Sputtering apparatus and method for forming tungsten film

Abstract

To provide a sputtering system and a film deposition method capable of depositing a low-resistance tungsten film.SOLUTION: The sputtering apparatus includes a substrate stage 2 for holding a substrate Sw in a vacuum chamber 1 in which a target 3 made of tungsten is installed, and a high-frequency power supply Hs for supplying high-frequency power to the substrate stage 2. When a first plasma atmosphere Pm1 is generated in a vacuum chamber 1 and sputtered particles are stuck and deposited on a substrate Sw by sputtering a target 3 to form a tungsten film, high-frequency power is supplied to a substrate stage 2 to generate a second plasma atmosphere Pm2, and positive ions in the first plasma atmosphere Pm1 are also made to collide with the substrate Sw. A ratio of an anode area to a cathode area is set in a range of 4.0 to 6.0, where the cathode area is an area of the substrate holding surface 2a of the substrate stage 2, and the anode area is a surface area in the vacuum chamber 1 functioning as one of the electrodes of the substrate stage 2 and the other of the electrodes of the second plasma atmosphere Pm2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sputtering apparatus for depositing a tungsten film by sputtering and a method for depositing a tungsten film. [Background technology]

[0002] For example, tungsten (W) films used as wiring layers in semiconductor devices are required to have low resistance, and it is known that the larger the crystal grains in a tungsten film, the lower its resistivity. Sputtering equipment is generally used to deposit such tungsten films, but tungsten has a very high melting point (approximately 3400°C). Therefore, when sputtering a tungsten target to grow crystal grains and form a low-resistivity tungsten film, the substrate (hereinafter also referred to as "substrate"), such as a silicon wafer, on which the tungsten film is to be deposited must be at a relatively high temperature.

[0003] Conventionally, Patent Document 1 discloses a method of generating a capacitively coupled second plasma atmosphere in a vacuum chamber by applying high frequency power to a substrate stage that holds a substrate in a vacuum chamber and functions as one of the electrodes (cathode electrode). This generates positive ions (Ar + and Kr + By colliding the ions with the substrate's deposition surface (tungsten film), the substrate temperature during deposition can be effectively increased by the so-called ion-assisted effect. However, if the ion-assisted effect is too strong, the tungsten film deposited on the substrate surface will be damaged. Therefore, the challenge is to maximize the ion-assisted effect without damaging the tungsten film. To achieve this, it is important that the self-bias potential, which is the negative DC component of the substrate potential when the high-frequency power is applied, does not become excessive, even when the high-frequency power is increased.

[0004] The ion-assisted effect can be thought of as the product of the flux (number) of positive ions colliding with the substrate and the kinetic energy of the positive ions. The flux of positive ions is related to the plasma density of the second plasma atmosphere generated in the region of the deposition space closest to the substrate; a higher plasma density increases the flux of positive ions colliding with the substrate. The plasma density of the second plasma atmosphere is primarily dependent on the high-frequency power input to the substrate stage. On the other hand, the kinetic energy of positive ions is related to the self-bias potential; a higher self-bias potential increases the kinetic energy of positive ions colliding with the substrate surface. If the kinetic energy becomes excessive, the grains of the tungsten film may be destroyed, or positive ions may penetrate into the tungsten film, increasing the resistivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-107470 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, an object of the present invention is to provide a sputtering apparatus and a tungsten film deposition method that can deposit a low-resistance tungsten film by making maximum use of the ion-assisted effect without causing the self-bias potential to become excessive, even when the high-frequency power input to the substrate stage is increased. [Means for solving the problem]

[0007] In order to solve the above problems, the sputtering apparatus of the present invention comprises a substrate stage that holds a substrate to be processed within a vacuum chamber in which a tungsten target is placed, and a high-frequency power supply that inputs high-frequency power to the substrate stage; a first plasma atmosphere of a rare gas is generated within the vacuum chamber; sputtered particles generated by sputtering of the target are attached and deposited on the substrate to be processed held by the substrate holding surface of the substrate stage to form a tungsten film; a capacitively coupled second plasma atmosphere is generated within the vacuum chamber by inputting high-frequency power to the substrate stage, which functions as one of the electrodes; and positive ions ionized in the first plasma atmosphere are caused to collide with the substrate to be processed; the area of ​​the substrate holding surface of the substrate stage to which high-frequency power is input is defined as the cathode area, and the surface area within the vacuum chamber that functions as the other electrode of the second plasma atmosphere, with the substrate stage as one electrode, is defined as the anode area; and the ratio of the anode area to the cathode area is set within the range of 4.0 to 6.0.

