Active gas generation apparatus including a metal housing, first and second auxiliary members, and a housing contact

An active gas generator that generates active gas by activating supplied material gas through discharge in a discharge space formed between a high-voltage side electrode component and a ground side electrode component of an active gas generation electrode group. A combined structure of covers completely separates the discharge space from an alternating-current voltage application space, and includes, independently from the alternating-current voltage application space, a material gas flow path for a material gas supply path, through which externally supplied material gas is guided to the discharge space. A housing contact space formed between a metal housing and each of the covers and an electrode component installation table is completely separated from the alternating-current voltage application space and the discharge space.

TECHNICAL FIELD

The present invention relates to an active gas generation apparatus including two electrodes installed in parallel to obtain active gas through energy of discharge caused by applying high voltage between the electrodes.

BACKGROUND ART

In an active gas generation apparatus including two electrodes installed in parallel to obtain active gas through the energy of a discharge phenomenon caused in a discharge space between the electrodes by applying high voltage between the electrodes, typically, alternating-current high voltage is applied to one of the electrodes, and the other electrode is set to a reference voltage such as a ground level.

In such an active gas generation apparatus, a high voltage of several kVrms (root mean square) is applied to one of electrodes as a high voltage power supply part. In a space other than the discharge space formed between the pair of electrodes, the distance between the power supply part and a ground part (the other electrode and any component place electrically connected therewith) is sufficiently provided to prevent insulation breakdown of gas in the space. However, from a microscopic viewpoint, it is impossible to avoid concentration of electric field intensity enough to cause insulation breakdown of a surrounding gas layer due to the shape and surface state of a metal component of the power supply part.

When insulation breakdown occurs in a space other than the discharge space, a phenomenon that causes evaporation of the constituent element of any component nearby occurs. When the nearby component is made of metal, the above-described phenomenon causes metal contamination in a semiconductor deposition process.

Examples of active gas generation apparatuses developed with such metal contamination taken into consideration include a plasma generation apparatus disclosed in Patent Document 1 and a plasma processing apparatus disclosed in Patent Document 2.

The plasma generation apparatus disclosed in Patent Document 1 performs dielectric barrier discharge at a discharge part provided between a high-voltage side electrode component and a ground side electrode component facing each other, and generates active gas by causing material gas to pass through the discharge part. In this apparatus, the discharge part and an alternating-current voltage application part are not separated from each other but exist in an identical space. After having passed through the alternating-current voltage application part, the material gas is supplied to the discharge space and finally to a processing chamber.

The plasma processing apparatus disclosed in Patent Document 2 employs a structure in which insulators are inserted and sealed at outer edge parts of electrode components facing each other. This structure is intended to prevent anomalous discharge from a discharge part to a housing (including a ground electrode) in which the electrode components are installed.

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY

Problem to be Solved by the Invention

However, in the plasma generation apparatus disclosed in Patent Document 1, discharge due to insulation breakdown of the material gas does not necessarily occur only at the discharge part. From a macroscopic viewpoint, it is designed to provide a sufficient insulation distance to prevent unnecessary discharge at a place other than the discharge part. Examples of such unnecessary discharge include anomalous discharge between a metal electrode of the high-voltage side electrode component through which alternating-current voltage is applied and a metal housing that houses the electrode component.

However, from a microscopic viewpoint, irregularities are inevitably formed on the surface of a current introduction terminal through which alternating-current voltage is applied and the surface of any metal component or the like connected therewith. It is extremely difficult to eliminate the probability that strong electric field regions are formed around some convex portions of the irregularities, and as a result, gas insulation breakdown, in other words, anomalous discharge occurs.

Thus, the plasma generation apparatus disclosed in Patent Document 1 has such a problem that the above-described insulation breakdown causes evaporation of any constituent element installed nearby, and the evaporated constituent element is mixed into the material gas and supplied to the discharge part and the processing chamber, which causes semiconductor metal contamination.

The plasma processing apparatus disclosed in Patent Document 2 is insufficient to prevent metal contamination mixture when anomalous discharge occurs. This is because the discharge part and the alternating-current voltage application part still exist in an identical space, and the material gas having passed through the alternating-current voltage application part proceeds to the discharge part and generates active gas, which is the same structural problem. Specifically, similarly to the plasma generation apparatus disclosed in Patent Document 1, the plasma processing apparatus disclosed in Patent Document 2 cannot avoid generation of metal contamination, and accordingly has the problem of degradation of the quality of generated active gas.

The present invention is intended to solve the problems as described above and provide an active gas generation apparatus capable of generating high quality active gas.

