JP2008251499A - Treatment device, and usage of treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment device provided with dielectric windows formed by favorably treating surfaces thereof in order to suppress the generation of abnormal discharging caused by a concentration of an electric field, and the usage of the treatment device. <P>SOLUTION: This microwave plasma treatment device 10 includes: a treatment vessel 100; the dielectric windows 136a formed on the treatment vessel 100; a gas supply source 144 supplying desired gas into a space of the treatment vessel 100; and a microwave generator outputting microwaves. Desired treatment is applied to a substrate G by gas supplied into the treatment vessel 100 by using the electric field energy of the microwaves outputted from the microwave generator and supplied into the treatment vessel 100 through the dielectric windows 136a. Surfaces of the dielectric windows 136a are previously heated at a low temperature by millimeter waves by using a millimeter-wave heater, and brought into a state having no unevenness relative to that before treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to surface processing of a dielectric member used for a dielectric window of a processing apparatus that performs desired processing.

  As a processing apparatus for performing a desired process on an object to be processed, for example, plasma CVD (Chemical Vapor Deposition) in which plasma is generated from gas using a high frequency output from a high frequency power source and a substrate is formed by the generated plasma. An apparatus is known (for example, Patent Document 1).

  In some plasma processing apparatuses, a part of the processing container (for example, a ceiling surface) is formed by a dielectric window. The dielectric window functions as an electrode unit that seals the inside of the processing container and supplies energy output from an energy source installed outside to the processing container.

Various materials such as quartz have been conventionally used as the material of the dielectric window having such a function, but in recent years, alumina (Al ₂ O ₃ ) has been frequently used. Alumina is relatively easy to manufacture and can be made large in dielectric window, it is difficult to break due to its high strength, its performance is stable, and it is advantageous in terms of cost. This is because these advantages are suitable for increasing the size of the dielectric window accompanying the increase in size of the substrate and improving the reliability of the processing apparatus.

JP 2005-142448 A

  When the surface of the alumina plate (dielectric member) for a dielectric window having the above functions is cut with a disk-shaped grindstone made of diamond or the like, it is shown in FIG. As a result of breakage within the grains (inside the crystal grains) or destruction of the grain boundaries (between the crystal grains constituting the alumina plate) indicated by B, minute irregularities are produced.

  For example, as shown in FIG. 3A, when the surface of the alumina plate is not uneven, when the microwave is supplied into the processing container through the alumina plate (dielectric window), the slot 134a of the slot antenna is used. From the bottom of the alumina plate, the electric field energy of the microwave that passes through the dielectric window 136a is not concentrated in one place, but is uniformly sent into the processing chamber U. However, as shown in FIG. 3B, when the surface of the alumina plate is uneven, the electric field energy is concentrated on the protrusions on the surface of the alumina plate.

  As a result, the electric field strength increases at the convex portion on the lower surface of the alumina plate, and abnormal discharge may be caused. In this case, damage such as cracks may occur in the dielectric window due to heat generated by abnormal discharge. Further, surface defects and defects are liable to cause a chemical reaction with the processing gas (reactive species) during the process, thereby corroding the dielectric window. As a result, the alumina flakes fall off from the surface of the dielectric window and are mixed on the object to be processed during plasma processing. When particles are generated during the plasma treatment in this way, the process performance deteriorates, and there arises a problem that the yield is lowered due to the manufacture of defective products and the productivity is lowered.

  On the other hand, as a method for suppressing the generation of particles, as shown in FIG. 2 (b), a method in which an alumina plate for a dielectric window is previously fired at a high temperature is conceivable. However, when the alumina plate is fired at a high temperature, not only the grain boundaries but also the grains are heated, and each crystal grain is deformed and adjacent grains are integrated (granular growth). As a result, the alumina plate is greatly deformed. For this reason, in high-temperature firing, it has been difficult to repair the grain boundary fracture and intragranular fracture of the alumina surface formed during cutting without deforming the alumina plate, and to process the alumina plate with a smooth surface without unevenness. .

  Accordingly, in order to solve the above problems, the present invention provides a dielectric member for a dielectric window of a plasma processing apparatus whose surface has been satisfactorily processed, a processing apparatus including the dielectric, and a method of using the processing apparatus. To do.

  That is, in order to solve the above problems, according to an aspect of the present invention, a processing container, a dielectric window provided in the processing container, and a gas supply source for supplying a desired gas into the processing container, An energy source that outputs desired energy, and is covered by a gas supplied into the processing container using energy output from the energy source and supplied into the processing container through the dielectric window. A processing apparatus for performing a desired process on a processing body is provided. The surface of the dielectric window provided in this processing apparatus is processed in advance by millimeter waves.

  According to this, the surface of the dielectric window is heated by millimeter waves. The heating by the millimeter wave is, for example, a method in which the surface layer portion of the object is sintered at a low temperature by irradiating the object with a millimeter wave having a frequency of 28 GHz (wavelength of about 12 mm). As shown in FIG. 2C, in millimeter wave heating, 28 GHz (or 24 GHz) millimeter waves are applied to the alumina plate to vibrate particles constituting the alumina plate, and the frictional heat is generated. The surface layer (grain boundary) between the particles is selectively heated and adhered by using. This makes it possible to sinter the alumina plate by several hundred degrees C lower than the heat-sintered heat of an electric furnace or the like without heating the inside of the crystal grains.

