JP2005174879A - Plasma processing method and plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment method capable of realizing efficient plasma treatment by preventing deactivation of an active species in plasma. <P>SOLUTION: This apparatus has a plurality of electrodes 1, 2 facing each other and a gas passage 3. In this plasma treatment method, the gas for generating plasma is introduced into the gas passage 3 and voltage is applied between the electrodes 1, 2 to generate plasma P in the gas passage 3 under pressure near the atmospheric pressure and the plasma P is blown out from the gas passage 3 for supplying it to the surface of an object 4 to be treated. The plasma P is supplied to the surface of the object 4 to be treated in the atmosphere with oxygen concentration below 12 volume %. By blowing out the plasma P into the atmosphere where the oxygen concentration is lower than the air to supply it on the surface of the object 4 to be processed, deactivation effect of oxygen on the active species in Plasma P can be reduced for preventing deactivation of the activated species. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention includes cleaning of foreign substances such as organic substances existing on the surface of the object to be processed, resist peeling and etching, improvement of organic film adhesion, metal oxide reduction, film formation, plating pretreatment, coating pretreatment, The present invention relates to a plasma processing method and a plasma processing apparatus used for surface treatment such as surface modification of various materials and parts, and particularly suitable for cleaning the surface of electronic parts that require precise bonding. It is.

  Conventionally, plasma processing is performed by supplying plasma (discharge gas containing active species) generated under atmospheric pressure or a pressure in the vicinity thereof to an object to be processed. For example, in the plasma processing method described in Patent Document 1, a reaction vessel is provided by providing a pair of electrodes outside the reaction vessel, introducing a plasma generating gas into the reaction vessel, and applying a voltage between the pair of electrodes. Plasma is generated inside, and this plasma is blown out from the reaction vessel and sprayed onto the object to be processed.

In such a plasma processing method, it is necessary to prevent the active species in the plasma from being deactivated between the place where the plasma is generated (the space in the reaction vessel sandwiched between the pair of electrodes) and the object to be processed. It is preferable for high processing efficiency. Therefore, conventionally, the distance between the reaction vessel and the object to be processed is reduced, but there is a possibility that problems such as the inability to process a thick object to be processed may occur.
JP 2003-303814 A

  The present invention has been made in view of the above points, and provides a plasma processing method and a plasma processing apparatus capable of increasing the efficiency of plasma processing by making it difficult to deactivate active species in plasma. It is the purpose.

  The plasma processing method of the present invention has a plurality of electrodes 1 and 2 and a gas flow path 3 arranged opposite to each other, introduces a plasma generating gas into the gas flow path 3 and applies a voltage between the electrodes 1 and 2. In the plasma processing method in which the plasma P is generated in the gas flow path 3 under a pressure close to atmospheric pressure, and the plasma P is blown out from the gas flow path 3 and supplied to the surface of the workpiece 4. The plasma P is supplied to the surface of the workpiece 4 in an atmosphere of 12% by volume or less.

  According to the present invention, the plasma P is blown into an atmosphere having an oxygen concentration lower than that of air and supplied to the surface of the workpiece 4, thereby reducing the oxygen deactivation effect on the active species in the plasma P and increasing the activity. The species can be made difficult to deactivate, and as a result, the plasma P containing a large amount of active species having high activity can be supplied to the surface of the workpiece 4 and the efficiency of the plasma treatment can be improved. It is.

  In the present invention, the plasma generating gas preferably contains at least one of a rare gas, a nitrogen gas, and a fluorine-containing gas.

  The plasma processing apparatus of the present invention is a plasma processing apparatus used in the plasma processing method according to claim 1 or 2, and covers a processing space 5 between the gas flow path 3 and the surface of the workpiece 4. It is characterized by being covered with.

  According to the present invention, the cover 6 can reduce the flow of air into and out of the processing space 5, and the oxygen concentration in the atmosphere for supplying plasma to the surface of the workpiece 4 can be easily maintained at 12% by volume or less. As a result, the plasma P containing a large amount of active species having high activity can be supplied to the surface of the object 4 to be processed, and the efficiency of the plasma processing can be improved.

  In the present invention, it is preferable to provide an exhaust amount adjusting means 7 for adjusting the exhaust amount from the inside of the cover 6, which makes it easy to keep the mixing ratio of the plasma generating gas and the air constant and uniform. Plasma treatment can be performed.

