JP3272945B2 - Manufacturing method of wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wiring board used in, for example, the information communication field, and more particularly to a method for manufacturing a wiring board using benzocyclobutene as an interlayer insulating film.

[0002]

2. Description of the Related Art In recent years, multimedia represented by the Internet has rapidly developed. With this development, various demands have been made in the information and communication field. For example, in data transfer between computers or between mobile portable terminals and computers, ultra-high speed and large capacity are required, and since multimedia is mainly for private demand, the cost of equipment to be used has been reduced. Highly required.

The hardware center of these devices is LSIs such as microprocessors and memories, and high-frequency components such as MMICs. Usually, these semiconductor chips are housed in a package and mounted on a printed wiring board or the like.

[0004] However, with the increase in the speed and the capacity of the data transfer as described above, it has become impossible to cope with the conventional mounting method. For example, due to the increase in clock frequency and the increase in wireless communication frequency, conventional printed wiring boards use epoxy resin as the board material, which causes a large signal delay, and a high-frequency signal causes a large loss. The problem of was seen. Furthermore, in order to improve the electrical characteristics, a flip-chip mounting method has been required in which a bump electrode called a bump is formed on an electrode pad of the LSI, and the LSI chip is directly mounted on the substrate. However, in the conventional printed wiring board, it is difficult to miniaturize wirings and pads, so that it is impossible to form a pattern corresponding to a flip chip requiring a pitch of 100 microns or less. As a board to solve this problem, a built-up type board that can handle flip chips by forming multilayer wiring with fine metal wiring on a printed wiring board using thin film technology and epoxy resin insulating film as an interlayer insulating film has been commercialized. ing. However, these substrates still have problems, and require high-speed digital signals and tens of GHz that will be required in the future.
In order to handle high-frequency signals, a substrate that handles high-speed and high-frequency signals cannot be realized unless the dielectric material is changed to a material having better electrical characteristics than epoxy resin. For these reasons, benzocyclobutene (BCB), which has better electrical, mechanical and thermal properties than epoxy resin, has been developed by Dow Chemical and adaptation to build-up substrates has been studied at various locations.

A multilayer wiring board using BCB can be manufactured by using, for example, a photoetching method as follows. 8 to 11 are views for explaining a method for manufacturing a wiring board using a conventional BCB.

As shown in FIG. 8, a first wiring 3 is usually formed on the surface of a printed circuit board 1 in advance.
A photosensitive BCB resin 2 is formed thereon by, for example, a spin coating method. Under predetermined conditions, pre-bake, exposure,
The groove 22 is formed by patterning by performing development.

Next, as shown in FIG. 9, a metal film 8 made of, for example, copper is formed on the patterned BCB film by a sputtering method or an evaporation method. Thereafter, as shown in FIG. 10, a resist layer is formed on the metal layer 8 by a spin coating method, and the resist film 9 is obtained by performing patterning.

Further, unnecessary metal layer 8 is removed by etching using resist film 9 as a mask, and then resist film 9 is removed, thereby obtaining a multilayered wiring board as shown in FIG.

In such a conventional manufacturing method, since a photo-etching process is used, the number of steps is large and the cost is high. Further, since the etching solution and the resist material are harmful to the human body and the environment, their use is not desirable from the viewpoint of environmental protection.

[0010]

As described above, the conventional B
Since the multi-layer wiring process using CB uses a general photo-etching process for forming wiring, the number of steps is large, the cost is high, and the use of an etchant has a problem in environmental protection. In addition, a conventional wiring board has a BC
The bonding strength between B and the metal film was insufficient, and the reliability was generally low.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method of manufacturing a highly reliable wiring board at a low cost by using a simplified process having no problem in environmental protection. is there.

