JPH0963792A - Magnetic neutral beam discharging plasma source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a compact plasma source for discharging magnetic neutral beam, and to facilitate the observation of plasma condition by providing a part of a magnetic field generating means and an electric field generating means in the upper surface side or the lower surface side of a vacuum chamber. SOLUTION: A first and a second magnetic field generating coils 2, 3 are provided outside of a vacuum chamber 1 in the same axis with a space, and a third magnetic field generating coil 4 is arranged outside of a bottom part of the vacuum chamber 1, and the current in the predetermined direction is flowed in these coils so as to form an annular magnetic neutral beam 5. A quartz plate 6 is horizontally provided in the vacuum chamber 1, and a high frequency coil 8 is fitted to the lower side thereof, and a strong electric field is generated by the coil 8 along the neutral beam 5. Gas is led from a gas lead-in port 9, and plasma is generated along the neutral beam 5. Furthermore, a window part 10 for observing the plasma condition is provided in the side wall of the vacuum chamber 1, and laser beam enters the inside of the chamber through this window part 10, and electron density and temperature are measured by the laser Thomson scattering so as to control the plasma.

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 plasma which is used to perform processing such as coating, 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 brought into a plasma state by discharge under a low pressure, and active species such as ions and neutral radicals generated thereby react with a material to be etched. The reaction product is desorbed into the gas phase, and various types are known. As an example, an etching gas is introduced into a vacuum container, and a magnetron discharge between a DC electric field and a magnetic field is used. An electron cyclotron resonance (ECR) is caused by an interaction between a microwave (2.45 GHz) and a magnetic field to generate an electron. Using an ECR plasma source that generates high-ionization plasma under low pressure by accelerating
There is a method of applying a high frequency electric power of 1 to make a plasma state. Various types of plasma CVD are also proposed, in which a high-energy plasma state is formed by RF plasma excitation, which decomposes the chemical bonds of the reaction gas to form a film by the reaction between activated particles. Has been done.

[0003]

Conventionally, in such a plasma utilizing apparatus, in most cases, spatial nonuniformity of density and temperature and nonuniformity in velocity space due to acceleration due to electric field exist. Therefore, when these are used to perform the intended action on the substrate, non-uniformity of the effect is likely to occur, especially not only charged particles but also radicals (chemically active species)
However, in a process such as etching, in which the existence of the above-mentioned phenomenon must be taken into consideration, the desired distribution, for example, uniformity can be ensured extremely empirically. Further, in sputtering, in order to improve the use efficiency of the target, the position of plasma is changed by mechanically displacing an electromagnet or a permanent magnet provided on the back side of the cathode so that the erosion region can be expanded as much as possible, or the electromagnet or It has been attempted to expand the erosion area as much as possible by devising the structure of the permanent magnet, but in each case, the problem is that the device itself becomes complicated and bulky, etc. There was a point.

In order to solve the problems of the conventional plasma utilizing apparatus, a magnetic neutral wire is first provided in the vacuum chamber as an apparatus for treating an object to be treated using plasma 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.

It is an object of the present invention to provide a magnetic neutral line discharge plasma source capable of further improving the previously proposed apparatus to make it simpler and more compact and to easily observe the state of plasma. There is.

[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. An electric field generating means for generating a discharge plasma in the magnetic neutral wire is provided, and a part of the magnetic field generating means and the electric field generating means are provided on the upper surface side or the lower surface side of the vacuum chamber. According to another feature of the present invention, in addition to the above configuration, an observing means for observing the discharge plasma generated in the vacuum chamber is provided with a position of a magnetic neutral wire formed in the vacuum chamber at a side surface portion of the vacuum chamber. It can be provided on a plane of approximately the same height.

[0007]

In the plasma source of the present invention having the above-described structure, the magnetic neutral line, that is, the magnetic field zero to the substrate is changed by changing the spatial structure of the magnetic field generating means or the exciting current flowing through the coil forming the magnetic field generating means. The position or shape (for example, the size of the ring) can be changed arbitrarily, and the position of the plasma formed in a ring shape can be changed arbitrarily. Plasma is generated by introducing a gas into the vacuum chamber, preheating it and igniting it, and then applying an electric field along the ring-shaped magnetic neutral line formed by the electric field generating means, and diffuses to the surroundings. . When the discharge current flowing along the magnetic neutral line is small, the charged particles of electrons or ions that are accelerated by the electric field in the direction perpendicular to the magnetic field are orbited by the magnetic field existing in the perpendicular direction if they deviate even slightly from the magnetic neutral line. Can be bent. This effect means that there is an effect of suppressing the generation of dangerous high-speed particles due to the acceleration of the electric field, and therefore the generated plasma has few high-speed acceleration particles and damage by it is unlikely to occur.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on the embodiments of the present invention shown in the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a plasma source according to an embodiment of the present invention. Reference numeral 1 denotes a vacuum chamber formed in a cylindrical shape, which can be made entirely of, for example, SUS material. On the outer side of the cylindrical peripheral wall of the cylindrical vacuum chamber 1, two first and second magnetic field generating coils 2 and 3 are provided coaxially apart from each other, and the circular bottom of the cylindrical vacuum chamber 1 is provided. A third magnetic field generating coil 4 is disposed on the outer side of the cylindrical magnetic field generating coil. Currents flowing in opposite directions are applied to the first and second magnetic field generating coils 2 and 3 provided on the outer side of the cylindrical peripheral wall. The third magnetic field generating coil 4 provided on the outer side includes the second magnetic field generating coil 3
The current flowing in the opposite direction to the current flowing in the. As a result, the first and second magnetic field generating coils 2,
A continuous magnetic field zero position is created inside the vacuum chamber 1 at an intermediate level of 3, and a ring-shaped magnetic neutral line 5 is formed. The position and size of the ring-shaped magnetic neutral wire 5 formed can be appropriately set by controlling the currents flowing through the three magnetic field generating coils 2, 3, 4.

