JP2020043168A - Resin substrate processing method and plasma processing apparatus - Google Patents

Abstract

To provide a method for processing a resin substrate, which can further flatten the surface of a resin substrate in which an inorganic member serving as a filler is dispersedly included in an organic member.SOLUTION: A processing method of a resin substrate according to the present invention includes a decompressible internal space, and using a chamber configured such that an object to be processed is subjected to plasma processing by a dry etching method in the internal space, a bias voltage of a first frequency λ1 is applied from a first power source to a first plate-shaped electrode on which the object to be processed is placed under an atmosphere in which a process gas for plasma processing is introduced into the chamber, an AC voltage of a second frequency λ2 is applied from a second power supply to a second electrode disposed at a position facing the first electrode. At this time, the second frequency λ2 [MHz] is set to 13.56 or more and 40.68 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for processing a resin substrate and a plasma processing apparatus capable of planarizing the surface of a resin substrate in which an inorganic member serving as a filler is dispersedly included in an organic member.

  In recent years, as a resin substrate for a printed circuit board, a method of forming a circuit by using a material called a prepreg, which is a glass cloth impregnated with an epoxy resin, and further using a build-up film thereon. Such a resin substrate is characterized by small dimensional changes, high frequency characteristics and high insulation resistance, and thus has high insulation properties, high mechanical strength, and long life. However, it is known that the resin substrate is difficult to process because it is made of a glass cloth impregnated with an epoxy resin.

With the reduction in size and weight of devices to be mounted, further thinning and higher density are also required for conductive portions including through wirings in a resin substrate. Conventionally, a plating method has been used as a method of forming a conductive portion including a through wiring on a resin substrate, and has responded to this demand (Patent Documents 1 and 2).
For example, in a conventional method, a non-through hole is previously formed by a desired method (a known method such as drilling or laser processing) from one main surface in a region where a through hole is provided toward a conductor provided on a resin substrate. Prepare a substrate on which is formed, form a through hole using an etchant from one main surface of the resin substrate, and then immerse the resin substrate in a plating solution to fill the through hole with a plating solution. Then, a conductive part of a thin film is formed in the through hole. However, as the diameter of the through hole is reduced, a series of operations (so-called wet process) for removing the etchant remaining in the through hole is becoming difficult. That is, there is a concern that the residue of the plating solution does not fall out of the through-hole and affects the subsequent steps.
The present inventors have already found a solution for a case where a non-through hole is formed in advance by such drilling, and have filed a patent application (Patent Document 3).

The present inventors have also studied and evaluated the situation of non-through holes formed in advance by laser processing. As a result, the non-through holes 11B (11) formed in advance in the resin substrate 10B (10) by the laser processing [FIG. 10 (a)] have V-shaped recesses (or mortars) as viewed from the side sectional direction. (FIG. 10B). In addition, it was also confirmed that the surface exposed to the laser beam, that is, the inclined surface 11Bs of the V-shaped concave portion had a damaged portion DA whose surface morphology was different from that of the non-exposed surface [FIG. 10 (b)].
The present inventors have already developed a solution and applied for a patent in the case of using a substrate on which a non-through hole is formed in advance by such laser processing (Patent Document 4).

  With the development described above, there is a prospect that the inner surface (inner surface, inner bottom surface) of the concave portion formed in the resin substrate can be flattened. However, in an application including a wiring through which a current having a further high-frequency characteristic (for example, 60 GHz) flows (for example, a wiring board of a supercomputer), it is necessary to consider the skin effect of the current. In order to cope with such high frequency characteristics, a surface roughness Ra of 0.2 μm or less is required. The skin effect is a phenomenon in which, when an alternating current flows through a conductor (such as a wiring), the current density is high at the surface of the conductor and decreases when the current is away from the surface. The higher the frequency, the more the current concentrates on the surface, and the higher the AC resistance of the conductor. If the substrate surface has irregularities and the surface roughness is large, the surface of a conductor (such as a wiring) formed along the surface also reflects the large roughness.

  For this reason, in applications in which a current having a high frequency characteristic is passed, the development of a new manufacturing method capable of further flattening one main surface (so-called substrate surface) of a resin substrate provided with a through hole is expected. I was

JP-A-2002-217536 JP-A-2004-146533 JP 2014-227423 A JP 2017-041607 A

  The present invention has been devised in view of such a conventional situation, and a resin substrate capable of further flattening the surface of a resin substrate in which an inorganic member serving as a filler is dispersedly included in an organic member. It is an object of the present invention to provide a processing method and a plasma processing apparatus.

