JPH02294491A - Microwave plasma treating device - Google Patents

Abstract

PURPOSE:To generate a wide and uniform discharge and to uniformly treat a large area in the microwave plasma treating device by providing plural microwave introducing means and using a planar radiator in a part of the means. CONSTITUTION:The microwave plasma treating device is provided with a vacuum chamber 1, a substrate holder 2 for holding a sample 3, a gaseous reactant introducing pipe 4, a discharge gas introducing pipe 5, a magnetic field generating means consisting of a main coil 6, a control coil 7, comb-shaped antennae 8a and 8b as the planar radiator, microwave power sources 9a and 9b, a gas supply system 10, high evacuating systems 12-14 and a deposition preventing plate 11. The antennae 8a and 8b are connected to discrete power sources 9a and 9b respectively through coaxial lines 19a and 19b to charge potentials opposite to each other to adjacent antenna rods 21, and the sum of the lengths of the left and right rods 21 is limited to conform to the wavelength of the microwave. Consequently, a microwave is radiated over a large area, and a large-area substrate is uniformly treated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a microwave plasma processing apparatus used for etching the surface of a material or depositing a thin film on a substrate using electron cyclotron resonance. especially. This article relates to a microwave plasma processing device suitable for uniform processing of large areas. [Prior art] This type of conventional microwave plasma processing equipment includes:
The one described in Japanese Unexamined Patent Publication No. 59-3018 is known. In this device, a discharge tube is installed in the vacuum chamber,
By attaching a coil to this and applying a magnetic field, and then introducing microwaves with the same frequency as the electron cyclotron frequency through a waveguide to cause a discharge, the reactant gas introduced into the vacuum chamber is decomposed. Depending on the method, material on a substrate, which is a sample placed in a vacuum chamber, is etched, or chemical vapor deposition is performed on the substrate.

However, in the above-mentioned apparatus, since microwaves are introduced through a waveguide, the size of the portion where discharge occurs is restricted by the size of the waveguide, making it difficult to process large-area substrates.

In order to enable processing of this large area substrate, for example, Japanese Patent Laid-Open No. 62-200730 or Japanese Patent Laid-Open No. 62-2
As shown in 98-1-06, it has been proposed to arrange a plurality of discharge tubes or cavities. This method effectively increases the discharge area without changing the size of each discharge tube. [Problems to be Solved by the Invention] Although the above-mentioned conventional technology takes into consideration the increase in the discharge area, insufficient consideration is given to the uniformity of processing inside each discharge tube and in the areas where discharges overlap. ,Also,
Since the microwave introduction means is limited to the discharge tube, it is not possible to install the microwave introduction means perpendicular to the substrate surface, and the device configuration is such that non-uniformity in processing is compensated for by other microwave introduction means. It was impossible. An object of the present invention is to provide a microwave plasma processing apparatus capable of processing a large area by introducing microwaves over a large area and causing discharge widely and uniformly. [Means for Solving the Problems] In order to achieve the above object, the present invention is mainly characterized by providing a plurality of microwave introduction means and using a flat radiator for at least one of them. be. The reason and structure are explained below. Increasing the discharge area by installing multiple microwave introducing means is effective for large area processing, but in order to improve the uniformity of the discharge, it is necessary to increase the discharge area between the discharge tube and the electron cyclotron resonance point. In between, it is necessary to install another means of introducing microwaves. In this case, if a discharge tube-shaped microwave introduction means is used, the microwaves supplied from the microwave introduction means above the microwave introduction means will not pass through and will not reach the electron cyclotron resonance point. Therefore, the only effective means of introducing microwaves is the one at the bottom, which makes it impossible to install multiple microwaves perpendicular to the substrate surface, and the original purpose cannot be achieved. Therefore, a comb-shaped flat radiator is used as the microwave introducing means. A comb-shaped planar radiator is most suitable for this purpose because it transmits microwaves except for a small part of the comb. Further, the discharge tube-shaped microwave introduction means is not necessarily necessary, and only a flat radiator may be used as the microwave introduction means. Unlike a discharge tube, a single flat radiator can generate a discharge over a wide area. Furthermore, for the above-mentioned reason, microwave transmission is not a necessary condition for the microwave introducing means at the top, so a flat radiator such as a slot-type antenna or a beam-type antenna can be used for this purpose. be. Furthermore, in this case, there is no need to open the upper part of the device, so that not only electromagnets but also permanent magnets can be used as the magnetic field forming means.

