Sputtering target, sputtering apparatus, and sputtering film deposition method

Abstract

This effectively reduces the possibility of damage to the sputtering target during the film deposition process. [Solution] The sputtering target (10) has a first region (10C) made of elemental carbon mixed with a second region (10M) made of an insulator.

Description

Technical Field

[0001] The present invention relates to a sputtering target, a sputtering apparatus, and a sputtering film formation method.

Background Art

[0002] A sputtering film formation method for forming an insulating film on a substrate by sputtering a target made of an insulator is known. In addition, a technique for a target made of magnesium oxide that can suppress the occurrence of damage to the target during film formation has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The prior art of Patent Document 1 attempts to alleviate the thermal shock during film formation and suppress the occurrence of damage to the target by adhering a heat insulating portion to the cathode electrode side of the target. However, it is expected to realize a sputtering method for an insulator that can more effectively reduce the possibility of damage to the target during film formation.

[0005] One aspect of the present invention has been made in view of the above problems, and an object thereof is to realize a sputtering film formation method that can effectively reduce the possibility of damage to the sputtering target during the film formation process.

Means for Solving the Problems

[0006] In order to solve the above problems, one aspect of the present disclosure is a sputtering target in which a first region composed of single 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. [Effects of the Invention]

[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. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a schematic configuration of a sputtering apparatus according to an embodiment of the present invention. [Figure 2] This is a schematic diagram showing a sputtering target according to Embodiment 1. [Figure 3] This is a schematic diagram showing a sputtering target according to Embodiment 2. [Modes for carrying out the invention]

[0011] [Embodiment 1] <Configuration of the sputtering apparatus> Figure 1 is a diagram showing a schematic configuration of a sputtering apparatus 1 according to an embodiment of this 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 around 0.1 Pa to 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 may be configured to have a bias voltage applied to it.

[0016] Generally, the sputtering target 10 held by the backing plate 31 is positioned above the workpiece W on the stage 41, and the sputtering apparatus 1 is configured such that the main surfaces of the backing plate 31 and the stage 41 facing the inside of the plasma chamber 20 are horizontal. Therefore, in the embodiments, when referring to the horizontal direction, the vertical direction, or up and down, these terms may be used on the premise that each part of the sputtering apparatus 1 is arranged in such a direction.

[0017] However, regarding the application of the present invention, the arrangement of each part of the sputtering apparatus 1 is not necessarily limited to such a case. 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 for generating 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 target power supply 39.

[0019] The backing plate 31 is a conductive plate-like member and is attached near the center of the upper wall surface of the plasma chamber 20 via the insulating flange 35. The insulating flange 35 serves to fix the backing plate 31 to the plasma chamber 20 while maintaining the vacuum inside the plasma chamber 20 and insulating it from the plasma chamber 20.

[0020] On the surface (upper surface) of the backing plate 31 opposite to the side holding the sputtering target 10, a magnet 34 for generating a magnetic field around the periphery of the sputtering target 10 and a conductive housing 32 surrounding the magnet 34 are provided. The upper 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 refrigerant path 33 through which a refrigerant (e.g., cooling water) for cooling the sputtering target 10 passes is formed between the magnet 34 and the housing 32. Further, a grounded anode 36 that covers the outer edge of the sputtering target 10 while having a gap with the sputtering target 10 is fixed to the surface of the insulating flange 35 on the plasma chamber 20 side.

[0022] When a high-frequency voltage is applied from the target power supply 39 to the sputtering target 10 through the housing 32 and the backing plate 31, the plasma source gas supplied from the gas line 61 inside the plasma chamber 20 is plasmaized. By sputtering the sputtering target 10 with the plasma thus generated, a film is formed 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 thereto.

[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 has an antenna 51 and an antenna power supply 59. The antenna 51 is arranged in parallel along a window portion 21 airtightly provided on the side wall of the plasma chamber 20 outside the plasma chamber 20. The window portion 21 is composed of a plate-like member made of an electromagnetic wave transmission material that transmits the electromagnetic wave generated by the antenna 51.

[0024] When a high-frequency current is introduced from the antenna power supply 59 into the antenna 51, an electromagnetic wave is generated from the antenna 51. Then, an induced electric field is generated inside the plasma chamber 20, and an inductively coupled plasma (ICP) is generated. That is, the antenna 51 is an ICP assist antenna that assists in the generation of plasma inside 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 thereto.

[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] Examples of such insulators include oxides called LATP, which are mainly composed of Li, Al, Ti, and PO4. For example, the composition formula Li 1+X Al X Ti 2-X The oxide may be represented by (PO4)3, and in particular may be an oxide with X=0.4, or it may be an oxide obtained by further substituting some of the elements of these compositional formulas with other elements.

[0028] Another example of such an insulator is an oxide called LLZO, which is mainly composed of Li, La, Zr, and O. An example is the composition formula Li7La3Zr2O. 12 The oxide may be represented by , or it may be an oxide in which part of the composition, for example Li or Zr, is further substituted with another element, such as Al, Ga, Ta, Nb, etc.

