US20080149273A1

US20080149273A1 - Plasma processing apparatus

Info

Publication number: US20080149273A1
Application number: US11/959,818
Authority: US
Inventors: Kazuhiro Gomi
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2006-12-20
Filing date: 2007-12-19
Publication date: 2008-06-26
Also published as: CN101207966A; KR100935144B1; JP2008153147A; KR20080058178A

Abstract

A plasma processing apparatus includes: a first electrode including a hollow penetrated through from an upper end thereof to a lower end thereof; a workpiece stage to place a workpiece; a second electrode arranged opposing to a lower end of the first electrode through the workpiece stage; a processing gas nozzle formed on an outer circumference side of an opening at the lower end of the hollow along a circumferential direction; a power source circuit including a power source applying a voltage between the first electrode and the second electrode; and a gas supply system supplying a processing gas to generate plasma to the processing gas nozzle. The plasma is generated by activating the processing gas that is ejected out of the processing gas nozzle and located around immediately below the opening at the lower end upon voltage application between the first electrode and the second electrode so as to process a surface of the workpiece by the plasma.

Description

BACKGROUND

1. Technical Field
The present invention relates to a plasma processing apparatus.
2. Related Art
To process a surface of a workpiece, so-called plasma chemical vaporization machining (hereinafter, abbreviated as “plasma CVM”) is employed. In the plasma CVM, a reaction gas is supplied to an electrode while a voltage or a high frequency wave is applied to the electrode so as to generate radical based on the reaction gas. The radical reacts with the workpiece, and generates a product by this radical reaction. The process is performed by removing the product.
In recent years, for a so-called etching process using active species such as radical that is excited by plasma, it is important to improve a processing speed by increasing density of radical.
In response to the above, a plasma processing apparatus using a roll electrode that can generate dense radical has been known (e.g. JP-A-2001-120988). Further, a plasma processing apparatus using a hollow cathode discharge electrode has been known (e.g. JP-A-2001-35692). Another example of the related art is disclosed in JP-A-1-125829.
Meanwhile, as an area to be processed becomes wider in recent years, a plasma processing apparatus having a simple configuration and enabling processing workpieces in various sizes is required.
In order to respond to the above, a plasma processing apparatus in related art scans an electrode or a workpiece, for example, so as to change positions relative to each other while processing.
However, the plasma processing apparatus as above cannot achieve sufficient processing efficiency and speed for processing workpieces. Moreover, a configuration of the apparatus itself is far from simple.

SUMMARY

An advantage of the present invention is to provide a plasma processing apparatus that is simply configured and able to process a surface of a workpiece in a short period of time.
The invention achieves as follows.
A plasma processing apparatus according to an aspect of the invention includes a first electrode having a hollow penetrated through from an upper end to a lower end thereof; a workpiece stage to place a workpiece; a second electrode arranged opposing to a lower end of the first electrode through the workpiece stage; a processing gas nozzle formed on an outer circumference side of an opening at the lower end of the hollow along a circumferential direction; a power source circuit including a power source applying a voltage between the first electrode and the second electrode; and a gas supply system supplying a processing gas to generate plasma to the processing gas nozzle. The plasma is generated by activating the processing gas that is ejected out of the processing gas nozzle and located around immediately below the opening at the lower end upon voltage application between the first electrode and the second electrode so as to process a surface of the workpiece by the plasma.
According to the above, the plasma concentrates around immediately below the opening at the lower end of the hollow that is penetrated, thereby improving efficiency of the plasma processing on the surface of the workpiece.
In this case, the processing gas ejected from the processing gas nozzle preferably flows in a direction toward the opening at the lower end and in a direction apart from the opening at the lower end.
Accordingly, the processing gas is likely to gather around immediately below the opening at the lower end, thereby increasing density of the plasma and enabling effectively processing the surface of the workpiece in a short period of time.
In this case, a flow of the processing gas from the opening at the lower end toward the upper end of the hollow is preferably formed in the hollow.
According to the above, a reaction product generated by the plasma processing flows toward the upper end of the hollow, thereby not decreasing the efficiency of the plasma processing.
In this case, it is preferable that the processing gas nozzle be intermittently formed on the outer circumference side of the opening along the circumferential direction.
According to this, the processing gas can effectively flow to around immediately below the opening at the lower end, increasing gas pressure around immediately below the opening at the lower end with a small amount of the gas.
In this case, the processing gas nozzle is preferably formed in an annular shape around a whole circumference of the opening at the lower end.
Accordingly, a larger amount of the processing gas evenly flows to around immediately below the opening at the lower end, thereby further increasing the gas pressure around immediately below the opening at the lower end and generating dense plasma.
In this case, the processing gas nozzle preferably ejects the processing gas in a direction inclined toward an extended line of a line connecting the upper end and the lower end of the hollow.
Accordingly, the processing gas assuredly flows toward the extended line of the line, thereby further increasing the gas pressure around immediately below the opening at the lower end and generating dense plasma.
In this case, the plasma processing apparatus preferably further includes a gas exhaust system exhausting the processing gas ejected from the processing gas nozzle from the upper end of the hollow of the first electrode.
Therefore, the reaction product generated by the plasma processing is assuredly exhausted, thereby not decreasing the efficiency of the plasma processing.
Further, wastes (electrode materials and the like) generated between the electrodes, or between the electrode and the workpiece by an abnormal electrical discharge is also exhausted and removed, thereby not decreasing the efficiency of the plasma processing.
In this case, the gas exhaust system preferably includes an outlet flow adjustment unit adjusting an amount of an outlet flow of the processing gas exhausted from the upper end of the hollow.
According to this, the processing gas is arranged to be an adequate amount of the outlet flow, thereby assuredly removing the reaction product while the plasma is kept around immediately below the opening at the lower end.
Further, although a processed shape is easy to vary due to ejection of the processing gas, the processed shape (trace of processing) can be controlled by intermittently controlling (adjusting) exhaust timing and adjusting gas pressure under the first electrode.
Furthermore, by intermittently controlling (adjusting) the exhaust timing so as to control a period in which radical stays in the (dense) plasma generation area, a processing speed (processing rate) is controlled.
In this case, the outlet flow adjustment unit preferably includes an outlet duct connected with the upper end of the hollow; a valve opening and shutting a flow passage in the outlet duct; and a pump formed on a downstream side of the outlet duct through the valve.
According to this, the amount of the outlet flow of the processing gas is assuredly arranged, thereby assuredly exhausting the reaction product while the plasma is kept around immediately below the opening at the lower end.
The plasma processing apparatus preferably further includes a cooling system to cool off the first electrode.
Accordingly, the first electrode generating heat by the discharge is cooled off, thereby stably generating dense plasma.
Further, by reducing a diameter of the hollow included in the first electrode, the first electrode is prevented from generating heat, thereby suppressing an adverse effect on the workpiece caused by heat generated by the discharge.
In this case, the first electrode has a surface facing to the second electrode and it is preferable that at least the surface be covered with a dielectric portion.
According to this, between a pair of the electrodes, a metal or the like forming the electrodes is not exposed, thereby preventing an ark discharge and evenly generating an electric field.
In this case, the processing gas nozzle is preferably formed on the dielectric portion.
Accordingly, between the first electrode and the second electrode, the metal or the like forming the electrodes is not exposed, thereby evenly generating an electric field and providing a glow-like discharge.
In this case, the dielectric portion preferably has an external diameter expanded more than an external diameter of the first electrode.
According to this, the processing gas flows without going wrong from the direction toward the opening at the lower end of the hollow to the direction apart from there, thereby controlling the flow of the processing gas.
In this case, the first electrode is preferably provided in a plurality of numbers.
According to this, the surface of the workpiece is processed in accordance therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a first embodiment of the invention.

