JP2837993B2 - Plasma processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma processing method,
Further, the present invention relates to a plasma processing apparatus used for performing the method.

[0002]

2. Description of the Related Art A method of processing an object to be processed using plasma has been applied in various fields. In particular, when the plasma is a reactive plasma accompanied by introduction of a reaction gas, it is very useful because it can be effectively used for forming a thin film or modifying a surface. However, since the conventional plasma processing method is a process using glow discharge plasma under a low pressure of 0.1 to 10 Torr, equipment that can form and control a low-pressure atmosphere is required, and large-area processing is difficult. As a result, manufacturing costs are high.

In view of this, a method has been proposed in which processing is performed using glow discharge plasma generated under a pressure near the atmospheric pressure instead of under a low pressure (Japanese Patent Laid-Open No. 1-306569,
JP-A-2-15171). Since these methods do not require equipment for forming and controlling a low-pressure atmosphere, realization of large-area processing and reduction of manufacturing cost can be expected, but have the following problems.

There is a problem that the plasma itself is non-uniform, so that uniform processing cannot be performed. For example, the degree of processing varies depending on the position of the object to be processed, or in the case of large-area processing, uniform processing cannot be performed over the entire surface. That is, in the case of using the conventional glow discharge plasma near the atmospheric pressure, as shown in FIGS. 6 and 7, the gas is supplied to the annular tube provided between the upper electrode 111 and the lower electrode 112 in front of the dielectric 119. It is blown out from a hole 114 which is sequentially opened along the longitudinal direction of the hole 113.
And the distance from the gas supply pipe 115 differs for each hole 114, the gas blowing pressure is not constant, and the pressure of the gas to be introduced varies depending on the position, so that uniform plasma is not obtained. The plasma fluctuates, causing a glow discharge to have a streak-like and non-uniform state, and inconveniences such as a different degree of processing depending on a position where the object 116 is placed are caused.

In order to improve the unevenness of the pressure of the gas to be introduced, as shown in FIG. 8, a large number of air holes 120 are provided in the upper electrode 111, and the gas is introduced from the air holes 120. (Japanese Patent Application Laid-Open No. S56-1)
6 9116 and JP Laid-Open No. 2-50969). But this remedy is still not enough. There is a remarkable difference in the degree of processing between the position just below the air hole and the other position in the processing object. As a result, for example, spots 117 having the same pattern as the pattern of the vent hole 120 of the upper electrode 111 shown in FIG.
Will occur on the surface. This is due to the difference in plasma density (concentration of ions and radicals) between the gas ejection path formed just below the vent and the rest, and the fact that the gas ejected from the vent directly hits the surface of the workpiece. Is due. There is a difference in plasma density between the gas ejection path and other places, and as shown in FIG. 11, vertical stripes 119 of glow discharge appear.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention does not require equipment for forming and controlling a low-pressure atmosphere, can eliminate non-uniform processing, and can appropriately process large areas and reduce manufacturing costs. It is an object of the present invention to provide a plasma processing method capable of realizing the above and an apparatus for performing the same.

[0007]

In order to solve the above-mentioned problems, a plasma processing method according to the present invention uses plasma generated between a pair of electrodes installed opposite to each other under a pressure near atmospheric pressure. In a plasma processing method for processing a surface of an object to be processed by plasma accompanying gas introduction from a ventilation hole opened on a surface of at least one of the electrodes facing the other electrode, the ventilation hole is opened. A porous body is provided on the surface so that gas from the vent enters the plasma through the porous body, and an apparatus for performing this method is opposed to the apparatus at a predetermined distance. It has a pair of electrodes arranged, and a large number of air holes are opened on a surface of at least one of the electrodes facing the other electrode. Let the ventilation In a plasma processing apparatus configured to process an object to be processed with plasma accompanied by introduction of gas from a porous body is provided on a surface on which the vent hole is opened, and gas from the vent hole is provided. It is configured to enter the plasma through the porous body.

