JP2002009435A - Processing method and forming method for via hole of organic substance substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable wiring in good contact with the top surface of a wiring layer exposed at the bottom of a via hole. SOLUTION: When a hydrogen radical is discharged from a nozzle 25e at a stage where all via holes are formed at necessary places on a substrate W by a laser drill main body 13, the hydrogen radical reduces the bottoms of the respective via holes, so the top surface of a metal conductive layer of Cu, etc., oxidized by desmearing in drill machining is reduced and purified to form a metal surface. Consequently, a connection of low connection resistance having high sticking strength can be obtained at a next film formation stage where metal conductive films for wiring are formed on metal conductive layers exposed at the via hole bottoms.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a via processing method and apparatus for processing a via hole formed by using a laser drill, and a via forming method using the same, and particularly to an adverse effect on the adhesion of an underlying conductive material. The present invention relates to a via processing method and the like that can prevent the occurrence of smear without causing a problem.

[0002]

2. Description of the Related Art As a method of forming a via in a wiring board, a method of forming a hole in a multilayer board constituting the wiring board by using a laser drill is known. When such laser processing is performed, a residue of a combustion gas called smear containing carbon as a main component adheres to the bottom and side surfaces of the obtained via hole. If such smears are left unattended, there is a problem that a wiring failure occurs in the next wiring step of connecting to a wiring layer made of a metal material such as Cu exposed at the bottom of the via hole. For this reason, a desmear process for removing smear as described above is provided after the laser processing and before the wiring process.

In the desmear process, smear on the inner surface of the via hole is oxidized and dissolved and removed using a solution such as potassium permanganate. Also, as another desmear process,
There is also a proposal to use a plasma process, which is a dry process, in response to a reduction in the diameter of a via hole. In this plasma treatment, smears attached to via holes are oxidized and decomposed by oxygen radicals in the plasma and scattered as carbon dioxide gas or the like in a plasma atmosphere.

[0004]

However, the above method has a problem that the surface of the wiring layer exposed at the bottom of the via hole is oxidized. In particular, surfaces other than desmears are usually oxidized. In other words, when the wiring layer is plated with Cu or the like, there is a problem that the adhesion (adhesion) of the plating layer deteriorates due to the presence of the oxide layer such as CuO.

Accordingly, the present invention provides a via processing method and apparatus which enables wiring with good adhesion to the surface of a wiring layer exposed at the bottom of a via hole, and enables such wiring with good adhesion. It is an object to provide a via forming method.

[0006]

In order to solve the above-mentioned problems, in the via processing method of the present invention, a laser beam is used on the insulating layer side of a substrate in which an insulating layer made of an organic material and a conductive layer made of a metal are joined. A via processing method for processing a via hole formed such that a conductive layer is exposed, comprising: a desmear step of removing smear adhered to the inside and the periphery of the via hole; and performing a plasma treatment on a surface of the conductive layer exposed inside the via hole. And a reducing step of reducing under a reduced reducing atmosphere.

In this case, since a reduction step is provided to reduce the surface of the conductive layer exposed inside the via hole under a reducing atmosphere in which the surface of the conductive layer is converted into a plasma, when the oxide film is formed on the surface of the conductive layer in the desmear step, This oxide film can be reduced to the original metal. Therefore, in the next wiring step of connecting to the conductive layer exposed inside the via hole, a wiring having high adhesion and low connection resistance can be obtained.

In a preferred embodiment of the above method, the desmearing step is performed at atmospheric pressure. That is, the desmear process can be simplified.

[0011] In a preferred embodiment of the method, the gas desmearing step comprises at least one around the via hole of the oxygen gas and CF ₄ gas under irradiation of the laser beam in the formation of the via hole, i.e. oxygen gas, CF ₄ gas and It is carried out by supplying a mixture of these and a gas containing them.

In this case, the oxygen gas or the like is supplied to the periphery of the via hole under the irradiation of the laser beam. Therefore, the oxygen gas or the like is excited by the laser beam incident on the via hole, and becomes a plasma containing oxygen radicals or the like to form a plasma inside the via hole. In addition, smear adhering to the periphery can be removed. That is,
In parallel with the formation of the via hole, the desmear process can be advanced without using any special means for forming a plasma, so that the via formation can be made simple and quick.

In a preferred embodiment of the above method, the reducing step is performed by supplying hydrogen plasma around the via hole.

In this case, since hydrogen plasma is supplied around the via hole in the reduction step, the oxide film formed on the surface of the conductive layer in the desmear step can be efficiently reduced to the original metal.

