JP4134077B2 - Microwave line plasma generator - Google Patents

Description

  This invention is intended to easily generate plasma, which is used for etching and cleaning processing in semiconductor processes, CVD processing of organic films, hydrophilic processing, sterilization processing of foods, etc. under relatively low pressure conditions such as atmospheric pressure. In particular, a line-shaped plasma generator suitable for plasma processing of a structure having a large area such as a large liquid crystal panel or a long film is provided.

Conventionally, a line plasma generator using such a microwave excites a gas by the propagation energy of the microwave traveling in a rectangular microwave waveguide, and converts this gas into a plasma. It is known that when a microwave travels in the longitudinal direction (rectangular length direction) of the wave tube, the plasma generation electric field strength in a direction perpendicular to the traveling direction (rectangular width direction) increases.
It is also known that the longer the propagation wavelength of the microwave in the waveguide, the higher the efficiency of the electromagnetic wave energy that contributes to the plasma formation in the longitudinal direction of the waveguide. The width can be increased by reducing the width of the waveguide. In the case of a commonly used microwave (wavelength 2.45 GH), when the width of the waveguide (lateral length) is changed from 61 mm to 62 mm, the propagation wavelength in the tube is the longest and the plasma excitation efficiency is maximized. I.e., the plasma discharge tube filled with gas for plasma generation can generate a strong linear plasma laterally by arranging transversely to the waveguide, the waveguide as described above Since the width is limited to about 61 to 62 mm, a longer line-shaped plasma cannot be obtained.
Therefore, the present inventors provided a slit in the side wall of the flat rectangular waveguide along the longitudinal direction of the waveguide (the propagation direction of the microwave), and the outside of the waveguide along the direction of the slit. Proposed a device that generates a line-shaped plasma in the vertical direction from a discharge tube by placing a vertically long plasma discharge tube close to each other and exciting the gas in the discharge tube by long-wavelength microwave electromagnetic energy radiated from a slit (Patent) Reference 1). As a result, even if the horizontal width of the waveguide is limited by the above, the vertical length can be freely increased, so that the line length of the plasma generated from the discharge tube can be sufficiently long, and a structure having a large area can be more efficiently formed. Plasma processing is now possible.
Japanese Patent Application No. 2004-159280

The present invention, the present inventors have invention further improves development of, as well as to be able to generate a more powerful line plasma, and provides a generic plasma source that can be easily carried in a compact.

In order to solve the above problems, the present invention provides a novel integrated coupling structure of a discharge tube for generating plasma and a rectangular microwave waveguide, and a flat rectangular waveguide for introducing microwaves. A vertically long opening is provided in a part of the casing surface of the tube along the microwave traveling direction, and a plasma discharge tube composed of a dielectric is formed in the vertically long opening, and a part of the outer wall of the discharge tube is a waveguide. The plasma generating gas is continuously introduced into the discharge tube so that the energy of the plasma generated in the discharge tube is extracted from the portion exposed from the waveguide of the discharge tube. A microwave line plasma generator characterized by comprising.

Preferred invention embodiments, the opening of the elongated along its longitudinal direction in the plasma discharge tube, to provide an arrangement for taking out the plasma generated in the plasma discharge tube from the elongated opening to direct plasma processing chamber.

Further, as another invention embodiment, the plasma discharge tube which is advanced into the waveguide by introducing both the reaction gas for plasma generation gas workpiece processing, using at the same time plasma both gas system I will provide a.

Furthermore, the embodiment of the present invention provides means for adjusting the vertical electric field intensity distribution in the waveguide so as to be uniform along the long axis direction of the discharge tube, and the variation in the generated plasma intensity in the line direction is provided. Can be easily adjusted, and a uniform and stable line-shaped plasma can be obtained in the length direction.
[Definition of terms]
In this specification, the plasma discharge tube means a tubular or vertically long casing made of a dielectric such as quartz, glass, or ceramic, and means a casing having a circular cross section, an ellipse, a square, or a polygon.
The plasma generation gas, helium, argon, xenon, krypton, fluorine, nitrogen, a gas containing at least one hydrogen means the likely gas plasma is generated by the action of the electromagnetic energy of the microwave.

