4. Thus, a wiring board having the structure shown in FIG. 10B is obtained.

  Next, a manufacturing process of the structure shown in FIG. A Cu film is formed on the insulating layer 101 using a normal sputtering method, and is processed into a predetermined pattern shape using a known photoetching method to form a wiring layer 2 made of Cu. Next, using a photosensitive polyimide precursor composition, an insulating layer 107 provided with a through hole 100 is formed by a well-known photolithography method. Next, a Cu film is formed using a normal sputtering method, and is processed into a predetermined pattern shape using a known photoetching method to form a wiring layer 103 made of a Cu conductor. Finally, a polyimide precursor composition is formed on the wiring layer 103 by spin coating or the like, and is cured by heating to form the polyimide layer 4. Thus, a wiring board having the structure shown in FIG. 10C is obtained.

  In any of the cases (a) to (c) described above, when the polyimide layer 4 is formed on the conductor (the wiring layers 102 and 103 and the via wiring 106), the formation of the polyimide layer 104 includes a polyimide precursor. A polyimide precursor composition is used. As the polyimide precursor, a polyimide precursor represented by the above general formula (Formula 1) is used, or a basic compound is further included in the composition. .

  In each of the cases (a) to (c) described above, it is desirable that the film thickness d of the polyimide layer 104 be 6.5 μm or less. However, in the cases of (b) and (c), the thickest part of the polyimide layer 4 is the pattern edge of the Cu conductor pattern. Therefore, it is desirable that the thickness d 'of the pattern edge portion is also set to 6.5 μm or less. However, since the difference between the thickness d of the flat portion and the thickness d ′ of the pattern edge portion is usually small, a sufficient effect can be obtained by setting the thickness d of the flat portion to 6.5 μm or less.

  The film thickness d of the insulating layer 104 is desirably set to 6.5 μm or less. However, when the film thickness d of the insulating layer 104 needs to be larger than 6.5 μm, the insulating layer 104 may have a multilayer structure of two or more layers. That is, if the thickness d of the layer directly formed on the wiring is set to 6.5 μm or less and an insulating layer is further formed on the surface of this layer, the entire thickness of the insulating layer 104 is made larger than 6.5 μm. Even so, a sufficient effect can be obtained.

  In any of the cases (a) to (c) described above, the insulating layer 101 may be made of any of a polymer material and a ceramic material. The wiring layer 102 made of a Cu conductor may have a wiring pattern formed by other methods, such as printing or an additive method, without using the above-described photolithography method. Further, in the above-described example, the Cu film is formed by a sputtering method, but a plating method or the like may be used. In the above-described example, the via 6 is formed by plating. However, the via 6 may be formed by forming a Cu film by a sputtering method and processing the film by well-known photo etching. The formation of the through hole is not limited to the method using the photosensitive material as described above, but may be performed by another method such as mechanical perforation.

  Further, the film formation of the polyimide precursor composition is not limited to application by spin coating or the like, and may be performed using another method such as placing a sheet made of the polyimide precursor composition. The heat curing of the polyimide precursor is desirably performed in an atmosphere containing less oxygen, such as in a nitrogen stream or in a vacuum.

  Further, in the above-described example, the wiring layers 102 and 103 are made of Cu alone, but Cr, Ti, and Ta are formed on the upper and lower surfaces of the wiring layers 102 and 103 in order to secure adhesion to the insulating layer 104. , W, Nb, and TiW may be formed. In this case, the effect of the present invention appears on the side wall of the Cu conductor pattern.

  Next, an example of a manufacturing process for forming a multilayer wiring board will be described. FIG. 11 is a cross-sectional view of a multilayer wiring board in the course of manufacturing when the thin-film multilayer wiring 112 is formed on the ceramic substrate 111 having the conductor wiring 119. The multilayer wiring board shown in FIG. 11 includes a ceramic substrate provided with conductor wiring 119, three insulating layers 110, a matching layer 114 for matching the thick film substrate 101 and the thin film multilayer wiring 102, and a planar wiring 116. , Via wiring 113, and via pad 115. Each insulating layer 110 includes a first polyimide film 117 and a second polyimide film 118, respectively. The multilayer wiring board is manufactured, for example, by the following steps (1) to (12).

(1) The ceramic substrate 111 is cleaned and oxygen plasma processing is performed to clean the substrate surface.

(2) After cleaning the substrate surface by reverse sputtering, Cr, Cu, and Cr are sequentially formed on the surface of the ceramic substrate 111 by a sputtering method to form a Cr / Cu / Cr laminated film. Here, Cr / Cu / Cr represents a structure in which a Cr film, a Cu film, and a Cr film are sequentially laminated in this order.

(3) A resist pattern is formed on the surface of the Cr / Cu / Cr laminated film by a known photolithography method, and the uppermost Cr film of the Cr / Cu / Cr laminated film is patterned by selective etching, followed by electroplating. To form a via 113a made of a Cu conductor. Further, the pattern of the Cr / Cu / Cr laminated film is separated by a well-known photo-etching method to form a pattern of the matching layer 114.

(4) The first polyimide precursor composition is applied by spin coating so as to cover the exposed portion of the surface of the ceramic substrate 111, the matching layer 114, and the via 113a, and is cured by heating to form the first insulating layer 110a. The first polyimide film 117a is formed. Here, the first polyimide precursor composition desirably contains, as the polyimide precursor, a polyimide precursor represented by the above general formula (Formula 1) or a basic compound. Further, it is desirable that the thickness of the first polyimide film 117a be 6.5 μm or less. By doing so, Cu diffusion into the first polyimide film 117a can be prevented.

(5) Next, the second polyimide precursor composition is applied to the surface of the first polyimide film 117a by spin coating, and is heated and cured to form the second polyimide film 118a of the first insulating layer 110a. . The thickness of the second polyimide film 118a may be determined according to the required thickness of the first insulating layer 110a. The second polyimide film 118a may be made of the same material as the first polyimide film 117a, but may be different, and it is preferable to use polyimide having a small thermal expansion. This low thermal expansion polyimide includes a polyimide having a repeating unit represented by the above general formula (Chem. 5) and a repeating unit represented by the above (Chem. 6), and a polyimide represented by the above general formula (Chem. 10). At least one of polyimide having a repeating unit to be performed and a repeating unit represented by the following formula (11) is preferable. Although the insulating layer 110 is a composite film of the two insulating films 117 and 118 here, an insulating film may be further formed on the surface of the second polyimide film 118 to form a composite film of three or more layers.

