JP4682371B2 - Single power source sputtering apparatus comprising an anode with magnetic field control - Google Patents

Description

  The present invention relates to a sputtering apparatus. Specifically, the present invention relates to a sputtering apparatus driven by a single power source. More particularly, the present invention relates to a sputtering apparatus that can generate high-energy charged particles with a low-frequency single drive power source. Furthermore, the present invention relates to a sputtering apparatus in which an anode disposed in a vacuum apparatus is designed to have a unique structure and driven by a low frequency power source to generate high energy charged particles. More specifically, the anode design is separated from the vacuum vessel and the substrate for film formation, and is shielded except for the path (path) of charged particles from the anode surface to the cathode, and the path is in the vicinity of the shielded anode surface. It is related with the sputtering device which attached the magnetic field formation means which gives a magnetic field to the direction which crosses orthogonally orthogonally, ie, the direction parallel to an anode surface.

  Furthermore, the present invention realizes an effect equivalent to or higher than that of the conventional bias sputtering method, which will be described later, which requires an independent power source and electrode separate from the film formation, without adding a power source. In particular, a new and extremely excellent sputtering apparatus that can reduce the forming temperature, improve the adhesion of the thin film, increase the density, etc. when thin films of various materials are formed on the substrate by sputtering. The present invention relates to a sputtering apparatus.

In describing the present invention, specific terms used are defined as follows.
That is, in the present invention, a charged particle refers to a charge medium that can move in a vacuum vessel such as electrons and ions generated by being turned into plasma. The discharge current refers to a current that flows as a movement of charged particles in a vacuumized vacuum vessel. The anode refers to the electrode from which the discharge current flows, and the cathode refers to the electrode into which the discharge current flows.

  Further, in the present invention, the anode surface and the cathode surface are surfaces of the anode and the cathode, respectively, and are surfaces that are not shielded by an insulator or a shield, and that work effectively against discharge current flow-in and flow-in. Say. Similarly, the effective path from the anode to the cathode of the charged particles is that the charged particles, which are the carriers of the discharge current, are not obstructed by an insulator or the like, and the charged particles actually move along the discharge current. This refers to the path that is carried from the flow out to the cathode, and there are many three-dimensional line segments (curves) in the sputtering apparatus. Further, the strongest magnetic field strength in the effective path from the anode of the charged particle to the cathode focuses on one of the many effective paths from the anode to the cathode of the charged particle, and the path from the cathode to the anode It is defined as the maximum value of the magnetic field strength that crosses vertically.

  Furthermore, in the present invention, the balanced or unbalanced magnetic field arrangement is the configuration of the magnetic field used to localize the plasma in the vicinity of the cathode surface on the cathode surface of the sputtering method that is usually widely used in the magnetron method. It refers to the name of the method. The balanced magnetic field arrangement usually uses a plurality of permanent magnets, and adjusts the strength of each magnet so that almost all the magnetic flux generated from the north pole of these magnets converges on the south pole of the magnet. This means a magnetic field arrangement for strongly localizing plasma near the surface. On the other hand, in the case of the unbalanced type, when the magnet strength is adjusted so that all of the magnetic flux generated from the N pole does not return to the S pole, and the magnetic flux distribution is such that a part of the magnetic flux is released to the space. Say. In the case of an unbalanced magnetic field configuration, the localization of plasma near the target surface is weaker than that of the balanced type, and is used when it is necessary to obtain a plasma that is relatively spread in the device space (“HYPERLINK” http http://www.kobelco.co.jp/p109/pvd/ubms.htm "http://www.kobelco.co.jp/p109/pvd/ubms.htm").

  So-called sputtering technology is widely used for thin film formation (sputtering deposition, deposition), pattern formation (patterning, etching), surface modification, etc., which are fundamental technologies that support the rise of today's electronics industry. Is one of the important technologies. The history is old, and various improvements and proposals have been made so far. Today, there are various methods as described below, and they are widely used in various technical fields.

  Prior Art No. 1; One of the most widely used anode designs in the current sputtering deposition technique is the method of using the conductor wall surface of the vacuum vessel as the anode. In other words, an anode as an independent electrode is not provided, and electric power of various frequencies and waveforms (direct current, alternating current, high frequency, etc.) is input between the cathode and the conductor wall surface of the vacuum vessel to generate a discharge. This configuration is shown and described with reference to FIG. First, the conductor inner wall surface (1) of the vacuum vessel functions as an anode surface, and a discharge current flows from here to the cathode surface. A conductor wall surface of a vacuum vessel serving as an anode and a cathode (2) insulated by an insulator (3) or the like are installed, and the cathode surface is disposed at an appropriate position in the internal space of the apparatus. At this time, it is a common practice to define a region serving as a cathode surface using an insulator (3) and a shield (4).

  In the most widely used magnetron type sputtering method, magnetic flux lines (8) are arranged in order to localize plasma in the vicinity of the cathode surface. There are variations such as a balanced type or an unbalanced type in the method of arranging the magnetic flux lines. In thin film formation by sputtering, the cathode surface is usually used as raw material, and various frequencies and waveforms (direct current, alternating current, high frequency, etc.) are applied between the cathode (2) and the anode (1) in a sputtering gas atmosphere such as argon. By doing so, plasma is generated. Various ions in the plasma are vaporized by sputtering the raw material components from the target by exchanging momentum from the cathode surface, and this vaporized raw material is held on the device wall that is the anode or a substrate holder that is kept at the same potential. A substrate on which a thin film is formed is obtained by depositing on the surface of the substrate (6).

