JP2000315861A - Apparatus and method for smear elimination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smear eliminating apparatus and a smear eliminating method which can eliminate smears effectively, without residue of smears. SOLUTION: In a smear eliminating method of a substrate, which eliminates smear left on a conducting film of the bottom part of a via hole formed in a substrate, by using plasma treatment, a substrate 4 is mounted on a lower electrode arranged facing an upper electrode, plasma generating gas containing oxygen is supplied in a treatment chamber between the lower electrode and the upper electrode, a high-frequency voltage is applied across the lower electrode and the upper electrode, and plasma treatment is performed in the condition that a distance D between the upper electrode and the lower electrode is at most 10 mm and the partial pressure of oxygen in the plasma generating gas is in the range of 100 to 10,000 Pa. Thereby ions generated by plasma are made to enter an object surface to be treated isotropically, and residue of smears can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for removing smear remaining in a via hole provided in a resin layer of a substrate.

[0002]

2. Description of the Related Art In a manufacturing process of a mounting board on which electronic components are mounted, a hole forming process is performed to form a via hole in an insulating resin layer formed so as to cover a circuit pattern on the surface of the board. The via hole is for conducting the circuit pattern to an external connection electrode such as a metal bump provided on the surface of the resin layer, and a conductive portion is formed inside the via hole after plating by a method such as plating.

[0003] One of the methods of drilling is laser processing. Laser processing has an advantage that a fine hole can be processed with high accuracy and high efficiency. However, when laser processing is used, resin residue (smear) remains as a thin film on the circuit pattern surface at the bottom of the hole. The smear must be removed because it causes a problem when the conductive portion is formed by a method such as plating.
In recent years, as a method for removing smear, plasma processing has been used in place of the wet processing for removing smear using an oxidizing agent such as a potassium permanganate solution which has been conventionally used. In the plasma processing, foreign matter such as smear attached to a processing target surface is removed by colliding ions generated by plasma discharge with a processing target. According to the plasma processing, there are many advantages, such as no need for waste liquid processing, as compared with the wet processing.

[0004]

However, the plasma processing used for removing smears has the following problems. Since the surface of the circuit pattern to which the smear adheres is provided with an anchor pattern having fine irregularities in order to improve the adhesion to the resin layer, the smear remaining in the concave portion of the pattern is shaded by the convex portion of the pattern. In range. For this reason, ions that are incident on the surface to be processed from the vertical direction during the plasma processing do not necessarily collide with all the smears existing on the surface. As a result, smears in the shaded portions of the projections remained unremoved after the plasma treatment, causing poor quality in the subsequent process. As described above, the conventional smear removing method has a problem that the smear tends to remain partially and quality cannot be ensured.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a smear removing apparatus and a smear removing method which can remove smear and can remove smear satisfactorily.

[0006]

According to a first aspect of the present invention, there is provided an apparatus for removing smear of a substrate, which removes smear remaining on a conductive film at the bottom of a via hole formed in the substrate by plasma processing. A lower electrode on which the substrate is mounted, an upper electrode disposed so as to face the lower electrode with a distance between the electrodes of 10 mm or less, and an airtight seal including the space between the lower electrode and the upper electrode are formed. A processing chamber, a gas supply means for supplying a plasma generating gas containing oxygen into the processing chamber, and a high-frequency power supply for applying a high-frequency voltage between the lower electrode and the upper electrode; Plasma treatment is performed under the condition that the partial pressure is in the range of 100 to 10000 Pa.

According to a second aspect of the present invention, there is provided a smear removing apparatus according to the first aspect, wherein the lower electrode and / or the upper electrode are covered with a dielectric.

According to a third aspect of the present invention, there is provided a method of removing smear of a substrate, which removes smear remaining on a conductive film at the bottom of a via hole formed in the substrate by plasma treatment. The substrate is placed on the disposed lower electrode, and a plasma generating gas containing oxygen is supplied to a processing chamber formed in an airtight manner outside including a space between the lower electrode and the upper electrode, and supplying the gas to the lower electrode. The plasma processing conditions when performing a plasma processing by applying a high frequency voltage between the upper electrode and the upper electrode are such that the distance between the lower electrode and the upper electrode is 10 mm or less, and the oxygen content of the plasma generating gas is The pressure is in the range of 100 to 10000 Pa.