(6) The surface of the obtained first insulating layer 110a is polished by a mechanical polishing method such as a tape wrap method or a polishing method, and cueing of the via 113a and flattening of the insulating layer 110a are performed. The surface of the surface 110a and the exposed portion of the via 113a are cleaned and the oxygen plasma treatment is performed to clean the surface.

(7) After forming a Cr / Cu / Cr laminated film on the surface of the insulating layer 110a and the exposed portion of the via 113a in the same manner as in the above (2) and (3), after patterning the uppermost Cr film, Cu is grown using electroplating, a via 113b made of Cu is formed, and a pattern of the Cr / Cu / Cr laminated film is separated to obtain a via pad 115a and a wiring layer 116a.

(8) In the same manner as in (4) above, the first polyimide precursor composition is applied by spin coating so as to cover the surface of the first insulating layer 110a and the planar wiring 116a, the via pad 115a, and the via 113b. Then, by heating and curing, a first polyimide film 117b of the second insulating layer 110b is formed. As in the case of the first insulating layer 110a, here, the first polyimide precursor composition contains, as the polyimide precursor, a polyimide precursor represented by the above general formula (Formula 1), Alternatively, it is desirable to include a basic compound. Further, it is desirable that the thickness of the first polyimide film 117b is also set to 6.5 μm or less.

(9) Next, in the same manner as in the above (5), a second polyimide film 118b is formed on the surface of the first polyimide film 117b. Thus, the second insulating layer 110b is formed.

(10) The surface of the obtained second insulating layer 110b is polished in the same manner as in the above (6), and the cue and flattening of the via 113a and the surface cleaning are performed. Similarly, the via 113c, the via pad 115b, and the wiring layer 116b are formed.

(11) Further, in the same manner as in (8) to (9) above, the third insulating layer 110c is formed so as to cover the surface of the second insulating layer 110b and the plane wiring 116b, the via pad 115b, and the via 113c. A first polyimide film 117c and a second polyimide film 118c are formed to obtain a third insulating layer 110c.

(12) As described above, the multi-layer wiring board in the process of manufacturing shown in FIG. 3 is manufactured. Further, by repeating the steps (10) to (11), the number of stacked wiring layers can be increased. When a desired lamination is obtained, finally, the surface is polished and cleaned, and then a surface electrode (not shown) for connection to a semiconductor chip or the like is formed, thereby obtaining a multilayer wiring board.

  In a manufacturing method conventionally used, in a polishing step corresponding to the above (6) and (10), a portion corresponding to the first insulating layer 110a around the via 113a and a second portion around the via 113b. In some cases, cracks were observed in portions corresponding to the insulating layer 110b. However, according to the first aspect of the present invention, the first polyimide film 117 is formed by using the polyimide precursor composition containing the polyimide precursor represented by the above general formula (Formula 1). , To suppress the occurrence of cracks. Further, according to the second aspect of the present invention, cracks are suppressed by forming the first polyimide film 117 using the polyimide precursor composition containing a basic compound. Furthermore, in the third aspect of the present invention, the occurrence of cracks is suppressed by setting the thickness of the first polyimide film 117 to 6.5 μm or less.

  Next, an example of a method of manufacturing a thick-film / thin-film composite wiring board in which thin-film metallization for forming thin-film wiring and I / O (input / output) pins on both surfaces of a thick-film multilayer board will be described with reference to FIG. explain.

  The wiring board shown in FIG. 12 has a metal layer pattern (matching layer) 114 for matching the thick film substrate 111 and the thin film wiring, a via 54, , A metal layer pattern (surface electrode) 127 for connection to a semiconductor chip or the like, and an insulating layer 110. The insulating layer 110 includes a first polyimide film (insulating film) 117 and a second polyimide film (insulating film) 118. On the other surface of the ceramic substrate 111, a metal layer pattern 121 composed of three layers for dispersing stress at the time of attaching input / output (I / O) pins and a metal layer pattern ( A surface electrode) 123, I / O pins 126 connected to the surface electrode 123 via solder 125, and a first insulating layer 122 and a second insulating layer 124.

  This wiring board can be manufactured by the following steps (21) to (30). Here, the surface on the side where the I / O pins 126 are located is referred to as a back surface, and the opposite surface is referred to as a front surface.

(21) After cleaning the ceramic substrate 111 and cleaning the front and back surfaces of the ceramic substrate 111 by oxygen plasma treatment, the Cr / Cu / Cr surface is formed on the front and back surfaces of the ceramic substrate 111 in the same manner as in (2) above. A laminated film is formed, and the surface of the backside Cr / Cu / Cr laminated film is covered with a protective film (not shown) made of a polyimide film or the like.

(22) A via 113 made of Cu is formed on the surface of the Cr / Cu / Cr laminated film on the surface side of the ceramic substrate 111 in the same manner as in (3) above, followed by pattern separation and a metal layer serving as a matching layer. A pattern (matching pad) 114 is obtained.

(23) A first polyimide precursor is applied in the same manner as in (4) above so as to cover the surface of the ceramic substrate 111 exposed in the process of (22), the matching pad 114 and the via 113, and is heat-cured. Thus, a first polyimide film 117 is formed.

(24) Next, the second polyimide precursor composition is applied to the surface of the first polyimide film 117 in the same manner as in the above (5), and is cured by heating to form the second polyimide film 118. As a result, an insulating film 110 having a two-layer structure is obtained. Note that the thickness of the second polyimide film 118 may be determined according to the required thickness of the insulating layer 110 formed on the surface.

(25) After removing the protective film (not shown) formed on the back surface by oxygen ashing or the like, pattern separation of the Cr / Cu / Cr laminated film on the back surface is performed by a known photo etching method. Then, a metal layer pattern 121 is formed.

(26) A polyimide precursor composition is applied and heated and cured in the same manner as in (24) above so as to cover the surface of the ceramic substrate 111 and the metal layer pattern 121 exposed in the step (25). A first insulating layer 122 on the back side is formed.

(27) A through hole reaching the metal layer pattern 61 is formed in the first insulating layer 122 by a known photoetching method or a laser ablation method, and the surface of the metal layer pattern 61 exposed by reverse sputtering and the first polyimide are formed. After cleaning the surface of the film 122, a Cr film is formed by a sputtering method or the like, and a thin film layer made of a metal (Ni or Ni-W) connectable to solder is formed on the surface of the Cr film. I do. Next, this metal film (Cr film and a film of a metal connectable to solder) is patterned by a well-known photo-etching method to obtain a surface electrode 123.

(28) A second polyimide precursor composition is applied to the surfaces of the surface electrode 123 and the first insulating layer 122 by spin coating, and cured by heating to form a second insulating layer 124.

