Sputtering target, sputtering apparatus, and sputtering film formation method
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NISSIN ELECTRIC CO LTD
- Filing Date
- 2025-10-24
- Publication Date
- 2026-06-25
AI Technical Summary
Existing sputtering methods for insulating materials fail to effectively reduce the possibility of target damage during film formation, particularly with materials like LATP and LLZO, due to thermal shock and low thermal conductivity, leading to inefficient film formation and target damage.
A sputtering target composed of a mixture of elemental carbon regions and insulator regions, where the carbon regions enhance thermal conductivity and are oxidized and gasified during the process, reducing thermal stress and preventing carbon incorporation into the film.
The method effectively reduces target damage and improves film formation efficiency by minimizing thermal stress and ensuring high thermal conductivity, while maintaining a high film formation rate without incorporating carbon into the deposited film.
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Abstract
Description
Sputtering target, sputtering apparatus, and sputtering film deposition method
[0001] The present invention relates to a sputtering target, a sputtering apparatus, and a sputtering film deposition method.
[0002] A sputtering method is known for forming an insulating film on a substrate by sputtering an insulating target. Furthermore, a technology using a magnesium oxide target has been proposed that can suppress target damage during film formation.
[0003] Japanese Patent Application Publication No. 2005-170665
[0004] The prior art described in Patent Document 1 attempts to mitigate thermal shock during film formation and suppress target damage by adhering a heat insulating layer to the cathode electrode side of the target. However, there is a need for a sputtering method for insulating materials that can more effectively reduce the possibility of target damage during film formation.
[0005] One aspect of the present invention has been made in view of the above-mentioned problems, and aims to realize a sputtering film deposition method that can effectively reduce the possibility of damage to the sputtering target during the film deposition process.
[0006] To solve the above problems, one aspect of the present disclosure is a sputtering target in which a first region composed of elemental carbon is mixed with a second region composed of an insulator.
[0007] To solve the above problems, another aspect of the present disclosure is a sputtering apparatus comprising: a plasma chamber in which plasma is generated; a gas line for introducing oxygen gas into the plasma chamber; and a sputtering target disposed in the plasma chamber, wherein a first region composed of a single carbon material is mixed with a second region composed of an insulator.
[0008] To solve the above problems, yet another aspect of the present disclosure is a sputtering film deposition method in which a sputtering target having regions composed of elemental carbon mixed with regions composed of an insulator is exposed to an oxygen-containing plasma to oxidize and gasify the carbon contained in the sputtering target, while the sputtered insulator is deposited on a substrate to form a film made of the insulator.
[0009] According to one aspect of this disclosure, a sputtering film deposition method can be realized that can effectively reduce the possibility of damage to the sputtering target during the film deposition process.
[0010] This figure shows the schematic configuration of a sputtering apparatus according to an embodiment. This is a schematic diagram showing a sputtering target according to Embodiment 1. This is a schematic diagram showing a sputtering target according to Embodiment 2.
[0011] [Embodiment 1] <Configuration of sputtering apparatus> Figure 1 is a diagram showing the schematic configuration of a sputtering apparatus 1 according to an embodiment of the present disclosure.
[0012] The sputtering apparatus 1 includes a plasma chamber 20. Inside the plasma chamber 20, the sputtering apparatus 1 includes a sputtering target 10, a backing plate 31, a stage 41, and a holder 42 for holding the workpiece W on which film formation is to be performed. Furthermore, the sputtering apparatus 1 includes a plasma generation mechanism 30 including the backing plate 31, an ICP assist mechanism 50, and a gas line 61.
[0013] The gas line 61 introduces the required gas into the plasma chamber 20. In this embodiment, the gas line 61 supplies argon gas and oxygen gas, which are plasma raw material gases when sputtering film deposition is performed. Therefore, the gas line 61 may be configured to include an argon gas introduction line for supplying gas containing argon gas and an oxygen gas introduction line for supplying gas containing oxygen gas.
[0014] The plasma chamber 20, which also serves as a vacuum vessel, has its internal space evacuated by an exhaust device (not shown) and controlled to the required vacuum level. The vacuum level used for sputtering film deposition is selected from a range that facilitates the generation of inductively coupled plasma (ICP), and is typically between 0.1 Pa and 10 Pa. As will be described in detail later, a window section 21 is provided in a part of the wall surface of the plasma chamber 20.
