Reactive ion plating apparatus and method

Abstract

To stably form an insulating film of high quality in a reactive ion plating apparatus and method.SOLUTION: In the reactive ion plating apparatus 10, an evaporation material 24 stored in a crucible 20 is heated and evaporated by an electron gun 22. In addition, the ionization power Wd is supplied to the crucible 20 as an anode and the hot cathode filament 34 that emits thermoelectrons as a cathode. Accordingly, the plasma 100 is induced. Further, the reactive gas is introduced into the vacuum chamber 12 through the hollow anode 46, and the hollow anode power Wh is supplied to the hollow anode 46. Accordingly, the hollow anode plasma 200 is induced. A hollow anode filament 48 is provided at a gas discharge port of the hollow anode 46. The hollow anode filament 48 becomes a stable anode by being heated by Joule heat.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reactive ion plating apparatus and method, and more particularly to a reactive ion plating apparatus and method for reacting particles of an evaporation material with particles of a reactive gas to form a reaction film, which is a compound of the particles of the evaporation material and the particles of the reactive gas, on the surface of a workpiece. [Background technology]

[0002] An example of this type of technology is disclosed in Patent Document 1. According to the technology disclosed in Patent Document 1, an evaporation material is contained in a container provided below a workpiece placed inside a vacuum chamber. A hot cathode is also provided between the container and the workpiece. After the vacuum chamber is evacuated, the evaporation material contained in the container is evaporated by the evaporation means, and thermions (primary electrons) are emitted from the hot cathode. A first ionization power (DC) is supplied to the pair of electrodes, with the container serving as the anode and the hot cathode serving as the cathode. The thermions emitted from the hot cathode are accelerated toward the container. These accelerated thermions collide inelastically with particles of the evaporation material, ionizing the particles. Electrons repelled from the particles of the evaporation material due to this ionization flow into the container. This phenomenon continues, inducing plasma (metal vapor plasma if the evaporation material is a metal). This plasma is a constant-voltage, high-current arc discharge. In addition, the amount of thermoelectrons emitted by the hot cathode is controlled so that the current component of the first ionizing power is constant. Note that the current component of the first ionizing power is correlated (proportional) to the amount of ions in the plasma, in other words, correlated (proportional) to the density of the plasma. In other words, the amount of thermoelectrons emitted by the hot cathode is controlled so that the plasma density is constant, and so-called feedback control is applied.

[0003] Furthermore, a reactive gas is introduced into the vacuum chamber through the hollow portion of the hollow anode. A second DC ionization power is then supplied to the pair of electrodes, with the hollow anode serving as the anode and the containing means serving as the cathode. Then, electrons in the plasma are accelerated toward the hollow anode, particularly toward the outlet of the hollow anode for the reactive gas into the vacuum chamber. The accelerated electrons then inelastically collide with reactive gas particles ejected from the outlet of the hollow anode, ionizing the reactive gas particles. As a result, a plasma is induced near the outlet of the hollow anode, creating a hollow anode plasma (gas plasma). Near the outlet of the hollow anode, the pressure of the reactive gas is high, i.e., the density of the reactive gas particles is high, resulting in a high-concentration hollow anode plasma. This hollow anode plasma is also a low-voltage, high-current arc discharge. Most of the electrons that contribute to the induction of hollow anode plasma are plasma electrons (electrons with energy lower than the ionization voltage) among the electrons in the main plasma induced by the supply of the first ionizing power described above. In other words, the thermoelectrons emitted from the hot cathode hardly contribute to the induction of hollow anode plasma.

[0004] Furthermore, bias power is supplied to the workpiece to accelerate the ionized particles of the evaporation material and the ionized particles of the reactive gas toward the surface of the workpiece, thereby forming a reaction film, which is a compound of the ionized particles of the evaporation material and the ionized particles of the reactive gas, on the surface of the workpiece. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6788081 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology disclosed in Patent Document 1 makes it possible to form various reaction films, such as high-quality conductive films, stably (with good reproducibility). However, there is a problem in that insulating films cannot be formed stably. This is presumably because, when a film formation process is performed to form an insulating film, the insulating film (strictly speaking, an insulating material) adheres (deposits) to the hollow anode, particularly around the outlet of the hollow anode, thereby reducing the function of the hollow anode as an anode (electrode).

[0007] That is, when the hollow anode's function as an anode deteriorates, the number of electrons moving from the main plasma toward the hollow anode decreases. This causes the hollow anode plasma to become unstable, and the amount of ions in the hollow anode plasma fluctuates. This also changes the shape and volume of the main plasma. In particular, when the volume of the main plasma changes, the overall amount (total amount) of ions in the main plasma changes, even if feedback control is applied to maintain a constant density of the main plasma, as described above. As a result, the amount of ions incident on the surface of the workpiece changes, which in turn causes the quality of the insulating coating formed on the surface of the workpiece to become unstable. For these reasons, it is presumed that the technology disclosed in Patent Document 1 is unable to stably form an insulating coating.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a novel reactive ion plating apparatus and method that can stably form a high-quality insulating coating. [Means for solving the problem]

[0009] To achieve this object, the present invention includes a first invention relating to a reactive ion plating apparatus and a second invention relating to a reactive ion plating method.

[0010] The first invention is a reactive ion plating apparatus that reacts particles of an evaporation material with particles of a reactive gas to form a reaction film, which is a compound of the evaporation material particles and the reactive gas particles, on the surface of an object to be treated, and includes a vacuum chamber. The object to be treated is placed inside the vacuum chamber. The interior of the vacuum chamber is also evacuated. The first invention further includes a container, an evaporation means, a hot cathode, a first ionization power supply means, a thermionic emission amount control means, a hollow anode, a second ionization power supply means, a heater, and a bias power supply means. The container is provided below the object to be treated inside the vacuum chamber. The container contains the evaporation material. The evaporation means evaporates the evaporation material contained in the container. The hot cathode is provided between the container and the object to be treated and emits thermions. The first ionization power supply means supplies a first ionization power to a pair of electrodes, with the container as the anode and the hot cathode as the cathode. The first ionization power is DC power for ionizing particles of the evaporation material evaporated by the evaporation means. The thermionic emission amount control means controls the amount of thermionic electrons emitted by the thermal cathode so that the current component of the first ionization power is constant. The hollow anode has a hollow portion through which a reactive gas flows, and the reactive gas is introduced into the vacuum chamber through this hollow portion. The second ionization power supply means supplies second ionization power to the pair of electrodes, with the hollow anode as the anode and the containing means as the cathode. The second ionization power is DC power for ionizing particles of the reactive gas introduced into the vacuum chamber. The heating element is provided at the hollow anode's outlet for discharging the reactive gas into the vacuum chamber. The heating element is heated to a temperature above the evaporation temperature of the particles of the evaporation material by receiving an inflow of electrons in the plasma induced by the supply of the first ionization power. The bias power supply means supplies bias power to the workpiece. This bias power is a power for accelerating the ionized particles of the evaporation material and the ionized particles of the reactive gas toward the surface of the workpiece.

[0011] The heating element may be, for example, a spiral element that surrounds the outlet of the hollow anode and extends spirally in the direction in which the reactive gas is discharged from the outlet.

[0012] It is also desirable that the heater be detachable from the discharge port of the hollow anode.

[0013] Furthermore, it is desirable that the heater can be attached to the outlet of the hollow anode without using any member such as a screw for attaching the heater to the outlet.

[0014] The voltage component of the second ionization power is higher than the space potential of the plasma induced by the supply of the first ionization power, and is set to the lowest possible voltage value within a range that can heat the heating body to a temperature higher than that of the evaporation material particles, for example, 10 V or higher and 60 V or lower.

[0015] Additionally, the first invention may further include an evaporation rate control means for controlling the evaporation rate of the evaporation material by the evaporation means so that the pressure inside the vacuum chamber is constant while the amount of reactive gas introduced into the vacuum chamber per unit time is constant.

[0016] A second aspect of the present invention is a reactive ion plating method for forming a reaction film, which is a compound of particles of an evaporation material and particles of a reactive gas, on the surface of a workpiece, by reacting particles of the evaporation material with particles of a reactive gas. The method includes an evaporation step. In the evaporation step, the evaporation material contained in a container provided below the workpiece is evaporated in a vacuum chamber in which the workpiece is placed and the interior is evacuated. The second aspect of the present invention further includes a thermionic emission step, a first ionization power supply step, a thermionic emission amount control step, a reactive gas introduction step, a second ionization power supply step, a heater heating step, and a bias power supply step. In the thermionic emission step, thermionic electrons are emitted from a hot cathode provided between the container and the workpiece. In the first ionization power supply step, a first ionization power is supplied to the pair of electrodes, with the container serving as the anode and the hot cathode serving as the cathode. This first ionization power is DC power for ionizing particles of the evaporation material evaporated in the evaporation step. In the thermionic emission amount control step, the amount of thermionic electrons emitted by the thermionic cathode is controlled so that the current component of the first ionization power is constant. In the reactive gas introduction step, a reactive gas is introduced into the vacuum chamber through a hollow anode having a hollow portion through which the reactive gas flows. In the second ionization power supply step, a second ionization power is supplied to a pair of electrodes, with the hollow anode serving as the anode and the container serving as the cathode. This second ionization power is DC power for ionizing particles of the reactive gas introduced into the vacuum chamber. In the heater heating step, electrons in the plasma induced by the supply of the first ionization power are introduced into a heater provided at an outlet of the hollow anode for the reactive gas into the vacuum chamber, thereby heating the heater to a temperature above the evaporation temperature of the particles of the evaporation material. Then, in the bias power supply step, bias power is supplied to the workpiece. This bias power is power for accelerating ionized particles of the evaporation material and ionized particles of the reactive gas toward the surface of the workpiece. [Effects of the Invention]

