JPH08100257A - Magnetron sputtering apparatus and its method - Google Patents

Abstract

PURPOSE: To provide a magnetron sputtering device using an annular target which has high efficiency of utilizing the target and is less changed in its film thickness distribution with lapse of time. CONSTITUTION: This magnetron sputtering apparatus has the annular flat plate target 2 and is arranged with magnets 33, 31 respectively having the same polarity on the front surface side and rear surface side of the target 2 along the inner peripheral edge of the target 2 and is arranged with magnets 34, 32 respectively having the same polarity on the front surface side and rear surface side of the target 2 along the outer peripheral edge of the target 2. The polarities of the magnets 33, 31 arranged along the inner periphery of the target 2 and the magnets 34, 32 arranged along the outer periphery of the target 2 are so determined as to have a reverse relation across the target 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron sputtering apparatus and method having a ring-shaped flat plate target.

[0002]

2. Description of the Related Art Magnetron sputtering technology is used as a technology for depositing a thin film on a substrate. The magnetron sputtering technique is capable of low-temperature and high-speed sputtering, and has become the mainstream in film forming apparatuses using the current sputtering technique. The magnetron sputtering technique forms a thin film by a method in which plasma is generated in the vicinity of a target by electric discharge or the like, particles of this plasma are caused to collide with the target, and the sputtered particles are attached to a substrate.

A conventional example will be described with reference to FIGS. 9, 10 and 11.

FIG. 9 is a sectional view of a cathode portion of a magnetron sputtering apparatus using a conventionally used ring-shaped flat plate target. Reference numeral 1 denotes a central axis, and the cathode portion has a rotationally symmetrical shape with respect to this axis. 2 is a ring-shaped flat plate target, 3 is a magnet arranged on the back surface of the target, and 4 is a target.
Is a magnetic field formed by the magnet 3. The cathode part having the above-mentioned structure was installed in the vacuum processing chamber so that the substrate and the target surface faced each other, and after the sputtering gas was introduced, power was supplied to the target 2 from a high voltage power supply for glow discharge, and it was trapped in the magnetic field lines. High-density plasma for sputtering is generated. When the ions in this plasma hit the target surface, the target atoms are sputtered,
A thin film is formed that adheres to the opposing surfaces of the substrate.
The plasma at this time is high in the region of 5. The target 2 is eroded by this plasma, and the erosion rate of the target is high in the vicinity of the region 5 where the plasma density is high, and the erosion rate of the target is locally high in the vicinity of 6.

FIG. 10 is a view showing an erosion shape when the target used in the above structure is used up to its utilization limit in a cross section including the central axis 1. However, the symmetrical portion with respect to the central axis is omitted. In FIG. 10, 9 is the shape of the target before sputtering, 10 is the sputtered portion, and 11 is the portion left unsputtered. As shown in FIG. 10, the vicinity of the point D is significantly eroded, and a V-shaped eroded surface is generated. When erosion of this shape occurs, the volume utilization efficiency of the target, that is, the ratio of the sputtered volume when the target is used up to the utilization limit in the volume of the target before sputtering (including the volume inside the inner circumference) It is about 20%, and there is a problem that an expensive target cannot be fully utilized. Further, when the erosion of this shape occurs, it causes a technical problem that the film forming speed and the film thickness distribution change with time.

Therefore, in order to solve these problems, JP-A-5-209266 and JP-A-5-179440 are used.
Techniques such as those described in Japanese Patent Publication have been devised. JP-A-5
The magnetron sputtering cathode described in JP-A-209266 has a magnetic flux on the back surface side of the target and a ferromagnetic material on the outer and inner circumferences of the target as in the conventional example shown in FIG. Is designed to extend beyond the surface of the target, so that the plasma density is more leveled and the erosion of the target is more leveled. FIG. 11 is a cross-sectional view showing the state of erosion at the limit of utilization of the target used for the magnetron sputtering cathode described in JP-A-5-209266. Similar to FIG. 10, 9 is the shape of the target before sputtering, 10 is the sputtered portion, and 11 is the remaining portion without being sputtered. It can be seen from FIG. 11 that the erosion progresses more uniformly than in the case of FIG. However, the erosion rate locally increases near point E.
At this time, the volume utilization efficiency including the inner volume of the inner circumference of the target is about 40%.

