Ceramic heater

Abstract

Provided is a ceramic heater capable of exhibiting improved thermal uniformity while maintaining corrosion resistance to corrosive gases such as halogen-based gases. This ceramic heater comprises: a ceramic plate assembly including an upper ceramic plate and a lower ceramic plate joined together at joining surfaces thereof; and a heater electrode embedded only in the lower ceramic plate. The upper ceramic plate includes a first ceramic material containing magnesium, aluminum, oxygen, and nitrogen as main components, and the first ceramic material contains, as a main phase, a magnesium-aluminum oxynitride phase in which a peak is observed at least at 2θ=47-50° in an XRD profile obtained by using Cu K alpha rays. The lower ceramic plate includes a second ceramic material containing yttrium, aluminum, oxygen, and nitrogen in a mixing ratio of 10-30 parts by weight of yttrium oxide to 100 parts by weight of aluminum nitride.

Description

Ceramic heater

[0001] This disclosure relates to a ceramic heater.

[0002] In thin-film deposition equipment for semiconductor manufacturing processes, ceramic heaters are used as support stages to uniformly control the wafer temperature. A widely used type of ceramic heater comprises a ceramic plate on which the wafer is placed, and a cylindrical ceramic shaft attached to this ceramic plate.

[0003] Patent Document 1 (Japanese Patent No. 5680665) discloses a heating device equipped with a susceptor having a heating surface for heating a semiconductor. This susceptor comprises a plate-shaped body and a surface corrosion-resistant layer, with the upper surface of the surface corrosion-resistant layer constituting the heating surface. The surface corrosion-resistant layer is composed of a ceramic material mainly composed of magnesium, aluminum, oxygen, and nitrogen, and this ceramic material mainly consists of a magnesium-aluminum oxynitride phase in which the XRD peak when using CuKα rays appears at least 2θ = 47 to 50°. Compared to aluminum nitride, this ceramic material is resistant to corrosive gases such as halogenated gases (e.g., NF ３ CF ４ , CLF ３ , Cl ２ , BCl ３ It is said to have excellent corrosion resistance to HBr. Furthermore, this document teaches that only the surface (first structure) can be made of the above-mentioned corrosion-resistant ceramic material, and a conventional material can be used for the substrate of the lower part (second structure). It is disclosed that an aluminum nitride powder was used as the raw material for the second structure, prepared by adding yttrium oxide powder in a ratio of 5.0% or 50% by mass to 100% by mass of aluminum nitride powder.

[0004] Patent No. 5680665

[0005] In semiconductor manufacturing processes, corrosive gases such as halogenated gases are commonly used for cleaning equipment to prevent wafer contamination. Therefore, components assembled into such semiconductor manufacturing equipment require high corrosion resistance. In this regard, Patent Document 1 discloses a corrosion-resistant ceramic material having a magnesium-aluminum oxynitride phase as the main phase, which exhibits excellent corrosion resistance to corrosive gases such as halogenated gases, with an XRD peak appearing at least at 2θ = 47 to 50°. Therefore, it is conceivable to construct the ceramic plate of a ceramic heater with such a corrosion-resistant ceramic material. However, this type of corrosion-resistant ceramic material has a low thermal conductivity, which presents a problem in that it results in poor uniform heating of the ceramic heater.

[0006] The present inventors have now discovered that by constructing the upper portion of the ceramic plate on which the wafer is placed with a first ceramic material having excellent corrosion resistance, and the other lower portion of the ceramic plate with a second ceramic material having excellent thermal conductivity, it is possible to provide a ceramic heater that can exhibit improved uniform heating while ensuring corrosion resistance to corrosive gases such as halogen-based gases.

[0007] Therefore, the object of the present invention is to provide a ceramic heater that can exhibit improved uniformity of heat while ensuring corrosion resistance to corrosive gases such as halogen-based gases.