  Thus, in surface processing using millimeter waves, particles can be firmly integrated at the interface by selectively heating the grain boundary portion of the sample. On the other hand, since the inside of the grains is hardly heated, the temperature can be lowered during sintering, and the grains can be integrated (granular growth) during firing to prevent the alumina plate from being deformed. Further, in the millimeter wave heating, the pointed portion of each crystal grain can be rounded as compared with the case where alumina is fired at a high temperature. As a result, the surface of the alumina can be processed into a smooth state without irregularities without deforming the alumina plate.

  In this way, when the surface of the alumina plate for the dielectric window is processed smoothly in advance, when performing the process in the plasma processing apparatus in which the alumina plate is disposed as the dielectric window, the dielectric window Concentration of electric field energy on the surface can be suppressed. Thereby, abnormal discharge can be suppressed, and the dielectric window can be prevented from being damaged by the heat at the time of abnormal discharge, or the alumina flakes can fall off from the dielectric window and be mixed into the object as particles. As a result, a product having good process performance can be stably manufactured.

  The dielectric window is preferably processed in advance by millimeter waves at a temperature of 1200 ° C. or higher. As a result of intensive studies, the inventors have found that the corners of each crystal grain forming the alumina plate are rounded and rounded when the alumina plate is fired at a temperature of 1200 ° C. or higher. Therefore, by using the alumina plate heated in millimeter waves at a temperature of 1200 ° C. or higher in this way for the dielectric window of the plasma processing apparatus, electric field energy is concentrated on the surface of the dielectric window during the process. It is possible to suppress the occurrence of abnormal discharge.

  The dielectric window is preferably processed in advance by millimeter waves at a temperature of 1600 ° C. or lower. Since the sintering temperature of the alumina powder molded body by the electric furnace with heat is about 1600 ° C., when the alumina is heated by millimeter waves at a temperature higher than 1600 ° C., the heating temperature rises and crystal grains grow and become larger. When the crystal grains become large, the contact area between the crystal grains becomes smaller than when the crystal grains are small, and the strength decreases. Therefore, if an alumina plate processed in millimeter waves at a temperature of 1600 ° C. or lower is used as a dielectric window of a plasma processing apparatus, the dielectric window has a large contact area between crystal grains, and thus is in process. Can be prevented from being damaged.

The dielectric window may be processed in advance by millimeter waves using a gas containing a component that composes the dielectric window. According to this, the surface layer of the dielectric window is modified by using the gas containing the material forming the dielectric window. For example, by performing millimeter-wave heating using a gas containing O ₂ in an oxygen atmosphere, the grains included in the O ₂ gas are broken down at the grain boundaries present on the surface of the alumina plate shown in FIG. (Oxygen deficiency) part can be compensated. In this way, the thermal stability can be enhanced by filling defects on the surface of the alumina plate with the same material as that constituting the alumina plate. As a result, the chemical and thermal strength of the alumina plate can be increased, and the reaction with the processing gas (reactive species) during the process occurs at the intragranular and grain boundary fractures generated on the surface of the alumina plate. Can be made difficult. As a result, generation of flakes causing particles from the surface of the dielectric window can be suppressed, and a chemical reaction can easily occur due to a defect in the alumina plate, without being used for plasma processing of the workpiece. The processing gas that disappears in the processing chamber can be reduced.

  In this way, if a pre-surface-treated alumina plate is used for the dielectric window, the particle size of the dielectric window can be increased while taking advantage of the advantage of alumina that it is relatively easy to manufacture. It is possible to suppress the occurrence of flakes that cause

  The dielectric window may be a single flat plate (plate) or may be composed of a plurality of dielectric window parts formed in a tile shape. In the case of a plurality of dielectric window parts, each dielectric window part is fixed to the processing container while being supported by a beam formed in a lattice shape.

  In order to solve the above problems, according to another aspect of the present invention, a processing container, a dielectric window provided in the processing container, and a gas supply source for supplying a desired gas into the processing container And a method of using the processing apparatus comprising an energy source that outputs desired energy. In this method of using the processing apparatus, the surface of the dielectric window is processed in advance with a millimeter wave, output from the energy source, and supplied to the processing container through the dielectric window. A desired process is performed on the object to be processed by the gas supplied into the container.

  In order to solve the above-described problems, according to another aspect of the present invention, there is provided a dielectric member for a dielectric window of a plasma processing apparatus whose surface is processed in advance by millimeter waves.

  According to these, for example, the surface of the dielectric member for the dielectric window of the plasma processing apparatus is made smooth with no irregularities in advance by millimeter wave heating, so that abnormalities occur near the dielectric window during plasma processing. The occurrence of discharge can be suppressed. As a result, it is possible to prevent the dielectric window from being damaged or the flakes from falling off the surface of the dielectric and causing particles due to heat generated by abnormal discharge.

  As described above, according to the present invention, it is possible to suppress the generation of dielectric flakes that cause particles by processing the surface of a dielectric for a processing apparatus well in advance.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment 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. In this specification, 1 mTorr is (10 ⁻³ × 101325/760) Pa, and 1 sccm is (10 ⁻⁶ / 60) m ³ / sec.

