JP3123175B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus for generating plasma using microwaves among plasma processing apparatuses such as an etching apparatus, a CVD apparatus, and an ashing apparatus for performing plasma processing such as VLSI. The present invention relates to a plasma processing apparatus capable of obtaining uniform plasma processing.

[0002]

2. Description of the Related Art A plasma processing apparatus using microwaves is disclosed in Japanese Patent Application Laid-Open No. 63-103088. The device states that by confining microwave power in a cavity resonator, it enhances the microwave electric field and efficiently generates plasma.

[0003]

In the above prior art, the electromagnetic field in the resonator is affected by the connection position of the waveguide for supplying the microwave to the cavity resonator, the structure of the antenna for radiating the microwave to the processing chamber, and the like. And the microwave cannot be uniformly radiated to the processing chamber. Therefore, the plasma generated in the processing chamber becomes non-uniform, and it becomes difficult to uniformly process the substrate.

[0004]

In order to solve the above-mentioned problem, the electromagnetic field in the cavity resonator is generated so that only a predetermined resonance mode is generated and other resonance modes are not mixed.

[0005]

The resonance state in the cavity can be theoretically obtained by solving Helmholtz's equation under the boundary condition that there is no tangential component of the electric field on the wall of the resonator. When the shape of the cavity resonator is a geometrically simple structure such as a cylinder or a rectangular parallelepiped, the resonance state can be easily obtained analytically. Therefore, a columnar or rectangular parallelepiped cavity resonator is often used.

However, in an actual cavity resonator used in a plasma processing apparatus, it is necessary to provide an antenna for exciting an electromagnetic field and an antenna for radiating microwaves in a processing chamber. Is impossible. Also, due to the influence of processing accuracy and the like, the actual resonance form may be different from the theoretically predicted one. This difference can be considered to be due to mixing of other resonance modes other than the desired resonance mode. Therefore, in order to excite only the desired resonance mode, a filter that gives a loss to other resonance modes may be loaded in the cavity resonator.

The method of constructing the filter will be described below. In general, the electric field has no tangential component on the surface of a material having high conductivity such as a metal, and is perpendicular to the surface. When a metal having high conductivity is loaded in a space where an electric field such as a microwave exists, the electric field changes so that the electric field becomes perpendicular to the metal surface. However, when a metal having high conductivity is loaded so that the surface is perpendicular to the electric field, the original electric field distribution does not change. Therefore, in order to excite only a desired resonance mode in the cavity resonator, a material having high conductivity may be loaded so that its surface is perpendicular to the electric field of the desired resonance mode. A resonance mode having an electric field component parallel to the loaded metal surface cannot exist in the cavity resonator, and the loaded metal plays a role as a filter.

If there is a position where the electric field becomes zero in the desired resonance state, a metal having high conductivity may be loaded at this position. As described above, since the electric field is perpendicular to the surface of the metal surface as a resonance mode, a resonance mode that does not satisfy this boundary condition cannot exist in the cavity resonator, and only a desired resonance mode can be excited.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an etching apparatus using the present invention. A substrate 2 to be processed is installed in the processing chamber 1 so as to face the slot plate 3. For example, the oscillation frequency 13.
A 56 MHz high frequency power supply 4 is connected, and a bias voltage suitable for processing can be applied. The processing chamber 1 is maintained at a predetermined pressure suitable for processing by a processing gas introduction system and an exhaust system (not shown). Microwave source 5
Is transmitted by the rectangular waveguide 6 and introduced into the cavity resonator 7 from the side. The cavity resonator 7 is cylindrical and has a resonance mode of T
One that resonates in the _M030 mode is used. FIG. 9 shows the radial electric field distribution of the TM ₀₃₀ mode of the cylindrical cavity resonator. The electric field vector 18 has only a component parallel to the central axis of the cavity resonator 7, and the strength of the electromagnetic field does not change in the direction of the central axis. The electromagnetic field in the _TM030 mode is rotationally symmetric with respect to the central axis, and the intensity of the electromagnetic field does not change in the circumferential direction. Cylindrical cavity resonator

The electromagnetic field in TM ₀₃₀ mode when the central axis of

## EQU1 ##

[0011]

