JP5478058B2 - Plasma processing equipment - Google Patents

Description

  The present invention relates to a plasma processing apparatus that plasmas a target object by exciting a gas with electromagnetic waves.

Among plasmas generated using electromagnetic waves, microwave plasma is generated by introducing microwaves into a processing chamber in a reduced pressure state through a dielectric plate (see, for example, cited document 1). In the microwave plasma processing apparatus, plasma electron density n _e is higher than the cut-off density n _c, the microwave can not enter into the plasma propagates between the dielectric plate and the plasma. During propagation, part of the microwave is absorbed by the plasma as an evanescent wave and used to maintain the plasma. Thus, the microwave propagating between the dielectric plate and the plasma is called, for example, a dielectric surface wave.

JP 2006-310794 A

When low-frequency electromagnetic waves are supplied to the plasma processing equipment, not only the dielectric surface wave that propagates between the dielectric plate and the plasma, but also the surface wave that propagates between the metal surface on the inner surface of the processing vessel and the plasma , Metal surface wave (conductor surface wave) is generated. MSW, the electron density of the plasma can not propagate lower than twice the cutoff density n _c. Since the cut-off density n _c is proportional to the square of the frequency of the electromagnetic wave, MSW low frequencies, can not propagate the electron density is not high. Furthermore, the metal surface wave has a characteristic that it is more difficult to attenuate as the frequency is lower.

At a frequency of 2450MHz, which is generally used in the generation of the plasma, not the value of the cut-off density _{n c} is 7.5 × ^{10 10 cm -3,} and the electron density of 1.5 × ¹⁰ 11 ^{cm -3} or more And metal surface waves do not propagate. For example, in a low density plasma with an electron density near the surface of about 1 × 10 ¹¹ cm ⁻³ , the metal surface wave does not propagate at all. Even when the electron density is higher, the propagation of metal surface waves is often not a problem because of the large attenuation. On the other hand, at a frequency of 915 MHz, for example, a metal surface wave propagates long on the inner surface of the processing chamber even in a low-density plasma having an electron density of about 1 × 10 ¹¹ cm ⁻³ near the surface.

  Therefore, when performing plasma processing using low-frequency electromagnetic waves, it is necessary to design an apparatus for controlling the propagation of not only dielectric surface waves but also metal surface waves. For example, if the distribution of standing waves of the metal surface wave formed on the metal electrode surface and the similar metal cover surface located in the vicinity of the metal electrode is different and the distribution is largely biased, the ceiling surface of the processing vessel In this case, the electric field energy distribution is biased. Further, when there is a step or a groove between the metal electrode and the metal cover, a state in which the gas does not easily flow and remains in the vicinity is generated, and unstable plasma is generated. In addition, when the dielectric plate or metal electrode is fixed to the ceiling surface of the processing vessel with a screw, an uncontrollable gap is created in the microwave transmission path, and the reflection of the microwave from the plasma side is increased, and the microwave energy is increased. There may be a case where the supply efficiency deteriorates. Since these affect the uniformity and stability of the plasma, it is possible to stably generate a uniform plasma by optimizing the shape, size, location and design of the metal electrode and its surroundings. Is required.

  Therefore, the present invention provides a plasma processing apparatus in which the metal electrode and its peripheral configuration are optimized in order to control the propagation of surface waves.

In order to solve the above-described problems, according to an aspect of the present invention, a processing container that excites a gas to plasma-treat a target object and an electromagnetic wave that is provided outside the processing container and outputs an electromagnetic wave A plurality of dielectric plates provided adjacent to a ceiling surface made of metal in the processing container and emitting the electromagnetic waves output from the electromagnetic wave source into the processing container, and a plasma side of each dielectric plate A plurality of rhombus-shaped metal electrodes that are provided one-to-one adjacent to each dielectric plate on the surface and expose a part of each dielectric plate from the periphery to the inside of the processing vessel, and each metal A length relative to the length of the short side of the cell region, which is defined by two straight lines parallel to the two diagonal lines of the electrode, and a minimum rectangular region including each metal electrode and each dielectric plate is defined as a cell region. Each metal so that the ratio of side lengths is 1.2 or less It identified the shape of electrode and the dielectric plate, the electromagnetic wave from the exposed was obtained portions of the dielectric plate, parts of the dielectric plate surface and the ceiling surface of the metal electrode is not provided A plasma processing apparatus is provided that is divided into a metal surface and propagates as a metal surface wave .

  According to this, the electromagnetic wave output from the electromagnetic wave source is transmitted through the dielectric plate from the peripheral edge of the diamond-shaped metal electrode provided adjacent to the ceiling surface in the processing container, and is emitted into the processing container. The metal electrode and the dielectric plate are virtual regions that divide the ceiling surface of the processing container, and are defined by two straight lines parallel to two diagonal lines of the metal electrode, and the metal electrode and the dielectric plate The smallest rectangular region including the body plate is defined as a cell region (see FIG. 2), and the metal electrode and the metal electrode are arranged so that the ratio of the long side length to the short side length of the cell region is 1.2 or less. The shape of the dielectric plate is specified.

  In order to generate a uniform plasma, it is desirable that the distribution of standing waves of the metal surface wave formed on the surface of the metal electrode and the surface of the metal cover is the same, and that there is no large deviation in the respective distributions. When the cell is square, standing waves having the same pattern are formed on the surface of the metal electrode and the surface of the metal cover. This is because metal surface waves having the same phase and the same intensity are supplied from corresponding positions around the metal electrode and the metal cover.

  On the other hand, when the cell is rectangular, standing waves having different patterns are formed on the metal electrode surface and the metal cover surface. This is because the phase and intensity of the metal surface wave supplied from the corresponding positions around the metal electrode and the metal cover do not match. Thus, when the symmetry of the standing wave of the metal surface wave formed on the metal electrode surface and the metal cover surface is poor, it is difficult to control the uniformity and it is difficult to excite uniform plasma. In order to generate a uniform plasma that can withstand practical use, the average value of the electric field intensity ratio of the metal surface wave at the corresponding position on the metal electrode surface and the metal cover surface is 1.5 or less, more preferably 1.1 or less. It is desirable that

  FIG. 4 shows the relationship between the aspect ratio of the cell and the electric field strength ratio of the metal surface wave at the corresponding position. This is a result of calculation by electromagnetic field simulation. According to this, in order to make the electric field strength ratio 1.5 or less, the cell aspect ratio should be 1.2 or less. Thereby, the distribution of the standing wave of the metal surface wave formed on the surface of the metal electrode and the surface of the metal cover can be made the same or approximate, and a state where each distribution is not biased can be maintained. As a result, uniform plasma can be generated.

