JP3491190B2 - 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 that uses plasma to perform processing such as etching, ashing, and CVD.

[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 manufacture of LSIs and LCDs. In particular, dry etching technology using plasma has become an indispensable basic technology.

Generally, as an excitation means for generating plasma, a case where a microwave of 2.45 GHz is used,
In some cases, 13.56 GHz RF (Radio Frequency) is used. The use of microwaves has the advantages that a higher density plasma can be obtained than the case of using RF, and that electrodes can be prevented because plasma generation does not require electrodes. . However, since it has a drawback that it is difficult to generate plasma with a uniform density in a relatively large area, this point is required for processing a large-diameter semiconductor substrate or a glass substrate such as an LCD. Need to overcome.

Therefore, for example, there is known a plasma processing apparatus using a dielectric line, which is proposed by the present applicant in Japanese Patent Laid-Open No. 62-5600. This device has a structure in which the upper wall of the reaction chamber is sealed with a heat-resistant plate that can transmit microwaves, and a dielectric line for introducing microwaves is provided above the plate, which is uniform over a large area. It is possible to generate microwave plasma.

FIG. 12 is a plan view showing this plasma processing apparatus, and FIG. 13 is a schematic vertical sectional view. In the figure, 1 is Al
It is a hollow rectangular parallelepiped reaction vessel made of a metal such as, and has a reaction chamber 2 formed therein. The upper part of the reaction chamber 2 has a microwave inlet 3, which is heat-resistant and microwave-transmissive, and has a small dielectric loss, and is made of a dielectric plate such as quartz glass or Al ₂ O _3. The introduction window 4 is hermetically sealed. In the reaction chamber 2,
A stage 7 for placing the object S to be processed is disposed at a position facing the microwave introduction window 4, and the reaction container 1
An exhaust port 6 connected to an exhaust device (not shown) is formed on the bottom wall of the reactor, and a gas supply pipe 5 for supplying a required reaction gas to the reaction chamber 2 is provided on one side wall of the reaction vessel 1. It is connected.

Above the microwave introduction window 4, there is a reaction chamber 2
An antenna portion 20 that is longer in one direction than the other and is flat is formed of a metal plate 22, and a dielectric line 21 is provided on the inner surface of the upper plate of the antenna portion 20. A microwave waveguide 23 is connected to the side of the antenna unit 20, and a microwave oscillator 26 is attached to the tip of the microwave waveguide 23.
An isolator 25 and a tuner 24 are provided in the middle of 23. As shown in the plan view of FIG. 12, the dielectric line 21 is located above the introduction part 211 inserted into the connecting part between the microwave waveguide 23 and the antenna part 20 and the microwave introduction window 4, and The shape of the rectangular portion 213 has a rectangular shape (main body portion) 213 having a width corresponding to the reaction chamber 2, and a rectangular shape having a tapered shape symmetrical with respect to the traveling direction of the microwave.
And a matching portion 212 of a taper type that connects the introducing portion 211 with the introducing portion 211.

In the plasma processing apparatus having the above-described structure, when the surface of the semiconductor substrate, for example, as the object S to be processed is subjected to etching processing, first, the exhaust port 6 is evacuated so that the inside of the reaction chamber 2 has a required degree of vacuum. Then, the reaction gas is supplied from the gas supply pipe 5. Next, the microwave is oscillated by the microwave oscillator 26, and the microwave adjusted to a predetermined frequency by the isolator 25 and the tuner 24 is introduced into the dielectric line 21 through the waveguide 23. Then, the electric field leaks from the open surface (lower surface) of the dielectric line 21, is exponentially attenuated in the direction perpendicular to the lower surface, passes through the microwave introduction window 4, and is guided into the reaction chamber 2. This electric field causes reaction chamber 2
When the plasma is generated in the above, the reaction gas is changed into an active gas such as ions and radicals by the energy, and the surface of the semiconductor substrate (S) on the stage 7 is subjected to a treatment such as etching by the active gas. .