[0012]

According to the method for manufacturing a wiring board of the present invention, first, a metal wiring and a benzocyclobutene insulating film as an insulating film between the metal wirings are formed on the substrate. In the manufacturing method, a step of forming and patterning a benzocyclobutene insulating film on a substrate provided with a wiring layer, a step of performing a plasma treatment using nitrogen gas on the surface of the benzocyclobutene insulating film, Forming a metal film on the surface of the benzocyclobutene insulating film, plating the metal film, and removing unnecessary plating by polishing. Secondly, in the method for manufacturing a wiring board according to the present invention, the wiring layer is provided on the substrate by using a metal wiring and a benzocyclobutene insulating film as an insulating film between the metal wirings. Forming a benzocyclobutene insulating film on a patterned substrate, patterning; forming a metal film on the surface of the patterned benzocyclobutene insulating film; and providing the metal film and the benzocyclobutene insulating film on the substrate. A heat treatment at a temperature of 230 ° C. to 270 ° C., a step of plating the metal film, and a step of removing unnecessary plating by polishing.

[0013]

According to the present invention, first, a benzocyclobutene insulating film is formed on a substrate provided with a wiring layer, and then, for example, according to a desired wiring or via pillar shape, a benzocyclobutene insulating film is formed. The butene insulating film is patterned to form a groove having a desired depth. Next, the surface of the benzocyclobutene insulating film in which the groove is formed by patterning is covered with a thin metal film to be a plating electrode by, for example, a vacuum deposition method, a sputtering method, or the like. Thereafter, a plating metal is applied on the metal film to fill the groove. Next, unnecessary plating deposited in places other than the grooves is removed by a polishing method. By repeatedly performing the process from forming such a benzocyclobutene insulating film to the process of removing unnecessary plating by a polishing method, a wiring board can be manufactured.

According to the multi-layer substrate process of the present invention, wiring can be formed by mechanical polishing, so that the process is simplified as compared with the conventional photoetching method, and an inexpensive wiring substrate can be realized. In addition, the photoetching method uses a large amount of a harmful etching solution, but the process according to the present invention does not use any etching solution, so that it also addresses environmental issues.

The metal film used in the present invention may be a single layer or a laminate. According to a first preferred embodiment of the present invention,
The metal film has a Cr layer on at least a side in contact with the BCB insulating film. Since this Cr layer has particularly good adhesiveness to BCB, the use of the Cr layer provides a better adhesive strength that can withstand mechanical polishing sufficiently, and a highly reliable wiring board can be obtained.

That is, using the process of the present invention,
By using Cr at the interface between the metal wiring and the BCB, the BC
In the bonding between B and the metal film, for example, a strength 200 times or more that of a normal process using only a copper thin film as a metal wiring is obtained, and high reliability is obtained. In addition, by improving the adhesive strength, mechanical polishing that has been impossible in the past can be performed.

According to a second preferred embodiment of the present invention, the method of the present invention further comprises, before the step of forming a metal film, a step of subjecting the surface of the BCB film to a plasma treatment using nitrogen gas. When plasma treatment using nitrogen gas is performed, better adhesive strength can be obtained, and a highly reliable wiring substrate can be obtained.

According to a third preferred aspect of the present invention, after the step of forming a metal film, a step of heat-treating the substrate provided with the metal film and the benzocyclobutene insulating film at a temperature of 230 ° C. to 270 ° C. Has further. By performing such a heat treatment, better adhesive strength can be obtained, and a highly reliable wiring board can be obtained.

Hereinafter, the present invention will be described in detail with reference to the drawings. 1 to 3 are diagrams for explaining a wiring process according to the present invention. In the present invention, since the curing temperature of BCB is as low as 210 to 250 ° C., for example, an inexpensive printed circuit board can be used as the base substrate. As shown in FIG. 1, the first copper wiring 3 is usually formed on the surface of the printed circuit board 1 in advance. A photosensitive BCB resin 2 is formed on the entire surface of the substrate by, for example, a spin coating method. Next, prebaking is performed at, for example, 80 ° C. for 20 minutes, exposure is performed at, for example, 600 mJ, and then patterning is performed by performing development to form grooves 21 and 22, thereby obtaining a cross-sectional shape as shown in FIG. Here, the groove 21 is a portion that will eventually become a wiring, and the groove 22 is a portion that will be a via pillar. In addition, the method of forming the deep groove 22 and the shallow groove 21 as shown in FIG. 1 by one development can be easily realized by, for example, forming a film for adjusting the amount of transmitted light on a glass mask at the time of exposure in advance. In this case, since the photosensitive BCB is a negative type, a chromium film is formed on the mask so that light is not applied to a portion where the groove pattern is formed. If this chromium film is formed to a thickness of, for example, 10 nm or less in accordance with a desired light transmitting material, the BCB film is exposed in a small amount, and a difference occurs in the developing speed from the portion where the thick chromium film is formed. By utilizing this phenomenon, a deep groove and a shallow groove can be simultaneously formed. As a means for applying a small amount of light, for example, a fine circle or square pattern of 1 micron or less is formed on a chromium film of about 1 micron used in a normal glass mask, and a small amount of light is applied to the BCB film. There is also a method.

