JP6867905B2 - Manufacturing method for wiring boards, semiconductor devices, and wiring boards - Google Patents

Description

The present invention relates to a wiring board, a semiconductor device, and a method for manufacturing a wiring board.

Various wiring boards are used in electronic devices such as personal computers and mobile phones. These wiring boards are manufactured by forming copper wiring, which has high electrical conductivity and is advantageous for speeding up the device, on the base material.

However, although copper wiring is easy to form, its surface layer portion may be oxidized during the manufacturing of the wiring board. In that case, the surface layer of the copper wiring whose resistance has been increased by oxidation is removed by etching with sulfuric acid or the like, but if the copper wiring is fine, most of the copper wiring is removed by etching. , It becomes difficult to make copper wiring finer.

Further, after commercialization, the copper wiring is oxidized depending on the usage environment, which causes a problem that the performance of the device is impaired.

Japanese Unexamined Patent Publication No. 2012-23102 Japanese Unexamined Patent Publication No. 60-223147

According to one aspect, it is an object of the present invention to provide a wiring board, a semiconductor device, and a method for manufacturing a wiring board, which can suppress oxidation of wiring containing copper.

According to one aspect, a substrate, formed on the substrate, a wiring containing copper, is formed on the surface of the wiring, a conductive polymer, including any of the polymer of titanium oxide, zirconium A wiring substrate with a film is provided.

According to one aspect, since the polymer film containing a polymer of either titanium oxide or zirconium oxide has an antioxidant function against copper, it is possible to suppress oxidation of the wiring under the polymer film.

FIG. 1 is a cross-sectional view of the silicon wafer used in the survey. FIG. 2 is a flowchart showing a method of forming a polymer film. 3 (a) and 3 (b) are cross-sectional views (No. 1) during the production of the sample. FIG. 4 is a cross-sectional view (No. 2) during the production of the sample. FIG. 5 is a diagram showing an example of a titanium chelate solution, an oligomer solution, and a zirconium chelate solution. FIG. 6 is a diagram showing an example of each component in the solution and the concentration of the component in the solution. FIG. 7 is a diagram showing an observation result of the color of the copper film after the heat treatment. FIG. 8 is a diagram showing the relationship between the color of the copper film and the thickness of the copper oxide film formed on the surface of the copper film. 9 (a) and 9 (b) are cross-sectional views (No. 1) of the semiconductor device according to the present embodiment during manufacturing. 10 (a) and 10 (b) are cross-sectional views (No. 2) of the semiconductor device according to the present embodiment during manufacturing. 11 (a) and 11 (b) are cross-sectional views (No. 3) of the semiconductor device according to the present embodiment during manufacturing. 12 (a) and 12 (b) are cross-sectional views (No. 4) of the semiconductor device according to the present embodiment during manufacturing. 13 (a) and 13 (b) are cross-sectional views (No. 5) of the semiconductor device according to the present embodiment during manufacturing. 14 (a) and 14 (b) are cross-sectional views (No. 6) of the semiconductor device according to the present embodiment during manufacturing. FIG. 15 is a cross-sectional view (No. 7) of the semiconductor device according to the present embodiment during manufacturing.

Prior to the description of the present embodiment, the matters examined by the inventor of the present application will be described.

The inventor of the present application conducted the following investigation to find a method for preventing oxidation of wiring containing copper.

FIG. 1 is a cross-sectional view of the silicon wafer used in the investigation.

As shown in FIG. 1, in this investigation, a copper film 2 imitating wiring was formed on the surface of the silicon wafer 1 to a thickness of about 500 nm.

Then, a titanium oxide polymer film was formed on the surface of the copper film 2 as follows.

FIG. 2 is a flowchart showing a method of forming the polymerized film. Further, FIGS. 3 to 4 are cross-sectional views during manufacturing of a sample using the silicon wafer 1.

First, in step S1 of FIG. 2, the silicon wafer 1 is immersed in an alkaline degreasing agent having a liquid temperature of about 40 ° C. to 60 ° C., and the copper film 2 is cleaned by maintaining the state for about 5 minutes.

After that, the silicon wafer 1 is pulled up from the degreasing agent.

