JP7519210B2 - Film forming equipment - Google Patents

Description

The present invention relates to a film forming apparatus.

As a film formation device for forming a film on the surface of a film formation target, for example, there is one that uses the ion plating method. In the ion plating method, particles of evaporated film formation material are diffused in a vacuum chamber and attached to the surface of the film formation target. Such a film formation device is equipped with a plasma source for generating a plasma beam, which is provided on the side wall of the vacuum vessel, a steering coil for directing the plasma beam generated by the plasma source into the vacuum vessel, a main hearth which is the main anode that holds the film formation material, and a ring hearth which is an auxiliary anode that surrounds the main hearth (for example, see Patent Document 1).

Japanese Patent Application Publication No. 9-256147

Here, in the above-mentioned film forming apparatus, a portion of the diffused film forming material may remain near the film forming material and accumulate around the main hearth and the annular hearth. If such deposits grow, they may affect the uniformity of the film formed on the surface of the film forming target. Furthermore, if the amount of deposition increases and the main hearth and the annular hearth are short-circuited with each other, this may hinder the film formation. Therefore, there was a need to remove the deposits, and there was a demand to slow down the growth of the deposits in order to reduce such removal work.

Therefore, the present invention aims to provide a film forming device that can slow down the growth of deposits.

The film forming apparatus of the present invention is a film forming apparatus that heats a film forming material with a plasma beam and attaches particles vaporized from the film forming material to a film forming target. It is equipped with a main anode that is filled with the film forming material and directs the plasma beam to the film forming material, an auxiliary anode that has a permanent magnet and an electromagnet and is arranged around the main anode and directs the plasma beam, and a power supply that supplies power to the electromagnet of the auxiliary anode, and the power supply changes the magnetic flux density above the main anode.

The film forming apparatus is equipped with a power supply that supplies power to the electromagnet of the auxiliary anode. This power supply changes the magnetic flux density above the main anode. When the magnetic flux density is changed in this way, it is possible to vary the position where the diffused film forming material concentrates and adheres around the main anode and auxiliary anode. The deposits formed in this way grow more slowly than deposits formed by the film forming material concentrating in a narrow area. As a result, the growth of the deposits can be slowed.

The power supply may change the magnetic flux density by superimposing an alternating current on the electromagnet. The power supply can easily change the magnetic flux density by superimposing an alternating current on the electromagnet.

The change in magnetic flux density may be a change in the area where the magnetic flux density is zero. In this way, when the area where the magnetic flux density is zero is changed, the position where the diffused film-forming material concentrates and adheres around the main anode and auxiliary anode can be changed. The deposits formed in this way grow more slowly than deposits formed by the film-forming material concentrating in a narrow area. As a result, the growth of the deposits can be slowed.

In the film forming apparatus, the power supply changes the magnetic flux density by superimposing an AC current on the electromagnet, and if the amplitude of the position at which the deposit of the film forming material is formed, which changes due to the superimposition of the AC current, is a, and the thickness of the deposit when the AC current is not superimposed on the electromagnet is σ, the power supply may superimpose the AC current on the electromagnet under the condition that a/σ is 2 or more. The power supply may also superimpose the AC current on the electromagnet under the condition that a/σ is 4 or more. In this case, the film forming material can be diffused with a wide amplitude a relative to the thickness σ of the deposit. Therefore, the growth of the deposit can be delayed.

The present invention provides a film forming device that can slow down the growth of deposits.

1 is a cross-sectional view showing a configuration of a film forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing the configuration in the vicinity of the main hearth. FIG. 2 is a schematic diagram showing a magnetic field in the vicinity of the main hearth. The relationship between the hearth coil current and the amount of fluctuation of deposits A, B, and C is shown. FIG. 4A is a diagram showing a growth model of deposits A and B, and FIG. 4B is a diagram showing the waveform of an AC current. The values of the formation positions PA and PB of the deposits A and B in the graph of FIG. 4 are extracted and plotted. 1 is a graph showing the relationship between the time average value of the flux intensity at an arbitrary position around the main hearth and the standard value "a/σ".

One embodiment of a film forming apparatus according to the present invention will be described in detail below with reference to the attached drawings. Note that in the description of the drawings, the same elements are given the same reference numerals, and duplicate descriptions will be omitted.