In a preferred embodiment of the above method, a plating layer is formed inside and around the via hole after the reduction step.

Further, another via forming method of the present invention is a method of forming a via on a substrate in which an insulating layer made of an organic material and a conductive layer made of a metal are joined, wherein the conductive layer is formed from the insulating layer side using a laser beam. When the via hole is formed so that the layer is exposed, oxygen is supplied to the vicinity of the laser beam incident position under substantially atmospheric pressure, thereby removing smear attached to the inside and the periphery of the via hole.

In this case, when forming the via hole, oxygen is supplied to the periphery of the incident position of the laser beam under substantially atmospheric pressure to remove the smear adhered to the inside and the periphery of the via hole. At the same time, the desmear process can proceed without using any special means for plasma conversion, and the via formation can be made simple and quick.

Further, the via processing apparatus of the present invention provides a via hole formed inside and around a via hole formed by irradiating a laser beam to an insulating layer side of a substrate in which an insulating layer made of an organic material and a conductive layer made of a metal are joined. The apparatus includes a desmear device for removing adhered smear, and a reducing device for reducing the surface of the conductive layer exposed inside the via hole under a reducing atmosphere in which the surface is converted into plasma.

In this case, since the reducing device reduces the surface of the conductive layer exposed inside the via hole in a reducing atmosphere in which the surface of the conductive layer is converted into a plasma, even if an oxide film is formed on the surface of the conductive layer in the desmear process, The original metal can be obtained by reducing the oxide film. Therefore, in the next wiring step of connecting to the conductive layer exposed inside the via hole, a wiring having high adhesion and low connection resistance can be obtained.

[0018]

[First Embodiment] FIG. 1 is a plan view illustrating the structure of a substrate processing apparatus incorporating a via forming apparatus according to a first embodiment of the present invention.

This substrate processing apparatus includes a via processing apparatus 10 for forming via holes in a desired arrangement in an organic insulating layer of a substrate W, a reduction processing apparatus 20 for processing via holes in a reducing atmosphere, and a reduction processing apparatus 20. Between the film forming apparatus 30 for forming a wiring layer for wiring in the via hole reduced in the above and the processing apparatuses 10, 20, 30.
And a transfer device 40 for delivering the same. Here, the via processing device 10 and the reduction processing device 20 function as a via processing device for processing the formed via holes. In addition,
The substrate W processed by this apparatus is a wiring substrate having a multilayer structure in which an insulating layer made of an organic material and a conductive layer made of a metal are joined.

FIG. 2 is a view for explaining the structure of the via processing apparatus 10. As shown in FIG. The via processing apparatus 10 includes a processing chamber 11 for processing a substrate W in an air atmosphere, a stage apparatus 12 for supporting the substrate W in place in the processing chamber 11, and a processing chamber 11 for processing the substrate W on the stage apparatus 12. A laser drill body 13 that constitutes a laser drill device for performing drilling by making the laser beam incident thereon, and a desmear section 14 that supplies oxygen gas into the processing chamber 11.

Here, the stage device 12 comprises a flat stage 12a for actually supporting the substrate W, and a stage 12a.
and a drive unit 12b for translating the laser beam a with respect to the laser drill body 13 in a horizontal plane. Stage 12a
Drive unit 12 controlled by a computer not shown
The substrate W can be moved three-dimensionally to an arbitrary position by using the laser drill body 13 in the processing chamber 11.
It is possible to support a plurality of via holes at appropriate positions on the substrate W.

Although not shown, the laser drill body 13 has a laser light source for generating a laser beam LB having photon energy enough to cause ablation in the organic insulating layer constituting the substrate W, and a laser beam from this laser light source. And a condensing optical system that converges the light LB into a spot on the substrate W through a transmission window 11 a provided in the processing chamber 11. As the former laser light source, an arbitrary light source corresponding to an organic material constituting an insulating layer such as a CO ₂ laser, an excimer laser, or a UV laser can be used. As the latter condensing optical system, a laser beam LB is used. 100 μm on the substrate W
Those that converge to a spot of m or less are used.

