JPH08203881A - Surface treatment system - Google Patents

Abstract

PURPOSE: To generate a low pressure high density plasma uniformly over a large area by providing a planar electrode made of a conductive plate having holes filled with a dielectric and vacuum sealing a vacuum vessel and radiating microwave, being fed from a coaxial tube of power supply mechanism, into the vacuum vessel through the holes of the conductive plate. CONSTITUTION: A planar electrode 42 is provided with a slot part 43 serving as an antenna for radiating microwave. The planar electrode 42 is formed of a planar conductive member and holes are made through the planar electrode 42, at the slot part 43 thereof, and filled with a dielectric 44. The planar electrode 42 is fixed hermetically, as an upper wall, to the upper part of a vacuum vessel 11. Since the slot part 43 is filled with the dielectric 44, the vacuum vessel 11 can be sealed hermetically by means of the planar electrode 42 itself. Microwave power is fed from a microwave power supply 20 to the planar electrode 42 through a coaxial pipe 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment apparatus and, more particularly, to a surface treatment of a substrate to be treated by using plasma generated by high frequency discharge, which is used for dry etching or plasma CVD in a semiconductor device manufacturing process. The present invention relates to a surface treatment device used.

[0002]

2. Description of the Related Art An example of a surface treatment apparatus used for dry etching, which is one step of manufacturing a semiconductor device, will be described. In order to actually perform pattern formation in the wiring pattern formation process that is indispensable for semiconductor device fabrication, plasma of a mixed gas containing a gas containing halogen as a main component is generated by discharge, and various active species (for example, atomic state) in the plasma are generated. A dry etching technique in which chlorine, atomic fluorine, a fluorocarbon compound, etc.) is reacted with a thin film on the surface to remove the thin film is generally used. As a means for converting gas into plasma, there is known a method of generating plasma by utilizing an interaction between an electric field and a magnetic field (electron cyclotron resonance) by a supplied microwave. An apparatus using this method is generally called an ECR surface treatment apparatus, and an apparatus using an air-core coil as a mechanism for generating a magnetic field is widely applied to dry etching, plasma CVD and the like.
Recently, a planar type ECR surface treatment apparatus, which is an improved type of the surface reaction apparatus utilizing ECR plasma, is also known (for example, JP-A-5-18785).

FIG. 5 shows an example of a conventional flat type ECR surface treating apparatus, and FIG. 6 shows a relationship between a magnetic field and an electric field in the flat type ECR surface treating apparatus.

The upper portion of the vacuum container 11 is the flange 1
An electrode 13 that is vacuum-sealed with 2 and includes a substrate holding mechanism is provided in the internal space. The substrate to be processed 14 is arranged on the electrode 13. The inside of the vacuum container 11 is decompressed to a required level by the exhaust mechanism 15. Electric power for biasing is supplied to the electrode 13 from a power supply 16. A planar electrode 17 for radiating electric power by microwaves is provided in an upper space inside the vacuum container 11, and the planar electrode 17 has a slot (through hole) 18 that operates as an antenna for microwave radiation. Is being processed. The location and shape of the slot 18 are arbitrarily selected to suit microwave radiation. In the vicinity of the planar electrode 17, a plurality of ring-shaped permanent magnets 19 for generating a magnetic field are arranged around the planar electrode 17. In this example, the permanent magnet 19 is fixed in a ring-shaped groove formed in the flange 12 for fixing the magnet. Further, as a mechanism for supplying microwaves to the planar electrode 17, a microwave power source 20, a coaxial tube 23 including an outer conductor 21 and an inner conductor 22, and a coaxial microwave introducing vacuum window 24 are provided. Although illustration is omitted for simplification of description, the microwave power source 20 and the planar electrode 17 are omitted.
Between the waveguide, as an element that constitutes the microwave circuit between
A matching device, a single-row tube, a directional coupler, a coaxial waveguide converter, etc. are provided as required.

In the above flat type ECR surface treatment apparatus, after introducing a predetermined gas into the vacuum container 11 up to a predetermined pressure by using a gas introduction system (not shown), electric power by microwave is introduced into the vacuum container 11 to generate an electric field. And the magnetic field are utilized to convert the gas into plasma and generate plasma 25. Various particles having high chemical activity in the plasma 25 are guided to the surface of the substrate 14 to be processed, and the surface is etched by utilizing a chemical reaction on the surface of the substrate. Usually, the substrate to be processed 1 is provided with energy to positive ions, which are one of highly active particles.
In order to lead to the surface of the electrode 4, bias power of high frequency, for example, is supplied to the electrode 13 using the power supply 16.

