JP2009205921A - Microwave plasma treatment device, and usage of microwave plasma treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave plasma treatment device making a gas supplying position appropriate. <P>SOLUTION: This microwave plasma treatment device 10 includes: a vessel 100 for exciting plasma in the inside; a microwave source 900 supplying microwaves for exciting plasma in the vessel; coaxial pipes 600, 315 and the like transmitting the microwaves supplied from the microwave source 900; a plurality of dielectric plates 305 adjacent to the coaxial pipes 315 in a state facing the inside of the vessel 100, and making the microwaves having been transmitted through the respective coaxial pipes permeate therethrough to be released to the inside of the vessel 100; a gas supply source 800 supplying gas for exciting the plasma in the vessel; and gas passages 810 penetrating the respective insides of the plurality of dielectric plates 305 for introducing the gas into the vessel from gas holes A being the penetrated holes. Gas holes B penetrating metal electrodes 310 and the gas holes A are arranged at equal intervals. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a microwave plasma processing apparatus that generates a plasma by exciting a gas with a microwave and performs a desired process on an object to be processed by the generated plasma, and more particularly to a gas supply.

Microwave plasma is generated by introducing microwaves into a processing chamber in a reduced pressure state through a dielectric plate. In the microwave plasma processing apparatus, plasma electron density n _e is higher than the cut-off density n _c of the formula (1), the microwave is reflected in the vicinity of the plasma surface can not penetrate into the plasma, It propagates between the dielectric plate and the plasma as a surface wave. During propagation, part of the microwave is absorbed by the plasma as an evanescent wave and used to maintain the plasma. (For example, see Non-Patent Document 1.) On the other hand, if the plasma electron density n _e is lower than the cut-off density n _c, microwave, because it can enter into the plasma, the plasma state becomes unstable due to the electric field energy of the microwave.

n _c = ε _{0 me} ω ² / e ² (1)
epsilon ₀ is the dielectric constant of vacuum, m _e is the electron mass, omega microwave angular frequency, e is an elementary electric charge.

In the microwave plasma processing apparatus, a microwave of 2.45 GHz is mainly used. (1) According to the formula, the cut-off density n _c is proportional to the square of the frequency of the microwave, if low frequencies, it is possible to lower the cut-off density n _c dramatically. As a result, uniform even low plasma electron density n _e plasma is generated, it is possible to widen the process window.

The Electrotechnical Society / Microwave Plasma Research Special Committee “Microwave Plasma Technology”, published by Ohmsha, published on September 25, 2003, p69

  In order to propagate a microwave having a low frequency, it is preferable to use a coaxial tube rather than a waveguide. The waveguide has a large propagation path because its size depends on the wavelength, whereas the coaxial tube does not depend on the wavelength, and a compact propagation path can be constructed. is there. Further, if the dielectric plate for transmitting the microwave to the plasma is supported by the coaxial tube, the beam supporting the dielectric plate is not necessary, and the structure of the lid portion of the container is simplified. As a result, there is no gap inside the container, and there is no fear of abnormal discharge occurring in the gap, and there is no need to process the dielectric plate with high accuracy so as not to create a gap.

  In the microwave plasma processing apparatus having the above structure, processes involving chemical reactions such as film formation and etching are performed. In such a process, it is necessary to generate uniform plasma over the entire surface of the object to be processed, and to make the density of the gas necessary for the process and the density of the reaction product gas generated by the chemical reaction uniform. For this purpose, it is desirable to provide a plurality of gas holes at a substantially equal pitch on the surface facing the object to be processed and to supply the gas uniformly from the gas holes into the container.

  In order to solve the above problems, a microwave plasma processing apparatus in which the gas supply position is optimized is provided.

  That is, according to an aspect of the present invention, a container in which plasma is excited inside, a microwave source that supplies a microwave for exciting plasma in the container, and a microwave that is supplied from the microwave source A conductor rod that propagates through the container, a plurality of dielectric plates that face the inside of the container, are adjacent to the conductor rod, transmit the microwave propagated through the conductor rod, and emit the microwave into the container, and the container A gas supply source for supplying a gas for exciting the plasma into the inside of the plurality of dielectric plates, and the gas is introduced into the container through a first gas hole serving as a through-hole. There is provided a microwave plasma processing apparatus including a first gas flow path.

  According to this, the first gas flow path penetrates the inside of each of the plurality of dielectric plates. The gas passes through the first gas flow path and is introduced into the container from the first gas hole opened to the container side at the end of the first gas flow path. As a result, by introducing a gas at a desired flow rate from an appropriate position of each dielectric plate, the density of the gas required for the process and the density of the reaction product gas generated by the chemical reaction are made uniform, A uniform plasma can be generated over the entire surface.

  The first gas hole may be arranged at the same position on each dielectric plate. According to this, not only the gas can be supplied uniformly, but all the dielectric plates have the same shape, so that the dielectric plates can be easily manufactured and the manufacturing cost can be reduced. Can do.