  In order to make the electric field strength ratio 1.1 or less, it is more preferable that the aspect ratio of the cell is 1.1 or less. According to this, furthermore, the distribution of the standing wave of the metal surface wave between the metal electrode and the metal cover can be made the same or approximate, and the unevenness of each distribution can be reduced to generate a more uniform plasma. Can do.

In order to solve the above-described problem, according to another aspect of the present invention, a processing vessel that excites a gas inside to plasma-treat a workpiece, and is provided outside the processing vessel and outputs an electromagnetic wave. An electromagnetic wave source, a plurality of dielectric plates provided adjacent to the ceiling surface in the processing container, and emitting electromagnetic waves output from the electromagnetic wave source into the processing container, and a plasma side surface of each dielectric plate A plurality of metal electrodes that are provided one-to-one adjacent to each dielectric plate and expose a part of each dielectric plate from the periphery to the inside of the processing vessel, and each dielectric on the ceiling surface of the processing vessel A plurality of metal covers that are the same as or similar to each metal electrode, and are provided with a filling dielectric in a groove between each metal electrode and each metal cover; The electromagnetic wave is generated from the exposed portion of each dielectric plate. The plasma processing apparatus propagates as each MSW divided into a surface and the surface of the metal cover of each metal electrode.

  According to this, the electromagnetic wave output from the electromagnetic wave source is provided adjacent to the ceiling surface in the processing container, and is transmitted into the processing container through the dielectric plate from the periphery of the metal electrode. A metal cover having the same or similar shape as the metal electrode is provided on the ceiling surface of the processing vessel not provided with the dielectric plate, and a filling dielectric is provided between the metal electrode and the metal cover. .

  In the groove (gap) between the metal electrode and the metal cover, gas does not flow easily and is likely to stop. For example, in the plasma cleaning process, it is difficult for the cleaning gas to enter the gap, and it is difficult to remove the film adhering to the inner surface of the gap. In addition, since the groove portion is surrounded by walls in three directions, the electron density of the plasma tends to decrease, and it is difficult to maintain a plasma with a stable density. Since the metal surface wave is supplied from the dielectric plate exposed between the metal electrode and the metal cover, if the plasma with a stable density is not maintained in this part, the entire plasma becomes unstable and non-uniform. turn into. In contrast, in the present invention, these problems can be solved by filling the groove between the metal electrode and the metal cover with a dielectric.

In order to solve the above-described problem, according to another aspect of the present invention, a processing vessel that excites a gas inside to plasma-treat a workpiece, and is provided outside the processing vessel and outputs an electromagnetic wave. An electromagnetic wave source, a plurality of dielectric plates provided adjacent to the ceiling surface in the processing container, and emitting electromagnetic waves output from the electromagnetic wave source into the processing container, and a plasma side surface of each dielectric plate A plurality of metal electrodes that are provided one-to-one adjacent to each dielectric plate and expose a part of each dielectric plate from the periphery to the inside of the processing vessel, and each dielectric on the ceiling surface of the processing vessel Conductive protrusions that are the same as or similar to each metal electrode, and a filling dielectric is provided in a groove between each metal electrode and the protrusion. the electromagnetic waves from the exposed was obtained portions of the dielectric plates, each metal The plasma processing apparatus propagates as each MSW divided into a pole of the surface the surface of the convex portion is provided.

  Also by this, by filling the space between the metal electrode and the convex portion with a dielectric material, it is possible to stably generate uniform plasma by eliminating a space in which gas does not flow easily and stays.

Around each of the metal electrodes, Sa Idokaba is provided, the electromagnetic waves from said exposed was obtained portions, respectively MSW divided into a surface and the surface of the side cover of the metal electrodes of each dielectric plate And the filling dielectric may be provided in a groove between each metal electrode and the side cover.

The filling dielectric may be disposed so as to be buried in a groove between each metal electrode and the protrusion, to flatten the groove, or to protrude from the groove. Good.

The filling dielectric may be disposed so as to surround the outer periphery of each metal electrode, and may have a portion protruding from the groove.

The filling dielectric may protrude from the groove at least near the center of each side of each metal electrode.

Wherein the projecting portion of the filling dielectric, protruding near the middle of each side of each metal electrode may be larger than the projection near the apex of each metal electrode.

The protruding portion of the filling dielectric may be formed point-symmetrically with respect to the center of each metal electrode.

The filling dielectric may be made of the same material as each dielectric plate.

In order to solve the above-described problem, according to another aspect of the present invention, a processing vessel that excites a gas inside to plasma-treat a workpiece, and is provided outside the processing vessel and outputs an electromagnetic wave. An electromagnetic wave source, a plurality of dielectric plates provided adjacent to the ceiling surface made of metal in the processing container, and emitting electromagnetic waves output from the electromagnetic wave source into the processing container, and plasma of each dielectric plate A plurality of metal electrodes that are provided one-to-one adjacent to each dielectric plate on the side surface and expose a part of each dielectric plate from the periphery to the inside of the processing vessel, and each metal electrode is The plurality of first screws and a plurality of second screws different from the plurality of first screws are fixed to the ceiling surface in the processing container, and the plurality of first screws are arranged at the center of each metal electrode. The metal electrodes are fixed at positions symmetrical with respect to each other, and the plurality of The second screw are arranged in mutually point-symmetric positions with respect to the center of each metal electrodes, and each metal electrode is fixed at the position different from positions of the plurality of first screw, the electromagnetic wave, each dielectric Provided is a plasma processing apparatus that divides from the exposed portion of the body plate into a surface of each metal electrode and a metal surface of the ceiling surface where each dielectric plate is not provided, and propagates as a metal surface wave respectively. Is done.

