JPH11236676A - Atmospheric pressure discharge plasma processing method - Google Patents

Abstract

[PROBLEMS] To use a discharge plasma generated under a pressure near the atmospheric pressure, which is industrially advantageous, to reduce the film thickness unevenness of the substrate to be processed by ± 10%.
Provided is a normal-pressure plasma processing method that can be suppressed within the range. A reaction gas is introduced into a space sandwiched between parallel plate type electrodes (82a, 82b) at a substantially uniform flow rate of ± 20% or less in flow velocity variation across the electrode width. In order to enable the introduction of such a reaction gas, for example, a swash plate facing the gas introduction direction is provided, and at the same time, the reaction gas is once introduced and diffused into a space that becomes narrower as the distance from the gas introduction port increases. After deflecting the gas flow direction substantially parallel to the traveling direction of the processing object W, has a length larger than the electrode width,
In addition, the electrodes 82a, 8a are formed through slits having a substantially constant width in the length direction or uniformly arranged small holes.
A gas introduction container I having a structure for blowing out between 2b is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called normal-pressure discharge plasma processing method for processing a substrate using discharge plasma generated under a pressure near atmospheric pressure.

[0002]

2. Description of the Related Art Conventionally, a thin film forming method utilizing plasma generated by glow discharge under low pressure conditions has been put to practical use. However, thin film formation under this low pressure condition requires a vacuum container or vacuum device, etc., and it is necessary to break the vacuum of the vacuum container every time processing is performed in batches and perform a new evacuation. Since both initial cost and running cost are high and industrially disadvantageous, they have been applied only to processing of expensive articles such as electronic parts and optical parts.

In order to solve such a problem, there has been proposed a method of utilizing discharge plasma under a pressure near the atmospheric pressure. For example, Japanese Patent Application Laid-Open No. 2-48626 discloses a method of performing treatment using plasma generated in a mixed atmosphere of helium and ketone at a pressure near the atmospheric pressure. In the gazette,
A method is disclosed in which a treatment is performed using plasma generated in an atmosphere near the atmospheric pressure composed of argon and acetone and / or helium.

[0004]

By the way, when a mixed gas necessary for a reaction under a pressure near the atmospheric pressure is introduced into the discharge space, it is more difficult to diffuse the gas than when the gas is diffused under a low pressure condition. As a result of the bias of the mixed gas, non-uniformity is likely to occur in the processing result.

That is, when introducing a gas into a chamber for forming a plasma processing space, a gas supply pipe is usually connected to one or several gas inlets. In the lower part, the gas is hardly diffused in the chamber, so that the gas density is higher at a position closer to the gas inlet, and the flow velocity of the gas is necessarily lower at a position farther from the gas inlet.

In the case where the purpose of the plasma treatment is to improve the wettability of the surface of the object to be treated, the uniformity of the treatment does not pose a particular problem as long as the effect is exerted on the entire treated surface.
On the other hand, when forming an anti-reflection film, a high-reflection film, or an optical thin film such as a filter, the processing unevenness is a serious problem as the overall performance is affected. That is, the processing unevenness at the time of processing such an optical thin film is as follows.
It is said that the deviation of the reflection wavelength, which appears to human eyes as color unevenness and in which the color unevenness can be ignored, is about 20 nm. When this is converted into a film thickness, it corresponds to about 100 to 200 °,
It suggests that it is necessary to suppress the film thickness unevenness within ± 10% for a film thickness of about 0 to 2000 °.

A method for uniformly introducing a gas into a normal-pressure discharge space is disclosed in JP-A-2-48626 and JP-A-6-48626.
No. -21149. However, in these methods, the presence of a portion where the flow of gas is stagnant, unevenness in processing due to the presence of holes in the electrode, and the like occur, and unevenness in film thickness over the entire surface of the substrate to be processed is suppressed to within ± 10%. It is difficult.

An object of the present invention is to use a discharge plasma generated under a pressure near the atmospheric pressure which is industrially advantageous, while suppressing the thickness unevenness of the substrate to be processed to within ± 10%. An object of the present invention is to provide a normal-pressure discharge plasma processing method capable of forming a high-performance optical thin film or the like at low cost.

