JPH05209268A - Plasma treating device - Google Patents

Abstract

PURPOSE:To improve the accuracy and the reliability of a device by forming an auxiliary magnetic field in the multipole cusp magnetic field to efficiently and uniformly confine the plasma to prevent the loss of plasma in a plasma treating device. CONSTITUTION:A wafer to be treated 5 is placed on a substrate electrode 9 in a reaction chamber 7 made by electrically insulating the substrate electrode 9 and a plasma generating electrode 10 respectively with a insulating body 8 and 12 and a magnet 2 for forming the multipole cusp magnetic field to confine the plasma is arranged so as to wrap the both electrodes 9, 10. Furthermore, after a shielding plate 13 is arranged between the magnet 2 and the plasma 1 placed in the center part, a reaction gas is supplied into the reaction chamber 7 evacuated by a vacuum device 14. Next, the plasma is generated on the wafer 5 by the electrode 10 and density of the plasma is enhanced and uniformalized by preventing the diffusion in circumferential direction with the multipole cusp magnetic field. Current is supplied to a lead wire 3 of the auxiliary magnetic field in a direction to which the magnet forming the cusp magnetic field generates the line of magnetic force of circumferential direction to make the line of magnetic force 4 into a rectangular like shape and the loss of the plasma 1 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when forming or processing a thin film by plasma, prevents the loss of plasma and generates it uniformly and at high density so that the object to be processed is of high quality and reliability. TECHNICAL FIELD The present invention relates to a plasma processing apparatus for forming a thin film having high efficiency, thin film processing having excellent selectivity and accuracy, and the like.

[0002]

2. Description of the Related Art As a conventional plasma processing apparatus, there is one described in Japanese Patent Publication No. 53-19319 as a sputtering film forming apparatus. According to this device, a pair of cathodes of the magnetic device is provided on the back side of the target material surface of the cathode,
Arc-shaped magnetic field lines generated by the magnetic device are formed along the cathode surface. Then, the charged particles of plasma generated by applying electric power to the cathode are subjected to cyclotron motion by the magnetic lines of force and restrained, so that high density plasma is generated as compared with a parallel plate type sputtering apparatus, and a high film formation rate. Is obtained.

Further, CVD (Chemical Vapor Deposit)
Ion) and etching apparatus are disclosed in JP-A-62-43335.
As described in Japanese Patent Publication No.
Some use microwaves in the ron Cycltron Resonance state. ECR is a state in which the frequency of microwaves matches the rotation frequency of electrons rotating in a magnetic field,
In the case of 2.45 GHz microwave, a magnetic field of 875 Gauss is applied in parallel with the microwave. When the condition is satisfied, the microwave can travel in the plasma regardless of the plasma density. Therefore, the plasma can be made to have a high density, and high-speed processing can be performed at a low pressure.

[0004]

In the case of the magnetron system, since the plasma is confined in the arc-shaped magnetic field lines generated on the cathode surface, only the plasma density of the region confined in the arc-shaped magnetic field lines is in the region on the other electrode. In comparison with this processing method, the bias sputtering method improves the film quality and film coverage of the film deposited on the substrate by drawing in ions by applying power to the substrate side as well. However, since the generated plasma is non-uniform, the distribution of ions attracted to the substrate is also non-uniform, and there is a problem that a uniform film quality or a uniform surface shape cannot be obtained on the substrate.

