JP3447147B2 - Metal compound polymer film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal compound polymer film in which a copper film is formed after forming a cobalt inorganic compound layer on a plastic film, particularly a polyimide film, and more particularly, a copper layer and a cobalt inorganic compound layer or a cobalt inorganic compound film. The present invention relates to a metal compound polymer film having good adhesiveness between a compound layer and a plastic film at high temperature. Such a metal compound polymer film is mainly used as a flexible circuit board.

[0002]

2. Description of the Related Art A flexible circuit board having a metal film formed on an insulating polymer film has a film thickness of about 10 μm.
The above-mentioned metal film and polymer film may be joined with an adhesive, but the thermal properties of the adhesive are inferior to the performance of the polymer film and the thickness of the metal film is 10 μm.
Since it is thick as described above, there are problems that it cannot be applied to high-density wiring in the semiconductor industry, that dimensional stability is poor, and that the product has a warp, because it is difficult to perform fine processing of several tens of μm. In order to solve this, a technique of forming a metal film without an adhesive has been studied. This is a method of forming a circuit pattern after forming a metal thin film by a thin film forming method such as vacuum deposition and sputtering. In this material, since the metal thin film is as thin as 1 μm or less, fine processing with a width of several tens of μm is easy.

That is, this is a technique for forming a finely processed conductor by further depositing and growing a metal by electrolytic plating or the like based on the circuit pattern formed as described above. Note that the latter technique is a technique that enables high-density wiring in the semiconductor industry, but there has been a problem of a decrease in adhesive force in a post process such as a circuit forming process and an electrolytic plating process. In JP-A-02-98994, a chromium layer having a thickness of 0.01 to 5 μm is formed by sputtering, and in JP-A-62-181488, it is 5-1000.
nm nickel layer or nickel-chromium layer by vapor deposition, JP-A-62-62551 discloses a chromium layer by vapor deposition, and JP-B-57-18357 discloses nickel, cobalt and zirconium. JP-A-57-18356 discloses a technique for forming a metal layer of palladium, etc. by an ion plating method, and a technique for forming a nickel, nickel-containing alloy layer by an inoplating method. .

However, although these known techniques have been partially successful, they are still unsatisfactory in performance as materials for enabling high-density wiring in the semiconductor industry, which is a hindrance to practical use. Was there. That is,
The problem of the metal layer peeling from the polyimide film was partially solved in the circuit pattern formation process using lithography technology and the electrolytic plating process of laminating the metal layer on the formation pattern for lowering the conduction resistance and improving the mechanical strength. However, sufficient performance could not be achieved in the heat resistance, which is the original characteristic of the flexible circuit board composed of the metal layer / polyimide film. For example, 15 in the air
There has been a problem that the adhesiveness between the metal layer and the polyimide film is remarkably lowered only by keeping the temperature at about 0 ° C. for 24 hours.

[0005]

Therefore, when a polyimide film is used as the plastic film and the inventors of the present invention diligently investigated the cause of the decrease in adhesiveness, it was found that reactive gases such as oxygen and air that permeate through the polyimide film. It has been found that the adhesiveness is affected, and further that the deterioration of the adhesiveness can be prevented by providing a gas barrier layer for blocking the passing gas (Japanese Patent Laid-Open No. 06-29634). ). As a result, it has been possible to obtain a flexible circuit board material composed of a metal layer / polyimide film that can be put to practical use in the semiconductor industry having the harsh process as described above. As a specific example, as a gas barrier layer, a substantially silicon oxide layer is formed on one surface of a polyimide film by plasma chemical vapor deposition (P-CVD) using tetramethyldisiloxane and oxygen as raw materials. A method of forming a ~ 300 nm thickness has been disclosed.

It has been found that such a method dramatically improves the gas barrier property of the film, and thus suppresses the deterioration of high temperature strength. However, there has been a problem that some of the films obtained by subjecting the film to secondary processing such as bending and cutting show a decrease in adhesiveness when subjected to a heating test. It is considered that a reactive gas such as oxygen or air that permeates through the polyimide film reacts with the metal layer in contact with the polyimide surface to partially generate a metal oxide. It was presumed that this metal oxide was the main cause of the exfoliation, but it was also found that the polyimide layer in contact with the metal layer was also oxidized by the metal layer acting as a catalyst.

In many cases, a copper layer is used as a metal layer for a flexible circuit board, but in this case, deterioration of adhesiveness after heating is a particular problem. A copper / polyimide film formed by forming a copper film with a copper layer by a sputtering method and then increasing the thickness of the copper layer by a plating method has a bonding strength of about 30% when treated at 150 ° C. for 24 hours. Go down to. Analysis of the copper / polyimide film having a reduced adhesive strength revealed that copper was diffused and oxidized in the polyimide film.