The film forming apparatus 1 according to the first embodiment shown in FIG. 1 is an ion plating apparatus used in the so-called ion plating method. For ease of explanation, FIG. 1 shows an XYZ coordinate system. The Y-axis direction is the direction in which the film forming object, which will be described later, is transported. The X-axis direction is the direction in which the film forming object faces a hearth mechanism, which will be described later. The Z-axis direction is the direction perpendicular to the X-axis direction and the Y-axis direction.

The film forming apparatus 1 is a so-called vertical type film forming apparatus in which the film forming target 11 is placed and transported in the vacuum chamber 10 with the film forming target 11 standing upright or tilted from the upright state so that the plate thickness direction of the film forming target 11 is horizontal (X-axis direction in FIG. 1). In this case, the X-axis direction is horizontal and the plate thickness direction of the film forming target 11, the Y-axis direction is horizontal, and the Z-axis direction is vertical. On the other hand, in one embodiment of the film forming apparatus according to the present invention, the film forming apparatus may be a so-called horizontal type film forming apparatus in which the film forming target is placed and transported in the vacuum chamber so that the plate thickness direction of the film forming target is approximately vertical. In this case, the Z-axis and Y-axis directions are horizontal, and the X-axis direction is vertical and the plate thickness direction. In the following embodiment, an embodiment of the film forming apparatus of the present invention will be described using the vertical type as an example.

The film forming apparatus 1 includes a hearth mechanism 2, a transport mechanism 3, a wheel hearth 6, a steering coil 5, a plasma source 7, a pressure adjustment device 8, a power supply 50, and a vacuum chamber 10.

The vacuum chamber 10 has a transfer chamber 10a for transferring the film-forming object 11 on which a film of the film-forming material is to be formed, a film-forming chamber 10b for diffusing the film-forming material Ma, and a plasma port 10c for receiving the plasma beam P irradiated from the plasma source 7 into the vacuum chamber 10. The transfer chamber 10a, the film-forming chamber 10b, and the plasma port 10c are interconnected. The transfer chamber 10a is set along a predetermined transfer direction (arrow D1 in the figure) (Y-axis). The vacuum chamber 10 is made of a conductive material and is connected to ground potential.

The transport mechanism 3 transports a holding member 16 that holds the film-forming object 11 in a transport direction D1 while facing the film-forming material Ma. For example, the holding member 16 is a frame that holds the outer edge of the film-forming object. The transport mechanism 3 is composed of multiple transport rollers 15 installed in the transport chamber 10a. The transport rollers 15 are arranged at equal intervals along the transport direction D1, and transport the holding member 16 in the transport direction D1 while supporting it. The film-forming object 11 is, for example, a plate-shaped member such as a glass substrate or a plastic substrate.

The plasma source 7 is a pressure gradient type, and its main body is connected to the deposition chamber 10b via a plasma port 10c provided on the side wall of the deposition chamber 10b. The plasma source 7 generates a plasma beam P in the vacuum chamber 10. The plasma beam P generated in the plasma source 7 is emitted from the plasma port 10c into the deposition chamber 10b. The emission direction of the plasma beam P is controlled by a steering coil 5 provided to surround the plasma port 10c. The steering coil 5 generates a magnetic field in the Y-axis direction and guides the plasma beam generated by the plasma source 7 to the center of the vacuum vessel.

The pressure adjustment device 8 is connected to the vacuum chamber 10 and adjusts the pressure inside the vacuum chamber 10. The pressure adjustment device 8 has a pressure reduction section, such as a turbomolecular pump or a cryopump, and a pressure measurement section that measures the pressure inside the vacuum chamber 10.

The hearth mechanism 2 is a mechanism for holding the film-forming material Ma. The hearth mechanism 2 is provided in the film-forming chamber 10b of the vacuum chamber 10, and is disposed in the negative direction of the X-axis as viewed from the transport mechanism 3. The hearth mechanism 2 has a main hearth 21, which is a main anode that guides the plasma beam P emitted from the plasma source 7 to the film-forming material Ma, or a main anode to which the plasma beam P emitted from the plasma source 7 is guided.

As shown in FIG. 2, the main hearth 21 has a cylindrical filling portion 21a that extends in the positive direction of the Z axis and is filled with the film-forming material Ma, and a flange portion 21b that protrudes from the filling portion 21a. The main hearth 21 is maintained at a positive potential with respect to the ground potential of the vacuum chamber 10, and therefore attracts the plasma beam P (see FIG. 1). A through hole 21c for filling the film-forming material Ma is formed in the filling portion 21a of the main hearth 21, into which the plasma beam P is incident. The tip portion of the film-forming material Ma is exposed to the film-forming chamber 10b at one end of the through hole 21c.