[0017] According to the present invention, a high-quality insulating coating can be stably formed in a reactive ion plating apparatus and method, and also according to the present invention, a high-quality conductive coating can be formed. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an ion plating apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a photograph showing the appearance of the tip of a hollow anode in one embodiment of the present invention. [Figure 3] FIG. 3 is a photograph showing the appearance of the tip of the hollow anode in one embodiment of the present invention, taken from a different angle. [Figure 4] FIG. 4 is a cross-sectional view of the tip of a hollow anode in one embodiment of the present invention. [Figure 5] FIG. 5 is an external view of a hollow anode filament in one embodiment of the present invention. [Figure 6] FIG. 6 is a photograph showing a part of the inside of a vacuum chamber in one embodiment of the present invention. [Figure 7] FIG. 7 is a photograph showing a state of a part of the inside of a vacuum chamber when a film forming process is being performed in one embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing the conditions of an experiment in one embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing experimental results in one embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing the results of analysis by X-ray diffraction of an yttria film formed by an experiment in one embodiment of the present invention. [Figure 11] FIG. 11 is a graph showing the hardness of yttria films formed by experiments in one embodiment of the present invention. [Figure 12] FIG. 12 is a diagram showing the transition of the substrate bias current when a film formation process for forming an yttria film is performed in an experiment in one embodiment of the present invention. [Figure 13]FIG. 13 is a diagram showing the transition of the hollow anode current when a film formation process for forming an yttria film is performed in an experiment in one embodiment of the present invention. [Figure 14] FIG. 14 is a diagram showing experimental conditions in another embodiment of the present invention. [Figure 15] FIG. 15 is a cross-sectional view of the tip of a hollow anode in another embodiment of the present invention. [Figure 16] FIG. 16 is an external view of a hollow anode filament in another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will be described with reference to FIGS.

[0020] As shown in FIG. 1, the reactive ion plating apparatus 10 according to this embodiment includes a generally cylindrical vacuum chamber 12. The vacuum chamber 12 is made of a metal having relatively high mechanical strength and high corrosion and heat resistance, such as stainless steel such as SUS304. The wall of the vacuum chamber 12, i.e., the vacuum chamber 12 itself, is grounded. That is, the vacuum chamber 12 itself is electrically at ground potential as a reference potential. The diameter (inner diameter) of the vacuum chamber 12 is, for example, approximately 700 mm. The height of the vacuum chamber 12 is, for example, approximately 1000 mm. The upper part of the vacuum chamber 12 is formed in a generally dome-like shape with an upward convex shape in order to improve its mechanical strength.

[0021] Furthermore, an exhaust port 12a is provided at an appropriate position on the wall of the vacuum chamber 12, for example, on the bottom. This exhaust port 12a is connected to a vacuum pump 16 serving as exhaust means via an exhaust pipe 14 outside the vacuum chamber 12. The vacuum pump 16 may be, for example, a diffusion pump, a turbomolecular pump, or a cryopump, but is not limited to these.

[0022] Focusing on the inside of the vacuum chamber 12, an evaporation source 18 is disposed near the bottom of the vacuum chamber 12. This evaporation source 18 includes a roughly cup-shaped (more specifically, roughly cylindrical with an open top) crucible 20 as a container, and a 270° deflection electron gun 22. The crucible 20 is made of, for example, copper (Cu) and contains an evaporation material 24, which will be the material for the target reaction film. Although not shown in detail, a hearth liner that matches the shape and dimensions of the crucible 20 is provided within the crucible 20. In practice, the evaporation material 24 is contained within the hearth liner. The hearth liner is made of, for example, tantalum (Ta), but is not limited to this. It may also be made of a high-melting-point metal other than tantalum, such as molybdenum (Mo) or tungsten (W), or a highly heat-resistant non-metallic material such as carbon (C). Furthermore, in the horizontal direction, the center (axis) of the crucible 20 roughly coincides with the center (axis) of the vacuum chamber 12, that is, the evaporation source 18 is disposed so that this coincides with the center (axis) of the vacuum chamber 12.

[0023] Meanwhile, the electron gun 22 is an example of an evaporation means for heating and evaporating the evaporation material 24 contained in the crucible 20 (hearth liner). Strictly speaking, the electron gun 22 constitutes the evaporation means in cooperation with an electron gun power supply 26 provided outside the vacuum chamber 12. That is, the electron gun 22 receives power from the electron gun power supply 26 and emits an electron beam 22a. This electron beam 22a is deflected by 270° and irradiates the evaporation material 24 in the crucible 20. This heats and melts the evaporation material 24, ultimately evaporating it. The output power Wg of the electron gun 22 is, for example, up to 10 kW. Although not shown in detail, the evaporation source 18 is equipped with a water-cooling mechanism to prevent the crucible 20 from overheating. The housing of the evaporation source 18, including the crucible 20, is grounded. 1, the top of the evaporation source 18 is covered with an appropriate crucible cover 20a (see FIG. 6) with the opening of the crucible 20 and the emission port 18a of the electron beam 22a exposed (open) to the outside of the evaporation source 18. The crucible cover 20a is made of a high-melting-point metal, for example, molybdenum, and is electrically and mechanically coupled to the housing of the evaporation source 18, i.e., is grounded via the housing of the evaporation source 18.

[0024] A substrate 28 serving as a workpiece is placed above the evaporation source 18. The substrate 28 is held by a substrate stand 30 serving as a holding means with its surface, or more precisely, the surface to be treated on which a reaction film is to be formed as a target, facing the evaporation source 18, particularly facing the opening of the crucible 20. The distance (in the vertical direction) between the evaporation source 18 and the surface to be treated of the substrate 28, or more precisely, the distance between (the upper edge of) the opening of the crucible 20 and the surface to be treated of the substrate 28, varies depending on various factors such as the shape and dimensions of the surface to be treated of the substrate 28, but is, for example, 250 mm to 700 mm.

[0025] The substrate stage 30 is connected to a substrate bias power supply unit 32 serving as bias power supply means outside the vacuum chamber 12. The substrate bias power supply unit 32 supplies a substrate bias power Wb to the substrate stage 30, and thus to the substrate 28. The substrate bias power Wb is a so-called bipolar pulse power in which its voltage component, a substrate bias voltage Vb, alternates between a high-level voltage of positive potential with respect to the ground potential and a low-level voltage of negative potential with respect to the ground potential. The high-level voltage of this substrate bias voltage Vb is constant, e.g., +37 V with respect to the ground potential. Meanwhile, the low-level voltage of the substrate bias voltage Vb can be changed as desired. The low-level voltage adjusts the average value (DC equivalent) of the substrate bias voltage Vb, particularly so that the average value of the substrate bias voltage Vb becomes a negative potential with respect to the ground potential. The average value of the substrate bias voltage Vb can be adjusted within a range of, e.g., −50 V to −700 V. Furthermore, the frequency of the substrate bias power Wb can also be arbitrarily adjusted within a range of, for example, 50 kHz to 250 kHz. In addition, the duty ratio of the substrate bias power Wb (the ratio of the period during which the substrate bias voltage Vb is a high-level voltage in one cycle of the substrate bias voltage Vb) can also be arbitrarily adjusted. Here, the frequency of the substrate bias power Wb is set to, for example, 100 kHz. The duty ratio of the substrate bias power Wb is set to, for example, 20%.

[0026] Furthermore, a hot cathode filament 34, which serves as an example of a hot cathode, is disposed between the evaporation source 18 and the substrate table 30 and closer to the evaporation source 18, in other words, slightly above the opening of the crucible 20. The hot cathode filament 34 is, for example, a tungsten linear body having a diameter of 1 mm, and is provided so as to extend horizontally at a position 10 to 100 mm above the opening of the crucible 20. Strictly speaking, the hot cathode filament 34 is formed in a spiral shape to increase its surface area and thereby increase the amount of thermoelectrons emitted, as described below. The spiral diameter of the spirally formed hot cathode filament 34 is, for example, 12 mm, the number of turns is, for example, 10 (turns), and the length of the spirally formed portion is, for example, 100 mm.

[0027] Here, for example, if the vertical distance between the opening of the crucible 20 and the hot cathode filament 34 (the spiral center of the hot cathode filament 34) is too short, the hot cathode filament 34 will obstruct the electron beam 22a irradiated from the electron gun 22 onto the evaporation material 24, which is extremely inconvenient. On the other hand, if the vertical distance is too long, the density of evaporated particles of the evaporation material 24 around the hot cathode filament 34, as described below, will decrease, making it difficult for the evaporated particles to be ionized, which is also inconvenient. For these reasons, the vertical distance is appropriately about 10 mm to 100 mm, as described above, and preferably 40 mm to 70 mm, e.g., 60 mm. Furthermore, the hot cathode filament 34 is positioned slightly off-center from the center of the crucible 20 in the horizontal direction, for example, about 20 mm off-center.