Therefore, in order to uniformly confine the plasma, a means for generating and confining the plasma in the space (not on the electrode) is required. In the ECR method, plasma generated in a space by electrodeless discharge is transported along a magnetic field to the substrate surface or is confined in the space.
As a plasma confinement means in the space, for example, “Plasma physics for nuclear fusion” written by Kenro Miyamoto: Iwanami Shoten (1
(987) p508 and cusp type and mirror type. The magnetic field obtained by passing currents in opposite directions through two sets of coils arranged coaxially is a cusp type, and the lines of magnetic force are convex with respect to the plasma. By passing currents in the same direction, a mirror magnetic field is obtained. The lines of magnetic force are concave with respect to the plasma. However, in the case of a mirror magnetic field, the shape of plasma is cylindrical, and for example, "Plasma Engineering" by Yoshino Nakano: Corona Publishing Co., Ltd. (1978) p26.
Since the plasma instability exists as described in 0, it is difficult to apply it to the plasma processing apparatus in consideration of the further increase in the diameter of the processed wafer in the future. On the other hand, in the case of a cusp magnetic field, the magnetic field lines have a magnetic field shape that spreads in the circumferential direction and are also excellent in terms of plasma stability, and a magnetic field shape based on the cusp magnetic field is desirable for confining a large area plasma. However, in the case of a cusp magnetic field, there is a plasma loss portion called a line cusp in the circumferential direction, and there is a problem of drainage due to plasma diffusion. When the flow-off amount is large, the plasma density does not increase even if the plasma on the electrode becomes uniform, and as described above, the flow-off plasma lowers the insulating property between the electrode and the wall surface around the electrode to cause abnormal discharge. Or the collision of ions with the wall surface causes the generation of dust from the electrode or wall material. Further, the ECR method requires a magnetic flux density close to 1 kGauss in the plasma generating part, and thus the diameter of the substrate to be processed is increased, but the electromagnet is large, the size of the device is large, and its handling is becoming difficult. Furthermore, since the direction of magnetic force lines differs in the radial direction on the substrate, even if the plasma density is uniform, the amount of incident ions, energy, and directionality can be changed by the difference in the impedance in the vertical and horizontal directions between the substrate and plasma. Non-uniformity occurs.
As a means for solving this, as in JP-A-1-42130, after passing a microwave through a cavity resonator, plasma is generated in a vacuum without a magnetic field. However, a multipole cusp magnetic field is formed around the plasma to prevent the plasma from diffusing in the circumferential direction. However, since the multipole cusp magnetic field also has the plasma loss portion as described above, there are problems that the plasma density is lowered, and that leakage plasma collides with the electrode constituent members to cause contamination. An object of the present invention is to perform plasma processing that can perform highly accurate and reliable processing without generating dust and the like by efficiently and uniformly confining plasma without having a strong magnetic field on the surface of a substrate to be processed. To provide a device.

[0006]

In order to achieve the above object of the present invention, in the plasma processing method of the present invention, an efficient electromagnetic field for confining plasma is formed around the substrate to be processed. .. In order to realize this, in the plasma processing apparatus of the present invention, an auxiliary magnetic field is formed in the cusp magnetic field of the multipole to increase the magnetic field strength of the plasma loss portion and prevent plasma loss.

[0007]

In order to make the plasma generated by the high frequency or microwave power uniform on the substrate to be processed and to carry out the uniform processing, it is necessary to have the plasma confining means only around the substrate to be processed.

Plasma is a particle (ion) having a positive charge
And negatively charged particles (electrons). Therefore, in plasma diffusion, since the mobility of electrons with a small mass is large, the balance of positive and negative charges is lost when the electrons diffuse, and an electric field is generated, which generally causes ambipolar diffusion by repeating the pattern of ion movement. It is said that. Therefore, it can be understood that the movement of the ions or electrons in the flow-out direction should be stopped to prevent the plasma loss. However, in order to further improve the confinement property, it is necessary to prevent the diffusion of electrons having high mobility.

As a general method for reducing the velocity component in the loss direction to prevent the above diffusion, there is a method using a magnetic field. The motion of the load current element does not cause any restriction in the direction parallel to the magnetic field, but the motion in the vertical direction is restricted. Therefore, a concentric magnetic field distribution in which the magnetic field strength increases in the radial direction is desirable.