FIG. 2 is a sectional view taken along a line A-A in FIG. 1.

FIG. 3 is a bottom view illustrating a dielectric portion in FIG. 1.

FIG. 4 is a bottom view illustrating a dielectric portion of a plasma processing apparatus according to a second embodiment of the invention.

FIG. 5 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a third embodiment of the invention.

FIG. 6 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a fifth embodiment of the invention.

FIG. 7 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a sixth embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A plasma processing apparatus will now be described in detail according to exemplary embodiments of the invention with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a first embodiment of the invention. FIG. 2 is a sectional view taken along a line A-A in FIG. 1 while FIG. 3 is a bottom view of a dielectric portion.
In the following description, the top side in FIG. 1 is described as “upper”, while the bottom side is described as “lower”.
As shown in FIG. 1, a plasma processing apparatus 1 is provided with a first electrode 2, a workpiece stage 100 to place a workpiece 10, a second electrode 3, a dielectric portion 4 accommodating the first electrode 2, a processing gas nozzle 5, a gas supply passage 6, a power source circuit 7, a gas supply system 8, and a gas exhaust system 9. The first electrode 2 has a hollow 40 penetrated through from an upper end to a lower end. The second electrode 3 is arranged opposing to the lower end of the first electrode 2 through the workpiece stage 100. The processing gas nozzle 5 is formed on an outer circumference side of an opening 422 located at the bottom side of the hollow 40 along a circumferential direction. The gas supply passage 6 leads a processing gas supplied from the gas supply system 8 to the processing gas nozzle 5. The power source circuit 7 includes a power source 72 applying a voltage between the first electrode 2 and the second electrode 3. The gas supply system 8 supplies the processing gas for generating plasma to the processing gas nozzle 5. The gas exhaust system 9 exhausts the processing gas ejected from the processing gas nozzle 5 out of the upper end of the hollow 40.
The plasma processing apparatus 1 generates plasma by activating the processing gas that is ejected out of the processing gas nozzle 5 and located around immediately below the opening 422 at the lower end upon voltage application between the first electrode 2 and the second electrode 3 so as to process a surface 101 of the workpiece 10 by the plasma.
In the embodiment, a case of etching or dicing by plasma will be explained.
Below, each part of a configuration of the plasma processing apparatus 1 will be described.
The first electrode 2 is arranged so as to oppose to the workpiece 10 placed on the workpiece stage 100. The first electrode 2 is a cylindrical electrode (so-called hollow cathode electrode) having the hollow 40 penetrating through from an upper center 21 of the upper end surface to a lower center 22 of the lower end surface.
The first electrode 2 having the hollow 40 allows electrons generated by a discharge in the hollow 40 to repeatedly collide with an inner wall of the first electrode 2, thereby leading a so-called confinement effect of electrons. Then, a part of the electrons or a gas ion ionized by the electrons collides with the electrode and generates second electrons. A part of the second electrons comes out from the opening 422 at the lower end to around immediately below the opening 422 (hereinafter, abbreviated as “a dense plasma generation area 301”). Therefore, density of the electrons in the hollow 40 and the dense plasma generation area 301 is increased. As a result, an intensity of an electric field in the hollow 40 and the dense plasma generation area 301 is increased. Then, dense plasma is generated in the hollow 40 and the dense plasma generation area 301, thereby effectively processing the surface 101 of the workpiece 10.
The hollow 40 is formed with an upper end surface opening 401 formed at the upper surface of the first electrode 2 and a lower end surface opening 402 formed at the bottom surface of the first electrode 2. Further, the upper end surface opening 401 is communicated with the gas exhaust system 9 to be described later. Further, the lower end surface opening 402 is communicated with the opening 422 on the bottom side (hereinafter, abbreviated as “opening”).
A cross sectional shape of the hollow 40 is not particularly limited, but may be a circular form, an elliptical form, a quadrilateral form or the like.
The first electrode 2 is accommodated in the dielectric portion 4 in a nearly cylindrical shape having a cavity 412, and a top surface 411 of the dielectric portion 4 is open (a portion other than the top end of the first electrode 2 in FIG. 1).
Since the first electrode 2 is accommodated in the dielectric portion 4 as the above, a metal or the like serving as an electrode is not exposed between the first electrode 2 and the second electrode 3. Therefore, an electric field is evenly generated in the first electrode 2.
Further, while impedance is prevented from increasing, a desired discharge at a relatively low voltage is generated, thereby securing plasma generation.
Furthermore, an insulation breakdown at voltage application is prevented, and an arc discharge is adequately prevented from occurring, thereby providing a glow-like and stable discharge.
The dielectric portion 4 includes a body 41 having the cavity 412 and a diameter expansion (flange) 42 having an outside diameter being expanded and formed on a bottom surface side of the body 41.
The outside diameter of the diameter expansion 42 is expanded more than that of the body 41, preventing turbulence of a gas flow and controlling the flow of the processing gas to be smooth.
The body 41 has the gas supply passage 6 formed along a circumferential direction of an outer circumference side of the cavity 412, which will be described later.
