JP4841177B2 - Plasma cleaning equipment - Google Patents

Description

  The present invention relates to a plasma cleaning processing apparatus.

  As an outline of the plasma cleaning process, the cleaning process is performed by generating plasma between the counter electrodes and passing an object to be processed between the counter electrodes where the plasma is generated.

  Ions, electrons, radicals, and ultraviolet rays exist in the plasma, and these are subjected to cleaning treatment such as dirt by etching (shaving in micro units) or ashing (combustion, peeling) on the specific processed material. .

The plasma is generated by filling a space between one ground electrode serving as a counter electrode and the other electric field applying electrode with a gas for generating plasma and applying a high frequency voltage to the electric field applying electrode.
JP 2002-110398 A

  Under pressure conditions near atmospheric pressure, the discharge interval between the opposing electrodes occupies an important factor in the discharge starting power when the plasma is initially turned on. Generally, it varies depending on the type of plasma generation gas filled between electrodes mainly composed of rare gases such as helium and argon, but if the discharge interval is narrow, the initial discharge due to sparks is more likely to occur. The discharge starting power can be low.

  On the other hand, it is known that when the discharge interval is widened, initial discharge due to sparks is less likely to occur, so that the discharge start power increases. The discharge interval and the discharge start power are in a proportional relationship.

  In particular, since the discharge interval becomes a cleaning processing space for processing the object to be processed, it is desirable that the discharge interval is widened and separated to accommodate various objects to be processed having different thicknesses. On the other hand, if the cleaning treatment space is expanded, there is a problem that requires high discharge starting power.

  Generally, the electric power for discharge cannot be used without limitation, and the upper limit is set for the discharge interval and the starting electric power for discharge depending on the conditions such as the protection of the apparatus main body and the specification mode. For this reason, even if an attempt is made to expand the cleaning processing space, there arises a problem that it cannot be expanded due to the startup power.

  In this case, it is possible to cope with this by making the one with a specification form one level higher, but this requires equipment and cost.

  Accordingly, an object of the present invention is to provide a plasma cleaning processing apparatus that can widen a discharge interval serving as a cleaning processing space for an object to be processed with respect to the starting power of a specification mode having an upper limit.

In order to achieve the above object, according to the present invention, firstly, a pair of counter electrodes for generating plasma under a pressure condition near atmospheric pressure, and between the electrodes via a derivative plate between the counter electrodes. And a process gas supply means for supplying a process gas from a supply pipe, and a third electrode extending from one electrode toward the other electrode is fixed on the dielectric plate between the counter electrodes. Alternatively, soft X-rays are irradiated only at the start of initial discharge.

Second, a pair of counter electrodes for generating plasma under pressure conditions near atmospheric pressure, and a process gas supply means for supplying a process gas from a supply pipe between the counter electrodes via a derivative plate has the between opposing electrodes, irradiating the fixed to Rutotomoni initial discharge start only soft X-ray to the third electrodes extending toward the one electrode to the other said dielectric board It is characterized by.

  According to the first aspect of the present invention, an initial discharge gap with a narrow discharge interval that makes it easy to generate an initial discharge due to a spark by the third electrode can be formed in a part of the counter electrode, so that the initial lighting of the plasma can be performed even with a low starting power. Is possible. As a result, it is possible to widen a discharge interval that becomes a cleaning processing space for the object to be processed. In addition, a simple structure in which the third electrode is provided is sufficient, and it is very preferable in terms of maintenance.

  On the other hand, since a lot of incidental electrons necessary for the initial discharge can be generated in the irradiation range space between the counter electrodes by the soft X-ray irradiation, the plasma can be initially lit even with a low starting power. As a result, it is possible to widen a discharge interval that becomes a cleaning processing space for the object to be processed. Further, since static electricity can be removed by soft X-rays, it is possible to avoid static electricity accidents at the time of contact, and the range of use can be expanded to easily processed objects.

  According to the second aspect of the present invention, by combining the third electrode and soft X-rays, the synergistic effect allows the start of discharge as shown in FIG. 8 in addition to the effect of the first aspect of the present invention. It is possible to reduce the required starting power to about 1/5. As a result, the discharge interval that becomes the cleaning processing space for the cleaning processing product can be greatly expanded.

  In the present invention, the third electrode is formed by a conducting wire that conducts maintenance-free electricity with a simple structure.

  Hereinafter, the first embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a schematic explanatory view showing the entire plasma cleaning processing apparatus according to the present invention, and FIG. 2 is an enlarged explanatory view of part A of FIG.

  The plasma cleaning apparatus 1 has a pair of counter electrodes 3, a process gas supply means 5 for supplying a process gas between the counter electrodes 3, and a third electrode 7 disposed between the counter electrodes 3. is doing.

  The pair of counter electrodes 3 includes a first electrode unit 9 and a second electrode unit 11, and the first electrode unit 9 is made of a material such as aluminum on a plate-like derivative 13 made of quartz glass or ceramic. The structure is provided with the electric field applying electrode 15 made of the above.

