JPH09219296A - Magnetic neutral discharge plasma source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the loss of plasma and damage to side walls by providing part of a magnetic field generating means in a vacuum chamber to form magnetic neutral conductors at a position where there is no magnetic field continuously existing in the chamber. SOLUTION: A treatment table 4 is arranged in a vacuum chamber 1 and a material to be treated is mounted thereon. Electromagnetic coils 6, 7 with the same size and structure are arranged outside the side walls of the vacuum chamber 1 and an electromagnetic coil 8 smaller than the electromagnetic coils 6, 7 is arranged in the vacuum chamber 1. A high frequency coil 9 is coaxially set up outside the upper wall of the vacuum chamber 1. When currents flow from respective power supplies to three coils 6, 7, 8 for excitation, concentric magnetic neutral conductors are formed inside the inner electromagnetic coil 8. High frequency discharge plasma is generated in the magnetic neutral conductors by a high frequency coil 9. Respective currents flowing in the electromagnetic coils 6, 7, 8 are controlled to change the diameters of the magnetic neutral conductors and a distance from the material 5 to be treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic neutral line discharge plasma generating magnetic neutral line used for performing processing such as coding, etching, sputtering, ashing, and CVD on an object to be processed such as a substrate and a target. The present invention relates to a source of actinic radiation plasma.

[0002]

2. Description of the Related Art Conventionally, for example, in plasma etching, a chemically active gas is turned into a plasma state by discharging under a low pressure, and active species such as generated ions and neutral radicals react with a material to be etched. The reaction product is desorbed into the gaseous phase, and various types are known. For example, by introducing an etching gas into a vacuum container and using magnetron discharge with a DC electric field, by accelerating electrons by causing electron cyclotron resonance (ECR) by interaction with microwaves (2.45 GHz) ECR due to high electron energy under low pressure
There are those that use a plasma source, and those that are in a plasma state by applying high-frequency power of 13.56 MHz. Also,
Various types of plasma CVD have also been proposed in which a plasma state is formed by RF plasma excitation, and thereby a chemical bond of a reaction gas is decomposed to form a film by a reaction between activated particles.

In such a plasma utilizing apparatus,
In most cases, there are spatial inhomogeneities in density and temperature, and inhomogeneities in the velocity space associated with acceleration by an electric field. Inhomogeneity is likely to occur, especially in processes such as etching where the behavior of radicals (chemically active species) as well as charged particles must be taken into consideration. There was a problem that could only be realized empirically. In sputtering, the electromagnet or permanent magnet provided on the back side of the cathode is mechanically displaced to change the position of plasma to increase the efficiency of use of the target so that the erosion region can be expanded as much as possible, or the electromagnet can be used. Alternatively, the structure of the permanent magnet has been devised to expand the erosion area as much as possible, but in either case, it is difficult to improve the use efficiency of the cathode, and the device itself becomes complicated or bulky. There was a problem.

In order to solve such a problem of the conventional plasma utilizing apparatus, first, as a device for treating an object to be treated using plasma in the vacuum chamber, a magnetic neutral wire is provided in the vacuum chamber. And a magnetic field generating means for generating a discharge plasma in the magnetic neutral wire by forming an electric field along the magnetic neutral wire formed in the vacuum chamber by the magnetic field generating means. A discharge plasma processing device has been proposed (see Japanese Patent Laid-Open No. 7-90632).
According to this proposal, the position and size of the magnetic neutral line formed by merely controlling the exciting current to the magnetic field generating means can be arbitrarily adjusted, and therefore the plasma generating position can be easily displaced, resulting in the process It has become possible to obtain an epoch-making effect in processing.