[0008] The following embodiments are provided according to this disclosure: [Embodiment 1] A ceramic heater comprising: a ceramic plate assembly including an upper ceramic plate and a lower ceramic plate joined to each other at a joint surface, the upper ceramic plate having a first surface opposite to the joint surface and the lower ceramic plate having a second surface opposite to the joint surface; and a heater electrode embedded only in the lower ceramic plate, wherein the upper ceramic plate comprises a first ceramic material mainly composed of magnesium, aluminum, oxygen and nitrogen, the first ceramic material mainly comprises a magnesium-aluminum oxynitride phase in which a peak is observed at least at 2θ = 47 to 50° in an XRD profile obtained by XRD using CuKα rays, and the lower ceramic plate comprises a second ceramic material containing yttrium, aluminum, oxygen and nitrogen in a ratio of 10 to 30 parts by weight of yttrium oxide to 100 parts by weight of aluminum nitride. [Aspect 2] The ceramic heater according to aspect 1, wherein the blending ratio of yttrium oxide to 100 parts by weight of aluminum nitride in the lower ceramic plate is 10 to 25 parts by weight. [Aspect 3] The second ceramic material is a composite material of yttrium oxide and aluminum nitride, or a Y material in which aluminum nitride is solid-dissolved in magnesium oxide. ２ O ３- A ceramic heater according to Embodiment 1 or 2, comprising an AlN solid solution and / or yttrium-aluminum oxynitride. [Embodiment 4] A ceramic heater according to any one of Embodiments 1 to 3, wherein the second ceramic material comprises a yttrium-aluminum oxynitride phase. [Embodiment 5] A ceramic heater according to any one of Embodiments 1 to 4, wherein the lower ceramic plate has a linear expansion coefficient of 5.9 to 6.7 ppm / K. [Embodiment 6] A ceramic heater according to any one of Embodiments 1 to 5, wherein the lower ceramic plate has a thermal conductivity of 50 to 140 W / m·K. [Embodiment 7] A ceramic heater according to any one of Embodiments 1 to 6, wherein the first ceramic material comprises a crystalline phase of MgO-AlN solid solution, in which aluminum nitride is solid-dissolved in magnesium oxide, as a secondary phase. [Embodiment 8] A ceramic heater according to any one of Embodiments 1 to 7, wherein the first ceramic material does not contain an AlN crystalline phase. [Aspect 9] A ceramic heater according to any one of aspects 1 to 8, further comprising an internal electrode which is an ESC electrode and / or an RF electrode embedded in the upper ceramic plate and / or the lower ceramic plate. [Aspect 10] A ceramic heater according to any one of aspects 1 to 9, wherein the average particle size of the ceramic particles constituting the upper ceramic plate is 1.1 times or more the average particle size of the ceramic particles constituting the lower ceramic plate.

[0009] This is a schematic cross-sectional view showing an example of a ceramic heater according to the present invention. This is a schematic cross-sectional view showing an example of a conventional ceramic heater. This is a temperature distribution map of the ceramic plate measured in Example 1. This is a temperature distribution map of the ceramic plate measured in Example 9. This is a temperature distribution map of the ceramic plate measured in Example 10.

[0010] The ceramic heater according to the present invention is a ceramic stand for supporting a wafer while controlling its temperature within a semiconductor manufacturing apparatus. Typically, the ceramic heater according to the present invention may be a ceramic heater for a semiconductor film deposition apparatus. Typical examples of film deposition apparatus include CVD (chemical vapor deposition) apparatus (e.g., thermal CVD apparatus, plasma CVD apparatus, photoCVD apparatus, and MOCVD apparatus) and PVD (physical vapor deposition) apparatus.