Means to Solve the Problem

An active gas generation apparatus according to the present invention includes: an active gas generation electrode group including a first electrode component and a second electrode component provided below the first electrode component; an alternating-current power source unit configured to apply alternating-current voltage to the first and second electrode components so that the first electrode component is at high voltage, a discharge space being formed between the first and second electrode components through application of the alternating-current voltage by the alternating-current power source unit, active gas obtained by activating material gas supplied to the discharge space being ejected through a gas ejection port provided in the second electrode component; a first auxiliary member provided to form an alternating-current voltage application space between the first auxiliary member and the first electrode component separately from the discharge space; a second auxiliary member made of a non-metallic material and supporting the active gas generation electrode group from the second electrode component side, the second auxiliary member including an auxiliary member gas discharge port through which active gas ejected from the gas ejection port passes; and a metal housing that houses all of the active gas generation electrode group and the second auxiliary member and at least part of the first auxiliary member, the housing including a housing gas discharge port through which the active gas passing through the auxiliary member gas discharge port is discharged to the outside, a housing contact space separated from the discharge space being provided between the housing and each of the first and second auxiliary members. The first auxiliary member includes a material gas flow path for a material gas supply path, through which externally supplied material gas is guided to the discharge space, independently from the alternating-current voltage application space and the housing contact space so that gas flow in the discharge space and gas flow in the alternating-current voltage application space are separated from each other and gas flow in the discharge space and gas flow in the housing contact space are separated from each other.

Effects of the Invention

In an active gas generation apparatus as the present application invention according to claim1, an alternating-current voltage application space is provided separately from a discharge space, and a first auxiliary member includes a material gas flow path for a material gas supply path, through which externally supplied material gas is guided to the discharge space, independently from the alternating-current voltage application space so that gas flow in the discharge space and gas flow in the alternating-current voltage application space are separated from each other.

Thus, it is possible to reliably avoid a first mixing phenomenon in which an evaporation material, such as the material of a first electrode component, generated when anomalous discharge occurs in the alternating-current voltage application space is mixed into the discharge space directly or through the material gas supply path.

In addition, in the present application invention according to claim1, a housing contact space is provided separately from the discharge space, and the first auxiliary member includes the material gas flow path for the material gas supply path independently from the housing contact space so that gas flow in the discharge space and gas flow in the housing contact space are separated from each other.

Thus, it is possible to reliably avoid a second mixing phenomenon in which an evaporation material generated in the housing contact space is mixed into the discharge space.

As a result, the active gas generation apparatus as the present application invention according to claim1can reliably avoid the first and second mixing phenomena described above and discharge high quality active gas to the outside.

DESCRIPTION OF EMBODIMENTS

<Outline of Active Gas Generation Apparatus>

The following describes particulars of an active gas generation apparatus common to Embodiments 1 to 3 described below. An active gas generation electrode group of dielectric barrier discharge is formed by opposingly disposing a pair of a high-voltage side electrode component and a ground side electrode component separately from each other by a gap length. In the active gas generation electrode group, a space formed between the high-voltage side electrode component and the ground side electrode component serves as a discharge space.

The active gas generation electrode group is housed in a metallic housing, and the active gas generation apparatus including the active gas generation electrode group and the housing is disposed right above a processing chamber in which a silicon wafer is subjected to deposition. A metal electrode is metallized on part of the surface of a dielectric electrode in the active gas generation electrode group so that the dielectric electrode and the metal electrode are integrally formed. The metallization is performed by a print burning method, a sputtering process, a vapor deposition process, or the like.

The metal electrode is connected with a high frequency power source. The ground side electrode component is grounded together with the housing, and fixed to a reference potential. Dielectric barrier discharge is caused in the discharge space of the active gas generation electrode group by applying an AC voltage V0p(zero peak value) of 10 kHz to 100 kHz and 2 kV to 10 kV to the active gas generation electrode group from the high frequency power source.

The active gas generation apparatus is supplied with material gas of nitrogen, oxygen, rare gases, hydrogen, fluorine, and the like from the outside through a gas supply port (material gas flow path). The material gas flows to the discharge space inside the electrode through a material gas supply path provided at an outer peripheral part of the active gas generation electrode group, and is activated in the discharge space inside. Gas containing this active gas is ejected through a gas ejection port provided at the ground side electrode component to the processing chamber outside the housing, and performs deposition.

FIG. 1is an explanatory diagram schematically illustrating a sectional structure of an active gas generation apparatus according to Embodiment 1 of the present invention.FIG. 2is an explanatory diagrams illustrating a main configuration part of the active gas generation apparatus according to Embodiment 1 in a disassembled state.FIGS. 1 and 2andFIGS. 3 and 4to be described later each illustrate an XYZ orthogonal coordinate system.

