Film deposition method

Abstract

To provide a film deposition method capable of stably forming a yttrium oxide film having conductivity to a base material.SOLUTION: A film deposition method comprises: arranging a target consisting of yttrium and a base material to be film-deposited in a chamber; introducing at least oxygen into the chamber; applying a predetermined bias voltage to the base material; evaporating the surface of the target in the oxygen to deposit a yttrium oxide film on the base material; and setting the bias voltage so that the porosity of the film is 0.5% or less to deposit the yttrium oxide film having a thickness of 40 μm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a film-forming method for forming a film excellent in plasma resistance on the surface of a substrate.

Background Art

[0002] Conventionally, for members used in an environment exposed to plasma such as semiconductor manufacturing equipment, materials excellent in plasma resistance have been demanded. Patent Document 1 discloses a technique for forming a yttrium oxide film on the surface of a substrate by an ion plating method using yttrium oxide (Y2O3) as a raw material in order to obtain such a material. Further, Patent Document 2 discloses a technique for forming a yttrium oxide film by a reactive sputtering method.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the methods described in Patent Documents 1 and 2, since the film-forming rate of the yttrium oxide film is relatively slow, in order to obtain a more practical film-forming rate, film formation by an arc ion plating method (vacuum arc method) is desirable. However, as a result of the present inventor's attempt to form a yttrium oxide film by the arc ion plating method, it was newly found that when the film thickness is increased, the porosity increases and the film-forming quality deteriorates.

[0005] The present invention has been conceived in view of the above problems, and an object thereof is to provide a film-forming method capable of stably forming a yttrium oxide film having a predetermined film thickness on a substrate by an arc ion plating method.

Means for Solving the Problems

[0006] In order to achieve the above object, the inventor of the present application repeatedly conducted experiments by an arc ion plating method to form a yttrium oxide film, and as a result, found a new film-forming method.

[0007] The film-forming method according to the present invention is a film-forming method for forming a yttrium oxide film on a substrate by an arc ion plating method, comprising arranging a target made of yttrium and the substrate in a chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen to form a yttrium oxide film on the substrate, and setting the bias voltage so that the porosity of the film is 0.5% or less to form a yttrium oxide film having a thickness of 40 μm or more.

[0008] When forming a yttrium oxide film by discharging yttrium in an oxygen atmosphere using an arc ion plating method, the porosity in the film tends to increase as the film thickness increases. However, by adjusting the bias voltage applied to the substrate during film formation, the porosity can be reduced even for a yttrium oxide film having a thickness of 40 μm or more. In particular, by suppressing the porosity to 0.5% or less, the etching rate can be reduced.

[0009] Further, the film forming method according to the present invention is a film forming method for forming a yttrium oxide film on a substrate which is an object to form a film, comprising arranging a target made of yttrium and the substrate in a chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen to form a yttrium oxide film on the substrate, and setting the bias voltage so that the density of the film is 5 g / cm 3 or more, and forming a yttrium oxide film having a thickness of 40 μm or more.

[0010] Further, the film forming method according to the present invention is a film forming method for forming a yttrium oxide film on a substrate which is an object to form a film, comprising arranging a target made of yttrium and the substrate in a chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen to form a yttrium oxide film on the substrate, and setting the bias voltage so that the hardness of the film is 9 GPa or more, and forming a yttrium oxide film having a thickness of 40 μm or more.

[0011] In the above method, it may further comprise setting the bias voltage so that the average is 25 V or more.

[0012] According to this method, by making the bias voltage to be adjusted 25 V or more on average, the porosity can be stably reduced.

[0013] In the above method, it may further comprise setting the bias voltage so that the average is less than 75 V.

[0014] According to this method, it is possible to prevent the stress acting on the film from increasing.

[0015] In the above method, the waveform of the bias voltage may be a pulse waveform.

[0016] In the above method, the bias voltage may be a constant value.

Advantages of the Invention

[0017] According to the film formation method of the present invention, a yttrium oxide film with a predetermined film thickness can be stably formed on a substrate by an arc ion plating method.

