JP4643929B2 - Plasma processing method and plasma processing apparatus - Google Patents

Description

The present invention relates to a plasma processing method and plasma processing in which a fine structure made of a conductor such as a substrate on which a circuit pattern or the like is formed can be plasma-treated without damaging an object to be processed formed on the non-conductor. Relates to the device.

Plasma processing is known as a method for modifying the surface of metal or plastic or cleaning and removing organic substances adhering to a substrate or the like. In the plasma treatment, a voltage is applied to a gas guided between electrodes to excite it into a plasma gas, and the surface of the object to be treated is treated with this plasma gas. In the conventional plasma processing apparatus, it was necessary to perform depressurization in order to generate plasma gas. However, in recent years, a method for generating plasma gas even under normal pressure has been devised, and the practical range is expanding dramatically (for example, Patent Document 1).

As a specific method of the plasma treatment, for example, a direct method in which a workpiece is disposed between electrodes and a voltage is applied while supplying a gas between the electrodes can be cited. In the direct method, the processing conditions and the like are extremely easy to control, and uniform processing is possible. However, an object to be processed in which a fine structure made of a conductor, such as a substrate on which a circuit pattern or the like is formed, is formed on a non-conductor is placed between electrodes, and the surface is subjected to plasma treatment by a direct method. As a result, a part of the circuit pattern or the like may be burnt and the circuit pattern may be damaged.
Further, as a specific method of plasma processing, a remote method is also known in which plasma gas generated between electrodes is sprayed on an object to be processed installed outside the electrodes. The remote method can be said to be a method with extremely high applicability because the surface of an object to be processed that cannot be accommodated between electrodes can be subjected to plasma treatment. However, when plasma processing is performed by a remote method on an object having a fine structure made of a conductor, such as a substrate on which a circuit pattern is formed, formed on a non-conductor, the occurrence of scorching etc. occurs compared to the direct method However, there is a problem that it is difficult to perform a sufficient plasma treatment.

JP 2003-168596 A

In view of the above situation, the present invention provides a plasma in which a fine structure made of a conductor such as a substrate on which a circuit pattern or the like is formed can be plasma-treated without damaging an object to be processed formed on a non-conductor. An object is to provide a processing method and a plasma processing apparatus.

In the plasma processing method according to the present invention, an object to be processed having a circuit pattern surface in which a plurality of independent circuit patterns made of a conductor are formed on a non-conductor is coated with a solid dielectric on the opposite surface. A plasma processing method of performing plasma processing on a surface opposite to the circuit pattern surface of the object to be processed by applying a voltage while supplying a gas between the pair of electrodes facing each other The circuit pattern surface of the object to be processed is directed to one electrode of the pair of electrodes, and at least the object to be processed is a solid dielectric covering the one electrode and the object to be processed. A separate thin film conductor is interposed between the solid dielectric covering the one electrode and the object to be processed, and fixed to the solid dielectric covering the one electrode. The thin film conductor Superposed, and a plasma processing method of contacting all of said plurality of circuit patterns by spread throughout the said thin film conductor the circuit pattern surface. In addition, the plasma processing apparatus according to the present invention is a surface opposite to the circuit pattern surface of the object to be processed having a circuit pattern surface in which a plurality of circuit patterns made of a conductor are formed on a non-conductor. A plasma processing apparatus for plasma processing, wherein a facing surface is coated with a solid dielectric, a pair of electrodes to which a voltage is applied while a gas is supplied therebetween, and one electrode of the pair of electrodes A solid dielectric covering at least one of the objects to be processed and a solid dielectric covering the one electrode, and the circuit pattern surface facing the solid dielectric Interposed between the object to be processed, fixed to a solid dielectric covering one of the electrodes, and the object to be processed is overlapped and spread over the entire circuit pattern surface. A thin film conductive member in contact with the hand, is a plasma processing apparatus having a.
The present invention is described in detail below.

