JP2010225296A - Inductively coupled antenna unit and plasma processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inductively coupled antenna unit that is easily attached/detached and generates high-density discharge plasma in a vacuum container, and to provide a plasma processing device formed by using the plurality of inductively coupled antenna units and having a predetermined area and high productivity. <P>SOLUTION: The inductively coupled antenna unit is formed of a dielectric housing 11, a lid 12 of the housing, and a U-shaped antenna conductor 14 mounted onto the lid, and the U-shaped portion of the antenna conductor is integrally housed within the housing. A metal pipe is adopted as the antenna conductor, and a thin hole 15 is formed in the U-shaped portion such that cooling gas is jetted into the housing through the hole to cool the antenna conductor and the dielectric housing. The antenna unit is easily attachable and detachable to and from an opening portion formed in a vacuum-container wall of a plasma processing device. The plurality of inductively coupled antenna units are arranged to form a highly-productive plasma processing device having any processing area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an inductively coupled high-frequency antenna and a plasma processing apparatus using the high-frequency antenna.

In recent years, as liquid crystal displays, amorphous solar cells, and the like have become significantly larger in size, the glass substrate size used in these devices has become very large, and plasma processing apparatuses that process the substrate surface have also increased in size. A plurality of small antennas are distributed around the vacuum vessel as a plasma processing device for forming a desired thin film on the substrate surface using discharge plasma or etching the substrate surface, and a high frequency current is applied to each small antenna. An inductively coupled plasma (ICP) system that generates discharge plasma using an electromagnetic field generated by flowing has been developed.

In general, ICP is known as a technique capable of obtaining a plasma having a high density, a low electron temperature, and a low ion energy even under a low gas pressure as compared with a capacitively coupled plasma (CCP). Patent Document 1 discloses an ICP-type plasma generation apparatus in which a plurality of small antennas are distributed and arranged. In this plasma generating apparatus, a U-shaped or U-shaped inductively coupled antenna is disposed in an opening provided on a wall surface of a vacuum vessel.

In an internal antenna type plasma processing apparatus in which an antenna conductor is introduced into a vacuum vessel, an electrostatic field is generated between the antenna conductor and discharge plasma. In general, in the internal antenna system, a negative DC self-bias voltage is generated in the antenna itself with respect to plasma. By this bias voltage, ions in the plasma are accelerated and incident on the antenna conductor, and the antenna conductor itself is sputtered.

For example, if the antenna conductor is copper, sputtered copper atoms and copper ions are mixed in the discharge plasma and adhere to and deposit on the inner wall of the vacuum vessel and the surface of the substrate to be processed. In the case of forming a thin film, there are problems such as contamination as impurities in the thin film. In order to prevent the contamination of impurities, it is common practice to cover the outer periphery of the antenna conductor with a dielectric pipe such as quartz. For example, Patent Literature 2 discloses a technique in which a 6 mm diameter copper pipe antenna conductor has an outer periphery coated with a 15 mm inner diameter quartz pipe.

However, in the above-described method in which the antenna conductor is introduced into the vacuum vessel, the temperature of the antenna conductor and the dielectric pipe due to the high-frequency current is so high that it is necessary to cool the antenna conductor and the dielectric pipe in order to suppress the temperature rise. It was. Although a method of circulating the cooling water using the antenna conductor as a pipe shape is adopted, the dielectric pipe is not cooled, so when the high frequency power is increased, the dielectric pipe is heated to 600 ° C. or more. There was a problem.

In addition, since the introduction end of the antenna conductor pipe has a vacuum seal while being connected to a water supply / drain pipe, a high frequency power feeding terminal, or an electrical connection to a ground terminal, the configuration is not only complicated, There were problems such as time required for attaching and detaching antennas and maintenance and inspection. Furthermore, the process of covering the outer periphery of the antenna conductor with an insulating material pipe such as quartz in accordance with the U-shaped or U-shaped antenna conductor is complicated and expensive. In the above structure, there is a problem that the insulating material pipe is easily damaged due to mechanical shock or thermal stress.

