TW201437407A - Film formation method for aluminum oxide and sputtering device - Google Patents

Abstract

This invention enables formation of an aluminum oxide film by sputtering with the stable oxidation degree and the higher film formation rate. The film formation method for the aluminum oxide of this invention comprises the following steps: a first plasma generation step for generating plasma in a vacuum container introduced with the sputtering gas and the reactive gas; a second plasma generation step for imposing the sputtering voltage on the aluminum target to generate the magnetron plasma by the magnetostatic field; and a control step for controlling the amount of reactive gas introduced into the vacuum container. In addition, in the second plasma generation step, the sputtering voltage is subject to voltage control; in the control step, by means of making the sputtering current value reach the target current value, the amount of reactive gas introduced in the second plasma generation step is controlled; the first plasma generation step uses a high frequency antenna with winding less than one loop, and the high frequency inductance-coupled plasma is generated in the second plasma generation step.

Description

Alumina film forming method and sputtering device

The present invention relates to a film forming technique for utilizing reactive sputtering of alumina for a passivation film of a solar cell tantalum substrate.

In recent years, along with the search for efficiency of solar cells, effective passivation films for p-type germanium surfaces have been sought. Moreover, regarding the p-type surface of the germanium wafer, the positive charge SiNx cannot be said to be suitable in field effect, and it is desirable to seek a film having a negative charge.

It is known that as the passivation film having the negative charge, alumina (Al ₂ O ₃ ) is preferred. Further, in order to use alumina as a passivation film, an ALD (Atomic Layer Deposition) method and a PE-CVD (Plasma Enhanced Chemical Vapor Deposition) method have been used. However, the film formation speed of the ALD method is extremely slow and the productivity is poor, so there is a problem that it is not suitable for mass production. Further, since the flammable liquid of the so-called TMD (trimethylaluminum) liquid is used in the PE-CVD method, there is a problem that it is necessary to pay close attention to the design of the device and the treatment of the raw material.

On the other hand, the formation of an aluminum oxide film by magnetron sputtering is also being studied. The magnetron sputtering method is widely used in the manufacturing fields of semiconductors, liquid crystal display devices, magnetic recording devices, optical films, and the like as one of film forming methods. In the magnetron sputtering method, there are a high frequency magnetron sputtering method (Patent Document 1) or a reactive DC (Direct Current) magnetron sputtering method (Patent Document 2), etc., the high frequency magnetron sputtering method. Use oxides, nitrides, fluorination A compound target such as a compound, which forms a film of a compound by using a high-frequency power source as a sputtering power source, which uses a metal target, uses a DC power source as a sputtering power source, and introduces a reaction. A gas is formed into a film of a metal oxide, a nitride, a fluoride or the like, and any method is widely used depending on the use.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-31493

[Patent Document 2] Japanese Patent Laid-Open No. Hei 8-232064

However, since the hardness of alumina is very high, or the surface of the target is covered with an oxide of aluminum, even if the methods of Patent Documents 1 and 2 are employed, there is a problem that it is difficult to increase the film formation speed. Further, in order to form an aluminum oxide film having a good passivation effect on the surface of the p-type Si in the sputtering method, it is necessary to control the degree of oxidation of the aluminum oxide to be formed into a film with high precision. However, in the case where the aluminum oxide film is formed by the methods of Patent Documents 1 and 2, the control of driving the sputtering power source in the electric power fixed mode (the power control of the sputtering voltage) is usually performed, and thus the oxidation degree of the aluminum oxide is performed. It becomes unstable due to film formation in the transition mode. Therefore, there is also a problem that the aluminum is excessively oxidized or the oxidation is insufficient, and the degree of oxidation of the alumina to be film-formed is unstable.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a technique for forming alumina on a film formation rate at a film formation rate which is stable in oxidation degree in reactive sputtering.

In order to solve the above problems, the film forming method of the first aspect is formed in a vacuum vessel provided with a magnetron cathode for forming a static magnetic field, and the reactive gas of the sputtering gas and the oxygen gas is reached by the pressure in the vacuum vessel. The target pressure is controlled and imported, and is set to The aluminum target of the cathode is sputtered to form an oxide film on the substrate opposite to the aluminum target; and the method includes the following steps: a first plasma generating step of introducing the sputtering gas and the reactive gas a plasma is generated in the vacuum vessel; a second plasma generating step is to apply a negative voltage, a DC pulse including a negative voltage and a positive voltage, or a sputtering voltage to the aluminum target, by the static magnetic field. Generating a magnetron plasma; and controlling a step of controlling an introduction amount of the reactive gas introduced into the vacuum vessel; and the second plasma generating step is a step of controlling a voltage of the sputtering voltage; the control step a step of controlling the introduction amount of the reactive gas in the second plasma generating step such that the sputtering current value flowing through the magnetron cathode reaches a target current value; the first plasma generating step is a high frequency inductive coupling generated in at least the second plasma generating step by using a high frequency antenna disposed in the vacuum container and including a conductor having a number of windings less than one turn Plasma.

The film forming method of the second aspect is the film forming method of the aluminum oxide according to the first aspect, wherein the target current value is the sputtering current when the degree of oxidation of the aluminum oxide to be film-formed becomes the following oxidation degree. The value is the degree of oxidation near the boundary between the stoichiometric amount of alumina and the degree of oxidation of each of the alumina having a lower oxidation degree than the stoichiometric amount of alumina.

The film forming method of the third aspect of the alumina is a film forming method of the first or second aspect, wherein the controlling step is a step of changing the luminous intensity of the plasma according to the reactive gas. The change in the sputtering current value is predicted, and the introduction amount of the reactive gas is controlled such that the sputtering current value reaches the target current value.

The film forming method of the aluminum oxide according to the fourth aspect is a film forming method of alumina according to the first or second aspect, wherein the sputtering voltage is a negative voltage.

The film forming method of the aluminum according to the fifth aspect is a film forming method of alumina according to the first or second aspect, wherein the target pressure is 0.2 Pa or more and 7 Pa or less.

The film forming method of the sixth aspect is a film forming method of the aluminum according to the fifth aspect, wherein the target pressure is 0.4 Pa or more and 2 Pa or less.

The film forming method of the aluminum oxide according to the seventh aspect is the film forming method of the first or second aspect, wherein the absolute value of the negative voltage of the sputtering voltage is 100 V or more and 300 V or less.

The film forming method of the aluminum oxide according to the eighth aspect is the film forming method of the aluminum oxide according to the seventh aspect, wherein the absolute value of the negative voltage of the sputtering voltage is 150 V or more and 250 V or less.