[0028] Both ends of the hot cathode filament 34 are connected to a hot cathode heating power supply 36, which serves as a hot cathode heating power supply means, outside the vacuum chamber 12. The hot cathode heating power supply 36 supplies AC hot cathode heating power Wf to the hot cathode filament 34 as hot cathode heating power. Upon receiving this hot cathode heating power Wf, the hot cathode filament 34 is heated and emits thermoelectrons. The hot cathode heating power supply 36 has a maximum capacity of, for example, 2.4 kW (=40 V × 60 A). The hot cathode heating power Wf may be DC power instead of AC power. In any case, it is sufficient for the hot cathode heating power supply 36 to heat the hot cathode filament 34 to a temperature sufficient to emit thermoelectrons from the hot cathode filament 34, for example, to about 2000°C to 2500°C. The hot cathode filament 34 is not limited to being made of tungsten, but may be made of other high melting point metals such as molybdenum and tantalum.

[0029] In addition, one end of the hot cathode filament 34 is connected to an ionization power supply 38 serving as first ionization power supply means outside the vacuum chamber 12. The ionization power supply 38 supplies ionization power Wd as first ionization power to the hot cathode filament 34. The ionization power Wd is DC power with a negative potential relative to the ground potential. In other words, the ionization power supply 38 supplies DC ionization power Wd to a pair of electrodes, with the grounded evaporation source 18 serving as the anode and the hot cathode filament 34 serving as the cathode. The ionization power supply 38 has a maximum capacity of, for example, 9 kW (= 60 V × 150 A).

[0030] A current detector 40 serving as an ionization current detection means is provided between the ionization power supply 38 and ground. The current detector 40 detects the current component of the ionization power Wd, or what is called the ionization current Id. The detection result of the ionization current Id by the current detector 40 is provided to a heating controller 42 serving as a thermionic emission amount control means.

[0031] The heating controller 42 controls the hot cathode heating power supply device 36 so that the ionization current Id detected by the current detector 40 remains constant, i.e., controls the heating temperature of the hot cathode filament 34. In other words, the amount of thermoelectrons emitted by the hot cathode filament 34 is controlled so that the ionization current Id remains constant.

[0032] Turning our attention again to the inside of the vacuum chamber 12, the terminal portions at both ends of the hot cathode filament 34 (the portions extending from both ends of the hot cathode filament 34 to the wall of the vacuum chamber 12) are covered with appropriate terminal covers 44. These terminal covers 44 are protective measures to prevent abnormal discharges caused by the adhesion of an insulating coating to the terminal portions at both ends of the hot cathode filament 34 during the formation of the target reaction film, particularly during the formation of an insulating coating. The terminal covers 44 are made of a high-melting-point metal, such as molybdenum. Although not shown in detail, the terminal covers 44 are electrically insulated from other elements, such as the vacuum chamber 12, and are, so to speak, electrically floating.

[0033] As will be described later, a discharge cleaning gas and a reactive gas are selectively introduced into the vacuum chamber 12. A gas inlet pipe, or more precisely, a tubular hollow anode 46, is provided for this purpose. The hollow anode 46 is a so-called circular tube, i.e., it has a hollow portion with a circular cross section perpendicular to its longitudinal direction. The hollow anode 46 is provided so that one end thereof serves as a gas outlet and is located inside the vacuum chamber 12, and the other end thereof serves as a gas supply / receive inlet and is located outside the vacuum chamber 12. As will be described later, a portion of the one end of the hollow anode 46, including the gas outlet, i.e., a tip 46a, is removable, i.e., detachable.

[0034] The gas outlet of the hollow anode 46 is provided at a predetermined position near the opening of the crucible 20, and more precisely, at a suitable position for accelerating electrons (plasma electrons) in the plasma 100 (described later) toward the hollow anode 46, thereby inducing the hollow anode plasma 200 (described later). However, the gas outlet of the hollow anode 46 is provided so as not to substantially come into contact with (a position where it is difficult to come into contact with) evaporated particles of the evaporation material 24 (described later). This is to prevent a reaction film (strictly speaking, a substance constituting the reaction film) from adhering (accumulating) to (the inside of) the gas outlet of the hollow anode 46, thereby narrowing the gas outlet.

[0035] Specifically, the gas outlet of the hollow anode 46 faces upward. The gas outlet of the hollow anode 46 is located at approximately the same vertical position as the opening of the crucible 20, or at a position higher than the opening of the crucible 20. In other words, the gas outlet of the hollow anode 46 is located at a height equal to or higher than the evaporation surface of the evaporation material 24 contained in the crucible 20. The vertical distance between the gas outlet of the hollow anode 46 and the opening of the crucible 20 is preferably 0 mm to 50 mm, e.g., 30 mm. The horizontal distance between the gas outlet of the hollow anode 46 and the opening of the crucible 20, specifically the distance between their centers (axes), is, for example, 140 mm, although it depends on various factors, such as the shape and dimensions of the evaporation source 18 including the crucible 20.

[0036] As described above, the tip portion 46a of the hollow anode 46 is detachable. To this end, the tip portion 46a has a male-threaded mounting portion 460, as shown in FIGS. 2 to 4. A female-threaded mounting portion (not shown) corresponding to the mounting portion 460 of the tip portion 46a is provided at the portion of the hollow anode 46 to which the tip portion 46a is attached. That is, the tip portion 46a is attached by threading the mounting portion 460 of the tip portion 46a into the mounting portion of the hollow anode 46. The tip portion 46a can be removed by releasing the threaded engagement between the mounting portion 460 of the tip portion 46a and the mounting portion of the hollow anode 46.

[0037] FIG. 2 is a photograph of the exterior of the tip portion 46a, specifically, a photograph of the tip portion 46a without a hollow anode filament 48 (described later) attached, and a photograph of the tip portion 46a with the hollow anode filament 48 attached, side by side. A ruler is also included in FIG. 2 to help understand the sizes of the tip portion 46a and the hollow anode filament 48. FIG. 3 is a photograph of the exterior of the tip portion 46a from a different angle. Specifically, FIG. 3(A) is a photograph of the exterior of the tip portion 46a without a hollow anode filament 48 attached, and FIG. 3(B) is a photograph of the exterior of the tip portion 46a with the hollow anode filament 48 attached. A ruler is also included in FIGS. 3(A) and 3(B). FIG. 4 is a cross-sectional view of the tip portion 46a, specifically, a cross-sectional view taken along a plane including the central axis of the tip portion 46a.

[0038] 4, the diameter (inner diameter) Da of the hollow portion 462 of the tip portion 46a varies along the central axis of the tip portion. For example, the diameter Db of the hollow portion 462 on the attachment portion 460 side of the tip portion 46a is smaller than the diameter Da' of the hollow portion 462 near the center of the tip portion 46a in the direction of the central axis. This is due to a balance with the diameter (outer diameter: thread diameter (nominal diameter)) Dc of the attachment portion 460. In contrast, the diameter Dd of the hollow portion 462 on the side of the tip portion 46a opposite the attachment portion 460 side, i.e., on the gas discharge port side, is larger than the diameter Da' of the hollow portion 462 near the center of the tip portion 46a in the direction of the central axis. This is also to prevent a reaction film from adhering to the gas discharge port and narrowing the gas discharge port.

[0039] As an example, the diameter Da' of the hollow portion 462 near the center in the central axis direction of the tip portion 46a is 4 mm. The diameter Db of the hollow portion 462 on the attachment portion 460 side of the tip portion 46a is 2 mm, and the diameter Dc of the attachment portion 460 is 6 mm (M6). The diameter Dd of the hollow portion 462 on the gas outlet side of the tip portion 46a is 7 mm. The diameter (outer diameter) De of the tip portion 46a is 12 mm. In addition, the dimension of the tip portion 46a in the central axis direction, or in other words the length La, is 70 mm, of which the length Lb of the attachment portion 460 is 10 mm. The length Lc of the portion of the hollow portion 462 in the tip portion 46a with the smaller diameter Db is 15 mm, and the length Ld of the portion of the hollow portion 462 with the larger diameter Dd is 5 mm. These dimensional values ​​are merely examples and are not limiting.

[0040] The tip 46a is made of a high-melting-point metal, such as tantalum, which is relatively easy to process. The rest of the hollow anode 46, excluding the tip 46a, is made of a highly corrosion-resistant and heat-resistant metal, such as stainless steel such as SUS304.

[0041] Furthermore, a hollow anode filament 48, which is an example of a heater, as shown in FIG. 5 is attached to the tip portion 46a. This hollow anode filament 48 is, for example, a spiral (coil) made of tungsten, and more specifically, is a member formed by spirally shaping a tungsten wire having a diameter (wire diameter) ds of 1 mm. The spiral diameter Ds of this hollow anode filament 48 is slightly smaller than the diameter De of the tip portion 46a, for example, 11.5 mm. The number of turns of the hollow anode filament 48 is, for example, 8 (turns), and the length dimension Ls of the hollow anode filament 48 is smaller than the length dimension La of the tip portion 46a, for example, 25 mm.

