JP2008019474A - Target holder for magnetron sputtering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a target holder for magnetron sputtering having simple structure, with which the utilization efficiency of a target can be enhanced by uniformizing erosion of the target. <P>SOLUTION: The target holder 10 has a plurality of permanent magnets 3 arranged on a back face side of a held target 1 and forms the magnetic field on an outer surface of the target 1 to promote evaporation of the target. The permanent magnets 3 are arranged in a deviating manner from a center of an outer surface of the target 1. When the target 1 is evaporated and worn due to the sputtering, the target or the permanent magnets 3 are mounted while changing their relative positions, and thus an area to be evaporated and worn of the target 1 is changed to prolong the service time of a solid evaporation raw material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention generally relates to a method for effectively using a target material which becomes a solid evaporation source in sputtering.
More specifically, the present invention relates to a target holder used for sputtering, and the holder is located on the back side of the target held by the holder, that is, on the opposite side of the evaporation surface of the target material, and is shifted from the center axis of the target. By disposing a permanent magnet, it is possible to move a region where the evaporation of the target is large.

In thin film formation, a sputtering method is used as a means for evaporating solids to form a film on the substrate surface.
In this method, a negative voltage is applied to a target as a solid evaporation source under reduced pressure so that ions in the discharge plasma generated in the vicinity of the target are incident on the target. The resulting solid is evaporated. As the ion species incident on the solid evaporation source, a rare gas ion having a high evaporation efficiency is selected, and generally, an argon ion generated using an argon gas available at a low cost is used.

In this case, since one order of solid atoms or molecules evaporates with respect to one incident argon ion, the evaporation rate is proportional to the number of incident ions. These ions are generated in the discharge plasma. Therefore, in order to increase the processing efficiency, it is necessary to increase the number of incident ions and increase the evaporation rate. To this end, it is necessary to increase the intensity of the discharge plasma.
In view of this, the magnetron sputtering method in which a magnet is arranged on the back side of the target (solid evaporation source) and a strong discharge plasma region is formed in the space near the target by the magnetic field. In general, an apparatus for this purpose uses a strong permanent magnet such as SmCo or NeFeB in which the polarities of N and S are opposite to each other on the central portion and the outer peripheral portion on the back side of the target.

The magnetron sputtering method improves the evaporation rate as compared with the conventional sputtering method, but has a problem of non-uniform evaporation of the solid evaporation source due to the strength of the magnetic field. The area of the target eroded by evaporation is called the erosion area. If the erosion non-uniformity is large, a region where the solid evaporation source disappears partially appears on the target, and this becomes a target use limit, and the target use efficiency decreases.
In the case of the reactive magnetron sputtering method, when erosion progresses greatly, the evaporation rate from the target changes, and the stoichiometric ratio of the formed film also changes.

In order to improve the non-uniformity of the erosion of the target, several measures have been considered.
For example, there is a method of moving an erosion region by translating a permanent magnet unit for evaporation installed on the back surface of a target using a driving device (see Patent Document 1 or Patent Document 2). Alternatively, as an evaporation magnet placed on the back side of the target, there is a method in which an electromagnet is used instead of a permanent magnet, and the evaporation area is controlled by adjusting the electromagnet strength (see, for example, Patent Document 3).
JP 2001-59171 A JP-A-6-136532 Japanese Patent Publication No. 6-86658

However, the former method requires a drive mechanism for parallel movement of the magnet unit, and the structure is complicated and expensive. Furthermore, the magnet unit can move in a direction parallel to the surface of the target, but cannot move in a direction perpendicular to the surface. Therefore, in order to correct the fluctuation amount of the evaporation amount, control by another means must be performed.
The latter method is a technique applied to a specific application, and since the position of the electromagnet is fixed, the effect of improving the erosion non-uniformity is small. In the case of a commercial apparatus, since a large ion current is passed through the magnetron sputtering target so as to form a film at a high speed, the solid evaporation source generates a large amount of heat. Therefore, a water cooling mechanism is provided in the target unit to prevent melting of the solid evaporation source, but its structure is complicated, and it is difficult to efficiently arrange the water cooling mechanism and the evaporation magnet.

