JP3720101B2 - Cathode electrode for magnetron sputtering - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cathode electrode for magnetron sputtering, and more particularly to a cathode electrode that can stably form a thin film with a uniform thickness and less particles on a substrate over a long period of time in a magnetron sputtering apparatus for forming a thin film.
[0002]
[Prior art]
Various types of electrode structures have been proposed in the conventional sputtering apparatus. Among them, magnetron type electrode structures are most frequently used industrially. The reason is that the deposition rate is high and the productivity is high. There are various types of conventional magnetron type electrodes. At present, a flat magnetron cathode electrode having a target having a planar shape is most useful industrially.
[0003]
In recent years, particularly for the production of liquid crystal display devices, it has been required to form a thin film with a uniform film thickness distribution on a large substrate having a large area. As such a sputtering apparatus, recently, a sputtering apparatus in which the substrate and the opposing electrode are stationary and the target consumption region is widened has been studied.
[0004]
In particular, focusing on the structure of the magnetron cathode electrode, in Japanese Patent Laid-Open Nos. 3-194298 and 5-239640, a magnet assembly composed of a plurality of magnet units is reciprocated with respect to a target. And a technique for improving the uniformity of the etching distribution of the target is disclosed.
[0005]
At present, the number of magnet units in the cathode electrode is five because it is the easiest to handle. In this case, the amplitude of the reciprocating motion is approximately half the width of the magnet unit. As an advantage of such a cathode electrode in which a plurality of magnet units reciprocate with a small amplitude, since sputtered atoms are incident substantially perpendicularly to the substrate, a method in which a single magnet unit is reciprocated with a large amplitude (inclined on the substrate). Compared to the increase in the number of incident sputtered atoms), the film quality of the film grown on the substrate is overwhelmingly good, and by finely adjusting the position of each magnet unit, the film thickness distribution uniformity can be improved on a large area substrate. It can be mentioned that good film formation is possible.
[0006]
[Problems to be solved by the invention]
Problems of the conventional sputtering apparatus will be described with reference to FIGS. FIG. 7 shows a cross-sectional structure of a main part of a sputtering apparatus having five magnet units. In this figure, only the basic configuration is shown so that the relative arrangement relationship of the target, the five magnet units, and the rectangular substrate can be understood, an Ar gas introduction mechanism, a vacuum exhaust mechanism, a substrate transport mechanism, a mechanism for water-cooling the target, The illustration of the reciprocating mechanism of the magnet assembly is omitted.
[0007]
The target 71 and the substrate 72 are disposed to face each other in a vacuum container (not shown). The target 71 is fixed on the back plate 73. At the position on the back surface of the back plate 73, a plurality of magnet units 74 for forming a tunnel-like and annular distribution of magnetic field lines on the surface of the target 71 are installed in parallel to each other. The planar shape of each magnet unit 74 is substantially rectangular, and a rod-shaped center magnet 74a (upper surface is, for example, S pole) at the center and an annular outer peripheral magnet (or peripheral magnet) 74b (upper surface is, for example, N pole) around it. The rectangular yoke 74c is installed on the back side of these magnets. As shown in the plan view of FIG. 8, these magnet units 74 are arranged so that the long side directions are parallel to each other. As a result, an annular plasma region is formed along the tunnel-like magnetic field lines on the target 71, and target atoms jumped out when ions generated by this plasma collide with the target surface are deposited on the opposing substrate 72. As a result, a thin film is formed.
[0008]
A thin film formed by using the sputtering apparatus as described above is used for manufacturing electronic components such as semiconductor devices and liquid crystal display devices. Here, the film thickness of the thin film formed on the substrate 72 is required to be very uniform. For example, the size of a substrate for a TFT (Thin Film Transister) liquid crystal display device is currently about 400 mm × 500 mm, and the variation in film thickness within this range must be ± 5% or less. In order to realize such a uniform film thickness distribution, as shown in FIG. 7, each magnet unit has a target surface corresponding to the location of each magnet unit adjacent to the magnet units at both ends, and the magnet unit. It is necessary to install such that the distance from the upper surface (hereinafter referred to as “T / M distance”) is larger than the T / M distance of other magnet units. The reason why such an arrangement is required is as follows.
