JPH06207272A - Magnetic circuit of permanent magnet for magnetron plasma - Google Patents

Abstract

PURPOSE:To provide a magnetic circuit of permanent magnets capable of forming loci of electrons over the entire area of a target and having excellent uniformity of magnetic fields by adjacently combining >=2 pieces of half or more rotating spiral rare earth magnets varying in magnetization directions. CONSTITUTION:The electrons within the plasma generated in magnetron are moved by the horizontal component of the leak magnetic field of the magnetic circuit of the permanent magnets disposed on the rear surface of the target. Two or more pieces of the rear earth magnets 40, 42 or 48, 50 varying in the magnetization directions are adjacently combined and the respective magnets are formed to half or more rotating spiral shapes in the magnetic circuit of the permanent magnets for magnetron plasma. For example, the magnetization directions of the two rare earth magnets 40, 42 are set perpendicular to the base of the magnetic circuit and the one N pole 44 is positioned adjacent to the other S pole 46. The magnetization directions are otherwise set parallel with the base of the magnetic circuit so that the same poles 52 adjacently face each other. The electrons are spirally moved by the magnetic lines of force running between both N and S poles, by which the plasma is generated uniformly over the entire area of the target.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet magnetic circuit for generating magnetron plasma for causing electrons in discharged gas to draw endless trajectories to promote ionization of the discharged gas. The permanent magnet magnetic circuit according to the present invention is optimal for use in, for example, a magnetron sputtering apparatus for producing thin films such as electrodes, wirings, and recording films, and a magnetron plasma etching apparatus for dry etching LSI.

[0002]

2. Description of the Related Art Magnetron sputtering using a magnetron has been conventionally performed as sputtering. In magnetron sputtering, first, an electrode is inserted into a gas such as argon in a container, and the gas is ionized by discharge. The electrons generated at this time collide with gas molecules such as argon and the target, so that the gas is further ionized and secondary electrons are also generated. At that time, the electrons and secondary electrons emitted by the discharge are trapped by the magnetic field and electric field of the magnetron, and perform a turning motion of a small diameter. Therefore, electrons can collide with gas molecules one after another. Therefore, the efficiency of ionization by the magnetron system is high. Next, the cations in the plasma collide with the cathode (the target to be sputtered) and knock out sputtered atoms (atoms forming the target). Finally, the sputtered atoms attach to the substrate placed on the anode, forming a film on the substrate surface.

Reactive ion etching is a mechanism in which ions in plasma etch a substrate exposed by applying a photoresist.

As described above, conventionally, the plasma generated in the magnetron has been widely used for sputtering and reactive ion etching. Since the magnetron system has a high ionization efficiency, it is 2 times more efficient than the normal high-pressure discharge system when performing sputtering and etching.
There is an advantage that ~ 3 times the efficiency can be obtained.

A permanent magnet magnetic circuit is provided to generate a magnetic field in the magnetron system. The permanent magnet magnetic circuit is provided on the back surface of the target in the case of flat type bipolar discharge sputtering, and usually on the back surface of the substrate in etching. The magnetic field created by the permanent magnet magnetic circuit leaks onto the target or the substrate, and the horizontal component of this leaked magnetic field is used to move the discharge electrons to promote the ionization of the gas.

When only a magnetic field exists in the moving region of the electrons, the electrons perform a spiral motion in a manner that they are captured by the magnetic force lines and wrapped around the magnetic force lines. However, in the case of, for example, a two-pole discharge type magnetron, an electric field is applied in a direction perpendicular to the discharge electrodes, so that a drift force proportional to the magnitude of (electric field) × (magnetic field) is applied to the electrons. As a result, the electrons move while drawing a cycloid curve so as to cross the lines of magnetic force. Only the magnetic field perpendicular to the electric field, that is, the horizontal component of the magnetic field, contributes to the drift force of the electrons. Therefore,
A permanent magnet magnetic circuit that produces a magnetic field with a strong horizontal magnetic field component and good magnetic field uniformity is desirable.