  According to this, the electromagnetic wave output from the electromagnetic wave source is provided adjacent to the ceiling surface in the processing container, and is transmitted into the processing container through the dielectric plate from the periphery of the metal electrode. The metal electrode is fixed to the ceiling surface in the processing container by a plurality of first screws and a plurality of second screws of a different type from the first screws.

  At the time of fixing, the metal electrode is fixed to the processing container by a plurality of first screws at a position where the distance from the center of the metal electrode is equal and equally spaced, with the dielectric sandwiched therebetween, and the metal electrode Are fixed to the processing container by a plurality of second screws at a position equal to the center of the first screw and at a position different from the positions of the four first screws.

  In this way, the metal electrode is fixed without electrical and mechanical bias by two types of screws provided point-symmetrically with respect to the center of the metal electrode. As a result, there is no gap in the dielectric that is the microwave transmission path, and the microwave wavelength and propagation speed do not change, so there is no difference in the actual impedance change from the design value, and the microwave from the plasma side Wave reflection can be reduced, and microwave energy supply efficiency can be improved. In particular, the unevenness of the electric field strength distribution of the metal electrode can be reduced depending on the diameter and position of the screw, and uniform plasma can be stably generated. Further, the heat on the plasma side can be released to the lid body 300 side through a plurality of screws.

  The diameter of the plurality of first screws may be smaller than the diameter of the plurality of second screws.

Four said 1st screws may be used with respect to one metal electrode, and may be located on the diagonal of each metal electrode.

The plurality of second screws may be used for one metal electrode, and may be located closer to the center of each metal electrode than the four first screws.

The shape of each metal electrode is square, the four second screw, respectively from the two first screw adjacent ones of the four first screw provided at equal intervals in equally spaced positions It may be provided. Moreover, the front end surfaces of the plurality of first screws and the plurality of second screws may be flush with the lower surface of each metal electrode. Further, a gas flow path may be provided in the plurality of first screws.

Each dielectric plate may be exposed on the ceiling surface in the processing container in a substantially band shape on the outer periphery of each metal electrode.

When the minimum rectangular area defined by two straight lines parallel to the two diagonal lines of each metal electrode and including each metal electrode and each dielectric plate is defined as a cell area, the length of the adjacent cell areas Each dielectric plate and each metal electrode may be regularly arranged so that the sides or the short sides coincide with each other and overlap each other . Moreover, it is preferable that the surface of the metal electrode on the plasma side is flat.

  As described above, according to the present invention, the propagation of the surface wave can be controlled by optimizing the configuration of the metal electrode and its periphery.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, the same reference numerals are given to the constituent elements having the same configuration and function, and redundant description is omitted.

(Configuration of plasma processing equipment)
First, the configuration of a microwave plasma processing apparatus (MSEP: Metal Surface Excitation Plasma) according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 schematically shows a longitudinal sectional view of the apparatus. FIG. 1 shows a 2-OO′-2 cross section of FIG. FIG. 2 is a ceiling surface of the microwave plasma processing apparatus 10 and shows a cross section 1-1 of FIG.

(Outline of microwave plasma processing equipment)
As shown in FIG. 1, the microwave plasma processing apparatus 10 includes a processing container 100 for plasma processing a glass substrate (hereinafter referred to as “substrate G”). The processing container 100 includes a container body 200 and a lid body 300. The container body 200 has a bottomed cubic shape with an upper portion opened, and the opening is closed by a lid 300. The lid body 300 includes an upper lid body 300a and a lower lid body 300b. An O-ring 205 is provided on a contact surface between the container main body 200 and the lower lid body 300b, whereby the container main body 200 and the lower lid body 300b are hermetically sealed to define a processing chamber. An O-ring 210 and an O-ring 215 are also provided on the contact surface between the upper lid body 300a and the lower lid body 300b, whereby the upper lid body 300a and the lower lid body 300b are sealed. The container body 200 and the lid body 300 are made of a metal such as an aluminum alloy, for example, and are electrically grounded.

  A susceptor 105 (stage) for placing the substrate G is provided inside the processing container 100. Susceptor 105 is made of, for example, aluminum nitride. The susceptor 105 is supported by a support 110, and a baffle plate 115 for controlling the gas flow in the processing chamber to a preferable state is provided around the susceptor 105. A gas exhaust pipe 120 is provided at the bottom of the processing container 100, and the gas in the processing container 100 is exhausted using a vacuum pump (not shown) provided outside the processing container 100.

  1 and 2, the metal electrode 310 and the metal cover 320 are regularly arranged on the ceiling surface of the processing container 100. The eight metal electrodes 310 are regularly arranged on the ceiling surface in the processing container so that the apexes of the adjacent metal electrodes 310 are closest to each other. The three metal covers 320 are respectively provided on portions where the metal electrode 310 is not provided, and are regularly arranged on the ceiling surface in the processing container so that the vertex of the metal cover 320 is closest to the vertex of the adjacent metal electrode 310. Is done. A side cover 350 that covers the metal electrode 310 and the metal cover 320 is provided on the outer periphery of the eight metal electrodes 310.

  The metal electrode 310 is provided adjacent to the dielectric plate 305 on the plasma-side surface (lower surface) of the dielectric plate 305 and exposes a part of the dielectric plate 305 from the periphery to the inside of the processing vessel 100. It is a flat plate. Here, the rhombus is a quadrilateral whose four sides are equal in length, and includes a square.

  The dielectric plate 305 is an octagonal flat plate that is slightly larger than the metal electrode 310 and has a corner near the apex of the metal electrode 310. The dielectric plate 305 is provided adjacent to the ceiling surface in a state sandwiched between the ceiling surface in the processing container and the metal electrode 310, and is substantially strip-shaped on the ceiling surface in the processing container on the outer periphery of the metal electrode 310. Exposed. The dielectric plate 305 emits the microwave output from the microwave source 900 from the band-shaped portion into the processing container.

  The eight dielectric plates 305 and the metal electrodes 310 are arranged at an equal pitch at a position inclined by approximately 45 ° with respect to the substrate G and the processing container 100. The pitch is determined such that the diagonal length of one dielectric plate 305 is 0.9 times or more the distance between the centers of adjacent dielectric plates 305. Thereby, the slightly cut corners of the dielectric plate 305 are arranged adjacent to each other.

