Ceramic base and method for manufacturing the same

Abstract

Disclosed are a ceramic base and a method for manufacturing the same, the ceramic base being excellent in volume resistance at high temperature and thermal conductivity at normal temperature, compared to a general ceramic base. The ceramic base contains alumina (Al2O3) and aluminum nitride (AlN), and does not contain a second phase including an aluminum oxynitride phase (AlON phase).

Description

Technical Field

[0001] This invention relates to a ceramic base and its manufacturing method, and more specifically to a ceramic base and its manufacturing method that are superior to conventional ceramic bases, particularly in terms of volume resistivity at high temperatures and thermal conductivity at room temperature. Background Technology

[0002] With the increasing miniaturization and high integration of semiconductor processes, the use of high-power plasma is inevitable. Therefore, vacuum plasma equipment utilizing high-temperature plasma is widely used in the etching of semiconductor devices and other processes for achieving ultra-fine shapes. Examples of such vacuum plasma equipment include: PECVD (plasma-enhanced chemical vapor deposition) equipment that forms vapor-deposited films on substrates using plasma chemical evaporation; sputtering equipment that forms vapor-deposited films physically; and dry etching equipment for etching substrates or materials coated on substrates into specific patterns.

[0003] However, due to the high-temperature plasma generated inside the vacuum plasma equipment, the cavity and its internal components are inevitably damaged. Furthermore, specific elements and contaminating particles generated from the surface of the cavity and its components can contaminate the interior. Especially in plasma etching equipment, the injection of reactive gases such as F and Cl into the plasma atmosphere places the inner walls of the cavity and its internal components in an extremely harsh corrosive environment. Generally, this corrosion first causes chemical and physical damage to the cavity and its internal components, and secondly generates contaminants and particles, leading to an increased defect rate and decreased quality of products manufactured through processes within the cavity.

[0004] Furthermore, if the cavity and its internal components are damaged, the damaged part of the equipment needs to be replaced, cleaned, or repaired, resulting in additional costs and requiring the production line to be suspended, thus increasing the manufacturing time required for the product. For these reasons, the traditional metal base inside the cavity has been replaced with a ceramic base. Examples of such ceramic bases include sintered aluminum nitride (AlN) or alumina (Al2O3) sintered materials with excellent thermal conductivity. Moreover, these ceramic bases are mainly used in heaters or electrostatic chucks in semiconductor manufacturing processes.

[0005] Aluminum nitride possesses excellent physical properties, including high-temperature stability, electrical insulation, and thermal conductivity. Furthermore, it has a coefficient of thermal expansion similar to silicon, making it primarily used in semiconductor manufacturing devices requiring high resistivity at high temperatures. Alumina is also a high-temperature stable material, exhibiting superior electrical insulation and higher hardness compared to aluminum nitride.

[0006] On the other hand, although semiconductor processes have been trending towards miniaturization and larger-aperture equipment to increase yield in recent years, these advancements have also created various problems in semiconductor manufacturing. Therefore, a new generation of semiconductor process technology is needed to overcome these issues. This process is carried out in a harsher environment of 600–700°C. To withstand this environment, the ceramic substrate must meet the following ceramic characteristics: a volume resistivity of 1.0E+10–1.0E+13 Ω·cm at 500°C and a thermal conductivity of 30 W / mK or higher, preferably 40 W / mK or higher, at room temperature.

[0007] However, the problem is that, for aluminum nitride, at 500℃, the volume resistivity decreases sharply, leading to leakage current. For alumina, the thermal conductivity at room temperature is very low, on the order of 20–30 W / mK. If the thermal conductivity at room temperature is only 20–30 W / mK, it results in larger temperature uniformity deviations and reduced production output. Furthermore, large temperature uniformity deviations in thermal conductivity may shorten product lifespan due to thermal stress and thermal shock. Therefore, a ceramic substrate with high volume resistivity to prevent leakage current even at temperatures above 500℃, and also high thermal conductivity at room temperature, is needed. Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Therefore, the object of the present invention is to provide a ceramic substrate, especially one with superior volume resistivity at high temperatures and thermal conductivity at room temperature compared to conventional ceramic substrates, and a method for manufacturing the same.

[0010] Methods for solving problems

[0011] To achieve the aforementioned objective, the present invention provides a ceramic substrate comprising aluminum oxide (Al2O3) and aluminum nitride (AlN), but excluding a second phase including an aluminum oxynitride phase (AlON phase).

[0012] Furthermore, the present invention provides a ceramic substrate comprising aluminum oxide (Al2O3) and a dopant, wherein the dopant includes any one or more of magnesium oxide (MgO), yttrium oxide (Y2O3), graphene, and rare earth composite oxides.

[0013] Furthermore, the present invention provides a method for manufacturing a ceramic base, comprising: step a), mixing alumina (Al2O3), aluminum nitride (AlN), an alcohol compound, and a binder; step b), drying the mixture to produce a powder after removing the alcohol compound component; step c), compressing and molding the dried powder to produce a preform processed into a certain shape; step d), degreasing the preform to remove the binder component; and step e), sintering and grinding the degreased preform.

[0014] Furthermore, the present invention provides a method for manufacturing a ceramic substrate, comprising: step a), mixing alumina (Al2O3), a dopant, an alcohol compound, and a binder; step b), drying the mixture to produce a powder after removing the alcohol compound component; step c), compressing and molding the dried powder to produce a preform processed into a certain shape; step d), degreasing the preform to remove the binder component; and step e), sintering and grinding the degreased preform, wherein the dopant includes any one or more of magnesium oxide (MgO), yttrium oxide (Y2O3), graphene, and rare earth composite oxides.