  A plurality of the first gas holes may be arranged at the same position on each dielectric plate. According to this, since the gas is supplied from the plurality of gas holes provided in each dielectric plate, the gas flow can be made more uniform.

  The plurality of first gas holes may be arranged at an equal pitch at the same position on each dielectric plate. According to this, since the gas is uniformly supplied from the plurality of gas holes provided in the dielectric plate at an equal pitch, the gas flow can be made more uniform.

  The plurality of dielectric plates may be arranged at an equal pitch, and the plurality of first gas holes may be arranged at a pitch of 1 / integer of the pitch at which each dielectric plate is arranged. For example, when a plurality of dielectric plates are arranged at a pitch of 300 mm and the first gas holes are arranged at 50 mm (that is, a pitch of 1/6 of the pitch of 300 mm for arranging the dielectric plates), A plurality of first gas holes can be arranged at a pitch of 50 mm across the dielectric plate. According to this, gas can be supplied uniformly over the entire surface below the dielectric plate. As a result, more uniform plasma can be generated over the entire surface above the object to be processed, and a favorable plasma treatment can be performed on the object to be processed.

  The pitch at which the plurality of first gas holes are arranged is determined so that the pressure inside the first gas flow path is 10 kPa or more and 50 kPa or less with respect to a desired gas flow rate flowing through the first gas flow path. May be.

  According to this, by controlling the pressure inside the first gas flow path to 10 kPa or more, the gas collision frequency proportional to the pressure is sufficiently larger than the angular frequency of the microwave in the gas flow path. The occurrence of abnormal discharge in the gas flow path can be prevented. Further, the gas flow rate can be controlled with high accuracy by controlling the pressure inside the first gas flow path to 50 kPa or less.

  The first gas hole may be provided with a gas nozzle having a plurality of pores. According to this, the conductance of the gas flowing through the gas nozzle can be controlled.

  In particular, the diameter of the plurality of pores is preferably smaller than twice the sheath width, and the aspect ratio of the plurality of pores is preferably 20 times or more. According to this, the gas that has entered the pores is turned into plasma and the dielectric plate burns out due to abnormal discharge in the pores, or the reactive gas causes a chemical reaction in the pores to cause pores. It is possible to avoid the reaction product from adhering inside.

  The first gas hole may be provided with a gas nozzle formed from a porous body. This also makes it possible to control the conductance of the gas flowing through the gas nozzle. Moreover, it is possible to prevent plasma from entering the gas nozzle by setting the pore diameter of the porous body to a desired value or less in consideration of the mean free path of gas.

  The plurality of dielectric plates are formed with through holes, connected to the conductor rods through the through holes formed in the dielectric, and at least a part is adjacent to the surface of the dielectric plate on the object side In this state, a plurality of metal electrodes exposed from the surface of the dielectric plate on the object side and the inside of each metal electrode are penetrated, and the gas is introduced into the container from the second gas hole which is a through-hole. And a second gas flow path introduced into.

  The electric field energy of microwaves has a property of concentrating on sharp points and angular points. For this reason, when the structure of the lid portion of the container becomes complicated, there is a possibility that the electric field energy of the microwave concentrated on the convex portion enters the gap and causes abnormal discharge in the gap portion.

However, according to such a configuration, the structure of the lid portion of the container can be simplified by holding each dielectric plate by each metal electrode connected to the conductor rod. As a result, there is no gap in the vicinity of the lid portion inside the container, and there is no fear of abnormal discharge occurring in the gap, and it is not necessary to process the dielectric plate with high accuracy so as not to create a gap.
Further, the gas can be supplied uniformly using not only the plurality of first gas holes provided in the dielectric plate but also the second gas holes penetrating the metal.

  The diameter of the second gas hole may be determined so that the conductance of the first gas hole is equal to the conductance of the second gas hole with respect to a desired gas flow rate.

  According to this, the gas introduced from each of the first gas hole and the second gas hole can be controlled to the same flow rate. Thereby, the density of the gas required for the process and the density of the reaction product gas generated by the chemical reaction can be made uniform over the entire surface of the object to be processed.

  The plurality of first gas holes and the second gas holes may be arranged at an equal pitch at the same position of each dielectric plate. Accordingly, the gas can be supplied uniformly over the entire surface above the object to be processed, and uniform plasma can be generated.

  Each of the plurality of dielectric plates may be provided with a recess at a point-symmetrical position about the metal electrode, and the same number of the plurality of first gas holes may be provided in each recess.

  According to this, a plurality of dielectric plates 305 having a good symmetry are arranged at an equal pitch, and furthermore, the same number of gas holes A are provided in each recess 305a. Due to the symmetry of the arrangement of the dielectric plates and the regularity of the arrangement of the gas holes, uniform plasma can be efficiently generated from the same number of gas holes A and uniformly introduced into the recess 305a. .

  A plurality of the conductor rods may be provided corresponding to the plurality of dielectric plates. The plurality of conductor bars may be engaged with the plurality of dielectric plates on a one-to-one basis. Furthermore, each of the plurality of conductor rods may be engaged with the dielectric plate at the center of each of the plurality of dielectric plates.