According to the present invention, the plasma generation gas in the discharge tube, so to involve microwave electromagnetic energy propagating in the waveguide directly, by plasma efficiency along powerful plasma from increasing in the longitudinal direction of the waveguide In addition to being able to generate in a line, the waveguide and plasma discharge tube are made compact in an integrated manner, so it is easy to carry and a highly versatile plasma generation source can be provided.
Furthermore, since a means for adjusting the electric field strength distribution of the spatial waveguide portion directly related to the plasmaization of the gas in the discharge tube in the waveguide along the longitudinal direction of the tube is provided, the longitudinal direction of the waveguide and the discharge tube is provided. Variations in the intensity of the plasma line based on processing strain can be easily adjusted, and uniform and stable plasma can be generated in the length direction.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a basic configuration of a microwave generator according to the present invention. A microwave waveguide 1 is made of a conductor such as aluminum or brass, and is a flat rectangular cavity type having a vertical length y width a thickness b. In the waveguide, microwaves are introduced from the direction of the arrow MW and travel in the longitudinal direction in the tube. Reference numeral 2 denotes a vertically long opening provided on the flat plane (H surface) of the waveguide, and a plasma discharge tube 3 is loaded in a state where a part of the plasma discharge tube 3 enters the waveguide 1. This is the discharge tube is not shown is introduced gas for plasma generation, including helium argon from the direction of arrow Gin, always gas derived in the direction of arrow Gout flows. Reference numeral 4 denotes a vertically long opening provided in the exposed portion of the discharge tube, and the gas introduced into the discharge tube is excited by the electromagnetic energy of the microwave propagating in the waveguide in the vertical direction to be in a plasma state. Then, the gas is discharged from the opening 4 into the processing chamber outside the tube in a line along the longitudinal direction of the waveguide.

εは誘電率、μは透磁率である。（ｒは、真空の値に対しての比を表す。たとえば、ε_r、μ_rは、それぞれ比誘電率と比透磁率を表す。） In the figure, when the wavelength of the microwave introduced into the waveguide 1 is λo, the wavelength λg of the microwave propagating in the waveguide is as described in the above-mentioned patent application 2004-159280 of the present inventors. It is desirable to select the waveguide width a so that λg is longer than the plasma line length y ′.

ε is a dielectric constant, and μ is a magnetic permeability. (R represents the ratio to the vacuum value. For example, ε _r and μ _r represent the relative permittivity and the relative permeability, respectively.)

  When a commonly used microwave with a frequency of 2.45 GHz and a wavelength of 120 mm is fed into this waveguide, according to the above equation, when the waveguide width a is selected to be 61.3 mm, the microwave in the waveguide The wavelength λg is 2467 mm, and a sufficiently long wavelength microwave can be run in the vertical axis direction. That is, it is effective for generating a long line plasma along the vertical axis direction y.

  FIG. 2 is a side view of the basic configuration of FIG. 1, and a plasma processing chamber T for processing an object to be processed S such as a liquid crystal substrate by a microwave guiding portion into the waveguide 1 and the generated plasma gas. FIG.

A plasma discharge tube 3 is loaded in a vertically long opening provided on the H surface of a flat rectangular waveguide 1 so that a part of the plasma discharge tube 3 bites into the inside of the waveguide as shown in the figure, and propagates through the waveguide. A gas in a plasma state by microwave electromagnetic energy is radiated into the processing chamber T as indicated by a dotted arrow pg. G is a reaction gas supply nozzle for supplying a reaction gas to the object S to be processed. The plasma pg radiated to the processing chamber T further promotes the reaction gas to be plasma, and a wide portion of the object to be processed S can be processed at once.