[0008]

In order to uniformly perform the processing such as etching and ashing on the object S to be processed, it is necessary to generate plasma uniformly in the reaction chamber 2. It is necessary to form a single mode electric field having a uniform intensity in the direction of microwave propagation in the plasma generation region. Further, since the electric field generated in the rectangular portion 213 of the dielectric line 21 is used for generating plasma, the matching portion
212 is not directly related. Therefore, the size of the device is reduced by shortening the length of the matching section 212 in the microwave traveling direction. However, if the matching portion 212 is simply shortened, the processing such as etching and ashing may become uneven. The reason for this is as follows.

The microwave oscillated by the microwave oscillator 26 is T, which is a fundamental mode of microwave propagation.
Propagating in microwave waveguide 23 in E10 mode,
While propagating in the matching section 212 via the introduction section 211 of 21, the propagation mode in the rectangular section 213 is determined. When the matching section 212 is made short and the taper is made steep, microwaves in the TE10 mode, which is the fundamental mode, are attenuated and a plurality of higher-order modes (TE30
Mode, TE50 mode, etc.) occur. Higher mode (T
Since the microwave propagation form in the E30 mode or TE50 mode has a phase different from that of the fundamental mode (TE10 mode), the actual propagation mode in the dielectric line 21 is a combination of a plurality of modes. .

Therefore, in the device using the dielectric line 21 having the matching portion 212 having a steep taper, an electric field having a non-uniform intensity distribution is generated by the superposition of a plurality of modes.
Is generated from. Above all, since the electric field generated in the rectangular portion 213 directly affects the generation of plasma, if the electric field is nonuniform, the plasma generated in the reaction chamber 2 also becomes nonuniform. Therefore, in order to reduce the size of the device, shortening the matching portion 212 by a simple method of sharpening the taper causes nonuniform processing.

Further, the relationship between processing uniformity and device size will be described. The microwave wave front when propagating through the dielectric line 21 has a plane as shown by a broken line in FIG. 14 with the opening surface of the microwave waveguide 23 as the phase center because the end of the matching portion 212 is inclined. Gradually changes to a curved surface. Therefore, the central position A of the boundary between the matching portion 212 and the rectangular portion 213,
A phase shift d occurs between the boundary and the end B. When this deviation d is large, a high-order mode is likely to occur.

Here, the width (length in the direction perpendicular to the microwave traveling direction) of the introduction portion 211 of the dielectric line 21 is W1, the width of the rectangular portion 213 is W2, and the microwave traveling direction of the matching portion 212 is set. When the length is Lt, the phase shift d is geometrically approximately proportional to the square of the difference between W1 and W2, and approximately inversely proportional to Lt, as shown in equation (1).

[0013]

[Equation 1]

In order to suppress the generation of higher-order modes and make the electric field strength distribution uniform so as not to have a large effect on the processing, it is necessary to make the phase shift d smaller than 3 / 8λg. I know it. Where λg is a dielectric line
It is the wavelength of the microwave propagating in 21. That is, λg = λ
₀ / √εr (λ ₀ : wavelength of microwave in vacuum, εr:
Relative permittivity of the dielectric line 21). By substituting these into the equation (1), the conditional equation (2) for obtaining the above-mentioned effect can be obtained. Lt> (W2-W1) ² / 3λg (2)

Therefore, in order to process a semiconductor substrate of φ200 mm, it is made of Teflon (registered trademark), and W1 = 96 mm, W
When the dielectric line 21 having 2 = 300 mm is used, the length Lt of the matching portion 212 satisfying the formula (2) is about 180 mm or more,
The device becomes larger.

The present invention has been made in view of the above circumstances, and suppresses the generation of a plurality of higher-order modes in the microwave propagation mode by forming the matching portion shape of the dielectric line into a step shape. Moreover, it is an object of the present invention to provide a plasma processing apparatus that can be downsized.

By providing a partition plate extending in the traveling direction of microwaves on the dielectric line, a plasma processing apparatus capable of uniformly propagating a single-mode microwave and making the plasma generation distribution uniform. With the goal.

