JP7163154B2 - Thin film manufacturing method, facing target type sputtering apparatus - Google Patents

Description

The present invention relates to sputtering technology, and more particularly to a facing target type sputtering apparatus.

Some of the devices used in electronic equipment, solar cells, etc., have thin films formed in a vacuum atmosphere. It is also important that the interface between the underlayer and the thin film is well formed.

However, in the magnetron sputtering method in which the substrate and the target face each other, particles with high kinetic energy of about several hundred eV collide with the substrate surface during the formation of the thin film. It may deteriorate the characteristics.

In particular, when an oxide target is used to form an oxide thin film with a sputtering gas to which oxygen gas is added, or when a metal target is used to form an oxide thin film by performing reactive sputtering with a sputtering gas to which oxygen gas is added, the oxide thin film is formed. When forming, negative oxygen ions generated near the target surface are accelerated to several hundred eV in the direction perpendicular to the target surface by the cathode sheath, and collide with the substrate surface, resulting in deterioration of film quality and interfacial characteristics. cause.

On the other hand, when particles (such as Ar ions) accelerated to a low kinetic energy of several tens of eV due to the potential difference between the plasma potential formed on the target surface and the substrate surface are irradiated onto the substrate surface, the formation of This is generally known as the ion assist effect.

However, when forming an oxide thin film on the substrate surface or the surface of the underlying film, etc., the kinetic energy is as small as several tens of eV when the interface between the underlying film and the oxide thin film is formed. Even if the particles are incident, an intermediate layer in which the base surface and the oxide thin film are mixed is formed at the interface, and the interface characteristics may be deteriorated.

For example, when forming an aluminum oxide thin film on the surface of a silicon substrate, oxygen gas is contained in the sputtering gas, and when positive ions of the oxygen gas are incident on the interface, a silicon oxide film is formed. Electrical characteristics deteriorate.

On the other hand, in the facing target type sputtering method, in which two targets are arranged facing each other and a thin film is formed on a substrate arranged on the side of the space between each target, the Since the high-energy negative ions are emitted from the target in a direction perpendicular to the target surface, they do not enter the substrate surface. Therefore, the substrate is not damaged and a high-quality oxide thin film can be formed.

On the other hand, a structure in which an anode is placed around a target that serves as a cathode, or a structure in which a mirror magnetic field is provided to confine the plasma, constrains the plasma between the opposing targets, so that the ion assist effect cannot be obtained.
Inventions devising anode electrodes are described in the following publications.

JP 2010-37566 A Japanese Utility Model Laid-Open No. 7-19361 JP 2006-199989 A

SUMMARY OF THE INVENTION The present invention was created to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a sputtering apparatus capable of forming an interface and a thin film with good characteristics.

In the facing target type sputtering apparatus, the ion assist effect is suppressed during the interface formation period, and the film quality is improved by using the low energy ion assist effect while suppressing the damage of negative ions with high kinetic energy during the thin film formation period. I discovered that it is possible.