In view of such problems, an object of the present invention is to obtain a target holder capable of uniforming the erosion of a target and increasing the utilization efficiency of the target with a simple structure in magnetron sputtering.
In addition to the above, another object of the present invention is to obtain a target holder capable of stabilizing the evaporation amount.
Another object of the present invention is to provide a target holder that can efficiently use an evaporation magnet in addition to the above.

  The magnetron sputtering target holder of the present invention has a target as a solid evaporation source attached to the outside of the holder, and a plurality of evaporation permanent magnets that create a magnetic field on the outer surface of the target are provided on the back side of the target. By arranging the permanent magnet for use in a position shifted from the center of the outer surface of the target, and by changing the attachment position of the evaporation permanent magnet or the target so that the relative position between the evaporation permanent magnet and the target can be changed, The first task is achieved.

The arrangement of the evaporating permanent magnet may be an arrangement shifted from at least one of the center in the longitudinal direction and the center in the width direction of the target outer surface.
The relative position of the evaporating permanent magnet and the target may be changed by rotating the target or the evaporating permanent magnet 180 degrees in the same direction. Alternatively, the evaporation permanent magnet may be arranged to be biased to one side from the center of the target, and when the evaporation of the target material is reduced, the evaporation permanent magnet may be translated to the other side of the target and reattached. Similar results are obtained.

  Further, in the above configuration, the evaporation permanent magnet can be moved away from or close to the target and a mechanism for moving these evaporation magnets perpendicularly to the surface of the target can be provided. It is possible to control and stabilize it.

The target holder includes a box-shaped case that forms a sealed space, the target mounting surface is installed on one outer surface of the box-shaped case, and the evaporating permanent magnet faces the outer surface in the sealed space. It is preferable that the box-shaped case to be accommodated has an inlet and an outlet that lead to the sealed space in order to introduce a fluid for cooling the mounting surface.
Also, a mounting member is provided movably in the sealed space of the box-shaped case, the evaporation permanent magnet is mounted on the mounting member, and the inlet and the outlet are opened between the mounting member and the outer surface of the box-shaped case. May be.
By effectively cooling the vicinity of the target material, it is possible to suppress the temperature rise of the evaporation magnet and increase the magnetic field efficiency.

In the target holder of the present invention, when the target is evaporated and depleted as a result of sputtering, the relative position between the evaporating permanent magnet and the target can be changed, and the evaporative depleted area of the target by the evaporating permanent magnet can be changed. . Therefore, it is possible to move the consumption region of the target for each predetermined sputtering, effectively use the target, and extend the usage time.
This requires only changing the attachment position of the evaporating permanent magnet or the target, and can be realized with a simple structure as compared with the parallel movement of the magnet by a conventional drive mechanism.

  Further, when the target material is depleted by erosion, the evaporation rate of the target material changes with a change in the magnetic line density near the target surface. Therefore, the target holder of the present invention moves the evaporation magnet vertically to move the position of the evaporation magnet in accordance with the retraction of the evaporation surface of the target, thereby reversing the magnetic field, and is stable even if the erosion of the target progresses. The evaporation rate can be maintained and a stable film thickness can be obtained on the object.

The target holder of the present invention further provides a sealed space on the back side of the case to which the target material is attached, arranges an evaporation magnet in this space, and introduces a cooling liquid into this space, whereby the target and the evaporation magnet are It is possible to cool effectively. This has a simple structure, can reduce the number of places causing water leakage, and can be an easy-to-use liquid cooling structure.
Furthermore, since both the cooling space and the evaporation magnet can be arranged close to the target material, the cooling capacity is high and the magnetic field efficiency of the evaporation magnet is increased.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an example of an embodiment of the present invention will be described with reference to the drawings.
1 and 2, a target holder for magnetron sputtering with a water cooling mechanism according to a preferred embodiment of the present invention is generally designated by the reference numeral 10. 1 shows a vertical section of the target holder 10 along the line BB in FIG. 2, and FIG. 2 shows a horizontal section along the line AA in FIG.
In addition to the structure shown in FIGS. 1 and 2, the target holder 10 is provided with a vertical movement mechanism for the evaporation magnet. This mechanism is shown in FIGS. 1 and 2 for ease of explanation. This is omitted and will be described later with reference to FIGS.

