Film forming method and film forming apparatus

Abstract

This invention provides a method for forming a metal film with good coverage and continuity on the inner surface of a metal film, such as a Cu-containing film as a seed layer or a Ta-containing film as a base layer of a Cu-containing film, when forming a film on the inner surface of a trench that is a micro-recess (Sf). A sputtering gas containing a rare gas is introduced into a vacuum chamber (1) in a vacuum atmosphere. A negative potential is applied to the target material (2), and a positive potential is applied to the reflector to generate plasma. Then, the introduction of the sputtering gas is stopped, and sputtering is performed on the target material while self-discharge occurs under low pressure. A high-frequency bias power is applied from a high-frequency power supply (61) via an impedance integrator (62) to a platform (5) on which the film is to be formed (Sw). At this time, an electronic matching device with electronically controlled variable reactance is used as the impedance integrator, and the high-frequency bias power is intermittently applied to the platform at a specific frequency.

Description

Technical Field

[0001] This invention relates to a film-forming method and a film-forming apparatus, and more specifically, to an invention that sets the film-forming object as an object having a plurality of micro-recesses formed on its surface, and uses SIS (Self-Ionized Sputter) technology to form a metal film with good coverage by sputtering on the inner surface of each micro-recess. Prior Technology

[0002] In the manufacturing process of semiconductor devices, there is a process of forming a metal film, such as a Cu film as a seed layer or a Ta film as a base layer of a Cu film, on the inner surface (inner side and inner bottom surface) of a trench that is a micro-recess. In the formation of such a metal film, a so-called self-ion sputtering apparatus is used. This apparatus has a vacuum chamber in which a metal target such as Cu or Ta is arranged facing the object to be deposited, and a magnetic field generating means disposed above the target and in the space below it to generate a leakage magnetic field, a gas introducing means for introducing sputtering gas containing a rare gas into the vacuum chamber, a sputtering power supply for applying a negative potential to the target, and a reflector plate arranged to surround the space below the target and applied a positive potential. Furthermore, within the vacuum chamber, a platform is set up for the object to be formed into a film, and high-frequency bias power is continuously supplied from a high-frequency power source via an impedance integrator that integrates the impedance of the plasma with the impedance of the high-frequency power source.

[0003] When forming a metal film using the aforementioned self-ion sputtering apparatus, sputtering gas is introduced into a vacuum chamber under a vacuum atmosphere, and a negative potential is applied to the target material while a positive potential is applied to the reflector. In this way, plasma is generated in the space below the target material. Using a magnetic field generated by a magnetic field generation method, the plasma is sealed into this space. If the introduction of sputtering gas is stopped in this state, self-discharge occurs under low pressure. Then, the ions of the sputtering gas in the plasma collide with the sputtering surface of the target material and are sputtered. Cu atoms or ionized Cu ions, dispersed from the target material and appropriately reflected by the reflector, are strongly drawn and adhered to the surface of the film-forming object, which contains various micro-recesses, with strong linear propagation towards the object to which a high-frequency bias potential is applied. Thus, a Cu film is formed.

[0004] Furthermore, some of the micro-recesses used for film deposition have high aspect ratios, and some have inner surfaces (sidewalls) that are not smooth (in other words, they have micro-unevenness). In addition, the thinning of the metal film deposited on the inner surfaces of the micro-recesses (e.g., film thickness in the range of 300 Å to 500 Å) is increasingly advanced. In such cases, if a Cu film is deposited using the aforementioned self-ion sputtering apparatus, not only will so-called overhangs occur, but the continuity of the Cu film (thin film) deposited on the inner surfaces of the micro-recesses will also be compromised (poor side coverage). If the continuity of the Cu film is compromised in this way, it will be difficult to properly embed Cu wiring using plating methods in subsequent processes. [Previous Technical Documents] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2010-209453 Summary of the Invention

[0006] [The problem the invention aims to solve] The present invention addresses the above-mentioned problems by providing a method and apparatus for forming a metal film that can achieve continuity and good coverage on the inner side of a micro-recessed area. [Methods used to solve problems]