[0005]

However, in principle, a magnetic neutral line formed by spatially connecting points of zero magnetic field always has four or more magnetic lines of force that cross the neutral line.
Most of the plasma generated by applying an electric field along the neutral line diffuses to the surroundings by collision with the overwhelming number of neutral gases existing around it, which do not lead to ionization, Part of the generated plasma moves along the magnetic lines of force intersecting with the magnetic neutral line. At this time, in particular, plasma moving along the magnetic field lines that rush into or contact the side wall collides with the side wall, a part of the plasma is lost, and the side wall is damaged, which may be a problem particularly when the temperature of the plasma is raised. FIG. 3 of the accompanying drawings shows the previously proposed discharge plasma processing apparatus, in which the inside of the vacuum chamber A is the plasma generation chamber A1.
And the substrate processing chamber A2, and three electromagnetic coils B, C, D are provided outside the plasma generation chamber A1. The upper and lower electromagnetic coils B, D2 flow currents in the same direction, and the middle electromagnetic coil C A reverse current is applied to the. Further, in FIG. 3, E is a high frequency coil, and in the substrate processing chamber A2,
A substrate F to be processed using the plasma generated in the plasma generation chamber A1 is shown. In the apparatus having such a configuration, the middle-stage electromagnetic coil C installed to form the magnetic neutral loop in the plasma generation chamber A1 made of a dielectric material is located outside the plasma generation chamber A1. As shown in the figure, among the four magnetic field lines that intersect at the magnetic neutral line, the one that goes to the side wall of the plasma generation chamber penetrates the plasma generation chamber, and the plasma flowing out along this line of magnetic force obviously hits the side wall and Losses and sidewall damage may occur. Therefore, an object of the present invention is to provide a magnetic neutral line discharge type plasma source that solves such problems.

[0006]

In order to achieve the above-mentioned object, according to the present invention, in a plasma source adapted to generate plasma by utilizing magnetic neutral line discharge in a vacuum chamber, the vacuum chamber A magnetic field generating means for forming a magnetic neutral line which is a position where the magnetic field is continuously present in the inside, and an electric field is formed along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means. The magnetic neutral wire has an electric field generating means for generating discharge plasma, and a part of the magnetic field generating means is provided in the vacuum chamber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In a magnetic neutral line discharge type plasma source according to the present invention, a magnetic neutral line which is a position of a magnetic field zero continuously existing in a vacuum chamber is formed. By providing a part in the vacuum chamber, it is possible to connect two of the magnetic force lines intersecting at the magnetic neutral line in a form surrounding the magnetic field generating means. The magnetic field generating means may include two magnetic field generating coils coaxially arranged outside the vacuum chamber with a space therebetween, and one magnetic field generating coil disposed inside the vacuum chamber coaxially with the vacuum chamber. One magnetic field generating coil disposed inside the vacuum chamber and coaxial with the vacuum chamber may be a room temperature superconducting coil. Further, in the present invention, the magnetic field generating means may use two cylindrical hollow magnets in place of the two magnetic field generating coils coaxially arranged outside the vacuum chamber at intervals. The electric field generating means can be composed of a high frequency coil. According to another feature of the present invention, when an object to be processed such as a wafer is placed below the magnetic neutral line formed in the vacuum chamber, an electric field generating means is provided outside the vacuum container above the magnetic neutral plane. Is provided.

When an electric current is passed through the electromagnetic coil provided in the vacuum chamber, the presence of a conducting wire from the wall of the vacuum chamber to the electromagnetic coil and the presence of unwinding and unwinding points in the electromagnetic coil make the magnetic field uniform in the azimuth direction. It is also possible that the plasma generation will be slightly affected by violating the above condition. The countermeasure is to use a ring (ring) made of a normal temperature superconductor, and since the same magnetic field as the current is constantly flowing along the ring, the other two coils above and below are used. If a magnetic field is applied in the same direction in the same direction as the magnetic field of the middle temperature superconductor ring in the opposite direction to the magnetic field of the middle temperature superconductor ring, the room temperature superconductor ring is automatically set to the middle position by the pressure of the magnetic field. It will be. At this time, the room-temperature superconductor ring is positioned slightly below due to its own weight, but this is practically no problem due to the use of a light material.