In the plasma processing method of the present invention, an object to be processed is disposed between a pair of opposing electrodes whose opposing surfaces are coated with a solid dielectric, and a voltage is applied while supplying a gas between the electrodes. Plasma treatment is applied to the object.
The present inventors have earnestly investigated the cause of damage to circuit patterns and the like when plasma processing is performed on an object having a fine structure made of a conductor formed on a non-conductor, such as a substrate on which a circuit pattern or the like is formed. As a result of investigation, it was found that a very large potential difference was generated between circuit patterns independent from each other when a voltage was applied, and this potential difference caused abnormal discharge between independent circuit patterns on the workpiece. . As a result of further intensive studies, it is possible to prevent the occurrence of such abnormal discharge by arranging a thin-film conductor having a constant thickness so as to be in contact with substantially the entire circuit pattern surface of the object to be processed. It was found that the plasma treatment can be performed without damage, and the present invention has been completed. This is considered because a large potential difference is not generated between independent circuit patterns by arranging such a thin film conductor so as to be in contact with the circuit pattern surface.

An object to be processed in the plasma processing method of the present invention has a structure in which a fine structure made of a conductor is formed on a non-conductor. Examples of such an object include a substrate on which a circuit pattern or the like is formed.

The thin film conductor is not particularly limited, and examples thereof include simple metals such as iron, copper, and aluminum; alloys such as stainless steel and brass; intermetallic compounds; and carbon.
There is no particular lower limit on the thickness of the thin film conductor, but a preferred lower limit is 0.01 μm. If it is less than 0.01 μm, sufficient durability may not be obtained.
The thin film conductor may have an independent sheet-like form, or may be formed on the surface of a solid dielectric by a method such as sputtering.

The thin film conductor is disposed so as to be in contact with substantially the entire surface on which a fine structure made of the conductor of the object to be processed is formed. If the thin film conductor is not in contact with the surface on which the microstructure of the object to be processed is formed, it cannot prevent abnormal discharge from occurring between independent circuit patterns, Abnormal discharge may occur between the thin film conductor.

For example, in a normal plasma processing apparatus, the thin film conductor and the object to be processed can be fixed so that the object to be processed does not move, or a solid dielectric is used. In order to prevent abnormal discharge (back discharge) from occurring due to the floating of
Since there are many means for fixing an object to be processed and / or a solid dielectric by vacuum suction such as an air chuck, a method using such fixing means can be mentioned. That is, when a plasma treatment is performed on a surface of a workpiece that has no circuit pattern, a porous thin film conductor is disposed on a solid dielectric on an electrode, and a fine structure made of the conductor is formed on the porous thin film conductor. The objects to be processed are stacked so that the formed surface is on the thin film conductor side, and fixed by a fixing means such as an air chuck. By such a method, a thin film conductor and a to-be-processed object can be made to contact reliably. The reason why the porous thin film conductor is used here is that fixing means such as an air chuck can be used as it is.
However, when such a porous thin film conductor is used, it is preferable that the size of the pore is smaller than the minimum pattern interval in the fine structure made of the conductor on the object to be processed. When the size of the hole is larger than the fine structure made of the conductor on the workpiece, the potential difference on the workpiece cannot be prevented at that portion, and the workpiece is damaged due to abnormal discharge. May end up. More preferably, the pore size of the porous thin film conductor is ½ or less of the minimum pattern interval of the fine structure made of the conductor on the object to be processed, and more preferably １ ／. It is the following.
Although it does not specifically limit as said porous thin film conductor, The nonwoven fabric etc. which consist of a metal mesh, punching metal, a metal fiber, and carbon fiber etc. are mentioned.