  The sputtering method with the simplest configuration shown in FIG. 1 is very widely used. However, when using the device wall as an anode, the anode potential corresponds to the ground potential (potential reference point, zero electron volt energy) for safety. As a result, the potential of the substrate is also held at the ground potential. The energy at which the particles forming the thin film are incident on the substrate surface is governed by the difference between the plasma potential and the substrate potential, and not only the mechanical properties such as density, hardness, adhesion, unevenness, etc. of the resulting thin film, but also electrical properties. This is very important because it greatly affects the optical characteristics. In particular, in order to realize high density, high hardness, high adhesion, and high smoothness, particles having high energy (energy of about 10 to 100 electron volts) are made incident on the substrate surface during film formation, and the energy is reduced. It is widely known that application to the surface of a substrate is extremely effective.

  In the magnetron sputtering apparatus shown in FIG. 1, the potential of the substrate is fixed to the ground potential, and the plasma potential is determined from the film forming conditions to about plus a few electron volts in the plasma used in the normal sputtering method. Since it cannot be changed freely, the energy level of the particles is plus a few electron volts-zero electron volts = several electron volts, and it is artificial to achieve high density, high hardness, high adhesion, and high smoothness. In particular, it has been almost impossible to increase the energy of various particles incident on the substrate surface to about 10 electron volts or more.

  Prior Art 2; Compared to the above prior art 1, the energy of particles incident on the surface of the substrate is increased, and the electrode on which the substrate is placed is used as the anode in order to realize high density, high hardness, high adhesion, and high smoothness. In addition, there is a sputtering technique called a bias sputtering method, in which a voltage called a bias is applied thereto by an independent power source.

  An outline of a typical bias sputtering apparatus is shown in FIG. The relationship between the anode (1), the cathode (2), the insulator (3), the shield (4), and the magnetic flux lines (8) is the same as that shown in FIG. The difference is that the substrate (6) is not an apparatus wall surface which is an anode, but is disposed on the independent bias electrode (7) disposed in the vacuum apparatus via an insulator (3). Therefore, by changing the potential of the bias electrode (7) with a bias application power source (not shown), the plasma potential is fixed to about plus a few electron volts, but the substrate potential is independently lower than the ground potential ( For example, the energy level of the particles can be set to several electron volts-minus 10 electron volts = ten several electron volts, and the energy when the raw material enters the substrate surface can be increased. As a result, high density, high hardness, high adhesion, and high smoothness of the thin film obtained can be realized.

  However, in this method, it is necessary to add a power source for bias, and one of the drawbacks is that the device becomes complicated and expensive. The power supply used in these sputtering systems is subjected to advanced circuit design and multiple protection circuits that are incomparable to ordinary stabilized power supplies because the behavior of the plasma that is the load is non-linear is essential. An expensive pulse power supply or the like is required. For this reason, the use of a plurality of power supplies that require such a complicated power supply circuit is directly linked to the price of the sputtering film forming apparatus, which significantly increases the price.

  In addition, power sources for sputtering (applying a potential for plasma discharge for film formation between the anode and the cathode) and for bias (applying a potential for biasing between the anode and the bias electrode) are mutually connected via plasma. To achieve high density, high hardness, high adhesion, and smoothness of the thin film at a low process temperature, lowering the bias potential (increasing to the minus side: minus 20 volts, minus 30 volts, etc.) Discharge is likely to be unstable, resulting in unstable sputtering film formation, causing problems in film quality degradation and reproducibility, and the worst discharge cannot be maintained. As a result, it has been pointed out that there is a problem that the failure frequency of the two power sources is increased.

Prior Art 3: Bipolar Pulse Sputtering Method The bias sputtering method described in the previous section was aimed at realizing high density, high hardness, high adhesion and high smoothness of a thin film at a low process temperature. On the other hand, a bipolar sputtering method is a sputtering method developed with the aim of speeding up film formation and stabilizing for a long time. A major obstacle in realizing high-speed stable film formation of an insulator thin film by a sputtering method is an insulator thin film formed on the surface of the anode. Since the insulating film formed on the anode surface inhibits the flow of current from the anode, it inhibits the application of power to the plasma for film formation, and as a result, it becomes difficult to maintain the discharge. It will stop. Therefore, in designing a sputtering apparatus, in order to maintain a stable discharge for a long time, contrivances such as placing the anode at a position where it is difficult to receive thin film formation have been made, but there is a limit to the operation over a long time, It was not enough.

  On the other hand, in the bipolar sputtering method, focusing on the fact that the insulator is not formed because the cathode surface is always subjected to etching because of the sputtering phenomenon, and is always kept clean. A method was proposed in which the electrode that was the anode at one moment worked as a cathode at the next moment and returned to the anode during the film formation, and a stable discharge was maintained for a long time during the formation of the insulator thin film. It was shown to be effective. This is a method called bipolar sputtering, in which an alternating potential of 1 to several 100 kHz is applied to two electrodes, and these two electrodes are balanced or unbalanced magnetic flux lines for promoting plasma localization. It is the feature that has the arrangement of.