  The plurality of dielectric plates may be rectangular plates. The plurality of dielectric plates may be arranged at equal intervals at a pitch that is an integral multiple of λg / 2.

  In order to solve the above problem, according to another aspect of the present invention, a microwave having a frequency of 1 GHz or less is output from a microwave source, and the microwave output from the microwave source is propagated to a conductor rod, The microwave propagating through the conductor rod is transmitted through a plurality of dielectric plates adjacent to the conductor rod, whereby the microwave is emitted into the container, and the first penetrates through the inside of the plurality of dielectric plates. A gas supplied from a gas supply source is introduced into the container through a first gas hole located at an end of the gas flow path of the gas, and the gas introduced into the container is excited by the emitted microwave. Thus, there is provided a method of using a microwave plasma processing apparatus for performing a desired plasma processing on an object to be processed.

According to this, a microwave with a frequency of 1 GHz or less is supplied into the container. Cut-off density n _c is proportional to the square of the frequency of the microwave, it is possible to lower the cut-off density n _c dramatically as compared with the case of using a 2.45GHz microwave. As a result, low plasma uniform plasma even electron density n _e is generated, it is possible to widen the process window may be subjected to various plasma process on a target object.

  In order to solve the above-mentioned problem, according to another aspect of the present invention, a container in which plasma is excited inside, a microwave source that supplies a microwave for exciting plasma in the container, A conductor rod for propagating microwaves supplied from the microwave source, and facing the inside of the container, adjacent to the conductor rod, and transmitting the microwave propagated through the conductor rod to be emitted into the container. A single or a plurality of dielectric plates, a gas supply source for supplying a gas for exciting plasma into the container, and the inside of each of the single or a plurality of dielectric plates, and through the through-holes There is provided a microwave plasma processing apparatus comprising: a first gas flow path for introducing the gas into a container through a certain first gas hole.

  According to the present invention, the density of the gas required for the process and the density of the reaction product gas generated by the chemical reaction can be made uniform over the entire surface of the workpiece.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the accompanying drawings, referring to FIG. 1 schematically showing a longitudinal section of the apparatus and FIG. 2 showing a ceiling surface of the apparatus for a microwave plasma processing apparatus according to an embodiment of the present invention. While explaining. 1 is a cross-sectional view of the device taken along line OO in FIG. In the following description and the accompanying drawings, components having the same configuration and function are denoted by the same reference numerals, and redundant description is omitted. Moreover, 1 sccm shall be 10 < ^-6 > / 60 (m < ³ > / sec).

(Configuration of plasma processing equipment)
The microwave plasma processing apparatus 10 includes a container 100 for plasma processing a glass substrate (hereinafter referred to as “substrate G”). The 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. An O-ring 205 is provided on the contact surface between the container main body 200 and the lid body 300, whereby the container main body 200 and the lid body 300 are sealed, and a processing chamber U is formed therein. The container body 200 and the lid body 300 are made of, for example, a metal such as aluminum and are electrically grounded.

  Inside the container 100, a susceptor 105 (stage) for placing the substrate G is provided. The susceptor 105 is made of, for example, aluminum nitride, and a power feeding unit 110 and a heater 115 are provided therein.

  A high frequency power supply 125 is connected to the power supply unit 110 via a matching unit 120 (for example, a capacitor). Further, a high-voltage DC power supply 135 is connected to the power feeding unit 110 via a coil 130. Matching device 120, high frequency power supply 125, coil 130, and high voltage DC power supply 135 are provided outside container 100. The high frequency power supply 125 and the high voltage DC power supply 135 are grounded.

  The power feeding unit 110 applies a predetermined bias voltage to the inside of the container 100 by the high frequency power output from the high frequency power source 125. The power feeding unit 110 is configured to electrostatically attract the substrate G with a DC voltage output from the high-voltage DC power supply 135.

  An AC power supply 140 provided outside the container 100 is connected to the heater 115, and the substrate G is held at a predetermined temperature by the AC voltage output from the AC power supply 140. The susceptor 105 is supported by a support body 145, and a baffle plate 150 for controlling the gas flow in the processing chamber U to a preferable state is provided around the susceptor 105.

  A gas discharge pipe 155 is provided at the bottom of the container 100, and the gas in the container 100 is discharged from the gas discharge pipe 155 using a vacuum pump (not shown) provided outside the container 100. The processing chamber U is depressurized to a desired degree of vacuum.

  The refrigerant supply source 700 is connected to the refrigerant pipe 705, and the refrigerant supplied from the refrigerant supply source 700 circulates in the refrigerant pipe 705 and returns to the refrigerant supply source 700, whereby the container 100 is brought to a desired temperature. To keep.

The two microwave sources 900 include a branching waveguide 905, eight coaxial waveguide converters 605, eight coaxial tubes 620, and eight branching coaxial tubes 640 positioned in parallel with the back direction of FIG. 7), each of the branch coaxial pipes 640 is connected to a propagation path including seven coaxial pipes 600, branch plates 610, and coaxial pipes 315. Thereby, the 120 kW (= 60 kW × 2 (2 W / cm ² )) microwaves output from the two microwave sources 900 propagate through the propagation path, pass through the plurality of dielectric plates 305, and enter the processing chamber. Supplied.