As illustrated inFIG. 2B and 2C, an active gas generation electrode group301includes a high-voltage side electrode component1A (first electrode component) and a ground side electrode component2A (second electrode component) provided below the high-voltage side electrode component1A.

The ground side electrode component2A includes a dielectric electrode211and metal electrodes201H and201L, and the dielectric electrode211has a rectangular flat plate structure having a longitudinal direction along the X direction and a transverse direction along the Y direction.

A plurality of gas ejection ports55are provided in the X direction at the center of the dielectric electrode211. The plurality of gas ejection ports55penetrate from the upper surface to the lower surface of the dielectric electrode211.

In addition, a wedge-shaped stepped part51is formed not to overlap with the plurality of gas ejection ports55in plan view but to have a shorter formation width in the Y direction at a position closer to each of the plurality of gas ejection ports55in plan view. Specifically, the wedge-shaped stepped part51is formed as an assembly of four rhombus singular parts51seach formed in a rhombic shape in plan view between the five gas ejection ports55and separated from each other, and two triangle singular parts51tprovided outside the gas ejection ports55at both ends among the five gas ejection ports55and each formed in a substantially isosceles triangular shape in plan view.

The dielectric electrode211further includes straight stepped parts52A and52B formed protruding upward at both end sides in the X direction. The straight stepped parts52A and52B extends in the Y direction over the total length of the dielectric electrode211in the transverse direction in plan view, and the gap length of a discharge space66is defined by the formation heights of the straight stepped parts52A and52B together with the formation height of the wedge-shaped stepped part51.

As illustrated inFIG. 2B, the metal electrodes201H and201L are formed on the lower surface of the dielectric electrode211, and disposed facing each other with a central region of the dielectric electrode211interposed therebetween in plan view. The metal electrodes201H and201L each have a substantially rectangular shape in plan view, and have a longitudinal direction along the X direction and a mutually facing direction along the Y direction orthogonal to the X direction.

The metal electrodes201H and201L are metallized on the lower surface of the dielectric electrode211, and as a result, integrally formed with the dielectric electrode211, constituting the ground side electrode component2A. The metallization is performed by, for example, a print burning method, a sputtering process, and an evaporation process.

Similarly to the dielectric electrode211, a dielectric electrode111of the high-voltage side electrode component1A has a rectangular flat plate structure having a longitudinal direction along the X direction and a transverse direction along the Y direction. The dielectric electrode111and the dielectric electrode211are made of, for example, ceramic.

Metal electrodes101H and101L are formed on the upper surface of the dielectric electrode111and disposed facing each other in plan view with, interposed therebetween, a central region in the same shape corresponding to the central region of the dielectric electrode211. Similarly to the metal electrodes201H and201L, the metal electrodes101H and101L each have a substantially rectangular shape in plan view, and have a longitudinal direction along the X direction and a mutually facing direction along the Y direction orthogonal to the X direction. Similarly to the metal electrodes201H and201L, the metal electrodes101H and101L can be formed on the upper surface of the dielectric electrode111by metallization.

As illustrated inFIG. 2C, the active gas generation electrode group301can be assembled by disposing the high-voltage side electrode component1A on the ground side electrode component2A. In this case, the high-voltage side electrode component1A is stacked and combined on the ground side electrode component2A while the central region of the dielectric electrode111in the high-voltage side electrode component1A and the central region of the dielectric electrode211in the ground side electrode component2A are positioned to overlap with each other in plan view. This can finally complete the active gas generation electrode group301.

A pair of spacers37are provided between the straight stepped parts52A and52B on both side surfaces extending in the X direction in the active gas generation electrode group301. The pair of spacers37are provided between the high-voltage side electrode component1A and the ground side electrode component2A, and the formation heights thereof define the gap length of the discharge space66together with the wedge-shaped stepped part51and the straight stepped parts52A and52B described above. The spacers37are made of a non-metallic material, and desirably made of the same material as that of the dielectric electrodes111and211.

In addition, the pair of spacers37are each provided with a plurality of through-holes37hextending in the Y direction so that material gas can be supplied from outside of the active gas generation electrode group301into the discharge space66between the high-voltage side electrode component1A and the ground side electrode component2A through the plurality of through-holes37h.

The discharge space is defined to be a region in which the metal electrodes101H and101L overlap with the metal electrodes201H and201L in plan view in a dielectric space across which the dielectric electrode111and the dielectric electrode211included in the active gas generation electrode group301face each other.

