Ceramics for a hearth liner and a hearth liner

Abstract

To provide a ceramic for a hearth liner that has a high-melting point, a high stiffness and a low thermal conductivity and is excellent in thermal-shock resistance.SOLUTION: A ceramic used for a hearth liner fitted to an electron beam heating crucible includes, by mass, 15.0-55.0% BN, one or more selected from 5.0-55.0% Si3N4 and 5.0-60.0% ZrO2, and 0-25.0% SiC, and has a porosity of 0.1% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to ceramics for a hearth liner and a hearth liner.

Background Art

[0002] When producing thin films of metals, ceramics, etc., an electron beam is irradiated onto a deposition material by a vacuum evaporation method, an ion plating method, etc. to heat and evaporate the thin film raw material, and film formation is performed on a substrate or the like. The deposition material is usually accommodated in a hearth liner disposed on a crucible (hearth) of an electron gun.

[0003] The roles of the hearth liner are mainly twofold. The first is to keep the inside of the hearth clean, facilitate cleaning, and reduce contamination by suppressing the welding and alloying of the deposition material to the crucible. The second is to easily raise the temperature of the deposition material by thermally insulating between the copper-made and constantly cooled hearth and the deposition material, thereby reducing energy loss.

[0004] As the material of the hearth liner, an appropriate one is selected from the viewpoints of reactivity (difficulty in alloying) with the deposition material, wettability, etc.

[0005] For example, Patent Document 1 discloses a hearth liner made of a material containing carbon, boron nitride, molybdenum, tungsten, tantalum, etc. Further, Patent Document 2 discloses a hearth liner formed of silicon nitride-based ceramics.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] For example, metal materials such as molybdenum and tungsten both have high melting points, so they have the advantage of being difficult to deform or melt. However, since these metal materials have high thermal conductivity and low heat insulation properties, it is difficult to evaporate a vapor deposition material with high thermal conductivity. Therefore, for a hearth liner using these metal materials, even if the output of the electron beam is increased, the vapor deposition material cannot be uniformly melted and evaporated, and there is a demerit that continuous film formation is difficult. In addition, since these metal materials may form an alloy with a low melting point such as Al, there are cases where the shape as a hearth liner cannot be maintained. The same applies when using tantalum with low thermal conductivity.

[0008] In the case of a hearth liner using carbon and boron nitride, since the strength is low, it cannot be used repeatedly. Also, in the case of a hearth liner using alumina, the thermal shock resistance is low, and it is damaged by heating with an electron beam and cooling after treatment, and cannot be used repeatedly. Silicon nitride-based ceramics have a problem that the cost of processing into a hearth liner shape is high because they are materials with high hardness and difficult to machine.

[0009] An object of the present invention is to provide ceramics for a hearth liner and a hearth liner that have a high melting point, high strength, low thermal conductivity, and excellent thermal shock resistance.

Means for Solving the Problems

[0010] The present inventors conducted a detailed study on the thermal shock resistance characteristics when using ceramics containing BN for a hearth liner, and obtained the following findings.

[0011] (A) For a hearth liner when forming a thin film of a vapor deposition material with high thermal conductivity such as aluminum, it is required to have a high melting point, high strength, low thermal conductivity, and excellent thermal shock resistance characteristics.

[0012] (B) Although BN has the property of excellent thermal shock resistance, it has a problem of low strength.

[0013] (C) Adding an appropriate amount of Si 3 N 4 and / or ZrO 2 to BN can increase the flexural strength. In particular, Si 3 N 4 has a high flexural strength and a low coefficient of thermal expansion, so it can enhance the thermal shock resistance. Also, ZrO 2 can reduce the volume resistivity at high temperatures, thus preventing the charging of the hearth liner.

[0014] (D) Generally, BN-based ceramics have high thermal conductivity, and ceramics with low Young's modulus and coefficient of thermal expansion are excellent in thermal shock resistance. However, even for ceramics with excellent thermal shock resistance, when the hearth liner manufactured using them is repeatedly used, damage may occur at an early stage. As a result of the inventors' detailed examination of such ceramics that were damaged at an early stage, it was found that the cause of the damage lies in the pores of the ceramics. That is, even if it is a BN-based ceramic generally considered to have excellent thermal shock resistance, when used as a hearth liner, the evaporated material that has melted enters the pores, and during heating and cooling, due to the difference in the coefficient of thermal expansion between the material constituting the hearth liner and the metal that has entered the pores of the hearth liner, thermal stress is generated and leads to damage.