  Further description will be continued with reference to FIG. 3 showing the cross section AA of FIG. The coaxial pipe 600 and the coaxial pipe 315 are constituted by cylindrical inner conductors (shaft portions) 600a and 315a and outer conductors 600b and 315b, both of which are made of metal.

  The inner conductor 315a protrudes outside the container 100 through the lid portion 300d. The lid portion 300d is a portion where the lid body 300 and the external conductor 315b are integrated on the upper surface of the lid body 300. The inner conductor 315 a is lifted toward the outside of the container 100 by the fixing mechanism 500 including the lifting portion 510, the spring member 515, and the short-circuit portion 520 using the elastic force of the spring member 515.

  The short-circuit portion 520 electrically short-circuits the inner conductor 315a of the coaxial tube 315 and the lid portion 300d. The short-circuit portion 520 includes a shield spiral, and is provided so that the internal conductor 315a can slide up and down. Thus, by providing the short circuit part 520, the heat | fever which flowed into the metal electrode 310 from the plasma can be efficiently escaped to a lid through the internal conductor 315a and the short circuit part 520.

  The branch plate 610 is formed in a cross shape and is formed of a metal such as copper. The branch plate 610 is connected to the inner conductor 600a of the coaxial tube 600 at the center thereof, and is connected to the four inner conductors 315a at the ends thereof. The distance between the connection position of the branch plate 610 and the internal conductor 315a and the short-circuit portion 520 is designed to be λg / 4 with respect to the microwave guide wavelength λg.

  A ring-shaped dielectric 410 is provided between the lid 300d and the internal conductor 315a. The ring-shaped dielectric 410 penetrates the inner conductor 315a. An O-ring 415a and an O-ring 415b are provided on the inner peripheral surface and the outer peripheral surface of the ring-shaped dielectric 410, whereby the inside of the processing chamber U is vacuum-sealed.

  The inner conductor 315 a of the coaxial tube 315 is connected to the metal electrode 310 through a through hole provided in the center of the dielectric plate 305. The metal electrode 310 is exposed on the surface of the dielectric plate 305 on the substrate side. The metal electrode 310 has a conical shape and is made of a metal such as aluminum (Al). According to such a configuration, the dielectric plate 305 is lifted by the spring member 515 via the internal conductor 315 a while being held by the metal electrode 310, and is fixed to the inner wall of the container 100.

The dielectric plate 305 shown in FIG. 2 is a substantially square plate of 148 mm × 148 mm made of alumina (Al ₂ O ₃ ). The dielectric plates 305 are arranged vertically and horizontally at equal intervals at a pitch that is an integral multiple of λg / 2 (here, 1 time) when the wavelength of the branched coaxial tube 640 is λg (328 mm at 915 MHz). Thereby, 224 (= 14 × 16) dielectric plates 305 are evenly arranged on the ceiling surface of the container 100 of 2277.4 mm × 2605 mm. The dielectric plate 305 is not necessarily limited to a substantially square shape, and may be a rectangular shape.

  Further, as shown in FIG. 4, the two dielectric plates 305 are provided on the lower surface (the surface on the plasma side) of the dielectric plate 305 so as to surround the metal electrode 310 and have eight recesses around the metal electrode 310. 305a is provided at a substantially point-symmetrical position. When the concave portion 305a is provided in the dielectric plate 305, the electric field strength inside the dielectric plate 305 is particularly strong, and high-density plasma is stably generated in the vicinity of the concave portion 305a, so that plasma stability and plasma excitation efficiency are improved. To do.

  A groove 300a is cut in the metal surface of the lid 300d. When a low-frequency microwave of 1 GHz or less is supplied, not only a surface wave (hereinafter simply referred to as a surface wave) propagates between the dielectric plate 305 and the plasma, but also the metal surface on the inner surface of the processing vessel and the plasma. Surface waves (hereinafter referred to as conductor surface waves) propagate between them. The groove 300a suppresses the propagation of the conductor surface wave generated on the metal surface of the conductor inside the container 100 such as the lid portion 300d.

(Gas supply)
Gas (including plasma excitation gas) supplied from the gas supply source 800 shown in FIG. 1 flows into the gas introduction path 315c penetrating the internal conductor 315a shown in FIG. 4 via the gas line 805. Further, the gas passes through the gas flow path 810 (corresponding to the first gas flow path) penetrating the dielectric plate 305, and from the eight gas holes A (corresponding to the first gas holes) that are the through holes. It is introduced into the processing chamber U. The gas also flows through a gas flow path 815 (corresponding to the second gas flow path) penetrating the inside of the metal electrode 310, and from the gas hole B (corresponding to the second gas hole) which is the through-hole, to the processing chamber. Introduced into U.