The processing method of the resin substrate according to the present invention,
A resin substrate processing method for flattening one main surface of the resin substrate, using a resin substrate in which an inorganic member serving as a filler is dispersedly contained in an organic member as an object to be processed,
Using a chamber configured to have a decompressible internal space, in which the object to be processed is subjected to plasma processing by a dry etching method in the internal space,
Under an atmosphere in which a process gas for plasma processing is introduced into the chamber,
A bias voltage having a first frequency λ1 is applied from a first power supply to a first plate-shaped electrode on which the object is placed, and a second electrode disposed at a position facing the first electrode. An AC voltage having a second frequency λ2 is applied to the electrode from a second power supply, and the second frequency λ2 [MHz] is set to 13.56 or more and 40.68 or less.

In the method for processing a resin substrate according to the present invention, it is preferable in claim 1 that the first frequency λ1 [MHz] is set to 1.00 or more and 2.00 or less.
In the method for processing a resin substrate according to the present invention, in claim 1, the output density S1 [W / cm ² ] of the AC voltage applied to the first electrode is set to 0.4 or more and 1.2 or less. It is preferable that the output density S2 [W / cm ² ] of the AC voltage applied to the two electrodes be 0.8 or more and 1.6 or less.
In the method for processing a resin substrate according to the present invention, it is preferable in claim 1 that the process pressure P [Pa] at the time of performing the plasma treatment is set to 10 or more and 15 or less.

A plasma processing apparatus according to the present invention includes an internal space that can be decompressed, a chamber configured to perform plasma processing on an object to be processed in the internal space; A first power supply configured to apply a bias voltage of a first frequency λ1 to the first electrode, and a first power supply configured to apply a bias voltage to the first electrode, A second electrode disposed at a position facing the first electrode, a second power supply for applying an AC voltage having a second frequency λ2 to the second electrode, and a plasma processing chamber inside the chamber. Means for introducing a process gas, and exhaust means for reducing the internal space of the chamber, at least comprising:
The first power supply has a first frequency λ1 [MHz] of a bias voltage for the first electrode in a range of 1.00 to 2.00, and the second power supply has an alternating current for the second electrode. The second frequency λ2 [MHz] of the voltage is in the range of 13.56 to 40.68.

  In the method for processing a resin substrate according to the present invention, an AC voltage having a second frequency λ2 is applied to a second electrode disposed at a position facing the first plate-shaped electrode on which the object to be processed is placed. An AC voltage having a second frequency λ2 is applied from a second power supply to the second electrode. At this time, by setting the second frequency λ2 [MHz] in the range of 13.56 or more and 40.68 or less, the surface of the resin substrate in which the inorganic member serving as the filler is dispersedly contained in the organic member is included. Further flattening becomes possible.

In the plasma processing apparatus according to the present invention, the first power supply configured to apply a bias voltage having the first frequency λ1 to the first plate-shaped electrode on which the object to be processed is mounted is provided with a bias voltage. The first frequency λ1 [MHz] of the voltage is in a range of 1.00 to 2.00.
12. A second power supply that applies an AC voltage having a second frequency λ2 to a second electrode disposed at a position facing the first electrode sets the second frequency λ2 [MHz] of the AC voltage to 13. The range is from 56 to 40.68. Thus, the present invention provides a plasma processing apparatus capable of further flattening the surface of a resin substrate in which an inorganic member serving as a filler is dispersedly included in an organic member.

FIG. 3A is a cross-sectional view of the resin substrate under three conditions, and FIG. 3B is an SEM photograph of the surface of the resin substrate. FIG. FIG. 4 is a diagram illustrating a method for observing the surface of a resin substrate. FIG. 4 is a cross-sectional view of a resin substrate and an SEM photograph of the substrate surface under the condition α (only bias power). Sectional view of the resin substrate and SEM photograph of the substrate surface under the condition γ (only high frequency power). FIG. 2 is a cross-sectional view of a resin substrate and an SEM photograph of the substrate surface under condition β (the present invention). FIG. 1 is a cross-sectional view illustrating a plasma processing apparatus according to the present invention. 9 is a list showing evaluation results of Experimental Example 1. 9 is a list showing evaluation results of Experimental Example 2. 9 is a list showing evaluation results of Experimental Example 3. The figure which shows the processing method of the resin substrate which has the concave part which carried out laser patterning.