The ninth aspect of the sputtering apparatus is controlled in a vacuum vessel provided with a magnetron cathode for forming a static magnetic field, and the reactive gas of the sputtering gas and the oxygen gas is controlled and introduced by the pressure in the vacuum vessel to reach the target pressure. Sputtering an aluminum target disposed on the cathode to form an oxide film on the substrate opposite to the aluminum target; and comprising: a plasma generating gas introduction portion that converts the sputtering gas and the reactivity a gas is introduced into the vacuum container; a control unit controls an introduction amount of the reactive gas introduced into the processing space by the plasma generating gas introduction unit; and a high frequency antenna is provided in the vacuum container and includes a roll a conductor having a number of turns; a high frequency power supply that supplies high frequency power to the high frequency antenna to generate a high frequency inductively coupled plasma in the vacuum vessel into which the sputtering gas and the reactive gas are introduced; And a power source for sputtering, which applies a negative voltage, a DC pulse including a negative voltage and a positive voltage, or a sputtering voltage to the aluminum target, so that a static magnetic field formed by the magnetron cathode generates a magnetron plasma in the vacuum vessel into which the sputtering gas and the reactive gas are introduced; and the sputtering power source controls the sputtering voltage by a constant voltage; The system controls the reactive gas introduced into the vacuum vessel by the plasma generating gas introduction portion during the generation of the magnetron plasma by the sputtering current value flowing through the magnetron cathode reaching a target current value The amount of import.

According to the invention, the first plasma generating step uses a high-frequency antenna provided in a vacuum vessel into which a reactive gas of a sputtering gas and oxygen gas is introduced, and includes a conductor having a number of windings less than one turn, at least the second plasma High frequency inductive coupling in a vacuum vessel during the production step Pulp. Moreover, the second plasma generating step applies a sputtering voltage to the target and generates a magnetron plasma. Therefore, the film formation speed is increased by the synergistic effect of the increase in oxygen radicals, the promotion of the oxidation reaction on the substrate to be coated, and the softening of the surface of the oxidized target caused by the formation of the substrate. Further, according to the present invention, the sputtering voltage is subjected to constant voltage control in the second plasma generating step, and the second plasma generating step is controlled in such a manner that the sputtering current value flowing through the magnetron cathode reaches the target current value. The amount of introduction of reactive gas. When the sputtering voltage is controlled by constant voltage, that is, when the sputtering power source is driven in the voltage fixed mode, the oxidation degree of the aluminum oxide film formed on the substrate is stabilized in the amount of oxygen in the vacuum container, that is, the reactivity. The corresponding balance of gas levels. Moreover, when the sputtering voltage is subjected to constant voltage control, the higher the degree of oxidation of the surface of the aluminum target, that is, the greater the amount of reactive gas in the vacuum vessel, the larger the sputtering current value becomes, and the film is formed. The degree of oxidation of the alumina on the substrate also becomes higher. Therefore, according to the present invention, the reactive gas is introduced into the vacuum vessel so that the sputtering current value reaches the target current value, irrespective of, for example, a disturbance factor such as a reactive gas generated by moisture adsorbed on the substrate. The degree of oxidation of the aluminum oxide film formed on the substrate is stabilized. That is, the alumina can be formed stably at a relatively high film formation rate.

10‧‧‧ Sputtering device

11‧‧‧ chamber

12‧‧‧ Magnets for magnetron sputtering

14‧‧‧Bottom plate (cathode)

15‧‧‧Substrate platform

17‧‧‧ Window Department

18‧‧‧ Targets. Antenna configuration department

19‧‧‧ Plasma generation gas introduction

20‧‧‧ gas inlet

24‧‧‧ Target Holding Department

51‧‧‧ Curve

52‧‧‧ Curve

53‧‧‧ Curve

54‧‧‧ Curve

55‧‧‧ Curve

60‧‧‧ Target (aluminum target)

74‧‧‧Substrate

80‧‧‧High frequency antenna

90‧‧‧The Plasma Generation Department

111‧‧‧ Spectroscope

112‧‧‧Probe

113‧‧‧Processing room

151‧‧‧Refrigerant

161‧‧‧High frequency power supply

162‧‧‧Power supply for sputtering

163‧‧‧Matching circuit

164‧‧‧ galvanometer

181‧‧‧target configuration block

182‧‧‧Antenna fixed block

189‧‧‧Anode

191‧‧‧Reactive Gas Supply Department

192‧‧‧Flow Controller

200‧‧‧Control Department

351‧‧‧ gate

411‧‧‧Protection tube

601‧‧‧dotted box

602‧‧‧dotted box

603‧‧‧dotted box

G1‧‧‧ curve

G2‧‧‧ curve

G3‧‧‧ Curve

Ia‧‧‧target current value

L1‧‧‧ dotted line

L2‧‧‧ dotted line

L3‧‧‧ dotted line

L4‧‧‧ dotted line

L11‧‧‧ curve

S1‧‧ points

S2‧‧ points

S3‧‧ points

S110‧‧‧Steps

S120‧‧‧ steps

S130‧‧‧Steps

S140‧‧‧Steps

S150‧‧ steps

S160‧‧‧ steps

S170‧‧‧Steps

S180‧‧‧Steps

S190‧‧ steps

S200‧‧‧ steps

S210‧‧‧Steps

S220‧‧‧Steps

T21‧‧‧ time

Time t0‧‧‧

Time t1‧‧‧

Time t2‧‧‧

Time t3‧‧‧

Time t4‧‧‧

Time t5‧‧‧

Time t6‧‧‧

Time t7‧‧‧

Time t8‧‧‧

Time t9‧‧‧

X‧‧‧ axis

Y‧‧‧ axis

Z‧‧‧ axis

Fig. 1 is a view showing a schematic configuration of a main part of a sputtering apparatus for realizing a film forming method of alumina according to an embodiment.

Fig. 2 is a side view showing an example of a high frequency antenna.

Fig. 3 is a schematic view for explaining a process of film formation by the film forming method of alumina of the embodiment.

Fig. 4 is a view schematically showing the effect of the film forming method of alumina in the embodiment.

Fig. 5 is a view showing an example of a time chart in the film formation method of alumina in the experimental embodiment.

Fig. 6 is a flow chart showing the procedure of the film forming method of alumina in the embodiment.

Fig. 7 is a flow chart showing the procedure of the film forming method of alumina in the embodiment.

Fig. 8 is a view schematically showing the relationship between the sputtering current value and the plasma luminous intensity of the reactive gas.

Fig. 9 is a view schematically showing an example of control of the amount of introduction of the reactive gas using the predicted change in the sputtering current value.

Hereinafter, an embodiment of the present invention will be described based on the drawings. In the drawings, the same reference numerals are given to the parts having the same configurations and functions, and the repeated description is omitted in the following description. Further, each drawing is schematically shown, and for example, the size and positional relationship of the objects in the respective drawings are not necessarily accurately shown. Further, in a part of the drawings, an XYZ orthogonal coordinate axis is attached to explain the direction. The direction of the Z axis in the coordinate axis indicates the direction of the vertical line, and the XY plane is the horizontal plane.

