JPH11111493A - Plasma processing equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a plasma processing apparatus capable of uniform processing over a large area. SOLUTION: A microwave distributor 27 has an introducing portion 27a having substantially the same width as the waveguide 23, a bifurcated branching portion 27b, and a bifurcated branching portion 27b. A parallel portion 27c extending parallel to the microwave traveling direction, and a dielectric line 28
And a divided portion 27d having substantially the same width as A stub 27e is provided at the center (branch point) of the boundary between the introduction part 27a and the branch part 27b. The dividing portion 27d is equally divided into four by partitioning plates 27f, 27g, 27g extending in the microwave traveling direction. Each part of the microwave distributor 27 has a length of n · λg / 4 (n: a positive integer) and forms a resonator structure. Four rectangular plates 28a, 28a, 28a, 28a made of a fluororesin, which constitute the dielectric line 28, are fitted in regions partitioned by the three partition plates 29. It is desirable that the width W of the waveguide 23, the width Wc of the parallel portion 27c, and the width Wd of each divided region are substantially equal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma processing apparatus for performing processes such as etching, ashing, and CVD using plasma.

[0002]

2. Description of the Related Art Plasma generated when external energy is applied to a reaction gas is widely used in processes such as etching, ashing, and CVD in the production of LSIs and LCDs. In particular, a dry etching technique using plasma has become an indispensable basic technique.

[0003] Generally, as a means for exciting plasma, a microwave of 2.45 GHz is used.
13.56 GHz RF (Radio Frequency) may be used. The use of microwaves has advantages such as higher density of plasma than the use of RF and the prevention of contamination because no electrodes are required for plasma generation. However, it has a drawback that it is difficult to generate plasma at a uniform density in a relatively large area, so that a large-diameter semiconductor substrate or an LCD glass substrate needs to be treated. It needs to be overcome.

[0004] For example, a plasma processing apparatus using a dielectric line proposed by the present applicant in Japanese Patent Application Laid-Open No. 62-5600 is known. This device has a structure in which the upper wall of the reaction chamber is sealed with a heat-resistant plate through which microwaves can pass, and a dielectric line for introducing microwaves is provided above it. It is possible to generate microwave plasma.

FIG. 4 is a schematic diagram showing this plasma processing apparatus.
FIG. 5 is a cross-sectional view, and FIG. 5 is a schematic cross-sectional view. 1 in the figure
Is a cylindrical reaction vessel made of a metal such as Al.
Constitutes a reaction chamber 2. The upper part of the reaction chamber 2
Heat resistant and microwave permeable
Quartz glass (SiO_Two), Alumina (Al
_TwoO_Three), Dielectric plate such as aluminum nitride (AlN)
In the microwave introduction window 4 made of
I have. The inside of the reaction chamber 2 faces the microwave introduction window 4
An object to be processed, for example, a semiconductor substrate S is placed at the position.
Stage 7 is provided, and the stage 7
High frequency power supply 9 is connected via matching box 8
ing. An exhaust device (not shown) is provided on the bottom wall of the reaction vessel 1.
An exhaust port 6 connected to the reaction vessel is formed.
A required reaction gas is introduced into the reaction chamber 2 on one side wall 1.
Gas inlet 5 is formed.

[0006] Above the microwave introduction window 4, a dielectric line 21 having a planar shape as shown in FIG. 5 is provided at a predetermined interval (air gap 20). Surrounded. A microwave waveguide 23 is connected to a side of the dielectric line 21, and a microwave oscillator 26 is attached to a tip of the microwave waveguide 23. The dielectric line 21 is
An introduction section 211 inserted into the microwave waveguide 23 and a rectangular section 213 positioned above the microwave introduction window 4 and large enough to cover the planar shape of the reaction chamber 2 are symmetrical with respect to the direction in which microwaves travel. It has a tapered shape and the rectangular part 213 and the introduction part 21
1 and a tapered portion 212 connecting to

In the plasma processing apparatus having the above-described structure, when an etching process is performed on the surface of the object to be processed, for example, the surface of the semiconductor substrate S, first, the gas is exhausted from the exhaust port 6 and the inside of the reaction chamber 2 is required. After setting the degree of vacuum and the pressure, the reaction gas is supplied from the gas supply pipe 5. Next, the microwave is oscillated in the microwave oscillator 26 and introduced into the dielectric line 21 via the waveguide 23. The microwave introduced from the introduction part 211 propagates through the tapered part 212, and further, the rectangular part 213
Spread within.