When the horizontal component of the magnetic field on the target (or substrate) is in only one direction, the electrons travel in one direction of the target (or substrate) because they travel across the magnetic field lines, and the plasma also deviates in that direction. Become. In order to prevent such escape of electrons, a permanent magnet is usually arranged so that a donut-shaped leakage magnetic field is generated on the magnet surface (FIG. 3).
In FIG. 3, the leakage magnetic field on the surface of the target (or substrate) 2 is like magnetic field lines 4, and when an electric field is applied in the direction indicated by reference numeral 6, the electrons 8 draw an endless track 10. As a result, the electrons 8 are confined in the leakage magnetic field region 12 and promote the ionization of the gas, so that high-density plasma is generated. In FIG. 3, reference numerals 14 and 16 denote magnetic field lines 4.
Shows the intersection with the surface of the target (or substrate) 2.

However, in a magnetic circuit for generating a donut-shaped leakage magnetic field, the horizontal magnetic field strength of the leakage magnetic field varies greatly depending on the location, and a higher density plasma is generated in a region having a stronger horizontal magnetic field strength. Therefore, in the sputtering apparatus, the larger the horizontal magnetic field strength, the larger the amount of sputtering that occurs, and the target is consumed. Therefore, there is a problem that the use efficiency of the target is poor and the thickness of the formed sputtered film becomes uneven.

Further, since the cations in the plasma generated in the region where the horizontal magnetic field intensity is strong have large kinetic energy, heavy atoms (the target is usually composed of several kinds of atoms, when the sputtered atoms are knocked out from the target, It is easy to knock out the heavier atom). That is, there is also a problem that the composition of the sputtered film varies depending on the location due to the difference in the horizontal magnetic field strength.

Also in the case of the etching apparatus, the plasma density is not constant and the etching depth varies depending on the position of the substrate.

Various magnet arrangements in a magnetic circuit have been conventionally considered in order to improve the above-mentioned drawbacks. For example, the concentric circle type was improved to have three rows of magnets (see FIG.
(A)), a modified concentric circle (Fig. 4 (b)), etc.
It has been proposed to rotate a magnetic circuit (or a substrate) to generate a leakage magnetic field in a wider area.

Further, there is also proposed a magnet (FIG. 4 (c)) intended to expand the leakage magnetic field region by combining a magnet magnetized in the horizontal direction and a magnet magnetized in the vertical direction.

In FIGS. 4 (a) to 4 (c), reference numeral 20,
Reference numerals 24 and 28 denote outer circumferences of back yokes installed below the magnets 22, 26 and 30, respectively. Further, reference numeral 32 in FIG. 4C represents the magnetization direction of the magnet magnetized in the horizontal direction.

All of the above magnetic circuits have been improved in that the target consumable region is expanded as compared with the simple concentric type. However, each conventional example has the following problems.

Those in which the magnetic circuit (or the substrate) is rotated by using three rows of magnets or by forming modified concentric circles,
It is effective for ensuring the uniformity of sputtering and etching. However, since the rotation is performed, the mechanism is complicated, the device is expensive, and dust is generated from the rotating shaft. Maintenance becomes complicated, and many problems occur with the device.

Further, in the modified concentric circle type, the substrate must be rotated without fail, and the manufacturing of the magnet is troublesome and troublesome, so that there is a problem that the apparatus becomes expensive.

The combination of a magnet magnetized in the horizontal direction and a magnet magnetized in the vertical direction increases the use efficiency of the target as compared with a simple concentric structure without a magnet magnetized in the horizontal direction. . This is because according to this magnet arrangement, the magnetomotive force of the magnet magnetized in the horizontal direction can be effectively used to generate a relatively strong magnetic field in the gap between the magnets in the vertical direction. However, since the magnetic field rises almost vertically in the magnets magnetized in the vertical direction at the outer peripheral portion and the central portion, there is a problem that the horizontal component of the magnetic field is reduced and the contribution of electrons to the infinite orbital motion is small.