[0015] The present invention has been made based on the above findings, and the gist of the invention is as follows. (1) Ceramics used for a hearth liner attached to a crucible for electron beam heating, by mass%, BN: 15.0 to 55.0%, and Si 3 N 4 : 5.0 to 55.0% and ZrO 2 : one or more selected from 5.0 to 60.0%, and SiC: 0 to 25.0%, and containing Ceramics for a hearth liner with a porosity of 0.1% or less. Ceramics for a hearth liner.

[0016] (2) By mass, MgO, Y 2 O 3 , CeO 2 , CaO, HfO 2 , TiO 2 , Al 2 O 3 , SiO 2 , MoO 3 , CrO, CoO, ZnO, Ga 2 O 3 , Ta 2 O 5 , NiO and V 2 O 5 Containing one or more selected from: 5.0 to 15.0% The ceramics for a hearth liner according to (1) above.

[0017] (3) The three-point bending strength measured by a method conforming to JIS R1601 is 200 MPa or more, the impact temperature ΔT at which no decrease in the residual bending strength measured by a method conforming to JIS R1648 is observed is 600 °C or more, and the thermal conductivity measured by a method conforming to JIS1611 is 10 to 80 W / (m·K). The ceramics for a hearth liner according to (1) or (2) above.

[0018] (4) A hearth liner using any of the ceramics according to (1) to (3) above. A hearth liner.

[0019] (5) The hearth liner according to (4) above, wherein the hearth liner contains a vapor deposition material having a thermal conductivity of 100 W / (m·K) or more. The hearth liner according to (4) above.

[0020] (6) The hearth liner according to (5) above, wherein the vapor deposition material is Al. The hearth liner according to (5) above.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide ceramics for a hearth liner and a hearth liner that have a high melting point, high strength, low thermal conductivity, and excellent thermal shock resistance.

Brief Description of the Drawings

[0022]

Figure 1

Embodiments for Carrying Out the Invention

[0023] 1. Hearth Liner The hearth liner according to the present embodiment is, for example, a hearth liner disposed on the crucible (hearth) of an electron gun that accommodates a thin film raw material (evaporation material) that is heated and evaporated by irradiating an electron beam in a vacuum evaporation method, an ion plating method, or the like.

[0024] Examples of the evaporation material include those having a thermal conductivity of 100 W / (m·K) or more. For example, Au, Ag, Al, Cu, Mg, Mo, W, etc. The hearth liner according to the present embodiment has sufficient heat insulation properties, can be efficiently melted, and has excellent thermal shock resistance. Therefore, even when repeatedly used for melting evaporation materials having a high thermal conductivity as described above, uniform melting can be maintained, and it has excellent durability. Since these evaporation materials have a high thermal conductivity of 100 W / (m·K) or more, excellent heat insulation properties are required for the hearth liner.

[0025] 2. Ceramics for Hearth Liner The ceramics for a hearth liner according to the present embodiment contains, by mass%, BN: 15.0 to 55.0%, Si 3 N 4 : 5.0 to 55.0% and ZrO 2 : one or more selected from 5.0 to 60.0%, and SiC: 0 to 25.0%. Hereinafter, the reasons for limiting the content of each component will be described.

[0026] (BN: 15.0 to 55.0%) BN has the property of excellent thermal shock resistance. In order to obtain sufficient thermal shock resistance as the ceramics for the hearth liner, it is necessary to contain 15.0% or more of BN. However, when the content exceeds 55.0%, even if one or more selected from Si 3 N 4 and ZrO 2 are contained, sufficient flexural strength cannot be obtained. Therefore, the content of BN is set to 15.0 - 55.0%. The lower limit is preferably 20.0%, more preferably 25.0%, and even more preferably 30.0%. The upper limit is preferably 50.0%, and more preferably 45.0%.

[0027] Note that as BN, there are those having a hexagonal or cubic crystal structure. Cubic BN is a hard material and difficult to machine, so it increases the processing cost for the shape of the hearth liner. Therefore, it is preferable to use hexagonal BN which is soft and easy to machine.

