Yttrium ingot and sputtering target using the same

Abstract

To provide a yttrium ingot having reduced particles, and a sputtering target using the same.SOLUTION: In a yttrium ingot, the number of pores with a diameter of 100 μm or higher is 0.1 piece / cm2 or lower, and relative density is 96% or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a yttrium ingot for thin film formation and a sputtering target using the same. [Background technology]

[0002] In semiconductor device manufacturing, microfabrication using dry etching with highly corrosive halogen gases such as fluorine-based and chlorine-based gases, or plasmas derived from these gases, is a crucial process. These corrosive gases and plasmas are known to corrode and damage the components of semiconductor manufacturing equipment, and the resulting particles can degrade device quality. Many components of semiconductor manufacturing equipment are consumables, and periodic replacement is performed to prevent yield reduction and quality degradation due to the aforementioned damage. Downtime due to component replacement and equipment maintenance reduces equipment utilization and worsens productivity, which is a problem. Therefore, there is a need for the development of components with excellent plasma resistance and gas corrosion resistance in semiconductor manufacturing processes.

[0003] With the miniaturization of semiconductor devices, the plasma used in the dry etching process is becoming denser, and yttrium oxide is attracting attention as a material that can withstand such high-density plasma. As a method for manufacturing components containing yttrium oxide, the mainstream industrial process is to form a yttrium oxide film on a substrate by thermal spraying, as described in Patent Document 1, from the perspective of manufacturing cost and the ability to scale up the components. However, since thermal spraying involves melting ceramic powder and rapidly solidifying it to form a film, surface defects and voids exist on the film surface. The presence of such defects worsens plasma resistance and causes particle generation, so there is a need for a method to efficiently form a dense yttrium oxide film.

[0004] Here, sputtering can be mentioned as one of the thin film formation methods other than thermal spraying. In sputtering, positive ions such as Ar ions are physically collided with a target placed on the cathode, and the material constituting the target is released by the collision energy, depositing a film on a substrate placed opposite it. There are DC sputtering, RF sputtering, and AC sputtering methods. Generally, thin film formation by sputtering is possible at lower temperatures compared to thin film formation by thermal spraying, and it is thought that it is possible to suppress the generation of defects such as voids and form a denser film. Furthermore, in film formation by sputtering, it is also possible to deposit oxides and nitrides by performing film formation using reactive sputtering, in which gases such as oxygen or nitrogen are introduced into the sputtering chamber. For example, as described in Non-Patent Literature 1, it is possible to deposit a yttrium oxide film on a substrate by reactive DC sputtering, in which a yttrium target is DC discharged and oxygen is introduced into the sputtering, but the quality of the film formed differs greatly depending on the sputtering conditions. Incidentally, in Non-Patent Literature 1, a yttrium target with a purity of 99.5% is used for film deposition, but the correlation between the physical properties of the sputtering target, such as density and purity, and the sputtering characteristics, as well as the relationship with the quality of the film formed by sputtering, has not been sufficiently investigated. Therefore, further investigation is needed regarding the physical properties of the yttrium target, the sputtering characteristics, and the characteristics of the formed film. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2006-307311 [Non-patent literature]

[0006] [Non-Patent Document 1] P.Lei et al. Surface & Coatings Technology 276(2015)39-46 [Overview of the project] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide a yttrium ingot with low particle count and a sputtering target using the same. [Means for solving the problem]

[0008] The inventors of this invention conducted extensive research on yttrium ingots suitable for yttrium sputtering targets. As a result, they discovered a yttrium ingot that produces a yttrium sputtering target with minimal particle generation, thus completing the present invention.