  According to the present invention, plasma is blown out into an atmosphere having a lower oxygen concentration than air and supplied to the surface of the object to be processed, thereby reducing the deactivation effect of oxygen on the active species in the plasma and losing the active species. As a result, plasma containing a large amount of highly active active species can be supplied to the surface of the object to be processed, so that the efficiency of the plasma processing can be increased.

  Hereinafter, the best mode for carrying out the present invention will be described.

  1 and 2 show an example of the plasma processing apparatus of the present invention. The plasma processing apparatus includes an electrode support housing 22 having a plurality (a pair) of electrodes 1 and 2, a gas nozzle 23, a cover 6, a transport roller 31, and the like.

  The electrodes 1 and 2 are formed in a substantially rectangular bar shape that is long in the width direction using a conductive metal material such as copper, aluminum, brass, stainless steel having high corrosion resistance (SUS304, etc.), titanium, 13 chromium steel, SUS410, etc. And the flowing water channel 37 for distribute | circulating a cooling water is provided in the inside over substantially full length. In FIG. 2, the width direction of the electrodes 1 and 2 is a direction orthogonal to the paper surface, and the plasma processing apparatus of the present invention performs plasma processing while conveying the workpiece 4 in the direction orthogonal to the width direction. It is.

  A dielectric coating 40 is formed on the entire surface of the electrodes 1 and 2 by a thermal spraying method of a ceramic material such as alumina, titania or zirconia. The dielectric coating 40 is preferably subjected to a sealing treatment. A particularly effective material for the dielectric coating 40 made of such a ceramic spray coating material is alumina.

  In forming the dielectric coating 40, enamel coating can also be performed using an inorganic material glaze made of silica, titania, alumina, tin oxide, zirconia, or the like as a raw material. In the case of the above-described thermal spraying method or enamel coating, the thickness of the dielectric coating 40 can be set to 0.1 to 3 mm, more preferably 0.3 to 1.5 mm. If the thickness of the dielectric coating 40 is less than 0.1 mm, the dielectric coating 40 may break down. If the thickness is more than 3 mm, it is difficult to apply a voltage between the opposing electrodes 1 and 2. As a result, the discharge may become unstable.

  The electrode support housing 22 is made of a metal material such as stainless steel and is formed long in the width direction like the electrodes 1 and 2. The electrode support housing 22 is formed with a slit-like gas flow path 3 penetrating vertically, and electrode receiving recesses 27 are formed on two inner surfaces of the electrode support housing 22 facing each other across the gas flow path 3. Is provided. The electrode support housing 22 is provided with a pair of electrodes 1 and 2 such that the electrodes 1 and 2 are accommodated one by one in each electrode accommodating recess 27. Here, an insulating spacer 28 formed of a synthetic resin or the like is provided between each of the electrodes 1 and 2 and the electrode support housing 22, whereby the electrodes 1 and 2 and the electrode support housing 22 are provided. Insulation is ensured. Further, the pair of electrodes 1 and 2 provided in the electrode support housing 22 are opposed to each other with the gas flow path 3 interposed therebetween, and the gas flow path 3 between the electrodes 1 and 2 is formed as a discharge space 45. Yes. The plasma processing apparatus of the present invention preferably includes an inter-gap distance adjusting mechanism for keeping the distance between the pair of opposed electrodes 1 and 2 constant over substantially the entire length of the electrode 1 in the width direction.

  As described above, the electrodes 1 and 2 provided on the electrode support housing 22 are arranged opposite to each other in the transport direction of the workpiece 4 by arranging them in a direction parallel to the transport direction of the workpiece 4 (horizontal direction). ing. Further, the workpiece 4 is transported in one direction indicated by an arrow in FIG. The opposing electrodes 1 and 2 are arranged to face each other substantially in parallel via the discharge space 45 with a predetermined interval. The distance between the body coatings 40, 40 is preferably 0.2 to 3 mm. If the distance between the facing electrodes 1 and 2 (distance between gaps) deviates from the above range, it may be difficult to stably generate a uniform glow-like discharge.

  In this plasma treatment apparatus, as shown in FIG. 3, a power supply 47 is electrically connected to the electrodes 1 and 2 via a step-up transformer 48.

