JPH08337887A - Plasma treatment device - Google Patents

Abstract

PURPOSE: To provide a small sized microwave plasma treatment device capable of generating a high density plasma of a large bored diameter and the device capable of uniformizing the density distribution of a plasma of a large bore diameter. CONSTITUTION: A microstrip antenna 1 of this device is composed of a small sized antenna module radiating a right-handed circularly polarized wave, which is arranged in three rows × three lines. When the power of the microwave feeding an electric power to the antenna modules 18a, 18b and 18c are Pa, Pb and Pc, respectively, the power is specified to be Pa<Pc<Pb in order to uniform the plasma density.

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 performing surface treatment such as etching of a substrate or thin film formation by using plasma, and in particular, a microwave generating plasma utilizing interaction between microwave and magnetic field. The present invention relates to an apparatus suitable for a plasma processing apparatus.

[0002]

2. Description of the Related Art In a microwave plasma processing apparatus, surface treatment such as etching or thin film formation of a semiconductor substrate is performed by using plasma generated by microwave. Since this treatment needs to be performed uniformly, high uniformity of plasma density is required. Further, in order to improve the processing speed, high density plasma is required.

In recent years, the size of semiconductor substrates has been shifting from 6 inches in diameter to 8 inches in diameter.
It is thought that it will be moved to 12 inches in diameter and 12 inches in diameter.
With such an increase in the diameter of the substrate, the plasma used for the processing is also required to have a large diameter. In order to generate a large-diameter plasma, the horn-type antenna that has been conventionally used becomes large in size, which leads to an increase in size of the entire apparatus. Further, even if the antenna is simply upsized, the radiated microwave distribution cannot be controlled, so that the controllability of the plasma density deteriorates. For this reason, an antenna that is small and has controllability of microwave distribution is required.

As a conventional technique, as described in Japanese Patent Laid-Open No. 6-61153, there is a technique using a planar antenna having a comb shape or a radial shape. No particular consideration was given to controllability or microwave absorption efficiency.

[0005]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a compact microwave plasma processing apparatus capable of producing a large diameter high density plasma.

A second object of the present invention is to provide a compact microwave plasma processing apparatus which can make the density distribution of large-diameter plasma uniform.

[0007]

A first invention for achieving the above first object is to provide a plasma processing apparatus for performing a surface treatment of a substrate by using plasma generated by a microwave radiated from an antenna, The antenna is provided with a plurality of microstrip antennas that radiate clockwise circularly polarized microwaves.

The right-handed circularly polarized wave generally means the following. That is, in a plane electromagnetic wave that propagates in space,
Right-polarized waves are those in which the direction of the electric field and magnetic field that oscillates in a plane perpendicular to the direction of rotation rotate clockwise as the wave progresses. Called circularly polarized.

A second aspect of the present invention for achieving the above second object is a plasma processing apparatus for performing surface treatment of a substrate using plasma generated by microwaves radiated from an antenna, wherein the antenna has a plurality of elements. A microstrip antenna is provided, the plurality of microstrip antennas are grouped into a plurality of groups, and a control means for controlling the microwave supplied to each group is provided.

[0010]

According to the first aspect of the present invention, by using the microstrip antenna as the antenna, the thickness of the antenna can be reduced to about 1 cm even if the diameter of the antenna is increased, so that the size of the antenna can be reduced. Accordingly, the plasma processing apparatus can be downsized. Further, by making the microwave radiated from the antenna into a right-handed circularly polarized wave which is easily absorbed by the plasma due to the electron cyclotron effect, the microwave can be efficiently absorbed in the plasma, so that a high density plasma is generated. It becomes possible. That is, according to the first aspect of the present invention, it is possible to generate high-density plasma having a large diameter with a small microwave plasma processing apparatus.

Further, according to the second invention, by using the microstrip antenna as the antenna, for the same reason as in the first invention, the size of the antenna is made small even if the diameter of the antenna is made large, and the plasma processing apparatus is provided. Can be made smaller. Further, the control unit controls the microwaves supplied to each of the plurality of groups, whereby the microwave distribution radiated from the antenna can be controlled so as to make the plasma density uniform. That is, according to the second aspect of the present invention, it is possible to make the density distribution of large-diameter plasma uniform with a small microwave plasma processing apparatus.