Next, the working relationship between the magnetic field and the electric field by the microwave will be described with reference to FIG. FIG. 6 shows magnetic field lines 31 generated by the ring-shaped permanent magnet 19 and an electric field 32 of microwaves generated from the slots 18 formed in the planar electrode 17. In this example, the magnetic field strength in the vacuum container 11 is strongest in the vicinity of the slot 18, and gradually decreases toward the inside of the vacuum container 11. The microwave frequency used for plasma generation is generally 2.45 GHz, and the magnetic flux density that satisfies the ECR condition at this time is 875 Gauss. Therefore, the magnetic flux density generated by the ring-shaped permanent magnet 19 is generated at a position slightly apart from the slot 18 (specifically, a position of a few mm to a few cm) so as to generate a uniform magnetic flux density surface of 875 Gauss satisfying the ECR condition. , The residual magnetic flux density of the ring-shaped permanent magnet 19 is determined.
In the example of FIG. 6, the magnetic field strength is EC in the microwave propagation path in the plasma 25 from the slot 18 to the ECR surface.
It has a structure that gradually decreases toward the R plane. Further, the electric field 32 of the microwave in the vicinity of the slot 18 in the vacuum container 11 is substantially orthogonal to the magnetic field 31. The above two conditions are indispensable for propagating the microwave to the ECR surface and generating the high density plasma 25.

The conventional planar type ECR surface treatment apparatus described above has been widely evaluated as a plasma source at present, and the evaluation as a surface treatment apparatus is also becoming widespread.

[0008]

The greatest feature of the ECR surface treatment apparatus is that high density plasma can be generated at a low gas pressure by utilizing the resonance phenomenon of the magnetic field and the microwave. However, 875 Gauss is required as the magnetic field strength for satisfying the resonance condition with respect to 2.45 GHz, which is the frequency of microwaves normally used. On the other hand, a silicon wafer used for semiconductor manufacturing has a diameter of about 250 mm, and plasma for processing the silicon wafer is required to be uniform over the wafer area.

The planar type ECR surface treatment apparatus shown in FIG. 5 uses a plurality of ring-shaped permanent magnets to overcome the drawbacks of the conventional apparatus of the type in which a magnetic field is generated by a general air-core coil. Therefore, it is possible to achieve effects such as generation of a large-area uniform plasma by using slots, simplification of a magnetic field generation mechanism by adopting a permanent magnet, and homogenization of high-frequency power bias because a magnetic field does not cross the wafer surface.

However, the plane type ECR surface treatment apparatus has a complicated mechanism for introducing microwaves,
In particular, because the coaxial vacuum window 24 has insufficient reliability,
There is a problem that microwave power that can be supplied is limited and it is difficult to generate high-density plasma. Further, when the microwave power is increased, abnormal discharge may occur around the slot 18, and due to lack of reliability of the device, it has not yet been introduced into the semiconductor manufacturing line.

An object of the present invention is to solve the above problems, and proposes a planar electrode for plasma generation having a novel structure, which enhances reliability when high density plasma is generated and achieves high density at low pressure. It is an object of the present invention to provide a surface treatment apparatus capable of uniformly generating plasma in a large area.

[0012]

The surface treatment apparatus according to the first aspect of the present invention includes a vacuum container, an exhaust mechanism for reducing the pressure inside the vacuum container, and a discharge gas introduced into the vacuum container. A surface treatment apparatus comprising a gas introduction mechanism, a power supply mechanism for supplying electric power by microwaves to discharge gas to generate plasma, and a substrate holding mechanism installed in a vacuum container. A planar electrode formed of a conductive plate having a hole filled with a dielectric material and fixed to the vacuum container so as to vacuum-seal the inside of the vacuum container, through the hole of the conductive plate, The microwave supplied by the coaxial tube is configured to be radiated into the vacuum container.

In the first aspect of the present invention, the conventional coaxial tube used for microwave introduction and the vacuum window are not used, and holes (slots) filled with a dielectric are formed in the planar electrode to form a coaxial tube. Microwaves are directly supplied to this planar electrode by using it, and the high-density plasma with good uniformity is easily generated by the microwave radiation from the holes. A hole filled with a dielectric material is most practical as a slot portion for radiating microwaves in the planar electrode. In addition, by filling the holes of the planar electrodes for supplying microwave power into the vacuum container with a dielectric, the slot itself has a structure that can withstand vacuum sealing. Conventionally, in order to supply microwave power Although necessary, it was possible to eliminate the coaxial vacuum window, which had poor reliability.