  Further, a gas nozzle 23 is disposed on the upper side (directly above) the electrode support housing 22. The gas nozzle 23 is formed to be substantially parallel to the width direction of the electrodes 1 and 2, and a slit-like nozzle port 35 is formed on the lower surface of the gas nozzle 23 over substantially the entire length of the gas nozzle 23 in the width direction. Yes. The gas nozzle 23 is disposed in a state where the nozzle port 35 is aligned with the upper opening of the gas flow path 3 of the electrode support housing 22.

  The electrode support housing 22 and the gas nozzle 23 are accommodated in the cover 6. The cover 6 is formed in a box using a resin plate material such as an acrylic resin plate, a metal plate, or the like. A carry-in port 24 parallel to the electrodes 1 and 2 is formed on one side of the cover 6. On the other side of the cover 6, a carry-out port 25 parallel to the electrodes 1 and 2 is formed. The carry-in port 24 and the carry-out port 25 are arranged opposite to each other below the electrodes 1 and 2. Further, a valve is provided as an exhaust amount adjusting means 7 on the upper surface of the cover 6 so that the gas in the cover 6 can be discharged by operating the handle 26. Although FIG. 2 shows the transparent cover 6, the present invention is not limited to this.

  The transport roller 31 is formed long in parallel with the electrodes 1 and 2, and a plurality of transport rollers 31 are arranged substantially horizontally in and out of the cover 6. Here, inside the cover 6, a processing space 5 is provided at a predetermined interval below the electrodes 1 and 2, and the conveyance roller 31 is disposed. Outside the cover 6, the carry-in port 24 and the carry-out port are provided. Conveying rollers 31 are arranged side by side immediately below 25.

  Using the plasma processing apparatus formed as described above, a flat plate-like object such as a glass plate for a liquid crystal panel display (LCD) under a pressure close to atmospheric pressure (93.3 to 106.7 kPa (700 to 800 Torr)). The plasma treatment is performed on the workpiece 4 as follows.

  First, a plasma generating gas is introduced into a gas nozzle 23 provided above a pair of electrodes 1 and 2 arranged opposite to each other, and the plasma generating gas is gradually blown out from the nozzle opening 35 while flowing in the width direction in the gas nozzle 23. Like that. The supply of the plasma generating gas to the gas nozzle 23 is performed through the introduction pipe 23a from a gas cylinder for preparing the plasma generating gas. The plasma generating gas supplied to the gas nozzle 23 is blown out substantially uniformly over the entire length of the gas nozzle 23 in the width direction.

  The plasma generating gas used in the present invention is not particularly limited as long as it can stably generate discharge, and noble gases can be used. In particular, the discharge starting voltage is 10 kV / at atmospheric pressure. A gas of cm or more is preferable. In the present invention, the plasma generating gas is mainly composed of a rare gas such as argon or helium, a nitrogen gas, or a fluorine-containing gas, and a mixed gas thereof, or a rare gas, nitrogen gas, a fluorine-containing gas, oxygen, hydrogen, and the like. , Methane, ammonia, air, water vapor, mixed gas with various organic monomers can be exemplified. In the present invention, the discharge start voltage of the plasma generating gas is preferably 100 kV / cm or less.

  Next, the plasma generating gas blown from the nozzle port 35 of the gas nozzle 23 is introduced into the gas flow path 3 and flows in the gas flow path 3 from the upstream (upper side) to the downstream (lower side), and then is opposed. Is introduced into the discharge space 45 between the pair of electrodes 1 and 2 through the upper opening. A voltage is applied by a power supply 47 between a pair of opposed electrodes 1 and 2 to generate a dielectric barrier discharge, and a plasma generating gas (molecule) introduced between the pair of opposed electrodes 1 and 2 Is excited by the action of an electric field applied between the opposing electrodes 1 and 2 to generate active species, whereby plasma (discharge gas) P is generated.