In order to prevent the diffusion and oxidation of copper, we have investigated the formation of various metal intermediate layers between the copper layer and the polyimide layer by the sputtering method to prevent the diffusion of copper into the polyimide layer. I've been Among these, it was found that when cobalt was used as the intermediate layer, it was effective in preventing the diffusion of copper into the polyimide layer. However, when cobalt is used as the intermediate layer, if the thickness of the cobalt intermediate layer is 50 nm or more, the decrease in the adhesive strength between the cobalt layer and the polyimide layer due to the heat treatment at 150 ° C. for 24 hours is suppressed, and the decrease in the adhesive strength is prevented. However, as the film thickness becomes thicker, especially at a film thickness of 500 nm or more, the copper layer-cobalt layer, or cobalt-cobalt layer, or the cobalt-cobalt layer after the heat treatment at 150 ° C. for 24 hours is performed. It was also found that there was a part that was easily peeled off between the layers. Therefore, even if the intermediate layer is formed to be thick to some extent, the cobalt-cobalt layer, the cobalt layer-
Techniques that do not lower the adhesiveness of the copper layer and the cobalt layer-polyimide layer were investigated.

[0009]

Means for Solving the Problems As a result of intensive studies by the present inventors, it was found that the above-mentioned problems can be solved by using a cobalt inorganic compound as the intermediate layer. That is, when using a cobalt-based cobalt inorganic compound as the intermediate layer, copper layer-cobalt inorganic compound layer,
The peeling between the cobalt inorganic compound-cobalt inorganic compound layer was eliminated, and the peeling between the cobalt inorganic compound-polyimide layer became difficult.

That is, the present invention is: (1) On one side or both sides of a plastic film,
A metal compound polymer film, characterized in that a cobalt inorganic compound layer having a thickness of 20 to 3000 nm is formed, and a copper layer is formed on the cobalt inorganic compound layer. (2) The plastic film is a polyimide film The metal compound polymer film (3) according to (1), wherein the cobalt inorganic compound layer is formed by a sputtering method, and the metal compound polymer film (4) according to (1) or (2) is a cobalt inorganic compound layer. The present invention relates to the metal compound polymer film according to any one of (1) to (3) selected from cobalt phosphide, cobalt sulfide, cobalt telluride, cobalt silicide, cobalt nitride, and cobalt carbide.

The metal compound polymer film formed according to the present invention provides a flexible circuit board material in which not only the characteristics during high-temperature test but also the performance deterioration during secondary processing are remarkably alleviated.

A detailed description will be given below. The plastic film that can be used in the present invention may be any film having so-called heat resistance such as polyethylene terephthalate, polyetheretherketone, polyetherimide, and polyaramidimide, but dimensional stability and strength. From the viewpoint of, a polyimide film is particularly preferable.
To give a concrete example as a polyimide film,
Commercially available polyimide films can be effectively used as product names such as Kapton, Upilex, and Apical. The thickness of the plastic film is not particularly limited, but is usually about 10 to 1000 μm.

In the method for producing a metal compound polymer film according to the present invention, first, the surface of the plastic film is pretreated in order to improve the adhesion to the metal compound. The method, considering that the main use of the metal compound polymer film is a circuit board, corona discharge treatment, plasma treatment, ultraviolet irradiation treatment is preferable, among which plasma treatment is sputtering used to form the cobalt inorganic compound layer. In many cases, the same device can be used, which is preferable.

As the cobalt inorganic compound layer, cobalt phosphide, cobalt sulfide, cobalt telluride, cobalt silicide, cobalt nitride, cobalt carbide or the like is used.

The cobalt inorganic compound thin film is formed by vacuum vapor deposition, ion plating, sputtering, C
Not only the dry forming method such as the VD method but also the wet thin film forming method such as the dipping method and the printing method can be used. The sputtering method, which is excellent in the adhesiveness of the thin film and the controllability of the thin film, is a particularly preferable method. The sputtering method is not particularly limited, and includes DC magnetron sputtering, high frequency magnetron sputtering,
A method such as ion beam sputtering is effectively used. It is understood by those skilled in the art that a target is appropriately selected and used according to the thin film to be formed.

