JP2006169610A - Sputtering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering system capable of improving the utilizing efficiency of a target material without causing the intrusion of impurities into a film in sputtering. <P>SOLUTION: Targets are arranged so as to surround a space at which plasma is generated during discharge, and at least the part located between a substrate and the plasma is provided with openings. In this way, the phenomenon that members other than the target material are sputtered is prevented, and the utilizing efficiency of the target material can be improved without causing the intrusion of impurities into a film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sputtering apparatus using plasma.

  As a technique for forming a film on a substrate by generating plasma in a vacuum, there is a sputtering technique. Because sputtered particles reach the substrate with high energy, the adhesion with the substrate can be increased and a dense film can be formed. Therefore, it is used for mass production of many products such as electronic parts and optical thin films. Yes.

  The conventional magnetron sputtering has a configuration as shown in FIG. 9, for example.

  In FIG. 9, 1 is a vacuum chamber, 2 is a target made of a material to be deposited, 3 is a backing plate, 13 is a magnet, and is magnetically coupled to a yoke 14 to form a magnetic circuit. By installing this magnetic circuit on the back surface of the target 2, high-density plasma can be generated on the target 2. 4 is a substrate, 5 is a gas introduction device, 6 is an exhaust device, 7 is an exhaust port, 8 is a valve, 9 is a ground shield, and 10 is a power source. When the power source 10 is a high frequency power source, impedance matching is performed by the matching adjustment circuit 11. After the inside of the vacuum chamber 1 is once made into a high vacuum through the exhaust port 7, a sputtering gas having a constant flow rate is introduced by the gas introduction device 5. A substrate 4 is placed at a position facing the target 2, and a high voltage is applied to the backing plate 3 by the power supply 10. As a result, high-density plasma is generated on the target 2. Ions extracted from the plasma are accelerated and collide with the target 2 to cause sputtering, and the sputtered particles ejected from the target 2 adhere to the opposing substrate 4 to form a thin film.

  It is possible to accelerate the ionization of the gas by effectively trapping electrons by the magnetic field lines generated from the magnetic circuit installed on the back surface of the target 2, thereby generating a higher density plasma and forming a film at a high speed. However, in such a configuration, a region in the vicinity where the magnetic field lines are parallel to the target surface is selectively eroded as the film is formed, and when the deepest part reaches the backing plate as shown in FIG. Many unused materials remain on the outer periphery of the target. Further, the spattering direction of the sputtered particles is not particularly controlled, and the ratio of sputtered particles that have jumped out of the target to adhere to the substrate to become a product is very low.

  Conventionally, a method of rotating a magnetron magnet has been used to improve the utilization efficiency of the target material, and efforts have been made to increase the utilization efficiency of the target material by devising the magnet design and the magnet movement method. However, even in these methods, it is difficult to uniformly erode the entire target surface. Further, as a method for controlling the direction of the sputtered particles, there is a method of installing a collimator between the target and the substrate. However, there is a problem that dust or a rate is reduced due to peeling of a film attached to the collimator.

  An example of Patent Document 1 is a means for reducing damage of charged particles flowing into a substrate by combining a plurality of cathodes.

Non-Patent Document 1 and Non-Patent Document 2 are examples of research on the ratio between the sheath voltage generated at the cathode electrode to which a high frequency is applied and the sheath voltage generated at the anode electrode.
Japanese Patent Laid-Open No. 10-8246 J. et al. W. Coburn and E.M. Kay, J .; Appl. Phys. 43,4965 (1972) H. R. Koenig and L. I. Maissel, IBM J .; Res. Develop. 14,168 (1970)

  As one means for efficiently eroding the entire surface of the target and concentrating the direction of the sputtered particles in the direction toward the substrate, in order to facilitate discharge in the sputter cathode in which a plurality of cathodes are opposed to each other, In some cases, some of the members were set to ground potential or floating potential, and the anode was used as an anode. However, dust from the film adhering to the anode and, conversely, impurities mixed into the film due to sputtering of the anode. There was a fear.

  An object of the present invention is to solve the above-described conventional problems, and to provide a sputtering apparatus that improves the efficiency of using a target material without causing impurities in the film.

  In order to achieve the above object, a sputtering apparatus according to claim 1 of the present invention has a target, which is a raw material, and a substrate holder on which a substrate is placed facing each other in a vacuum chamber. In a sputtering apparatus for forming a thin film by generating a plasma by applying a voltage, the target is a concave target having an opening on the substrate holder side, and is formed with a flat or curved integrated structure. This makes it possible to improve the utilization efficiency of the target material without introducing impurities into the film.