[0009]
If the T / M distances of the magnet units 74 are all set to the same distance, as a film forming phenomenon, the film thickness at the center of the substrate is necessarily larger than the film thickness at the edge of the substrate. That is, the film thickness decreases at the edge of the substrate, and the required film thickness distribution uniformity cannot be ensured. In order to correct this and obtain a uniform film thickness distribution, it is necessary to make the T / M distance of the magnet unit at the position corresponding to the edge of the substrate smaller than the others. However, if only the T / M distance of the outermost magnet unit is shortened, the film thickness only at the substrate end tends to increase too much. Therefore, a configuration is adopted in which the T / M distance between the magnet units adjacent to the magnet units at both ends is appropriately increased. In this way, the optimal arrangement of the magnet units is an alphabetic W-shaped arrangement.
[0010]
However, when a thin film is manufactured over a long period of time by setting an appropriate magnet reciprocating motion amplitude (about half of the short width of the magnet unit) using a magnet assembly including a magnet unit having such an arrangement, The planar shape of the erosion part is as shown in FIG. A hatched portion 75 in FIG. 9 is a portion where the target 71 has been etched, that is, erosion has occurred. What is characteristic here is that the erosion width in the vertical direction (long side direction of the magnet unit) in FIG. 9 becomes small at the locations on the target corresponding to the magnet units adjacent to the magnet units at both ends, and is not locally The erosion part 76 is generated.
[0011]
In general, there is a considerable probability that sputtered atoms are scattered by collisions with gas molecules and return to the target. Therefore, when such a non-erosion portion 76 exists, film deposition occurs in the non-erosion portion 76 due to long-term use. The film deposited in this way is very unfavorable because it easily peels off and causes particles on the substrate. In addition, the target utilization rate indicating how effectively the target is used can be kept low.
[0012]
The above phenomenon occurs because of the magnetic field distribution of each magnet unit and the W-shaped arrangement of five magnet units. It is known that the center of the track type erosion part on the target coincides with the position where the component Bz perpendicular to the target surface of the magnetic field generated by the magnet unit becomes zero. In the normally used magnet unit arrangement as shown in FIG. 7, as the T / M distance increases, the width in the vertical direction (magnet unit long side direction) of the circular locus connecting the positions where Bz becomes zero decreases. . Accordingly, as shown in FIG. 7, the vertical width of the erosion part 75 of the target 71 is small at a position corresponding to two magnet units arranged so that the T / M distance is larger than that of other magnet units. As a result, as shown in FIG. 9, a non-erosion portion 76 is formed.
[0013]
It is clear that the non-erosion portion 76 shown in FIG. 9 disappears if the amplitude of the magnet reciprocation is further increased. However, in this case, there is a disadvantage that the good film thickness distribution uniformity, which is an advantage of the cathode electrode in which the plurality of magnet units as described above reciprocate with a small amplitude, is impaired.
[0014]
An object of the present invention is to solve the above problem, and in a magnetron sputtering apparatus, while maintaining good film thickness distribution uniformity, eliminating the occurrence of local non-erosion parts, and increasing the erosion area of the target as much as possible. It is an object of the present invention to provide a magnetron sputtering cathode electrode capable of forming a stable film without generating particles on a substrate over a long period of time.
[0015]
[Means and Actions for Solving the Problems]
In order to achieve the above object, the cathode electrode for magnetron sputtering according to the first aspect of the present invention (corresponding to claim 1) is a magnet unit having a long planar shape behind a rectangular target, and the long sides thereof are parallel to each other. A plurality of magnet devices (magnet assemblies) arranged so that each of the plurality of magnet units forms a tunnel-like magnetic field line on the target, and the magnet devices are configured to reciprocate, The T / M distance of the magnet unit adjacent to each of the magnet units at both ends among the plurality of magnet units is made larger than the T / M distance of the other magnet unit, and the length of the adjacent magnet unit in the long side direction Is configured to be longer than the length of the other magnet unit.
[0016]
In the first aspect of the present invention, the length in the long side direction of the adjacent magnet unit in which the T / M distance is increased as compared with the case of the other magnet unit is set longer than the length of the other magnet unit by a desired length. By increasing the length, the local non-erosion portion that has conventionally occurred in the target can be eliminated, and the width of the erosion portion on the target surface can be formed uniformly.
[0017]
A magnetron sputtering cathode electrode according to a second aspect of the present invention (corresponding to claim 2) is the magnetron sputtering cathode electrode according to the first aspect of the present invention, wherein the adjacent magnet unit is provided with a length adjusting mechanism that makes the length in the long side direction variable. Configured to provide. In the second aspect of the present invention, the lengths of the adjacent magnet units can be freely adjusted as necessary, and the utility becomes high by making them variable according to the situation.