Next, the process proceeds to step S2, and the copper film 2 is washed with pure water at room temperature for about 20 to 60 seconds.

Next, the process proceeds to step S3, and the surface of the copper film 2 is dried with air.

Subsequently, the process proceeds to step S4, and the silicon wafer 1 is immersed in IPA (Isopropyl Alcohol) to replace the water remaining on the surface of the copper film 2 with IPA.

Then, the process proceeds to step S5, and the surface of the copper film 2 is dried with air.

After that, the process proceeds to step S6, and the silicon wafer 1 is immersed in the solution of the organometallic complex.

FIG. 3A is a diagram schematically showing step S6.

In the example of FIG. 3A, the titanium chelate solution 4 is placed in the container 3 and the silicon wafer 1 is immersed in the solution 4. The temperature of the solution 4 is room temperature, and the immersion time is about 20 to 60 seconds.

The solution 4 is prepared by diluting an organometallic complex solution such as a commercially available titanium chelate solution with a diluting solvent.

FIG. 5 is a diagram showing an example of a commercially available organometallic complex solution manufactured by Matsumoto Fine Chemicals Co., Ltd.

In this example, one of the organometallic complex solutions of FIG. 5 is used. As shown in FIG. 5, the organic metal complex solution is not limited to the titanium chelate solution, and a titanium oligomer solution or a zirconium chelate solution may be used as the organic metal complex solution.

These organometallic complex solutions are divided into a solvent system containing an organic solvent and an aqueous solvent system. Of these, when a solvent-based organic metal complex solution is used, the organic metal complex solution can be uniformly adhered to the surface of the copper film 2 by replacing the water content of the copper film 2 with IPA in step S4. it can.

FIG. 6 is a diagram showing an example of each component in the solution 4 and the concentration of the component in the solution 4.

As shown in FIG. 6, the solution 4 is made from an organometallic complex solution, a diluting solvent, a surfactant, and a thickener.

The concentration of the organometallic complex solution in Solution 4 is 0.1 vol% to 10 vol%, and the concentration of the surfactant is 0.01 vol% to 1 vol%. The concentration of the thickener in the solution 4 is 0.1 wt% to 10 wt%.

Although a plurality of materials are listed as an example of the diluting solvent in FIG. 6, at least one of these materials may be used as the diluting solvent. The same applies to surfactants and thickeners.

See FIG. 2 again.

After immersing the silicon wafer 1 in the solution 4 as described above, the process proceeds to step S7, and the silicon wafer 1 is pulled up from the solution 4.

FIG. 3B is a cross-sectional view of the silicon wafer 1 when it is pulled up from the solution 4 in this way.

As shown in FIG. 3B, the coating film 5 of the solution 4 is formed on the surface of the copper film 2.

The method of forming the coating film 5 by immersing the silicon wafer 1 in the solution 4 in this way is called dip coating. The method for forming the coating film 5 is not limited to dip coating, and the coating film 5 may be formed by spin coating or a sol-gel method.

In this example, since the thickener is added to the solution 4 as described above, the thickness of the coating film 5 can be made uniform by the solution 4 having an appropriate viscosity.

Further, the thickness of the coating film 5 can be controlled by the immersion time of the silicon wafer 1 in the solution 4, and the longer the immersion time, the thicker the coating film 5 can be obtained.

See FIG. 2 again.

Next, the process proceeds to step S8, in which the coating film 5 is heated to a temperature of about 100 ° C. to 300 ° C. in an oven (not shown), and the state is maintained for about 30 seconds.

As a result, as shown in the following formula (1), the titanium chelate (Ti (OR) ₄ : R is an alkyl group) contained in the coating film 5 is hydrolyzed and the hydrolysis product (Ti (OR) ₃ OH) is hydrolyzed. ) Is generated, and the solvent of the coating film 5 is removed by heating.

Hereinafter, such heat treatment is also referred to as prebaking.

In order to prevent the surface of the copper film 2 from being oxidized during the prebaking, it is preferable to carry out this step in an inert atmosphere such as nitrogen gas.