  Hereinafter, a method for processing a resin substrate and a plasma processing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a cross-sectional view (a) of a resin substrate under three conditions and an SEM photograph (b) of the substrate surface. The three conditions (conditions α, β, and γ) in FIG. 1 are cases where the combination of “the presence or absence of bias power” and “the presence or absence of high-frequency power” is changed in order to generate plasma during film formation. That is, the condition α is a case where “only bias power” is applied, and the condition γ is a case where “only high frequency power” is applied. Conditions α and γ are both comparative examples. On the other hand, the condition β is a case where “both bias power and high frequency power” are applied, and corresponds to the present invention. In FIG. 1A and FIG. 1B, in order from the left, after processing under the condition α, after processing under the condition β, after processing under the condition γ, unprocessed (before processing) is shown.
FIG. 2 is a diagram illustrating a method of observing the surface of the resin substrate. Using a scanning electron microscope (SEM), the surface of the substrate formed by the method for processing a resin substrate according to the present invention (the surface of an unprocessed substrate before processing) was observed. View-A (Top) means that observation was made from a direction perpendicular to one surface (surface) of the resin substrate.

The present invention uses a substrate 1 composed of a resin substrate 2 in which an inorganic member 2a serving as a filler is dispersed and contained in an organic member 2b, and a conductor 3 provided on the resin substrate 2. This is a method for processing a resin substrate for smoothing the surface of the resin substrate 2 by subjecting one main surface 2s (the upper surface in FIG. 1) to a plasma treatment.
However, the present invention relates to a method of processing a resin substrate in which a through hole (not shown) is formed from one main surface 2s (the upper surface in FIG. 1) of the resin substrate 2 toward the conductor 3 (Patent Document 4). May be combined. FIG. 1 shows a configuration in which the conductor 3 is provided on the other main surface 2r of the resin substrate 2, but the positional relationship between the resin substrate 2 and the conductor 3 is not limited to this. May be arranged in the resin substrate 2.

  The method for processing a resin substrate according to the present invention will be described in detail below with respect to a case where plasma processing is performed on one main surface 2s of the resin substrate 2. However, the present invention may be applied to a resin substrate provided with a through hole (not shown) described in Patent Document 4 in advance. As the resin substrate 2, for example, a material in which an inorganic member 2a made of silica or the like is dispersed and contained in an organic member 2b made of epoxy or the like is preferably used.

As a process gas used in the dry etching method, a gas containing fluorine (hereinafter, also referred to as an F-based gas) is preferable. For example, SF ₆ , NF ₃ , CF ₄ , CHF ₃ , CH ₂ F ₂ , CH ₃ F, C such as _{2 F 6, C 3 F 8} , C 4 F 8 and the like.
Examples of the gas to be added to the process gas include O ₂ , N ₂ , and a mixed gas of O ₂ and N ₂ .

In the method for processing a resin substrate according to the present invention, plasma processing is performed on one main surface 2s of the resin substrate (object to be processed) 2 using a dry etching method. At this time, the process gas for plasma processing is introduced into the chamber, and the atmosphere is set to a predetermined film forming pressure.
In the method for processing a resin substrate according to the present invention, a bias voltage having a first frequency λ1 is applied from a first power supply to a plate-like first electrode on which the object is placed under this atmosphere. At the same time, an AC voltage having a second frequency λ2 is applied from a second power supply to a second electrode disposed at a position facing the first electrode. At this time, the second frequency λ2 [MHz] is set to 13.56 or more and 40.68 or less.
By adopting the second frequency λ2 having such a specific range, it becomes possible to flatten the surface of the resin substrate in which the inorganic member serving as the filler is dispersedly included in the organic member.

By setting the second frequency λ2 [MHz] in the range of 13.56 to 40.68 and the first frequency λ1 [MHz] in the range of 1.00 to 2.00, the resin Flattening of the surface of the substrate can be further achieved.
In this case, the output density S1 [W / cm ² ] of the AC voltage applied to the first electrode is set to 0.4 or more and 1.2 or less, and the output density S2 of the AC voltage applied to the second electrode is adjusted. [W / cm ² ] is preferably set to 0.8 or more and 1.6 or less. Thereby, the surface roughness Ra of the substrate after the plasma processing can be suppressed to less than 100 nm.
In the present invention, it is preferable that the process pressure P [Pa] at the time of performing the plasma treatment is set to 10 or more and 15 or less. Thus, the surface roughness Ra of the substrate after the plasma processing can be suppressed to less than 100 nm, and the amount of Via dimensional change can also be made less than 500 nm.
Therefore, according to the method for processing a resin substrate according to the present invention, it is possible to provide a resin substrate suitable for an application including a wiring through which a current having a high frequency characteristic (for example, 60 GHz) flows.

  The above-described method for processing a resin substrate according to the present invention is, for example, a parallel plate plasma etching apparatus (hereinafter, referred to as a plasma processing apparatus) for generating a plasma by introducing a gas from above as shown in FIG. 10). In FIG. 6, reference numeral 11 denotes a chamber for performing plasma processing therein, and includes a gas introduction system 12 connected to gas supply sources 12a and 12b such as gas cylinders, and an exhaust system 13 connected to a vacuum pump. In FIG. 6, valves and flow meters provided for the respective gas supply sources 12a and 12b are not shown. However, as will be described later, the plasma processing apparatus 10 in FIG. 6 also performs opening / closing control and flow rate control of gas introduction, and accordingly, a valve and a flow rate are appropriately provided in necessary portions of the gas introduction system 12.