(29) The surface of the insulating layer 110 on the front side is polished by using a mechanical polishing method such as a tape wrap method or a polishing method, and cueing and flattening of the via 113 are performed. After the surface is cleaned and the surface on the front side is further cleaned by reverse sputtering, a metal (Ni-W or Ni-W or Ni ) Are sequentially formed. Then, the surface electrode 127 is formed by patterning the Cr film and a metal film connectable to the solder by a known photo-etching method.

(30) Through holes (through holes) reaching the front surface electrode 123 on the rear surface side are made in the second insulating film 124 on the rear surface side by a laser ablation method or the like, and a part of the surface of the rear surface side front electrode 123 is exposed. Thereafter, an Au layer (not shown) is provided on the exposed portions of the front and back surface electrodes 127 and 123 by displacement plating or the like. Finally, the I / O pins 126 are connected to the front surface electrode 123 on the back surface using the solder 125.

  Thus, the wiring substrate shown in FIG. 4 is manufactured. In the above process example, a two-layer insulating layer 110 is formed on the front side, and two single-layer insulating layers 122 and 124 are formed on the rear side.

  Among the above steps, the first polyimide film 117 formed on the front side (formed by step (23)) and the first insulating layer 122 formed on the back side (formed by step (26)) Formed using the first polyimide precursor composition. Here, the first polyimide precursor composition desirably contains, as the polyimide precursor, a polyimide precursor represented by the above general formula (Formula 1) or a basic compound. Further, the same polyimide precursor composition may be used for forming the first polyimide film 117 and the formation of the first insulating layer 122, or different compositions may be used. Note that the thickness of each of the first polyimide film 117 and the first insulating film 122 is desirably 6.5 μm or less. According to the present invention, it is possible to prevent Cu from diffusing into the first polyimide film 117 and the first insulating layer 122, thereby avoiding deterioration in heat resistance and reduction in mechanical strength.

  Actually, cracks and the like have been found in the insulating layer 110 around the vias 113 in the polishing step corresponding to the step (29), but cracks do not occur in the above steps to which the present invention is applied. Note that the number of the insulating layers 110 on the front side may be three or more.

  The second polyimide film 118 formed on the front side (formed by the step (24)) and the second insulating layer 124 formed on the back side (formed by the step (28)) It is formed using a polyimide precursor composition. The second polyimide precursor composition may be the same as the first polyimide precursor composition, but may be different. The formation of the second polyimide film 118 and the formation of the second insulating layer The same polyimide precursor composition or different compositions may be used for the formation of 124, but it is preferable to use polyimide having little thermal expansion in each case.

  This low thermal expansion polyimide includes a polyimide having a repeating unit represented by the general formula (Chemical Formula 5) and a repeating unit represented by the chemical formula (Chemical Formula 6), and a polyimide represented by the general formula (Chemical Formula 10). At least one of polyimide having a repeating unit to be performed and a repeating unit represented by the following formula (11) is preferable.

  Next, embodiments of the present invention will be described with reference to the drawings. In each of the synthesis examples described below, an E-type viscometer (DV □ -E type digital viscometer (manufactured by Tokimec Co., Ltd.)) was used for measuring the viscosity.

First, a polyimide precursor was synthesized, and a basic compound was appropriately added to the reaction solution to obtain a polyimide precursor composition as a varnish in which the reaction solvent remained (Synthesis Examples 1 to 10, 14 to 16). Table 2 shows the solid content concentration and viscosity of the obtained varnish.

The abbreviations of the compounds used in Table 2 are:
BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride ODPA: 3,3 ′, 4,4′-oxydiphthalic dianhydride TPDA: p-terphenyl-3,3 ″, 4 4 "-tetracarboxylic dianhydride m-TPDA: m-terphenyl-3,3", 4,4 "-tetracarboxylic dianhydride DDE: 4,4'-diaminodiphenylether BAPB: 4, 4'-bis (4-aminophenoxy) biphenyl BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane HFBAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoro Propane PDA: p-phenylenediamine DMBP: 3,3'-dimethyl-4,4'-diaminobiphenyl DAPM: 3-dimethylaminopropyl methacrylate 4-MPY: - methylpyridine PMDA: pyromellitic acid dianhydride BTDA: 3,4,3 ', showing the 4'-benzophenone tetracarboxylic dianhydride.

<Synthesis example 1>
At room temperature under a nitrogen stream, 30.0 g (0.15 mol) of 4,4′-diaminodiphenyl ether as a diamine component was added to N, N-dimethylacetamide (DMAc) and 1-methyl-2-pyrrolidone (NMP). Was dissolved in 420 g of a 1: 1 mixed solvent with stirring. Subsequently, 44.1 g (0.15 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was mixed in as an acid dianhydride, and dissolved while stirring under a nitrogen stream (total solid content concentration). 15 wt / wt%). The viscosity of the reaction solution reached 600 poise 6 hours after the addition of the acid dianhydride. Further, this solution was heated in a temperature range of 55 to 70 ° C. for about 6 hours to adjust its viscosity to 30 poise, thereby obtaining a polyimide precursor composition (varnish number 1 in Table 2) used when manufacturing a wiring structure. .

<Synthesis Example 2>
To the polyimide precursor composition obtained in the same manner as in Synthesis Example 1, 51.4 g (0.30 mol) of 3-dimethylaminopropyl methacrylate was added as a basic compound. After the addition, the viscosity of the solution increased to 55 poise. Next, the solution was heated at 35 ° C. for 4 hours to have a viscosity of 40 poise to obtain a polyimide precursor composition (varnish number 2 in Table 2) used when manufacturing a wiring structure.

<Synthesis examples 3 to 10, 14 to 15>
Using the components shown in the columns of varnish numbers 3 to 10 and 14 to 15 in Table 2, a polyimide precursor was synthesized in the same manner as in Synthesis Example 1 or Synthesis Example 2, and the solid content and the solid content shown in Table 2 were obtained. A polyimide precursor composition having a viscosity (varnish numbers 3 to 10, 14 to 16) was obtained. In these synthesis examples, the amounts of the acid dianhydride and the diamine were each 0.15 mol, and when the basic compound was added, the amounts were 0.30 mol, as in Synthesis Examples 1 and 2.

<Comparative synthesis example>
A polyimide precursor was synthesized in the same manner as in Synthesis Example 1 using 0.15 mol of each of the raw materials shown in Table 3 to obtain a polyimide precursor composition (varnish numbers 11 to 13 in Table 3). In addition, in Table 3, the compound name was described using the same abbreviation as Table 2.

