JPH03253565A - Sputtering device using dipole ring type magnetic circuit - Google Patents

Abstract

PURPOSE:To make improvement in the efficiency of using a target and the working efficiency of the device by setting the length in the central axial direction of the magnetic circuit of the segment permanent magnets existing in the polar positions of the magnetic circuit shorter than the length in the central axial direction of the other permanent magnets. CONSTITUTION:The length in the central axial direction of the magnetic circuit of the segment permanent magnets 52a', 52b' existing in the polar position of the dipole ring type magnetic circuit 50' is set shorter than the length in the central axial direction of the adjacent segment permanent magnets 52b, 52h, 52d, 52f. The converging angle in the peripheral part of the polar position magnets of the target 12 is decreased by this structure. The target consisting of a magnetic material is, therefore, uniformly satd. and a uniform horizontal magnetic field intensity is obtd. on the target surface. The use of the thick film target is enabled and the improvement in the working efficiency of the device is made.

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 10 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 for holding a substrate 14 for film formation. do. Reference number 18
is an electrode for applying a high frequency voltage to the target 12.

It is not clear from Fig. 4 that target 12, 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 usage efficiency of the target is extremely poor due to uneven consumption of the target surface, for example, the usage 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 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. is 3
However, there was a problem that the production cost was high.

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

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 it has two poles, an N pole and an S pole, 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. Generally, the greater the number of segment permanent magnets, the better the magnetic field uniformity, but in practice, between 8 and 16 segment permanent magnets are manufactured. Furthermore, each segment permanent magnet may be held by a back yoke (not shown). 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 described above, in magnetron sputtering, inert gas ions are restrained by the magnetic flux generated on the target surface, so the magnetic flux intensity 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 tnm 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. Generally, a 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 top and bottom 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). Segmented permanent magnets 52e draw magnetic flux in target 12 to the top and bottom. Therefore, in the peripheral part of the target 12 near the pole position permanent magnet, the horizontal component of the magnetic field increases, and conversely, the magnetic flux within the target in this part 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 the use efficiency of the target is not sufficiently satisfactory.

[Object of the Invention] The object of the present invention is to make the length of two segment permanent magnets located at the pole positions of a dipole ring type magnetic circuit shorter in the center axis direction than the length of the other segment permanent magnets in the center axis direction. It is an object of the present invention to provide a sputtering apparatus that solves the above-mentioned drawbacks.

[Means and effects for solving the problem] 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 the forming device: Among the plurality of segment permanent magnets constituting the dipole ring type magnetic circuit, the length of the segment permanent magnet located at the pole position in the central axis direction of the magnetic circuit is different from that of the other segment permanent magnet located at the pole position other than the pole position. This is a sputtering device that uses a dipole ring type magnetic circuit characterized by being shorter than the length of the segment permanent magnet in the central axis direction.

[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. 2 is a side view of 1, viewed from a direction perpendicular to its central axis (see Fig. 2). The magnetic circuit shown in FIG. 1 is used by being incorporated into the conventional sputtering apparatus shown in FIG. 4, for example. still,
FIG. 1 corresponds to FIG. 7. Figure 2 is line C-D in Figure 1.
FIG.

As shown in FIG. 2, a dipole ring type magnetic circuit 50
Segment permanent magnets 52a' and 52 at the pole position of
The length of the magnetic circuit e' in the central axis direction (in the direction parallel to the paper surface in Fig. 2) is determined by the length of each adjacent segment permanent magnet (5
2b, 52h) and (52d, 52f) in the central axis direction.

By shortening the length of the segment magnet at the pole position in the central axis direction in this manner, the focusing angle of the peripheral portion of the target 12 near the pole position magnet can be reduced, as shown in FIG. Therefore, the soft magnetic target is uniformly saturated, and a uniform horizontal magnetic field strength can be obtained on the target surface.

In the above explanation, the length of only the magnet at the pole position (the length in the direction of the center axis of the magnetic circuit) is shortened, and the length of the other segment permanent magnets in the direction of the center axis is set as shown in FIG. . However, the length of the pole position magnet may be the shortest, and the lengths of the other segment permanent magnets may be increased in order as they move away from the pole position magnet. 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 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 C-D in FIG. 1.
3 is a sectional view corresponding to FIG. 2 explaining the present invention, FIG. 4 is a diagram explaining a conventional sputtering apparatus, and FIGS. 5 and 6 are respectively related to conventional sputtering equipment. 7 is a schematic side view of a conventional dipole ring type magnetic circuit, FIG. 8 is a sectional view taken along a plane including line A-B in FIG. 7, and FIG. 9 is a conventional dipole ring type magnetic circuit. FIG. 8 is a sectional view corresponding to FIG. 8 for explaining an example. In the figure, 12 is a target, 50' is a dipole type magnetic circuit, 52a' and 52e' are segment permanent magnets located at the pole positions of the Guypole ring type magnetic circuit, and 52b, 5
2c, 52d, 52f, 52g, and 52h indicate segment permanent magnets located at positions other than the pole positions, respectively.

Claims (3)

[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, the length of the magnetic circuit of the segmented permanent magnet at the pole position in the central axis direction is shorter than the length of the other segmented permanent magnets located at positions other than the pole position. A sputtering device that uses a dipole ring type magnetic circuit. (2) The sputtering apparatus according to claim 1, wherein the length of each of the plurality of segment permanent magnets in the direction of the central axis increases as the distance from the segment magnet located at the pole position increases. (3) The sputtering apparatus according to claim 1 or 2, wherein the target is a soft magnetic material.