JPH07122397A - Plasma treatment apparatus - Google Patents

Abstract

PURPOSE:To provide a plasma treatment apparatus by which plasma with uniform density distribution and large surface area is obtained by improving the structure of an antenna for the plasma treatment apparatus by ICP. CONSTITUTION:An antenna 5 to induce a high frequency electric field in a vacuum container 2 is composed by setting or crossing one or more than one antenna elements. The electric field intensity is uniformalized by overlaying the high frequency electric fields induced by each antenna element and thus the density distribution of plasma generated and maintained by the high frequency electric fields is uniformalized. The more the number of the antenna elements and the number of the crossing times are increased, the more the high frequency electric fields induced by each antenna element is composed and the evenness of the electric field intensity distribution is improved. Furthermore, when high frequency electric power with phase difference corresponding to the crossing angle between antenna elements is applied, the direction of the composed electric field is rotated spatially and consequently the evenness of the intensity ditribution of electric fields is improved.

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 generally used for industrial plasma processing such as a semiconductor integrated circuit manufacturing process and surface treatment of a steel sheet. As a plasma generating means, electromagnetic induction from an antenna is used. An ICP (Inductivel) that induces a high-frequency electric field in the vacuum container by coupling and turns the processing gas introduced into the vacuum container into plasma
A plasma processing apparatus is configured using a y-coupled plasma method. Specifically, by controlling the distribution of the high-frequency electric field described above, high-density plasma is generated in a large area and in a uniform distribution, and a large-diameter object to be processed is generated. The present invention relates to a plasma processing apparatus that can perform an appropriate plasma processing on an object.

[0002]

2. Description of the Related Art A plasma processing apparatus using the above ICP has a feature that plasma can be generated without using the confinement effect of plasma by a magnetic field. However, ICP basically generates plasma only near the antenna. Therefore, in an early ICP in which an antenna coil is wound around a cylindrical quartz tube and plasma is generated in the quartz tube by its electromagnetic induction, it is not possible to ensure the cross-sectional area uniformity of the plasma with respect to the cylinder, and a large-diameter object to be processed. There was a drawback that it could not be processed. In recent years, it has become possible to obtain high-density and large-area plasma by ICP by using a planar loop antenna instead of the solenoid type antenna as described above. Since the plasma obtained by this ICP does not need to use a magnetic field, it is provided with conditions advantageous for the recent integrated circuit manufacturing process in which high integration of integrated circuits and large diameter of semiconductor substrates are remarkable, and the large size of ICP There are high expectations for plasma processing equipment.

FIG. 12 shows an I using the above loop antenna.
It is a schematic diagram explaining the plasma generation mechanism by CP. When the loop antenna 32 is arranged near the high frequency introduction window 31 provided in the vacuum container 30 and high frequency power is applied to the loop antenna 32, a high frequency magnetic field B is generated orthogonal to the loop as shown in the figure. This high frequency magnetic field B
As a result, a high-frequency electric field E is induced in the vacuum container 30, and the high-frequency electric field E accelerates electrons generated by natural radiation or the like from the processing gas introduced into the vacuum container 30. The accelerated kinetic energy of the electron is given to the neutral atom by collision of the electron with the neutral atom, and the neutral atom is ionized to generate ions and electrons. The density of plasma generated is increased by repeating the process in which newly generated electrons are accelerated by the high frequency electric field E. When the plasma density rises to a certain extent, the response frequency of the electrons in the plasma rises, so the plasma acts like a conductor and begins to block electromagnetic waves, and electromagnetic waves other than special modes cannot enter the plasma. Therefore, only the plasma surface increases the density, and the ion-excited species are diffused inside the plasma. As described above, in the plasma by ICP, the plasma is generated by the high-frequency electric field E induced by the antenna 32, and the generated plasma is maintained. Therefore, the plasma behavior in the case of plasma generation using a magnetic field is complicated. High density plasma can be obtained with a simple device.