[0028] (Si 3 N 4 : 5.0 - 55.0% and ZrO 2 : one or more selected from 5.0 - 60.0%) Si 3 N 4 and ZrO 2 are effective in imparting a high flexural strength of 200 MPa or more to the ceramics, so it is necessary to contain one or both of them.

[0029] In particular, Si 3 N 4 is good to contain 5.0% or more in order to impart high thermal shock resistance in addition to the effect of imparting high flexural strength to the ceramics. However, when the content of Si 3 N 4 exceeds 55.0%, it becomes too hard and difficult to process into the hearth liner. Therefore, Si 3 N 4The content shall be 5.0 to 55.0%. The lower limit is preferably 10.0% and more preferably 15.0%. The upper limit is preferably 50.0% and more preferably 45.0%.

[0030] On the other hand, ZrO 2 In addition to the effect of imparting high flexural strength to the ceramics, it can reduce the volume resistivity at high temperatures. Therefore, there is an advantage that the charging of the hearth liner can be suppressed and the occurrence of irradiation defects of the electron beam can be suppressed. Also, since ZrO 2 has a low thermal conductivity, there is also an advantage that it facilitates the temperature rise of the vapor deposition material during use. Therefore, when containing ZrO 2 , it is good to contain 5.0% or more. However, when the content of ZrO 2 exceeds 60.0%, the thermal expansion coefficient becomes too high and the thermal shock resistance deteriorates. Therefore, the content of ZrO 2 shall be 5.0 to 60.0%. The lower limit is preferably 10.0% and more preferably 15.0%. The upper limit is preferably 55.0%, more preferably 50.0%, and even more preferably 45.0%.

[0031] Note that as ZrO 2 , there are those having a monoclinic, tetragonal or cubic crystal structure. Generally, in order to impart high strength to ZrO 2 ceramics, tetragonal ZrO 2 in which several percent of an oxide is solid-solved is preferably used. However, this tetragonal ZrO 2 undergoes a phase transition to a monoclinic phase when exposed for a long time even at a low temperature (less than 200 °C), and the dimensions of the ceramics change during this phase transition. This phase transition progresses, for example, at 40 °C or higher and more significantly at 150 °C or higher. Therefore, when such ceramics are used in a hearth liner, shape defects may occur due to phase transformation during electron beam irradiation. For this reason, as ZrO 2 , it is more preferable to use cubic ZrO 2 that does not undergo a phase transition, that is, does not change in dimensions, at the use temperature. Note that cubic ZrO 2It contains elements such as about 3 mol% of Y, but the content of ZrO 2 also includes the amounts of these elements. However, since monoclinic ZrO 2 has lower strength than tetragonal or cubic ZrO 2 , even when the crystal structure contains monoclinic, the proportion is preferably 50% or less, more preferably 10% or less, and may be 0%.

[0032] (SiC: 0 to 25.0%) In SiC, which is a composite of one or more selected from BN, Si 3 N 4 and ZrO 2 , the volume resistivity can be lowered without significantly degrading the basic performance. Therefore, SiC may be contained. The above effects can be obtained even with a small amount of addition, but become significant when the content is 10.0% or more. However, when the content of SiC exceeds 25.0%, the flexural strength decreases. Thus, SiC may be contained, but its content should be 25.0% or less. The lower limit is preferably 12.0%, more preferably 15.0%. The upper limit is preferably 22.0%, more preferably 20.0%.

[0033] (Other components) The ceramics for the hearth liner according to this embodiment may contain 5.0 to 15.0% of a sintering aid in addition to the above components. Oxides that can be used as the sintering aid include MgO, Y 2 O 3 , CeO 2 , CaO, HfO 2 , TiO 2 , Al 2 O 3 , SiO 2 , MoO 3 , CrO, CoO, ZnO, Ga 2 O 3 , Ta 2 O 5 , NiO and V 2 O 5One or more selected from are exemplified. Since these oxides can promote densification by forming a liquid phase during firing, they are effective in reducing the porosity, and because their thermal conductivity is lower than that of BN, they contribute to low thermal conductivity. In order to obtain these effects, the total content of these oxides is preferably 5.0% or more. However, when the total content of these oxides is excessive, it causes a decrease in flexural strength, so it is preferably 15.0% or less. The lower limit is preferably 6.0%, more preferably 7.0%. The upper limit is preferably 12.0%, more preferably 10.0%.