Next, the process proceeds to step S9 of FIG. 2, in which the coating film 5 is heated to a temperature of about 100 ° C. to 300 ° C. in an oven (not shown), and the state is maintained for a time of about 1 minute to 60 minutes.

FIG. 4 is a cross-sectional view of the silicon wafer 1 when heated in this way.

By this heating, as shown in the following formula (2), the titanium chelate (Ti (OR) ₄ ) remaining in the coating film 5 and the hydrolysis product (Ti (OR) ₃ OH) undergo a polycondensation reaction. A dialkoxy titanium polymer is produced.

Then, the dialkoxytitanium polymer reacts with the moisture in the air to form a titanium oxide polymer, and the coating film 5 becomes a polymer film 6 containing the polymer.

The titanium oxide polymer contained in the polymer film 6 has a three-dimensional network structure as shown in the following formula (3).

When a zirconium chelate is used instead of the titanium chelate contained in the solution 4 (see FIG. 3A), the polymer film 6 contains a zirconium oxide polymer.

From the above, the sample P used for this survey was completed.

The inventor of the present application observes the color of the copper film 2 after heat-treating a plurality of samples P in the air in order to confirm whether or not the polymerized film 6 has a function of preventing the copper film 2 from being oxidized. did.

The result is shown in FIG.

FIG. 7 is a diagram showing an observation result of the color of the copper film 2 after the heat treatment.

As shown in FIG. 7, in this investigation, a titanium chelate solution and a zirconium chelate solution were used as the organometallic complex solution, and the thickness of the polymerization film 6 was changed for each sample P. The thickness of the polymerized film 6 was measured with a fluorescent X-ray film thickness meter. In addition, this survey was conducted by changing the heat treatment temperature and heat treatment time for each sample P.

From the results of FIG. 7, it was confirmed that the color of the copper film 2 was copper in all the samples except the sample number 2, and the copper oxide film was not formed on the copper film 2.

In sample number 2, the color was dark brown. The thickness of the copper oxide film can be empirically determined from FIG. 8 based on the color.

FIG. 8 is a diagram showing the relationship between the color of the copper film 2 and the thickness of the copper oxide film formed on the surface of the copper film 2.

According to FIG. 8, the thickness of the oxide film when it becomes dark brown is about 20 nm to 35 nm. Therefore, it was found that the oxidation of the copper film 2 was suppressed to some extent also in the sample number 2 of FIG.

From the above results, it was clarified that the polymerized film 6 has an antioxidant function for preventing the oxidation of copper.

The present embodiment will be described below.

(The present embodiment)
In the present embodiment, a semiconductor device is manufactured by mounting a semiconductor element on a wiring board as follows.

9 to 15 are cross-sectional views of the semiconductor device according to the present embodiment during manufacturing.

First, as shown in FIG. 9A, a glass substrate is prepared as the base material 20. The silicon substrate may be used as the base material 20.

Next, as shown in FIG. 9B, a plurality of through holes 20a are formed in the base material 20 by laser processing or etching processing.

When a silicon substrate is used as the base material 20, in order to insulate both ends of the through hole 20a, the entire surface of the base material 20 including the inner surface of the through hole 20a is thermally oxidized to provide an insulating silicon oxide film. May be formed.

Subsequently, as shown in FIG. 10A, a copper film of about 0.05 μm to 1 μm was formed as a seed layer 21 on the entire surface of the base material 20 including the inner surface of the through hole 20a by a sputtering method or an electrolytic plating method. Form to thickness.

Next, as shown in FIG. 10B, a photoresist is applied to the entire upper surface and the lower surface of the base material 20, and by exposing and developing the photoresist, a resist having an opening 22a overlapping the through hole 20a is provided. The layer 22 is formed.

Then, by supplying power from the seed layer 21, an electrolytic copper plating film is grown as a wiring 23 on the seed layer 21 in the opening 22a to a thickness of about 5 μm to 50 μm.

After that, as shown in FIG. 11A, the resist layer 22 is removed.

Subsequently, as shown in FIG. 11B, the seed layer 21 of the portion not covered by the wiring 23 is removed by wet etching while using, for example, a sulfuric acid-overwater etching solution as the wet etching solution.

