Film formation method

Abstract

The film-forming method comprises placing a yttrium target (20) and a substrate (W) to which the film is to be formed in a processing chamber (12), introducing oxygen into the processing chamber (12), applying a specific bias voltage to the substrate (W), causing the surface of the target (20) to evaporate in oxygen, forming a yttrium oxide film on the substrate (W), setting the oxygen partial pressure in the processing chamber (12) during the evaporation to a pressure of less than 0.4 Pa, and the oxygen to yttrium ratio (O / Y) in the yttrium oxide film on the substrate (W) to be 1.5 or less.

Description

Film formation method The present invention relates to a film forming method for forming a film having excellent plasma resistance on the surface of a substrate. Conventionally, for components used in semiconductor manufacturing equipment exposed to plasma, materials with excellent plasma resistance are required. Patent Document 1 discloses that in order to obtain such a material, yttrium oxide (Yttrium oxide) is formed on the surface of a substrate by a thermal spraying method. 2O 3) Membrane technology. In this technology, the Y 2O 3. Plasma spraying using powder as raw material forms a film of yttrium oxide on the surface of components where damage caused by plasma becomes a problem. On the other hand, in recent years, the formation of yttrium oxide films on substrates via a vacuum film deposition method (PVD method: Physical Vapor Deposition) has been under review. In such a PVD method, since an ionized material is used to form a film on a substrate, a dense film can be formed compared to a sputtering method that may have defects within the film. Generally speaking, it is known that a certain proportion of the evaporated atoms in the PVD method are ionized and become ions. Therefore, by applying a voltage (bias) to the substrate on which the film is formed and changing the energy of the incident ions, the density of the film and the film properties (crystal structure or mechanical properties) can be controlled. Among PVD methods, AIP (arc ion plating) is a film-forming method based on the evaporation and ionization of cathode materials through vacuum arc discharge under high current (tens to hundreds of amperes) and low voltage conditions. In this case, when forming films of insulating materials such as oxides, reactive film formation is required using a metal target in an oxygen-containing atmosphere. Because the cathode discharge surface is oxidized, areas where arc discharge does not occur exist on the cathode surface. Oxide accumulates in these areas, and as this area expands, it becomes difficult to maintain discharge. To address this problem, Patent Document 2 discloses that stable discharge can be achieved by using an evaporation source with a weak magnetic field of 3 to 50 gauss. Patent Document 3 discloses the use of this method to apply bipolar pulses to form oxides in pure oxygen. Furthermore, the same document discloses the formation of films of oxides containing Zr, Cr, Mo, Al, Si, Fe, Co, Ni, and Y by superimposing a high-current pulse arc on a direct current. [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Application Publication No. 2001-164354 [Patent Document 2] Japanese Patent Application Publication No. 5306198 [Patent Document 3] Japanese Patent Application Publication No. 5877147 The present inventors used the method disclosed in Patent Document 2 to try to form Y 2O 3 films, but a problem was found in that oxides formed on the target surface during long-term discharge, which eventually prevented discharge. Furthermore, the high-current pulse arc system described in Patent Document 3 has a complex and expensive power supply system compared to conventional DC power supplies, making it difficult to apply industrially. An object of the present invention is to provide a film forming method capable of stably maintaining discharge during film formation when stably forming an yttrium oxide film having conductivity to a substrate using an arc ion plating method. To achieve the above-mentioned objectives, the inventors of this case conducted repeated and intensive experiments to form a conductive yttrium oxide film, and as a result, discovered a new film formation method. The film forming method of the present invention is a film forming method for forming an yttrium oxide film on a substrate as an object to be formed by arc ion plating. The method comprises arranging a target composed of yttrium and the aforementioned substrate in a processing chamber, introducing at least oxygen into the aforementioned processing chamber, applying a specific bias voltage to the aforementioned