[0018]

The invention according to claim 1 is
An electric field is generated by the microwave introduced into the plate-shaped dielectric line extending in the microwave traveling direction through the microwave waveguide, and the electric field is transmitted to the reaction chamber opposite to one surface of the dielectric line. In a plasma processing apparatus that processes an object to be processed in the reaction chamber by generating plasma by introducing the microwave through a microwave introduction port, the dielectric line has an introduction part inserted into the microwave waveguide. When the has a body portion having a shape corresponding to the microwave introduction port, and a matching unit for connecting the these inlet portion and the body portion, the width W1 of the inlet section conductor of the microwave guide
It is almost the same as the internal dimension of the part where the insertion part is inserted ,
The width W2 of the main body is longer than the introduction part and is substantially the same as the microwave introduction port , and the matching part has a shape that connects the introduction part and the main body part in a stepwise manner in the microwave traveling direction. , The width W3 of the matching portion is W1 <W3 <
W2, and a conductor plate extending in the microwave traveling direction is embedded in the main body in order to divide the main body in the width direction.

Since the matching portion has a width different from that of the introduction portion, the phase at the time of microwave propagation is different. Therefore microwaves
The fundamental propagation mode in the introduction part having substantially the same width as the microwave waveguide is converted into the higher mode. At this time, since the matching section does not have a slope with respect to the microwave traveling direction, even if the length of the matching section is shortened, the reflected wave at the edge of the matching section has almost no effect. Therefore, even if the matching section is shortened to downsize the apparatus, it is possible to suppress the occurrence of a plurality of higher-order modes. The converted mode is determined by the width and length of the matching portion. The regions divided by the conductor plate in the width direction each function like a waveguide, and propagate the microwave of the higher-order mode.

According to a second aspect of the present invention, in the first aspect, the shape of the dielectric line is symmetrical with respect to a line in the microwave traveling direction, and impedances at respective portions of the dielectric line are matched by the matching section. It is characterized by being.

As a result, the phase of the microwave at the center of the dielectric line becomes substantially equal to the phase at the end.
Therefore, the microwave propagates with its wavefront held in a substantially planar shape, and there is almost no phase shift between the center position of the boundary between the matching portion and the main body and the end of the boundary. This makes it possible to suppress the generation of a plurality of higher-order modes, and the microwave of one higher-order mode has a phase shift in the same plane perpendicular to the traveling direction in each region divided by the conductor plate. Propagate efficiently and uniformly without causing

According to a third aspect of the present invention, in the second aspect, the length of the matching portion in the microwave traveling direction is λg / 2.
(Λg = λ ₀ / √εr, λ ₀ : wavelength of microwave in vacuum, εr: relative permittivity of dielectric line), which is approximately an integral multiple of
The width W3 of the matching portion is substantially an integral multiple of the width W1 of the introduction portion, and the width W2 of the main body portion is a substantially integral multiple of the width W1 of the introduction portion.

By setting each integer value that is an integral multiple to a predetermined value, it is possible to convert to a predetermined higher-order mode. For example, if the width of the main body is three times the width of the introduction section, the width of the matching section is twice that of the introduction section, and the length is half the wavelength of the microwave propagating in the dielectric line, the TE10 basic Mode to T
It can be converted to the higher order mode of E30.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a plan view showing a plasma processing apparatus according to the present invention, and FIG.
3 is a rear perspective view of the dielectric line shown in FIG. The configuration other than the dielectric line is similar to that of the conventional device shown in FIG. That is, the upper part of the reaction chamber 2 has a microwave inlet 3, and is made of quartz glass, a dielectric plate such as Al ₂ O ₃ which has heat resistance and microwave transparency and has a small dielectric loss. It is hermetically sealed by the microwave introduction window 4. In the reaction chamber 2, at a position facing the microwave introduction window 4,
A stage 7 for mounting the object S to be processed is arranged, an exhaust port 6 connected to an exhaust device (not shown) is formed in the bottom wall of the reaction container 1, and the reaction container 1 A gas supply pipe 5 for supplying a desired reaction gas to the reaction chamber 2 is connected to the side wall.