At this time, the microwave propagates in the traveling direction, and is reflected by the metal plate 22 surrounding both edges of the rectangular portion 213 to form a standing wave in the dielectric line 21 (rectangular portion 213). As described above, while the microwave propagates back and forth through the dielectric line 21, a leakage electric field is formed below the dielectric line 21, and the leakage electric field exponentially attenuates in the vertical direction of the lower surface while the microwave is attenuated. The light passes through the wave introduction window 4 and is guided into the reaction chamber 2. When plasma is generated in the reaction chamber 2 by the electric field, the energy changes the reaction gas into an active gas such as ions and radicals, and the active gas causes the surface of the semiconductor substrate S on the stage 7 to undergo processing such as etching. Is applied.

[0009]

In order to uniformly perform processes such as etching and ashing on the workpiece S, it is necessary that plasma is uniformly generated in the reaction chamber 2. It is necessary to form a single-mode electric field having uniform intensity in the traveling direction of the microwave in the plasma generation region. However, when the dielectric line 21 having the tapered portion 212 having the tapered edge is used, there are problems as described below.

In general, the width of the waveguide 23 is smaller than the diameter of the reaction chamber 2 in a plan view, so that the introduction part 211 corresponding to the width of the waveguide 23 and the rectangular part corresponding to the diameter of the reaction chamber 2 are formed. Department
The conventional matching portion (tapered portion 212) between the two portions 213 is tapered at both edges as shown in FIG. Since the taper angle θ affects the propagation mode of the microwave, the taper angle θ is simply increased to shorten the taper portion 212 to reduce the size of the apparatus, and the processing speed of the processing target S is reduced. In-plane uniformity may deteriorate.

The principle will be described. The microwave oscillated by the microwave oscillator 26 propagates through the microwave waveguide 23 in the TE10 mode, which is the fundamental mode of the microwave propagation mode, and propagates through the tapered portion 212 through the introduction portion 211 of the dielectric line 21. Next, the propagation mode in the rectangular part 213 is determined. Here, when the taper of the taper portion 212 is made steep (the taper angle θ is increased), the microwave in the TE10 mode, which is the basic mode, is attenuated, and a plurality of higher-order modes (TE30 mode, TE50 mode, etc.) are generated. I do. Since the propagation mode of the microwave in the higher-order mode (TE30 mode or TE50 mode) has a phase different from that of the fundamental mode (TE10 mode), a plurality of modes are superimposed on the actual propagation mode in the dielectric line 21. It will be.

When a plurality of modes including a higher-order mode are superimposed, microwaves are not propagated uniformly and the dielectric line
The intensity distribution of the electric field leaking from 21 also becomes non-uniform. Since the intensity distribution of the electric field generated by the rectangular portion 213 directly affects the generation of plasma, if this is non-uniform, the reaction chamber 2
There is a problem in that the plasma generated inside becomes non-uniform. Therefore, in order to reduce the size of the device, shortening the taper portion 212 by a simple method of making the taper steep is
This leads to uneven processing.

The present invention has been made in view of such circumstances, and has a configuration in which microwaves distributed by a microwave distributor are propagated to a dielectric line, so that a large area can be obtained without increasing the size. It is an object of the present invention to provide a plasma processing apparatus capable of performing uniform processing.

[0014]

According to the first aspect of the present invention,
Through a microwave waveguide, an electric field is generated by microwaves introduced into a plate-shaped dielectric line extending in the microwave traveling direction, and plasma is generated using the electric field,
In a plasma processing apparatus that performs processing on an object to be processed, the plasma processing apparatus includes a microwave distributor that is provided between the microwave waveguide and the dielectric line and has a plurality of branch paths.
The dielectric line is constituted by a plurality of rectangular plates extending from the tip of the branch path, and the plurality of rectangular plates are separated by a conductor plate.

In the microwave distributor, a fundamental mode microwave propagates through each branch and is guided to a plurality of rectangular plates forming a dielectric line. Therefore, an electric field having the same phase can be supplied from a plurality of rectangular plates constituting the dielectric line without increasing the number of microwave oscillation sources. In addition, since the rectangular plates are separated by the conductive plate, it is possible to prevent microwaves propagating through the rectangular plates from interfering with each other.

According to a second aspect of the present invention, in the first aspect, the widths of the branch path and the rectangular plate are substantially equal to the width of the microwave waveguide.

Since the widths are different, it is not necessary to provide a necessary matching portion, and only a microwave in a substantially fundamental mode propagates through each rectangular plate constituting the dielectric waveguide. By suppressing the generation of higher-order mode microwaves, the microwaves are uniformly propagated, and an electric field having a uniform intensity distribution leaks without the microwaves being abnormally radiated from the dielectric line. Therefore, uniform and stable plasma is generated and maintained in the reaction chamber, and uniform processing can be performed even in a large area.

According to a third aspect of the present invention, in the first or second aspect, the shape of the microwave distributor is symmetric with respect to a line extending in the microwave traveling direction.

