Yttrium sputtering target and method for manufacturing the same

Abstract

To provide a yttrium sputtering target having few particles, and enabling high-output film production.SOLUTION: In a yttrium sputtering target, an adhesion rate between a backing plate and a yttrium ingot is 90% or more. The number of pores with a diameter of 100 μm or more in the yttrium ingot part is 0.1 / cm2 or less, and a relative density is 96% or more, and further an average particle diameter (D50) of the yttrium ingot part is 3,000 μm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a yttrium sputtering target for thin film formation and a method for manufacturing the same.

Background Art

[0002] In semiconductor device manufacturing, microfabrication by dry etching using highly corrosive halogen-based gases such as fluorine-based and chlorine-based gases or their plasmas is one of the important processes. It is known that these corrosive gases and plasmas corrode and damage the components of semiconductor manufacturing equipment, and the resulting particles cause a decrease in device quality. Many components of semiconductor manufacturing equipment are consumables, and regular replacement is carried out to prevent the reduction in yield and quality due to the above damage. The downtime associated with component replacement and equipment maintenance also causes a decrease in equipment operation rate and deterioration of productivity, and in semiconductor manufacturing processes, the development of components with excellent plasma resistance and gas corrosion resistance is required.

[0003] With the miniaturization of semiconductor elements, the plasma used in the dry etching process has been densified, and yttrium oxide has attracted attention as a material that can withstand such high-density plasma. As a method for manufacturing a member containing yttrium oxide, from the viewpoints of manufacturing cost and enlargement, a method of forming a yttrium oxide film on a substrate by a spraying method as in Patent Document 1 is the mainstream as an industrial process. However, since the spraying method forms a film by melting ceramic powder and rapidly solidifying it, surface defects and voids exist on the film surface. The presence of such defects deteriorates plasma resistance and also causes the generation of particles, so a method for efficiently forming a dense yttrium oxide film is required.

[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 objective of the present invention is to provide a yttrium sputtering target that enables film deposition at high power and produces fewer particles. [Means for solving the problem]

[0008] The inventors of this invention conducted thorough research on yttrium sputtering targets and, as a result, discovered that it is possible to obtain a yttrium sputtering target that generates fewer particles, thus completing the present invention.

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

[0010] The present invention relates to a yttrium sputtering target characterized by having an adhesion rate of 90% or more between the backing plate and the yttrium ingot.

[0011] The yttrium sputtering target of the present invention is characterized by having an adhesion rate of 90% or more to the backing plate. More preferably, it is 95% or more, and even more preferably 98% or more. By achieving the above adhesion rate, the heat generated in the target during sputtering is rapidly dissipated, and even when film is deposited at high power to increase the film deposition rate, it is possible to prevent the sputtering target from overheating and the solder material from melting.

[0012] The bonding ratio between the yttrium ingot and the backing plate can be determined, for example, by ultrasonic testing. When determining the bonding ratio by ultrasonic testing, it is preferable to adjust the measurement conditions using a pseudo-defect sample in which a pseudo-void hole is provided in the center of a plate material of a predetermined size. The measurement sensitivity is adjusted so that the area of ​​the detected defect matches the area of ​​the predetermined void hole. It is preferable that the material of the pseudo-defect sample is the same as the material of the sputtering target. It is preferable that the distance from the ultrasonic incident surface to the bottom surface of the void hole in the pseudo-defect sample is the same as the distance from the ultrasonic incident surface to the bonding layer of the sputtering target.

[0013] The yttrium ingot in the yttrium sputtering target of the present invention has a pore count of 0.1 pores / cm² with a diameter of 100 μm or more. 2 Preferably, the values ​​are less than or equal to 0.01 pieces / cm², and more preferably 0.01 pieces / cm². 2 The following, and especially preferably 0.005 pieces / cm 2The following applies: If there are many pores with a diameter of 100 μm or more, it can cause abnormal discharges and particles during sputtering.

[0014] Furthermore, the relative density of the yttrium ingot portion is preferably 96% or higher, more preferably 98% or higher, more preferably 99% or higher, and particularly preferably 99.8% or higher. Below 96%, the ingots, especially large ones, are prone to cracking, making it difficult to manufacture ingots with good yield. Moreover, when high power is applied to such ingots during sputtering, cracking is likely to occur during discharge, which reduces the productivity of the film deposition process and is therefore undesirable.

[0015] The average particle size (D50) of the yttrium ingot portion is preferably 3000 μm or less, more preferably 1 μm to 2000 μm, more preferably 1 μm to 1500 μm, and particularly preferably 1 μm to 1000 μm.