According to the present invention, the plasma treatment is performed under the condition that the distance between the electrodes between the upper electrode and the lower electrode is 10 mm or less and the oxygen partial pressure of the plasma generating gas is in the range of 100 to 10000 Pa. The ions can be made to be isotropically incident on the surface to be treated, so that the residual smear can be reduced. Also, preferably, by covering the electrodes with a dielectric, concentration of discharge can be prevented and uniform plasma can be generated.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a side sectional view of a device for removing smear of a substrate according to an embodiment of the present invention, FIG. 2 is a graph showing plasma processing conditions of the device for removing smear of the substrate, and FIGS.
(B), FIGS. 4 (a) and 4 (b) are explanatory diagrams of the smear removal processing of the substrate, FIG. 5 is a graph showing the etching rate of the smear removal device of the substrate, and FIG. 6 is a diagram of the smear removal device of the substrate. It is a side sectional view.

First, the structure of a device for removing smear from a substrate will be described with reference to FIG. In FIG. 1, a base member 2 is made of a conductor such as aluminum, and the surface of the base member 2 is covered with a dielectric 3 such as alumina. The base member 2 and the dielectric 3 constitute a lower electrode.
A substrate 4 to be processed is placed on the dielectric 3 of the lower electrode. That is, the lower electrode is a substrate mounting portion.

Above the lower electrode, a case member 5 is provided so as to be able to move up and down by means of raising and lowering means (not shown). A stepped opening is provided in the center of the case member 5, and a conductive portion 6 made of a conductor such as aluminum is provided in the opening.
Are fitted via an insulating member 5a. The conductive portion is mounted on the case member 5 while maintaining a gap where no discharge is generated by the voltage applied during the plasma processing.

On the lower surface of the conductive portion 6, a concave portion 6a is provided over substantially the entire surface, and the concave portion 6a is covered with a dielectric 7 similar to the dielectric 3 of the lower electrode. Conductive part 6
And the dielectric 7 constitute an upper electrode. In a state where the case member 5 is lowered to be in contact with the base member 2, the upper electrode faces the lower electrode at a predetermined distance D between the electrodes. In the present embodiment, the dimensions of each part are set so that the distance D between the electrodes is 10 mm or less. Here, an example in which the dielectrics 3 and 7 are provided for the upper electrode and the lower electrode, respectively, is shown. However, these are not indispensable constitutional requirements. In addition, there is an effect that the plasma processing can be performed uniformly.

A space between the upper electrode and the lower electrode is formed in a processing chamber 9 airtightly formed by a sealing member 8 to the outside.
It has become. A supply / exhaust hole 2 a communicating with the processing chamber 9 is provided in the base member 2, and a vacuum exhaust unit 10 and a vacuum gauge 11 are connected to the supply / exhaust hole 2 a. By driving the evacuation unit 10 while measuring the degree of vacuum with the vacuum gauge 11, the degree of vacuum in the processing chamber 9 can be set to a predetermined degree of vacuum.

The conductive portion 6 is provided with an air supply hole 6b, and the air supply hole 6b is connected to the plasma gas supply portion 12. By driving the plasma gas supply unit 12,
A plasma generating gas containing oxygen gas is supplied to the concave portion 6a of the upper electrode via the intake hole 6b, and is supplied into the processing chamber 9 from a large number of gas holes 7a provided in the dielectric 7. At this time, the evacuation unit 1 is based on the detected value of the degree of vacuum of the vacuum gauge 11.
By controlling 0 and the plasma gas supply unit 12 by the control unit 15, the oxygen partial pressure of the plasma generation gas supplied into the processing chamber 9 can be set to a predetermined range.