A shape of the body 41 is not particularly limited, but may be a cylindrical shape, a circular truncated cone or the like, for example.
A bottom surface 421 of the diameter expansion 42 has the opening 422 formed in a center thereof as shown in FIG. 3. The opening 422 (the opening at the lower end of the hollow 40) exhausts a reaction product generated by the plasma processing from between the first electrode 2 and the second electrode 3 (hereinafter, referred to as a plasma generation area 30).
As above, the opening 422 formed in the bottom surface 421 of the diameter expansion 42 allows the processing gas including the reaction product generated by the plasma processing to exhaust from the plasma generation area 30, thereby preventing decrease of a processing speed caused by the reaction product remaining in the plasma generation area 30.
Further, since the opening 422 is formed in the bottom surface 421, the processing gas flows from the opening 422 to an upper end of the hollow 40, preventing the reaction product from adhering to the surface 101 of the workpiece 10.
Further, the dense plasma generation area 301 has high dense plasma, and thus the reaction product is easy to gather in the center. Therefore, the opening 422 formed in the center of the bottom surface 421 can effectively exhaust the reaction product.
As shown in FIG. 3, the bottom surface 421 of the diameter expansion 42 has the processing gas nozzle 5 intermittently formed along a circumferential direction of an outer circumference side of the opening 422. Further, the processing gas nozzle 5 made open in the bottom surface 421 of the diameter expansion 42 so as to be located facing toward the workpiece 10.
As above, the processing gas nozzle 5 intermittently formed along the circumferential direction of the outer circumference side of the opening 422 allows the processing gas to flow effectively to the plasma generation area 30, thereby increasing gas pressure in the plasma generation area 30 with a less amount of the gas.
Further, the processing gas flows from the processing gas nozzle 5 toward in a direction of an extended line (hereinafter, referred to as a line 20) of a line connecting the upper end and the lower end of the hollow 40 collides with another flow at the line 20, and then flows in a direction apart from the line 20. Therefore, the processing gas activated (by electrolytic dissociation, ionization, excitation, or the like) can remain in the plasma generation area 30 longer, improving a processing rate.
A cross sectional shape of the processing gas nozzle 5 is not particularly limited, but may be a circular form, a strip form, or the like.
The processing gas nozzle 5 is communicated with the gas supply passage 6 formed to extend in a vertical direction in the body 41 of the dielectric portion 4.
The gas supply passage 6 includes a gas introduction passage 61, a bifurcating channel 62, and an annular conduit 63. The gas introduction passage 61 is formed on the side of the gas supply system 8 introducing the processing gas into the processing gas nozzle 5. The bifurcating channel 62 is bifurcated from the gas introduction passage 61 and leads the processing gas to the processing gas nozzle 5. Further, the annular conduit 63 leads the processing gas from the gas introduction passage 61 to the bifurcating channel 62.
The annular conduit 63 is formed in an annular shape in a middle area of the body 41 of the dielectric portion 4. The annular conduit 63 is communicated with an end of the gas introduction passage 61 extending in a vertical direction inside of the body 41. The other end of the gas introduction passage 61 is open in the top surface 411 of the body 41 and communicated with a processing gas tube 84 of the gas supply system 8. In the embodiment, two of the gas introduction passages 61 are formed opposing to each other through the first electrode 2 in the body 41.
The annular conduit 63 is communicated with an end of the bifurcating channel 62 extending in the vertical direction inside of the body 41. The other end of the bifurcating channel 62 is communicated with the processing gas nozzle 5. In the embodiment, as shown in FIGS. 1 and 2, eight of the bifurcating channels 62 from the annular conduit 63 are arranged at equal spaces.
Cross sectional shapes of the gas introduction passages 61, the bifurcating channels 62, and the annular conduit 63 are not particularly limited, but may be a circular form, a strip form, or the like.
The gas supply passage 6 in a configuration as above can reduce flow path resistance of the processing gas flowing in the gas introduction passages 61 (the bifurcating channels 62) comparing to a case introducing the processing gas to the processing gas nozzle 5 by using a single passage as the gas introduction passage 61. Therefore, the processing gas is effectively distributed to the bifurcating channels 62.
Materials composing the dielectric portion 4 are: for example, various plastics such as polytetrafluoroethylene, and polyethylene terephthalate; various glasses such as silica glass; and inorganic oxide, and the like. As the inorganic oxide, for example, dielectric materials such as metal oxide such as alumina (Al₂O₃), SiO₂, ZrO₂, TiO₂, nitride such as silicon nitride, and compound oxide such as barium titanate (BaTiO₃) are cited. Among them, a metal oxide is preferable to use, and further, alumina is more preferable. By using such a material, the arc discharge in the electric field is more assuredly prevented from occurring.
The first electrode 2 has an upper end exposed from the dielectric portion 4. Since the first electrode 2 is an electrode to apply a voltage, the exposed portion is coupled to the power source 72 through a wiring line 71 for electrical coupling.
A material composing the first electrode 2 is not particularly limited, but may include a metal such as copper, aluminum, iron, and silver, various alloys such as a stainless steel, a brass, and an aluminum alloy, an intermetallic compound, and various carbon materials.