In the figure, reference numeral 5 denotes a microwave generation source, 6 denotes a microwave guide tube, and 7 denotes an electromagnetic wave reflecting portion, which includes a movable reflector 8 for adjusting the wavelength of the reflected wave. The reflecting plate 8 is of a plunger type, and the microwave wavelength λg traveling in the waveguide can be finely adjusted by adjusting the position to the left and right, thereby making the plasma generation intensity in the entire length direction. It can be adjusted to be uniform throughout. Gin, Gout is introduced and derived piping system of the plasma generation gas into the same discharge pipe as in FIG.

FIG. 3 is a cross-sectional view of the waveguide 1 in the basic configuration apparatus of FIG. 1, showing cross sections perpendicular to the traveling direction of the microwaves, and (a), (b), (c), and (d) are the plasma discharge tube 3 and This is an embodiment in which the mode of coupling and loading with the waveguide 1 is made different.

FIG. 3A shows an embodiment in which about one third of the diameter of the plasma discharge tube 3 is inserted into the waveguide, and the microwave energy propagates through the periphery of the discharge tube in a direction perpendicular to the paper surface. . According to the experiments by the present inventors, it has been found that the plasma generation efficiency increases as the electric field strength in the k portion near the lower surface of the discharge tube increases, so that the microwave propagation propagates through the gap in the waveguide (k gap) in this portion. It was made small enough not to cause any trouble. That is, the thickness b1 inside the waveguide is designed to be a sufficient k if necessary.
FIG. 3B shows an embodiment in which the slit width on the H surface of the waveguide is slightly increased so that the plasma discharge tube is inserted into the waveguide by about half of its diameter. The thickness b2 of the waveguide is b1. Although slightly thicker, the plasma generation operation is the same as in FIG.

FIG. 3 (c) shows an embodiment in which the plasma discharge tube is a rectangular dielectric casing 3 ′, which is cut into the waveguide 1, and the operation of plasma generation is the same as (a) and (b). Absent.

FIG. 3D is an example in which the plasma discharge tube 3 is loaded on the side wall surface 1b of the waveguide, and is an example applicable when the plasma radiation direction needs to be taken out to the side.

FIG. 4 is an embodiment designed to increase the plasma generation efficiency by narrowing the gap k when the thickness b ′ of the waveguide cannot be reduced due to the microwave propagation conditions in the waveguide. Is the same as in the case of FIG. The figure shows a case where the plasma processing chamber T is arranged directly on the upper portion of the waveguide 1, and G is a reactive gas supply nozzle portion.

  3 and 4 show the example in which the plasma discharge tube is mounted on the upper wall surface (H surface) or the side wall surface of the waveguide. However, the discharge tube may be mounted on the lower surface of the waveguide. It is natural. Further, without providing an opening for gas emission in the discharge tube, the light energy (such as ultraviolet rays) of plasma generated in the discharge tube may be taken out to the processing chamber. In this case, the tube wall of the discharge tube is preferably made of a highly translucent dielectric (such as quartz glass).

FIG. 5 is an example in which the embodiment of FIG. 3 is further developed, and is an embodiment in which plasma discharge tubes 3 and 3 ′ are simultaneously loaded on the upper wall surface 1 a and the lower wall surface 1 c of the waveguide 1. By making the microwave input to the waveguide sufficiently strong and designing the field strength of the gap k to be sufficiently strong, plasma can be generated simultaneously in both the upper and lower directions. In this example, both discharge tubes are not provided with openings , but are made of a dielectric material having a good light transmission property, and light pf generated by plasma generated in the tubes can be directly used in the plasma processing chamber.

Next, FIG. 6, the plasma discharge tube 3 accommodating a gas for plasma generation is an example of accommodating through a slight gap 2 'to the longitudinal opening 2 of the waveguide 1.
Even if the discharge tube 3 is not airtightly attached to the opening 2 of the waveguide 1 as shown in the figure, the electric field strength at the gap k portion between the lower surface of the discharge tube and the inner surface of the waveguide is set to the optimum condition. As a result, plasma can be generated in a line shape in the discharge tube, and the plasma is emitted upward from the opening 4 as indicated by pg in the figure. Of course, also in this embodiment, it is possible to block the opening of the discharge tube and use plasma as light energy.