[0007]

According to the conventional method of arranging the magnet on the back surface of the target, a V-shaped erosion surface is formed as shown in FIG. As the erosion progresses in this shape, the target becomes locally thin, and when the thickness reaches a predetermined value or less, the target is used up, and the target cannot be used any more. However, there is a problem that an expensive target cannot be fully utilized because the target still has a sufficient material for forming a thin film. Further, if the erosion locally progresses rapidly, the distribution of sputtered particles changes with time, and the rate of attachment to the substrate changes, so even if the film thickness of the film formed on the substrate at the initial stage of erosion is uniform. However, there is a problem that the film thickness becomes non-uniform at the end of erosion.

In order to solve this problem, the above-mentioned Japanese Unexamined Patent Publication No.
Also in the technique described in Japanese Patent No. 209266, as shown in FIG. 11, local erosion still occurs near the point E, which reduces the utilization efficiency of the target and makes the thickness of the thin film attached to the substrate uneven. There is a problem.

FIG. 8 is a diagram showing the changes over time in the distribution of the film thickness produced on a substrate having an inner diameter of 40 mm and an outer diameter of 120 mm, as integrated power. The vertical axis represents the relative film thickness when the film thickness at the inner peripheral edge of the substrate is 1. The horizontal axis represents the distance from the center point. As shown in this figure, the conventional example has a problem that the film thickness distribution changes significantly with time.

The present invention solves these problems described above,
An object of the present invention is to provide a magnetron sputtering apparatus and method in which local erosion does not occur.

[0011]

In order to achieve the above-mentioned object, the present invention provides a magnetron sputtering apparatus having a ring-shaped flat plate target, in which the surface side of the target is located along the inner peripheral edge of the target. Magnets having the same polarity are arranged on the back surface side, magnets having the same polarity are arranged on the front surface side and the back surface side of the target at positions along the outer peripheral edge portion of the target, and along the inner circumference of the target. It is characterized in that the polarities of the magnets arranged as described above and the magnets arranged along the outer circumference of the target have an opposite relationship with the target sandwiched therebetween.

In order to achieve the above object, the present invention provides
In a magnetron sputtering method in which a thin film is formed on the substrate by generating plasma in the vicinity of a target of a ring-shaped flat plate arranged to face the substrate in a vacuum processing chamber, the position of the target along an inner peripheral edge of the target Magnets having the same polarity are arranged on the front surface side and the back surface side of the target, respectively, and magnets having the same polarity are arranged on the front surface side and the back surface side of the target at positions along the outer peripheral edge of the target, respectively. The magnets arranged along the inner circumference of the target and the magnets arranged along the outer circumference of the target are set so that the polarities thereof are opposite to each other across the target, and electric power is supplied to the target. , The magnet arranged along the inner circumference of the target, and the magnet arranged along the outer circumference of the target, on the target surface. Substantially in parallel and to generate a magnetic field having a uniform strength generally, evenly distributed approximately the plasma,
It is characterized in that a thin film is formed on the substrate.

[0013]

In the sputtering device, the direction in which particles are sputtered depends on the direction of the target surface. Therefore, when the angle between the target surface and the substrate surface changes with time due to erosion, the film thickness of the thin film formed on the substrate surface also changes with time. In the initial stage of erosion, the target is a flat surface and is arranged parallel to the substrate surface, so that the thickness of the thin film formed on the substrate surface is almost uniform. However, when the erosion progresses and the target surface becomes a curved surface, the thickness of the thin film formed on the substrate surface becomes uneven. Therefore, in order to keep the film thickness of the thin film formed on the substrate uniform, it is necessary to have an erosion surface close to a plane parallel to the target surface before erosion even if the erosion of the target progresses. As the erosion progresses in this way, the state of sputtering of the target hardly changes between the initial stage and when the target is used up to the limit of use, so that even if the erosion progresses, the change in the film thickness distribution with time decreases.