Although not claimed , when plasma processing is performed on the circuit pattern surface of the object to be processed, a porous thin film conductor having sufficiently small holes with respect to the circuit pattern interval and the object to be processed are processed. The thin film conductor and the object to be processed are overlapped so that the surface on which the fine structure composed of the conductor of the object is formed is in contact with the thin film conductor, and the weight of the conductor having an appropriate weight is superimposed thereon. Can be reliably contacted. In this case, the upper limit of the thickness of the thin film conductor is 1 mm. When the thickness exceeds 1 mm, the thin film conductor itself functions as an electrode, and the plasma gas hardly reaches the object to be processed. When a porous body having pores sufficiently larger than a circuit pattern interval made of a conductor on the object to be processed is used as the weight made of the object to be processed, a fine structure made of the conductor of the object to be processed is obtained. Plasma treatment can be performed on the formed surface.

In the plasma processing method of the present invention, an object to be processed is disposed between a pair of opposed electrodes.
Examples of the electrode include, but are not limited to, for example, simple metals such as iron, copper, and aluminum; alloys such as stainless steel and brass; and intermetallic compounds. The facing surfaces of the electrodes are covered with a solid dielectric. ing. In this case, it is preferable that the fixed dielectric and the electrode are in close contact with each other and that the opposing surface of the electrode is completely covered. If there is a portion where the electrodes directly face each other without being covered by the fixed dielectric, arc discharge may occur from the portion and it may be difficult to maintain the plasma state.

The solid dielectric is not particularly limited. For example, plastic such as polytetrafluoroethylene and polyethylene terephthalate; metal oxide such as glass, silicon dioxide, aluminum oxide, zirconium dioxide, and titanium dioxide; double oxidation such as barium titanate The thing etc. which consist of things etc. are mentioned. In addition, as the solid dielectric covering the flat plate electrode, in addition to those directly adhering (coating) to the electrode surface such as ceramic coating and enamel treatment, a ceramic plate such as a quartz plate, glass plate, alumina plate or the like is applied to the electrode surface. It may be in close contact.
The preferable lower limit of the thickness of the solid dielectric is 0.1 mm, and the preferable upper limit is 2 mm.

The distance between the pair of electrodes facing each other is appropriately determined in consideration of the thickness of the solid dielectric covering the electrode, the magnitude of the applied voltage, the purpose of using plasma, etc. The preferred lower limit is 0
. 1 mm, and a preferable upper limit is 50 mm. If it is less than 0.1 mm, it may be difficult to install the electrodes with a gap between them, and if it exceeds 50 mm, uniform glow discharge plasma may not be generated. A more preferable upper limit is 5 mm.

In the plasma processing method of the present invention, a plasma process is performed on an object to be processed by applying a voltage while supplying a gas between the electrodes.
As the gas, any conventionally known gas can be used as long as it can generate a plasma gas. In addition, there is no particular limitation in the pulse discharge plasma described later, but a mixture of nitrogen gas, nitrogen and oxygen is used. Gas etc. are suitable. Above all, the mixed gas with oxygen is
It is suitable because of its high decomposition effect on organic matter.

While supplying such a gas between the electrodes facing each other, an electric field such as a high frequency, a pulse wave, or a microwave is applied to generate glow discharge plasma, thereby generating a plasma gas.
As the electric field in this case, a pulse electric field is preferable, and in particular, a pulse electric field having a rising time and / or a falling time of 10 μs or less is preferable. When the rise time and / or fall time of the pulse electric field exceeds 10 μs, the discharge state tends to shift to arc discharge and becomes unstable, and it may be difficult to maintain a high-density plasma state. More preferably, it is 5 μs or less. The shorter the rise time and / or fall time of the electric field, the more efficiently the ionization of the gas at the time of plasma generation, and an efficient plasma gas can be obtained.
In this specification, the rise time of electrolysis means the time that the voltage (absolute value) continuously increases, and the fall time means the time that the voltage (absolute value) continuously decreases. .