  In the chamber 11, plate-like electrodes 14 and 15 are provided in parallel vertically, and a high-frequency power supply 16 a for applying high-frequency power to the upper electrode 14 and a bias voltage for the lower electrode 15 are provided. Bias power supplies 16b for supplying electric power are electrically connected to each other. A substrate Sub to be etched (corresponding to the “resin substrate 2” described above) is mounted on the lower electrode 15. However, the resin substrate 2 may be a “resin substrate 2 in which the non-through holes 5 are formed in advance”.

  The upper electrode 14 is constituted by a hollow electrode provided with a shower plate 18 on the front surface thereof, and the gas introduction system 12 is connected to the hollow portion 19 to react the reaction gas introduced into the hollow portion 19 with the shower plate 18. The gas is uniformly ejected from the large number of gas ejection ports 18a into the chamber 11. The lower electrode 15 has a function as a heater for heating the substrate Sub. The gas introduction system 12 is provided with a process gas supply source 12a and an additional gas supply source 12b, which are supplied when performing the etching process, and these gases can be introduced by adjusting the flow rate thereof. It has been.

  A desired gas (process gas + additional gas) is introduced from the gas introduction system 12 into the evacuated chamber 11, adjusted to a predetermined pressure, and then high-frequency power (for example, 27.12 MHz) is supplied from the high-frequency power supply 16a. Thus, plasma is generated between the electrodes 14 and 15. If necessary, high-frequency power (for example, 2 MHz) is applied to the electrode 15 from the bias power supply 16b as bias power. At this time, the substrate Sub placed on the electrode 15 is controlled to have a predetermined temperature.

Thus, the substrate Sub placed on the electrode 15 is exposed to plasma for a desired time, and when a flat substrate Sub is used, one surface side (the upper surface side in FIG. 6) of the substrate Sub is used. Is etched.
When a “substrate substrate in which a non-through hole is formed in advance” is used as the substrate Sub instead of the flat substrate Sub, together with one main surface surrounding the opening of the non-through hole, The inner bottom surface of the non-through hole is also etched. The etching process in this case is performed until the inner bottom surface of the non-through hole is processed by etching, the reference numeral 3 is exposed, and the non-through hole becomes a through hole. At that time, one main surface surrounding the opening of the non-through hole is also affected by the etching process.

  After the through hole is formed, a thin film seed layer is formed on the inner surface and the inner bottom surface of the through hole together with one main surface surrounding the opening of the through hole to bury the through hole with a conductive member. It must be formed in advance. The state of coating of the thin film with the seed layer is affected by the surface shape (profile) of the “one main surface surrounding the opening of the through hole” and the “inner surface and inner bottom surface of the through hole” forming the coating surface. . Therefore, a technique for controlling the surface profile on each of these surfaces to a desired shape is also required.

  The method for processing a resin substrate according to the present invention uses the plasma processing apparatus 10 as shown in FIG. 6 described above, and applies a bias of a first frequency λ1 to a first plate-shaped electrode on which an object to be processed is placed. The basic configuration is that a voltage is applied from a first power supply, and an AC voltage having a second frequency λ2 is applied from a second power supply to a second electrode disposed at a position facing the first electrode. And

  First, in order to compare with the resin substrate processing method according to the present invention (in which a bias voltage is applied to the first electrode and an AC voltage is applied to the second electrode), Experimental Example 1 (when applying an AC voltage to the second electrode and applying a bias voltage to the first electrode) and Preliminary Experimental Example 2 (when applying no bias voltage to the first electrode, A description will be given of the result of the study on the case where an AC voltage is applied to the second electrode.

(Preliminary experiment 1)
Preliminary experiment 1 is a case where an AC voltage is not applied to the second electrode and a bias voltage is applied to the first electrode.
Table 1 below shows the film forming conditions of the preliminary experiment 1.

  The rightmost side in FIG. 1 is a resin substrate that has not been processed (before performing plasma processing). The upper part (a) shows a sectional view of the resin substrate, and the lower part (b) shows an SEM photograph of the substrate surface. The untreated resin substrate 2 includes, for example, an inorganic member (also referred to as a Si filler) 2a made of silica or the like dispersed and contained in an organic member 2b made of epoxy or the like. The inorganic member 2a is embedded in the organic member 2b. In the resin substrate in this state, concave portions are discretely observed on the surface, the surface roughness Ra is about 70 nm, and the resin substrate has a smooth surface morphology.