<About the implementation form:> <1. Composition of sputtering device>

Fig. 1 is a view showing a schematic configuration of a main part of a sputtering apparatus 10 for realizing a film forming method of alumina according to an embodiment. FIG. 2 is a side view showing an example of the high frequency antenna 80. Hereinafter, the configuration of the sputtering apparatus 10 will be described with reference to Figs. 1 and 2 .

The sputtering apparatus 10 is a device for sputtering a plate-shaped single metal aluminum target (also simply referred to as "target") 60 by ions to form a specific thin film on the surface of the substrate 74. Aluminum is electrically conductive.

The sputtering apparatus 10 includes a member ("vacuum container") 11 which can be vacuumed by a vacuum pump (not shown); the plasma generates a gas introduction portion 19 which introduces a plasma generating gas into the The inside of the chamber 11 for vacuum evacuation; the target holding portion 24, which is disposed in the chamber 11 and holds the target 60; the substrate stage 15, which holds the substrate 74 of the film formation target; and a power source 162 for sputtering. Further, the sputtering apparatus 10 further includes a control unit 200 including a computer or the like and collectively controlling the operation of each unit of the sputtering apparatus 10, and a reactive gas supply unit 191 for supplying a reactive gas of oxygen to the chamber 11. Internal; flow controller 192, which is designed The light is placed in the piping path of the reactive gas supply unit 191, and the beam splitter 111 measures the intensity of the light incident on the fiber probe. The control unit 200 is electrically connected to each of the sputtering apparatus 10, and various information necessary for controlling the sputtering apparatus 10 such as a target current value is stored in advance in the memory unit in the control unit 200.

The substrate stage 15 holds the substrate 74 in a manner opposed to the surface (the surface on the +Z side) of the target 60 held by the target holding portion 24 and the surface (the surface on the -Z side) of the substrate 74 by a specific distance. . Immediately below the substrate 74 (near the -Z side of the substrate 74), a film-forming baffle (not shown) that can be opened and closed is provided over at least the entire area of the substrate 74. Further, the sputtering power supply 162 is provided with a DC sputtering voltage ("cathode applied voltage", "bias voltage") for applying a negative voltage to the bottom plate ("cathode") 14, or a pulse containing a negative voltage and a positive voltage. The sputtering voltage ("pulse DC voltage") or the AC sputtering voltage generates an electric field for the magnetron plasma between the target 60 and the substrate 74 held on the substrate stage 15. The sputtering power source 162 is driven in a voltage-fixed mode, and the voltage output from the sputtering power source 162 is controlled so as to be a constant voltage. That is, the sputtering power source 162 performs constant voltage control of the sputtering voltage. The sputtering current value ("bias current value") flowing through the magnetron cathode described below is detected by the ammeter 164 provided in the sputtering power source 162, and supplied to the control unit 200. A high-quality passivation film can be formed by stabilizing the oxidation degree ("oxidation rate" and "oxidation state") of the surface of the aluminum target 60 during the film formation of alumina. When the constant voltage control is performed, the degree of oxidation of the alumina to be film-formed can be easily stabilized as compared with the case where constant power control is performed. Further, the substrate stage 15 is provided with a heater or a cooling mechanism (not shown) to control the temperature of the substrate 74.

Further, the sputtering apparatus 10 further includes a plasma generating unit 90 that generates a high-frequency inductive coupling plasma of the plasma generating gas introduced into the chamber 11. The substrate stage 15 is provided on the inner wall of the upper portion of the chamber 11 via a mounting member.

Further, the plasma generating unit 90 includes a linear high-frequency antenna ("plasma source") 80 disposed along the side surface without contacting the side surface of the target 60. The high frequency antenna 80 is composed of a metal tubular conductor. Moreover, the plasma generating portion 90 generates sputtering gas and reactivity by the high frequency antenna 80. The respective high frequency inductive coupling of the gas.

Moreover, the sputtering apparatus 10 forms a film on a two-dimensional region on the substrate 74 by sputtering using a target 60 of a mixed plasma of a magnetron plasma and a high frequency inductively coupled plasma. The magnetron generated by the static magnetic field formed by the magnetron sputtering magnet 12 is generated on the surface portion of the target 60 to generate a magnetically controlled plasma, which is generated by the high frequency inductively coupled plasma plasma generating portion 90. The plasma produces a high frequency inductively coupled plasma of the gas.

An openable and closable gate 351 is disposed on a side surface of the chamber 11. The substrate 74 to be film-formed is carried into the chamber 11 from the gate 351, and is attached to the substrate stage 15 by a fixing member (not shown), and then formed into a film by sputtering, and is carried out from the gate 351 to the chamber 11 External. When the substrate 74 is formed, the substrate 74 is carried into the chamber 11 before the film formation, and the internal space of the chamber 11 is opened by a vacuum pump (not shown) in a state where the gate 351 is closed. The processing chamber 113 is evacuated.

Then, in a state where the gate 351 is closed, the plasma generating gas is introduced into the chamber 11 from the gas introduction port 20 of the plasma generating gas introduction portion 19, whereby the processing chamber 113 is maintained at a fixed pressure and fixed gas. Under partial pressure. The gas introduction port 20 is formed, for example, at a portion between the high frequency antenna 80 and the target 60. When the plasma generating unit 90 includes a plurality of high frequency antennas 80, the gas inlet ports 20 are provided at positions corresponding to the respective high frequency antennas 80, for example.

In order to form a film of aluminum oxide by reactive sputtering, the sputtering apparatus 10 can use a sputtering gas such as an inert gas of Ar gas or Kr gas or a reactive gas of oxygen (O ₂ ) as electricity. The slurry produces a gas. The sputtering gas system is supplied from the sputtering gas supply unit (not shown) via the plasma generation gas introduction unit 19. Further, the plasma generated gas introduction unit 19 is connected to the flow rate controller 192 via a pipe, and the flow rate controller 192 is connected to the reactive gas supply unit 191 that supplies the stored reactive gas via a pipe. Further, the control unit 200 monitors the value of the sputtering current supplied from the sputtering power source 162, and the control unit 200 controls the flow rate of the reactive gas supplied from the reactive gas supply unit 191 to the chamber 11 by controlling the flow rate controller 192. The amount of import. Further, on the side wall of the chamber 11, a window portion 17 for sealing the inside of the chamber 11 and allowing the plasma in the chamber 11 to emit light is provided, and in the vicinity of the window portion, the plasma light is incident on the surface. The probe 112 of the beam splitter 111. The spectroscope 111 is configured to split the light having a wavelength of 777 nm which is a wavelength of the bright line of the plasma which is a reactive gas of oxygen, and to detect the intensity. The luminous intensity of the spectroscopic plasma detected by the spectroscope 111 via the window portion 17 is supplied to the control unit 200. The control unit 200 can control the introduction amount of the reactive gas as follows, based on the intensity of the plasma luminescence of the reactive gas of oxygen in the supplied luminescence intensity.