In order to efficiently apply the induction electric field to the magnetic neutral loop formed inside the middle coil when the coil is provided in the vacuum chamber, an electric field generating means is provided between the middle coil and the magnetic neutral loop. A coaxial concentric high-frequency coil is required to be installed, but this also causes the high-frequency coil to be provided in a vacuum, resulting in complicated structure and high-frequency electromagnetic induction to the middle coil. As a measure against induction of a high frequency electric field to the middle coil, it has already been proposed in Japanese Patent Laid-Open No. 7-90632 that the middle coil has a double cross section, and the inside is used as a stationary magnetic field coil conductor and the outside as a high frequency coil conductor. Although the skin effect of the high frequency current is positively used, in the case of the present invention, since it is installed in the vacuum chamber, a device for penetrating the vacuum chamber and connecting to the high frequency power source is required. .

A patent application has already been made regarding the fact that a high-frequency coil as an electric field generating means is positively moved coaxially above or below the same plane as the magnetic neutral line or in the vicinity thereof and the size (radius) thereof is appropriately selected. Although it is proposed in Japanese Patent Laid-Open No. 7-217967, the present invention positively utilizes this, and when the object to be processed such as a wafer is set below the magnetic neutral loop, the high frequency coil is placed above the magnetic neutral loop and outside the vacuum container. It will be installed in and will be activated. At the same time, by attaching an outer cylinder having a thin cross-section to the middle coil, it is possible to prevent penetration of the induction electric field into the middle coil by the high frequency coil.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows in principle an embodiment of the present invention. 1 is a vacuum chamber made of a cylindrical dielectric,
The gas is exhausted from the exhaust port 2 at the bottom and the used gas is introduced from the gas inlet 3 at the top. A processing table 4 is arranged in the vacuum chamber 1, and an object 5 to be processed is placed thereon.
Is installed. Outside the side wall of the vacuum chamber 1, electromagnetic coils 6 and 7 of the same size are arranged, and these electromagnetic coils 6 and 7 are connected in series with a constant current power source (not shown).
It is connected to the. Inside the vacuum chamber 1 at a level between the electromagnetic coils 6 and 7, a small electromagnetic coil 8 is arranged by the electromagnetic coils 6 and 7, and thin support rods (shown in the figure) are provided from three positions on the inner wall of the vacuum chamber 1. (Not shown), and is connected to an external constant current power source (not shown) through one of the support rods. A high frequency coil 9 is coaxially installed outside the upper wall of the vacuum chamber 1 and connected to a 13.56 MHz high frequency power source (not shown).

In the operation of the illustrated apparatus thus constructed, the internal electromagnetic coil 8 is generated by exciting the three electromagnetic coils 6, 7, 8 by supplying currents from the respective power sources.
A concentric magnetic neutral wire is formed inside the. A high frequency discharge plasma is generated by the high frequency coil 9 in the magnetic neutral line. In this case, since a high frequency is used, plasma is always generated from the magnetic neutral line and springs out. By controlling the currents flowing through the two upper and lower external electromagnetic coils 6 and 7 and the current flowing through the internal electromagnetic coil 8, respectively, the diameter of the concentric magnetic neutral wire and the object to be processed 5 The distance can be changed. Regarding the magnetic field lines generated by the excitation of the electromagnetic coil, when a middle-stage electromagnetic coil is provided outside as shown in FIG. 4, two of the magnetic field lines that cross the magnetic neutral line are adjacent to the side wall near the neutral line. Although they intersect, in the present invention, since the middle-stage electromagnetic coil is provided inside,
As shown in FIG. 2, the two lines of magnetic force are connected to each other in a shape surrounding the cross section of the electromagnetic coil 8 in the vacuum chamber 1 without crossing the side wall. That is, the two magnetic force lines merge around the conductor cross section of the electromagnetic coil 8 to avoid crossing and contact with the side wall of the vacuum chamber 1, and plasma loss and side wall damage can be reduced.