(Equation 1) J ₀ : Zero-order Bessel function j: Imaginary unit J ₁ : First-order Bessel function ε: Dielectric constant of vacuum ω: Angular frequency of microwave k _c = ρ ₀₃ / a = ω / c c: Speed of light (= 3.0 × 10 ⁸ m / s) a: radius of the cavity resonator ρ ₀₃ = 8.654 Further, when the microwave frequency is 2.45 GHz, for example, the position where the electric field becomes zero at the radius of 46.8 mm and the radius of 107.5 mm. And the radius of the cavity resonator 7 is 1
68.5 mm. The cavity resonator 7 is made of a metal having high conductivity, for example, copper or aluminum, and has an inner surface plated with silver to further reduce the loss. A coupling hole 8 is provided in the slot plate 3. Generally, when the coupling hole 8 is provided so as to form a slot antenna, microwaves can be efficiently radiated. It is known that the slot antenna is desirably provided on the surface of the slot plate 3 at right angles to the surface current flowing by the microwave. The surface current flows perpendicular to the magnetic flux density of the microwave.
Therefore, it is desirable to provide the slot in parallel with the magnetic flux density of the microwave. For this reason, the coupling hole 8 has an elongated shape in the circumferential direction as shown in FIG. 13 in consideration of the desired resonance mode of the cavity resonator 7 being the _TM030 mode. However, only the central coupling hole 8 is circular for simplicity. On the processing chamber side of the slot plate 3, a dielectric component 10 for introducing microwaves while maintaining the processing chamber 1 at a predetermined pressure is provided. As a material of the dielectric component 10, a material such as quartz, which has a small loss with respect to microwaves, is used. A mode filter 9 made of a metal having high conductivity, for example, copper or aluminum is loaded inside the cavity resonator 7. The structure of the mode filter 9 is shown in FIGS. The mode filter 9 is plated with silver to reduce the loss of microwaves, similarly to the inner surface of the cavity resonator 7.
Unnecessary modes that disturb the plasma uniformity are suppressed by the mode filter 9, and only the desired _TM030 mode is excited. Since unnecessary resonance is suppressed, uniform plasma processing can be easily performed on the substrate 2 even when the process conditions are changed. By changing the processing gas, the first embodiment can be used as a plasma processing apparatus such as a CVD apparatus or an ashing apparatus.

FIGS. 2 to 8 show the structure of a mode filter for exciting only the _TM030 mode of the cylindrical cavity resonator. Hereinafter, each mode filter will be described. The mode filter shown in FIGS. 2 and 3 is provided with a plurality of coupling holes 12 for electromagnetic field coupling in a cylinder 11 made of a thin metal plate. 2 shows a top view and FIG. 3 shows a side view. The cylinder 11 is made of a metal having a high conductivity, such as copper or aluminum, and its surface is plated with a metal having a high conductivity, such as silver, to reduce microwave loss. The cylinder 11 is installed in the resonator such that its central axis coincides with the central axis of the cavity resonator 7. The radius of the cylinder 11 is determined so that the surface of the cylinder comes to a position where the electric field of the _TM030 mode becomes zero. The microwave frequency is 2.45
For GHz, the radius of the cylinder is 46.8 mm or 10
7.5 mm. In the first embodiment, an example is shown in which both the mode filters having a radius of 46.8 mm and a radius of 107.5 mm are loaded inside the cavity resonator 7, but only one of them may be loaded. The shape of the coupling hole 12 is desirably provided in a slot shape in parallel with the microwave magnetic field in order to strengthen the coupling of the electromagnetic field, but may be arbitrarily set according to a desired degree of coupling. If you control the strength of the bond,
Electromagnetic fields inside and outside the cylinder can be controlled. That is, if the electromagnetic field is excited from outside the cylinder by weakening the coupling, the electromagnetic field inside the cylinder becomes weaker than the electromagnetic field outside the cylinder,
The intensity of the microwave radiated from each coupling hole 12 of the slot plate 3 can be adjusted. Therefore, the distribution of generated plasma can be controlled, and uniform plasma processing can be performed more easily.

The mode filter shown in FIGS. 4 and 5 is a spiral 13 made of a highly conductive metal such as copper or aluminum. 4 shows a top view and FIG. 5 shows a side view. The surface of the spiral 13 is plated with a material having high conductivity, for example, silver or the like, to reduce microwave loss. The spiral 13 has a TM like the cylinder shown in FIGS.
Because it is installed at the position where the electric field of ₀₃₀ mode becomes zero,
The radius of the spiral 13 is such that the microwave frequency is 2.45 GHz.
Is 46.8 mm or 107.5 mm. The smaller the diameter of the wire is, the smaller the degree of disturbing the electromagnetic field of the _TM030 mode is desirable. As with the cylinders shown in FIGS. 2 and 3, a spiral having a radius of 46.8 mm and a spiral having a radius of 107.5 mm may be simultaneously loaded in the cavity resonator 7, or only one of them may be loaded. The degree of coupling between the electromagnetic fields inside and outside the spiral can be controlled by changing the pitch of the spiral 13.