[0004]

[Problems to be Solved by the Invention] However, ICP
As described above, since the plasma generated by the antenna is generated by the high frequency electric field induced by the antenna, the plasma density distribution is affected by the intensity distribution of the high frequency electric field. That is, the intensity of the high-frequency electric field is high immediately below the loop of the antenna and weakens at the center of the loop, resulting in a donut-shaped plasma density distribution, which makes it difficult to obtain a uniform density distribution. According to the present invention, in constructing a plasma processing apparatus using the plasma of the ICP,
In order to solve the above problems associated with CP, it is an object of the present invention to provide a plasma processing apparatus that improves the configuration of the antenna that causes the above problems and that can generate plasma in a large area with a uniform plasma density distribution. is there.

[0005]

In order to achieve the above object, the first means adopted by the present invention is to convert a processing gas introduced into a vacuum container into a plasma by a high frequency electric field induced by electromagnetic induction from an antenna. In the plasma processing apparatus for plasma-processing an object to be processed arranged in the vacuum container with the plasma, the antenna has 1 or 2
A plasma processing apparatus is characterized in that the above antenna elements are arranged in a crossed manner.
The high-frequency power is supplied to each of the cross-arranged antenna elements by applying a phase difference corresponding to the crossing angle at which the antenna elements intersect, or by connecting the cross-arranging antenna elements in series and applying a high frequency. It is possible to employ a configuration or a configuration in which the power applied to each of the cross-arranged antenna elements can be adjusted. Further, it is possible to employ a configuration in which the parallel spacing of the plurality of antenna elements is coarser toward the outside, or a configuration in which the parallel spacing of the plurality of antenna elements is closer to the outside. Further, the second means adopted by the present invention is that the processing gas introduced into the vacuum vessel is turned into plasma by the high frequency electric field induced by the electromagnetic induction from the antenna, and the plasma causes the plasma to be treated placed in the vacuum vessel. In a plasma processing apparatus for plasma processing an object, the antenna is composed of a first antenna formed by arranging one or more antenna elements in a crossed manner, and a loop having the same shape as the inner shape of the vacuum container. It is configured as a plasma processing apparatus including a second antenna.

[0006]

According to the present invention, an antenna for inducing a high frequency electric field in a vacuum container is constructed by arranging one or more antenna elements in a crossed manner. By synthesizing the high-frequency electric fields induced by each of the cross-arranged antenna elements, the electric field strength is made uniform, and the plasma density distribution generated and maintained by the high-frequency electric field is made uniform. As the number of antenna elements and the number of cross-arranged antenna elements increase, the high-frequency electric field induced by each antenna element is combined, and the uniformity of the electric field strength distribution improves. Furthermore, when a high frequency is applied by giving a phase difference corresponding to the crossing angle between the antenna elements, the direction of the combined electric field is spatially rotated, so that the uniformization of the electric field strength is further improved. Further, the high-frequency power applied to each antenna element can be adjusted individually to determine the plasma density distribution. Further, the electric field intensity distribution can be adjusted by changing the parallel spacing of the plurality of antenna elements, and the plasma density distribution corresponding to the content of the plasma processing can be obtained. Claims 1 to 6 correspond to this. Further, since the plasma generated in the vacuum container is consumed on the wall surface of the vacuum container, by increasing the plasma density in the plasma peripheral portion to compensate for the above consumption,
Uniformity of plasma density distribution can be achieved. In the present invention, in addition to the antenna (first antenna) having the above-described configuration, a loop antenna (second antenna) having the same shape as the inner shape of the vacuum container is used in combination, so that a high frequency wave induced from the loop antenna is generated. The density distribution around the plasma is increased by the action of the electric field. Claim 7 corresponds to this.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention. 1 is a schematic diagram showing the configuration of a plasma processing apparatus according to an embodiment of the present invention, FIG. 2 is a plan view showing the configuration of a first embodiment of an antenna, and FIG. 3 is a basic configuration of the antenna and its operation. 4 is a schematic diagram for explaining the synthesis of a high frequency electric field, FIG. 5 is a graph showing an electron density distribution of plasma generated by the antenna having the configuration of the first embodiment, and FIG. 6 is a second diagram of the antenna. FIG. 7 is a schematic diagram showing a configuration of an embodiment, FIG. 7 is a schematic diagram showing a configuration of a third embodiment of the antenna, FIG. 8 is a schematic diagram showing a configuration of a fourth embodiment of the antenna, and FIG. 9 is a configuration of a fifth embodiment of the antenna. FIG. 10 is a schematic diagram showing the configuration of the sixth embodiment of the antenna, and FIG. 11 is a graph showing the electron density distribution of plasma by the loop antenna. In FIG. 1, a plasma processing apparatus 1 according to the embodiment has a high frequency introduction window 3 on a central axis 9 of a vacuum container 2 provided with an exhaust port 7 for vacuum exhaust and a gas introduction port 8 for introducing a processing gas. With
An antenna 5 is arranged outside the high frequency introduction window 3. In the configuration of this embodiment, the diameter of the vacuum container is 500
mm, and the high-frequency introduction window 3 has a diameter of 200 mm.
In the above configuration, the high frequency power source 6 to 13.56MH
A high frequency of z and a maximum electric power of 2 KW is supplied to the antenna 5, and the high frequency electric field induced by the inductive coupling from the antenna 5 causes plasma generation by the ICP that turns the Ar gas introduced into the vacuum container 2 into plasma.