The shape of the first electrode 2 is not limited as long as it has a hollow. As for examples thereof, a cylindrical shape, a prismatic shape and the like are cited.
The second electrode 3 is arranged so as to oppose to the first electrode 2 through the workpiece 10 placed on the workpiece stage 100, and directly connected to ground by the wiring line 71. Since the second electrode 3 also serves as the workpiece stage 100, the workpiece 10 is placed so as to have contact with a top surface (the workpiece stage 100) of the second electrode 3.
As a material composing the second electrode 3, the same materials as those of the first electrode 2 are cited, but not particularly limited to them. As a shape of the second electrode 3, the same shapes as those of the first electrode 2 are cited, but not particularly limited to them.
The power source circuit 7 includes the power source 72 for high frequency and the wiring line 71. The power source 72 for high frequency applies a voltage between the first electrode 2 and the second electrode 3. The wiring line 71 electrically couples the second electrode 3, the power source 72, and the first electrode 2. Although it is not illustrated, a matching circuit (impedance-matching circuit) corresponding to an electric power to be supplied, a frequency adjuster (circuit) for changing frequency of the power source 72, or a voltage adjuster (circuit) for changing a maximum value (amplitude) of an application voltage of the power source 72 can be installed if necessary. Accordingly, a processing condition of the plasma processing to the workpiece 10 is adequately adjustable.
The first electrode 2 is coupled to the power source (power source portion) 72 for high frequency through the wiring line (cable) 71, and the second electrode 3 is coupled to the power source 72 for high frequency through the wiring line 71, thereby composing the power source circuit 7. A part of the power source circuit 7, that is, the wiring line 71 on a second electrode 3 side is connected to ground.
When the plasma processing is performed on the workpiece 10, the power source 72 for high frequency operates to apply a voltage between the first electrode 2 and the second electrode 3. At this time, an electric field is generated among inside of the hollow 40 of the first electrode 2, the first electrode 2, and the second electrode 3. Then, a discharge occurs upon gas supply, generating plasma.
Further, the frequency of the power source 72 is not limited, but it is preferable to be 10 to 70 MHz, more preferable to be 10 to 40 MHz.
The gas supply system 8 supplies the processing gas for generating plasma to the gas supply passage 6. The gas supply system 8 includes a gas cylinder (gas supply source) 81, a mass flow controller (flow controller) 82, a valve (flow passage switching unit) 83, and the processing gas tube 84. The gas cylinder 81 includes a predetermined gas filled therein to supply. The mass flow controller 82 controls a mass flow of the gas supplied from the gas cylinder 81. The valve 83 opens and shuts a flow passage of the processing gas tube 84 on a downstream side lower than the mass flow controller 82. The processing gas tube 84 is connected to the gas supply passage 6.
The gas supply system 8 as above sends the predetermined gas from the gas cylinder 81 and adjusts the mass flow with the mass flow controller 82. Then, the gas supply system 8 introduces (supplies) the processing gas to the processing gas nozzle 5 from the gas introduction passage 61 opening in the top surface 411 of the body 41 of the dielectric portion 4 through the processing gas tube 84.
For the gas (processing gas) to be used for plasma processing as above, various gases are adopted depending on a processing purpose. When etching or dicing is processed as the embodiment, various halogenated gases can be used. Example of the halogenated gases are a compound gas containing fluorine atoms such as CF₄, C₂F₆, C₃F₆, C₄F₈, CClF₃, and SF₆, and a compound gas containing chlorine atoms such as Cl₂, BCl₃, and CCl₄.
Further, for other processing purposes, following processing gases can be used respectively.
(a) To heat the surface 101 of the workpiece 10, N2, O2 or the like is used, for example.
(b) To make the surface 101 of the workpiece 10 water-repellent (liquid-repellent), the compound gas containing fluorine atoms is used, for example.
(c) To make the surface 101 of the workpiece 10 hydrophilic (lyophilic), a compound containing oxygen atoms such as O₃, H₂O, and air, a compound containing nitrogen atoms such as N₂, and NH₃, a compound containing sulfur atoms such as SO₂, and SO₃are used, for example. Accordingly, surface energy is increased by forming a hydrophilic functional group such as a carbonyl group, a hydroxyl group, or an amino group on the surface 101 of the workpiece 10, thereby obtaining a hydrophilic surface. Alternatively, a polymerizable monomer having a hydrophilic group such as acrylic acid and methacrylic acid can be deposited (formed) to obtain a hydrophilic polymerized film.
(d) To add electric and optical functions to the surface 101 of the workpiece 10, a metal-hydrogen compound using a metal such as Si, Ti, and Sn, a metal-halogen compound, and metal alkoxide (an organic metal compound) can be used in order to form a metal oxide thin film such as SiO₂, TiO₂, and SnO₂on the surface 101 of the workpiece 10.
(e) To remove a resist material for resist processing and organic matter contamination, an oxygen gas can be used, for example.
As the processing gas above, a mixed gas made of the processing gas described above and a carrier gas (hereinafter, also referred to simply as a gas) is generally used. The “carrier gas” here indicates a gas introduced so as to a start discharge and maintain the discharge.
In this case, the gas cylinder 81 can be filled with the mixed gas (the processing gas and the carrier gas) to use. Alternatively, the processing gas and the carrier gas can be filled in separate gas cylinders and mixed at a predetermined mixing ratio in a middle of the processing gas tube 84.