As a result, a plurality of branch paths having the same shape can be formed.

According to a fourth aspect of the present invention, in the first, second or third aspect, the distance from the base end of the microwave distributor to the tip of each branch is substantially equal. Features.

Thus, the microwaves are distributed to the respective rectangular plates of the dielectric waveguide with the same phase and the same power, so that an equal electric field can be generated from each rectangular plate.

The invention according to claim 5 is the invention according to claims 1, 2, and 3.
Or 4 is characterized in that a phase adjusting member is provided at a branch point of the microwave distributor.

It is possible to suppress the phase from being shifted at the time of branching.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic sectional view showing a plasma processing apparatus according to the present invention, and FIG.
Is a schematic cross-sectional view thereof. In the figure, reference numeral 1 denotes a cylindrical reaction vessel made of a metal such as Al, in which a reaction chamber 2 is provided.
Is composed. The upper part of the reaction chamber 2 is hermetically sealed by a microwave introduction window 4. Microwave introduction window 4
Is made of a dielectric plate made of quartz glass (SiO ₂ ), alumina (Al ₂ O ₃ ), aluminum nitride (AlN), or the like, which has heat resistance and microwave permeability and has a small dielectric loss. An O-ring (not shown) is used to maintain the airtightness between the reaction vessel 1 and the microwave introduction window 4.
In the reaction chamber 2, at a position facing the microwave introduction window 4, a stage 7 for mounting, for example, a semiconductor substrate S, which is an object to be processed, is provided. The high frequency power supply 9 is connected via the. An exhaust port 6 connected to an exhaust device (not shown) is formed on the bottom wall of the reaction vessel 1, and a gas for introducing a required reaction gas into the reaction chamber 2 is provided on one side wall of the reaction vessel 1. An inlet 5 is formed.

A dielectric line 28 having a planar shape as shown in FIG. 2 is provided above the microwave introduction window 4 at a predetermined interval (air gap 20). Surrounded. On the side of the dielectric line 28, A
A microwave waveguide 23 (wavelength λg in the microwave tube) is connected via a microwave distributor 27 formed of a metal such as l, and a microwave oscillator 26 (wavelength λ) is provided at the tip thereof.
Is attached.

FIG. 3 is a schematic view showing the planar shape (cross section) of the microwave distributor 27. The microwave distributor 27 includes an introduction portion 27a having substantially the same width as the waveguide 23 (width W = 96 mm), a bifurcated bifurcation 27b, and a bifurcation 27b. It has a parallel portion 27c extending in parallel with the microwave traveling direction from the tip and a divided portion 27d having substantially the same width as the dielectric line. A stub 27e is provided at the center (branch point) of the boundary between the introduction part 27a and the branch part 27b. Division 27d
Is divided at the center in the width direction by a partition plate 27f extending in the microwave traveling direction. The end on the dielectric line 28 side from the position 2 · λg / 4 from the boundary between the parallel portion 27c and the divided portion 27d. The part is further divided by partitioning plates 27g, 27g to have a half width.

Each part of the microwave distributor 27 has a length of n · λg / 4 (n: a positive integer) in the microwave traveling direction so that microwaves can be efficiently introduced. Form a resonator structure. The length of the introduction part 27a is λ
g / 4, the length of the branch portion 27b is 3 · λg / 4, the length of the parallel portion 27c is λg / 4, and the length of the split portion 27d is 2 · λg / 4. , 27g longer.

The installation area of the dielectric line 27 is divided into four sections perpendicular to the microwave traveling direction by three partition plates 29 extending in the microwave traveling direction. The mounting positions of the three partition plates 29 are matched with the partition plates 27f, 27g, and 27g. In each of the four equally divided regions, four rectangular plates 28a, 28a, 28a, 28a made of a fluororesin such as Teflon (registered trademark), which constitute the dielectric line 28, are provided.
Are fitted. Then, the width W of the waveguide 23 and the parallel portion 27
It is desirable that the width Wc of c and the width Wd of each of the divided areas be substantially equal.

The operation of the apparatus of the present invention configured as described above will be described. When an etching process is performed on the surface of the object to be processed, for example, the surface of the semiconductor substrate S, first, the gas is exhausted from the exhaust port 6 to set the inside of the reaction chamber 2 to a required degree of vacuum and pressure. Supply gas. Next, the microwave (wavelength λ)
Is oscillated and introduced into the microwave distributor 27 via the waveguide 23.