  As described above, since the dielectric plate 305 has a shape with good symmetry, uniform plasma is likely to be generated in one dielectric plate 305. In addition, by arranging the plurality of dielectric plates 305 at equal intervals that are integral multiples of λg / 2, uniform plasma can be generated when microwaves are introduced using the inner conductor 315a of the coaxial tube. .

  Further, in the present embodiment, the same number (one in FIG. 4) of gas holes A is provided in each recess 305a. Thereby, uniform plasma can be efficiently generated from the gas introduced into the recess 305a from the same number of gas holes A.

(Optimization of gas supply position)
If the gas hole A is provided at the same position of each dielectric plate 305, the shape of all the dielectric plates 305 becomes the same, so that the dielectric plates 305 can be easily manufactured. In order to arrange the gas holes at the same position on each dielectric plate 305 and arrange the gas holes at an equal pitch, the pitch of the gas holes is set to 1 / integer of the pitch of the dielectric plate 305.

  If the dielectric plates 305 are arranged vertically and horizontally at a pitch of λg (in-tube wavelength of coaxial tube) / 2, for example, the pitch of the gas holes may be λg / 2m (m = 1 or more integer). . It is preferable to reduce the pitch of the gas holes (to increase m), because the gas flow becomes uniform and the pressure of the gas flow path decreases due to the increase of gas holes. Since the proportional collision frequency of the gas is sufficiently higher than the angular frequency of the microwave, the risk of discharge in the gas flow path formed in the gas dielectric increases, and the manufacturing cost increases. Moreover, the pitch of the gas holes cannot be reduced unnecessarily due to structural limitations.

  FIG. 4 is an example when m = 3. The gas holes A are provided at a pitch of λg / 6 (= 54.6 mm) around the gas hole B opened through the metal electrode 310. Thus, one gas hole A is provided in each of the eight recessed portions 305a on the lower surface of the dielectric plate at equal intervals with the gas hole B below the metal electrode 310 as the center.

(Conductance)
In order to discharge gas evenly from the gas holes A and B, it is necessary to make the conductances of the gas holes A and B substantially equal. Therefore, first, a general formula representing the conductance of the gas flowing through the gas hole will be described.

  The pressure region satisfying the cylinder diameter D >> gas mean free path λ is called the viscous flow region, and the molecules move while colliding with each other. In this region, conductance is proportional to pressure. Conversely, the pressure region satisfying the cylinder diameter D << gas mean free path λ is called the molecular flow region. The molecules collide with the tube wall and there are few interactions between the molecules. That is, the factor that hinders gas transport is a phenomenon in which molecules collide with the tube wall and scatter, and the magnitude of conductance does not depend on pressure.

A conductance G _hole of a cylinder having a length L and a diameter D shown on the left in FIG. 5 is approximately expressed by Expression (2).

Here, Q represents the amount (flow rate) of gas flowing per unit time (Pa · m ³ / s), and ΔP represents the difference (P ₁ −P ₂ ) between the upstream pressure and the downstream pressure of the cylinder. The first term on the right side of the cylindrical conductance G _hole is the viscous flow conductance, and the second term is the molecular flow conductance. The gas viscosity coefficient η included in the viscous flow is derived from the gas molecule (atom) mass M, the Boltzmann constant k, the gas temperature T, and the gas collision diameter σ as shown in the above equation.

The conductance G _orifice (critical pressure condition P ₁ > ˜2P ₂ ) of the orifice having the diameter D is approximately expressed by the equation (3).

Here, Q represents a volume flow rate (m ³ / s), and ΔP represents a difference (P ₁ −P ₂ ) between the upstream pressure and the downstream pressure of the orifice. C _C included in the conductance G _orifice is a contraction coefficient (0.82 in the case of an orifice), N _L is the Roschmitt number, γ is the gas specific heat ratio, and A ₁ is the area of the orifice.

The conductance G of the gas hole is approximately expressed by the following equation (4) using the equations (2) and (3).
1 / G = 1 / G _orifice + 1 / G _hole (4)

For example, according to equation (2), when P ₁ >> P ₂ , the viscous flow conductance term is generally proportional to the pressure P ₁ . Further, in the case of P ₁ >> P ₂ and when the pressure of the gas flow path is 10 kPa or more, the mean free path λ of the gas is several μm or less, which is sufficiently larger than the diameter D of the gas hole of several tens of μm or more. Get smaller. As a result, in the equation (2), the viscous flow conductance term is sufficiently larger than the molecular flow conductance term, so the molecular flow conductance term is negligible. Therefore, ΔP (= Q / G _hole ) is approximately proportional to Q / ΔP. That is, ΔP is approximately proportional to Q ^1/2 .

On the other hand, according to the equation (3), the orifice conductance G _orifice does not depend on the pressure P ₁ . Therefore, ΔP (= Q / G _orifice ) is approximately proportional to Q. From this result, the pressure difference between the upstream pressure P ₁ and downstream pressure P ₂ increases, the orifice is seen that a large influence on the flowability of the gas than cylindrical.