  In the plasma treatment of the present invention, it is preferable to apply a voltage having a continuous alternating waveform with a frequency of 30 to 500 kHz between a pair of electrodes 1 and 2 facing each other by a power supply 47 and a voltage with an electric field strength of 50 to 200 kV / cm. Is preferably applied. The above-mentioned continuous alternating waveform does not cause a pause period in which no voltage is applied between a pair of opposed electrodes 1 and 2 as in a pulse waveform, and a voltage is continuously generated between a pair of opposed electrodes 1 and 2. For example, a sinusoidal waveform can be used. A pulse waveform voltage (pulse voltage waveform) can also be applied between the electrodes 1 and 2. The pulse waveform voltage is a voltage in which a constant period of voltage is repeatedly applied with a pause period. For example, the rising time and the falling time are 100 μsec or less, the repetition frequency is 0.5 to 1000 kHz, the electrode 1, By applying a waveform having an electric field strength of 0.5 to 200 kV / cm applied between the two, stable processing can be performed. Further, it is preferable that the flow rate of the gas supplied to the gap (discharge space 45) between the opposing electrodes 1 and 2 is 5 to 20 m / sec. In adjusting the gas flow velocity, the distance between the electrodes 1 and 2 facing each other, the gas flow rate, and the like are adjusted.

  The plasma P generated as described above is blown out in the form of a curtain as a plasma jet over the entire length in the width direction of the electrodes 1 and 2 from the downstream opening of the discharge space 45 to the processing space 5 immediately below. However, at this time, the composition of the gas in the processing space 5 is set to an oxygen concentration of 12% by volume or less. Then, as shown in FIG. 2, the workpiece 4 is carried into the cover 6 from the carry-in port 24 while being moved on the transport roll 31, and then passed through the treatment space 5 in the cover 6. 4 is further conveyed, and the workpiece 4 is unloaded from the unloading port 25. When the workpiece 4 is transported in this way, the plasma P can be sprayed and supplied (exposed) to the surface of the workpiece 4 when passing through the processing space 5, and plasma processing of the workpiece 4 is performed. It is something that can be done. In the present invention, the object to be processed 4 can be transported 1 to 10 mm below the electrodes 1 and 2 to perform the plasma treatment, but this distance is determined when the plasma generating gas is supplied to the gas flow path 3. Can be appropriately adjusted according to the flow rate of the material, the conveyance speed of the object 4 and the like, and is not limited to the above values.

  The present invention is characterized in that, as described above, the oxygen concentration in the processing space 5 for supplying the plasma P to the workpiece 4 is 12 vol% or less, and the plasma P is supplied to the surface of the workpiece 4 in this atmosphere. Thus, the plasma P can be blown out and supplied to the surface of the workpiece 4 in an atmosphere having an oxygen concentration lower than that of air, and the deactivating action of oxygen on the active species in the plasma P is reduced. As a result, the plasma P containing a large amount of highly active active species can be supplied to the surface of the workpiece 4 and the efficiency of the plasma processing can be improved. It is something that can be done. That is, when the processing space 5 for blowing out the plasma P is normal air, the oxygen concentration is about 19% by volume. Therefore, when the plasma P is released into such an atmosphere, the active species of the plasma P contributing to the plasma processing However, in the present invention, the active species of the plasma P can be reduced because the oxygen concentration is low.

  For example, when the plasma generating gas is a mixed gas of argon and oxygen and the oxygen concentration is 2% by volume, electrons and argon ions and radicals and oxygen ions and radicals are generated in the discharge space 45. The active species of the plasma P are rapidly deactivated when the processing space 5 below the electrodes 1 and 2 is released in the case of air, and installed downstream of the gas flow path 3 by the active species that survived without being deactivated. The processed object 4 is subjected to plasma treatment such as surface modification. Here, if the gas composition of the processing space 5 is maintained at the same composition as the plasma generating gas, that is, the gas composition of the processing space 5 is a mixed gas of argon and oxygen having an oxygen concentration of 2% by volume. At the same time as the active species are deactivated, a slight amount of new active species is generated in the processing space 5, and as a result, it is presumed that the lifetime of the active species reaching the workpiece 4 is increased, and the effect of the plasma treatment is also increased. Is. On the other hand, when the processing space 5 from which the plasma P is emitted is air, the active species of the plasma P collide with nitrogen or oxygen in the air and are easily deactivated. As a result, the effect of the plasma processing is reduced. is there. Therefore, it is important to control (manage) the oxygen concentration in the processing space 5 from which the plasma P is emitted.