Hereinafter, the present invention will be described specifically. Examples of the type of plasma in the present invention include glow discharge plasma that is generated in association with generation of a glow discharge in a plasma generating gas under a pressure near atmospheric pressure. As the pressure near the atmospheric pressure, usually, 200 to 1500 mmHg
, Preferably 500-1000 mmH
g, more preferably a pressure in the range of 700 to 850 mmHg. If the pressure is lower than 200 mmHg or exceeds 1500 mmHg, the pressure difference from the atmosphere increases, and the advantage due to the pressure near the atmospheric pressure is reduced. More specifically, if the pressure is less than 200 mmHg, the inflow of air cannot be performed unless the reaction tank is airtight, and the inconvenience of processing cannot be achieved.
If it exceeds 1500 mmHg, there is a disadvantage that the plasma tends to be unstable.

The gas introduced into the plasma includes helium gas, which easily generates plasma. When the plasma is a reactive plasma, a reaction gas is introduced into the plasma. As the reaction gas, oxygen gas,
Examples of such gases include carbon tetrafluoride (CF ₄ ) gas, hydrogen gas, argon gas (Ar), nitrogen gas (N ₂ ), and reactive monomers, and are usually introduced in a form mixed with the helium gas. You. Helium gas acts as a carrier gas. In this case, the gas to be mixed is turned into plasma by the Penning effect of the helium gas, and the energy of the metastable state of the helium gas is very high (about 20 ev) as compared with other gases, so that the lifetime is very long. The plasma is stable even under the atmospheric pressure, and the processing can be smoothly performed.

The mixing ratio of the helium gas and the other gas in the mixed gas that is the reaction gas is usually 99.8:
The range is about 0.2 to 75:25, but is not limited to this range. Examples of the porous body in the present invention include porous bodies (porous dielectrics) made of dielectric materials such as porous glass, porous ceramics, glass fiber aggregates used for filters, and polymer fiber aggregates. Can be When the porous body is a dielectric material, it is preferable because it has a function of expanding the generated glow discharge. However, the porous body may be a porous metal body made of a metal material. The thickness of the porous body is usually
It is about 0.5 to 15 mm.

[0011] These porous bodies have an extremely large number of micropores and have gas permeability, and the micropores are opened in random directions on the dielectric surface. Therefore, the permeated gas is blown out from the entire surface in a specific direction with little deviation. The average pore diameter of the fine pores in this porous body is preferably 500 μm or less.
If it exceeds 500 μm, the flow of the gas to be introduced is dispersed throughout and the effect of making the gas uniform is weakened, and it tends to be difficult to form a uniform plasma. However, if the average pore size is too small, the porous body may be damaged by excessive pressure loss,
Since it becomes difficult to secure an appropriate gas flow rate, it is desired that the average pore diameter does not become less than 0.2 μm.

Next, an apparatus for performing the plasma processing method of the present invention will be described with reference to the drawings. The plasma processing apparatus shown in FIG. 1 includes a reaction tank 1, and a gas inlet 11 and a gas outlet 12 are provided in the tank wall.
Two flat electrodes, an upper electrode 2 and a lower electrode 3, are installed in the tank in parallel so as to face each other at a predetermined distance. A solid dielectric 6 is placed on the surface of the lower electrode 3. The upper electrode 2 is connected to the output of an AC power supply 5, and the lower electrode 3 is grounded.

A flow path 15 is provided inside the upper electrode 2 and a number of ventilation holes 16 are opened on a surface of the upper electrode 2 facing the lower electrode 3. A porous dielectric 20 as a porous body is disposed on a surface of the upper electrode 2 where the ventilation holes 16 are opened. As a result, the gas entering from the gas inlet 11 passes through the porous dielectric 20 through the vent 16 and is introduced into the plasma. Note that a heater 19 is provided inside the lower electrode 3 so that the temperature of the workpiece 4 can be freely adjusted. In the case of this device, the upper electrode 2 comprises a front plate 2a provided with a large number of ventilation holes and a back plate 2b for the gas flow path 15.