(Gas hole shape)
As shown in FIGS. 4 and 5, the gas hole A provided in the dielectric plate is formed from a gas nozzle 820 in which a large number of thin tubes hl are bundled. The diameters and numbers of the narrow tubes hl inside the gas nozzle 820 are determined on the condition that gas does not enter the ultrathin tubes and the flow rate of the gas is accurately controlled. In order to prevent gas from entering each ultrathin tube, it is necessary to consider the relationship between the diameter D of the gas hole and the mean free path, sheath pressure, and aspect ratio of the gas. In order to accurately control the gas flow rate, the conductance needs to be set to an appropriate value.

  The gas nozzle 820 is installed at the end of a gas flow path 810 provided inside the dielectric plate 305. When gas enters the gas nozzle 820 from the container side, the gas in the gas nozzle 820 is turned into plasma by microwave electric field energy that passes through the dielectric plate 305. As a result, abnormal discharge occurs in the gas flow path 810 and the gas nozzle 820 in the dielectric plate, the dielectric plate 305 is burned out, or the reactive gas causes a chemical reaction inside the narrow hole hl of the gas nozzle 820. There arises a problem that the reaction product adheres to the fine hole hl.

  Therefore, the diameter of the narrow hole hl of the gas nozzle 820 is set to a size (for example, a diameter of 50 μm) that prevents the plasma excitation gas from entering the gas nozzle 820 based on the mean free path of the plasma excitation gas.

  For the gas hole B provided in the dielectric plate 305, the diameter of the gas hole B is smaller than twice the sheath width, and the aspect ratio (the length of the gas hole / the diameter of the gas hole) is set to 20 times or more. In the gas flow path 810 inside the dielectric, the plasma is prevented from entering and the pressure of the gas flow path 810 when a desired gas flows is increased (electron collision frequency >> microwave angular frequency). Do not discharge.

FIG. 6 shows the result of calculating the gas flow path pressure for Ar gas based on the equation (4). Under the conditions under which the process is performed, the electron density in the vicinity of the dielectric plate is at most 2 × 10 ¹² cm ⁻³ , and the sheath width at this time is approximately 26 μm. Therefore, in order to prevent plasma from entering the gas nozzle 820 in the gas hole A, the diameter of the thin tube hl of the gas nozzle 820 is 50 μm, which is twice or less the sheath width, and the length of the gas hole (narrow tube) is 4 mm.

  In FIG. 6, when (a) a gas hole A (a gas nozzle 820 in which 18 thin tubes hl having a gas hole diameter of 50 μm and a gas hole length of 4 mm) are provided in the dielectric plate 305, (b) the gas hole B is formed in the metal electrode 310. The relationship between the gas flow rate (sccm) and the gas flow path pressure (kPa) is shown for the case where the tip of a gas pipe having a gas hole diameter of 118 μm and a gas hole length of 4 mm is provided.

  If the pressure in the gas flow path is too low, the gas collision frequency proportional to the pressure is sufficiently higher than the angular frequency of the microwave in the gas flow path, and abnormal discharge occurs in the gas flow path. Therefore, it is desirable that the pressure of the gas flow path be 10 kPa or more. On the other hand, if the pressure of the gas flow path is too high, it becomes difficult to control the gas flow rate, so the pressure of the gas flow path is desirably 50 kPa or less.

  As shown in FIG. 4, when the gas holes are provided at a pitch of 54.6 mm, the gas flow rate per gas hole is about 2 to 10 sccm under the condition where the process is performed. The number of the thin tubes hl inside the gas nozzle 820 is set to 18 so that the pressure of the gas flow path falls within the range of 10 to 50 kPa in this flow rate range.

  Next, the gas holes provided in the metal electrode 310 so that the conductance of the gas holes B provided in the metal electrode 310 is substantially equal to the conductance of the gas holes A provided in the dielectric plate 305 at a desired gas flow rate (2 to 10 sccm). The diameter was determined to be 118 μm, and the length of the gas hole was determined to be 4 mm.

  As a result, the gas is turned into plasma inside the gas nozzle 820, abnormal discharge occurs inside the narrow hole hl, the dielectric plate 305 burns out, or the reactive gas undergoes a chemical reaction inside the narrow hole hl. It is possible to eliminate the problem that the reaction product adheres to the fine hole hl. Further, by determining the diameters of the gas hole A and the gas hole B so that the conductances are the same, the gas flow can be accurately controlled.

  As shown in FIG. 7, the gas nozzle 820 may be formed of a porous P or a combination of the porous P and the gas nozzle N. Further, the gas hole B provided in the metal electrode 310 may be porous, or may be a combination of a porous and a nozzle in which an ultrathin tube is bundled. However, it is preferable that the structure of the gas hole B is the same as that of the gas hole A provided in the dielectric plate 305 because the conductance can be easily made the same.

  According to the microwave plasma processing apparatus according to the present embodiment described above, by optimizing the gas supply position and optimizing the shape and structure of the gas holes, the gas density and chemical reaction required for the process can be improved. The density of the generated reaction product gas can be made uniform over the entire surface of the object to be processed.

