JPH06310866A - Multilayer wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the reaction of a wiring layer and an insulating layer without increasing manufacturing processes in a multilayered wiring board wherein the wiring interlayer insulating film is an organic polymer insulating film, and realize a multilayered wiring board of high reliability. CONSTITUTION:On a ceramic board 1, wiring conductor (copper) 3 whose surface is flat is formed by electrolytic plating, via a base conductor film 2. The wiring conductor 3 surface is covered with a reaction preventing film 4 by nonelectrolytic plating, and the film 4 surface is covered with an anti-oxidant film 8, which is desirably formed by, e.g. substitution plating of gold. Since the surface layer part of the reaction preventing film 4 as the base is dissolved and the left part is plated with gold, so that a special surface treatment for cleaning the surface is made unnecessary. Further a polyimide interlayer insulating film 6 is formed, holes for wiring connection are formed, and a base conductor film 7 is formed. The forming processes from the wiring conductor (copper) 3 to the base conductor film 7 are repeated by the number of time corresponding with the number of lamination layers of wiring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board and a method for manufacturing the same, and more particularly to a high-density mounting wiring for mounting a large number of LSI chips such as a multi-chip module used in an exchange or a computer. The present invention relates to a suitable multilayer wiring board and a manufacturing method thereof.

[0002]

2. Description of the Related Art Development of multi-chip module mounting technology for high-density mounting of a plurality of LSI bare chips and minute circuit components is progressing in order to improve processing capacity such as increasing capacity and speed of electronic computers and exchanges. ing. As a multilayer wiring board used for mounting this type of module, it is essential to use a multilayer wiring board having a small dielectric constant insulating layer and a low resistance wiring layer. A multi-layer wiring board that uses copper as a wiring layer and a polyimide insulating layer as an interlayer insulating film is known to satisfy such conditions. This type of multilayer wiring board is referred to as a copper-polyimide multilayer wiring board here.

A conventional board structure, which is a representative example of this copper-polyimide multilayer wiring board, and a method of manufacturing the same will be described below with reference to FIG. In FIG. 2, as shown in FIG. 2A, a base conductor film 2 is formed on a ceramic substrate 1 by electroless copper plating or chromium / copper sputtering.

Next, as shown in FIG. 2B, a resist pattern 5 is formed on a portion 2b of the underlying conductor film 2 excluding the wiring formation region 2a, and then copper is formed on the wiring formation region 2a by electrolytic copper plating. A conductor layer 3 is formed, and a reaction preventive film 4 (copper-polyimide reaction preventive) is further laminated thereon by electrolytic chromium plating to obtain a wiring layer.

Next, as shown in FIG. 2C, after removing the resist pattern 5 for forming an insulating layer, the exposed unnecessary underlying conductor film 2b is removed by etching, and the entire surface is covered so as to cover the wiring layer. A polyimide insulating layer 6 is formed.

Then, as shown in FIG. 2D, the wiring layers formed on the same substrate are connected with a low connection resistance,
In order to form the wiring layer, first, a hole is made in the polyimide insulating layer 6 on the wiring layer, the exposed main portion of the reaction preventive film 4 is removed by etching, and the oxide on the exposed surface portion of the conductor layer 3 is removed. After that, the base conductor film 7 of the second wiring layer is formed on the polyimide insulating layer 6 from the exposed connection portion.

Next, by repeating the steps of FIGS. 2 (b) to 2 (d), a three-layer wiring structure in which the polyimide insulating layer 6 shown in FIG. 2 (e) is used as an interlayer insulating film and copper is used as a wiring layer Is formed.

[0008] Incidentally, as a technique related to this type of technology, for example, Nikkei Microdevices February 1989 issue,
Pp. 50-60.

[0009]

However, the above-mentioned conventional techniques have the following problems. That is, the copper-polyimide reaction preventive film 4 is formed only on the surface of the copper conductor 3 and not on the side surface thereof. Therefore, for example, when a polyimide containing a carboxyl group is used, the carboxyl group is acetic acid, so that in the portion where the copper conductor 3 and the polyimide insulating layer 6 are in direct contact, the acetic acid causes a copper-polyimide reaction. I will end up. Therefore, contact between the side surface of the copper conductor 2 and the polyimide insulating layer 6 must be prevented.

Further, as shown in FIG. 2D, a step of etching away the reaction preventive film 4 and a step of removing the oxide film on the exposed surface portion of the copper conductor 3 are required at the time of forming the wiring interlayer connection portion. However, there is a problem that over-etching of the reaction preventive film 4 is likely to occur.