FIG. 7 shows an embodiment in which means for increasing the electric field strength in this portion is provided by substantially reducing the waveguide space gap k on the lower surface of the plasma discharge tube with the thickness b of the waveguide increased to some extent. is there. That is, a wall plate 9 of a second conductor is attached to the inside of the lower wall surface of the waveguide 1, and a central portion (a portion facing the lower surface of the discharge tube) 9a of this wall plate is recessed inward as shown in the figure. As a result, the electric field density, that is, the electric field strength in the gap k is increased while ensuring a sufficiently large microwave propagation volume. As a result, microwave electromagnetic energy acts strongly on the gas in the discharge tube, and high-density plasma can be generated.

  Reference numeral 10 denotes a conductive brush provided in a narrow space (gap portion k) on the lower surface of the discharge tube. By adjusting the vertical position of the brush 10 from the outside of the waveguide by the screw mechanism 11, the gap k is obtained. Finely adjust the electric field strength of the part. By providing a plurality of brush mechanisms in the direction perpendicular to the paper surface, that is, along the longitudinal direction of the discharge tube (the direction of y ′ in FIG. 2), the non-uniformity of the intensity in the line direction of the plasma generated from the discharge tube is reduced. Can be adjusted.

For example, if the processing accuracy of the inner wall surface of the waveguide varies in the length direction, or if the diameter of the plasma discharge tube and the material of the tube are not the same in the length direction, the degree of plasma excitation by the microwave is in the length direction. Therefore, the intensity of the generated plasma becomes non-uniform along the line. For example, if the intensity of the plasma generated from the discharge tube is weak near both ends of the tube, the electric field strength in this portion can be increased by adjusting the conductive brush in the lower gap near the both ends of the discharge tube closer to the discharge tube. Thus, the intensity of the generated line plasma can be made uniform in the axial direction as a whole.

Next, FIG. 8 shows another embodiment of the present invention, both introduced and reaction gas with a plasma generating gas into the plasma discharge tube 33, substantially at the same time excited to a plasma state both gas discharge tube This is an example.

  The discharge tube 33 is made of a dielectric material such as quartz or ceramic, and has an inverted U-shaped cross section as shown in the figure. For example, the discharge tube 33 is vertically long with a length y ′ of 800 mm to 1000 mm (such as a U-shaped side groove block). shape). B is a support block for supporting the waveguide 11, and gas introduction paths G1 and G2 for supplying gas to the discharge tube 33 are provided on the left and right.

G1 is a gas introducing path for plasma generation such as He and Ar, G2 is an introducing path for a reactive gas used for plasma processing of a workpiece such as an etching gas, and W is a cooling liquid for cooling the generated heat of the discharge tube by the plasma. It is a reflux path. This cooling liquid reflux path is to prevent the waveguide 11 and the discharge tube 33 and the support block B thereof from becoming hot due to the plasma heat in the discharge tube, and if necessary, between the waveguide and the tube G1 or the discharge. It may also be provided on the side of the tube.

The inverted U-shaped discharge tube 33 is held by the block B with its head portion 33 ′ entering the inside of the waveguide 11 as shown in the figure, and an opening 4 for plasma emission is provided below. . Reference numeral 12 denotes a portion (conductor) where the inner wall of the waveguide is expanded, which is an inner wall portion for increasing the electric field strength of the k portion, similar to 9a in FIG. S1 and S2 are gas diffusion baffle plates, the operation of which will be described in detail with reference to FIG.

As can be seen in the figure, to facilitate plasma generation by introducing He, the discharged without the easy deposition and etching gas i.e. plasma generating gas such as Ar from line G1 is closer to the waveguide, hardly discharged By introducing a reactive gas from the side closer to the opening 4, the plasma discharge tube can be prevented by preventing reaction (such as etching by etching) and alteration of the dielectric surface near the plasma excitation part (head part) due to the reactive gas. It can be protected, and stable discharge can be maintained.