  First, a microwave plasma processing apparatus according to an embodiment of the present invention will be described with reference to FIG. Note that the microwave plasma processing apparatus is an example of a processing apparatus that performs a desired process on a target object with a desired gas.

(Configuration of microwave plasma processing equipment)
A microwave plasma processing apparatus 10 according to the present embodiment includes a processing container 100 and a lid 102. The processing container 100 has a bottomed cubic shape with an upper portion opened. The processing container 100 and the lid body 102 are sealed by an O-ring 104 disposed on the contact surface between the processing container 100 and the lid body 102, thereby forming a processing chamber U in which plasma processing is performed. The processing container 100 and the lid 102 are made of, for example, a metal such as aluminum and are electrically grounded.

  The processing vessel 100 is provided with a stage 106 on which a glass substrate (hereinafter referred to as “substrate”) G is placed. The stage 106 is made of, for example, aluminum nitride, and a power feeding unit 108 and a heater 110 are provided therein.

  A high frequency power source 114 is connected to the power feeding unit 108 via a matching unit 112 (for example, a capacitor). In addition, a high-voltage DC power supply 118 is connected to the power supply unit 108 via a coil 116. The matching unit 112, the high frequency power source 114, the coil 116, and the high voltage DC power source 118 are provided outside the processing container 100. The high frequency power supply 114 and the high voltage DC power supply 118 are grounded.

  The power supply unit 108 applies a predetermined bias voltage to the inside of the processing container 100 by the high-frequency power output from the high-frequency power source 114. The power supply unit 108 is configured to electrostatically attract the substrate G with a DC voltage output from the high-voltage DC power supply 118.

  An AC power source 120 provided outside the processing container 100 is connected to the heater 110, and the substrate G is held at a predetermined temperature by an AC voltage output from the AC power source 120.

  The bottom surface of the processing container 100 is opened in a cylindrical shape, and one end of a bellows 122 is attached to the outer peripheral edge thereof. The other end of the bellows 122 is fixed to the elevating plate 124. In this way, the opening at the bottom of the processing container 100 is sealed by the bellows 122 and the elevating plate 24.

  The stage 106 is supported by a cylindrical body 126 disposed on the lifting plate 124, and moves up and down integrally with the lifting plate 124 and the cylindrical body 126. Thereby, the stage 106 is adjusted to a height corresponding to the processing process. A baffle plate 128 for controlling the gas flow in the processing chamber U to a preferable state is provided around the stage 106.

  A vacuum pump (not shown) is provided outside the processing container 100 at the bottom of the processing container 100, and the processing chamber U is discharged by discharging the gas in the processing container 100 through the gas discharge pipe 130. The pressure is reduced to a desired degree of vacuum.

The lid 102 is provided with six waveguides 132, a slot antenna 134, and a dielectric window 136 (consisting of a plurality of dielectric parts 136a). The six waveguides 132 have a rectangular cross-sectional shape and are arranged in parallel inside the lid 102. The inside of each waveguide 132 is filled with a dielectric member 132a such as fluororesin (for example, Teflon (registered trademark)), alumina (Al ₂ O ₃ ), quartz, and the like, and λg ₁ = λc by the dielectric member 132a. The in-tube wavelength λg ₁ of each waveguide 132 is controlled according to the equation / (ε ₁ ) ^1/2 . Here, λc is the wavelength of free space, and ε ₁ is the dielectric constant of the dielectric member 132a.

  Each waveguide 132 is opened at the top, and a movable portion 132b is inserted in the opening so as to be movable up and down. The movable portion 132b is made of a conductive material that is a nonmagnetic metal body such as aluminum.

  An elevating mechanism 132c is provided outside the lid 102 and on the upper surface of each movable portion 132b. The lifting mechanism 132c moves the movable portion 132b up and down up to the upper surface of the dielectric member 132a. Thereby, the height of the waveguide 132 can be changed arbitrarily. A slot antenna 134 that functions as an antenna is provided below each waveguide 132. The slot antenna 134 is provided with a slot 134 a on the lower surface of each waveguide 132. The number of slots 134a formed on the lower surface of each waveguide 132 is arbitrary.

  The dielectric window 136 is composed of a plurality of dielectric parts 136a, and each dielectric part 136a is made of alumina. The dielectric part 136a may be formed of a dielectric material such as quartz glass, AlN, sapphire, SiN, or ceramics.

  On the lower surface of the slot antenna 134, a lattice-like beam 138 is provided to fix the plurality of dielectric parts 136 a to the ceiling surface of the processing container 100 while supporting the plurality of dielectric parts 136 a. The beam 138 is formed of a conductive material that is a nonmagnetic metal body such as aluminum.

  Below the beam 138, a plurality of gas pipes 140 are suspended from the entire ceiling surface in a state where the gas pipes 140 are supported by the support 142 at both ends thereof. The gas pipe 140 is made of a dielectric material such as alumina.