An opening is provided at the bottom of the chamber 11, and the opening is blocked from the lower side to accommodate the bottom plate 14 and the magnetron sputtering magnet (permanent magnet) 12 (collectively referred to as a magnetron cathode), and The target of the high frequency antenna 80. Antenna arrangement unit 18. Target. The connection portion between the antenna arrangement portion 18 and the bottom portion of the chamber 11 is ensured to be airtight by the sealing material. Therefore, the target. The wall of the antenna arrangement portion 18 functions as a part of the wall of the chamber 11. For the target. The antenna arrangement portion 18 is provided with a target arrangement block (target arrangement portion) 181 at a position directly below the substrate stage 15. And, in the target. A pair of antenna fixing blocks 182 are provided in the wall of the antenna arrangement portion 18 (that is, in the wall of the chamber 11) and on the side of the target arrangement block 181 so as to sandwich the target arrangement block 181. The magnetron cathode forms a static magnetic field near the surface of the target 60.

A processing chamber 113 of the chamber 11 is provided above the target arranging block 181. The magnetron sputtering magnet 12 is placed in the target arrangement block 181. A bottom plate 14 is disposed on the upper surface of the magnet 12 for magnetron sputtering, and a substrate platform 15 opposed to the bottom plate 14 is disposed on the upper inner wall of the chamber 11. The substrate platform 15 is grounded. Furthermore, the substrate platform 15 can also be in an ungrounded floating state. The position of the magnetron sputtering magnet 12 in the upper and lower directions is adjusted so that the upper surface of the target 60 placed on the bottom plate 14 provided on the upper surface thereof is disposed on the target. The vicinity of the upper end of the antenna arrangement portion 18 (the same position as the upper end is not required). Further, the target 60 is held by the bottom plate 14 and the target holding portion 24 on the upper surface (surface on the +Z side) of the bottom plate 14. By providing the magnetron sputtering magnet 12 and the bottom plate 14 (collectively referred to as magnetron cathodes) in this manner, the target 60 is disposed on the surface of the chamber 11. Into the space of the processing chamber 113.

The magnetron sputtering magnet 12 forms a static magnetic field (magnetostatic magnetic field) in a region including the surface of the target 60 held by the target holding portion 24, so that plasma can be formed on the surface portion of the target 60. The plasma of the surface portion of the target 60 is diffused according to the partial pressure of the plasma generated by the plasma introduced into the chamber 11, or the magnetron magnetic field generated by the magnet 12 for magnetron sputtering or the voltage applied to the target. The intensity changes and so on.

Further, a boundary between the upper end of the target arranging block 181 and the processing chamber 113 of the chamber 11 extends inward from the side wall of the target arranging block 181 and maintains a certain distance from the vicinity of the edge of the target 60 (including the portion of the edge). In this manner, an anode 189 is provided.

A high frequency antenna 80 is inserted into the antenna fixing block 182. Further, the sputtering apparatus 10 includes a high-frequency power source 161 that supplies high-frequency power to the high-frequency antenna 80. The high frequency power source 161 is connected to the high frequency antenna 80 via the matching circuit 163.

The high frequency antenna 80 is used to support the generation of plasma by magnetron sputtering. For example, as shown in FIG. 2, the tubular conductor made of metal is bent into a U shape, and the two antenna fixing blocks 182 are "U. There is one state in the state of the word upside down. Furthermore, the configuration of the high frequency antenna 80 can be variously changed. As the shape of the high-frequency antenna 80, for example, an arc shape can also be adopted. Also, the number of coils of the high frequency antenna 80 is less than one turn. In order to prevent the occurrence of the standing wave, the length of the radio-frequency antenna 80 is preferably set to be a length equal to or less than 1/4 of the wavelength of the power supplied from the high-frequency power source 161. The high frequency power is supplied from one end of the high frequency antenna and the other end is grounded. Thereby an inductively coupled plasma is produced. When such a high-frequency antenna 80 is used, the inductance of the antenna is lower than that of the method of generating an inductively coupled plasma using a coil-like (spiral) antenna, so that the voltage of the antenna can be reduced, so that plasma damage can be suppressed. Further, since the length of the antenna is shortened to 1/4 or less of the wavelength of the high frequency, it is possible to suppress sputtering unevenness (non-uniformity) due to plasma unevenness due to the influence of the standing wave. Moreover, since the antenna can be housed in the chamber, the sputtering efficiency can be improved. Further, according to the substrate size of the film formation object, the number of the high frequency antennas 80 is increased, and the size of the target material is increased, whereby even the substrate size is increased. In the case of a big situation, it is also possible to increase the sputtering speed.

The U-shaped high-frequency antenna is equivalent to an inductively coupled antenna with less than one turn of the coil. Since the inductance is lower than the inductive coupling antenna with more than one turn, the high-frequency voltage generated at both ends of the high-frequency antenna is reduced. The high frequency oscillation accompanying the plasma potential generated for the capacitive coupling of the generated plasma is suppressed. Therefore, the excess electron loss accompanying the oscillation of the plasma potential to the ground potential is reduced, and the plasma potential is lowered. Thereby, a film formation process with low ion damage on the substrate can be realized. The metal tubular conductor constituting the high-frequency antenna 80 has a function of cooling the high-frequency antenna 80 by passing the refrigerant 151 such as water through the inside of the sputtering apparatus 10. The position of the high-frequency antenna 80 in the height direction is adjusted such that the bottom of the "U" is about several centimeters higher than the height of the upper surface of the target 60 so that the plasma density near the surface of the target 60 is Become higher. Further, since the target 60 and the bottom plate 14 and the like are also abnormally high in temperature, it is preferable to cool the refrigerant 151 in the same manner as the high-frequency antenna 80.

One of the upper end sides of the high-frequency antenna 80 penetrates the antenna fixing block 182 and protrudes toward the inner side of the chamber 11. The protruding portion of the high frequency antenna 80 is covered by a protective tube 411 containing a dielectric such as quartz.

Furthermore, the maximum value of the horizontal magnetic flux density of the magnetron sputtering magnet 12 on the surface of the target 60 is 20 to 50 mT (millitesla), even in the case of support without a high frequency inductive coupling antenna. A lower magnetic flux density (60 to 100 mT) can also produce sufficient plasma.

The substrate stage 15 can hold the substrate 74 by a claw-shaped member or the like (not shown) provided on the lower surface of the substrate stage 15. The substrate 74 includes, for example, a germanium wafer or the like.

The sputtering apparatus 10 configured as described above introduces a sputtering gas and a reactive gas of oxygen into the chamber 11 provided with the bottom plate 14, and sputters the aluminum target 60 provided on the cathode to be used with the target. Aluminium 60 is formed on the substrate 74 opposite to the substrate 74.