9 is a cross-sectional view taken along the line II ′ of FIG. 8, and the left side view is partially omitted because the longitudinal length y of the waveguide 11 is longer than the thickness b. A plurality of gas introduction paths G1 and G2 are provided at equal intervals along the longitudinal axis of the support block B of the waveguide toward the side surface of the discharge tube 33, from which gas is introduced into the discharge tube. Other reference numerals denote the same members as those in FIG. Although the introduction part of the microwave to the waveguide 11 is omitted in the figure, it is applied from the left direction of the figure .

FIG. 10 is a cross-sectional view taken along the line II-II ′ in FIG.
Reference numeral 33 ″ in the figure denotes an opening for introducing a gas into the plasma discharge tube 33, which is provided in the side of the discharge tube in the form of a slit in the longitudinal direction. This slit is vertically elongated along both side surfaces of the discharge tube. In order to maintain the mechanical strength of the tube, it becomes a burrow-like opening row. Further, the gas introduction path G1 is provided with a widening portion in the vicinity of the gas introduction portion to the discharge tube as shown in FIG. G1 ′, and the gas introduced from G1 is diffused in the length direction of the discharge tube and discharged. It is introduced into the pipe. S1 and S2 are baffle plates arranged in the widened part G1 ′ of the gas introduction paths G1 and G2, that is, gas diffusion plates provided with a large number of holes. The flow of the gas introduced from the pipes G1 and G2 is changed in the discharge tube. It spreads in the vertical axis direction and is guided into the discharge tube.

In the present invention, since the purpose is to generate a uniform plasma in the longitudinal direction of the waveguide, it is important to make the gas flow as uniform as possible. Plasma generation gas in the present embodiment in order that also as uniformly introduced in the longitudinal direction from the side of the reaction gas also discharge tube, discharge in a state of being diffused gas longitudinally through the baffle plates S1, S2 Introduce evenly into the tube. By doing so, radicals generated by the plasma reaction can be made uniform, and uniform plasma stable in the longitudinal direction can be obtained. The other symbols indicate the same members as in FIGS.

In the above embodiment, the plasma generation gas in G1, has been described to be introduced to separate the reaction gases G2, may be simultaneously placed from both introduction path while mixing both gas, thus This improves gas mixing in the plasma discharge tube and contributes to plasma stabilization. Further, in addition to G1 and G2, gas introduction paths may be provided in three layers and four layers, and different types of reaction gases may be individually introduced into the respective pipelines.

Also in the case of not using the semiconductor and surface cleaning and food sterilization, particularly the reaction gas of the liquid crystal panel, G1, G2 or both to add plasma generation gas such as He or sequestering one reactive gas inlet pipe May be.

In the embodiment, since the microwave waveguide and the plasma discharge tube are operated near the atmospheric pressure, an airtight seal near the mounting portion between the waveguide and the discharge tube and the opening for extracting plasma is unnecessary. There is no complicated honey mechanism and inconvenience of handling like the conventional vacuum plasma generator.

  The waveguide used in the present invention introduces microwaves into the tube via a guide tube or the like, and if necessary, a high frequency coil is attached to the waveguide to additionally provide high frequency power. The electromagnetic wave energy in the waveguide may be strengthened.

Also blocked the opening of the plasma discharge tube with a dielectric in these examples, it is of course capable of using only the tube of the plasma light (such as ultraviolet light).

The line plasma generation apparatus of the present invention can generate a stable line-shaped plasma along the longitudinal direction of a rectangular waveguide, so that it is efficient even for an object to be processed having a large area in a short time. Thus, plasma processing and processing can be performed.
Furthermore, a portable plasma generator that can be used in an atmospheric pressure state and in which a plasma discharge tube and a microwave waveguide are integrally and compactly coupled and loaded is obtained, so that it can be used in food kitchens such as hotels, restaurants, and convenience stores. It can be easily used for sterilization and disinfection, and its industrial utility is extremely large.

