JPH104263A - Electronic circuit board and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: Various kinds of electronic circuit boards, such as an increase in wiring resistance due to a reaction between Cu and polyimide, an increase in dielectric constant of an insulating layer, and a decrease in connectivity between the wiring layer and the insulating layer. Defects are reliably and easily suppressed. An inorganic oxide thin film is formed on a surface of a substrate where Cu is exposed, and a polyimide insulating film is formed thereon.
This is formed by forming a through hole or the like into the thin film insulating layer 12.
Then, a thin-film wiring layer 13 and a thin-film insulating layer 14 are sequentially stacked thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick-film / thin-film hybrid multilayer electronic circuit board used for a large-sized computer or the like, and more particularly to an electronic circuit board using a wiring material of Cu and a thin-film insulating material of polyimide. .

[0002]

2. Description of the Related Art In recent years, module boards used in large-sized computers and the like are required to transmit high-frequency signals at high speed in order to quickly transmit and receive signals between LSI elements mounted on the boards. . In addition, as the signal speed increases, the operating temperature of the module substrate becomes more severe, and reliability and durability are also important factors that determine the performance of the module substrate. In order to solve these problems and realize a high-performance module substrate, materials required for the module substrate are required to have a low dielectric constant for the insulator and a high dielectric constant for the internal wiring. And that these materials have good physical compatibility (eg, have close thermal expansion coefficients) and good chemical compatibility (eg,
Strong bonding force between the two).

FIG. 4 shows a cross-sectional view of a thick-film / thin-film hybrid electronic circuit board often used as an example of an electronic circuit board. In this example, thin film insulating layers 12 and 14 made of a polyimide insulating film 4 and thin film wiring layers 13 and 15 made of a metal thin film 5 are formed on a substrate 11 made of an insulator 1 and a metal body 2. The thin film wiring layer 15 serves as a solder connection electrode 33, and a module substrate is formed by connecting an LSI element to this upper layer via solder. By using a material that satisfies the conditions described above for this module substrate, an ideal electronic circuit substrate can be realized.

[0004] Specifically, materials suitable for an electronic circuit board are described below. An insulating material is a polyimide dielectric film, and a metal material is Cu or Ag. In particular, Cu has a low electric resistance and a high electromigration resistance, and therefore, in many cases, Cu is used as a wiring material in high-performance electronic circuit boards that transmit signals with a high current density. As for the insulating material of the thin film, it is common to use polyimide because of its low dielectric constant and thermal / chemical stability.

However, when CU and polyimide are combined, Cu and polyamic acid which is a precursor of polyimide cause a chemical reaction. Polyamic acid to produce a copper oxide Cu ₂ O reacts with Cu, the Cu ₂ O is diffused into the polyimide. This phenomenon causes adverse effects such as an increase in the electric resistance of the Cu wiring, an increase in the dielectric constant of the polyimide, and a decrease in the adhesiveness between Cu / polyimide. The polyimide is formed by uniformly coating a varnish-like polyimide precursor on the entire substrate by a spin coater, and heat-treating the polyimide precursor to imidize the polyimide. Therefore, C
When u is exposed, the polyamic acid comes into contact, and a chemical reaction occurs. In the case of the electronic circuit board shown in FIG. 3, when forming the thin film insulating layer 12 on the substrate 11, the opportunity to come into contact with Cu as the thick film pad 31 and the polyamic acid serving as the thin film insulating layer 12 is obtained. May cause a bad defect.

[0006] Examples of countermeasures against this problem include Cr and N.
There is a method in which a metal thin film that does not react with polyimide such as i is provided at the interface between Cu and polyimide to form a reaction barrier layer. For thin-film Cu wiring, for example, Cr / Cu / C
A method of forming a laminated film like r and covering at least a plane horizontal to the substrate (excluding the side wall of the wiring) with a barrier metal is often used. Literature (Journa
l of Vacuum Science and T
"Oxygen induced adhesion" described in technology A9 (6) (1991).
degradation at metal / poly
When the polyimide is formed directly on Cu, the peel strength is 14 g / m.
m, but the interface between Cu and polyimide
Alternatively, when Ni is formed, the formation of a deteriorated layer due to the Cu / polyimide reaction is avoided, so that the peel strength is Cr.
In the case of, it is reported that it is improved to 24 g / mm, and in the case of Ni, it is improved to 47 g / mm.

[0007]

However, a serious problem arises when the method of providing a barrier metal on the electronic circuit board shown in FIG. 4 is used. Hereinafter, the problem will be described with reference to FIGS.