  In principle, the gas supply source 144 controls the opening and closing of the valve and the opening of the mass flow controller (both not shown), so that a gas having a large binding energy passes through the gas flow path 146a and penetrates the beam 138 in principle. The gas is supplied to the space between the dielectric parts 136a and the gas pipe 140 from the plurality of gas introduction pipes 148a, the gas having a small binding energy is passed through the gas flow path 146b, and the gas pipes 140 from the plurality of gas introduction pipes 148b penetrating the beam 138. Supply below.

  A cooling water supply source 152 is connected to the cooling water pipe 150, and the cooling water supplied from the cooling water supply source 152 circulates in the cooling water pipe 150 and returns to the cooling water supply source 152, so that the lid The body 102 is kept at a desired temperature.

  With the configuration described above, the microwave plasma processing apparatus 10 propagates microwaves output from a microwave generator (not shown) to the six waveguides 132 and passes them through the slots 134a of the slot antenna 134, so that a plurality of The dielectric parts 136a are transmitted and supplied to the inside of the processing vessel 100. Plasma is generated from the gas supplied into the processing chamber 100 by the electric field energy of the microwave supplied in this manner, and a desired thin film is formed on the substrate G in the processing chamber U by the generated plasma.

(Alumina surface irregularities)
The surface of the alumina plate for a dielectric window having such a function is subjected to intra-grain (crystal grains) shown in A of FIG. 2A when it is cut by a disk-shaped grindstone formed of diamond or the like. And the grain boundary (boundary between crystal grains constituting the dielectric window) shown in FIG.

  For example, as shown in FIG. 3A, when the surface of the alumina plate is not uneven, when the microwave is supplied into the processing container through the alumina plate (dielectric window), the slot 134a of the slot antenna is used. From the bottom of the alumina plate, the electric field energy of the microwave that passes through the dielectric window 136a is not concentrated in one place, but is uniformly sent into the processing chamber U. However, as shown in FIG. 3B, when the surface of the alumina plate is uneven, the electric field energy is concentrated on the protrusions on the surface of the alumina plate.

  In this way, in the place where the electric field energy is concentrated on the lower surface of the alumina plate, the electric field strength becomes high, causing abnormal discharge, and the dielectric window may be broken by the heat generated thereby. In addition, defects or defects on the surface of the alumina plate due to intragranular or intergranular fracture tend to cause a chemical reaction with the processing gas during the process, and as a result, the dielectric window may corrode. As a result, the alumina flakes fall off from the surface of the dielectric window and are mixed on the substrate being plasma processed. When particles are generated in this way, the process performance deteriorates, resulting in a problem that the yield decreases due to the manufacture of defective products, and the productivity decreases.

  On the other hand, as a method for suppressing the generation of particles, as shown in FIG. 2B, there is a method in which an alumina plate for a dielectric window is fired at a high temperature in advance. However, when the alumina plate is fired at a high temperature, not only the grain boundaries but also the grains are heated, and each crystal grain is deformed and adjacent grains are integrated (granular growth). As a result, the alumina plate is greatly deformed. For this reason, in high-temperature firing, it is difficult to repair the grain boundary fracture and intragranular fracture on the alumina surface without deforming the alumina plate, and to process the alumina plate with a smooth surface without unevenness.

(Selective heating by millimeter wave)
Therefore, in the present embodiment, as the surface treatment of the alumina plate P for the dielectric part 136a, a method of sintering the alumina plate at a low temperature by using the millimeter wave heating device shown in FIG. 4 is used. FIG. 4A is a longitudinal sectional view of the millimeter wave heating device 300 cut along a plane parallel to the longitudinal direction, and FIG. 4B is a cross-sectional view along the AA plane shown in FIG. FIG. 3 is a cross-sectional view of the millimeter wave heating device 300 cut away.

  The millimeter wave heating apparatus 300 includes a heating furnace 305, a millimeter wave generation source 310, a millimeter wave waveguide 315, a gas supply source 320, and a thermocouple 325. The heating furnace 305 is a cylindrical metal container and has a hexagonal cross section inside (more precisely, every other hexagonal piece is shortened, in fact, a shape close to a triangular shape). ) Reflector 305a is disposed. A mounting table 305b is installed on the bottom surface of the reflecting plate 305a. An alumina plate P is placed on the mounting table 305b, and the alumina plate P is further insulated by covering the alumina plate P with a heat insulating material 305c.

  The millimeter wave generation source 310 is installed outside the heating furnace 305 and generates a millimeter wave of 24 GHz or 28 GHz. The millimeter wave waveguide 315 is a tubular member that connects the heating furnace 305 and the millimeter wave generation source 310, and propagates the millimeter wave output from the millimeter wave generation source 310 to the internal space of the heating furnace 305.

  The gas supply source 320 includes a plurality of valves V, a plurality of mass flow controllers MFC, an argon gas supply source 320a, an oxygen gas supply source 320b, and a nitrogen gas supply source 320c. The gas supply unit 320 supplies a desired type of gas to the heating furnace 305 at a desired concentration by opening / closing each valve V and adjusting the opening of each mass flow controller MFC. The thermocouple 325 is a temperature sensor attached to the mounting table 305b, and thereby manages the temperature of the mounting table 305b. The inside of the heating furnace 305 is depressurized to a desired degree of vacuum by a vacuum pump (not shown) connected to the exhaust pipe 330.