As the carrier gas, a noble gas such as He, Ne, Ar, or Xe can be used. They can be used singly or in combination of two or more.
A percentage (mixing ratio) of the processing gas in the mixed gas slightly varies depending on the processing purpose. The ratio of the processing gas in the mixed gas is not limited to, but preferably at 1 (one) to 10%, and more preferably at 5 to 10%. Therefore, an electric discharge is effectively started and desired plasma processing is performed by the processing gas.
The mass flow of the gas supplied is adequately determined depending on a type of the gas, a processing purpose, a processing level and the like. In general, it is preferably about from 30 SCCM to 50 SLM. Accordingly, pressure in the plasma generation area 30 is effectively increased, thereby enabling a fine process.
The gas exhaust system 9 exhausts the plasma generated in the plasma generation area 30, a reaction product, an inactive processing gas from the upper end surface opening 401 of the hollow 40 to recover them.
The gas exhaust system 9 includes an outlet flow adjustment unit 90 and an abatement unit 95. The outlet flow adjustment unit 90 adjusts an outlet flow of the processing gas exhausted from the upper end surface opening 401 of the hollow 40. The abatement unit 95 such as an abatement device for perfluorocompound (PFC) destruction and a scrubber is formed on a downstream side of an outlet duct 91.
The outlet flow adjustment unit 90 includes the outlet duct 91, a valve (flow passage switching unit) 92, a mass flow controller 93, and a pump 94. The outlet duct 91 connected to the upper end surface opening 401 of the hollow 40, and the valve 92 opens and shuts a flow passage of the outlet duct 91. The mass flow controller 93 adjusts the mass flow of the gas exhausted by the pump 94 that is formed on the downstream side of the outlet duct 91 through the valve 92.
The gas exhaust system 9 as above opens the valve 92 and starts the pump 94 so as to provisionally make the hollow 40 be in a reduced pressure condition. Next, the gas exhaust system 9 starts the mass flow controller 93, adjusting the outlet flow. Then, the gas exhaust system 9 exhausts the processing gas including a reaction product and plasma from the upper end surface opening 401 to the outlet duct 91 so as to exhaust them from the abatement unit 95 to outside.
The processing gas exhausted from the processing gas nozzle 5 flows in two directions that are a direction toward the line 20 and a direction apart from the line 20. The processing gas flowing toward the line 20 reaches around the line 20 (the dense plasma generation area 301) and pressure of the processing gas is increased. At this time, the pump 94 of the gas exhaust system 9 operates and inside of the outlet duct 91 is provisionally in the reduced pressure condition. Therefore, due to difference of the pressure between the dense plasma generation area 301 and the outlet duct 91, the processing gas flows from the dense plasma generation area 301 to the opening 422. Then, a flow of the processing gas from the lower end surface opening 402 of the hollow 40 toward the upper end surface opening 401 of the hollow 40 is formed. As a result, the processing gas is exhausted from the upper end surface opening 401 to the outlet duct 91.
As above, since the plasma processing apparatus 1 is provided with the gas exhaust system 9, the gas exhaust system 9 induces the outlet flow, thereby assuredly exhausting the reaction product generated by plasma processing.
Further, the gas exhaust system 9 can adjust the outlet flow of the processing gas, keeping dense plasma in the dense plasma generation area 301. As a result, the surface 101 of the workpiece 10 is processed in a short period of time without decreasing the processing rate.
Further, the flow of the processing gas from the opening 422 toward the upper end surface opening 401 of the hollow 40 is assuredly formed, thereby effectively supplying a new processing gas to the dense plasma generation area 301.
Further, since the processing gas flows from the lower end to the upper end of the hollow 40, the gas exhaust system 9 can exhaust foreign matters (wastes of an electrode material and the like) caused by discharge of the first electrode 2 and derived from the first electrode 2, and foreign matters generated in the plasma generation area 30 by an abnormal electrical discharge. As a result, the surface 101 is prevented from being contaminated by the foreign matters, while efficiency of the plasma processing is prevented from decreasing.
Further, due to ejection of the processing gas from the processing gas nozzle 5, a processed shape is easy to vary. Therefore, timing to exhaust is intermittently controlled (adjusted) and gas pressure under the first electrode 2 is adjusted, controlling the processed shape (trace of processing).
Further, the timing to exhaust is intermittently controlled (adjusted) so as to control a period in which radical stays in the plasma generation area 30 (301), controlling a processing speed.
Even when the gas exhaust system 9 is not formed, as shown in a fourth embodiment to be described later, pressure in the dense plasma generation area 301 is increased, a flow of the processing gas from the opening 422 toward the upper end surface opening 401 of the hollow 40 is naturally formed due to difference of the pressure with that of air.
The workpiece 10 may be, but not be limited to, a substrate used for electronic apparatuses in the embodiment. Specific examples of a material of the workpiece 10 may include, for example, various glasses such as a silica glass, a non-alkali glass, and quartz crystal, various ceramics such as almina, silica, and titania, various semiconductor materials such as silicon, gallium-arsenic, various plastic (resin material) such as polyethylene, polypropylene, polystyrene, polycarbonate, polyethylene terephthalate, polytetrafluoroethylene, polyimide, crystalline liquid polymer, phenol, epoxy, and acrylic resin, which are dielectric materials. Among them, in particular, the various glasses such as quartz crystal and a silica glass, and the various semiconductor materials are preferably used.