[0018]
A cathode electrode for magnetron sputtering according to the third aspect of the present invention (corresponding to claim 3) is disposed behind the target, forms a tunnel-like magnetic field line on the target, and has a magnet unit having a long planar shape. Yes, the magnet unit is divided into an end and a center, and the end and the center are joined via a guide, and the length of the magnet unit is adjusted by changing the position of the end with respect to the center. Configured to provide a length adjusting mechanism.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.
[0020]
FIG. 1 is a longitudinal sectional view showing the configuration of the main part of a cathode electrode for magnetron sputtering which is an embodiment of the present invention.
[0021]
A cathode body (cathode body) 14 is attached to an opening 12 formed in the wall 11 constituting a part of the vacuum vessel via an insulating spacer 13, and a back plate 15 is attached to the upper part of the cathode body 14. The inside of the vacuum vessel is held in a required vacuum state by an evacuation mechanism (not shown), and is configured as a chamber for film-forming the loaded substrate. Part of the wall of the substrate processing chamber is formed by the cathode body 14 and the back plate 15, and the atmosphere side and the vacuum chamber side are separated from each other.
[0022]
A target 16 made of a predetermined material is bonded to the surface of the back plate 15 with a low melting point brazing material such as indium. A shield 17 is provided around the target 16 to prevent the portions other than the target from being etched. A water cooling jacket 18 for cooling the back plate 15 and the target 16 is provided on the atmosphere side of the back plate 15. In order to uniformly cool the entire back plate 15, a water channel 19 is provided throughout the water cooling jacket 18, cooling water is introduced from the water introduction pipe 20, and cooling after use from the water discharge pipe 21. The water is drained. Behind the water cooling jacket 18, two types of magnet units 22 a and 22 b having a structure to be described later are alternately arranged.
[0023]
As in the case of the conventional magnet unit shown in FIG. 8, the magnetic pole in each magnet unit is composed of a central magnetic pole (for example, the surface is an S pole) and an outer peripheral magnetic pole (also called a peripheral magnet: for example, the surface is an N pole). . The magnet units 22 a and 22 b are fixed on the magnet base 23. A magnet assembly (magnet device) is constituted by the magnet base 23 and the five magnet units 22a and 22b provided thereon. The magnet base 23 is preferably restrained by two guide rails 24 arranged in parallel so that the magnet assembly can reciprocate in the left-right direction in FIG.
[0024]
The magnet base 23 on which the five magnet units are mounted is connected to the rotating disk 28 via a coupling mechanism unit including a pin 25, an arm 26, and a pin 27. The rotating disk 28 is coupled to a motor 29, and is rotated by the rotation of the shaft of the motor 29 so that the magnet base 23 is swung left and right by the connecting mechanism portion. A plurality of holes for fixing the pin 27 are provided on the rotating disk 28, and the swing distance of the magnet base 23 can be changed by changing the installation position of the pin 27.
[0025]
The motor 29 is fixed to a cathode cover 30 that covers the entire cathode electrode. The cathode body 14, the back plate 15, the target 16, and the water cooling jacket 18 are electrically coupled to each other, and are insulated from other portions, and power is supplied to this portion from an external power supply 31. The external power supply 31 holds the cathode body 14 and the like at a predetermined potential.
[0026]
As shown in FIG. 1, by providing a step on the magnet base 23 in the magnet assembly, the magnet unit 22b adjacent to the magnet units at both ends has a T / M distance equal to that of the other magnet unit 22a. It is arranged to be larger than that. The T / M distance of the magnet unit 22b is set to an arbitrary distance at which the erosion portion can be formed uniformly in the target 16.
[0027]
FIG. 2 is a plan view of five magnet units, showing the form and arrangement of each magnet unit. Each of the magnet units 22a and 22b has a substantially rectangular planar shape, and includes the substantially rod-shaped center magnet 32 and the rectangular ring-shaped outer peripheral magnet 33 arranged around the magnet as described above. The long side direction of the magnet unit is orthogonal to the paper surface of FIG. 1, and the short side direction of the magnet unit coincides with the arrangement direction of the magnet units. As is apparent from FIG. 2, the structure of the magnet unit 22b adjacent to the magnet units at both ends of the five magnet units arranged is different from the structure of the other magnet unit 22a, and the long side direction of the magnet unit 22b is The length is longer than the length of the other magnet unit 22a.