substrate, causing the surface of the aforementioned target to evaporate in oxygen, and forming an yttrium oxide film on the aforementioned substrate. The oxygen partial pressure in the aforementioned processing chamber during the aforementioned evaporation is set to a pressure of less than 0.4 Pa, and the O / Y ratio of oxygen to yttrium in the aforementioned yttrium oxide film on the aforementioned substrate is set to a pressure of less than 1.5. The following describes an embodiment of the present invention in detail with reference to the accompanying drawings. FIG1 is a schematic diagram showing the schematic configuration of a film forming apparatus 10 for performing a film forming method according to an embodiment of the present invention. The film forming method according to an embodiment of the present invention forms a film having excellent plasma resistance on the surface of a substrate. However, the film forming apparatus 10 shown in FIG1 is merely an example of a film forming apparatus for implementing the film forming method according to an embodiment of the present invention, and the film forming apparatus for implementing the aforementioned film forming method is not limited to the apparatus shown in FIG1 . The film forming apparatus 1 forms a film on the surface of a workpiece W (substrate) disposed within a vacuum chamber 2 using a physical vapor deposition method (PVD method). Examples of the film forming apparatus 1 include an AIP apparatus that forms a film using an arc ion plating method and a sputtering apparatus that forms a film using a sputtering method. The film forming apparatus 10 is an arc ion plating apparatus and includes a vacuum chamber 12 , a rotating stage 14 , a plurality of substrate holders 16 , a bias power supply 18 , a target 20 serving as an evaporation source, an arc power supply 22 , a heater 24 , an argon tank 30 , an oxygen tank 32 , a vacuum pump P, and a controller 50 . The vacuum chamber 12 houses a turntable 14 and a plurality of substrate holders 16 disposed on the turntable 14. The interior of the vacuum chamber 12 (i.e., the space housing the turntable 14 and the plurality of substrate holders 16) is maintained in a vacuum or near-vacuum state by a vacuum pump P during various processes, including film formation. The vacuum chamber 12 is provided with a gas inlet 12A and an exhaust port 12B. The turntable 14 has a circular plate shape with a centerline extending in the vertical direction in FIG. 1 . The turntable 14 is disposed within the vacuum chamber 12 . During the film formation process, the turntable 14 rotates about its centerline while supporting a plurality of substrate holders 16 . However, the turntable 14 may further include a turntable on which a plurality of substrate holders 16 are disposed, so that each of the plurality of substrate holders 16 can rotate. The number of substrate holders 16 is not limited to the two shown in FIG. 1 . The plurality of substrate holders 16 each hold a workpiece W on which a film is to be formed. In this embodiment, the workpiece W is placed on the outer peripheral surface of the substrate holder 16. However, only a portion of the workpiece W is shown in FIG1 . In this embodiment, the workpiece W is made of A6061 alloy (Al alloy) and is a 20 mm x 20 mm square plate. However, the material and shape of the workpiece W are not limited thereto. The plurality of substrate holders 16 are each formed of a conductive material, such as stainless steel. The plurality of substrate holders 16 are arranged at equal intervals in the circumferential direction of the turntable 14 . In this state, the center lines of the plurality of substrate holders 16 are parallel to the center line of the turntable 14 . The bias power supply 18 applies a negative bias voltage to each of the plurality of substrate holders 16 via the turntable 14. In this embodiment, the bias power supply 18 intermittently applies a negative bias voltage to each of the plurality of substrate holders 16. That is, the bias power supply 18 is a pulse power supply. When a DC bias is applied as the bias voltage in a case where the resistance of the film formed on the workpiece W is relatively high, a problem of charge accumulation due to incident ions (charging) may sometimes occur. On the other hand, by applying a pulse voltage as the bias voltage, as in this embodiment, even when the resistance of the film formed on the workpiece W is relatively high, the above-mentioned problem can be suppressed. More specifically, by switching the bias voltage between the negative side and 0V or the positive side under the μS or mS command as a pulse voltage, the charging problem can be