A shape of the workpiece 10 may be a plate like shape, a long layered shape, or the like.
[Operating Method of the Plasma Processing Apparatus]
Next, operations (performances) of the plasma processing apparatus 1 will be described.
The workpiece 10 is placed in the center of the second electrode 3 (the workpiece stage 100). The power source circuit 7 is started and the valve 83 is opened. Then, a mass flow of the gas is adjusted by the mass flow controller 82 so as to flow the gas from the gas cylinder 81. According to the above, the gas sent out from the gas cylinder 81 flows in the processing gas tube 84 and is introduced to the gas introduction passage 61. The processing gas introduced to the gas introduction passage 61 flows downward through the annular conduit 63 in the middle of the body 41. Then, the processing gas flowing in the annular conduit 63 goes down in the bifurcating channel 62 and goes out of the processing gas nozzle 5.
The processing gas ejected from the processing gas nozzle 5 is ejected toward directly below right after the ejection. However, the processing gas runs into the workpiece 10 located immediately below the processing gas nozzle 5 and is divided so that a part of the gas flows in the direction toward the line 20 (in the direction of the dense plasma generation area 301) while a part of the gas flows in the direction apart from the line 20 (in the circumferential direction of the outer circumference). Then, the processing gas gathers in the dense plasma generation area 301, increasing gas pressure.
Further, due to the operation of the power source circuit 7, a high frequency voltage is applied between the first electrode 2 and the second electrode 3, generating an electric field in the plasma generation area 30 and the hollow 40.
At this time, electrons generated in the hollow 40 repeatedly collide with an inner wall of the hollow 40, enhancing efficiency of ionization. Then, a part of the electrons or a part of second electrons generated by a gas ion ionized by the electron colliding with the electrode comes out from the opening 422 to the dense plasma generation area 301. As a result, an intensity of an electric field in the hollow 40 and the dense plasma generating area 301 is increased.
The closer to the outer circumferential direction of the dense plasma generation area 301, the smaller the density of the processing gas becomes, generating a glow discharge state.
The processing gas flowing into the plasma generation area 30 is activated by a discharge, thereby generating plasma.
Then, the plasma (activated gas) generated comes in contact with the surface 101 of the workpiece 10, processing (etching, dicing, or the like) the surface 101.
Since gas pressure has been increased in the dense plasma generation area 301, an unreacted processing gas, plasma, and the processing gas including a reaction product generated by plasma processing flows toward the opening 422 due to pressure difference between the dense plasma generation area 301 and the outlet duct 91. The processing gas having flown toward the opening 422 flows to the lower end surface opening 402 from the opening 422. Then, the processing gas flows to the upper end surface opening 401 passing through the hollow 40 from the lower end surface opening 402.
At this time, the pump 94 is started and the valve 92 is opened. Then the outlet flow of the gas is adjusted with the mass flow controller 93. According to the above, the processing gas is sucked and exhausted out of the abatement unit 95 to outside after flowing through the outlet duct 91 connected to the upper end surface opening 401. Further, the reaction product is exhausted to outside from the abatement unit 95 or recovered by the abatement unit 95.
The plasma processing apparatus 1 as above performs plasma processing on a desired position on the workpiece 10 placed on the second electrode 3 while moving the first electrode in an x axis direction and a y axis direction with respect to the workpiece 10 by a moving unit (not shown).
For example, while plasma is generated, the first electrode 2 is scanned in a y-axis positive direction of the surface 101. Then, after the first electrode 2 is moved for a predetermined pitch (for example, for an outside diameter of the first electrode 2 only) in the x-axis direction, it is scanned in a y-axis negative direction. By sequentially repeating such scanning (movement), a whole of the surface 101 of the workpiece 10 can be processed.
Further, in the scanning method of the first electrode 2 described above, when the first electrode 2 is moved for the predetermined pitch in the x-axis direction, plasma generation may be stopped once. Then, after it is moved for the predetermined pitch in the x-axis direction, plasma can be generated again to process.
The operation as above allows the surface 101 of the workpiece 10 to be processed effectively regardless of a size of the workpiece 10.
Further, instead of moving the first electrode 2, the second electrode 3 on which the workpiece 10 is placed, or the workpiece 10 can be moved in a similar way to moving the first electrode 2 described above.
The processing apparatus 1 described above is applicable to an electronic parts field to perform a process for a crystal resonator, drilling on a sensor board, grooving, electrode forming (solar cells, filters, multi-layered substrates), de-smearing treatment for a printed circuit board, patterning of HDD parts, a semiconductor field to perform deburring of an IC resin mold package, drilling on a device wafer, grooving of a ceramics wafer, a FPD related field for conductive membrane removing and barrier forming, in addition, oxidized insulating film processing and removing, strain-free processing for glasses (quartz), quartz crystal processing, and the like. Furthermore, the application can expand to micro-electro-mechanical systems (MEMS) or the like. Employing a photo resist mask also allows fine patterning.