<2. About the film formation process of alumina>

Fig. 3 is a schematic view for explaining a phenomenon which is more likely to occur in the film formation process by the film formation method of alumina using the embodiment. Fig. 4 is a view schematically showing the effect of the film forming method of alumina in the embodiment. The curve G1 of Fig. 4 shows the film formation speed and oxygen of the reactive magnetron sputtering-based alumina (Al ₂ O ₃ ) in the usual case (when the support of the plasma generation by the high-frequency inductively coupled plasma is not performed). The relationship between quantity. Curves G2 and G3 indicate the relationship between the film formation speed and the amount of oxygen in the film formation method of alumina according to the present embodiment, which is supported by plasma generation of high-frequency inductively coupled plasma. The curve G2 corresponds to a case where a DC voltage to which a negative voltage is applied is used as a sputtering voltage, and a curve G3 corresponds to a case where a pulsed DC voltage or an AC voltage is applied as a sputtering voltage.

<2-1. About the speed of film formation speed>

In the film formation process of the reactive magnetron sputtering alumina (Al ₂ O ₃ ) in the usual (when the support of the plasma generation based on the high-frequency inductively coupled plasma is not performed), if the chamber 11 is inside The increase in oxygen partial pressure promotes the oxidation reaction on the surface of the target 60. If the partial pressure of oxygen is further increased, the surface is substantially covered by stoichiometric alumina (Al ₂ O ₃ ). Since the stoichiometric alumina hardness is high, the sputtering yield is lowered, and as a result, the film formation speed is lowered (including the region of the point S1 on the right side of the paper surface from the broken line L1 of the curve G1 of Fig. 4).

By dashed boxes 601 through 603 (FIG. 3) surrounds a portion of the schematic diagram, respectively forming aluminum oxide (Al ₂ O ₃₎ of the process, a portion of the alumina-based (Al ₂ O ₃₎ of the deposition process can be predicted The method of forming a film of alumina according to the embodiment, that is, performing reactive magnetron sputtering supported by plasma generation by high-frequency inductively coupled plasma generated by the high-frequency antenna 80. Furthermore, it is also predicted that in this case, the above-described generation process of the usual reactive magnetron sputtering is also produced.

According to the method for forming a film of alumina according to the present embodiment, which is supported by plasma generation of high-frequency inductively coupled plasma, even a DC voltage of a negative voltage, a pulsed DC voltage including a negative voltage and a positive voltage, or an AC voltage is applied. Either one of the sputtering voltages can sufficiently increase the density of the high frequency inductively coupled plasma. Further, in the processing chamber 113, radicals become abnormally larger than ions. Further, oxygen radicals actively act on the surface of the substrate 74 of the film formation object, thereby promoting the generation of the stoichiometric amount of alumina (Al ₂ O ₃ ) on the surface of the substrate 74. Thus, the result of the oxidation of the surface of the oxygen radical-based substrate 74 is promoted (the pattern diagram in the dashed box 602), and the surface of the target can be selected with a lower amount of oxygen added to the sputtering condition, thereby promoting a low degree of oxidation. Sputtering in the state of stoichiometric oxidation of alumina, i.e., non-stoichiometric alumina (AlO), softens the surface of the target (pattern diagram within dashed box 601). That is, the surface of the target becomes a soft state of alumina having a lower degree of oxidation, and the sputtering yield is improved. On the other hand, the AlO particles sputtered from the target are formed by the added oxygen radicals. The vacuum space on the surface of the substrate or between the substrate and the target is changed to stoichiometric alumina (Al ₂ O ₃ ) to form a film on the substrate (schematic diagram in the dashed box 602). Therefore, the deposition rate of the aluminum oxide on the substrate surface of the film formation object is higher than that of the conventional reactive magnetron sputtering which is not supported by the plasma generation of the high frequency inductively coupled plasma (including the curve G2 of FIG. 4). A region between the broken line L2 and the broken line L3 at the point S2, and a region between the broken line L3 and the broken line L4 including the point S3 of the curve G3.

Further, a method of forming a film of alumina according to the present embodiment in which a pulsed direct current voltage or an alternating current voltage is applied as a sputtering voltage is applied to a target material with a voltage including a negative voltage and a positive voltage. With the effect of applying a negative DC voltage and the effect of directing electrons to the surface of the target, the softening of the chemical reaction using the surface of the target is further promoted by the oxygen radicals on the surface of the target (in the dashed box 603) Pattern diagram) to further promote non-stoichiometric AlO sputtering from the surface of the target. Thereby, the sputtering yield of the target is further improved, and the formation of an oxide film on the target can be suppressed. Therefore, according to the method for forming a film of alumina according to the embodiment in which a pulsed direct current voltage or an alternating current voltage is applied as a sputtering voltage, there is support for plasma generation based on high-frequency inductively coupled plasma, and compared with application of a negative direct current voltage. As a method of forming a film of alumina according to the embodiment of the sputtering voltage, the film forming speed can be further increased (including the dotted line L3 and the broken line L4 at the point S3 corresponding to the fastest film forming speed of the curve G3 of Fig. 4; Area).

<2-2. Stabilization of oxidation degree>

In the sputtering apparatus 10, the sputtering voltage is subjected to constant voltage control in the generation process of the magnetron plasma, and the sputtering current flowing through the magnetron cathode by the control unit 200 in the process of generating the magnetron plasma The amount of introduction of the reactive gas into the chamber 11 is controlled in such a manner that the value reaches the target current value. Specifically, based on the difference between the detected sputtering current value and the target current value, the following processing is performed: if the sign of the difference is positive, the amount of introduction of the reactive gas is reduced according to the difference, and the sign of the difference is If it is negative, the amount of introduction of the reactive gas is increased according to the difference. The value of the introduction amount to be added or subtracted is obtained, for example, by the control unit 200 by referring to an operation formula previously stored in the memory unit of the control unit 200, a table indicating the correspondence relationship, or the like.

When the sputtering voltage is subjected to constant voltage control, that is, when the sputtering power source 162 is driven in the voltage fixed mode, the oxidation degree of the aluminum oxide film formed on the substrate 74 is stabilized by the amount of oxygen in the chamber 11. That is, the equilibrium point of the corresponding amount of reactive gas.

Moreover, the higher the degree of oxidation of the surface of the target 60, the more secondary electrons are released by the target 60 when it is sputtered. Therefore, when the sputtering voltage is subjected to constant voltage control, the higher the degree of oxidation of the surface of the target 60, that is, the larger the amount of reactive gas in the chamber 11, the larger the sputtering current value becomes, and The degree of oxidation of the alumina formed on the substrate 74 also becomes higher.