  Further, the sputtering apparatus according to claim 2 is the sputtering apparatus according to claim 1, wherein a magnetic field generating means is installed outside the target in order to generate a magnetic field substantially parallel to the substrate. It is possible to improve the utilization efficiency of the target material without causing impurities in the film.

  The sputtering apparatus according to claim 3, wherein the ratio of the target height H to the target width W (H / L) is 1.0 or more. It is possible to improve the utilization efficiency of the target material without introducing impurities into the film.

  The sputtering apparatus according to claim 4 is configured such that a plurality of targets as raw materials and a substrate holder on which a substrate is placed face each other in a vacuum chamber, and plasma is generated by applying a high voltage to the target. In a sputtering apparatus for forming a thin film by generating, a planar or curved concave target is formed by the plurality of targets, and an opening is provided on the substrate holder side of the concave target. Thus, the target material utilization efficiency can be improved without causing impurities to be mixed into the film.

  The sputtering apparatus according to claim 5 is the sputtering apparatus according to claim 4, wherein a magnetic field generating means is installed outside the target in order to generate a magnetic field substantially parallel to the substrate. It is possible to improve the utilization efficiency of the target material without causing impurities in the film.

  The sputtering apparatus according to claim 6, wherein a ratio of a target height H to a target width W (H / L) is 1.0 or more. It is possible to improve the utilization efficiency of the target material without introducing impurities into the film.

  The sputtering apparatus according to claim 7 connects a part of a plurality of targets divided into one pole of a high-frequency power source, and connects the opposite pole of the high-frequency power source to the remaining part or all of the target The sputtering apparatus according to any one of claims 4 to 6, wherein the target material utilization efficiency can be improved without causing impurities to be mixed into the film. is there.

  The sputtering apparatus according to claim 8 is characterized in that a high frequency voltage is applied to a part of the target divided into a plurality of parts, and the remaining part or all of the target is connected to ground. To the sputtering apparatus according to any one of claims 6 to 6, and the target material utilization efficiency can be improved without causing impurities to be mixed into the film.

  The sputtering apparatus according to claim 9 is characterized in that a collimator for controlling the direction of the sputtered particles is installed in an opening provided in a portion located between the substrate and the plasma. It is a sputtering device as described in any one of claim | item 7, It is possible to improve target material utilization efficiency, without raising the impurity mixing in a film | membrane.

  Further, the sputtering apparatus according to claim 10 is characterized in that a combination of applying the same potential among a plurality of divided targets is changed during film formation or with target erosion. The sputtering apparatus according to any one of Items 9 and the target material utilization efficiency can be improved without causing impurities to be mixed into the film.

  As described above, according to the sputtering apparatus of the present invention, the possibility that ions extracted from plasma are sputtered other than the target made of the raw material can be reduced, and impurities can be prevented from being mixed into the film. In addition, since the target surrounds the plasma, the sputtered particles effectively jump out toward the substrate. For this reason, it is possible to improve material utilization efficiency.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic diagram of a sputtering apparatus according to Embodiment 1 of the present invention. FIG. 2 shows an outline viewed from the substrate side. 1 is a cross-sectional view taken along the line AB in FIG.

  In FIG. 1, 1 is a vacuum chamber, 2 is a target made of a material to be deposited, a part of the target 2 is set to ground potential, and the rest is connected to a high-frequency power source 10 via a matching adjustment circuit 11. ing. The setting of the potential is not limited to this embodiment, and a part of the potential may be connected to a high frequency power source and the rest may be set to the ground potential.

  4 is a substrate, 5 is a gas introduction device, 6 is an exhaust device, 7 is an exhaust port, 8 is a valve, 9 is a ground shield, 10 is a high-frequency power source, and 11 is a matching adjustment circuit. After the inside of the vacuum chamber 1 is set to a high vacuum through the exhaust port 7, a sputtering gas with a constant flow rate is introduced by the gas introduction device 5. As a sputtering gas, a rare gas such as Ar or Xe is generally used.

  Hereinafter, an example using Ar will be described. A substrate 4 is placed at a position facing the target 2, and a high frequency voltage is applied to the backing plate 3 by the power supply 10. Thereby, high density plasma is generated on the target. Ions extracted from the plasma are accelerated and collide with the target 2 to cause sputtering. Some of the sputtered particles that have jumped out of the target are reattached to different parts of the target, but are sputtered again and finally jump out toward the substrate side. For this reason, it is guessed that material utilization efficiency can be improved.