The present invention was created based on the above findings, and the present invention applies a sputtering voltage, which is an alternating voltage, to first and second targets that are spaced apart and arranged to face each other, respectively, A thin film manufacturing method for forming a thin film on a substrate surface positioned laterally of a sputtering space that is a space between second targets, wherein the anode is disposed laterally of the sputtering space on the opposite side of the substrate. After the thin film is grown on the surface of the substrate by connecting the electrode and the ground potential with a low impedance value, the sputtering of the first and second targets is started, and the thin film is formed to a predetermined thickness. 3. A thin film manufacturing method in which the anode electrode and the ground potential are connected at a higher impedance value than the low impedance value, and the first and second targets are sputtered to grow the thin film.
Further, according to the present invention, the sputtering gas introduced into the sputtering space contains an additive gas consisting of one or both of oxygen gas and nitrogen gas, and a rare gas. Sputtering of the first and second targets is started, and a thin film of a reaction product of the metal atoms exposed on the surfaces of the first and second targets and the additive gas is formed on the surface of the substrate to the predetermined thickness. It is a thin film manufacturing method in which a
In the present invention, the first and second targets are made of the same material, the first and second targets are made of either aluminum oxide or metal aluminum, and the thin film formed is an oxide It is an aluminum thin film, and after the aluminum oxide thin film is formed to a thickness of 4 nm or more and 6 nm or less, the thin film manufacturing method connects the anode electrode and the ground potential with the high impedance value.
In addition, the present invention includes: first and second targets spaced apart and opposed to each other; an AC power source for applying a sputtering voltage, which is an AC voltage, to the first and second targets; a sputtering chamber in which a sputtering space between two targets is arranged and which forms a cylindrical shape having two openings together with the first and second targets; a film forming tank in which a film forming space facing one of the openings is disposed; and an anode disposed on the side of the sputtering space and in a position facing the other opening. and a switching device electrically connecting the anode electrode to ground potential, the switching device providing a low impedance connection between the anode electrode and the ground potential at the frequency of the sputtering voltage. The sputtering apparatus has a low impedance device connected to the target and a high impedance device connected at a high impedance, and sputters the first and second targets to form a thin film on the substrate placed in the film deposition tank.
Further, according to the present invention, the low-impedance device is an LC series-connected circuit capable of changing a reactance value, and by changing the reactance value, a resonance frequency value can be changed, and the reactance value of the LC series-connected circuit is It is a sputtering apparatus having a control device for controlling the.
Further, the present invention has a first inductance element and a first capacitance element whose capacitance value is changed by the control device, and the first inductance element and the first capacitance element are connected in series. and the variable capacitance value of the first capacitance element includes a value that causes the LC series connection circuit to undergo series resonance at the frequency of the sputtering voltage.
Further, the present invention has a second capacitance element connected in parallel with the first inductance element, and the high impedance device has the second capacitance element and the first inductance element connected in parallel. In the first LC parallel connection circuit, the second capacitance element has a capacitance value changeable by the control device, and the changeable capacitance value range of the second capacitance element includes: the sputtering voltage A sputtering apparatus comprising a value that causes the first LC parallel-connected circuit to parallel-resonate at a frequency.
Further, the present invention has a second capacitance element connected in parallel with the first inductance element, and the high impedance device has the second capacitance element and the first inductance element connected in parallel. a first LC parallel-connected circuit, said first LC parallel-connected circuit being brought to parallel resonance at the frequency of said sputtering voltage.
Further, the present invention has a second inductance element connected in parallel with the first capacitance element, and the high impedance device has a second inductance element in which the first capacitance element and the second inductance element are connected in parallel. The sputtering apparatus comprises two LC parallel-connected circuits, wherein the variable capacitance value range of the first capacitance element includes a value for parallel resonance of the second LC parallel-connected circuit.
Further, according to the present invention, the first and second targets are made of the same material, which is either aluminum oxide or metal aluminum, the sputtering gas contains oxygen, and the thin film formed is It is a sputtering device that is an aluminum oxide thin film.

An unnecessary thin film is not formed at the interface, and a thin film with good characteristics can be obtained. In particular, no unnecessary thin film is formed between the underlayer and the oxide thin film, and a thin film with good characteristics can be formed.

An example of the sputtering apparatus of the present invention (a) to (e): diagrams for explaining the internal circuit of the switching device Graph showing the relationship between the sputtering voltage and the current flowing through the substrate holder when the impedance between the anode electrode and the ground potential is different

<Sputtering device>
Reference numeral 2 in FIG. 1 denotes a sputtering apparatus of the present invention, which has a sputtering tank 14 and a film forming tank 17 .

The sputtering tank 14 has a rectangular cylindrical shape and has four rectangular or square sides and two openings 34 , 35 .

Mounting holes 13a and 13b are provided in two of the four side surfaces facing each other, and parts of the first target device 11a and the second target device 11b are provided in the respective mounting holes 13a and 13b. inserted respectively.

The first and second target devices 11a and 11b have first and second backing plates 42a and 42b, respectively. Two targets 5a, 5b are fixed respectively.

In the portions of the first and second backing plates 42a and 42b where the first and second targets 5a and 5b are arranged, the first and second target devices 11a and 11b contact the edges of the mounting holes 13a and 13b. Instead, the first and second targets 5a and 5b are fitted into the mounting holes 13a and 13b so as to be exposed inside the sputtering tank 14. As shown in FIG.