  The metal cover 320 is provided on a portion of the ceiling surface of the processing container 100 where the dielectric plate 305 is not provided, and is the same as or similar to the metal electrode 310. The metal cover 310 and the metal cover 320 are thicker by the thickness of the dielectric plate 305. A groove between the metal electrode 310 and the metal cover 320 is filled with a filling dielectric 315. According to such a shape, the height of the ceiling surface becomes substantially equal, and at the same time, the dent of the portion where the dielectric plate 305 is exposed is filled, and the metal electrode 310 and the periphery thereof are repeated in substantially the same pattern.

  The dielectric plate 305 is made of alumina, and the metal electrode 310, the metal cover 320, and the side cover 350 are made of an aluminum alloy. In this embodiment, the eight dielectric plates 305 and the metal electrodes 310 are arranged in four rows in two rows. However, the present invention is not limited to this, and the increase in the number of the dielectric plates 305 and the metal electrodes 310 is also reduced. You can also.

  Referring to FIG. 2, the dielectric plate 305 and the metal electrode 310 are fixed to the lid body 300 by a first screw 380 and a second screw 390. Similarly, the metal cover 320 and the side cover 350 are fixed to the lid 300 by the first screw 380 and the second screw 390. A main gas flow path 330 is provided between the upper lid body 300a and the lower lid body 300b. The main gas flow path 330 divides the gas into the first gas flow paths 325 a provided in the plurality of first screws 380. A narrow tube 335 that narrows the flow path is fitted into the inlet of the first gas flow path 325a. The thin tube 335 is made of ceramics or metal. A second gas flow path 310a1 is provided between the metal electrode 310 and the dielectric plate 305. Second gas flow paths 320 a 1 and 320 a 2 are also provided between the metal cover 320 and the lid 300 and between the side cover 350 and the lid 300. The tip surfaces of the first screw 380 and the second screw 390 are flush with the lower surfaces of the metal electrode 310, the metal cover 320, and the side cover 350 so as not to disturb the plasma distribution. The first gas discharge holes 345a opened in the metal electrode 310 and the second gas discharge holes 345b1 and 345b2 opened in the metal cover 320 and the side cover 350 are opened downward at an equal pitch. The first screw 380 and the second screw 390 may be integrated with the metal electrode 310, the metal cover 320, and the side cover 350.

  The gas output from the gas supply source 905 passes through the first gas flow path 325a (branch gas flow path) from the main gas flow path 330, and the second gas flow path 310a1 and the metal cover 320 in the metal electrode 310. The first gas discharge hole 345a and the second gas discharge holes 345b1 and 345b2 are supplied to the processing chamber through the second gas flow paths 320a1 and 320a2 in the side cover 350. An O-ring 220 is provided on the contact surface between the lower lid 300 b and the dielectric plate 305 in the vicinity of the outer periphery of the first coaxial waveguide 610, and the atmosphere in the first coaxial waveguide 610 is placed inside the processing container 100. It is designed not to enter.

  In this way, by forming the gas shower plate on the metal surface of the ceiling portion, it has been possible to suppress the etching of the dielectric plate surface caused by ions in the plasma and the deposition of reaction products on the inner wall of the processing vessel, It is possible to reduce contamination and particles. Further, unlike a dielectric, a metal can be easily processed, so that the cost can be greatly reduced.

  An inner conductor 610a is inserted into the outer conductor 610b of the first coaxial waveguide formed by digging the lid 300. Similarly, the inner conductors 620a to 640a of the second to fourth coaxial waveguides are inserted into the outer conductors 620b to 640b of the second to fourth coaxial waveguides formed by digging the lid body 300, and the upper portions thereof Is covered with a lid cover 660. The inner conductor of each coaxial tube is made of copper with good thermal conductivity.

  Microwaves are supplied from the microwave source 900 and are supplied from the fourth coaxial waveguide (inner / outer conductors 640a and 640b) through the third coaxial waveguide (inner and outer conductors 630a and 630b) to the first coaxial waveguide (inner and outer conductors 610a and 610b). ) And the second coaxial waveguide (inner and outer conductors 620a and 620b). The surface of the dielectric plate 305 is covered with a metal film 305a except for a portion where the microwave is incident on the dielectric plate 305 from the first coaxial waveguide 610 and a portion where the microwave is emitted from the dielectric plate 305. Yes. Accordingly, the propagation of the microwave is not disturbed by the gap generated between the dielectric plate 305 and the adjacent member, and the microwave can be stably guided into the processing container.

  The microwaves emitted from the dielectric plate 305 are propagated through the surfaces of the metal electrode 310, the metal cover 320, and the side cover 350 while being equally divided into electric power as surface waves. Hereinafter, the surface wave propagating between the metal surface on the inner surface of the processing vessel and the plasma is referred to as a metal surface wave. Thereby, a metal surface wave propagates to the entire ceiling surface, and uniform plasma is stably generated below the ceiling surface of the microwave plasma processing apparatus 10 according to the present embodiment.

  The side cover 350 is formed with an octagonal groove 340 so as to surround the entire eight dielectric plates 305, and metal surface waves propagating on the ceiling surface are prevented from propagating outside the groove 340. To do. A plurality of grooves 340 may be formed in multiple in parallel. A convex portion may be provided instead of the groove 340. The groove 340 and the convex part are examples of the propagation obstacle part.

  A region having the center point of the adjacent metal cover 320 around the metal electrode 310 as a center is hereinafter referred to as a cell region Cel (see FIG. 2). On the ceiling surface, the same pattern configuration is regularly arranged for eight cells with the cell region Cel as a unit.

  The refrigerant supply source 910 is connected to the refrigerant pipe 910a inside the lid, and the refrigerant supplied from the refrigerant supply source 910 circulates in the refrigerant pipe 910a inside the lid and returns to the refrigerant supply source 910 again. The processing container 100 is kept at a desired temperature. A refrigerant pipe 910b passes through the inner conductor 640a of the fourth coaxial waveguide in the longitudinal direction. Heating of the internal conductor 640a is suppressed by passing the coolant through this flow path.