JP 2004-228354 A JP 11-317299 A

In view of the above-mentioned difficult problems, the present invention provides an inductively coupled antenna unit (hereinafter abbreviated as an ICP antenna unit) that can be easily attached to and detached from an opening formed in a vacuum vessel wall and that can be easily maintained and inspected. The purpose is to do. Another object of the present invention is to generate high-density discharge plasma efficiently and stably. It is another object of the present invention to provide a discharge plasma processing apparatus of an arbitrary size by using a plurality of the ICP antenna units.

The present invention was invented in the course of developing an inductively coupled high-frequency antenna for use in a high-frequency discharge plasma processing apparatus, and was able to solve the difficult problems. In the present invention, a dielectric casing, an inductive coupling antenna conductor such as a U-shape or a U-shape (hereinafter abbreviated as an ICP antenna conductor), and a lid attached with the ICP antenna conductor are integrated. It is an ICP antenna unit. The feeding side introduction portion and the ground side introduction portion of the ICP antenna conductor are attached to the lid through through or through feedthrough, and the U-shaped portion or U-shaped portion of the ICP antenna conductor is in the dielectric casing. It is housed. The ICP antenna unit according to the present invention is configured to be detachable from an opening formed in a vacuum vessel wall of a high frequency plasma processing apparatus or the like.

The feeding side introduction portion of the ICP antenna conductor is disposed at one end portion in the longitudinal direction of the lid, and the ground side introduction portion is disposed at the other end portion, and the U-shaped portion or U-shaped portion of the ICP antenna conductor is It is installed almost parallel to the bottom plate in the dielectric casing.

According to the present invention, the shape of the antenna conductor portion of the ICP antenna can be U-shaped, U-shaped, N-shaped or M-shaped, and a plane formed by the shape is formed on a bottom plate or a side plate in the dielectric casing. It is characterized by being arranged substantially in parallel. It is desirable that the total length of the ICP antenna conductor having the shape is equal to or less than a quarter wavelength of a high frequency to be fed. The ratio of the short side (interval between the parallel portions of the antenna conductor) to the long side of the rectangle formed by the U-shaped or U-shaped portion of the inductively coupled antenna conductor is preferably 0.05 to 0.5.

The dielectric casing is preferably made of a dielectric material having a small dielectric loss with respect to a high-frequency electric field, such as metal oxide, nitride, carbide, or fluoride. Suitable dielectric materials are quartz, alumina, zirconia, silicon nitride, silicon carbide, and the like. In addition, the dielectric casing is provided with a flange around the opening, and the flange and the lid are fixed with a seal member interposed therebetween to be integrated.

The high frequency antenna conductor is a metal pipe, for example, a copper pipe, and a plurality of pores are provided in a portion accommodated in the dielectric casing, and a cooling gas is ejected from the pores into the dielectric casing to thereby generate an ICP antenna. The conductor and the dielectric casing are cooled. It is desirable to determine the position and direction of the pores provided in the ICP antenna conductor pipe so that cooling gas is blown almost uniformly onto the inner wall surface of the dielectric casing. The antenna conductor is preferably a metal conductor having high electrical conductivity and thermal conductivity, and a copper pipe or an aluminum pipe can be used.

The lid is provided with an exhaust port, and the exhaust port and the antenna conductor pipe are connected by a flexible tube via a heat exchanger and a pump. ICP by circulating cooling gas
The antenna conductor and the dielectric casing are cooled. The cooling gas may be air, but is preferably an inert gas such as argon gas or nitrogen gas.

Further, the ICP antenna unit according to the present invention can be attached to an opening provided on the vacuum vessel wall of the plasma processing apparatus by sandwiching a vacuum seal member so that the inside of the vacuum vessel can be maintained at a predetermined degree of vacuum. It is possible to provide a plasma processing apparatus in which the antenna unit can be easily attached / detached, maintained, and inspected.

One end of the ICP antenna conductor is connected to a high frequency power source through a matching unit, and the other end is grounded. If necessary, it can be grounded via a capacitor. By supplying high-frequency power to one end of the ICP antenna conductor and causing a high-frequency current to flow through the ICP antenna conductor, discharge plasma of a raw material gas can be generated in the vacuum vessel. As the high-frequency power, 13.56 MHz high-frequency power can be supplied, but it is not limited to this frequency.