The conductive section 6 is connected to a high-frequency power supply section 13. The base member 2 and the high-frequency power supply unit 13 are connected to a common grounding unit 14, and by driving the high-frequency power supply unit 13, the space between the conductive unit 6 and the base member 2, that is, between the upper electrode and the lower electrode. Is applied with a high-frequency voltage. In this embodiment, the high-frequency power supply unit 13 is connected to the conductive unit 6 (upper electrode).
(Lower electrode).

Next, the plasma processing conditions in the plasma processing for removing smear will be described with reference to FIG. The plasma processing conditions are defined by the distance between the electrodes and the partial pressure of oxygen gas in the processing chamber 9 in which the substrate to be processed is placed. In FIG. 2, a zone 20 indicated by rough hatching corresponds to a condition conventionally used in ordinary plasma processing, and a distance between electrodes is approximately 20 to 50 mm, and a partial pressure of oxygen gas is approximately 1 to 20 Pa. It has become. On the other hand, the zone 21 indicated by dense hatching corresponds to the plasma processing conditions in the present embodiment, and the distance D between the electrodes is 10 mm or less, and the partial pressure of oxygen gas is in the range of 100 to 10000 Pa. The significance of using such plasma processing conditions will be described later.

Next, removal of smear from the substrate will be described with reference to FIGS. First, the substrate 4 to be processed will be described. As shown in FIG. 3A, a copper circuit pattern 4a, which is a conductive film, is formed on the surface of the substrate 4, and the circuit pattern 4a is covered with an insulating resin layer 4b.
The circuit pattern 4a is formed on the insulating resin layer 4b.
A via hole 4c for conducting with an electrode formed on the upper surface of the substrate b is formed. A thin film smear 4d is attached to the surface of the circuit pattern 4a at the bottom of the via hole 4c. The smear 4d remains without being removed after the formation of the via hole by laser processing in the previous step. On the surface of the circuit pattern 4a, an anchor pattern having fine irregularities for improving the adhesion with the insulating resin layer is formed in advance, and the smear 4d is formed between the protrusions 4a 'of the anchor pattern. Remains.

In order to remove the smear 4d in the above state, the substrate 4 after the via hole is formed is subjected to a smear removing process. First, the substrate 4 is placed on the lower electrode 2 of the smear removing device. After lowering the case member 5 to make the processing chamber 9 airtight, the evacuation unit 10 is driven to
The inside is evacuated to a predetermined degree of vacuum. Next, the plasma gas supply unit 12 is driven to supply a plasma generation gas including an oxygen gas into the processing chamber 9. At this time, the partial pressure of the oxygen gas in the processing chamber is set in a range of 100 to 10000 Pa. Then, in this state, the high-frequency power supply unit 13 is driven to apply a high-frequency voltage between the base member 2 and the conductive unit 6.

As a result, a plasma discharge is generated between the lower electrode and the upper electrode, and an oxygen gas plasma is generated in the processing chamber 9. At this time, due to the action of the dielectrics 7 and 3 covering the upper electrode and the lower electrode, plasma discharge is generated uniformly without being locally concentrated, and is uniform over the entire range of the substrate 4 to be processed. Plasma treatment can be performed. In the process of this plasma treatment, as shown in FIG. 3B, oxygen ions 23 in which oxygen molecules 22 in the plasma generating gas are ionized by plasma discharge collide with the surface of the smear 4d. Thus, the smear 4d is oxidized by the oxygen ions 23 and is removed from the surface of the circuit pattern 4a.

As described above, since the projections 4a 'are present on the surface of the circuit pattern 4a, the smears 4 adhering to the portions that enter between the projections and shade the projections are provided.
d is not completely removed by the oxygen ions 23 incident on the surface of the circuit pattern 4a from the vertical direction, and tends to remain even after the plasma processing. Smear 4d in this state
Also, by applying the plasma processing conditions described in the present embodiment, good smear removal can be performed for the reasons described below.