[0015] Invention Effects

[0016] The ceramic substrate and its manufacturing method provided by the present invention have advantages, especially in terms of volume resistivity at high temperatures and thermal conductivity at room temperature, which are superior to those of conventional ceramic substrates. Attached Figure Description

[0017] Figure 1 This is an XRD chart showing the physical properties of the ceramic substrate depending on the sintering temperature.

[0018] Figure 2 This is a graph showing the correlation between alumina content and sintering temperature. Detailed Implementation

[0019] The present invention will now be described in detail.

[0020] The ceramic substrate provided in one embodiment of the present invention (first embodiment) comprises alumina (Al2O3) and aluminum nitride (AlN), but does not contain a second phase including the aluminum oxynitride phase (AlON phase).

[0021] With the increasing miniaturization and high integration of semiconductor processes, the use of high-power plasma is inevitable. Therefore, vacuum plasma equipment utilizing high-temperature plasma has become widely used to etch semiconductor devices or achieve other ultra-fine shapes. In response, ceramic substrates made of aluminum nitride (AlN) or alumina (Al2O3) sintered bodies, which offer superior plasma corrosion resistance, are being used in the field to replace conventional metal substrates. In particular, in recent years, to achieve process miniaturization and equipment enlargement aimed at increasing yield in semiconductor manufacturing, semiconductor manufacturing processes are being carried out in harsher environments of 600–700°C. To withstand this environment, ceramic substrates must meet ceramic properties such as a volume resistivity of 1.0E+10 to 1.0E+13 Ω·cm at 500°C and a thermal conductivity of 30 W / mK or higher, preferably 40 W / mK or higher, at room temperature.

[0022] However, the problem is that, for aluminum nitride, the volume resistivity drops sharply at 500℃, showing a tendency to generate leakage current. For alumina, the thermal conductivity at room temperature is very low, on the order of 20-30 W / mK. If the thermal conductivity at room temperature is only 20-30 W / mK, problems such as large temperature uniformity deviations and reduced production output will occur. Moreover, with large temperature uniformity deviations in thermal conductivity, thermal stress and thermal shock may shorten the product's lifespan. To address this, after multi-faceted research, the applicant has invented a ceramic base that can be used at temperatures above 500℃. This ceramic base maintains high volume resistivity even at temperatures above 500℃, preventing leakage current, and its thermal conductivity at room temperature is also higher than usual, thus solving the aforementioned problems.

[0023] The ceramic substrate provided in the first embodiment of the present invention is a sintered body containing alumina (Al2O3) and aluminum nitride (AlN) as the main phase. The alumina not only has excellent electrical insulation and high hardness, but is also stable at high temperatures. The aluminum nitride has physical properties that are stable at high temperatures and have excellent electrical insulation and thermal conductivity.

[0024] In particular, the present invention overcomes all the problems that arise when alumina and aluminum nitride are used individually, as well as the problems that arise when alumina and aluminum nitride are not mixed in the optimal ratio, by mixing the alumina and aluminum nitride in the optimal ratio. Specifically, when alumina and aluminum nitride are mixed in the optimal ratio as described in the present invention, as shown in Table 5 below, the crystalline phase remains unchanged, such as no second phase such as the aluminum oxynitride phase is formed (i.e., no second phase including the aluminum oxynitride phase is present), and the alumina and aluminum nitride phases are uniformly mixed and distributed, thereby maximizing the physical properties of the substrate. Furthermore, in the process of manufacturing the ceramic substrate, the sintering process is carried out at an optimal temperature (less than 1,650°C, preferably 1,300°C or higher and less than 1,650°C), thereby more thoroughly preventing the formation of a second phase. Moreover, the ceramic base thus satisfies the ceramic characteristics of having a volume resistivity of 1.0E+10~1.0E+13Ω·cm at 500℃ and a thermal conductivity of 30W / mk or higher at room temperature.

[0025] The ceramic substrates provided in the first embodiments of the present invention contain more than 68% by weight and less than 99.8% by weight, preferably 70-95% by weight, more preferably 70-80% by weight, and most preferably 73-77% by weight of alumina. Furthermore, the ceramic substrates provided in the first embodiments of the present invention contain more than 0.2% by weight and less than 32% by weight, preferably 5-30% by weight, more preferably 20-30% by weight, and most preferably 23-27% by weight of aluminum nitride. If the alumina and aluminum nitride cannot each meet the aforementioned content ranges, the volume resistivity at 500°C or the thermal conductivity at room temperature will not meet the required conditions, and the ceramic substrate will not meet the ceramic properties that require a volume resistivity of 1.0E+10 to 1.0E+13 Ω·cm at 500°C and a thermal conductivity of 30 W / mK or higher at room temperature.

[0026] The alumina and aluminum nitride are preferably 99% or higher in purity, preferably have nanoscale particles, and preferably are all used in powder form.

[0027] More specifically, the alumina particles can have a size ranging from nanometers to micrometers. For example, the alumina particles can be obtained by mixing alumina particles with a size of 3-5 μm and alumina particles with a size of 50 nm in a weight ratio of approximately 7:3, followed by pulverization using a ball-milling process. However, this is not limited to the examples described; for instance, the particle size and mixing ratio can vary considerably, and the ball-milling process may also be excluded.