At the time of processing, first, a helium gas which also serves as a plasma generating gas and a carrier gas is introduced from the gas inlet 11 and the AC power supply 5 is operated to start supplying AC power. Then, a glow discharge is generated between the electrodes 2 and 3 to generate plasma. Thereafter, an appropriate type of reaction gas participating in the reaction is mixed into the helium gas. Then, the reaction gas is introduced into the plasma together with the helium gas through the porous dielectric 20 through the ventilation hole 16, so that the plasma becomes a reactive plasma. This reactive plasma is used to perform a surface treatment or the like of the workpiece 4.

FIG. 2 shows another plasma processing apparatus according to the present invention. This device is suitable for continuous processing. In FIG. 2, the components denoted by the same reference numerals as those in FIG. 1 are the same as those in FIG. The plasma processing apparatus of FIG. 2 includes a belt conveyor 50 that passes through the inside of the reaction tank 1, and the workpiece 4 is
0, is carried between the upper electrode 2 and the lower electrode 3, and after the treatment, is again carried on the conveyor 50, and at the same time, the next object to be processed 4 is placed on the upper electrode 2 and the lower electrode 3. It is to be carried in between. Cylinder 51,5
2 helium gas or reaction gas as needed.
The mixture is mixed at 3 and sent through a pipe 54.

The frequency of the AC power supply 5 used is
Although not particularly limited, usually, 100 Hz to 20 Hz
It is on the order of MHz. The higher the frequency, the shorter the processing time, but the stronger the heating action of the workpiece 4, the greater the need for cooling.

[0017]

According to the present invention, the processing plasma is generated under a pressure near the atmospheric pressure (atmospheric pressure plasma).
Therefore, equipment for forming and controlling the low-pressure atmosphere is not required, and large-area processing can be realized and manufacturing costs can be easily reduced. When the processing space in which the plasma exists is at a pressure near the atmospheric pressure, the processing space can be easily widened, which is suitable not only for processing a large area at one time, but also for loading the processing object into the processing space and processing space. Can be easily and quickly carried out, and continuous processing is also facilitated. In addition, it is also possible to handle a substance containing a volatile component or a low-melting substance as a treatment object.

In the present invention, unlike the prior art,
Since the uniformity of the plasma is high, uniform processing can be performed on the object to be processed, and processing can be performed to the same extent even in a large-area processing. Appropriate large-area processing can be realized. Unlike low-pressure plasma, atmospheric pressure plasma does not become uniform unless the overall pressure is uniform. In the case of the atmospheric pressure plasma, since gas diffusion is small and the mean free path is short, the plasma is easily affected by the pressure, and unless the pressure is strictly made uniform, the plasma does not become highly uniform.
High pressure areas have a high gas density and a high plasma density (ion and radical concentrations), which results in non-uniformity.

On the other hand, in the past, the flow of the reaction gas is stronger than that of the surroundings because the gas blowout direction is just below the vent of the electrode. Therefore, uneven gas flow and uneven pressure occur. If the flow of the reaction gas is not uniform, the entire pressure between the electrodes will not be uniform. In the case of the present invention, a very large number of micropores are opened in a random direction in the porous body, and the gas for reaction is such that gas entering from the rear surface is widely distributed from all over the surface with little deviation in direction. Since the gas is blown out from the back surface, the pressure becomes uniform, and the plasma itself becomes uniform. As a result, the processing becomes uniform. In the case of thin film formation, a film having a uniform thickness can be formed, and in the case of surface reforming, the same level of reforming can be performed over the entire surface without any strength.

Further, it is presumed that the gas receives a pressure loss when passing through the porous body, and the gas hardly collides directly with the object to be processed, which also contributes to uniform processing. This is because, when the gas directly collides with the object to be processed, radicals are forcibly adsorbed to the object to be processed, and this is considered to be a cause of non-uniform processing. Further, the electrode having the porous body on the front surface is not easily stained, and the porous body provided on the front surface of the electrode under the atmospheric pressure can be easily replaced.