[0034] In the ceramics for a hearth liner according to the present embodiment, in addition to the above compounds, compounds such as AlN, Yb 2 O 3 , TiN, TiC, WC may be included, but the content of these components (the balance) is preferably 5.0% or less, more preferably 3.0% or less, and may even be 0%. That is, the total content of the above compounds may be 100%. The content (% by mass) of each component can be measured by ICP emission spectrometry.

[0035] (Typical example) The ceramics for a hearth liner according to the present embodiment have the above components, but among Si 3 N 4 and ZrO 2 , Si 3 N 4 is a component particularly effective for obtaining thermal shock characteristics (specifically, the shock temperature ΔT is 800 °C or higher), and its effect becomes remarkable when the content is 20.0% or more. Therefore, ceramics containing 20.0% or more of Si 3 N 4 are suitable for use in a hearth liner for vapor deposition of a material with a high melting point (melting point: 1000 °C or higher) such as Cu. On the other hand, ZrO 2It can reduce the volume resistivity at high temperatures and can also reduce the thermal conductivity (specifically, 50 W / (m·K) or less). Therefore, it has the merit of preventing the charging of the hearth liner and facilitating the temperature rise of the vapor deposition material. The effect becomes remarkable when the content is 20.0% or more. For this reason, in particular, the ceramics for hearth liners used for vapor deposition of high-melting-point materials preferably have the following component (A), and the ceramics for hearth liners that require improvement in electron beam irradiation accuracy and energy-saving effects preferably have the following component (B). Note that the sintering aid and the balance are the same as the examples shown above. (A) By mass, BN: 15.0 to 55.0% and, Si 3 N 4 : 20.0 to 55.0% and, ZrO 2 : 0 to 60.0% and, SiC: 0 to 25.0%, a component containing. (B) By mass, BN: 15.0 to 55.0% and, Si 3 N 4 : 0 to 55.0% and, ZrO 2 : 20.0 to 60.0% and, SiC: 0 to 25.0%, a component containing.

[0036] (Porosity) The ceramics according to this embodiment not only have sufficient thermal shock resistance characteristics when used for the hearth liner, but it is also important that the hearth liner is not easily damaged even when used repeatedly. BN-based ceramics manufactured by a normal manufacturing method have the demerit that when used as a hearth liner, the melted evaporation material enters the pores, and due to the difference in thermal expansion coefficients during heating and cooling, thermal stress is generated and it leads to breakage. In the ceramics according to this embodiment, the porosity needs to be 0.1% or less. Note that the porosity is measured according to JIS R1634.

[0037] (Particle size) Regarding the above compound, when its particle size is large, it reduces the flexural strength. Therefore, it is preferably as small as possible, preferably with an average particle size of 5.0 μm or less, more preferably an average particle size of 3.0 μm or less, and even more preferably an average particle size of 2.0 μm or less.

[0038] (Flexural strength) The ceramics according to this embodiment are required to have sufficient mechanical properties when used for a hearth liner. For this reason, based on the three-point flexural strength measured by a method conforming to JIS R1601 being 200 MPa or more, it is more preferably 400 MPa or more.

[0039] (Thermal shock resistance) The ceramics according to this embodiment are required to have sufficient thermal shock resistance when used for a hearth liner. For this reason, based on the shock temperature ΔT at which no decrease in the residual flexural strength is observed, measured by a method conforming to JIS R1648, being 600 °C or more, it is more preferably based on 800 °C or more.

[0040] (Thermal conductivity) The ceramics according to this embodiment are required to have a sufficiently low thermal conductivity when used for a hearth liner. For this reason, based on the thermal conductivity measured by a method conforming to JIS1611 being 10 - 80 W / (m·K), it is more preferably based on 10 - 40 W / (m·K).