[0029] Figure 2 is a schematic representation of the sputtering target 10. As shown in the enlarged portion of Figure 2, the sputtering target 10 is composed of two regions. In the figure, the first region 10C is a region made of elemental carbon (C), and the second region 10M is a region made of the above-mentioned insulating material. The volume ratio of the first region 10C is preferably 1% to 40%.

[0030] In Embodiment 1, the second region 10M is the matrix of the sputtering target 10, and the first region 10C, which consists of particulate carbon, is dispersed within the second region 10M. To improve heat conduction, it is preferable that the particulate carbon is connected in contact with each other, as shown in Figure 1. However, the particulate carbon may also be scattered throughout the second region 10M.

[0031] Here, elemental carbon includes graphite, carbon fiber, carbon nanotubes, diamond, fullerenes, etc. The first region 10C, which consists of elemental carbon, may contain impurities that do not significantly impair the properties of elemental carbon, for example, impurities at an atomic ratio of 1% or less. An example of such impurities is what is generally called ash. Another example of an impurity is oxygen, which originates from the surface oxidation region of the first raw material, as described later.

[0032] The following describes an example of a method for manufacturing a sputtering target 10. The first raw material is a carbon powder, such as particulate, flaky, or fibrous material, referred to as carbon filler. Such carbon powders, referred to as carbon filler, are widely used industrially and are 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. The mixture is then 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 depositing 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 insulating material such as LATP or LLZO is sputtered from the second region 10M and adheres to the surface of the opposing workpiece W, thereby forming an insulating film.

[0038] Furthermore, argon ions and other elements 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 (CO2), etc. Therefore, the sputtered carbon atoms are hardly incorporated into the film formed on the substrate surface of the workpiece W.

[0039] 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 (CO2), etc., and removed from the sputtering target 10. As a result, sputtering of carbon atoms from the surface of the sputtering target 10 is suppressed. The gasified carbon atoms are exhausted from the plasma chamber 20 by an exhaust device.

[0040] Generally, while sputtering is in progress, ions collide with the surface of the sputtering target, causing the sputtering target to continue heating from the side exposed to the plasma chamber. Conventionally, insulating materials such as LATP and LLZO have low thermal conductivity, making it unavoidable that a large temperature difference occurs between the front and back sides of the sputtering target. Furthermore, due to the low thermal conductivity, the in-plane temperature distribution of the sputtering target during sputtering tends to be large.

[0041] Furthermore, insulating materials such as LATP and LLZO have poor sputtering efficiency and low deposition rates, requiring a long time to deposit the required film thickness, and thus the heating time tends to be prolonged. As a result, sputtering targets used for depositing insulating materials such as LATP and LLZO have been damaged due to these temperature differences and temperature distributions.

[0042] In this embodiment, a first region 10C made of carbon is dispersed throughout the sputtering target 10. The thermal conductivity of carbon is significantly higher than that of insulators such as LATP and LLZO. Therefore, thermal conductivity is improved in the sputtering target 10, and temperature differences and temperature distributions in the thickness direction within the sputtering target 10 are less likely to occur.

[0043] Therefore, according to this embodiment, the possibility of damage to the sputtering target 10 during the film deposition process caused by these factors can be effectively reduced. Moreover, as described above, the carbon in the sputtering target 10 is not incorporated into the deposited insulating film.

[0044] As mentioned above, an example was shown in which a high-frequency voltage is applied to the sputtering target 10 from the target power supply 39. However, the power supplied to the sputtering target 10 from the target power supply 39 does not necessarily have to be high-frequency power. If the sputtering target is insulating, sputtering will not proceed easily and the film deposition rate will be very small unless high-frequency power is biased to the sputtering target.

[0045] However, in this embodiment, since the sputtering target 10 is made conductive, sputtering proceeds even if the voltage applied to the sputtering target 10 is a DC voltage. In this case, the bias mechanism for the sputtering target 10, including the target power supply 39, does not need to be compatible with high frequencies, and can be made simpler than when high frequency compatibility is required.

[0046] <Variation> 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 morphology 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 a 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 insulating material. The volume ratio of the first region 11C is preferably 1% or more and 10% or less.

[0049] In Embodiment 1, 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 consists 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, ranging from 1 to 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〕 One aspect of this 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 this 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 internally, 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 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.

[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. [Explanation of Symbols]

[0063] 1. Sputtering device 10, 11 Sputtering targets 10C, 11C 1st area 10M, 11F 2nd area 20 Plasma Room 30 Plasma generation mechanism 31 Backing Plate 32 Housing 33 Refrigerant pathway 34 Magnets 35 Insulating flange 36 Anodes 39 Power supply for target 41 stages 42 holders 51 Antenna 59 Antenna power supply 61 Gas Line W - Object to be processed (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. A 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 plasma chamber in which plasma is generated inside, A gas line for introducing oxygen gas into the plasma chamber, A sputtering apparatus comprising 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 target in which regions composed of elemental carbon are mixed with regions composed of an insulator, A sputtering film deposition method comprising: exposing the sputtering target 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.

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