Therefore, by introducing the reactive gas into the chamber 11 so that the sputtering current value reaches the target current value, regardless of interference factors such as reactive gases generated by moisture adsorbed on the substrate 74, etc., it is possible to form. The degree of oxidation of the aluminum oxide film on the substrate 74 is stable. That is, the alumina can be formed on the surface of the substrate 74 stably and at a relatively high deposition rate.

Further, the target current value to be referred to when controlling the introduction amount of the reactive gas is preferably set to a sputtering current value when the degree of oxidation of the alumina to be formed becomes the following oxidation degree, that is, stoichiometric alumina and oxidation. Each of the aluminas having a lower stoichiometric amount of alumina The degree of oxidation near the boundary of the degree of oxidation.

Here, in FIG. 4, when the amount of oxygen in the region on the right side of the paper is more than the broken line L3, a stoichiometric amount of alumina (Al ₂ O ₃ ) is generated on the surface of the substrate 74, and oxygen is located on the left side of the paper surface than the broken line L3. When measured, non-stoichiometric alumina (AlO) is produced. Further, it is understood that the degree of oxidation of the alumina formed on the surface of the substrate 74 is, for example, the film formation condition at a point S2 near the dotted line L3 in Fig. 4, that is, the stoichiometric amount of alumina and the degree of oxidation are more stoichiometric. When the degree of oxidation near the boundary of the oxidation degree of each of the alumina having a low alumina is formed, the film is formed into a alumina which exhibits a preferable passivation effect.

Therefore, the degree of oxidation of the alumina corresponding to the target current value of the sputtering apparatus 10 is an oxidation degree at which the passivation effect of alumina becomes high, and is also a degree of oxidation at a faster film formation speed. Therefore, alumina which is suitable for a passivation film of a p-type germanium substrate and exhibits a high passivation effect can be stably formed at a relatively high film formation speed.

<3. Action of Sputtering Device>

Fig. 6 and Fig. 7 are flowcharts showing the procedure of the film forming method of alumina in the embodiment. The sputtering apparatus 10 forms a static magnetic field in the vicinity of the target 60 by a magnet for magnetron sputtering (permanent magnet) 12. Moreover, FIG. 5 is an example of a time chart in the case of realizing the film formation method of the alumina of the embodiment by experiment.

First, after the film formation shutter (not shown) is closed, the target 60 and the substrate 74 are carried from the gate 351 into the processing chamber 113 of the chamber 11. Then, the substrate 74 and the target 60 are attached to the substrate stage 15 and the bottom plate 14, respectively, and the gate 351 is closed (step S110, time t0 in FIG. 5). Furthermore, after the gate 351 is closed, the temperature in the processing chamber 113 is adjusted to a specific temperature.

Then, after the inside of the chamber 11 is evacuated by the vacuum pump, the gas is introduced into the chamber 11 via the plasma generating gas introduction portion 19 so that the processing chamber 113 of the chamber 11 reaches the target pressure, and the introduction of the inert gas such as Ar into the chamber 11 is started. The gas is sputtered (step S120, time t1 of Fig. 5). As the target pressure, it is preferred to use a pressure of 0.2 Pa or more and 7 Pa or less. Further, it is preferable to use a pressure of 0.4 Pa or more and 2 Pa or less. However, the target pressure is not limited to these Pressure can also be used with a wider range of pressures. In the case where the target pressure is 3 Pa or less, the high-frequency inductively coupled plasma after ignition may be added to the step of temporarily increasing the pressure in the film forming chamber to 3 Pa or more. The reason for this is that the high-frequency inductively coupled plasma using the antenna has a characteristic that it is difficult to ignite under a pressure of 3 Pa or less. Furthermore, once the plasma is ignited, the plasma can continue to be produced even after returning to a lower pressure (target pressure).

Then, a plasma generation process ("first plasma generation process") is performed by inputting high frequency power from the high frequency power source 161 to the high frequency antenna 80 (step S130, time t2 of FIG. 5). A high frequency inductive magnetic field is formed around the high frequency antenna 80 to generate a high frequency inductively coupled plasma of the sputtering gas. In the subsequent processing step, if oxygen reactive gas is supplied into the chamber 11, the first plasma generating step also generates a high frequency inductively coupled plasma of the reactive gas. The supply of the high-frequency power continues until the film formation process of the alumina is completed.

Then, by using the substrate 14 and the sputtering power source 162 (applying a bias voltage), a sputtering voltage including a DC voltage of a negative voltage, a sputtering voltage including a negative voltage and a positive voltage, or a sputtering of an alternating current. The voltage is applied to the sputtering voltage application process (step S140, time t3 of Fig. 5). Thereby, a magnetron plasma generation process ("second plasma generation process") is performed. Further, when a DC voltage of a negative voltage is used as the sputtering voltage, damage to the interface is further suppressed, and alumina can be formed on the substrate 74. Further, as the frequency of the pulsed direct current voltage and the alternating current voltage, for example, 20 to 100 kHz is used, and other frequencies may be used. The sputtering voltage is preferably such that the absolute value of the negative voltage is 100 V or more and the control is 300 V or less (negative voltage is -100 V or less and -300 V or more), and more preferably 150 V or more and controlled to 250 V or less (negative voltage is -150 V) The following is -250V or more). However, the range of the sputtering voltage is not limited to these ranges, and a wider range of voltages can be used. In the subsequent processing step, when the reactive gas is supplied into the chamber 11, the second plasma generating step also generates a magnetron plasma of the reactive gas. Further, the application process of the sputtering voltage is continued until the film formation process of the aluminum oxide is completed.

Next, before the sputtering current value monitored by the control unit 200 becomes a value lower than the specific current value, only the pre-sputtering by the sputtering gas is performed, and the initial oxide film adhering to the surface of the target 60 is sufficiently Sputtering is removed (step S150).

When the initial oxide film on the surface of the target 60 is sufficiently removed, the sputtering current value becomes a substantially constant value at a low value, and thus the reactive gas of oxygen from the reactive gas supply portion 191 at this time (more accurate) In other words, the supply of the 5% oxygen and the diluted mixed gas of the inert gas such as Ar) is started via the flow rate controller 192 and the plasma generated gas introduction unit 19 (step S160, time t4 in FIG. 5). Further, after the supply of the reactive gas is started, the pressure of the processing chamber 113 is maintained at the target pressure. Further, in terms of the nature of the sputtering, the sputtering current value also drops in a short time after the supply of the reactive gas is started.

Then, the introduction amount of the reactive gas to be supplied is gradually increased, and the sputtering current value is temporarily increased to be equal to or higher than the target current value. Thereafter, the introduction amount of the reactive gas is gradually reduced, and the sputtering current value is lowered. When the sputtering current value reaches the target current value, the film forming baffle is opened to start the film formation of the aluminum oxide on the surface of the substrate 74. The treatment is started, and the introduction amount of the reactive gas is started to be controlled so that the sputtering current value is maintained as the target current value (step S170, time t5 of FIG. 5). Further, in the experimental results of Fig. 5, the elapsed time from time t3 to time t5 was 5 minutes.