[0009]

In order to achieve the above object, a normal pressure discharge plasma processing method according to the present invention provides a solid dielectric material on at least one surface of a pair of electrodes facing each other under a pressure near atmospheric pressure. In a plasma processing method using plasma generated by applying a pulsed electric field between a pair of electrodes in a state where a body is arranged, the pair of electrodes are parallel flat plates whose opposing surfaces are substantially smooth. In addition to the electrodes, the reaction gas is introduced into a space interposed between the electrodes at a substantially uniform flow rate of ± 20% or less in the flow rate variation across the electrode width (claim 1). ).

Here, in the present invention, the object to be processed is caused to travel in a certain direction between the pair of electrodes, and the reaction gas is introduced in a direction parallel to the traveling direction of the object to be processed. ) Is desirable.

In the present invention, as a specific method for introducing the reaction gas between the electrodes at a substantially uniform flow rate of ± 20% or less in the flow rate between the electrodes as described above, The reaction gas supplied from the pipe has a swash plate facing the gas introduction direction, and is guided and diffused in a section that becomes narrower as the distance from the gas introduction port increases, and at the same time, the reaction gas is substantially moved in the traveling direction of the workpiece. After deflecting the gas flow direction in parallel, a gas introduction container having a length greater than the electrode width, and having a structure to blow out between the electrodes through a slit having a substantially constant width in the length direction. The method used (claim 3) can be mentioned.

Another specific method for introducing a reactant gas between the electrodes at a substantially uniform flow rate also involves reacting a reactant gas supplied from a gas pipe with a cross section in a gas introduction direction between the electrodes. Is diffused in the first section, which gradually expands, and then led to a second section, whose cross section gradually reduces in the gas blowing direction, via a grid or a mesh-like wall surface, and at the end of the second section. A method using a gas introduction container having a structure provided to have a length greater than the electrode width and having a structure for blowing out between the electrodes through a slit having a substantially constant width in the length direction (claim 4). Can be mentioned.

Here, in the present invention, the pressure near the atmospheric pressure means a pressure of 100 to 800 Torr.
Preferably, the pressure range is 80 Torr.

In order to achieve the object of the present invention of suppressing the thickness unevenness of the substrate to be processed to within ± 10%, it is first necessary to form a uniform electric field over a large area. In order to form such a uniform electric field, it is most suitable that the electrode structure is a parallel plate.

Particularly in a glow discharge near atmospheric pressure,
Since the gas molecule density is higher than that of the low gas pressure discharge, the lifetime until recombination after ionization is short, and the mean free path of electrons is short. For this reason, the glow discharge space is limited to the space between the electrodes, and the distance between the electrodes at which a stable discharge that does not reach an arc can be maintained is up to about 4 mm. Therefore, in order to maintain the parallelism of the electrode spacing, the electrode surface must be smooth without protrusions. That is,
This is because protrusions on the electrode surface cause electric field concentration at that portion, which causes arc discharge. Therefore, it is desirable that the facing surface of the electrode to be used has a surface roughness (roughness) or protrusion of 1 μm or less.

In order to achieve the object of the present invention, in addition to obtaining a uniform electric field using the above-described electrodes, the gas existing between the electrodes causes laminar flow on the object to be processed. Our studies have revealed that it is necessary that the flow rate be formed and that its flow rate be substantially uniform over the processing width of the substrate.

According to the present invention, the film thickness distribution of the film formed on the object to be processed traveling in the normal pressure plasma discharge space is ± 10%.
For the first time, it has become possible to control it to within%.

The uniformity of the film thickness distribution in the width direction (the direction perpendicular to the running direction) of the object to be processed is uniform by using a substantially constant electric field and a gas introduction container for blowing gas at a substantially constant flow rate in the width direction. It is thought to be obtained by glow discharge. In addition, it is considered that the uniformity of the film thickness distribution in the traveling direction of the object is obtained by exposing the object to plasma ionized from a gas blown toward the object.

As the gas introduction container for blowing out the reaction gas at a substantially constant flow rate in the width direction, the container used in the invention according to claim 3 or 4 can be suitably mentioned.

That is, in order to blow out gas at a substantially constant flow rate in a certain direction, according to the study of the present inventors, a gas is introduced into a compartment from one gas introduction hole, and the gas is turbulent.
It has been found that it is necessary to rectify gas in the target direction and to emit gas from a slit having a uniform width.