  Here, in order to sputter the entire surface of the target, it is necessary to also sputter the target surface set to the ground potential. In glow discharge, a region called a sheath exists in front of both the cathode and anode electrodes. The time-averaged potential has a shape that greatly drops in the sheath portion in the direction from the plasma toward both electrodes. This is caused by a difference in follow-up property to a high frequency caused by a mass difference between ions and electrons. In a conventional sputtering apparatus, sputtering is caused by accelerating ions by a large potential difference generated on the cathode side.

  On the other hand, the relationship between the magnitudes of the sheath drop voltages in both electrodes is determined by the area ratio of the anode electrode to the cathode electrode. As a study on parallel plate capacitively coupled plasma discharge, there is a very simplified model by Koenig et al., Where the anode electrode area is S1, the cathode electrode area is S2, the anode side sheath voltage drop is V1, and the cathode side sheath voltage drop. When the voltage is V2,

It is said that it becomes a relationship.

  On the other hand, experimentally, Coburn et al.

There is a report that it is close.

  We also experimented with magnetron discharge in a magnetic field. An inner chamber for determining a discharge space was installed in a vacuum vessel, and high frequency power of 13.56 MHz was applied to an Al target having a φ200 mm size disposed therein to cause plasma discharge by Ar gas. The discharge pressure was 0.67 Pa. The anode area is changed by changing the diameter of the inner chamber from φ300 mm to φ480 mm, the input power is changed from 0.5 to 1.5 kW in each inner chamber, and the target voltage waveform is changed with a high-voltage probe and a digital oscilloscope. It was measured. The voltage drop in the sheath was obtained from this waveform, and plotted in a graph with the horizontal axis representing the electrode area ratio and the vertical axis representing the voltage ratio in each sheath. (FIG. 3) The shape is almost similar to the result of Equation 2 by Coburn et al., And the order of the right side is approximately 0.84 as a result of fitting.

  From the above, the area ratio of the portion of the target 2 set to the ground potential in FIG. 1 and the portion of the target 2 connected to the high-frequency power source is set to a shape close to 1.0. By doing so, it is possible to distribute the effective voltage generated in both electrodes almost evenly.

  To what extent the area ratio is reduced, the entire surface is effectively sputtered depends on the input power and target material, but from the results shown in FIG. Since the voltage distribution can be kept within approximately 1: 2, it is considered that the entire target can be sputtered in a balanced manner.

  In addition to the above embodiment, as a method for connecting the power source, the target 2 may be divided into two as shown in FIG. 4 and connected to both poles of the high frequency power source.

  In addition, as shown in FIG. 5, it is possible to further increase the directivity of the sputtered particles by narrowing the opening on the surface close to the target substrate. As the size of the opening is smaller, the material utilization efficiency is improved, but conversely, since the film formation rate is lowered, the productivity is lowered. In general, it is preferable to set the same size as the substrate size.

  In addition, as shown in FIG. 6, the directivity can be further improved by installing a collimator 12 as a means for controlling the direction of sputtered particles in the opening on the surface near the target substrate. The means for controlling the direction of the sputtered particles may be, for example, a mesh or honeycomb. The configuration shown in FIG. 6 can improve directivity as compared with the configuration shown in FIG. 5, and is suitable for film formation for controlling the structure of film growth, film formation embedded in a groove shape, and the like. it is conceivable that.

  Further, as shown in FIG. 7, the target may be divided into a plurality of groups, divided into a group operating as an anode and a group operating as a cathode, and connected to a power source or ground, or set to a floating potential. According to this, since it is possible to easily set the ratio of the anode electrode area to the cathode electrode area, it becomes easier to control the plasma.

  Further, the combination of the plurality of targets may be changed during film formation. According to this, the problem that the target erosion progresses unevenly can be reduced. Further, the combination may be changed over time with production.

  According to the configuration of FIG. 7, the initial cost of the equipment is increased, but it is thought that the running cost can be reduced because the entire target can be sputtered more uniformly and more stably. It is considered more preferable.

  In the above example, the magnetic field is not applied to the discharge space. However, the plasma density may be improved by applying the magnetic field, and the magnetic field applying means may be rotated or moved. The magnetic field applying means may be a permanent magnet or an electromagnet coil.