Brief Description of the Drawings

[0018]

Figure 1

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Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a film forming apparatus 10 for performing the film forming method according to this embodiment. The film forming method according to this embodiment is a method of forming a film excellent in plasma resistance on the surface of a substrate.

[0020] Note that the film forming apparatus 10 shown in FIG. 1 shows an example of a film forming apparatus for carrying out the film forming method according to this embodiment, and the film forming apparatus for carrying out the film forming method is not limited to that shown in FIG. 1. This film forming apparatus 10 is an apparatus for forming a film on the surface of a workpiece W (substrate) disposed in a vacuum chamber 12 by using a physical vapor deposition method (PVD method: Physical Vapor Deposition). This film forming apparatus 10 includes an AIP (Arc Ion Plating) apparatus that forms a film using an arc ion plating method, a sputtering apparatus that forms a film using a sputtering method, and the like.

[0021] The film forming apparatus 10 is an arc ion plating apparatus. The film forming apparatus 10 includes a vacuum chamber 12, a rotary table 14, a plurality of substrate holders 16, a bias power supply 18, a target 20 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.

[0022] The vacuum chamber 12 houses the rotary table 14 and a plurality of substrate holders 16 disposed on the rotary table 14. The interior of the vacuum chamber 12 (that is, the space in which the rotary table 14 and the plurality of substrate holders 16 are housed) is maintained in a vacuum or a state close to a vacuum by the vacuum pump P in various processes including the film forming process. The vacuum chamber 12 is provided with a gas inlet 12A and an exhaust port 12B.

[0023] The rotary table 14 has a disk shape including a center line extending in the vertical direction in FIG. 1. The rotary table 14 is disposed within the vacuum chamber 12. In the film forming process, the rotary table 14 rotates about its center line while supporting a plurality of substrate holders 16. Note that the rotary table 14 may further include a turntable on which each of the plurality of substrate holders 16 is individually disposed so that each of the plurality of substrate holders 16 can rotate. The number of substrate holders 16 is not limited to two in FIG. 1.

[0024] Each of the plurality of substrate holders 16 supports a workpiece W (substrate) which is an object for forming a film. In the present embodiment, the workpiece W is disposed on the outer peripheral surface of the substrate holder 16. Note that in FIG. 1, only some of the workpieces W are illustrated.

[0025] In the present embodiment, the workpiece W is made of an A6061 alloy (Al alloy) (also referred to as an Al substrate) and is a square plate piece of 20 mm × 20 mm. Note that the material and shape of the workpiece W are not limited thereto.

[0026] Each of the plurality of substrate holders 16 is formed of a conductive material. The conductive material is, for example, stainless steel.

[0027] The plurality of substrate holders 16 are arranged at equal intervals in the circumferential direction of the rotary table 14. In this state, the center line of each of the plurality of substrate holders 16 is parallel to the center line of the rotary table 14.

[0028] The bias power supply 18 applies a negative bias voltage to each of the plurality of substrate holders 16 via the rotary table 14. In the present 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 the resistance of the film formed on the workpiece W is relatively high, if a DC bias is applied as the bias voltage, a problem (charge-up) may occur in which charges accumulate due to the incident ions. On the other hand, by applying a pulse voltage as the bias voltage as in the present embodiment, even when the resistance of the film formed on the workpiece W is relatively high, the above problem can be suppressed. More specifically, as the pulse voltage, by switching the bias between the negative side and 0V or the positive side on the order of μS or mS, the problem of charge-up can be suppressed.

[0029] Note that when the bias power supply 18 is not applying a negative bias voltage during the film formation process, no bias is applied. Alternatively, the bias power supply 18 can 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.

[0030] If the negative bias voltage and the positive bias voltage are alternately applied, the bias power supply 18 may be, for example, an AC power supply (AC power source) or an RF power supply (RF power source).

[0031] The target 20 is a disc-shaped member made of yttrium. As an example, the target 20 is a disc with a diameter of 100 mm.

[0032] The arc power source 22 is a DC power source that functions as a discharge power source for generating a vacuum arc discharge on the target 20 disposed in the vacuum chamber 12. At this time, the target 20 functions as the cathode in the discharge. On the other hand, as shown in FIG. 1, the vacuum chamber 12 functions as the anode in the discharge. The target 20 receives the discharge generated by the arc power source 22 and emits ions of evaporated yttrium from its surface. Note that the arc power source 22, together with the target 20, constitutes an arc evaporation source.