The metal electrodes101H and101L and the metal electrodes201H and201L are connected with a (high-voltage) high frequency power source5(alternating-current power source unit). Specifically, the metal electrodes201H and201L of the ground side electrode component2A are grounded through a metal component (not illustrated) selectively provided inside a metal housing34and an electrode component installation table33, and in the present embodiment, an alternating-current voltage having a zero peak value fixed to 2 kV to 10 kV and a frequency set to be 10 kHz to 100 kHz is applied between each of the metal electrodes101H and101L and the corresponding one of the metal electrodes201H and201L from the high frequency power source5. The electrode component installation table33except for the above-described metal component is made of an insulating material, for example, ceramic. The above-described metal component may be installed such that, for example, like an active gas discharge port33kto be described later, a plurality of through-holes vertically penetrating through the electrode component installation table33are provided, and the above-described metal component is provided in each of the plurality of through-holes to electrically connect the metal electrodes201H and201L of the ground side electrode component2A to a metal housing44.

As illustrated inFIG. 1, in the active gas generation apparatus according to Embodiment 1, the active gas generation electrode group301(including the high-voltage side electrode component1A and the ground side electrode component2A) having the above-described configuration is housed in the metal housing34by using a cover31, a cover32, and the electrode component installation table33.

As described above, the high frequency power source5(alternating-current power source unit) configured to apply alternating-current voltage so that the high-voltage side electrode component1A is at a high voltage relative to the active gas generation electrode group301is provided. Through the alternating-current voltage application by the high frequency power source5, the discharge space66is formed between the high-voltage side electrode component1A and the ground side electrode component2A, and active gas obtained by activating the material gas supplied to the discharge space66is ejected downward through the plurality of gas ejection ports55provided in the ground side electrode component2A.

A first auxiliary member formed by combining the covers31and32is provided above the high-voltage side electrode component1A to form, together with the high-voltage side electrode component1A, an alternating-current voltage application space R31separated from the discharge space66.

The electrode component installation table33as a second auxiliary member has a main surface33b(refer toFIG. 2D) on which the entire lower surface of the ground side electrode component2A is disposed to support the active gas generation electrode group301from the ground side electrode component2A side. The outer peripheral part of the electrode component installation table33includes an outer peripheral protrusion part33xprotruding upward (+Z direction) from the main surface33b, and the outer peripheral protrusion part33xsurrounds the entire active gas generation electrode group301to form a side surface space R33(refer toFIG. 1andFIG. 2C) between the outer peripheral protrusion part33xand the spacers37.

As illustrated inFIG. 1andFIG. 2D, the electrode component installation table33includes a plurality of active gas passing ports33iand a plurality of active gas discharge ports33kthrough which the active gas ejected from the plurality of gas ejection ports55passes and is guided downward. The plurality of active gas passing ports33iare disposed to coincide with the plurality of gas ejection ports55in plan view, and the plurality of active gas discharge ports33kare provided below the plurality of active gas passing ports33i, respectively. A combination of each active gas passing port33iand the corresponding active gas discharge ports33kforms an auxiliary member gas discharge port through which the active gas ejected from the corresponding gas ejection port55passes.

As illustrated inFIG. 2A, the cover32as part of the first auxiliary member is formed in a rectangular annular shape in plan view and disposed on an end part of the high-voltage side electrode component1A and the outer peripheral protrusion part33xof the electrode component installation table33. A hollow region32cas an inner periphery region of the cover32is smaller than the shape of the high-voltage side electrode component1A in plan view, and disposed on the high-voltage side electrode component1A and within the high-voltage side electrode component1A. An outer peripheral region of the electrode component installation table33is larger than the high-voltage side electrode component1A in plan view, and disposed including the entire high-voltage side electrode component1A.

In addition, as illustrated inFIG. 1andFIG. 2A, the cover32includes a material gas flow path32hpenetrating through the cover32in the vertical direction (Z direction). The material gas flow path32hlinearly extends in the X direction at a central part in a long side region of the cover32extending in the X direction. The side surface space R33is positioned below the material gas flow path32h.

In addition, the cover31is disposed on the cover32. The cover31has a lower part formed a rectangular annular shape identical to that of the cover32in plan view, and an upper part formed in a rectangular shape in plan view, an end part of the upper part being disposed on the upper surface of the metal housing34. A hollow region31cas an inner periphery region of the cover31has a shape identical to that of the hollow region32cof the cover32in plan view. The end part of the upper part of the cover31is fixed to the upper surface of the metal housing34by using fixation means such as a bolt.

As illustrated inFIG. 1, the cover31includes a vertically penetrating material gas flow path31hformed in a cylindrical shape, and part of the material gas flow path32his positioned below the material gas flow path31h. Similarly to the material gas flow path32h, the material gas flow path31hmay be linearly formed extending in the X direction at a central part in a long side region of the cover31extending in the X direction so that the entire material gas flow path32his positioned below the material gas flow path31h.