  A high frequency is applied to the electric field applying electrode 15 by a plasma generating power source 17.

  The high frequency is preferably a sine wave of 50 kHz to 27.12 MHz, but may be a pulse wave.

  The second electrode unit 11 has a structure in which a ground electrode 21 made of a material such as aluminum is provided on a plate-like derivative 19 made of quartz glass or ceramic, and the ground electrode 21 is grounded. Yes.

  The electric field application electrode 15 and the ground electrode 21 are of a water cooling type in which cooling paths 23 through which cooling water flows are provided.

  The derivative 13 of the electric field applying electrode 15 and the derivative 19 of the ground electrode 21 are opposed to each other in the vertical direction to create a plasma space. One of the upper and lower discharge intervals 27 creating the plasma space, FIG. 1, the right side is a supply portion 29 through which process gas is sent, and the other is an opening 33 for taking in and out the workpiece 31, and the inside is a cleaning processing space. ing.

  The supply unit 29 is a means for connecting and communicating with the process gas supply unit 5 via a supply pipe 35 having a nozzle port. The supply and discharge of the process gas is performed by opening or closing a control valve 37 provided on the way. Shut-off control is possible.

  Examples of the process gas include helium, argon, oxygen, nitrogen, hydrogen, etc., and these can be used alone or as a mixed gas in combination.

  On the other hand, the third electrode 7 described above is disposed between the derivative 19 of the ground electrode 21 and the derivative 13 of the electric field applying electrode 15 that form a plasma space. The third electrode 7 may be in any position as long as it does not get in the way when the workpiece 31 is set within the discharge interval 27 serving as a cleaning processing space.

  The material of the third electrode 7 is formed of a conducting wire that conducts electricity, and the tip has a pointed shape so that spark discharge is easy. The material of the third electrode 7 is optimally a copper wire made of copper or an aluminum wire made of aluminum, and has a shape extending from the derivative 19 of the ground electrode 21 toward the derivative 13 of the electric field applying electrode 15. .

  As a result, an initial discharge gap d narrower than the discharge interval 27 is created by the third electrode 7 as shown in FIG. The shape of the third electrode 7 is a pin shape, but may be a thin strip shape.

  According to the plasma cleaning apparatus 1 configured as described above, plasma is generated by applying a high-frequency voltage to one electric field application electrode 15 in which the process gas is filled between the counter electrodes 3. In this case, even if the interval between the discharge intervals 27 serving as the cleaning treatment space is widened, a spark discharge is generated between the third electrodes 7 that form the initial discharge gap d, which is triggered and becomes the discharge interval 27. A stable glow discharge spreading over the entire surface can be obtained. The starting power at this time can be lower than that in the conventional example without the third electrode 7. The experimental results are shown in FIG.

  FIG. 3 shows a comparison of power (starting power W) at the time of plasma lighting, for example, by expanding the space between the counter electrodes 3 to 0.5 mm to 10 mm, and the present invention is indicated by a solid line. The conventional example is indicated by a dotted line, and the helium gas is filled between the electrodes. The vertical axis represents the starting power (W), and the horizontal axis represents the discharge interval (mm). In the present invention, the third electrode 7 is disposed at each discharge interval. As for the characteristics of the power source used, the voltage increases with the increase in output up to 200 W. Above that, the output cannot be increased in consideration of the protection of the power supply, the voltage takes a sine waveform, and when the output is 200 W, the effective value is 1.4 kV.

  Here, referring to the starting power (W) when the discharge interval is 10 mm, it was found that 200 W was necessary in the conventional example, but in the present invention, about 140 W is sufficient by the third electrode 7. Assuming that the upper limit that can be used is up to 200 W, the discharge interval 27 serving as a cleaning treatment space can be expanded to 10 mm or more in the present invention as shown by a virtual line.

  As a result, it is possible to expand to various types of workpieces having different thicknesses.

  Further, a simple structure in which the third electrode 7 is provided is sufficient, and it is very preferable in terms of maintenance and management.

  4 to 6 show the second embodiment.

  In the second embodiment, instead of the third electrode 7, a soft X-ray is irradiated between the entire surface of the opening 33 and the counter electrode 3.

  The soft X-ray source 39 for irradiating soft X-rays is arranged in front of the opening 33, and the irradiation angle θ is about 120 degrees, although it varies depending on the arrangement position from the opening 33 to the soft X-ray source 39. ing.

The wavelength of the soft X-ray is 1.3 × 10 ^{−4 to} 4.1 × 10 ⁻⁴ μm (energy is 9.5 KeV, to 3 keV), and has a property close to that of vacuum ultraviolet rays. The tube voltage of the soft X-ray source 39 is DC 9.5 kV, the tube current is 150 μA, and it has the function of removing static electricity by ionization and generating incidental electrons necessary for initial discharge in the irradiation atmosphere.