  It is desirable that there is no gap between the dielectric plate 305 and the lid 300 or between the dielectric plate 305 and the metal electrode 310. This is because if there is an uncontrolled gap, the wavelength of the microwave propagating through the dielectric plate 305 becomes unstable, which affects the plasma uniformity and the load impedance viewed from the coaxial tube. In addition, if there is a large gap (0.2 mm or more), there is a possibility of discharging in the gap. Therefore, when the nut 435 is tightened, the dielectric plate 305 and the lower lid 300b and the dielectric plate 305 and the metal electrode 310 are in close contact with each other.

  If the nut 435 is tightened with an excessive torque, the dielectric plate 305 may be stressed and cracked. In addition, even when the nut 435 is tightened, there is a risk of cracking due to stress when plasma is generated and the temperature of each part rises without cracking. For this reason, the metal electrode 310 can always be lifted through the first screw 380 with an appropriate force (a force slightly larger than the force that closes the dielectric plate 305 and the lower lid 300b by crushing the O-ring 220). A wave washer 430b having an optimal spring force is inserted between the nut 435 and the lower lid 300b so as to be able to do so. When the nut 435 is tightened, the deformation amount is constant without being tightened until the wave washer 430b becomes flat.

  A washer 430a is provided between the nut 435 and the wave washer 430b, but may or may not be present. Further, a washer 430c is provided between the wave washer 430b and the lower lid 300b. Usually, there is a gap between the first screw 380 and the lid 300, and the gas in the main gas flow path 330 flows to the first gas flow path 310a through this gap. When this uncontrolled gas flow rate is large, there is a problem that the gas discharge from the first gas discharge hole 345a becomes non-uniform. Therefore, the gap between the washer 430c and the first screw 380 is reduced, and the thickness of the washer 430c is increased to suppress the flow rate of the gas flowing through the outside of the first screw 380.

  Next, in order to control the propagation of the metal surface wave in the microwave plasma processing apparatus 10 described above, the point that the configuration of the metal electrode 310 and its periphery is optimized will be described in more detail. The first is that the aspect ratio of the cell region Cel is optimized. The second point is that a filling dielectric 315 is embedded in a groove between the metal electrode 310 and the metal cover 320 or the like. The third point is that the type and shape of the screw for fixing the metal electrode 310, the fixing position, etc. are optimized.

<Aspect ratio of cell>
First, the point that the aspect ratio of the cell region Cel is optimized will be described. As shown in FIG. 2, the cell region Cel is a virtual region that divides the ceiling surface of the processing container 100, and is defined by two straight lines parallel to the two diagonal lines D <b> 1 and D <b> 2 of the metal electrode 310. A minimum rectangular region including the metal electrode 310 and the dielectric plate 305.

  In order to generate uniform plasma, it is desirable that the distribution of standing waves of the metal surface wave formed on the surface of the metal electrode and the surface of the metal cover is the same, and that there is no significant bias in the distribution. Therefore, the shapes of the metal electrode 310 and the dielectric plate 305 are specified so that the ratio of the length of the long side to the length of the short side of the cell region Cel is 1.2 or less.

  When the cell is square, standing waves having the same pattern are formed on the surface of the metal electrode and the surface of the metal cover. This is because metal surface waves having the same phase and the same intensity are supplied from corresponding positions around the metal electrode and the metal cover. FIG. 3 is a simulation result showing standing wave patterns of metal surface waves formed on the surface of the metal electrode 310 and the surface of the metal cover 320. The white part is the part where the electric field is strong, and the black part is the part where the electric field is weak. Only the upper right 1/4 portion of the metal electrode 310, the lower left 1/4 portion of the metal cover 320, and the dielectric plate 305 portion therebetween are shown.

  On the surface of the metal electrode, there are antinodes of standing waves at positions A1, B1, and C1 in FIG. On the other hand, antinodes of standing waves having the same intensity as those on the surface of the metal electrode are seen at the positions of the metal cover surface corresponding to these, A2, B2, and C2.

  On the other hand, when the cell is rectangular, standing waves having different patterns are formed on the surface of the metal electrode and the surface of the metal cover as shown in FIG. This is because the phases and intensities of the metal surface waves supplied from corresponding positions around the metal electrode 310 and the metal cover 320 do not match.

  In the positions A1, B1, and C1 of the standing wave antinodes on the metal electrode surface and the corresponding positions A2, B2, and C2 of the antinodes on the metal cover surface, the electric field at A2 is weaker than A1, and at B2. It can be seen that the electric field is stronger than B1, and the electric field at C2 is weaker than C1.

  Thus, when the symmetry of the standing wave of the metal surface wave formed on the metal electrode surface and the metal cover surface is poor, it is difficult to control the uniformity and it is difficult to excite uniform plasma. In order to generate a uniform plasma that can withstand practical use, the average value of the electric field intensity ratio of the metal surface wave at the corresponding position on the metal electrode surface and the metal cover surface is 1.5 or less, more preferably 1.1 or less. It is desirable that

  FIG. 4 shows the relationship between the aspect ratio of the cell and the electric field strength ratio of the metal surface wave at the corresponding position. This is a result of calculation by electromagnetic field simulation. The vertical axis represents the value of the metal field 310 and the metal cover 320 having the highest electric field intensity at the position of A1 (A2), B1 (B2), and C1 (C2) as the smaller value. The divided ratio is averaged for A, B, and C. When the cell was a square (when the aspect ratio was 1), the length of one side of the cell was 214 mm. When the aspect ratio is other than 1, the aspect ratio is changed while keeping the cell area constant.

  When the cell is a square (when the aspect ratio is 1), the electric field strength ratio is 1 because the electric field strength of the metal surface wave at the corresponding position is the same everywhere. It can be seen that the field strength ratio increases as the aspect ratio of the cell increases.

  From the results of FIG. 4, it can be seen that the cell aspect ratio should be 1.2 or less in order to make the field strength ratio 1.5 or less. Thereby, distribution of the standing wave of the metal surface wave formed on the metal electrode surface and the metal cover surface can be made the same or approximate. As a result, each distribution is not greatly biased, and uniform plasma can be generated.