That is, in this embodiment, the plasma processing is performed under a partial pressure of oxygen gas which is 10 to 100 times as high as the plasma processing conditions conventionally used. Therefore, oxygen molecules 22 existing in the space of the processing chamber 9
And the density of the oxygen ions 23 is high, so that the etching effect on the smear 4d due to the collision of the oxygen ions 23 is greater than in the conventional case.

FIG. 5 shows that the oxygen gas partial pressure is 100 to 1000.
It shows a change in the etching rate when it is changed in the range of 0 Pa. As can be seen from FIG. 5, the etching rate tends to increase as the oxygen gas partial pressure increases. However, when the pressure exceeds 10,000 Pa, the plasma discharge itself becomes unstable, so that a partial pressure of oxygen gas of 10,000 Pa or more cannot be used as a condition of the plasma treatment for the purpose of the etching effect. That is, as a practical plasma processing condition, an oxygen gas partial pressure in a range of 100 to 10000 Pa that can perform stable plasma discharge and obtain an etching rate as high as possible is used.

Here, the distance D between the electrodes is set to 10 mm or less for the following reason. The above-mentioned etching rate has a correlation with the value of the product PD of the oxygen gas partial pressure P of the plasma generating gas and the interelectrode distance D.
It has a characteristic that it becomes maximum when D is a specific value. Therefore, if the above-described high oxygen gas partial pressure is employed to realize a high etching rate while maintaining this specific value, the distance D between the electrodes inevitably becomes the distance between the electrodes under the plasma processing conditions conventionally used. This is a small value compared to. The condition of the inter-electrode distance of 10 mm or less in the present embodiment is set in this manner.

By performing the plasma treatment under the condition of a high oxygen gas partial pressure, the following excellent effects can be obtained in addition to the improvement of the etching rate. That is, by performing the plasma treatment under a high oxygen gas partial pressure, the oxygen ions 23 can be obliquely incident on the shaded portion of the projection 4a 'as shown in FIG. Under a high oxygen gas partial pressure, it is highly probable that the oxygen ions 23 collide with the oxygen molecules 22 existing in this space and change the incident direction before reaching the surface of the circuit pattern 4a. This is because the light is incident in one direction. As a result, as shown in FIG. 4A, the oxygen ion 2 is also applied to the smear 4d behind the convex portion 4a '.
After the plasma treatment, the smear 4d remaining at the bottom of the via hole 4c as shown in FIG.
Is completely removed from the surface of the circuit pattern 4a.

Further, since it is not necessary to evacuate the processing chamber to a high vacuum, the time for evacuating and introducing the atmosphere at the time of vacuum breakage can be shortened. Tact time is greatly reduced as compared with the conventional method, and improvement in processing efficiency is realized.

Since a high degree of vacuum is not required, the structure of a vacuum system such as a vacuum pump of a plasma etching apparatus can be simplified. Further, when the substrate is held in the processing chamber for the same reason, a differential pressure between the pressure in the processing chamber and the suction pressure for vacuum suction can be easily secured. It can be held on an electrode. Therefore, simplification of the mechanism of the plasma etching apparatus and cost reduction are realized. In addition, even when compared with the wet processing of performing etching using a chemical solution, which has been conventionally performed, high efficiency, low cost, no waste liquid is discharged, and there is no risk of environmental pollution.
Has excellent features.

In addition, in terms of quality, under the above conditions, the distance between the electrodes is set to be narrower than in the conventional case, so that the distribution of plasma generated between the electrodes becomes uniform, and the uniform etching effect is obtained at any position on the substrate. You can get
Stable quality without variation can be secured.