The performance confirmation test by the inventors, which confirmed that high density plasma can be generated using the microstrip antenna, will be described below. 3 and 4 show a schematic configuration of the microstrip antenna used for the test. FIG. 3 is a top view of the circuit-patterned microstrip antenna, and FIG. 4 is a cross-sectional view of the vicinity of the feeding portion 19 of FIG. The microstrip antenna is a ground conductor 20.
The dielectric 21 and the metal foil 22 are superposed on each other, and the circuit pattern of FIG. 3 is formed by etching the metal foil 22. In the power feeding section 19, the coaxial cable 1
The central conductor 7 and the feeder 7 are connected.

In this microstrip antenna, the frequency characteristic of the antenna is broadened so that the radiation characteristic of the microwave from the antenna is not easily influenced by the plasma state. As a method thereof, one antenna module is configured with four radiating elements 23, and the distance of the feeding line 7 connecting each radiating element 23 and the feeding section 19 is shifted by ¼ wavelength of the wavelength of microwaves, and each radiating is performed. The reflected waves from the elements were made to cancel each other out. With this configuration, the radiating element 23 can have a wider band than one radiating element 23. Also, as the dielectric 21 of the substrate,
By using one with a small relative permittivity and a large thickness,
Further, a wider band can be achieved.

The microwave radiated from this antenna is absorbed in plasma by the electron cyclotron effect. The electron cyclotron effect is
In the case of 2.45 GHz, it is a phenomenon that the right-handed circularly polarized microwave is easily absorbed in the region where the magnetic field strength is about 875 Gauss. Therefore, the microwave radiated from the antenna should be right-handed circularly polarized wave. Therefore, the plasma can be efficiently absorbed. To do so, in the microstrip antenna shown in FIG. 3, the four radiating elements 2 are arranged so that the radiated microwave is a right-handed circularly polarized wave.
The direction of the power supply line 7 for supplying power to 3 is rotated clockwise by 90 degrees.

FIG. 5 shows a schematic configuration of a test apparatus using the microstrip antenna shown in FIG. This device is configured so that the distance between the microstrip antenna 1 and the plasma 6 can be changed. In this device, the microwave generated by the microwave source 4 is supplied to the microstrip antenna 1 through the waveguide 15, the converter 16 and the coaxial tube 25, and the frequency of 2.
The microwave 3 of 45 GHz is radiated. Microwave 3
Propagates through the introduction window 5 into the vacuum container 8 and ionizes the neutral gas 9 by the microwave 3 to generate plasma 6. In order to increase the efficiency of accelerating the electrons by the microwave 3, a magnetic field is generated in the vacuum container 8 by a magnetic field generator 12 such as an electromagnet, and the electron cyclotron effect is maximized 875.
A Gauss magnetic field is generated almost in the center of the vacuum container 8. The density of the plasma 6 generated using this apparatus was measured at the plasma measurement position 40 shown in FIG. 5 using the Langmuir probe.

FIG. 6 shows the relationship between the distance L between the microstrip antenna 1 and the plasma 6 and the plasma density at the plasma measurement position 40. Here, the power of the microwave input to the microstrip antenna 1 is about 1 kW. From the figure, the plasma density is
It was found that the plasma can be densified by separating the microstrip antenna 1 from the plasma 6 by about 4 cm or more.
This means that the microwave radiated from one radiating element 23 of the microstrip antenna 1 is linearly polarized,
A circularly polarized wave is formed at a position sufficiently distant from the microstrip antenna 1, and it is necessary that the circularly polarized wave is sufficiently formed before it is incident on the plasma in order for the microwave to be absorbed by the plasma. This is because.

From the above, in order to generate a high density plasma, it is necessary to make the microwave radiated from the microstrip antenna into a right-handed circularly polarized wave which is easily absorbed by the plasma by the electron cyclotron effect. It was Further, it is possible to widen the frequency band of the microstrip antenna to make it less susceptible to the plasma state, and to keep the distance between the microstrip antenna and the plasma so that the clockwise circularly polarized wave is sufficiently formed.
It was found to be more effective for producing high density plasma.