The annular hearth 6 is an auxiliary anode having an electromagnet for guiding the plasma beam P. The annular hearth 6 is arranged around the filling section 21a of the main hearth 21 that holds the film-forming material Ma. The annular hearth 6 has a coil 6a (electromagnet), a permanent magnet 6b, and an annular container 6c, and the coil 6a and the permanent magnet 6b are housed in the annular container 6c. The annular hearth 6 controls the direction of the plasma beam P incident on the film-forming material Ma or the direction of the plasma beam P incident on the main hearth 21 depending on the magnitude of the current flowing through the coil 6a.

Examples of the film-forming material Ma include transparent conductive materials such as ITO and ZnO. When the film-forming material Ma is made of a conductive material, when the plasma beam P is irradiated to the main hearth 21, the plasma beam P directly enters the film-forming material Ma, the tip of the film-forming material Ma is heated and vaporized, and the film-forming material particles Mb ionized by the plasma beam P diffuse into the film-forming chamber 10b. The film-forming material particles Mb diffused into the film-forming chamber 10b move upward (in the positive direction of the Z axis) of the film-forming chamber 10b and adhere to the surface of the film-forming target object 11 in the transfer chamber 10a. The film-forming material Ma is a solid material formed into a cylindrical shape of a predetermined length, and multiple pieces of the film-forming material Ma are filled into the hearth mechanism 2 at one time. Then, the film-forming material Ma is sequentially pushed out from the lower direction of the hearth mechanism 2 according to the consumption of the film-forming material Ma so that the tip of the topmost film-forming material Ma maintains a predetermined positional relationship with the upper end of the main hearth 21.

The hearth mechanism 2 also has an outer rim 28 arranged around the main hearth 21. This outer rim 28 prevents a short circuit between the main hearth 21 and the annular hearth 6 caused by deposition of the film-forming material Ma around the main hearth 21 during film formation.

The outer rim 28 is a cylindrical container with a bottom. The outer rim 28 has a side wall 28b that surrounds the filling portion 21a of the main hearth 21, and a bottom 28c that is provided at the end of the side wall 28b on the flange portion 21b side of the main hearth 21. A circular opening 28a is formed in the bottom 28c of the outer rim 28, through which the filling portion 21a of the main hearth 21 is inserted. The upper part of the side wall 28b of the outer rim 28 gradually warps toward the side of the outer rim 28, and opens toward the deposition chamber 10b.

The power supply 50 is a device that supplies power to the coil 6a of the annular hearth 6. The power supply 50 changes the magnetic flux density above the main hearth 21. Specifically, the power supply 50 changes the magnetic flux density by superimposing an alternating current on the coil 6a. In this embodiment, the change in magnetic flux density is caused by shifting the area above the main hearth 21 where the magnetic flux density is zero. The current from the power supply 50 forms a sine wave (see FIG. 5(b)). The power supply 50 sets the frequency, the center current value (offset), and the amplitude (the magnitude of the current that changes to the positive and negative sides relative to the center current value).

The power supply 50 superimposes an AC current on the coil 6a under the condition that a/σ is 2 or more. More preferably, the power supply 50 superimposes an AC current on the coil 6a under the condition that a/σ is 4 or more. Here, "a" refers to the amplitude of the deposition position of the film-forming material that changes due to the superposition of the AC current. A detailed explanation of the amplitude a will be given later. "σ" refers to the thickness of the deposit when no AC current is superimposed on the coil 6a.

In FIG. 2, deposit A is likely to form in the curved portion near the top end of the outer rim 28. Deposit B is likely to form at the bottom 28c. Deposit C is likely to form at the tip of the main hearth 21. Of these, deposits A and B grow to extend significantly at specific locations. If the power supply 50 does not superimpose an AC current, deposits A and B extend to a predetermined thickness. The thickness of the extending portions of deposits A and B at this time is "σ". Thickness σ may be obtained by forming deposits A and B and taking actual measurements at a stage prior to setting the AC power conditions of the power supply 50, for example, when the film forming apparatus 1 is introduced or manufactured.