After the film formation process is started, the control of the introduction amount of the reactive gas is continued, and the sputtering current value is maintained at the target current value. Further, in the experimental results shown in Fig. 5, the introduction amount of the reactive gas was repeatedly increased or decreased based on the curve L11, and gradually increased with the passage of time. It is caused by the following interference factors, that is, for example, the moisture attached to and remaining on the substrate 74 is equal to the instantaneous decomposition of the plasma, the oxygen (reactive gas) is rapidly increased, and the residual moisture is generated from the film formation process. The reactive gas is reduced. As a result of controlling the introduction amount of the reactive gas supplied from the reactive gas supply unit 191 so that the sputtering current value reaches the target current value, the introduction amount is gradually increased. In the control of the introduction amount, the sputtering current value can also be predicted according to the change of the plasma luminous intensity of the reactive gas. The change is to control the introduction amount of the reactive gas in such a manner that the sputtering current value reaches the target current value. Thereby, the accuracy of maintaining the sputtering current value as the target current value is further improved.

Fig. 8 is a view schematically showing the relationship between the sputtering current value and the plasma luminous intensity of the reactive gas. FIG. 9 is a view schematically showing an example of control of the introduction amount (oxygen supply amount) of the reactive gas using the predicted change in the sputtering current value.

As described above, the sputtering current value is a current value corresponding to the degree of oxidation of aluminum on the surface of the target 60, and the time delay due to the nature of the oxidation reaction causes the sputtering current value to be relative to the oxygen in the processing chamber 113. The change in the luminous intensity of the plasma of the reactive gas is delayed. Specifically, when the sputtering current changes as the curve 51 with respect to the target current value Ia, for example, the plasma luminous intensity of the reactive gas changes as shown by the curve 52, for example. Thus, the plasma luminous intensity of the reactive gas changes temporally earlier than the sputtering current value according to the change in the sputtering current value.

In Fig. 9, when the introduction amount (oxygen supply amount) of the oxygen-reactive gas introduced into the processing chamber 113 at the time T21 is controlled to a fixed value as shown by the curve 55, the sputtering is performed with respect to the target current value Ia. The current value is represented by curve 53, and the plasma luminescence intensity of the reactive gas is indicated by curve 54. Time T21 is the time to obtain the most up-to-date information in the experiment. In this case, the plasma luminescence intensity of the reactive gas becomes small during the period immediately before the time T21, so it can be predicted that after the time T21, the sputtering current value is also, for example, the dotted line in FIG. 9 after the lapse of time. As shown, it becomes smaller. In this case, after the time T21, before the sputtering current value actually changes, the sputtering current value and the target can be made by increasing the introduction amount of the reactive gas such as the portion indicated by the broken line of the curve 55. The deviation of the current value Ia is smaller. Therefore, the degree of oxidation of the alumina to be film-formed can be made more stable and the alumina can be formed on the substrate 74. Further, since the light is transmitted through the window portion 17, the plasma luminous intensity of the reactive gas detected by the spectroscope 111 has an absolute intensity of the plasma light detected by the spectroscope 111 due to the dirt of the window portion 17. In the case where the value is deviated, in order to change the direction of the change in the luminous intensity of the plasma, it is preferable to control the introduction of the reactive gas based on the direction of the change. the amount.

Returning to Fig. 7, when the film thickness of the film-formed alumina reaches a specific thickness (or a specific time elapses), the film formation baffle is closed, and the film formation process is terminated (step S180, time t6 of Fig. 5). Further, in the experimental results of Fig. 5, the elapsed time from time t5 to time t6 was 20 minutes. Then, the sputtering voltage (bias) is applied to the substrate 14 by the sputtering power source 162 (step S190, time t7 of FIG. 5), and after the stop (or at the same time as the stop), the high frequency power supply 161 is stopped. The frequency antenna 80 supplies high frequency power (step S200, time t8 of Fig. 5). Next, the supply of the gas is stopped (step S210, time t9 in Fig. 5), the gate 351 is opened, and the substrate 74 is carried out from the processing chamber 113 of the chamber 11 (step S220).

According to the film forming method of alumina according to the embodiment of the present invention, the first plasma generating step uses a conductor provided in the chamber 11 into which the reactive gas of the sputtering gas and the oxygen gas is introduced and which includes the number of coils less than one turn. The high frequency antenna 80 generates high frequency inductively coupled plasma in the chamber 11 at least in the second plasma generating step. Further, the second plasma generating step applies a sputtering voltage to the target 60 to generate a magnetron plasma. Therefore, the film formation speed is high by the increase in oxygen radicals, the promotion of the oxidation reaction on the substrate 74 of the film formation target, and the softening effect of the surface of the oxidized target 60 generated by the oxidation target 60. Chemical. Further, according to the present invention, the sputtering voltage is subjected to constant voltage control in the second plasma generating step, and the second plasma generating step is controlled in such a manner that the sputtering current value flowing through the magnetron cathode reaches the target current value. The amount of introduction of reactive gas. When the sputtering voltage is controlled by constant voltage, that is, when the sputtering power source is driven in the voltage fixed mode, the degree of oxidation of the aluminum oxide film formed on the substrate 74 is stabilized by the amount of oxygen in the chamber 11, that is, The amount of reactive gas corresponds to a stable equilibrium point. Further, in the case where the sputtering voltage is subjected to constant voltage control, the higher the degree of oxidation of the surface of the aluminum target 60, that is, the larger the amount of reactive gas in the chamber 11, the larger the sputtering current value becomes, and The degree of oxidation of the alumina of the film on the substrate 74 also becomes higher. Therefore, according to the present invention, the reactive gas is introduced into the chamber 11 by the sputtering current value reaching the target current value irrespective of, for example, moisture adsorbed on the substrate 74 or the like. The degree of oxidation of the aluminum oxide film formed on the substrate 74 can be stabilized by an interference factor such as a reactive gas. That is, the alumina can be formed stably at a relatively high film formation rate.

Further, according to the film forming method of alumina according to the present embodiment as described above, the target current value is a sputtering current value when the degree of oxidation of the alumina to be formed is the following oxidation degree, that is, stoichiometric alumina and oxidation. The degree of oxidation near the boundary of the oxidation degree of each of the aluminas having a lower stoichiometric amount of alumina. The degree of oxidation is an oxidation degree at which the passivation effect of the alumina to be film-formed becomes high, and is also a degree of oxidation at a faster film formation rate. Therefore, alumina which is suitable for a passivation film of a p-type germanium substrate and exhibits a preferable passivation effect can be stably formed at a relatively fast film formation speed.