[0028] Furthermore, the average particle size (D50) of the aluminum nitride particles can be 0.5–1.5 μm, preferably 0.8–1.3 μm, and more preferably 0.9–1.2 μm. If the average particle size (D50) of the aluminum nitride particles is less than 0.5 μm, the reaction temperature becomes lower, which may lead to the formation of a second phase due to reaction with alumina at low temperatures. Furthermore, if the average particle size (D50) of the aluminum nitride particles exceeds 1.5 μm, a close-packed / tightly packed structure will not form with alumina, resulting in a decrease in density during final sintering. Moreover, in this invention, it is preferable to exclude aluminum nitride particles with nanoscale dimensions as much as possible.

[0029] On the other hand, the ceramic substrate provided in the first embodiment may also include a dopant as needed. The dopant may be used to further improve the thermal conductivity of the ceramic substrate.

[0030] For example, when attempting to apply conventional sintered materials to a substrate and using semiconductor ceramic heaters or electrostatic chucks at temperatures above 500°C, the substrate may sometimes break due to thermal shock because it cannot keep up with rapid temperature changes of the heating element. However, if dopants are incorporated into the heater or electrostatic chuck to improve the substrate's thermal shock resistance, the heat from the heating element can be transferred efficiently, preventing the substrate from breaking due to thermal shock.

[0031] Furthermore, as dopants in these inventions, examples include any one or more of magnesium oxide (MgO), yttrium oxide (Y2O3), graphene, and rare earth composite oxides.

[0032] When the dopant is also included in the ceramic substrate, it may contain 0.05 to 2 parts by weight, preferably 0.1 to 1 part by weight, and more preferably 0.2 to 0.8 parts by weight, relative to 100 parts by weight of the total alumina and aluminum nitride. If less than 0.05 parts by weight of the dopant is included relative to 100 parts by weight of the total alumina and aluminum nitride, or if it is not included at all, the same problems that have occurred in the past may occur, or the effect that can be obtained by using the dopant may be significantly reduced, the improvement in thermal conductivity may be minimal, and there may also be problems with incomplete sintering. Furthermore, when the content of the dopant relative to 100 parts by weight of the total alumina and aluminum nitride exceeds 2 parts by weight, the dispersion effect deteriorates, which may actually reduce the thermal conductivity, and there may be a trend of lower sintering density. There may also be problems such as the product color darkening or the product displaying the original color of the dopant due to the influence of the dopant. Furthermore, the dopant suitable for use in this invention has a purity of 99% or higher. Furthermore, it is preferable to include dopants in amounts of 0.05 to 0.5% by weight.

[0033] Magnesium oxide, as one of the dopants, can be included to improve the thermal conductivity and volume resistivity of the ceramic substrate. The magnesium oxide can induce the formation of MgAl₂O₄ or MgAlON phases through sintering with the alumina and / or aluminum nitride. However, excessive formation of MgAl₂O₄ or MgAlON phases may lead to lower density, which in turn reduces thermal conductivity. Therefore, even when using the same composition, the content of each component must be adjusted. For example, in this invention, the content of any one or more of the MgAl₂O₄ and MgAlON phases in the final ceramic substrate can be less than 1% by weight, preferably less than 0.8% by weight, and more preferably less than 0.6% by weight, relative to the total weight of the ceramic substrate. Furthermore, the particle size of the magnesium oxide is not particularly limited, but nano-sized particles that would produce relatively weak effects are preferably excluded.

[0034] The yttrium oxide (Y₂O₃) can be included to improve the thermal conductivity of the ceramic substrate. The purity of the yttrium oxide is preferably 99% or higher. For improving physical properties through densification, it is suitable that the yttrium oxide particles have a nanoscale size, and these yttrium oxide particles are preferably used in powder form. More specifically, the average particle size (D50) of the yttrium oxide particles can be 50–150 nm, preferably 70–120 nm, and more preferably 90–100 nm. If the average particle size (D50) of the yttrium oxide particles is less than 50 nm, even if a trace amount of yttrium oxide is included, due to the characteristics of nanoscale yttrium oxide powder, problems such as the sintered body having the color of yttrium oxide particles (yellow, etc.) may occur. Furthermore, if the average particle size (D50) of the yttrium oxide particles exceeds 150 nm, an incomplete sintered body may be formed during sintering, potentially leading to a decrease in thermal conductivity due to a decrease in density. These problems may be even more pronounced when the average particle size (D50) of the yttrium oxide particles is in the micrometer range.

[0035] The graphene may also be included to improve the thermal conductivity of the ceramic substrate. The graphene preferably has a purity of 99% or higher, and the graphene particles have a nanoscale size. It is preferable to use these graphene particles in powder form (graphene nanopowder, GNP). More specifically, the average particle size (D50) of the graphene particles can be 0.1–1.5 nm, preferably 0.3–1 nm, and more preferably 0.5–0.8 nm. If the average particle size (D50) of the graphene particles is less than 0.1 nm, it is not large enough to provide sufficient bridging between the graphene particles, and the effect of improving thermal conductivity may be minimal or nonexistent. Furthermore, if the average particle size (D50) of the graphene particles exceeds 1.5 nm, these graphene particles may become intertwined and difficult to disperse, potentially leading to a decrease in thermal conductivity due to a decrease in density.

[0036] Finally, the rare-earth composite oxide contains two or more rare-earth metals selected from the group consisting of: scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (YB), and lutetium (Lu). The purity of the rare-earth composite oxide containing such rare-earth metals is preferably 99% or higher. The rare-earth composite oxide is preferably in the form of a powder, and the size of the powder particles is not particularly limited.