In addition, the cover31includes, at the upper part, a vertically penetrating purge gas supply port31pas a second gas supply port for purge gas as second gas other than the material gas, and a vertically penetrating purge gas discharge port31eas a second gas discharge port. The purge gas supply port31pand the purge gas discharge port31eare each formed in a cylindrical shape. The purge gas supply port31pand the purge gas discharge port31eare each provided so that a lower part thereof reaches the hollow region31c. The purge gas supply port31pand the purge gas discharge port31eare provided independently from the material gas flow path31hto avoid mixture of the purge gas and the material gas. The purge gas supplied through the purge gas supply port31pis nitrogen or inert gas. The purge gas supply port31pand the purge gas discharge port31eare also formed independently from the discharge space66and a housing contact space R34to be described later.

The first auxiliary member as a combined structure of the covers31and32provides the alternating-current voltage application space R31composed of the hollow region31cof the cover31and the hollow region32cof the cover32above the high-voltage side electrode component1A.

Since the covers31and32are formed in rectangular annular shapes in plan view as described above, the alternating-current voltage application space R31is an independent space completely separated from the other space by the high-voltage side electrode component1A and the covers31and32. The side surface space R33is completely separated from the other space except for the discharge space66and the material gas flow paths31hand32hby a bottom surface of the cover32, an end part region of the main surface33bof the electrode component installation table33, and the outer peripheral protrusion part33x.

In addition, a material gas supply path connected with the discharge space66from the outside above the material gas flow path31his formed by the material gas flow path31h, the material gas flow path32h, the side surface space R33, and the plurality of through-holes37hprovided in the spacers37. The material gas flow paths31hand32hare provided independently from the hollow regions31cand32c.

Thus, the material gas supply path guided to the discharge space66from above the material gas flow path31his formed independently from the alternating-current voltage application space R31by the material gas flow paths31hand32h, the side surface space R33, and the plurality of through-holes37hof the spacers37.

As a result, the alternating-current voltage application space R31and the discharge space66are not spatially connected with each other through the material gas supply path, and thus gas flow can be completely separated between the alternating-current voltage application space R31and the discharge space66.

The cover32is made of a non-metallic material. The cover32is desirably made of the same material as that of the dielectric electrodes111and211to handle any anomalous discharge occurring in the material gas flow path32h. The cover31is made of a metallic material. The formation height of the cover32is set to provide a sufficient distance from the metal electrodes101H and101L as high-voltage application regions so that the cover31is installed in a region having a low electric field intensity.

Alternatively, the cover32may be made of an insulation material, such as quartz or silicon nitride, that is generated by the active gas and causes no problem inside the generation apparatus. In this case, no problem occurs to deposition when anomalous discharge occurs in the material gas supply path (for example, the cover32and the spacers37) and a constituent element evaporates and mixes into the material gas.

In this manner, any metallic material is completely excluded from the material gas supply path provided at a position relatively close to the high-voltage side electrode component1A as a strong electric field region, thereby preventing metal contamination due to the metal component.

The metal housing34houses, in an internal hollow space part, all of the active gas generation electrode group301(the high-voltage side electrode component1A and the ground side electrode component2A), the cover32, and the electrode component installation table33, and the lower part of the cover31.

The electrode component installation table33is disposed on a bottom surface34bof the hollow space part of the metal housing34, and an active gas discharge port34k(housing gas discharge port) is positioned below the active gas discharge ports33k. With this configuration, the active gas ejected from the gas ejection ports55is ejected, along gas flow8, to an external processing chamber provided below or the like through the active gas passing ports33i, the active gas discharge ports33k, and the active gas discharge port34k.

The housing contact space R34is provided between a side surface34dof the hollow space part of the metal housing34, and each of the electrode component installation table33, the cover32, and a side surface region at a lower part of the cover31, and part of a bottom surface region of the upper part of the cover31. In this manner, the housing contact space R34is provided between the metal housing34and the outside of the covers31and32and the electrode component installation table33. The housing contact space R34is provided mainly to provide an insulation distance from the metal electrodes101H and101L of the active gas generation electrode group301.

As described above, the alternating-current voltage application space R31is an internal space completely independent from the other space by the high-voltage side electrode component1A and the covers31and32, and the discharge space66is an internal space independent from the other space except for the material gas supply path. With this configuration, the housing contact space R34is separated from the alternating-current voltage application space R31and the discharge space66.

In addition, since the material gas flow paths31hand32hfor the material gas supply path are provided independently from the housing contact space R34, the above-described material gas supply path reaching the discharge space66is an internal space independent from the other space, and accordingly, gas flow in the discharge space66is completely separated from gas flow in the housing contact space R34.