Further, in the wiring layer formed directly on the ceramic substrate, the irregularities on the surface of the ceramic substrate affect the irregularities on the surface of the copper conductor 3, whereby the chromium formed on the concave portion as the reaction preventive film 4 is formed. The film thickness becomes uneven and a thin portion is generated, and the copper-polyimide easily reacts.

Further, the base conductor film 7 is formed when the second wiring layer is formed on the polyimide insulating layer 6, but in the conventional electroless plating, the adhesion between the polyimide insulating layer 6 and the plated conductor 7 is improved. In order to obtain it, a step of roughening the polyimide insulating surface is required, and the number of steps is increased.

Further, even when the chromium / copper base conductor film (2, 7) is formed by sputtering instead of plating, the number of steps such as etching is increased, and an expensive sputtering device is required. Therefore, in order to obtain an inexpensive wiring board, it is necessary to increase the adhesion without increasing the number of steps.

Therefore, an object of the present invention is to solve these conventional problems, and the first object of the present invention is to sequentially coat a reaction preventing film and an antioxidant film including the surface and the side surface of a wiring layer. The purpose of the present invention is to realize a highly reliable multilayer wiring board by preventing the reaction between the wiring layer and the polyimide insulating layer by adopting a two-layer structure. The second purpose is to realize a manufacturing method with a reduced number of steps. Especially.

[0015]

A first object of the present invention is to laminate a reaction-preventing film and an anti-oxidizing film on the surface and the side surface of a wiring layer formed on a ceramic substrate via an underlying conductor film, This is achieved by a multilayer wiring board formed by forming an organic polymer insulating layer as an interlayer insulating film. Polyimide is most suitable for the organic polymer insulating layer, but other well-known organic insulating materials such as photosensitive polyimide, polyimide silicon, ladder silicon (poly ladder organosiloxane), and polyamide are used. In the following description, polyimide will be described as a typical example.

Further, preferably, when a new wiring layer is repeatedly formed on the interlayer insulating film made of polyimide with the underlying conductor film interposed therebetween, when laminating the multilayer wiring layers such as the second wiring layer and the third wiring layer. That is, an organic polymer insulating film containing insulating fine particles is formed thinner than the fine particle diameter on the flattened interlayer insulating film, and the fine particles are fixed to the surface to make the surface of the insulating layer uneven. Due to the surface unevenness, the underlying conductor film provided when forming a new wiring layer is firmly connected to the interlayer insulating film, and the adhesiveness is remarkably improved. As a substitute technique for making the surface uneven, there is a method of polishing the surface of the insulating layer, but fixing the fine particles is easier and more preferable than that.

As the insulating fine particles, any insulating material may be used, but it is preferable to use fine particles of resin such as polyimide for forming an interlayer insulating film, and those having an average particle diameter of about 1 to 5 μm. used.

As the reaction preventive film, a plated conductor film such as polyimide which is difficult to react with the interlayer insulating film is used. For example, electroless plating such as nickel or chromium having a film thickness of 1 to 5 μm or electrolytic plating is used. However, in practice, electroless nickel plating is particularly preferable.

As the anti-oxidation film, any oxidation resistant conductor may be used, and normally a gold thin film (for example, 0.5 μm or less) is used. Electroless displacement plating is particularly preferable in view of the relationship with the manufacturing method described later (process simplification and reliability improvement).

The second object is to provide a step of forming a first wiring conductor layer on a ceramic substrate through an underlying conductor film by electrolytic plating, and a reaction prevention film and an oxidation prevention film on the conductor layer. A step of sequentially stacking by a plating method and covering the entire surface of the first wiring conductor layer with these two-layer films; a step of forming an organic polymer insulating layer as an interlayer insulating film on the entire surface; A step of forming an opening for forming a circuit in an interlayer insulating film on the wiring conductor layer, and forming a second wiring conductor layer on the interlayer insulating film including the opening for forming the circuit via a base conductor film. And a step of repeating the above-mentioned steps by the number of times corresponding to the number of laminated multilayer wirings.

Preferably, subsequently to the step of forming the organic polymer insulating layer as the interlayer insulating film, an organic polymer insulating film containing insulating fine particles is formed thinner than the fine particle diameter, and the fine particles are formed on the surface. This is achieved by a method for manufacturing a multilayer wiring board, which includes a step of making the surface of the insulating layer uneven by fixing.