[0037] The rare earth composite oxide can further improve the thermal conductivity of the ceramic substrate, and by using the rare earth composite oxide, the time required for desorption can be reduced. As mentioned above, the rare earth composite oxide contains two or more rare earth metals, preferably two to five different rare earth metals.

[0038] Examples of rare earth composite oxides containing 2 to 5 different rare earth metals include composite oxides containing two different rare earth metals, such as europium-gadolinium composite oxide (EuGdO). X ), samarium-gadolinium composite oxide (SmGdO) X ), cerium-europium composite oxide (CeEuO) X ), samarium-cerium composite oxide (SmCeO) X Gadolinium-Samarium composite oxide (GdSmO) X ) and lanthanum-cerium composite oxide (LaCeO) X); composite oxides containing three different rare earth metals, such as samarium-cerium-europium composite oxide (SmCeEuO); X ), Gadolinium-cerium-lanthanum composite oxide (GdCeLaO) X ) and europium-gadolinium-samarium composite oxide (EuGdSmO) X ); composite oxides containing four different rare earth metals, such as samarium-cerium-gadolinium-europium composite oxide (SmCeGdEuO). X ) and gadolinium-samarium-europium-lanthanum composite oxides (GdSmEuLaO) X ); and composite oxides containing five different rare earth metals, such as samarium-cerium-europium-gadolinium-lanthanum composite oxides (SmCeEuGdLaO). X In addition, as long as it is a composite oxide containing 2 to 5 different rare earth metals (oxides), its use is not subject to special restrictions.

[0039] The rare earth composite oxide containing 2 to 5 different rare earth metals can contain multiple different rare earth metals in various proportions. For example, the rare earth composite oxide containing 2 to 5 different rare earth metals can be appropriately blended in a way that maximizes the target effect of the rare earth composite oxide. For example, it can contain two rare earth metals (oxides) in a weight ratio of 2.5 to 3.5:1, or three rare earth metals (oxides) in a weight ratio of 1 to 3.5: 0.5 to 2.5:1, or four rare earth metals (oxides) in a weight ratio of 1.5 to 3.5: 0.5 to 2.5:1 to 2.5:1, or five rare earth metals (oxides) in a weight ratio of 1 to 3: 0.5 to 1.5: 0.5 to 1.5:1 to 2:1. For example, regarding the weight ratio of each rare earth metal (oxide), SmCeEuO X The ratio can be 2:1:1, GdCeLaO X It can be 3:2:1, EuGdSmO X It can be 1.5:1.5:1, SmCeGdEuO X It can be 2:1:1.5:1, GdSmEuLaO X It can be 3:2:2:1, SmCeEuGdLaO X It could be 2:1:1:1.5:1.

[0040] In the aforementioned rare-earth composite oxide, any one rare-earth metal can be dissolved in the remaining (or any) rare-earth metal oxide. This alters the crystallinity of the rare-earth metal oxide, resulting in an increase in oxygen lattice defects compared to a single rare-earth metal oxide. This increased oxygen lattice defect enhances the interfacial reactivity of the rare-earth composite oxide, enabling it to react effectively with interfacial or lattice oxygen at the various constituent components within the ceramic matrix.

[0041] Furthermore, examples of rare earth metal oxides containing one rare earth metal include scandium oxide (Sc2O3), lanthanum oxide (La2O3), cerium oxide (CeO2), and praseodymium oxide (Pr6O3). 11 The dopants of this invention do not include rare earth metal oxides containing only one rare earth metal.

[0042] On the other hand, in the above description, the dopant includes any one or more of the remaining rare earth metal oxides other than magnesium oxide, yttrium oxide, graphene, and yttrium oxide. Magnesium oxide is suitable as a dopant in this invention. Furthermore, it is preferable to use magnesium oxide and graphene together as dopant. More preferably, magnesium oxide, graphene, and yttrium oxide are used together as dopant. Most preferably, magnesium oxide, graphene, yttrium oxide, and rare earth composite oxides are used together as dopant.

[0043] When magnesium oxide and graphene are used together as dopants, 0.05 to 0.5 parts by weight of magnesium oxide and 0.05 to 0.5 parts by weight of graphene may be included relative to 100 parts by weight of the total weight of aluminum oxide and aluminum nitride.

[0044] Furthermore, when magnesium oxide, graphene, and yttrium oxide are used together as dopants, 0.05 to 0.5 parts by weight of magnesium oxide, 0.05 to 0.5 parts by weight of graphene, and 0.05 to 0.5 parts by weight of yttrium oxide may be included relative to 100 parts by weight of the total weight of aluminum oxide and aluminum nitride.

[0045] Furthermore, when magnesium oxide, graphene, yttrium oxide, and rare earth composite oxides are used together as dopants, relative to 100 parts by weight of the total weight of aluminum oxide and aluminum nitride, the composition may include 0.05 to 0.5 parts by weight of magnesium oxide, 0.05 to 0.5 parts by weight of graphene, 0.05 to 0.5 parts by weight of yttrium oxide, and 0.05 to 0.5 parts by weight of rare earth composite oxides.

[0046] Next, the ceramic substrate provided in the second embodiment of the present invention will be described. The ceramic substrate provided in the second embodiment of the present invention comprises alumina (Al2O3) and a dopant, wherein the dopant includes any one or more of magnesium oxide (MgO), yttrium oxide (Y2O3), graphene, and rare earth composite oxides.

