JPH03257159A - Sputtering device formed by using dipole ring type magnetic circuit - Google Patents

Abstract

PURPOSE:To generate uniform horizontal magnetic fields on a target surface and to enhance the using efficiency of the target and the operating efficiency of the device by forming the yokes in the polar positions among the yokes for converging magnetic fluxes provided in segment permanent magnets to the thickness smaller than the thickness of the other yokes. CONSTITUTION:The respective yokes 60a to 60h for converging the magnetic fluxes are provided on the other magnets 52 exclusive of the magnets 52c and 52g among the plural segment permanent magnets 52a to 52h constituting the dipole ring type magnetic circuit 50'. The yokes 60a and 60e provided in the magnets 52a and 52e existing in the polar positions are formed to the thickness smaller than the thickness of the other yokes 60, by which the distance between the yokes 60 and the peripheral part of the target 12 is increased. The converging angle of the peripheral part near the magnets in the polar positions of the target 12 is, therefore, decreased. The target consisting of a soft magnetic material is uniformly satd. in this way and the uniform horizontal magnetic field intensity is obtd. on the target surface.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sputtering apparatus, and in particular, the present invention relates to a sputtering apparatus that sputters sample atoms in a vacuum by magnetron sputtering using a dipole ring type magnetic circuit from the surface of a target to which a high frequency voltage is applied. The present invention relates to a sputtering device that forms a thin film on the surface of a substrate by emitting water.

The present invention is suitable when a soft magnetic material such as iron is used as a target.

[Prior Art] As is well known, sputtering apparatuses are widely used for thin film production in the electronic and electrical fields. Sputtering is roughly divided into two types: DC sputtering, which is performed by applying a direct current voltage to a target, and RF sputtering, which is performed by applying a high frequency voltage to the target. Furthermore, this D
C and RF sputtering are classified into conventional mode and magnetron mode, respectively. In other words, a total of four types of sputtering are known.

Of these four types of sputtering, magnetron mode applies a magnetic field to the target and confines the plasma generated by applying a high voltage to an inert gas within the magnetic field, thereby increasing sputtering efficiency and increasing the deposition rate. It is possible to increase the speed and suppress the temperature rise of the substrate on which the thin film is formed. For this reason, when mass production is aimed at, magnetron mode is usually adopted for both DC and RF sputtering.

An example of a conventional sputtering apparatus will be briefly described with reference to FIG. The sputtering apparatus 1110 shown in FIG. 4 is a two-pole sputtering apparatus, in which one of two flat plates is used as a sputtering target (cathode) 12, and the other flat plate is used as a substrate holder 16 that holds a substrate 14 for film formation. do. Reference number 18 is an electrode for applying a high frequency voltage to the target 12.

Although it is not clear from FIG. 4, the target 12 and the electrode 1
8 and the substrate holder 16 each have a disk shape. The magnet 20 adjacent to the target 12 is annular and is arranged to surround other cylindrical magnets 22. A broken line 24 indicates a container in which the illustrated device is housed, 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, etc. are provided on the outside of the container 24. ing. Note that 26 is an inert gas ion, 28 is a plasma, 30 is a sputtered atom, and 32 is a shutter.

Various sputtering apparatuses using the magnetron mode have been proposed in addition to the apparatus shown in FIG. However, this type of conventional device has the following drawbacks.

In other words, in conventional magnetron mode sputtering equipment,
Since the magnetic field distribution on the target surface is not uniform, 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 consumption of the surface of the target, for example, the use efficiency ranges from about 10% to about 30%.
% (volume ratio). Furthermore, magnetic flux leakage is less likely to occur when the target is made of soft magnetic material (e.g. iron), but once the target begins to wear out, the magnetic flux will concentrate more and more at the thinner worn parts, causing the target to become thinner locally. There was a problem in that the consumption rate decreased, and the consumable area became funnel-shaped, resulting in an extremely low usage efficiency. This situation is shown in FIGS. 5 and 6.

FIG. 5 is a simplified perspective view of target 12 of FIG. 4, showing target 12 having an annular, non-uniform erosion groove 40. FIG. This groove 40 is connected to the annular permanent magnet 20 (
This is caused by magnetic flux leaking to the outside (Fig. 4). Due to this non-uniform wear of the target surface, the efficiency of use of the target is extremely limited as described above. Incidentally, FIG. 6 is a diagram showing a cross section passing through the center of the target 12 in FIG. 5.