Next, an electrode film 5 for copper plating is formed by, for example, a vacuum evaporation method. At this time, how much the metal film 5 can be formed on the BCB with high adhesive strength affects the process yield. In the present invention, since mechanical polishing is finally performed, strong adhesive strength is required in this step.

We conducted experiments under many conditions and succeeded in forming an electrode film having an adhesion strength exceeding 200 times the adhesion strength of BCB and a copper thin film which is generally performed. FIG. 4 shows that after performing the plasma treatment on the surface of the BCB film,
FIG. 3 is a graph showing a relationship between a gas used for plasma treatment and an adhesive strength between a metal film and a BCB insulating film when a metal film is formed. Here, a Cr film was used as the metal film. In addition, in all the adhesive strength measurements, a 90-degree peel test method, which is used as a standard method for bonding copper foil and adhesive strength in printed circuit board technology, was used. Further, the adhesive strength was represented by a ratio when the adhesive strength between the BCB and the copper thin film was set to 1. FIG. 4 shows that N ₂ gas is particularly excellent as a gas used for the plasma processing.

FIG. 5 shows the type of the metal film to be formed and the type of the metal film and the BCB insulating film when the metal film is formed after performing the plasma treatment on the surface of the BCB film using N ₂ gas. FIG. 3 is a graph showing a relationship with an adhesive strength. FIG. 5 shows that the Cr film has the strongest adhesive strength. Moreover, the adhesive strength was 200 times or more the adhesive strength between copper and the BCB insulating film.

FIG. 6 shows BCB subjected to O ₂ plasma treatment.
FIG. 4 is a graph showing the ratio between the adhesive strength before heat treatment and the adhesive strength after heat treatment when various metal films are formed on the film and heat treatment is performed at 250 ° C. for 60 minutes. From FIG. 6, it can be seen that the heat treatment increases the bonding strength of metal films other than copper by 5 to 13 times.

Although the heat treatment is performed at 250 ° C. here, the heat treatment temperature is not limited to 250 ° C. FIG.
FIG. 5 is a graph showing the relationship between the heat treatment temperature and the adhesive strength when a Cr film is formed on the BCB film after the N ₂ plasma treatment, and the heat treatment is performed while changing the temperature. The adhesive strength before the heat treatment is 80 gf · cm. However, the adhesive strength gradually increases with an increase in the heat treatment temperature, and at around 220 ° C., the adhesive strength becomes 200 gf enough to withstand the polishing treatment.
・ It exceeds cm and becomes constant around 250 ° C. But 3
When the temperature exceeds 00 ° C., decomposition of BCB itself starts, and it tends to be difficult to function as an insulating film. This indicates that the preferable heat treatment temperature range is from 220 ° C. to 300 ° C.

As described above, Cr is used as the metal film, plasma processing is performed on the BCB insulating film before forming the metal film, or 220 to 300 after forming the metal film.
By performing the heat treatment at a temperature of ° C., higher adhesive strength can be obtained. The adhesive strength enough to withstand the treatment by polishing is about 200 f · cm. If the metal to be plated is Cu, if the metal to be plated is Cu, Cr /
A laminated structure of Cu is preferable. The thickness of each film is 10 for Cr.
Preferably, the thickness ranges from 0 Å to 1 μm, and the Cu content ranges from 5,000 Å to 2 μm.