[0018]

Embodiments of the present invention will be described below. In Figure 1,
1 shows a first embodiment of a plasma processing apparatus using the present invention. This device is a gas supply device for supplying a microwave 3 and a microwave 3 supplied from the microwave source 4 into the vacuum container 8 from the introduction window 5 and a neutral gas 9 into the vacuum container 8. 10, an exhaust device 11 for exhausting gas in the vacuum container 8, a magnetic field generator 12 for generating a magnetic field in a plasma generation region in the vacuum container 8, a semiconductor substrate for performing surface treatment such as etching and thin film formation using the plasma 6. It is composed of a holder 14 for installing 13 and a high frequency power source 24 for applying a high frequency electric field to the holder 14.

In the configuration of FIG. 1, the microwave generated by the microwave source 4 using a magnetron is supplied to the microstrip antenna 1 through the waveguide 15, the converter 16 and the coaxial cable 17. The microwave 3 radiated from the microstrip antenna 1 propagates through the introduction window 5 into the vacuum container 8 and accelerates electrons to collide and ionize the neutral gas 9 to generate plasma 6. The neutral gas 9 is supplied into the vacuum container 8 by the gas supply device 10, and then exhausted by the exhaust device 11. In order to increase the efficiency of accelerating the electrons by the microwave, the electron cyclotron effect is used by generating a magnetic field in the vacuum container 8 by the magnetic field generator 12 using an electromagnet. The electron cyclotron effect becomes maximum at a magnetic field strength of about 875 Gauss when a microwave having a frequency of 2.45 GHz is used, and the microwave absorption efficiency by plasma becomes maximum. Therefore, a magnetic field of about 875 Gauss is generated in the vacuum container 8.

As described in the prior art, in the microwave plasma processing apparatus, it is necessary to make the plasma density distribution uniform in order to make the processing of the semiconductor substrate uniform. In order to make the plasma density distribution uniform, the distribution of the neutral gas 9 and the distribution of the magnetic field in the vacuum container 8 were mainly controlled in the conventional apparatus, but in the present embodiment, the distribution of the incident microwave 3 is also controlled. A means for controlling and making the plasma density uniform is provided.

Microstrip antenna 1 of this embodiment
2, the small antenna modules shown in FIG. 3 are arranged in 3 columns × 3 rows. Figure 2
So, of each antenna module,
The a and the corners are represented by 18b, and the other ones are represented by 18c. Note that FIG. 2 shows an example in which a total of nine antenna modules of 3 columns × 3 rows are arranged, but in order to generate a plasma of a larger area, 4 columns × 4 rows, 5 columns × 5 rows. By increasing the number of modules, a large-area plasma can be easily generated.

In the example shown in FIG. 2, three microwave sources are provided, and the microwave source 4a is the antenna module 1
8a, the microwave source 4b is an antenna module 18b
In addition, the microwave source 4c supplies power to the antenna module 18c via the coaxial cables 17, respectively. Here, since there are a plurality of antenna modules 18b and 18c, the power of the microwaves fed from the microwave sources 4b and 4c is evenly distributed to each antenna module using the distributor 26.

Now, the microwave power supplied to the antenna module 18a is Pa, and the antenna module 18 is
The power of the microwaves supplied to b is Pb, and the power of the microwaves supplied to the antenna module 18c is Pc. When the microwaves are incident on the plasma with a uniform distribution, the plasma density distribution tends to become stronger in the center.Therefore, in order to make the plasma density uniform, the power of the microwaves fed to the antenna module near the center should be adjusted. Since it may be smaller than the power of microwaves supplied to the antenna module in the peripheral portion, Pa <Pc <Pb may be set. The control of Pa, Pb and Pc can be easily performed by adjusting the output power of the microwave sources 4a, 4b and 4c. Further, as a method of controlling the power supplied to the antenna module, the power of one microwave source may be branched by using a branch circuit having a variable division ratio.

As described with reference to FIG. 6, in order to generate a high density plasma using the microstrip antenna shown in FIG. 3, a distance of 4 cm or more is required between the antenna and the plasma. Therefore, in this embodiment, a distance L of 4 cm or more is provided between the microstrip antenna 1 and the plasma 6.