By the way, since the purpose of the present invention is to perform uniform plasma processing by reducing the influence of the microwave intensity distribution, in any case, the planar radiators are arranged so as to mutually compensate for the non-uniformity of the discharge. There is a need to. For this reason, it is necessary not only to arrange them on the same plane, but also to arrange them vertically. Specifically, the comb-shaped antennas may be arranged at different angles, orthogonally, or at a certain angle. Furthermore, since it is more economical to have fewer microwave introducing means, it is desirable to select the topmost microwave introducing means that can produce as uniform a discharge over a large area as possible. As a microwave power source, one with a frequency of 2.45 GIlz is available at low cost. The electron cyclotron resonance magnetic field strength for this frequency of 2.45 GHz is 0.0875T.
Therefore, sufficient magnetic field strength can be obtained not only with electromagnets (coils) but also with permanent magnets. Since the plane radiator is an antenna for microwave radiation, it can be made of a good conductor such as copper or aluminum. In the case of a slot-type antenna, the slot shape may be any shape that can be used as an antenna in general, such as one in which elongated holes are arranged in parallel, one in which holes are arranged in a radial pattern, or one in which holes are formed in concentric circles. In the case of a beam-type antenna, any commonly used antenna may be used. Note that the plane radiator may be installed outside the vacuum chamber, but in that case, a window made of quartz or the like that transmits microwaves is required in the vacuum chamber. In the case of a flat radiator, a coaxial line can be used to supply microwaves. The gas necessary for film formation or etching can be introduced between the microwave introduction means at the bottom and the sample. If the discharge gas and the reaction gas are introduced separately, the gas necessary for film formation or etching can be introduced between the microwave introduction means at the bottom. The discharge gas may be introduced near the sample, and the reaction gas may be introduced near the sample.

The sample is attached to a sample holding means with a built-in heater and placed facing the discharge tube or flat radiator.

The vacuum chamber is evacuated by a turbo-molecular pump, and the pressure during film formation is 1O-1 to io'Pa. [Function] In the above configuration, the waveguide is in front of it, and the plane radiator is in front of it. Microwaves are emitted in the front and back direction of the plane.The direction of the electric field is parallel to the plane.Magnets are installed near these microwave introducing means to form a magnetic field perpendicular to the sample surface. Then, the electron is captured by the magnetic field, causes electron cyclotron resonance at a point that satisfies the condition of the following equation (1), and is accelerated. Where, f: rotation frequency B: magnetic flux density q: charge of the electron m: charge of the electron It is mass.

The radiated microwave energy is absorbed as kinetic energy of electrons. The accelerated electrons collide with the discharge gas in the vacuum chamber, expelling electrons from the gas and sustaining the discharge, while also decomposing the reactive gas and generating active species for film formation or etching. Film-forming active species diffuse onto the sample surface and form a thin film. In addition, the etching active species causes a chemical reaction or physical collision with the sample material, etching the sample. In the present invention, since microwaves are introduced by a plurality of microwave introduction means including a plane radiator, microwaves can be emitted uniformly over a large area, and therefore, a large area of a sample can be uniformly processed. becomes possible. [Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 10.

Embodiment 1: FIG. 1 is a longitudinal sectional view of a microwave plasma processing apparatus which is a first embodiment of the present invention. This apparatus includes a vacuum chamber 1, a substrate stand 2 as a sample holding means, a reaction gas introduction tube 4 as a reaction gas introduction means, a discharge gas introduction tube 5 as a discharge gas introduction means, and a magnetic field forming means. A main coil 6, a control coil 7, a comb-shaped antenna 8a as a planar radiator. 8b, microwave power sources 9a and 9b, a gas supply system 10, a high vacuum exhaust system (numerals 12 to 16), and an adhesion prevention plate 11. The inside of the vacuum chamber 1 is evacuated to a high vacuum by a high vacuum exhaust system. As shown in FIG. 1, this high vacuum evacuation system includes a turbo molecular pump 12, a rotary pump l3, a gate valve l4, an auxiliary valve l5, and a roughing valve 16.