suppressed. However, the bias power supply 18 does not apply a bias voltage when a negative bias voltage is not applied during the film formation process. Alternatively, the bias power supply 18 may alternately apply a negative bias voltage and a positive bias voltage to each of the plurality of substrate holders 16. The absolute value of the negative bias voltage is greater than the absolute value of the positive bias voltage. However, the negative bias voltage and the positive bias voltage are applied alternately, and the bias power supply 18 may be, for example, an alternating current power supply (AC power supply) or a high frequency power supply (RF power supply). The target 20 is a disk-shaped member made of yttrium. As an example, the target 20 is a disk with a diameter of 100 mm. The arc power supply 22 is a DC power supply that acts as a discharge power source for generating a vacuum arc discharge on a target 20 placed in the vacuum chamber 2. In this case, the target 20 functions as the cathode in this discharge. Meanwhile, as shown in FIG1 , the vacuum chamber 12 functions as the anode in this discharge. The target 20 receives the discharge generated by the arc power supply 22, and evaporated yttrium ions are released from its surface. However, the arc power supply 22 and the target 20 together constitute the arc evaporation source. The heater 24 is provided in the vacuum chamber 12 and generates heat by receiving current from a heater power supply (not shown). As a result, the environment in the vacuum chamber 12 and the workpiece W are heated. The argon tank 30 contains argon and supplies argon gas to the vacuum chamber 12. Similarly, the oxygen tank 32 contains oxygen and supplies oxygen to the vacuum chamber 12. However, the amount of gas supplied from these tanks is controlled by adjusting the opening of a regulator (not shown) in response to a command from the controller 50. In another embodiment, the gas supply amount can be manually adjusted by an operator. The vacuum pump P makes the internal space of the vacuum chamber 12 a vacuum state (evacuation) through the exhaust port 12B. In addition to the aforementioned regulators, the controller 50 also controls the vacuum pump P, various voltages and currents of the bias power supply 18, the arc power supply 22, and the heater 24, and also controls the rotation of the turntable 14. [Example] Next, examples of the film forming method of this embodiment will be described. In the following description, oxygen is sometimes represented by O and yttrium is sometimes represented by Y. The present invention is not limited to the scope of the following examples. <Example 1> Hereinafter, Example 1 will be described. When executing this film forming method, as shown in FIG1 , a target 20 and a workpiece W are installed in a film forming apparatus 10 , and a vacuum chamber 12 is evacuated by a vacuum pump P to a vacuum state. Next, after preheating the workpiece W in the vacuum chamber 12 by the heater 24, argon gas is introduced from the argon tank 30 through the gas inlet 12A into the vacuum chamber 12 to bombard the surface of the workpiece W with argon ions as a pretreatment. Here, bombardment refers to generating heavy, inert gas ions such as argon ions by plasma discharge, irradiating the workpiece W with these ions, and heating the surface of the workpiece W. This heating cleans the surface. After the bombardment, pure oxygen gas is introduced at a flow rate of about 240 sccm and a pressure in the processing chamber of about 1 Pa. However, in other embodiments, pure oxygen gas Ar-O 2 A mixed gas (e.g., Ar 450 sccm, oxygen 50-75 sccm) can be introduced to bring the pressure in the processing chamber close to 2 Pa. However, in order to stably maintain the discharge, it is desirable to set the total pressure in the processing chamber to a range of 0.6 Pa to 4 Pa. Next, while the target 20 functions as a cathode, discharge is generated within the vacuum chamber 12 to form an yttrium oxide film on the workpiece W. At this time, the temperature of the workpiece W during film formation is approximately 300°C (between 200°C and 400°C), the arc current is in the range of 100A to 150A, and the voltage applied to the workpiece W is a unipolar pulse with a frequency of 200kHz and a duty of 56% or 300kHz and a duty of 60% so that the average voltage varies between 10 and 50V. The thickness of the yttrium oxide film formed on the workpiece W is approximately 5 to 100μm. However, as mentioned above, as an example, A6061Al (20mm×20mm square plate shape) is used for the workpiece W. The amount of oxygen in the formed yttrium oxide film is controlled by changing the pressure of the oxygen