In the present invention, when the plasma generating gas is prepared, the oxygen concentration of the plasma generating gas is adjusted by controlling the mixing ratio of oxygen and other gases, and the processing space 5 is covered with the cover 6. As a result, the gas blown into the processing space 5 is less mixed with the air, and the exhaust amount adjusting means 7 adjusts the exhaust amount of the gas from the inside of the cover 6 to cover from the carry-in port 24 and the carry-out port 25. The mixing ratio of the plasma generating gas blown into the processing space 5 and the air is adjusted by adjusting the amount of air flowing into the processing space 6. By these, the oxygen in the processing space 5 during the plasma processing is adjusted. The concentration can be controlled to be constant. In order to make it easy to set the oxygen concentration in the cover 6 to the predetermined value, it is preferable to use an oxygen concentration meter constituted by a zirconia sensor or the like.
In the present invention, it is preferable that the oxygen concentration of the processing space 5 at the time of the plasma processing is 100 ppm or more by volume in terms of preventing a decrease in plasma processing capability.

  FIG. 4 shows another embodiment. In this plasma processing apparatus, a loader cassette 33 storing a large number of workpieces 4 before plasma processing and an undercassette 35 storing a large number of workpieces 4 after plasma processing are provided in a cover 6. Is. Further, the cover 6 is not formed with the carry-in port 24 or the carry-out port 25 as described above, and a plurality of transport rollers 31 are provided between the loader cassette 33 and the undercassette 35 and the electrodes 1 and 2. They are arranged side by side so as to pass through the lower side. Other configurations are formed in the same manner as in the above embodiment.

  In this plasma processing apparatus, the carry-in port 24 and the carry-out port 25 are not formed in the cover 6, and the inside of the cover 6 can be hermetically sealed during plasma processing. It is easy to control the oxygen concentration. That is, when the plasma processing is performed on the workpiece 4 under the pressure near the atmospheric pressure using the plasma processing apparatus, the processing is performed as follows. First, a large number of workpieces 4 are set in the loader cassette 33 before plasma processing. Next, after the cover 6 is sealed, in the same manner as described above, a gas for generating plasma is introduced into the gas nozzle 23 provided above the pair of opposed electrodes 1 and 2 through the introduction pipe 23a and the gas nozzle. The gas for plasma generation is gradually blown out from the nozzle port 35 while flowing in the width direction within the nozzle 23. Next, the plasma generating gas blown from the nozzle port 35 of the gas nozzle 23 is introduced into the gas flow path 3 in the same manner as described above, and the gas flow path 3 is moved from upstream (upper side) to downstream (lower side). After flowing, it is introduced from the upper opening into the discharge space 45 between the pair of opposed electrodes 1 and 2. A voltage is applied by a power supply 47 between a pair of opposed electrodes 1 and 2 to generate a dielectric barrier discharge, and a plasma generating gas (molecule) introduced between the pair of opposed electrodes 1 and 2 Is excited by the action of an electric field applied between the opposing electrodes 1 and 2 to generate active species, whereby plasma (discharge gas) P is generated. The plasma P is blown out as a plasma jet from the downstream opening of the discharge space 45 into the processing space 5 immediately below the plasma space as a plasma jet over the entire length in the width direction of the electrodes 1 and 2.

  After the plasma P is generated in this way, one object 4 to be processed is taken out from the loader cassette 33 using a transfer means such as a robot and placed on the transport roller 31 so as to pass through the processing space 5. By conveying the processing object 4, when passing through the processing space 5, the plasma P can be sprayed and supplied (exposed) to the surface of the processing object 4, and the processing of the processing object 4 can be performed. Is. And the to-be-processed object 4 which performed the plasma process is accommodated in the undercassette 35 from the conveyance roller 31 using transfer means, such as a robot. After the plasma treatment is sequentially performed on a large number of workpieces 4 in this manner, the inside of the cover 6 is opened and the workpiece 4 after the plasma treatment is taken out from the undercassette 35. In this way, the inside of the cover 6 can be hermetically sealed and plasma processing can be performed, and air can hardly enter and leave the cover 6 during the plasma processing, and the oxygen concentration in the cover 6 can be easily controlled.