  The resin substrate obtained by subjecting such a resin substrate to the resin substrate processing method according to Preliminary Experiment 1 is the first one from the left in FIG. That is, a case where an AC voltage (expressed as high-frequency power in FIG. 1) is not applied to the second electrode and a bias voltage is applied to the first electrode (referred to as condition α: FIG. Is displayed). The upper part (a) shows a sectional view of the resin substrate, and the lower part (b) shows an SEM photograph of the substrate surface.

  FIG. 3 shows a cross-sectional view of the resin substrate and an SEM photograph of the substrate surface under the condition α (only bias power). FIG. 3A shows an unprocessed state, FIG. 3B shows a state after plasma processing, and FIG. 3C shows a state in which wiring is formed.

  In the case of the preliminary experiment 1 (condition α), plasma is generated near the first electrode, and the plasma is drawn into the surface of the resin substrate by the bias voltage. Thereby, the inorganic member 2a is removed together with the organic member 2b. As a result, as shown in FIG. 3 (b), the surface 2As of the substrate after the plasma treatment has a portion where the inorganic member 2a is removed, a concave portion 2as (α), and the resin member 2b is removed. And a flat portion 2bs (α). Therefore, the recesses remained on the surface of the resin substrate after the plasma treatment, and the surface roughness Ra was 0.27 μm.

In the case where wirings (denoted as laminated wirings 9a and 9b in FIG. 3C) are formed on the surface of such a resin substrate, the wirings 9a and 9b are also locally moved up and down due to the presence of the concave portion 2as (α). Therefore, it is difficult to form a flat surface for the wiring.
Therefore, it has been found that the plasma processing under the condition α is not suitable for an application having a wiring through which a current having a high frequency characteristic (for example, 60 GHz) flows.

(Preliminary experiment 2)
Preliminary experiment 2 is a case where a bias voltage is not applied to the first electrode and an AC voltage is applied to the second electrode.
Table 2 below shows the film forming conditions of the preliminary experiment 2.

In Preliminary Experiment 2, as in Preliminary Experiment 1, an untreated (before plasma-treated) resin substrate shown on the rightmost side in FIG. 1 was used.
The resin substrate obtained by applying the resin substrate processing method according to Preliminary Experiment 2 to such a resin substrate is the third one from the left in FIG. That is, a case where an AC voltage (expressed as “high-frequency power” in FIG. 1) is applied to the second electrode and no bias voltage is applied to the first electrode (referred to as condition γ: FIG. Only "). The upper part (a) shows a sectional view of the resin substrate, and the lower part (b) shows an SEM photograph of the substrate surface.

  FIG. 4 is a cross-sectional view of the resin substrate and an SEM photograph of the substrate surface under the condition γ (only high-frequency power). FIG. 4A shows an unprocessed state, FIG. 4B shows a state after plasma processing, and FIG. 4C shows a state in which wiring is formed.

  In the case of Preliminary Experiment 2 (condition γ), plasma is generated near the second electrode and no bias voltage is applied, so that the amount of plasma drawn into the surface of the resin substrate is small. Thereby, the organic member 2b is removed. As a result, as shown in FIG. 4 (b), the surface 2As of the substrate after the plasma processing has a portion in which the inorganic member 2a is not removed and a local convex portion 2as (γ) and the resin member 2b are removed. And a flat portion 2bs (γ). Therefore, the projections remained on the surface of the resin substrate after the plasma treatment, and the surface roughness Ra was 0.28 μm.

In the case where wirings (denoted as laminated wirings 9a and 9b in FIG. 4C) are formed on the surface of such a resin substrate, the wirings 9a and 9b are also locally raised and lowered due to the presence of the protrusions 2as (γ). Therefore, it is difficult for the wiring to form a flat surface.
Therefore, it has been found that the plasma treatment under the condition γ is not suitable for an application having a wiring through which a current having a high frequency characteristic (for example, 60 GHz) flows.

(Preliminary experiment 3)
The preliminary experiment 3 is a case where a bias voltage is applied to the first electrode and an AC voltage is applied to the second electrode.
Table 3 below shows the film forming conditions of the preliminary experiment 3.

In Preliminary Experiment 3, as in Preliminary Experiment 1, an untreated (before plasma-treated) resin substrate shown on the rightmost side in FIG. 1 was used.
The resin substrate obtained by applying the resin substrate processing method according to Preliminary Experiment 3 to such a resin substrate is the second one from the left in FIG. That is, a case where an AC voltage (expressed as high-frequency power in FIG. 1) is applied to the second electrode and a bias voltage is applied to the first electrode (referred to as condition β: “high-frequency power + bias” in FIG. 1) Power "). The upper part (a) shows a sectional view of the resin substrate, and the lower part (b) shows an SEM photograph of the substrate surface.