[0011] Figure 1 shows one embodiment of a ceramic heater. The ceramic heater 10 shown in Figure 1 comprises a ceramic plate assembly 12 and a heater electrode 14. The ceramic plate assembly 12 includes an upper ceramic plate 12a and a lower ceramic plate 12b joined to each other at a joint surface 12c. The ceramic plate assembly 12 has a first surface 12d of the upper ceramic plate 12a opposite to the joint surface 12c, and a second surface 12e of the lower ceramic plate 12b opposite to the joint surface 12c. The heater electrode 14 is embedded only within the lower ceramic plate 12b. The upper ceramic plate 12a contains a first ceramic material mainly composed of magnesium, aluminum, oxygen, and nitrogen. This first ceramic material mainly contains a magnesium-aluminum oxynitride phase, and this magnesium-aluminum oxynitride phase shows a peak at at least 2θ = 47 to 50° in the XRD profile obtained by XRD using CuKα rays. On the other hand, the lower ceramic plate 12b contains a second ceramic material comprising yttrium, aluminum, oxygen, and nitrogen in a ratio of 10 to 30 parts by weight of yttrium oxide to 100 parts by weight of aluminum nitride. By constructing the upper ceramic plate 12a on which the wafer of the ceramic plate assembly 12 is placed from a first ceramic material with excellent corrosion resistance, and the lower ceramic plate 12b from a second ceramic material with excellent thermal conductivity, it is possible to provide a ceramic heater 10 that exhibits improved uniform heating while ensuring corrosion resistance to corrosive gases such as halogen-based gases.

[0012] That is, as described above, high corrosion resistance is required for the members assembled in the semiconductor manufacturing apparatus. In this regard, Patent Document 1 discloses a corrosion-resistant ceramic material having a magnesium-aluminum oxynitride phase with few XRD peaks appearing at least at 2θ = 47 to 50° as a main phase, as a material excellent in corrosion resistance against corrosive gases such as halogen-based gases (for example, NF ３ , CF ４ , ClF ３ , Cl ２ , BCl ３ and HBr). Therefore, as shown in FIG. 2, it is conceivable to configure the ceramic plate 13 of the ceramic heater 11 with such a corrosion-resistant ceramic material. However, since this type of corrosion-resistant ceramic material has low thermal conductivity, there is a problem that the heat uniformity of the ceramic heater 11 is inferior. That is, when the thermal conductivity is low, the heat generated at the heater electrode 14 is unlikely to be evenly transmitted over the entire ceramic plate 13, and large unevenness occurs in the temperature distribution within the plane of the ceramic plate 13, and the maximum temperature difference within the plane tends to increase. In this regard, in the present invention, the upper ceramic plate 12a on the first surface 12d side where the wafer of the ceramic plate assembly 12 is placed and can be exposed to corrosive gases such as halogen-based gases is made of a first ceramic material having excellent corrosion resistance, thereby ensuring corrosion resistance against corrosive gases such as halogen-based gases. On the other hand, the lower ceramic plate 12b on the second surface 12e side and inside which the heater electrode 14 is embedded is made of a second ceramic material having excellent thermal conductivity, so that the heat generated at the heater electrode 14 is likely to be evenly transmitted over the entire lower ceramic plate 12b or the ceramic plate assembly 12, making the temperature distribution within the plane of the ceramic plate assembly 12 uniform (that is, reducing the maximum temperature difference within the plane). As a result, improved heat uniformity can be realized. Moreover, the second ceramic material constituting the lower ceramic plate 12b has a very close linear expansion coefficient to the first ceramic material constituting the upper ceramic plate 12a. Therefore, when the upper ceramic plate 12a and the lower ceramic plate 12b are joined and used as the ceramic plate assembly 12, there is also an advantage that breakage due to the difference in linear expansion coefficient is unlikely to occur.

[0013] The ceramic plate assembly 12 includes an upper ceramic plate 12a and a lower ceramic plate 12b, which are joined to each other at a joint surface 12c.

[0014] The ceramic plate bond 12 is typically disc-shaped. However, the plan view shape of the disc-shaped ceramic plate bond 12 does not need to be a perfect circle; for example, it may be an incomplete circle with a portion missing, such as an orientation flat. The size of the ceramic plate bond 12 is not particularly limited and can be appropriately determined according to the diameter of the wafer in which it is intended to be used, but in the case of a circle, the diameter is typically 150 to 450 mm, and especially for 300 mm silicon wafers, it is typically 320 to 380 mm. The thickness of the ceramic plate bond 12 is typically 10 to 25 mm.