In this state, the portions near the edges of the first and second backing plates 42a and 42b are attached to the sputtering tank 14 via target-side insulating members 12a and 12b having electrical insulation.

The surfaces of the first and second targets 5a and 5b exposed inside the sputtering tank 14 are opposed to each other at a constant distance, and the space sandwiched between the surfaces of the first and second targets 5a and 5b is sputtered. When called the space 18, the openings 34 and 35 are portions of the sides of the sputtering space 18 where the wall surface of the sputtering tank 14 and the first and second targets 5a and 5b are not arranged.

Here, the one opening 34 and the other opening 35 are positioned opposite to each other with the sputtering space 18 interposed therebetween. A certain film forming space 19 is arranged, and the anode electrode 15 is arranged at a lateral position on the other side of the opening 35 , and the anode electrode 15 faces the film forming space 19 through the sputtering space 18 . .
The film forming tank 17 is attached to the sputtering tank 14 via an inter-tank insulating member 46, and the anode electrode 15 is attached to the first and second backing plates 42a and 42b via target-side insulating members 12a and 12b. installed.

In this example, a substrate holder 45 is arranged in the film formation space 19, and the substrate 10, which is a film formation object, is arranged in the substrate holder 45. As shown in FIG. Reference numeral 51 is a substrate bias device. As another example, the present invention also includes a sputtering apparatus in which the film forming space 19 is provided with a moving device for holding and moving the substrate, the surface of which faces toward the sputtering space 18 , within the film forming space 19 .

Of the two surfaces of the first and second backing plates 42a and 42b, the surfaces opposite to the surfaces on which the first and second targets 5a and 5b are attached are provided with ring-shaped magnet devices 43a and 43b, respectively. are placed.

The magnet devices 43a on one side and the magnet devices 43b on the other side have magnetic poles with different polarities directed toward the sputtering space 18, and the first and second targets 5a and 5a are placed between the two magnet devices 43a and 43b. , 5b are formed, and the sputtering space 18 is surrounded by the cylindrical magnetic flux and the first and second targets 5a and 5b facing each other. Yokes 44a and 44b are attached to the sides of the magnet devices 43a and 43b opposite to the sputtering space 18 .

The sputtering tank 14 and the first and second target devices 11a and 11b are covered with a metal housing 16. As shown in FIG.

A sputtering power source 31 is arranged outside the housing 16, and a voltage output terminal 33 of the sputtering power source 31 is connected to the first and second backing plates 42a and 42b of the first and second target devices 11a and 11b. ing. The voltage output terminal 33 is connected to the first and second backing plates 42a and 42b, and the sputtering power supply 31 outputs a sputtering voltage, which is an AC voltage, to the voltage output terminal 33, and the sputtering voltage is applied to the first and second backing plates. It is applied to the two backing plates 42a, 42b. The frequency of the sputtering voltage is between 1 MHz and 100 MHz.

<Procedure for thin film manufacturing>
A gas source 52 is connected to one or both of the sputtering tank 14 and the film forming tank 17 , and an evacuation device 53 is connected to one or both of the sputtering tank 14 and the film forming tank 17 . After evacuating the inside of the sputtering tank 14 and the inside of the film forming tank 17 to form a vacuum atmosphere, the substrate 10 is carried into the film forming tank 17 while maintaining the vacuum atmosphere. and face the sputtering space 18 . Although the substrate 10 is placed on the substrate holder 45 and is stationary here, it may be moved as described above.

The film forming tank 17 and the housing 16 are electrically connected and grounded. The anode electrode 15 and the sputtering bath 14 are connected to the ground potential via the switching device 20 .
It is also possible not to electrically connect the anode electrode 15 and the sputtering tank 14 .

The switching device 20 has an electrode-side terminal 25 and a ground-side terminal 26 , and the electrode-side terminal 25 and the ground-side terminal 26 are connected by the impedance of the internal circuit of the switching device 20 . A control device 28 is connected to the switching device 20 and the internal impedance value is changed by the control device 28 .

The anode electrode 15 is connected to the electrode-side terminal 25, and the ground-side terminal 26 is connected to the ground potential directly or via the housing 16. Here, the housing 16 is connected to the ground terminal of the sputtering power source 31, which is the ground potential. assumed to be connected.