[0028]
The structure of the end of the magnet unit 22a is shown in FIG. The magnet unit 22a is made of a central magnet 32 extending in the long side direction and having an end formed in a T shape, an outer peripheral magnet 33 arranged so as to surround the magnet, and a soft magnetic material for fixing these magnets. The yoke 34 is configured. This structure is the same as that used in the prior art.
[0029]
FIG. 4 shows the structure of the end of the magnet unit 22b, and FIG. 5 shows a cross section along the center line in the long side direction of the magnet unit 22b. The structure of the magnet unit 22b is basically similar to that of the magnet unit 22a, and includes a central magnet 42 corresponding to the central magnet 32, an outer peripheral magnet 43 corresponding to the outer peripheral magnet 33, and a yoke 44 corresponding to the yoke 34. The magnet unit 22b differs from the magnet unit 22a in that, as shown in FIGS. 2, 4, and 5, in the magnet unit 22b, both end portions (hereinafter referred to as “end portions”) 35 of the magnet unit 22b are magnet units. It has a structure separated from a central portion (hereinafter referred to as “central portion”) 36, and each end portion 35 is coupled to the central portion 36 via a guide 37. Accordingly, each of the central magnet 42, the outer peripheral magnet 43, and the yoke 44 is divided into both end portions and a central portion. The dimensions of the central magnet 42, the outer peripheral magnet 43, and the yoke 44 that are not separated from each other are the same as those of the central magnet 32, the outer peripheral magnet 33, and the yoke 34 of the magnet unit 22a. The magnet unit 22b corresponds to what is obtained by cutting the magnet unit 22a at two points.
[0030]
As shown in FIG. 5, one end of the guide 37 is fixed to the yoke 44 of the central portion 36. The yoke 44 of the end portion 35 has a fitting structure with the other end of the guide 37, and the entire end portion 35 can move in the left-right direction in FIG. 4 or FIG. A screw hole 38 is provided in the end surface of the yoke 44 of the end portion 35, and a long screw 39 is inserted into the screw hole 38. A protrusion 40 is formed at the tip of the long screw 39, and the protrusion 40 is fitted to the end of the guide 37 as shown in FIG.
[0031]
The long screw 39 has a structure that can freely rotate with respect to the guide 37, whereas the yoke 44 of the end portion 35 is screw-coupled to the long screw 39, so that the magnet unit is rotated by the rotation of the long screw 39. The entire end portion 35 of 22b can move in the left-right direction in FIG. Thereby, the entire length of the magnet unit 22 b can be adjusted to an arbitrary length by the rotation of the long screw 39. In this embodiment, the length is preferably adjusted to achieve the object.
[0032]
Since the structure of the magnet unit 22b is configured such that there is a gap between the central portion 36 and the two end portions 35 as described above, the magnetic field distribution on the surface of the target 16 is the magnetic field distribution of the magnet unit 22a. Of course, it will be changed. However, since the length of this gap is actually about 5 mm at the maximum, and is smaller than the T / M distance of 30 to 40 mm, the magnetic field distribution on the target surface does not change so much. Actually, even when the gap length is set to the maximum of 5 mm, it can be confirmed that a tunnel-like magnetic field line for forming magnetron plasma is formed at a location corresponding to the gap on the target surface.
[0033]
By setting the shape / arrangement of each magnet unit as described above, the following operation occurs. In order to realize a uniform film thickness distribution on the processing surface of the substrate facing the target 16, the T / M distances of the five magnet units 22a and 22b are adjusted, and the magnet units 22b adjacent to the magnet units at both ends are adjusted. The T / M distance is set to be larger than the T / M distances of other magnet units. In this case, the width of the erosion part in the long side direction of the magnet unit is reduced at the location on the target 16 corresponding to the magnet unit 22b. The reason is as described above in “Problems to be Solved by the Invention”.
[0034]
In the present embodiment, since the magnet unit 22b having the above-described structure is used at a position adjacent to the magnet units at both ends, the erosion width in the long side direction of the magnet unit is reduced at a position on the target 16 corresponding to the magnet unit 22b. The length of the magnet unit is extended corresponding to the minute. Thereby, the tendency for the erosion width to decrease can be canceled, and the erosion width in the long side direction of the magnet unit can be made uniform over the entire surface of the target 16.