Further, if there is a portion where the erosion is locally fast, the target cannot be used when the film thickness of the portion where the erosion is fast becomes less than a predetermined value. Therefore,
In order to increase the target utilization rate, it is necessary to make the erosion progress as evenly as possible.

The magnetron sputtering technique is characterized in that the electromagnetic force due to the outer product of the velocity vector of the ion and the vector of the magnetic field causes the particles to rotate and the chances of the particles colliding with the target are increased. The chance that the ion collides with the target depends on the rotation period of the ion. The shorter the rotation period, that is, the faster the magnetic field moves and the faster the ion moves, the greater the chance of collision with the target. Therefore, the erosion should be perpendicular to the magnetic field and the electric field that moves the ions so that this cross product is maximized. Normal,
Since the electric field is formed perpendicular to the target surface, it is desirable to form the magnetic field parallel to the target surface. Further, since the rate of erosion of the target also depends on the plasma density, it is desirable to form a magnetic field with uniform intensity and in parallel with the target surface over the entire surface of the target in order to distribute the plasma as evenly as possible. .

The inventors of the present invention arrange magnets on the front surface and the back surface of the target along the inner circumference and the outer circumference of the target in order to form such a magnetic field. It was confirmed by computer simulation that by reversing the polarities, it is possible to form a magnetic field that is parallel to the target surface and has an almost uniform strength. FIG. 2 shows a state of magnetic field lines near the target cross section by computer simulation. As shown in this figure, a magnetic field that is nearly parallel to the target surface is formed on the target surface, and there is no great variation in the magnetic field strength, that is, the spacing between magnetic force lines. Therefore, in this magnetic field, the plasma is evenly distributed, and since the rotation period of the ions is also uniform, the erosion of the target proceeds uniformly.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION As an embodiment of the present invention, an inner diameter 32
A magnetron sputtering apparatus using a ring-shaped target having a size of mm, an outer diameter of 152 mm, and a thickness of 6 mm will be described as an example with reference to FIGS. 1 to 7 and 12.

First, FIG. 1 shows the configuration of a magnetron sputtering apparatus according to one embodiment of the present invention. FIG. 12 is a plan view of this device. A magnetron sputtering method according to another embodiment of the present invention will be described in the description of the above apparatus.

The structure of the cathode portion used here has a central axis 1
The ring-shaped target 2 is rotationally symmetric with respect to, and is surrounded by the outer circumference earth shield 12, and surrounds the inner circumference earth shield 11 that is inwardly surrounded. Reference numeral 35 denotes a yoke that supports the cathode portion, which is made of a magnetic material SS41 alloy and has a side plate (outer peripheral portion) 35b having an inner diameter of 180 mm, a thickness of 9 mm, and a height of 90 mm, and a bottom plate having a thickness of 15 mm,
Further, it has a cylindrical protrusion (center portion) 35a having a diameter of 10 mm and a height of 87.5 mm from the bottom plate. The target 2 is preferably made of, for example, an aluminum alloy or a dielectric material containing SiO ₂ . York 35
Is preferably composed of, for example, SUS400 stainless steel or a magnetic material of an iron-based material. In FIG.
Reference numeral 73 is a vacuum processing chamber, 72 is a substrate, and 70 is a power source for supplying high frequency power to an electrode which is a target back plate 21 described later. A direct current power source may be used instead of the high frequency power source.

A back plate 21 is in contact with the back surface of the target 2, and water is flowed through the gap 22 to cool the target 2. Illustration of the means for introducing and discharging water is omitted. Back plate 21
Is preferably composed of SUS304 when placing importance on the fact that the amount of adsorbed gas generated in the material is small, and SUS303 when placing emphasis on workability of the material.