First, in a method of providing a reaction barrier metal on a Cu pad 31 as a metal body 2 of a substrate 11, FIG.
After the thin film metal 6 is formed on the entire surface of the substrate as shown in FIG. 5B, the thin film must be patterned to electrically separate the respective electrodes as shown in FIG. 5C. At this time, as shown in FIG. 6, when the exposure 21 of the Cu surface occurs due to the displacement of the pattern of the thin film and the position of the Cu electrode, the polyimide formed thereon and the Cu electrode come into contact,
A reaction between Cu / polyimide occurs. FIG.
The short circuit 22 between the Cu pads due to the pattern shift as shown in FIG. From the above, quite high accuracy is required for the alignment of the thin film pattern. Further, even if the positioning accuracy of the thin film pattern can be improved, if the positioning accuracy of the Cu pad 31 on the substrate 11 side is poor, the same pattern shift occurs. In other words, it is extremely difficult to cover all of the reaction barrier metals with respect to a large number of electrode pads on the surface of the substrate 11 without displacement, and it is practically inapplicable to an electronic circuit board having a fine wiring pattern. Technology.

An object of the present invention is to provide an electronic circuit board capable of reliably and easily avoiding various defects caused by a reaction between Cu and polyimide, and a method for manufacturing the same.

[0010]

In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a semiconductor device, comprising a substrate comprising an insulator and a metal body, at least a portion of which is exposed on the surface thereof. An electronic circuit board in which wiring layers are sequentially laminated, wherein an inorganic insulating film is formed on the substrate surface, a polyimide insulating film is formed thereon, and a metal wiring layer is further laminated thereon in order. It is a substrate.

[0011] The present invention also relates to an electronic circuit board in which a polyimide insulating layer and a metal wiring layer are sequentially laminated on a substrate comprising an insulator and a metal body, at least a part of which is exposed on the surface thereof. An electronic circuit board, comprising: an inorganic insulating film formed thereon and directly above a metal wiring layer; and a polyimide insulating film formed thereon.

Further, the present invention is an electronic circuit board comprising a polyimide insulating layer and a metal wiring, wherein an inorganic insulating film is present on a boundary surface between the polyimide insulating layer and the metal wiring.

The present invention is also an electronic circuit board characterized in that the metal body is Cu.

According to the present invention, there is provided an electronic circuit board wherein the metal wiring is made of Cu.

Further, according to the present invention, the insulator is made of SiO ₂ , B ₂ O ₃ ,
An electronic circuit board characterized by being a glass ceramic comprising a glass matrix mainly composed of K ₂ O and Al ₂ O ₃ and dispersed particles mainly composed of mullite.

According to the present invention, there is provided an electronic circuit board, wherein the inorganic insulating film is made of one of alumina and titania.

The present invention also provides an electronic circuit board in which a polyimide insulating layer and a metal wiring layer are sequentially laminated on a substrate comprising an insulator and a metal body, at least a part of which is exposed on the surface thereof. A method of manufacturing an electronic circuit board, comprising: forming an inorganic insulating film thereon, forming a polyimide insulating film thereon, and further laminating a metal wiring layer thereon.

The present invention also relates to an electronic circuit board in which a polyimide insulating layer and a metal wiring layer are sequentially laminated on a substrate comprising an insulator and a metal body, at least a part of which is exposed on the surface thereof. A method for manufacturing an electronic circuit board, comprising: forming an inorganic insulating film on an upper portion and immediately above a metal wiring layer; and forming a polyimide insulating film on the inorganic insulating film. Further, the present invention is a method for manufacturing an electronic circuit board, comprising: an electronic circuit board comprising a polyimide insulating layer and a metal wiring, wherein an inorganic insulating film is formed on a boundary surface between the polyimide insulating layer and the metal wiring.

Further, the present invention is a method for manufacturing an electronic circuit board, wherein the metal body is Cu.

Further, the present invention is a method for manufacturing an electronic circuit board, wherein the metal wiring is made of Cu.

Further, according to the present invention, the insulator is made of SiO ₂ , B ₂ O ₃ ,
A method for manufacturing an electronic circuit board, comprising a glass ceramic comprising a glass matrix mainly composed of K ₂ O and Al ₂ O ₃ and dispersed particles mainly composed of mullite.

Further, the present invention is a method for manufacturing an electronic circuit board, wherein the inorganic insulating film is made of one of alumina and titania.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment of the present invention, a manufacturing process thereof will be described with reference to FIG.