In order to solve the above problems, the horizontal magnetic field region which leaks to the target (or substrate) is enlarged with a simple shape, and sputtering (or etching) is performed.
There is a need for a magnetic circuit that can improve the efficiency of the.

[0019]

An object of the present invention is to improve a permanent magnet magnetic circuit used for magnetron plasma generation such as sputtering and etching so that electrons in the magnetron plasma are distributed over almost the entire target (or substrate). It is an object of the present invention to provide a permanent magnet magnetic circuit having a leakage magnetic field distribution that enables a trajectory to be drawn.

[0020]

Two rare earth magnets having different magnetization directions are adjacent to each other, and each of the two rare earth magnets has a spiral shape of half a revolution or more. Use a circuit. The magnetization directions of the two rare earth magnets are perpendicular to the bottom surface of the magnetic circuit, and one N pole of these two rare earth magnets is adjacent to the other S pole. Furthermore, the magnetization directions of the two rare earth magnets are parallel to the bottom surface of the magnetic circuit, and the two rare earth magnets are adjacent to each other so that the same poles face each other.

[0021]

EXAMPLE The present invention proposes a magnet arrangement in which two magnets having different magnetization directions are adjacent to each other and are spirally formed.
An example is shown in FIG. Spiral parts 40, 42, 48,
50 is a magnet, and magnets 40 and 42, magnets 48 and 50
Are magnetized in different directions. Reference numeral 54,
Reference numeral 56 denotes the outer circumference of the back yoke installed below the magnets 40 and 42 and 48 and 50.

There are infinite ways to combine the two magnets that are adjacent to each other in different magnetization directions. As shown in FIG. 1A, when the magnetization directions of the two magnets are perpendicular to the bottom surface of the magnetic circuit and are opposite to each other (symbols 44 and 46 in the figure indicate the magnetization directions of the respective magnets. Symbol 44) Indicates the direction from this side of the paper to the other side, and the symbol 46 indicates the opposite direction) and the case where they are parallel and opposite to each other as shown in FIG. 1 (b) (the arrows 52 in the figure indicate the respective directions). Magnetizing direction of magnets), and one or both magnets are magnetized in any direction between perpendicular and parallel to the bottom surface of the magnetic circuit. In any combination, the magnetic field generated by these magnets causes the electrons to move on the magnet surface.

When the magnetizing direction of the magnet is perpendicular to the bottom surface of the magnetic circuit (FIG. 1A), the N pole and the S pole appear on the surface of the adjacent magnets, respectively. In this case, adjacent N and S
Since the magnetic field lines run between the magnetic pole faces, a strong horizontal magnetic field is generated near the boundary between the two magnets, and the electrons generated by the discharge move so as to cross the horizontal magnetic field. Therefore, FIG.
In the spiral magnetic circuit of, the electrons move in the boundary region of the adjacent magnets along the arrow 60 shown in FIG.

The electrons moving along the arrow 60 collide with gas molecules in the magnetron plasma one after another and ionize them. Secondary electrons generated at that time also move along the arrow 60. These electrons can move along the spiral magnet boundary from the outer circumference to the center and ionize the gas over almost the entire target (or substrate). Therefore, it becomes possible to generate plasma in a wider range over the entire target (or substrate) than in the case of the conventional donut-shaped leakage magnetic field flux.

When the magnetizing directions of the magnets are parallel (see FIG.
In (b)), it is necessary that the same poles (N-N poles or S-S poles) face each other. In this case, the electrons are
It moves along the arrow 62 shown in (b). Unlike the case where the magnetization is oriented in the vertical direction (FIG. 1A), the lines of magnetic force do not go in and out vertically, so that the region of the portion where the horizontal magnetic field strength of the leakage magnetic field is strong is wide. Therefore, plasma is generated in a wider area over the entire surface of the target (or the substrate). Therefore, a magnetic circuit with horizontal magnetization and opposite poles (FIG. 1B) is more advantageous than a magnetic circuit with vertical magnetization orientation (FIG. 1A) in terms of plasma generation.