[0015] The thickness of the upper ceramic plate 12a is not particularly limited as long as it is thick enough to ensure the desired corrosion resistance, but it is preferably thinner than the thickness of the lower ceramic plate 12b. The preferred thickness of the upper ceramic plate 12a is 0.5 to 5 mm, and more preferably 1 to 2 mm. On the other hand, the thickness of the lower ceramic plate 12b is preferably thicker than the upper ceramic plate 12a from the viewpoint of improving uniform heat distribution by maximizing the area with high thermal conductivity. The thickness of the lower ceramic plate 12b is 6 to 25 mm, and more preferably 10 to 20 mm. Furthermore, the thickness of the lower ceramic plate 12b is preferably 3 to 10 times the thickness of the upper ceramic plate 12a, and more preferably 5 to 6 times.

[0016] The upper ceramic plate 12a contains a first ceramic material mainly composed of magnesium, aluminum, oxygen, and nitrogen. This first ceramic material mainly contains a magnesium-aluminum oxynitride phase, and the magnesium-aluminum oxynitride phase shows a peak at at least 2θ = 47 to 50° in the XRD profile obtained by X-ray diffraction (XRD) using CuKα rays. The first ceramic material may be a known ceramic material as disclosed in Patent Document 1 (Japanese Patent No. 5680665). Since this magnesium-aluminum oxynitride has corrosion resistance to halogen-based plasmas that is equivalent to or higher than that of spinel, which is known to be a material with higher corrosion resistance than alumina, it is considered that the first ceramic material mainly composed of this oxynitride will also have high corrosion resistance. Furthermore, this magnesium-aluminum oxynitride can have corrosion resistance equivalent to that of spinel, but with a lower coefficient of linear thermal expansion than spinel.

[0017] The first ceramic material may contain a crystalline phase of MgO-AlN solid solution, in which aluminum nitride is solid-dissolved in magnesium oxide, as a secondary phase. Since this MgO-AlN solid solution also has high corrosion resistance, its inclusion as a secondary phase is not problematic. This MgO-AlN solid solution may appear with XRD peaks on the (200) and (220) planes when using CuKα radiation at 2θ = 42.9 to 44.8° and 62.3 to 65.2°, which are between the peaks of the cubic crystal of magnesium oxide and the peaks of the cubic crystal of aluminum nitride. Alternatively, the XRD peak on the (111) plane may appear at 2θ = 36.9 to 39°, which is between the peaks of the cubic crystal of magnesium oxide and the peaks of the cubic crystal of aluminum nitride. Since the peak on the (111) plane may be difficult to distinguish from the peaks of other crystalline phases, it is also acceptable for only the XRD peaks on the (200) and (220) planes to appear within the above ranges.

[0018] To obtain corrosion resistance equivalent to or higher than that of spinel, the first ceramic material preferably has a low AlN crystal phase content, and more preferably does not contain any AlN crystal phase. This is because the presence of AlN crystal phase as a secondary phase tends to reduce corrosion resistance. Furthermore, since spinel has higher corrosion resistance than alumina and AlN crystals, the first ceramic material may contain a small amount of spinel. However, since spinel has lower corrosion resistance than the magnesium-aluminum oxynitride phase and MgO-AlN solid solution, the spinel content is preferably less than the content of the magnesium-aluminum oxynitride phase and MgO-AlN solid solution. On the other hand, to have corrosion resistance equivalent to that of spinel while having a low coefficient of linear thermal expansion, the first ceramic material may contain small amounts of spinel or AlN crystal phase.

[0019] For the first ceramic material, in order to obtain corrosion resistance equivalent to or higher than that of spinel, the molar ratio of magnesium to aluminum in the raw material powder is preferably 0.20 to 2, and more preferably 0.75 to 2. On the other hand, in order to have corrosion resistance equivalent to that of spinel while having a low coefficient of linear thermal expansion, the molar ratio of magnesium to aluminum in the raw material powder of the first ceramic material is preferably 0.05 to 1.5 or less, and more preferably 0.1 to 1.