[0015] A holder 42 for holding the workpiece W is mounted or held on the stage 41. The stage 41 may be provided with an appropriate rotation mechanism for uniformizing the distribution of film deposition on the workpiece W, and may also be provided with a temperature control mechanism for heating or cooling the workpiece W. The stage 41 may be grounded, or it may be configured to have a bias voltage applied to it.
[0016] Typically, the sputtering apparatus 1 is configured such that the sputtering target 10, held by the backing plate 31, is positioned above the workpiece W on the stage 41, and the main surfaces of the backing plate 31 and the stage 41 facing inward into the plasma chamber 20 are horizontal. Therefore, in embodiments, when terms such as horizontal, vertical, up, or down are used, these terms may be used on the premise that the parts of the sputtering apparatus 1 are arranged in these orientations.
[0017] However, the arrangement of the parts of the sputtering apparatus 1 is not necessarily limited to this example for the application of the present invention. The distance between the workpiece W and the sputtering target 10 is preferably about 50 to 300 mm.
[0018] The plasma generation mechanism 30 is a mechanism that generates magnetron sputtering on the sputtering target 10. The plasma generation mechanism 30 includes a backing plate 31, a housing 32, a refrigerant path 33, a magnet 34, an insulating flange 35, an anode 36, and a power supply 39 for the target.
[0019] The backing plate 31 is a conductive plate-shaped member and is attached to the upper wall of the plasma chamber 20 near the center via an insulating flange 35. The insulating flange 35 maintains the vacuum inside the plasma chamber 20 while fixing the backing plate 31 to the plasma chamber 20 and insulating it from the plasma chamber 20.
[0020] On the backing plate 31, on the surface (top surface) opposite to the side that holds the sputtering target 10, a magnet 34 for generating a magnetic field around the sputtering target 10 and a conductive housing 32 surrounding the magnet 34 are provided. The top surface of the housing 32 is exposed to the outside of the plasma chamber 20 and is electrically connected to the target power supply 39.
[0021] A coolant path 33 is formed between the magnet 34 and the housing 32, through which a coolant (e.g., cooling water) for cooling the sputtering target 10 passes. In addition, a grounded anode 36 is fixed to the plasma chamber 20 side surface of the insulating flange 35, covering the outer edge of the sputtering target 10 while maintaining a gap between itself and the sputtering target 10.
[0022] A high-frequency voltage is applied to the sputtering target 10 from the target power supply 39 via the housing 32 and backing plate 31, causing the plasma source gas supplied from the gas line 61 to become plasma inside the plasma chamber 20. The sputtering target 10 is then sputtered by the generated plasma, resulting in film formation on the surface of the workpiece W. The frequency of the high-frequency power supplied by the target power supply 39 is generally 13.56 MHz, but is not limited to this.
[0023] The ICP assist mechanism 50 is a plasma source for increasing the plasma density inside the plasma chamber 20 and promoting sputtering. The ICP assist mechanism 50 includes an antenna 51 and an antenna power supply 59. The antenna 51 is positioned outside the plasma chamber 20, parallel to a window portion 21 that is airtightly provided in the side wall of the plasma chamber 20. The window portion 21 is made of a plate-shaped member made of an electromagnetic wave-transmitting material that allows electromagnetic waves generated by the antenna 51 to pass through.
[0024] When a high-frequency current is introduced to the antenna 51 from the antenna power supply 59, electromagnetic waves are generated from the antenna 51. This induces an induced electric field within the plasma chamber 20, generating inductively coupled plasma (ICP). In other words, the antenna 51 is an ICP support antenna that assists in the generation of plasma within the plasma chamber 20. The frequency of the high-frequency power supplied from the antenna power supply 59 is generally 13.56 MHz, but is not limited to this.
[0025] <Sputtering Target> The sputtering target 10 according to Embodiment 1 will be described below. The sputtering target 10 is a raw material for forming an insulating film. Preferably, it is a raw material for forming an insulating film that is an oxide. Preferably, the insulating material is a compound containing at least one of lithium or sodium.
[0026] More specifically, the sputtering target 10 is preferably used as a raw material for forming an insulator that will become a solid electrolyte having at least one of lithium-ion conductivity or sodium-ion conductivity by sputtering.