Next, the condition of "a/σ" will be described in more detail with reference to Fig. 3 to Fig. 7. The magnetic field distribution in the vicinity of the main hearth 21 will be described with reference to Fig. 3. Fig. 3 shows the magnetic field distribution in a state where the plasma beam emitted from the plasma source 7 is guided to the main hearth 21 by the annular hearth 6. The arrows in the figure indicate the direction of the magnetic field lines. The magnetic field in the vicinity of the main hearth 21 is affected by the magnetic field due to the annular hearth 6, the magnetic field due to the steering coil 5, and the magnetic field due to the self-induction of the plasma beam P. Due to these influences, a region where the magnetic flux density is 0 is formed. As shown in Fig. 3, in the configuration of the film-forming apparatus 1 of this embodiment, the magnetic field is distributed asymmetrically with respect to the central axis CL of the annular hearth 6. Therefore, the position where the magnetic flux density is 0 is formed at a position shifted from the central axis CL. However, in the simulation for setting the condition of "a/σ", the plasma beam P is assumed to be not eccentric, and the calculation is performed assuming that the magnetic field is distributed symmetrically with respect to the central axis CL. At this time, regions E1 and E2 where the magnetic flux density is 0 exist on the central axis CL above the main hearth 21.

When the current supplied to the coil 6a of the annular hearth 6 (hereinafter sometimes referred to as the hearth coil current) is set to a predetermined value, if the region where the magnetic flux density is zero is taken as "region E1," then as the hearth coil current is increased, the region where the magnetic flux density is zero moves to "region E2," which is higher than region E1. As the value of the hearth coil current is increased, the region where the magnetic flux density is high expands upward. This is presumably because, as the hearth coil current is increased, the position of the region where the magnetic flux density is zero shifts upward, and the flow of the plasma beam P also moves upward. Therefore, when the power supply 50 superimposes an alternating current, the magnetic field distribution changes repeatedly, and the region where the magnetic flux density is zero fluctuates so as to move back and forth in the vertical direction.

Just as the magnetic field distribution changes as described above, the electric potential distribution also changes with changes in the hearth coil current. The change in the electric potential distribution changes the way the ions fly, and the positions and velocities of deposits A and B change.

For example, as shown in FIG. 2, the formation positions of deposits A and B formed with a predetermined hearth coil current without superimposing an AC current are "PA" and "PB". When an axis extending in the extension direction of deposits A and B and passing through the peak positions of deposits A and B is set, the formation positions PA and PB are set at the intersection of the axis and the formation surface of deposits A and B (the surface of the outer rim 28 in FIG. 2). At this time, when the hearth coil current is low, the formation position PA1 is set at a position far from the main hearth 21, and when the hearth coil current is high, the formation position PA2 is set at a position close to the main hearth 21. Also, when the hearth coil current is low, the formation position PB1 is set at a position close to the main hearth 21, and when the hearth coil current is high, the formation position PB2 is set at a position far from the main hearth 21. FIG. 4 shows the relationship between the hearth coil current and the amount of fluctuation of deposits A, B, and C. The results shown in FIG. 4 are obtained by simulation. Here, a DC hearth coil current of a predetermined current value is applied to the coil 6a without superimposing an AC current. The horizontal axis indicates the magnitude of the hearth coil current, and the vertical axis indicates the distance from the reference position to the formation positions of deposits A, B, and C. In FIG. 4, the formation positions of deposits A, B, and C when the hearth coil current is set to 0 A are set to the reference positions.

As described above, the formation positions PA and PB of the deposits A and B vary with the variation of the hearth coil current. Therefore, when the power supply 50 superimposes an AC current, the formation positions PA and PB of the deposits A and B also vary periodically as the hearth coil current varies periodically to draw a sine wave (see FIG. 5(b)). As shown in FIG. 5(b), the hearth coil current draws a sine wave with the current value C1 as the center value, the current value C2 as the maximum value, and the current value C3 as the minimum value. The growth model of the deposits A and B at this time is shown in FIG. 5(a). The horizontal axis indicates the positions of the formation positions PA and PB, and the vertical axis indicates the flux intensity. The flux intensity is a parameter indicating the amount (height) of the deposition material particles at a certain position. It is assumed that the peak positions of the flux intensity are the formation positions PA and PB of the deposits A and B. The distribution of flux intensity when the hearth coil current is at a current value C1 is shown in graph G1, the distribution of flux intensity when the hearth coil current is at a current value C2 is shown in graph G2, and the distribution of flux intensity when the hearth coil current is at a current value C3 is shown in graph G3. Thus, the fluctuation width 2a of the formation positions PA, PB of the deposits A, B is shown as the distance between the peak position of graph G2 and the peak position of graph G3. The amplitude a of the formation positions PA, PB of the deposits A, B at this time is defined as half the size of the fluctuation width 2a. For example, when an AC current is not superimposed, the film forming material is concentrated at one formation position PA, PB, so that the growth of the deposits A, B is accelerated. In contrast, when an AC current is superimposed, as shown in FIG. 5(a), the position where the film forming material is attached periodically fluctuates within the range of the fluctuation width 2a. Therefore, since the film forming material is dispersed, the growth (extension in the extension direction) of the deposits A, B can be delayed.