[0008] In order to solve the above problems, the present invention provides a method for forming a tungsten film, which includes the steps of introducing a rare gas into a vacuum chamber in which a tungsten target is placed, applying power to the target to generate a first plasma atmosphere of the rare gas in the vacuum chamber, scattering sputter particles generated by sputtering on the sputtering surface of the target, and causing them to adhere and deposit on a substrate to be processed held by a substrate stage to form a tungsten film; and applying high frequency power to the substrate stage, which functions as one of the electrodes, to generate a capacitively coupled second plasma in the vacuum chamber during film formation. The method includes a step of generating a first plasma atmosphere and causing positive ions ionized in the first plasma atmosphere to collide with the substrate to be processed, and further includes a step of adjusting the self-bias potential, which is the negative DC component of the potential of the substrate to be processed, independently of the high-frequency power input to the substrate stage, by defining the area of ​​the substrate holding surface of the substrate stage to which high-frequency power is input as the cathode area and the surface area within the vacuum chamber, which functions as the other electrode of the second plasma atmosphere with the substrate stage as one electrode, as the anode area, and changing the ratio of the anode area to the cathode area within a range of 4.0 to 6.0.

[0009] By the way, the self-bias potential (V DC ) is known to be expressed by the following formula 1.

number

[0010] In the above formula 1, V RF is the V of the high frequency power supply PP value, (C K -C A ) / (C K +C A The ) part indicates the capacitance of the ion sheath formed on the surface of one electrode (cathode electrode) and the other electrode (anode electrode), and the capacitance of the ion sheath is highly dependent on the surface area of ​​the electrodes. PP If we can lower the value, V DC V PP The value depends on the load impedance during film formation, so if the load impedance can be reduced, V PP value, and thus V DC On the other hand, the high-frequency power input from the high-frequency power supply to the substrate stage as one electrode (cathode electrode) passes through the second plasma atmosphere and returns to the high-frequency power supply from a portion of the vacuum chamber at ground potential (for example, a shield unit at ground potential that surrounds the target or the film formation space between the target and the substrate stage) that functions as the other electrode (anode electrode) (the circuit in which the power flows from the anode electrode to the high-frequency power supply (hereinafter this can be referred to as the "return circuit").The load impedance seen from the high-frequency power supply is mainly composed of the plasma impedance of the second plasma atmosphere and the impedance in the return circuit.

[0011] Based on the above, we have conducted extensive research focusing on the area ratio of the cathode electrode to the anode electrode, and have discovered that if the ratio of the anode area to the cathode area is set in the range of 4.0 to 6.0, even if the high-frequency power input to the substrate stage is increased, the self-bias potential does not become excessive, and damage to the tungsten film can be suppressed while forming a low-resistance tungsten film. In other words, in this invention, the self-bias potential, which is the negative DC component of the substrate potential, is adjusted independently of the high-frequency power input to the substrate stage according to the ratio of the anode area to the cathode area. A relatively high-frequency power is input to generate a high-density second plasma atmosphere in the film formation space near the substrate to be processed, and the optimal self-bias potential accelerates positive ions to collide with the substrate to be processed. This makes it possible to maximize the ion-assisted effect and form a low-resistance tungsten film. If the ratio of the anode area to the cathode area is greater than 6.0, it becomes difficult to adjust the self-bias potential independently of the high-frequency power, and damage to the tungsten film by positive ions increases. On the other hand, if the ratio of the anode area to the cathode area is less than 4.0, even if the high-frequency power input to the substrate stage is increased, the plasma density of the second plasma atmosphere cannot be sufficiently increased (i.e., the flux of positive ions does not increase sufficiently), and the ion-assisted effect cannot grow crystal grains in the tungsten film.