Further, according to the present invention, a part of the vacuum vessel wall, for example, a top plate, is provided with a plurality of openings at regular intervals, and the ICP antenna unit is attached to each opening so that high frequency power is supplied to each ICP antenna conductor. Is supplied, it is possible to generate a uniform discharge plasma over a large area in the vacuum vessel. Further, the density distribution of the discharge plasma can be adjusted and made uniform by controlling the high frequency power supplied to each ICP antenna unit.

According to the present invention, it is possible to provide an ICP antenna unit that can be easily attached to and detached from the plasma processing apparatus and that is easy to perform maintenance and inspection at low cost. In addition, high-density discharge plasma can be generated efficiently and stably. Furthermore, by using a plurality of ICP antenna units, a plasma processing apparatus of any size can be provided at a low cost.

It is a cross-sectional schematic diagram for demonstrating the ICP antenna unit of this invention. It is a figure which shows the relationship between high frequency electric power and discharge plasma density. It is a schematic plan view of the shape of an ICP antenna conductor. It is a principal part cross-sectional schematic diagram of the ICP antenna unit employ | adopted in the present Example 3. FIG. It is a plane conceptual diagram for demonstrating Example 4 equipped with the several ICP antenna unit.

A preferred form of the ICP antenna unit according to the present invention comprises a dielectric housing, a lid of the housing, and a U-shaped or U-shaped ICP antenna conductor attached to the lid, The U-shaped portion or U-shaped portion of the antenna conductor is housed in the housing. The ICP antenna conductor is attached through the lid or through a feedthrough. For example, a copper pipe is used as the ICP antenna conductor, and a U-shaped portion or U-shaped portion is provided with pores, and a cooling gas is injected into the housing to cool the ICP antenna conductor and the dielectric housing. To do.

The ICP antenna unit according to the present invention is used with a vacuum seal member sandwiched between openings formed in a vacuum vessel wall of a plasma processing apparatus or the like. One feeding terminal of the ICP antenna conductor is connected to a high frequency power source, and the other terminal is grounded directly or via a capacitor. Furthermore, a plurality of openings are formed in the vacuum vessel wall of the high-frequency plasma processing apparatus, etc., and a discharge seal of an arbitrary area is generated by mounting the ICP antenna unit according to the present invention with a vacuum seal member interposed between the openings. Can be made.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
1237178928734_0
These are the schematic sectional drawings which show the ICP antenna unit which can be utilized suitably in order to implement this invention. This ICP antenna unit is composed of a dielectric casing 11, a lid 12, and a U-shaped ICP antenna conductor 14 attached to the lid. A copper pipe having an outer diameter of 6.4 mm was adopted as the antenna conductor 14 and attached to the lid 12 via a feedthrough 16. The lid and the feedthrough 16 and the feedthrough and the ICP antenna conductor 14 were mounted via a vacuum seal member 21 so as not to cause gas leakage.

The dielectric casing has a rectangular parallelepiped shape, and its internal dimensions are a short side of 1.8 cm, a long side of 13 cm, and a depth of 5 cm. The length of the flat part 14a of the ICP antenna conductor 14 was 10 cm, and the distance between the antenna conductor and the inner bottom plate of the dielectric casing (dielectric window part 17) was adjusted to 0.6 cm.

A large number of pores 15 are provided in the U-shaped portion of the ICP antenna conductor 14 existing in the dielectric casing. The pores were opened so that the cooling gas was injected almost uniformly onto the inner wall surface of the dielectric casing. An exhaust port 18 is provided in the lid, and a heat exchanger (not shown) and a pump (not shown) are connected by a flexible tube 22 between the exhaust port and the ICP antenna conductor pipe. The cooling gas was introduced from both ends of the antenna conductor pipe and recovered from an exhaust port provided in the lid.