[0007] To address the aforementioned issues, the film-forming method of the present invention involves setting the film-forming object as an object having a plurality of micro-recesses formed on its surface, and forming a metal film on the inner surface of each micro-recession of the film-forming object placed in a vacuum chamber. This film-forming method includes: introducing a sputtering gas containing a rare gas into a vacuum chamber; applying an electric current with a negative potential to a metal target to generate plasma; then stopping the introduction of the sputtering gas; and sputtering the target while allowing self-discharge to occur under low pressure. The process of applying a positive potential to a reflector arranged to surround the space between the film-forming object and the target material; and the process of supplying high-frequency bias power to a platform on which the film-forming object is set from a high-frequency power source via an impedance integrator that integrates the impedance of the plasma and the impedance of the high-frequency power source. In the process of supplying high-frequency bias power, an electronic matching device with electronically controlled variable reactance is used as the impedance integrator, and high-frequency bias power is intermittently supplied to the platform at a specific frequency.

[0008] Therefore, the electronic matching device, as an impedance integrator, has the characteristic of integrating impedance in a shorter time of a few milliseconds compared to a matching device that mechanically drives a variable capacitor. Furthermore, it is well known that a high Vdc occurs instantaneously at the initial application of high-frequency bias power via the impedance integrator. Note that in this invention, the device is configured to "use an electronic matching device as an impedance integrator, and when applying high-frequency bias power to the platform, intermittently apply the high-frequency bias power at a specific frequency (e.g., switching the power application on and off)".

[0009] Based on this, not only do metal atoms or their ions from the target side adhere to the inner surface of the micro-recess, but due to the high Vdc instantaneously generated each time a high-frequency bias voltage is applied, the metal film on the inner bottom surface of the micro-recess is also re-sputtered. This re-sputtered product adheres and accumulates on the inner surface of the micro-recess from the opposite direction to that from the target side. Therefore, even when the inner surface of the micro-recess is not smooth, a metal film with continuity and good coverage can be formed at a specific thickness on the inner surface of the micro-recess. Furthermore, by changing the applied high-frequency bias voltage, the height position of the micro-recess, primarily where the re-sputtered product is attached, from the inner bottom surface can be adjusted.

[0010] Furthermore, it has been confirmed that intermittently applying high-frequency bias power at a specific frequency can effectively suppress drooping. Drooping occurs because if a positive potential is applied to the reflector while high-frequency bias power is continuously applied to the platform, Cu ions are directly attracted and attached to the film-forming object with strong linear propagation. In this case, the Cu ions are not only attracted and attached perpendicularly to the surface of the film-forming object, but also at an angle relative to the perpendicular direction (i.e., they are injected at an angle relative to the film-forming object). Consequently, the electric field tends to concentrate at the corner between the surface of the film-forming object and the micro-recesses. In contrast, in this invention, this electric field concentration is suppressed by intermittently applying high-frequency bias power. Furthermore, in the OFF state of the high-frequency bias voltage, the attraction of Cu ions to the substrate disappears instantaneously. As a result, the Cu ions are injected perpendicularly to the surface of the substrate Sw and their trajectory is corrected. Consequently, it can be inferred that the occurrence of drooping can be suppressed as much as possible.

[0011] Furthermore, in cases where it is desirable to re-sputter a metal film deposited on the bottom surface of a micro-recess and form a metal film with good coverage on the inner side surface of the micro-recess, as is the case in this invention, it is ideal to preferentially form a metal film on the bottom surface of the micro-recess from the outset. Therefore, in this invention, the following configuration is adopted: that is, the aforementioned high-frequency bias power input process includes: a first process in which, at the initial stage of film formation, the aforementioned high-frequency bias power is set to a first power (for example, in the range of 10W to 100W depending on the aspect ratio of the micro-recess, preferably 50W), and a metal film is preferentially formed on the bottom surface of each micro-recess; and a second process in which a second power larger than the first power (for example, in the range of 500W to 900W, preferably 700W) is applied and the high-frequency bias power is input.

[0012] This allows for the reliable deposition of a metal film with a specific thickness, achieving good continuity and coverage on the inner surface of the micro-recesses. Ideally, when the aspect ratio of the micro-recesses is 3 or higher, the following configuration is preferred: the frequency during intermittent application of high-frequency bias power is set to a range of 1 kHz to 20 kHz; and the duty cycle during intermittent application of high-frequency bias power is set to a range of 50% to 90%. Furthermore, the ratio of the film thickness during the first power application to the film thickness during the second power application can be set, for example, to 1:3. Furthermore, while it is possible to continuously or intermittently increase the high-frequency bias voltage when applying it, in cases where the overall film deposition time is short (e.g., less than 10 seconds), the film deposition time will be longer when the high-frequency bias voltage is low, potentially failing to effectively improve the side coverage. Therefore, in cases where the film deposition time is set to be short to accommodate the desired film thickness, it is ideal to apply the high-frequency bias voltage in two stages.