[0012] The sputtering apparatus further includes a shield unit at ground potential surrounding the deposition space between the target and the substrate stage, including the periphery of the target and the substrate stage. When this shield unit functions as the other electrode, the shield unit can have a shield plate positioned around the substrate stage. A first surface portion of the shield plate facing the deposition space, located on the substrate stage side, has a lower impedance value than a second surface portion other than the first surface portion, thereby reducing the anode area. In this case, an insulator may be disposed on the second surface portion, covering the second surface portion. This advantageously allows the ratio of the anode area to the cathode area to be within the predetermined range using an existing sputtering apparatus. It has been confirmed that reducing the area of ​​the first surface portion of the flat plate facing the deposition space, located on the substrate stage side, reduces the thickness of the tungsten film near the outer edge of the substrate and worsens the in-plane thickness uniformity compared to reducing the area of ​​the second surface portion other than the first surface portion. This is thought to be because, when the second plasma atmosphere is generated in the film formation space, a capacitively coupled plasma atmosphere is also generated locally between the substrate stage and the shield plate of the shield unit, and reducing the anode area of ​​the first surface portion increases the impedance, thereby reducing the plasma density of the locally generated plasma atmosphere.In contrast, by adopting the above configuration, the decrease in film thickness on the outer edge side of the substrate is suppressed, and the in-plane film thickness uniformity can be improved. [Brief explanation of the drawings]

[0013] [Figure 1] 1(a) is a schematic cross-sectional view of the sputtering apparatus of the present embodiment, and FIG. 1(b) is a cross-sectional view taken along line Ib-Ib in FIG. 1(a). [Figure 2] 2A is a graph showing the film thickness of a tungsten film obtained by the present invention, and FIG. 2B is a graph showing the resistivity of a tungsten film obtained by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, with reference to the drawings, an embodiment of the sputtering apparatus and the tungsten film deposition method of the present invention will be described using as an example a case where a substrate to be processed is a silicon wafer on which an SiO2 film is deposited to a predetermined thickness (hereinafter referred to as "substrate Sw") and a tungsten film is deposited on the deposition surface Sw1 of the substrate Sw by the so-called deposit-down method.

[0015] Referring to FIG. 1, the SM is a magnetron sputtering apparatus according to this embodiment, and includes a vacuum chamber 1 capable of forming a vacuum atmosphere. An exhaust pipe 11 connected to a vacuum pump unit Pu, such as a turbomolecular pump or a dry pump, is connected to the bottom wall of the vacuum chamber 1, allowing the inside of the vacuum chamber 1 to be evacuated to a vacuum. A gas pipe 13, equipped with a mass flow controller 12, is connected to the side wall of the vacuum chamber 1, allowing a rare gas (e.g., argon gas or krypton gas) to be introduced into the vacuum chamber 1 at a predetermined flow rate. A substrate stage 2 for holding a substrate Sw is provided on the inner surface of the bottom wall of the vacuum chamber 1. The substrate stage 2 is disposed on the bottom wall of the vacuum chamber 1 via an insulator I1, and the substrate Sw is positioned and held with its film formation surface Sw1 facing upward. The output of a high-frequency power source Hs is connected to the substrate stage 2 via a matching box Mb via a coaxial cable, allowing high-frequency power of a predetermined frequency (2 to 27 MHz) to be applied to the substrate stage 2. Although not specifically shown or described, a resistance heater is incorporated into the substrate stage 2, and the substrate Sw can be heated to a predetermined temperature range (for example, a range of 100°C to 400°C). Also, a cathode unit Uc is installed above the vacuum chamber 1.