flowing into the processing chamber, that is, the oxygen partial pressure (oxygen flow rate). Next, a method for evaluating the yttrium oxide film formed on the workpiece W will be described together with its indices. (1) A test piece (workpiece W) formed by measuring the O / Y ratio (the ratio of oxygen to yttrium in the yttrium oxide film on the workpiece W) was cut along the film thickness direction and embedded in a resin for evaluation. After polishing, the O and Y values ​​were measured at 10 points in the film using EDX (Energy Dispersive X-ray Spectroscopy) from the cross-sectional direction, and the O / Y ratio was calculated based on the average value. (2) Resistance of the Yttrium Oxide Film: Electrodes were placed in contact with the back and front surfaces of the workpiece W (substrate). A voltage (3.5 to 350 mV, varying depending on the resistance) was applied between the two electrodes. The film resistance was calculated from the current flowing through the electrodes. A REOHMHITESTER (HIOKI 3540) was used for this measurement. FIG2 shows the resistance of yttrium oxide films with different O / Y ratios. As mentioned above, the O / Y ratio is controlled by changing the oxygen partial pressure (flow rate) in the processing chamber. As shown in FIG2 , when the O / Y ratio of the yttrium oxide film is less than 1.4, the resistance of the film decreases sharply, thereby confirming that it has conductivity. However, it is more desirable to set the O / Y ratio to 1.35 or less. At this time, the resistance of the aforementioned yttrium oxide film can be stably maintained below 10,000Ω. In this measurement, since the upper limit of the resistance value measured by the measuring machine is 30,000Ω, the measurement points of 30,000Ω in FIG2 all show resistances above it. However, when forming a film with oxygen alone and the oxygen flow rate is low, the pressure in the processing chamber becomes low, the discharge voltage increases, and the discharge becomes unstable. Therefore, it is more desirable to further introduce Ar gas into the processing chamber to form a film with Ar-O 2 atmosphere. As an example, only 50 sccm of oxygen is introduced into the processing chamber, and the pressure in the chamber during discharge is 1×10 -2 When the pressure in the processing chamber is 2.5 Pa, the discharge voltage is as high as 25 V. When 450 sccm of Ar gas and 50 sccm of oxygen gas are introduced, respectively, the discharge voltage is reduced to around 17 V, and the discharge can be stably maintained. However, it is more preferable to introduce Ar gas so that the pressure in the processing chamber during discharge is 1 Pa or more. However, the yttrium oxide film in the present invention refers to the Y 2O 3 and Y mixed state, by changing Y 2O 3 and Y ratio, and as a result, the ratio of Y to O in the film changes. In the present invention, such Y 2O The film in which Y and Y are mixed is generally referred to as an "yttrium oxide film." However, the ratio of Y to O in this case is an atomic ratio. As an example, the thickness of the yttrium oxide film on the workpiece W is 50 μm or more. <Example 2> Next, Example 2 will be described. In Example 2, a target 20 (100 mm in diameter) made of metal Y was attached to the arc evaporation source of an arc ion plating apparatus ( FIG. 1 ) connected to an arc power supply 22 composed of a DC power supply. After vacuum evacuation and preheating, 150 sccm or 450 sccm of argon gas was introduced into the vacuum chamber 2. At this time, the pressure (total pressure) within the vacuum chamber 2 was introduced so that it was approximately 1 to 2 Pa. Then, a certain amount of pure oxygen gas (e.g., 45 sccm) was introduced, and the arc evaporation source was discharged for 5 minutes at a current of 100 A to 150 A. The change in discharge voltage during this period was measured. Subsequently, the amount of oxygen within the vacuum chamber 2 was increased, and the 5-minute discharge process was repeated until the oxygen flow rate at which the discharge voltage sharply increased was reached. FIG3 is a graph showing the relationship between the oxygen flow rate and the oxygen partial pressure introduced into the vacuum chamber 2 in Example 2. The oxygen partial pressure is calculated by multiplying the total pressure within the vacuum chamber 2, measured by a diaphragm pressure gauge (manufactured by MKS), by the oxygen flow rate, and then dividing the result by the total gas flow rate (argon + oxygen). As shown in FIG3 , the oxygen partial pressure varies approximately linearly with respect to the oxygen flow rate. Figures 4 and 5 are graphs showing the relationship between the oxygen partial pressure