The target holder 10 has a bottomed box-shaped case 2 made of copper having an opening 2a on one side (upper in FIG. 1) and a bottom 2b on the other side (lower in FIG. 1), and the opening 2a. It has a flat back cover 5 made of SUS to be closed. The case 2 further includes a flat collar 2c around the opening 2a.
A mounting surface 2d for a flat target 1 serving as a solid evaporation source is provided on the opposite side of the case 2 from the back cover 5, that is, on the outer surface of the bottom 2b. The mounting surface 2d is configured to fix the target 1 by fastening means (not shown).

The back cover 5 is attached to the flange portion 2 c of the case via a seal 12, and forms a sealed space that becomes the cooling space portion 9 in the case 2. The back cover 5 and the case 2 are detachably coupled with a bolt (not shown).
The back cover 5 is provided with an inlet pipe 6 and an outlet pipe 7 for cooling fluid at positions substantially at both ends in the longitudinal direction. The inlet pipe 6 and the outlet pipe 7 are connected to the cooling space 9 in the case when the back cover 5 is attached to the case 2.

  In the cooling space 9, a flat mounting member 4 made of SUS304 is accommodated in a floating state, that is, movably between the back cover 5 and the case bottom 2b. The attachment member 4 includes holes 4 a and 4 b having diameters larger than those of the inlet pipe 6 and the outlet pipe 7 at positions corresponding to the inlet pipe 6 and the outlet pipe 7, respectively. The attachment member 4 passes through the inlet pipe 6 and the outlet pipe 7 through the holes 4a and 4b, respectively, and is movable along these pipes.

A plurality of SmCo permanent magnets 3 are further installed in the cooling space 9 on the back side of the target 1, that is, on the side between the mounting member 4 and the case bottom 2 b.
The magnet 3 is preferably a rare earth magnet having a strong magnetic force such as SmCo or NeFeB. In addition, since a large permanent magnet is difficult to manufacture and handle, it is preferable that a large number of small magnets be fixed and integrated with a magnetic material such as mild steel or a non-magnetic material such as SUS304 stainless steel.

These magnets 3 are arranged side by side in a row. In the present embodiment, three rows 3a, 3b, 3c are formed at equal intervals along the longitudinal direction of the case 2 (both sides are symmetrical with respect to the center), and two rows 3d, 3e are formed along the width direction of the case 2. is doing.
The magnet arrays 3a to 3e are integrally attached to the attachment member 4 to constitute a target evaporation magnet 30 (described later with reference to FIG. 5), and approach or move away from the target 1 on the case attachment surface 2d together with the attachment member 4. It is possible to move in the cooling space 9.

As shown in FIG. 2, these magnet rows are arranged in the longitudinal direction of the case. The row 3b on one side is along the side wall of the case 2, the row 3c on the opposite side is separated from the side wall of the case 2, 3 a is also separated from the center line CL of the case 2. Thus, the magnet arrays 3a, 3b, 3c are arranged so as to be shifted to one side with respect to the center line CL of the case 2 as a whole. The magnet rows 3d and 3e in the case width direction are arranged along the side walls on both sides of the case 2.
Further, as can be clearly seen in FIG. 2, the permanent magnet 3 is arranged so that the NS polarity is opposite between the central row and the surrounding row with respect to the target 1, and the magnetron sputtering magnet is arranged. Constitute.

The cooling inlet pipe 6 and outlet pipe 7 described above have openings 6a and 7a that penetrate the attachment member 4 and connect to the cooling space 9 between the magnet arrays 3a to 3e.
The target holder 10 is connected to a cooling system (not shown) via an inlet pipe 6 and an outlet pipe 7. The coolant of the cooling system flows into the cooling space 9 between the magnet arrays 3a to 3e through the opening 6a of the inlet pipe 6, removes the heat of the target 1 from the case bottom 2b, and evaporates the magnet 30 in this space. Protect from heat. Thereafter, the coolant flows out of the target holder 10 through the opening 7 a of the outlet pipe 7. A part of the cooling liquid passes through the gaps between the holes 4 a and 4 b of the mounting member 4 and the inlet and outlet pipes 6 and 7, and also flows into the cooling space portion 9 on the back cover 5 side. Cool down.