The mode filter shown in FIGS. 6 and 7 has a plurality of wires 14 made of a metal having high conductivity, for example, copper or aluminum.
The upper and lower parts are fixed by a donut-shaped member 15 made of the same material. 6 shows a top view and FIG. 7 shows a side view. The surface is plated with a highly conductive material such as silver to reduce microwave loss. The wires 14 are arranged on the circumference because they are arranged at positions where the electric field of the _TM030 mode becomes zero. The radius of the circle on which each wire is arranged is 46.8 mm or 107.5 mm when using a microwave having a frequency of 2.45 GHz.
Becomes It is desirable that the diameter of the wire 14 and the thickness of the donut-shaped member 15 be small, since the degree of disturbing the electromagnetic field in the _TM030 mode is small. By changing the number of wires 14, the degree of coupling between the electromagnetic field inside and outside the mode filter can be controlled.

FIG. 8 shows a state in which a mode filter having another structure is loaded inside the cavity resonator 7. This mode filter has a structure in which a circular hole 17 is formed in the center of a circular plate 16 of a thin plate of a metal having high conductivity, for example, copper or aluminum, and the surface is made of silver or the like in order to reduce microwave loss. Plated with highly conductive material. Since the electric field of the TM ₀₃₀ mode with only the component parallel to the central axis of the cavity resonator 7, even when loaded with vertically disc 16 to the central axis TM ₀₃₀
Do not disturb the mode. A resonance mode having an electric field component in a direction perpendicular to the central axis of the cavity resonator 7 can be effectively suppressed. FIG. 8 shows an example in which two disks 16 are loaded,
The number may be arbitrarily determined. The holes 17 are for coupling electromagnetic fields, and the shape and number thereof are arbitrary.

The desired resonance mode of the cavity resonator 7 is TM
_Although the case of the ₀₃₀ mode has been described, other resonance modes can be similarly considered. That is, a method of loading a mode filter such that a surface of a metal having high conductivity is located at a position where the electric field of a desired resonance mode is zero, or a method of loading a metal having high conductivity perpendicular to the electric field of a desired resonance mode By using, only a desired resonance state can be obtained.

The desired resonance mode of the cylindrical cavity resonator is TM
Examples of resonance modes other than the ₀₃₀ mode

The case of the TM ₀₁₁ mode will now be described. The electric field distribution of TM ₀₁₁ mode is

It can be expressed as follows. However, it is expressed in a cylindrical coordinate system in which the central axis of the cylindrical cavity resonator is the z-axis.

[0019]

(Equation 2) j: imaginary unit J ₀ : 0th order Bessel function J ₁ : 1st order Bessel function ε: dielectric constant of vacuum ω: angular frequency of microwave k _c = ρ ₀₁ / a a: radius of cavity resonator ρ ₀₁ = 2. 405 β = √k ² −k _c ² k = ω / c c: speed of light (= 3.0 × 10 ⁸ m / s) FIG. 10 shows the distribution of the electric field vector in the TM ₀₁₁ mode of the cylindrical cavity resonator. The electric field of the TM ₀₁₁ mode becomes zero only at the center point of the center axis 19 of the cavity resonator shown by the broken line except for the wall surface. Therefore, it is impossible to form a mode filter having a metal surface at a position where the electric field is zero. Therefore, the mode filter is designed by a method in which the surface is arranged in a direction perpendicular to the electric field vector of the TM ₀₁₁ mode. For example, a mode filter as shown in FIGS. 11 and 12 can be configured. 11 shows a top view and FIG. 12 shows a side view. The inner surface 20 of the cavity resonator is indicated by a dashed line. The height of the cylindrical cavity resonator that resonates in the _TM011 mode is, for example, 2.45 in the microwave frequency.
GHz, the radius of the cylindrical cavity is 100 mm.
2 mm. The mode filter is configured by combining the ring-shaped wire 21 and the bow-shaped wire 22. The wire is made of a metal having a high conductivity, for example, copper, and its surface is plated with a material having a higher conductivity, for example, silver. It is desirable that the diameters of the ring-shaped wire 21 and the bow-shaped wire 22 are small. Although the example in which the number of the bow-shaped wires 22 is eight and the number of the ring-shaped wires 21 are three is shown, the number of each may be set arbitrarily.