  With this configuration, in the millimeter wave heating apparatus 300, first, the alumina plate P is accommodated in the heating furnace 305, placed on the mounting table 305b in the reflecting plate 305a, and the top is covered with the heat insulating material 305c. Thereafter, a millimeter wave is output from the millimeter wave generation source 310, the output millimeter wave is introduced into the heating furnace 305 through the millimeter wave introduction tube 315, and further reflected and diffused by the reflecting plate 305a. The alumina plate P is efficiently irradiated with waves.

In this way, the state of the alumina plate P during irradiation of the millimeter wave to the alumina plate P will be described. As shown in FIG. 2 (c), in the case of sintering by millimeter waves, the dielectric constant in the grains constituting the alumina plate P, which is a dielectric member, is ε, and the dielectric constant of the grain boundaries is ε ₀ . If the electric field strength of E is E and the electric field strength of the grain boundary is E ₀ , the dielectric constant × the electric field strength is constant.
εE = ε ₀ E ₀
Holds. Therefore,
E ₀ = ε / ε ₀ · E (1)
It becomes.
This indicates that the electric field strength of the grain boundary part is higher by ε / ε ₀ times than the intragranular part.

Generally, the dielectric constant of the piezoelectric epsilon is a kind of a dielectric, with more than 10 times the value of the dielectric constant epsilon ₀ of the atmosphere. That is, ε / ε ₀ ≧ 10. When this is applied to the equation (1), the electric field intensity E _{0 at} the grain boundary becomes 10 times or more the electric field intensity E within the grain. Thus, the electric field strength E at the grain boundary increases as the dielectric constant ε of the crystal grain increases.

At this time, the electric field energy E _v0 at the grain boundary is expressed by the following equation.
E _v0 = 1/2 · ε ₀ E ₀ ² (2)
Substituting equation (1) into equation (2),
E _v0 = 1/2 · (ε ² / ε ₀ ) E ² = ε / ε ₀ (1 / 2ε · E ² )

On the other hand, electric field energy _{E v} in the grains, since a ^1/2 · εE 2,
E _v0 = ε / ε ₀ E _v (3)
Therefore, the energy of the grain boundary part is higher by ε / ε ₀ times than the intragranular part.

When the alumina plate P is heated by millimeter waves, the dielectric constant ε of alumina is 8 to 9, and the dielectric constant ε ₀ of the grain boundary (in vacuum) is 8.854E-12 (F / m). Therefore, from the equation (1), the electric field intensity E at the grain boundary is about nine times the electric field intensity E ₀ within the grain. From the equation (3), the electric field energy E _{v0 at} the grain boundary is about nine times the electric field energy E _v within the grain.

  From the above, it can be seen that very strong energy is applied to the grain boundaries of the alumina plate P compared to the inside of the grains. As a result, the grain boundary of the alumina plate P is selectively heated, and the inside of the grain is hardly heated. In this way, according to the millimeter wave heating device 300, the alumina plate can be sintered by several hundred degrees Celsius lower than the heat-sintered heat of an electric furnace or the like without heating the inside of the crystal grains. In addition, since the grain boundary is selectively heated, the crystal grains are not deformed and adjacent crystal grains are not integrated with each other (that is, the grains do not grow). As a result, the crystal grains can be firmly bonded without deforming the alumina plate P.

(Alumina plate surface treatment experiment)
Based on the above logic, the inventors actually sintered the alumina plate P using the millimeter wave heating device 300. At this time, as shown in FIG. 5, the inventors set the firing temperature to 1100 ° C., 1200 ° C., 1300 ° C., 1400 ° C. in four stages, and the atmosphere in the heating furnace 305 was opened to the atmosphere. The experiment was conducted with three patterns of 100% nitrogen atmosphere by supplying argon gas and nitrogen gas from the atmosphere and gas supply source and 100% nitrogen atmosphere by supplying argon gas and oxygen gas from the gas supply source.

  In the case of 1100 ° C. and 1200 ° C., the inventors raised the temperature by 50 ° C. per minute at atmospheric pressure, controlled to the target temperature, fired for 3 hours, and then lowered the temperature to 200 ° C. in 1 hour. . In the case of 1300 ° C. and 1400 ° C., the inventors raised the temperature by 30 ° C. per minute at atmospheric pressure, controlled to the target temperature, fired for 3 hours, and then lowered the temperature to 200 ° C. in 1 hour. . The shape of the surface of the alumina plate P (FIGS. 6 to 8) and the composition state of the surface layer of the alumina plate P (FIGS. 9 to 11) under each condition obtained as a result will be discussed below.

(Alumina plate surface flattening)
First, the inventors considered the surface shape of the alumina plate P based on the experimental results shown in FIGS. 6 to 8 captured by the electron microscope (SEM) are obtained by enlarging the surface of the alumina plate P by 10,000 times. Among these, Fig.6 (a) shows the surface of the alumina plate P of the initial state which is after a cutting process and is not surface-treated at all. 6 (b), 6 (c), 6 (d), and 6 (e) show an alumina plate P at each firing temperature of 1100 ° C, 1200 ° C, 1300 ° C, and 1400 ° C in an air atmosphere. It is the surface of the alumina plate P at the time of heating a millimeter wave. 7 (a) to 7 (d) and 8 (a) to 8 (d) show a 100% nitrogen atmosphere and a 100% oxygen atmosphere. It is the surface of the alumina plate P when heated.