  FIG. 3 shows a conceptual diagram of the bipolar sputtering method. Prepare an electrode (9) (cathode / anode) having the same design as the cathode used in a normal sputtering apparatus, and arrange two sets of the insulator (3), shield (4), and magnetic flux lines (8), Each electrode surface holds a target substance which is a raw material for the thin film material to be formed. By applying an AC potential of 1 to several 100 kHz between the two electrodes by an AC power source (not shown), the raw materials on the surfaces of the two sets of electrodes (9) operate as described above while alternately switching the polarities. . That is, while operating as a cathode, the raw material is vaporized at the same time as being cleaned by etching due to the sputtering phenomenon. While acting as the anode, it takes charge of power to the plasma, and during that time, the formation of the insulator progresses, but at the next moment it switches to the cathode and cleans it so that it maintains a long discharge when forming the insulator thin film Is possible.

  As described above, the bipolar sputtering method is a technique developed for sputtering an insulating thin film over a long period of time or stably and rapidly forming a film. However, the effect of increasing the energy when the raw material is incident on the substrate surface. It has also been reported to be effective in reducing the formation temperature, improving the adhesion of thin films, and increasing the density, etc., and is also used for such purposes in actual processes to achieve the prescribed effect. It has been reported that it was possible (for example, Non-Patent Document 1).

  The power supply of the bipolar sputtering system uses only one AC power supply of various waveforms such as a pulse and a rectangular wave whose polarity is switched at a cycle of 1 to several hundred kHz, so that the power source interference problem does not occur as in the bias sputtering system. . However, the AC power supply having various waveforms such as pulses and rectangular waves whose polarity is switched at a cycle of 1 to several hundred kHz is significantly more expensive than the power supply used normally, and therefore the apparatus price is generally more expensive than the bias sputtering method. This is the biggest drawback.

In addition, the reason why this method was originally developed was not intended to reduce the forming temperature, improve the smoothness of the thin film, improve the adhesion, and increase the density, but intended for a stable film forming operation over a long period of time. It was. For this reason, when the raw material particles are incident on the surface of the substrate by this method, there is a limit to the aim of setting the incident energy to a high level, which is only about 10 electron volts at most and has reached a sufficient level. However, quality effects such as reduction of the forming temperature expected in the film forming operation, smoothness of the thin film, improvement of adhesion, and improvement of density are absolutely superior to the bias sputtering method. I could not say. According to recent research, it was announced that this method could not reduce the formation temperature, improve the smoothness of the thin film, improve the adhesion, increase the density, etc., and attempts to overcome this cause. However, for example, refer to Non-Patent Document 1, it is a situation that has not been fully elucidated and has reached an effective means.
P. Frach, K.M. Goedicke, C.I. GotfriendandH. Bartzsch, Surf. Coat. Technol. 142 (2001) 628-634

The prior art is as described above, and all of them are technically and costly. In particular, both the bias sputtering of the conventional technique 2 and the bipolar sputtering method of the conventional technique 3 aim at increasing the energy of the particles, and the high density, high hardness, high adhesion, and high smoothness of the thin film at a low process temperature. Widely used in film formation processes that are required to be achieved. However, extremely high particle energies such as when forming a hard coating for prolonging the life of cutting tools or when trying to form a thin film crystallized by sputtering at a low process temperature on a substrate with low heat resistance such as a plastic substrate. When necessary, it is necessary to further increase the energy of the particles, and neither bias sputtering nor bipolar sputtering was sufficient.

  In addition, since both the bias sputtering method and the bipolar sputtering method require a plurality of extremely expensive power supply designs for sputtering, the cost of the apparatus has to be high, and it is difficult to design it inexpensively. It was. For this reason, the development of a sputtering method capable of obtaining high energy particles with a single power source method exists as an economic and technical background, and the development thereof has been demanded. Furthermore, in the bias sputtering method, interference occurs between multiple power sources using plasma as a medium, which hinders sputtering operations, particularly film forming operations that require high quality uniformity, and causes abnormal discharge. It causes inconveniences such as stoppage and power failure. These problems are one of the issues that are urgently solved, and in order to achieve this, it is required to effectively realize high energy particles and solve them with a single power source.

  The present invention has been made in view of the above circumstances, and the thin film formation temperature is reduced by increasing the energy when the raw material is incident on the substrate surface as compared with the conventional bias sputtering method and bipolar sputtering method. Can improve the adhesion of thin film and thin film, increase the density of thin film, etc., and can be driven stably with only a single relatively inexpensive power source to keep the device price low and enable stable discharge A sputtering apparatus is to be provided.

  In addition, when it is necessary to increase the energy when the target component particles to be sputtered are incident on the substrate surface, it has been impossible to achieve in the past by combining the present invention and the bias sputtering method. It is an object of the present invention to provide a sputtering method that makes it possible to increase the energy of particles incident on a substrate surface up to the energy region.