The target 2 and the back plate 21 are made of an insulator 4.
It is insulated from the earth shields 11, 12 by 1, 42. The means 70 for applying a negative potential to the target 2 is the power source 70. The insulators 41, 42 are preferably made of alumina or polytetrafluoroethylene, for example. The earth shields 11 and 12 are made of, for example, a non-magnetic material such as copper, or a weak magnetic material SUS303 or 30.
4 is preferable. Also, earth shield 1
Water cooling passages 11a and 12a are provided at the lower portions of 1 and 12, respectively.
It is preferable that the ground shields 11 and 12 are cooled by forming cooling water through the passages 11a and 12a. The earth shields 11 and 12 are both grounded, but may be floating.

Inside the inner circumference earth shield 11, an inner diameter of 10 mm, a thickness of 5 mm and a height of 10 are made of a material having a residual magnetic flux density of 12.1 k Gauss and a holding force of 11.6 k Oersted.
A pair of ring-shaped permanent magnets 31 and 33 of mm are arranged, one permanent magnet 33 is located on the front surface side of the target 2, and the other permanent magnet 31 is located on the back surface side of the target 2. It has a north pole. Inside the outer circumference earth shield 12, a pair of ring-shaped permanent magnets 32 and 34 made of the same material as the inner circumference magnets 31 and 33 and having an inner diameter of 162 mm, a thickness of 9 mm, and a height of 5 mm are arranged. The magnet 34 is located on the front surface side of the target 2 and the other permanent magnet 32 is located on the back surface side of the target, and the inner circumference of the ring is the S pole. The permanent magnets 31 and 33 are, for example,
It is preferably composed of neodymium / iron / boron magnets. Further, each magnet 31, 33, 34, 32 is composed of a plurality of divided bodies 61, 60, respectively, as shown in FIG. Also, the magnets 31, 33, 34,
The polarity of 32 is opposite to that of FIG.
Instead of arranging the pole on the target side, the S pole may be arranged, and in the magnets 34 and 32, the N pole may be arranged on the target side instead of the S pole. In addition, the inner magnet 33,
The positions of the magnet 31 and the magnets 34, 32 on the outer peripheral side are relative to each other in FIG.
Are arranged so that the central axes along the horizontal direction in are substantially coincident with each other.

By selecting the strength of the permanent magnets 31, 32, 33 and 34, the shape of the rings of the magnets, the distance between the magnets and the shape of the yoke as described above, the direction of the magnetic field lines on the surface of the target is selected. It was possible to configure so that there are two points in the radial direction in which is parallel to the target surface.
Note that the direction in which the lines of magnetic force are parallel to the target surface is not limited to two, but may be one.

FIG. 2 is a drawing in which the lines of magnetic force in the magnet arrangement of the embodiment of FIG. 1 are drawn on a plane passing through the central axis 1. However, since the magnetic force lines are formed symmetrically with respect to the central axis, one side is not shown. When the target is arranged so that the target surface comes near AA ′ in this figure, there are points where the magnetic lines of force are parallel to the target surface near points B and C.

The cathode part constructed as described above operates in the magnetron sputtering apparatus as follows.

As in the conventional example, the cathode portion having the above structure is placed in the vacuum processing chamber 73 with an inner diameter of 40 mm and an outer diameter of 120 mm.
The substrate 72 is placed so that its central axis coincides with the target surface and faces the target surface at a distance of 35 mm. After introducing the sputtering gas,
When power is supplied to the target 2 from a high-voltage power source for glow discharge, which is an example of the power source 70, high-density plasma for sputtering trapped in the lines of magnetic force is generated. When the ions in the plasma hit the target surface, the target atoms are sputtered and adhere to the facing surfaces of the substrate to form a thin film.

FIG. 3 shows an erosion shape when the target is used up to the use limit, in a cross section including the central axis 1. However, illustration is omitted for a portion symmetrical with respect to the central axis. Reference numeral 51 is the shape of the target before sputtering, 52 is the sputtered portion, and 53 is the portion remaining without being sputtered. At this time, the volume utilization efficiency including the volume inside the inner circumference of the target is 57%, which is a significant improvement over the conventional volume utilization efficiency of 40%.