Figure 6 is a plot of the values of the formation positions PA and PB of deposits A and B from the graph in Figure 4. By setting one of the hearth coil currents in this graph as the center value and setting the amplitude of the AC current, the fluctuation width 2a is determined, and therefore the amplitude a is determined. For example, if the center value of the hearth coil current is 20A and the amplitude is 10A, the distance between the formation position PA at 30A and the formation position PA at 10A is the fluctuation width 2a when deposit A is formed. Also, half the value of the fluctuation width 2a is the amplitude a (= 10 mm). Also, the distance between the formation position PB at 30A and the formation position PB at 10A is the fluctuation width 2a when deposit B is formed. Also, half the value of the fluctuation width 2a is the amplitude a (= 3.5 mm). Here, the amplitude a can be expressed as a standard value "a/σ" by dividing it by the thickness σ of deposits A and B. The thickness σ of deposit A was measured to be 5 mm, and the thickness σ of deposit B was measured to be 1 mm. Therefore, if the center value of the hearth coil current is 20 A and the amplitude is 10 A, the standard value "a/σ" of deposit A is 2, and the standard value "a/σ" of deposit B is 3.5. In this way, by referring to the standard value "a/σ", it is possible to compare the magnitude of the amplitude a of the region where the ion flux is concentrated relative to the spread (thickness σ) of the ion flux.

7 shows the relationship between the time average value of the flux strength at any position around the main hearth 21 and the standard value "a/σ". The horizontal axis of FIG. 7 shows the standard value "a/σ", and the vertical axis shows the standard value of the time average value of the flux strength. The standard value of the time average value of the flux strength is a value that indicates the magnitude of the flux strength relative to the standard value "a/σ=1", which is set as the standard value (=1). As shown in FIG. 7, it can be seen that the flux strength attached to any point decreases as the standard value "a/σ" increases. In particular, the flux strength can be rapidly reduced until the standard value "a/σ" becomes 2. Therefore, it can be seen that the power source 50 preferably superimposes an AC current on the coil 6a under the condition that a/σ is 2 or more. Also, the flux strength can be rapidly reduced until the standard value "a/σ" becomes 4. Therefore, it can be seen that the power source 50 preferably superimposes an AC current on the coil 6a under the condition that a/σ is 4 or more.

In order to achieve the above-mentioned condition of the standard value "a/σ", there is no particular limitation on how the power supply 50 sets the frequency, center current value, and amplitude. As an example, the frequency may be set in the range of 10 to 100 Hz. In this range, it is possible to prevent energy loss as heat loss in the copper plate due to a frequency that is too high, and to prevent the formation of a layer structure in the film due to a frequency that is too low. The center current value may be set in the range of 20 to 40 A. The amplitude may be set in the range of 2 to 20 A.

Next, the operation and effects of the film forming apparatus 1 according to this embodiment will be described.

The film forming apparatus 1 according to this embodiment heats the film forming material Ma with a plasma beam P and attaches particles vaporized from the film forming material Ma to the film forming target 11. It is equipped with a main hearth 21, which is filled with the film forming material Ma and serves as the main anode that guides the plasma beam P to the film forming material Ma, a ring hearth 6, which has a permanent magnet 6b and a coil 6a and is arranged around the main hearth 21 and serves as the auxiliary anode that guides the plasma beam P, and a power source 50 that supplies power to the coil 6a of the ring hearth 6, and changes the magnetic flux density above the main hearth 21.

The film forming apparatus 1 changes the magnetic flux density above the main hearth 21. When the magnetic flux density is changed in this way, it is possible to vary the position where the diffused film forming material concentrates and adheres around the main hearth 21 and the annular hearth 6. The deposits formed in this way grow more slowly than deposits formed by the film forming material concentrating in a narrow area. As a result, the growth of the deposits can be slowed.