  From these results, the alumina plate P is rounded with the corners of each crystal grain being removed from about 1200 ° C. in any atmosphere, and the degree of rounding increases as the firing temperature rises. The fact that each crystal grain is rounded means that fine irregularities are eliminated on the surface of the alumina plate P, and the surface of the alumina plate P is smooth. Therefore, as shown in FIG. 5, the inventors have processed the surface shape of the alumina plate P well by millimeter wave heating in any case where the atmosphere is air, nitrogen 100%, and oxygen 100%. The conclusion that it is a case of 1200 degreeC or more was drawn.

  By using the alumina plate P processed in millimeter waves at a temperature of 1200 ° C. or more in this way for the dielectric window 136 of the microwave plasma processing apparatus 10, electric field energy is generated on the surface of the dielectric window 136 during the process. Concentration can be suppressed, thereby preventing occurrence of abnormal discharge.

  In addition, it is preferable that the dielectric window 136 formed of alumina is preliminarily heated by millimeter waves at 1600 ° C. or less. Since the sintering temperature of the alumina powder molded body by the electric furnace with heat is about 1600 ° C., when the alumina is heated by millimeter waves at a temperature higher than 1600 ° C., the heating temperature rises and crystal grains grow and become larger. When the crystal grains become large, the contact area between the crystal grains becomes smaller than when the crystal grains are small, and the strength decreases. Therefore, if the alumina plate P processed by millimeter waves at a temperature of 1600 ° C. or less is used for the dielectric window 136 of the microwave plasma processing apparatus 10, the dielectric window 136 has a large contact area between crystal grains and is strong. Therefore, it is possible to prevent damage during the process.

(Alumina plate surface modification)
Next, the inventors considered the composition state of the surface layer of the alumina plate based on the analysis result by X-ray photoelectron spectroscopy (XPS) on the surface of the alumina plate P shown in FIGS. From these results, although there was some variation, the kinetic energy of the photoelectrons of the alumina plate P after sintering was smaller than the initial state (before millimeter wave heating) in all cases. This result is discussed below.

  When the millimeter wave heating is performed at 1100 ° C. to 1400 ° C. in the oxygen atmosphere shown in FIG. 10, compared to the case where the millimeter wave heating is performed at the same temperature in the air atmosphere shown in FIG. The kinetic energy of photoelectrons is small. Further, when the millimeter wave is heated at the same temperature in the nitrogen atmosphere shown in FIG. 11, the photoelectrons for each initial state of the alumina plate surface layer are compared with the case where the millimeter wave is heated at the same temperature in the oxygen atmosphere shown in FIG. There is a tendency for the kinetic energy of to be slightly smaller.

  This indicates that the deficient portion of the alumina plate P was replenished with oxygen in the oxygen atmosphere, and the surface layer of the alumina plate P was almost modified by Al—O bonds. The deficient portion of the plate P is replenished with oxygen and hydrogen contained in the atmosphere, and the surface layer of the alumina plate P has been modified so that Al—OH bonds are mixed with Al—O bonds. In the nitrogen atmosphere, the deficient portion of the alumina plate P is replenished with nitrogen, and the surface layer of the alumina plate P is modified so that Al—N bonds are mixed in Al—O bonds. .

The reason why this is considered will be explained focusing on millimeter wave heating in an oxygen atmosphere and an air atmosphere. When the deficient portion of the alumina plate P is filled with OH groups, Al (OH) ₃ is present in a part of the surface layer of the alumina plate P. Referring to FIG. 12A, Al (OH) ₃ has _three oxygen atoms O around one aluminum atom Al. On the other hand, Al ₂ O ₃ has 1.5 oxygen atoms O around one aluminum atom Al.

  In order for photoelectrons to jump out from the inner shell of one aluminum atom Al while being energetically pulled by three oxygen atoms O having an electronegativity of 3.5, energy is required for 1.5 oxygen atoms O. Rather than the photoelectrons jumping out from the inner shell of one aluminum atom Al while being pulled, the larger the number of oxygen atoms to be pulled, the greater the kinetic energy of the photoelectrons. Therefore, in the case of the modification including OH shown in FIG. 9, the kinetic energy of the photoelectrons is larger than that in the modification of only O shown in FIG. 10 with respect to the initial state. That is, from the comparison of the results of FIG. 9 and FIG. 10, in the case of the air atmosphere, the defect portion of the alumina plate P was modified including not only O but also OH, and in the case of the oxygen atmosphere. Can be derived from the fact that all the defective portions of the alumina plate P were modified with O. Similarly, from the comparison of the results of FIGS. 10 and 11, in the case of a nitrogen atmosphere, the deficient portion of the alumina plate P was modified with N having an electronegativity of 3.5, so that the kinetic energy of photoelectrons is small. Can be derived.

(Thermal stability to each modification of the alumina plate surface)
Next, when the alumina plate surface layer is modified in a state where Al—O is contained in Al—O by the air atmosphere as described above, the state of only Al—O in the oxygen atmosphere is obtained. When it was modified to a state containing Al—N in a nitrogen atmosphere, which case was considered to be chemically and thermally stable.