2A to 2E are circuit diagrams showing the inside of the switching devices 20, 20 ₁ to 20 ₄ . In FIG. A switching device 20 is schematically shown having a switch element S1 as _an internal circuit which becomes a low-impedance circuit connecting at low impedance in the ON state, and becomes a high-impedance circuit connecting at high impedance in the OFF state.

This switch element S1 is switched on and off by the control device 28, and when the switch element S1 is turned on, the anode electrode ₁₅ is connected to the _ground potential with low impedance. The portion where the ground-side terminal 26 of the switching device 20 is mechanically and electrically connected to the housing 16 is close to the portion where the ground terminal of the sputtering power supply 31 is connected to the housing 16. Therefore, the switch element S ₁ is turned on, the anode electrode 15 is electrically connected to ground potential in a near short circuit.

The film forming tank 17 is electrically connected to the housing 16 at the end of the housing 16, and the film forming tank 17 is connected to the housing 16 at a location far from the portion of the housing 16 connected to the ground terminal of the sputtering power supply 31. Therefore, the film forming tank 17 is electrically connected to the ground potential by the impedance of the housing 16, and the switch element S1 is in the ON state rather _than the impedance of the housing 16. The impedance at this time is a small value.

A sputtering gas is introduced from a gas source 52 into the interior of the sputtering chamber 14 and the interior of the film forming chamber 17, both of which are in a vacuum atmosphere. The sputtering gas introduced from the gas source 52 contains a rare gas such as argon gas and either one or both of oxygen gas and nitrogen gas.

The controller 28 turns on the switch element S1 to operate the sputtering power source 31, and applies a sputtering voltage to the _first and second targets 5a and 5b through the first and second backing plates 42a and 42b. to generate plasma in the sputtering space 18 .

In the sputtering space 18, the surface of the anode electrode 15 and the wall surface of the film formation tank 17 face each other. The plasma in space 18 is attracted to the anode electrode 15 which is near ground potential, and the amount of plasma that spreads to the substrate 10 located in the deposition space 19 is small.

In this state, the first and second targets 5a and 5b are sputtered, and metal atoms exposed on the surfaces of the first and second targets 5a and 5b react chemically with the additive gas on the surface of the substrate 10. A thin film of the resulting reaction product grows.

When a thin film is grown on the surface of the substrate 10 in a state where the anode electrode 15 has a lower impedance than the film forming tank 17 and is connected to the ground potential, the plasma incident on the surface of the substrate 10 and the growing thin film Since the number of positive ions is small, a thin film is not formed at the interface between the substrate 10 and the thin film affected by the positive ions.

In this example, the first and second targets 5a and 5b are aluminum plates or aluminum oxide plates, and the sputtering gas contains a rare gas such as argon gas and oxygen gas. In the case of , an aluminum oxide thin film grows on the surface of the substrate 10 without forming silicon oxide on the surface.

When the thin film on the surface of the substrate 10 has grown to _a predetermined thickness, the control device 28 turns off the switch element S1 to change the impedance value between the anode electrode 15 and the ground potential to that between the deposition tank 17 and the ground potential. When the impedance value between the plasma and the sputtering space 18 is increased, the plasma formed in the sputtering space 18 is attracted to the wall surface of the film forming tank 17 , and as a result, the plasma being grown on the surface of the substrate 10 located between the wall surface and the sputtering space 18 . Positive ions in the plasma are incident on the thin film.

In this example, when the aluminum oxide thin film has grown to a predetermined thickness in the range of 4 nm or more and 6 nm or _less , the switch element S1 is changed from the on state to the off state by the control device 28, and the impedance of the switch device 20 changes from low impedance to low impedance. After the impedance is changed to high impedance, a dense aluminum oxide thin film is formed by the ion assist effect in which positive ions are incident on the growing thin film.

When the aluminum oxide thin film has grown to a predetermined thickness, the sputtering voltage is stopped to extinguish the plasma, and the substrate 10 with the aluminum oxide thin film formed thereon is moved from the film forming chamber 17 into a vacuum chamber of another vacuum processing apparatus. be.

