JP2016157820A - Magnet unit for magnetron sputtering device, and sputtering method using the magnet unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet unit for magnetron sputtering device which is capable of efficiently removing a re-deposit film that is formed at a target center, by means of dummy sputtering in the case of deposition, and reproduces in-plane distribution of film thickness or film quality when sputtering for deposition is performed after the end of dummy sputtering.SOLUTION: The magnet unit for magnetron sputtering is disposed at a back side of a sputtering surface of a target 3 and rotationally driven with a center 3c of the target as a rotational center. The magnet unit comprises a first magnet body 5 and a second magnet body 6 that surrounds the first magnet body and within a predetermined range between the center of the target and an outer circumference, a magnetic field leaked from the target is generated in such a manner that a line L1 passing a position where a vertical component of the magnetic field becomes zero, is closed in an endless shape. Movement means is provided which radially moves in portions 61a and 61b of the second magnet body that is positioned at a center side of the target, and the magnet unit is freely deformable in such a manner that a part of the line passing the position where the vertical component of the magnetic field becomes zero is spread over the center of the target.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a magnet unit for a magnetron sputtering apparatus and a sputtering method, and more particularly to a device capable of removing a redeposit film formed at the center of a target in a short time.

  For example, in a manufacturing process of a semiconductor device such as a nonvolatile memory, a magnetron sputtering apparatus is used to form a dielectric film on a surface of a substrate to be processed such as a semiconductor wafer with high productivity. In a magnetron sputtering apparatus, a magnet unit is usually arranged on the side facing away from the sputtering surface of a circular target in plan view.

  As a magnet unit, for example, a plurality of magnet pieces having the same magnetization are arranged in a ring in a predetermined region between the center and the outer periphery of the target in order to erode the target substantially uniformly and to increase the life. A first magnet body; and a second magnet body in which a plurality of magnet pieces having the same magnetization as the first magnet body are arranged in a ring so as to surround the first magnet body. A magnetic field that leaks from the target is generated so that the line passing through the position where the vertical component of the magnetic field becomes zero (that is, the point where the plasma density is highest) is closed endlessly, and the center of the target is the rotation center during sputtering. What is rotationally driven is generally known. When rotating the magnet unit during sputtering in this way, a line passing through the position where the vertical component of the magnetic field is zero is the center of the target in order to prevent the central region including the target center from being locally eroded. A non-erodible region that is normally designed to fall within a predetermined range between the outer periphery and the outer periphery and that is not substantially eroded by sputtering may remain in the central region of the target.

  In the non-erosion region remaining in the central region of the target, sputtered particles generated by sputtering of the target are reattached during sputtering, and a redeposited film is formed. This redeposited film may become a particle or the like and cause a decrease in product yield. For this reason, before the redepo film having a predetermined thickness or more is formed, the redeposite film is removed by performing dummy sputtering under conditions (for example, low pressure) different from the film formation conditions. However, the redepo film is removed. It takes a lot of time to reduce the production efficiency. For example, Patent Document 1 discloses that the first magnet body is moved in the radial direction integrally in order to change the erosion area of the target. However, in this case, the erosion region on the entire surface of the target is different between the sputtering for film formation and the dummy sputtering, and the erosion shape on the entire surface of the target changes. As a result, if the first magnet body is returned to the original position after dummy sputtering and sputtering for film formation is performed, for example, the scattering distribution of sputtered particles changes due to the change in the erosion shape of the target. As a result, there arises a problem that the film cannot be formed with good reproducibility of the in-plane distribution of the film thickness and the in-plane distribution of the film quality.

JP 2004-269952 A

  In view of the above points, the present invention can efficiently remove the redeposition film formed at the center of the target during film formation by dummy sputtering, and when sputtering for film formation is performed after completion of dummy sputtering. It is an object of the present invention to provide a magnet unit and a sputtering method for a magnetron sputtering apparatus that can reproduce the in-plane distribution of film thickness and the in-plane distribution of film quality.