In the plasma processing apparatus 1 having the above-described structure, in order to uniformly perform the plasma processing on the processing surface of the object 4 to be processed arranged in the vacuum container 2, the vacuum container 2
The density distribution of the plasma 20 generated inside should be uniform, and the area should be larger than that of the object 4. In order to make the plasma 20 have a large area and a uniform density distribution, it is an important factor that the high-frequency electric field from the antenna 5 is induced in the plasma generation region with a uniform intensity distribution. The configuration of the antenna 5 according to the embodiment will be sequentially described below. FIG. 2 shows the configuration of the antenna 5 according to the first embodiment. As shown in the figure, the first antenna frame element 11 and the second antenna frame element 11 are formed by arranging a plurality of straight lines in parallel.
The antenna element frame 12 is orthogonally crossed, and the first antenna element frame 11 and the second antenna element frame 12 are connected by the phase advancing capacitor 10. Each antenna element frame 11,
The antenna element 12 has the antenna element 11x and the antenna element 12y formed in the illustrated shape on a substrate having a thickness of 0.3 mm and a size of 250 × 200 mm, and the antenna element 11x and the antenna element 12y are insulated by a Teflon coating and overlapped to form a grid-shaped antenna 5. High frequency power is supplied to this antenna 5 from a high frequency power supply 6 through a matching circuit.

The action of inducing a high frequency electric field in the vacuum container 2 by the antenna 5 will be described with reference to the basic configuration of the antenna 5. The antenna 5c having the basic configuration shown in FIG. 3 is an antenna element 13x formed by one straight line.
And 13y are insulated and crossed at right angles, and the antenna element 13
A phase advancing capacitor 10 is connected between x and 13y. When high-frequency power is supplied from the high-frequency power source 6 to the antenna 5c, magnetic fields Bx and By are generated so as to surround the straight lines of the antenna elements 13x and 13y, respectively, and inside the vacuum container 2 covered by the magnetic fields Bx and By. Magnetic field Bx, By
Electric fields Ex and Ey that are orthogonal to are induced. That is, the electric fields Ex and Ey are formed parallel to the linear directions of the antenna elements 13x and 13y, respectively. Antenna element 13
A capacitor 10 for phase advance is connected between x and 13y,
9 corresponding to the crossing angle of each antenna element 13x, 13y
Since the phase difference of 0 degree is given, each electric field Ex, Ey
Change causes a phase difference of 90 degrees as shown in FIG.
Therefore, the electric field E generated by both antenna elements 13x and 13y
The combined electric field E of x and Ey will rotate spatially,
A uniform electric field distribution can be obtained in the circumferential direction around the intersection position.

