JP2789252B2 - Sputtering equipment using dipole ring type magnetic circuit - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a sputtering apparatus, and more particularly, to a method in which sample atoms are evacuated from a target surface to which a high-frequency voltage is applied by magnetron sputtering using a dipole ring type magnetic circuit. The present invention relates to a sputtering apparatus for forming a thin film on a surface of a substrate by emitting the thin film on a surface of a substrate. The present invention is suitable when a soft magnetic material such as iron is used as a target.

[Prior Art] As is well known, a sputtering apparatus is widely used for thin film production in the field of electronics and electricity. Sputtering is broadly classified into the following two types: DC sputtering performed by applying a DC voltage to a target and RF sputtering performed by applying a high-frequency voltage to a target. Further, the DC and RF sputtering are classified into a conventional mode and a magnetron mode, respectively. That is, a total of four types of sputtering are known.

Among these four types of sputtering, the magnetron mode applies a magnetic field to the target, applies a high voltage to the inert gas, and confines the generated plasma in the magnetic field, thereby increasing the sputtering efficiency and increasing the deposition rate. It is possible to increase the temperature and suppress the temperature rise of the substrate on which the thin film is formed. For this reason, DC and DC
In any of the RF sputtering, it is common to employ the magnetron mode.

An example of a conventional sputtering apparatus will be briefly described with reference to FIG. The sputtering apparatus 10 shown in FIG. 4 is a bipolar sputtering apparatus, in which one of two flat plates is used as a target (cathode) 12 to be sputtered and the other flat plate is used as a substrate 14 for film formation.
As a substrate holder 16. Reference numeral 18 denotes an electrode for applying a high-frequency voltage to the target 12.

Although not clear from FIG. 4, the target 12, the electrode 18
The substrate holder 16 has a disk shape. Target 12
Are adjacent to each other, and are arranged so as to surround the other columnar magnet 22. A dashed line 24 indicates a container that houses the illustrated device, and a device for evacuating the inside of the container, a target electrode, an inert gas supply source such as argon gas, a vacuum gauge, and the like are provided outside the container 24. ing. In addition, 26
Denotes an inert gas ion, 28 denotes plasma, 30 denotes sputtered atoms, and 32 denotes a shutter.

The sputtering device using the magnetron mode is the fourth type.
Various proposals have been made in addition to the illustrated apparatus. However, this type of conventional device has the following disadvantages.

That is, in the conventional magnetron mode sputtering apparatus, the magnetic field distribution on the target surface is not uniform, so that the plasma intensity on the target surface is not uniform. In other words, the use efficiency of the target is extremely poor due to uneven wear of the target surface. For example, the use efficiency is about 10% to about 30%.
% (Volume ratio). Furthermore, when the target is a soft magnetic material (for example, iron), magnetic flux leakage does not easily occur. However, once the target starts to be worn, the magnetic flux is increasingly concentrated on the thinned consumable portion, and the thickness of the target is locally reduced. There is a problem that the consumption point becomes funnel-shaped and the use efficiency is extremely reduced. This situation is shown in FIG. 5 and FIG.

FIG. 5 is a simplified perspective view of the target 12 of FIG. 4, wherein the target 12 has a V-shaped groove eroded non-uniformly and annularly.
40 is shown. This groove 40 is formed in the annular permanent magnet 20 (fourth
(Fig.) Due to the magnetic flux leaking outside. Due to the uneven consumption of the target surface, the use efficiency of the target is extremely limited as described above. FIG. 6 is a view showing a cross section passing through the center of the target 12 in FIG.

In order to eliminate such defects, there has been conventionally proposed an apparatus for moving a magnet disposed in the vicinity of the target so that the target is consumed as uniformly as possible (for example, Japanese Patent Application Laid-Open No. 61-69964; JP-A-61-147873, JP-A-6-147873
2-7854). However, even with these methods, the target use efficiency is at most about 40% (volume ratio), and since the magnetic circuit is moved, there is a problem in the complexity and reliability of the apparatus. Further, when the target is a magnetic material, a method has been proposed in which slits are provided in the vertical and horizontal directions over the entire surface of the target to prevent the leakage magnetic flux from being concentrated at one place. Is about 30%, and the production cost is high.

In order to solve such a problem, the applicant of the present application has previously proposed a sputtering apparatus using a dipole ring type magnetic circuit (Japanese Patent Application No. 2-31093 filed on February 12, 1990).
And 2-31094).

Before describing the dipole ring type magnetic circuit directly related to the present invention, it will be explained why RF sputtering and application of a horizontal uniform magnetic field uniformize the surface consumption of the target and increase the deposition rate. In this specification, the term “horizontal uniform magnetic field” refers to a uniform magnetic field parallel to the surface of a target.