[0021]

Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments. Example 1 In Example 1, a silicon oxide thin film was formed on the surface of a slide glass (object to be processed) using the plasma processing apparatus having the configuration shown in FIG. The slide glass (made of soda lime glass) has a diameter of 210 mm and a thickness of 1.5 mm, and has a temperature of 100 ° C.

The electrode spacing in the plasma processing apparatus is 20 mm
The porous body is made of a glass fiber aggregate for a filter which is a porous dielectric (thickness 0.5 mm, average pore diameter 500 μm).
m). The gas introduced into the plasma is He (15
00 ccm) and a reaction gas of tetraethoxysilane (1.95 × 10 ⁻² ccm), and a glow discharge plasma is generated under atmospheric pressure to produce a gas of about 300 ° C./cm ^2.
It was thin film formation at a minute deposition rate. The frequency of the AC power supply is 15 kHz, and the supply power is 50 W.

The plasma was in a uniform state as shown in FIG. 3, and a thin film 25 having a uniform thickness was formed on the slide glass 24 as shown in FIG. The thin film 25 showed a uniform interference color. The measurement result of the film thickness distribution is shown by a solid line in FIG. The variation in thickness was within the range of ± 0.01 μm. The thickness variation range was determined from the difference between the maximum and minimum film thickness values and the average film thickness value.

Example 2 A thin film was formed in the same manner as in Example 1, except that a glass fiber assembly for a filter (thickness: 1.0 mm, average pore diameter: 10 μm) was used as the porous body. The state of the plasma was slightly different from that of Example 1, but the color was faint. The plasma was uniform without streaks, and the film thickness was also uniform. The film formation rate was about 150Å / min.

Example 3 In Example 1, the porous body was made of porous glass for a filter plate (thickness: 7 mm, average pore diameter: 40 to 100), which was a porous dielectric.
μm), except that a thin film was formed. The state of the plasma was about the same as in Example 1, was uniform without streaks, and the film thickness had a variation of ± 0.02 μm.
m and was uniform. Incidentally, the film formation rate was about 200 Å / min.

Example 4 In Example 4, the surface of a Teflon sheet (object to be processed) was modified using a plasma processing apparatus having the structure shown in FIG.
The Teflon sheet was made of Takilon and had a length and width of 60 mm and a thickness of 1.0 mm, and the temperature was room temperature. The electrode spacing in the plasma processing apparatus was 10 mm, and the porous body was a glass fiber assembly for a filter (thickness 0.5
mm, average pore diameter 500 μm). The gas introduced into the plasma was a mixed gas of He (5000 ccm) and oxygen gas (100 ccm), which was a reaction gas, and glow discharge plasma was generated under atmospheric pressure to perform the treatment.
The frequency of the AC power supply is 15 kHz, and the supply power is 100 W.

The state of the plasma was almost the same as in Example 1, and was uniform without streaks. Thereafter, an epoxy resin-impregnated glass cloth prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.1 mm was applied to the Teflon sheet and a copper foil (thickness: 3).
5 μm), and 170 ° C.
It was heated and pressed under the conditions of 40 kgf / cm ² for 120 minutes and laminated and bonded. The molded article was cut into a width of 1 cm, and the peel strength was measured. The measurement result was 0.3 kgf / cm ² .

Comparative Example 1 A thin film was formed in the same manner as in Example 1 except that the porous body was not used. The state of the plasma was different from that of Example 1 and a vertical streak appeared and was not uniform.
Non-uniform interference fringes were spotted on the glass surface.

The measurement result of the film thickness distribution is shown by a dashed line in FIG. The variation in thickness was as large as ± 0.1 μm, and the unevenness was large and not uniform. Comparative Example 2 In Example 1, gas introduction was performed without using a porous body.
A thin film was formed in the same manner except for using the annular tube 113 shown in FIG.