<Experimental example 1>
30 g of a polyimide precursor varnish of varnish number 1 in Table 2 (synthesized in Synthesis Example 1) was placed in a 200-ml round-bottom flask, and atomized copper (particle size: about 15 μm, purity: 99.999 wt / wt%) was added in an amount of 0.1 g. 3 g was added, and the mixture was stirred at a speed of 300 rpm for 30 minutes under a nitrogen stream. The temperature at the time of stirring was set to three types of 23 ° C, 50 ° C, and 80 ° C. At this time, when the oxygen concentration inside the flask was measured with an oxygen concentration meter, all were about 500 ppm (vol / vol).

  Next, the varnish was pressure-filtered with nitrogen through a filter having a pore size of 3 μm to completely remove unreacted copper from the varnish. The filtered varnish was spin-coated on a glass substrate, and prebaked at 130 ° C. for 30 minutes under a nitrogen stream, after which the polyimide precursor film formed from the varnish was peeled off. Next, the polyimide precursor film was mounted on a frame, baked at 200 ° C. for 30 minutes under a nitrogen stream, and baked at 350 ° C. for 30 minutes to obtain a polyimide film in which copper was uniformly dispersed. The concentration of copper present in the film was quantified by a fluorescent X-ray method. The result is shown in FIG. This indicates the amount of copper eluted in the varnish as a result of the reaction between the varnish, which is a polyimide precursor, and copper. From the results of this experimental example, as shown in this figure, copper hardly eluted into the varnish even when the temperature was increased, and the use of a low acidity polyimide precursor and a low oxygen concentration atmosphere were It turns out that it is extremely effective in suppressing the reaction between the body and copper.

<Experimental example 2>
The same experiment as in Experimental Example 1 was performed except that a varnish containing a basic compound, which is shown as a varnish number 2 in Table 2, was used. The result is shown in FIG. As shown in this figure, almost no copper elutes in the varnish even when the temperature rises, and the use of the polyimide precursor with low acidity and the low oxygen concentration atmosphere cause the reaction between the polyimide precursor and copper. It was shown to be extremely effective in deterring. In this example, it can be seen that the reactivity with copper is further suppressed as compared with the case of Experimental Example 1.

<Experimental example 3>
The same experiment as in Experimental Example 1 was performed, except that a varnish containing a basic compound, which is shown as a varnish number 16 in Table 2, was used. The result is shown in FIG. In this experimental example, unlike the experimental example 2, although polyamic acid having a high acidity of the carboxyl group was used, as shown in FIG. 13, almost no copper was eluted in the varnish even when the temperature was increased. However, it can be seen that the reaction between the polyimide precursor and copper was suppressed by the addition of the basic compound and the atmosphere having a low oxygen concentration.

<Comparative experiment example 1>
The same experiment as in Experimental Example 1 was performed except that varnish number 13 in Table 3 was used as the varnish. The result is shown in FIG. As shown in this figure, the amount of copper eluted into the varnish increases with an increase in temperature, and the absolute amount is much larger than that in the above-mentioned Experimental Examples 1 to 3. Therefore, even under an atmosphere having a low oxygen concentration, it is difficult to use a polyimide precursor having a high acidity and to suppress the reaction between the polyimide precursor and copper unless a basic compound for lowering the acidity is added. It is thought to be. Actually, a similar experiment was performed at a lower oxygen concentration and 80 ppm (vol / vol), but the result was almost the same as that in FIG.

<Experimental example 4>
A chromium film having a thickness of 0.05 μm and a copper film having a thickness of 2 μm are sequentially formed on a silicon wafer (4 inches in diameter) by a sputtering method, and a varnish (varnish number 2 in Table 2) is formed thereon. (Prepared in Synthesis Example 2) was spin-coated, charged into a baking furnace at 23 ° C. under a nitrogen stream, heated at a rate of 2 ° C. per minute, and maintained at 400 ° C. for 60 minutes. At this time, the oxygen concentration in the baking furnace was 6 to 10 ppm (vol / vol). The concentration of copper in the taken-out wafer was measured in the depth direction from the polyimide side by SIMS (Secondary Ion Mass Spectrometry). FIG. 5 shows the results. FIG. 5A is a partial cross-sectional view of the measured wafer. This wafer has a chromium layer 54, a copper layer 55, and a polyimide layer 56 on a substrate 53 in this order. FIG. 5B is a graph of a measurement result by the SIMS method. The measurement result of Experimental Example 3 is shown as a curve 51.

  From this figure, it can be seen that, in this experimental example, the copper concentration is kept low up to near the pole interface between polyimide and copper. Further, in this experimental example, particularly in a region where the copper concentration is 4000 ppm (wt / wt) or more near the interface, the copper is present at a high concentration only in an extremely thin thickness of 0.1 μm or less. From these results, not only in the temperature range of room temperature to 80 ° C. as shown in the above-mentioned Experimental Examples 1 and 2, but also in the entire temperature process for forming the polyimide, the atmosphere having a low oxygen concentration and the polyimide precursor having a low acidity were obtained. It can be seen that the use of the body can suppress the reaction between copper and the polyimide and prevent the decomposition of the polyimide.

  It should be noted that even if a heat treatment at 400 ° C. was further added under a nitrogen stream to the wafer manufactured for SIMS in this experimental example, the measurement result by the SIMS method hardly changed. Therefore, from this result, it can be seen that after the polyimide precursor is completely imidized, copper hardly enters the polyimide side.

<Comparative experiment example 2>
The copper concentration of the prepared wafer was measured in the same manner as in Experimental Example 3 except that varnish number 13 was used as the varnish. The result is shown as a curve 52 in FIG. From this figure, it can be seen that when a varnish having a high acidity is used, a large amount of copper is eluted on the polyimide side even when the oxygen concentration is reduced. In particular, in the region where the copper concentration is 4000 ppm (wt / wt) or more in the vicinity of the interface, copper exists over an extremely thick region of about 2 μm, and even in the polyimide surface, copper is 1000 ppm (wt / wt) in most regions. It turns out that it exists in the above high concentration.

  In addition, when a heat treatment at 400 ° C. was further added under a nitrogen stream to the wafer manufactured for SIMS in this comparative experimental example for 10 hours, the polyimide film became extremely brittle, cracks occurred everywhere, Peeling of the film was also observed. Incidentally, the same heat treatment was performed on the varnish of varnish number 13 directly formed on the silicon wafer without forming the copper film, but no significant change such as the brittleness of the polyimide film was found. Accordingly, it can be understood that the cause of the brittleness of the polyimide film and the occurrence of cracks is that a large amount of copper was eluted into the polyimide.