and the discharge voltage in Example 2. Figure 4 shows the results when the arc current is 100 A, and Figure 5 shows the results when the arc current is 150 A. Figures 4 and 5 both show experiments with two levels of argon gas introduction (150 sccm and 450 sccm). As shown in Figures 4 and 5, the discharge voltage increases with the oxygen partial pressure, and it can be seen that between 0.3 and 0.4 Pa, the discharge voltage rises sharply as the oxygen partial pressure increases. However, this phenomenon is viewed from the perspective of discharge voltage. In the system used in this experiment, the discharge voltage is desirably below 20 V. This shows that in order to maintain stable discharge during film formation, the oxygen partial pressure in the vacuum chamber 2 must be controlled to less than 0.4 Pa, even if it is high. <Example 3> Next, Example 3 is described. In Example 3, a target 20 (diameter 100 mm) made of metal Y is installed on the arc evaporation source of the arc ion plating device (Figure 1) connected to the arc power supply 22 composed of a DC power supply, and after vacuum exhaust and preheating, 150 sccm of argon gas is introduced into the vacuum chamber 2. At this time, the pressure (total pressure) in the vacuum chamber 2 is introduced in a manner of being around 2 Pa. Then, pure oxygen gas is introduced, and the arc evaporation source is discharged at a current of 125 A to form an yttrium oxide film on the Si substrate (workpiece W) with a target thickness of 3 μm. However, a pulse bias (voltage -10 V, frequency 200 kHz, pulse width 2.8 μS) is applied during film formation. Then, the surface roughness (Ra) of the formed film is measured using a stylus surface roughness meter (Tokyo Seimitsu SURFCOM TOUCH550). FIG6 is a graph showing the surface roughness of the yttrium oxide film formed by varying the oxygen partial pressure in Example 3. As shown in FIG6 , the surface roughness increases as the oxygen partial pressure decreases. As the surface roughness increases, polishing or the like is required for practical use. Therefore, the surface roughness is preferably 0.4 μm or less. To this end, it is desirable to use the oxygen partial pressure (x) = 0.17 Pa obtained by substituting Ra(y) = 0.4 into the regression equation (y = -1.7628x + 0.6961) based on the results of FIG6 as the lower limit of the partial pressure. Thus, the oxygen partial pressure during film formation is preferably set to 0.17 Pa or more. Example 4 Next, Example 4 will be described. In Example 4, a target 20 (100 mm in diameter) made of metal Y was attached to the arc evaporation source of an arc ion plating apparatus ( FIG. 1 ) connected to an arc power supply 22 comprised of a DC power supply. After vacuum evacuation and preheating, 450 sccm of argon gas was introduced into the vacuum chamber 2. This was done so that the pressure (total pressure) within the vacuum chamber 2 was approximately 2 Pa. Then, 50 sccm of pure oxygen gas was introduced, and the arc evaporation source was discharged at a current of 100 A for 400 minutes. The changes in the oxygen partial pressure and discharge voltage within the vacuum chamber 2 were measured. Fig. 7 is a graph showing changes in oxygen partial pressure during long-term discharge in Example 4. Fig. 8 is a graph showing changes in discharge voltage during long-term discharge in Example 4. As shown in Figures 7 and 8 , it can be seen that by controlling the oxygen partial pressure in the vacuum chamber 2 to less than 0.4 Pa, the discharge voltage is stabilized (below 20 V), and long-term discharge is possible. However, the above-mentioned Examples 2 and 4 were designed for the purpose of evaluating discharge characteristics, and no film formation was actually performed. As described above, when the discharge current (arc current) is in the range of 100 A to 150 A and the amount of argon gas introduced is in the range of 150 sccm to 450 sccm, the discharge can be stably maintained by adjusting the oxygen partial pressure in the vacuum chamber 2 within the range of less than 0.4 Pa. Example 5 Next, Example 5 will be described. In Example 5, a target 20 (100 mm in diameter) made of metal Y was attached to the arc evaporation source of an arc ion plating apparatus ( FIG. 1 ) connected to an arc power supply 22 comprised of a DC power supply. After vacuum evacuation and preheating, the target was bombarded with argon ions. Following this gas bombardment, pure oxygen gas at a flow rate of approximately 240 sccm, or a mixed gas of argon and pure oxygen (450 sccm Ar, 50-75 sccm Oxygen), was introduced into the vacuum chamber 2 to a total pressure of approximately 2 Pa. Subsequently, discharge was performed