The desmear section 14 includes a gas container 14a for storing oxygen gas, a flow rate adjusting section 14b for adjusting the amount of oxygen gas flowing out of the gas container 14a, and a laser beam on the substrate W in the processing chamber 11. A nozzle 14c for discharging oxygen gas in the vicinity of the LB incident spot. During processing by the laser drill body 13, when oxygen gas is discharged from the nozzle 14c, the oxygen gas is turned into plasma in the vicinity of the via hole, that is, in the vicinity of the incident spot by the action of the laser beam LB. That is, since oxygen molecules are converted into oxygen radicals to decompose organic substances constituting smear, such a desmear can be formed without providing a device (microwave generator, vacuum vessel, etc.) for converting oxygen gas into plasma. It can be performed simply and quickly in parallel with laser processing.
The desmear reaction described above is shown below for reference.

[0024] ^{_{O * + C x H y O}} z → mCO 2 ↑ + nH 2 O ↑ O *: oxygen radical C _x H _y O _z: Sumiya x, y, z, m, n: the drilling by natural number of the laser beam LB The inside of the via hole of the substrate W being heated while being advanced is thermally active, and the above-described decomposition reaction is likely to occur here.

Although not shown, the processing chamber 11 is provided with a ventilation mechanism, so that unnecessary gas generated during laser processing or desmearing can be quickly removed.
It is discharged outside to keep the inside of the processing chamber 11 clean.

FIG. 3 is a diagram for explaining the structure of the reduction processing device 20. The reduction processing apparatus 20 includes an airtight processing chamber 21 for processing a substrate W, and a substrate W in the processing chamber 21.
And a radical supply device 25 that supplies hydrogen radicals into the processing chamber 21, and an exhaust device 26 that exhausts unnecessary gas in the processing chamber 21 to keep the inside clean.

The radical supply device 25 temporarily stores a gas container 25a for storing hydrogen gas, a flow rate adjusting unit 25b for adjusting the amount of hydrogen gas flowing out of the gas container 25a, and hydrogen gas passing through the flow rate adjusting unit 25b. A plasma chamber 25c, a coil 25d that converts hydrogen gas in the plasma chamber 25c into plasma to form hydrogen radicals,
A nozzle 25e for discharging hydrogen radicals onto the substrate W;

In the via processing apparatus 10, a substrate W having all via holes formed at important points on the substrate W is carried into the processing chamber 21 of the reduction processing apparatus 20, and hydrogen radicals are discharged from the nozzle 25e. Reduce the bottom of each via hole. Thus, the surface of the metal conductive layer of Cu or the like oxidized during desmearing that proceeds simultaneously with the drilling can be reduced and purified to obtain a metal surface.
Therefore, in the next film forming step of forming a metal conductive film for wiring on the metal conductive layer exposed at the bottom of the via hole,
Connections having high adhesion and low connection resistance can be obtained. Hereinafter, for reference, the metal conductive layer of the substrate W is C
The reaction when u was used is shown.

CuO + H ₂ ^* → H ₂ O ↑ + Cu The reduction of the bottom of the via hole can be performed while scanning the substrate W with respect to the nozzle 25 e. This allows
More uniform reduction becomes possible.

Returning to FIG. 1, a detailed description of the structure of the film forming apparatus 30 is omitted, but a metal conductive film for wiring, such as Cu wiring, is formed on the substrate W after via formation and via processing by a dry process. This is an apparatus for forming a film. As a dry process, for example, ion plating,
Various techniques such as sputter film formation and vapor deposition can be used. Further, in order to form a metal conductive film for wiring, an electroplating method can be used. In this case, specifically, a Cu seed layer is first provided by applying electroless copper plating to the substrate W after via formation, and then a Cu wiring layer can be formed by electrolytic plating.

The transport device 40 supports the substrate W and
1 is provided. The transfer robot 42 unloads the unprocessed substrate W from the cassette CA received from the outside, moves along the passage 41, and loads the substrate W into the via processing device 10. Also, the transfer robot 42
The substrate W processed by the via processing device 10 is transferred to the next reduction processing device 20, further transferred to the next film forming device 30, or the substrate W processed by the film forming device 30 is transferred to the cassette C.
Store in A.

FIG. 4 is a view for explaining typical processing by the substrate processing apparatus of FIG. FIG. 4A is a diagram schematically illustrating a side cross section showing a state of the substrate W before via formation. The substrate W has a multilayer structure in which an insulating layer IL made of an organic material and a conductive layer CL made of a metal are joined.

