JPH0927278A - Magnetic field generator for magnetron plasma - Google Patents

Abstract

(57) [Abstract] (Correction) [Problem] Magnetron capable of generating uniform plasma over a wide range, improving target utilization efficiency when used for sputtering, and capable of high quality etching when used for etching. Magnetic field generator for plasma. A magnetic field generator for a magnetron plasma installed and used in a magnetron device for generating high-density plasma, the dipole ring magnet comprising a plurality of anisotropic segment columnar magnets arranged in a ring shape. The plurality of anisotropic segment columnar magnets are arranged asymmetrically with respect to the direction of the magnetic field formed in the dipole ring magnet so that the magnetic field strength distribution of the central cross section in the longitudinal direction of the magnet has a gradient. Magnetic field generator for magnetron plasma.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generator for magnetron plasma that generates a magnetic field with good magnetic field homogeneity. A magnetron device provided with the magnetic field generator for magnetron plasma according to the present invention is an electric or electronic device. It is suitable for use in magnetron sputtering and magnetron etching performed in the industrial field.

[0002]

2. Description of the Related Art Conventionally, magnetron plasma has been used for performing sputtering and etching.
The magnetron plasma is produced by a magnetron device as follows. First, an electrode is inserted into a gas such as argon in a container and discharged, whereby the gas is ionized and secondary electrons are generated. The secondary electrons also collide with gas molecules and the gas is further ionized. At this time, the electrons and secondary electrons emitted by the discharge receive a force due to a magnetic field and an electric field generated by the magnetron device, and drift. Therefore, when the electrons make a drift motion, they can collide with gas molecules one after another, and can ionize the gas one after another. At the time of the ionization, new electrons are generated again, and the electrons also collide with gas molecules to further ionize the gas. The magnetron plasma repeats such a process and has a very high ionization efficiency. As described above, when the magnetron device is used, the ionization rate of the gas is high, and high-density plasma can be generated. For this reason, the method using the magnetron device for sputtering and etching has an advantage that the efficiency can be obtained two to three times as compared with the case where the normal high-pressure discharge method is used.

FIG. 5 shows an example of a sputtering device using a conventional magnetron discharge device. FIG. 5A is a vertical cross-sectional view of the sputtering apparatus, and FIG. 5B is a diagram showing the movement of electrons in this apparatus. The substrate 14 and the target 16 are provided between the parallel plate electrodes 10 and 12
A magnetic field generator 18 for magnetron plasma is installed on the back surface of 12. A high frequency is normally applied between both electrodes 10 and 12, and the direction of the electric field when the electrode 10 is an anode and the electrode 12 is a cathode is shown by an arrow 20 in FIG. FIG. 5 (a)
Conventional magnetic field generator for magnetron plasma 18
The disk-shaped permanent magnet 24 is provided in the hole of the doughnut-shaped permanent magnet 22, and the lower surfaces thereof are connected by the yoke 26. This conventional magnetron plasma magnetic field generator
Magnetic field lines 28a and 28b show that the magnetic field generated by 18 leaks onto the target 16. Magnetic field lines 28a and 28b of the leakage magnetic field on the surface of the target 16 generated by the conventional magnetic field generator 18 for magnetron plasma are like magnetic field lines 30 of FIG. 5B when viewed in perspective, where the direction of the electric field is When in the direction of the arrow 20, the electron 32 draws an endless orbit 34 while making a drift motion in the cross product direction of the electric field and the magnetic field. As a result,
32 is bound near the surface of the target 16 and promotes ionization of gas. Therefore, the apparatus of FIG. 5 can generate high density plasma.