Second Embodiment

FIG. 4 is a bottom view illustrating a schematic configuration of a dielectric portion of a plasma processing apparatus according to a second embodiment of the invention.
Here, the difference of the plasma processing apparatus in the second embodiment from the first embodiment will be mainly explained, and the same contents of them are omitted.
The plasma processing apparatus 1 in the second embodiment is different from the one in the first embodiment at a point in which the processing gas nozzle 5 is formed in an annular shape in a circumferential direction all around the outer circumference of the opening 422. Therefore, a whole circumference of the annular conduit 63 extends downward in the body 41 as it is so as to be the bifurcating channel 62, communicating with the processing gas nozzle 5.
The processing gas nozzle 5 is arranged in the annular shape in the circumferential direction all around the outer circumference of the opening 422 as above, making more of the processing gas evenly flow into the dense plasma generation area 301. Therefore, gas pressure in the dense plasma generation area 301 is further increased, generating dense plasma.
Further, the bifurcating channel 62 forms a channel having an annular shape, reducing resistance of the processing gas flowing in the bifurcating channel 62 more than a case of the first embodiment.

Third Embodiment

FIG. 5 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a third embodiment of the invention.
In the following description, the top side in FIG. 5 is described as “upper”, while the bottom side is described as “lower”.
The difference of the plasma processing apparatus in the third embodiment from the first embodiment will be mainly explained, and the same contents of them are omitted.
The plasma processing apparatus 1 according to the third embodiment differs from the plasma processing apparatus 1 in the first embodiment at a point below.
The processing gas nozzle 5 formed at the bottom surface 421 of the diameter expansion 42 is inclined toward the dense plasma generation area 301.
The nozzle 5 inclined in a direction of the dense plasma generation area 301 as above, assuredly flowing the ejected processing gas to the dense plasma generation area 301. Therefore, the processing gas is more concentrated due to an enclosing effect of the processing gas. As a result, gas pressure in the dense plasma generation area 301 is increased, generating dense plasma.
Further, in the bottom surface 421 of the diameter expansion 42 and on an inner circumference side located more medially than the nozzle 5, a recess 424 having a bottom surface 423 is formed.
Further, the annular conduit 63 in an annular shape is formed on a lower end of the body 41 of the dielectric portion 4. The annular conduit 63 is communicated with an end of the gas introduction passage 61. The other end of the gas introduction passage 61 is open in a lower end lateral surface 413 of the body 41 and communicated with the processing gas tube 84 of the gas supply system 8.
The annular conduit 63 is communicated with the end of the bifurcating channel 62 extending in the vertical direction of the body 41. The other end of the bifurcating channel 62 is communicated with the nozzle 5 inclined toward the dense plasma generation area 301. Further, the nozzle 5 is open on a lateral side of the recess 424. In the third embodiment, eight of the nozzles 5 are intermittently formed on the lateral side of the recess 424.
The nozzle 5 may be formed in an annular shape all around the opening 422. In this case, the nozzle 5 is formed in a circular truncated cone.
An inclination angle of the nozzle 5 with respect to the line 20, is not limited to, but about from 0.5 to 40 degrees, for example. Further, the inclination angle of the nozzle 5 can be adequately changeable in a range between 0 (zero that is the same as the case in the first embodiment) to 40 degrees (e.g. a configuration using a movable nozzle, a configuration making the diameter expansion 42 detachable (replaceable) from the body 41, or the like).

Fourth Embodiment

The difference of the plasma processing apparatus in a fourth embodiment from the third embodiment will be mainly explained, and the same contents of them are omitted.
The plasma processing apparatus 1 in the fourth embodiment has the same configuration as that of the first embodiment other than not having the gas exhaust system 9.
Since the plasma processing apparatus 1 in the fourth embodiment does not include the gas exhaust system 9, a configuration of the plasma processing apparatus 1 is simplified. Further, the plasma processing apparatus 1 excluding the gas exhaust system 9 allows an installation space thereof to be reduced.
Further, the plasma processing apparatus 1 has a different operation to exhaust the processing gas from that of the third embodiment as excluding the gas exhaust system 9.
That is, the processing gas ejected from the processing gas nozzle 5 flows in two directions that are a direction toward the line 20 and a direction apart from the line 20. The processing gas flowing toward the line 20 reaches around the line 20 (dense plasma generation area 301) and pressure of the processing gas is increased. At this time, due to pressure difference between the dense plasma generation area 301 and the outlet duct 91, the processing gas flows from the dense plasma generation area 301 to the opening 422. Then, a natural flow of the processing gas from the lower end surface opening 402 of the hollow 40 toward the upper end surface opening 401 of the hollow 40 is formed. As a result, the processing gas is exhausted from the upper end surface opening 401.
The plasma processing apparatus 1 in the fourth embodiment may include an exhaust pipe to exhaust the exhausted processing gas to a predetermined place.

Fifth Embodiment

FIG. 6 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a fifth embodiment of the invention.
Here, the difference of the plasma processing apparatus in the fifth embodiment from the first embodiment will be mainly explained, and the same contents of them are omitted.
The plasma processing apparatus 1 in the fifth embodiment has the same configuration as that of the first embodiment other than including a cooling system 50 formed therein.
The cooling system 50 includes a refrigerant tank 501 storing and supplying a refrigerant, a refrigerant pipe 502, a coolant jacket 503 connected to the refrigerant pipe 502, a refrigerant outlet duct 504 exhausting the refrigerant from the coolant jacket 503, and a refrigerant recovery tank 505 recovering the refrigerant.
The refrigerant tank 501 stores a refrigerant to be used for cooling the first electrode 2.
As the refrigerant as above, various refrigerants can be used, and typically, water is used. Further, a substitute fluorocarbon refrigerant, an inorganic compound refrigerant such as ammono and carbon dioxide, an organic compound refrigerant such as isobutene can be used. These refrigerants may be used in combination of two or more.
The coolant jacket 503 is formed in the body 41 of the dielectric portion 4 so as to come in contact with an outer circumference surface of the first electrode 2. Further, the coolant jacket 503 is spirally formed around the first electrode 2 so as to surround it.
The coolant jacket 503 is formed so as to come in contact with the outer circumference surface of the first electrode 2 as above, assuredly cooling the first electrode 2.
An end side of the coolant jacket 503 is open in the top surface 411 of the body 41 and communicated with the refrigerant pipe 502. On the other hand, the other end side of the coolant jacket 503 is communicated with the refrigerant outlet duct 504 extending in a vertical direction inside of the body 41 on an outer circumference side of the coolant jacket 503 in a spiral shape.
The cooling system 50 as above is formed so as to regulate a temperature of the first electrode 2 generating heat by a discharge, stably generating plasma. As a result, the surface 101 of the workpiece 10 is processed at constant processing efficiency.
Next, an operation example of the cooling system 50 will be described.
Before operating the power source circuit 7, a refrigerant is send out from the refrigerant tank 501 to the refrigerant pipe 502. The refrigerant sent to the refrigerant pipe 502 flows at a predetermined mass flow in the coolant jacket 503, and then is recovered by the refrigerant recovery tank 505 passing through the refrigerant outlet duct 504. The refrigerant recovered can be used as a refrigerant again.
At this time, the refrigerant exchanges heat with the first electrode 2 while flowing in the coolant jacket 503, cooling the first electrode 2.
The coolant jacket 503 may be formed in the first electrode 2 similarly to the configuration described above.
Further, the cooling system 50 may be the hollow 40 having a reduced internal diameter. Reducing the internal diameter of the hollow 40 can suppress heat generation of the first electrode 2 by a discharge. Therefore, an adverse effect on the surface 101 of the workpiece 10 due to the heat generated by the discharge is prevented and suppressed.