[0016] The cathode unit Uc includes a target 3 made of tungsten with a predetermined purity (e.g., 99.99 wt%) and positioned facing the substrate Sw. The magnet unit 4 is located outside the vacuum chamber 1 and applies a leakage magnetic field penetrating the target 3 to the film formation space 1a. A known magnet unit 4 can be used as the magnet unit 4, and a detailed description thereof will be omitted here. The target 3 has a shape (circular in plan view) that conforms to the contours of the substrate Sw and has an area slightly larger than that of the substrate Sw. A backing plate 31 is attached to one side of the target 3. The target 3 is detachably attached to the vacuum chamber 1 with an insulator 12 interposed between the portion of the backing plate 31 that extends outward from the target 3. The output of a DC power supply Ps is connected to the target 3, allowing a predetermined DC power with a negative potential to be applied to the target 3. A shield unit Us is also provided within the vacuum chamber 1, surrounding the film formation space 1a between the substrate stage 2 and the target 3.

[0017] The shield unit Us includes an upper shield plate 5u and a lower shield plate 5d, each made of a conductive material such as stainless steel and electrically connected to the vacuum chamber 1 at ground potential. The upper shield plate 5u has a cylindrical main body 51 that surrounds a portion of the film formation space 1a and an upper flat plate 52 formed by bending the upper end of the main body 51 toward the inside of the vacuum chamber 1. When the upper shield plate 5u is attached to the vacuum chamber 1, the upper flat plate 52 is positioned around the target 3 with a gap therebetween and approximately flush with the sputtering surface 3a when not in use. The lower shield plate 5d has a cylindrical main body 53 that surrounds a portion of the film formation space 1a and a lower flat plate 54 formed by bending the lower end of the main body 53 toward the inside of the vacuum chamber 1. When the lower shield plate 5d is attached to the vacuum chamber 1, the lower plate portion 54 is positioned around the substrate stage 2 with a gap therebetween and in a position that is approximately flush with the substrate holding surface 2a of the substrate stage 2, and the upper end of the main body portion 53 of the lower shield plate 5d overlaps the lower end of the main body portion 51 of the upper shield plate 5u over a predetermined length in the vertical direction, thereby preventing sputtered particles from passing through from the film formation space 1a. Note that in this embodiment, the upper shield plate 5u and the lower shield plate 5d are described using an example in which the upper plate portion 52 and the lower plate portion 54 are integrally formed, but this is not limited to this, and the upper plate portion 52 and the lower plate portion 54 can also be formed as separate bodies. Furthermore, the lower plate portion 54 of the lower shield plate 5d that constitutes the "shield plate" of this embodiment includes one whose surface is curved convexly upward and one whose surface is inclined downward toward the outside of the vacuum chamber 1.

[0018] When a tungsten film is formed on the substrate Sw, a rare gas (argon gas or krypton gas) is introduced into the vacuum chamber 1 in a vacuum atmosphere at a controlled flow rate (the pressure in the vacuum chamber 1 is set to, for example, a range of 0.1 Pa to 3.0 Pa), and a predetermined power is applied to the target 3 (for example, a range of 0.5 kW to 1.5 kW depending on the area of ​​the sputtering surface 3a). Then, a first plasma atmosphere Pm1 of the rare gas is generated in the vacuum chamber 1, and positive ions (Ar + and Kr +) collide with the sputtering surface 3a of the target 3, and sputter particles generated by sputtering of the target 3 adhere to and deposit on the film formation surface Sw1 of the substrate Sw held by the substrate holding surface 2a of the substrate stage 2, thereby forming a tungsten film. During the formation of the tungsten film, high frequency power (for example, in the range of 200 W to 1200 W) is input to the substrate stage 2 from the high frequency power supply Hs, and a capacitively coupled second plasma atmosphere Pm2 is generated in the vacuum chamber 1, and positive ions (Ar + and Kr + ) also collide with the film formation surface Sw1 of the substrate Sw. At this time, the substrate stage 2, to which high-frequency power is applied, functions as one electrode (cathode electrode) that attracts ionized positive ions in the first plasma atmosphere Pm1, while the target 3 and the shield unit Us at ground potential function as the other electrode (anode electrode). (In other words, the anode area can be expressed as the sum of the surface area of ​​the sputtering surface 3a of the target 3 and the internal surface area of ​​the shield unit Us facing the film formation space 1a.) This allows the ion-assisted effect of colliding positive ions with the film formation surface Sw1 of the substrate Sw to effectively increase the substrate temperature during film formation. However, it is necessary to maximize the ion-assisted effect without damaging the tungsten film.