However, in order to form a concentric magnetic field distribution, it is necessary to pass a current through the center of the concentric circle in the direction perpendicular to the circle, and this is impossible because the substrate to be processed is located in that portion. There is a multipole cusp magnetic field that is similar to the concentric magnetic field distribution and can be realized with a simple magnetic field configuration. A plurality of magnets are arranged concentrically and the magnetic poles are alternately arranged in the radial direction. Thereby, a plurality of concave magnetic fields can be formed with respect to the plasma, and the circumferential component of the magnetic force lines prevents the plasma from diffusing in the radial direction. However, since the lines of magnetic force open in the radial direction at the place where the lines of magnetic force enter and leave the magnet, plasma loss occurs through the place (see FIG. 2). In order to reduce this plasma loss, it is necessary to reduce the radial component of the magnetic force lines in the circumferential direction as much as possible. However, the distribution of magnetic force lines is uniquely determined by the arrangement and shape of the magnets that generate the magnetic force lines. Further, as the size of the substrate to be processed becomes larger, the plasma confinement region becomes larger, so that the distance between the magnets forming the multipole cusp magnetic field increases in the radial direction, and the angle formed by the adjacent magnets approaches 2π. The arc castle begins to be drawn, and the loss part of the plasma becomes larger. In order to reduce the loss portion, an auxiliary magnetic field generating mechanism is provided in the vicinity of the magnet so that magnetic force lines extending vertically from the magnet suddenly change their directions in the circumferential direction. (See FIG. 1) Further, there is a method of circumferentially arranging a plurality of electromagnets wound in a coil shape as a means for forming a magnetic field close to a concentric circle around the plasma generation site (see FIG. 4). A circumferential magnet is generated on the side surface of the electromagnet, and a cusp magnetic field is generated in the gap between the magnets to prevent plasma from diffusing in the circumferential direction.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in more detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a multipole cusp magnetic field having an auxiliary magnetic field provided around the plasma generating part for implementing the plasma processing apparatus of the present invention. A plurality of magnets 2 are arranged on the circumference with the magnetic poles reversed so as to surround the plasma 1 located at the center. Conductors 3 are arranged perpendicular to the plane of the drawing in the vicinity of both ends inside the magnet. FIG. 2 shows the shape of the magnetic force lines 4 when a normal multipole cusp magnetic field is formed. The magnetic force lines 4 show a gentle convex shape with respect to the plasma 1 and are located near the center of each magnet. The magnetic field strength of the plasma loss portion is not strong and the plasma loss is large. On the other hand, as in the case of FIG. 1, when an electric current is applied to the conductor 3 for the auxiliary magnetic field in a direction in which magnetic lines of force in the same direction as the magnet forming the cusp magnetic field are generated, the magnetic lines of force 4 become rectangular as shown in the figure. The shape is close, and the magnetic field strength in the vicinity of the plasma loss portion increases, so that the loss of the plasma 1 can be prevented.

FIG. 3 is a vertical sectional view of the entire plasma processing apparatus of the present invention. As shown in FIG. 3, the plasma processing apparatus of this embodiment is connected to a power source 6 for mounting a wafer 5 to be processed and is opposed to a substrate electrode 9 insulated by a processing chamber 7 and an insulator 8 and the electrode 9. Plasma generating electrode 1
0 (in the case of the parallel plate type, it means a surface-treated metal disk connected to a high frequency or DC power source, and in the case of the ECR type, it means a microwave plasma source. In FIG. 3, the case of the parallel plate type is shown. .) Is connected to the power supply 11 and the insulator 1
2 is installed so as to be insulated from the processing chamber 7. A plurality of magnets 2 for forming a multipole cusp magnetic field for plasma confinement are arranged so as to surround the electrodes 9 and 10. Further, a coil (not shown in the figure) for generating an auxiliary magnetic field between the magnet 2 and the plasma 1 and a shield plate 13
Is installed. After the wafer 5 is placed on the electrode 9, the entire processing chamber 7 is evacuated by the vacuum device 14 to introduce the reaction gas into the processing chamber 7. Here, the plasma generating electrode 10
Plasma 1 is generated on the wafer 5 by. Since the plasma 1 can be prevented from being diffused in the circumferential direction by the multipole cusp magnetic field, the plasma density becomes high and becomes almost uniform. However, simply arranging the magnets 2 having different polarities alternately on the circumference causes a large plasma loss in the cusp loss portion (particularly where the magnetic field lines 4 emitted from the magnets are separated into the left and right magnets 2 adjacent to each other). I will end up. Therefore, the region having the circumferential direction component of the magnetic force lines 4 is extended by the auxiliary magnetic field to increase the magnetic field strength of the cusp loss portion and reduce the plasma loss.
Ions in the plasma collide with the wall surface of the processing chamber 7 due to the bias voltage generated between the plasma and the wall surface of the processing chamber 7, and the adsorbed substances or gas components in the gas phase such as H ₂ O adhering to the wall surface of the processing chamber are discharged. Products of radicals of the reaction gas carried along with the plasma are sputtered by the ions and are mixed in the gas phase, which causes undesired non-uniform processing on the wafer 5.

FIG. 4 shows a second embodiment of the present invention. With the same configuration as the first embodiment, a plurality of magnetic field generators 15 instead of magnets are provided around the periphery of the wafer on the DC power supply 1.
Connect to 6 and place. The magnetic field generator 15 is composed of a plurality of coil-shaped conductors centered around a certain circumference, and a current in the opposite direction is applied to adjacent coils from a power source to obtain magnetic lines of force parallel to the circumference on the side surfaces of the coils. The lines of magnetic force repel each other in adjacent portions of the coil to form a cusp-like magnetic field. According to this method, the number of plasma loss parts can be reduced. Although the number of coils is four in FIG. 4, it should be noted that an arbitrary even number can be installed.