[0020] The first ceramic material can be manufactured by molding a mixed powder of magnesium oxide, alumina, and aluminum nitride, and then firing it. For example, to obtain corrosion resistance equivalent to or higher than that of spinel, it is preferable to mold a powder mixed with magnesium oxide in an amount of 15 to 66.2% by mass (e.g., 37 to 66.2% by mass), alumina in an amount of 63% by mass or less, and aluminum nitride in an amount of 57.7% by mass or less, and then fire it. On the other hand, to obtain corrosion resistance equivalent to that of spinel while lowering the coefficient of linear thermal expansion and increasing temperature uniformity, it is preferable to mold a powder mixed with magnesium oxide in an amount of 5 to 60% by mass or less, alumina in an amount of 60% by mass or less, and aluminum nitride in an amount of 90% by mass or less, and then fire it. From the viewpoint of obtaining magnesium-aluminum oxynitride, the firing temperature should be 1750°C or higher. The upper limit of the firing temperature is not particularly limited, but it may be, for example, 1850°C or 1900°C. Firing is preferably carried out by hot press firing, and the pressing pressure during hot press firing should be 50 to 300 kgf / cm². ２ It is preferable to keep it within this range. The atmosphere during firing should be one that does not affect the firing of the oxide raw material, and preferably an inert atmosphere such as a nitrogen atmosphere, argon atmosphere, or helium atmosphere.

[0021] The lower ceramic plate 12b contains a second ceramic material. The second ceramic material contains yttrium, aluminum, oxygen, and nitrogen in a ratio of yttrium oxide to 100 parts by weight of aluminum nitride, preferably 10 to 15 parts by weight. The ratio of yttrium oxide to 100 parts by weight of aluminum nitride referred to here means the weight ratio of yttrium oxide powder to 100 parts by weight of aluminum nitride powder in the raw material powder used to produce the second ceramic material, and does not mean that the second ceramic material finally obtained as a sintered body after mixing, sintering, etc., contains aluminum nitride and yttrium oxide independently. In this regard, the second ceramic material constituting the lower ceramic plate 12b is a composite material of yttrium oxide and aluminum nitride, and Y in which aluminum nitride is solid-dissolved in magnesium oxide. ２ O ３It is preferably included an AlN solid solution and / or a yttrium-aluminum oxynitride, and more preferably, the second ceramic material includes a yttrium-aluminum oxynitride phase.

[0022] The lower ceramic plate 12b preferably has a linear expansion coefficient of 5.9 ppm / K or more and 6.7 ppm / K or less, and more preferably exceeds 5.9 ppm / K and is less than 6.7 ppm / K. When within such a range, the difference from the linear expansion coefficient of the first ceramic material (for example, 6.1 ppm / K) becomes extremely small. That is, since the linear expansion coefficients of the upper ceramic plate 12a and the lower ceramic plate 12b are extremely close, when the upper ceramic plate 12a and the lower ceramic plate 12b are joined and used as the ceramic plate joined body 12, breakage due to the difference in linear expansion coefficient is less likely to occur. From such a viewpoint, the absolute value of the difference between the linear expansion coefficient of the upper ceramic plate 12a and the linear expansion coefficient of the lower ceramic plate 12b is preferably less than 0.2 ppm / K, and more preferably 0.1 ppm / K or less. In this specification, the linear expansion coefficient is defined as the average linear thermal expansion coefficient at 40 to 1000 °C measured in an argon atmosphere using a commercially available dilatometer in accordance with JIS R 1618:2002.

[0023] The lower ceramic plate 12b preferably has a thermal conductivity of 50 W / m·K or more and 140 W / m·K or less, and more preferably exceeds 50 W / m·K and is less than 140 W / m·K. Since such a thermal conductivity is significantly higher than the thermal conductivity of the first ceramic material (for example, 8 W / m·K), the heat generated at the heater electrode 14 is likely to be evenly transmitted over the entire lower ceramic plate 12b or the ceramic plate joined body 12, making the temperature distribution within the ceramic plate joined body 12 uniform (that is, reducing the maximum in-plane temperature difference), and as a result, improved heat uniformity can be more effectively realized. In this specification, the thermal conductivity can be measured by the laser flash method in accordance with the method described in JIS R 1611:2020 by collecting a sample processed into a cylindrical shape with a diameter of 10 mm and a thickness of 3 mm from the ceramic plate.