with the metal Y target 20 acting as a cathode, forming an yttrium oxide film on a workpiece W. During film formation, the temperature of the workpiece W is approximately 300°C, the arc current is between 100 and 150 A, and the voltage applied to the workpiece W is a unipolar pulse with a frequency of 200 kHz and a duty of 56% or 300 kHz and a duty of 60%, with the average voltage varying between 10 and 50 V. The thickness of the formed film is approximately 5 to 100 μm. A6061Al (20×20 squares) is used as the substrate for the workpiece W. Furthermore, the oxygen content in the yttrium oxide film is controlled by varying the oxygen partial pressure (oxygen flow rate) within the vacuum chamber 2. FIG9 is a graph showing the O / Y ratio of yttrium oxide films formed by varying the oxygen partial pressure in Example 5. However, the method for calculating the O / Y ratio is the same as described above. As shown in FIG9 , it can be confirmed that the O / Y ratio of the yttrium oxide film formed within the oxygen partial pressure range of less than 0.4 Pa is 1.5 or less (1.51 or less). The embodiments of the present invention have been described in detail above. The yttrium oxide film obtained by the film formation method of the present invention is widely applicable to components exposed to plasma, such as semiconductor manufacturing equipment. In particular, forming the yttrium oxide film using arc ion plating allows for a denser film with higher plasma resistance than film formation using thermal spraying. The film forming method of the present invention is a film forming method for forming an yttrium oxide film on a substrate as an object of film formation by arc ion plating. The method comprises: arranging a target 20 composed of yttrium and a workpiece W (substrate) in a vacuum chamber 2, introducing at least oxygen into the vacuum chamber 2, applying a specific bias voltage to the workpiece W, causing the surface of the target 20 to evaporate in oxygen, and forming an yttrium oxide film on the workpiece W. The oxygen partial pressure in the vacuum chamber 2 during the above-mentioned evaporation is set to a pressure of less than 0.4 Pa, and the O / Y ratio of oxygen to yttrium in the above-mentioned yttrium oxide film on the workpiece W is set to a pressure of less than 1.5. According to this film formation method, by controlling the oxygen partial pressure within the vacuum chamber 2 during film formation and thereby varying the oxygen content in the yttrium oxide film, the film resistance can be reduced, resulting in a conductive yttrium oxide film. In particular, since the oxygen partial pressure is set to less than 0.4 Pa, it is possible to suppress the formation of oxides on the surface of the target 20, which would increase the discharge voltage and make it difficult to sustain the discharge. In the above method, it is desirable to further set the oxygen partial pressure in the vacuum chamber 2 during the evaporation so that the O / Y ratio is less than 1.4. According to this method, the resistance of the film can be further reduced, and a conductive yttrium oxide film can be stably obtained. In the above method, it is desirable to further include setting the oxygen partial pressure within the vacuum chamber 2 so that the resistance of the yttrium oxide film is 10,000 Ω or less. According to this method, by controlling the oxygen partial pressure during film formation and varying the amount of oxygen in the film, a conductive yttrium oxide film having a resistance of 10,000 Ω or less can be stably obtained. The above method preferably further comprises setting the oxygen partial pressure so that the discharge voltage during film formation is 20 V or less. According to this method, the increase rate of the discharge voltage due to the increase in the discharge voltage is suppressed by the oxygen partial pressure, and the discharge during film formation can be stably maintained. In the above method, it is desirable that the oxygen partial pressure is further set to be not less than 0.17 Pa. According to this method, it is possible to suppress the roughness of the formed film from increasing as the oxygen partial pressure decreases. In the above method, it is desirable to further include introducing argon in addition to oxygen into the vacuum chamber 2. According to this method, the discharge voltage during film formation can be reduced, and the discharge during film formation can be stabilized. The above method preferably further comprises applying a pulse voltage as the bias voltage to the workpiece W. According to this method, even when the resistance of the film formed on the workpiece W is relatively high, an increase