The ICP antenna unit disclosed in the present embodiment is mounted on the opening 24 of the top plate 23 of the vacuum vessel with a vacuum seal member 21 interposed therebetween, and one feeding terminal 19 of the ICP antenna conductor 14 is a matching unit (not shown). ) To the high frequency power source 20 and the other power supply terminal was grounded. A mixed gas of argon and hydrogen having a gas pressure of 1 Pascal was introduced into the vacuum vessel, and high-frequency power with a frequency of 13.56 MHz and an output of 1 kW was supplied to generate discharge plasma in the vacuum vessel.

The discharge plasma was filled in the vacuum vessel, and the plasma density in the vacuum vessel 10 cm away from the window 17 surface of the dielectric casing 11 was 1.2 × 10 ¹¹ / cm ³ . As shown in FIG. 2, the plasma density increases almost in proportion to the high frequency power. Moreover, it became clear that it decreased in inverse proportion to the distance from the ICP antenna conductor surface.

In this example, the temperature of the ICP antenna conductor and the dielectric casing could be kept at 80 ° C. or lower by circulating nitrogen gas as the cooling gas. As the cooling gas, it is possible to circulate the atmosphere. When the atmosphere is circulated, a heat exchanger is not necessary, and it is introduced from the ICP antenna conductor pipe and exhausted from the exhaust port 18 provided in the lid. Can be cooled.

FIG. 3 shows a schematic plan view of the ICP antenna conductor of the ICP antenna unit used in the second embodiment according to the present invention. The ICP antenna conductor shown in FIG. 3A is used in Example 1, and the ICP antenna conductor used in Example 2 has the shape shown in FIG. An ICP antenna conductor feeding side introduction portion 27 and a ground side introduction portion 28 are attached to one end portion of the lid body 12, and the U-shaped portion of the ICP antenna conductor is bent at a substantially right angle with respect to the introduction portion, and the U-shape The surface surrounded by the portion was configured to be substantially parallel to the bottom plate (dielectric window portion 17) of the inside 13 of the dielectric casing. The length of the U-shaped portion of the antenna conductor 14 was 10 cm, and the interval was 3 cm.

In the case of the U-shaped antenna conductor used in this example, high-frequency currents flow in opposite directions in parallel portions of the antenna conductor, so that the generated magnetic lines of force are generated perpendicular to the plane surrounded by the parallel portion of the antenna conductor, The magnetic field strength is about twice that of the first embodiment. Therefore, discharge plasma can be generated with a relatively small high-frequency power, and discharge plasma can be stably generated even in a low gas pressure region where discharge is difficult to occur, for example, 0.5 Pascal or less.

The ICP antenna unit using the ICP antenna conductor having the shape shown in FIG. 3B is mounted with the vacuum seal member 21 sandwiched in the opening 24 of the top plate 23 of the vacuum container, and one of the ICP antenna conductors 14 is mounted. A high frequency power source 20 was connected to the power supply terminal 19 via a matching unit (not shown), and the other power supply terminal was grounded. A discharge plasma was generated under the same conditions as in Example 1. The plasma density in the vacuum vessel 10 cm away from the window 17 surface of the dielectric housing 11 was 1.8 × 10 ¹¹ / cm ³ .

According to the present invention, the ICP antenna conductor is not limited to the U-shape and U-shape, and may be N-shaped, S-shaped, or the like as shown in FIG. In general, a circular ICP antenna conductor is used. In the case of a circular antenna, when the radius is r and the current is I, the strength H _o of the magnetic field generated at the center is expressed by the following equation.
H _o = I / 2r
On the other hand, when the distance between the parallel portions of the U-shaped ICP antenna conductor according to the present invention is d, the magnetic field strength H ₁₁ at the center is expressed by the following equation:
H ₁₁ = 2I / πd
It is represented by When a U-shaped antenna is used, the strength of the magnetic field is (4r / πd) times that of a circular antenna. Since it is inversely proportional to the interval between the parallel portions of the antenna conductor, the strength of the induced magnetic field can be increased by reducing the interval. In this example, when the antenna conductor having the same length was used, a magnetic field strength about 1.7 times that of the circular antenna was obtained. The ratio d / L of the distance d between the parallel portions to the length L of the long side of the rectangle surrounded by the U-shaped portion of the ICP antenna conductor is not particularly limited, but is 0.05 to 0.5. It is desirable.