The present invention is not limited to the above embodiment, but may be applied to, for example, a tape substrate 24 as shown in FIG. As shown in FIG. 6B, a resin layer 24 such as polyimide is formed on the copper film 24a, and a via hole 24c is provided in the resin layer 24b. Smear remains at the bottom of the via hole 24c as in the case of the via hole 4c of the substrate 4 described above. This smear is removed by the plasma treatment. In the example shown in FIG. 6, the tape-shaped substrate 24 travels in the processing chamber 9 of the smear removing apparatus while keeping the tape-shaped substrate 24 in a continuous tape shape. At this time, a clamp portion 18 is provided at a contact portion between the case member 5 and the lower electrode 2 to seal a contact surface with the tape-shaped substrate 24 to keep the inside of the processing chamber 9 airtight. Also in this case, the distance between the electrodes between the upper electrode and the lower electrode is 10 mm or less,
And the oxygen partial pressure of the plasma generating gas is 100 to 1000
By performing the plasma treatment under the condition of 0 Pa,
Smear at the bottom of the via hole 24c can be satisfactorily removed.

[0030]

According to the present invention, the plasma treatment can be performed under the conditions that the distance between the upper electrode and the lower electrode is 10 mm or less and the oxygen partial pressure of the plasma generating gas is in the range of 100 to 10000 Pa. With this configuration, it is possible to generate plasma under a high oxygen gas partial pressure and to cause ions to be isotropically incident on the surface to be processed, thereby greatly reducing smear residue.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a substrate smear removing apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing plasma processing conditions of the apparatus for removing smear of a substrate according to one embodiment of the present invention;

FIG. 3A is an explanatory diagram of a smear removing process of a substrate according to an embodiment of the present invention; FIG. 3B is an explanatory diagram of a smear removing process of the substrate according to an embodiment of the present invention;

FIG. 4 (a) is an explanatory diagram of a smear removing process for a substrate according to an embodiment of the present invention; and (b) is an explanatory diagram of a smear removing process for the substrate according to an embodiment of the present invention.

FIG. 5 is a graph showing an etching rate of the apparatus for removing smear of a substrate according to one embodiment of the present invention;

FIG. 6 is a side sectional view of the substrate smear removing apparatus according to one embodiment of the present invention;

[Explanation of symbols]

 Reference Signs List 2 Base member 3, 7 Dielectric 4 Substrate 4a Circuit pattern 4b Insulating resin layer 4c Via hole 6 Conductor 10 Vacuum exhaust unit 12 Plasma gas supply unit 13 High frequency power supply unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E317 AA24 BB01 BB11 CD01 CD27 CD32 CD36 GG16 5E343 AA07 AA11 BB67 EE08 EE36 EE40 EE46 FF23 FF30 GG11

Claims (4)

[Claims] 1. An apparatus for removing smear of a substrate, which removes smear remaining on a conductive film at the bottom of a via hole formed in the substrate by plasma processing, comprising: a lower electrode on which the substrate is mounted; An upper electrode disposed to face with an electrode distance of 10 mm or less, a processing chamber formed airtight with the outside including a space between the lower electrode and the upper electrode,
A gas supply means for supplying a plasma generation gas containing oxygen into the processing chamber; and a high frequency power supply for applying a high frequency voltage between the lower electrode and the upper electrode, wherein the oxygen partial pressure of the plasma generation gas is 100 A smear removing apparatus for performing plasma processing under conditions in a range of from 1 to 10,000 Pa. 2. The smear removing apparatus according to claim 1, wherein said lower electrode and / or upper electrode is covered with a dielectric. 3. A method of removing smear of a substrate by plasma treatment for removing smear remaining on a conductive film at a bottom of a via hole formed in the substrate, wherein the smear is removed on a lower electrode arranged opposite to an upper electrode. A substrate is placed, and a plasma generating gas containing oxygen is supplied to a processing chamber formed in an airtight manner outside including a space between the lower electrode and the upper electrode, and a high-frequency voltage is applied between the lower electrode and the upper electrode. Is applied, the plasma processing conditions are such that the distance between the lower electrode and the upper electrode is 10 mm or less, and the oxygen partial pressure of the plasma generating gas is 100 to 1000.
A method for removing smear from a substrate, wherein the smear is in a range of 0 Pa. 4. The smear removing method according to claim 3, wherein the plasma treatment is performed while the lower electrode and / or the upper electrode are covered with a dielectric.