Then, as shown in FIG. 12A, the titanium oxide polymer film 6 is formed on the surface 23a of the wiring 23 according to the flowchart of FIG.

The material of the polymer film 6 is not limited to the titanium oxide polymer. For example, by using a zirconium chelate in step S6 of FIG. 2, a polymer film 6 containing a polymer of zirconium oxide may be formed.

When forming the polymerized film 6, the base material 20 is immersed in the solution 4 as shown in FIG. 3A, but when the base material 20 is pulled up from the solution 4, the solution 4 is released from the surface of the base material 20. Since it is naturally excluded, the polymerized film 6 can be selectively formed only on the surface 23a of the wiring 23.

Further, as described above, since the polymerized film 6 has an antioxidant function of copper, the polymerized film 6 can suppress the oxidation of the wiring 23 during the production.

The surface 23a has an upper surface 23x and a side surface 23y, each of which is covered with the polymerization film 6. As a result, not only the upper surface 23x but also the side surface 23y can be protected by the polymer film 6, and the wiring 23 can be suppressed from being oxidized from the side surface 23y.

The film thickness of the polymerized film 6 is not particularly limited, but in this example, the polymerized film 6 is formed to a thickness of 20 nm to 100 nm. The reason why the lower limit of the film thickness is set to 20 nm is that if it is thinner than this, oxygen in the atmosphere easily permeates through the polymer film 6, and it becomes difficult for the polymer film 6 to prevent the wiring 23 from being oxidized. .. Further, the upper limit of the film thickness is set to 100 nm because the antioxidant effect of the wiring 23 by the polymer film 6 is saturated at a film thickness of about 100 nm.

Next, as shown in FIG. 12B, the stress of the wiring 23 is relaxed by performing a heat treatment for heating the wiring 23 to 100 ° C. to 200 ° C. in the atmosphere for a time of about 10 minutes to 1 hour.

At this time, in the present embodiment, since the surface 23a of the wiring 23 is covered with the polymer film 6 having an antioxidant function of copper, it is possible to suppress the oxidation of the wiring 23 by oxygen contained in the atmosphere.

Subsequently, as shown in FIG. 13A, a photosensitive solder resist is applied to both main surfaces of the base material 20, and the first solder resist layer 25 and the second solder are exposed and developed by exposing and developing the photosensitive solder resist. It forms a resist layer 26. Each of these solder resist layers 25 and 26 is formed with openings 25a and 26a overlapping the wiring 23.

Next, as shown in FIG. 13B, the polymer film 6 exposed from the opening 25a of the first solder resist layer 25 is removed by plasma treatment, and the surface 23a of the wiring 23 is exposed from the opening 25a.

A protective layer for protecting the wiring 23 may be formed by electroless plating on the wiring 23 exposed from the opening 25a. As such a protective layer, for example, there is a laminated film in which a nickel plating film and a gold plating film are laminated in order. Further, a laminated film in which a nickel plating film, a palladium plating film, and a gold plating film are laminated in this order may be formed as the protective layer.

Further, these protective layers may be formed on the polymer film 6 exposed from the opening 26a of the second solder resist layer 26.

Next, as shown in FIG. 14A, the base material 20 and the solder resist layers 25 and 26 are cut along the cutting line L to obtain a plurality of wiring boards 30 according to the present embodiment.

After that, the process moves to the process of mounting the semiconductor element on the wiring board 30.

First, as shown in FIG. 14B, a semiconductor element 31 provided with a plurality of electrodes 32 is prepared, and the opening 25a of the first solder resist layer 25 is aligned with the electrodes 32.

Then, after connecting the wiring 23 and the electrode 32 via the solder bump 33, the gap between the wiring board 30 and the semiconductor element 31 is filled with the underfill resin 34 to increase the connection strength between the two.

At this time, in the present embodiment, since the polymer film 6 is removed from the opening 25a in the step of FIG. 13B, the connection resistance between the wiring 23 and the electrode 32 can be suppressed as much as possible. When the semiconductor element 31 that does not need to suppress the connection resistance is used, the step of FIG. 13B may be omitted and the polymer film 6 may be left in the opening 25a.