The grid-shaped antenna 5 having the structure of the first embodiment is obtained by increasing the number of each straight line of the antenna 5c having the basic structure, and the distribution of the combined rotation of the induced electric field is arranged in a grid. Therefore, the electric field distribution is made more uniform. The antenna 5 having the configuration of the first embodiment is applied to the plasma processing apparatus 1 shown in FIG. 1, and the measurement result of the electron density distribution of the plasma when the plasma 20 is generated is shown in FIG.
Shown in. High-frequency power of 500 W supplied to the antenna 5,
With the density distribution of Ar gas at a pressure of 1 Torr, it is shown that uniform plasma was obtained in the shape of a disk slightly larger than the diameter of the high frequency introducing window of 200 mm. The plasma generated by this configuration is from 1 mTorr to 500 Torr
It was uniform in the shape of a disc, and once generated, it was possible to maintain the plasma up to atmospheric pressure, and the plasma was maintained up to 0.1 mTorr even without a magnetic field. This is nothing but showing the wide range of application of plasma generation according to the structure of this embodiment. When the grid spacing of the antennas 5 formed in the grid shape is given a high density, the distribution of the induced electric field can be adjusted, and the plasma density distribution can be controlled.
In the second embodiment shown in FIG. 6, the outer grid intervals of the respective antenna elements 11a and 12a forming the antenna 5a are closely formed. Since the plasma is generally consumed on the wall surface of the vacuum container 2, a uniform plasma density distribution can be obtained by increasing the plasma density distribution in the peripheral portion to compensate for the consumption. In addition, in the third embodiment shown in FIG. 7, each antenna element 11b, 1 which composes the antenna 5b.
The inner grid spacing of each 2b is closely formed to strengthen the electric field at the center. The plasma obtained by such a distribution of the electric field strength has a density distribution concentrated in a part, which is effective when processing is performed using only active species generated in the plasma.

Further, the antenna 5 can be constructed not only by orthogonally intersecting the antenna elements as in each of the above-described configurations, but also by configuring as in the fourth and fifth embodiments shown in FIGS. 8 and 9. In the configuration of the antenna 5d shown in FIG. 8, the linear antenna elements 14a, 14b, 14c are crossed at both ends to form a triangle, and the antenna elements 14a, 14b,
14c are connected via a phase shifter 16, and the high frequency power from the high frequency power supply 6 is sequentially given a phase difference and supplied to each antenna element. By setting the phase difference between the antenna elements in this case to 120 degrees, the uniformization due to the rotation of the combined electric field can be obtained. Similarly, in the configuration of the antenna 5e shown in FIG. 9, the linear antenna elements 15a, 1
5b, 15c, 15d, and 15e are crossed at each end to form a pentagon, and each antenna element 15a, 15
b, 15c, 15d and 15e are connected via a phase shifter 17. In this configuration, the phase difference between the antenna elements is 72 degrees, so that the composite electric field can be made uniform by rotation. The antenna 5 described above, the antenna 5c of the basic configuration thereof, and the antennas 5a, 5 of the variation mode
In b, 5d, and 5e, a phase difference is given between the antenna elements to make them uniform by rotation of the combined electric field. However, even if they are connected in series without giving a phase difference, the effect of electrical case is obtained. be able to. For example, when the electric fields are combined orthogonally, the electric field is formed as a non-rotating electric field of 45 degrees on the crossing axis, and there is no part where the electric field strength becomes zero at the center like a loop antenna, and a uniform plasma density distribution is obtained. Can be obtained. Further, by individually adjusting the supply of the high frequency power to each antenna element in each of the embodiments described above, the distribution of the electric field strength for each antenna element can be determined, and thus the plasma density distribution can be changed to a desired state. Becomes

In the grid-shaped antenna 5a shown in the second embodiment, the grid interval is changed to supplement the plasma consumed on the wall surface of the vacuum container 2 (FIG. 6), but FIG. 10 is shown. As in the configuration of the sixth embodiment, the grid antenna 5 (first antenna) and the loop antenna 1
8 (second antenna) can also be used together to supplement the consumption of the plasma peripheral part. The electron density distribution of plasma by the grid-shaped antenna 5 is uniform in a disc shape as shown in FIG. 5, and the electron density distribution decreases in the peripheral portion. On the other hand, under the same conditions, the loop antenna 18 with a diameter of 200 mm
The electron density distribution of plasma alone is a density distribution in which a ring-shaped peak is generated immediately below the loop line as shown in FIG. The plasma that these two antennas work on is
Since the state is such that the density distributions shown in FIGS. 5 and 11 are combined, a high density distribution is obtained in the plasma peripheral portion, and a uniform state is obtained by supplementing the consumption on the wall surface. In the present embodiment, the shape of the loop antenna 18 is formed in a ring shape because the vacuum container 2 is cylindrical, but when the vacuum container 2 is rectangular, it is formed in a rectangular loop. Although the antenna 5 is arranged outside the vacuum container 2 in the above embodiment, the antenna 5 may be arranged inside the vacuum container 2 by being covered with an insulating material.