FIG. 4B is a diagram for explaining a stage in which via formation has been completed in the via processing apparatus 10. When a spot of a laser beam is made incident on an appropriate portion of the insulating layer IL, a via hole VH is formed here by ablation, and the conductive layer CL is formed.
Reach up to. In such drilling, the nozzle 1
When oxygen gas is supplied from around 4c around the via hole VH,
Oxygen molecules become oxygen radicals under the influence of the laser beam, and desmear, which decomposes smear, which is a by-product of drilling, also proceeds. However, in desmearing due to oxygen radicals, the surface of conductive layer CL exposed at the bottom of via hole VH is oxidized to form oxide layer OL.

FIG. 4C is a view for explaining the return processing in the return processing apparatus 20. When hydrogen radicals are supplied from the nozzle 25e onto the surface of the substrate W, the oxide layer OL at the bottom of the via hole VH formed by desmear which proceeds simultaneously with drilling is reduced and purified, and the metal surface is exposed at the bottom of the via hole VH. Can be.

FIG. 4D is a view for explaining film formation in the film forming apparatus 30. In the film forming apparatus 30, a wiring C is applied to the substrate W after via formation by a dry process.
The u wiring film WL is formed uniformly. The Cu wiring film WL formed in this manner is appropriately patterned in a process after using photolithography. The Cu wiring film WL thus patterned is connected to the conductive layer CL at the bottom of the via hole VH in close contact with the conductive layer CL, and has a low resistance at the time of connection. When the adhesion between the Cu wiring film WL and the conductive layer CL is not good, it is necessary to add a step of roughening the resin surface around the via hole VH by, for example, a chemical method using a permanganate-based chemical. Occurs.

[Second Embodiment] FIG. 5 is a plan view illustrating the structure of a via forming apparatus according to a second embodiment of the present invention. Via forming apparatus 110 according to the second embodiment of the present invention
Is a partially modified apparatus of the first embodiment, in which a reduction processing apparatus 20 is incorporated into a via processing apparatus 10 to form one processing apparatus, and via processing and reduction processing are performed collectively. Therefore, the same portions are denoted by the same reference numerals, and redundant description will be omitted.

The via forming apparatus 110 includes an airtight processing chamber 21 for processing a substrate W, a stage device 12 for supporting the substrate W in place in the processing chamber 21, and a stage 12.
Laser drill body 13 for drilling upper substrate W
And the desmear section 14 for supplying oxygen gas into the processing chamber 21.
A radical supply device 25 that supplies hydrogen radicals into the processing chamber 21; and an exhaust device 26 that keeps the inside of the processing chamber 21 clean by depressurizing and exhausting unnecessary gas in the processing chamber 21.

The operation of the substrate processing apparatus incorporating the via forming apparatus according to the second embodiment will be described. First, the substrate W carried into the processing chamber 21 of the via forming apparatus 110 is drilled by a laser beam from the laser drill body 13 in an air atmosphere, and a via hole VH is formed at an appropriate place. FIG. 4B). By supplying an oxygen gas from the nozzle 14c to the vicinity of the via hole VH during such drilling, oxygen is activated by the laser beam, and desmear, which decomposes smear by oxygen radicals, proceeds simultaneously.

Next, the pressure in the processing chamber 21 is reduced,
When hydrogen radicals are supplied from e to the surface of the substrate W, the oxide layer OL formed at the bottom of the via hole VH is reduced and purified by desmear, and a clean metal surface can be exposed at the bottom of the via hole VH (FIG. 4). (C)).

On the substrate W on which the via formation has been completed, a Cu wiring film WL for wiring is uniformly formed by the same film forming apparatus 30 as shown in FIG. The Cu wiring film WL formed in this manner is appropriately patterned in a process after using photolithography. The Cu wiring film WL thus patterned is connected to the conductive layer CL at the bottom of the via hole VH in close contact with the conductive layer CL, and has a low resistance at the time of connection.

[Third Embodiment] FIG. 6 is a plan view illustrating the structure of a substrate processing apparatus incorporating a via forming apparatus according to a third embodiment of the present invention. This device is a partially modified device of the first embodiment.

The substrate processing apparatus includes a laser drilling device 110 for forming via holes in a desired arrangement in the organic insulating layer of the substrate W, and a desmearing device 210 for removing smear attached to the via holes formed by the laser drilling device 110.
A reduction processing apparatus 20 for processing via holes in a reducing atmosphere, and a film forming apparatus 30 for forming a wiring layer for wiring in the via holes reduced by the reduction processing apparatus 20
And a transfer device 40 that transfers the substrate W between the laser drill device 210, the desmear device 310, the reduction processing device 20, and the film forming device 30. Laser drill device 110
And the desmear device 210 are the via processing device 10 shown in FIG.
The functions of via formation and via processing are divided into two devices.