As shown in FIG.
A substrate 3 as a sample is placed on the upper surface of the substrate stand 2. Furthermore, a heater 17 for heating the substrate 3 is built inside the substrate stand 2 . This heater 17 is energized by a heater power supply l8. The reaction gas introduction tube 4 and the discharge gas introduction tube 5 are installed inside the vacuum chamber 1 and are connected to a gas supply system IO outside the vacuum chamber 1, respectively. When introducing the reactive gas and the discharge gas separately as in this example, the reactive gas is injected toward the substrate table 2 side, and the discharge gas is injected toward the comb-shaped antenna 8 side, as shown in Fig. 1. , a reaction gas introduction tube 4 and a discharge gas introduction tube 5 are arranged. The main coil 6 is capable of forming an electron cyclotron resonance point at any location between the adhesion prevention plate l1 and the substrate 3 within the vacuum chamber l. The control coil 7 is arranged outside the vacuum chamber 1 and is adapted to control the shape of the magnetic field lines produced by the main coil 6. The comb-shaped antenna 8 is installed inside the vacuum chamber 1 in the figure, but since the electron cyclotron resonance point only needs to be inside the vacuum chamber 1, the location where the comb-shaped antenna 8 exists is not necessarily inside the vacuum chamber 1. It doesn't have to be. This comb-shaped antenna 8 is made of copper, aluminum, or the like, which is a good conductor. Furthermore, the shape of the comb-shaped antenna 8 must be such that opposite potentials are applied to adjacent antenna rods 2l, as shown in FIG. The length of each antenna rod 21 is 61 mm+, and the left and right sides are made to match the wavelength of the microwave. For this reason, it is impossible to cause discharge over a large area with one comb-shaped antenna 8;
This can be handled by increasing the number of elements or installing a plurality of comb-shaped antennas 8 on the same plane as necessary. The comb-shaped antennas 8a and 8b each have a coaxial line 19a. 1
The comb-shaped antenna 8 and the microwave power supply 9 constitute microwave power supply means. It should be noted that the number of microwave power sources 9 is not necessarily the same as the number of microwave introducing means as long as the uniformity is sufficient.

The adhesion prevention plate 1l is made of quartz or the like, and prevents the film or powder produced by the decomposition products of the reaction gas from adhering to the comb-shaped antenna 8.
This is to prevent the comb-shaped antenna 8 from being spattered and its components being taken into the film on the substrate 3. Next, a specific example of plasma processing using the above-mentioned apparatus will be explained.

As the comb-shaped antenna 8, as shown in Fig. 3, a two-element antenna and a three-element antenna were used. antenna rod 21
The length of each piece is 61mm. In the case of the comb-shaped antenna 8, the electric field is strong between the antenna rods 21 and weak directly below the antenna rod 21, so the comb-shaped antennas 8a and 8b are arranged offset as shown in FIG. 3(a).
In addition to this arrangement, the arrangement shown in Figure 3 (b) is used to ensure uniform discharge.
), there is also a method of stacking multiple pieces at 90 degrees or any arbitrary rotation angle.

A 100 mst x 100 mm glass substrate is used as the substrate 3, and the specific procedure for forming a silicon nitride film on this glass substrate by chemical vapor deposition will be described. (i) With the glass substrate 3 attached to the substrate stand 2,
The inside of vacuum chamber 1 was evacuated to a high vacuum of 10-'Pa. (it) Inject nitrogen gas as a discharge gas at a rate of about 8 seconds (8 cm per minute in standard conditions) from the discharge gas introduction tube 5.
10 sec of monosilane gas as a reaction gas was introduced into each vacuum chamber 1 from the reaction gas introduction tube 4, and the pressure inside the vacuum chamber 1 was maintained at 0.133 Pa. (Quick) Heater power supply 1 is connected to the heater 17 built in the board stand 3.
8 and heated the substrate 3 to 150°C.

(God) When the temperature of the board 3 became stable, a current of about 1 OA was passed through the main coil 6, and a current of about 5 A was passed through the control coil 7. (V) Coaxial line 19a from microwave power supplies 9a and 9b,
19b to the comb-shaped antennas 8a and 8b, respectively.
．． A 45 GHz, 50 W microwave was applied to start the discharge. As a result, a silicon nitride film with a thickness of about 500 nm was formed almost uniformly on the 100 mm x 100+ am glass substrate in 10 minutes. In FIG. 4, a comb-shaped antenna 8a. The film thickness distribution in the case of 8b alone (the input power too and other conditions are the same as in this example) and the film thickness distribution in the case of this example using both are shown.

