JPH06212420A - Sputtering or etching method - Google Patents

Abstract

PURPOSE:To uniformize the plasma density on a target surface and to execute efficient sputtering and etching by rotating a spiral type permanent magnet magnetic circuit having a specific structure. CONSTITUTION:Two magnets varying, in magnetization direction are disposed adjacent to each other and the magnetic circuit disposed with the magnets in a spiral form is used. The spiral parts 40, 42, 48, 50 are the magnets. The magnets 40 and 42 and the magnets 48 and 50 are magnetized in the directions different from each other. Since the magnets of the magnetic circuit are spiral, magnetic fields are allowed to leak to a wide range from the outer peripheral part to the central part and the plasma is generated over nearly the entire surface of the target or the substrate. Sputtering or etching is executed by rotating the spiral type magnetic circuit (or target or substrate).

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As sputtering, magnetron sputtering utilizing magnetron plasma has been conventionally performed. 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, magnetron plasma has been widely used for sputtering and reactive ion etching. Since the magnetron system has high ionization efficiency, there is an advantage that the efficiency is 2-3 times as high as that of the normal high-pressure discharge system when performing sputtering and etching.

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).
Although not shown in FIG. 3, a permanent magnet magnetic circuit having an appropriate magnet arrangement is provided on the back surface of the target 2, so that a donut-shaped leakage magnetic field appears on the target surface. In FIG. 3, the leakage magnetic field on the surface of the target 2 is like magnetic field lines 4, and when an electric field is applied in the direction indicated by reference numeral 6, the electron 8 draws an endless orbit 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 indicate where the magnetic force lines 4 intersect with the surface of the target 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. That is, the plasma density becomes non-uniform. Therefore, in the sputtering apparatus, the larger the horizontal magnetic field strength region (higher plasma density region) is, the larger sputtering occurs and the target is consumed, resulting in poor target use efficiency and the non-uniform thickness of the sputtered film formed. There is a problem that becomes.

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 back yokes installed below the magnets 22, 26 and 30. In addition, reference numeral 3 in FIG.
2 represents the direction of magnetization of a magnet magnetized in the horizontal direction.

In any of the above magnetic circuits, the plasma density is uniform and improved as compared with the simple concentric type.
However, since each is a modification of the concentric magnetic circuit, it is not possible to generate a leakage magnetic field up to the center of the target (or substrate), and there is a limit to the uniformity of plasma density.

In order to solve the above problems, a horizontal magnetic field region leaking to a target (or a substrate) can be enlarged and the generated plasma density can be made uniform, and a sputtering and etching method using a magnetic circuit instead of a concentric magnetic circuit. Is required.

[0016]

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 sputtering and etching method using a permanent magnet magnetic circuit having a leakage magnetic field distribution that enables a trajectory to be drawn.

[0017]

[MEANS FOR SOLVING THE PROBLEMS] Rotating a permanent magnet magnetic circuit for magnetron plasma in which 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. To perform sputtering or etching. Further, the magnetization directions of the two rare earth magnets are perpendicular to the bottom surface of the magnetic circuit, one N pole of the two rare earth magnets is adjacent to the other S pole, and each has a spiral shape of half a revolution or more. The permanent magnet magnetic circuit for magnetron plasma is rotated to perform sputtering or etching. Furthermore, the magnetization directions of the two rare earth magnets are parallel to the bottom surface of the magnetic circuit, the two rare earth magnets are adjacent to each other so that the same poles face each other, and each has a spiral shape of more than half a turn. Sputtering or etching is performed by rotating the permanent magnet magnetic circuit for magnetron plasma.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, two magnets having different magnetization directions are arranged adjacent to each other, and a magnetic circuit having magnets arranged in a spiral shape is used. The magnetic circuit is rotated to perform sputtering and etching.