[0042] As shown in FIGS. 2 and 3(B), the hollow anode filament 48 is attached to the gas outlet side of the tip portion 46a. Specifically, the hollow anode filament 48 is attached so as to surround the gas outlet of the tip portion 46a and extend in the gas discharge direction from the gas outlet, in other words, extend along the central axis of the tip portion 46a. At this time, the hollow anode filament 48 is attached to the tip portion 46a in a state in which the helical diameter Ds of the side attached to the tip portion 46a is slightly widened manually (by external force). After the hollow anode filament 48 is attached to the tip portion 46a, the hollow anode filament 48 is fixed to the tip portion 46a by its elasticity, tightening the outer periphery of the tip portion 46a. In other words, the hollow anode filament 48 is fixed to the tip portion 46a without using a fixing member such as a screw for fixing the hollow anode filament to the tip portion 46a. Naturally, the hollow anode filament 48 can be removed from the tip portion 46 a, that is, it can be attached to and detached from the tip portion 46 a. Note that a portion of the hollow anode filament 48, for example, a portion not greater than half of its length Ls, more specifically, a portion of about three turns, is attached so as to surround the periphery of the gas discharge port side of the tip portion 46 a.

[0043] 6 is a photograph of a portion including the crucible 20, the hot cathode filament 34, the tip 46a of the hollow anode 46, and the hollow anode filament 48 in the vacuum chamber 12. The lower left side in FIG. 6 corresponds to the front side of the reactive ion plating apparatus 10, and the upper right side in FIG. 6 corresponds to the rear side of the reactive ion plating apparatus 10. The upper left side in FIG. 6 corresponds to the left side of the reactive ion plating apparatus 10, and the lower right side in FIG. 6 corresponds to the right side of the reactive ion plating apparatus 10.

[0044] As shown in Fig. 6, the hot cathode filament 34 is provided so as to extend in the left-right direction of the reactive ion plating apparatus 10. The hot cathode filament 34 is provided at a position slightly offset from the center of the crucible 20 toward the front side of the reactive ion plating apparatus 10 in the horizontal direction, more specifically, at a position approximately 20 mm away from the center of the crucible 20 as described above. The tip 46a of the hollow anode 46 is provided at a position on the rear side of the reactive ion plating apparatus 10 relative to the crucible 20 and the hot cathode filament 34. In addition, a hollow anode filament 48 is attached to the tip 46a of the hollow anode 46. Note that in Fig. 6, yttrium (Y) as the evaporation material 24 is contained in the crucible 20; strictly speaking, the yttrium contained in the crucible 20 is once melted and then cooled and solidified.

[0045] 1 again, the gas supply inlet (the other end) of hollow anode 46 is connected to supply sources (not shown) of discharge cleaning gas and reactive gas outside vacuum chamber 12. Specifically, each supply source is connected to the gas supply inlet of hollow anode 46 via appropriate piping (not shown). Each piping is provided with a mass flow controller (not shown) as flow rate control means for controlling the flow rate Q of the gas flowing through the piping, and an opening / closing valve (not shown) as opening / closing means for opening and closing the piping.

[0046] Additionally, the hollow anode 46 is connected to a hollow anode power supply 50 serving as second ionization power supply means outside the vacuum chamber 12. The hollow anode power supply 50 supplies hollow anode power Wh as second ionization power to the hollow anode 46. This hollow anode power Wh is DC power with a positive potential relative to the ground potential. In other words, the hollow anode power supply 50 supplies DC hollow anode power Wh to a pair of electrodes, with the hollow anode 46 as the anode and the grounded evaporation source 18 as the cathode. The hollow anode power supply 50 has a maximum capacity of, for example, 3 kW (= 60 V × 50 A).

[0047] In addition, a pressure gauge 52 serving as pressure measurement means for measuring the pressure P within the vacuum chamber 12 is provided at an appropriate position within the vacuum chamber 12; more specifically, a gauge portion (measurement portion) 52a of the pressure gauge 52 is provided. The main body of the pressure gauge 52 is provided outside the vacuum chamber 12. For example, a Penning vacuum gauge is used as this pressure gauge 52, but the pressure gauge is not limited to this, and a gauge portion 52a other than the Penning vacuum gauge, such as an ionization vacuum gauge, may also be used. In addition, in FIG. 1, the gauge portion 52a of the pressure gauge 52 is provided near the substrate table 30, but in reality, the gauge portion 52a is provided at a position where it is less affected by the adhesion of evaporated particles of the evaporation material 24 (described later), for example, near the exhaust port 12a.

[0048] The measurement result of the pressure P by the pressure gauge 52 is given to an evaporation rate controller 54 located outside the vacuum chamber 12. The evaporation rate controller 54 controls the output Wg of the electron gun 22 via the electron gun power supply device 26 so that the pressure P inside the vacuum chamber 12 measured by the pressure gauge 52 remains constant, that is, controls the evaporation rate, which is the amount of evaporation of the evaporation material 24 per unit time.

[0049] Furthermore, a shutter 56 is provided in the vacuum chamber 12 between the hot cathode filament 34 and the substrate stage 30, preferably at a position closer to the hot cathode filament 34. This shutter 56 is selectively shifted by a shutter drive mechanism (not shown) between an open state in which the processing surface of the substrate 28 is exposed toward the opening of the crucible 20 and a closed state in which the processing surface of the substrate 28 is shielded from the opening of the crucible 20. This shutter 56 has relatively high mechanical strength, high corrosion resistance, high heat resistance, and is formed of a non-magnetic metal, such as stainless steel SUS304. The shutter 56 is electrically insulated from other elements such as the vacuum chamber 12, i.e., is electrically floating. The vertical distance between the shutter 56 (or its lower surface) and the opening of the crucible 20 is, for example, approximately 100 mm.

[0050] Although not shown, a suitable heater is provided at an appropriate position within the vacuum chamber 12 as heating means for heating the substrate 28. Examples of such heaters include a carbon heater, a lamp heater, a sheath heater, and a ceramic heater. The heater receives heater heating power from a heater heating power supply device located outside the vacuum chamber 12, thereby appropriately heating the substrate 28.

[0051] The reactive ion plating apparatus 10 according to this embodiment having such a configuration differs from the so-called conventional technology disclosed in the aforementioned Patent Document 1 in that it is provided with a hollow anode filament 48. As described above, the conventional technology is unable to stably form an insulating coating, but the reactive ion plating apparatus 10 according to this embodiment has the extremely beneficial effect of being able to stably form the insulating coating. That is, by providing the hollow anode filament 48 to the conventional technology, that is, by simply adding an extremely simple and inexpensive configuration of providing the hollow anode filament 48 to the conventional technology, the extremely beneficial effect of being able to stably form an insulating coating is achieved.

[0052] To explain this in detail, a configuration in which the hollow anode filament 48 is removed from the reactive ion plating apparatus 10 according to this embodiment will be prepared as a conventional technique. First, a case in which an yttria (yttrium oxide: Y2O3) film, which is one of insulating coatings, is formed using this conventional technique will be described.

[0053] As mentioned above, Figure 2 is a photograph showing the tip 46a of the hollow anode 46 without the hollow anode filament 48 attached and the tip 46a of the hollow anode 46 with the hollow anode filament 48 attached, side by side, and the tip 46a of the hollow anode 46 without the hollow anode filament 48 attached is, in other words, the tip 46a of the hollow anode 46 in the prior art. It can be said that the tip 46a of the hollow anode 46 with the hollow anode filament 48 attached in Figure 2 is the tip 46a of the hollow anode 46 in this embodiment. Similarly, it can be said that the tip 46a of the hollow anode 46 in a state where the hollow anode filament 48 is not attached, as shown in Figure 3(A), is the tip 46a of the hollow anode 46 in the prior art, and the tip 46a of the hollow anode 46 in a state where the hollow anode filament 48 is attached, as shown in Figure 3(B), is the tip 46a of the hollow anode 46 in this embodiment.

[0054] When forming an yttria film using conventional technology, high-purity yttrium is placed in a crucible 20 as an evaporation material 24, which is the material for the yttria film. The yttrium as the evaporation material 24 is, for example, but not limited to, granular matter with a diameter of approximately 3 mm to 5 mm. A substrate 28 is attached to a substrate stand 30. The vacuum chamber 12 is then closed.

[0055] The vacuum chamber 12 is then pumped to a pressure of 1×10 -3 The pressure is evacuated to a pressure P of about 100 Pa, and so-called evacuation is performed. Simultaneously with this evacuation, a heat treatment is performed to heat the substrate 28 using the heater described above, and the substrate 28 is heated to, for example, about 200° C. During this evacuation and heat treatment, the shutter 56 is kept closed, partly to protect the evaporation material 24 in the crucible 20 (from contaminants, etc.).

[0056] After this evacuation and heat treatment is performed for a predetermined time, for example, 2 hours, a discharge cleaning process is performed to clean the surface to be treated of the substrate 28. Specifically, with the shutter 56 closed, argon (Ar) gas and hydrogen (H2) gas as discharge cleaning gases are simultaneously introduced into the vacuum chamber 12, more specifically, through the hollow portion of the hollow anode 46. Then, the pressure P in the vacuum chamber 12 is increased to, for example, 7×10 -2 The partial pressure of argon gas is maintained at 1.5×10 Pa or less. -2 Pa, and the partial pressure of hydrogen gas is 5.5 × 10 -2 The voltage Vp is set to Pa. Furthermore, hot cathode heating power Wf is supplied to the hot cathode filament 34. This heats the hot cathode filament 34, causing thermions to be emitted from the hot cathode filament 34. At the same time, ionizing power Wd is supplied to the hot cathode filament 34. That is, the hot cathode filament 34 serves as the cathode, and the evaporation source 18 serves as the anode, and DC ionizing power Wd is supplied to this pair of electrodes.