[0019] In this embodiment, focusing on the plasma impedance of the second plasma atmosphere Pm2, the cathode area is defined as the area of ​​the substrate holding surface 2a of the substrate stage 2 to which high-frequency power is applied from the high-frequency power supply Hs, and the anode area is defined as the surface area within the vacuum chamber 1 that functions as the other electrode (anode electrode) of the second plasma atmosphere Pm2, with the substrate stage serving as one electrode (cathode electrode). The ratio of the anode area to the cathode area is set to be in the range of 4.0 to 6.0. Specifically, as shown in FIG. 1(b), the surface of the lower flat plate 54 facing the film formation space 1a is divided into two concentric regions: a first surface portion 54a located on the substrate stage 2 side and a second surface portion 54b other than the first surface portion 54a. The second surface portion 54b is covered with an insulator 6 so that it has a relatively high impedance. As a result, the second surface portion 54b does not function as an anode electrode, and the anode area is substantially reduced. The insulator 6 may be, for example, a foil or plate made of alumina. The distance d1 from the inner edge of the lower flat plate portion 54, which defines the surface portion that functions as the anode electrode, to the circumference that forms the interface between the first surface portion 54a and the second surface portion 54b is set in consideration of the ratio of the anode area to the cathode area and film thickness distribution and other deposition results. The plasma density of the second plasma atmosphere also depends on the DC power input to the target 3 and the strength of the magnetic field applied by the magnet unit 4, so the ratio of the anode area to the cathode area must be adjusted taking these factors into account.

[0020] According to the above embodiment, even if the high-frequency power input to the substrate stage 2 is increased during film formation, the self-bias potential does not become excessive, and a low-resistance tungsten film can be formed while suppressing damage to the tungsten film. In other words, by inputting a relatively high-frequency power to generate a high-density second plasma atmosphere in the film formation space near the substrate Sw and accelerating positive ions at an optimal self-bias potential to collide with the substrate Sw, a low-resistance tungsten film can be formed by making the most of the ion-assisted effect. Note that if the ratio of the anode area to the cathode area is greater than 6.0, it becomes difficult to adjust the self-bias potential independently of the high-frequency power, and damage to the tungsten film caused by positive ions increases. On the other hand, if the ratio of the anode area to the cathode area is less than 4.0, the surface of the shield unit Us facing the film formation space 1a may be sputtered, or if high-power (e.g., 650 W or more) high-frequency power is applied to the substrate stage 2 to generate the second plasma atmosphere Pm2, plasma leakage to the shield unit Us may occur. Even if the high-frequency power applied to the substrate stage 2 is increased, the plasma density of the second plasma atmosphere Pm2 cannot be sufficiently increased, and crystal grains of the tungsten film cannot be grown. Furthermore, by covering the second surface portion 54b of the lower plate portion 54 with the insulator 6, the anode area is reduced, making it easy to apply to existing sputtering equipment. Furthermore, the reduction in film thickness at the outer edge of the substrate Sw is suppressed, improving the in-plane film thickness uniformity.