  FIG. 5 shows a cross-sectional view of the resin substrate and an SEM photograph of the substrate surface under the condition β (high-frequency power + bias power). FIG. 5A shows an unprocessed state, FIG. 5B shows a state after plasma processing, and FIG. 5C shows a state in which wiring is formed.

  In the case of the preliminary experiment 3 (condition β), plasma generated by combining the plasmas generated in the preliminary experiments 1 and 2 described above is drawn into the surface of the resin substrate. Thus, the organic member 2b is removed, and the inorganic member 2a is also removed. As a result, as shown in FIG. 5B, the surface 2As of the resin substrate after the plasma treatment has a flat portion 2bs (β) from which the organic member 2b has been removed and a part (upper part) of the inorganic member 2a. ) Is removed from the flat portion 2as (β). Therefore, on the surface of the resin substrate after the plasma treatment, the inorganic member 2as (β) and the organic member 2bs (β) are flush with each other, and only fine irregularities remain, and the surface roughness Ra is 0. It was 11 μm.

In the case where wirings (denoted as laminated wirings 9a and 9b in FIG. 5C) are formed on the surface of such a resin substrate, the surface of the resin substrate after the plasma processing is extremely smooth, so that the wiring is also flat. It is possible to form a smooth surface.
Therefore, it has been found that the plasma processing under the condition β is suitable for an application having a wiring through which a current having a high frequency characteristic (for example, 60 GHz) flows.

From the results of the preliminary experiment 1 and the preliminary experiment 2, it is extremely difficult to solve the problem of the present invention when etching is performed by applying an AC voltage to only one of the electrodes (the first electrode or the second electrode). It proved difficult.
Also, from the result of the preliminary experiment 3, the problem of the present invention may be solved when the AC voltage is applied to both electrodes (first electrode and second electrode) at the same time and the etching process is performed. Was found.

(Experimental example 1)
Experimental Example 1 is based on the result of Preliminary Experiment 3 and is based on the resin substrate processing method according to the present invention (when applying a bias voltage to the first electrode and applying an AC voltage to the second electrode). The operation and effect of applying voltages of different frequencies to the first electrode and the second electrode individually using the above two power sources were verified. The result will be described with reference to FIG.

  The rightmost side in FIG. 1 is a resin substrate that has not been processed (before performing plasma processing). The upper part (a) shows a sectional view of the resin substrate, and the lower part (b) shows an SEM photograph of the substrate surface. The unprocessed resin substrate 2 includes, for example, an inorganic member 2a made of silica or the like dispersed and contained in an organic member 2b made of epoxy or the like. The inorganic member 2a is embedded in the organic member 2b. In the resin substrate in this state, concave portions are discretely observed on the surface, the surface roughness Ra is about 70 nm, and the resin substrate has a smooth surface morphology.

The resin substrate obtained by subjecting such a resin substrate to the resin substrate processing method according to the present invention is the second one from the left in FIG. That is, this is a case where an AC voltage (expressed as high-frequency power in FIG. 1) is applied to the second electrode and a bias voltage is applied to the first electrode (referred to as condition β). The upper part (a) shows a sectional view of the resin substrate, and the lower part (b) shows an SEM photograph of the substrate surface.
In the resin substrate treated under the condition β, the inorganic member 2a and the organic member 2b were etched to the same level by the plasma, and as a result, a surface roughness Ra of about 0.1 μm was obtained.

Hereinafter, two parameters for determining the condition β [frequency λ2 of the AC voltage applied to the second electrode (shown as upper RF in FIG. 7), bias voltage applied to the first electrode (shown as lower RF in FIG. 7) Of the frequency [lambda] 1] was changed, and an optimal numerical range for the condition [beta] was examined.
Five conditions of 12.5, 13.56, 27.12, 40.68, and 60 are used as the frequency λ2 [MHz], and five conditions of 100 k, 400 k, 1M, 2M, and 13.56 M are used as the frequency λ1 [Hz]. Conditions were used. Here, k represents 10 ³ and M represents 10 ⁶ .
FIG. 7 shows the evaluation results of Experimental Example 1.

The following points became clear from FIG. However, in the following, 27.12 MHz is abbreviated as 27 MHz, and 40.68 MHz is abbreviated as 40 MHz.
(A1) Regarding the upper RF, when λ2 was larger than 40 MHz, in-plane uniformity failure occurred due to generation of a standing wave. If λ2 is smaller than 13.56 MHz, the etching rate is low due to the low plasma density, and the processing time is long.
(A2) Regarding the lower RF, when λ1 was larger than 2 MHz, the ion etching component was low and the ion etching shape was poor. When λ1 is smaller than 1 MHz, abnormal discharge frequently occurs, and it is difficult to establish a stable manufacturing process.