  In order to solve the above problems, a magnet unit for a magnetron sputtering apparatus of the present invention, which is disposed on the side facing the sputtering surface of a circular target in plan view and is driven to rotate about the center of the target, is a first unit. A line passing through a position where the vertical component of the magnetic field is zero in a predetermined range between the center and the outer periphery of the target, and the second magnet body surrounding the periphery of the first magnet body. The magnetic field leaking from the target is generated so as to be closed, and the moving means for moving the second magnet body portion located on the center side of the target in the radial direction is provided, and the line passing through the position where the vertical component of the magnetic field becomes zero It is characterized in that a part can be deformed so as to straddle the center of the target. In the present invention, “a part of a line passing through a position where the vertical component of the magnetic field is zero straddles the target center” is not only the case where the line strictly strides (passes) the center of the target, but also the center of the target. This includes the case where the line is deformed so that the region can be an eroded region.

  In the present invention, the moving means may be composed of a yoke that holds a portion of the second magnet body and an actuator that is coupled to the yoke. According to this, the part of a 2nd magnet body can be moved to radial direction by driving an actuator.

  In order to solve the above-mentioned problem, the sputtering method of the present invention using a sputtering apparatus comprising the above-described magnet unit is characterized in that the vertical component of the magnetic field falls within a predetermined range between the center and the outer periphery of the target by the first and second magnet bodies Sputtering the sputtering surface of the target and depositing and depositing the sputtered particles on the substrate to form a film on the substrate surface in a state where a leakage magnetic field is generated from the target so that the line passing through the position where zero becomes zero is closed endlessly In the state where the film forming step and the part of the second magnet body located on the center side of the target are moved so that a part of the line passing through the position where the vertical component of the magnetic field becomes zero straddle the target center And a dummy sputtering step of sputtering the sputtering surface of the target.

  According to the present invention, the first and second magnet bodies generate a leakage magnetic field from the sputtering surface so that the line passing through the position where the vertical component of the magnetic field is zero between the center and the outer periphery of the target is closed endlessly. When the film is formed in such a state, a redeposited film is formed in the central region which is the non-eroding region of the target. At the time of dummy sputtering for removing the redeposite film, the redepo film can be efficiently removed by deforming part of the line passing through the position where the vertical component of the magnetic field becomes zero so as to straddle the target center. In addition, since only the portion of the second magnet body located on the center side of the target is moved, the target is excluded except for the central region of the target between the sputtering for film formation (film formation process) and the dummy sputtering. The erosion area does not change. For this reason, if the second magnet body part is returned to the original position after dummy sputtering and sputtering for film formation is performed, the film thickness distribution in the film surface and the film quality surface distribution can be formed with good reproducibility. it can.

The schematic diagram which shows a magnetron sputtering apparatus provided with the magnet unit of embodiment of this invention. The expanded sectional view of the magnet unit shown in FIG. The top view which shows a moving means typically. The figure explaining the deformation | transformation of the line which passes along the position where the perpendicular | vertical component of a magnetic field becomes zero.

  Hereinafter, with reference to the drawings, a magnet unit according to an embodiment of the present invention will be described with reference to an example of a magnetron sputtering apparatus (hereinafter referred to as “sputtering apparatus”). In the following, terms indicating directions such as “up” and “down” are based on FIG.

  As shown in FIG. 1, the sputtering apparatus SM includes a vacuum chamber 1 that can be maintained at a predetermined degree of vacuum via a vacuum exhaust means P such as a rotary pump or a turbo molecular pump. A gas pipe 11 provided with a mass flow controller 10 is connected to the side wall of the vacuum chamber 1 so that sputtering gas can be introduced into the vacuum chamber 1 from a gas source (not shown). The sputtering gas includes not only a rare gas such as Ar but also oxygen gas when reactive sputtering is performed.

  A substrate stage 2 is disposed at the bottom of the vacuum chamber 1. The substrate stage 2 has a known electrostatic chuck (not shown). By applying a chuck voltage to the electrodes of the electrostatic chuck from a chuck power source, the substrate W is placed on the substrate stage 2 with its film formation surface facing up. It can be held by suction.