First, SiO ₂ , B ₂ O ₃ , K
_An insulator 1 composed of a glass ceramic composed of a glass matrix mainly composed of ₂ O and Al ₂ O ₃ and dispersed particles composed mainly of mullite, and a metallic body 2 composed of Cu were used. . A thick film Cu pad 31 is formed on the surface of the substrate 11 on which the thin film wiring layer is to be formed.

First, the inorganic oxide thin film 3 is formed on the substrate 11.
To form The conditions of the inorganic insulating film suitable for the present invention include high insulating properties, good adhesion to Cu, ceramics, and polyimide, thermal and chemical stability, and the like. Specifically, alumina (Al ₂ O ₃ ) or titania (TiO ₂ ) is suitable. In this embodiment, alumina was used as the inorganic oxide thin film 3. Alumina is one of the constituents of the glass ceramic which is the insulator 1, and therefore has good adhesion to the ceramic and a risk of peeling or cracking during heating due to a difference in thermal expansion coefficient. Less is. It has also been confirmed that the adhesiveness to Cu polyimide is good.

The thickness of the alumina as the inorganic oxide thin film 3 was 10 nm. The value of 10 nm was determined based on the reaction barrier property of Cu / polyimide with alumina and the adhesiveness of the Cu / alumina / polyimide laminated film. First, the reaction barrier property between Cu and polyimide by alumina was determined by SIMS (Secondary Ion Mass).
(Spectrometry). FIG. 7 shows the result. This figure is a measurement of the concentration distribution of Cu particles in the depth direction of the polyimide in the laminated film composed of Cu / alumina / polyimide. The vertical axis represents the concentration of Cu. There are three types of samples, Cu / polyimide (no alumina) and Cu / alumina (film thickness 10n, respectively).
m) / polyimide, Cu / alumina (film thickness 100 nm)
/ Polyimide film structure. Looking at the figure,
For a sample consisting of Cu / polyimide without the presence of alumina, the Cu concentration in the polyimide was approximately 10 ¹⁹ at.
om / cm ³ , whereas the sample having 10 nm thick alumina at the Cu / polyimide interface is about 1
0 ¹⁷ atom / cm ³ and the concentration of Cu are reduced to about 1/100, which indicates that alumina suppresses diffusion of Cu into polyimide. If the thickness of the alumina film is further increased to 100 nm, the Cu concentration in the polyimide is further reduced, and the concentration near the SIMS measurement limit is about 1%.
It has dropped to 0 ¹⁶ atom / cm ³ . From this result, it can be determined that the effect of suppressing the Cu / polyimide reaction increases as the thickness of the alumina film increases, but the effect can be sufficiently suppressed even with a thickness of about 10 nm.

Next, the results of evaluating the adhesiveness of the Cu / alumina / polyimide laminated film by a vertical tensile test are shown in FIG.
Shown in The samples subjected to this test are three samples having the same film configuration as in the SIMS analysis. Although there was no significant difference in the tensile strength value between the samples, a difference was observed in the peeled portion. With respect to the samples without alumina, about 2/3 of the samples peeled off at the Cu / polyimide interface, whereas the samples with 10 nm of alumina did not show any Cu / polyimide peeling. Similarly, 100n of alumina
No peeling between Cu / polyimide was observed in the sample in which m was formed. This is due to the presence of alumina
This is due to the fact that the deterioration of the u / polyimide interface could be avoided and that the adhesion of alumina to Cu and polyimide was good.
It can be said that the same effect as that of the film is obtained. Also, from the results of this test, it was found that the alumina film thickness of 10 nm was sufficient for Cu /
It can be seen that the effect of suppressing the reaction between polyimides can be obtained.

The alumina was formed by sputtering. Alumina having a purity of 99.9% was used as a target. Before film formation, the substrate is heated in a vacuum chamber at 150 ° C. for 60 minutes, RF power 1 kW, Ar gas flow rate 90 S
Film formation was performed under the conditions of CCM, an oxygen gas flow rate of 10 SCCM, and a gas pressure of 0.2 Pa in the film formation chamber. The reason why oxygen was introduced into the film formation atmosphere was that when a film was formed only with Ar, even if the target was alumina (Al ₂ O ₃ ), the formed thin film lacked oxygen and had an O / Al composition ratio of alumina. 1.5 which is the value of
The reactive sputtering is caused by introducing oxygen, and a desired O / Al composition ratio is obtained. Regarding the film forming method, for example, electron beam evaporation or the like may be used. What is required of the film forming method is that the film quality and film thickness have little variation within the substrate,
Another advantage is that a film of stable quality can be formed with good reproducibility.

Further, as an advantage of the inorganic oxide thin film 3, there is no need to perform patterning as described in the section of the prior art, which is required when a metal thin film is formed. Therefore, the process becomes simpler and the problem of alignment accuracy in the photolithography process is eliminated, so that a finer pattern electronic circuit board can be formed.