FIG. 7 is a view for explaining the structure of the laser drill device 210. The laser drilling device 210 is obtained by removing the desmear portion 14 from the via processing device 10 of FIG. 2 illustrating the first embodiment, and includes a processing chamber 11, a stage device 12, and a laser drill body 13.

FIG. 8 is a view for explaining the structure of the desmear device 310. The desmear apparatus 310 includes a processing chamber 311 for processing the substrate W, and a desmear apparatus main body 314 that discharges oxygen radicals onto the drilled substrate W supported on the stage 312.

The desmear apparatus main body 314 includes a gas container 314a for storing oxygen gas and a flow rate adjusting unit 3 for adjusting the amount and timing of gas flowing out of the gas container 314a.
14b, a plasma chamber 314c for temporarily storing the gas that has passed through the flow rate controller 314b, and a plasma chamber 3
A coil 314d for converting oxygen gas in 14c into plasma to form oxygen radicals, and a nozzle 314e for discharging oxygen radical gas onto the substrate W are provided.

When oxygen radicals are ejected from the nozzle 314e onto the substrate W mounted on the stage 312, organic substances constituting smear attached to the via holes are decomposed by oxygen radicals, and desmear is achieved.

FIG. 9 is a view for explaining typical processing by the substrate processing apparatus of FIG. Here, FIG. 9A shows a state of the substrate W before via formation, as in FIG. 4A.

FIG. 9B is a diagram illustrating a stage in which via formation has been completed by the laser drilling device 210. That is,
When a laser beam spot is incident on an appropriate portion of the insulating layer IL, a via hole VH reaching the conductive layer CL is formed here. At this time, smear SM adheres to the bottom and side walls of via hole VH as a by-product of drilling.

FIG. 9C is a diagram for explaining the processing in the desmear device 310. When the substrate W is transported from the laser drilling device 210 to the desmear device 310 and oxygen radicals are supplied onto the substrate W from the nozzle 314e, desmearing in which oxygen radicals decompose smears attached to the bottom and side walls of the via hole VH proceeds. At this time, in the desmear due to oxygen radicals, the conductive layer C exposed at the bottom of the via hole VH
The surface of L is oxidized to form an oxide layer OL.

FIG. 9D is a diagram for explaining the processing in the reduction processing device 20. Referring to FIG. 3, the nozzle 25e
When hydrogen radicals are supplied from above to the substrate W, the oxide layer OL formed by desmear is reduced and purified, and the metal surface can be exposed at the bottom of the via hole VH.

FIG. 9E is a view for explaining film formation in the film forming apparatus 30. The substrate W is transported from the reduction processing apparatus 20 to the film forming apparatus 30, and a wiring film W for wiring made of Cu or the like is formed on the substrate W after via formation by a dry process.
L is formed uniformly. The wiring film WL thus formed is appropriately patterned in a process after using photolithography.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment. For example, desmear performed by the desmear apparatus 310 may be a wet process without using a laser, for example. That is, in the first apparatus, the smear inside the via hole VH is oxidized and dissolved and removed using a solution of potassium permanganate or the like, and in the next apparatus, the oxide layer OL formed by desmear is reduced and purified. The metal surface can be exposed at the bottom of the via hole VH.

The conductive layer CL and the wiring film WL include Cu
However, other metals such as Al can be used.

The desmear performed by the desmear apparatus 310 is not limited to the case where oxygen radicals are used, but may be one obtained by radicalizing carbon fluoride. In this case, the fluorocarbon is decomposed as follows and CF ₆ + O ₂
→ CO ₂ + 3F ₂ The metal filler inside the resin is removed by the F ₂ thus obtained.

Further, the shape of the via hole VH formed in the substrate W is not limited to a cylindrical shape, but may be a groove shape. In this case as well, the smear in the via hole is satisfactorily removed by the above-described method, and The surface of the metal exposed at the bottom of the substrate can be reduced to improve the adhesion of the wiring and the like.

[0056]

As is apparent from the above description, according to the via processing method of the present invention, a reduction step is provided, and the surface of the conductive layer exposed inside the via hole is reduced in a reducing atmosphere in which a plasma is formed. Therefore, even when an oxide film is formed on the surface of the conductive layer in the desmear process, the oxide film can be reduced to the original metal. Therefore, in the next wiring step of connecting to the conductive layer exposed inside the via hole, a wiring having high adhesion and low connection resistance can be obtained.