in charge accumulated by incident ions can be suppressed. Furthermore, it is desirable to obtain a high-resistance yttrium oxide film having an O / Y ratio of 1.4 or higher and 1.5 or lower. In this case, as described above, excellent discharge stability can be achieved by setting the oxygen partial pressure in the vacuum chamber 2 to less than 0.4 Pa and the yttrium oxide film having an O / Y ratio of 1.5 or lower. Furthermore, if the oxygen flow rate (oxygen partial pressure) is high during film formation, oxides will form on the surface of the metal target 20, increasing the discharge voltage and making it difficult to maintain discharge. As in the previous embodiment, since the rate of increase in discharge voltage tends to increase with increasing discharge voltage, it is desirable to adjust the oxygen flow rate (oxygen partial pressure) so that the discharge voltage is below 20 V, preferably below 18 V. Furthermore, since the roughness of the formed film increases as the oxygen partial pressure within the vacuum chamber 2 decreases, the oxygen partial pressure is preferably above 0.17 Pa. However, these are merely examples, and the present invention is not to be construed in any limiting sense by the description of the above-mentioned embodiments. In the present invention, the substrate is not limited to being composed of an insulating material; it may also be composed of a conductive material. In the present invention, the alternating application of negative and positive bias voltages is not limited to the pulsed form described in the above-mentioned embodiments; for example, a sinusoidal form may also be employed. Furthermore, if the arc current is too low, the discharge becomes unstable, while if it is too high, the target may be heated. Therefore, for a target with a diameter of approximately 100 mm, it is desirable to set the arc current between 50 A and 200 A. The film forming method of the present invention is a film forming method for forming an yttrium oxide film on a substrate as an object to be formed by arc ion plating. The method comprises arranging a target composed of yttrium and the aforementioned substrate in a processing chamber, introducing at least oxygen into the aforementioned processing chamber, applying a specific bias voltage to the aforementioned substrate, causing the surface of the aforementioned target to evaporate in oxygen, and forming an yttrium oxide film on the aforementioned substrate. The oxygen partial pressure in the aforementioned processing chamber during the aforementioned evaporation is set to a pressure of less than 0.4 Pa, and the O / Y ratio of oxygen to yttrium in the aforementioned yttrium oxide film on the aforementioned substrate is set to a pressure of less than 1.5. According to this method, by controlling the oxygen partial pressure within the processing chamber during film formation and thereby varying the oxygen content in the yttrium oxide film, the film resistance can be reduced, resulting in a conductive yttrium oxide film. In particular, by setting the oxygen partial pressure to less than 0.4 Pa, it is possible to suppress the formation of oxides on the target surface, which would increase the discharge voltage and make it difficult to sustain the discharge. The method may further include setting the oxygen partial pressure in the processing chamber during the evaporation so that the O / Y ratio is less than 1.4. According to this method, the resistance of the film can be further reduced, and a conductive yttrium oxide film can be stably obtained. The method may further include setting the oxygen partial pressure in the processing chamber so that the resistance of the yttrium oxide film is 10,000Ω or less. According to this method, by controlling the oxygen partial pressure during film formation to change the oxygen content in the film, a conductive yttrium oxide film having a resistance of 10,000 Ω or less can be stably obtained. The above method may further include setting the oxygen partial pressure so that the discharge voltage during film formation is 20 V or less. According to this method, the increase in the rate of increase of the discharge voltage due to an increase in the discharge voltage is suppressed by the oxygen partial pressure, and the discharge during film formation can be stably maintained. In the above method, the oxygen partial pressure may be further set to 0.17 Pa or higher. According to this method, it is possible to suppress the roughness of the formed film from increasing as the oxygen partial pressure decreases. The above method may further include introducing argon into the processing chamber in addition to oxygen. According to this method, the discharge voltage during film formation can be reduced, and the discharge during film formation can be stabilized. The above method may further include applying a pulse voltage to the substrate as the bias voltage. According to this method, even when the resistance of the film formed on the substrate is relatively high, it is possible to suppress an increase in charge accumulated by incident ions. According to the present invention, a film forming method can be provided that can stably maintain discharge during film formation when stably forming an yttrium oxide film having conductivity to a substrate using arc ion plating. 