  In the invention described in Patent Document 1 described above, a plurality of cathodes are combined in order to reduce damage to the substrate, but there is a problem that it is difficult to maintain discharge at a low pressure. A member such as an electronic reflector is installed in a part of the screen. On the other hand, in the present invention, it is possible to maintain a stable discharge without installing a structure other than the target material to be a product inside the target forming the box shape.

  This eliminates the problem of dust due to reattachment of sputtered particles and the problem of impurity contamination due to sputtering of a member other than the target material, so that higher quality film formation is possible.

  In these respects, the present invention is technically completely different from the invention described in Patent Document 1.

(Embodiment 2)
FIG. 8 is a schematic diagram of a sputtering apparatus according to Embodiment 2 of the present invention.

  In FIG. 8, the same components as those in FIG. Although the target 2 has been described as an example of an integral configuration, it may be divided.

  The configuration of the present embodiment is advantageous in that discharge is possible in principle even with a DC power supply, unlike the first embodiment described above.

However, when the same potential is applied to the target, the earth shield acts as an anode. In this case, it is preferable to apply a magnetic field from the outside in order to improve discharge stability.
When the substrate size is small, the cathode can be made small, and it is easy to apply a strong magnetic field up to the center of the discharge space. Therefore, the target opening is preferably smaller than about 100 mm.

  In the first and second embodiments, the case where the target has a rectangular shape has been described. However, the shape is not particularly limited, and may be, for example, a cylindrical shape. In addition, the present invention can be variously modified and implemented without departing from the spirit of the present invention.

  The sputtering apparatus and method of the present invention can improve target material utilization efficiency without introducing impurities into the film, and can realize low-cost film formation.

Schematic of sputtering apparatus in Embodiment 1 of the present invention Schematic of sputtering apparatus in Embodiment 1 of the present invention Diagram showing the relationship between the electrode area ratio and sheath voltage ratio in magnetron discharge The figure which shows the different form of the sputtering device in Embodiment 1 of this invention. The figure which shows the different form of the sputtering device in Embodiment 1 of this invention. The figure which shows the different form of the sputtering device in Embodiment 1 of this invention. The figure which shows the different form of the sputtering device in Embodiment 1 of this invention. Schematic of sputtering apparatus in Embodiment 2 of the present invention Schematic diagram of an example of conventional sputtering equipment The figure which shows the target erosion shape in the example of the conventional sputtering device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Target 3 Backing plate 4 Substrate 5 Gas introduction device 6 Exhaust device 7 Exhaust port 8 Valve 9 Earth shield 10 High frequency power supply 11 Matching adjustment circuit 12 Collimator 13 Magnet 14 Yoke 15 Target erosion part

Claims (10)

In a sputtering apparatus in which a target that is a raw material and a substrate holder on which a substrate is placed are placed facing each other in a vacuum chamber, and a thin film is formed by generating plasma by applying a high voltage to the target.
The said target is a concave target which provided the opening in the said substrate holder side, and was formed by the planar or curved integral structure. The sputtering apparatus according to claim 1, wherein a magnetic field generating unit is installed outside the target in order to generate a magnetic field substantially parallel to the substrate. 3. The sputtering apparatus according to claim 1, wherein the ratio of the target height H to the target width W (H / L) is 1.0 or more. In a sputtering apparatus in which a plurality of targets as raw materials and a substrate holder on which a substrate is placed face each other in a vacuum chamber and a thin film is formed by generating plasma by applying a high voltage to the target.
A flat or curved concave target is formed by the plurality of targets, and an opening is provided on the substrate holder side of the concave target. The sputtering apparatus according to claim 4, wherein a magnetic field generating means is installed outside the target in order to generate a magnetic field substantially parallel to the substrate. 6. The sputtering apparatus according to claim 4, wherein the ratio of the target height H to the target width W (H / L) is 1.0 or more. 5. A part of the target divided into a plurality is connected to one pole of a high-frequency power source, and the opposite part of the high-frequency power source is connected to the remaining part or all of the target for use. The sputtering apparatus according to claim 6. 7. The high-frequency voltage is applied to a part of the target divided into a plurality of parts, and the remaining part or all of the target is connected to the ground. 8. Sputtering equipment. The sputtering apparatus according to any one of claims 1 to 7, wherein a collimator for controlling the direction of sputtered particles is installed in an opening provided in a portion located between the substrate and the plasma. . 10. The sputtering apparatus according to claim 4, wherein, among the plurality of divided targets, a combination to which the same potential is applied is changed during film formation or with target erosion. 11. .

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