The microstrip antenna 1 in this embodiment has 95% of the power supplied from the microwave source 4.
% Or more can be radiated to the plasma 6, but about 5% of the power is converted into heat energy in the antenna part. The power generated by the microwave source 4 is as high as 2 kW when it is large, and the maximum heat energy generated by the antenna unit is about 100 W. If this heat is not removed efficiently, the antenna will heat up and break. Therefore, in order to cool the antenna, on the side opposite to the plasma 6 of the microstrip antenna 1,
A cooling pipe 41 for flowing cooling water is provided to cool the antenna.

Next, the second embodiment of the plasma processing apparatus according to the present invention will be described with reference to FIG. Although the basic device configuration of this embodiment is the same as that of the first embodiment, the difference from the first embodiment is that the outer peripheral shape of the antenna and the cross section (horizontal section) of the plasma are circular. It is that you are. The rest of the configuration is the same as that of the first embodiment, so its explanation is omitted here.

In this embodiment, in order to make the microwave distribution as uniform as possible in the circumferential direction of the device, a square small radiating element 23 is used as an antenna pattern arranged in the circumferential direction as shown in FIG. Circular polarized waves can be emitted from each radiating element 23. This principle will be described with reference to FIG. In the antenna of FIG. 9, power is supplied from the power supply unit 19 to the radiating element 23 via the power supply line 7 at two points 27a and 27b. At this time, the phase of the microwave reaching 27a reaches 27b by making the distance from the power feeding unit 19 to 27a shorter than the distance from 19 to 27b by a quarter wavelength of the wavelength of the microwave. It is 90 degrees faster than the microwave phase. Thus, by supplying the microwaves whose phases are shifted by 90 degrees to the two adjacent sides of the square radiating element 23, the right-handed circularly polarized wave can be emitted from one radiating element.

In the antenna of FIG. 8, radiating elements 23 are concentrically doubly arranged and power is supplied to the inner and outer radiating elements 23 from two different microwave sources 4a and 4b, respectively.
When the plasma is generated with a uniform microwave distribution, the plasma tends to be concentrated in the central portion. Therefore, in order to avoid this, in the present embodiment, the power of the microwave source 4b for feeding the outer radiating element is set to the inner radiating element. It is made stronger than the power of the microwave source 4a that supplies power to the. In this embodiment, the radiating elements are concentrically arranged in double, but when the size of the apparatus is further increased, the microwave distribution is adjusted by arranging the elements in triple or quadruple to change the plasma distribution. Can be uniform.

Next, a third embodiment of the plasma processing apparatus using the present invention will be described with reference to FIGS.
Although the basic device configuration of this embodiment is the same as that of the second embodiment, the difference from the second embodiment is that the permanent magnet 42 is used as the magnetic field generator. The rest of the configuration is the same as that of the second embodiment, so the explanation is omitted here.

In this embodiment, a cylindrical permanent magnet 42 as a magnetic field generator is provided on the microstrip antenna 1. The permanent magnet 42 is placed above each radiating element 23 of the microstrip antenna 1.
The magnetic field produced by a permanent magnet is approximately inversely proportional to the cube of the distance from the permanent magnet. Therefore, a huge permanent magnet is usually required when the distance between the permanent magnet and the plasma is large. In this embodiment, since the thickness of the antenna can be reduced by using the microstrip antenna, it is possible to reduce the size of the permanent magnet by shortening the distance between the permanent magnet and the plasma. Further, in this embodiment, a small auxiliary electromagnet 43 is provided in order to adjust the magnetic field distribution generated by the permanent magnet 42 and improve the controllability of the plasma density distribution. The control of the magnetic field distribution is also used to make the plasma density more uniform.

[0031]

According to the present invention, the microwave radiated from the microstrip antenna is made into the right-handed circularly polarized wave which is easily absorbed by the plasma due to the electron cyclotron effect, so that the microwave plasma processing apparatus of a small size can be made large. It is possible to generate high-density plasma having a caliber.

Further, the control means controls the microwaves supplied to the microstrip antennas divided into a plurality of groups for each group, so that the density distribution of the large-diameter plasma is made uniform by the small microwave plasma processing apparatus. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a plasma processing apparatus using the present invention.