Next, as shown in FIG. 15, a solder bump is mounted as an external connection terminal 36 on the polymer film 6 exposed from the opening 26a of the second solder resist layer 26.

In addition, in order to prevent the connection resistance between the external connection terminal 36 and the wiring 23 from increasing due to the polymer film 6, the polymer film 6 may be removed from the opening 26a in advance before this step.

Further, when the external connection terminal 36 is unnecessary, it is not necessary to mount the external connection terminal 36 on the polymer film 6.

As described above, the basic structure of the semiconductor device 40 according to the present embodiment is completed.

According to the above-described embodiment, the polymer film 6 of titanium oxide or zirconium oxide is formed on the surface 23a of the wiring 23 in the step of FIG. 12A. Since the polymerized film 6 has a function of preventing the oxidation of copper, it is possible to prevent the wiring 23 from being oxidized during the manufacturing of the wiring board 30.

As a result, it is not necessary to remove the oxidized surface layer portion of the wiring 23 with sulfuric acid or the like, and the wiring 23 can be easily miniaturized.

In particular, in this example, since the heat treatment is performed in the atmosphere in the step of FIG. 12B, the practical benefit of preventing the oxidation of the wiring 23 by the polymerized film 6 is particularly high.

Although the present embodiment has been described in detail above, the present embodiment is not limited to the above.

For example, in the above, the wiring 23 is formed on the base material 20 made of silicon or glass, but the wiring 23 is formed on the resin insulating layer such as epoxy resin or polyimide resin and polymerized on the wiring 23. The film 6 may be formed.

1 ... Silicon wafer, 2 ... Copper film, 3 ... Container, 4 ... Solution, 5 ... Coating film, 6 ... Polymer film, 20 ... Substrate , 20a ... Through hole, 21 ... Seed layer, 22 ... Resist layer, 22a, 25a, 26a ... opening, 23 ... wiring, 23a ... surface, 23x ... top surface, 23y ... side surface, 25 ... first solder resist layer, 26 ... second solder resist layer, 30 ... wiring board, 31 ... semiconductor element, 32 ... Electrode, 33 ... Solder bump, 34 ... Underfill resin, 36 ... External connection terminal, 40 ... Semiconductor device.

Claims (10)

With the base material
The wiring containing copper formed on the base material and
A conductive polymer film containing a polymer of either titanium oxide or zirconium oxide formed on the surface of the wiring, and
Wiring board with. The surface of the wiring has a side surface and an upper surface.
The wiring board according to claim 1, wherein the polymerized film is formed on each of the side surface and the upper surface. It has a solder resist layer formed on the wiring and the polymerized film, and has.
An opening is formed in the solder resist layer,
The wiring board according to claim 1 or 2, wherein the polymerized film is exposed from the opening. A wiring substrate having a base material, a wiring containing copper formed on the base material, and a conductive polymerized film containing a polymer of either titanium oxide or zirconium oxide formed on the surface of the wiring. When,
A semiconductor element mounted on the wiring board and electrically connected to the wiring,
Semiconductor device with. The wiring board has a solder resist layer formed on the wiring and the polymerized film.
An opening is formed in the solder resist layer,
The semiconductor device according to claim 4, wherein the polymer film is exposed from the opening. The process of forming wiring containing copper on the base material,
A step of forming a conductive polymerized film of either titanium oxide or zirconium oxide on the surface of the wiring, and
A method of manufacturing a wiring board having. The method for manufacturing a wiring board according to claim 6 , further comprising a step of heat-treating the wiring after the step of forming the polymerized film. The step of forming the polymerized film is
A step of forming a coating film of a solution of a titanium chelate, a titanium oligomer, or a zirconium chelate on the surface of the wiring.
A method for manufacturing a wiring board according to claim 6 or claim 7, characterized in that a step of the polymerization film by polymerizing and heating the coating film. The method for manufacturing a wiring board according to claim 8 , wherein the step of heating the coating film is performed in an atmosphere of an inert gas. A step of forming a solder resist layer on the wiring and the polymerized film, and
The step of forming an opening in the solder resist layer and
Have,
The method for manufacturing a wiring board according to any one of claims 6 to 9, wherein the polymerized film is exposed from the opening.

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