Further, in the magnetic circuit of perpendicular magnetization orientation, the magnetic field lines do not flow far away from the magnet surface, so that the magnetic field strength in the perpendicular direction decreases rapidly. Therefore, it is less preferable to use a magnetic circuit having a perpendicular magnetization orientation when the target (or the substrate) is thick, and it is more preferable to use a magnetic circuit having a horizontally magnetized homopolar opposing arrangement.

However, in manufacturing a magnetic circuit, it is more difficult to manufacture a magnetic circuit with horizontal magnetization orientation. This is because, in the case of a magnetic circuit with perpendicular magnetization orientation, a disk-shaped magnetic circuit is manufactured and magnetized with pulse magnetizing coils for each of N pole and S pole, so that N pole and S pole are nested. It is possible to produce a spiral magnetized pattern, but in the case of a horizontally magnetized homopolar opposing magnetic circuit, pulse magnetization is not possible. This is because these must be assembled after magnetizing.

Therefore, in manufacturing the magnetic circuit, the efficiency of plasma generation in the magnetron plasma is improved,
It suffices to compare the manufacturing difficulty and the like and select the type of magnetic circuit suitable for the application.

In the present invention, the magnet is formed in a spiral shape as shown in FIG. 1 because the magnetic field is leaked in a wide range from the outer peripheral portion to the central portion to generate plasma over the entire surface of the target (or the substrate). is there. In order to leak the magnetic field over almost the entire surface of the target (or substrate),
It is necessary to make the spiral more than half a turn, and more preferably one turn or more. Increasing the rotation speed of the spiral increases the area of the leakage magnetic field, which is desirable but difficult to manufacture.
Also in this respect, an appropriate number of rotations may be selected depending on the application.

Rare earth magnets are preferable to ferrite magnets and cast magnets for the permanent magnets used in the magnetic circuit of the present invention. This is because the rare earth magnet can obtain a stronger horizontal magnetic field strength. As a rare earth magnet, SmCo ₅
System, SmCo ₁₇ system, NdFeB system sintered magnets and the like can be used. When using an NdFeB magnet, it is necessary to apply a coating in consideration of corrosion resistance and degassing, and it is particularly desirable to apply a metal coating such as Ni plating.

[0031]

EFFECTS OF THE INVENTION Two rare earth magnets having different magnetization directions are adjacent to each other, and the two rare earth magnets each have a spiral shape of a half rotation or more, and a leakage occurs on a target (or a substrate) by a permanent magnet magnetic circuit. The horizontal magnetic field area of the magnetic field was significantly increased. Therefore, the electrons in the magnetron plasma can trace their trajectories over almost the entire area of the target (or the substrate), and the efficiency of ionization of the gas in the magnetron plasma is greatly improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a permanent magnet magnetic circuit according to the present invention.

FIG. 2 is a diagram illustrating movement of electrons on a permanent magnet magnetic circuit according to the present invention.

FIG. 3 is a magnetic circuit for generating a donut-shaped leakage magnetic field;
The figure explaining the motion of the electron by the leak magnetic field.

FIG. 4 is a conventional example of a permanent magnet magnetic circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H05H 1/46 9014-2G

Claims (3)

[Claims] 1. A permanent magnet magnetic circuit for magnetron plasma, wherein two rare earth magnets having different magnetization directions are adjacent to each other, and each of the two rare earth magnets has a spiral shape of at least half rotation. 2. The magnetization directions of the two rare earth magnets are perpendicular to the bottom surface of the magnetic circuit, and one N pole of the two rare earth magnets is adjacent to the other S pole. A permanent magnet magnetic circuit for magnetron plasma according to claim 1. 3. The magnetization directions of the two rare earth magnets are parallel to the bottom surface of the magnetic circuit, and the two rare earth magnets are adjacent to each other so that the same poles face each other. 2. A permanent magnet magnetic circuit for magnetron plasma according to claim 1.