According to the Metal Data Book (edited by the Japan Institute of Metals, revised 2nd edition, p90, p92 Maruzen), the standard free energy of formation ΔG of alumina (Al ₂ O ₃ ) at room temperature is
2 / 3Al + O ₂ = 2 / 3Al ₂ O ₃ (1070 kJ / mol, O ₂ normalized)
It is represented by When this is converted into ΔG per 1 mol of Al ₂ O ₃ , it becomes 1605 kJ / mol. Since 6 mol of Al—O bond is contained per 1 mol of Al ₂ O ₃ chemical formula, the standard free energy of formation ΔG per bond of Al—O is 267.5 kJ / mol.

On the other hand, according to the data book, the standard free energy of formation ΔG of aluminum nitride (AlN) at room temperature is
2Al + N ₂ = 2AlN (575 kJ / mol, N ₂ normalized)
It is represented by This is 287.5 kJ / mol when converted to ΔG per mol of AlN. Since 3 mol of Al—N bond (triple bond) is contained per 1 mol of AlN chemical formula, the standard free energy of formation ΔG per bond of Al—N is 95.8 kJ / mol.

  According to this, the standard free energy of formation ΔG per Al—O bond is larger than the standard free energy of formation ΔG per Al—N bond. Thereby, when it is modified to an Al-O state by an oxygen atmosphere, it is more thermally (chemically) stable than when it is modified to a state containing Al-N by a nitrogen atmosphere. It can be said.

  This conclusion can also be derived from the electronegativity shown in FIG. That is, the electronegativity of Al—O is 3.5, whereas the electronegativity of Al—N is 3.0. “The degree of ionicity and covalentness of chemical bonds is related to the difference in electronegativity of bonded atoms (Barlow physical chemistry (bottom), p565).” The degree of chemical bonding is higher in the case of modification with Al-N having a lower electronegativity. Therefore, also from the viewpoint of electronegativity, when it is modified to an Al-O state by an oxygen atmosphere, compared with the case of being modified to a state containing Al-N by a nitrogen atmosphere, the chemical, thermal, It can be said that it is stable.

  Then, in the case where Al-O is modified to include Al-OH in an air atmosphere, and in the case where it is modified to Al-O in an oxygen atmosphere, both cases are chemically and thermally stable. Are you doing it? About this, it can conclude that the case where it reformed to the state of Al-O by oxygen atmosphere is more chemically and thermally stable from the following reasons.

Al (OH) ₃ begins to undergo dehydration condensation reaction at 300 ° C. and is converted to Al ₂ O ₃ . For example, according to the Chemical Dictionary (Kyoritsu Publishing Co., Ltd. edited by the Chemical Dictionary Dictionary), the properties of aluminum hydroxide are described as “relatively easily lose water to become aluminum oxide when heated.” Yes. This indicates that the state of Al (OH) ₃ is more chemically and thermally unstable than the state of Al ₂ O ₃ and easily shifts to Al ₂ O ₃ when heated.

More specifically, it is considered that the surface layer of the alumina plate P modified to the state of Al (OH) ₃ loses moisture due to heating during the process, and a part thereof is lost. For this reason, the reactive species (processing gas) react with the composition components of the alumina plate P and the deposits on the alumina plate P in the defective portion. As a result, the reactive species should react on the substrate, but disappear at the lower portion of the dielectric window 136 in the processing chamber, and flakes composed of reaction products and the like are generated from the surface of the dielectric window 136. May cause particles.

On the other hand, the surface layer of the alumina plate P modified to the Al—O state is chemically and thermally stable as compared with the case where the surface is modified to the Al (OH) ₃ state. Therefore, the defect does not occur even during the process. Therefore, it is possible to suppress a situation where flakes that cause particles are generated from the surface of the dielectric window 136. From the above, the inventors have concluded that when modified to an Al—O state, it is more chemically and thermally stable than when modified to a state containing Al—OH.

  From the above considerations, the inventors produce an alumina plate that is chemically and thermally strong when the alumina plate P is heated by millimeter waves at 1200 ° C. or higher and 1600 ° C. or lower in an oxygen atmosphere. I was able to do that.

  As described above, in this embodiment, the surface of the alumina plate P for the dielectric window is processed smoothly by millimeter wave heating in advance, so that the microplate in which the alumina plate P is disposed as the dielectric window 136 is used. When the process is executed in the wave plasma processing apparatus 10, it is possible to suppress the concentration of electric field energy on the surface of the dielectric window 136. As a result, abnormal discharge can be suppressed, and it is possible to prevent the dielectric window from being damaged by the heat during abnormal discharge, or the alumina flakes from dropping from the dielectric window and mixing into the workpiece as particles. Can do.

  In addition to this, in this embodiment, the dielectric window 136 of the microwave plasma processing apparatus 10 having high chemical stability can be formed by modifying the surface layer of the alumina plate P by millimeter wave heating. In particular, the surface layer of the alumina plate P is modified with Al-O by millimeter-wave heating using a gas containing a component that constitutes the alumina plate P, so that a chemically stable dielectric window 136 is obtained. Can be formed. As a result, a product having good process performance can be stably manufactured.