[0013] In this invention, it has been confirmed that when the aforementioned metal film is a Cu-containing film formed as a seed layer or a Ta-containing film formed as a base layer of the aforementioned Cu-containing film, the Cu-containing film or Ta-containing film can be formed with a relatively thin film thickness (e.g., a film thickness in the range of 200 Å to 700 Å) while maintaining film continuity and good coverage on the inner surface of the micro-recesses. Furthermore, in this invention, "Cu-containing film" refers to a film mainly composed of Cu element, and composed of Cu element at 90 at% or more. Also, "Ta-containing film" includes not only pure Ta films, but also Ta nitride films, oxide films, and oxynitride films.

[0014] Furthermore, to solve the aforementioned problems, the film-forming apparatus of the present invention comprises an object having a plurality of micro-recesses formed on its surface, and is used to form a metal film on the inner surface of each micro-recess of the object being formed within a vacuum chamber. This film-forming apparatus includes: a gas introduction means for introducing a sputtering gas containing a rare gas into a vacuum chamber; a sputtering power source for applying a negative potential to a metal target; and a reflector arranged to surround the space between the object being formed and the target, and subjected to... A positive potential is applied; and a platform is provided with a film-forming object. High-frequency bias power is supplied from a high-frequency power supply through an impedance integrator that integrates the impedance of the plasma with the impedance of the high-frequency power supply side. After plasma is generated in the space in front of the sputtering surface of the target, the introduction of sputtering gas is stopped, and sputtering of the target is performed while self-discharging under low pressure. The impedance integrator is constructed by an electronic matching device with electronically controlled variable reactance. The high-frequency power supply is configured to intermittently supply high-frequency bias power at a specific frequency. Simple Explanation of the Diagram

[0015] [Figure 1] is a schematic cross-sectional view showing the film-forming apparatus of this embodiment. [Figure 2] is a diagram illustrating the input of high-frequency bias voltage during film formation. [Figure 3](a) and (b) are illustrations of the pattern of sputtered particles being pulled and attached toward the object to be film-formed after being ionized. [Figure 4](a) and (b) are SEM images of experimental results demonstrating the effects of the present invention. Implementation

[0016] Hereinafter, referring to the drawings, an example will be provided of a film deposition method and film deposition apparatus of the present invention, in which "an insulating layer is formed on the surface of a semiconductor substrate (hereinafter referred to as "substrate Sw") such as a silicon wafer, and a plurality of micro-recesses Sf are formed on the insulating layer in a specific pattern, and a film deposition apparatus is provided as an ion sputtering apparatus SM, and a metal film such as a Cu film or a Ta film is formed on the inner side surface Sf1 and the inner bottom surface Sf2 of the micro-recesses Sf with good coverage". Furthermore, the present invention, as for "micro-recesses", can be suitably used, for example, for those with "an opening diameter d1 of 0.65 μm or less and an aspect ratio of 3 or more". Since a known method can be used to form such micro-recesses, a detailed description will be omitted here. The following are terms used to describe the orientation based on Figure 1, which is used to demonstrate the self-ion sputtering apparatus SM in a set position.

[0017] Referring to Figure 1, the self-ion sputtering apparatus SM of this embodiment includes a vacuum chamber 1 capable of creating a vacuum atmosphere. A cathode unit Uc is disposed on the upper part of the vacuum chamber 1. The cathode unit Uc comprises a copper or tantalum target 2 of a specific purity and a magnet unit 3 disposed above the target 2. The target 2 is mounted on a back plate 21a with its sputtering surface 21b facing downwards, and is detachably mounted at the upper opening of the vacuum chamber 1 via an insulator 11a. The magnet unit 3 is used to generate a magnetic field in the space below the sputtering surface 21b, and during sputtering, captures electrons ionized below the sputtering surface 21b and efficiently ionizes sputtering particles ejected from the target 2. Since this type of magnet unit 3 is readily available, a detailed description is omitted here. At the target material 2, an output from the first DC power supply E1, which serves as the sputtering power source, is connected. During film formation, a specific power (18kW or more) with a negative potential can be applied to the target material 2.