In order to eliminate such drawbacks, devices have been proposed in the past that try to wear out the target as uniformly as possible by moving a magnet placed near the target (for example, Japanese Patent Laid-Open No. 61-69964, Kaisho 61-14787
No. 3, JP-A-62-7854). However, even with these methods, the target usage efficiency is at most about 40% (volume ratio), and since the magnetic circuit is moved, there are problems with the complexity and reliability of the device. Furthermore, when the target is a magnetic material, a method has been proposed in which slits are made in the vertical and horizontal directions over the entire surface of the target to prevent leakage magnetic flux from concentrating in one place, but this method reduces the efficiency of target usage. is 3
However, there was a problem that the production cost was high.

In order to solve such problems, the applicant for the patent of this application previously proposed a sputtering device using a dipole ring type magnetic circuit (patent IJi (1) filed on February 12, 1990).
) and (2)).

Before describing the dipole ring type magnetic circuit that is directly related to the present invention, it will be explained why RF sputtering and application of a horizontal-like magnetic field make the surface wear of the target uniform and increase the deposition rate. Note that in this specification, a horizontal-like magnetic field refers to a uniform magnetic field in a direction parallel to the surface of the target.

When a horizontal-like magnetic field is applied near the target surface, electrons of the inert gas discharged by direct current or high frequency voltage move across the magnetic flux. In DC sputtering, electrons in the plasma move in one direction, so plasma generation is biased toward the edge of the target, and even if a horizontal magnetic field is applied, target consumption is not uniform. However, in RF sputtering, plasma is generated by high frequency voltage, so
A horizontal-like magnetic field generates a uniform plasma on the target surface. In other words, the target surface is uniformly worn away. A horizontal-like magnetic field generated by a dipole ring type magnetic circuit, which will be described later, is generated on the back side of the target 12 (target 1
Compared to the method (Fig. 4) in which the magnetic field is applied from the upper side of the target 12 (on the drawing), a horizontal magnetic field can be applied to the surface of the target 12, so the film formation speed is equal to or higher than that of DC magnetron sputtering. Become.

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

FIG. 7 shows a dipole ring type magnetic circuit 50 and a target 12 (same as in FIG. 2), and other parts are the same as, for example, the conventional example shown in FIG. 4, so illustrations are omitted.

That is, in the apparatus shown in FIG. 4, a dipole ring type magnetic circuit 50 (seventh
Figure) should be placed.

FIG. 7 will be explained in more detail. Dipole ring type magnetic circuit (hereinafter sometimes simply referred to as magnetic circuit) 50
Eight anisotropic permanent magnets (anisotropic segment permanent magnets) 52a to 52h are arranged in a ring shape, and are supported by a frame (ring yoke) 54 and a plurality of segment magnet adjusters 56.

The adjusting tool 56 moves the corresponding segment magnet in the radial direction of the magnetic circuit 50 to adjust the magnetic field. Note that, in order to make the drawing easier to read, all the adjusting tools 56 are not numbered. The arrows in the segment permanent magnets 52a to 52h each indicate the magnetization direction of the magnet. The magnetization direction of the segment magnet is different for each segment, and the magnetization direction rotates twice during one rotation around the ring. It is called a dipole ring type because two poles, an N pole and an S pole, appear on the side surfaces (segment permanent magnets 52a and 52e). That is, the segmented permanent magnets 52a and 52e are segmented permanent magnets at pole positions. A white 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 central axis direction can be increased (that is, the length of the segment permanent magnet can be extended in the central axis direction (Fig. 8)), or that multiple rings can be used. The objective is to facilitate the adjustment of a uniform magnetic field generation space. The number of segment permanent magnets may be an even number of 4 or more. - Although the magnetic field homogeneity improves as the number of segment permanent magnets increases, practically, between 8 and 16 segment permanent magnets are manufactured. Furthermore, there are cases where the segment permanent magnets are each held by a back yoke, but this is omitted in FIG. 7. The target 12 is placed within the magnetic circuit 50 and is typically placed at the center of the height of the magnetic circuit (height along the central axis). By moving the position of the target 12 relative to the magnetic circuit along the central axis, the magnetic field strength on the surface of the target 12 can be adjusted.