<Experimental example 5>
A chromium film having a thickness of 0.05 μm and a copper film having a thickness of 2 μm were sequentially formed on a silicon wafer (4 inches in diameter) by a sputtering method, and a varnish of varnish number 2 in Table 2 was formed thereon. After spin-coating and throwing into a baking furnace at 23 ° C. under a nitrogen stream, the temperature was raised at a rate of 2 ° C./minute, and after reaching 400 ° C., the temperature was kept for 60 minutes and then taken out. At this time, the oxygen concentration in the baking furnace was adjusted to 4 ppm of 10 ppm (0.001 vol / vol%), 1000 ppm (0.1 vol / vol%), 10,000 ppm (1 vol / vol%), and 20.6 vol / vol% (air). Type. Next, the chromium film on which the copper film and the polyimide film were formed was peeled off from the wafer, and chromium and copper were removed by wet etching from the three-layer film of chromium, copper, and polyimide to obtain a polyimide film. Was.

  The amount of copper contained in the polyimide film thus obtained was quantified by a fluorescent X-ray method. The result is shown as a curve 61 in FIG. As shown in this figure, from this experimental example, it is understood that copper is hardly eluted in the polyimide in the region where the oxygen concentration is low, but when it exceeds 1 vol / vol%, the amount of copper sharply increases. . Therefore, even when viewed over the entire temperature process for forming the polyimide, by using an atmosphere having a low oxygen concentration and a polyimide precursor having a low acidity, it is possible to effectively suppress the reaction between copper and the polyimide. Is possible. FIG. 6 shows that it is effective to keep the oxygen concentration at 0.5 vol / vol% or less in order to practically suppress the reaction between copper and polyimide.

<Comparative experiment example 3>
The same experiment as in Experimental Example 5 was performed, except that varnish number 13 in Table 3 was used as the varnish. The result is shown as a curve 62 in FIG. As shown in this figure, it is understood from this comparative experimental example that when a varnish having a high acidity is used, a large amount of copper is eluted on the polyimide side even when the oxygen concentration is reduced. By the way, in this example, when the atmosphere at the time of baking was air, the polyimide film to be formed was extremely brittle, so it was impossible to peel it off, and it was not possible to quantify copper.

<Experimental example 6>
An electrode was formed of aluminum on the polyimide film produced in Experimental Example 5, and the dielectric constant of the polyimide film was measured. The results are shown in the column of varnish number 2 in Table 4. The relative dielectric constant of polyimide formed by directly applying varnish number 2 on a silicon wafer is 3.1. As shown in the table, from the results of Experimental Example 5, the dielectric constant greatly increases when the oxygen concentration in the bake atmosphere is 1 vol / vol% or more, but is not higher than 1000 ppm (vol / vol). It turns out that it shows the normal value of 1. In the case of a polyimide film formed directly from varnish number 2 on a silicon wafer, a large increase in the dielectric constant was not observed even when baked in air. Elution seems to be the cause. As seen from this example, by using an atmosphere having a low oxygen concentration and a polyimide precursor having a low acidity, it is possible to effectively suppress an increase in the dielectric constant.

<Comparative experiment example 4>
The same experiment as in Example 5 was performed except that varnish number 13 was used as the varnish. The results are shown in the column of varnish number 13 in Table 4. Since the relative dielectric constant of polyimide formed by applying varnish number 13 directly on a silicon wafer is 3.5, the dielectric constant increases from an oxygen concentration of 10 ppm (vol / vol) based on the experimental results shown in this table. It can be seen that when the temperature exceeds 1 vol / vol%, it rapidly increases. The comparison with Example 5 shows that it is difficult to suppress an increase in the dielectric constant when a polyimide precursor having a high acidity is used even when the oxygen concentration in the bake atmosphere is kept low.

<Example 1>
In this example, a varnish of varnish number 1 in Table 2 and a varnish of varnish number 9 in Table 2 were used to fabricate a copper-polyimide multilayer wiring structure. FIG. 1 shows a manufacturing process of a copper-polyimide multilayer wiring structure in this embodiment.

(1) First, a mullite ceramic substrate 11 (127 mm square, 3 mm thickness shown in FIG. 1A) having a tungsten wiring 22 therein was prepared.

(2) A chromium layer (thickness: 0.05 μm) and a copper layer (0.5 μm) are sequentially formed on a surface of the substrate 11 on which a wiring layer is to be formed by a sputtering method as a plating base film. (FIG. 1B).

(3) Next, a positive resist 13 was spin-coated on the electrode layer 12 and heated at 90 ° C. for 30 minutes in a nitrogen atmosphere. At this time, the film thickness of the resist 13 was 10 μm (FIG. 1C). The substrate with the resist film 13 thus obtained is exposed, developed, and rinsed with a predetermined mask to obtain a predetermined resist pattern (FIG. 1D), and then subjected to copper plating by an electroplating method. Thus, a copper wiring layer 14 was obtained (FIG. 1E). The plating solution composition is CuSO4 / 5H2O (70 g / l), H2SO4 (140 g / l), HCl (50 ppm (wt / vol)), the current density is 1.0 (A / dm2), and 8 μm thick copper is obtained. The time required for this was 35 minutes. After completion of the copper plating, the substrate was washed with water and dried at 90 ° C. for 1 hour.

(4) Further, the steps of (3) (FIGS. 1 (c) to (e)) are repeated (FIGS. 1 (f) to (h)), and after forming the copper via wiring 14a, the resist 13 is stripped. (FIG. 1 (i)).

(5) Then, of the copper and chromium which are the plating base films, the portions not in contact with the copper plating layers 14 and 14a formed in the steps (3) and (4) are replaced with an ammonium chloride-based etching solution and an excess. Each was selectively removed with a potassium manganate-based etching solution (FIG. 1 (j)).

(6) Next, a varnish of varnish No. 1 in Table 2 was spin-coated as a polyimide precursor directly in contact with copper, and put into a heating furnace at 30 ° C. under a nitrogen stream having an oxygen concentration of 500 ppm (vol / vol). Then, the temperature is increased at 4 ° C./minute, and maintained at 200 ° C. for 30 minutes, then further increased at 4 ° C./minute, and heated at 350 ° C. for 60 minutes in the same nitrogen atmosphere to form the first insulating film 16. Was formed. The film thickness after heating was 5 μm. In this embodiment, the thickness of the first insulating film 16, the second insulating film 17, and the polyimide layer 15 is such that the first insulating film 16 is directly under the insulating layer (ceramic The measurement was performed at a position in contact with the substrate 11 or the polyimide layer 15).