  For this reason, as a result of intensive studies by the present inventors, it has been found that increasing the energy of incident particles in the bipolar sputtering method, which was the subject of discussion as described above, is the effect of the magnetic field in the vicinity of the electrode serving as the anode. In the sputtering apparatus, the cathode plays the most important role of holding the material from which the thin film is formed, generating plasma in the vicinity of the surface, and vaporizing the raw material by the sputtering phenomenon. For this reason, research is widely conducted on the cathode among the elements constituting the sputtering apparatus. In particular, the magnetic field arrangement, control method, and design method in the vicinity of the cathode for localizing the plasma more densely in the vicinity of the cathode surface have been extensively studied, and there is no time to enumerate patent applications.

On the other hand, the anode surface does not vaporize the raw material, and it is rarely necessary to control the plasma by using a magnetic field near the anode surface. The basic idea was that there would be no need. For this reason, research on the magnetic field design of the anode is extremely small compared to that of the cathode, and it cannot be said that it is fulfilling.
As a result of diligent research in the present inventors, it was naturally determined from the conventional film formation conditions, etc., and conventionally, the plasma potential that could not be freely changed, the film formation conditions were the same as before, It has been found that the plasma potential can be increased.

  In general, the means for realizing it is to set the strongest magnetic field strength in each path to at least a specific value for all effective paths from the anode to the cathode of the charged particles, that is, 10 gauss or more. It can be said that the magnetic field design of the entire sputtering apparatus is performed. When the magnetic field design is properly performed, the effect of increasing the plasma potential is recognized even if the strongest magnetic field strength in each path is about 5 gauss for all effective paths from the anode to the cathode of the charged particles, but the thin film is reduced. In order to achieve high density, high hardness, high adhesion, and high smoothness at the process temperature, it is necessary to increase the energy of the incident particles to the substrate to about 10 electron volts. For all effective paths from the anode to the cathode, the strongest magnetic field strength in each path needs to be 10 gauss or more, and it is particularly preferable to set it in the range of 30 gauss to 10000 gauss.

  Sputtering film formation is basically a stable and feasible condition if the magnetic field design is generally set to 10 gauss or more, preferably 30 gauss to 10000 gauss. Therefore, it is more effective to select the optimum magnetic field strength by comparing each film forming material, film forming speed, film forming condition and its stability, film quality of the obtained thin film, etc. Nor. Of these, the range of 30 to 5000 gauss is often optimal, and is a temporary measure. Regarding the magnetic field design for realizing such an effect, the magnetic field design of the entire sputtering apparatus is such that the strongest magnetic field strength in each path is 10 gauss or more for all effective paths from the anode to the cathode of the charged particles. However, it is not always necessary to design the magnetic field of the anode or its vicinity so as to satisfy the above condition.

  However, in general, various magnetic field designs for localizing the deposition plasma have already been performed in the vicinity of the cathode, and a new magnetic field design that satisfies the conditions of the present invention is newly established in the vicinity of the cathode. It is virtually impossible to apply various magnetic field designs to localize the presence without disturbing it.

  Further, even if an attempt is made to realize the present invention by applying a magnetic field design to the cathode and the vicinity thereof, or the space in the sputtering apparatus excluding the anode and the vicinity thereof, the space in the sputtering apparatus is naturally the cathode. Since the raw material particles released from the surface must move to the surface of the substrate to form a thin film, it is necessary for the raw material particles to reach the substrate for the arrangement of magnets for generating a magnetic field. It is difficult with the major limitation of not obstructing.

  For this reason, since it becomes necessary to arrange a magnetic field in a relatively wide space, there is a high possibility that the magnetic field strength of a magnet, which is a practical magnetic field generating means, will be insufficient. Furthermore, in this space, the effective path from the anode to the cathode of the charged particles is easy to be complicated, so the magnetic field design for keeping the strongest magnetic field strength in each path to 10 gauss or more for all effective paths. It is not easy.

  On the other hand, it is the most practical and effective means to apply the magnetic field design in the vicinity of the anode surface, more specifically, in the space in the sputtering apparatus immediately above the anode surface. This method will be described with reference to FIG. With respect to the design of the cathode (2) and its magnetic field (8), the same configuration as that of a normal sputtering method can be used. For the anode (1), an independent electrode, not the device wall surface, is installed insulated from the device wall surface by an insulator (3). Further, a substantially uniform magnetic flux line (8) is arranged immediately above the anode surface so as to be substantially parallel to the anode surface by the magnet (5) so that the magnetic field strength in the direction parallel to the anode surface is 10 gauss or more. Since the magnetic field strength can be controlled by the strength of the magnet, the distance between the magnets, and the like, it can be optimized for each application using this.

  This is easily realized by arranging the N pole and S pole of two permanent magnets facing each other. The advantages of this method are not only that it can be easily realized and the design is very easy, but also that the magnetic field strength parallel to the anode surface can be formed very uniformly. Further, there is a path to the anode surface without passing through the magnetic field region using the shield (4) or the like so that all effective paths from the anode to the cathode of the charged particles pass through the region where the magnetic field is generated. Shield to prevent it from occurring.