[0035]
The shape of the erosion part of the target 16 after a thin film is produced over a long period of time by using a cathode electrode having the magnet units 22a and 22b having the structure and arrangement as described above, setting an appropriate magnet reciprocation amplitude Is shown in FIG. A hatched portion 41 in FIG. 6 is a portion where the target 16 has been etched, that is, a portion where erosion has occurred. It can be seen that the phenomenon that the erosion width in the vertical direction decreases at the position on the target corresponding to the magnet units adjacent to the magnet units at both ends, as seen in the conventional example, disappears. Therefore, the non-erosion portion where film deposition occurs is also lost, and the generation of particles caused by peeling of the deposited film is suppressed even after long-term use.
[0036]
In the above embodiment, the magnet unit 22b adjacent to the magnet units at both ends is divided into three parts, but it is obvious that the same effect can be obtained even with a two-part structure. Furthermore, even if the division is not performed, the same effect can be obtained if the length of the magnet units adjacent to the magnet units at both ends can be appropriately set.
[0037]
In the above embodiment, the number of magnet units is five. However, the number of magnet units is not limited to this, and even in the case of a plurality of magnet units, the length of the magnet units adjacent to the magnet units at both ends is longer than that of other magnet units. Then, the same effect as the above embodiment can be obtained.
[0038]
【The invention's effect】
As is apparent from the above description, according to the present invention, a plurality of long magnet units are arranged behind the rectangular target so that their long sides are parallel to each other, and these magnet units are swung. In the magnetron sputtering cathode electrode thus made, the length of the magnet unit adjacent to the magnet units at both ends and having a T / M distance larger than that of the other magnet units is longer than that of the other magnet units. Since it is configured to be longer by a desired length, the local non-erosion part on the target can be eliminated, and the erosion region can be enlarged compared to the conventional one, which can greatly reduce the particles generated on the substrate. Along with this, the target utilization rate can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a cathode electrode showing an embodiment of the present invention.
FIG. 2 is a plan view showing a planar shape and arrangement of five magnet units in the embodiment shown in FIG.
3 is an external perspective view showing the form of the end of an odd-numbered magnet unit counted from the end of the magnet units shown in FIG. 2; FIG.
4 is an external perspective view showing the configuration of end portions of second and fourth magnet units counted from the end of the magnet unit shown in FIG. 2; FIG.
FIG. 5 is a central sectional view in the longitudinal direction of the magnet unit shown in FIG. 4;
FIG. 6 is a plan view showing an erosion shape on a target after a film is formed over a long period of time using a cathode electrode according to an embodiment of the present invention.
FIG. 7 is a cross-sectional view of a main part showing the positional relationship between a magnet unit, a target, and a substrate in a conventional cathode electrode.
FIG. 8 is a plan view showing the shape and arrangement of a conventional cathode electrode magnet unit.
FIG. 9 is a plan view showing an erosion shape on a target after forming a film over a long period of time using a conventional cathode electrode.
[Explanation of symbols]
14 Cathode body 16 Back plate 22a, 22b Magnet unit 23 Magnet base 29 Motor 32, 42 Center magnet 33, 43 Outer magnet 34, 44 Yoke 35 Magnet unit end (end)
36 Magnet unit center (center)
37 Guide

Claims (3)

Behind the target is equipped with a magnet device in which a plurality of magnet units having a long planar shape are arranged so that their long sides are parallel to each other, and the magnet unit forms a tunnel-like magnetic field line on the target. In the cathode electrode for magnetron sputtering configured to reciprocate,
The T / M distance of the magnet unit adjacent to each of the magnet units at both ends of the plurality of magnet units is made larger than the T / M distance of the other magnet unit, and the length of the adjacent magnet unit in the long side direction is set. A cathode for magnetron sputtering, wherein the length is longer than the length of the other magnet unit.   2. The cathode electrode for magnetron sputtering according to claim 1, wherein a length adjusting mechanism for changing the length in the long side direction is provided in the adjacent magnet unit. In the cathode electrode for magnetron sputtering, which is arranged behind the target, forms a tunnel-like magnetic field line on the target, and has a magnet unit having a long planar shape,
The magnet unit is divided into an end portion and a central portion, the end portion and the central portion are coupled via a guide, and the position of the end portion relative to the central portion is changed to change the length of the magnet unit in the long side direction. A cathode electrode for magnetron sputtering, comprising a length adjusting mechanism for adjusting the thickness.

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