[0047] The applicant confirms that, in addition to the ceramic base provided in the first embodiment described above, the ceramic base provided in the second embodiment also possesses excellent volume resistivity and thermal conductivity. The ceramic base provided in the second embodiment will be described in detail below.

[0048] The ceramic substrate provided in the second embodiment has a structure that excludes only aluminum nitride from the ceramic substrate of the first embodiment, which also includes dopants. Here, the alumina content is the balance excluding the total dopant content. Specifically, it may contain 0.05 to 2 wt%, preferably 1 to 2 wt%, and more preferably 1.5 to 2 wt%, of the dopant relative to the total weight of the ceramic substrate. Furthermore, it may contain 98 to 99.95 wt%, preferably 98 to 99 wt%, and more preferably 98 to 98.5 wt%, of the alumina relative to the total weight of the ceramic substrate. If the alumina and dopant content is not within the stated range, the present invention will not exhibit the target volume resistivity and thermal conductivity characteristics, etc.

[0049] Furthermore, the dopants suitable for this application all possess a purity of 99% or higher. It is also preferable to include 0.05 to 0.5% by weight of each dopant. On the other hand, in the case where the ceramic substrate provided in the second embodiment contains magnesium oxide (MgO) as a dopant, a MgAl₂O₄ spinel phase may form due to the sintering reaction between alumina and magnesium oxide. If an excessive amount of the MgAl₂O₄ spinel phase is formed, the thermal conductivity will decrease; therefore, even when using the same composition, the content of each component must be adjusted.

[0050] On the other hand, the above description describes the case where the dopant includes any one or more of the remaining rare earth metal oxides other than magnesium oxide, yttrium oxide, graphene, and yttrium oxide. The ceramic substrate suitable for the second embodiment also substantially includes magnesium oxide as a dopant, similar to the first embodiment. Furthermore, it is preferable to use magnesium oxide and graphene together as dopant. More preferably, magnesium oxide, graphene, and yttrium oxide are used together as dopant. Most preferably, magnesium oxide, graphene, yttrium oxide, and rare earth composite oxides are used together as dopant.

[0051] If magnesium oxide and graphene are used together as dopants, the mixture may contain 0.05 to 0.5% by weight of the magnesium oxide and 0.05 to 0.5% by weight of the graphene.

[0052] Furthermore, when magnesium oxide, yttrium oxide, and graphene are used together as dopants, the mixture may contain 0.05 to 0.5% by weight of the magnesium oxide, 0.05 to 0.5% by weight of the yttrium oxide, and 0.05 to 0.5% by weight of the graphene.

[0053] Especially when magnesium oxide, yttrium oxide, graphene, and rare earth composite oxides are used together as dopants, the content may include 0.05 to 0.5% by weight of the magnesium oxide, 0.05 to 0.5% by weight of the yttrium oxide, 0.05 to 0.5% by weight of the graphene, and 0.05 to 0.5% by weight of the rare earth composite oxides.

[0054] The ceramic substrate provided by the present invention, as described above, has a volume resistivity of 1.0E+10 to 1.0E+13 Ω·cm at 500°C and a thermal conductivity of 30 W / mK or higher at room temperature, preferably 40 to 60 W / mK. That is, the purpose of the present invention can only be achieved if the ceramic heater simultaneously meets the requirements of both the volume resistivity at 500°C and the thermal conductivity at room temperature.

[0055] If the required volume resistivity cannot be met, it will be difficult to apply this ceramic substrate to next-generation semiconductor manufacturing processes. Even if it is applied, a sharp increase in leakage current may occur. Furthermore, if the required thermal conductivity cannot be met, problems such as increased temperature uniformity deviation leading to reduced yield may arise, and product lifespan may be shortened due to thermal stress and thermal shock.

[0056] Next, the manufacturing method of the ceramic base provided by the present invention will be described.

[0057] First, the method for manufacturing a ceramic substrate provided in the first embodiment includes: step a), mixing alumina (Al2O3), aluminum nitride (AlN), an alcohol compound, and a binder; step b), drying the mixture to produce a powder after removing the alcohol compound component; step c), compressing and molding the dried powder to produce a preform processed into a certain shape; step d), degreasing the preform to remove the binder component; and step e), sintering and grinding the degreased preform.

[0058] Furthermore, dopants can be added and mixed in step a) as needed. Examples of such dopants include magnesium oxide (MgO), yttrium oxide (Y2O3), graphene, and rare earth composite oxides.

[0059] The alcohol compound used in step a) is used to appropriately mix these raw materials. Examples of alcohol compounds with 1 to 5 carbon atoms include ethanol, methanol, and isopropanol. Similarly, the binder used in step a) is used to improve the binding force of these raw materials. Examples of binders include polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).

[0060] Step b) is the drying of the powder mixture mixed in step a) to remove the alcohol component. The drying can be carried out using methods known in the art, such as spray drying and vacuum drying. The drying time can be widely applied depending on the physical properties of the target ceramic substrate.

[0061] Step c) involves compressing and molding the dried powder to create a preform of a specific shape. This compression molding is a first molding process (i.e., first molding) used to control the powder dried in step b) to a target size and shape; examples include stamping. In this case, cold isostatic pressing (CIP) can be performed as needed to produce a more compact product. Preferably, the stamping is performed at room temperature and normal atmospheric pressure, but it is not limited to this; the atmosphere during molding is acceptable as long as it does not affect the molding of the mixture. Furthermore, after the molding process in step c), the preform can be manufactured by processing methods such as green body processing (performed before sintering, also known as unprocessed processing).