[0018] Inside the vacuum chamber 1, a conductive reflector 4 is disposed. The reflector 4 is a cylindrical component that covers the target material 2 and extends downwards, with its lower end set to a height approximately half the distance between the target material 2 and the substrate Sw. The reflector 4 is connected to an output from a second DC power supply E2, and a positive potential (5V~100V) is applied during film deposition to reflect ionized sputtered particles, assisting in their strong linear propagation towards the substrate Sw. At the lower part of the vacuum chamber 1, a platform 5 is disposed directly opposite the target material 2. Although not specifically illustrated, an electrostatic adsorption mechanism is provided on the platform 5 to position and hold the substrate Sw. Furthermore, a heating and cooling mechanism is incorporated into platform 5, which, for example, can control the temperature range within which agglomeration does not occur during Cu film deposition. At platform 5, an output from a high-frequency bias power supply 61 is connected via an impedance integrator 62 that integrates the impedance between the plasma and the platform. During film deposition, the high-frequency bias power supply is applied to platform 5 and even to the substrate Sw, and is configured to actively pull and attach metal atom ions toward the substrate Sw side.

[0019] As the high-frequency bias power supply 61, for example, it utilizes a known device capable of outputting power of 10kW or less at a frequency of 13.56MHz, and further includes a known pulse generation circuit (not shown). Also, as shown in Figure 2, it is configured to control the ON / OFF of the switching element (not shown) of the pulse generation circuit and output high-frequency bias power at a specific frequency. As the impedance integrator 62, it uses an electronic matching device (see the enlarged portion in Figure 1) with electronically controlled variable reactances 62a and 62b that can integrate the impedance of the plasma with the impedance of the high-frequency bias power supply 61 side within a few milliseconds. Since such an electronic matching device is a known device, its control circuit and control method are also included here, and detailed descriptions are omitted.

[0020] On the side wall of the vacuum chamber 1, a gas pipe 7 is connected to introduce sputtering gas, such as argon, which is a rare gas, constituting a gas introduction means. The sputtering gas, whose flow rate is controlled by a mass flow controller 71 intermediately located at the gas pipe 7, is introduced into the vacuum chamber 1, which is in a vacuum atmosphere. The aforementioned self-ion sputtering apparatus SM has a controller Cr, which is known to be equipped with a microcomputer or sequencer. The controller Cr manages the operation of various machines, such as the first and second DC power supplies E1 and E2, the high-frequency bias power supply 61, and the mass flow controller 71. The following describes the film formation method in detail, taking the formation of a Cu film using the self-ion sputtering apparatus SM as an example.

[0021] The substrate Sw is positioned and held on platform 5 within a vacuum chamber 1 containing a copper object of a specific purity, which serves as the target material 2. Then, the vacuum chamber 1 is evacuated to a specific pressure (e.g., 10⁻⁵ Pa) using an unspecified vacuum evacuation method. If the pressure within the vacuum chamber 1 reaches a specific value, the mass flow controller 71 controls the introduction of Ar gas into the vacuum chamber 1 at a specific flow rate (e.g., 10 sccm to 20 sccm). Subsequently, a positive potential (e.g., 5V to 100V) is applied to the reflector 4 using a second DC power supply E2, and a specific power with a negative potential (e.g., 18kW to 24kW) is applied to the target material 2 using a first DC power supply E1. Finally, a high-frequency bias power (e.g., 50W to 1300W) is applied to platform 5 via impedance integrator 62 using a high-frequency bias power supply 61. In this way, plasma is generated in the space below the target 2. The plasma is sealed in this space by the leakage magnetic field from the magnet unit 3. If the mass flow controller 71 is controlled and the introduction of sputtering gas is stopped in this state, self-discharge occurs under low pressure. Then, the ions of sputtering gas in the plasma collide with the sputtering surface 21b of the target 2 and are sputtered. Cu atoms or ionized Cu ions that are scattered from the target 2 and appropriately reflected by the reflector plate 4 are strongly attracted and attached to the substrate Sw surface with strong linear advancement, and are attached and deposited on the inner surfaces Sf1 and Sf2 of each micro-recess Sf, and a Cu film is formed.