FIG. 14 shows a cavity resonator that can be used in the embodiment of the present invention. In the cavity resonator shown in FIG. 14, a rectangular waveguide 6 for transmitting microwaves from a microwave generation source to the cavity resonator is connected to a side surface of a first cylindrical cavity resonator 21. The resonance state of the cavity resonator 21 is TM
₀₁₀ mode. A coupling hole 23 for coupling an electromagnetic field with the second cavity resonator 22 is provided on the lower surface of the cavity resonator 21. The resonance mode of the cavity resonator 22 is the _TM030 mode. The electric field 18 of the TM ₀₁₀ mode and the TM ₀₃₀ mode, which are resonance states inside the cavity resonator 21 and the cavity resonator 22, is shown.
Since the _TM010 mode is obtained by extracting only the central portion of the _TM030 mode, the electromagnetic fields of the two at the coupling hole 23 are completely matched, and the cavity resonator 22 can be efficiently excited. Any of the mode filters shown in FIGS. 2 to 8 may be loaded inside the cavity resonator 22. When the microwave frequency is, for example, 2.45 GHz, the inner radius of each of the cavity resonators 21 and 22 is 46.8 mm, 1
07.5 mm. By exciting the cavity resonator 22 using the cavity resonator 21, the bias of the electromagnetic field due to the connection of the rectangular waveguide 6 does not reach the cavity resonator 22,
The resonance state in the cavity resonator 22 can be more easily unified. Therefore, uniform plasma processing can be obtained.

[0021]

According to the present invention, uniform plasma processing can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a plasma processing apparatus using the present invention.

FIG. 2 is a diagram illustrating a mode filter used in an embodiment of the present invention.

FIG. 3 is a diagram showing a mode filter used in an embodiment of the present invention.

FIG. 4 is a diagram showing a mode filter used in an embodiment of the present invention.

FIG. 5 is a diagram showing a mode filter used in an embodiment of the present invention.

FIG. 6 is a diagram showing a mode filter used in an embodiment of the present invention.

FIG. 7 is a diagram showing a mode filter used in an embodiment of the present invention.

FIG. 8 is a diagram showing a cavity resonator and a mode filter used in the embodiment of the present invention.

FIG. 9 is a diagram showing an electric field distribution in a _TM030 mode.

FIG. 10 is a diagram showing an electric field distribution in a TM ₀₁₁ mode.

FIG. 11 is a diagram showing a mode filter used in an embodiment of the present invention.

FIG. 12 is a diagram showing a mode filter used in an embodiment of the present invention.

FIG. 13 is a view showing a structure of a slot plate.

FIG. 14 is a diagram showing a cavity resonator used in an example of the present invention.

[Description of Signs] 1 ... Processing chamber, 2 ... Substrate to be processed, 3 ... Slot plate, 4 ... High frequency power supply, 5 ... Microwave generation source, 6 ... Rectangular waveguide, 7 ... Cavity resonator, 8 ... Coupling hole , 9: Mode filter, 10: Dielectric component, 11: Cylinder, 12: Coupling hole, 13: Spiral, 14: Wire rod, 15: Donut-shaped member, 16: Disk, 17: Hole, 18: Electric field vector, 19 ... Center axis, 20 ... Inner surface of cavity resonator, 21 ... Cavity resonator, 22 ... Cavity resonator, 23 ... Coupling hole.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H01L 21/3065 H01L 21/31 C 21/31 21/302 B (58) Fields surveyed (Int.Cl. ⁷ , DB name) H05H 1/46 H01L 21/3065 C23C 16/50 C23F 4/00

Claims (5)

(57) [Claims] 1. A microwave generation source for generating a microwave.
Means , and a microwave generated by the microwave source.
Placing the cavity resonator means for resonating a, a substrate to be processed therein
A processing chamber means having a mounting base for the coupling plate means for electromagnetically coupling the <br/> cavity resonator means and the processing chamber means, before
The processing chamber means and the cavity resonator means are separated.
From the microwave source means to the cavity resonator means
And dielectrics component you introduced into the <br/> processing chamber is introduced by transmitting the microwaves are caused to resonate, and gas introducing means for introducing a process gas into the processing chamber, the processing chamber a plasma processing apparatus including a vacuum exhaust means for maintaining the pressure suitable for the treatment, desired within said cavity resonator means
Microwaves that resonate in modes other than
A plasma processing apparatus, wherein a mode filter section for switching is provided in the cavity resonator means . A plasma processing apparatus 2. A method according to claim 1, wherein said mode filter unit is made of high conductivity metal, characterized in that the surface is provided at a position where the electric field of the desired resonant mode does not exist Plasma processing equipment. 3. A plasma processing apparatus according to claim 1, said mode filter unit, a spiral made of a desired high linear material conductivity which wires are arranged in a position where an electric field is not present in the resonant mode Characteristic plasma processing apparatus. 4. A plasma processing apparatus according to claim 1, wherein the mode filter unit is characterized by a structure in which high conductivity plurality of wires is disposed at a position at which the electric field is not present in a desired resonant mode Plasma processing equipment. 5. The plasma processing apparatus according to claim 1, wherein the mode filter section is a metal plate having a high conductivity arranged so that a surface thereof is perpendicular to an electric field of a desired resonance mode. Plasma processing apparatus.