  Further, it can be seen that the cell aspect ratio should be 1.1 or less in order to make the electric field strength ratio 1.1 or less. According to this, the distribution of the standing wave of the metal surface wave formed on the surface of the metal electrode and the surface of the metal cover can be made more identical or approximate. As a result, each distribution is not greatly biased, and uniform plasma can be generated.

<Embedding dielectric for filling>
Next, the point that the filling dielectric 315 is embedded between the metal electrode 310 and the metal cover 320 will be described.

  In the groove part Gap between the metal electrode 310 and the metal cover 320 shown in FIG. 5A, gas hardly flows and is likely to stay. For example, in the plasma cleaning process, there is a problem that the cleaning gas does not easily enter the gap and the film attached to the inner surface of the gap is difficult to remove.

  In addition, since the groove-shaped gap is surrounded by walls in three directions, the electron density of the plasma tends to decrease, and it is difficult to maintain a plasma with a stable density. Since the metal surface wave is supplied from the dielectric plate 305 between the metal electrode 310 and the metal cover 320 or the side cover 350, the plasma as a whole is not effective unless a stable and stable plasma is maintained in this portion. There is a problem that it becomes stable and non-uniform.

  Further, the microwave transmitted through the dielectric plate 305 propagates separately on the surface of the metal electrode and the surface of the metal cover. However, in the groove portion Gap shown in FIG. 5B, the intensity of the electric field E applied to the sheath region S is increased. There is a problem that bias is likely to occur and there is a difference in energy distribution between the metal surface wave MS1 propagating on the surface of the metal electrode 310 and the metal surface wave MS2 propagating on the surface of the metal cover 320 or the side cover 350.

  In contrast, as shown in FIG. 1, in the microwave plasma processing apparatus 10 according to the present embodiment, the filling dielectric 315 is embedded in the groove portion Gap. As a result, there is no groove and the space between the metal electrode 310 and the metal cover 320 or the side cover 350 becomes flat. According to this, there is no space where the cleaning gas is difficult to enter, cleaning efficiency is increased, and maintenance is facilitated. In addition, there is no space for generating unstable plasma with undefined density, so that abnormal discharge can be prevented and uniform plasma can be generated stably. Furthermore, as shown in FIG. 6A, since microwaves are supplied into the processing container via the filling dielectric 315, the sheath region S and the metal cover (from the filling dielectric 315 to the metal electrode side) Alternatively, the intensity of the electric field E applied to the sheath region on the side cover side is less likely to be biased, and the metal surface wave MS1 propagating on the surface of the metal electrode 310 and the metal surface wave propagating on the surface of the metal cover 320 (or side cover 350). Energy is equally distributed to MS2. As a result, uniform plasma is stably generated.

  In FIG. 6A, the filling dielectric 315 is disposed so as to flatten the groove between the metal electrode 310 and the side cover 350 (or the metal cover 320). However, the filling dielectric 315 may protrude from the groove as shown in FIG. Moreover, as shown in FIG.6 (c), you may be buried in the said groove | channel. In either case, it can function to prevent gas from staying around the metal electrode and stably maintain a uniform plasma. In FIG. 6C, a convex portion 300c that is the same as or similar to the metal electrode 310 is provided in a portion of the ceiling surface of the processing vessel (lid body 300) where the dielectric plate 305 is not provided. A filling dielectric 315 is provided between the portion 300 c and the metal electrode 310. The dielectric plate 305 and the filling dielectric 315 may be integrated.

  FIG. 7 shows one metal electrode 310 and its periphery. The end of the metal electrode 310 is chamfered and provided with an inclination. The filling dielectric 315 is a frame-like member disposed on the lower surface (plasma side surface) of the dielectric plate 305 exposed from the periphery of the metal electrode 310 so as to surround the outer periphery of the metal electrode 310. The outer periphery of the filling dielectric 315 is the same octagon as the dielectric plate 305. Protruding portions 315 a are formed near the center of each side of the metal electrode 310 of the filling dielectric 315. The filling dielectric 315 slightly protrudes in the vicinity of the apex of the metal electrode 310 (protruding portion 315b). The protruding portion 315 a near the center of the metal electrode 310 protrudes toward the plasma side from the protruding portion 315 b near the vertex of the metal electrode 310. The protrusion of the filling dielectric 315 is formed point-symmetrically with respect to the center of the metal electrode 310. Thereby, the electric field intensity distribution around the metal electrode can be eliminated, and uniform plasma can be generated.

<Metal electrode fixing screw>
Finally, the point which optimized the kind of screw which fixes the metal electrode 310, a shape, a fixing position, etc. is demonstrated. FIG. 8 shows a metal electrode 310 included in one cell region Cel. FIG. 9 is a 3-3 cross section of FIG.

  The dielectric plate 305 and the metal electrode 310 shown in FIG. 9 are provided in a portion that blocks vacuum and the atmosphere. For this reason, a large pressure is applied to the dielectric plate 305 and the metal electrode 310 from the atmosphere side toward the vacuum side inside the O-ring 220. Furthermore, a large lower force is applied to the dielectric plate 305 and the metal electrode 310 by the elastic force of the O-ring 220. Therefore, a gap is easily generated between the dielectric plate 305 and the lid 300.

  Increasing the cell size reduces the number of cells per device and reduces costs. However, when the cell size is increased, there is a problem that a gap is likely to be formed in the vicinity of the dielectric plate 305, and heat input from the plasma is increased so that the metal electrode 310 is overheated.

  Microwaves cannot penetrate the conductor. For this reason, the microwave propagates through the first coaxial waveguide 610, passes through the dielectric plate 305, further passes through the filling dielectric 315, and is introduced into the processing chamber. At the time of design, the design value of the microwave transmission path is determined in advance in consideration of the transmission efficiency of the microwave without a gap. However, in practice, a slight gap is generated. In this case, during the process, the microwave wavelength and propagation speed change due to the gap, so that the actual impedance change differs from the design value, and the reflection of the microwave from the plasma side increases and the microwave The energy supply efficiency of the wave becomes worse. Further, when the reflection of the microwave from the plasma side is increased, the microwave standing wave ratio (standing wave peak ratio) is increased inside the first coaxial waveguide 610 in FIG. In some cases, discharge occurs and the inside of the first coaxial waveguide 610 is heated or abnormal discharge occurs.