FIG. 4 shows the erosion shape when the target of FIG. 1 is used up to the limit of utilization, that is, the accumulated power, that is, the change over time. The horizontal axis is the distance from the central axis, the vertical axis is the erosion depth, and each curve shows the appearance of the erosion surface when each integrated power is applied. As shown in this figure, it can be seen that the entire surface of the target has been eroded from the initial film formation to the limit of utilization of the target, and the erosion shape has hardly changed. From this, it is understood that stable film formation is possible according to the present embodiment.
Further, as can be seen from this figure, according to the present embodiment, there is no point where the erosion locally progresses rapidly, so it can be seen that the utilization efficiency of the target also increases.

FIG. 5 shows the relationship between the maximum value of the erosion depth and the integrated power, that is, how the maximum value of the erosion depth changes with time. As can be seen from this figure, the erosion speed is almost constant, and the number of particles sputtered from the target per unit time hardly changes with time.

FIG. 6 is a diagram showing the relationship between the film forming rate and the integrated power when the target of FIG. In this figure, the film formation rate at the center point of the substrate is observed. From this figure, the rate of change of the film formation rate is 10%, which is a significant improvement over the rate of change of the conventional example of about 20%.

FIG. 7 shows the change over time in the film thickness distribution when the target of FIG. The vertical axis represents a relative film thickness distribution when the film thickness at the inner peripheral edge of the substrate is 1. As can be seen from this figure, the state of film formation hardly changes with time over the entire surface of the substrate. Furthermore, it can be seen that the film thickness distribution is even within 5% from the beginning to the end of the target. Also,
As compared with FIG. 8, which is a diagram showing the film thickness distribution of the conventional example, it can be seen that the problem of non-uniformity of the film thickness distribution due to the erosion of the target is significantly improved, and the film is stably formed.

Further, a moving device 71 such as a cylinder for moving the yoke 35 along the central axis 1 is arranged, and based on the result of FIG. 4, the yoke is moved up and down along the central axis 1 in FIG. The point where the direction of the lines of magnetic force is parallel to the surface of the target can be adjusted so that it is almost always located on the surface of the target. As a result, the target can be eroded over the entire surface, and a uniform thin film can be formed on the substrate.

The present invention is not limited to the embodiment of the ring-shaped target 2 as shown in FIGS. 1 and 12, but is also applicable to the elliptical ring-shaped target 102 as shown in FIG. can do. In this case, the target 102 may be composed of a plurality of divided bodies, and the magnets 131, 133, 134, and 132 corresponding to the magnets 31, 33, 34, and 32 of FIG. You may comprise from 160. In addition, in FIG. 13, 135, 135a, and 135b are 3 in FIG.
5, a yoke corresponding to 5, 35a, and 35b, a yoke central portion, and a yoke outer peripheral portion, respectively.

[0034]

As described above, according to the present invention, a stable and uniform thin film can be formed on a substrate even if the target is used up to its utilization limit. Further, the utilization efficiency of the expensive target is improved, and the waste is reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the invention.

FIG. 2 is a diagram showing a state of a magnetic field in the same embodiment.

FIG. 3 is a view showing an eroded surface at a usage limit of the target of the same embodiment.

FIG. 4 is a view showing a change with time of an eroded surface of the target of the same embodiment.

FIG. 5 is a view showing a change over time in the depth of erosion of the target of the same embodiment.

FIG. 6 is a view showing a change with time of a film forming rate of the substrate of the same embodiment.

FIG. 7 is a view showing a change over time in the distribution of the film thickness of the substrate of the same embodiment.

FIG. 8 is a diagram showing changes over time in the distribution of the film thickness of the substrate of the conventional example.

FIG. 9 is a diagram showing a configuration of a conventional example.

FIG. 10 is a diagram showing an eroded surface at the limit of utilization of the target of the conventional example.

FIG. 11 is a diagram showing an eroded surface at the limit of use of the target of the conventional example.

12 is a plan view of the magnetron sputtering apparatus according to the embodiment shown in FIG.