  The even electrons are accelerated by the voltage applied between the electrodes when they exist in the space, collide with atoms and molecules in the space, and an α action is generated that ionizes the atoms and molecules. Electrons newly generated by this α action are accelerated by the voltage applied between the electrodes, the α action repeats, the number of electrons in the space increases, and discharge occurs when a certain condition (spark condition) is met. Insulation breakdown (all-path breakdown) occurs.

  From the above, if there are no accidental electrons in the space, it is necessary to apply a very high voltage between the electrodes and extract the electrons from the electrodes themselves into the space. For example, it is considered that the α action develops at a low voltage and the spark condition is satisfied.

  Since other components are the same as those in the first embodiment, the same reference numerals are used and detailed description thereof is omitted.

  Therefore, according to the plasma cleaning processing apparatus 1 of the second embodiment, the soft X-rays irradiated at the time of initial lighting of plasma generate even electrons necessary between the counter electrodes 3 at the time of initial lighting, and low startup. Initial lighting of plasma was obtained with electric power (W). The experimental results are shown in FIG. FIG. 6 is performed under the same conditions as described in the first embodiment, and there is not much difference between the third electrode 7 and the conventional example, but it is still used. Assuming that the upper limit is 200 W, in the present invention, the plasma space 27 serving as a cleaning processing space can be expanded to 10 mm or more.

  Further, since soft X-rays can remove static electricity charged on the object to be processed 31, it is possible to avoid an accident of static electricity at the time of contact, and it is possible to expand the use range to the object to be processed which is easily charged.

  7 and 8 show a third embodiment.

  The third embodiment is a plasma cleaning apparatus 1 that combines the first and second embodiments described above. That is, the third electrode 7 is disposed between the counter electrodes 3, while the soft X-ray source 39 emits soft X-rays through the opening 33.

  Since the conditions such as the material and shape of the third electrode 7 are the same as those in the first embodiment, the same reference numerals are used and detailed description thereof is omitted.

  Since the conditions such as the function and irradiation angle of the soft X-ray source 39 are the same as those in the second embodiment, the same reference numerals are used and detailed description thereof is omitted.

  Therefore, according to the plasma cleaning apparatus 1 of the third embodiment, since soft X-rays are irradiated between the counter electrodes 3 provided with the third electrodes 7, Due to the synergistic effect of the action of soft X-rays, the starting power at the initial plasma lighting can be greatly reduced. The experimental results are shown in FIG.

  FIG. 8 is performed under the same conditions as described in the first embodiment. When the discharge interval is 10 mm, the present invention is compared with the conventional example of 200 W. The initial lighting of the plasma is possible with about 40 W and a starting power (W) that is significantly lower than 1/5. As a result, the discharge interval serving as the cleaning processing space can be greatly widened.

  In addition, the effect of removing the object to be processed by soft X-rays can also be expected.

BRIEF DESCRIPTION OF THE DRAWINGS Outline explanatory drawing which showed 1st Embodiment of the plasma cleaning processing apparatus concerning this invention. The enlarged explanatory view of the A section of FIG. Explanatory drawing of the experimental data which compared the prior art example with the discharge space | interval of a counter electrode, and the starting power by this invention. The same explanatory drawing as FIG. 1 which showed 2nd Embodiment of the plasma cleaning apparatus. The schematic plan view which showed the irradiation angle which irradiates a soft X-ray between the counter electrodes of a plasma cleaning apparatus. Explanatory drawing of the experimental data which compared the prior art example with the discharge space | interval of the counter electrode by 2nd Embodiment, and the starting power by this invention. The same explanatory drawing as FIG. 1 which showed 3rd Embodiment of the plasma cleaning apparatus. Explanatory drawing of the experimental data which compared the prior art example with the discharge space | interval of the counter electrode by 3rd Embodiment, and the starting power by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma cleaning processing apparatus 3 Counter electrode 5 Process gas supply means 7 3rd electrode 9 1st electrode unit 11 2nd electrode unit 15 Electric field application electrode 17 Power supply for plasma generation 21 Ground electrode 27 Discharge interval 31 Processed object 33 Opening port d Initial discharge gap

Claims (3)

A pair of counter electrodes for generating plasma under pressure conditions near atmospheric pressure, and a process gas supply means for supplying a process gas from a supply pipe between the counter electrodes via a derivative plate, A plasma is characterized in that a third electrode extending from one electrode to the other electrode is fixed on the dielectric plate between the counter electrodes, or soft X-rays are irradiated only at the start of initial discharge. Cleaning processing equipment. A pair of counter electrodes for generating plasma under pressure conditions near atmospheric pressure, and a process gas supply means for supplying a process gas from a supply pipe between the counter electrodes via a derivative plate, between the counter electrode, and irradiating the third fixed electrodes on the dielectric board to Rutotomoni initial discharge start only soft X-rays extending toward the one electrode to the other electrode Plasma cleaning processing equipment. 3. The plasma cleaning apparatus according to claim 1, wherein the third electrode is formed by a conducting wire that conducts electricity.

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