  Further, a varnish of varnish No. 9 in Table 2 which becomes a polyimide having low thermal expansion was spin-coated, put into a heating furnace at 140 ° C. under a nitrogen stream having an oxygen concentration of 500 ppm (vol / vol), and held for 60 minutes. The temperature is increased at 4 ° C./minute, and maintained at 200 ° C. for 30 minutes. Then, the temperature is further increased at 4 ° C./minute and heated at 350 ° C. for 60 minutes in the same nitrogen atmosphere to form the second insulating film 17 did. The film thickness of the portion 17 obtained by heating from the varnish number 9 was 13 μm.

  The total thickness of the polyimide film 15 obtained by combining the first insulating film 16 and the second insulating film 17 thus obtained was 18 μm (FIG. 1 (k)).

(7) The surface of the obtained polyimide layer 15 is polished with a tape (# 500 to # 4000) to which alumina particles are adhered, and the polyimide layer 15 is flattened so that the thickness of all the polyimide films 15 is 16 μm ( FIG. 1 (l)).

(8) Further, the steps (2) to (7) (FIGS. 1 (b) to (l)) were repeated three times to obtain a copper-polyimide multilayer wiring structure having four wiring layers.

  In the multilayer wiring structure obtained by the above steps, there was no void or peeling near the interface between Cu and polyimide, no cracks, etc., and good electrical conduction was obtained over all wirings.

<Examples 2 to 4>
A first insulating film (polyimide layer formed on the copper surface) 16 is formed using a varnish number 2, a varnish number 4, and a varnish number 6 of a polyimide precursor varnish in Table 2, respectively. (Polyimide layer of low thermal expansion polyimide formed on first insulating film) 17 was formed in the same manner as in Example 1, except that polyimide precursor varnish of varnish number 9 in Table 2 was formed. A copper-polyimide multilayer wiring structure having five wiring layers was obtained. However, in Example 1, the steps (2) to (7) were repeated three times in the step (8), whereas in Examples 7 to 9, the steps were repeated four times. In the obtained multilayer wiring structure, there was no void or peeling near the interface between Cu and polyimide, no cracks, etc., and good electrical conduction was obtained over all wirings.

<Examples 5 to 11>
The first insulating film 16 is formed using a varnish number 3, a varnish number 5, a varnish number 7, a varnish number 8, a varnish number 14, a varnish number 15, and a varnish number 16 shown in Table 2 by using a polyimide precursor varnish. Except that the insulating film 17 of No. 2 was formed using the polyimide varnish of varnish No. 10 in Table 2, a copper-polyimide multilayer wiring structure having five wiring layers was formed in the same manner as in Example 7. Got. In the completed multilayer wiring structure, there were no voids or peeling near the interface between Cu and polyimide, no cracks, etc., and good electrical continuity was obtained over all wirings.

<Comparative Examples 1-2>
A wiring structure was manufactured in the same manner as in steps (1) to (7) of Example 1 except that the first insulating film 16 was formed using varnish number 11 or varnish number 12 in Table 3.

  In Comparative Examples 1 and 2, in the step (6), a polyimide precursor varnish of varnish number 11 or varnish number 12 was applied on Cu of the wiring, and heated at 350 ° C. for 60 minutes to form a first insulating material. A film 16 was formed. When the first insulating film 16 was observed with a microscope, the varnish number 11 (Comparative Example 1) and the varnish number 12 (Comparative Example 2) showed that the periphery of the polyimide Cu wiring was green-brown. Was discolored.

  Further, in the same manner as in Example 1, a polyimide precursor varnish of varnish number 9 was applied and heated at 350 ° C. for 60 minutes to form a second insulating film 17. When the multilayer wiring structure having the polyimide layer 15 thus formed was observed with a microscope, the varnish number 11 (Comparative Example 1) and the varnish number 12 (Comparative Example 2) showed that Swelling was observed between the first insulating film 16 and the second insulating film 17.

  Thereafter, in step (7), when the polyimide was flattened by tape polishing, a groove was formed between the first insulating film 16 and the Cu wiring 14, and peeling was observed. This is considered to be due to the fact that after a large amount of Cu was eluted into the polyimide, the polyimide film was exposed to a high temperature of 350 ° C., so that a portion of the polyimide film centered on the interface with Cu was decomposed and the adhesiveness of the interface was reduced. .

<Comparative Example 3>
The first insulating film 16 is formed using the varnish of varnish No. 2 in Table 2, and the second insulating film 17 is also formed of varnish No. 2 instead of varnish No. 9 which is a low thermal expansion polyimide. A multilayer wiring structure was manufactured in the same manner as in Example 1, except that the multilayer wiring structure was formed using a varnish.

  As a result, when the polyimide film 15 was formed (step (6)) and then the polyimide film 15 was planarized by polishing (step (7)), cracks were observed around the copper via wiring 14a. Thereafter, when the electrode 12 for plating was formed by a sputtering method (second step (2)), disconnection of the electrode 12 was observed at a crack portion. Furthermore, when plating of the upper layer wiring was performed (second step (3)), many portions where no plating was generated were found. From this stage, the process could not proceed further, and in this comparative example, the wiring structure was not completed.

<Example 12>
A wiring structure having four wiring layers 14 is prepared in the same manner as in Example 1, and chromium (0.05 μm) and chromium (0.05 μm) are formed on the exposed portion of the uppermost via wiring 14 a and the surface of the polyimide layer 15 around the exposed portion. After forming a film by sputtering in the order of copper (5 μm), chromium (0.05 μm), and nickel (2 μm), patterning was performed by wet etching using a resist to form the surface electrode 25. Further, a protective film 26 was formed around the surface electrode 25 in order to prevent the spread of solder at the time of solder connection with the LSI. The protective film 26 is formed by spin-coating a varnish No. 2 polyimide precursor varnish, throwing it into a baking furnace at 30 ° C. in a nitrogen stream, heating at 4 ° C. per minute, and holding for 60 minutes after reaching 400 ° C. did. At this time, the oxygen concentration in the baking furnace was 0.1 vol / vol%. FIG. 7 shows the obtained wiring structure. The opening 27 of the protective film 26 of the wiring structure thus manufactured was processed with an excimer laser using KrF gas to form a connection with the LSI. The protective film 26 was formed well, and no abnormality was observed.

<Example 13>
In this embodiment, a part of the wiring is formed by a sputtering method, so that a wiring structure having a structure similar to the structure shown in FIG. 1 is obtained. FIG. 14 shows a manufacturing process in this embodiment.

(1) First, Cr is deposited by a sputtering method on the surface of the ceramic substrate 11 having the wiring 22 to form a first Cr layer 132 having a thickness of 0.05 μm, and the surface of the first Cr layer 132 is formed by sputtering. A conductor layer 133 (thickness: 6 μm) containing Cu as a main component is formed by a method, and Cr is deposited on the surface of the Cu layer 123 by a sputtering method to form a second Cr layer 134 having a thickness of 0.05 μm. (FIG. 14A).