[0009] In other words, embodiments of the present invention are as follows. (1) The number of pores with a diameter of 100 μm or more in the yttrium ingot is 0.1 pores / cm². 2 The following is a yttrium ingot characterized by having a relative density of 96% or higher. (2) The yttrium ingot according to (1), characterized in that the average particle size (D50) is 3000 μm or less. (3) The yttrium ingot according to (1) or (2), characterized in that the surface roughness of the sputtered surface when used as a target is 10 nm or more and 2 μm or less. (4) A yttrium ingot according to any one of (1) to (3), characterized in that when the content of rare earth elements is REwt%, and the content of metal elements other than rare earth elements is Mwt%, 98 ≤ 100 - RE - M < 99.999. (5) A yttrium sputtering target characterized by being made of a yttrium ingot as described in any of (1) to (4). (6) The sputtering target described in (5), comprising a packing plate and a yttrium ingot. (7) A yttrium sputtering target according to (5) or (6), characterized in that the adhesion rate between the backing plate and the yttrium ingot is 90% or more. A method for producing a yttrium oxide film, characterized by sputtering using a yttrium sputtering target described in any of (8), (5), to (7).

[0010] The present invention will be described in detail below.

[0011] The yttrium ingot of the present invention has a pore count of 0.1 pores / cm² with a diameter of 100 μm or more. 2 The following is a yttrium ingot characterized by having a relative density of 96% or higher.

[0012] The yttrium ingot of the present invention has a pore count of 0.1 pores / cm² with a diameter of 100 μm or more. 2 The following is the case, preferably 0.01 pieces / cm². 2 The following, and more preferably 0.005 pieces / cm 2 The following applies: 0.1 pores / cm² with a diameter of 100 μm or more. 2 If the amount is excessive, it can cause abnormal discharge or particles during sputtering.

[0013] Furthermore, the relative density is 96% or higher, preferably 98% or higher, more preferably 99% or higher, and even more preferably 99.8% or higher. Below 96%, particularly large ingots, they are prone to cracking, making it impossible to manufacture ingots with good yield. Moreover, when high power is applied to sputtering using such ingots, cracking is likely to occur during discharge, which reduces the productivity of the film deposition process and is therefore undesirable.

[0014] The average particle size (D50) of the yttrium ingot is 3000 μm or less, preferably 1 μm to 2000 μm, more preferably 1 μm to 1500 μm, and particularly preferably 1 μm to 1000 μm.

[0015] The surface roughness of the yttrium ingot of the present invention is important, specifically the surface roughness of the sputtering surface when used as a sputtering target. Preferably, the surface roughness of the sputtering surface when used as a target is 10 nm to 2 μm, more preferably 10 nm to 1 μm, and even more preferably 10 nm to 0.3 μm. The sputtering surface refers to the area where sputtered particles are actually released (erosion area). By setting the surface roughness to 2 μm or less, the specific surface area of ​​the surface layer is reduced, and the surface oxygen of the easily oxidized yttrium is reduced, thereby preventing arcing during film formation and abnormal discharge due to increased resistivity. Furthermore, by setting the surface roughness to 10 nm or more, it is possible to reattach the particles generated in small amounts during sputtering to the target surface, thereby suppressing particle adhesion to the film.

[0016] Next, the yttrium ingot in this invention preferably has a volume resistivity of 0.00001 Ω·cm or more and 1 Ω·cm or less, and more preferably 0.00001 Ω·cm or more and 0.001 Ω·cm or less. Yttrium is very easily oxidized, and oxidation proceeds naturally in the atmosphere. Since the yttrium oxide formed by oxidation is an insulator, it can cause abnormal discharge during sputtering, especially when forming films by DC discharge. By keeping the volume resistivity within the above range, it is possible to obtain stable discharge characteristics in DC sputtering, RF sputtering, and AC sputtering.

[0017] Next, regarding the impurity content of the yttrium ingot, when the content of rare earth elements is REwt% and the content of metal elements other than rare earth elements is Mwt%, then 98 ≤ 100-RE-M < 99.999, more preferably 99 ≤ 100-RE-M < 99.999, and even more preferably 99.9 ≤ 100-RE-M < 99.999. Reducing the amount of impurities and increasing the purity of the yttrium target makes it possible to suppress abnormal discharge and particle generation. However, increasing the purity further complicates the purification process and increases the manufacturing cost, which is undesirable. The inventors investigated the correlation between the amount of impurities and discharge characteristics within the above range and determined a purity that can be suitably used in sputter deposition.