Further, according to the method for forming a film of alumina according to the present embodiment as described above, in the control step, the light of the plasma corresponding to the reactive gas which changes in response to the change in the actual sputtering current value is used. The change in intensity predicts the change in the value of the sputtering current, and controls the amount of introduction of the reactive gas in such a manner that the sputtering current value reaches the target current value. Therefore, the degree of oxidation can be made more stable and the alumina can be formed.

Moreover, according to the film forming method of the alumina of this embodiment as described above, the sputtering voltage is a negative voltage. Therefore, damage to the interface can be further suppressed, and alumina can be formed on the substrate 74 to form a better alumina than the passivation film of the solar cell ruthenium substrate.

The present invention has been described and illustrated in detail, but the description above is exemplified in all aspects and is not limited to the aspects. Therefore, the present invention can be appropriately changed or omitted within the scope of the invention. For example, in order to improve the maintenance performance, the high-frequency antenna may not be arranged such that the straight portion of the central portion of the U shape is protruded from the antenna fixing block 182, and the balance between the self-maintenance and the ability to generate plasma may be determined. Arranged in such a manner that the upper half of the straight portion is protruded. Further, when a plurality of substrates 74 are continuously formed into a film, the upper wall surface of the chamber 11 may be removed, and a plurality of substrate stages 15 on which the substrate 74 are attached may be provided so that no gap is formed in the upper portion of the chamber 11. In a manner that the adjacent substrate platforms 15 are butted against each other at the front end and the rear end, and are arranged in the transport direction, the substrate platforms 15 are transported. The film formation process for each of the substrates 74 is performed. In this case, when the initial oxide film of the target 60 is removed by pre-sputtering, for example, by using the substrate stage 15 at the foremost end among the plurality of substrate stages 15 as a dummy substrate on which the substrate 74 is not mounted. The initial oxide film can be removed without using a film forming baffle.

10‧‧‧ Sputtering device

11‧‧‧ chamber

12‧‧‧ Magnets for magnetron sputtering

14‧‧‧Bottom plate (cathode)

15‧‧‧Substrate platform

17‧‧‧ Window Department

18‧‧‧ Targets. Antenna configuration department

19‧‧‧ Plasma generation gas introduction

20‧‧‧ gas inlet

24‧‧‧ Target Holding Department

60‧‧‧ Target (aluminum target)

74‧‧‧Substrate

80‧‧‧High frequency antenna

90‧‧‧The Plasma Generation Department

111‧‧‧ Spectroscope

112‧‧‧Probe

113‧‧‧Processing room

151‧‧‧Refrigerant

161‧‧‧High frequency power supply

162‧‧‧Power supply for sputtering

163‧‧‧Matching circuit

164‧‧‧ galvanometer

181‧‧‧target configuration block

182‧‧‧Antenna fixed block

189‧‧‧Anode

191‧‧‧Reactive Gas Supply Department

192‧‧‧Flow Controller

200‧‧‧Control Department

351‧‧‧ gate

411‧‧‧Protection tube

X‧‧‧ axis

Y‧‧‧ axis

Z‧‧‧ axis

Claims (9)

A method for forming a film of alumina, which is controlled in a vacuum vessel provided with a magnetron cathode for forming a static magnetic field, and controls a sputtering gas and a reactive gas of oxygen to a target pressure in a state in which the pressure in the vacuum vessel reaches a target pressure Introducing, sputtering an aluminum target disposed on the cathode, forming an oxide film on the substrate opposite to the aluminum target; and comprising the steps of: a first plasma generating step of introducing the sputtering gas And a plasma generated in the vacuum vessel of the reactive gas; and a second plasma generating step of applying a negative voltage, a DC pulse including a negative voltage and a positive voltage, and a sputtering voltage to the aluminum target, Generating a magnetron plasma by the static magnetic field; and controlling a step of controlling an introduction amount of the reactive gas introduced into the vacuum vessel; and the second plasma generating step is to perform constant voltage control on the sputtering voltage a step of controlling the reactive gas in the second plasma generating step by a method in which a sputtering current value flowing through the magnetron cathode reaches a target current value a step of introducing the amount of the first plasma generation step by using a high frequency antenna provided in the vacuum container and including a conductor having a number of windings less than one turn, and generating a high frequency inductor at least in the second plasma generating step The step of coupling the plasma. The method of forming a film of alumina according to claim 1, wherein the target current value is a degree of oxidation of the alumina of the film formed into a stoichiometric amount of alumina and a degree of oxidation of the alumina having a lower oxidation degree than the stoichiometric amount of alumina. The above-mentioned sputtering current value at the time of oxidation near the boundary. The method for forming a film of alumina according to claim 1 or 2, wherein the controlling step predicts a change in the sputtering current value according to a change in the luminous intensity of the plasma of the reactive gas, and the sputtering current value is as described above. The amount of the target current value is controlled to control the introduction amount of the above reactive gas. A method of forming a film of alumina according to claim 1 or 2, wherein said sputtering voltage is a negative voltage. The method of forming a film of alumina according to claim 1 or 2, wherein the target pressure is 0.2 Pa or more and 7 Pa or less. The method of forming a film of alumina according to claim 5, wherein the target pressure is 0.4 Pa or more and 2 Pa or less. The method for forming a film of alumina according to claim 1 or 2, wherein the absolute value of the negative voltage of the sputtering voltage is 100 V or more and 300 V or less. The method of forming a film of alumina according to claim 7, wherein the absolute value of the negative voltage of the sputtering voltage is 150 V or more and 250 V or less. A sputtering apparatus is provided in a vacuum vessel provided with a magnetron cathode for forming a static magnetic field, and the reactive gas of the sputtering gas and the oxygen gas is controlled and introduced in such a manner that the pressure in the vacuum vessel reaches a target pressure. An aluminum target disposed on the cathode is sputtered to form an oxide film on the substrate opposite to the aluminum target; and includes a member: a plasma generating gas introduction portion that introduces the sputtering gas and the reactive gas a control unit that controls an introduction amount of the reactive gas introduced into the processing space by the plasma generating gas introduction unit, and a high frequency antenna provided in the vacuum container and including a number of volumes a conductor of one turn; a high frequency power supply that supplies high frequency power to the above high frequency antenna to enable introduction a high-frequency inductively coupled plasma is generated in the vacuum container having the sputtering gas and the reactive gas; and a power source for sputtering, which applies a negative voltage to the aluminum target, a DC pulse including a negative voltage and a positive voltage, and an alternating current Any one of a sputtering voltage such that a magnetron is generated in the vacuum vessel into which the sputtering gas and the reactive gas are introduced by a static magnetic field formed by the magnetron; and the sputtering power source Performing constant voltage control on the sputtering voltage; the control unit controls the plasma generation gas introduction during the generation of the magnetron plasma by the sputtering current value flowing through the magnetron cathode reaching a target current value The amount of introduction of the above-mentioned reactive gas introduced into the vacuum container.