Further, in the case of FIG. 4, there is also a case where a mechanism for inverting the current flowing through the coil is installed in the power source 16. When the wall surface and plasma come into contact with each other, an electric field is generated at the interface, and when a magnetic field is present at this time, the plasma receives a force according to Fleming's law and moves in a direction perpendicular to the electric field and the magnetic field. In the case of the present invention, an electric field is generated in the radial direction on the shield plate inside the coil, and a magnetic field is generated on a plane parallel to the wafer, so that a force acts on the plasma in a direction perpendicular to the wafer. Since the force has different directions of magnetic force lines generated by the adjacent coils, the force acting on the plasma alternates between the substrate electrode and the plasma generating electrode side and affects the uniformity of plasma in the peripheral portion. In particular, in a process that sensitively affects the density of plasma, nonuniformity may occur in plasma processing such as CVD. At this time, by changing the direction of the current flowing through the coil at regular intervals, the force generated around the plasma alternates between the substrate electrode and the plasma generating electrode side, and the plasma density becomes constant on average, and uniform processing of the wafer is performed. It will be possible.

[0016]

As described above, when plasma processing is performed using the plasma processing apparatus of the present invention, the plasma generated during the plasma processing has a predetermined confined space (for example, on the surface of the wafer that is the object to be processed). In addition to the above, the electrodes are discharged due to the occurrence of abnormal discharge other than in the plasma generation part, or the collision of ions from the plasma on the wall surface, and the adsorbed substances such as the processing chamber constituent members and moisture contained in the constituent members. It is possible to prevent the particles from being sputtered or dissociated and being mixed into the atmosphere of the processing chamber. As a result, the wafer surface is free of contamination and foreign matter during plasma processing,
Since the predetermined processing can be performed uniformly on the wafer surface with high reliability, high-accuracy and high-quality processing can be performed and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multipole cusp magnetic field having an auxiliary magnetic field according to the first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a normal multipole cusp magnetic field.

FIG. 3 is a vertical sectional view of a plasma processing apparatus using the first embodiment of the present invention.

FIG. 4 is a transverse sectional view of a multipole cusp magnetic field according to a second embodiment of the present invention.

[Explanation of symbols]

1 ... Plasma, 2 ... Magnet, 3 ... Conductor wire, 4 ... Magnetic field line, 5 ... Wafer, 6 ... Power supply, 7 ... Reaction chamber, 8 ...
Insulator, 9 ... Substrate electrode, 10 ... Plasma generating electrode,
11 ... Power source, 12 ... Insulator, 13 ... Shielding plate, 14
...... Vacuum device, 15 ... Magnetic field generator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C30B 25/18 9040-4G H05H 1/16 9014-2G // H01L 21/31 C 8518-4M

Claims (4)

[Claims] 1. On the object to be treated, the reaction gas is transported to the object to be treated in a state where at least one kind of the reaction gas turned into plasma by excitation is confined by a (multipole) cusp magnetic field. In the plasma processing apparatus for forming a thin film in, or processing the thin film, or performing sputtering film formation by drawing ions into the electrode to which electric power is applied from the reaction gas, the magnetic force line that is the plasma loss part of the cusp magnetic field is A plasma processing apparatus, characterized in that a magnetic field generating means different from the cusp magnetic field is provided in the vicinity of a portion of the plasma processing apparatus in the radial direction. 2. The plasma processing apparatus according to claim 1, wherein an even number of permanent magnets are arranged substantially concentrically with the plasma, and the magnetic poles of the permanent magnets are alternately arranged in the circumferential direction to form a cusp magnetic field plasma. A plasma processing apparatus comprising a magnetic field generating means for correcting the cusp magnetic field so that the magnetic field shape in the vicinity of the loss portion increases in the circumferential magnetic field component. 3. The plasma processing apparatus according to claim 1, wherein the magnetic field generating means for correcting the cusp magnetic field is an electromagnet, and magnetic field lines in the same direction as the magnetic field lines from the magnet are formed inside both ends of the magnet forming the cusp magnetic field. A plasma processing apparatus characterized in that an electric current is caused to flow in the direction in which the electric field is generated. 4. A plasma processing apparatus according to claim 1, wherein the cusp magnetic field generating means is an electromagnet in which a plurality of conductive wires wound in a coil shape are evenly arranged substantially concentrically with the plasma, and between adjacent coils. A plasma processing apparatus, wherein a reverse current is applied.