As a structure of the gas introduction container satisfying such conditions, there can be mentioned a structure as exemplified in FIGS. 1, 2 and 4 to 6.

FIGS. 1, 2 and 4 show examples of the gas introduction container used in the third aspect.

FIG. 1A is a sectional view of FIG.
(B) is a view taken in the direction of the arrow B, and (C) is a cross-sectional view taken along the line CC as well, and a gas supply port G is connected to one end of the rectangular container 1 in the longitudinal direction. 11 and the swash plate 12 is provided on the diagonal line of the container 1 so as to face the gas introduction direction, thereby forming a section which becomes narrower as the distance from the gas introduction port 11 increases. The gas is made turbulent, the density in the compartment is made substantially uniform, the flow velocity is made substantially uniform, and at the same time, after the direction is deflected, the uniform gas provided near the edge of the container 1 is provided. It has a structure in which gas is rectified and blown out from many small hole groups 13.

FIG. 2A is a cross-sectional view, and FIG. 2B is a cross-sectional view taken along the line BB. As shown in FIG. A first chamber 21 is provided, and a second chamber 22 into which gas from the small hole group 13 is introduced is provided. In the second chamber 22, a partition plate 24 having a uniform gap 23 at one end is arranged. A slit 25 having a uniform width is formed in the vicinity of the edge, and the small hole group 1 of the first chamber 21 is formed.
Gas coming out of 3 goes around the partition plate 24 and the slit 2
5 is configured to be discharged into the discharge space as a laminar flow. This makes it possible to further average the flow of the gas that has flowed out of the small hole group 13.

Further, as shown in FIG. 4, the container 1 shown in FIG. 1 is used as a first chamber 31 as shown in FIG. A second chamber 32 into which gas discharged from the hole group 13 is introduced is provided.
Has a structure in which a slit 33 having a uniform width is formed in the vicinity of the edge, and a number of ball beads 34 are sealed in the inside thereof.
And is blown out from the slit 33.

In the gas introduction container shown in FIGS. 1, 2 and 4, the larger the turbulent space, the better, and its width is desirably larger than the electrode width.

Although the size of the container is limited by the size of the discharge device to which it is attached, it is desirable that the depth of the turbulent space is at least に 対 し て or more of the width.

In the configuration of FIG. 2, the size of each small hole of the small hole group 13 also depends on the length of the partition plate 24.
A diameter of about 1 to 10 mm is desirable. If it is less than 1 mm, the reaction product may be clogged when a highly reactive gas is passed, and if it exceeds 10 mm, the rectifying effect becomes thin.

Further, in the configuration shown in FIG. 2, a first chamber 21 having a gas inlet 11 and a second chamber 22 on the gas blowing side are provided.
May have the same size or different sizes. For example, as shown in FIG. 3, when the size of the second chamber 22 on the gas blowing side is made smaller than that of the first chamber 21,
The uniformity of the flow velocity of the gas introduced into the normal pressure discharge space is further improved.

The ball beads 34 in the configuration of FIG.
A rectifying effect corresponding to the small hole group 13 in FIGS. 1 and 2 is realized. The material of the ball beads 34 may be selected from those having no reactivity with gas, and specific examples include glass, polytetrafluoroethylene, titanium oxide, or a spherical body or metal sphere coated with them. it can.

FIGS. 5 and 6 show examples of the gas introduction container used in claim 4 in a state where the wall of the container is seen through.

In each of these examples, a space 41 or 51 whose cross section gradually expands in a gas introduction direction (blowing direction) A between the electrodes, and a grid-like partition wall 42 or 52 with respect to the space 41 or 51. And a space 43 or 53 whose cross section gradually reduces in the direction A, and a slit 44 or 54 having a uniform width is provided at the end of the space 43 or 53. Have. In the example shown in FIG. 5, the reactive gas is introduced from the gas supply pipe G in the direction in which the space 41 is enlarged in the cross section of the space 41, and in the example shown in FIG.

According to such a structure, the gas supplied from the gas supply pipe G is turbulent in the space 41 or 51, and the space 43 or 52 is passed through the grid-like partition 42 or 52.
Alternatively, the flow is gradually rectified by flowing into the slit 53 and is discharged from the slit 44 or 54 as a laminar flow.