[0027] Such insulators include those called LATP, which are composed of Li, Al, Ti, and PO. ４ Examples include oxides whose main component is Li. １＋Ｘ Al Ｘ Ti ２－Ｘ (PO ４ ) ３It may be an oxide represented by [formula], and in particular, it may be an oxide with X = 0.4, or it may be an oxide in which a part of the elements is further substituted with other elements from the oxides of these compositional formulas.
[0028] Also, as such an insulator, an oxide mainly composed of Li, La, Zr, and O, called LLZO, can be mentioned. As an example, the compositional formula is Li ７ La ３ Zr ２ O １２ It may be an oxide represented by [formula], or it may be an oxide in which a part of the composition, for example, a part of Li or Zr, is further substituted with other elements, such as Al, Ga, Ta, Nb, etc.
[0029] FIG. 2 is a diagram schematically showing the sputtering target 10. As shown in the partially enlarged view in FIG. 2, the sputtering target 10 is configured such that two regions are mixed. In the figure, the first region 10C is a region made of single carbon (C), and the second region 10M is a region made of the above-mentioned insulator. The volume ratio of the first region 10C is preferably 1% or more and 40% or less.
[0030] In Embodiment 1, the second region 10M is the substrate (matrix) of the sputtering target 10, and in the second region 10M, the first region 10C made of particulate carbon is dispersed and present. In order to achieve better thermal conductivity, as shown in FIG. 2, it is preferable that the particulate carbon is in a state of being connected so as to be in contact with each other. However, it may also be in a state where the particulate carbon is scattered in the second region 10M.
[0031] Here, single carbon includes graphite, carbon fiber, carbon nanotube, diamond, fullerene, etc. The first region 10C made of single carbon may contain impurities that do not significantly impair the properties of single carbon, for example, impurities with an atomic ratio of 1% or less. Examples of such impurities include those generally referred to as ash content. Another example of impurities is oxygen resulting from the surface oxidation region of the first raw material described later.
[0032] The following describes an example of a method for manufacturing a sputtering target 10. The first raw material is a particulate, flaky, or fibrous carbon powder, often referred to as carbon filler. Such carbon powders, often referred to as carbon filler, are widely used industrially and readily available. Examples of the first raw material include carbon black, such as acetylene black, Ketjen black, furnace black, channel black, and thermal lamp black.
[0033] When such carbon powder is in particulate form, it is preferable that its particle size is 1% or less of the short side of the plate-shaped sputtering target 10 to be created. In particular, when such carbon powder is in particulate form, it is preferable that the central particle diameter is in the range of 0.1 to 100 μm.
[0034] A second raw material is an insulating powder such as LATP or LLZO. Preferably, the central particle size of such powder is in the range of 0.01 to 100 μm. The first raw material and the second raw material are mixed in a ratio such that the volume ratio of the first region 10C is a required value, and the mixture is molded into a required shape and sintered to produce the sputtering target 10 shown in Figure 2.
[0035] <Sputtering Method> The following describes a method for forming an insulating film on the surface of a workpiece W using a sputtering apparatus 1 to which a sputtering target 10 is applied.
[0036] A holder 42, on which the substrate W to be processed is mounted, is placed on the stage 41, and the plasma chamber 20 is evacuated. Next, argon gas and oxygen gas, which will be the plasma raw material gases, are supplied from the gas line 61. The exhaust system is controlled to maintain the required vacuum level inside the plasma chamber 20. The plasma generation mechanism 30 and the ICP assist mechanism 50 are operated to generate plasma inside the plasma chamber 20.
[0037] The plasma generated at this time is a mixed plasma of oxygen and argon. Oxygen ions, argon ions, etc. in the plasma collide with the surface of the sputtering target 10, and an insulator such as LATP or LLZO is sputtered from the second region 10M and adheres to the surface of the opposing workpiece W, forming a film of the insulator.
[0038] Also, argon ions, etc. in the plasma sputter carbon atoms from the first region 10C, but the sputtered carbon atoms immediately react with oxygen ions, oxygen radicals, etc. in the atmosphere and are oxidized and gasified as carbon monoxide (CO) or carbon dioxide (CO ２ ). Therefore, the sputtered carbon atoms are hardly incorporated into the film formed on the substrate surface of the workpiece W.