Above the microwave introduction window 4, the reaction chamber 2 is provided.
An antenna portion 20 which is flatter in one direction than the other is formed by a metal plate 22, and a dielectric line 31 is provided on the inner surface of the upper plate of the antenna portion 20. A microwave waveguide 23 is connected to the side of the antenna unit 20, and a microwave oscillator 26 is attached to the tip thereof. An isolator 25 and a tuner 24 are provided in the middle of the microwave waveguide 23.

The dielectric line 31 is located above the introduction part 311 inserted in the connecting part between the microwave waveguide 23 and the antenna part 20 and the microwave introduction window 4, and is substantially conforming to this shape. , A rectangular portion 313 that is approximately three times as long as the introduction portion 311 in a direction (width direction) perpendicular to the traveling direction of microwaves, and a step-shaped matching portion 312 that connects the rectangular portion 313 and the introduction portion 311.
Have and. The size of the matching section 312 is designed so that the phase velocity of the microwave propagating in the widthwise central portion of the dielectric line 31 is approximately the same as the phase velocity of the microwave propagating in the widthwise end portion, and the impedance is matched. Has been done.

Further, the length L of the matching portion 312 in the microwave traveling direction is an integral multiple of λg / 2 (n · λg / 2, λg = λ ₀ / √ε
r, n: integer, λ ₀ : wavelength of microwave in vacuum, ε
r: relative permittivity of the dielectric line 21) is desirable.
The width W3 of the matching portion 312 is preferably an integral multiple (m · W1, m: integer) of the width W1 of the introduction portion 311.

Further, the rectangular portion 313 is divided into a plurality of pieces in the width direction by a partition plate (conductor plate) 314 embedded in the microwave traveling direction and made of a thin metal (thickness 2 mm) such as Al. The width W2 of the rectangular portion 313 is preferably an integral multiple (k · W1, k: integer) of the width W1 of the introduction portion 311. Further, it is desirable that the rectangular portion 313 be partitioned by the partition plate 314 so as to be divided into k equal parts in the width direction. That is,
It is desirable to provide the partition plate 314 so as to divide the width W2 of the rectangular portion 313 into k areas of width W1. For example, k =
In the case of 3, the partition plate 314 is provided so as to divide the rectangular portion 313 into three equal parts in the width direction.

The operation of the plasma processing apparatus thus configured will be described. The microwave oscillated by the microwave oscillator 26 is adjusted to a predetermined frequency by the isolator 25 and the tuner 24, and introduced into the dielectric line 31 via the microwave waveguide 23. The microwave is converted from the fundamental propagation mode into one higher mode determined by the step shape of the matching section 312 without generating a reflected wave at the step matching section 312. At this time, the microwave propagates with its wavefront held in a substantially planar shape as shown in FIG. 3, so that the center position A of the boundary between the matching part 312 and the rectangular part 313 and the end part B of the boundary part. With, there is almost no phase shift. The high-order mode microwaves generated in the matching section 312 are efficiently and uniformly propagated by the partition plate 314 embedded in the dielectric line 31 in the same plane perpendicular to the traveling direction without causing phase shift. .

As a result, an electric field having a uniform intensity distribution leaks from the rectangular portion 313. Therefore, this uniform electric field is introduced into the reaction chamber 2 through the microwave introduction window 4, where plasma having a uniform density distribution is generated. As a result, the processing such as etching and ashing is uniformly performed on the surface of the processing object S on the stage 7. Further, the length of the matching section 312 in the microwave traveling direction can be shortened under the condition that it is an integral multiple of λg / 2, and the size of the device can be greatly reduced.