FIG. 2 is a detailed view of the microstrip antenna of FIG.

FIG. 3 is a top view of the microstrip antenna of FIG.

FIG. 4 is a cross-sectional view of the vicinity of the power feeding portion of FIG.

FIG. 5 is a schematic configuration diagram of a test device for confirming the performance of the present invention.

FIG. 6 is a diagram showing the relationship between the distance between the microstrip antenna and the plasma and the plasma density.

FIG. 7 is a diagram showing a second embodiment of the plasma processing apparatus using the present invention.

FIG. 8 is a detailed view of the microstrip antenna of FIG.

9 is a detailed view of the radiating element of FIG.

FIG. 10 is a diagram showing a third embodiment of the plasma processing apparatus using the present invention.

11 is a detailed view of the microstrip antenna of FIG.

[Explanation of symbols]

1 ... Microstrip antenna, 3 ... Microwave, 4
... microwave source, 5 ... introduction window, 6 ... plasma, 7 ... power supply line, 8 ... vacuum container, 9 ... neutral gas, 10 ... gas supply device, 11 ... exhaust device, 12 ... magnetic field generator, 13 ... semiconductor substrate , 14 ... Holder, 15 ... Waveguide, 16 ... Transducer, 17 ... Coaxial cable, 18, 18a, 18b, 18
c ... Antenna module, 19 ... Feed part, 20 ... Ground conductor, 21 ... Dielectric material, 22 ... Metal foil, 23 ... Radiating element,
40 ... Plasma measurement position, 41 ... Cooling pipe, 42 ... Permanent magnet, 43 ... Electromagnet.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location // H01L 21/3065 H01L 21/302 B (72) Inventor Tsutomu Tezuka Omika-cho, Hitachi City, Ibaraki Prefecture 7-1-1, Hitachi Ltd., Hitachi Research Laboratory (72) Inventor Yuichi Ikeda 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Research Laboratory

Claims (12)

[Claims] 1. A plasma processing apparatus for surface-treating a substrate using plasma generated by microwaves radiated from an antenna, wherein the antenna comprises a plurality of microstrip antennas radiating clockwise circularly polarized microwaves. A plasma processing apparatus comprising: 2. The plasma processing apparatus according to claim 1, wherein the microstrip antenna includes a plurality of radiating elements that radiate microwaves. 3. The plasma processing apparatus according to claim 1, wherein the microstrip antenna includes a plurality of feeding parts in one radiating element that radiates microwaves. 4. The space according to claim 1, wherein a space is provided between the antenna and the plasma for the microwave radiated from the antenna to form a right-handed circularly polarized wave. And a plasma processing apparatus. 5. A plasma processing apparatus for processing a surface of a substrate by using plasma generated by microwaves radiated from an antenna, wherein the antenna includes a plurality of microstrip antennas, and the plurality of microstrip antennas include a plurality of groups. A plasma processing apparatus, characterized by comprising control means for controlling microwaves supplied to each group. 6. The plasma processing apparatus according to claim 5, wherein the control means controls the microwave power supplied to each of the plurality of groups. 7. The microstrip antenna according to claim 5, wherein the plurality of microstrip antennas are arranged substantially on a two-dimensional plane.
The plurality of microstrip antennas are grouped into a group located at least in a central part and a group located in a peripheral part, and the control means positions the microwave power supplied to the group located in the peripheral part in the central part. The plasma processing apparatus is characterized in that the microwave power is controlled to be stronger than the microwave power supplied to the group. 8. The plasma processing apparatus according to claim 1, wherein the microstrip antenna has a wide frequency band by increasing a dielectric thickness of an antenna substrate. 9. The plasma processing apparatus according to claim 1, wherein the microstrip antenna has a wide frequency band by reducing a dielectric constant of a dielectric material of an antenna substrate. 10. The plasma processing apparatus according to claim 1, wherein the microstrip antenna has a wide frequency band by including a plurality of microwave radiation elements. 11. A plasma processing apparatus according to claim 1, further comprising means for cooling the microstrip antenna. 12. The plasma processing apparatus according to claim 1, wherein a magnetic field is generated in a plasma generation region by providing a permanent magnet on the opposite side of the microstrip antenna from the plasma.