When a horizontal uniform magnetic field is applied near the target surface,
The electrons of the inert gas discharged by the direct current or the high frequency voltage move so as to cross the magnetic flux. In DC sputtering, electrons in the plasma move in one direction, so that the plasma generation is biased toward the end of the target, and even if a horizontal uniform magnetic field is applied, the consumption of the target is not uniform. However, in RF sputtering, plasma is generated by a high-frequency voltage, so that a uniform plasma is generated on the target surface by a horizontal uniform magnetic field. That is, the target surface is uniformly consumed. A horizontal uniform magnetic field generated by a dipole ring type magnetic circuit to be described later is a method in which a magnetic field is applied from the back side of the target 12 (above the target 12 (on the drawing)) (FIG. 4).
Since a horizontal uniform magnetic field can be applied to the surface of the target 12 as compared with the method described above, the film forming speed is equal to or higher than that of DC magnetron sputtering.

Next, a dipole ring type magnetic circuit directly related to the present invention will be described with reference to FIG.

FIG. 7 shows a dipole ring type magnetic circuit 50 and a target 12 (the same as in FIG. 2), and the other parts are, for example, those of FIG.
The illustration is omitted because it is the same as the conventional example shown in the figure. That is, in the apparatus shown in FIG. 4, a dipole ring type magnetic circuit 50 (FIG. 7) may be arranged so as to surround the periphery of the target 12.

FIG. 7 will be described in more detail. Dipole ring type magnetic circuit (hereinafter sometimes simply referred to as magnetic circuit) 50
Is an arrangement of eight anisotropic permanent magnets (anisotropic segment permanent magnets) 52a to 52h in a ring,
It is supported by 54 and a plurality of segment magnet adjusters 56. The adjustment tool 56 moves the corresponding segment magnet in the radial direction of the magnetic circuit 50 to adjust the magnetic field. In addition, in order to make the drawing easy to see, the numbers of the adjusting tools 56 are not given to all. Arrows in the segment permanent magnets 52a to 52h indicate the magnetization directions of the magnets. The magnetization direction of the segment magnet differs for each segment, and the magnetization direction makes two rotations during one round of the ring. Side (segment permanent magnet
52a and 52e) are referred to as a dipole ring type because two poles, an N pole and an S pole, appear. That is, the segment permanent magnets 52a and 52e are segment permanent magnets at the pole positions. An outline arrow 58 indicates the magnetization direction of the uniform magnetic field formed inside the magnetic circuit 50.

The advantage of the dipole ring type magnetic circuit is that the length of the ring in the direction of the central axis is increased (that is, the length of the segment permanent magnet in the direction of the central axis (FIG. 8)) is increased, or
The purpose is to easily adjust the uniform magnetic field generation space by using a plurality of rings. The number of segment permanent magnets may be an even number of four or more. Generally, the greater the number of segment permanent magnets, the better the magnetic field uniformity,
Practically, it is manufactured between 8 and 16. Further, the segment permanent magnets may be respectively held by back yokes (not shown). The target 12 is installed in the magnetic circuit 50 and is usually located at the center of the height of the magnetic circuit (height along the central axis). By moving the position of the target 12 with respect to the magnetic circuit along the central axis, the intensity of the magnetic field on the surface of the target 12 can be adjusted.

As described above, in the magnetron sputtering, the inert gas ions are restrained by the magnetic flux generated on the target surface, so that the magnetic flux intensity and the magnetic field uniformity on the target surface are important. The better the uniformity of the horizontal magnetic field, the better,
Practically, it may be 5% or less. For example, when the magnetic field strength at a height of 3 mm above the target surface is 50 G (Gauss) or less, the film forming speed becomes slow. Therefore, a magnetic field exceeding 50 G is required.
Generally, a magnetic field of about 300 G is preferable. That is, as the magnetic field increases, the deposition rate increases, but when the magnetic field is too strong, the discharge conditions become severe.

By the way, the lengths of the respective segment permanent magnets along the central axis (the axis perpendicular to the paper surface in FIG. 7) of the dipole ring type magnetic circuit shown in FIG. 7 are all equal. FIG.
FIG. 8 is a cross-sectional view taken along a plane including line AB in FIG. 7;
This shows that the lengths of the respective segment permanent magnets along the central axis (the axis parallel to the paper surface in FIG. 8) of the dipole ring type magnetic circuit are equal (however, the segment permanent magnets 52
b, 52c, 52d are not shown).

As described above, since the lengths of the respective segment permanent magnets of the dipole ring type magnetic circuit along the central axis are equal, there are the following problems. That is, when the target is a soft magnetic material such as iron, a magnetic flux converging action occurs inside the target, so that the horizontal magnetic field intensity is not uniform on the target surface. This situation is schematically shown in FIG.

As shown in FIG. 9, the magnetic flux from the upper and lower portions of the segment permanent magnet 52a at the pole position (N pole) is attracted to the soft magnetic target 12, while at the other pole position (S pole). The segment permanent magnets 52e draw the magnetic flux in the target 12 upward and downward. Therefore, in the peripheral portion of the target 12 near the pole position permanent magnet, the horizontal component of the magnetic field increases, and conversely, the magnetic flux in the target at this portion decreases.
That is, since the magnetic field near the pole position on the surface of the target 12 is not uniform, the rate of increase in the use efficiency of the target has not been sufficiently satisfied.