[0018] The yttrium ingot of the present invention can be machined into a plate shape using machining machines such as a surface grinder, a cylindrical grinder, a lathe, a cutting machine, and a machining center.

[0019] The manufacturing method of the yttrium ingot of the present invention is not particularly limited. In melting and solidification for high purity such as vacuum melting and EB melting, pores with a diameter of 100 μm or more are likely to occur due to vaporization during melting, so it is difficult to obtain an ingot with few pores as it is. Therefore, it is preferable to compress the ingot produced by the melting method by hot isostatic pressing (HIP method) to crush the pores. However, since yttrium is a material that is easily oxidized, it is preferable to seal the outer periphery with a metal. The HIP temperature is preferably 1000 °C or lower. Also, since yttrium is relatively brittle, the pressure is preferably 100 MPa or lower. By doing so, it becomes possible to obtain a yttrium ingot with few pores having a diameter of 100 μm or more.

[0020] The yttrium ingot of the present invention can be used as a sputtering target made of a yttrium ingot. As a method for manufacturing the sputtering target, the sputtering target can be obtained by bonding (bonding) using indium solder or the like to a backing plate or a backing tube made of oxygen-free copper, titanium, etc. as needed. Among them, it is preferable to use a sputtering target made of a packing plate and a yttrium ingot.

[0021] The surface roughness of the yttrium ingot side of the bonding surface between the yttrium ingot and the backing plate (bonding surface roughness) is preferably 10 nm to 2 μm, more preferably 10 nm to 1 μm, and even more preferably 10 nm to 0.3 μm. By setting it to 2 μm or less, the specific surface area of ​​the surface layer is reduced, and the surface oxygen of the easily oxidized yttrium is reduced, thereby preventing delamination in the oxidized area during bonding. Furthermore, if the bonding surface is treated in an oxidized state, the treatment cannot be performed due to the peeling of the oxide layer, ultimately reducing the adhesion rate. Setting it to 10 nm or more improves the interlocking between the surface and the substrate treatment surface, further improving the adhesive strength and enabling high-power discharge.

[0022] The backing plate is used to efficiently attach the ingot, which is the thin film material portion of the sputtering target, to the sputtering apparatus. Furthermore, the backing plate is cooled by water cooling or other means to prevent the ingot from overheating during sputtering. The bonding material used is indium or indium alloy, which has high thermal conductivity and is easy to use as solder.

[0023] Furthermore, there are no particular restrictions on the material of the backing plate; copper, stainless steel, titanium, etc., can be used.

[0024] Furthermore, in a sputtering target consisting of a packing plate and a yttrium ingot, the adhesion rate between the yttrium ingot and the backing plate is 90% or higher, more preferably 95% or higher, and even more preferably 98% or higher. By achieving the above adhesion rate, the heat generated on the target during sputtering is quickly dissipated, preventing the sputtering target from overheating and causing the solder material to melt.

[0025] When bonding, it is preferable to polish the yttrium ingot and promptly perform surface treatment. Over time, the surface of the yttrium ingot oxidizes, and this oxide film makes adhesion with the solder material difficult. Therefore, the oxide layer on the yttrium surface should be removed before bonding, and surface treatment should be performed promptly. The treatment method is not particularly limited, but it is preferable to apply a metal that adheres well to the solder material by vapor deposition, plating, or treatment with an ultrasonic soldering iron. This allows the solder and yttrium to bond without delamination. Preferably, the time from oxide treatment to surface treatment should be within 3 hours.