The state of the plasma was different from that of Example 1 and streaks appeared and were not uniform. The measurement result of the film thickness distribution is shown by a dashed line in FIG. Variation in thickness is ±
It was about 0.1 μm and was not uniform. -Comparative Example 3-In Example 4, except that the porous dielectric was not used,
The Teflon sheet was modified in the same manner.

Similarly, the peel strength was measured.
It was 0.05 kgf / cm ² , which was far inferior to the examples.

[0032]

According to the plasma processing method of the present invention, since the processing plasma is a plasma under a pressure near the atmospheric pressure, equipment for forming and controlling a low-pressure atmosphere is not required, and the processing space can be widened easily. In addition to being suitable for processing a large area at a time, continuous processing is easy and the uniformity of the plasma is high, so that the processing target can be uniformly processed and the cost can be reduced. , Very practical.

The plasma processing apparatus of the present invention is very useful because the above-described practical plasma processing method can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration example of a plasma processing apparatus according to an embodiment.

FIG. 2 is an explanatory diagram illustrating another configuration example of the plasma processing apparatus according to the embodiment.

FIG. 3 is an explanatory diagram showing plasma in the plasma processing apparatus of the embodiment.

FIG. 4 is a perspective view illustrating an object to be processed processed by the plasma processing apparatus of the embodiment.

FIG. 5 is a graph showing thickness distribution measurement results of thin films formed in Examples and Comparative Examples.

FIG. 6 is an explanatory view showing a conventional plasma processing apparatus.

FIG. 7 is a plan view showing an annular tube of the plasma processing apparatus of FIG. 6;

FIG. 8 is an explanatory view showing another conventional plasma processing apparatus.

FIG. 9 is a plan view showing a ventilation hole forming surface of an upper electrode of the plasma processing apparatus of FIG. 8;

10 is a perspective view illustrating an object to be processed processed by the plasma processing apparatus of FIG. 8;

FIG. 11 is an explanatory diagram showing plasma in the processing apparatus of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Upper electrode 3 Lower electrode 4 Workpiece 5 AC power supply 16 Vent hole 20 Porous dielectric (porous material)

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasushi Sawada 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. Masuhiro Kokoma 843-15 Shimo-Nikura, Wako-shi, Saitama (56) References JP-A-2-50969 (JP, A) JP-A-62-218577 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) C23C 16/00-16/56 C23F 4/00-4/04 H05H 1/46 H01L 21/205 H01L 21/302

Claims (5)

(57) [Claims] Claims: 1. A plasma generated between a pair of electrodes placed opposite to each other under a pressure near atmospheric pressure,
In a plasma processing method for processing a surface of an object to be processed by plasma accompanied by gas introduction from a ventilation hole opened to a surface of at least one of the electrodes facing the other electrode, the plasma processing method may include a step of: To a random direction
A plasma processing method, comprising: providing a porous body having a large number of fine holes that are open facing each other; and allowing gas from the vent to enter the plasma through the porous body. And a pair of electrodes disposed opposite to each other at a predetermined distance, and a plurality of ventilation holes are opened on a surface of at least one of the electrodes facing the other electrode. In a plasma processing apparatus configured to process an object to be processed with plasma generated between the electrodes under a pressure close to the atmospheric pressure and accompanied by gas introduction from the vent, a surface above the surface where the vent is opened Faces a random direction
A plasma processing apparatus, comprising: a porous body having a large number of fine pores which are opened by opening; and a gas from the vent holes enters the plasma through the porous body. Wherein the porous body is a plasma processing apparatus 請 Motomeko 2 wherein ing a dielectric material. 4. A plasma plasma processing apparatus Oh Ru請 <br/> Motomeko 2 or 3, wherein in the glow discharge plasma. 5. The porous body has an average pore diameter of 500 μm.
The plasma processing apparatus according to any one of Der Ru請 Motomeko 2,3,4 below.