In FIG. 2, computer-simulated isomagnetism is obtained when currents of the same direction are applied to the first and third magnetic field generating coils 2 and 4, and currents of opposite directions are applied to the second magnetic field generating coil 3. A line diagram is shown. The current flowing through the first magnetic field generating coil 2 is 250 A, the current flowing through the second magnetic field generating coil 3 is -730 A, and the current flowing through the third magnetic field generating coil 4 is 26 A.
It is 00A. From this equimagnetism diagram, it is recognized that the position of continuous magnetic field zero is at the intermediate level between the first and second magnetic field generating coils 2 and 3.

Returning to FIG. 1 again, at the level of the second magnetic field generating coil 3, a quartz plate 6 is horizontally provided in the vacuum chamber 1 by a support body 7, and an electric field is generated below the quartz plate 6. A high-frequency coil 8 forming a means is attached. By applying a high frequency induction electric field (for example, 13.56 MHz) along the ring-shaped magnetic neutral line 5 by the high frequency coil 8, a strong electric field can be generated along the magnetic neutral line at the position where the magnetic field is zero. . Also, the vacuum chamber 1
Is connected to an exhaust system (not shown), and the vacuum chamber 1 is previously kept at a high vacuum. A gas inlet 9 is provided for generating plasma, and this gas inlet 9
Gas that becomes more plasma is introduced, and plasma is generated along the magnetic neutral line by the high-frequency induction electric field.

Further, the first and second magnetic field generating coils 2, 3
In between, a window portion 10 for observing the state of plasma in the vacuum chamber 1 is provided on the cylindrical peripheral wall of the vacuum chamber 1, and a laser beam for observation can be incident through the window portion 10 to the inside. In addition, the laser Thomson scattering method is used to measure the electron density and temperature (velocity distribution function unless Maxwell distribution). With this configuration, it is possible to measure various characteristics of the plasma around the magnetic neutral line 5, such as the electron velocity distribution function, without disturbing the plasma generated in the vacuum chamber 1.

In the operation of the illustrated apparatus thus configured, the high frequency discharge plasma generated by the high frequency coil 8 in the magnetic neutral wire 5 formed in the vacuum chamber 1 diffuses to the surroundings and is processed (see FIG. (Not shown). In this case, since a high frequency is used, plasma is always generated and springs from inside the magnetic neutral line. Then, by observing the internal plasma state through the observation window portion 10 and appropriately controlling the combination of the current values passed through the first, second, and third magnetic field generating coils 2, 3, and 4 in accordance with the state, an annular shape is obtained. The diameter and the position of the magnetic neutral wire 5 can be adjusted, and this changes to enable control of the annular magnetic neutral wire discharge plasma.

FIG. 3 is a block diagram showing an example of a control system for the current flowing through each coil of the apparatus of the embodiment shown in FIG.
The illustrated control system has a control device 11 composed of a computer or a sequencer, and the control device 11 has first, second and third magnetic field forming coils 2 according to a preset program,
Control signal 1 for instructing the value and direction of the current flowing through 3, 4
DC power supply for exciting the magnetic field forming coils 2, 3, and 4 through the interface circuits 15, 16 and 17
The electric current is supplied to each of 18, 19, and 20 to control the current flowing from each of these power supplies to each magnetic field forming coil. Also the control device 11
Supplies a control signal 21 for instructing ON / OFF of the current flowing to the high frequency coil 8 and power to the high frequency power supply 23 of the high frequency coil 8 via the interface circuit 22. This high frequency power supply 23 is connected to a high frequency coil 8 via a matching box 24.
Connected to. Further, in the preferred embodiment of the present invention, an apparatus 25 for observing the plasma state generated in the vacuum chamber 1 is provided, and a detection signal from the observation apparatus 25 is sent to the control unit 11 as a feedback signal to control signals for each power source. Is to be adjusted. In addition, a bias voltage (DC or high frequency) suitable for plasma processing is applied to the cathode 27 from the cathode bias power supply 26.