  From the above results, it was found that the frequency λ2 [MHz] of the AC voltage (shown as upper RF in FIG. 7) applied to the second electrode is preferably in the range of 13.56 to 40. Further, when λ2 is in the range of 13.56 to 40, the frequency λ1 [Hz] of the bias voltage (shown as lower RF in FIG. 7) applied to the first electrode is preferably in the range of 1M to 2M. It was confirmed that.

(Experimental example 2)
In Experimental Example 2, the operation and effect of separately applying voltages of different output densities to the first electrode and the second electrode were verified from the viewpoint of the surface roughness Ra after the plasma treatment. At this time, based on the results of the above-described Experimental Example 1, the frequency λ2 of the AC voltage applied to the second electrode and the frequency λ1 of the bias voltage applied to the first electrode are determined by specific frequencies (λ2 = 27 MHz, λ1 = 2 MHz). ).

  The same unprocessed resin substrate 2 as that in Experimental Example 1 was used. That is, the unprocessed resin substrate 2 includes, for example, an inorganic member 2a made of silica or the like dispersed and contained in an organic member 2b made of epoxy or the like. The inorganic member 2a is embedded in the organic member 2b. In the resin substrate in this state, concave portions are discretely observed on the surface, the surface roughness Ra is about 70 nm, and the resin substrate has a smooth surface morphology.

The other two parameters that determine the condition β [the output density S2 of the AC voltage applied to the second electrode (shown as upper RF in FIG. 8), the bias voltage applied to the first electrode (shown as lower RF in FIG. 8) Was changed, and the optimal numerical range for the condition β was examined. Note that the output density is also called a power density.
Power density S2 [W / cm ^2] using 6 conditions 0,0.4,0.8,1.2,1.6,2.0 as power density S1 0 as [W / cm ^2] , 0.4, 0.8, 1.2, 1.6 and 2.0. Other conditions are the same as those in Experimental Example 1.
FIG. 8 shows the evaluation results of Experimental Example 2.

From FIG. 8, the following points became clear.
(B1) S1 [W / cm ² ] of the lower RF greatly affects the surface roughness Ra after the plasma processing. In the case of S1 = 0, discharge was not possible or smear removal was difficult, which was not good. If S1 = 2.0, Ra exceeds 300 nm, which is not preferable.
(B2) When S1 [W / cm ² ] of the lower RF is in a range of 0.4 or more and 1.2 or less, Ra of S2 [W / cm ² ] of the upper RF is 300 nm or less in a wide range. However, when S2 is 0.4 or less, Ra remains in the range of 150 to 300 nm. Also, when S2 was 2.0, it was confirmed that Ra tended to be in the range of 150 to 300 nm.

From the above results, it is preferable that the output density S1 [W / cm ² ] of the AC voltage (shown as lower RF in FIG. 8) applied to the first electrode is in the range of 0.4 to 1.2. I understood. However, depending on the condition of S2, S1 may be 1.6.
When S1 is in the range of 0.4 to 1.2, the output density S2 [W / cm ² ] of the AC voltage (shown as upper RF in FIG. 8) applied to the second electrode is 0.8 to 1 It is preferably in the range of 0.6 or less. By selecting S2 in this range, Ra can be set in the range of 100 nm to 150 nm. In particular, when S2 is in the range of 1.2 or more and 1.6 or less, Ra can be set to less than 100 nm, which is more preferable.

(Experimental example 3)
In Experimental Example 3, when the process pressure during the etching process was changed, verification was performed from the viewpoint of the surface roughness Ra after the plasma process. At this time, based on the results of the above-described Experimental Example 1, the frequency λ2 of the AC voltage applied to the second electrode and the frequency λ1 of the bias voltage applied to the first electrode are set to a specific frequency (λ2 = 27 [MHz], λ1 = 2 [MHz]). Further, based on the results of the above-described Experimental Example 2, the output density S2 of the AC voltage applied to the second electrode and the output density S1 of the bias voltage applied to the first electrode are determined by a specific output density (S2 = 1.2 [W / cm ² ], S1 = 0.8 [W / cm ² ]).

  The same unprocessed resin substrate 2 as in Experimental Examples 1 and 2 was used. That is, the unprocessed resin substrate 2 includes, for example, an inorganic member 2a made of silica or the like dispersed and contained in an organic member 2b made of epoxy or the like. The inorganic member 2a is embedded in the organic member 2b. In the resin substrate in this state, concave portions are discretely observed on the surface, the surface roughness Ra is about 70 nm, and the resin substrate has a smooth surface morphology.