[0057] Then, thermoelectrons emitted from the hot cathode filament 34 (cathode) are accelerated toward the evaporation source 18 (anode), particularly toward the crucible 20 located close to the hot cathode filament 34. These accelerated thermoelectrons inelastically collide with particles (atoms or molecules) of the argon gas and hydrogen gas, respectively. As a result, the argon gas and hydrogen gas particles are ionized, generating argon ions and hydrogen ions. Furthermore, as a result of this ionization, electrons are ejected from the (outermost shells of) the argon gas and hydrogen gas particles, respectively, and these ejected electrons flow into the crucible 20 (anode). As this phenomenon continues, plasma 100 containing argon ions and hydrogen ions is induced. This plasma 100 is in the form of a low-voltage, high-current arc discharge. Note that the introduction of argon gas and hydrogen gas into the vacuum chamber 12 may be initiated separately (at different times) rather than simultaneously.

[0058] At this time, the ionization voltage Vd, which is the voltage component of the ionization power Wd, is set to an appropriate constant value. At the same time, the hot cathode heating power Wf is controlled so that the ionization current Id, which is the current component of the ionization power Wd, becomes an appropriate constant value, i.e., the amount of thermoelectrons emitted by the hot cathode filament 34 is controlled. The ionization current Id represents the current flowing into the crucible 20 serving as the anode, and is proportional to the amount of ions (argon ions and hydrogen ions in this case) in the plasma 100, or in other words, the density of the plasma 100. In short, the amount of thermoelectrons emitted by the hot cathode filament 34 is controlled, i.e., feedback control is applied, so that the density of the plasma 100 remains constant.

[0059] In addition, hollow anode power Wh is supplied to the hollow anode 46. That is, the hollow anode 46 serves as the anode, and the evaporation source 18 serves as the cathode. Direct current hollow anode power Wh is supplied to this pair of electrodes. This accelerates electrons in the plasma 100 toward the hollow anode 46, particularly toward the gas outlet (at the tip 46 a) of the hollow anode 46, which is located close to the plasma 100. These accelerated electrons inelastically collide with particles of argon gas and hydrogen gas discharged from the gas outlet of the hollow anode 46. As a result, particles of argon gas and hydrogen gas are actively (efficiently) ionized near the gas outlet of the hollow anode 46, in other words, hollow anode plasma 200 is induced. Near the gas outlet of the hollow anode 46, the pressures of the argon gas and hydrogen gas are high, i.e., the density of the argon gas and hydrogen gas particles is high, and therefore, high-density hollow anode plasma 200 is induced. This embodiment of hollow anode plasma 200 is also a low voltage, high current arc discharge.

[0060] Most of the electrons that contribute to the induction of hollow anode plasma 200 are plasma electrons among the electrons in the main plasma 100 induced by the supply of ionizing power Wd. In other words, the thermoelectrons emitted from the hot cathode filament 34 do not contribute to the induction of hollow anode plasma 200. This is thought to be due to the large distance between the hot cathode filament 34 and the gas outlet port of the hollow anode 46. As evidence, it was confirmed that even when hot cathode heating power Wf is supplied to the hot cathode filament 34 and hollow anode power Wh is supplied to the hollow anode 46, the main plasma 100 and the hollow anode plasma 200 are not induced when ionizing power Wd is not supplied.

[0061] With main plasma 100 and hollow anode plasma 200 induced in this manner, substrate bias power Wb is further supplied to substrate 28. Specifically, substrate bias power Wb is supplied such that the average value of substrate bias voltage Vb is negative with respect to ground potential, e.g., −600 V. Then, shutter 56 is opened. Then, argon ions and hydrogen ions in main plasma 100 and hollow anode plasma 200 are accelerated toward and incident on the surface of substrate 28 to be processed. As a result, the surface of substrate 28 to be processed is cleaned by a sputtering (bombardment) action caused by argon ions colliding with the surface of substrate 28 to be processed, and a chemical reaction (reduction) action caused by hydrogen ions chemically reacting with impurities such as organic contaminants and oxide films adhering to the surface of substrate 28 to be processed.

[0062] This discharge cleaning process is continued until the cleaning level of the processing surface of substrate 28 reaches a desired level. After this discharge cleaning process is completed, shutter 56 is closed. At the same time, the introduction of argon gas and hydrogen gas into vacuum chamber 12 is stopped. This temporarily extinguishes main plasma 100 and hollow anode plasma 200. Then, a film formation process is performed to form a target yttria film on the processing surface of substrate 28.

[0063] In this film formation process, oxygen (O2) gas as a reactive gas is introduced into the vacuum chamber 12. Then, when the pressure P in the vacuum chamber 12 is, for example, 0.1 Pa (=1×10 -1 The pressure is maintained at or below 100 Pa. Furthermore, the electron gun 22 of the evaporation source 18 is energized. This causes the electron gun 22 to emit an electron beam 22a, which is irradiated onto the evaporation material 24 in the crucible 20. The evaporation material 24 is heated, melted, and then evaporated by the irradiation of the electron beam 22a. At this time, the hot cathode filament 34 is supplied with hot cathode heating power Wf and ionization power Wd. Therefore, similar to the discharge cleaning process described above, the thermoelectrons emitted from the hot cathode filament 34 are accelerated toward the crucible 20 (as the anode) (and the yttrium as the melted evaporation material 24 in the crucible 20). The accelerated electrons then inelastically collide with evaporated particles of the evaporation material 24, or so-called evaporation particles. This ionizes the evaporated particles of the evaporation material 24, generating yttrium ions. Furthermore, as a result of this ionization, electrons are ejected from (the outermost shell of) the evaporated particles of the evaporation material 24, and these ejected electrons flow into the crucible 20, which serves as the anode. Concurrently, electrons accelerated from the hot cathode filament 34 toward the crucible 20 also collide inelastically with oxygen gas particles. As a result, the oxygen gas particles are also ionized, and oxygen ions are generated. Furthermore, as the oxygen gas particles are ionized, electrons are ejected from the oxygen gas particles, and these ejected electrons also flow into the crucible 20. As this phenomenon continues, the main plasma 100 is once again induced by the arc discharge.

[0064] In this case, the ionization voltage Vd, which is the voltage component of the ionization power Wd, is set to an appropriate constant value. At the same time, the hot cathode heating power Wf is controlled so that the ionization current Id, which is the current component of the ionization power Wd, is kept at an appropriate constant value. Furthermore, the substrate bias power Wb is adjusted so that the average value of its voltage component, the substrate bias voltage Vb, is an appropriate negative value relative to the ground potential.

[0065] Furthermore, hollow anode power Wh is being supplied to hollow anode 46. Therefore, as in the discharge cleaning process described above, electrons in main plasma 100 are accelerated toward the gas outlet of hollow anode 46. These accelerated electrons inelastically collide with oxygen gas particles being discharged from the gas outlet of hollow anode 46. As a result, oxygen gas particles are actively (intensively) ionized also near the gas outlet of hollow anode 46, and hollow anode plasma 200 is once again induced by arc discharge.

[0066] With main plasma 100 and hollow anode plasma 200 thus induced, shutter 56 is opened. Then, ions in main plasma 100 and hollow anode plasma 200 are accelerated toward the surface of substrate 28 to be processed and are incident on the surface of substrate 28. As a result, an yttria film, which is a compound of yttrium particles containing yttrium ions and oxygen particles containing oxygen ions, is formed on the surface of substrate 28 to be processed.

[0067] Additionally, in this film formation process, the flow rate Q of the reactive gas introduced into the vacuum chamber 12 is kept constant. The output Wg of the electron gun 22 is controlled so that the pressure P inside the vacuum chamber 12 is kept constant, i.e., the evaporation rate of the evaporation material 24 is controlled. This control is derived from a stoichiometric viewpoint, and details thereof are disclosed in Patent Document 1. This control stabilizes the formation rate of the yttria film, i.e., the film formation rate. In other words, the film formation rate can be stabilized without using a dedicated means for monitoring the film formation rate, such as a film thickness monitor.

[0068] This film formation process is continued until an yttria film of the desired thickness is formed. After this film formation process is completed, the shutter 56 is closed. Then, the power supply to the electron gun 22 is stopped. At the same time, the introduction of oxygen gas into the vacuum chamber 12 is stopped. Furthermore, the supply of the substrate bias power Wb to the substrate 28 is stopped. In addition, the supply of the hot cathode heating power Wf to the hot cathode filament 34 is stopped, and the supply of the ionization power Wd to the hot cathode filament 34 is stopped. Then, the supply of the hollow anode power Wh to the hollow anode 46 is stopped. As a result, the main plasma 100 and the hollow anode plasma 200 are extinguished.

[0069] Then, the vacuum chamber 12 is again evacuated, and after a suitable cooling period of about 30 minutes is allowed to stand in this state, the pressure in the vacuum chamber 12 is gradually returned to atmospheric pressure. The vacuum chamber 12 is then opened, and the substrate 28 is removed from the vacuum chamber 12. This completes the series of processes including the film formation process for forming the yttria film.