It is preferable that the running direction of the object to be processed and the blowing direction of the reactive gas be parallel between the electrodes. In general, it is better to treat the object in the same direction as the direction of the gas blowout to improve the processing efficiency. However, when oxygen inhibition by entrained air is a problem, the direction of the object is opposite to the direction of the traveling. It is advisable to introduce gas in the area.

As an example of the case where the oxygen inhibition becomes a problem, there is a case where a fluoride film, a nitride film, or an oxide film is formed on the surface of the object to be processed.

In the present invention, the flow rate of the gas flow is 0.1 to
Preferably, it is 50 SLM. If it is less than 0.1 SLM, the flow of the gas is interrupted and a laminar flow cannot be formed. In addition, when the gas exceeds 50 SLM, not all gas contributes to the treatment, which is not only uneconomical, but also causes vortices in gaps and seams in the container, disturbing the flow, resulting in uneven treatment. .

The material of each of the above-mentioned gas introduction vessels is not particularly limited as long as the exemplified structure can be realized, but it is necessary to select the material according to the vaporization temperature of the reactive gas passing therethrough. ABS when it is gaseous at normal temperature and pressure
(Acrylonitrile-butadiene-styrene copolymer), polycarbonate, acryl, vinyl chloride, polytetrafluoroethylene, and other resins. When using a gas that can be liquefied and solidified at normal temperature and normal pressure, such as when introducing a liquid material or a solid material by vaporization, iron, copper,
It is desirable to use a metal such as aluminum, and it is more desirable to use a stainless steel for ease of manufacture.

In the present invention, the conditions for generating glow discharge between the opposing electrodes under normal pressure to generate plasma are not particularly limited, but the discharge current density is 0.2 to 300 mA. / Cm ² , it has been found that a method of forming a pulsed electric field is more suitable for the study of the present inventors.

The term “discharge current density” as used herein refers to a value obtained by dividing the value of the current flowing between the electrodes by discharge by the area of the discharge space in the direction orthogonal to the direction of current flow, as in the present invention. In the case where the electrodes are used, the value corresponds to a value obtained by dividing the current value by the facing area.

[0040]

EXAMPLES The results of measuring the flow rate of a gas actually flowing through a gas introduction vessel to which the present invention is applied and the results of measuring the flow rate of a gas between parallel plate type discharge electrodes using such a gas introduction vessel are described below. An example of introducing and actually performing plasma processing
It is described together with each comparative example.

<Example 1-1> The gas introduction container shown in FIG. 2 (made of acrylic resin, 400 mm wide × 100 mm long ×
Height 50 mm, the ratio of the size of the first chamber 21 to the second chamber 22 is 50:50, the thickness of the partition plate 20 provided with the small hole group 13 is 5 mm, the width of the slit 25 is 2 mm, and the small hole group 13 7 holes of 4 mm in diameter are arranged at equal intervals) and the flow rate is 10 SL
M nitrogen gas was supplied, and the flow velocity of the gas flow blown out from the slit 25 was measured at 50 mm intervals. FIG. 7 shows the measurement results.

<Embodiment 1-2> As shown in FIGS. 3A and 3B, the size ratio of the first chamber 21 and the second chamber 22 of the gas introduction container is set to approximately 60:40, Example 1 was repeated except that the plate thickness of the partition plate 20 provided with the hole group 13 was set to 15 mm.
Same as 1. FIG. 7 shows the measurement results of the gas flow velocity.

<Embodiment 2> The gas introduction container shown in FIG. 4 (made of high-density polyethylene, 400 mm wide × 250 m long)
mx 200 mm height, stainless steel 1 as partition 42
A mesh of 00 was used, the width of the slit 44 was 2 mm, and the blowing angle was 45 °. FIG. 7 shows the measurement results of the gas flow velocity.

<Comparative Example 1> FIG. 8 shows a gas introduction container used in Comparative Example 1. In the figure, (A) is a front view, and (B) is a BB cross-sectional view thereof. This gas introduction container has a uniform gap 7 at one end in a rectangular parallelepiped container 71.
2, a slit 74 having a uniform width is formed near the edge of the container 71,
Has a structure in which two gas inlets are provided and gas supply pipes G are connected to each.