10: Film forming apparatus 12: Vacuum chamber 12A: Gas inlet 12B: Exhaust port 1 14: Rotary stage 16: Substrate holder 18: Bias power supply 20: Target 22: Arc power supply 24: Heater 30: Argon tank 32: Oxygen tank 50: Controller W: Workpiece P: Vacuum pump [Figure 1] Figure 1 is a schematic diagram showing the schematic configuration of a film formation apparatus used to perform a film formation method according to an embodiment of the present invention. [Figure 2] Figure 2 is a graph showing the relationship between the O / Y ratio (the ratio of oxygen to yttrium) in the yttrium oxide film on the substrate and the electrical resistance of the yttrium oxide film, in an embodiment of the present invention. [Figure 3] Figure 3 is a graph showing the relationship between oxygen flow rate and oxygen partial pressure, in an embodiment of the present invention. [Figure 4] Figure 4 is a graph showing the relationship between oxygen partial pressure and discharge voltage, in an embodiment of the present invention. [Figure 5] Figure 5 is a graph showing the relationship between oxygen partial pressure and discharge voltage, in an embodiment of the present invention. [Figure 6] Figure 6 is a graph showing the surface roughness of yttrium oxide films formed by varying the oxygen partial pressure, in an embodiment of the present invention. [Figure 7] Figure 7 is a graph showing the change in oxygen partial pressure during long-term discharge, in an embodiment of the present invention. [Figure 8] Figure 8 is a graph showing the change in discharge voltage during long-term discharge, in an embodiment of the present invention. [Figure 9] Figure 9 is a graph showing the O / Y ratio of yttrium oxide films formed by varying the oxygen partial pressure, in an embodiment of the present invention. 10: Film forming device 12: Vacuum Chamber 12A: Gas inlet 12B: Exhaust port 1 14: Rotating table 16: substrate support 18: Bias power supply 20: Target 22: Arc power supply 24: Heater 30: Argon tank 32: Oxygen tank 50:Controller

Claims

1. A film-forming method for forming a yttrium oxide film on a substrate to which the film is to be formed by arc ion plating, comprising: placing a target made of yttrium and the substrate in a processing chamber; introducing oxygen into the processing chamber; applying a specific bias voltage to the substrate to cause the surface of the target to evaporate in oxygen; forming a yttrium oxide film on the substrate; setting the oxygen partial pressure in the processing chamber during evaporation to a pressure of less than 0.4 Pa; setting the oxygen to yttrium ratio (atomic ratio) in the yttrium oxide film on the substrate to a pressure of 1.5 or less; and setting the total pressure in the processing chamber to a range of 0.6 Pa to 4 Pa.

2. The film-forming method as described in claim 1, wherein, It also has the ability to set the oxygen partial pressure in the aforementioned processing chamber during the aforementioned evaporation so that the aforementioned O / Y ratio (atomic ratio) is less than 1.

4.

3. The film-forming method as described in claim 2, wherein, It also has the ability to set the oxygen partial pressure in the aforementioned processing chamber so that the resistance of the aforementioned yttrium oxide film is below 10000Ω.

4. The film-forming method as described in claim 1, wherein, It also has the ability to set the aforementioned oxygen partial pressure so that the discharge voltage during film formation is below 20V.

5. The film-forming method as described in claim 1, wherein, Furthermore, it possesses an oxygen partial pressure of 0.17 Pa or higher.

6. A film-forming method as described in any of claims 1 to 5, wherein, It also has the capability to introduce argon into the aforementioned treatment chamber in addition to oxygen.

7. A film-forming method as described in any of claims 1 to 5, wherein, It also has the capability to apply a pulse voltage to the aforementioned substrate as the aforementioned bias voltage.

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