[0024] The average particle size of the ceramic particles constituting the upper ceramic plate 12a is preferably 1.1 times or more than the average particle size of the ceramic particles constituting the lower ceramic plate 12b, more preferably 1.2 to 2.5 times, and even more preferably 1.3 to 2.3 times. A larger average particle size in the upper ceramic plate 12a reduces the proportion of grain boundaries, thereby reducing the rate of corrosion at grain boundaries. Furthermore, reducing the average particle size of the lower ceramic plate 12b increases its density, making it less susceptible to cracks caused by differences in thermal expansion. The average particle size can be measured using the intercept method described later in the examples.

[0025] The second ceramic material can be manufactured by molding a mixed powder prepared by adding 100 parts by weight of aluminum nitride powder to 10 to 30 parts by weight, preferably 10 to 25 parts by weight, more preferably 10 to 20 parts by weight, and particularly preferably 15 to 20 parts by weight, of yttrium oxide powder in a blending ratio, and then firing it. From the viewpoint of obtaining a desired high thermal conductivity material, a firing temperature of 1750°C or higher is preferable. The upper limit of the firing temperature is not particularly limited, but for example, it may be 1850°C or 1900°C. Firing is preferably carried out by hot press firing, and the press pressure during hot press firing is 50 to 300 kgf / cm². ２ It is preferable to keep it within this range. The atmosphere during firing should be one that does not affect the firing of the oxide raw material, and preferably an inert atmosphere such as a nitrogen atmosphere, argon atmosphere, or helium atmosphere.

[0026] The method for joining the upper ceramic plate 12a and the lower ceramic plate 12b can be carried out using known methods and is not particularly limited. Therefore, the upper ceramic plate 12a and the lower ceramic plate 12b may be joined by integral sintering or by adhesive. Examples of such adhesives include silicone adhesives, acrylic adhesives, and Al alloy adhesives. Alternatively, the upper ceramic plate 12a and the lower ceramic plate 12b may be joined via an intermediate layer (for example, composed of a composite ceramic obtained by sintering a mixture of a first ceramic material and a second ceramic material), but the present invention is advantageous in that such an intermediate layer can be omitted. That is, Patent Document 1 (Japanese Patent No. 5680665) describes that an intermediate layer can further suppress delamination between the first structure and the second structure due to differences in thermal expansion coefficients. However, in the present invention, as described above, the second ceramic material constituting the lower ceramic plate 12b has a coefficient of thermal expansion very close to that of the first ceramic material constituting the upper ceramic plate 12a. Therefore, the upper ceramic plate 12a and the lower ceramic plate 12b can be joined together without difficulty, and the resulting ceramic plate joint 12 is less prone to damage caused by differences in coefficient of thermal expansion. In addition, the manufacturing process is shortened and manufacturing efficiency is improved by eliminating the intermediate layer.

[0027] As shown in FIG. 1, a heater electrode 14 is embedded in the lower ceramic plate 12b. The heater electrode 14 is embedded only in the lower ceramic plate 12b. This is because the upper ceramic plate 12a has low thermal conductivity, and embedding the heater electrode 14 in the upper ceramic plate 12a is not preferable from the viewpoint of realizing uniform heat distribution. The heater electrode 14 is not particularly limited, and for example, it may be a conductive coil wired in one stroke over the entire area of the lower ceramic plate 12b. The one-stroke form can be various known forms such as alternating repetition of progress and return, or a spiral shape. Heater rods 16 are connected to both ends of the heater electrode 14 for power supply, and the heater rods 16 are connected to a heater power source (not shown) through the internal space S of the ceramic shaft 24. When power is supplied from the heater power source, the heater electrode 14 generates heat and heats the wafer placed on the first surface 12d. The heater electrode 14 is not limited to a coil, and may be, for example, a ribbon (elongated thin plate) or a mesh.