  In any of the above-described embodiments, the case where the workpiece 4 is transported substantially horizontally has been described. However, the present invention is not limited to this, and the present invention transports the workpiece 4 in any direction (for example, the vertical direction). It can also be applied to cases. In the present invention, the number of electrodes can be arbitrarily set as necessary as long as it is two or more. Further, the voltage application conditions are not limited to those described above. For example, the frequency, waveform shape, electric field strength, gas flow rate, and the like of the applied voltage can be arbitrarily set as necessary.

  Hereinafter, the present invention will be described specifically by way of examples.

(Example 1)
The plasma processing apparatus shown in FIGS. The electrodes 1 and 2 are made of stainless steel having a length of 1100 mm, and an alumina layer having a thickness of 1 mm is formed on the surfaces of the electrodes 1 and 2 by a thermal spraying method to form a dielectric coating 40. Further, cooling water was circulated inside the electrodes 1 and 2. The pair of electrodes 1 and 2 formed in this way were arranged to face each other with an interval of 1 mm when not discharged. Further, when not discharged, a plasma generating gas was allowed to flow through the gas flow path 3 from the upstream side so that the gas flow rate was 10 m / sec. As a plasma generating gas, a mixed gas of argon and oxygen (oxygen concentration: 3% by volume) was used.

  The voltage applied between the pair of electrodes 1 and 2 was a frequency of 50 kHz, an electric field strength of 100 kV / cm, and the waveform was a sine wave. Under such conditions, plasma P is generated under atmospheric pressure, and passes through a 1000 × 1200 mm liquid crystal glass plate as a workpiece 4 at a speed of 8 m / min at a position 5 mm away from the downstream side of the electrodes 1 and 2. Plasma treatment was performed.

  The composition of the gas in the entire space in the cover 6 including the processing space 5 is a mixed composition of the above-described plasma generating gas and air, but the oxygen concentration of the gas in the cover 6 is constant at 5 ± 0.3% by volume. Thus, the exhaust amount adjusting means 7 controls the exhaust amount from the cover 6 by adjusting it. The oxygen concentration in the cover 6 was monitored by an oxygen concentration meter comprising a zirconia sensor (not shown) in the cover 6 and controlled based on this result.

  As a result, the water contact angle of the workpiece 4 that was about 50 ° when not treated was about 5 °. On the other hand, when the treatment was performed by blowing out the plasma P in a state where the cover 6 was not installed and the treatment space 5 was opened in the air, the contact angle of water of the workpiece 4 was 15 °. In addition, the contact angle of water took the average value of 100 arbitrary points of glass.

(Example 2)
The plasma processing apparatus shown in FIGS. The electrodes 1 and 2 are made of stainless steel having a length of 1100 mm, and an alumina layer having a thickness of 1 mm is formed on the surfaces of the electrodes 1 and 2 by a thermal spraying method to form a dielectric coating 40. Further, cooling water was circulated inside the electrodes 1 and 2. The pair of electrodes 1 and 2 formed in this way were arranged to face each other with an interval of 1 mm when not discharged. Further, when not discharged, a plasma generating gas was allowed to flow through the gas flow path 3 from the upstream side so that the gas flow rate was 10 m / sec. As a plasma generation gas, a mixed gas of nitrogen and oxygen (oxygen concentration 0.1 volume%) was used.

  The voltage applied between the pair of electrodes 1 and 2 was a frequency of 10 kHz, an electric field strength of 100 kV / cm, and the waveform was pulsed. Under such conditions, plasma 3 is generated under atmospheric pressure, and passes through a 1000 × 1200 mm liquid crystal glass plate as a workpiece 4 at a speed of 6 m / min at a position 5 mm away from the downstream side of electrodes 1 and 2. Plasma treatment was performed.

  The composition of the gas in the entire space in the cover 6 including the processing space 5 is a mixed composition of the above-described plasma generating gas and air, but the oxygen concentration of the gas in the cover 6 is constant at 1 ± 0.1% by volume. Thus, the exhaust amount adjusting means 7 controls the exhaust amount from the cover 6 by adjusting it. The oxygen concentration in the cover 6 was monitored by an oxygen concentration meter comprising a zirconia sensor (not shown) in the cover 6 and controlled based on this result.