Next, the vertical movement mechanism for the evaporation magnet will be described with reference to FIGS. 4 is a top view of the target holder 10 including the mechanism, and FIG. 3 is a cross-sectional view taken along the line CC in FIG.
The vertical movement mechanism 40 includes five gears 42 and 44 installed on the target holder. The gears 42 and 44 have rotating shafts 41 and 43, respectively, and these rotating shafts are rotatably attached to a support portion 5a formed on the back cover 5. As clearly seen in FIG. 4, the four gears 42 are arranged to form four corners of a square, and the remaining one gear 44 is in the center thereof and meshes and engages with the four gears 42, respectively.
An O-ring 46 for sealing and a stopper 47 for preventing the rotation shaft from falling off are provided between the rotation shafts 41 and 43 and the support portion 5a and the back cover 5, respectively.

The rotating shaft 41 of the gear 42 extends through the back cover 5 to the cooling space 9 of the case 2 and is provided with an external screw 41a at the lower end thereof. On the other hand, the mounting member 4 in the case 2 includes an inner screw 4c at a position corresponding to the rotation shaft 41 of the four gears, and corresponds to the outer screw 41a of the rotation shaft 41 so as to move up and down by the rotation of these gears. The inner screw 4c is engaged and engaged.
In the central gear 44, another gear 45 for driving the mechanism is attached to the rotary shaft 43 thereof. When the gear 45 is driven manually or by an electric motor or the like, the gear 44 moves to rotate the four gears 42 and the rotating shaft 41. Accordingly, the attachment member 4 moves up and down via the inner screw 4a engaged with the outer screw 41a of the rotating shaft 41.

The vertical movement mechanism 40 thus moves the mounting member 4 and the permanent magnet 3 on the same member in the vertical direction with respect to the case 2.
The holes 4a and 4b of the mounting member 4 are further arranged so that the mounting member 4 does not come into contact with the inlet pipe 6 and the outlet pipe 7 when the mounting member 4 moves up and down. The size of the permanent magnet 3 is set so as not to be affected by the inclination of the permanent magnet 3.
Further, the target mounting surface 2d and the fastening means (not shown) of the case 2 are mounted by rotating the target 1 by 180 degrees with the evaporation surface facing the outside of the target holder (downward in FIG. 1). Form to get.

  With such a configuration, the target holder of the present invention is mounted by rotating the target 1 or the evaporation magnet 30 by rotating 180 degrees without changing the direction with respect to the previous mounting position. Sputter discharge is generated and used in a new area outside the area that was mainly evaporated in this step, thereby improving the target life.

This will be described in more detail with reference to FIG.
FIG. 5 shows a cross section of the target holder 10 along the line DD in FIG. 1, and the discharge region when the target 1 is rotated or attached or when the magnet 30 is moved in the direction perpendicular to the target 1. Illustrates the change in. 5A shows a state where the target 1 and the magnet 30 are in the positions shown in FIG. 1, FIG. 5B shows a state where the target is rotated by 180 degrees, and FIG. 5C shows a state shown in FIG. FIG. 5D shows a state in which the evaporation magnet 30 is moved away from the target 1, and FIG. 5D shows a state in which the target 1 is rotated 180 degrees from the state shown in FIG. 5C.

The target holder 10 having such a configuration can ensure a uniform erosion area of the target 1 and a stable evaporation rate.
That is, the permanent magnet 3 shown in FIG. 2 is disposed closer to one side than the center line CL of the target holder 10. The region where erosion occurs in the target is between the magnet row 3a at the center and the magnet rows 3b and 3c on both sides thereof. Therefore, when the erosion of the target 1 has progressed due to use, the erosion becomes a new target in the next use by rotating the target 1 180 degrees and reattaching it as shown in FIGS. 5B and 5D. The erosion area is averaged.

A similar effect can also be obtained by rotating the attachment member 4 in the case 2 180 degrees and reattaching it, and changing the positions of the magnet arrays 3a to 3c with respect to the target 1. In this case, in this embodiment, the back cover 5 is rotated 180 degrees with respect to the case 2 together with the evaporation magnets 30 and reattached to change the position of the magnet rows 3a-3c.
Further, when the target is configured by arranging a plurality of plates instead of a single plate, the same effect can be obtained by a method of rotating individual pieces by 180 degrees.
Further, in the present embodiment, as shown in FIGS. 5C and 5D, the evaporation magnet 30 is moved away from the target 1, and a stable evaporation rate can be ensured even if the erosion of the target proceeds.