  Therefore, in the metal electrode 310 according to the present embodiment, the metal electrode 310 and the dielectric plate 305 are firmly attached and fixed to the lid body 300. That is, as shown in FIG. 8 and FIG. 9, the metal electrode 310 has a ceiling surface inside the lid 300 by four first screws 380 and four second screws 390 different from the first screws 380. It is firmly fixed to. The four first screws 380 and the four second screws 390 fix the metal electrode 310 at an axially symmetric position with respect to the center of the metal electrode 310. The four first screws 380 are located on the diagonal lines D1 and D2 of the metal electrode 310.

  The four second screws 390 fix the metal electrode 310 at a position equal to the distance from the center of the metal electrode 310 and different from the position of the four first screws 380. The four second screws 390 are located closer to the center of the metal electrode 310 than the four first screws 380. The diameters of the four first screws 380 are smaller than the diameters of the four second screws 390. The four first screws 380 and the four second screws 390 are symmetrical with respect to the center of the metal electrode.

  As described above, the second screw 390 is provided in addition to the first screw 380, and the positions and diameters of the first screw 380 and the second screw 390 are optimized, thereby appropriately distributing the metal surface wave. It is possible to generate a more uniform plasma by adjusting to. Furthermore, the reflection of microwaves from the plasma side can be further suppressed by appropriately adjusting the impedance.

  When the metal electrode 310 has a square shape, the four second screws 390 are respectively located at positions equidistant from the adjacent first screws 380 among the four first screws 380 provided at equal intervals. Provided. Specifically, as shown in FIG. 8, the four second screws 390 are provided on straight lines B1 and B2 connecting the center of the metal electrode 310 and the apex of the cell region Cel. The four first screws 380 and the four second screws 390 are point-symmetric with respect to the center of the metal electrode.

  The four second screws 390 may be exposed from the metal electrode 310 in the same plane as the plasma surface of the metal electrode 310 like the four first screws 380 of FIG. As described above, the dielectric plate 305 and the metal electrode 310 may be held on the ceiling surface without being exposed to the plasma surface of the metal electrode 310. Note that the number of the first screws 380 and the second screws 390 need not be four.

  Thereby, by not providing a gap, a groove, or the like in the microwave propagation path, the reflection of the microwave from the plasma side can be reduced, and the supply efficiency of the microwave energy can be increased. As a result, the electron density is high and uniform plasma can be generated stably. Further, heat on the plasma side can be released to the lid 300 side through the first screw 380 and the second screw 390. In the present embodiment, since the diameters and arrangement positions of the first and second screws are optimized, the electric field of the metal electrode 310 can be made uniform.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, the metal electrode 310 may have a polygon other than a diamond shape.

  In each of the embodiments described above, the microwave source 900 that outputs a microwave of 915 MHz is described. However, a microwave source that outputs a microwave of 896 MHz, 922 MHz, 2.45 GHz, or the like may be used. The microwave source is an example of an electromagnetic wave source that generates an electromagnetic wave for exciting plasma, and includes a magnetron and a high-frequency power source as long as the electromagnetic wave source outputs an electromagnetic wave of 100 MHz or higher.

  The microwave plasma processing apparatus can execute various processes for finely processing an object to be processed with plasma, such as a film formation process, a diffusion process, an etching process, an ashing process, and a plasma doping process.

  For example, the plasma processing apparatus according to the present invention can process a large-area glass substrate, a circular silicon wafer, and a square SOI (Silicon On Insulator) substrate.

It is a longitudinal cross-sectional view (2-O-O'-2 sectional drawing of FIG. 2) of the microwave plasma processing apparatus concerning 1st Embodiment. It is 1-1 sectional drawing of FIG. It is the simulation result which showed the standing wave pattern of the metal surface wave formed in the surface of a metal electrode and a metal cover. It is the figure which showed the relationship of the electric field strength ratio of the metal surface wave in the position corresponding to the aspect ratio of a cell. FIGS. 5A and 5B are diagrams for explaining the electric field strength distribution when there is no filling dielectric between the metal electrode and the metal cover. FIGS. 6A, 6B, and 6C are diagrams for explaining the electric field strength distribution in the case where there is a filling dielectric between the metal electrode and the metal cover. It is the figure which showed the metal electrode provided in the ceiling surface, and its periphery. FIG. 8 is a bottom view of FIG. 7. It is 3-3 sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Microwave plasma processing apparatus 100 Processing container 300 Cover body 300a Upper cover body 300b Lower cover body 305 Dielectric board 310 Metal electrode 315 Filling dielectric 320 Metal cover 330 Main gas flow path 340 Groove 350 Side cover 380 First screw 390 Second screw 610 First coaxial tube 900 Microwave source 905 Gas supply source 910 Refrigerant supply source Cel Cell region

Claims (22)