[0031]

【Example】

Example 1. Electric field leaking from the open surface (lower surface) of the conventional dielectric line 21 (FIG. 14) having the tapered matching part 212 and the dielectric line 31 (FIG. 3) of the present invention having the stepwise matching part 312. The strength was actually measured. Dielectric line 21, 31
Is made of Teflon (registered trademark), and its sizes are as follows. <Dielectric line 21> Width W1 of the introduction part 211: 96 mm Width W2 of the rectangular part 213: 300 mm Length L of the rectangular part 213: 330 mm Length Lt of the matching part 212: 150 mm <Dielectric line 31> of the introduction part 311 Width W1: 96 mm Width of rectangular portion 313 W2: 300 mm Length of rectangular portion 313 L: 330 mm Width of matching portion 312 W3: 200 mm Length of matching portion 312 Ls: 39 mm (λg≈78 mm)

The measurement point was measured with the point A as the origin, and the loop antenna was scanned in the microwave traveling direction Z and the width direction Y perpendicular to this direction to move to the measurement point. The measuring range is 330 mm in the Z direction and ± 140 mm in the Y direction. Figure 4,
5 is a graph showing the distribution of electric field strength | Ex | ² in the Z (Y = 0 mm) direction and the Y (Z = 165 mm) direction of the open surface of the conventional dielectric line 21, and FIGS. , The Z (Y = 0 mm) direction of the open surface of the dielectric line 31 of the present invention, and the Y (Z = 16
5 is a graph showing the distribution of electric field strength | Ex | ^{2 in} the (5 mm) direction.

In the conventional dielectric line 21, it can be seen from FIG. 4 that the electric field strength is higher and gradually lower on the incident side with respect to the microwave traveling direction Z. Further, it can be seen from FIG. 5 that the TE10 mode and the TE30 mode are mixed in the width direction Y. Therefore, it cannot be said that the electric field strength is uniform.

On the other hand, in the dielectric line 31 of the present invention, it can be seen from FIG. 6 that the uniform electric field strengths are distributed in a sinusoidal shape in the microwave traveling direction Z. Moreover, from FIG. 7, three sinusoidal distributions having substantially equal intensities were observed in the width direction Y, and it was confirmed that only the TE30 mode exists in each region partitioned by the partition plate 314. Therefore, it can be said that the shape of the dielectric line 31 is effective for making the electric field strength distribution uniform.

Example 2. Next, the results of examining the uniformity of plasma in the reaction chamber 2 in the conventional device having the dielectric line 21 and the device of the present invention having the dielectric line 31 will be described. The dielectric lines 21 and 31 are the same as those used in the first embodiment. Then, Ar was used as the reaction gas, the gas flow rate was set to 30 sccm, the pressure was set to 10 mTorr, and the ion current density of the plasma generated by the microwave power of 1 kW was measured by the probe at a position 60 mm below the microwave introduction window 4. . 8 and 9 are graphs showing distributions of ion current densities in the Z (Y = 0 mm) direction and the Y (Z = 165 mm) direction in the conventional device, and FIGS. It is a graph which shows the distribution of the ion current density in the Y = 0 mm) direction and the Y (Z = 165 mm) direction.

In the conventional device, it can be seen from FIG. 8 that the ion saturation current density is gradually decreased in the microwave traveling direction, the main mode electric field is attenuated, and the higher mode is generated. Further, it can be seen from FIG. 9 that the ion saturation current densities greatly differ in the Y direction, and the microwave phase velocities are not uniform in the width direction.

On the other hand, in the device of the present invention, the ion saturation current density is not attenuated in the Z direction (FIG. 10), the density distribution in the Y direction is substantially uniform (FIG. 11), and the plasma is very uniform. You can see that it is generated in.

[0038]

As described above, in the plasma processing apparatus according to the present invention, since the dielectric line is formed in a step shape in the microwave traveling direction , the introduced microwave does not generate a reflected wave. , The fundamental propagation mode is converted into one higher-order mode determined by the step shape of the matching part, and the wavefront shape to be propagated is kept substantially flat,
There is almost no phase shift between the central position of the boundary between the matching portion and the main body and the end. Furthermore, since each region of the main body section partitioned by the conductor plate functions in the same way as the waveguide, the microwave of the higher mode generated in the matching section does not cause phase shift in the plane perpendicular to the traveling direction. The present invention has excellent effects such as efficient and uniform propagation.