[0039] The carbon atoms in the first region 10C exposed on the surface of the sputtering target 10 also react with oxygen ions, oxygen radicals, etc. in the atmosphere and are oxidized and gasified as carbon monoxide (CO) or carbon dioxide (CO ２ ) and are removed from the sputtering target 10. Therefore, the sputtering of carbon atoms from the surface of the sputtering target 10 itself is suppressed. The carbon atoms gasified as described above are exhausted from the plasma chamber 20 by an exhaust device.
[0040] Generally, while sputtering continues, ions collide with the surface of the sputtering target, so the sputtering target continues to be heated from the side of the surface exposed to the plasma chamber. Conventionally, insulators such as LATP and LLZO have a low thermal conductivity, and it has been inevitable that a large temperature difference occurs between the front and back sides of the surface of the sputtering target. Also, due to the low thermal conductivity, the in-plane temperature distribution of the sputtering target during sputtering tends to become large.
[0041] Furthermore, insulators such as LATP and LLZO have poor sputtering efficiency and a low film formation rate, so it takes time to form a film with the required film thickness, and such heating time tends to be long. Therefore, due to such temperature differences and temperature distributions, the sputtering targets for forming films of insulators such as LATP and LLZO have been damaged.
[0042] In the present embodiment, the first region 10C made of carbon exists so as to be dispersed throughout the sputtering target 10. The thermal conductivity of carbon is higher in each stage compared to insulators such as LATP and LLZO. Therefore, in the sputtering target 10, heat conduction is improved, and temperature differences and temperature distributions in the thickness direction in the sputtering target 10 are less likely to occur.
[0043] Therefore, according to the present embodiment, the possibility of damage to the sputtering target 10 during the film formation process due to these can be effectively reduced. Moreover, as described above, the carbon in the sputtering target 10 is not incorporated into the film of the formed insulator.
[0044] As described above, an example in which a high-frequency voltage is applied from the target power supply 39 to the sputtering target 10 has been shown, but the power supplied from the target power supply 39 to the sputtering target 10 does not necessarily have to be high-frequency power. When the sputtering target is insulating, if high-frequency power is not biased to the sputtering target, sputtering is difficult to proceed and the film formation rate becomes very small.
[0045] However, in the present embodiment, since the sputtering target 10 is provided with conductivity, sputtering proceeds even if the voltage applied to the sputtering target 10 is a DC voltage. In this case, there is no need to make the bias mechanism to the sputtering target 10 including the target power supply 39 compatible with high frequencies, and it can be made simpler than in the case of making it compatible with high frequencies.
[0046] <Modification> As described above, various shapes of carbon fillers can be used as the first raw material when manufacturing the sputtering target 10. When granular fillers are used, a first region 10C is formed based on a granular shape as shown in Figure 2.
[0047] In particular, when carbon fibers are used as filler, it is possible to form a mesh-like first region 10C within the sputtering target 10. Alternatively, by aligning the longitudinal direction of the carbon fibers with the thickness direction of the sputtering target 10 to form the first region 10C, the heat conduction in the thickness direction of the sputtering target 10 can be further improved, and damage can be effectively prevented.
[0048] [Embodiment 2] Figure 3 is a schematic representation of the sputtering target 11 according to Embodiment 2. As shown in the partially enlarged view in Figure 3, the sputtering target 11 is configured such that two regions are mixed together. In the figure, the first region 11C is a region made of elemental carbon (C), and the second region 11F is a region made of the above-mentioned insulator. The volume ratio of the first region 11C is preferably 1% or more and 10% or less.
[0049] In Embodiment 2, the first region 11C is configured as a porous material. In other words, the first region 11C can be said to be made of porous carbon. The insulating material supported in the voids of the porous material constitutes the second region 11F. In other words, the second region 11F can be said to be made of insulating material filled in the voids of the porous material.
[0050] Thus, the first region 11C, which is made of elemental carbon and has a significantly higher thermal conductivity compared to insulators, is configured as a continuous region throughout the sputtering target 11, resulting in good overall thermal conductivity of the sputtering target 11.