  As a result, the water contact angle of the workpiece 4 that was about 50 ° when not treated was about 5 °. On the other hand, when the treatment was performed by blowing the plasma P in a state where the cover 6 was not installed and the treatment space 5 was opened in the air, the contact angle of water of the workpiece 4 was 20 °. In addition, the contact angle of water took the average value of 100 arbitrary points of the glass for liquid crystals (processed object 4).

  In this example, plasma treatment was performed while changing the oxygen concentration in the atmosphere of the treatment space 5 to measure the water contact angle of the workpiece 4. As a result, the relationship between the change in oxygen concentration and the change in water contact angle is as shown in FIG. That is, when the oxygen concentration in the atmosphere of the processing space 5 exceeds 12% by volume, it can be seen that the water contact angle of the workpiece 4 after the plasma processing is rapidly increased and the plasma processing performance is deteriorated.

(Example 3)
The plasma processing apparatus shown in FIG. 3 was formed. The electrodes 1 and 2 are made of stainless steel having a length of 300 mm, and an alumina layer having a thickness of 1 mm is formed on the surfaces of the electrodes 1 and 2 using a thermal spraying method to form a dielectric coating 40. Further, cooling water was circulated inside the electrodes 1 and 2. The pair of electrodes 1 and 2 formed in this way were arranged to face each other with an interval of 1 mm when not discharged. Further, when not discharged, the plasma generating gas was flowed from the upstream side to the gas flow path 36 so that the gas flow rate became 10 m / sec. As the plasma generating gas, a mixed gas of 98.5% by volume of nitrogen, 1% by volume of CF ₄ gas and 0.5% by volume of oxygen was used.

  The voltage applied between the pair of electrodes 1 and 2 was a frequency of 10 kHz, an electric field strength of 100 kV / cm, and the waveform was pulsed. Plasma P was generated under atmospheric pressure under such conditions, and plasma treatment was performed by passing the workpiece 4 at a speed of 2 m per minute at a position 5 mm away from the downstream side of the electrodes 1 and 2.

  The composition of the gas in the entire space in the cover 6 including the processing space 5 is a mixed composition of the above plasma generating gas and air, but the oxygen concentration of the gas in the cover 6 is 0.5 ± 0.1% by volume. The exhaust amount from the cover 6 was adjusted and controlled by the exhaust amount adjusting means 7 so as to be constant. The oxygen concentration in the cover 6 was monitored by an oxygen concentration meter comprising a zirconia sensor (not shown) in the cover 6 and controlled based on this result.

  The object to be processed 4 was obtained by applying a negative resist to a thickness of 1 micron on an 8-inch silicon wafer. As a result, the negative resist was ashed with a thickness of about 0.4 microns. On the other hand, when the plasma P was blown out with the cover 6 not installed and the processing space 5 opened to the air, the ashing amount of the negative resist was 0.03 microns. The ashing amount was an average value of 100 arbitrary points on the silicon wafer (processing object 4). The ashing amount was measured with an ellipsometer.

It is a schematic sectional drawing which shows an example of embodiment of this invention. It is a schematic perspective view same as the above. It is a schematic sectional drawing which shows an example of a circuit same as the above. It is a schematic sectional drawing which shows other embodiment same as the above. It is a graph which shows the result in Example 2 same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode 2 Electrode 3 Gas flow path 4 Object to be processed 5 Processing space 6 Cover 7 Exhaust amount adjustment means

Claims (4)

  It has a plurality of electrodes arranged opposite to each other and a gas flow path. Plasma is generated in the gas flow path under a pressure near atmospheric pressure by introducing a plasma generating gas into the gas flow path and applying a voltage between the electrodes. In the plasma processing method in which the plasma is blown out from the gas flow path and supplied to the surface of the object to be processed, the plasma is supplied to the surface of the object to be processed in an atmosphere having an oxygen concentration of 12% by volume or less. A plasma processing method.   The plasma processing method according to claim 1, wherein the plasma generation gas contains at least one of a rare gas, a nitrogen gas, and a fluorine-containing gas.   3. A plasma processing apparatus used in the plasma processing method according to claim 1, wherein a processing space between the gas flow path and the surface of the object to be processed is covered with a cover. . 4. The plasma processing apparatus according to claim 3, further comprising an exhaust amount adjusting means for adjusting an exhaust amount from the inside of the cover.

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