[Brief description of drawings]

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

2 is a rear perspective view of the dielectric line shown in FIG. 1. FIG.

FIG. 3 is a plan view of the dielectric line shown in FIG.

FIG. 4 is a graph showing an electric field strength distribution in a Z (Y = 0 mm) direction on an open surface of a conventional dielectric line.

FIG. 5: Y (Z = 165 mm) on the open surface of a conventional dielectric line
It is a graph which shows the electric field intensity distribution of a direction.

FIG. 6 is Z (Y = 0 mm) of the open surface of the dielectric line of the present invention.
It is a graph which shows the electric field intensity distribution of a direction.

FIG. 7 shows Y (Z = 165 m) on the open surface of the dielectric line of the present invention.
It is a graph which shows the electric field intensity distribution of (m) direction.

FIG. 8 is a graph showing the distribution of ion current density in the Z (Y = 0 mm) direction in the conventional device.

FIG. 9 is a graph showing the distribution of the ion current density in the Y (Z = 165 mm) direction in the conventional device.

FIG. 10 is a graph showing the distribution of ion current density in the Z (Y = 0 mm) direction in the device of the present invention.

FIG. 11 is a graph showing the distribution of ion current density in the Y (Z = 165 mm) direction in the device of the present invention.

FIG. 12 is a schematic plan view showing a conventional plasma processing apparatus.

FIG. 13 is a schematic vertical sectional view showing a conventional plasma processing apparatus.

FIG. 14 is a plan view of the dielectric line shown in FIGS.

[Explanation of symbols]

2 reaction chamber 3 Microwave inlet 23 microwave waveguide 31 Dielectric circuit 311 Introduction 312 Matching unit 313 Rectangular part 314 partition board S Processing object

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-9-129613 (JP, A) JP-A 9-69398 (JP, A) JP-A 10-189295 (JP, A) JP-A 62- 5600 (JP, A) JP 8-316198 (JP, A) JP 5-129095 (JP, A) JP 9-181052 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05H 1/46 H01L 21/3065

Claims (3)

(57) [Claims] 1. An electric field is generated by a microwave introduced into a plate-shaped dielectric line extending in a microwave traveling direction through a microwave waveguide, and the electric field is arranged opposite to one surface side of the dielectric line. In the plasma processing apparatus for processing the object to be processed in the reaction chamber by introducing plasma into the reaction chamber through the microwave introduction port, the dielectric line is inserted into the microwave waveguide. The introduction portion, a main body portion having a shape corresponding to the microwave introduction port, and a matching portion connecting the introduction portion and the main body portion, and the width W1 of the introduction portion is equal to that of the microwave waveguide . is substantially the same as the inner dimension of the portion introduction portion is inserted, the width W2 of the body portion is substantially the same as the inlet portion larger than the microwave introduction port, the matching section the inlet portion and The book The body portion has a shape that is connected stepwise in the microwave traveling direction, the width W3 of the matching portion is W1 <W3 <W2, and the body portion has the width W3 in the width direction. A plasma processing apparatus, wherein a conductor plate extending in the microwave traveling direction is embedded so as to be divided. 2. The shape of the dielectric line is symmetric with respect to a line in the microwave traveling direction, and impedances at respective parts of the dielectric line are matched by the matching part. Plasma processing equipment. 3. The length of the matching portion in the microwave traveling direction is λg / 2 (λg = λ ₀ / √εr, λ ₀ : wavelength of microwave in vacuum, εr: relative permittivity of dielectric line). And the width W3 of the matching portion is a substantially integer multiple of the width W1 of the introduction portion, and the width W2 of the main body portion is a substantially integer multiple of the width W1 of the introduction portion. The plasma processing apparatus according to claim 2.