[0004] By the way, what contributes to the drift motion of electrons is a component perpendicular to the electric field of the magnetic field. That is, in the case of FIG. 5, only the component horizontal to the target contributes to the drift motion of the electrons to ionize the gas. In the magnetron sputtering apparatus using the magnetic field generator for magnetron plasma as shown in FIG. 5, a donut-shaped magnetic field is formed (see FIG. 6A), and the horizontal component of the magnetic field varies greatly depending on the location, and the horizontal magnetic field component is strong. Higher density plasma is generated in the region (see FIG. 6B). Therefore,
The larger the horizontal magnetic field component is, the larger the sputtering occurs, and the target is partially consumed to reduce the utilization efficiency of the target. In general, targets are expensive and are an economic problem. Further, even in a magnetron etching apparatus using a similar magnetron plasma magnetic field generator, quality problems such as intensive etching of a part of the wafer occur. In addition, the non-uniform plasma causes a potential distribution in the wafer surface (charge-up), which causes device breakdown.

In order to solve such a point, a horizontal magnetic field generator having a uniform magnetic field component is desired. For example,
A dipole ring magnet in which a plurality of anisotropic segment columnar magnets are arranged in a ring shape is known as a device for obtaining a uniform horizontal magnetic field. By the way, the magnetic field of the dipole ring magnet is a horizontal magnetic field that is oriented in only one direction, unlike the donut-shaped magnetic field produced by the conventional device (FIG. 5). Therefore, if the electrons remain as they are, the electrons make a drift motion and proceed in one direction, leading to nonuniform plasma density. Therefore, it is necessary to rotate the dipole ring magnet along the circumferential direction of the ring to change the direction of the electron drift motion. However, in reality, it is not possible to make the plasma density uniform over a wide range only by rotating the dipole ring magnet.

FIG. 3 (a) is a top view of the dipole ring magnet, and FIG. 3 (b) is a sectional view taken along the line AB in FIG. 3 (a). A plurality of anisotropic segment columnar magnets 40 are housed in a non-magnetic mount 42 to form a dipole ring magnet. Anisotropic segment columnar magnet 40
The number of is 8 or more and is usually selected from 8 to 64. FIG. 3 shows the case of 16 pieces. The cross-sectional shape of the anisotropic segment columnar magnet is arbitrary, and may be, for example, a circle, a square, a rectangle, or a trapezoid. A square was used in FIG. The arrow drawn in the anisotropic segment columnar magnet 40 indicates the direction of magnetization of this anisotropic segment columnar magnet. By arranging the magnetization directions as shown in FIG. 3, a magnetic field having the direction indicated by the arrow 43 is generated in the ring.

When this dipole ring magnetic field is used as a magnetic field generator for magnetron plasma, parallel plate electrodes 36
A substrate 38 and a target 39 are provided between the and.
A high frequency is usually applied between the electrodes 36 and 37. In FIG. 3, the directions of the electric fields when the plate 36 is the anode and the plate 37 is the cathode are shown by arrows 44 and 45. At this time, the central cross section of the dipole ring magnet in the length direction is made to coincide with the central cross section of the plasma space 46 in which plasma is generated. That is, the target is adjusted in the case of sputtering and the wafer is adjusted in the case of etching to match the central cross section of the dipole ring magnet in the length direction. this is,
Because the magnetic field homogeneity in the central part in the length direction of the dipole ring magnet is better than the magnetic field homogeneity in the end part, and in the central part in the length direction, in principle, only the horizontal component of the magnetic field exists. This is because the plasma generated can be made more uniform when the central portion is a space in which plasma is generated.

A uniform magnetic field can be obtained in the plasma space 46 by the magnetic field generator composed of a dipole ring magnet, but the electrons make a drift motion in the outer product direction of the electric field and the magnetic field to move in the Y-axis direction shown in FIG. Proceeding in the negative direction, the plasma density is low in the positive direction of the Y-axis, and the plasma density is high in the negative direction of the Y-axis (see FIG. 4B). Therefore, in order to change the direction of the electron drift motion, it is necessary to rotate the dipole ring magnet along the circumferential direction of the ring, but in reality it is not possible to make the plasma density uniform over a wide range only by rotating the dipole ring magnet. .