[0028] An internal electrode 18, which is an ESC electrode and / or an RF electrode, may be embedded in the upper ceramic plate 12a and / or the lower ceramic plate 12b. When a high frequency is applied to the RF electrode, film formation by a plasma CVD process becomes possible. The ESC electrode is an abbreviation for an electrostatic chuck (ESC) electrode and is also referred to as an electrostatic electrode. When a voltage is applied by an external power source, the ESC electrode chucks the wafer placed on the first surface 12d of the ceramic plate assembly 12 by the Johnson-Rahbek force. The ESC electrode is preferably a circular thin-layer electrode having a slightly smaller diameter than the ceramic plate assembly 12, and may be, for example, a mesh-shaped electrode formed by weaving thin metal wires into a net shape to form a sheet. The ESC electrode may be used as a plasma electrode. That is, by applying a high frequency to the ESC electrode, the ESC electrode can also be used as an RF electrode, and film formation by a plasma CVD process can also be performed. A terminal rod 20 such as an RF rod or an ESC rod for power supply is connected to the RF electrode or the ESC electrode, and can be connected to an external power source (not shown) through the terminal rod 20.

[0029] The ceramic plate assembly 12 (particularly the lower ceramic plate 12b) may be provided with a temperature sensing hole 22. The temperature sensing hole 22 can be a thermocouple hole commonly used in ceramic heaters. Therefore, the temperature of the ceramic plate assembly 12 can be measured by inserting a thermocouple or resistance thermometer into the temperature sensing hole 22. The temperature sensing hole 22 can be a vertical hole, a horizontal hole, or a combination thereof, and should be formed to suit the area to be measured.

[0030] The ceramic shaft 24 is a cylindrical shaft attached to the second surface 12e of the ceramic plate assembly 12, and may have a similar configuration to ceramic shafts used in known ceramic susceptors or ceramic heaters. The internal space S is configured to allow elongated members such as heater rods 16, terminal rods 20, and thermocouples to pass through it. The ceramic shaft 24 is preferably made of the same type of ceramic material as the ceramic plate assembly 12. Therefore, the ceramic shaft 24 preferably contains aluminum nitride or aluminum oxide, and more preferably aluminum nitride. The ceramic shaft 24 is preferably joined to the second surface 12e of the ceramic plate assembly 12 by solid-state bonding or diffusion bonding. The outer diameter of the ceramic shaft 24 is not particularly limited, but is preferably 40 to 60 mm. The inner diameter of the ceramic shaft 24 (diameter of the internal space S) is also not particularly limited, but is preferably 33 to 55 mm.

[0031] The present invention will be further described in detail by the following examples. However, the present invention is not limited to the following examples.

[0032] Examples 1-8 (Comparative or Reference) Prior to disclosing embodiments of the ceramic heater according to the present invention, the following examples show ceramic plates formed by a single layer of conventional ceramic materials such as those disclosed in Patent Document 1 (Examples 1, 7, and 8 (Comparative Examples)) or the second ceramic material of the present invention (Examples 2-6 (Reference Examples)).

[0033] (1) Fabrication of the ceramic heater A ceramic heater 11 having a single-layer ceramic plate 13 as shown in Figure 2 was fabricated using the components shown below, following a known procedure.

[0034] <Components and their specifications> - Ceramic plate 13: A disc-shaped sintered body (second ceramic material) containing yttrium, aluminum, oxygen, and nitrogen, in a ratio of yttrium oxide to 100 parts by weight of aluminum nitride to the values ​​shown in Table 1 (diameter: 360 mm, thickness: 15 mm) (with heater electrode 14 and internal electrode 18 embedded inside) - Heater electrode 14: A coil-shaped resistance heating element embedded in the ceramic plate 13 at a depth of 6.5 mm from the first surface 13a, according to a predetermined circuit pattern. - Heater rod 16: Two nickel terminal rods connected to the heater electrode 14. - Internal electrode 18 (RF / ESC electrode): A molybdenum electrode layer embedded at a depth of 1.0 mm from the first surface 13a of the ceramic plate 13. - Terminal rod 20 (RF / ESC rod): A single nickel terminal rod. - Ceramic shaft 24: A cylindrical aluminum nitride sintered body (height: 170 mm, maximum outer diameter: 90 mm, minimum outer diameter: 50 mm, inner diameter: 40 mm).