[0051] An example of a method for manufacturing the sputtering target 11 is described below. The powdered insulating material is filled into the pores of granular porous carbon. Here, the diameter of the pores in the porous carbon is relatively large, between 1 and 100 μm, and it is preferable that the diameter of the pores is 10 to 10,000 times the particle size of the powder. It is preferable that the central particle diameter of the powdered insulating material is in the range of 0.01 to 10 μm.
[0052] To fill the pores of the porous carbon with the powdered insulating material, a method may be used in which the porous carbon is immersed in a liquid containing dispersed powdered insulating material. Subsequently, the porous carbon filled with insulating material is molded into the required shape and fired to produce the sputtering target 11.
[0053] Even when the sputtering target 11 according to Embodiment 2 is applied to the sputtering apparatus 1, the possibility of damage to the sputtering target 11 during the film deposition process can be effectively reduced, similar to the case of Embodiment 1. Furthermore, the amount of carbon in the sputtering target 11 incorporated into the deposited insulating film is similarly small.
[0054] [Summary] Embodiment 1 of the present disclosure is a sputtering target in which a first region composed of elemental carbon is mixed with a second region composed of an insulator.
[0055] Aspect 2 of the present disclosure is a sputtering target made of an oxide, in the present aspect 1.
[0056] A third aspect of the present disclosure is a sputtering target in which the insulator is a compound comprising at least one of lithium or sodium, in the first or second aspect described above.
[0057] Aspect 4 of the present disclosure is a sputtering target for forming a solid electrolyte having at least one of lithium-ion conductivity or sodium-ion conductivity by sputtering, as described in any of aspects 1 to 3 above.
[0058] Aspect 5 of the present disclosure is a sputtering target in any of aspects 1 to 4 above, wherein the first region is formed as a porous body, and the insulator supported in the voids of the porous body constitutes the second region.
[0059] Aspect 6 of the present disclosure is a sputtering apparatus comprising a plasma chamber in which plasma is generated, a gas line for introducing oxygen gas into the plasma chamber, and a sputtering target arranged in the plasma chamber according to any of the above aspects 1 to 5.
[0060] Aspect 7 of the present disclosure is a sputtering apparatus in which, in aspect 6 above, the apparatus further comprises an antenna provided outside the plasma chamber for generating electromagnetic waves to be introduced into the plasma chamber.
[0061] Aspect 8 of the present disclosure is a sputtering film deposition method in which a sputtering target having regions composed of a single carbon element mixed with regions composed of an insulator is exposed to an oxygen-containing plasma to oxidize and gasify the carbon contained in the sputtering target, while the sputtered insulator is deposited on a substrate to form a film made of the insulator.
[0062] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.
[0063] 1. Sputtering apparatus 10, 11. Sputtering targets 10C, 11C 1st region 10M, 11F 2nd region 20. Plasma chamber 30. Plasma generation mechanism 31. Backing plate 32. Housing 33. Coolant path 34. Magnet 35. Insulating flange 36. Anode 39. Power supply for target 41. Stage 42. Holder 51. Antenna 59. Power supply for antenna 61. Gas line W. Workpiece (substrate)
Claims
1. A sputtering target in which a first region composed of elemental carbon is mixed with a second region composed of an insulator.
2. The sputtering target according to claim 1, wherein the insulator is made of an oxide.
3. The sputtering target according to claim 1, wherein the insulator is made of a compound containing at least one of lithium or sodium.
4. The sputtering target according to claim 1 for forming a solid electrolyte having at least one of lithium-ion conductivity or sodium-ion conductivity by sputtering.
5. The sputtering target according to claim 1, wherein the first region is formed as a porous body, and the insulator supported in the voids of the porous body constitutes the second region.
6. A sputtering apparatus comprising: a plasma chamber in which plasma is generated internally; a gas line for introducing oxygen gas into the plasma chamber; and a sputtering target according to any one of claims 1 to 5, disposed within the plasma chamber.
7. The sputtering apparatus according to claim 6, further comprising an antenna provided outside the plasma chamber for generating electromagnetic waves to be introduced into the plasma chamber.
8. A sputtering film deposition method comprising exposing a sputtering target, in which regions composed of elemental carbon are mixed with regions composed of an insulator, to an oxygen-containing plasma to oxidize and gasify the carbon contained in the sputtering target, while depositing the sputtered insulator onto a substrate to form a film made of the insulator.