[0062] Step d) is a step of degreasing the preform to remove the adhesive component. The degreasing process is used to remove the adhesive and oily contaminants, and can be carried out at a temperature of 350–600°C for up to 60 hours.

[0063] Step e) involves sintering (second forming) and grinding the degreased preform to manufacture a ceramic substrate. The sintering is a second forming process (i.e., second molding) used to further improve the volume resistivity, etc., of the ceramic substrate, and hot pressing is preferred. Furthermore, when the degreased preform is sintered at a temperature above 1650°C, alumina reacts with aluminum nitride to form an aluminum oxynitride phase, which can lead to a decrease in thermal conductivity. Therefore, the sintering in step e) must be performed at a temperature below 1650°C, preferably above 1300°C and below 1650°C.

[0064] Furthermore, the method for manufacturing a ceramic substrate provided in the second embodiment includes: step a), mixing alumina (Al2O3), a dopant, an alcohol compound, and a binder; step b), drying the mixture to produce a powder after removing the alcohol compound component; step c), compressing and molding the dried powder to produce a preform processed into a certain shape; step d), degreasing the preform to remove the binder component; and step e), sintering and grinding the degreased preform, wherein the dopant includes any one or more of magnesium oxide (MgO), yttrium oxide (Y2O3), graphene, and rare earth composite oxides.

[0065] The ceramic substrate of the present invention, manufactured by the above method, can be widely used in semiconductor manufacturing process apparatus or components, and is preferably used as a material for heaters or electrostatic chucks in semiconductor manufacturing processes. Its application areas are not particularly limited; for example, it can also be used in fields where ceramic materials are used in high-temperature plasma environments.

[0066] The present invention will now be described in more detail through specific embodiments. These embodiments are intended to illustrate the invention, and the invention is not limited to them.

[0067] [Examples 1-8, Comparative Examples 1-8] Manufacturing of ceramic base

[0068] The raw materials were mixed according to the composition shown in Table 1 below, with trace amounts of ethanol and polyvinyl butyral (binder) added, and then dried. Next, the dried mixture was stamped and processed to produce a preform. After degreasing at 500°C for 30 hours, the degreased preform was sintered and ground in a high-temperature pressure sintering furnace (250 bar pressure, 1,630°C) to produce a ceramic base.

[0069] Table 1

[0070]

[0071] *Dopant unit: weight %

[0072] *Rare earth composite oxide: Ceria-doped Samarium (CDS) [Experimental Example 1] Volumetric electrical properties of ceramic substrate Evaluation of resistance and thermal conductivity (1)

[0073] After applying a voltage of 500 V / mm to each of the ceramic substrates manufactured in Examples 1 to 8 and Comparative Examples 1 to 8, the current was measured at one minute (measured in a vacuum atmosphere and at room temperature), and the volume resistivity was calculated. The results are shown in Table 2 below.

[0074] Furthermore, for each ceramic base manufactured in Examples 1 to 8 and Comparative Examples 1 to 8, after preparing samples according to the ASTM C0408-88R11 standard using a NETZSCH LFA 467 instrument, the thermal conductivity was measured at room temperature and calculated. The results are also shown in Table 2 below.

[0075] Furthermore, the density values ​​of each ceramic base manufactured in Examples 1 to 8 and Comparative Examples 1 to 8 were calculated using the Archimedes method, and the results are shown in Table 2 below.

[0076] Table 2

[0077]

[0078] The volume resistivity and thermal conductivity of each ceramic substrate manufactured in Examples 1 to 8 and Comparative Examples 1 to 8 were measured, and the results are shown in Table 2. The ceramic substrates of Examples 1 to 8 all meet the volume resistivity (1.0E+10Ω·cm~1.0E+13Ω·cm) required by the next-generation semiconductor manufacturing process at 500°C.

[0079] Furthermore, in terms of thermal conductivity, comparisons between Examples 1 and 2 and Comparative Examples 1 and 2, Examples 3 and 4 and Comparative Examples 3 and 4, Examples 5 and 6 and Comparative Examples 5 and 6, and Examples 7 and 8 and Comparative Examples 7 and 8 confirm that Examples 1 to 8, which used each dopant at a content of 0.05 to 0.5% by weight, are superior to Comparative Examples 1 to 8, which used any one dopant at a content of more than 0.05 to 0.5% by weight.

[0080] In particular, in Examples 7 and 8, which used all dopants in amounts of 0.05 to 0.5% by weight, the thermal conductivity at room temperature exceeded 40 W / mk.

[0081] Furthermore, comparing Example 2 and Comparative Example 2, Example 2 used 0.5 wt% MgO, while Comparative Example 2 used 1 wt% MgO. Although the difference in content was not significant, the thermal conductivity decreased sharply as the MgO content increased from 0.5 wt% to 1 wt%. This is because if the MgO content exceeds 0.5 wt%, an excess (exceeding 0.6 wt%) of MgAl₂O₄ or MgAlON phase is generated in the final product, leading to an increase in its fraction. This result can be confirmed by Table 3 below.

[0082] Table 3

[0083]

[0084] *Dopant unit: weight %

[0085] [Manufacturing Examples 1-7] Manufacturing and physical property evaluation of ceramic substrates

[0086] To derive the optimal mixing ratio of alumina and aluminum nitride, ceramic substrates containing only alumina and aluminum nitride in the ratios shown in Table 4 below were manufactured (the manufacturing method was the same as that of Example 1, except for the composition).