In the illustrated embodiment, the magnetic field generating coil is provided outside the plasma generating chamber, but it may be provided inside instead from the viewpoint of the strength of the magnetic field.
Further, the shape thereof may be a polygonal ring shape or a rectangular ring shape instead of the ring shape according to the shape of the object to be processed (substrate or wafer) or the target. Further, the number of magnetic field generating coils is three in the illustrated embodiment, but it is not limited to three as long as it can form a magnetic neutral wire, and for example, a plurality of annular plasma layers may be formed. If desired, a plurality of magnetic field generating coils of three or more may be provided and a ring-shaped magnetic neutral wire may be formed in multiple layers instead of one ring-shaped magnetic neutral wire to precisely operate the plasma. Further, although the third magnetic field generating coil is provided outside the circular bottom wall of the cylindrical vacuum chamber 1, it may be provided outside the circular top wall of the vacuum chamber 1 as a matter of course. Further, instead of the magnetic field generating coil, a magnet may be used to form continuous magnetic field zero positions. Furthermore, the electric field generating coil can also be provided on the circular top wall side of the vacuum chamber 1 or, alternatively, can be provided in combination with the third magnetic field generating coil.

[0015]

As described above, according to the present invention, since a part of the magnetic field generating means and the electric field generating means are provided on the upper side or the lower side of the vacuum chamber, a space for providing means for observing the plasma state is provided. Can be taken along the peripheral wall of the vacuum chamber at the same level as the magnetic neutral line generation position, and various characteristics of the plasma can be controlled while feedback controlling the magnetic field generation means according to the plasma state. Furthermore, since the electric field generating means is provided on the upper side or the lower side of the vacuum chamber, SUS material can be used as the vacuum chamber material of the peripheral wall by using a material that passes high frequency waves only on the upper surface or the lower surface of the vacuum chamber. As compared with the case where a quartz tube or the like is used for the peripheral wall, the device can be constructed at a lower cost and more compactly.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing the configuration of a magnetic neutral line discharge plasma source according to an embodiment of the present invention.

FIG. 2 is a graph showing how the zero position of the magnetic field and the gradient of the magnetic field change according to the change of the exciting current due to computer simulation.

3 is a schematic block diagram showing an example of a control system of the apparatus shown in FIG.

[Explanation of symbols]

 1: Vacuum chamber 2: First magnetic field generating coil 3: Second magnetic field generating coil 4: Third magnetic field generating coil 5: Magnetic neutral wire 6: Quartz plate 7: Insulator 8: High frequency coil 9: Gas introduction Mouth 10: Window

Claims (8)

[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 generating 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. A magnetic neutral line discharge plasma source, wherein a part of the magnetic field generating means and the electric field generating means are provided on the upper surface side or the lower surface side of the vacuum chamber. 2. The magnetic field generating means comprises two magnetic field generating coils coaxially arranged on the side surface of the vacuum chamber with a space and one magnetic field arranged coaxially with the vacuum chamber on the upper surface side or the lower surface side of the vacuum chamber. A magnetic neutral line discharge plasma source according to claim 1, comprising a generating coil. 3. A constant current in a direction opposite to each other is applied to two magnetic field generating coils coaxially arranged on the side surface of the vacuum chamber with a space therebetween, and is arranged coaxially with the vacuum chamber on the upper surface side or the lower surface side of the vacuum chamber. By generating a constant magnetic field in a direction opposite to the current flowing through the coil immediately above the above two coils, the two magnetic field generating coils are coaxially arranged at the side of the vacuum chamber with a space between them. The magnetic neutral line discharge plasma source according to claim 2, wherein an annular magnetic neutral line is formed between the coils. 4. The magnetic according to claim 3, wherein the relative position between the radius of the generated annular magnetic neutral wire and the magnetic field generating coil is adjusted by controlling the exciting current flowing in each magnetic field generating coil. Neutral discharge plasma source. 5. The magnetic neutral line discharge plasma source according to claim 1, wherein the electric field generating means comprises a high frequency coil. 6. The magnetic neutral line discharge plasma source according to claim 1, wherein the magnetic field generating means comprises a permanent magnet. 7. A plasma source configured to generate plasma by utilizing magnetic neutral line discharge in a vacuum chamber, which forms a magnetic neutral line which is a position where a magnetic field is continuously present in the vacuum chamber. And a magnetic field generating means for generating 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. Then, a part of the magnetic field generating means and the electric field generating means are provided on the upper surface side or the lower surface side of the vacuum chamber, and the observation means for observing the discharge plasma generated in the vacuum chamber is formed inside the vacuum chamber on the side surface part of the vacuum chamber. A magnetic neutral line discharge plasma source provided on a plane having substantially the same height as the position of the magnetic neutral line to be generated. 8. The magnetic neutral line discharge plasma source according to claim 7, wherein the excitation of the magnetic field generating means is controlled according to the discharge plasma state observed by the discharge plasma observing means.