[0026] Furthermore, thin films can also be manufactured by sputtering using the obtained yttrium sputtering target. [Effects of the Invention]

[0027] The yttrium ingot of the present invention has high strength, and when used as a sputtering target, it does not crack even under high power, enabling high productivity. [Examples]

[0028] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The measurements in these examples were performed as follows. (1) Relative density The relative density was determined by measuring the bulk density using the Archimedes method in accordance with JIS R 1634, and the true density of metallic yttrium (4.47 g / cm³) was used. 3 The relative density was calculated by dividing by ). (2) Measurement of pore ratio The overall image was measured using X-ray transmission imaging, and pores larger than 100 μm were extracted and their number and size were measured. The number of pores / cm² was then calculated from the measured area. 2 It was converted to [a certain value]. (3) Volume resistivity The result was obtained by measuring at three or more locations using the four-probe method and averaging the results. (4) Average particle diameter (D50) After mirror polishing and electrolytic etching, observation was carried out with an optical microscope, and the average particle diameter (D50) was measured by the diameter method from the obtained tissue image. At least three arbitrary points or more were observed, and measurements were made on 300 or more particles. The average value here refers to the 50% particle diameter. (5) Measurement method of adhesion rate Measurement was carried out with an ultrasonic flaw detector, and the adhesion rate was calculated. (6) Measurement of surface roughness (Ra) Using a surface roughness measuring device manufactured by Mitutoyo, the surface roughness Ra was measured. (7) Analysis of the amount of metal impurities The analysis value of a sample cut out from an arbitrary part after grinding 1 mm or more from the surface of the yttrium ingot after firing was used as measurement data.

[0029] Measurement method: Glow discharge mass spectrometry (GDMS) (Example 1) A yttrium ingot subjected to pore reduction treatment was prepared and measured, and good results were obtained. The yttrium ingot characteristics are shown below.

[0030] Relative density: 100.3% Pore rate: 0.004 pieces / cm 2 Surface roughness: 430 nm (using a #400 file) Before bonding, the bonding surface was surface polished using a #400 file to a predetermined surface roughness, and after one hour, indium solder was applied using an ultrasonic soldering iron and surface treatment was performed.

[0031] (Examples 2 - 3) Yttrium ingots and yttrium targets were produced in the same manner as in Example 1 except that the method of surface treatment was changed. The ingot characteristics of yttrium are shown in Table 1. Example 2 was carried out with a #1000 file, and Example 3 was carried out with a #3000 file, resulting in the surface roughness shown in Table 1. (Comparative Example 1) A predetermined yttrium ingot was prepared and the same treatment as in Example 1 was carried out except that pore reduction treatment was not performed. The characteristics of the obtained ingot are shown in Table 1. (Comparative Example 2) Yttrium ingots were fabricated by thermal spraying. The properties of the obtained ingots are shown in Table 1.

[0032] [Table 1]

Claims

1. The number of pores with a diameter of 100 μm or more in the yttrium ingot is 0.1 pores / cm². ２ A yttrium ingot characterized by having the following characteristics: a relative density of 96% or more, and when the content of rare earth elements is REwt%, and the content of metal elements other than rare earth elements is Mwt%, then 98 ≤ 100 - RE - M < 99.

999.

2. The yttrium ingot according to claim 1, characterized in that the average particle size (D50) is 3000 μm or less.

3. The yttrium ingot according to claim 1 or 2, characterized in that the number of pores with a diameter of 100 μm or more in the yttrium ingot is 0.01 pores / cm² or less.

4. A yttrium ingot according to any one of claims 1 to 3, characterized in that its relative density is 98% or higher.

5. A yttrium sputtering target characterized by being made of a yttrium ingot according to any one of claims 1 to 4.

6. The sputtering target according to claim 5, comprising a packing plate and a yttrium ingot.

7. The yttrium sputtering target according to claim 5 or 6, characterized in that the adhesion rate between the backing plate and the yttrium ingot is 90% or more.

8. A method for producing a yttrium oxide film, characterized by sputtering using a yttrium sputtering target according to any one of claims 5 to 7.

Images