According to a second aspect of the present invention, in the first aspect of the present invention, a plurality of holes formed in the planar electrode are arranged at radial positions centered on a point on the conductive plate, and near the center of the radial positions. A microwave is supplied.

According to a third aspect of the present invention, in the first aspect, the holes of the planar electrode are formed as arcs on one circle or a plurality of concentric circles, and a microwave is generated near the center of the circle or the plurality of concentric circles. It is characterized by being supplied.

In the second and third aspects of the present invention, the holes forming the slot portions are preferably arranged at a ring-shaped radial position, and microwave power is effectively radiated into the vacuum container to generate plasma. It was made possible to generate it in the discharge space and use it.

In a fourth aspect of the present invention according to any one of the first to third aspects, a plurality of ring-shaped permanent magnets are installed at positions where the conductive plate forming the planar electrode does not interfere with the holes, and the vicinity of the holes is provided. It is characterized by generating a magnetic field.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the plurality of ring-shaped permanent magnets are magnetized in the radial direction of the ring-shaped permanent magnets, and the adjacent ring-shaped permanent magnets are magnetized in the same direction. It is characterized by being in the opposite direction.

In the fourth and fifth aspects of the present invention, a ring-shaped permanent magnet for magnetic field generation is directly provided on the planar electrode, and the ring-shaped permanent magnet is magnetized in the radial direction so that an electric field generated by microwaves is generated. And make the magnetic field by the permanent magnet orthogonal to
The interaction between the magnetic field and the electric field by the microwave is made effective.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, elements that are substantially the same as the elements described in FIG. 5 are given the same reference numerals. The inside of the vacuum container 11 is used as a discharge space, and the electrode 13 on which the target substrate 14 is arranged is arranged inside this. Electrode 1
Reference numeral 3 is attached to the lower wall of the vacuum container 11 in a floating potential state using an insulator 41. The electrode 13 is supplied with a substrate holding mechanism. A planar electrode 42 is provided on the upper wall portion of the vacuum container 11. The planar electrode 42 according to the present embodiment also has a function of keeping the internal space of the vacuum container 11 in vacuum. Therefore, in the device according to this embodiment, the flange 12 of the conventional device is used.
The member corresponding to is not used, and the planar electrode 42 itself also serves as the flange 12. The substrate to be processed 14 placed on the electrode 13 is arranged so as to face the planar electrode 42 of the vacuum container 11. In order to operate the device according to the present embodiment as a discharge reaction device, the discharge is included and the power supply 1 is used.
6, the power for biasing is used to evacuate the vacuum container 11 to a predetermined pressure using the air supply mechanism 15, and then a gas used for the discharge reaction is introduced to a predetermined pressure using a gas introduction mechanism (not shown).

Referring to FIGS. 1 and 2, the planar electrode 42
The structure and action of will be described. The planar electrode 42 has a slot portion 43 that operates as an antenna for microwave radiation.
Is formed. The planar electrode 42 is formed by using a plate-shaped conductive member such as a metal plate, and the slot portion 43 has a hole penetrating the planar electrode 42 and a dielectric 44 densely filled in the hole. Formed from. Although the slot portion 43 is not actually a hole itself, it has substantially the same action as the slot 18 of the conventional device, that is, it has a radiating action into the vacuum container that allows microwaves to pass therethrough, and is therefore referred to as a "slot portion". Since the planar electrode 42 is attached to the upper portion of the vacuum container 11 as the upper wall of the vacuum container 11 so that the internal space is airtight, and the slot portion 43 is filled with the dielectric 44, the planar electrode 42 itself. This enables vacuum sealing of the internal space of the vacuum container 11.

A dielectric 44 filled in the slot 43
The conditions required for the above are that the dielectric loss is small, that the airtightness is good, and that it has a certain degree of heat resistance. Regarding the airtightness, it is necessary that the adhesion between the conductive plate forming the planar electrode 42 and the wall of the vacuum container 11 is good. Materials that satisfy such conditions include inorganic materials such as glass, quartz, and alumina ceramics, and organic materials such as Teflon, polyimide, and silicon resin. The gas species used in the surface treatment process, the microwave power used, etc. It is appropriately selected according to the conditions of.

Further, as shown in FIGS. 1 and 2, a plurality of ring-shaped permanent magnets 45 for generating a magnetic field are arranged on the outer surface of the planar electrode 42. In this embodiment, a magnetic circuit is configured by concentrically arranging four ring-shaped permanent magnets 45 having different diameters. The ring-shaped permanent magnet 45 is embedded in a ring-shaped groove formed on the outer surface of the planar electrode 42. Ring-shaped permanent magnet 45
Are all magnetized in the radial direction, and adjacent permanent magnets are magnetized in opposite directions.