[0033] The heater 24 is provided inside the vacuum chamber 12 and generates heat by receiving current supply from a heater power source (not shown). As a result, the environment inside the vacuum chamber 12 and the workpiece W are heated.

[0034] The argon tank 30 stores argon inside and supplies argon gas to the vacuum chamber 12. Similarly, the oxygen tank 32 stores oxygen inside and supplies oxygen to the vacuum chamber 12. Note that the gas supply amounts from these tanks are controlled by adjusting the opening degree of a regulator (not shown) in response to commands from the controller 50. In other embodiments, the gas supply amounts may be adjusted manually by an operator.

[0035] The vacuum pump P evacuates the internal space of the vacuum chamber 12 to a vacuum state (evacuation) through the exhaust port 12B.

[0036] In addition to the above regulator, the controller 50 controls the vacuum pump P, controls various voltage or current values of the bias power source 18, the arc power source 22, and the heater 24, and controls the rotation of the rotary table 14, etc.

Example

[0037] Next, an example of the film formation method according to the present embodiment will be described. In the following description, oxygen may be denoted as O and yttrium as Y. Further, the present invention is not limited to the scope of the following examples. When performing the film formation method, as shown in FIG. 1, a target 20 and a workpiece W are installed in a film formation apparatus 10, and the inside of a vacuum chamber 12 is evacuated by a vacuum pump P to be in a vacuum state.

[0038] Next, after preheating inside the vacuum chamber 12 by a heater 24, argon gas is introduced into the vacuum chamber 12 from an argon tank 30 through a gas inlet 12A, and as a pretreatment, bombardment is performed on the surface of the workpiece W with argon gas ions. Here, bombardment means generating heavy inert gas ions such as argon ions by plasma discharge, irradiating the workpiece W with these ions to heat and sputter the surface of the workpiece W, and cleaning moisture and contaminants on the surface.

[0039] After the above bombardment, pure oxygen gas is introduced at a flow rate of about 240 sccm so that the pressure inside the chamber becomes around 1 Pa. In other embodiments, instead of pure oxygen gas, an Ar - O2 mixed gas (for example, Ar 450 sccm, oxygen 50 sccm) may be introduced so that the pressure inside the chamber becomes around 2 Pa. In addition, in order to stably maintain the discharge, it is desirable that the total pressure inside the chamber be set in the range of 0.6 Pa or more and 4 Pa or less.

[0040] Next, while making the target 20 function as a cathode, discharge is generated in the vacuum chamber 12 to form a yttrium oxide film on the work W. At this time, the temperature of the work W during film formation is around 300 °C (200 °C or higher and 400 °C or lower), the arc current is in the range of 100 A or higher and 125 A or lower, and the voltage applied to the work W is a unipolar pulse (pulse waveform) or a DC bias (DC voltage) with a frequency of 200 kHz and a DUTY of 56%, and the average voltage is changed between 10 and 100 V. The film thickness of the yttrium oxide film formed on the work W is about 10 to 100 μm. As described above, as an example, A6061Al (a square piece with a size of 20 mm × 20 mm) is used for the work W. The amount of oxygen in the formed yttrium oxide film is controlled by changing the pressure of oxygen flowing into the chamber, that is, the oxygen partial pressure (oxygen flow rate).

[0041] Next, the evaluation method of the yttrium oxide film formed on the work W will be described together with its indicators.

[0042] (1) Evaluation of porosity The test piece (work W made of an Al substrate) on which the film was formed was cut along the film thickness direction, embedded in the resin for evaluation, and its cross-section was observed with a SEM (Scanning Electron Microscope) from the cross-section direction. Then, using the SEM image at a magnification of 500 times, the voids of the film observable in the cross-section were calculated by image analysis. At this time, as an example, ImageJ 1.50b was used for the analysis software. The procedure of image analysis is as follows. (Step 1) Cut out the analysis part from the image. At this time, a region with a depth of approximately 20 μm from the surface of the film is cut out. (Step 2) Binarize the image. The binarization conditions were a threshold value of 110 and 256 gradations. (Step 3) Calculate the defective (void) area.