[0022]

The operation of the present invention will be described with reference to a copper-polyimide multilayer substrate as a typical example. A reaction preventing film and an oxidation preventing film are sequentially laminated on a copper wiring conductor layer by a plating method to form the first copper wiring conductor. The entire surface of the layer is covered with these two-layer films. First, since the reaction preventive film is formed by the plating method,
Since the entire surface of the copper wiring conductor layer can be uniformly covered and the copper wiring conductor layer and the polyimide do not come into direct contact with each other,
Both reactions can be completely prevented.

Next, regarding the formation of an anti-oxidation film, since this is also formed by a plating method, a particularly preferred displacement plating method forms a plating film even if the surface layer portion of the reaction-preventing film which is the base is oxidized. Since the antioxidant film is plated from the one side where the surface layer of the reaction preventive film is dissolved, the oxide in the surface layer part of the reaction preventive film is inevitably removed as the plating of the antioxidant film progresses. Therefore, the surface layer portion of the reaction preventive film can be removed and cleaned without performing a special etching process.

Further, conventionally, when forming a wiring interlayer connecting portion,
Although the reaction preventive film etching and the copper conductor surface treatment process are required, none of them are required in the present invention, and the wiring interlayer connection portion shape defect can be eliminated, and the wiring interlayer connection portion forming step can be simplified.

Further, by forming an organic polymer insulating film containing insulating fine particles thinner than the fine particle diameter on the wiring interlayer insulating layer and fixing the fine particles on the surface, the surface of the interlayer insulating layer can be easily roughened. As a result, when the underlying conductor layer is formed by, for example, electroless plating when forming the second wiring layer, the adhesion of the electroless plating to the wiring interlayer insulating layer can be further increased due to the surface irregularities. .

Further, by forming the wiring layer on the ceramic substrate by electrolytic plating, the irregularities on the surface of the ceramic substrate can be flattened, and the coverage of the reaction preventive film can be further improved, resulting in an effective copper-polyimide reaction. It can be prevented.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a process sectional view showing the structure and manufacturing process of a multilayer wiring board according to an embodiment of the present invention. Here, in order to clarify the characteristic point of the present invention, FIGS. 3 and 4 showing conventional examples are used as auxiliary drawings as necessary.

By the process shown in FIG. 1A, a two-layer film including a chromium layer having a film thickness of 0.1 μm and a copper layer having a film thickness of 0.1 μm is formed on the ceramic substrate 1 according to a well-known sputtering film forming method. A base conductor film 2 composed of is formed.

Next, by the process shown in FIG. 1B, a resist pattern 5 is formed in the interlayer insulating film forming region 2b except the first wiring layer forming region 2a on the underlying conductor film 2. . Subsequent to this, electrolytic copper plating is performed to easily flatten the surface irregularities of the ceramic substrate 1 by the leveling effect at the time of plating to form a copper conductor 3 having a flat surface and a film thickness of 5 μm.

On the other hand, in the prior art, as shown in FIG. 3A, chromium is used as the base conductor film 2 / copper is used as the wiring conductor layer 3 / reaction preventive film is formed on the ceramic substrate 1 by the sputter deposition method. Chromium is sequentially formed as 4 and a resist pattern 5 is selectively formed thereon as a wiring layer forming mask. Then, as shown in FIG.
Wiring is separated from the layer film to form a circuit. In this case, in the sputtering film forming method, irregularities on the surface of the ceramic substrate 1 and irregularities that cannot be covered by the underlying chromium 2 are formed on the surface of the copper conductor 3. This greatly influences the film formation of the reaction preventive film 4, and as shown in the figure, a film formation defect portion (polyimide-copper contact portion) 11 occurs. Therefore, FIG. 3 (c)
As shown in FIG. 5, when polyimide is formed as the interlayer insulating film 6, the reaction between the surface of the copper conductor 3 and the polyimide 6 is avoided because the defective film forming portion of the reaction preventing film 4 and the polyimide-copper contact portion 11 exist. Absent.

Next, as shown in the step of FIG. 1C, the resist pattern 5 is removed and the copper conductor 3 is used as a mask to expose the underlying conductor film (two layers of chromium / copper) in the interlayer insulating film formation region 2b. The film 2 is removed by etching to separate the wiring. Next, as the reaction preventing film 4, nickel is formed on the surface of the copper conductor 3 by 2 μm by electroless plating, and the surface is completely covered by nickel plating. In this way, the reaction preventing film 4 can completely prevent the copper-polyimide reaction.