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a uniform plasma over a wide range by using a dipole ring magnet in a magnetic field generator used in a sputtering or etching apparatus utilizing magnetron plasma, which is improved on the above points. It is to provide a magnetic field generator for magnetron plasma capable of performing the above.

[0010]

DISCLOSURE OF THE INVENTION The present invention is an improvement over the above-mentioned drawbacks of the dipole ring magnet, which is used in a magnetic field generator for a magnetron plasma installed in a magnetron device for producing high density plasma. Of the anisotropic segment columnar magnets are arranged in a ring shape, and the plurality of anisotropic segment columnar magnets are formed so that the magnetic field strength distribution of the central cross section in the length direction of the dipole ring magnets has a gradient. The gist of the magnetic field generator for magnetron plasma is characterized in that it is arranged asymmetrically with respect to the direction of the magnetic field formed in the dipole ring magnet, which is installed in the magnetron device that generates high-density plasma. Used to obtain a uniform plasma density distribution.

The details of the present invention will be described below. The present invention
This is a modification of the conventional dipole ring magnet (FIG. 3) in order to improve the non-uniformity of the plasma density when used as a magnetic field generator for magnetron plasma. FIG. 1A shows a top view of a dipole ring magnet which is a magnetic field generator for magnetron plasma of the present invention.
FIG. 1B shows a cross-sectional portion when FIG. 1A is cut along the line GH. Multiple anisotropic segment columnar magnets 50
Are housed in a non-magnetic mount 52 to form a dipole ring magnet. The number of the anisotropic segment columnar magnets 50 is 8 or more and is usually selected from 8 to 64. FIG. 1 shows the case of 11 pieces. The cross-sectional shape of the anisotropic segment columnar magnet is arbitrary, and may be, for example, a circle, a square, a rectangle, or a trapezoid.
A square is used in FIG. The arrow drawn in each anisotropic segment columnar magnet indicates the direction of magnetization of this anisotropic segment columnar magnet. When the magnetization directions are arranged as shown in FIG. 1A, a magnetic field having the direction indicated by the arrow 53 is generated in the ring. This dipole ring magnet
The anisotropic segment columnar magnets are arranged asymmetrically with respect to the X-axis so that the magnetic field strength has a gradient in the Y-axis direction as shown in FIG. Incidentally, due to the symmetry of the structure, they are arranged symmetrically about the Y axis. As described above, in order to arrange the anisotropic segment columnar magnets asymmetrically with respect to the X axis,
For example, there is a method of reducing the number of anisotropic segment columnar magnets in a region where the magnetic field strength is low. In FIG. 1 (a), FIG.
From the anisotropic segment columnar magnets 50 (1) to 50 (16) of the conventional type dipole ring magnet shown in (a) to the anisotropic segment columnar magnets 50 (10), 50 (11), 50 (13), 50
(15) and 50 (16) are deleted. In addition, a method of cutting each anisotropic segment columnar magnet at the central portion in the lengthwise direction to form a gap and changing the strength of the magnetic field can be used together, if necessary. The anisotropic segment columnar magnet may be a known one, for example, a cylinder,
Rare earth magnets such as prisms and trapezoids, ferrite magnets, alnico magnets, etc. are exemplified. Although only the dipole ring magnet is shown in FIG. 1 and the other parts of the magnetic field generator for magnetron plasma are omitted, this may be performed in the same manner as in the case of the conventional dipole ring magnet as shown in FIG. 3B.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to Examples and Comparative Examples. Example 11 11 pieces of anisotropic segmented columnar magnets 50 having a size of 30 mm × 30 mm and a length of 150 mm and made of prismatic Nd-Fe-B magnets are shown in FIG.
A dipole ring magnet arranged as shown in (a) is produced,
This was installed in a magnetic field generator for magnetron plasma, and the horizontal magnetic field distribution and plasma distribution in the plasma space 56 of the central cross section were measured by the following method. The results are shown in FIGS. 2 (a) and 2 (b). It can be seen from FIG. 2 (a) that the magnetic field distribution has a gradient of positive high and negative negative in the Y-axis direction, and as a result, a uniform plasma distribution is obtained as shown in FIG. 2 (b).