The power supply 50 may change the magnetic flux density by superimposing an alternating current on the coil 6a. The power supply 50 can easily change the magnetic flux density by superimposing an alternating current on the coil 6a.

The change in magnetic flux density may be a change in the area where the magnetic flux density is zero. In this way, when the area where the magnetic flux density is zero is changed, the position where the diffused film-forming material concentrates and adheres around the main hearth 21 and the annular hearth 6 can be changed. The deposits formed in this way grow more slowly than deposits formed by the film-forming material concentrating in a narrow area. As a result, the growth of the deposits can be slowed.

In the film forming apparatus 1, the power supply 50 changes the magnetic flux density by superimposing an AC current on the coil a. If the amplitude of the position where the deposit of the film forming material is formed, which changes due to the superimposition of the AC current, is a, and the thickness of the deposit when the AC current is not superimposed on the coil 6a is σ, the power supply 50 may superimpose an AC current on the coil 6a under the condition that a/σ is 2 or more. The power supply 50 may also superimpose an AC current on the coil 6a under the condition that a/σ is 4 or more. In this case, the film forming material can be diffused with a wide amplitude a relative to the thickness σ of the deposit. Therefore, the growth of the deposit can be delayed.

The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention, as described below.

In the above embodiment, a film formation device using an ion plating method is exemplified. Alternatively, the present invention can be applied to a plasma deposition device, dust plasma device, or general plasma device, as long as the deposition device has a fixed evaporation source.

In the above embodiment, the power supply varies the area above the main anode where the magnetic flux density is zero by superimposing an alternating current on the electromagnet. However, the method of varying the area where the magnetic flux density is zero is not particularly limited.

For example, the power supply may finely switch the value of the direct current. For example, the power supply may finely switch the direct current to form a waveform similar to that shown in FIG. 5(b). Note that when the ring hearth is installed and the magnet is oriented in the direction described in the above embodiment, a point where the magnetic flux density is zero (even if the coil current is zero) is formed, so the way the current flows may be changed as appropriate.

In the above embodiment, the power supply changes the area where the magnetic flux density is zero, thereby changing the area where deposits occur and slowing down the growth of the deposits. However, the power supply only needs to be able to change the area where deposits occur by changing the magnetic flux density, and is not necessarily limited to a method of changing the area where the magnetic flux density is zero.

For example, in addition to the coil 6a in the above embodiment, another coil may be added and the magnetic flux density at the deposit generation position may be changed by turning the current on and off or changing the current value. Also, the magnetic flux density at the deposit generation position may be changed by placing a permanent magnet and moving its position.

1...film formation device, 6...ring hearth, 6a...coil (electromagnet), 6b...permanent magnet, 7...plasma source, 11...film formation target, 21...main hearth, 50...power source.

Claims (5)

A film forming apparatus that heats a film forming material by a plasma beam and causes particles vaporized from the film forming material to adhere to a film forming target, comprising:
a main anode that is filled with the deposition material and that directs the plasma beam to the deposition material;
an auxiliary anode having a permanent magnet and an electromagnet and disposed around the main anode to guide the plasma beam;
a power source for supplying power to the electromagnet of the auxiliary anode;
The power supply changes a magnetic flux density above the main anode so as to vary over time a position around the main anode and the auxiliary anode where the film forming material is concentrated and deposited . The film forming apparatus of claim 1, wherein the power source changes the magnetic flux density by superimposing an alternating current on the electromagnet. the plasma beam is provided by a plasma source;
3. The film forming apparatus according to claim 1, wherein the change in the magnetic flux density is a change in an area where the magnetic flux density is zero between the main anode and the auxiliary anode and between the plasma source and the plasma source . The power source changes the magnetic flux density by superimposing an alternating current on the electromagnet,
When the amplitude of the position of the deposit of the film-forming material around the main anode and the auxiliary anode, which changes due to the superposition of the AC current, is a, and the thickness of the deposit when the AC current is not superimposed on the electromagnet is σ,
4. The film forming apparatus according to claim 2, wherein the power source superimposes an alternating current on the electromagnet under a condition that a/σ is 2 or more. The film forming apparatus according to claim 4 , wherein the power source superimposes an alternating current on the electromagnet under a condition that a/σ is 4 or more.

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