Next, as shown in FIG. 2, using this metal film, electroplating is performed to form a plating film 4. The plating can be performed until the groove 22 is completely filled. Further, as shown in FIG. 3, the upper plating film is mechanically polished until the wiring 6 and the via pillar 7 are formed. As the polishing method, for example, a buff polishing method generally used in a printed circuit board process is considered to be good from the viewpoint of cost and precision, but a polishing device for surface finishing of semiconductor wafers and a polishing device for back lapping are used. The polishing method used may be used.

In the foregoing, an example of the wiring board and the method of manufacturing the same according to the present invention has been described. In the conventional method, the yield is determined by the patterning of the resist. However, in the present invention, since no resist is used, a patterning step of the resist is not required, and the yield is very good. Also, in the conventional method,
In the etching process, an etchant harmful to the human body and the environment is used. However, in the present invention, since no photoresist method is used, an etchant is not required, and it is friendly to the human body and the global environment.

[0028]

As described above, according to the method of the present invention, since the steps can be simplified, a wiring board which is inexpensive and has excellent electric characteristics can be realized. Further, since the adhesive strength between the BCB and the metal film is improved, high reliability can be obtained. Further, according to the present invention, since no etchant is used, a method having no problem in environmental protection can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a wiring process of the present invention.

FIG. 2 is a diagram for explaining a wiring process of the present invention.

FIG. 3 is a diagram for explaining a wiring process of the present invention.

FIG. 4 is a graph showing the relationship between the gas used in the plasma treatment and the adhesive strength.

FIG. 5 is a graph showing the relationship between the type of metal film formed on the BCB insulating film and the adhesive strength.

FIG. 6 is a graph showing the relationship between the type of a metal film and the ratio of adhesive strength before and after heat treatment.

FIG. 7 is a graph showing the relationship between heat treatment temperature and adhesive strength.

FIG. 8 is a view for explaining a conventional method of manufacturing a wiring board using BCB.

FIG. 9 is a view for explaining a conventional method of manufacturing a wiring board using BCB.

FIG. 10 is a view for explaining a conventional method of manufacturing a wiring board using BCB.

FIG. 11 is a view for explaining a conventional method of manufacturing a wiring board using BCB.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... BCB film 3 ... First wiring 4 ... Plating film 5 ... Metal film 6 ... Wiring 7 ... Via pillar 8 ... Metal layer 9 ... Resist 10 ... Thin film wiring 21 ... Groove to be wiring 22 ... Via pillar Become a groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-17798 (JP, A) JP-A-4-167596 (JP, A) JP-A-9-59758 (JP, A) JP-A-8-179 134639 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/28-21/288 H01L 21/44-21/445 H01L 29/40-29/43 H01L 29/47 H01L 29/872 H01L 21/3205 H01L 21/321 H01L 21/768 H01L 21/3213 H01L 21/31 H01L 21/312 H01L 21/47 H05K 3/42

Claims (3)

(57) [Claims] 1. A method of manufacturing a wiring board comprising a metal wiring and a benzocyclobutene insulating film as an insulating film between the metal wirings on a substrate, wherein the benzocyclobutene insulating film is formed on the substrate provided with the wiring layer. film is formed, plug using the steps of patterning, the nitrogen gas in the benzocyclobutene insulating film surface
This comprising the step of applying a Zuma processing step the plasma treated benzocyclobutene surface of the insulating film to form a metal film, a step of plating on the metal film, and removing unnecessary plating by polishing <br/> A method for manufacturing a wiring board. 2. A method according to claim 1, further comprising the steps of: forming a metal wiring on said substrate;
Constructed using benzocyclobutene insulating film as edge film
In the method of manufacturing a wiring board, benzocyclobutene insulation is provided on a substrate on which a wiring layer is provided.
Forming and patterning a film, and forming a gold layer on the patterned benzocyclobutene insulating film surface.
Forming a metal film, and a substrate provided with the metal film and the benzocyclobutene insulating film
A heat treatment at a temperature of 230 ° C. to 270 ° C., a step of plating the metal film , and a step of removing unnecessary plating by polishing.
And a method of manufacturing a wiring board. 3. The method according to claim 1, wherein the metal film is at least benzocyclo.
It has a Cr layer on the side in contact with the butene insulating film.
The method for manufacturing a wiring board according to claim 1.