After the sputtering voltage is stopped, the switch element S1 is turned _on , the switching device 20 is changed from high impedance to low impedance, and thin film growth on the surface of the substrate 10 newly carried into the inside of the film forming tank 17 starts. be done.

The reaction product of the metal atoms exposed on the surfaces of the first and second targets 5a and 5b and the additive gas is a metal nitride when the additive gas is nitrogen gas, and the additive gas is oxygen gas and nitrogen gas. If it consists of a gas, it is a metal oxynitride.

The switch element S ₁ is an element that schematically shows switching between high impedance and low impedance, and specifically includes switching devices 20 ₁ and 20 ₂ shown in FIGS. 2(b) and 2(c), for example. The switching devices 20 ₁ , 20 ₂ have first and second capacitance elements C ₁ , C ₂ and a first inductance element L ₁ , the first inductance element L ₁ and the second capacitance element L 1 C ₂ is connected in parallel to form an LC parallel connection circuit 21 ₁ which is a high impedance circuit.

In the switching device 20 ₁ of FIG. 2(b), one end of the LC parallel connection circuit 21 ₁ is connected to the ground side terminal 26, and the other end is connected to the electrode side terminal 25 by the first capacitance element C ₁ . In the switching device 20 ₂ of 2(c), one end of the LC parallel connection circuit 21 ₁ is connected to the electrode-side terminal 25, and the other end is connected to the ground-side terminal 26 by the first capacitance element C ₁ . In the switching devices 20 ₁ and 20 ₂ of 2(b) and 2(c), the first capacitance element C ₁ and the first inductance element L ₁ are connected in series to form an LC series connection circuit 22 which is a low impedance circuit. It is configured.

The first capacitance element C1 and the _second capacitance element _C2 are electronic devices whose capacitance values are changed by an input control signal. For example, when input to the circuit, the capacitance value of the variable capacitor is changed by the control circuit to a value according to the content of the input control signal.

The variable capacitance value of the first capacitance element C ₁ includes a value that causes the LC series circuit 22 to series-resonate at the frequency of the sputtering voltage, before the sputtering voltage is output from the sputtering power supply 31 . At this time, a control signal is input to the _first capacitance element C1, and the _first capacitance element C1 is changed to a capacitance value that brings the LC series connection circuit 22 into resonance at the frequency of the sputtering voltage.

Since the electrode-side terminal 25 and the ground-side terminal 26 are connected by the LC series connection circuit 22, the anode electrode 15 is connected to the ground potential by the low-impedance LC series connection circuit 22 in resonance.

At this time, a control signal is also input to the second capacitance element C ₂ to set the second capacitance element C ₂ to a capacitance value that does not cause the LC parallel connection circuit 21 ₁ to resonate at the frequency of the sputtering voltage. can be set to

After the LC series connection circuit 22 is brought into a resonant state, sputtering of the first and second sputtering targets 5a and 5b is started, and a thin film is grown while the plasma is attracted to the anode electrode 15. FIG.

The variable capacitance value of the _second capacitance element C2 includes a capacitance value that causes the LC parallel connection circuit 211 to parallel _- resonate at the frequency of the sputtering voltage.

When the thin film grows to a predetermined thickness, a control signal is input to the _first capacitance element C1, and the _first capacitance element C1 is changed to a capacitance value that cancels the resonance state of the LC series connection circuit 22. At the same time, a control signal is also input to the _second capacitance element C2, the _second capacitance element C2 is set to a capacitance value at which the LC parallel connection circuit 211 is in _a parallel resonance state, and the anode electrode 15 is set to a resonance state. It is connected to the ground potential by the high-impedance LC parallel connection circuit 21 ₁ in the state. Therefore, the plasma moves to the substrate 10 side, and the thin film grows in a state in which positive ions are incident on the substrate 10 .

If a capacitor whose capacitance value is not variable but has a capacitance value that allows the LC parallel connection circuit 21 ₁ to resonate in parallel at the frequency of the sputtering voltage is used as the second capacitance element C ₂ , the anode electrode 15 will be LC When the series-connected circuit 22 is in a series-resonant state, the LC series-connected circuit 22 is connected to the ground potential at _a low impedance. is connected to ground potential with a high impedance value of

Also, in the switching devices 20 ₁ and 20 ₂ of FIGS. 2(b) and 2(c), the capacitance value of at least the first capacitance element C ₁ is changed, but the first and second capacitance elements C ₁ and C ₂ A capacitor with a fixed capacitance value is used for the _first inductance element L1, and an electronic device with a variable inductance value is used for the _first inductance element L1. The parallel connection circuit 21 ₁ and the parallel connection circuit 21 1 may be brought into a resonance state separately.