[0022] In this embodiment, when a high-frequency bias power supply 61 is applied to the platform 5 during Cu film formation, the switching element (not shown) of the pulse generation circuit is controlled to ON / OFF, and the high-frequency bias power is applied intermittently at a specific frequency. Furthermore, the high-frequency bias power is applied in two stages, large and small (see Figure 2). That is, at the initial stage of Cu film formation, the high-frequency bias power is set to a first power (e.g., in the range of 10W to 100W, ideally 50W) (first stage). After a certain period, it is changed to a second power (e.g., in the range of 500W to 900W, ideally 700W), which is larger than the first power, and the high-frequency bias power continues to be applied (second stage). At this point, the application times of the first and second electrical powers can be set based on the desired Cu film thickness, with the ratio of the film thickness during the application of the first power to that during the application of the second power being, for example, 1:3. Furthermore, the frequency of intermittent application of the high-frequency bias power is set to a range of 1kHz to 20kHz, and the duty ratio (the ON time in one cycle) is set to a range of 50% to 90%. Additionally, if the frequency is lower than 1kHz or the duty ratio is lower than 50%, the adhesion of Sf1 to the inner surface cannot be effectively achieved through resputtering. On the other hand, if the duty ratio is higher than 90%, the in-plane uniformity of the film thickness distribution will be compromised. Furthermore, if the frequency is higher than 20kHz, a problem will occur where "void will be generated in the micro-recesses Sf when Cu wiring is embedded by plating in subsequent processes".

[0023] Based on this, at the initial stage of Cu film formation, the material ejected from the target 2 preferentially adheres to and accumulates on the inner bottom surface Sf2 of each micro-recess Sf, thus forming the Cu film. Subsequently, if the high-frequency bias voltage is changed from the first voltage to the second voltage, not only Cu atoms or ionized Cu ions from the target 2 side, but also the Cu film on the inner bottom surface Sf2 of the micro-recess Sf will be re-sputtered due to the instantaneously generated high Vdc each time the high-frequency bias voltage is applied. This re-sputtered product adheres to and accumulates on the inner side surface Sf1 of the micro-recess Sf from the opposite direction (downward) to those from the target side. Therefore, even when the inner side surface Sf1 of the micro-recess Sf is not perfectly smooth, a Cu film with good continuity and coverage can be formed on the inner side surface Sf1 to achieve a specific film thickness. At this time, if the applied high-frequency bias voltage is changed, the height position of the micro-recesses Sf, which are mainly attached to the product that has been resputtered, can be adjusted from the inner bottom surface Sf2.

[0024] Furthermore, if the Cu film is formed as described above, the occurrence of sagging can be suppressed as much as possible. It can be inferred that the sagging is caused by the fact that, as in the previous example, if a positive potential is applied to the reflector 4 while a high-frequency bias voltage is continuously applied to the platform 5, the Cu ions will be directly attracted and attached to the substrate Sw in a state of strong linear propagation. However, as shown in Figure 3(a), some Cu ions are attracted and attached not only in a direction perpendicular to the surface (top) of the substrate Sw, but also in a state that is inclined relative to the vertical direction (that is, they are injected at an angle relative to the substrate Sw). Consequently, the electric field tends to concentrate at the corner between the surface of the substrate Sw and the inner side of the micro-recess.

[0025] In contrast, in this embodiment, the concentration of electric field is suppressed by intermittently applying high-frequency bias power. Furthermore, it can be deduced that, as shown in Figure 3(b), each time the high-frequency bias power is applied to the OFF state, the attraction of Cu ions to the substrate Sw disappears instantaneously. As a result, the Cu ions are orbitally corrected, entering from a direction perpendicular to the surface of the substrate Sw, thereby suppressing sagging as much as possible. Consequently, even when the inner surface Sf1 of the micro-recesses Sf is not smooth, a Cu film with good continuity and coverage at the inner surface Sf1 can be formed with a relatively thin film thickness (e.g., 200 Å to 700 Å). Furthermore, it has been confirmed that the above-mentioned film formation method is effective even when the target material 2 is made of tantalum of a specific purity, and a Ta film is formed on the inner surfaces Sf1 and Sf2 of each micro-recess Sf. Also, if the potential applied to the reflector 4 is changed by intermittently applying high-frequency bias power at a specific frequency, the film formation rate can be changed accordingly. In this case, it has been confirmed that the film thickness distribution within the substrate Sw surface can be made slightly constant regardless of the potential applied to the reflector 4.