The magnetic circuit used in the present invention has already been applied for a patent by the present inventor. An embodiment thereof is shown in FIG. 1 and will be described below. The spiral portions 40, 42, 48 and 50 are magnets, and the magnets 40 and 42 and the magnets 48 and 50 are magnetized in directions different from each other. Reference numerals 54 and 56 denote the outer circumferences of the back yokes installed below the magnets 40 and 42, 48 and 50.

There are infinite ways to combine the two magnets adjacent to each other so that the magnetization directions thereof are different from each other. 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 magnets is perpendicular to the bottom surface of the magnetic circuit (FIG. 1 (a)), the N pole and the S pole appear on the surfaces 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 upon collision with the target or gas molecule 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 magnetization 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).

Since the magnet of the magnetic circuit used in the present invention has a spiral shape as shown in FIG. 1, the magnetic field is leaked in a wide range from the outer peripheral portion to the central portion, and the target (or substrate)
It is possible to generate plasma over almost the entire surface of the. However, even in the spiral magnetic circuit, the plasma density cannot be made uniform over the entire surface of the target (or the substrate). This is because the plasma density is high in a region where the horizontal component of the leakage magnetic field is large, and is low in a region where the horizontal component is small.

The present invention proposes a method of rotating a spiral magnetic circuit (or a target or a substrate) to perform sputtering and etching in order to solve the above-mentioned problem of nonuniform plasma density.

In the above-mentioned spiral magnetic circuit, plasma is generated from the outer peripheral portion to the central portion, so that the magnetic circuit and the target (or substrate) are made to coincide with each other in center, and either one is rotated to make the entire surface of the target (or substrate). The plasma density can be made uniform. That is, unlike the conventional case where the concentric magnetic circuit had to be eccentric to rotate, the rotation mechanism is simple and the space required for rotation is small.

A rare earth magnet is desirable as the permanent magnet used in the magnetic circuit used in the sputtering and etching method of the present invention. This is because a strong horizontal magnetic field strength can be obtained by using a rare earth magnet. For example, Sm ₂ Co
₁₇ magnets and NdFeB magnets can be used.

In order to leak the magnetic field over substantially the entire surface of the target (or the substrate), it is necessary to make the spiral of the magnetic circuit half rotation or more, and more preferably one rotation or more. However, if the number of revolutions of the spiral is increased too much (for example, 3 revolutions or more), the region of the leakage magnetic field increases, which is desirable, but it is difficult to manufacture the magnetic circuit. Therefore, it is desirable that the number of revolutions of the spiral is 1 or more and 3 or less.

The number of rotations when rotating the spiral magnetic circuit must be several rpm or more, preferably about 20 to 500 rpm. This is because if the number of rotations is too low, there is no difference from the case of stationary, and if the number of rotations is too high, the rotating mechanism becomes complicated and the influence of the eddy current generated by the rotation becomes large, and the leakage magnetic field becomes large. Because it becomes smaller.

[0030]

By the method of rotating the spiral permanent magnet magnetic circuit to perform sputtering and etching, the plasma density on the target (or substrate) surface becomes uniform, and even if the gas in the vacuum container is at a low pressure. Now, sputtering and etching can be performed efficiently.

[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. Sputtering is performed by rotating a permanent magnet magnetic circuit for magnetron plasma, in which 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 rotation or more. Alternatively, a method of sputtering and etching is characterized in that etching is performed. 2. The magnetization directions of the two rare earth magnets are perpendicular to the bottom surface of the magnetic circuit, one N pole of the two rare earth magnets is adjacent to the other S pole, and each of the two rare earth magnets is The sputtering and etching method according to claim 1, wherein the sputtering or etching is performed by rotating a permanent magnet magnetic circuit for magnetron plasma, which has a spiral shape of more than half a revolution. 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. The sputtering and etching method according to claim 1, wherein sputtering or etching is performed by rotating a permanent magnet magnetic circuit for magnetron plasma, which has a spiral shape of rotation or more.