Next, as shown in the step of FIG. 1D, 0.1 μm of gold is formed as an antioxidant film 8 on the reaction preventive film 4 by displacement plating. In the present invention, this step is a particularly important step in simplifying the step as described in detail below.

In the conventional method, as shown in FIG.
When the holes for connecting the interlayer wirings are formed in the insulating layer 6, the surface of the reaction preventive film 4 and the copper conductor 3 is etched to remove the oxide film and the like. At that time, as shown in this figure, the reaction preventive film is formed. 4 is likely to have a defect in the hole shape for interlayer connection such as overetching. To improve this, Fig. 4
As shown in (e), after the reaction-preventing film 4 was etched, the interlayer insulating film 6 made of polyimide was again wet or dry-etched to enlarge the opening diameter of the hole, and the reaction-preventing film 4 made of chromium was exposed. . However, this method has a problem that the base conductor film 7 is likely to be peeled off in the subsequent second wiring layer forming step due to contamination of the surface of the copper conductor 3 or alteration of the surface of the polyimide 6.

However, in this embodiment, in order to solve these problems, as shown in FIG. 1D, the reaction preventive film 4 is formed.
By laminating the anti-oxidation film 8 on the upper side by displacement plating, the surface treatment step, which has been indispensable in the past, is made unnecessary and the defective shape of the interlayer connection hole is improved.

That is, according to the displacement plating of gold formed as the anti-oxidation film 8 of this embodiment, the reaction preventive film 4 serving as the base is formed.
Since the gold plating is formed on the surface of the reaction preventive layer 4 as it dissolves, even if the surface layer of the reaction-preventing film 4 is oxidized, the self-cleaning action at the time of gold plating substantially eliminates them. Oxides are dissolved and removed.

Next, as shown in the step of FIG. 1E, a polyimide layer is formed as an interlayer insulating layer 6 on the entire surface of the wiring layer so as to cover the wiring layer.

Then, as shown in the step of FIG. 1F, after the polyimide layer at a predetermined portion necessary for circuit connection is etched to form an interlayer connection hole, the underlying conductor film shown in FIG. The base conductor film 7 made of a two-layer film of chromium / copper is formed by the same process as the forming process of 2.

Finally, as shown in the step of FIG. 1 (g), the steps of FIG. 1 (b) to FIG. 1 (f) were repeated to manufacture a multilayer wiring board having three-layer wiring.

Example 2 This example shows a modification of the step of FIG. 1 (f) in Example 1, that is, the step of forming the underlying conductor film 7 after forming the polyimide interlayer insulating film 6. A cross-sectional view of the main part is shown in FIG. When forming the underlying conductor film 7 by the sputter deposition method of FIG. 1F by electroless plating, electroless plating with sufficient adhesion on the polyimide interlayer insulating film 6 does not increase the number of steps. Must be formed in the process.

This embodiment realizes this, and FIG.
The polyimide resin 12 containing the polyimide particles 9 as insulating fine particles on the polyimide interlayer insulating film 6 as shown in FIG.
Is applied to form a film having a film thickness equal to or smaller than the particle size of the polyimide particles 9, and the surface of the polyimide interlayer insulating film 6 is made uneven according to the surface shape of the fine particles fixed by the polyimide resin 12, and the underlying conductor film 7 is formed thereon. Is formed.

The underlying conductor film 7 was formed by a single layer of electroless copper plating instead of the chromium / copper two-layer film formed by the sputtering method of Example 1. Chromium / copper 2 instead of copper plating single layer
It goes without saying that a layer plating film may be used. By forming the unevenness, the adhesion of the plating base conductor film 7 to the polyimide interlayer insulating film 6 could be significantly increased.

[0042]

As described above in detail, according to the present invention, the intended purpose can be achieved. That is, when a copper-polyimide multilayer substrate is described as a typical example, since the copper conductor forming the wiring layer is covered with the copper-polyimide reaction preventing film and the oxidation preventing film by electroless plating, the wiring layer (copper conductor)
The copper-polyimide reaction can be prevented irrespective of the pattern shape and the step of etching the copper-polyimide reaction preventing film and the copper conductor surface treatment step are not required at the time of forming the wiring interlayer connection portion. As a result, it is possible to eliminate the defective shape of the wiring interlayer connecting portion and simplify the wiring interlayer connecting portion forming step.

By forming the wiring layer on the ceramic substrate by electrolytic plating, the irregularities on the surface of the ceramic substrate can be flattened, the coverage of the reaction preventive film is improved, and as a result, the copper-polyimide reaction is completely prevented. be able to.