[Object of the Invention] An object of the present invention is to make the shape of a cross section in a direction perpendicular to the central axis of a dipole ring type magnetic circuit elliptical, and to set the distance between a segment permanent magnet located at a pole position and a target to another segment permanent magnet. An object of the present invention is to provide a sputtering apparatus which is longer than the distance to the target and solves the above-mentioned disadvantages.

[Means and Actions for Solving the Problems] In the present invention, a thin film is formed on a surface of a substrate by emitting sample atoms into a vacuum from a surface of a target to which a high-frequency voltage is applied by magnetron sputtering using a dipole ring magnetic circuit. In the forming apparatus: a cross section in a direction perpendicular to a central axis of the dipole ring type magnetic circuit is substantially elliptical, and a pole position among a plurality of segment permanent magnets constituting the dipole ring type magnetic circuit. Wherein the magnetization direction of the segment permanent magnet is aligned with the major axis direction of the elliptical shape.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

1 to 3, the same parts as those shown in FIGS. 7 to 9 are denoted by the same reference numerals. The description of the parts already described in FIGS. 1 to 3 may be omitted.

FIG. 1 shows a dipole ring type magnetic circuit 5 according to the present invention.
FIG. 3 is a side view as viewed from the direction of a central axis 0 ′ (see FIG. 2). The magnetic circuit shown in FIG. 1 is used, for example, by being incorporated in the conventional sputtering apparatus shown in FIG. Figure 2 shows the first
It is sectional drawing cut | disconnected by the plane containing line CD of the figure.

As is apparent from FIG. 1, the cross section of the dipole ring type magnetic circuit 50 'in the direction perpendicular to the central axis (see FIG. 2) is substantially elliptical, and a plurality of dipole ring type magnetic circuits 50' are formed. Each of the segment permanent magnets 52a to 52h is provided inside a back yoke 62 having an elliptical cross section.
As in the case of FIG. 7, the adjuster 56 is for adjusting the magnetic field by moving the corresponding segment magnet forward or backward in the direction of the central axis of the magnetic circuit 50 '.

As shown in FIG. 1, a dipole ring type magnetic circuit 5
Of the plurality of segment permanent magnets 52a to 52h constituting 0 ', the magnetization directions of the segment permanent magnets 52a and 52e at the pole positions match the major axis direction of the ellipse.

Thus, the segment magnet 52 at the pole position of the magnetic circuit 50 '
By making the magnetization directions of a and 52e coincide with the major axis direction of the ellipse, as shown in FIG. 3, the convergence angle of the target 12 near the pole position magnet can be reduced. In other words, by moving the segment permanent magnet at the pole position away from the target 12, the magnetic flux focusing on the target 12 is reduced, so that the target 12 is uniformly saturated. Therefore, a uniform horizontal magnetic field intensity can be obtained on the target surface.

According to the present invention, a uniform horizontal magnetic field can be obtained in any case of a non-magnetic target and a ferromagnetic target, so that a thick film target can be used. This means
This is very advantageous from the viewpoint of the operating efficiency of the sputtering apparatus and the efficiency of using the target.

[Effects of the Invention] As described above, according to the present invention, it is possible to generate a uniform horizontal magnetic field particularly on the surface of a soft magnetic target, so that the use efficiency of the target and the operation efficiency of the apparatus are dramatically increased. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a dipole ring type magnetic circuit for a sputtering apparatus according to the present invention, and FIG. 2 is a line CD of FIG.
FIG. 3 is a cross-sectional view for explaining the present invention (corresponding to FIG. 2), FIG. 4 is a diagram for explaining a conventional sputtering apparatus, and FIGS. FIG. 7 is a schematic side view of a conventional dipole ring type magnetic circuit, FIG. 8 is a cross-sectional view cut along a plane including line AB in FIG. 7, and FIG. FIG. 9 is a cross-sectional view (corresponding to FIG. 8) for explaining a conventional example. In the figure, 12 is a target, 50 'is a dipole magnetic circuit,
52a 'and 52e' are segment permanent magnets at the pole positions of the dipole ring type magnetic circuit, 52b, 52c, 52d, 52f, 52g and 52, respectively.
h indicates the segment permanent magnets located at positions other than the pole positions.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 14 / 35,14 / 34

Claims (2)

(57) [Claims] An apparatus for forming a thin film on a surface of a substrate by emitting sample atoms into a vacuum by magnetron sputtering from a surface of a target to which a high-frequency voltage is applied using a dipole ring type magnetic circuit. The shape of the cross section in the direction perpendicular to the central axis of the circuit is substantially elliptical, and among the plurality of segment permanent magnets constituting the dipole ring type magnetic circuit, the magnetization direction of the segment permanent magnet at the pole position is A sputter apparatus using a dipole ring type magnetic circuit, which coincides with a major axis direction of an elliptical shape. 2. The sputtering apparatus according to claim 1, wherein said target is a soft magnetic material.