Magnetron sputtering was performed using the above-described target holder of the present invention. The results will be described next.
FIG. 6 schematically shows a reaction vessel portion of the magnetron sputtering apparatus used for this implementation. This apparatus has a structure shown in a separate application (Japanese Patent Laid-Open No. 2000-38663) of the present inventors and includes four target holders 10 shown in FIGS. (A direction perpendicular to the paper surface of FIG. 5). The target holders 10 are arranged in pairs and inclined so that the two adjacent targets 1 and the surface of the target 1 have an inclination angle α = 120 degrees in the width direction. It is composed. Thus, the apparatus used for the implementation includes a total of four target holders 10 and targets 1 in two pairs.

In FIG. 6, reference numeral 31 denotes a vacuum chamber (reaction chamber), 33 denotes a door, and 34 denotes a rotary table on which a substrate on which thin films are laminated is placed, which rotates in the direction of the arrow to make the laminated thin films uniform. Etc. Reference numeral 35 indicates a heater for heating the substrate. Reference numeral 36 denotes a shutter that blocks between the target 1 and the table 34 when the substrate is heated and when the target is activated, thereby preventing impurities from being deposited on the substrate on the table. This shutter cuts off the space between the heater 35 and the target 1 and the table 34 during ion bombardment and vapor deposition to prevent film deposition on the heater. An electromagnet 37 assists the generation of plasma, and expands the plasma region and stabilizes the plasma.
Since the other structure of the magnetron sputtering apparatus is the same as that of a well-known thing, description is abbreviate | omitted.

With this apparatus, a TiN film coating test was repeatedly performed under the same conditions, the change in the film thickness laminated on the substrate was examined, and the utilization limit of the target was investigated.
The target was a Ti target having a thickness of 5 mm, and Ar (argon) gas was flowed as sputtering gas and N ₂ (nitrogen) gas was flowed as reaction gas. The coating process was performed in the order of evacuation, heating of the workpiece with a heater, sputtering cleaning of the test piece surface with argon bombardment, TiN coating, and cooling. The time for consuming the target, that is, the time for the TiN coating treatment was fixed at 2 hours. The current applied per target was constant at 4.5 A, and the operation was performed in the constant current mode. Since the power applied to one target reaches 3 Kw, cooling water was passed through the target holder to prevent overheating of the target.

In the test, the arrangement of the evaporation magnet 30 was changed to the four positions shown in FIG.
The evaporation magnet 30 in the first test was arranged as shown in FIG. With this arrangement, the coating process was repeated up to 20 charges, and the change in film thickness was examined. The thickness of the TiN film of the first charge was 5.6 μm, and the film thickness increased slightly until the first 4th charge, and then decreased. Then, at the 16th charge, it became 30% thinner than the film thickness at the 1st charge, and the color tone started to change from gold to dark gold. Therefore, the 16th charge was defined as the use limit of the solid evaporation source in the first evaporation magnet arrangement. The evaporation state of the target surface is as shown by erosion 21 in FIG.

Next, as shown in FIG. 5B, the target was rotated by 180 degrees, and the TiN coating process was repeated under the same conditions as in the first test. The film thickness showed the same change as in the first test, and decreased to the original 70% around 15 charges. The surface of the target after evaporation was erosion 22, and the coating charge of almost the same number as the arrangement of FIG. 5A was possible.
Further, the evaporation magnet 30 was placed away from the Ti target 1 and installed as shown in FIG. When the evaporation test was repeated in this arrangement, the film thickness followed the same tendency as the previous two tests. The target material could be used at a stable evaporation rate up to erosion 23 in FIG.
Next, the target 1 was further rotated 180 degrees from the state of FIG. 5C and attached, and the final test was performed with the arrangement shown in FIG. 5D. In this test, a stable evaporation tendency similar to the evaporation magnet arrangement in the previous three times was obtained, and the target could be used stably until the final erosion 24.