Comparative Example 1 A dipole ring magnet having 16 anisotropic segment columnar magnets same as those used in the embodiment was arranged as shown in FIG. 3 (a), and was installed in a magnetic field generator for magnetron plasma. Similarly, the horizontal magnetic field distribution and plasma distribution were measured. The results are shown in FIGS. 4 (a) and 4 (b). The magnetic field distribution is uniform in both the X-axis and Y-axis directions, but the plasma distribution is not uniform.

Comparative Example 2 Further, as Comparative Example 2, the measurement results of the horizontal magnetic field distribution and the plasma distribution by a magnetic field generator for magnetron plasma (FIG. 5) currently used industrially are shown in FIG. 6 (a).
And shown in FIG. 6 (b). The horizontal magnetic field distribution and plasma distribution were measured as follows. Horizontal magnetic field distribution measurement method Move the Hall element in the evaluation space and read the value at the measurement point with a Gauss meter. Plasma distribution measurement method By the electrostatic probe method, the probe is moved within the evaluation space, and the current-voltage characteristics when a voltage is applied to the probe are measured. From this current-voltage characteristic, various plasma quantities such as electron temperature and electron density are obtained, and the plasma distribution is obtained.

[0015]

As described above, according to the magnetic field generator for magnetron plasma of the present invention, it is possible to generate a uniform plasma over a wider area than the conventional one. Therefore, the magnetic field generator for magnetron plasma of the present invention,
When used for sputtering, the utilization efficiency of the target can be increased. Further, even when used for etching, there is a great advantage that high quality etching can be performed.

[Brief description of drawings]

FIG. 1A is a top view of a magnetic field generator for a magnetron plasma including a dipole ring magnet of the present invention.
FIG. 1B is a diagram showing a cross-sectional portion when FIG. 1A is cut along the line GH.

FIG. 2 is a diagram showing (a) horizontal magnetic field intensity distribution and (b) plasma distribution generated by the magnetic field generator of the present invention.

FIG. 3A is a top view of a conventional magnetic field generator for a magnetron plasma including a dipole ring magnet, and FIG.
3A is a cross-sectional view of FIG. 3A taken along the line AB.

FIG. 4 is a diagram showing (a) horizontal magnetic field intensity distribution and (b) plasma distribution generated by a conventional dipole ring magnet magnetic field generator.

FIG. 5A is a longitudinal sectional view of a magnetron plasma apparatus including a conventional magnetic field generator, and FIG. 5B is a diagram showing movement of electrons in the apparatus.

FIG. 6 is a diagram showing (a) horizontal magnetic field intensity distribution and (b) plasma distribution generated by a conventional magnetic field generator using the magnet of FIG. 2.

[Explanation of symbols]

 10, 12, 36, 37 ... Electrodes 14, 38 ... Substrate 16, 38 ... Target 18 ... Magnetron plasma generator 20, 44, 45 ... Direction of electric field 22 ... Donut-shaped permanent magnet 24 ... Disk-shaped permanent magnet 26 ... Yoke 28a , 28b, 30 ... Magnetic field lines 32 ... Electrons 34 ... Endless orbits 40, 50 ... Anisotropic segment columnar magnets 42, 52 ... Stand 43, 53 ... Direction of magnetic field 46, 56 ... Plasma space

Claims (1)

[Claims] 1. A magnetic field generator for a magnetron plasma, which is used by being installed in a magnetron device for generating high density plasma, comprising a dipole ring magnet in which a plurality of anisotropic segment columnar magnets are arranged in a ring shape. Arranging the plurality of anisotropic segment columnar magnets asymmetrically with respect to the direction of the magnetic field formed in the dipole ring magnet so that the magnetic field strength distribution of the central section in the length direction of the ring magnet has a gradient. A characteristic magnetic field generator for magnetron plasma.