The thickness of the cobalt inorganic compound layer should be such that the adhesiveness with the polyimide layer can be maintained, 20 to 3000 nm,
30-1000 nm is preferable. If the film thickness is too thin, there may be a part where the metal is laminated and a part where the metal is not laminated, that is, there is a problem in the uniformity of the cobalt inorganic compound thin film, and if it is too thick, the formation of the cobalt inorganic compound thin film layer However, it is not preferable in terms of production efficiency, but there is no part in which the adhesive strength between the copper layer-cobalt inorganic compound layer, the cobalt inorganic compound-cobalt inorganic compound layer, and the cobalt inorganic compound-polyimide layer decreases. .

The metal compound polymer film produced by the present invention using polyimide as the plastic film will be described in more detail below. First, referring to the drawings, FIG. 1 shows a metal compound polymer film of the present invention, and FIGS. 2 and 3 show an embodiment of a material for a flexible circuit board made by using the metal compound polymer film of the present invention. 1, 1 is a polyimide film, 2 and 2'are cobalt inorganic compound layers, 3 is a copper thin film, and 4 is a circuit copper film layer.

The basis of the present invention is, as shown in FIG. 1, a metal compound comprising a polyimide film 1, a metal cobalt inorganic compound layer 2 and a copper thin film 3 formed on the main surface of the polyimide film. It is a polymer film. Figure 2
As shown in, a copper thin film 4 for a circuit is formed on the copper thin film 3 of the metal compound polymer film to obtain a flexible circuit board material. In addition, as shown in FIG. 3, the present invention is not limited to the one in which the cobalt inorganic compound layer 2 is laminated on one surface of the polyimide film 1 as described above, and the cobalt inorganic compound layer 2 ′, the polyimide film 1, and the cobalt film. It goes without saying that a multilayer thin film laminated on both surfaces such as the inorganic compound layer 2 is also included. Where 2 and 2 '
It goes without saying that different cobalt inorganic compounds may be used for the respective cobalt inorganic compound layers.

The case of using tetracobalt triphosphide for the cobalt inorganic compound layer will be described in more detail. For example, a tetracobalt triphosphide thin film is formed on the main surface of the polyimide by the RF magnetron sputtering method using argon gas. As the tetracobalt triphosphate target, a commercially available product such as a tetracobalt triphosphate target manufactured by Kojundo Chemical Laboratory Co., Ltd. is used.

An example of a method for forming a copper layer on a cobalt inorganic compound layer is as follows. First, a copper thin film is formed to a thickness of about 50 to 500 nm by a DC sputtering method using argon gas, and then a copper plating method, for example, a copper sulfate solution is used. A copper layer having a thickness of about 5 to 50 μm is formed by electrolytic plating.

The thickness of these metal thin films is determined by providing a mask on a part of the sample during sputtering or plating, and then removing the mask and measuring the step difference between the masked part and a non-masked part using a step measuring machine. I asked.
When the length of the step portion exceeds the measurement limit of the device, the sputtering or plating time was adjusted so as to be within the measurement limit.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. Example 1 A polyimide film (Kapton V) having a film thickness of 50.0 μm was used, and the surface of the polyimide film was treated by glow discharge of oxygen on one surface of the polyimide film. Purity Chemical Research Laboratory] was used as a target to form a tetracobalt triphosphide layer having a thickness of 500 nm by an RF magnetron sputtering method using argon gas. Immediately thereafter, a copper thin film layer having a thickness of 250 nm was formed by a DC magnetron sputtering method using argon gas with copper as a target. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the circuit copper film obtained by such a method to the polyimide film was measured, the average strength in normal state was 1.2 kg / cm. This was placed in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner, averaging 1.2 kg /
cm, and no decrease in adhesive strength was observed.

On the other hand, before putting it in an oven at 150 ° C,
The film was wound around a stainless steel rod having a diameter of 10 mm, 5 times on each side, 10 times in total, and then placed in an oven at 150 ° C. and held for 10 days, and the adhesive strength was measured in the same manner. cm, and in this case also, no decrease in adhesive strength was observed. Moreover, when these were subjected to elemental analysis of peeling interfaces by Auger electron spectroscopy, it was confirmed that all of the peeling interfaces were tetracobalt triphosphate-polyimide layers.

Example 2 A polyimide film (Kapton V) having a film thickness of 50.0 μm was used, and the surface of the polyimide film was treated by glow discharge of oxygen on one surface of the polyimide film. Purity Chemical Laboratory] was used as a target to form a cobalt sulfide layer having a thickness of 30 nm by an RF magnetron sputtering method using argon gas. Immediately thereafter, a copper thin film layer having a thickness of 250 nm was formed by a DC magnetron sputtering method using argon gas with copper as a target. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the copper film for a circuit obtained by such a method to the polyimide film was measured, it was 1.1 kg / cm on average in normal strength. After placing this in an oven at 150 ° C for 10 days,
Similarly, when the adhesive force was measured, the average was 1.1 kg / cm.
The decrease in adhesive strength was not observed.