[0041] (Vickers hardness) The ceramics according to this embodiment are required to have a sufficiently low hardness from the viewpoint of ease of processing into a hearth liner. For this reason, based on the Vickers hardness measured by a method conforming to JIS1610 being 1.0 - 8.0 GPa. With such hardness, it becomes possible to process the hearth liner shape by dry cutting instead of wet processing using a diamond tool.

[0042] 3. Method for manufacturing ceramics and hearth liners Hereinafter, an example of the method for manufacturing ceramics according to the present invention will be described.

[0043] Sintering raw material powder such as BN powder is mixed with a sintering aid by a known method such as a ball mill. That is, in a container, it is mixed with each powder, a solvent, and ceramic or resin balls with cores to form a slurry. At this time, water or alcohol can be used as the solvent. Furthermore, additives such as a dispersant or a binder may be used as necessary. Note that, as the sintering raw material powder such as BN powder, those having an average particle size of 0.5 to 3.0 μm were used.

[0044] The obtained slurry is granulated by a known method such as spray drying or a vacuum evaporator. That is, it is spray-dried with a spray dryer to granulate or dried with a vacuum evaporator to powderize.

[0045] The obtained powder is sintered under high temperature and high pressure by a known method such as hot pressing or HIP (hot isostatic pressing) to obtain a ceramic sintered body. In the case of hot pressing, it may be fired in a nitrogen atmosphere. Also, the firing temperature is preferably in the range of 1300 to 1900 °C. If the temperature is too low, sintering will be insufficient, and if it is too high, problems such as elution of oxide components will occur.

[0046] The applied pressure is suitably in the range of 25 to 50 MPa. Also, the duration of the applied pressure depends on the temperature and dimensions, but is usually about 1 to 4 hours. Also, in the case of HIP, the firing conditions such as temperature and applied pressure may be set appropriately. However, known firing methods such as normal pressure firing method or atmosphere pressure sintering method cannot be adopted. This is because the porosity of the obtained ceramics cannot be made 0.1% or less.

[0047] The obtained ceramics are processed into a predetermined shape by dry cutting using a superhard tool such as WC.

Example

[0048] To confirm the effects of the present invention, the sintering raw material powder and the sintering aid were mixed at the compounding ratios shown in Table 1 together with water, a dispersant, a resin, and ceramic balls, and the resulting slurry was spray-dried with a spray dryer to form granules. The obtained granules were filled into a graphite die, and hot press (HP) firing was performed at 1800 °C for 2 hours at various pressures in a nitrogen atmosphere to obtain a test piece with dimensions of 150 mm in length × 150 mm in width × 30 mm in thickness.

[0049] Test pieces were sampled from the obtained test pieces and various tests were conducted. The results are also shown in Table 2.

[0050] <Porosity> The porosity was measured according to JIS R1634.

[0051] <Flexural strength> The three-point bending strength was measured by a method conforming to JIS R1601. It is based on being 200 MPa or more.

[0052] <Thermal shock resistance> The shock temperature ΔT at which no decrease in the residual flexural strength was observed was measured by a method conforming to JIS R1648. It is based on being 600 °C or more.

[0053] <Thermal conductivity> The thermal conductivity was measured by a method conforming to JIS1611. It is based on being 10 to 80 W / (m·K).

[0054] <Vickers hardness> The Vickers hardness was measured by a method conforming to JIS1610. It is based on being 1.0 to 8.0 GPa.

[0055] A hearth liner was obtained by dry cutting using a WC tool from a part of the obtained test piece. For each hearth liner, the possibility of uniform dissolution of the evaporation material and the presence or absence of breakage when repeatedly used were confirmed. These results are also shown in Table 2.

[0056] Note that "uniform dissolution" in Table 2 indicates the possibility of uniform dissolution of the evaporation materials (Al, Cu). When each evaporation material could be uniformly dissolved, it was evaluated as ○, and when it could not, it was evaluated as ×. Also, "repeated use test" in Table 2 shows the results of investigating the presence or absence of breakage when repeatedly used 10 times as a hearth liner. When it broke within less than 5 uses, it was evaluated as ×, when it broke after 5 or more uses, it was evaluated as ○, and when it did not break even after 10 uses, it was evaluated as ◎.