After the formation of alumina is completed, a thin-film insulating layer 12 made of the polyimide insulating film 4 is formed thereon. For the polyimide, PIQ (R) manufactured by Hitachi Chemical was used. First, a polyimide precursor in a varnish state is dropped on a substrate, and this is uniformly coated on the substrate by a spin rotator. The condition of the spin rotator is 1000 rpm × 60 seconds at room temperature. Next, prebaking is performed in a baking furnace at 90 ° C. in a nitrogen atmosphere for 30 minutes. Thereafter, through holes 32 are formed in the polyimide by photolithography. A positive resist was used as a resist, and an alkali developing solution called NMD-3 manufactured by Tokyo Ohka Kogyo was used as a polyimide etching solution. After the polyimide is etched, the resist is peeled off, and the film is cured by performing a heat treatment. Heating conditions are as follows: first, a baking furnace at 140 ° C., then a baking furnace at 200 ° C., and finally, a baking furnace at 350 ° C. for 60 minutes. The heating atmosphere is a nitrogen atmosphere. Thus, a thin-film insulating layer 12 having a shape as shown in FIG. 2C is obtained.

Next, a thin film wiring layer 13 is formed on this upper layer. For the thin film wiring layer 13, a Cr / Cu / Cr laminated film was used. Sputtering was used for the film formation method. The film thickness was 0.075 μ, 3 μ, and 0.05 μ, respectively. Lower layer Cr
Plays the role of an adhesive layer for ensuring the adhesion between Cu and the underlying substrate. Further, the upper layer Cr plays a role of a reaction barrier layer for suppressing a reaction between Cu and polyimide formed thereon.

Here, when the formation of the thin film insulating layer 12 in FIG. 2C is completed, alumina as the inorganic oxide 3 remains at the bottom of the through hole, and the metal thin film 5 is directly formed in this state. Then, electrical contact cannot be made with the lower Cu pad 31 due to the alumina. The sputter etching mechanism provided in the sputtering apparatus was used for removing the alumina at the bottom of the through hole. First, when a metal thin film is formed, sputter etching is generally used for the purpose of removing foreign substances adhering to the formation surface and ensuring adhesiveness. Accordingly, if it is confirmed that alumina having a thickness of 10 nm is removed by sputter etching, the number of steps is not particularly increased. FIG. 9 is a graph showing the relationship between the sputter etching time and the etching amount of alumina. From this figure, it can be seen that if sputter etching is performed for three minutes, 10 nm alumina is almost removed. In this embodiment, the sputter etching time is set to 6 minutes in consideration of a margin.

The metal thin film 5 formed on the entire surface of the substrate as a Cr / Cu / Cr laminated film is patterned by a photolithography process to become a thin film wiring layer 13. Thereafter, the above-described method is repeated to alternately form the thin film insulating layers and the thin film wiring layers, thereby forming an electronic circuit board. In this embodiment, the thin film insulating layer 14 and the thin film wiring layer 15 are formed, and the thin film insulating layer and the thin film wiring layer are each formed in two layers to complete the process.

As a second embodiment of the present invention, a thick film C
FIG. 3 shows a manufacturing process for the purpose of suppressing the reaction between the thin film Cu and the polyimide in addition to u.
This will be described with reference to FIG.

The same substrate 11 as in Example 1 is used. A method for forming the inorganic oxide thin film 3 on the substrate 11;
The method of forming the polyimide film 4 as the thin film insulating layer 12 is the same as that shown in Example 1.

Next, the thin film wiring layer 13 is formed. A Cr / Cu laminated film is used for the thin film wiring layer 13. The thickness of Cr is 0.075 μm, and the thickness of Cu is 3 μm. The Cr / Cu thin film formed over the entire surface of the substrate is processed by photolithography to complete the thin film wiring layer 13.

Next, alumina as the inorganic oxide thin film 3 is again formed on the entire surface of the substrate on the thin film wiring layer 13 by sputtering. The forming conditions are the same as those described in Example 1. Further, a polyimide film 4 as a second insulating layer 14 is coated thereon to form a through hole. The forming conditions are the same as those described in Example 1. Finally, a thin film wiring layer 15 is formed on this upper layer to complete the process. Thin film wiring layer 1
3 and the thin film wiring layer 15 are secured by sputter etching as in Example 1.

[0038]

According to the present invention, various defects such as an increase in the wiring resistance, an increase in the dielectric constant of the insulating layer, and a decrease in the adhesiveness between the wiring layer and the insulating layer caused by the reaction between Cu and polyimide can be reliably prevented. In addition, it has the effect of being easily deterred.