On the other hand, before putting it in an oven at 150 ° C,
The film was wound around a stainless steel rod having a diameter of 10 mm, 5 times on each side, 10 times in total, placed in an oven at 150 ° C. and held for 10 days, and the adhesive strength was measured in the same manner. cm, and in this case also, no decrease in adhesive strength was observed. Moreover, when these were subjected to elemental analysis of the peeling interface by Auger electron spectroscopy, it was confirmed that all the peeling interfaces were between the cobalt sulfide-polyimide layers.

Example 3 A polyimide film (Kapton V) having a film thickness of 50.0 μm was used. On one surface of the polyimide film, the surface of the polyimide film was treated by glow discharge of oxygen, and then cobalt telluride [Co., Ltd.] was used. A high-purity chemical research institute] was used as a target to form a cobalt telluride layer having a thickness of 300 nm by an RF magnetron sputtering method using argon gas. Immediately thereafter, a copper thin film layer having a thickness of 250 nm was formed by a DC magnetron sputtering method using argon gas with copper as a target.
Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the circuit copper film obtained by such a method to the polyimide film was measured, the average strength in normal state was 1.4 kg / cm on average. This was placed in an oven at 150 ° C. and kept for 10 days, and the adhesive strength was measured in the same manner.
It was kg / cm, and no decrease in adhesive strength was observed.

On the other hand, before putting it in an oven at 150 ° C,
The film was wound around a stainless steel rod having a diameter of 10 mm, 5 times on each side, 10 times in total, and then placed in an oven at 150 ° C. and kept for 10 days, and the adhesive strength was measured in the same manner. cm, and in this case also, no decrease in adhesive strength was observed. In addition, elemental analysis of the exfoliation interfaces by Auger electron spectroscopy revealed that cobalt telluride-
It was confirmed to be between the polyimide layers.

Example 4 A polyimide film (Kapton V) having a film thickness of 50.0 μm was used. On one surface of the polyimide film, the surface of the polyimide film was treated by glow discharge of oxygen. The purity of the chemical chemistry laboratory] was used as a target to form a cobalt silicide layer having a thickness of 1000 nm by an RF magnetron sputtering method using argon gas. After that, immediately target copper,
A 250 nm-thick copper thin film layer was formed by a DC magnetron sputtering method using argon gas. next,
The thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive strength of the copper film for a circuit obtained by such a method to the polyimide film was measured, the average strength in normal state was 1.0 kg / cm on average.
This was placed in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner, averaging 1.0 kg /
cm, and no decrease in adhesive strength was observed.

On the other hand, before putting it in an oven at 150 ° C,
The film was wound around a stainless steel rod having a diameter of 10 mm, 5 times on each side, 10 times in total, and then placed in an oven at 150 ° C. and held for 10 days, and the adhesive strength was measured in the same manner. cm, and in this case also, no decrease in adhesive strength was observed. Further, elemental analysis of the exfoliation interfaces by Auger electron spectroscopy confirmed that all of the exfoliation interfaces were between cobalt silicide-polyimide layers.

Example 5 A polyimide film (Kapton V) having a film thickness of 50.0 μm was used. On one surface of this polyimide film, the surface of the polyimide film was treated by glow discharge of oxygen, and then tricobalt dinitride was used as a target. Thickness of 7 by RF magnetron sputtering with argon gas
A 00 nm tricobalt dinitride layer was formed. afterwards,
Immediately target copper with DC by argon gas
A 250 nm thick copper thin film layer was formed by magnetron sputtering. Next, the thickness of the copper film for the circuit is reduced to 20 μm by electrolytically plating copper on the copper thin film.
m. When the adhesive strength of the circuit copper film obtained by such a method to the polyimide film was measured, the average strength in normal state was 1.2 kg / cm. This was placed in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner. The average was 1.2 kg / cm, and no decrease in adhesive strength was observed.

On the other hand, before putting it in an oven at 150 ° C,
The film was wound around a stainless steel rod having a diameter of 10 mm, 5 times on each side, 10 times in total, and then placed in an oven at 150 ° C. and held for 10 days, and the adhesive strength was measured in the same manner. cm, and in this case also, no decrease in adhesive strength was observed. In addition, elemental analysis of exfoliation interfaces by Auger electron spectroscopy showed that tricobalt dinitride-
It was confirmed to be between the polyimide layers.