  In the opening formed in the upper wall of the vacuum chamber 1, a circular target 3 in plan view is arranged so that the sputtering surface 31 faces the substrate stage 2. The target 3 is made of a metal or an insulator that is appropriately selected according to the composition of the thin film to be deposited on the substrate W, and is made to have an outer shape that is slightly larger than the substrate W by a known method. On the upper surface of the target 3 (the surface opposite to the sputtering surface 31 in FIG. 1), a copper backing plate 32 that cools the target 3 during film formation by sputtering is made of a material having high thermal conductivity such as indium or tin. The outer peripheral portion of the backing plate 32 is attached to the upper wall of the vacuum chamber 1 via the insulating member I. A sputtering power source E is connected to the target 3 so that DC power or AC power having a negative potential can be applied to the target 3 during sputtering.

  The magnet unit 4 is arranged on the side opposite to the sputtering surface 31 of the target 3 (above the backing plate 32), and generates a magnetic field that leaks to the space below the sputtering surface 31 of the target 3, so that the sputtering surface 31 is exposed during sputtering. The sputtered particles scattered from the target 3 are efficiently ionized by capturing electrons etc. ionized below. The magnet unit 4 includes a yoke 41, a first magnet body 5 in which a plurality of (12 in this embodiment) magnet pieces 51 a to 51 l having the same magnetization are arranged in a ring on the lower surface of the yoke 41, The first magnet body 5 and the second magnet body 6 in which a plurality of (18 in the present embodiment) magnet pieces 61a to 61r are arranged in an annular shape so as to surround the periphery of the magnet body 5. . The yoke 41 is connected to a rotating shaft of a rotating means (not shown), and the first and second magnet bodies 5 and 6 can be driven to rotate about the center of the target 3 by rotating the rotating shaft. It has become.

  As shown in FIG. 4, the first and second magnet bodies 5 and 6 have a center of the target 3 in order to prevent the central region including the center of the target 3 from being locally eroded during sputtering. A line L1 passing through a position where the vertical component of the magnetic field becomes zero is closed endlessly within a predetermined range between 3c and the outer periphery (in other words, a non-eroding region that is not substantially eroded by sputtering in the central region of the target 3) So that a magnetic field leaking from the target 3 is generated.

  The magnet unit 4 of the present embodiment is provided with a moving means 7 that moves in the radial direction the portion of the second magnet body 6 that is located on the center side of the target 3, and the line passing through the position where the vertical component of the magnetic field becomes zero A part is configured to be deformable so as to straddle the center 3c of the target. The moving means 7 includes a yoke 71 that holds the second magnet body 6 (magnet pieces 61 a and 61 b) and an actuator 72 that is connected to the yoke 71. According to such a configuration, the magnet pieces 61a and 61b can be easily moved by extending and contracting the actuator 72 in the radial direction. The moving distance of the magnet pieces 61a and 61b can be set in the range of 5 to 10 mm, for example. A through hole 41 a having a contour that is slightly larger in the radial direction than the outer shape of the yoke 71 is opened in the central portion of the yoke 41, and the actuator 72 is disposed on the upper surface of the yoke 41 with the yoke 71 disposed in the through hole 41 a. It is fixed by a fixing member 73. In the present embodiment, the magnet pieces 51 a and 51 b of the first magnet body 5 are also held by the yoke 71 and moved together with the magnet pieces 61 a and 61 b of the second magnet body 6.

  The sputtering apparatus SM has known control means (not shown) including a microcomputer, a sequencer, etc., and controls the operation of the mass flow controller 10, the operation of the vacuum exhaust means P, the drive of the actuator 72, and the like. ing. Hereinafter, the sputtering method of the embodiment of the present invention using the sputtering apparatus SM will be described.

First, when the first and second magnet bodies 5 and 6 are positioned at the positions indicated by the solid lines in FIG. 4, the position where the vertical component of the magnetic field becomes zero in a predetermined range between the center 3 c and the outer periphery of the target 3. A magnetic field leaking from the target 3 is generated so that the passing line L1 is closed endlessly. In this state, the vacuum chamber 1 in which the alumina target 3 is arranged is evacuated to a predetermined degree of vacuum (for example, 1 × 10 ⁻⁵ Pa), and the substrate W is placed in the vacuum chamber 1 by a transfer robot (not shown). Then, the substrate W is transferred to the substrate stage 2 and electrostatically attracted. At this time, the substrate stage 2 may be heated by a heater or the like, and the substrate W may be heated to a predetermined temperature. Next, argon gas as a sputtering gas is introduced at a predetermined flow rate, and AC power (for example, 13.56 MHz, 4 kW high frequency power) is supplied from the sputtering power source E to the target 3 to form plasma in the vacuum chamber 1. . As a result, the sputtering surface 31 of the target 3 is sputtered, and the sputtered particles scattered are attached and deposited on the surface of the substrate W to form an alumina film (film forming step).