As another parameter for determining the condition β, the process pressure during the etching process was changed, and the optimum numerical range for the condition β was examined. Six conditions of 1, 5, 10, 15, 20, and 40 were used as the process pressure [Pa]. Other conditions are the same as those in Experimental Example 1.
FIG. 9 shows the evaluation results of Experimental Example 3.

From FIG. 9, the following points became clear.
(C1) The process pressure P has a great influence on the surface roughness Ra after the plasma processing. In the case of P = 1 [Pa], the via dimension change amount exceeded 2.0 μm, so that it was not good. When P = 40 [Pa], Ra exceeds 300 nm, which is not preferable.
(C2) On the other hand, when the process pressure P [Pa] is 5 or more, the Ra can be suppressed to the range of 150 nm to 200 nm, and the dimensional change amount of Via can be suppressed to the range of 500 nm to 800 nm.
(C3) When the process pressure P [Pa] is 20 or less, Ra can be within the range of 200 nm or more and 300 nm or less, and the dimensional change amount of Via can be within the range of 1.0 μm or more and 2.0 μm or less.
(C4) In particular, when the process pressure P [Pa] is in the range of 10 or more and 15 or less, Ra is less than 150 nm, and the via dimensional change is also less than 500 nm. .

From the above results, it has been clarified that the process pressure P has a great influence on the Via dimensional change as well as the surface roughness Ra after the plasma treatment.
That is, according to the present invention, by setting the process pressure P [Pa] to be in the range of 10 or more and 15 or less, “the surface of the resin substrate in which the inorganic member serving as the filler is dispersed and contained in the organic member is further flattened. A possible method of processing a resin substrate "can be provided, and it has been confirmed that suitable plasma processing can be performed on a resin substrate having a Via dimension formed in advance on the surface of the resin substrate.

  As described above, the method for processing a resin substrate and the plasma processing apparatus according to the present invention have been described. However, the present invention is not limited to these, and can be appropriately changed without departing from the spirit of the invention.

  The present invention is widely applicable to a resin substrate processing method and a plasma processing apparatus. In particular, the present invention is suitable for a resin substrate for an application (for example, a wiring board of a supercomputer) provided with a wiring through which a current having a high frequency characteristic (for example, 60 GHz) flows.

  1 substrate, 2 resin substrates, 2a inorganic member, 2b organic member, 3 conductors.

Claims (5)

A resin substrate processing method for flattening one main surface of the resin substrate, using a resin substrate in which an inorganic member serving as a filler is dispersedly contained in an organic member as an object to be processed,
Using a chamber configured to have a decompressible internal space, in which the object to be processed is subjected to plasma processing by a dry etching method in the internal space,
Under an atmosphere in which a process gas for plasma processing is introduced into the chamber,
A bias voltage having a first frequency λ1 is applied from a first power supply to a first plate-shaped electrode on which the object is placed,
An AC voltage having a second frequency λ2 is applied from a second power supply to a second electrode disposed at a position facing the first electrode,
The second frequency λ2 [MHz] is 13.56 or more and 40.68 or less,
A method for processing a resin substrate, comprising: The first frequency λ1 [MHz] is set to 1.00 or more and 2.00 or less,
The method for processing a resin substrate according to claim 1, wherein: The power density S1 [W / cm ^2] of the AC voltage applied to the first electrode with a 0.4 to 1.2, the power density S2 of the AC voltage applied to the second electrode [W / cm ² ] Is set to 0.8 or more and 1.6 or less. The method for processing a resin substrate according to claim 1, wherein   The method of processing a resin substrate according to claim 1, wherein a process pressure P [Pa] at the time of performing the plasma processing is set to 10 or more and 15 or less. A plasma processing apparatus, comprising: a chamber provided with an internal space that can be decompressed and configured to perform plasma processing on an object to be processed in the internal space; and a chamber disposed in the chamber and mounting the object to be processed. A first plate-shaped electrode to be placed, a first power supply configured to apply a bias voltage of a first frequency λ1 to the first electrode, and A second electrode disposed at a position facing one electrode, a second power supply for applying an alternating voltage of a second frequency λ2 to the second electrode, and a process gas for plasma processing in the chamber. Means for introducing, and exhaust means for decompressing the internal space of the chamber, at least,
The first power supply has a first frequency λ1 [MHz] of a bias voltage for the first electrode in a range of 1.00 to 2.00,
The second power supply has a second frequency λ2 [MHz] of an AC voltage applied to the second electrode in a range of 13.56 to 40.68.
A plasma processing apparatus characterized by the above-mentioned.