  As a result, all effective paths from the anode (1) to the cathode (2) of the charged particles pass through the uniform magnetic field region. Therefore, the strongest magnetic field strength in each path is automatically set to the magnet arrangement. It is guaranteed that the value is equal to or greater than the desired value determined from the above, and the conditions of the present invention can be satisfied. Further, as an advanced means, it is possible to limit the effective area of the anode by arranging the shutter (10) whose opening degree can be adjusted so as to be in contact with the shield (4). An effect similar to that obtained by adjusting the strength of the magnet and the distance between the magnets can be obtained. Even if the substrate (6) is installed on the apparatus wall surface as shown in FIG. 4 to obtain the ground potential, the effect of the present invention can be sufficiently obtained. However, the substrate (6) is bias-sputtered in applications that require a stronger effect. It is also possible to apply a bias potential by disposing it on the electrode used sometimes (bias electrode (7) in FIG. 2).

  The effect corresponding to the object or the object of the present invention can be achieved only by applying the magnetic field design. However, as a result of further earnest research, the inventors have used the magnetic field design and DC discharge in combination. It has been found that it is effective for increasing the energy of the incident particles on the substrate in order to realize the highest density, high hardness, high adhesion and smoothness of the thin film at a low process temperature. A specific method will be described with reference to FIG. First, a negative electrode of a normal sputtering DC power supply (not shown) is connected to the sputtering cathode (2) in the sputtering apparatus, and the sputtering DC power supply (not shown) is applied to the anode (1) subjected to the magnetic field design. A positive electrode (not shown) is connected, and a direct current voltage is applied between them to generate a plasma for sputtering to form a film.

  Inclusion on the substrate to achieve high density, high hardness, high adhesion, and smoothness of the thin film at low process temperature even when various sputtering AC (low to high frequency) power supplies are used instead of sputtering DC power supplies Although the increase in energy of the particles can be realized, the increase in energy of the incident particles is most remarkable when a DC power source is used. In the case of an AC power source, as the frequency increases from a low frequency to a high frequency, the effect of increasing the energy of the incident particles gradually decreases. In other words, it is most effective to combine the magnetic field configuration with the simplest and cheapest DC power source, so it is possible to combine the DC power source with the magnetic field design from the viewpoint of increasing the energy of the incident particles and also from the viewpoint of reducing the price of the device preferable.

As described above, the configuration of the present invention is as described in (1) to (9) below.
(1) A sputtering apparatus in which the magnetic field design of the entire sputtering apparatus is performed so that the strongest magnetic field intensity in each path is 10 gauss or more with respect to an effective path from the anode to the cathode of charged particles.
(2) A mechanism for arranging magnetic flux substantially parallel to the anode surface is attached to or near the anode surface, and a vertical magnetic field is set to 10 gauss or more, preferably in the range of 30 to 10000 gauss in each effective path of charged particles. The sputtering apparatus according to claim 1, wherein:
(3) The sputtering apparatus according to claim 1, wherein a shutter capable of adjusting an opening is installed in the vicinity of the anode, and the energy of incident particles on the substrate is adjusted by adjusting the opening.
(4) The sputtering apparatus according to any one of claims 1 to 3, wherein the energy of incident particles on the substrate is further increased by applying a bias potential to the substrate on which the sputtering film formation is performed.
(5) The sputtering apparatus according to any one of claims 1 to 4, wherein the electrode used as the anode is provided with a magnetic field arrangement similar to the magnetic field arrangement usually applied to the sputtering cathode.
(6) The sputtering apparatus according to claim 5, wherein the magnetic field arrangement is a balanced magnetic field arrangement.
(7) The sputtering apparatus according to claim 5, wherein the magnetic field arrangement is an unbalanced magnetic field arrangement. (8) The sputtering apparatus according to any one of claims 1 to 5, wherein discharge is generated by applying a low-frequency voltage between 0 hertz (direct current) and 1000 hertz between the anode and the cathode.
(9) The sputtering apparatus according to claim 6, wherein a discharge is generated by applying a DC voltage between the anode and the cathode.

  The present invention does not use an independent power supply for bias application other than the sputtering film forming power supply as in the conventional bias sputtering system with the above configuration, and the sputtering film forming power supply alone is equivalent to or equivalent to the bias sputtering system. The above high density, high hardness, high adhesion, and high smoothness can be realized at a low process temperature. The significance is great. In addition, the cost can be reduced and the significance is great as compared with the case of a conventional device that requires a plurality of power supplies or related control mechanisms therefor. In addition, it is possible to eradicate the cause of instability of plasma discharge due to interference of both power sources for sputtering film formation and bias application via plasma, which has been regarded as the weakest point of bias sputtering method. And deserves special mention.

  The interference of the power source causes the plasma to become unstable and the discharge to stop due to abnormal discharge, naturally destabilizes the sputtering film formation, and causes problems in the quality and reproducibility of the thin film obtained. Furthermore, the interference between the two power sources that control this plasma in the bias sputtering method is because the failure frequency of the power source due to abnormal discharge becomes significantly higher when compared with the case where only the film forming power source for sputtering is used alone. Although it has been pointed out as a further disadvantage that economic and time loss occurs, the present invention has an effect of eradicating the above-mentioned problems arising from interference between two power sources in principle in these bias sputtering methods. .