(2) Next, a resist layer 135 (having a thickness of 17 μm) is formed on the surface of the second Cr layer 134 except for a portion 136 where a via is to be formed (FIG. 14B). The exposed Cr layer 134 is removed by etching to expose the lower Cu layer 134, and a via wiring 137 (having a height of 17 μm) containing Cu as a main component is formed by plating (FIG. 14). (C)) After removing the resist layer 135 (FIG. 14D). The plating method was the same as in Example 1.

(3) A photosensitive resist 138 is applied so as to cover the formed via wiring 137 and the surface of the second Cr layer 134 exposed by peeling of the resist layer 135 (FIG. 14E), and a predetermined mask After exposure and development to form a predetermined pattern (FIG. 14 (f)), the exposed conductor layers 132 to 134 were removed by etching (FIG. 14 (g)), and the resist 138 was removed. (FIG. 14 (h)).

(4) A varnish of varnish No. 2 in Table 2 is spin-coated so as to cover the remaining conductor layers 132 to 134, the via wiring 137, and the surface of the substrate 11, and then placed in a heating furnace at 70 ° C. and an oxygen concentration of 100 ppm. In a (vol / vol) nitrogen stream, the temperature was raised at 2 ° C. per minute. When the temperature reached 350 ° C., the temperature was maintained at 350 ° C. for 60 minutes, and then cooled. Thus, as shown in FIG. 14I, a first polyimide film 139 having a thickness of 6 μm was formed.

(5) The varnish of varnish No. 9 in Table 2 was spin-coated on the surface of the obtained first polyimide film 139, and placed in a heating furnace at 140 ° C. under a nitrogen stream having an oxygen concentration of 100 ppm (vol / vol). After holding at 140 ° C. for 60 minutes, the temperature was raised at 4 ° C./min. When it reached, it was kept at 350 ° C. for 60 minutes and cooled. As a result, as shown in FIG. 14J, a second polyimide film 140 having a thickness of 14 μm was formed, and an insulating film 131 having a two-layer structure was obtained. The thickness of the obtained insulating film 131 was 20 μm.

(6) Finally, the insulating film 131 is polished and flattened by a method similar to that of the first embodiment until the film thickness becomes 18 μm, and as shown in FIG. Was.

  Further, the above steps (1) to (6) were repeated three times to obtain a copper-polyimide multilayer wiring structure having four wiring layers. In the obtained multilayer wiring structure, voids, peeling, cracks and the like were not detected near the interface between copper and polyimide, and good electrical continuity was obtained over all wirings.

<Comparative Example 4>
A wiring structure was produced in the same manner as in Example 11, except that varnish number 11 in Table 3 was used as a polyimide precursor for forming protective film 26. After varnish number 11 was applied and baked, it was taken out and observed. As a result, a portion of the side wall of the electrode 25 where the polyimide film 26 turned brown and a portion where blisters were generated were observed. Next, when the opening 27 of the protective film 26 was processed by an excimer laser using KrF gas, a place where the polyimide layer 26 was peeled off at the end of the electrode 25 was found. This is considered to be a result of the reaction between the polyimide precursor and copper on the side wall at the end of the electrode 25.

FIG. 4 is an explanatory diagram illustrating a manufacturing process of the Cu-polyimide multilayer wiring structure of Example 1. 4 is a graph showing the reactivity between copper and a polyimide precursor in Experimental Example 1. 9 is a graph showing the reactivity between copper and a polyimide precursor in Experimental Example 2. 3 is a graph showing the reactivity between copper and a polyimide precursor in Comparative Experimental Example 1. It is the graph which shows the observation result by SIMS of the concentration distribution of the copper eluted in the polyimide film, and the partial sectional view of the observation object. It is a graph which shows the measurement result of the amount of copper eluted in the polyimide film by the fluorescent X-ray method. FIG. 21 is a partial cross-sectional view of a multilayer wiring structure manufactured in Example 12. It is sectional drawing of the wiring structure of a prior art. 4 is a graph showing the relationship between the thickness of polyimide and the concentration of eluted Cu. It is sectional drawing which shows the structural example of the wiring board of this invention. FIG. 2 is a cross-sectional view illustrating a structural example of a multilayer wiring board of the present invention. It is sectional drawing which shows the structural example of the multilayer substrate of this invention. 6 is a graph showing the reactivity between copper and a polyimide precursor in Example 3. FIG. 37 is an explanatory diagram illustrating the manufacturing process of the multilayer wiring structure in the thirteenth embodiment.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... wiring, 3 ... via wiring, 4 ... polyimide film, 11 ... ceramic substrate, 12 ... electrode layer, 13 ... photoresist, 14 ... copper wiring, 14a ... via wiring, 15 ... polyimide film, 16 ... First insulating film, 17 second insulating film, 22 tungsten wiring, 25 surface electrode, 26 protective film, 27 opening, 100 through hole, 101 insulating layer, 102, 103 wiring Layer: 104: polyimide layer, 105: via pad, 106: via, 107: insulating layer, 110: insulating layer, 110a: first insulating layer, 110b: second insulating layer, 110c: third insulating layer, 111 ... ceramic wiring board, 112 ... thin film multilayer wiring board, 113, 113a, 113b, 113c ... via, 114 ... matching layer, 115, 115a, 115b ... via pad, 116, 116 , 116b: wiring, 117: first polyimide film, 117a: first polyimide film of the first insulating layer, 117b: first polyimide film of the second insulating layer, 117c: third of the third insulating layer 1 polyimide film, 118... Second polyimide film, 118 a... Second polyimide film of the first insulating layer, 118 b. Second polyimide film of the second insulating layer, 118 c. Second polyimide film, 119: conductor wiring, 120: insulating layer, 121: metal layer, 122: first insulating layer, 123, 127: surface electrode, 124: second insulating layer, 125: solder, 126 ... Input / output pins, 131: insulating layer, 132: first Cr layer, 133: Cu layer, 134: second Cr layer, 135: resist layer, 136: via forming portion, 137: via, 138: photosensitive resist Layer, 139 ... first Polyimide film, 140 ... second polyimide film.

Claims (24)

In a wiring structure having a wiring layer and an insulating layer,
The wiring of the wiring layer is at least partially made of copper,
At least a part of the insulating layer is made of a first polyimide having a repeating unit represented by the following general formula (Formula 1).

(Wherein R1 is

And R2 is a divalent organic group containing an aromatic ring. ) In claim 1,
R2 is at least one divalent organic group selected from the following (Chemical Formula 3).