[0087] Furthermore, the volume resistivity and thermal conductivity of each of the ceramic substrates were measured, and the results are shown in Table 5 below (the experimental conditions were the same as in Experimental Example 1).

[0088] Table 4

[0089] <![CDATA[Al2O3:AlN (weight ratio)]]> Manufacturing Example 1 100：0 Manufacturing Example 2 99.8：0.2 Manufacturing Example 3 95：5 Manufacturing Example 4 85：15 Manufacturing Example 5 75：25 Manufacturing Example 6 68：32 Manufacturing Example 7 60：40

[0090] Table 5

[0091]

[0092] *Al2O3 and AlN are measured in weight percent.

[0093] As can be seen from Tables 4 and 5, the ratio of aluminum nitride phase varies depending on the addition ratio of aluminum nitride, resulting in different volume resistivity at high temperature and thermal conductivity at room temperature.

[0094] More specifically, the changes in physical property values ​​based on the different addition ratios of aluminum nitride were confirmed. After XRD, no aluminum oxynitride phase was formed in the final products of Manufacturing Examples 1 to 7. Furthermore, the volume resistivity and thermal conductivity of Manufacturing Examples 3 to 5 all met the requirements, with Manufacturing Example 5, which mixed alumina and aluminum nitride at a weight ratio of 75:25, being the best overall.

[0095] Therefore, if the aluminum nitride content is too low, it will form the Al2O3 phase as the main phase, which has almost no effect on improving thermal conductivity. If the aluminum nitride content is too high, the ratio of AlN phase will increase. Although it has the effect of improving thermal conductivity, the volume resistivity and hardness will decrease.

[0096] [Manufacturing Examples 5-1 to 5-5] Evaluation of the physical properties of ceramic substrates based on sintering temperature

[0097] In manufacturing example 5, aluminum oxide and aluminum nitride were mixed in a weight ratio of 75:25, which was the best overall. Based on this result, as shown in Table 6 below, ceramic substrates were manufactured by setting only the sintering temperature differently (the manufacturing method was the same as in example 1, except for the composition and sintering temperature).

[0098] Then, the volume resistivity and thermal conductivity of each of the ceramic substrates were measured, and the results are shown in Table 7 below (the experimental conditions were the same as in Experimental Example 1).

[0099] Table 6

[0100] <![CDATA[Al2O3:AlN (weight ratio)]]> Sintering temperature (°C) Manufacturing Example 5-1 75：25 1,500 Manufacturing Example 5-2 75：25 1,550 Manufacturing Example 5-3 75：25 1,630 Manufacturing Example 5-4 75：25 1,650 Manufacturing Example 5-5 75：25 1,700

[0101] Table 7

[0102]

[0103] *Al2O3, AlN, and AlON are measured in weight percent.

[0104] Alumina reacts with aluminum nitride at temperatures above a certain level to form the aluminum oxynitride phase. Although the aluminum oxynitride phase has high electrical insulation properties, its low thermal conductivity means that the formation of this phase significantly affects the physical properties. Figure 1 This is an XRD chart showing the physical properties of the ceramic substrate depending on the sintering temperature. Figure 2 This is a graph showing the correlation between alumina content and sintering temperature. (Refer to...) Figure 1 , Figure 2 As shown in Table 1, sintering at 1500°C resulted in unsintered material, making it impossible to measure volume resistivity, and the measured thermal conductivity and density were very low. XRD analysis revealed that an aluminum oxynitride phase was formed at sintering temperatures above 1650°C. Higher aluminum oxynitride content led to higher volume resistivity, but a sharp decrease in thermal conductivity. Therefore, it is evident that sintering in this invention is preferably performed at temperatures below 1650°C.

[0105] [Examples 9-20, Comparative Examples 9-20] Manufacturing of ceramic base

[0106] Based on the experimental results of Manufacturing Examples 5-3, and according to the composition shown in Table 8 below, the raw materials were mixed, with an additional trace amount of ethanol and polyvinyl butyral (binder), and then dried. Next, the dried mixture was stamped and processed to produce a preform. After degreasing at 500°C for 30 hours, the degreased preform was sintered and ground in a high-temperature pressure sintering furnace (250 bar pressure, 1,630°C) to produce a ceramic base.

[0107] Table 8

[0108]

[0109]

[0110]

[0111] *Dopant unit: weight %

[0112] [Experimental Example 2] Evaluation of volume resistivity and thermal conductivity of ceramic substrate (2)

[0113] After applying a voltage of 500 V / mm to each of the ceramic substrates manufactured in Examples 9-20 and Comparative Examples 9-20, the current was measured at one minute (measured in a vacuum atmosphere and at room temperature), and the volume resistivity was calculated. The results are shown in Table 9 below.

[0114] Furthermore, for each ceramic base manufactured in Examples 9 to 20 and Comparative Examples 9 to 20, after preparing samples according to the ASTM C0408-88R11 standard using a NETZSCH LFA 467 instrument, the thermal conductivity was measured at room temperature and calculated. The results are also shown in Table 9 below.

[0115] Furthermore, the density values ​​of each ceramic base manufactured in Examples 9 to 20 and Comparative Examples 9 to 20 were calculated using the Archimedes method, and the results are shown in Table 9 below.