The preferable lower limit of the electric field strength of the electric field is 10 kV / cm, and the preferable upper limit is 1000 kV / c.
m. If it is less than 10 kV / cm, it may take too much time to generate plasma gas, and if it exceeds 1000 kV / cm, arc discharge is likely to occur and it may be difficult to maintain a high-density plasma state. .

A preferable lower limit of the frequency of the electric field is 0.5 kHz. If it is less than 0.5 kHz, the plasma density is low, and it may take too much time to generate plasma gas. An upper limit is not specifically limited, 13.56 MHz currently used regularly, 50 MHz currently used experimentally
However, it is preferably 500 kHz or less in consideration of ease of matching with the load and handleability.

The preferable lower limit of one pulse duration in the pulse electric field is 0.5 μs, and the preferable upper limit is 200 μs. When it exceeds 200 μs, it becomes easy to shift to arc discharge.
In the present specification, one pulse duration means a continuous ON time of one pulse in a pulse electric field composed of repetition of ON and OFF.
Moreover, the preferable lower limit of the OFF time at this time is 0.5 μs, and the preferable upper limit is 1000 μs.
The upper limit is more preferably 500 μs.

Moreover, it does not specifically limit as a speed | rate which supplies the said gas between the electrodes which oppose, What is necessary is just to adjust suitably according to the state of a plasma, process conditions, etc., but a preferable minimum is 1 m / s and a preferable upper limit is 50 m / s. . If it is less than 1 m / s, a current path is likely to be formed, and the discharge may become unstable. A more preferable lower limit is 2 m / s, and a more preferable upper limit is 20 m / sec.

The plasma gas can be generated and used under any pressure, but is preferably used under a pressure near atmospheric pressure.
In the present specification, under the pressure near atmospheric pressure is 1.333 × 10 ^{4 to} 10.664 ×.
It means under a pressure of 10 ⁴ Pa. Among these, the range of 9.331 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa, which allows easy pressure adjustment and simplifies the configuration of the apparatus, is preferable. However, when the inside of the apparatus is evacuated after surrounding the entire apparatus with a chamber or the like, the processing gas may be introduced from the vicinity of the electrode within a range in which abnormal discharge does not occur.

In the plasma processing method of the present invention, for example, the opposing surface 1 is coated with a solid dielectric.
This can be easily performed by using a plasma processing apparatus having a structure having a pair of electrodes and a thin layer conductor having a thickness of 1 mm or less disposed on a solid dielectric covering one of the electrodes. it can.
Such a plasma processing apparatus is also one aspect of the present invention.
When the plasma processing apparatus of the present invention has means for fixing the object to be processed and / or the solid dielectric by vacuum suction, the thin film conductor is a porous thin film conductor. Is preferred.

According to the present invention, a plasma processing method capable of performing plasma processing without damaging a target object formed on a non-conductor with a fine structure made of a conductor such as a substrate on which a circuit pattern or the like is formed, and A plasma processing apparatus can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
Using the plasma processing apparatus shown in FIG. 1, the surface of the circuit board on which the circuit pattern made of copper was formed on the surface of the polyimide resin film was subjected to plasma processing. Note that the size of the smallest structural portion on the circuit pattern is 500 μm.
In the apparatus shown in FIG. 1, the electrode 1 and the electrode 8 are disposed to face each other. A workpiece 6 can be fixed by suction from a suction port 4 on a solid dielectric 3 provided on the surface of one electrode 1 and by a fixing auxiliary member 7. A porous thin film conductor 5 is interposed between the solid dielectric 3 and the object 6 to be processed. The porous thin film conductor 5 has a thickness of 50 μm and a width of 5
A mesh knitted so that 0 μm gold wires were equidistantly spaced by 100 μm was used. Also,
FIG. 2 is an enlarged view of a contact portion between the porous thin film conductor 5 and the workpiece 6. As shown in FIG. 2, the circuit pattern 62 of the workpiece 6 is surely in contact with the gold wire of the porous thin film conductor 5 by being fixed by the suction and fixing auxiliary member 7 from the suction port 4. .