[0026] To confirm the above effects, a Cu film was formed using the self-ion sputtering apparatus SM shown in Figure 1. The substrate Sw was prepared by "forming a silicon oxide film covering the entire surface of a φ300mm Si wafer, then patterning fine recesses (70nm wide, 210nm deep) within this silicon oxide film using a known method, and subsequently depositing TaN and Ta at the inner surfaces Sf1 and Sf2 of the fine recesses Sf with a film thickness of 13nm". The target material was a Cu target with a composition of 99.9999%. As for the film formation conditions, the following were set: "The distance between the sputtering surface 21b of the target 2 and the substrate Sw was set to 300 mm, the power input to the target 2 was set to 16 kW (current 38 A), the voltage input to the reflector 4 was set to 100 V, the flow rate of the initially introduced argon gas was set to 10 sccm, and the temperature of the substrate Sw was maintained below room temperature while Cu film formation was carried out for a specific time."

[0027] In Comparative Experiment 1, the high-frequency bias voltage was set to 700W and continuously applied from the beginning of film deposition. In contrast, in Inventive Experiment 1, the frequency was set to 1kHz and the power efficiency ratio was set to 50%, while the high-frequency bias voltage was applied intermittently. Furthermore, at the beginning of film deposition, the high-frequency bias voltage was set to 50W and Cu film deposition was performed for a specific time. Afterward, the high-frequency bias voltage was changed to 700W, and Cu film deposition was performed. Figures 4(a) and (b) are SEM images of the central portion of the substrate Sw in Inventive Experiment 1 and Comparative Experiment 2, respectively. Based on this, in Comparative Experiment 1, the surface film thickness of the substrate Sw is 36 nm, the film thickness of the inner bottom surface Sf2 of the micro-recess Sf is 7.1 nm, the average film thickness of the inner surface Sf1 is 6.2 nm, and the overhang (that is, the film thickness of the Cu film protruding towards the inner side of the micro-recess Sf at the position where the surface of the substrate Sw intersects with the upper end of the inner surface Sf1 of the micro-recess Sf) is 19.1 nm (see Figure 4(b)). In contrast, in Experiment 1 of the invention, the film thickness on the surface of the substrate Sw was 39.7 nm, the film thickness on the inner bottom surface Sf2 of the micro-recess Sf was 12.7 nm, the average film thickness on the inner surface Sf1 was 7.5 nm, and the overhang was 13.9 nm. Compared with the case of Comparative Experiment 1, the side coverage was improved, the overhang was suppressed, and the asymmetry was also small. Furthermore, it was confirmed that a Cu film was formed continuously on the inner surface Sf1 (see Figure 4(a)).

[0028] Next, as Invention Experiment 2, the frequency was set to 10kHz, and the power ratio was set to 10%, 50%, and 90%. Other film formation conditions were the same as in Invention Experiment 1, and Cu films were formed. The images were then analyzed using SEM images. It was confirmed that when the power ratio was 10%, there were areas on the substrate surface where the film thickness on the inner bottom surface was thinner compared to Comparative Experiment 1, and the overhang was not significantly reduced. On the other hand, it was confirmed that when the power ratio was 50% or 90%, the film thickness on the inner surface increased by more than 1nm compared to the comparative experiment, and the overhang was reduced by more than 5nm. Next, as Invention Experiment 3, the power ratio was set to 50%, and the frequency was set to 1kHz, 10kHz, and 20kHz. Other film formation conditions were the same as in Invention Experiment 1, and Cu films were formed. Based on this, it is confirmed that if the frequency falls within the range of 1kHz to 20kHz, the film thickness on the inner surface is increased by more than 1nm compared to the above comparative experiment 1. At the inner surface Sf1, a Cu film is formed continuously, and the overhang is reduced by more than 5nm. At the same time, the asymmetry is also small.

[0029] Next, as Invention Experiment 4, a comparison was made between "the case where the high-frequency bias power was set to 30W and continuously applied from the beginning of film formation (Invention Experiment 4)" and "the case where the high-frequency bias power was set to 0W and Cu film formation was performed (Comparative Experiment 2)". Based on this, it was confirmed that although the film thickness on the inner surface of the micro-recess was almost the same in Invention Experiment 4 and Comparative Experiment 2, the film thickness on the inner surface of the micro-recess in Invention Experiment 4 was increased by 1.3 to 1.6 times compared to Comparative Experiment 2, and sagging was also suppressed. Based on this, it was confirmed that if a smaller initial high-frequency bias power is applied at the beginning of film formation, a metal film can be preferentially formed on the inner bottom surface of the micro-recess.