Example 6 A polyimide film (Kapton V) having a film thickness of 50.0 μm was used, and the surface of the polyimide film was treated by glow discharge of oxygen on one surface of this polyimide film, and then cobalt carbide was used as a target for argon gas. 200 by RF magnetron sputtering method
nm cobalt carbide layer was formed. Immediately thereafter, a copper thin film layer having a thickness of 250 nm was formed by a DC magnetron sputtering method using argon gas with copper as a target. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesion of the copper film for a circuit obtained by such a method to the polyimide film was measured, the average strength was 1.
It was 3 kg / cm. This was put in an oven at 150 ° C. and kept for 10 days, and then the adhesive strength was measured in the same manner. The average was 1.3 kg / cm, and no decrease in the adhesive strength was observed.

On the other hand, before putting it in an oven at 150 ° C,
The film was wound around a stainless steel rod having a diameter of 10 mm, 5 times on each side, 10 times in total, then put in an oven at 150 ° C. and kept for 10 days, and the adhesive strength was measured in the same manner. cm, and in this case also, no decrease in adhesive strength was observed. Moreover, when these were subjected to elemental analysis of the exfoliation interface by Auger electron spectroscopy, it was confirmed that all of the exfoliation interfaces were between cobalt carbide-polyimide layers.

(Comparative Example 1) A polyimide film (Kapton V) having a film thickness of 50.0 μm was used. On one side of the polyimide film, the surface of the polyimide film was treated by glow discharge of oxygen. Chemical Laboratory] was used as a target to form a cobalt layer having a thickness of 600 nm by a DC magnetron sputtering method using argon gas. Immediately thereafter, a copper thin film layer having a thickness of 250 nm was formed by a DC magnetron sputtering method using argon gas with copper as a target. Next, the thickness of the circuit copper film was set to 20 μm by electrolytically plating copper on the copper thin film. When the adhesive force to the polyimide film of the circuit copper film obtained by such a method was measured,
The normal strength was 1.0 kg / cm on average, and there was a portion where the adhesive strength was reduced to about 0.1 kg / cm. This was placed in an oven at 150 ° C. and kept for 10 days, and the adhesive strength was measured in the same manner.
The adhesive strength was g / cm, and although the average value did not show a decrease in adhesive strength, the adhesive strength was still partially 0.1 kg /
It was recognized that there was a portion that dropped to about cm.

On the other hand, before putting it in an oven at 150 ° C,
The film was wound around a stainless steel rod having a diameter of 10 mm, 5 times on each side, 10 times in total, and then placed in an oven at 150 ° C. and held for 10 days, and the adhesive strength was measured in the same manner. cm, and even in this case, the average value did not show a decrease in adhesive strength, but there was also a part where the adhesive strength was decreased to about 0.1 kg / cm. In addition, when these elements were subjected to elemental analysis of the peeling interface by Auger electron spectroscopy,
Most of the peeling interfaces were between the cobalt-polyimide layers, but the peeling interfaces in the part where the adhesive strength was lowered were between the cobalt-cobalt layers and the cobalt-copper layers.

[0036]

As is clear from the above examples and comparative examples, the metal compound polymer film formed according to the present invention not only deteriorates the characteristics during the high temperature test but also deteriorates the performance during the secondary processing. It is a very useful invention for the semiconductor industry because it provides a flexible circuit board material in which the above-mentioned is significantly relaxed.

[Brief description of drawings]

FIG. 1 is a layer structure of an example of a metal compound polymer film of the present invention.

FIG. 2 is a layer structure of an embodiment of the material for a flexible circuit board of the present invention.

FIG. 3 is a layer structure of one embodiment of the material for a flexible circuit board of the present invention.

[Explanation of symbols]

1 Polyimide film 2, 2'cobalt inorganic compound layer 3,3 'Copper thin film Copper film for 4, 4'circuits

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuhiro Fukuda 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (56) Reference JP-A-8-332697 (JP, A) JP-A-8 −330693 (JP, A) JP-B-52-25868 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3/38 H05K 1/03 H05K 1/09 B32B 15/08 C23C 14/00-14/58

Claims (4)

(57) [Claims] 1. A metal compound polymer film, comprising: forming a cobalt inorganic compound layer having a thickness of 20 to 3000 nm on one side or both sides of a plastic film, and forming a copper layer on the cobalt inorganic compound layer. 2. The metal compound polymer film according to claim 1, wherein the plastic film is a polyimide film. 3. The metal compound polymer film according to claim 1, wherein the cobalt inorganic compound layer is formed by a sputtering method. 4. The cobalt inorganic compound layer comprises cobalt phosphide,
The metal compound polymer film according to claim 1, which is selected from cobalt sulfide, cobalt telluride, cobalt silicide, cobalt nitride, and cobalt carbide.