In this way, by using a plurality of comb-shaped antennas 8, uniformity is improved. It should be noted that the reason why the film thickness in this example is not the sum of the values obtained when each individual antenna is used is because the film formation rate depends on the flow rate of monosilane. In this embodiment, comb-shaped antennas 8a, 8b
are placed inside the vacuum chamber 1, so that the powder or film produced by the decomposition product of monosilane may adhere to the comb-shaped antennas 8a and 8b.
The comb antenna 8a. 8b is sputtered and its components are taken into the film on the glass substrate 3, the comb-shaped antennas 8a. A quartz anti-adhesion plate 11 was provided on the front surface of 8b. Furthermore, when four sets of the above-mentioned comb-shaped antennas 8a and 8b were arranged on the same plane and a film was formed on a glass substrate of 200+a weight x 200+am, similarly good results of uniformity were obtained. Embodiment 2: In the second embodiment, two comb-shaped antennas 8 having the shape shown in FIG. 5 are stacked vertically on a glass substrate as a planar radiator. Other equipment deposition and film deposition conditions are the same as in the first embodiment. A planar radiator with this shape has the advantage that the discharge area can be increased regardless of the wavelength of the microwave. In the case of this example, one set has 5
5 elements, 1 each of 3 elements and 27I elements.
Individual use, effective discharge area approximately 250m+m x 250+
It was set as i+m.

Using the apparatus of this example, under the same conditions as the first example.
When silicon nitride was formed into a film on a 200a+m x 200mm glass substrate, the film thickness increased to about 4 cm in 30 minutes.
A nearly uniform film of 00n■ was formed. Embodiment 3: The third embodiment is an apparatus having a configuration as shown in FIG. In this embodiment, a slot plate 25 as shown in FIG. 7 or 8 is used in the top plane radiator.
In Fig. 6, the same functional parts as in Fig. 1 are given the same reference numerals. As mentioned above, since microwave transmission is not a necessary condition only for the uppermost microwave introducing means, the slot plate 25 having the above shape can be used. For the specific experiment, the one shown in Figure 7 was used. The diameter of this slot plate 25 is 200 mm, the length of each slot 26 is 61 mm, and the left and right sides are made to match the wavelength of the microwave. Note that the width of the slot 26 was 5 Ilm. When a film was formed using the apparatus of this example in the same manner as in the second example, it was found that 100 wmX
Good uniformity was obtained within the 100mm substrate. Embodiment 4: The fourth embodiment is an apparatus having a configuration as shown in FIG. 9. In this embodiment, a permanent magnet 30 and an auxiliary coil 31 are used as magnetic field forming means. In addition, in Figure 9,
Parts with the same functions as those in Figure 1 are given the same reference numerals. The permanent magnet 30 needs to be strong.

Specific examples include rare earth cobalt magnets such as SmCo, oxide magnets such as barium ferrite (Ba0.6FezOW), and alloy magnets such as alnico.

The permanent magnet 30 made of these materials can secure a magnetic field strength of 0.2T or more on the surface, and it is quite possible to provide a flat radiator until the magnetic field weakens to 0.0875T. In order to obtain a device capable of processing a large area, a large-area permanent magnet 30 is required, and for this purpose, inexpensive barium ferrite or castable alnico are practical.
In addition, the auxiliary coil 3l strengthens the permanent magnet 30,
Used to adjust the position of the electron cyclotron resonance point.
The permanent magnet 30 may be located either inside or outside the vacuum chamber 1 as long as the electron cyclotron resonance point is below the bottom plane radiator and inside the vacuum chamber 1. In the case of this embodiment, there is an advantage that a magnetic field necessary and sufficient to cause electron cyclotron resonance can be obtained economically by using the permanent magnet 30. Embodiment 5: In the fifth embodiment, as shown in FIG. 10, a discharge tube 35 and a 5-element comb-shaped antenna 8 are used together as microwave introduction means. Note that 36 is a waveguide, and the first
In Figure 0, the same functional parts as in Figure 1 are given the same reference numerals. When microwaves are introduced by the discharge tube 35, uniformity can only be obtained in a limited area in the center, but by combining it with the slat-shaped antenna 8 in this way, it becomes possible to treat a large area. Further, a plurality of discharge tubes 35 and a plurality of comb-shaped antennas 8 may be used. Example 6: In the sixth example, dry etching was performed using a microwave plasma processing apparatus having the same configuration as the first example shown in FIG. As a sample, 100mm
A polysilicon film prepared by conventional high-frequency CVD method was used on a glass substrate with a size of 100 mm. Film thickness is approximately 200n
It is m. This sample was mounted on the substrate stand 2, and high vacuum evacuation was performed in the same manner as in the first example.