  Here, during the film forming process, a part of the sputtered particles scattered from the target 3 is reattached to the non-erosion region existing in the central region of the target, and a redeposited film is formed. If this redeposited film is peeled off from the target 3 and deposited on the substrate W, it may become particles or the like and cause a decrease in product yield. Therefore, for example, when the accumulated power input time (integrated power) from the power source E to the target 3 reaches a predetermined value (for example, 1.5 kWh), the next dummy sputtering step is performed.

  In the dummy sputtering step, by extending the actuator 72, the magnet pieces 61a and 61b (and the magnet pieces 51a and 51b) which are parts of the second magnet body 6 located on the center side of the target 3 as shown by a virtual line in FIG. ) Is moved 5 to 10 mm in the radial direction, and a part L2 of the line L1 passing through the position where the vertical component of the magnetic field becomes zero is deformed so as to straddle the center 3c of the target 3. In this state, the target 3 is sputtered (dummy sputtering). As the conditions for dummy sputtering, conditions (for example, low pressure) different from those at the time of film formation can be used. By this dummy sputtering, the redeposite film adhering to the central region which is the non-eroding region of the target 3 can be efficiently removed. At this time, only the magnet pieces 61a and 61b (51a and 51b) positioned on the center side of the target 3 are moved, and the other magnet pieces 61c to 61r (51c to 51l) are not moved. The erosion area of the target 3 does not change except for the central area of the target 3 between the processes. For this reason, when the dummy sputtering process is performed for a predetermined time (for example, 150 seconds), the actuator 72 is contracted to return the magnet pieces 61a and 61b (51a and 51b) to their original positions, and the film forming process is performed. The film can be formed with good reproducibility of the internal distribution and the distribution within the film quality plane.

Next, an experiment was conducted to confirm the effect of the present invention using the sputtering apparatus SM. In the invention experiment, the substrate W was a φ300 mm silicon wafer, the target 3 was an φ440 mm alumina target, and the distance between the substrate W and the target 3 (distance between TSs) was 70 mm. The substrate W is held by the substrate stage 2, and argon gas is introduced as a sputtering gas into the vacuum chamber 1 at a flow rate of 200 sccm (at this time, the pressure in the vacuum chamber 1 is 2.7 Pa). Plasma was formed by applying high-frequency power of 13.56 MHz and 4 kW, and the target 3 was sputtered to form an alumina film on the surface of the substrate W for 130 seconds. As a result of measuring the average film thickness and the in-plane distribution, the average film thickness was 46.45 mm and the in-plane distribution was 1.37%. When such film formation was repeated, it was confirmed that a redeposition film was formed in the central region of the target 3, and it was found that the central region of the target 3 became a non-erodible region. Next, after carrying out the board | substrate W, the dummy board | substrate was hold | maintained, the actuator 72 was extended 10 mm, and magnet piece 61a, 61b (51a, 51b) was moved to radial direction. In this state, the target 3 was sputtered (dummy sputtering process). In the dummy sputtering process, the flow rate of argon gas was set to 35 sccm (at this time, the pressure in the vacuum chamber 1 was 1.6 × 10 ⁻¹ Pa), and the input power to the target 3 was the same as in the film forming process. When the target 3 after observing the dummy sputtering for 90 seconds was observed, it was confirmed that the redeposition film was removed. Thereafter, the actuator was contracted to return the magnet piece to its original position, and the film forming step was performed again. As a result of measuring the average film thickness and the in-plane distribution, the average film thickness is 46.21 nm and the in-plane distribution is 1.24%, so that the film thickness can be formed with good reproducibility. I understood.

  A comparative experiment with respect to the above-described invention experiment was performed as follows. When the first and second magnet bodies 5 and 6 are not moved when performing dummy sputtering, the redeposited film is not removed even if the dummy sputtering is performed for 90 sec. It was confirmed that the film was removed. Thus, it has been found that the redeposition film can be efficiently removed by moving the magnet piece in the radial direction during dummy sputtering.