It is a perspective view which shows the basic concept of the microwave generator of this invention. It is a side view for operation | movement description of the microwave generator of the Example of this invention comprised based on the basic concept of FIG. 2 is a cross-sectional view of the waveguide portion of the embodiment of FIG. 2 as viewed from a direction perpendicular to the paper surface, wherein (a), (b), (c), and (d) are various types of coupled loading of the waveguide and the plasma discharge tube. This is an example. It is sectional drawing similar to FIG. 2, and is an Example figure which shows another aspect of the coupling mechanism of a plasma discharge tube and a waveguide. FIG. 6 is a cross-sectional view similar to FIG. 2, showing an embodiment in which two plasma discharge tubes having no opening are mounted on the top and bottom of the waveguide. FIG. 3 is a cross-sectional view similar to FIG. 2 in another embodiment of the present invention. It is an Example of the mechanism which adjusts the electric field strength of the microwave waveguide applicable to each said Example of this invention. It is a sectional side view which shows the other Example of this invention. FIG. 9 is a view taken along the line I-I ′ of the embodiment of FIG. 8. FIG. 9 is a sectional view taken along the line II-II ′ of the embodiment of FIG. 8.

Explanation of symbols

1,11 microwave waveguide 2 waveguide opening wall surface provided with a longitudinal opening 3 and 33 plasma discharge tube 4 Vertical provided a plasma discharge tube 5 microwave source 6 microwave guide tube 7 microwave reflection Part 8 Movable reflector 9 Second wall plate (conductor) for adjusting electric field strength in the waveguide
10 Conductor brush 11 Screw mechanism 12 Convex part of conductor inner surface (conductor)
T Plasma processing chamber Z Reactant gas supply nozzle B into object G reaction chamber Gas guide path W to waveguide support block G1, G2 plasma discharge tube Coolant reflux path S1, S2 Gas diffusion member

Claims (8)

A part of the casing of a flat rectangular waveguide into which microwaves are introduced is provided with a vertically long opening along the microwave traveling direction, and a plasma discharge tube made of a dielectric is discharged into the opening. part of an outer wall of the tube is mounted so as to enter the interior of the waveguide, by continuously introducing the discharge tube to the plasma generation gas, the gas is excited into a plasma state in the discharge tube, the plasma microwave line plasma generating apparatus characterized by the energy generated is constructed as taken out from the portion exposed to the guiding tube outer of said discharge tube from. A longitudinally long opening of the waveguide is provided in a housing surface (H surface) on the flat surface side of the waveguide, and a part of the outer wall of the plasma discharge tube enters the waveguide along the longitudinally long opening. The microwave line plasma generator according to claim 1, wherein the microwave line plasma generator is mounted . A vertically long opening is provided in the tube wall portion of the plasma discharge tube exposed from the waveguide along the length direction of the plasma discharge tube, and plasma generated in the plasma discharge tube from the longitudinal opening is supplied to the plasma processing chamber. The microwave line plasma generator according to claim 1, wherein the microwave line plasma generator is configured to be extracted . To the plasma discharge tube, introducing a plasma generating gas and the reaction gas at the same time, the plasma generated in the plasma discharge tube according to claim 3, characterized by being configured to retrieve the plasma processing chamber from said elongated opening Microwave line plasma generator . A reactive gas discharge port G for plasma processing is provided in the vicinity of the outside of the plasma discharge tube , and the reactive gas is excited into a plasma state by plasma emitted from the discharge tube. Item 4. The microwave line plasma generator according to any one of Items 1 to 3 . In the waveguide, conductors 9 and 9a for adjusting the electric field strength of the constricted portion are provided in a space portion k where the waveguide formed between the plasma discharge tube and the inner surface of the waveguide is constricted. microwave line plasma generator according to any one of claims 1 to 5, characterized in that. The microwave line plasma generator according to claim 6 , further comprising means 11 for adjusting a relative position between the conductor and the plasma discharge tube . The constricted field strength adjusting conductor provided in the space between the plasma discharge tube and the waveguide surface, provided plurality along a longitudinal axis of the waveguide, the conductor and the plasma The electric field intensity distribution along the longitudinal direction of the waveguide can be made uniform by additionally providing means 11 for adjusting the position relative to the outer surface of the discharge tube from the outside of the waveguide. 1 to the microwave line plasma generator according to any one of 7.

Images