[0043] (2) Evaluation of film stress As shown in Fig. 2, the warpage amount of the Al plate of the sample on which the yttria film (yttrium oxide film) was formed on the work W of 20 × 20 × 5 mm was measured with a stylus type surface roughness meter for the warpage at a length of 10 mm, and the stress σ was measured from the following Stoney's formula (1).

[0044]

Number

[0045] In Formula 1 and FIG. 2, σ is stress, E is the Young's modulus of the substrate, which is 72 GPa, bs is the thickness of the substrate, which is 5 mm, δs is the amount of deflection in mm, ls is the length of the cantilever beam, which is 5 mm, and ds is the film thickness in μm.

[0046] (3) Evaluation of the density of the film An yttria film with a thickness of about 100 μm was formed on an Al plate of 30×30×5 mm. The weight increase of the substrate before and after film formation was measured, and the volume of the film was calculated from the film thickness and the film formation area (900 mm 2 ), and its density was calculated.

[0047] (4) Evaluation of the hardness of the film The Al substrate on which the film was formed was cut, resin-embedded, and a nanoindenter was used from the cross-sectional direction. Ten load-unload curves were measured at intervals of 10 μm in the thickness direction with a maximum load of 5 mN using a Berkovich-type indenter. Tip curvature correction was performed according to OLIVER et al. (W.C. Oliver, G.m. Pharr; J. Mater. Res, 7, 1564 (1992) or J.B. Pechica, W.C. Oliver; Physica Scripta, T19, 61 (1987)), and the cross-sectional average hardness was measured.

[0048] (5) Evaluation of the etching resistance The etching resistance of the formed film was evaluated under the following apparatus and conditions. · Apparatus used: ICP etching apparatus · Gas composition: Ar:CHF3:O2 = 130:14:5 (flow ratio) · Pressure: 9 Pa · Power: Coil 13.56 MHz, 1 kW, Sample 13.56 MHz, 0.9 kW (Vdc about 950 V)

[0049] Figure 3 shows a cross-sectional SEM image of the yttrium oxide film formed at a bias voltage of 10V. As shown in Figure 3, it can be seen that the voids in the film increase in the regions with a greater film thickness (regions closer to the surface). The reason for the formation of such voids is considered to be nodule growth with particles specific to the vacuum arc method (molten particles scattered from the target, macro particles) as nuclei.

[0050] Figure 4 is a graph showing the relationship between the distance from the interface with the substrate and the porosity in that region in the thickness direction for the film formed at a bias voltage of 10V. This porosity corresponds to the result of dividing the inside of the film into 20μm segments and calculating the porosity in each part. The porosity at a distance of 10μm from the interface indicates the average porosity in the range from 0 to 20μm with the interface taken as 0. Similarly, the plot at 70μm in Figure 4 represents the average porosity in the range from 60 to 80μm. As shown in Figure 4, the porosity increases with the increase in film thickness. In particular, it can be seen that when the film thickness (distance from the interface) exceeds 40μm, the porosity reaches approximately 0.5%. As shown in Figures 3 and 4, almost no voids are observed near the interface between the film and the substrate, but it has been found that the porosity increases in the upper part of the film.

[0051] Figure 5 is a graph showing the relationship between the porosity of the film and the plasma etching rate. As shown in Figure 5, the etching rate increases with the increase in the porosity in the film. By setting the porosity to 0.5% or less, the etching rate can be suppressed to 1.75μm / hr or less. In semiconductor manufacturing equipment, which is an example of the application field of the present invention, etching processes using plasma are frequently used. In recent years, due to the increasing complexity of semiconductor device structures, the problem has arisen that the internal members of the equipment are etched, damaged, and consumed by plasma due to the prolonged etching time. For this reason, materials that are difficult to be etched by plasma (i.e., have a low etching rate) (e.g., Y2O3 film) are used to coat the members. Materials with a low etching rate are suitable as protective materials for semiconductor manufacturing equipment members because, in addition to the small consumption of the members due to etching and the long time until member replacement (long life), the release of contaminants is small.