[0030] The above description, while referring to embodiments of the present invention, allows for various modifications without departing from the technical concept of the invention. In the above embodiments, an example is provided where a well-known pulse generation circuit is installed at the high-frequency bias power supply 61 and ON / OFF control is performed at a specific frequency; however, it is not limited to any embodiment where high-frequency bias power can be intermittently applied to the platform 5. Furthermore, while an example is provided where an electronic matching device is used as the impedance integrator 62, it is not limited to any embodiment where the impedance of the plasma and the impedance on the high-frequency bias power supply 61 side can be integrated in a short time (a few milliseconds). Moreover, while the above embodiments are described using a metal film such as a Cu or Ta film as an example, it is not limited to this. For example, the present invention is also widely applicable to situations such as "setting the target material 2 as tantalum of a specific purity, and introducing reactive gases such as nitrogen or oxygen into the film formation process to form a nitride film, oxide film or oxynitride film (including Ta film) with good coverage on the inner surface of the micro-recesses Sf".

[0031] SM: Self-ion sputtering apparatus Sw: Substrate (object to be coated) Sf: fine concave part Sf1: Inner side Sf2: Inner bottom surface 1: Vacuum chamber 2: Target Material 4: Reflector 5: Platform 61: High-frequency bias power supply 62: Electronic matching circuit (impedance matching circuit) 7: Gas tube (a component of gas introduction methods)

Claims

1. A film deposition method comprising: setting an object to be deposited as having a plurality of micro-recesses formed on its surface; and depositing a metal film on the inner surface of each micro-recess of the object to be deposited within a vacuum chamber; the method comprising: introducing a sputtering gas containing a rare gas into a vacuum chamber in a vacuum atmosphere; applying an electric current with a negative potential to a metal target to generate plasma; then stopping the introduction of the sputtering gas and sputtering the target while performing self-discharge under low pressure; applying a positive potential to a reflector arranged to surround the space between the object to be deposited and the target; and applying a high-frequency bias voltage to a platform on which the object to be deposited is positioned from a high-frequency power source via an impedance integrator that integrates the impedance of the plasma with the impedance of the high-frequency power source. In the process of supplying high-frequency bias power, an electronic matching device with electronically controlled variable reactance is used as an impedance integrator, and high-frequency bias power is intermittently supplied to the platform at a specific frequency.

2. The film-forming method as described in claim 1, wherein, The aforementioned high-frequency bias power input process includes: a first process, which is to set the aforementioned high-frequency bias power as the first power at the beginning of film formation and preferentially form a metal film at the bottom surface inside each micro-recess; and a second process, which is to change to a second power that is larger than the first power and input the high-frequency bias power.

3. The film-forming method as described in claim 1, wherein, When intermittently applying high-frequency bias power, the aforementioned frequency is set to the range of 1kHz to 20kHz.

4. The film-forming method as described in claim 1, wherein, The duty ratio is set within the range of 50% to 90% when high-frequency bias power is intermittently supplied.

5. The film-forming method as described in any of claims 2 to 4, wherein, The aforementioned metal film is either a Cu-containing film formed as a seed layer or a Ta-containing film formed as a base layer of the aforementioned Cu-containing film.

6. A film-forming apparatus comprising: a film-forming object having a plurality of micro-recesses formed on its surface; and a metal film formed on the inner surface of each micro-recess of the film-forming object disposed within a vacuum chamber; the film-forming apparatus comprising: a gas introduction means for introducing a sputtering gas containing a rare gas into a vacuum chamber; a sputtering power source for applying a negative potential to a metal target; a reflector configured to surround the space between the film-forming object and the target and having a positive potential applied thereto; and a platform on which the film-forming object is disposed and is supplied with high-frequency bias power from a high-frequency power source via an impedance integrator that integrates the impedance of the plasma with the impedance of the high-frequency power source side; wherein, after plasma is generated in the space in front of the sputtering surface of the target, the introduction of the sputtering gas is stopped, and sputtering is performed on the target while self-discharge occurs under low pressure. An impedance integrator is constructed by an electronic matching device with a variable reactance that is electronically controlled. A high-frequency power supply is configured to intermittently supply high-frequency bias power at a specific frequency.

Images