As shown in FIG. 2, the planar electrode 42 has a circular shape. A plurality of the slot portions 43 are formed,
It is desirable that the planar electrode 42 is formed at a radial position from a point such as the center. In the case of the present embodiment, for example, four slot portions 43 are formed at radial positions when viewed from the center point in the space between the second permanent magnet 45 and the third permanent magnet 45 from the inside, for example. . Since the four slot portions 43 are arranged on the ring shape, each of them has an arc shape. Further, the slot portion 43 is
It may be formed between other ring-shaped permanent magnets, and the slot portions may be arranged in concentric circles.
Furthermore, in the present embodiment, an example in which four ring-shaped permanent magnets 45 are used is shown, but different numbers may have better performance depending on the purpose of application. The magnetization direction is
The operation is exactly the same even if the direction of each permanent magnet 45 is reversed.

Due to its structure, form and material, the planar electrode 42 has such strength that it does not practically deform with respect to the pressure difference between atmospheric pressure and vacuum. On the other hand, it is desirable that the thickness of the planar electrode 42 is as thin as possible in order to propagate the microwave through the dielectric 44 inside the slot 43. The thickness of the planar electrode 42 is determined by the balance of these two conditions. As shown in the present embodiment, the slot portion 43 is formed by dividing a ring-shaped one into a plurality of portions (four in this embodiment) and providing a bridging portion 46, thereby supplementing the mechanical strength of the slot portion 43 with a flat surface. It is practically effective to make the electrode 42 thin. If the width of the bridging portion 46 is sufficiently shorter than the wavelength of the microwave used for discharging, and the length of the divided slot portions 43 is equal to or more than a quarter of the wavelength of the microwave. For example, there are no particular restrictions on the length of the bridging portion 46 and the number of divisions.

Next, the structure for supplying microwave power and the plasma generation method according to this embodiment will be described. When microwave power is supplied from the microwave power source 20 to the planar electrode 42 through the coaxial tube 23 including the outer conductor 21 and the inner conductor 22, the dielectric material of the slot portion 43 installed in the planar electrode 42. Through 44, electric power by microwaves is radiated into the vacuum container 11.
The microwave power is absorbed by the gas introduced into the vacuum container 11, and plasma 25 is generated in the vacuum container 11. A predetermined surface treatment is applied to the surface of the substrate to be processed 14 by utilizing the action of the plasma 25. At this time,
If the intensity of the magnetic field generated from the plurality of ring-shaped permanent magnets 45 is set so that the electron cyclotron resonance condition with respect to the frequency of the supplied microwaves is satisfied in the space in the vacuum container 11 near the slot 43, the plasma 25 The generation efficiency of can be made very high.

The structure of the microwave introduction part will be described. The microwave power used in the surface treatment apparatus is usually in the range of 10 W to several kW. As the coaxial tube 47 for propagating such electric power, the outer conductor 4 is used.
It is common to use the one having the inner diameter of 8 standardized to 20 mm or 39 mm. On the other hand, with respect to the diameter of the slot portion 43, although it differs depending on the intended process, it is usually necessary that the diameter thereof be the same as or slightly smaller than the diameter of the substrate to be processed 14. Since most of the diameter of the substrate to be processed 14 is in the range of 150 mm to 300 mm, the slot portion 43 and the coaxial tube 47 cannot be directly connected. Therefore, in the present embodiment, the discharge planar electrodes 42 of the outer conductor 48 and the inner conductor 49.
A coaxial tube 47 having a tapered portion is connected to a portion 47a connected to the. This prevents deterioration of power utilization efficiency due to impedance mismatch.

The action of the magnetic field and the electric field of the microwave will be described with reference to FIG. In FIG. 3, the ring-shaped permanent magnet 45
The magnetic field lines (magnetic field) 50 generated by the above and the electric field 51 of the microwave generated by the slot portion 43 provided in the planar electrode 42 are shown. In the propagation path of microwaves in the plasma 52 from the slot portion 43 to the ECR surface, the magnetic field strength has a structure that gradually decreases toward the ECR surface. Further, the electric field 51 due to the microwave is orthogonal to the magnetic field lines 50 almost all over. The above two conditions are indispensable for propagating microwaves to the ECR plane and generating high-density plasma, as already described in the section of the prior art. Also in this embodiment, by comparing the magnetizing directions of the plurality of ring-shaped permanent magnets 45 with each other in the radial direction and the magnetizing directions of the adjacent ring-shaped permanent magnets 45 with each other in the opposite directions, comparison between FIGS. As is clear from
The magnetic field and the electric field can be interacted with each other similarly to the conventional planar type ECR surface treatment apparatus, and the plasma can be generated by taking advantage of the ECR.