[0052] Figure 6 is a graph showing the relationship between the bias voltage and the porosity, and shows the results for the case of pulse bias (AC bias) and DC bias, respectively. The porosity is also measured in a region about 20 μm from the surface of a film with a thickness of 50 μm or more. As shown in Figure 6, in the case of pulse bias, by setting the bias voltage during film formation to 25 V or more, even for a thick film with a thickness of 50 μm or more, the porosity in the range of 20 μm from the surface of the film can be suppressed to 0.5% or less. Similarly, in the case of DC bias, by setting the bias voltage during film formation to 25 V or more, the porosity can be suppressed to 0.5% or less. When the applied voltage is a pulse voltage, the bias voltage can be calculated by time averaging.

[0053] Figure 7 is a graph showing the relationship between the bias voltage applied during film formation and the density of the film. Figure 8 is a graph showing the relationship between the density of the film and the etching rate. As shown in Figures 7 and 8, it has been newly found that not only the porosity of the film but also the etching rate changes with an increase in the film density measured from the weight change of the substrate. And in order to keep the etching rate low, it can be seen that the density of the film should be 5 g / cm 3 or more.

[0054] Figure 9 is a graph showing the relationship between the bias voltage applied during film formation and the hardness of the film. Figure 10 is a graph showing the relationship between the hardness of the film and the etching rate. As shown in Figures 9 and 10, it has been newly found that not only the porosity of the film but also the etching rate changes with an increase in the hardness of the film measured in the cross-sectional direction. Similarly, it can be seen that in order to keep the etching rate low, the average hardness of the film should be 9 GPa or more.

[0055] FIG. 11 is a graph showing the relationship between the bias voltage applied during film formation and the stress of the film. As shown in FIG. 11, when the bias voltage is increased, the porosity of the film decreases, the etching rate by plasma irradiation decreases, while an increase in the residual stress generated in the film is observed. From this, it is preferable that the bias voltage is set to less than 75V.

[0056] As described above, the film formation method according to the present embodiment is a method of forming a yttrium oxide film on a substrate that is an object of forming a film by an arc ion plating method. The method includes arranging a target made of yttrium and the substrate in the chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen, and forming a yttrium oxide film on the substrate, and setting the bias voltage so that the porosity of the film becomes 0.5% or less, and forming a yttrium oxide film having a thickness of 40 μm or more.

[0057] According to such a method, it is possible to stably form a yttrium oxide film at a practical film formation rate while suppressing the porosity of the film using the bias voltage as a control parameter.

[0058] In other words, regarding the film formation method according to the present embodiment, the method includes arranging a target made of yttrium and the substrate in the chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen, and forming a yttrium oxide film on the substrate, and setting the bias voltage so that the density of the film becomes 5 g / cm 3 or more, and forming a yttrium oxide film having a thickness of 40 μm or more. Also in this method, the same effects as described above can be obtained.

[0059] Furthermore, in other words, regarding the film formation method, the method includes disposing a target made of yttrium and the substrate in the chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen to form a yttrium oxide film on the substrate, and setting the bias voltage so that the hardness of the film is 9 GPa or more to form a yttrium oxide film with a thickness of 40 μm or more. Also in this method, the same effects as described above can be achieved.

[0060] These methods form a yttrium oxide film on a substrate by an arc ion plating method at a practical film formation rate and have a common technical effect in keeping the etching rate of the film low.

[0061] When the film thickness of yttrium oxide is 50 μm or more, the effect of applying the above bias voltage is further manifested, and when it is 80 μm or more, the effect is further manifested.

[0062] Also, the porosity is more preferably 0.3% or less, and even more preferably 0.1% or less.

[0063] Here, it is desirable that the bias voltage is set to an average of 25 V or more. Also, it is more desirable that the bias voltage is set to an average of 30 V or more, and even more desirable that the bias voltage is set to an average of 50 V or more. On the other hand, as described above, when the bias voltage is 75 V or more on average, the stress increases, so it is preferably set to less than 75 V. At this time, as shown in FIG. 6, by setting the bias voltage to 40 V or more, the porosity can be suppressed regardless of whether it is a pulse bias or a DC bias. Note that compared with a pulse bias, a DC bias can be said to have a constant value.