Component Device According to an Embodiment of the Present Invention FIGS. 1 and 3
As a result of performing SiO ₂ sputtering with Ar gas using the device of the structure previously proposed as shown in Fig. 4, the sidewall of the coil near the middle stage is devitrified and the etching rate at the same time by the process of about 500 times in the device previously proposed. Also fell to about 80% of the initial value, whereas none of them was found in the device according to the present invention.

[0014]

As described above, in the present invention, a part of the magnetic field generating means for forming the magnetic neutral line which is the position of the magnetic field zero continuously existing in the vacuum chamber is part of the vacuum chamber. Since the magnetic lines of force crossing the magnetic neutral line do not cross or contact the side wall in the vicinity of the neutral line, it is possible to reduce plasma loss and side wall damage. Therefore, the present invention is an indispensable technique for effective use of the magnetic neutral line discharge plasma, and is a technique indispensable for various plasma treatments such as sputtering and etching particularly for semiconductor manufacturing in which impurities are not mixed. At the same time, since the side wall and the peripheral wall can be prevented from being damaged, the performance of the apparatus can be further improved, and a very useful magnetic neutral line discharge type plasma source capable of realizing a great reduction in maintenance can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing in principle an embodiment of the present invention.

FIG. 2 is a schematic enlarged partial cross-sectional view explaining the operation of the apparatus shown in FIG.

FIG. 3 is a schematic diagram showing in principle the previously proposed device.

4 is a schematic enlarged partial cross-sectional view explaining the operation of the apparatus shown in FIG.

[Explanation of symbols]

 1: Vacuum chamber 2: Exhaust port 3: Gas inlet port 4: Processing table 5: Object to be treated 6: Electromagnetic coil 7: Electromagnetic coil 8: Electromagnetic coil 9: High frequency coil

Claims (7)

[Claims] 1. A plasma source in which a plasma is generated by utilizing a magnetic neutral line discharge in a vacuum chamber, and a magnetic neutral line which is a position of a magnetic field zero continuously existing in the vacuum chamber is formed. And a magnetic field generating means for applying an electric field along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means to generate discharge plasma in the magnetic neutral line. Have,
A magnetic neutral line discharge plasma source characterized in that a part of a magnetic field generating means is provided in a vacuum chamber. 2. A magnetic field generating means, and two magnetic field generating coils coaxially arranged outside the vacuum chamber at intervals.
The magnetic neutral line discharge plasma source according to claim 1, comprising one magnetic field generating coil arranged coaxially with the vacuum chamber inside the vacuum chamber. 3. The magnetic neutral line discharge plasma source according to claim 2, wherein one magnetic field generating coil arranged coaxially with the vacuum chamber inside the vacuum chamber comprises a room temperature superconducting coil. 4. The magnetic neutral line discharge plasma source according to claim 1, wherein the magnetic field generating means comprises two cylindrical hollow magnets coaxially arranged outside the vacuum chamber at intervals. 5. The magnetic neutral line discharge plasma source according to claim 1, wherein the electric field generating means comprises a high frequency coil. 6. A plasma source configured to generate a plasma by utilizing a magnetic neutral line discharge in a vacuum chamber, which forms a magnetic neutral line which is a position of a magnetic field zero continuously existing in the vacuum chamber. And a magnetic field generating means for applying an electric field along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means to generate discharge plasma in the magnetic neutral line. Have,
A part of the magnetic field generating means is provided in the vacuum chamber, and the electric field is generated on a plane having a height different from the position of the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means installed in the vacuum chamber. A magnetic neutral line discharge plasma source characterized by comprising means. 7. The magnetic neutral line discharge plasma source according to claim 6, wherein the electric field generating means is provided at a position facing the object to be processed through a plane forming the magnetic neutral line and outside the vacuum container. .