In this manner, the alternating-current voltage application space R31, the discharge space66, and the material gas supply path including the material gas flow paths31hand32hare provided independently from the housing contact space R34so that gas flow therein is separated from gas flow in the housing contact space R34.

An O ring70is provided surrounding the material gas flow paths31hand32hat a contact surface between the cover31and the cover32. Similarly, another O ring70is provided surrounding the material gas flow path32hand the side surface space R33at a contact surface between the cover32and the electrode component installation table33. These O rings70increase the degree of sealing of the material gas supply path from the other space.

In addition, another O ring70is provided surrounding the active gas passing ports33iat a contact surface between the ground side electrode component2A and the electrode component installation table33, and another O ring70is provided surrounding the active gas discharge ports33kand34kat a contact surface between the electrode component installation table33and the metal housing34. These O rings70increase the degrees of sealing of the active gas passing ports33i, the active gas discharge ports33k, and the active gas discharge port34kfrom the other space. InFIG. 1, each O ring70is illustrated with a small circle.

FIG. 4is an explanatory diagram schematically illustrating a typical structure of a conventional active gas generation apparatus. As illustrated inFIG. 4, a metal housing84houses an active gas generation electrode group composed of a high-voltage side electrode component81and a ground side electrode component82. The high-voltage side electrode component81is formed by providing a metal electrode801on a dielectric electrode811, and the ground side electrode component82is formed by providing a metal electrode below a dielectric electrode.

The high frequency power source5is provided between the metal electrode801of the high-voltage side electrode component81and the metal housing84, and the ground level is electrically connected with the metal electrode of the ground side electrode component82through the metal housing84.

A discharge space86is formed between the high-voltage side electrode component81and the ground side electrode component82through high-voltage application by the high frequency power source5. The active gas is ejected downward through a gas ejection port85provided in the ground side electrode component82.

The metal housing84includes a main surface84bon a bottom surface of a hollow space part, and an outer peripheral protrusion part84xprotruding upward (+Z direction) from the main surface84balong the outer periphery of the main surface84b. The ground side electrode component82is disposed on the main surface84b, and an end part of a dielectric electrode812of the high-voltage side electrode component81is disposed on the outer peripheral protrusion part84x.

The metal housing84is also provided with a material supply port84hat an upper part, and an active gas discharge port84kpositioned below the gas ejection port85at a lower part. With this configuration, the active gas ejected from the gas ejection ports55is discharged to the outside through the active gas discharge port84kalong gas flow88.

An alternating-current voltage application space R81is formed by the high-voltage side electrode component81and the metal housing84and connected with the discharge space86through a flow path84yprovided in the outer peripheral protrusion part84x.

The following describes effects of the active gas generation apparatus according to Embodiment 1 in comparison with the conventional active gas generation apparatus illustrated inFIG. 4.

In the active gas generation apparatus according to Embodiment 1, the alternating-current voltage application space R31is separated from the discharge space66, and the first auxiliary member composed of the covers31and32includes the material gas flow paths31hand32hfor the material gas supply path that guide externally supplied material gas to the discharge space66independently from the alternating-current voltage application space R31, thereby completely separating gas flow in the discharge space66from gas flow in the alternating-current voltage application space R31.

This can reliably avoid a first mixing phenomenon in which an evaporation material, such as the material of the high-voltage side electrode component1A (the metal electrodes101H and101L, in particular), generated when anomalous discharge D2occurs in the alternating-current voltage application space R31is mixed into the discharge space66directly or through the material gas supply path. p However, in the conventional active gas generation apparatus illustrated inFIG. 4, since the alternating-current voltage application space R81and the discharge space86are spatially connected with each other through the flow path84y, it is impossible to avoid the first mixing phenomenon in which the above-described evaporation material generated in the alternating-current voltage application space R81is mixed into the flow path84yas the material gas supply path.

In addition, in the active gas generation apparatus according to Embodiment 1, the housing contact space R34is separated from the discharge space66, and the first auxiliary member composed of the covers31and32includes the material gas flow paths31hand32hfor the material gas supply path independently from the housing contact space R34, thereby completely separating gas flow in the discharge space66from gas flow in the housing contact space R34.

With this configuration, it is also possible to reliably avoid a second mixing phenomenon in which an evaporation material generated by anomalous discharge D3or the like in the housing contact space R34is mixed into the discharge space66.

However, in the conventional active gas generation apparatus, anomalous discharge D4may occur from the alternating-current voltage application space R81toward the metal housing84through the high-voltage side electrode component81and the ground side electrode component82. In this case, it is impossible to avoid the second mixing phenomenon in which an evaporation material generated in a space (space corresponding to the housing contact space R34in Embodiment 1) on the main surface84bhaving an upper part exposed with no ground side electrode component82disposed above is mixed into the discharge space86.