[0057]

Table 1

[0058]

Table 2

[0059] As shown in Tables 1 and 2, for Nos. 1 to 6, ceramics having the components defined in the present invention and having sufficiently high bending strength and thermal shock resistance were obtained. Since these ceramics have a sufficiently low thermal conductivity, uniform dissolution is possible, and since they have a sufficiently low hardness, they are excellent in workability. Since the porosity of these ceramics is sufficiently low, the hearth liners manufactured using them were less likely to break even when repeatedly used.

[0060] On the other hand, No. 7 had the components defined in the present invention, and thus had the desired bending strength, thermal shock resistance, thermal conductivity, and hardness. However, since the porosity was as high as 0.4%, the hearth liner manufactured using this ceramic broke at an early stage when repeatedly used.

[0061] Nos. 8 to 19 had the components defined in the present invention, but the pressure during hot pressing was too small, resulting in a high porosity and insufficient bending strength. In particular, for Nos. 14 to 19 that were hot pressed at normal pressure, the shape was unstable and the test could not be performed.

[0062] Nos. 20 to 26 are all examples that do not satisfy the components defined in the present invention, and one or more of the performances of bending strength, thermal shock resistance, thermal conductivity, and hardness did not meet the desired conditions. In particular, in No. 21, although the thermal shock characteristics as ceramics are high, the bending strength is low. Therefore, in the hearth liner using this, it was damaged at an early stage when repeatedly used. Also, in Nos. 22 to 26, uniform dissolution could not be achieved.

[0063] Table 3 shows the results (Nos. 27 and 28) of manufacturing ceramics by the same method as in Nos. 1 and 2, except that starting material powder with a large average particle size of 3.0 to 6.0 μm was used, in order to show the difference in bending strength due to the difference in average crystal grain size.

[0064]

Table 3

[0065] As shown in Table 3, it can be seen that even for ceramics with the same components, the bending strength decreases as the average particle size increases.

[0066] FIG. 1 shows the relationship between the impact temperature ΔT (°C) and the residual bending strength for Nos. 1, 2, and 20. As shown in FIG. 1, the bending strength of No. 20 is superior to that of No. 1 when the impact temperature ΔT is 0°C, but is much lower than that of No. 1 when the impact temperature ΔT is 400°C. That is, No. 20 is not suitable for use in a hearth liner that repeatedly undergoes rapid temperature increases and decreases. On the other hand, No. 1 can maintain a bending strength of about 250 MPa when the impact temperature ΔT is between 0 and 600°C. No. 2 can maintain a bending strength of about 460 MPa when the impact temperature ΔT is between 0 and 1000°C.

Industrial Applicability

[0067] According to the present invention, it is possible to provide ceramics for a hearth liner and a hearth liner that have a high melting point, high strength, low thermal conductivity, and excellent thermal shock resistance.

Claims

1. A ceramic used for a hearth liner attached to a crucible for electron beam heating, by mass%, BN: 15.0 to 55.0%, Si ３ N ４ : 5.0 to 55.0% and ZrO ２ : one or more selected from 5.0 to 60.0% and, SiC: 0 to 25.0%, and contains, the total content of BN, Si₃N₄, ZrO₂ and SiC is 80% or more, the porosity is 0.1% or less, a ceramic for a hearth liner.

2. by mass%, MgO, Y ２ O ３ , CeO ２ , CaO, HfO ２ , TiO ２ , Al ２ O ３ , SiO ２ , MoO 3 , CrO, CoO, ZnO, Ga ２ O ３ , Ta ２ O ５ , NiO and V ２ O ５ selected from one or more of: containing 5.0 to 15.0% the ceramic for a hearth liner according to Claim 1.

3. The three-point bending strength measured by a method conforming to JIS R1601 is 200 MPa or more, and the impact temperature ΔT at which no decrease in the residual bending strength is observed, measured by a method conforming to JIS R1648, is 600 °C or more, and the thermal conductivity measured by a method conforming to JIS 1611 is 10 to 80 W / (m·K), the ceramic for a hearth liner according to Claim 1 or 2.

4. Using any of the ceramics described in Claims 1 to 3, a hearth liner.

5. the hearth liner contains a vapor deposition material having a thermal conductivity of 100 W / (m·K) or more, the hearth liner according to Claim 4.

6. the vapor deposition material is Al, the hearth liner according to Claim 5.

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