In this case, the inductance value of the _first inductance element L1 at which the LC series connection circuit 22 is in _a resonant state is different from the inductance value of the _first inductance element L1 at which the LC parallel connection circuit 211 is in a resonant state. It is sufficient to use the first and second capacitance elements C ₁ and C ₂ whose capacitance values are as follows.

Next, the switching devices 20 ₃ and 20 ₄ of FIGS. 2(d) and 2(e) have a first capacitance element C ₁ and first and second inductance elements L ₁ and L ₂ . One capacitance element C ₁ and a second inductance element L ₂ are connected in parallel to form an LC parallel connection circuit 21 ₂ .

In FIG. 2(d), one end of the LC parallel connection circuit 21 ₂ is connected to the ground-side terminal 26, and the other end is connected to the electrode-side terminal 25 by the first inductance element L ₁ . One end of the LC parallel connection circuit 21 ₂ is connected to the electrode side terminal 25, and the other end is connected to the ground side terminal 26 by the first inductance element L ₁ . In the switching devices 20 ₃ and 20 ₄ of FIGS. 2(d) and 2(e), the first capacitance element C ₁ and the first inductance element L ₁ are connected in series to form an LC series connection circuit 22. .

Before the sputtering voltage is output from the sputtering power supply 31, a control signal is input to the _first capacitance element C1, and the _first capacitance element C1 is controlled by the LC series connection circuit 22 at the frequency of the sputtering voltage. The capacitance value is set to be in a resonant state, and the anode electrode 15 is connected to the ground potential by the low-impedance LC series connection circuit 22 in a resonant state.

The LC series connection circuit 22 is brought into a resonance state, the sputtering of the first and second targets 5a and 5b is started, and after a thin film is formed to a predetermined thickness, a control signal is input to the _first capacitance element C1. At the frequency of the sputtering voltage, the _first capacitance element C1 releases the series resonance state of the LC series connection circuit 22 and brings the LC parallel connection circuit ₂₁₂ into the parallel resonance state.

Since the impedance value of the LC parallel connection circuit 212 in the parallel resonance state is larger _than the impedance value of the LC series connection circuit 22 in the series resonance state, the anode electrode is connected to the ground potential with a high impedance value, and the ion assist effect is maintained. A thin film is grown in it.

In the switching devices 20 ₃ and 20 ₄ of FIGS. 2(d) and 2(e), the capacitance value of at least the _first capacitance element C1 is changed, but a capacitor with a fixed capacitance value is used for the _first capacitance element C1. By controlling the inductance value of at least the _first inductance element L1, the LC series connection circuit 22 and the LC parallel connection circuit ₂₁₂ can be made to resonate with different inductance values at the frequency of the sputtering voltage. can. When controlling only the inductance value of the _first inductance element L1, the LC parallel connection circuit ₂₁₂ is connected in parallel with the _first capacitance element C1 and the _second inductance element L2 at the frequency of the sputtering voltage. An element having a capacitance value and an inductance value that are in a resonant state may be used.

FIG. 3 is a graph showing the relationship between the 13.56 MHz AC voltage (0.5 Pa, 200 W) applied to the first and second targets 5a and 5b during sputtering and the current flowing through the substrate holder. The impedance value between the anode electrode 15 and the ground potential is set to ⅓ of the impedance value obtained when the graph labeled A is measured when the graph labeled B is measured.

Graph A, in which the impedance value between the anode electrode 15 and the ground potential is small, has less current than graph B, in which the impedance value is large.