By the way, with the arrangement in which the evaporation magnet is fixed at one position, a stable 2-hour coating process can be performed 15 to 16 times. The maximum erosion depth of the Ti target by these processes was about 2.4 mm. When the target material is not rotated or when the evaporation magnet 30 is not moved, the target has a life span and needs to be replaced.
On the other hand, according to the target holder of the present invention, since the above coating process can be repeated four times, even a relatively thin target having a plate thickness of 5 mm can be used in a stable evaporation form up to four times as many times as before. Is possible.

Although the present invention has been described with reference to specific embodiments and examples, the present invention is not limited to these.
For example, although the above-described embodiment is configured to change the position of the evaporation magnet together with the back cover 5, instead of this, the holes 4 a and 4 b of the mounting member 4 are formed into a long hole shape along the width direction. Alternatively, by installing the vertical movement mechanism 40 at the center of the case 2, only the attachment member 4 can be attached by rotating 180 degrees, and the relative position of the permanent magnet 3 with respect to the target 1 can be changed.
Further, when the target is configured by arranging a plurality of plates instead of a single plate, the same effect can be obtained by a method of rotating individual pieces by 180 degrees.
Thus, the target holder of the present invention can take various forms within the scope of the appended claims.

FIG. 3 is a vertical sectional view of the magnetron sputtering target holder provided with a water cooling mechanism according to the embodiment of the present invention, taken along line BB in FIG. 2. FIG. 2 is a horizontal sectional view of the target holder along the line AA in FIG. 1. FIG. 2 is a vertical sectional view similar to FIG. 1, additionally showing a vertical movement mechanism of the evaporation magnet of the target holder. It is a top view which adds and shows the vertical direction moving mechanism of the magnet for evaporation of this target holder. (A)-(b) is sectional drawing along DD line of FIG. 1 of this target holder, The target material is depleted by rotating and reattaching a target material, or the movement of the evaporation magnet ( Evaporation) situation. It is the schematic which shows the reaction container part of the magnetron sputtering apparatus incorporating the target holder of this invention.

Explanation of symbols

1 Target (Solid evaporation source)
2 Case 2a (Target) mounting surface 3 Permanent magnet 4 (Permanent magnet) mounting member 5 Back cover 6 Inlet pipe 7 Outlet pipe 9 Cooling space (sealed space)
10 Target Holder 30 Evaporation Magnet 40 Vertical Movement Mechanism (of Evaporation Magnet)

Claims (5)

  A target holder for magnetron sputtering, a target to be a solid evaporation source is attached to the outside of the holder, and a plurality of evaporation permanent magnets that create a magnetic field on the outer surface of the target are provided on the back side of the target. For permanent magnetron sputtering, the permanent magnets are displaced from the center of the outer surface of the target and the permanent magnets for evaporation or the mounting position of the target can be changed so that the relative positions of the permanent magnets for evaporation and the target can be changed. Target holder.   2. A magnetron sputtering apparatus according to claim 1, further comprising a mechanism for moving the evaporating permanent magnet perpendicularly to the outer surface of the target, wherein the evaporating permanent magnet is movably installed so as to move away from or approach the target. Target holder.   3. The target holder according to claim 1, further comprising a box-shaped case forming a sealed space, wherein a target mounting surface is disposed on one outer surface of the box-shaped case, and the evaporating permanent magnet has an outer surface thereof. And a box-shaped case having an inlet and an outlet leading to the sealed space for introducing a fluid for cooling the mounting surface.   4. The target holder according to claim 3, wherein an attachment member is provided so as to be movable in a sealed space of the box-like case, an evaporation permanent magnet is attached to the attachment member, and the inlet and outlet are connected to the attachment member and the box-like case. Target holder for magnetron sputtering opened between the outer surface of the magnetron.   In a magnetron sputtering target holder, a mounting surface for mounting a target as a solid evaporation source to the outside of the holder, and a plurality of evaporation for creating a magnetic field on the outer surface of the target installed on the opposite side of the target with respect to the mounting surface The permanent magnets for evaporation are arranged so as to be shifted from at least one of the longitudinal center and the width center of the target outer surface, and the target or the evaporation permanent magnet is rotated by 180 degrees in the same direction. Target holder for magnetron sputtering formed so that it can be attached.