First, the microwaves introduced into the introduction part 27a are stubs 27e provided at the boundary with the branch part 27b.
, The phase is adjusted, and the light is branched in two directions of the branching portion 27b and proceeds. Then, the light travels through a parallel portion 27c, which is two straight waveguides, and enters a divided portion 27d having a width of 4W. Since the microwave distributor 27 is symmetric with respect to a line extending in the microwave traveling direction, the microwaves introduced into any regions have substantially the same optical path shape and length. Therefore, these microwaves have the same phase and the same power.

The microwave introduced into the dielectric line 28 is
This is the same as the fundamental mode rectangle TE10 propagating through the waveguide 23. Therefore, the generation of higher-order modes is suppressed in any region, and the microwaves propagate uniformly without causing radiation. As a result, the electric field of the generated surface wave is uniformly distributed and attenuated exponentially in the vertical direction of the lower surface,
The light passes through the microwave introduction window 4 and is guided into the reaction chamber 2.
A uniform plasma is generated in the reaction chamber 2 by the uniform electric field, and the energy changes the reaction gas into an active gas such as ions and radicals. The active gas causes the surface of the semiconductor substrate S on the stage 7 to be etched, for example. And the like are uniformly applied.

In FIGS. 2 and 3, the width W of the waveguide 23, the width Wc of the parallel portion 27c, and the width Wd of each divided area are substantially equal. A matching portion having a tapered shape may be appropriately provided. In this case, the expansion of the width is smaller than in the conventional case, so that the tapered alignment portion can be made relatively short.

By changing the shape of the microwave distributor 27, a predetermined number of branches can be obtained, and the microwaves are evenly distributed to the dielectric line 28 having an area corresponding to the large-sized workpiece S. be able to. Conversely, when the object to be processed is small, a plurality of reaction chambers (or stages) respectively corresponding to the rectangular plates 28a of the dielectric line 28 are provided, and a processing object having a size corresponding to one rectangular plate 28a is provided. A configuration in which a plurality of objects are processed at one time can be adopted.

[0034]

[Embodiment] An etching process was performed by setting the respective sizes and processing conditions of the above-described plasma processing apparatus as follows. Reaction vessel 1 (reaction chamber 2) inner diameter: 340 mm Microwave introduction window 4 Diameter: 440 mm Thickness: 20 mm Microwave waveguide 23 Width: 96 mm Microwave distributor 27 Length: 370 mm Dielectric line 28 Length: 400 mm Width: 96 mm Thickness: 20 mm Oscillation wavelength 2.45 GHz Reaction gas C ₄ F ₈ / O ₂ workpiece S Diameter: 200 mm (8 inches, semiconductor substrate)

As a result, uniform plasma was generated in the reaction chamber 2 and a large-area semiconductor substrate could be uniformly processed.

[0036]

As described above, in the plasma processing apparatus according to the present invention, in the microwave distributor, the fundamental mode microwave propagates through each branch and is guided to the plurality of rectangular plates of the dielectric waveguide. Since only the fundamental mode microwaves are propagated by the rectangular plate, generation of higher order mode microwaves is suppressed, microwaves are uniformly propagated, and an electric field having a uniform intensity distribution leaks from the dielectric line, The present invention has excellent effects, for example, uniform and stable plasma is generated and maintained, and uniform processing can be performed even in a large area.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a plasma processing apparatus according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a plasma processing apparatus according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a microwave distributor.

FIG. 4 is a schematic longitudinal sectional view showing a conventional plasma processing apparatus.

FIG. 5 is a schematic cross-sectional view showing a conventional plasma processing apparatus.

[Explanation of symbols]

 23 Microwave waveguide 27 Microwave distributor 27a Introducing part 27b Branch part 27c Parallel part 27d Dividing part 27e Stub 28 Dielectric line 28a Rectangular plate S Workpiece

Claims (5)

[Claims] 1. An electric field is generated by a microwave introduced into a plate-shaped dielectric line extending in the direction of microwave propagation through a microwave waveguide, and a plasma is generated using the electric field to generate a plasma. In a plasma processing apparatus for processing an object, the plasma processing apparatus further includes a microwave distributor provided between the microwave waveguide and the dielectric line and having a plurality of branch paths, wherein the dielectric line includes the branch line. A plasma processing apparatus comprising: a plurality of rectangular plates extending from a front end of a road; and a plurality of rectangular plates separated by a conductive plate. 2. The plasma processing apparatus according to claim 1, wherein widths of the branch path and the rectangular plate are substantially equal to a width of the microwave waveguide. 3. The plasma processing apparatus according to claim 1, wherein the shape of the microwave distributor is symmetric with respect to a line extending in the microwave traveling direction. 4. The plasma processing apparatus according to claim 1, wherein a distance from a base end of the microwave distributor to a front end of each branch is substantially equal. . 5. A phase adjusting member provided at a branch point of the microwave distributor.
5. The plasma processing apparatus according to 2, 3, or 4.