The container 71 is made of acrylic resin and has a width of 400 m.
m × length 60 mm × height 50 mm, slit 74
Was 2 mm, and the gas blowing angle from the slit 74 was 45 °.

The procedure was the same as in Example 1-1, except that the above gas introduction container was used. FIG. 7 shows the measurement results of the gas flow velocity.

<Evaluation of Performance of Gas Introducing Container> As is clear from the graph of FIG. 7, in Examples 1-1, 1-2 and Example 2, the flow velocity has a substantially constant distribution in the length direction of the slit. On the other hand, in Comparative Example 1, there was a large fluctuation,
The uniformity of the gas flow rate by the gas introduction container used in the present invention was confirmed. Further, as is clear from the results of Example 1-1 and Example 1-2, when the ratio of the first chamber 21 to the entire gas introduction container is set to be larger than that of the second chamber 22 (gas blowing side), the gas flow rate It was also confirmed that the uniformity of the composition was further improved.

Example 3 A film was formed on the surface of the substrate W to be processed by using the normal pressure plasma processing apparatus shown in FIG.

The apparatus has a structure in which parallel plate type discharge electrodes 82a and 82b are provided in a stainless steel chamber 81, and the electrodes 82a and 82b are dielectric coated electrodes (electrode width 350 mm × length 150 mm, As the dielectric material, a metal oxide of 10% by weight of titanium oxide + 90% by weight of aluminum oxide (1.5 mm coating) was used, and the distance between the electrodes was 2 mm. The periphery of the electrode was insulated with a 30 mm-thick acetal resin (trade name: Delrin), and the gas introduction container I shown in FIG. The substrate W to be treated is a polyethylene terephthalate film (Lumirror T50, width 300 mm, manufactured by Toray Industries, Inc.)
It was made to roll and run between the electrodes 82a and 82b.

After evacuating the apparatus, a mixture of 0.2 SLM of propylene hexafluoride and 9.8 SLM of nitrogen gas was introduced to 1013 hPa.

The substrate W to be processed is run at 1 m / min.
A pulse electric field (peak value 29 kV, frequency 8 kHz, rising speed 1) from the high frequency power source 83 between the electrodes 82 a and 82 b
0 μs) was applied to generate glow discharge, and a fluorocarbon polymer film was formed on the surface of the substrate.

Comparative Example 2 The procedure was the same as in Example 3 except that the gas introduction container shown in FIG. 8 was used.

<Comparative Example 3> A gas outlet shown in FIG. 10, that is, a rectangular gas flow path 91 was formed by a pipe made of polytetrafluoroethylene, and a gas passage 91 having a diameter of 2 mm was formed inside the gas flow path 91 between the electrodes. Example 3 was the same as Example 3 except that gas was introduced using a large number of holes 92 arranged at 10 mm intervals.

<Comparative Example 4> A dielectric-coated electrode with gas blowing holes (electrode width: 350 mm x length: 150 mm, metal oxide of 10% by weight of titanium oxide + 90% by weight of aluminum oxide as a dielectric material having a thickness of 1.5 mm) Except that gas was introduced by using a cover and holes having a diameter of 1 mm arranged in a matrix at intervals of 1 cm).

<Evaluation of Film-Forming Results by Examples and Comparative Examples> For the processed products of Example 3 and Comparative Examples 2 to 4, the film thickness was measured using an empsometer (D
VA-36VW) and 2c in the width and running directions
It was measured at m intervals. The planar distribution of the film thickness for each is shown in FIGS.

As is clear from these figures, in the processed product obtained according to the third embodiment of the present invention, the variation in film thickness over the entire surface is within ± 10% of the average film thickness. In the processed product obtained in the comparative example, a large deviation occurs in the film thickness. This bias is considered to be caused by the non-uniform flow of the gas in the width direction of the object in Comparative Examples 2 and 3. In Comparative Example 4, the electric field was non-uniform due to holes in the electrodes. The cause is considered to be the cause.