2 Sputtering device 5a First target 5b Second target 15 Anode electrode 18 Sputtering space 19 Film forming space 20 Switching devices 21 ₁ , 21 ₂ LC parallel connection Circuit 22 --- LC series connection circuit 31 --- Sputtering power sources 34, 35 --- Opening C ₁ --- First capacitance element C ₂ --- Second capacitance element L ₁ --- First inductance element L ₂ --- second inductance element

Claims (10)

A sputtering voltage, which is an alternating voltage, is applied to first and second targets which are spaced apart and opposed to each other, respectively, and a substrate is positioned on the side of the sputtering space, which is the space between the first and second targets. A thin film manufacturing method for forming a thin film on a surface,
An anode electrode disposed on the side of the sputtering space opposite to the substrate is connected with a ground potential with a low impedance value to start sputtering of the first and second targets and the substrate. grow a thin film on the surface,
After the thin film is formed to a predetermined thickness, the anode electrode and the ground potential are connected at a high impedance value larger than the low impedance value, and the first and second targets are sputtered to perform the A thin film manufacturing method for growing a thin film. The sputtering gas introduced into the sputtering space contains an additive gas consisting of one or both of oxygen gas and nitrogen gas, and a rare gas,
Sputtering of the first and second targets is started to form a thin film of a reaction product of the metal atoms exposed on the surfaces of the first and second targets and the additive gas on the surface of the substrate. 2. The thin film manufacturing method according to claim 1, wherein the thin film is grown thick. the first and second targets are the same material,
The first and second targets use either aluminum oxide or metal aluminum,
The thin film formed is an aluminum oxide thin film,
3. The thin film manufacturing method according to claim 2, wherein after the aluminum oxide thin film is formed to a thickness of 4 nm or more and 6 nm or less, the anode electrode and the ground potential are connected at the high impedance value. first and second targets spaced apart and facing each other;
an AC power supply that applies a sputtering voltage, which is an AC voltage, to the first and second targets;
a sputtering chamber in which a sputtering space between the first and second targets is arranged and which forms a cylindrical shape having two openings together with the first and second targets;
a film formation tank in which a film formation space is arranged at a position facing one of the two openings, which is located on the side of the sputtering space;
an anode electrode disposed on the side of the sputtering space and facing the other opening;
a switching device electrically connecting the anode electrode to ground potential;
The switching device has a low impedance device that connects the anode electrode and the ground potential with a low impedance and a high impedance device that connects the anode electrode and the ground potential with a high impedance at the frequency of the sputtering voltage. A sputtering apparatus for sputtering two targets to form a thin film on the substrate placed in the film forming tank. The low impedance device is an LC series connection circuit capable of changing the reactance value and changing the value of the resonance frequency by changing the reactance value,
5. A sputtering apparatus according to claim 4, further comprising a controller for controlling the reactance value of said LC series connection circuit. a first inductance element and a first capacitance element whose capacitance value is changed by the controller;
The LC series connection circuit is configured by connecting the first inductance element and the first capacitance element in series,
6. The sputtering apparatus of claim 5, wherein the variable capacitance value of said first capacitance element includes a value that causes said LC series circuit to series-resonate at the frequency of said sputtering voltage. a second capacitance element connected in parallel with the first inductance element;
The high impedance device is a first LC parallel connection circuit in which the second capacitance element and the first inductance element are connected in parallel,
The second capacitance element is variable in capacitance value by the controller, and the range of variable capacitance values of the second capacitance element includes the first LC parallel connection circuit at the frequency of the sputtering voltage. 7. The sputtering apparatus according to claim 6, wherein the value for causing parallel resonance of is included. a second capacitance element connected in parallel with the first inductance element;
The high impedance device is a first LC parallel connection circuit in which the second capacitance element and the first inductance element are connected in parallel,
7. The sputtering apparatus of claim 6, wherein said first LC parallel connection circuit is made parallel resonant at the frequency of said sputtering voltage. a second inductance element connected in parallel with the first capacitance element;
The high impedance device is a second LC parallel connection circuit in which the first capacitance element and the second inductance element are connected in parallel, and the variable capacitance value range of the first capacitance element is 7. The sputtering apparatus according to claim 6, further comprising a value for causing parallel resonance of said second LC parallel connection circuit. the first and second targets are made of the same material and are either aluminum oxide or metallic aluminum;
The sputtering gas contains oxygen,
10. A sputtering apparatus according to any one of claims 4 to 9, wherein said thin film to be formed is an aluminum oxide thin film.

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