[0016] In the yttrium sputtering target of the present invention, the surface roughness of the yttrium ingot is important as it relates to the surface roughness of the sputtering surface when used as a sputtering target. Preferably, the surface roughness of the sputtering surface of the yttrium ingot portion 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 emitted (erosion area). 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 arcing during film formation and abnormal discharge due to increased resistivity. By setting it 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.

[0017] Next, it is preferable that the volume resistivity of the yttrium ingot portion of the yttrium target in the present invention is 0.00001 Ω·cm or more and 1 Ω·cm or less, more preferably 0.00001 Ω·cm or more and 0.001 Ω·cm or less. Yttrium is very easy to oxidize, and oxidation naturally progresses in the atmosphere. Since yttrium oxide formed by oxidation is an insulator, it causes abnormal discharge particularly during sputter discharge such as when forming a film by DC discharge. By setting the volume resistivity within the above range, stable discharge characteristics can be obtained in any of DC sputtering, RF sputtering, and AC sputtering.

[0018] When the content of rare earth elements in the yttrium ingot portion is REwt% and the content of metal elements other than rare earths is Mwt%, 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. By reducing the amount of impurities and further purifying the purity of the yttrium sputtering target, it is possible to suppress abnormal discharge and particle generation. When making it even higher purity, the process in purification becomes complicated and the production cost becomes high, which is not preferable. The inventors of the present invention examined the correlation between the amount of impurities and discharge characteristics within the above range and determined the purity that can be suitably used in sputter film formation.

[0019] The yttrium ingot can be machined into a plate shape using a machining machine such as a surface grinding machine, cylindrical grinding machine, lathe, cutting machine, machining center, etc.

[0020] The manufacturing method of the yttrium ingot in the yttrium sputtering target of the present invention is not particularly limited. In melting and solidification for high purification 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 the hot isostatic pressing method (HIP method) to crush the pores.

[0021] The backing plate is for efficiently attaching an ingot, which is the thin film material part of the sputtering target, to the sputtering apparatus. Also, to prevent the ingot part from overheating during sputtering, the backing plate part is cooled by water cooling or the like. The material used for adhesion is indium or an indium alloy with high thermal conductivity and easy to use as solder.

[0022] Also, the material of the backing plate is not particularly limited, and copper, stainless steel, titanium, etc. can be used.

[0023] As a method for manufacturing the sputtering target of the present invention, a sputtering target can be obtained by bonding (bonding) indium solder or the like to a backing plate made of oxygen-free copper, titanium, etc. as needed.

[0024] When bonding, it is preferable to polish the yttrium ingot and promptly perform surface treatment.

[0025] The surface roughness of the yttrium ingot on the adhesion surface of the yttrium ingot and the backing plate is preferably 10 nm or more and 2 μm or less, more preferably 10 nm or more and 1 μm or less, and even more preferably 10 nm or more and 0.3 μm or less. By setting it to 2 μm or less, the specific surface area of the surface layer can be reduced, and by reducing the surface oxygen of yttrium, which is easily oxidized, peeling at the oxidized part during adhesion can be prevented. Also, in the treatment of the adhesion surface in the oxidized state, the treatment cannot be performed due to the peeling of the oxide layer, and finally the adhesion rate decreases. By setting it to 10 nm or more, the engagement between the surface and the base treatment surface is improved, the adhesion force is further enhanced, and high-power discharge becomes possible.

[0026] Furthermore, the surface of yttrium ingots oxidizes over time, and this oxide film makes adhesion to the solder difficult. Therefore, the oxide layer on the surface of the yttrium ingot should be removed before bonding, and the surface should be treated promptly. While the treatment method is not particularly limited, it is preferable to apply a metal that adheres well to the solder material through 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.

[0027] Furthermore, thin films can also be manufactured by sputtering using the obtained sputtering target. [Effects of the Invention]

[0028] The yttrium sputtering target of the present invention has a high adhesion rate to the backing plate, and when used as a sputtering target, it does not crack even under high power, making it possible to achieve high productivity. [Examples]

[0029] 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, the material was observed under an optical microscope, and the average particle size (D50) was measured using the diameter method from the resulting microstructure images. At least three arbitrary points were observed, and measurements were taken for more than 300 particles. The average value here refers to the 50% particle size. (5) Method for measuring adhesion ratio The adhesion rate was calculated by measuring it using an ultrasonic flaw detection device. (6) Measurement of surface roughness (Ra) The surface roughness Ra was measured using a surface roughness measuring device manufactured by Mitutoyo. (7) Analysis of metal impurity content The analytical data was obtained from samples cut from any part of the yttrium ingot after grinding the surface by at least 1 mm following firing.