According to another via processing method of the present invention, when forming a via hole, oxygen is supplied to the vicinity of the laser beam incident position under substantially atmospheric pressure, thereby adhering to the inside and the periphery of the via hole. Removes smears
In parallel with the formation of the via hole, the desmear process can proceed without using any special means for plasma generation, and the formation of the via can be made simple and quick.

Further, according to the via processing apparatus of the present invention, since the reduction device reduces the surface of the conductive layer exposed inside the via hole under a reducing atmosphere in which the plasma is formed, the oxide film is formed on the surface of the conductive layer in the desmear process. Is formed, this oxide film can be reduced to the original metal. Therefore, in the next wiring step of connecting to the conductive layer exposed inside the via hole, a wiring having high adhesion and low connection resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating a structure of a substrate processing apparatus incorporating a via forming apparatus according to a first embodiment.

FIG. 2 is a view for explaining the structure of a via processing apparatus constituting the substrate processing apparatus of FIG. 1;

FIG. 3 is a view for explaining the structure of a reduction processing apparatus constituting the substrate processing apparatus of FIG. 1;

FIGS. 4A to 4D are views for explaining typical processing by the substrate processing apparatus of FIG. 1;

FIG. 5 is a diagram illustrating a structure of a via forming apparatus according to a second embodiment.

FIG. 6 is a plan view illustrating a structure of a substrate processing apparatus incorporating a via forming apparatus according to a third embodiment.

FIG. 7 is a diagram illustrating the structure of a laser drilling apparatus that constitutes the substrate processing apparatus of FIG.

FIG. 8 is a diagram illustrating a structure of a desmear apparatus included in the substrate processing apparatus of FIG.

FIGS. 9A to 9E are views for explaining typical processing by the substrate processing apparatus of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Via processing apparatus 11 Processing chamber 12 Stage apparatus 13 Laser drill main body 14 Desmear part 14a Gas container 14b Flow rate adjustment part 14c Nozzle 20 Reduction processing apparatus 21 Processing chamber 22 Stage apparatus 25 Radical supply apparatus 26 Exhaust apparatus 30 Film formation apparatus 40 Transport apparatus CL conductive layer IL insulating layer OL oxide layer VH via hole W substrate WL wiring film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/46 H05K 3/46 N XY // B23K 26/12 B23K 26/12 B23K 101: 42 B23K 101 : 42 F term (reference) 4E068 AF01 CG01 CH05 CJ01 CJ04 DA11 5E317 AA24 BB01 BB11 CC31 CD01 CD11 CD27 CD32 GG11 5E346 AA12 AA15 AA32 AA43 BB01 CC08 CC31 FF02 FF03 FF12 GG01 GG15 GG16 GG17 H07

Claims (7)

[Claims] 1. A via treatment for treating a via hole formed on a substrate, in which an insulating layer made of an organic material and a conductive layer made of a metal are joined, on a side of the insulating layer using a laser beam so that the conductive layer is exposed. A method comprising the steps of: a desmearing step of removing smear adhering inside and around a via hole; and a reducing step of reducing a surface of the conductive layer exposed inside the via hole under a reducing atmosphere in which a plasma is formed. Processing method. 2. The via processing method according to claim 1, wherein the desmearing step is performed under atmospheric pressure. 3. The desmearing step is performed by supplying a gas containing at least one of an oxygen gas and a CF ₄ gas to the periphery of the via hole under irradiation of the laser beam when forming the via hole. 3. The via processing method according to claim 1, wherein: 4. The via processing method according to claim 1, wherein the reducing step is performed by supplying hydrogen plasma around the via hole. 5. The via processing method according to claim 1, wherein a plating layer is formed inside and around the via hole after the reducing step. 6. A method of forming a via on a substrate in which an insulating layer made of an organic material and a conductive layer made of a metal are joined, wherein a via hole is formed using a laser beam so that the conductive layer is exposed from the insulating layer side. A via forming method, characterized in that, at the time of forming, vias are supplied under substantially atmospheric pressure to the periphery of the incident position of the laser beam to remove smears attached to the inside and the periphery of the via hole. 7. A desmear that removes smear adhering to and inside a via hole formed by irradiating a laser beam to the insulating layer side of a substrate in which an insulating layer made of an organic material and a conductive layer made of a metal are joined. A via processing apparatus comprising: a device; and a reducing device that reduces the surface of the conductive layer exposed inside the via hole under a reducing atmosphere in which the surface is converted into plasma.