  Note that the number of gas holes A arranged on the ceiling surface of the container 100 may be plural or singular.

  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 invention of the microwave plasma processing apparatus can be made the embodiment of the method of using the microwave plasma processing apparatus.

(Frequency limitation)
By using the microwave plasma processing apparatus 10 according to each of the embodiments described above, a microwave having a frequency of 1 GHz or less is output from the microwave source 900, so that favorable plasma processing can be realized. In conventional microwave plasma processing apparatus is mainly, although 2.45GHz microwave was used, according to the above (1), the cut-off density n _c is proportional to the square of the frequency of the microwave . Therefore, if the frequency to 1 GHz, it is possible to lower the cut-off density _{n c} to about 1/7 in the case of 2.45 GHz. As a result, a uniform or low plasma electron density n _e plasma is generated, it is possible to widen the process window.

NF gas is one of the gases that are most difficult to ignite. Cut-off density _{n c} is practical equal frequency as 1.4 × ¹⁰ 11 ^{cm -3} is an electron density in the case of using the NF gas is 1 GHz. That is, if a frequency of 1 GHz or less is selected as the microwave frequency, uniform plasma can be excited with a practical power density using any gas.

  Therefore, by using a microwave of 1 GHz or less, a surface wave does not spread in a single gas state with a certain level of power of a microwave with a frequency of 2.45 GHz, and a F-type single that could not excite a uniform and stable plasma. Even with one gas, a uniform and stable plasma can be excited. Accordingly, the cleaning gas is excited using a practical microwave power, and the inside of the plasma processing apparatus can be cleaned by the plasma generated thereby.

  For example, a microwave having a frequency of 1 GHz or less is output from the microwave source 900, and the microwave output from the microwave source 900 is propagated to the coaxial waveguides (640, 620, 600, 315). Microwaves propagating through the coaxial tube are transmitted through a plurality of dielectric plates 305 adjacent to the coaxial tube, thereby releasing the microwaves into the container 100. The gas hole A is located at the end of the gas flow path 810 that penetrates the inside of the plurality of dielectric plates 305. From this gas hole A, the cleaning gas supplied from the gas supply source 800 is introduced into the container 100, and the gas introduced into the container 100 is excited by the emitted microwaves to cause the substrate G to have a desired plasma treatment. Apply. The inside of the plasma processing apparatus can be cleaned only with the F-based gas by the low-frequency microwave.

  The introduction of “Microwave Plasma Technology” published by Ohmsha, published on September 25, 2003, edited by the IEEJ / Microwave Plasma Research Special Committee, In this specification, the microwave frequency is set to 300 MHz or higher.

  As mentioned above, although one 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, according to the microwave plasma processing apparatus of the present invention, a large-area glass substrate, a circular silicon wafer, or a square SOI (Silicon On Insulator) substrate can be processed.

  In addition, the dielectric plate provided in the plasma processing apparatus according to the present invention may be a plasma processing apparatus having a plurality of dielectric plates 305, and as shown in FIG. A plasma processing apparatus having a body plate 305 may be used.

  Also in the plasma processing apparatus of FIG. 8, the gas (including the plasma excitation gas) flows into the gas introduction path 315c penetrating the inner conductor 315a. Further, the gas passes through the gas flow path 810 (corresponding to the first gas flow path) penetrating the dielectric plate 305 and has a plurality of gas holes A (first gas holes) arranged uniformly on the ceiling surface. To the processing chamber U. The gas also flows through a gas flow path 815 (corresponding to the second gas flow path) penetrating the inside of the metal electrode 310, and from the gas hole B (corresponding to the second gas hole) which is the through-hole, to the processing chamber. Introduced into U.

  Also by this, since the gas holes A and B are provided at the same pitch in one dielectric plate 305 and the metal electrode 310, uniform plasma can be generated.

  In the microwave plasma processing apparatus according to the present invention, any plasma processing such as film formation processing, diffusion processing, etching processing, and ashing processing can be performed.

It is a longitudinal cross-sectional view of the microwave plasma processing apparatus concerning one Embodiment of this invention. It is the figure which showed the ceiling surface of the microwave plasma processing apparatus concerning the embodiment. It is sectional drawing to which the cover part vicinity concerning the embodiment was expanded. It is a figure for demonstrating the position of the gas hole of the dielectric material board concerning the embodiment. It is the figure which showed the gas nozzle attached to the gas hole concerning the embodiment. It is the graph which showed the relationship between the pressure of a gas flow path and gas flow volume, and the conductance of gas. It is the figure which showed the other gas nozzle. It is a longitudinal cross-sectional view of the microwave plasma processing apparatus concerning other one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Microwave plasma processing apparatus 100 Container 200 Container main body 205,415a, 415b O-ring 300 Lid body 300a Groove 300d Lid part 305 Dielectric plate 305a Recessed part 310 Metal electrode 315, 600, 620, 640 Coaxial pipe 315a, 600a Inner conductor 410 Ring-shaped dielectric 500 Fixing mechanism 515 Spring member 520 Short-circuit 605 Coaxial waveguide converter 610 Branch plate 900 Microwave source 905 Branch waveguide U Processing chamber