While supplying nitrogen gas between the electrode 1 and the electrode 8, the pulse rise time 5 μs, the voltage 16
It was subjected to glow discharge plasma treatment kV _P-P, the surface of the circuit board by applying a pulsed electric field frequency 50 kHz.

(Comparative Example 1)
Example 1 except that no porous thin film conductor was interposed between the solid dielectric 3 and the portion 6 to be processed.
The surface of the circuit board was subjected to plasma treatment by the same method as described above.

(Evaluation)
The circuit boards subjected to the plasma treatment in Example 1 and Comparative Example 1 were evaluated by the following methods.
The results are shown in Table 1.

(1) Evaluation of plasma treatment The plasma treatment surface of the circuit board was measured for changes in the contact angle of water before and after the plasma treatment using a contact angle meter.

(2) Evaluation of surface state The circuit pattern surface of the circuit board was observed visually and evaluated according to the following criteria.
◯: No damage such as scorching is observed.
X: Damage that was seen as scorching was found in a part of the circuit.

According to the present invention, a plasma processing method capable of performing plasma processing without damaging a target object formed on a non-conductor with a fine structure made of a conductor such as a substrate on which a circuit pattern or the like is formed, and A plasma processing apparatus can be provided.

1 is a schematic diagram showing a plasma processing apparatus used in Example 1. FIG. It is the figure which expanded the contact part of the porous thin film conductor 5 and the to-be-processed object 6 in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 8 Electrode 2, 9 Resin housing 3 Solid dielectric material 4 Suction port 5 Porous thin film conductor 6 To-be-processed object 61 Polyimide resin film 62 Circuit pattern 7 Fixing auxiliary member

Claims (4)

An object to be processed having a circuit pattern surface in which a plurality of independent circuit patterns made of a conductor are formed on a non-conductor is disposed between a pair of opposed electrodes whose opposite surfaces are covered with a solid dielectric. And applying a voltage while supplying a gas between the electrodes to perform a plasma treatment on the surface opposite to the circuit pattern surface of the workpiece,
The circuit pattern surface of the object to be processed is directed to one electrode of the pair of electrodes, and a thin film separate from at least the object to be processed among the solid dielectric covering the one electrode and the object to be processed An electric conductor is interposed between the solid dielectric covering the one electrode and the object to be processed, and fixed to the solid dielectric covering the one electrode, and the object to be processed is fixed to the thin film conductor And the thin film conductor is spread over the entire circuit pattern surface so as to be in contact with all of the plurality of circuit patterns.   The thin film conductor is a porous thin film conductor, and the size of the pores of the thin film conductor is smaller than a minimum pattern interval among the circuit patterns independent of each other. The plasma processing method as described. A plasma processing apparatus for performing plasma processing on a surface opposite to the circuit pattern surface of an object to be processed having a circuit pattern surface on which a plurality of independent circuit patterns made of a conductor are formed on a non-conductor,
A pair of opposing electrodes, the opposing surfaces of which are coated with a solid dielectric, to which a voltage is applied while a gas is supplied therebetween,
The solid dielectric covering one electrode of the pair of electrodes and the object to be processed are separated from at least the object to be processed, and the solid dielectric covering the one electrode and the solid dielectric The circuit pattern surface is interposed between the object to be processed, fixed to a solid dielectric covering the one electrode, and the object to be processed is overlaid on the entire circuit pattern surface. A thin film conductor that contacts and contacts all of the plurality of circuit patterns;
A plasma processing apparatus comprising:   Furthermore, it has means for fixing the object to be processed and / or the solid dielectric by vacuum suction, and the thin film conductor is a porous thin film conductor, and the size of the hole of the thin film conductor is 4. The plasma processing apparatus according to claim 3, wherein the circuit pattern is smaller than a minimum pattern interval among circuit patterns independent from each other.

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