FIG. 4 shows a second embodiment of the surface treatment apparatus according to the present invention. In this embodiment, the slot portion 43 is formed in a crank shape in the radial direction inside the planar electrode 42, and is filled with the dielectric material 44 as in the first embodiment. The position of the slot portion 43 is between the second and third ring-shaped permanent magnets 53 from the inner side on the atmosphere-side electrode surface, and the second-side ring-shaped permanent magnet 53 on the vacuum side electrode surface. It is desirable to match it with the center position of the magnet width. The dielectric 44 filled in the slot 43
The material is selected as in the first embodiment. Further, in this embodiment, the magnetization directions of the plurality of ring-shaped permanent magnets 53 are
As in the case of the conventional device, the ring-shaped axial direction is adopted. This is because the arrangement relationship between the magnetic field and the microwave electric field in this embodiment is the same as in the case of the conventional device shown in FIG.

In each of the above embodiments, the ring-shaped permanent magnet 4 is used.
Although 5, 53 are incorporated in the planar electrode 42, they may be arranged outside the planar electrode 42.

[0032]

As is apparent from the above description, according to the present invention, in the flat type ECR surface treatment device, the reliability is low by devising the structure of the flat electrode and the magnetizing direction of the ring-shaped permanent magnet. By eliminating the conventional vacuum window for microwave introduction and eliminating unnecessary discharge inside the slot, it is possible to stably and efficiently generate high-density plasma in the planar ECR surface treatment device, and to treat the substrate to be treated. It is possible to maintain good uniformity and improve the practicality. Particularly, according to the present invention, various high-speed and uniform large-area treatments can be performed in a surface treatment apparatus such as a dry etching apparatus or a CVD apparatus which is a plasma process apparatus.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a surface treatment apparatus according to the present invention.

FIG. 2 is a plan view for explaining the structure of a planar electrode.

FIG. 3 is a sectional view for explaining the working relationship between the magnetic field and the electric field generated by the microwave in the first embodiment.

FIG. 4 is a sectional view showing a second embodiment of the surface treatment apparatus according to the present invention.

FIG. 5 is a sectional view showing a conventional flat type ECR surface treatment apparatus.

FIG. 6 is a cross-sectional view for explaining a working relationship between a magnetic field and an electric field generated by microwaves in a conventional planar ECR surface treatment apparatus.

[Explanation of symbols]

 11 Vacuum Container 13 Electrode 14 Substrate 15 Exhaust Mechanism 42 Planar Electrode 43 Slot Section 44 Dielectric 45, 53 Ring Permanent Magnet 47 Coaxial Tube 48 External Conductor 49 Inner Conductor 50 Magnetic Field (Magnetic Field) 51 Electric Field 52 Plasma

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C30B 33/12 7202-4G H01L 21/205 H05H 1/46 C 9216-2G

Claims (5)

[Claims] 1. A vacuum vessel, an evacuation mechanism for reducing the pressure inside the vacuum vessel, a gas introduction mechanism for introducing a discharge gas into the vacuum vessel, and a microwave for discharging the gas to generate plasma. In a surface treatment apparatus comprising a power supply mechanism for supplying power according to, and a substrate holding mechanism installed in the vacuum container, the power supply mechanism is formed of a conductive plate having a hole filled with a dielectric and The vacuum container is provided with a planar electrode fixed to the vacuum container so as to seal the inside of the vacuum container, and the microwave supplied by the coaxial tube of the power supply mechanism is radiated into the vacuum container through the hole. A surface treatment device characterized in that 2. A plurality of the holes formed in the planar electrode are arranged at radial positions around a point on the conductive plate, and the microwave is supplied near the center of the radial positions. The surface treatment apparatus according to claim 1, wherein 3. The hole of the planar electrode is formed as an arc on one circle or a plurality of concentric circles, and a microwave is supplied to the circle or the vicinity of the center of the plurality of concentric circles. The surface treatment apparatus according to claim 1. 4. A plurality of ring-shaped permanent magnets are installed at a position where they do not interfere with the hole in the conductive plate forming the planar electrode, and a magnetic field is generated in the vicinity of the hole. Item 4. The surface treatment device according to any one of items 1 to 3. 5. The magnetization direction of the plurality of ring-shaped permanent magnets is a radial direction of the ring-shaped permanent magnets, and the magnetization directions of adjacent ring-shaped permanent magnets are opposite to each other. Item 4. The surface treatment apparatus according to item 4.