? Then, add 27 sc of Freon 115 from the reaction gas introduction pipe 4.
cI1, sulfur hexafluoride gas was flowed for 3 sec+*, and the pressure inside the vacuum chamber 1 was maintained at 1.33 Pa. Furthermore, 2.45G is applied to each of the comb-shaped antennas 8a and 8b.
A microwave of 300 W at Hz was applied to start the discharge. the result. In 30 seconds, a polysilicon film of approximately 100 nm thick was deposited on the 100! Etching could be done uniformly over the area of III x room■. [Effects of the Invention] According to the present invention, in a microwave plasma processing apparatus, a plurality of microwave introducing means including a plane radiator can
Since microwaves are introduced into the vacuum chamber,
Microwave radiation can be applied over a large area, making it possible to process large-area substrates. Also, using multiple microwave power supply means,
By carefully arranging the microwave introduction means, the device is configured to produce a discharge with good uniformity, making it possible to perform plasma treatment with good uniformity over a large area.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a microwave plasma processing apparatus according to a first embodiment of the present invention, FIG. 2 is a plan view showing an example of a comb-shaped antenna as a plane radiator, and FIG. FIG. 4 is a perspective view showing an example of an antenna arrangement, FIG. 4 is a view showing the measurement results of film thickness distribution during silicon nitride film formation by discharge of a comb-shaped antenna, and FIG. 5 is a plan view of a second embodiment of the present invention. FIG. 6 is a plan view showing a comb-shaped antenna as a radiator, FIG. 6 is a longitudinal sectional view showing a device equipped with a comb-shaped antenna and a slot antenna according to a third embodiment of the present invention, and FIGS. 7 and 8 are FIG. 9 is a plan view showing an example of a slot plate as a flat radiator, FIG. 9 is a longitudinal cross-sectional view showing a device equipped with a permanent magnet and an auxiliary coil as a magnetic field forming means according to a fourth embodiment of the present invention, and FIG. The figure is a longitudinal sectional view showing a device equipped with a discharge tube and a comb-shaped antenna as a microwave introducing means according to a fifth embodiment of the present invention. Explanation of symbols 1... Vacuum chamber 3... Substrate 5... Discharge gas introduction tube 7... Control coil 9... Microwave power source l1... Anti-adhesive plate l8... Heater power source 2l. ...Antenna rod 26...Slot 31...Auxiliary coil 36...Waveguide

Claims (1)

[Claims] 1. Microwave plasma processing in which a vacuum chamber is provided with a sample holding means, a reaction gas and discharge gas introduction means, a magnetic field forming means for causing electron cyclotron resonance, and a microwave power supply means. 1. A microwave plasma processing apparatus, characterized in that the microwave supply means includes a plurality of microwave introduction means, and at least one of the microwave introduction means uses a flat radiator. 2. The microwave plasma processing apparatus according to claim 1, wherein at least one of the microwave introducing means is installed at a position other than on the same plane parallel to the sample substrate on the sample holding means. Microwave plasma processing equipment. 3. The microwave plasma processing apparatus according to claim 1, wherein a plurality of microwave power supply means are used for the plurality of microwave introduction means. 4. In the microwave plasma processing apparatus according to claim 1, there is provided a microwave plasma processing apparatus between the plane radiator used as the microwave introducing means and the electron cyclotron resonance point, which is impermeable to the reaction gas and the discharge gas and is not transparent to the reaction gas and the discharge gas. A microwave plasma processing apparatus characterized in that a separation means made of a transparent material is installed.