[0021] In order to confirm the above-mentioned effect, the following experiment was carried out using the sputtering apparatus SM. In invention experiment 1, the area of ​​the substrate holding surface 2a of the substrate stage 2 of the sputtering apparatus SM was set to 660 cm 2 , the surface area of ​​the sputtering surface 3a of the target 3 is 1520 cm 2 The inner surface area of ​​the upper shield plate 5u facing the film formation space 1a is 562 cm 2 The inner surface area of ​​the lower shield plate 5d facing the film formation space 1a is 2011 cm 2 , and the second surface portion 54b of the lower flat plate portion 54 of the lower shield plate 5d is set to the insulator 6 (1143 cm2 ), and the ratio of the anode area to the cathode area was set to 4.47. A 300 mm diameter silicon wafer with a SiO2 film deposited over its entire surface was used as the substrate Sw. Krypton gas was introduced into the vacuum chamber 1 at a flow rate of 46 sccm. A tungsten film was deposited on the substrate Sw for 20 seconds, with 1.2 kW of DC power applied to the tungsten target 3 and 450 W of 13.56 MHz radio frequency power applied to the substrate stage 2. The thickness and resistivity of the resulting tungsten film were then measured. Figures 2(a) and 2(b) show the in-plane thickness and resistivity of the tungsten film obtained in Invention Experiment 1, respectively, as solid lines. The tungsten film obtained in Invention Experiment 1 had an average thickness of 18.96 nm and an average resistivity of 10.79 μΩcm. The value obtained by dividing the average resistivity by the average thickness was 0.5691.

[0022] As a comparative experiment to the above-mentioned Inventive Experiment 1, a tungsten film was formed under the same conditions as the above-mentioned Inventive Experiment 1, except that the second surface portion 54b of the lower flat portion 54 of the lower shield plate 5d was not covered with the insulator 6 and the ratio of the anode area to the cathode area was set to 6.20. The thickness and resistivity of the resulting tungsten film were then measured. In Figures 2(a) and 2(b), the in-plane thickness and resistivity of the tungsten film obtained in the comparative experiment are indicated by dashed-dotted lines. The average thickness and resistivity of the tungsten film obtained in the comparative experiment were 18.76 nm and 10.69 μΩcm, respectively. The value obtained by dividing the average resistivity by the average thickness was 0.5698. These results confirmed that the tungsten film obtained in Inventive Experiment 1 had a lower resistivity relative to the thickness compared to the comparative experiment (i.e., a lower resistivity for the same tungsten film thickness).

[0023] In addition, as an invention experiment 2, the area of ​​the insulator 6 covering the second surface portion 54b of the lower flat plate portion 54 of the lower shield plate 5d was set to 130 cm 2A tungsten film was formed under the same conditions as in Inventive Experiment 1, except that the ratio of the anode area to the cathode area was set to 6.0, and the thickness and resistivity of the resulting tungsten film were then measured. As in Inventive Experiment 1, it was confirmed that the tungsten film obtained in Inventive Experiment 2 also had a lower resistivity relative to the film thickness compared to that of the comparative experiment.

[0024] Next, multiple tungsten films were deposited under the same deposition conditions as in Invention Experiment 1, except for varying the RF power applied to the substrate stage 2. The thickness and resistivity of each tungsten film were measured. In Figures 2(a) and (b), the dashed lines indicate the in-plane thickness and resistivity of the tungsten film deposited using 500 W of RF power (Invention Experiment 3). The average thickness and resistivity of the tungsten film deposited in Invention Experiment 3 were 18.10 nm and 10.77 μΩcm, respectively. The dashed lines in Figures 2(a) and (b) indicate the in-plane thickness and resistivity of the tungsten film deposited using 550 W of RF power (Invention Experiment 4). The average thickness and resistivity of the tungsten film deposited in Invention Experiment 4 were 17.37 nm and 10.88 μΩcm, respectively. From the results of these experiments, it was confirmed that the resistivity of the tungsten film hardly changes, and the film thickness decreases as the radio frequency power is increased. In other words, if the thickness of the tungsten film remains the same, the resistivity decreases as the radio frequency power is increased.

[0025] Although the above describes an embodiment of the present invention, various modifications are possible without departing from the scope of the technical concept of the present invention. In the above embodiment, a magnetron-type sputtering apparatus SM was described as an example. However, this is not limited thereto. The present invention can also be applied to apparatuses that generate a first plasma using other known methods. Furthermore, in the above embodiment, the anode area is reduced by covering the second surface portion 54b of the lower plate portion 54 of the lower shield plate 5d with an insulator 6. However, this is not limited thereto. The portion of the lower plate portion 54 that constitutes the second surface portion 54b can be formed of an insulating material such as alumina or quartz. Furthermore, when attaching the insulator 6 to the second surface portion 54b, instead of attaching a foil-shaped (film-shaped) insulator 6, a ring-shaped plate can be attached from its top surface, or multiple rectangular insulating plates can be attached without gaps. Furthermore, in order to reduce the anode area, the example has been described in which the inner surface of the lower shield plate 5d is partially covered with an insulator, but the portion covered with the insulator is not limited to this, and for example, the inner surface of the upper shield plate 5u may be covered with an insulator 6. [Explanation of symbols]