[0070] In this manner, an yttria film is formed. However, in the prior art, an insulating coating called the yttria film adheres to the hollow anode 46, particularly around the gas outlet of the hollow anode 46 (at its tip 46 a), which reduces the anode function of the hollow anode 46. This reduces the number of electrons flowing from the main plasma 100 toward the hollow anode 46, destabilizing the hollow anode plasma 200 and causing the amount of ions in the hollow anode plasma 200 to fluctuate, specifically, to decrease. Furthermore, the reduction in electrons flowing from the main plasma 100 toward the hollow anode 46 changes the shape and volume of the main plasma 100, particularly reducing its volume. When the volume of the main plasma 100 decreases, the overall amount (total amount) of ions in the main plasma 100 decreases, even if feedback control is applied to maintain a constant density of the main plasma 100, as described above. As a result, the amount of ions incident on the surface of the substrate 28 to be processed decreases, which in turn reduces the quality of the yttria film formed on the surface of the substrate 28, making it unstable. For these reasons, it is presumed that conventional techniques are unable to stably form insulating films such as yttria films.

[0071] Furthermore, in the prior art, to induce the main plasma 100, the thermoelectrons emitted from the hot cathode filament 34 are accelerated toward the crucible 20 (which serves as the anode) as described above. However, strictly speaking, they are accelerated not only toward the crucible 20 but also toward an appropriate location at ground potential, such as the crucible cover 20a. That is, the crucible cover 20a also functions as an anode for inducing the main plasma 100. However, when a film formation process is performed to form an insulating coating, the insulating coating also adheres to the crucible cover 20a, thereby reducing the crucible cover's function as an anode. This changes the shape and volume of the main plasma 100, particularly reducing its volume. As a result, the amount of ions incident on the surface of the substrate 28 being processed decreases, which means the amount of ions becomes unstable. This is presumably one of the reasons why the insulating coating cannot be formed stably.

[0072] On the other hand, when forming an insulating coating using the reactive ion plating apparatus 10 according to this embodiment, a series of processes including film formation are performed in the same manner as in the conventional technology, but the insulating coating can be stably formed by the reactive ion plating apparatus 10 according to this embodiment. That is, by simply adding an extremely simple and inexpensive configuration in which the hollow anode filament 48 is attached to the hollow anode 46 (the tip 46a thereof), it becomes possible to stably form an insulating coating.

[0073] Specifically, when a film formation process for forming an insulating coating is performed using the reactive ion plating apparatus 10 according to this embodiment, a main plasma 100 and a hollow anode plasma 200 are induced, as in the prior art. In particular, the hollow anode plasma 200 is induced when electrons in the main plasma 100, as they are accelerated toward the gas outlet of the hollow anode 46, inelastically collide with particles of the reactive gas discharged from the gas outlet of the hollow anode 46.

[0074] As described above, the hollow anode filament 48 is attached to the hollow anode 46. The hollow anode filament 48 is made of tungsten, a high-melting-point metal, and is electrically connected to the hollow anode 46, i.e., functions as a part of the hollow anode 46. Therefore, electrons accelerated from the main plasma 100 toward the gas outlet of the hollow anode 46 also flow into the hollow anode filament 48. The hollow anode filament 48 is helical, which increases its surface area and facilitates capturing electrons accelerated toward the hollow anode filament 48. Furthermore, the hollow anode filament 48 has a diameter ds of 1 mm and therefore has a small heat capacity. For these reasons, the hollow anode filament 48 is heated (self-heated) by Joule heat due to the inflow of electrons from the main plasma 100. The heating temperature of the hollow anode filament 48 is estimated to be close to 2000°C.

[0075] FIG. 7 is a photograph of a portion of the vacuum chamber 12 during a film-forming process to form an yttria film as an insulating coating, specifically, a portion including the crucible 20, the hot cathode filament 34, the tip 46a of the hollow anode 46, and the hollow anode filament 48. As shown in FIG. 7, the hollow anode filament 48 is red-hot, and from its red-hot state, it is estimated that the hollow anode filament 48 has been heated to nearly 2000°C. In FIG. 7, the pale white area with a slight purplish tint is the main plasma 100. Although it is difficult to see in FIG. 7, the area surrounded by the hollow anode filament 48 is pale white, which is the hollow anode plasma 200 (however, in FIG. 7, the reference numeral "200" representing the hollow anode plasma 200 has been omitted for ease of viewing).

[0076] In this way, the hollow anode filament 48 is heated to nearly 2000°C. This temperature is above the evaporation temperature of various materials commonly used as the evaporation material 24, including yttrium. In other words, it is above the evaporation temperature of particles (evaporation particles and their ions) of the evaporation material 24. Therefore, during the film-forming process to form an insulating coating, particles of the evaporation material 24 adhere to the surface of the hollow anode filament 48. However, the particles adhering to the surface of the hollow anode filament 48 are re-evaporated when the hollow anode filament 48 is heated to a temperature above its evaporation temperature. Therefore, no insulating coating adheres to the surface of the hollow anode filament 48, and as a result, the hollow anode filament 48 maintains its function as a part of the hollow anode 46. In other words, even if an insulating coating adheres to the hollow anode 46 itself, such as the gas outlet port of the hollow anode 46, the hollow anode filament 48 functions as a stable anode.

[0077] In this way, the hollow anode filament 48 functions as a stable anode, stabilizing the amount of electrons flowing from the main plasma 100 into the hollow anode filament 48. This stabilizes the hollow anode plasma 200, i.e., the amount of ions in the hollow anode plasma 200. Furthermore, stabilizing the amount of electrons flowing from the main plasma 100 into the hollow anode filament 48 stabilizes the shape and volume of the main plasma 100, i.e., the total amount of ions in the main plasma 100. As a result, the amount of ions incident on the processing surface of the substrate 28 is stabilized, and thus the quality of the insulating coating formed on the surface of the substrate 28 is stabilized. For these reasons, this embodiment enables stable formation of an insulating coating.

[0078] Strictly speaking, the heating temperature of the hollow anode filament 48 also depends on the hollow anode voltage Vh, which is a voltage component of the hollow anode power Wh. For example, the higher the hollow anode voltage Vh, the higher the heating temperature of the hollow anode filament 48. On the other hand, the hollow anode voltage Vh is the space potential of the hollow anode plasma 200 itself. Therefore, the higher the hollow anode voltage Vh, the higher the space potential of the hollow anode plasma 200. If the hollow anode voltage Vh is excessively high, abnormal discharge is likely to occur. Experience has shown that abnormal discharge is likely to occur when the space potential of the hollow anode plasma 200 exceeds 60 V. Therefore, it is important that the hollow anode voltage Vh be as low as possible within a range that allows the hollow anode filament 48 to be heated to the evaporation temperature of the evaporation material 24 or higher, for example, 60 V or less. Furthermore, in order to accelerate electrons in the main plasma 100 toward the hollow anode 46, the hollow anode voltage Vh must be higher than the space potential of the main plasma 100. Incidentally, the space potential of the main plasma 100 is generally about 5 V to 8 V, which is lower than 10 V, regardless of the conditions. Therefore, it is essential that the hollow anode voltage Vh be set to, for example, 10 V or higher. For these reasons, the hollow anode voltage Vh is appropriately set within a range of 10 V or higher and 60 V or lower, depending on various conditions, such as the type of evaporation material 24.

[0079] Furthermore, as mentioned above, in the prior art, the adhesion of an insulating coating to the crucible cover 20a changes the shape and volume of the main plasma 100, which is presumably one of the reasons why the desired insulating coating cannot be stably formed. However, in this embodiment, an insulating coating also adheres to the crucible cover 20a. However, in this embodiment, the hollow anode filament 48 functions as a stable anode, stabilizing the hollow anode plasma 200 and ultimately stabilizing the shape and volume of the main plasma 100. This state is stably maintained regardless of whether an insulating coating is attached to the crucible cover 20a. Therefore, according to this embodiment, the shape and volume of the main plasma 100 are stabilized regardless of whether an insulating coating is attached to the crucible cover 20a, thereby enabling the desired insulating coating to be stably formed.

[0080] As described above, according to this example, an insulating film can be stably formed. In order to verify this, the following experiment was carried out.

[0081] That is, in addition to this example and the conventional technology, a configuration in which the hollow anode voltage Vh, which is a voltage component of the hollow anode power Wh, is set to 0 V, i.e., a configuration in which the hollow anode power Wh is not supplied, was prepared as a reference technology. Then, an yttria film was actually formed as an insulating coating using each of this example, the reference technology, and the conventional technology, and the properties of the films were compared. The film formation conditions used in this experiment are shown in Figure 8. The experimental results are shown in Figure 9.

[0082] As shown in FIG. 8, in this experiment, the flow rate Q [O2] of oxygen gas as a reactive gas introduced into the vacuum chamber 12 was set to 100 mL / min. Additionally, the pressure P within the vacuum chamber 12 was set to 0.015 Pa. More precisely, the output Wg of the electron gun 22 was controlled so that the pressure P within the vacuum chamber 12 was kept constant at 0.015 Pa. This control caused the output Wg of the electron gun 22 to fluctuate between 2.52 kW and 2.70 kW. More specifically, the emission current Ig varied between 280 mA and 300 mA while the acceleration voltage Vg of the electron gun 22 was kept constant at 9 kV. Furthermore, the ionization power Wd was set to a constant 250 W. More specifically, the hot cathode heating power Wf was controlled so that the ionization current Id was kept constant at 10 A while the ionization voltage Vd was kept constant at 25 V. The hollow anode voltage Vh was set to 0 V or 30 V; specifically, it was set to 30 V in this example and the conventional technology, and to 0 V in the reference technology. The substrate bias voltage Vb (average value) was set to -600 V. The frequency of this substrate bias voltage Vb was 100 kHz, and the duty ratio was 20%. The film formation time was set to 45 min.