Claims (21)

A container in which plasma is excited,
A microwave source for supplying a microwave for exciting plasma in the container;
A conductor rod for propagating microwaves supplied from the microwave source;
A plurality of dielectric plates facing the inside of the container, adjacent to the conductor rod, and transmitting microwaves propagating through the conductor rod to be emitted into the container;
A gas supply source for supplying a gas for exciting plasma in the container;
A microwave plasma processing apparatus comprising: a first gas flow path that penetrates through each of the plurality of dielectric plates and introduces the gas into the container through a first gas hole that is a through-hole.   The microwave plasma processing apparatus according to claim 1, wherein the first gas hole is disposed at the same position of each dielectric plate.   The microwave plasma processing apparatus according to claim 2, wherein a plurality of the first gas holes are arranged at the same position of each dielectric plate.   The microwave plasma processing apparatus according to claim 3, wherein the plurality of first gas holes are arranged at an equal pitch at the same position of each dielectric plate. The plurality of dielectric plates are arranged at an equal pitch,
5. The microwave plasma processing apparatus according to claim 4, wherein the plurality of first gas holes are arranged at a pitch of 1 / integer of a pitch at which each dielectric plate is arranged.   The pitch at which the plurality of first gas holes are arranged is determined so that the pressure inside the first gas channel is 10 kPa or more and 50 kPa or less with respect to a desired gas flow rate flowing through the first gas channel. The microwave plasma processing apparatus according to claim 5.   The microwave plasma processing apparatus according to claim 1, wherein the first gas hole is provided with a gas nozzle having a plurality of pores.   The microwave plasma processing apparatus according to claim 7, wherein a diameter of the plurality of pores is smaller than twice a sheath width, and an aspect ratio of the plurality of pores is 20 times or more.   The microwave plasma processing apparatus according to claim 1, wherein the first gas hole is provided with a gas nozzle formed of a porous body. Through holes are formed in the plurality of dielectric plates,
The dielectric plate is connected to the conductor rod through a through hole formed in the dielectric, and at least part of the dielectric plate is adjacent to the surface of the dielectric plate to be processed from the surface of the dielectric plate. A plurality of exposed metal electrodes;
A second gas flow path which penetrates the inside of each metal electrode and introduces the gas into the container from a second gas hole which is a through hole thereof. The described microwave plasma processing apparatus.   The diameter of the second gas hole is determined such that a conductance of the first gas hole is equal to a conductance of the second gas hole with respect to a desired gas flow rate. Microwave plasma processing equipment.   12. The microwave plasma processing apparatus according to claim 10, wherein the plurality of first gas holes and the second gas holes are arranged at an equal pitch at the same position of each dielectric plate. Each of the plurality of dielectric plates is provided with a recess at a point-symmetrical position around the metal electrode,
The microwave plasma processing apparatus according to claim 10, wherein the same number of the plurality of first gas holes is provided in each recess.   The microwave plasma processing apparatus according to claim 1, wherein a plurality of the conductive rods are provided corresponding to the plurality of dielectric plates.   The microwave plasma processing apparatus according to claim 14, wherein the plurality of conductor rods are engaged with the plurality of dielectric plates on a one-to-one basis.   The microwave plasma processing apparatus according to claim 15, wherein each of the plurality of conductor rods is engaged with the dielectric plate at a central portion of each of the plurality of dielectric plates.   The microwave plasma processing apparatus according to claim 1, wherein the plurality of dielectric plates are rectangular plates.   The microwave plasma processing apparatus according to claim 1, wherein the plurality of dielectric plates are arranged at equal intervals at a pitch that is an integral multiple of λg / 2.   The plasma processing apparatus according to claim 1, wherein the microwave source outputs a microwave having a frequency of 1 GHz or less. A microwave with a frequency of 1 GHz or less is output from the microwave source,
Propagating the microwave output from the microwave source to the conductor rod,
Microwaves propagated through the conductor rods are transmitted through a plurality of dielectric plates adjacent to the conductor rods to emit microwaves into the container,
A gas supplied from a gas supply source is introduced into the container from a first gas hole located at an end of a first gas flow path penetrating the inside of the plurality of dielectric plates;
A method of using a microwave plasma processing apparatus for exciting a gas introduced into the container by the emitted microwave to perform a desired plasma processing on a target object. A container in which plasma is excited,
A microwave source for supplying a microwave for exciting plasma in the container;
A conductor rod for propagating microwaves supplied from the microwave source;
A single or a plurality of dielectric plates facing the inside of the container, adjacent to the conductor rod, and transmitting microwaves propagating through the conductor rod to be emitted into the container;
A gas supply source for supplying a gas for exciting plasma in the container;
A microwave plasma comprising: a first gas passage that penetrates through each of the single or plural dielectric plates and introduces the gas into the container from a first gas hole that is a through-hole of the dielectric plate. Processing equipment.

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