As mentioned above, in magnetron sputtering, inert gas ions are restrained by the magnetic flux generated on the target surface, so the magnetic flux strength and magnetic field uniformity on the target surface are important. The better the uniformity of the horizontal magnetic field, the better, but practically it is sufficient if it is 5% or less. For example, if the magnetic field strength at a height of 3 mm above the target surface is 50 G (Gauss) or less, the film formation rate will be slow, so a magnetic field exceeding 50 G is required. -Magnetic field of about 300G is preferable.

That is, the stronger the magnetic field, the higher the film formation rate, but if the magnetic field is too strong, there is a problem that the discharge conditions become severe.

Incidentally, the lengths of the segment permanent magnets along the central axis (the axis perpendicular to the plane of paper in FIG. 7) of the dipole ring type magnetic circuit shown in FIG. 7 are all equal. FIG. 8 is a cross-sectional view taken along a plane including line A-B in FIG. (However, segment permanent magnet 52
b.

52c, 52d are not shown).

As described above, since the lengths along the central axis of each segment of the permanent magnet in the dipole ring type magnetic circuit are equal, the following problem occurs. That is, when the target is a soft magnetic material such as iron, the horizontal magnetic field strength is not uniform on the target surface because a magnetic flux is focused inside the target. This situation is schematically shown in FIG.

As shown in FIG. 9, the magnetic flux from the upper and lower parts of the segment permanent magnet 52a at the pole position fit (N pole) is drawn to the soft magnetic target 12, while the magnetic flux from the other pole position (S pole) Certain segment permanent magnets 52e draw the magnetic flux in the target 12 to the top and bottom. Therefore, target 1
In the peripheral area near the second pole position permanent magnet, the horizontal component of the magnetic field increases, and conversely, the magnetic flux within the target in this area decreases. In other words, since the magnetic field near the pole position on the surface of the target 12 is not uniform, the rate of increase in target usage efficiency is not sufficiently satisfactory.

[Object of the Invention] An object of the present invention is to provide a magnetic flux focusing yoke on two segment permanent magnets at the pole positions of a dipole ring type magnetic circuit, and to reduce the thickness of the magnetic flux focusing yokes of the segment permanent magnets at the pole positions. It is an object of the present invention to provide a sputtering apparatus which solves the above-mentioned conventional drawbacks by making the thickness of the magnetic flux focusing yoke provided on other segment permanent magnets thinner than that of the other segment permanent magnets.

[Means and effects for solving problem R] The present invention emits sample atoms into a vacuum by magnetron sputtering using a dipole ring type magnetic circuit from the surface of a target to which a high frequency voltage is applied, thereby forming a thin film on the surface of a substrate. In a device for forming: Among the plurality of segmented permanent magnets constituting the dipole ring type magnetic circuit, the plurality of segmented permanent magnets excluding the segmented permanent magnet magnetized in the opposite direction to the magnetization direction of the segmented permanent magnet at the pole position. A dipole characterized in that the magnet is provided with a magnetic flux focusing yoke, and the thickness of the magnetic flux focusing yoke of the segment permanent magnet at the pole position is made thinner than the thickness of the magnetic flux focusing yoke provided on the other segment permanent magnets. This is a sputtering device that uses a ring-shaped magnetic circuit.

[Example] The present invention will be described in detail below with reference to FIGS. 1 to 3.

In FIGS. 1 to 3, the same parts as those shown in FIGS. 7 to 9 described above are given the same reference numerals. Descriptions of parts already described in FIGS. 1 to 3 may be omitted.

FIG. 1 shows a dipole ring type magnetic circuit 50 according to the present invention.
FIG. 7 is a side view seen from the direction of the central axis (see FIG. 2) of FIG. The magnetic circuit shown in FIG. 1 is used by being incorporated into the conventional sputtering apparatus shown in FIG. 4, for example. FIG. 2 is a sectional view taken along a plane including line CD in FIG. 1. .