[0083] In this experiment, the substrate stand 30 was a disk stand with a diameter of 360 mm and a thickness of 3 mm. The distance between the opening of the crucible 20 and the surface of the substrate 28 to be processed was 450 mm. The diameter of the opening of the crucible 20 was 60 mm. A tungsten hearth liner with a weight of 73 g was set in the crucible 20, and approximately 112 g of yttrium was filled into the hearth liner.

[0084] 9 showing the results of this experiment, for example, focusing on the film thickness, the film thickness (4.96 μm) of the yttria film formed by this example is clearly smaller than the film thicknesses (6.61 μm and 6.50 μm) of the yttria films formed by the reference technology and the conventional technology, respectively. From another perspective, focusing on the film deposition rate, the film deposition rate (6.61 μm / h) of this example is clearly smaller than the film deposition rates (8.81 μm / h and 8.67 μm / h) of the reference technology and the conventional technology, respectively. This means that the yttria film formed by this example is denser and has higher hardness than the yttria films formed by the reference technology and the conventional technology, respectively.

[0085] As evidence, the crystal structure of the yttria film formed in this experiment was analyzed by X-ray diffraction (XRD), and the results shown in Figure 10 were obtained. As shown in Figure 10, the yttria films formed by the reference technology (thick short dashed line) and the conventional technology (thick long dashed line) each exhibit a large peak in the (222) plane orientation, i.e., a preferred orientation. In contrast, the yttria film formed in this example (thick solid line) exhibits peaks in the (222) and (440) plane orientations, and the magnitudes (intensities) of these peaks are comparable. In particular, the peak in the (222) plane orientation is approximately 0.1 to 0.2 times larger than the peak in the yttria films formed by the reference technology and the conventional technology. From this, it is inferred that the yttria film formed in this example is microcrystalline (amorphous) and therefore dense. In the analysis results shown in FIG. 10, peaks representing SUS304 are also seen, but this is because the substrate 28 used for analysis is SUS304.

[0086] 9, the Knoop hardness of the yttria film formed by this example is clearly higher than that of the yttria film formed by the reference technology and the conventional technology, regardless of the indenter load, 200 g, 100 g, 50 g, or 25 g. Figure 11 shows this Knoop hardness in a graph, and it can be intuitively understood from Figure 11 that this example (thick solid line with a circle) forms a yttria film with a higher hardness than either the reference technology (thick short dashed line with a square) or the conventional technology (thick long dashed line with a triangle).

[0087] Referring again to FIG. 9, focusing on the internal stress, the internal stress (-2.81 GPa) of the yttria film formed by this example is clearly greater in absolute value than the internal stresses (-1.21 GPa and -1.21 GPa) of the yttria films formed by the reference technology and the conventional technology, respectively. When this internal stress is a negative value, it indicates that the internal stress is compressive stress, and the larger the absolute value, the greater the compressive stress and the higher the hardness. Therefore, this internal stress also indicates that the yttria film formed by this example is harder than the yttria films formed by the reference technology and the conventional technology, respectively.

[0088] 12 shows the transition of the substrate bias current Ib, which is the current component of the substrate bias power Wb, during the deposition process for forming the yttria film. The substrate bias current Ib is correlated with (proportional to) the amount of ions incident on the substrate table 30, i.e., correlated with (proportional to) the amount of ions incident on the surface of the substrate 28 to be processed.

[0089] As shown in FIG. 12 , for example, in the case of the conventional technology (thick dashed line with triangles), the substrate bias current Ib is large at the beginning of the film formation process, which is the desired value. Therefore, the desired amount of ions is incident on the surface of the substrate 28 to be processed. However, as the film formation process progresses, particularly after about 15 minutes have passed since the start of the film formation process, the substrate bias current Ib begins to decrease, which means that the amount of ions incident on the surface of the substrate 28 to be processed begins to decrease. As mentioned above, this is presumably due to the formation of an insulating film around the gas outlet port of the hollow anode 46, which reduces the anode function of the hollow anode 46. The formation of an insulating film on the crucible cover 20a is also presumably a factor. Then, after about 25 minutes have passed since the start of the film formation process, the substrate bias current Ib settles somewhat, but its value is still about two-thirds of what it was at the beginning of the film formation process. As described above, in the prior art, the substrate bias current Ib is unstable, i.e., the amount of ions incident on the processed surface of the substrate 28 fluctuates, and therefore it is presumed that an insulating coating cannot be stably formed.

[0090] Similarly, in the reference technology (shown by the thick dashed line with squares), the substrate bias current Ib is large at the beginning of the film formation process, which is the desired value. However, as the film formation process progresses, the substrate bias current Ib decreases. After about 20 minutes from the start of the film formation process, the substrate bias current Ib settles somewhat, but its value remains at about two-thirds of its initial value. In other words, the reference technology also exhibits unstable substrate bias current Ib, which in turn results in an unstable amount of ions incident on the surface of the substrate 28 being processed. As mentioned above, in the reference technology, the hollow anode power Wh is not supplied, so the hollow anode 46 does not function as an anode (it functions solely as a gas introduction tube), and the hollow anode filament 48 does not glow red. Therefore, it is presumed that the unstable substrate bias current Ib is due to the adhesion of an insulating coating to the crucible cover 20a. Therefore, the reference technology does not allow for stable formation of an insulating coating.

[0091] In contrast, in this embodiment (thick solid line with circles), the substrate bias current Ib is stable and maintains the desired value from the start to the end of the film formation process. That is, the amount of ions incident on the surface to be processed of the substrate 28 is stable. This suggests that this embodiment allows for the stable formation of an insulating coating.

[0092] 13 shows the transition of hollow anode current Ih, which is a current component of hollow anode power Wh, during the deposition process for forming the yttria film. Hollow anode current Ih is correlated (proportional) to the amount of electrons flowing into hollow anode 46, or in other words, correlated (proportional) to the amount of ions in hollow anode plasma 200.

[0093] 13, for example, in the case of the conventional technology (thick dashed line with triangles), the hollow anode current Ih is stable for a while after the start of the film formation process. However, after about 15 minutes have passed since the start of the film formation process, the hollow anode current Ih begins to decrease, i.e., the amount of ions in hollow anode plasma 200 begins to decrease. Then, after about 25 minutes have passed since the start of the film formation process, the hollow anode current Ih settles somewhat, but its value is still about two-thirds of what it was at the start of the film formation process. Thus, in the conventional technology, the hollow anode current Ih is unstable, which means that the amount of ions in hollow anode plasma 200 fluctuates. In other words, hollow anode plasma 200 is unstable.

[0094] Focusing on the reference technology (thick dashed line with squares), the hollow anode current Ih is significantly smaller than, for example, the hollow anode current Ih in the prior art. As mentioned above, this is because, in the reference technology, the hollow anode 46 does not function as an anode in the first place. Nevertheless, the hollow anode current Ih in the reference technology exhibits a small value, which is presumably due to some electrons in the main plasma 100 flowing into the hollow anode 46.

[0095] In contrast, in this embodiment (thick solid line with circles), the hollow anode current Ih is stable and, moreover, is much larger than the hollow anode current Ih in the prior art. This is presumably because hollow anode filament 48 functions as a stable anode, causing a large amount of electrons in main plasma 100 to flow into hollow anode filament 48. This indicates that in this embodiment, the amount of ions in hollow anode plasma 200 is extremely large, i.e., the density of hollow anode plasma 200 is extremely high. This presumably enables this embodiment to stably form a dense, highly hard, or in other words, high-quality, insulating coating.

[0096] As described above, according to this embodiment, insulating films such as yttria films can be formed stably with high quality. In particular, since yttria films have high plasma resistance, this embodiment is extremely useful in fields that require high plasma resistance, such as semiconductor etching equipment. Naturally, according to this embodiment, not only insulating films but also conductive films can be formed stably with high quality.

[0097] This example is a specific example of the present invention and does not limit the technical scope of the present invention. The present invention can also be applied to aspects other than this example.

[0098] For example, in this example, the formation of an yttria film as an insulating film has been described in detail, but the present invention can also be applied to the formation of insulating films other than the yttria film. As an example, a silicon nitride (Si3N4) film was formed and an experiment was conducted to confirm its properties. The film formation conditions for this silicon nitride film experiment are shown in Figure 14.

[0099] As shown in FIG. 14 , in the experiment on silicon nitride films, the flow rate Q [N] of nitrogen (N2) gas as a reactive gas introduced into the vacuum chamber 12 was set to 80 mL / min. Additionally, the pressure P in the vacuum chamber 12 was set to 0.08 Pa. More precisely, the output Wg of the electron gun 22 was controlled so that the pressure P in the vacuum chamber 12 was kept constant at 0.08 Pa. This control caused the output Wg of the electron gun 22 to fluctuate between 3.69 kW and 3.78 kW. Specifically, with the acceleration voltage Vg of the electron gun 22 kept constant at 9 kV, the emission current Ig fluctuated between 410 mA and 420 mA. Furthermore, the ionization power Wd was kept constant at 1.2 kW. Specifically, with the ionization voltage Vd kept constant at 40 V, the hot cathode heating power Wf was controlled so that the ionization current Id was kept constant at 30 A. The hollow anode voltage Vh was set to 40 V. The substrate bias voltage Vb (average value) was set to −600 V. The frequency of the substrate bias voltage Vb was 100 kHz, and the duty ratio was 20%. The film formation time was set to 40 minutes.