  The size of the substrate G to be processed by the processing apparatus may be 730 mm × 920 mm or more, for example, a G4.5 substrate size of 730 mm × 920 mm (diameter in the chamber: 1000 mm × 1190 mm) or 1100 mm × 1300 mm It may be a G5 substrate size (diameter in chamber: 1470 mm × 1590 mm). Further, the target object to be processed is not limited to the substrate G having the size described above, and may be, for example, a 200 mm or 300 mm silicon wafer.

  In the above embodiment, the operations of the respective units are related to each other, and can be replaced as a series of operations in consideration of the relationship between each other. And by replacing in this way, the embodiment of the processing apparatus can be made the embodiment of the method of using the processing apparatus.

  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 plasma processing apparatus using the dielectric member according to the present invention is not limited to the above-described microwave plasma processing apparatus having a plurality of dielectric window parts, but an RLSA (Radial Line Slot Antenna) type microwave plasma processing. It can be used for various CVD processing apparatuses and plasma processing apparatuses such as an apparatus, an inductively coupled plasma (ICP) plasma processing apparatus, an electron cyclotron (ECR) plasma processing apparatus, and a thermal CVD processing apparatus. it can.

It is a schematic block diagram of the microwave plasma processing apparatus concerning one Embodiment of this invention. It is a figure for demonstrating the surface processing of the alumina plate concerning the embodiment. It is a figure for demonstrating concentration of the electric field on the surface of the alumina plate concerning the embodiment. Fig.4 (a) is a longitudinal cross-sectional view of the millimeter wave heating apparatus concerning the embodiment, FIG.4 (b) is sectional drawing which cut | disconnected the apparatus in the AA surface. It is the figure which showed the result of the surface processing on the sintering conditions of each alumina plate, and each condition. FIG. 6A is a diagram showing the surface shape of the alumina plate in the initial state, and FIG. 6B to FIG. 6E are diagrams showing the surface shape of the alumina plate in the air atmosphere. . Fig.7 (a)-FIG.7 (d) are the figures which showed the surface shape of the alumina plate in nitrogen atmosphere. FIG. 8A to FIG. 8D are diagrams showing the surface shape of an alumina plate in an oxygen atmosphere. It is the figure which showed the combined state of the alumina plate before and behind millimeter wave sintering in an atmospheric condition. It is the figure which showed the combined state of the alumina plate before and behind millimeter wave sintering in nitrogen atmosphere. It is the figure which showed the combined state of the alumina plate before and behind millimeter wave sintering in oxygen atmosphere. 12A shows the relationship between the composition of the substance and the kinetic energy of Al photoelectrons, and FIG. 12B shows the relationship between the electronegativity and the kinetic energy of Al photoelectrons.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Microwave plasma processing apparatus 100 Processing container 136 Dielectric window 136a Dielectric part 144,320 Gas supply source 300 Millimeter wave heating apparatus A Intragranular fracture B Intergranular fracture P Alumina plate

Claims (12)

A processing container, a dielectric window provided in the processing container, a gas supply source that supplies a desired gas into the processing container, and an energy source that outputs desired energy are output from the energy source. A processing apparatus for performing a desired process on an object to be processed by a gas supplied into the processing container using energy supplied into the processing container through the dielectric window,
A processing apparatus in which a surface of the dielectric window is processed in advance by millimeter waves.   The processing apparatus according to claim 1, wherein the processing by the millimeter wave includes heating a surface of the dielectric window by a millimeter wave.   The processing apparatus according to claim 1, wherein the processing by the millimeter wave includes heating the surface of the dielectric window with a millimeter wave to smooth the surface. The dielectric window is
The processing apparatus as described in any one of Claims 1-3 currently processed by the millimeter wave at the temperature of 1200 degreeC or more. The dielectric window is
The processing apparatus according to claim 4, which has been processed in advance by millimeter waves at a temperature of 1600 ° C. or less. The dielectric window is
The processing apparatus according to any one of claims 1 to 5, wherein the processing apparatus is previously processed by a millimeter wave using a gas containing a component constituting the dielectric window.   The processing apparatus according to claim 1, wherein a material of the dielectric window is alumina ceramic. The dielectric window is
The processing apparatus according to any one of claims 1 to 7, wherein the processing apparatus is previously processed by millimeter waves using O ₂ gas.   The processing apparatus according to claim 1, wherein the heating by the millimeter wave is performed in an oxygen atmosphere. The dielectric window is
Consists of multiple dielectric window parts,
Each dielectric window part
The processing apparatus according to any one of claims 1 to 9, wherein the processing apparatus is fixed to the processing container using a beam formed in a lattice shape so that at least a surface processed in advance by millimeter waves faces the stage. . A method of using a processing apparatus comprising: a processing container; a dielectric window provided in the processing container; a gas supply source that supplies a desired gas into the processing container; and an energy source that outputs desired energy. And
The surface of the dielectric window is pre-processed by millimeter waves,
Method of using a processing apparatus for performing a desired process on an object to be processed by a gas supplied into the processing container using energy output from the energy source and supplied into the processing container through the dielectric window .   A dielectric member for a dielectric window of a plasma processing apparatus whose surface has been processed in advance by millimeter waves.