[0064] In order to obtain a practical film formation rate, it is desirable to form a film by an arc ion plating method rather than a known ion plating method or reactive sputtering method. For example, in a known etching apparatus or the like, it is common to use a film having a thickness of 100 μm or more, and a problem is that the film formation rate is slow in the ion plating or sputtering method. On the other hand, the inventors of the present invention have found that, as a unique problem of the arc ion plating method in which a film formation rate is expected, a problem that the porosity increases as the film thickness increases is remarkably generated, and in particular, such a problem occurs in the formation of a film having a thickness of 40 μm or more and 100 μm or less. Then, the inventor newly found that this problem can be solved by adjusting the bias voltage. In the thickness region as described above, it is difficult to reduce the porosity and realize a practical film formation rate by a known sputtering method.

[0065] Note that the desirable lower limit value of the bias voltage varies slightly depending on the apparatus, but the inventor has confirmed that by setting the bias voltage to 25 V or more, the above variation can be absorbed and good film formation can be realized.

[0066] In addition, the yttrium oxide film in the present invention is a state in which Y2O3 and Y are mixed in the film, and as a result of the change in the ratio of Y2O3 and Y, the ratio of Y and O in the film changes. In the present invention, a film in such a state where Y2O3 and Y are mixed is collectively referred to as a "yttrium oxide film". Note that the ratio of Y and O in this case is an atomic ratio.

[0067] As described above, the embodiments of the present invention have been described in detail. The yttrium oxide film obtained by the film formation method according to the present invention can be widely applied to a member exposed to plasma, as represented by a semiconductor manufacturing apparatus or the like.

[0068] Note that these are merely examples, and the present invention should not be construed as being limited in any way by the description of the above embodiments. In the present invention, the substrate is not limited to being made of an insulating material, and may be made of a conductive material. In the present invention, the mode of alternately applying a negative bias voltage and a positive bias voltage or a negative bias and no bias (0 V) is not limited to the pulse shape described in the above embodiments, and may be, for example, a sine wave shape, a rectangular wave shape, or a triangular wave shape. Also, if the arc current is too small, the discharge will not be stable, and if it is too large, the target may be heated. Therefore, it is desirable to set the arc current in the range of 50 A or more and 200 A or less for a target with a diameter of about 100 mm.

Explanation of Reference Numerals

[0069] 10 Film forming apparatus 12 Vacuum chamber 14 Rotating table 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 W (substrate)

Claims

1. A film forming method for forming a yttrium oxide film on a substrate to be filmed by an arc ion plating method, placing a target made of yttrium and the substrate in the chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen to form a yttrium oxide film on the substrate, setting the bias voltage so that the porosity of the film is 0.5% or less, and forming a yttrium oxide film having a thickness of 40 μm or more, A film forming method comprising the steps of:

2. A film forming method for forming a yttrium oxide film on a substrate to be filmed by an arc ion plating method, placing a target made of yttrium and the substrate in the chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen to form a yttrium oxide film on the substrate, The density of the film is 5 g / cm ３ The bias voltage is set so as to be 5 g / cm or more, and a yttrium oxide film having a thickness of 40 µm or more is formed; A film forming method comprising the steps of:

3. A film forming method for forming a yttrium oxide film on a substrate to be filmed by an arc ion plating method, placing a target made of yttrium and the substrate in the chamber, introducing at least oxygen into the chamber, applying a predetermined bias voltage to the substrate, evaporating the surface of the target in oxygen to form a yttrium oxide film on the substrate, setting the bias voltage so that the hardness of the film is 9 GPa or more, and forming a yttrium oxide film having a thickness of 40 μm or more, A film forming method comprising the steps of:

4. The film forming method according to any one of Claims 1 to 3, further comprising setting the bias voltage to an average of 25 V or more.

5. The film forming method according to any one of Claims 1 to 3, further comprising setting the bias voltage to an average of less than 75 V.

6. The film forming method according to any one of Claims 1 to 3, wherein the waveform of the bias voltage is a pulse waveform.

7. The film forming method according to any one of Claims 1 to 3, wherein the bias voltage is a constant value.

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