[0100] The substrate stage 30 used in the silicon nitride film experiment was the same as that used in the yttria film experiment described above, i.e., a circular plate with a diameter of 360 mm and a thickness of 3 mm. The distance between the opening of the crucible 20 and the surface of the substrate 28 to be processed was also 450 mm, the same as in the yttria film experiment described above. However, the diameter of the opening of the crucible 20 was 80 mm. A carbon hearth liner with a weight of 70 g was set in the crucible 20, and approximately 110 g of silicon was filled into the hearth liner.

[0101] In the experiment on this silicon nitride film, although not shown in the figure, the results showed that the silicon nitride film could be stably formed. Specifically, a high-hardness silicon nitride film was formed, with a film thickness of 1.3 μm and a Knoop hardness of 2700 HK when the indenter load was 25 g. Furthermore, the silicon nitride film formed in this experiment was transparent, and its refractive index was 2.08. This confirmed that a high-quality silicon nitride film was formed.

[0102] In the experiment on this silicon nitride film, the substrate bias current Ib during the film formation process was stable at approximately 1 A. The hollow anode current Ih was also stable at approximately 30 A.

[0103] In addition, although detailed explanation including illustrations is omitted, it has also been confirmed that a gadolinium oxide (Gd3O2) film can be formed stably with high quality. Thus, according to the present invention, various insulating films can be formed stably with high quality.

[0104] Furthermore, while the hollow anode filament 48 is described as a tungsten filament with a diameter (wire diameter) ds of 1 mm formed into a spiral, this is not limiting. For example, the diameter ds of the hollow anode filament 48 may be smaller than 1 mm. The smaller the diameter ds of the hollow anode filament 48, the easier it is to heat, which is advantageous. However, the smaller the diameter ds of the hollow anode filament 48, the lower the mechanical strength of the hollow anode filament 48, which is disadvantageous. In particular, the hollow anode filament 48 is periodically subjected to a blasting treatment, and the blasting treatment is performed while attached to the tip 46a of the hollow anode 46, so it is required to have a certain level of mechanical strength. Therefore, the diameter ds of the hollow anode filament 48 needs to be at least a certain level. However, if the diameter ds is excessively large, the heat capacity of the hollow anode filament 48 itself increases, making it difficult to heat. For these reasons, it is essential that the diameter ds of the hollow anode filament 48 be 0.5 mm or more and 2.0 mm or less.

[0105] In addition, the tip 46a of the hollow anode 46 may have a configuration as shown in FIG. 15. The tip 46a shown in FIG. 15 has a smaller diameter (outer diameter) Df on the gas outlet side, thereby providing a step 464 on the outer periphery of the tip 46a on the gas outlet side. When the tip 46a shown in FIG. 15 is used, the hollow anode filament 48 is configured so that its spiral diameter Ds is slightly smaller to match the diameter Df of the tip 46a on the gas outlet side. With this configuration, the step 464 functions as a stopper, preventing the hollow anode filament 48 from sliding downward. Alternatively, the hollow anode filament 48 may be attached to the hollow anode 46 simply by being placed on the step 464.

[0106] Additionally, when the tip portion 46a shown in FIG. 15 is employed, the hollow anode filament 48 may have a configuration as shown in FIG. 16. The hollow anode filament 48 shown in FIG. 16 has an extremely short (flat) cylindrical base portion 480 and a plurality of straight-rod-shaped electron inlet portions 482, 482, ... connected to the base portion 480. Each electron inlet portion 482 is provided to extend from one end of the base portion 480 along the central axis of the base portion 480. The hollow anode filament 48 shown in FIG. 16 is attached to the tip portion 46a by placing the base portion 480 on the step 464 of the tip portion 46a with each electron inlet portion 482 facing in the same direction as the gas outlet of the tip portion 46a shown in FIG. 15. 16, like the spiral hollow anode filament 48 described above, has a small heat capacity and a shape that makes it easy to capture electrons accelerated from the main plasma 100, and therefore exhibits the same effects as the spiral hollow anode filament 48. Of course, a hollow anode filament 48 having a configuration different from that shown in FIG. 16 may also be employed.

[0107] The present invention is not limited to application to the reactive ion plating apparatus 10, but can also be applied to a reactive ion plating method. [Explanation of symbols]

[0108] 10...Ion plating equipment 12...Vacuum chamber 18...evaporation source 20...crucible 22...Electron gun 24...evaporation material 28... Circuit board 32...Substrate bias power supply 34... Hot cathode filament 36…Hot cathode heating power supply device 38...Ionization power supply 40...Current detector 42... Heating controller 46…Hollow anode 46a...Tip 48...Hollow anode filament 50…Power supply device for hollow anode 52... Pressure gauge 54...Evaporation rate controller

Claims

1. A reactive ion plating apparatus that reacts particles of an evaporation material with particles of a reactive gas to form a reaction film, which is a compound of the particles of the evaporation material and the particles of the reactive gas, on a surface of a workpiece, comprising: a vacuum chamber in which the workpiece is placed and the inside of which is evacuated; a storage means for storing the evaporation material, the storage means being disposed below the object to be processed inside the vacuum chamber; an evaporation means for evaporating the evaporation material contained in the containing means; a hot cathode that is disposed between the container and the object to be treated and that emits thermoelectrons; a first ionization power supply means for supplying a first ionization power of DC to the containing means and the hot cathode, with the containing means serving as an anode and the hot cathode serving as a cathode, for ionizing particles of the evaporation material evaporated by the evaporation means; a thermoelectron emission amount control means for controlling the amount of thermions emitted by the hot cathode so that the current component of the first ionization power is constant; a hollow anode having a hollow portion through which the reactive gas flows and through which the reactive gas is introduced into the vacuum chamber; a second ionization power supply means for supplying a second ionization power of DC to the hollow anode and the containing means, with the hollow anode serving as an anode and the containing means serving as a cathode, for ionizing particles of the reactive gas introduced into the vacuum chamber; a heating element that is provided at an outlet of the hollow anode for the reactive gas into the vacuum chamber, and that is heated to a temperature equal to or higher than the evaporation temperature of particles of the evaporation material by receiving an inflow of electrons in the plasma induced by the supply of the first ionizing power; and A reactive ion plating apparatus comprising a bias power supply means for supplying bias power to the workpiece to accelerate the ionized particles of the evaporation material and the ionized particles of the reactive gas toward the surface of the workpiece.

2. 2. The reactive ion plating apparatus according to claim 1, wherein the heating element is a spiral element that surrounds the outlet and extends spirally in the direction in which the reactive gas is discharged from the outlet.

3. 2. The reactive ion plating apparatus according to claim 1, wherein the heater is detachable from the discharge port.

4. 4. The reactive ion plating apparatus according to claim 3, wherein the heater can be attached to the discharge port without using a member for attaching the heater to the discharge port.

5. 2. The reactive ion plating apparatus according to claim 1, wherein the voltage component of the second ionizing power is 10V or more and 60V or less.

6. 2. The reactive ion plating apparatus according to claim 1, further comprising an evaporation rate control means for controlling the evaporation rate of the evaporation material by the evaporation means so that the pressure inside the vacuum chamber is constant while the amount of reactive gas introduced into the vacuum chamber per unit time is constant.

7. 1. A reactive ion plating method for forming a reaction film, which is a compound of particles of an evaporation material and particles of a reactive gas, on a surface of a workpiece, the method comprising: an evaporation step of evaporating the evaporation material contained in a container provided below the object to be processed in a vacuum chamber in which the object to be processed is placed and the inside of the vacuum chamber is evacuated; a thermionic emission step of emitting thermoelectrons from a thermionic cathode provided between the container and the object to be treated; a first ionization power supply step of supplying a first ionization power of DC to the containing means and the hot cathode, with the containing means serving as an anode and the hot cathode serving as a cathode, for ionizing particles of the evaporation material evaporated in the evaporation step; a thermionic emission amount control step of controlling the amount of thermionic electrons emitted by the hot cathode so that the current component of the first ionization power is constant; a reactive gas introducing step of introducing the reactive gas into the vacuum chamber through a hollow portion of a hollow anode having a hollow portion through which the reactive gas flows; a second ionization power supply step of supplying a second ionization power of DC to the hollow anode and the containing means, with the hollow anode serving as an anode and the containing means serving as a cathode, for ionizing particles of the reactive gas introduced into the vacuum chamber; a heater heating step of heating a heater provided at an outlet of the hollow anode for discharging the reactive gas into the vacuum chamber to a temperature equal to or higher than the evaporation temperature of particles of the evaporation material by causing electrons in the plasma induced by the supply of the first ionizing power to flow into the heater; and A reactive ion plating method including a bias power supply step of supplying bias power to the workpiece to accelerate ionized particles of the evaporation material and ionized particles of the reactive gas toward the surface of the workpiece.

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