  Furthermore, the superior point of the present invention is that the incident energy of the particles to the substrate can be set in a high energy region that could not be reached by the conventional method by combining the sputtering by the design of the present invention and the bias sputtering method. That is. In the bias sputtering method, the increase in the incident energy of particles on the substrate is realized by increasing the voltage applied by the bias power source to the negative side. However, if the voltage applied by the bias power supply is increased to the negative side with the aim of increasing the incident energy of the particles on the substrate, the abnormal discharge due to the interference of the power supply described above becomes remarkable, and even the maintenance of the discharge does not remain, and the film formation is not good. It becomes possible. This phenomenon dominates the upper limit of the incident energy of particles on the substrate by the bias method. However, as described above, by adding a bias electrode and a bias power source to the sputtering apparatus designed according to the present invention, the effect is synergistically excellent, and the incident energy of particles to the substrate is further increased. Can be raised higher. Thereby, the application range of sputtering can be expanded, and it is expected to greatly contribute to the development of various technical fields.

  Compared with the bipolar sputtering method, AC power sources of various waveforms such as pulses and rectangular waves whose polarities that are essential in this bipolar sputtering method are switched with a period of 1 to several hundreds kHz are significantly more expensive than power sources that are usually used. Therefore, by applying the present invention, the effect of suppressing the apparatus price by applying the present invention in which only one DC power source, which is the simplest and cheapest type, is used as the power source for sputtering film formation is remarkable. Further, as will be shown in the examples described later, the effect of increasing the incident energy of particles to the substrate when the bipolar sputtering method is applied is also compared with the case of applying the present invention (no bias application, substrate potential grounding). In terms of the ability to achieve inferior, high density, high hardness, high adhesion, and high smoothness at low process temperatures, the present invention has been experimentally confirmed to exceed the bipolar sputtering method, and is clearly superior. is there.

Effect of the invention;
Magnetic flux substantially parallel to the anode surface provided by the magnetic field design set in the present invention (magnetic field)
Has a function of inducing a winding motion of various charged particles in the plasma around the magnetic flux by the Lorentz force, and exerting a force in the direction of capturing the charged particles, that is, a force that hinders the movement of the charged particles. The movement of the charged particles is an electric current, and the force that prevents the movement of the charged particles acts as a resistance (impedance).

  In this way, the magnetic flux substantially parallel to the anode surface acts as an increase in impedance to the plasma current about to flow out of the anode, and has the effect of pushing up the plasma potential. When the potential of the plasma is pushed up, the potential difference from the ground potential to the plasma potential increases, and in a normal case where the substrate is kept at the ground potential, the energy of particles incident on the surface of the substrate (substrate potential = potential ground potential to plasma The potential difference up to the potential has a positive correlation).

  In the present invention, the shield in the vicinity of the anode has an effect of restricting the moving path of the charged particles in order to assist the effective path of the charged particles to pass through the region where the magnetic field design is performed. In addition, the shutter having an adjustable opening in the vicinity of the anode in the present invention has an effect of adjusting the effective area of the anode, and as a result, has an effect of adjusting the impedance. Impedance adjustment makes it possible to adjust the potential of the plasma and thus the energy of particles incident on the surface of the substrate on the same principle as described above.

  In the present invention, the bias electrode is electrically disconnected from the wall surface of the apparatus, which is generally set to the ground potential by an insulator, so that the potential of the substrate disposed on the bias electrode is set to a potential different from the ground potential. There is an action that makes it possible. By setting the voltage by the power supply for bias application, the potential of the bias electrode, that is, the potential of the substrate in this case lower than the ground potential (zero potential) (minus side), the plasma potential to the substrate potential (minus in this case) The potential difference is made larger than when the substrate is kept at ground potential.

In the present invention, the setting of the frequency of the power source for sputtering (using direct current, alternating current, whether alternating current is low frequency or high frequency) and its operation will be described.
When plasma is generated by applying an alternating voltage between the cathode and the anode, the behavior of the charged particles is almost the same as that of each charged particle in the space in the sputtering apparatus. It only vibrates at the particle position. In this case, even if there is a region with high impedance induced by the magnetic field in the path from the anode to the cathode, the charged particles oscillating away from this region are not affected by this impedance, and as a result The plasma potential cannot be increased.

  However, the amplitude of the charged particle oscillation increases as the frequency decreases, and the number of charged particles passing through the high-impedance region increases accordingly. This phenomenon becomes most noticeable when the discharge is maintained at a DC voltage. In other words, the lower the frequency used, the greater the effect of increasing the impedance derived from the effect of winding on the magnetic field. As a result, the potential of the plasma is pushed up, and the energy of particles incident on the substrate surface increases. In summary, performing a low frequency, particularly direct current discharge, has the effect of promoting an increase in the energy of particles incident on the substrate surface mediated by the plasma impedance. It is also possible to adjust the energy of particles incident on the substrate surface by selecting the frequency using this action.

  Embodiments of the present invention will be described below with reference to FIGS. 4 to 8 and examples. However, this is merely an example for explaining the present invention, and is not intended to limit the present invention.

  In FIG. 4 showing this embodiment, the substrate (6) is installed on the wall surface of the apparatus having a ground potential, and no bias electrode or bias power source is used. The substrate used was made of a mirror-polished stainless steel plate (10 mm square, 0.5 mm thickness), and the cathode (2) was made of titanium metal having a cathode surface area of 200 mm × 135 mm, in the vicinity of the surface. Has a balanced magnetic field (8) that is most commonly used in the sputtering method. In the normal sputtering method, the anode (1) employs a method in which the vacuum vessel wall surface is used as the anode as shown in FIG. 1. In the present invention, the anode (1) is separated from the substrate (6) and the vacuum vessel. Independently designed in a vacuum vessel through an insulator.