As shown in FIG. 1, a dipole ring type magnetic circuit 50
A plurality of segment permanent magnets 52a to 52 configuring '
A magnetic flux focusing yoke 60 is attached to each of the segment permanent magnets other than the segment permanent magnets 52C and 52g in h.
a, 60b, 60d.

60d, 60e, 60f and 60h are provided.

The reason why the segment permanent magnets 52c and 52g are not provided with a magnetic flux focusing yoke is because these magnets do not emit magnetic flux into the magnetic circuit, so the magnetic flux focusing yoke is unnecessary. Reference number 62 is a back yoke that supports the segment permanent magnets.

As shown in FIGS. 1 and 2, the respective thicknesses of the magnetic flux focusing yokes 60a and 62e provided on the segment permanent magnets 52a' and 52e' at the pole positions (the central axis of the magnetic circuit (see FIG. 2) ) and the length in the perpendicular direction) are made thinner than the thickness of other magnetic flux focusing yokes.

By reducing the thickness of the magnetic flux focusing yokes 60a and 60e provided on the segment magnets at the pole positions in this manner, the distance between the magnetic flux focusing yokes and the target peripheral area is increased. Therefore, as shown in FIG. 3, the focusing angle of the peripheral portion of the target 12 near the pole position magnet can be reduced. By doing so, the soft magnetic target is uniformly saturated and a uniform horizontal magnetic field strength can be obtained on the target surface.

In the above description, only the thickness of the magnetic flux focusing yoke provided at the pole position is thin, and the thickness of the magnetic flux focusing yoke provided on the other segment permanent magnets is the same. However, if the number of segment permanent magnets is set to 16, for example,
The thickness of the magnetic flux focusing yoke provided on the pole position magnet is made the thinnest, and the thickness of the magnetic flux focusing yoke provided on the other segment permanent magnets is increased in order as the distance from the pole position magnet yoke increases. Good too. Such a configuration can generate a good homogeneous horizontal magnetic field on the target surface when discontinuities in magnetic flux flow occur between the segment magnets.

According to the present invention, a -like horizontal magnetic field can be obtained for both non-magnetic targets and ferromagnetic targets, so that thick-film targets can also be used. This is extremely advantageous in terms of operating efficiency of the sputtering apparatus and target usage efficiency.

[Effects of the Invention] As explained 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, thereby dramatically increasing the usage efficiency of the target and the operating efficiency of the device. be able to.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the present invention in detail, Fig. 2 is a sectional view taken along a plane including line C-D in Fig. 1, and Fig. 3 corresponds to Fig. 2 for explaining the present invention. 4 is a diagram for explaining a conventional sputtering apparatus, FIGS. 5 and 6 are diagrams for explaining conventional examples, and FIG. 7 is a diagram for explaining a conventional dipole ring type magnetic circuit. Figure 8 is the 7th figure.
9 is a cross-sectional view taken along a plane including 1iA-B in the figure, and FIG. 9 is a cross-sectional view corresponding to FIG. 8 for explaining the conventional example. In the figure, 12 is a target, 50' is a Goupole type magnetic circuit, 52a' and 52e' are segment permanent magnets located at the pole positions of the Gouypole ring type magnetic circuit, and 52b, 5
2c, 52d, 52f, 52g+ 52h are segment permanent magnets located at positions other than the pole positions, respectively; 60a, 60b, 6
0d, 60d, 60e, 60f, and 60h each indicate a magnetic flux focusing yoke. Figure 1

Claims (2)

[Claims] (1) In an apparatus that forms a thin film on the surface of a substrate by ejecting sample atoms into vacuum by magnetron sputtering using a dipole ring type magnetic circuit from the surface of a target to which a high frequency voltage is applied, the dipole ring type magnetic circuit described above is used. Among the plurality of segmented permanent magnets, a magnetic flux focusing yoke is provided on the plurality of segmented permanent magnets, excluding a segmented permanent magnet magnetized in a direction opposite to the magnetization direction of the segmented permanent magnet at the pole position, A sputtering device using a dipole ring type magnetic circuit characterized in that the thickness of a magnetic flux focusing yoke of one segment permanent magnet is made thinner than the thickness of a magnetic flux focusing yoke provided on another segment permanent magnet. (2) The sputtering apparatus according to claim 1, wherein the target is a soft magnetic material.