[0026] SM...sputtering device, Hs...high frequency power supply, Pm1...first plasma atmosphere, Pm2...second plasma atmosphere, Sw...substrate (substrate to be processed), 1...vacuum chamber, 1a...film formation space, 2...substrate stage, 2a...substrate holding surface, 3...target, 3a...sputtering surface, Us...shield unit, 54...lower flat plate portion (shield plate), 54a...first surface portion, 54b...second surface portion, 6...insulator.

Claims

1. The apparatus includes a substrate stage that holds a substrate to be processed within a vacuum chamber in which a tungsten target is placed, and a high-frequency power source that supplies high-frequency power to the substrate stage; A sputtering apparatus configured to generate a first plasma atmosphere of a rare gas in a vacuum chamber, and to deposit sputtered particles generated by sputtering a target on a substrate to be processed held on a substrate holding surface of a substrate stage to form a tungsten film, by applying high frequency power to the substrate stage which functions as one of the electrodes, to generate a capacitively coupled second plasma atmosphere in the vacuum chamber, and to cause positive ions ionized in the first plasma atmosphere to collide with the substrate to be processed, A sputtering apparatus characterized in that the area of ​​the substrate holding surface of the substrate stage to which high frequency power is applied is defined as the cathode area, and the surface area within a vacuum chamber in which the substrate stage serves as one electrode and functions as the other electrode in a second plasma atmosphere is defined as the anode area, and the ratio of the anode area to the cathode area is set in the range of 4.0 to 6.

0.

2. 2. The sputtering apparatus according to claim 1, further comprising a shield unit at ground potential surrounding a film formation space between the target and the substrate stage, the shield unit functioning as the other electrode, The sputtering apparatus is characterized in that the shield unit has a shield plate positioned around the substrate stage, and a first surface portion of the surface of the shield plate facing the film formation space, which is positioned on the substrate stage side, has a lower impedance value than a second surface portion other than the first surface portion, thereby reducing the anode area.

3. 3. The sputtering apparatus according to claim 2, wherein the second surface portion is covered with an insulator.

4. a step of introducing a rare gas into a vacuum chamber in which a tungsten target is placed, applying power to the target to generate a first plasma atmosphere of the rare gas in the vacuum chamber, scattering sputter particles generated by sputtering of the sputtering surface of the target, and causing the particles to adhere and deposit on a substrate to be processed held by a substrate stage, thereby forming a tungsten film; a step of applying high frequency power to a substrate stage functioning as one of the electrodes during film formation to generate a capacitively coupled second plasma atmosphere in the vacuum chamber, and causing positive ions ionized in the first plasma atmosphere to collide with the substrate to be processed, The method for forming a tungsten film further comprises a step of adjusting a self-bias potential, which is a negative DC component of the potential of the substrate to be processed, independently of the high frequency power input to the substrate stage, by defining the area of ​​the substrate holding surface of the substrate stage to which high frequency power is input as the cathode area, and defining the surface area within a vacuum chamber in which the substrate stage is used as one electrode and functions as the other electrode in a second plasma atmosphere as the anode area, and changing the ratio of the anode area to the cathode area within a range of 4.0 to 6.

0.

5. 5. The tungsten film deposition method according to claim 4, wherein when the second plasma atmosphere is generated, a shield unit at a ground potential surrounding a deposition space between the target and the substrate stage is made to function as the other electrode, A tungsten film forming method, characterized in that a first surface portion of the surface of the shield plate of the shield unit located around the substrate stage, which is located on the substrate stage side, is set to a lower impedance value compared to a second surface portion other than the first surface portion, thereby reducing the anode area.

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