As a result, the active gas generation apparatus according to Embodiment 1 can reliably avoid the above-described first and second mixing phenomena that cannot be avoided by the conventional active gas generation apparatus, thereby achieving the effect of discharging high quality active gas to the outside.

In addition, in the active gas generation apparatus according to Embodiment 1, the purge gas as the second gas other than the material gas can be supplied into the alternating-current voltage application space R31through the purge gas supply port31p. Thus, any evaporation material generated when anomalous discharge occurs in the alternating-current voltage application space R31can be removed to the outside through the purge gas discharge port31e.

Since the above-described material gas supply path is provided independently from the alternating-current voltage application space R31, the material gas is not affected by the purge gas supply.

FIG. 3is an explanatory diagram schematically illustrating a sectional structure of an active gas generation apparatus according to Embodiment 2 of the present invention.

The active gas generation electrode group including the high-voltage side electrode component1A, the ground side electrode component2A, and the spacers37has the same configuration as that of the active gas generation electrode group301in Embodiment 1.

A cover41and a gas seal unit cover42included in the first auxiliary member correspond to the cover31and the cover32in Embodiment 1. A material gas flow path41h, a purge gas supply port41p(second gas supply port), and a purge gas discharge port41e(second gas discharge port) formed in the cover41correspond to the material gas flow path31h, the purge gas supply port31p, and the purge gas discharge port31eformed in the cover31.

A material gas flow path42hformed in the gas seal unit cover42corresponds to the material gas flow path32hformed in the cover32.

An electrode component installation table43as the second auxiliary member corresponds to the electrode component installation table33in Embodiment 1, and an active gas passing port43iand an active gas discharge port43kcorrespond to the active gas passing ports33iand the active gas discharge ports33k. The auxiliary member gas discharge port is formed by the active gas passing port43iand an active gas discharge port44k.

The metal housing44corresponds to the metal housing34in Embodiment 1, and the active gas discharge port44kcorresponds to the active gas discharge port34k.

An alternating-current voltage application space R41corresponds to the alternating-current voltage application space R31, and a housing contact space R44corresponds to the housing contact space R34.

The following description is mainly made on any characteristic part of Embodiment 2. Components having an identical reference sign or a correspondence relation described above have the same characteristics as those in Embodiment 1 except for contents described below, and description thereof will be omitted.

The gas seal unit cover42holds an outer peripheral part of each of the high-voltage side electrode component1A and the ground side electrode component2A by vertically sandwiching the part. In other words, the gas seal unit cover42functions as an electrode group holder configured to solely hold the active gas generation electrode group301.

In the gas seal unit cover42, the material gas flow path42his bent toward the spacers37halfway through its length and directly connected with the plurality of through-holes37hof the spacers37.

In the electrode component installation table43, the ground side electrode component2A is disposed on a main surface43sat an upper part, and part of the gas seal unit cover42is disposed on a stepped part43dprovided in an outer peripheral region of the main surface43sand having a formation height lower than that of the main surface43s, thereby supporting the active gas generation electrode group301including the gas seal unit cover42from the ground side electrode component2A side.

In this manner, the electrode component installation table43as the second auxiliary member, together with the gas seal unit cover42, supports the active gas generation electrode group301from the ground side electrode component2A side.

Similarly to the covers31and32in Embodiment 1, the first auxiliary member as a combined structure of the cover41and the gas seal unit cover42provides the alternating-current voltage application space R41above the high-voltage side electrode component1A.

In Embodiment 2, the material gas supply path connected with the discharge space66from the outside above the material gas flow path41his formed by the material gas flow path41h, the material gas flow path42hand the plurality of through-holes37hprovided in the spacers37.

Thus, in the active gas generation apparatus according to Embodiment 2, the above-described material gas supply path guided to the discharge space66from above the material gas flow path41his formed independently from the alternating-current voltage application space R41. In other words, gas flow in the discharge space66is completely separated from gas flow in the alternating-current voltage application space R41.

The housing contact space R44is provided between a side surface44dof a hollow space part of the metal housing44and each of the electrode component installation table43, the gas seal unit cover42, a side surface region of a lower part of the cover41, and part of a bottom surface region at an upper part of the cover41.

Similarly to the alternating-current voltage application space R31in Embodiment 1, the alternating-current voltage application space R41is a space completely independent from the other space by the high-voltage side electrode component1A, the cover41, and the gas seal unit cover42, and the material gas supply path reaching the discharge space66is completely separated from the other space. With this configuration, the housing contact space R44is completely separated from the alternating-current voltage application space R41and the discharge space66. In other words, gas flow in the discharge space66is completely separated from gas flow in the housing contact space R44.