[0030] Measurement method: Glow discharge mass spectrometry (GDMS) (Example 1) A specified yttrium ingot was prepared, and measurements were performed, yielding favorable results. The properties of the yttrium ingot are shown below. Relative density: 100.3% Pore ​​rate: 0.004 pores / cm 2 Surface roughness: 430nm (using #400 sandpaper) Before bonding, the bonding surface was polished using #400 grit sandpaper to achieve the desired surface roughness. After 1 hour, indium solder was applied using an ultrasonic soldering iron, and after surface treatment, the backing plate was bonded using indium solder.

[0031] (Examples 2-3) Yttrium ingots and yttrium sputtering targets were prepared in the same manner as in Example 1, except that the surface treatment method was changed. The characteristics of the yttrium ingots are shown in Table 1. Example 2 was treated with a #1000 grit sandpaper, and Example 3 with a #3000 grit sandpaper, resulting in the surface roughness shown in Table 1.

[0032] Furthermore, the measurement results for metal impurities are shown in Table 2. (Comparative Example 1) Comparative Example 1 was prepared in the same manner as Example 1, except that the bonding surface was polished with #80 grit sandpaper. (Comparative Example 2) After 72 hours of surface polishing of the bonding surface of the yttrium ingot, the same treatment as in Example 1 was performed.

[0033] The adhesion rates of the sputtering targets in Examples 1-3 and Comparative Examples 1-2 were measured. The adhesion rates were measured using an ultrasonic imaging inspection device (model: AT LINE, manufactured by Hitachi Construction Machinery Fine Tech Co., Ltd.) equipped with an ultrasonic flaw detector (model: I3-0508-T). Prior to measurement, a dummy sample made of the same material as the sputtering target was used, and the sensitivity was adjusted so that the area of ​​the detected defects matched the area of ​​the dummy holes in the dummy sample. The measurement conditions were as follows.

[0034] Gain (sound wave intensity): 15dB Measurement pitch: 0.61mm Echo level: ≥3.1V Ultrasound injection: Target side The adhesion rate of the sputtering target was measured using the analysis program included with the device. The measurement results are shown in Table 1.

[0035] The sputtering targets of Examples 1 to 3 were mounted in a DC sputtering apparatus to deposit yttrium films. Subsequently, annealing was performed in an oxygen atmosphere to obtain yttrium oxide films. The sputtering conditions were as follows:

[0036] Target size: Φ101.6 × 6mmt Power: 200W Spatter gas: Ar Gas pressure: 0.5 Pa Film thickness: 5 μm When the sputtering target of Comparative Example 1 was sputtered, the surface roughness of the bonding surface was large, causing peeling during the bonding process. Due to the small bonding area, heat conduction was poor, and DC discharge was not possible.

[0037] When the sputtering target of Comparative Example 2 was sputtered, delamination due to the oxide layer was assumed to occur, resulting in a low adhesion rate and inability to perform DC discharge.

[0038] Table 3 shows the number of arcing events during film deposition. Arcing was counted as the number of times the voltage dropped by 20V or more from the deposition voltage. In all three examples (1-3), the number of arcing events was low (<1 time / hour). A low number of arcing events makes it possible to reduce particle generation.

[0039] [Table 1]

[0040] [Table 2]

[0041] [Table 3]

Claims

1. The adhesion rate between the backing plate and the yttrium ingot is 90% or higher, and the number of pores with a diameter of 100 μm or more in the yttrium ingot portion is 0.1 pores / cm². ２ The following is a yttrium sputtering target characterized in that the surface roughness of the yttrium ingot on the bonding surface between the yttrium ingot and the backing plate is 10 nm or more and 2 μm or less.

2. The yttrium sputtering target according to claim 1, characterized in that the relative density of the yttrium ingot portion is 96% or more.

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

4. A yttrium sputtering target according to any one of claims 1 to 3, characterized in that the surface roughness of the sputtered surface when used as a target for the yttrium ingot portion is 10 nm or more and 2 μm or less.

5. A yttrium sputtering target according to any one of claims 1 to 4, characterized in that when the content of rare earth elements in the yttrium ingot portion is REwt%, and the content of metal elements other than rare earth elements is Mwt%, 98 ≤ 100 - RE - M < 99.

999.

6. A method for producing a yttrium oxide film, characterized by sputtering using a yttrium sputtering target according to any one of claims 1 to 5.

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