  In this embodiment, the anode surface material and area were the same as that of the cathode surface, but titanium metal having the same area of 200 mm × 135 mm was used. However, the magnetic field was placed on the cathode for the sputtering cathode used in the cathode (2). Rather than a balanced magnetic field arrangement for localizing in the vicinity of the surface, the N pole and S pole of two 200 mm long rod-shaped permanent magnets (5) are placed directly above the anode face so that they are directly above the anode face. The magnetic flux lines (8) were arranged substantially parallel to the anode surface. The intensity of the magnetic field in this case is 63 gauss when measured so that the magnetic flux line passes perpendicularly to the probe surface (Hall element) of Handy Gauss meter No. 5080 manufactured by SYPRIS in the center region of the magnetic flux line (8). Met.

  Further, in order to prevent the charged particles from passing through the region other than the region where the magnetic flux lines are arranged and from the cathode surface to the anode surface, the movement of the charged particles was restricted by using the shield (4). In FIG. 4, the magnet (5) and the shield are shown as if they were attached to the anode, but this is not limited to attaching these components to the anode. However, considering the ease of design, manufacture, and handling, it is more reasonable and preferable to integrate these parts so that they can be assembled with the anode.

  The drive power supply is a DC sputtering power supply in this embodiment, the positive terminal of the output terminal is connected to the anode (1) of this embodiment, the negative electrode is connected to the cathode (2), and the applied power is constant at 500 watts. Controlled and adjusted. As the atmospheric gas in the sputtering apparatus, the most common argon gas was used as the sputtering gas, and the pressure was controlled to be constant at 0.5 Pascal. In addition, in order to measure the incident energy of particles on the substrate, a mass / energy analyzer (EQP300 manufactured by HEIDEN, UK, not shown) was installed adjacent to the substrate.

  FIG. 6 shows the measurement results of the incident energy of particles (argon ions) onto the substrate when this example is applied. According to this figure, the number of particles having an energy of about 15 electron volts is the largest, but it is worth mentioning that a large percentage of high-energy particles of 30 electron volts or more, which are absolutely unattainable in the usual sputtering method. And was incident on the substrate surface. Incidentally, since one electron volt corresponds to a temperature difference of 10,000 degrees or more when converted to a temperature, those skilled in the art can easily understand how excellent the present invention is from this measurement result. It is thought.

  In this way, the present invention provides a bias sputtering method (by applying a negative potential to the substrate, which is set to the same potential as the bias electrode as shown in FIG. The effect equivalent to the case where a negative potential of 35 volts is applied to the bias electrode in the method of increasing the incident energy) is realized as a stable discharge with only one sputtering power source without using the bias electrode and the bias power source. It was made and its significance is extremely large.

  Further, as described above, when it is desired to increase the energy of the incident particles to the substrate, the adjustment can be performed by increasing the strength of the magnet. As another embodiment of the present invention, as shown in FIG. 5, a magnetic field design (balanced type, unbalanced type, etc.) used as a cathode in a normal sputtering method is also applied to the anode, and sputtering by direct current discharge is performed. You can also This is because the N and S poles of the two permanent magnets (5) shown in FIG. 4 are placed directly above the anode surface, so that the magnetic flux lines (8) are placed almost parallel to the anode surface just above the anode surface. Compared with the case of FIG. 4, since the component perpendicular to the anode surface of the magnetic flux is dominant near the center of the anode and a loss occurs, the effect of increasing the energy of the incident particles is slightly compared with the embodiment of FIG. Although it is difficult to obtain, the effect of realizing sufficiently high density, high hardness, high adhesion, and high smoothness of the thin film at a low process temperature can be obtained by taking measures such as increasing the magnetic field strength.

Comparative Example 1;
In order to verify the effect of the present invention, it was compared with the incident energy of particles (argon ions) on the substrate in the case of adopting the structure of a normal sputtering method (FIG. 1). In order to adopt a normal sputtering system configuration, the entire anode, i.e., the anode (1) and its insulator (3), the shield (4), the magnet (5), which has been subjected to the specific magnetic field design from this embodiment shown in FIG. ), And the configuration is the same as that obtained by removing the magnetic flux (8). For this reason, also in this comparative example, the anode with the above magnetic field design was removed from the previous embodiment, the positive electrode of the output terminal of the DC sputtering power supply was connected to the apparatus wall surface, and the negative electrode was connected to the cathode (2). Control was made constant at 500 watts. The other configuration is exactly the same as that of the above-described embodiment.

  FIG. 7 shows the measurement results of the incident energy of particles (argon ions) on the substrate in this case. It can be seen that the incident energy to the substrate has an energy distribution having a maximum value in the vicinity of 5 electron volts, and particles having an energy of 10 electron volts or more are hardly observed. In other words, by applying the anode with the magnetic field control of the present invention in comparison with this comparative example, it is possible to raise the energy of particles that could only be obtained at 10 electron volts or less in a normal sputtering method to a maximum of about 35 electron volts. became.