FIG. 4 shows a schematic cross-sectional view of the main part of the ICP antenna unit employed in the third embodiment. As the ICP antenna conductor 14, a copper pipe having an outer diameter of 6.4 mm formed into a shape as shown in FIG. 4 was used. The ICP antenna conductor feed side introduction portion 27 and the ground side introduction portion 28 are provided at substantially the center of the lid body 12, and the surface surrounding the U-shaped portion of the ICP antenna conductor is connected to the long side plate of the dielectric casing 11. It was installed so that it was almost parallel. The distance between the ICP antenna conductor 14 and the side plate of the dielectric housing 11 was 5 mm.

In this embodiment, the lid body 12 is made of an insulating material and the feedthrough is omitted. The ICP antenna conductor 14 was directly attached to the lid 12 via the gas seal member 21. A large number of pores were provided around the U-shaped portion of the ICP antenna conductor, and the antenna conductor and the dielectric casing were cooled by ejecting cooling gas. The cooling gas was recovered from the exhaust port 18 provided in the lid 12.

The ICP antenna unit was attached to the opening 24 of the vacuum vessel 23 in the same manner as in Example 1. The U-shaped part of the antenna conductor was mounted so as to protrude inward from the inner wall surface of the vacuum vessel. A high frequency power source 20 was connected to one power supply terminal 19 via a matching unit (not shown), and the other power supply terminal was grounded. A mixed gas of argon and hydrogen having a gas pressure of 0.5 Pascal was introduced into the vacuum vessel, and high-frequency power with a frequency of 13.56 MHz and an output of 1 kW was supplied to generate discharge plasma in the vacuum vessel.

The discharge plasma was filled in the vacuum chamber, and the plasma density in the vacuum chamber 10 cm away from the window 17 surface of the dielectric housing 11 was 2.2 × 10 ¹¹ / cm ³ . In the case of the second embodiment, since the surface surrounded by the U-shaped portion of the ICP antenna conductor is parallel to the inner wall surface of the vacuum vessel, only the power of one side of the generated electromagnetic field can be utilized. Induction electromagnetic fields on both sides of the surface surrounded by the antenna conductor can be utilized. Further, the lines of magnetic force generated by the antenna conductor are generated substantially parallel to the inner wall surface of the vacuum vessel. Therefore, the electrons in the plasma are constrained by the magnetic field lines and the dissipation to the surface of the vacuum vessel is suppressed, so that high-density and stable discharge plasma can be generated in the vacuum vessel.

An embodiment using a plurality of ICP antenna units will be described. FIG. 5 shows an arrangement plan view of ICP antenna conductors for an example in which two ICP antenna units are mounted on a top plate which is a part of a vacuum vessel. In this embodiment, one set of two ICP antenna units is formed, and both antenna units are arranged at a predetermined interval. The feeding terminals of both ICP antenna conductors 14 are connected by a feeding bar 25, and a high-frequency power feeding point is provided at the center of the feeding bar 25. The ground-side power supply terminal was connected in the same manner, and a power supply point was provided at the center to be grounded.

The distance between the feed point and the feed terminals of both antennas was substantially the same, and the position of the feed point was adjusted so that the impedances of both ICP antenna units with respect to the high frequency power viewed from the feed point were equivalent. A mixed gas of argon and hydrogen having a gas pressure of 0.5 Pascal was introduced into the vacuum vessel, and high frequency power with a frequency of 13.56 MHz and an output of 1 kW was supplied to the feeding point to excite discharge plasma in the vacuum vessel.

In this example, almost the same discharge plasma could be generated in the vacuum vessel with each of the two ICP antenna units. The plasma density distribution at a certain distance from the top plate surface varies depending on the spacing of each antenna unit, discharge gas pressure, high-frequency power, etc., but the condition for obtaining a uniform plasma density distribution is a matter of design, and discharge of any area is possible. Plasma can be generated.