In the experiment of the present invention, for comparison with the prior art, the pressure in the vacuum chamber at the time of dummy sputtering was set lower than that at the time of film formation as in the prior art, but this is not restrictive. If dummy sputtering is performed in the range of pressure from the prior art to the pressure at the time of film formation (ie, 1.6 × 10 ⁻¹ Pa to 2.7 Pa), as in the above-described invention experiment, the redeposition can be efficiently performed by 90 sec dummy sputtering. It was confirmed that the film could be removed.

  In addition, when performing dummy sputtering, all the magnet pieces 51a to 51l of the first magnet body 5 are integrally moved in the radial direction as in the conventional example, and dummy sputtering is performed for 90 seconds under the same conditions as described above. It was confirmed that the film could be removed. However, after the dummy sputtering, the first magnet body 5 was returned to its original position and the film forming process was performed. As a result, the average film thickness was 47.56 nm and the film thickness in-plane distribution was 2.25%. It was found that the film could not be formed with good reproducibility of the in-plane distribution. This is because the erosion region changed over the entire target 3 between the film forming process and the dummy sputtering process, and after performing the dummy sputtering process, the magnet pieces 51a to 51l are returned to their original positions. Even if it is performed, it is assumed that the film cannot be formed with good reproducibility of the in-plane distribution of film thickness and in-plane distribution of film quality.

  The present invention is not limited to the above embodiment. For example, although the case where the magnet pieces 61a and 61b and the magnet pieces 51a and 51b located on the center 3c side of the target 3 are moved has been described in the above embodiment, the effect of the present invention can be achieved by moving the magnet pieces 61a and 61b. Is obtained.

  In the above embodiment, the dummy substrate is held on the substrate stage 2 at the time of dummy sputtering, but a known shutter that can be moved forward and backward is provided between the target 3 and the stage 2, and the shutter is interposed between the two at the time of dummy sputtering. You may make it enter. According to this, the time for taking in and out the dummy substrate becomes unnecessary, and the throughput may be improved.

  L1 ... a line passing through a position where the vertical component of the magnetic field is zero, L2 ... a part of a line L1 passing through a position where the vertical component of the magnetic field deformed so as to straddle the center of the target is zero, SM ... a magnetron sputtering apparatus, W ... substrate, 3 ... target, 3c ... center of target 3, 4 ... magnet unit, 5 ... first magnet body, 6 ... second magnet body, 61a, 61b ... magnet piece (the first located on the center side of the target) 2 magnet body 6), 7 ... moving means, 71 ... yoke, 72 ... actuator.

Claims (3)

A magnet unit for a magnetron sputtering apparatus that is disposed on the side facing away from the sputtering surface of a circular target in plan view and is driven to rotate around the center of the target,
A line having a first magnet body and a second magnet body surrounding the first magnet body and passing through a position where the vertical component of the magnetic field is zero is within a predetermined range between the center and the outer periphery of the target. In those that generate a magnetic field that leaks from the target to endlessly close,
Provided with a moving means for moving the second magnet body portion located on the center side of the target in the radial direction, the portion passing through the position where the vertical component of the magnetic field is zero can be deformed so as to straddle the center of the target A magnet unit for a magnetron sputtering apparatus.   2. The magnet unit for a magnetron sputtering apparatus according to claim 1, wherein the moving means includes a yoke for holding a portion of the second magnet body and an actuator connected to the yoke. In a sputtering method using a magnetron sputtering apparatus comprising the magnet unit for the magnetron sputtering apparatus according to claim 1,
In a state in which a leakage magnetic field is generated from the target so that a line passing through a position where the vertical component of the magnetic field becomes zero is closed endlessly in a predetermined range between the center and the outer periphery of the target by the first and second magnet bodies A film forming step of sputtering the target sputtering surface and depositing and depositing sputtered particles on the substrate to form a film on the substrate surface;
Sputter the sputtering surface of the target while moving the part of the second magnet body located on the center side of the target and deforming so that a part of the line passing through the position where the vertical component of the magnetic field becomes zero straddles the target center And a dummy sputtering step.

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