[0116] Table 9

[0117]

[0118]

[0119] The volume resistivity and thermal conductivity of each ceramic substrate manufactured in Examples 9 to 20 and Comparative Examples 9 to 20 were measured, and the results are shown in Table 9. All ceramic substrates of Examples 9 to 20 met the volume resistivity (1.0E+10Ω·cm to 1.0E+13Ω·cm) required by the next-generation semiconductor manufacturing process at 500°C.

[0120] Furthermore, regarding thermal conductivity, comparisons between Examples 9-11 and Comparative Examples 9-11, Examples 12-14 and Comparative Examples 12-14, Examples 15-17 and Comparative Examples 15-17, and Examples 18-20 and Comparative Examples 18-20 confirm that Examples 9-20, which used 0.05-0.5% by weight of each dopant, are superior to Comparative Examples 9-20, which used more than 0.05-0.5% by weight of any one dopant.

[0121] On the other hand, when GNP (graphene nanoparticles) is added as a dopant in addition to MgO, the effect is minimal when less than 0.05% by weight of GNP is used, but thermal conductivity is improved when 0.05 to 0.5% by weight is used. Moreover, when more than 0.5% by weight of GNP is used, the volume resistivity, density, and hardness show a sharp decreasing trend.

[0122] Furthermore, when nano-sized yttrium oxide (Y₂O₃) is added as a dopant in addition to MgO and GNP, improvements in sinterability and increases in volume resistivity and thermal conductivity are also achieved when using 0.05–0.5 wt%. However, when more than 0.5 wt% of yttrium oxide is used, a large number of second phases, such as YAP, YAM, and YAG, are formed due to their reaction with alumina, resulting in a decrease in thermal conductivity.

[0123] Furthermore, it can be confirmed that when rare earth composite oxides, in addition to MgO, GNP, and Nano Y2O3, are added as dopants, the volume resistivity and thermal conductivity tend to increase when 0.05–0.5% by weight are used, as dopant density and hardness also increase. Conversely, when rare earth composite oxides with a content exceeding 0.5% by weight are used, both volume resistivity and thermal conductivity decrease sharply.

[0124] Furthermore, comparing Example 11 and Comparative Example 10, Example 11 used 0.5 wt% MgO, while Comparative Example 10 used 1 wt% MgO. Although the difference in content was not significant, the thermal conductivity decreased sharply as the MgO content increased from 0.5 wt% to 1 wt%. This is because if the MgO content exceeds 0.5 wt%, an excess (exceeding 0.6 wt%) of MgAl₂O₄ or MgAlON phase is generated in the final product, leading to an increase in its fraction. This result can be confirmed by Table 10 below.

[0125] Table 10

[0126]

[0127] *Dopant unit: weight%.

Claims

1. A ceramic base, characterized in that, The ceramic substrate comprises alumina and aluminum nitride. The ceramic substrate does not contain a second phase, including the aluminum oxynitride phase. The alumina content is greater than 68% by weight and less than 95% by weight, and the aluminum nitride content is greater than 5% by weight and less than 32% by weight. The ceramic substrate has a volume resistivity of 1.0E+10 to 1.0E+13 Ω·cm at 500℃ and a thermal conductivity of 30 to 60 W / mK at room temperature. Of which, relative to 100 parts by weight of the total weight of the alumina and aluminum nitride, the ceramic substrate further contains 0.05 to 0.5 parts by weight of yttrium oxide (Y2O3).

2. The ceramic base according to claim 1, characterized in that, The ceramic substrate also contains one or more dopants selected from magnesium oxide, graphene, and rare earth composite oxides.

3. The ceramic base according to claim 2, characterized in that, The dopant comprises 0.05 to 2 parts by weight relative to 100 parts by weight of the total weight of the aluminum oxide and aluminum nitride.

4. The ceramic base according to claim 2, characterized in that, The dopants include magnesium oxide and graphene. Relative to 100 parts by weight of the total weight of the aluminum oxide and aluminum nitride, the product contains 0.05 to 0.5 parts by weight of the magnesium oxide and 0.05 to 0.5 parts by weight of the graphene.

5. The ceramic base according to claim 2, characterized in that, The dopants include magnesium oxide, graphene, and rare earth composite oxides. Relative to 100 parts by weight of the total weight of the aluminum oxide and aluminum nitride, the composition includes 0.05 to 0.5 parts by weight of the magnesium oxide, 0.05 to 0.5 parts by weight of the graphene, and 0.05 to 0.5 parts by weight of the rare earth composite oxide.

6. The ceramic base according to claim 2, characterized in that, The volume resistivity of the ceramic substrate at 500℃ is 1.0E+10~1.0E+13Ω·cm, and its thermal conductivity at room temperature is 40~60W / mk.

7. A method for manufacturing a ceramic base, used to manufacture the ceramic base according to claim 1, characterized in that, include: Step a) involves mixing aluminum oxide, aluminum nitride, yttrium oxide (Y2O3), an alcohol compound, and a binder to prepare a mixture; Step b) involves drying the mixture to produce a powder from which the alcohol compound component has been removed; Step c) The dried powder is compressed and shaped to produce a preform of a certain shape; Step d) involves degreasing the preform to remove the adhesive components; as well as Step e) involves sintering and grinding the degreased preform.

8. The method for manufacturing a ceramic base according to claim 7, characterized in that, The sintering in step e) is carried out at a temperature less than 1,650°C.

9. The method for manufacturing a ceramic base according to claim 7, characterized in that, In step a), one or more dopants selected from magnesium oxide, graphene, and rare earth composite oxides are added and mixed.

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