Further, when the underlying conductor film is formed on the polyimide interlayer insulating film by electroless plating, by fixing insulating fine particles on the polyimide interlayer insulating film in advance to make the surface uneven, electroless plating is performed. It is possible to increase the adhesion force of the above, and it is possible to provide a low-resistance, low-dielectric-constant multilayer wiring board at low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a multilayer wiring board according to an embodiment (Example 1) of the present invention.

FIG. 2 is a cross-sectional view showing an example of a manufacturing process of a conventional multilayer wiring board.

FIG. 3 is a sectional view showing a conventional manufacturing process.

FIG. 4 is a sectional view showing a conventional manufacturing process.

FIG. 5 is a cross-sectional manufacturing process diagram of a main part of a multilayer wiring board according to another embodiment (second embodiment) of the present invention.

[Explanation of symbols]

1 ... Ceramic substrate, 2 ... Base conductor, 2a
... Wiring formation region of base conductor, 2b ... Non-wiring formation region of base conductor, 3 ... Wiring layer (copper conductor), 4 ... Reaction preventive film, 5 ... Resist pattern, 6 ... Wiring interlayer insulating film (polyimide), 7 ... Base conductor,
8 ... Antioxidation film, 9 ... Insulating fine particles,
10 ... Lower chrome film, 11 ... Polyimide-copper contact part,
12 ... Polyimide resin containing fine particles.

Front page continuation (72) Inventor Satoru Hashimoto 216 Totsuka-cho, Totsuka-ku, Yokohama, Kanagawa Prefectural Information & Communication Division, Hitachi, Ltd. (72) Mori Morita 216 Totsuka-cho, Totsuka-ku, Yokohama, Kanagawa Information & Communication Division, Hitachi, Ltd.

Claims (10)

[Claims] 1. A surface layer and a side surface of a wiring layer formed on a ceramic substrate with a base conductor film interposed therebetween are laminated and coated with a two-layer film including a reaction-preventing film and an anti-oxidizing film to form an organic polymer as an interlayer insulating film. A multilayer wiring board formed by forming an insulating layer. 2. The multilayer wiring board according to claim 1, wherein the organic polymer insulating layer is composed of polyimide. 3. The multilayer wiring board according to claim 1, wherein the reaction preventing film is made of nickel. 4. The multilayer wiring board according to claim 1, wherein the antioxidant film is made of gold. 5. A multilayer wiring board in which a new wiring layer is laminated on the interlayer insulating film via a base conductor film, and an organic polymer insulating film containing insulating particles is provided on the interlayer insulating film with a fine particle diameter. 2. The multilayer wiring board according to claim 1, wherein a new wiring layer is laminated on a surface layer which is formed to be thinner and is made uneven by fixing fine particles on the surface, with a plating base conductor film interposed therebetween. 6. The multilayer wiring board according to claim 5, wherein the insulating fine particles are made of resin fine particles forming an interlayer insulating film. 7. A step of forming a first wiring conductor layer on a ceramic substrate by electrolytic plating through a base conductor film,
A step of sequentially laminating a reaction prevention film and an oxidation prevention film on the conductor layer by a plating method and covering the entire surface of the first wiring conductor layer with these two-layer films, and forming an interlayer insulating film on the entire surface. A step of forming an organic polymer insulating layer, a step of forming an opening for circuit formation in the interlayer insulating film on the first wiring conductor layer, and a step of forming an opening for circuit formation on the interlayer insulating film. And a step of forming a second wiring conductor layer via an underlying conductor film, and a step of successively repeating the above-mentioned steps by the number of times corresponding to the number of laminated layers of the multilayer wiring. Production method. 8. An organic polymer insulating film containing insulating fine particles is formed to be thinner than the fine particle diameter, following the step of forming an organic polymer insulating layer as the interlayer insulating film.
The method for manufacturing a multilayer wiring board according to claim 7, which further comprises a step of making the surface of the insulating layer uneven by fixing fine particles on the surface. 9. The method for manufacturing a multilayer wiring board according to claim 7, wherein the reaction preventing film is formed by electroless nickel plating, and the oxidation preventing film is formed by electroless gold displacement plating. 10. The step of forming a base conductor film on an interlayer insulating film including an opening for circuit formation as described above, which is a step of forming the base conductor film by electroless plating.
Alternatively, the method for manufacturing a multilayer wiring board according to item 8.