[0057]

As described above, according to the present invention, a uniform film having a thickness unevenness of ± 10% or less can be obtained by a process using discharge plasma generated under a pressure near the atmospheric pressure which is industrially advantageous. And a high-performance optical thin film or the like can be formed at a low cost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a gas introduction container that can be used in the present invention.

FIG. 2 is an explanatory diagram of another configuration example of the gas introduction container that can be used in the present invention, and is a diagram showing the gas introduction container used in Examples 1-1 and 3;

FIG. 3 is an explanatory diagram of still another configuration example of the gas introduction container that can be used in the present invention, and is a diagram showing the gas introduction container used in Example 1-2.

FIG. 4 is an explanatory diagram of still another configuration example of the gas introduction container that can be used in the present invention.

FIG. 5 is an explanatory diagram of still another configuration example of the gas introduction container that can be used in the present invention.

FIG. 6 is an explanatory diagram of still another configuration example of the gas introduction container that can be used in the present invention.

FIG. 7 shows Examples 1-1 and 1-2 and Example 2 of the present invention.
And the graph which shows the measurement result of the distribution of the gas flow velocity in the comparative example 1

FIG. 8 is an explanatory diagram of a configuration of a gas introduction container used in Comparative Example 1.

FIG. 9 is a schematic view showing a configuration of an atmospheric pressure plasma processing apparatus used in Embodiment 3 of the present invention.

FIG. 10 is an explanatory diagram of a configuration of a gas outlet used in Comparative Example 3.

FIG. 11 is a graph showing a film thickness distribution of a processed product obtained in Example 3.

FIG. 12 is a graph showing a film thickness distribution of a processed product obtained in Comparative Example 2.

FIG. 13 is a graph showing a film thickness distribution of a processed product obtained in Comparative Example 3.

FIG. 14 is a graph showing a film thickness distribution of a processed product obtained in Comparative Example 4.

[Explanation of symbols]

 Reference Signs List 1 container (first chamber) 11 gas inlet 12 baffle plate 13 small hole group 21, 31 first chamber 22, 32 second chamber 23 gap 24 partition plate 25, 33 slit 34 ball bead 41, 51 The cross section is gradually enlarged Spaces 42, 52 lattice-shaped partition walls 43, 53 spaces in which the cross section gradually decreases 44, 54 slits 81 chambers 82a, 82b discharge electrodes 83 high-frequency power supply G gas supply pipe I gas introduction container W substrate to be processed

Claims (4)

[Claims] 1. A pulsed electric field is applied between a pair of electrodes while a solid dielectric is disposed on at least one of the opposing surfaces of the pair of electrodes under a pressure near the atmospheric pressure. In the plasma processing method using generated plasma, the pair of electrodes is a parallel plate electrode whose opposing surfaces are each substantially smooth, and a fluctuation width of the flow velocity over the electrode width is in a space interposed between the electrodes. ± 2
A normal pressure discharge plasma processing method, wherein a reaction gas is introduced at a substantially uniform flow rate of 0% or less. 2. The method according to claim 1, wherein the object to be processed is caused to travel in a certain direction between the pair of electrodes, and the reaction gas is introduced in a direction parallel to the traveling direction of the object to be processed. Atmospheric pressure discharge plasma treatment method. 3. A swash plate facing the gas introduction direction, wherein the swash plate is once guided and diffused in a section which becomes narrower as the distance from the gas introduction port increases, and at the same time, the gas flow is substantially parallel to the running direction of the object to be processed. After deflecting the direction, through a slit having a length larger than the electrode width and having a substantially constant width in the length direction, or through a number of small holes uniformly arranged over a dimension larger than the electrode width. The normal pressure discharge according to claim 1 or 2, wherein a reaction gas is introduced between the electrodes at a substantially uniform flow rate by using a gas introduction container having a structure for blowing out the gas between the electrodes. Plasma treatment method. 4. After diffusing in a first section whose cross section gradually expands in the gas introduction direction between the electrodes, the cross section gradually shrinks in the gas blowing direction via a lattice or mesh-like wall surface. To the second section, and blows out between the electrodes via a slit provided at the end of the second section and having a length greater than the electrode width and having a substantially constant width in the length direction. 3. The normal pressure discharge plasma processing method according to claim 1, wherein the reaction gas is introduced between the electrodes at a substantially uniform flow rate using a gas introduction container having a structure.