FIG. 13 is a plan view of a magnetron sputtering apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 1 central axis 2 target 31 magnets arranged on the inner peripheral back side 32 magnets arranged on the outer peripheral rear side 33 magnets arranged on the inner peripheral front side 34 magnet arranged on the outer peripheral front side

Claims (12)

[Claims] 1. A magnetron sputtering apparatus having a ring-shaped flat plate target, wherein magnets having the same polarity are arranged on the front surface side and the back surface side of the target at positions along the inner peripheral edge of the target, respectively. Magnets having the same polarity are arranged on the front surface side and the back surface side of the target at positions along the outer peripheral edge of the magnet, and the magnets arranged along the inner circumference of the target and the outer circumference of the target. A magnetron sputtering apparatus characterized in that the polarities of the magnets arranged are opposite to each other with a target interposed therebetween. 2. The magnetron sputtering according to claim 1, wherein the strength of each magnet is adjusted so that at least one point on the surface of the target where the direction of the magnetic field becomes parallel to the target surface exists in the radial direction of the target. apparatus. 3. The magnetron sputtering generation side of the magnets arranged along the inner circumference of the target is covered with a shield, and the magnetron sputtering generation side of the magnets arranged along the outer circumference of the target is covered with a shield. The magnetron sputtering apparatus according to claim 1, wherein both shields are insulated from the target and are grounded or floated. 4. The magnetron sputtering apparatus according to claim 3, wherein a water cooling passage is formed in the shield, and the shield is cooled by a water cooling method. 5. A yoke supporting the magnets arranged along the inner circumference of the target and the magnets arranged along the outer circumference of the target is movable along the central axis so as to be positionally adjustable with respect to the target. The magnetron sputtering apparatus according to claim 1, further comprising a moving device that is capable of moving the yoke along the central axis. 6. An electrode for supplying electric power to the target is disposed on the lower surface of the target, and a water cooling passage is formed in this electrode to cool the electrode by a water cooling method. The magnetron sputtering device according to any one of to 5. 7. A magnetron sputtering method in which a thin film is formed on a substrate by generating plasma in the vicinity of a target of a ring-shaped flat plate arranged to face the substrate in a vacuum processing chamber, wherein an inner peripheral edge of the target is formed. A magnet having the same polarity is disposed on the front surface side and the back surface side of the target along the positions, respectively, and a magnet having the same polarity on the front surface side and the back surface side of the target along the outer peripheral edge of the target, respectively. The target arranged along the inner circumference of the target and the magnets arranged along the outer circumference of the target such that the polarities thereof are opposite to each other across the target. Power is supplied to the target by the magnets arranged along the inner circumference of the target and the magnets arranged along the outer circumference of the target. By generating a magnetic field having a parallel and generally evenly strength generally the target surface, the plasma evenly distributed generally a magnetron sputtering method is characterized in that so as to form a thin film on the substrate. 8. The magnetron sputtering according to claim 7, wherein the strength of each magnet is adjusted so that at least one point on the surface of the target where the direction of the magnetic field is parallel to the target surface exists in the radial direction of the target. Method. 9. The magnetron sputtering generation side of the magnets arranged along the inner circumference of the target is covered with a shield, and the magnetron sputtering generation side of the magnets arranged along the outer circumference of the target is covered with a shield. 9. The magnetron sputtering method according to claim 7, wherein both shields are insulated from the target and are grounded or floated. 10. The magnetron sputtering method according to claim 9, wherein a water cooling passage is formed in the shield, and the shield is cooled by a water cooling method. 11. A yoke supporting a magnet arranged along an inner circumference of the target and a magnet arranged along an outer circumference of the target is movable along a central axis so as to be positionally adjustable with respect to the target. And a moving device for moving the yoke along the central axis.
11. The magnetron sputtering method according to any one of 10. 12. An electrode for supplying electric power to the target is disposed on the lower surface of the target, and a water cooling passage is formed in this electrode to cool the electrode by a water cooling method. The magnetron sputtering method according to any one of 1 to 11.