Comparative Example 2; Bipolar Sputtering Method FIG. 3 is a conceptual diagram of the bipolar sputtering method. Although this was also explained in the section of means for realizing the invention, the greatest feature of this technique is that the two electrodes (9) perform sputtering film formation while the roles of the cathode and the anode are alternately switched at a cycle of about 1 to 100 kilohertz. It is to progress. In this comparative example, both electrodes are made of titanium metal having an area of 200 mm × 135 mm. In order to alternate the roles of the cathode and anode of the two electrodes with a period of about 1 to 100 kilohertz, an AC sputtering power supply (not shown) of about 1 to 100 kilohertz is used.

  In this comparative example, a power source that generates an alternating rectangular pulse wave whose polarity is switched at a period of 50 kHz is adjusted so that the effective power is 500 watts. The substrate (6) is installed on the wall surface of the apparatus having a ground potential, and the bias electrode (7) and the bias power source (not shown) are not used at all. Further, a stainless steel plate (10 mm square, 0.5 mm thickness) subjected to mirror polishing was used as the substrate. As the atmospheric gas in the sputtering apparatus, the most common argon gas was used as the sputtering gas, and the pressure was controlled to be constant at 0.5 Pascal.

  In addition, in order to measure the incident energy of particles on the substrate, a mass / energy analyzer (EQP300 manufactured by HEIDEN, UK, not shown) was installed adjacent to the substrate. Configurations other than these electrodes and the power source were unified with those of the example and comparative example 1. FIG. 8 shows the measurement results of the incident energy of particles (argon ions) on the substrate in this case. It can be seen that the energy incident on the substrate has an energy distribution having a maximum value near 10 electron volts, and particles having an energy of 20 electron volts or more are hardly observed.

In other words, the incident energy to the substrate by the bipolar sputtering method is higher than the normal DC sputtering method of Comparative Example 1 by about several electron volts, but it is clear when compared with the maximum 35 electron volts when the present invention is implemented. It was found that there are few high energy particles.
As a result of the above, when comparing the Example, Comparative Example 1 and Comparative Example 2, the simple configuration just by applying the magnetic field design of the present invention was taken, and by combining this with an inexpensive DC power source, The significance of the great effect is clear.

  In the present invention, it is possible to increase the incident energy of particles on a substrate to a high energy region that could not be obtained by any of the sputtering methods so far, and to enable stable operation by using a power source for sputtering film formation alone. Sputtering operations that have succeeded in reducing costs and have been required to achieve high incident energy, sputtering operations that require operation at as low a temperature as possible, or sputtering that require high-quality film forming operations. It can be provided for operation, etc., and it can be applied to various technical fields such as cutting tool surface processing, surface processing to plastics with low heat resistance, not to mention electro-technical field, and greatly contributes to industrial development widely. It is expected.

Schematic of the most common sputtering apparatus. 1 is a schematic view of a bias sputtering apparatus that increases the incident energy of particles to a substrate by applying a bias voltage to the substrate. 1 is a schematic view of a bipolar sputtering apparatus developed mainly for the long-term stabilization of sputter deposition of an insulator thin film. An embodiment of the present invention in which a magnetic flux substantially parallel to the anode surface is arranged using a permanent magnet, and this is combined with discharge by a DC sputtering power source. An embodiment of the present invention in which the same balance type magnetic flux as that of the cathode is disposed on the anode, and this is combined with discharge by a DC sputtering power source. The measurement result (actual value) of the incident energy of the particle | grains (argon ion) to a base | substrate at the time of applying the Example of this invention. The measurement result (actual value) of the incident energy of the particle | grains (argon ion) to a base | substrate at the time of applying the normal direct current | flow sputtering system of the comparative example 1. FIG. The measurement result (actual value) of the incident energy of the particle | grains (argon ion) to a base | substrate at the time of applying the bipolar sputtering system of the comparative example 2. FIG.

Explanation of symbols

(1): Anode (2): Cathode (3): Insulator (4): Shield (5): Magnet (6): Substrate (7): Bias electrode (8): Magnetic flux line (9): Cathode / Anode (10): Shutter

Claims (4)

A mechanism for arranging magnetic flux substantially parallel to the anode surface is attached to or near the anode surface, and sputtering is performed so that the strongest magnetic field strength in each path is 10 Gauss or more with respect to an effective path from the anode to the cathode of the charged particles. Sputtering in which a magnetic field design of the entire apparatus is performed, and a discharge is generated by applying a DC voltage between the anode and the cathode, and the magnetic field arrangement of the anode is a balanced magnetic field arrangement or an unbalanced magnetic field arrangement apparatus.   The sputtering apparatus according to claim 1, wherein a magnetic field in a direction perpendicular to each effective path of the charged particles is set in a range of 30 gauss to 10000 gauss.   The sputtering apparatus according to claim 1, wherein a shutter capable of adjusting an opening is installed in the vicinity of the anode, and the energy of incident particles on the substrate is adjusted by adjusting the opening.   4. The sputtering apparatus according to claim 1, wherein a bias potential is applied to the substrate on which the sputtering film formation is performed to further increase the energy of incident particles on the substrate.

Images