Further, since the present invention does not use a patterning step, it has an effect of preventing an adverse effect such as an increase in man-hours and a decrease in wiring density due to a limit of alignment accuracy.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of an electronic circuit board of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of one embodiment of the electronic circuit board of the present invention.

FIG. 3 is an explanatory view showing a manufacturing process of a second embodiment of the electronic circuit board of the present invention.

FIG. 4 is a cross-sectional view of a conventional electronic circuit board.

FIG. 5 is an explanatory view showing a manufacturing process of a conventional electronic circuit board.

FIG. 6 is a sectional view showing various defects of a conventional electronic circuit board.

FIG. 7 shows a sample composed of Cu / alumina / polyimide,
FIG. 4 is a characteristic diagram showing the concentration of Cu in polyimide.

FIG. 8 shows a sample composed of Cu / alumina / polyimide,
FIG. 3 is a characteristic diagram showing an adhesive strength by a tensile test.

FIG. 9 is a characteristic diagram showing a relationship between a sputter etching time and an etching amount of alumina.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulator, 2 ... Metal body, 3 ... Inorganic oxide thin film, 4 ... Polyimide insulating film, 5 ... Metal thin film, 11 ... Substrate, 12 ... Thin film insulating layer, 13 ... Thin film wiring layer, 14 ... Thin film insulating layer, 15: thin film wiring layer, 31: thick film pad, 33: solder connection electrode.

Continued on the front page (72) Inventor Hidetaka Shigi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Production Research Laboratory

Claims (14)

[Claims] 1. An electronic circuit board comprising an insulator and a metal body, wherein a polyimide insulating layer and a metal wiring layer are sequentially laminated on a substrate on which at least a part of the metal body is exposed on the surface thereof. An electronic circuit board, comprising: an inorganic insulating film formed thereon; the above-described polyimide insulating film formed thereon; and the above-described metal wiring layer further laminated thereon. 2. An electronic circuit board comprising an insulator and a metal body, wherein a polyimide insulating layer and a metal wiring layer are sequentially laminated on a substrate on which at least a part of the metal body is exposed on the surface thereof. An electronic circuit board comprising: an inorganic insulating film formed directly on the metal wiring layer; and the polyimide insulating film formed thereon. 3. An electronic circuit board comprising a polyimide insulating layer and a metal wiring layer, wherein an inorganic insulating film is present at a boundary between the polyimide insulating layer and the metal wiring layer. 4. The electronic circuit board according to claim 1, wherein said metal body is Cu. 5. The electronic circuit board according to claim 1, wherein said metal wiring layer is made of Cu. 6. The method according to claim 1, wherein the insulator comprises a glass matrix mainly composed of SiO ₂ , B ₂ O ₃ , K ₂ O, and Al ₂ O ₃ and dispersed particles mainly composed of mullite. Electronic circuit board that is glass ceramic. 7. The electronic circuit board according to claim 1, wherein said inorganic insulating film is made of one of alumina and titania. 8. An electronic circuit board in which a polyimide insulating layer and a metal wiring layer are sequentially laminated on a substrate made of an insulator and a metal body and at least a part of the metal body is exposed on the surface thereof. A method for manufacturing an electronic circuit board, comprising: forming an inorganic insulating film thereon, forming the polyimide insulating film thereon, and further laminating the metal wiring layer thereon. 9. An electronic circuit board comprising an insulator and a metal body, wherein a polyimide insulating layer and a metal wiring layer are sequentially laminated on a substrate on which at least a part of the metal body is exposed. A method for manufacturing an electronic circuit board, comprising: forming an inorganic insulating film on the metal wiring layer and directly above the metal wiring layer; and forming the polyimide insulating film on the inorganic insulating film. 10. A method of manufacturing an electronic circuit board, comprising: an electronic circuit board comprising a polyimide insulating layer and a metal wiring layer, wherein an inorganic insulating film is formed on a boundary surface between the polyimide insulating layer and the metal wiring layer. . 11. The method according to claim 1, wherein said metal body is Cu. 12. The method according to claim 1, wherein said metal wiring layer is made of Cu. 13. The insulator according to claim 1, wherein the insulator comprises a glass matrix mainly composed of SiO ₂ , B ₂ O ₃ , K ₂ O and Al ₂ O ₃ and dispersed particles mainly composed of mullite. A method for manufacturing an electronic circuit board made of glass ceramic. 14. The method according to claim 1, wherein said inorganic insulating film is made of one of alumina and titania.