A processing container for exciting a gas inside to plasma-treat the object to be processed;
An electromagnetic wave source provided outside the processing vessel and outputting an electromagnetic wave;
A plurality of dielectric plates provided adjacent to a ceiling surface made of metal in the processing container, and emitting electromagnetic waves output from the electromagnetic wave source into the processing container;
A plurality of rhombus-shaped metal electrodes that are provided on a one-to-one basis adjacent to each dielectric plate on the plasma side surface of each dielectric plate and expose a part of each dielectric plate from the periphery to the inside of the processing vessel And comprising
The length of the short side of the cell region is defined as a cell region that is defined by two straight lines parallel to the two diagonals of each metal electrode and includes each metal electrode and each dielectric plate. The shape of each metal electrode and each dielectric plate is specified so that the ratio of the length of the long side to 1.2 or less ,
The electromagnetic waves propagate from the exposed portions of the dielectric plates into the surface of the metal electrodes and the metal surface of the ceiling surface where the dielectric plates are not provided, and propagate as metal surface waves. plasma processing apparatus for.   The plasma processing apparatus according to claim 1, wherein the shape of each metal electrode and each dielectric plate is specified so that a ratio of a length of the long side to a length of the short side of the cell region is 1.1 or less. . A processing container for exciting a gas inside to plasma-treat the object to be processed;
An electromagnetic wave source provided outside the processing vessel and outputting an electromagnetic wave;
A plurality of dielectric plates provided adjacent to a ceiling surface in the processing container, and emitting electromagnetic waves output from the electromagnetic wave source into the processing container;
A plurality of metal electrodes provided in a one-to-one relationship adjacent to each dielectric plate on the plasma side surface of each dielectric plate, and exposing a part of each dielectric plate from the periphery to the inside of the processing container;
A plurality of metal covers of the same or similar shape as each metal electrode, provided in a portion of the ceiling surface of the processing vessel where each dielectric plate is not provided,
A filling dielectric is provided in a groove between each metal electrode and each metal cover,
The plasma processing apparatus , wherein the electromagnetic wave is divided into a surface of each metal electrode and a surface of each metal cover from the exposed portion of each dielectric plate and propagates as a metal surface wave .   The plasma processing apparatus according to claim 3, wherein a thickness obtained by adding a thickness of the metal electrode and a thickness of the dielectric plate is substantially equal to a thickness of the metal cover. A processing container for exciting a gas inside to plasma-treat the object to be processed;
An electromagnetic wave source provided outside the processing vessel and outputting an electromagnetic wave;
A plurality of dielectric plates provided adjacent to a ceiling surface in the processing container, and emitting electromagnetic waves output from the electromagnetic wave source into the processing container;
A plurality of metal electrodes provided in a one-to-one relationship adjacent to each dielectric plate on the plasma side surface of each dielectric plate, and exposing a part of each dielectric plate from the periphery to the inside of the processing container;
Provided in a portion of the ceiling surface of the processing vessel where each dielectric plate is not provided, and provided with a conductive protrusion that is the same as or similar to each metal electrode,
A filling dielectric is provided in a groove between each metal electrode and the convex portion,
The plasma processing apparatus , wherein the electromagnetic wave is divided into a surface of each metal electrode and a surface of the convex portion from the exposed portion of each dielectric plate and propagates as a metal surface wave . Around each of the metal electrodes, Sa Idokaba is provided,
The electromagnetic wave is propagated as a metal surface wave from the exposed portion of each dielectric plate, divided into a surface of each metal electrode and a surface of the side cover, respectively.
The plasma processing apparatus according to claim 3, wherein the filling dielectric is provided in a groove between each metal electrode and the side cover.   7. The filling dielectric according to claim 3, wherein the filling dielectric is disposed in a state of being buried in the groove, flattening the groove, or protruding from the groove. Plasma processing equipment.   The plasma processing apparatus according to claim 7, wherein the filling dielectric is disposed so as to surround an outer periphery of each metal electrode and has a portion protruding from the groove.   The plasma processing apparatus according to claim 8, wherein the filling dielectric protrudes from the groove at least near the center of each side of each metal electrode.   10. The plasma processing apparatus according to claim 8, wherein in the protruding portion of the filling dielectric, the protrusion in the vicinity of the center of each side of each metal electrode is larger than the protrusion in the vicinity of the apex of each metal electrode.   The plasma processing apparatus according to claim 8, wherein the protruding portion of the filling dielectric is formed point-symmetrically with respect to the center of each metal electrode.   The plasma processing apparatus according to claim 3, wherein the filling dielectric is made of the same material as each dielectric plate. A processing container for exciting a gas inside to plasma-treat the object to be processed;
An electromagnetic wave source provided outside the processing vessel and outputting an electromagnetic wave;
A plurality of dielectric plates provided adjacent to a ceiling surface made of metal in the processing container, and emitting electromagnetic waves output from the electromagnetic wave source into the processing container;
A plurality of metal electrodes provided one-on-one adjacent to each dielectric plate on the plasma side surface of each dielectric plate and exposing a part of each dielectric plate from the periphery to the inside of the processing container; Prepared,
Each metal electrode is fixed to the ceiling surface in the processing container by a plurality of first screws and a plurality of second screws different from the plurality of first screws,
The plurality of first screws fix the metal electrodes at points symmetrical with respect to the center of the metal electrodes,
The plurality of second screws are arranged at points symmetrical to each other with respect to the center of each metal electrode, and fix each metal electrode at a position different from the position of the plurality of first screws,
The electromagnetic waves propagate from the exposed portions of the dielectric plates into the surface of the metal electrodes and the metal surface of the ceiling surface where the dielectric plates are not provided, and propagate as metal surface waves. Plasma processing equipment.   The plasma processing apparatus according to claim 13, wherein a diameter of the plurality of first screws is smaller than a diameter of the plurality of second screws.   The plasma processing apparatus according to claim 13, wherein four of the plurality of first screws are used for one metal electrode and are located on a diagonal line of each metal electrode.   The plasma processing apparatus according to claim 15, wherein four of the plurality of second screws are used for one metal electrode, and are located closer to the center of each metal electrode than the four first screws. . The shape of each metal electrode is square, the four second screw, respectively from the two first screw adjacent ones of the four first screw provided at equal intervals in equally spaced positions The plasma processing apparatus in any one of Claims 13-16 provided.   18. The plasma processing apparatus according to claim 13, wherein tip surfaces of the plurality of first screws and the plurality of second screws are flush with a lower surface of each metal electrode.   The plasma processing apparatus according to claim 13, wherein a gas flow path is provided in the plurality of first screws.   20. The plasma processing apparatus according to claim 1, wherein each dielectric plate is exposed to a ceiling surface in the processing container in a substantially band shape on an outer periphery of each metal electrode.   When the minimum rectangular area defined by two straight lines parallel to the two diagonal lines of each metal electrode and including each metal electrode and each dielectric plate is defined as a cell area, the length of the adjacent cell areas 21. The plasma processing apparatus according to claim 1, wherein the dielectric plates and the metal electrodes are regularly arranged so that the sides or the short sides coincide with each other and overlap each other.   The plasma processing apparatus according to any one of claims 1 to 21, wherein a surface of the metal electrode on a plasma side is flat.