In the above embodiment, one set of two ICP antenna units has been described. However, the number of ICP antenna units is not limited to two, and may be three or four. Furthermore, by disposing a plurality of sets of a plurality of ICP antenna units, a large area discharge plasma can be generated, and a plasma processing apparatus excellent in mass productivity can be provided.

11 .. Dielectric housing, 12 .. Lid, 13 .. Inside housing, 14 .. Antenna conductor, 15 .. Gas outlet, 16 .. Feedthrough, 17 .. Dielectric window, 18. · Exhaust port, 19 ·· Feeding terminal, 20 · · High frequency power supply, 21 · · Vacuum seal member, 22 · · Gas tube, 23 · · Vacuum container, 24 · · Opening portion · · · Feed bar, 26 · · · Buttock

Claims (14)

A dielectric housing that holds an inductively coupled antenna unit such as a U-shape or a U-shape and is installed in an airtight manner in an opening provided on a wall surface of a vacuum vessel such as a plasma processing apparatus. And an inductive coupling type antenna conductor such as a U-shape or a U-shape is attached to the lid body through a feed-through or a feed-through. An inductively coupled antenna unit characterized in that a letter-shaped part or a U-shaped part is accommodated in the dielectric casing. The feeding-side introduction portion and the ground-side introduction portion of the inductively coupled antenna are at both ends in the longitudinal direction of the rectangular lid, and the U-shaped or U-shaped antenna conductor portion is formed on the bottom plate in the dielectric casing. The inductively coupled antenna unit according to claim 1, wherein the inductively coupled antenna unit is arranged substantially in parallel. The shape of the antenna conductor portion of the inductively coupled antenna is U-shaped, U-shaped, N-shaped, M-shaped, or the like, and its total length is less than a quarter wavelength of the high frequency to be fed, and the surface formed by the shape 2. The inductively coupled antenna unit according to claim 1, wherein is disposed substantially parallel to a bottom plate or a side plate in the dielectric casing. 4. The ratio of the short side to the long side of the rectangle enclosed by the U-shaped or U-shaped portion of the inductively coupled antenna conductor is 0.05 to 0.5. 5. Inductively coupled antenna unit. 5. The inductively coupled antenna unit according to claim 1, wherein a material of the dielectric casing is a metal oxide, a nitride, a carbide, or a fluoride. 6. The inductively coupled antenna unit according to claim 1, wherein a material of the dielectric casing is quartz, alumina, zirconia, yttria, silicon nitride, or silicon carbide. The dielectric body has a flange around the opening, and the flange and the lid are fixed with a seal member interposed therebetween, and integrated. The inductively coupled antenna unit according to claim 6. The inductively coupled antenna conductor is a metal pipe, and a plurality of pores are provided in a portion accommodated in the dielectric casing, and a cooling gas is ejected from the pores into the dielectric casing. The inductively coupled antenna unit according to claim 1, wherein the antenna conductor and the dielectric housing can be cooled. The induction according to any one of claims 1 to 8, wherein a pore provided in the inductively coupled antenna conductor pipe is perforated so as to blow cooling gas almost uniformly onto the inner wall surface of the dielectric casing. Combined antenna unit. The inductively coupled antenna conductor pipe and an exhaust port provided in the lid are connected by a flexible tube via a heat exchanger and a pump, and the cooling gas is introduced from the antenna conductor pipe and recovered from the exhaust port. The inductively coupled antenna unit according to any one of claims 1 to 9. The inductively coupled antenna unit according to claim 1, wherein the cooling gas is an inert gas such as argon gas or nitrogen gas. A plasma processing apparatus provided with an inductively coupled antenna, wherein the inductively coupled antenna unit according to any one of claims 1 to 11 is mounted on a vessel wall of the vacuum vessel. 13. The plasma processing apparatus according to claim 12, wherein the inductively coupled antenna unit is mounted with a vacuum seal member sandwiched between openings provided in a vacuum vessel wall. The plasma processing apparatus according to claim 12, wherein a plurality of openings are provided in the vacuum vessel wall, and the antenna unit according to claim 1 is attached to each opening.

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