In claim 1,
A wiring structure, wherein the polyimide is obtained by heating and curing a polyimide precursor composition containing at least a polyimide precursor and a basic compound. In a wiring structure having a wiring layer and an insulating layer,
The wiring of the wiring layer is at least partially made of copper,
A wiring structure, wherein at least a part of the insulating layer is made of a first polyimide obtained by heating and curing a polyimide precursor composition containing at least a polyimide precursor and a basic compound. In claim 3 or 4,
The wiring structure, wherein the basic compound is at least one amine compound selected from the following (Chemical Formula 4).

In claim 3 or 4,
The wiring structure, wherein the polyimide precursor composition contains one or more molecules of the basic compound for one carboxyl group of the polyimide precursor. In claim 1 or 4,
The insulating layer includes at least a first insulating film formed on the wiring layer, and a second insulating film formed on the first insulating film;
The first insulating film is made of the first polyimide,
The wiring structure, wherein the second insulating film is made of a second polyimide having a smaller coefficient of thermal expansion than the first polyimide. In claim 1 or 4,
A wiring structure, wherein the thickness of the insulating film is 6.5 μm or less. In claim 7,
The wiring structure, wherein the thickness of the first insulating film is 6.5 μm or less. In claim 7,
A wiring structure, wherein the thickness of the second insulating film is larger than the thickness of the first insulating film. In claim 7,
The second polyimide,
It has a repeating unit represented by the following general formula (Chemical formula 5) and a repeating unit represented by the following general formula (Chemical formula 6), and is contained in one molecule and represented by the general formula (Chemical formula 5). When the sum of the number of units and the number of repeating units represented by the general formula (Formula 6) is 100, the number of repeating units represented by the general formula (Formula 5) is less than 95, and A wiring structure, wherein the number of repeating units represented by (Formula 6) is 5 or more.

(Wherein, R3 is the following (Chemical Formula 7)

And at least one tetravalent organic group selected from the group consisting of

And at least one divalent organic group selected from the group consisting of

At least one divalent organic group selected from ) In claim 7,
The second polyimide,
It has a repeating unit represented by the following general formula (Chemical formula 10) and a repeating unit represented by the following general formula (Chemical formula 11), and is contained in one molecule and represented by the general formula (Chemical formula 10). When the sum of the number of units and the number of repeating units represented by the general formula (Formula 11) is 100, the number of repeating units represented by the general formula (Formula 10) is 85 to 50, and A wiring structure, wherein the number of repeating units represented by the formula (Formula 11) is 50 to 15.

(Wherein, R3 is the following (Chemical Formula 7)

Wherein R6 is at least one tetravalent organic group selected from

Wherein at least one divalent organic group selected from the group consisting of

At least one divalent organic group selected from ) In a method for manufacturing a wiring structure having a wiring layer and an insulating layer,
Forming a wiring layer at least partially made of copper,
On the wiring layer, a first polyimide precursor layer, which is a layer of a first polyimide precursor composition containing a first polyimide precursor having a repeating unit represented by the following general formula (Formula 1), Forming,
Heating the first polyimide precursor layer to form a first polyimide layer.

(Wherein R1 is

And R2 is a divalent organic group containing an aromatic ring. ) In claim 13,
R2 is at least one divalent organic group selected from the following (Chemical Formula 3).

In claim 13,
The method for producing a wiring structure, wherein the first polyimide precursor composition further comprises a basic compound. In a method for manufacturing a wiring structure having a wiring layer and an insulating layer,
Forming a wiring layer at least partially made of copper,
Forming a first polyimide precursor layer, which is a layer of a first polyimide precursor composition including a first polyimide precursor including a polyimide precursor and a basic compound, on the wiring layer;
Heating the first polyimide precursor layer to form a first polyimide layer. In claim 13 or 16,
The step of forming the first polyimide precursor layer,
A method for manufacturing a wiring structure, wherein the method is performed in an atmosphere having an oxygen concentration of 0.5 v / v% or less. In claim 15 or 16,
The method for producing a wiring structure, wherein the basic compound is at least one amine compound selected from the following (Chemical Formula 4).

In claim 13 or 16,
After the first polyimide layer forming step,
On the surface of the first polyimide layer, a second polyimide precursor layer, which is a layer of a second polyimide precursor composition containing a precursor of the second polyimide having a smaller coefficient of thermal expansion than the first polyimide, Forming,
A second polyimide layer forming step of heating the second polyimide precursor layer to form a second polyimide layer. In claim 19,
The second polyimide,
It has a repeating unit represented by the following general formula (Chemical formula 5) and a repeating unit represented by the following general formula (Chemical formula 6), and the number of the repeating units represented by the general formula (Chemical formula 5) and the general formula ( When the sum of the number of repeating units represented by Chemical Formula 6) and the number of repeating units represented by Chemical Formula 6 is 100, the number of repeating units represented by General Formula (Formula 5) is less than 95, and is represented by General Formula (Formula 6). Wherein the number of repeating units is 5 or more.

(Wherein, R3 is the following (Chemical Formula 7)

And at least one tetravalent organic group selected from the group consisting of

And at least one divalent organic group selected from the group consisting of

At least one divalent organic group selected from ) In claim 19,
The second polyimide precursor,
It has a repeating unit represented by the following general formula (Chemical formula 10) and a repeating unit having a structure represented by the following general formula (Chemical formula 11). When the sum of the number of the repeating units represented by the formula (Formula 11) and the number of the repeating units is 100, the number of the repeating units represented by the formula (Formula 10) is 85 to 50, and the formula (Formula 11) Wherein the number of repeating units represented by is from 50 to 15.

(Wherein, R3 is the following (Chemical Formula 7)

Wherein R6 is at least one tetravalent organic group selected from

Wherein R7 is at least one divalent organic group selected from

At least one divalent organic group selected from ) In claim 13 or 16,
The step of forming the first polyimide precursor layer is a step of forming the first polyimide precursor layer to a thickness such that the film thickness of the first polyimide layer is 6.5 μm or less. A method for manufacturing a wiring structure, comprising: In a wiring structure having at least a part of a wiring made of copper and an insulating layer made of polyimide,
Inhibiting the diffusion of copper to the insulating layer, having a diffusion blocking layer made of an organic polymer compound,
A wiring structure, wherein at least a part of the wiring is covered with the diffusion blocking layer.













In a method for manufacturing a wiring structure having a wiring layer and an insulating layer,
Forming a wiring at least partially made of copper,
Forming a diffusion blocking layer made of an organic polymer compound so as to cover the exposed portion of the wiring,
Forming an insulating layer made of polyimide on the surface of the diffusion blocking layer.

Images