As a result, similarly to Embodiment 1, the active gas generation apparatus according to Embodiment 2 can reliably avoid the first and second mixing phenomena, thereby achieving the effect of discharging high quality active gas to the outside.

In addition, similarly to Embodiment 1, the active gas generation apparatus according to Embodiment 2 can supply the purge gas into the alternating-current voltage application space R41through the purge gas supply port41p, and thus any evaporation material generated when anomalous discharge occurs in the alternating-current voltage application space R41can be removed to the outside through the purge gas discharge port41e.

Unlike Embodiment 1, no side surface space R33is provided as the material gas supply path in Embodiment 2, which can enhance the function of shielding the material gas between the material gas supply path and each of the alternating-current voltage application space R41and the housing contact space R44.

In addition, the active gas generation apparatus according to Embodiment 2 includes the gas seal unit cover42functioning as the electrode group holder configured to solely hold the active gas generation electrode group301.

Since Embodiment 2 has this characteristic, the combined structural body of the active gas generation electrode group301and the gas seal unit cover42can be transported as a necessary minimum component when the active gas generation electrode group301needs to be replaced in maintenance or the like, which leads to improvement of convenience.

When the active gas generation electrode group301needs to be replaced in the active gas generation apparatus according to Embodiment 1, the active gas generation electrode group301needs to be transported alone, or “the electrode component installation table33+the active gas generation electrode group301+the covers31and32” need to be collectively transported as one combined structural body.

In the former transport case, it is cumbersome that the high-voltage side electrode component1A and the ground side electrode component2A need to be individually transported and it is not easy to fix the components, which causes a problem with increase of the risk of damage on the high-voltage side electrode component1A or the ground side electrode component2A mainly made of ceramic. In the latter transport case, it is a problem that the combined structural body is too large as a minimum unit.

In the active gas generation apparatus according to Embodiment 2, however, the combined structural body of the active gas generation electrode group301and the gas seal unit cover42can be transported as a necessary minimum component, and thus the above-described problems in Embodiment 1 do not occur.

Embodiment 3 has the same basic configuration as that of Embodiment 1 illustratedFIGS. 1 and 2or Embodiment 2 illustrated inFIG. 3. Specifically, the discharge space66, the alternating-current voltage application space R31(R41), and the housing contact space R34(R44) are completely separated from one another, and thus gas generated in one of the spaces does not mix into the other spaces.

In Embodiment 3, the pressure in the discharge space66is substantially set to be a relatively low atmospheric pressure of 10 kPa to 30 kPa approximately. In this pressure setting, the material gas is, for example, gas containing nitrogen of 100%.

In the discharge space66as a space in which a discharge D1is generated to activate the material gas, the discharge desirably starts at a lower voltage. The discharge D1is caused by insulation breakdown of the gas when the electric field intensity exceeds a particular value.

The electric field intensity that causes insulation breakdown is determined by the kind of the material gas and the pressure, and is lower at a lower pressure in the vicinity of atmospheric pressure. For this reason, the above-described pressure setting is applied to the discharge space66.

It is desirable not to generate discharge as much as possible in the alternating-current voltage application space R31(R41) and the housing contact space R34(R44). The most reliable method of preventing anomalous discharge from being generated as unexpected discharge is to provide a sufficient insulation distance, but the distance is limited due to problems with the installation space of the active gas generation electrode group301, and thus in Embodiment 3, the electric field intensity at insulation breakdown is increased by increasing the pressure. However, the pressure has an upper limit value substantially determined by the strength of components, and thus the pressure at the alternating-current voltage application space R31and the housing contact space R34is desirably 100 kPa to 300 kPa (absolute pressure) approximately.

In the structure described in Embodiment 1 or Embodiment 2, the discharge space66and a gas layer in each of the alternating-current voltage application space R31and the housing contact space R34are separated from each other, and thus it is possible to perform such pressure setting suitable for each of the discharge space66, the alternating-current voltage application space R31, and the housing contact space R34that the discharge D1in the discharge space66occurs at a lower applied voltage by setting the pressure in the discharge space66to be lower than the pressure in the alternating-current voltage application space R31and the housing contact space R34, and that the discharge is reduced by setting a relatively high pressure in the alternating-current voltage application space R31and the housing contact space R34.

In this manner, the active gas generation apparatus according to Embodiment 3 can set relatively low pressure in the discharge space66so that a discharge phenomenon occurs at a lower applied voltage, and can set relatively high pressure in the alternating-current voltage application space R31and the housing contact space R34so that no discharge phenomenon occurs.

The present invention is described above in detail, but the above description is exemplary in any aspect, and the present invention is not limited to the description. Numerous modifications not exemplarily described would be thought of without departing from the scope of the present invention.