[0013]

As described above, according to the present invention, the processing gas introduced into the vacuum container is turned into plasma by the high frequency electric field induced by the antenna constructed by arranging the antenna elements in a crossed manner. By combining the high frequency electric field of each antenna element, the electric field strength is made uniform,
The plasma density distribution that is generated and maintained by the high-frequency electric field is made uniform. As the number of antenna elements crossed increases, the high-frequency electric field induced by each antenna element is synthesized and the electric field strength distribution is made uniform. Furthermore, when a high frequency is applied by giving a phase difference corresponding to the crossing angle between the antenna elements, the direction of the combined electric field is spatially rotated, so that the uniformization of the electric field strength is further improved. Further, the power applied to each of the plurality of antenna elements is adjusted. Alternatively, the electric field intensity distribution can be adjusted by changing the parallel spacing of the plurality of antenna elements, and the plasma density distribution corresponding to the content of the plasma processing can be obtained. (Claims 1 to 6) Further, by using a loop antenna (second antenna) having the same shape as the inner shape of the vacuum container in combination with the antenna (first antenna) having the above-mentioned configuration, the loop antenna Since the density distribution around the plasma can be increased by the action of the high-frequency electric field induced from the plasma, the plasma density around the plasma consumed by the wall of the vacuum chamber is increased to compensate for the above consumption, and the uniformity of the plasma density distribution is improved. Can be achieved.
(Claim 7)

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing the configuration of a first embodiment of the antenna.

FIG. 3 is a schematic diagram illustrating a basic configuration of an antenna and its operation.

FIG. 4 is an explanatory diagram illustrating synthesis of a high frequency electric field.

FIG. 5 is a graph showing an electron density distribution of plasma generated by the configuration of the embodiment.

FIG. 6 is a schematic diagram showing the configuration of a second embodiment of the antenna.

FIG. 7 is a schematic diagram showing a configuration of a third embodiment of the antenna.

FIG. 8 is a schematic diagram showing the configuration of a fourth embodiment of the antenna.

FIG. 9 is a schematic diagram showing the configuration of a fifth embodiment of the antenna.

FIG. 10 is a schematic diagram showing the configuration of an antenna according to a sixth embodiment.

FIG. 11 is a graph showing an electron density distribution of plasma by a loop antenna.

FIG. 12 is a schematic diagram illustrating a plasma generation mechanism of an ICP having a conventional configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Plasma processing apparatus 2 ... Vacuum container 3 ... High frequency introduction window 4 ... Object to be processed 5, 5a, 5b, 5c, 5d, 5e ... Antenna 11, 12, 13, 14, 15 ... Antenna element 18 ... Loop antenna (first 2 antennas)

Claims (7)

[Claims] 1. A plasma processing for converting a processing gas introduced into a vacuum container into a plasma by a high frequency electric field induced by electromagnetic induction from an antenna, and subjecting an object placed in the vacuum container to a plasma treatment by the plasma. In the apparatus, the above-mentioned antenna is configured by arranging one or more antenna elements so as to cross each other. 2. The plasma processing apparatus according to claim 1, wherein a high frequency is applied to each antenna element with a phase difference corresponding to an intersection angle at which the antenna elements intersect. 3. The plasma processing apparatus according to claim 1, wherein the cross-arranged antenna elements are connected in series to apply a high frequency. 4. The plasma processing apparatus according to claim 1, wherein the magnitude of the high-frequency power applied to each of the cross-arranged antenna elements can be individually adjusted. 5. The plasma processing apparatus according to claim 1, wherein the parallel spacing of the plurality of antenna elements is rougher toward the outside. 6. The plasma processing apparatus according to claim 1, wherein the parallel spacing of the plurality of antenna elements is closer to the outside. 7. A plasma processing apparatus for converting a processing gas introduced into a vacuum container into a plasma by a high frequency electric field induced by electromagnetic induction from an antenna, and subjecting an object to be processed placed in the vacuum container to plasma by the plasma. In above, the antenna comprises a first antenna configured by arranging one or more antenna elements in a crossed manner, and a second antenna configured by a loop having the same shape as the inner shape of the vacuum container. A plasma processing apparatus characterized by the above.