Sixth Embodiment

FIG. 7 is a longitudinal sectional view schematically illustrating a configuration of a plasma processing apparatus according to a sixth embodiment of the invention.
In the following description, the top side in FIG. 7 is described as “upper”, while the bottom side is described as “lower”.
The difference of the plasma processing apparatus in the sixth embodiment from the first embodiment will be mainly explained, and the same contents of them are omitted.
The plasma processing apparatus 1 in the sixth embodiment has the same configuration as that of the first embodiment other than that three of the first electrodes 2 accommodated in the dielectric portion 4 are coupled in parallel, and the gas supply passages 6 formed between the first electrodes 2 are shared respectively between them.
In the plasma processing apparatus 1 in the sixth embodiment, as shown in FIG. 7, the first electrodes 2 are coupled to the power source 72 through the wiring line 71 so that each of them is electrically connected.
Further, the outlet duct 91 of the gas exhaust system 9 bifurcates, and each of them is coupled to the upper end surface opening 401.
Furthermore, the processing gas tube 84 of the gas exhaust system 9 bifurcates, and each of them is coupled to the gas introduction passage 61.
Each of the first electrodes 2 may be formed to be detachable so as to correspond to any kinds of the workpiece 10.
As the above, the plasma processing apparatus 1 having a plurality of the first electrodes 2 can form a plurality of the plasma generation areas 30 with respect to the number of the first electrodes 2. Therefore, the surface 101 of the workpiece 10 is extremely rapidly processed.
Further, as the plurality of the first electrodes 2 are included, it is possible to process any kinds of the workpiece 10, such as one having a large area.
While the plasma processing apparatus according to the invention has been described based on the illustrated embodiments as above, it is not intended to limit the invention. Each element of the plasma processing apparatus of the invention may be replaced with any other configurations having similar functions. In other instances, given elements can be added to the configurations described above.
The invention may also be a combination of arbitrary two or more configurations of the plasma processing apparatus according to the embodiments. For example, a combination of the configurations in the first and fourth embodiments, a combination of the configurations in the third and fifth embodiments, a combination of the configurations in the fourth and sixth embodiments and the like are possible.
Further, the moving unit to move the second electrode 3 may include, but it is not particularly limited to, various moving mechanisms, for example.
A power source for high frequency may be one to supply a direct current as long as it has a same potential.

Claims

1. A plasma processing apparatus, comprising:

a first electrode including a hollow penetrated through from an upper end thereof to a lower end thereof;

a workpiece stage to place a workpiece;

a second electrode arranged opposing to a lower end of the first electrode through the workpiece stage;

a processing gas nozzle formed on an outer circumference side of an opening at the lower end of the hollow along a circumferential direction;

a power source circuit including a power source applying a voltage between the first electrode and the second electrode; and

a gas supply system supplying a processing gas to generate plasma to the processing gas nozzle, wherein the plasma is generated by activating the processing gas that is ejected out of the processing gas nozzle and located around immediately below the opening at the lower end upon voltage application between the first electrode and the second electrode so as to process a surface of the workpiece by the plasma.

2. The plasma processing apparatus according to claim 1, wherein the processing gas ejected from the processing gas nozzle flows in a direction toward the opening at the lower end and in a direction apart from the opening at the lower end.

3. The plasma processing apparatus according to claim 1, wherein a flow of the processing gas from the opening at the lower end toward the upper end of the hollow is formed in the hollow.

4. The plasma processing apparatus according to claim 1, wherein the processing gas nozzle is intermittently formed on the outer circumference side of the opening along the circumferential direction.

5. The plasma processing apparatus according to claim 1, wherein the processing gas nozzle is formed in an annular shape around a whole circumference of the opening at the lower end.

6. The plasma processing apparatus according to claim 1, wherein the processing gas nozzle ejects the processing gas in a direction inclined toward an extended line of a line connecting the upper end and the lower end of the hollow.

7. The plasma processing apparatus according to claim 1, further comprising a gas exhaust system exhausting the processing gas ejected from the processing gas nozzle from the upper end of the hollow of the first electrode.

8. The plasma processing apparatus according to claim 7, wherein the gas exhaust system includes an outlet flow adjustment unit adjusting an amount of an outlet flow of the processing gas exhausted from the upper end of the hollow.

9. The plasma processing apparatus according to claim 8, wherein the outlet flow adjustment unit includes:

an outlet duct connected with the upper end of the hollow;

a valve opening and shutting a flow passage in the outlet duct; and

a pump formed on a downstream side of the outlet duct through the valve.

10. The plasma processing apparatus according to claim 1, further comprising a cooling system to cool off the first electrode.

11. The plasma processing apparatus according to claim 1, wherein the first electrode has a surface facing to the second electrode, at least the surface being covered with a dielectric portion.

12. The plasma processing apparatus according to claim 11, wherein the processing gas nozzle is formed on the dielectric portion.

13. The plasma processing apparatus according to claim 11, wherein the dielectric portion has an external diameter expanded more than an external diameter of the first electrode.

14. The plasma processing apparatus according to claim 1, wherein the first electrode is provided in a plurality of numbers.