[0035] (Preparation of Ceramic Plate) The ceramic plate 13 in which the heater electrode 14 described above is embedded was prepared by the following procedure. First, 100 parts by weight of aluminum nitride powder was mixed with yttrium oxide powder in the following proportions: 5 parts by weight (Example 1), 10 parts by weight (Example 2), 15 parts by weight (Example 3), 20 parts by weight (Example 4), 25 parts by weight (Example 5), 30 parts by weight (Example 6), 40 parts by weight (Example 7), or 50 parts by weight (Example 8). The mixture was wet-mixed for 4 hours using isopropyl alcohol as a solvent, a nylon pot, and nylon pebbles. The resulting slurry was dried at 110°C in a nitrogen stream and then passed through a 30-mesh sieve to obtain a blended powder. This blended powder was heat-treated at 450°C for 5 hours or more in an atmospheric environment to burn off and remove any carbon components that had been mixed in during the wet mixing. In this way, yttrium oxide-containing aluminum nitride powder was obtained. Next, the yttrium oxide-containing aluminum nitride powder was press-molded to obtain the first compacted powder. On the obtained first compact, the heater electrode 14 was placed together with yttrium oxide-containing aluminum nitride powder according to a predetermined circuit pattern and press-molded to obtain a second compact with the heater electrode 14 embedded inside. On the obtained second compact, the yttrium oxide-containing aluminum nitride powder and the internal electrode 18 were placed and press-molded to obtain a third compact with the internal electrode 18 further embedded inside. Thus, a press-molded body consisting of yttrium oxide-containing aluminum nitride compact with the heater electrode 14 and internal electrode 18 embedded inside was obtained as shown in Figure 2. The obtained press-molded body (laminated body) was subjected to a nitrogen atmosphere at a maximum temperature of 1810°C for 5 hours at a rate of 90 kg / cm³. ２ By hot-press firing under pressure, a ceramic plate 13 was obtained in which a heater electrode 14 and an internal electrode 18 were embedded inside.

[0036] (2) The following evaluations were performed on the ceramic heaters that were evaluated.

[0037] <Coefficient of Linear Thermal Expansion> In accordance with JIS R 1618:2002, the average coefficient of linear thermal expansion of ceramic plates at temperatures from 40 to 1000°C was measured in an argon atmosphere using a dilatometer (Bruker AXS). The results are shown in Table 1.

[0038] <Thermal Conductivity> Thermal conductivity was measured by taking a sample from a ceramic plate that had been processed into a cylindrical shape with a diameter of 10 mm and a thickness of 3 mm, and using the laser flash method in accordance with the method described in JIS R 1611:2020. The results are shown in Table 1.

[0039] <Average grain size> The grain size of the ceramic particles constituting the ceramic plate 13 was measured using the intercept method. Specifically, an arbitrary number of line segments were drawn on an SEM image of the polished surface of the ceramic plate 13, and the number of crystal particles n intersected by the line segment of length L was determined. If the end of a line segment was located within a crystal particle, that crystal particle was counted as 1 / 2. The value obtained by dividing the length L of the line segment by n (L / n) was taken as the average crystal grain size (i.e., average intercept length), and the value obtained by multiplying this average crystal grain size by a coefficient of 1.5 was taken as the average grain size.

[0040] <Uniform Heating> The ceramic heater 11 was installed inside the chamber of the film deposition apparatus. The chamber was evacuated and N ２ Introducing gas into the chamber ２ The gas pressure was set to 3 Torr. The ceramic heater 11 was heated to a set temperature of 650°C by supplying power to the heater electrode 14 via the heater rod 16. At this set temperature, the temperature distribution on the first surface 13a of the ceramic plate 13 was measured using an infrared camera. Figure 3 shows the temperature distribution map on the surface of the ceramic heater in Example 1 (maximum in-plane temperature difference: 0.4°C). Based on the obtained temperature distribution map, the difference between the highest and lowest temperatures within the measurement area (i.e., the maximum in-plane temperature difference) was determined as an indicator of uniformity and evaluated according to the following criteria. The results are shown in Table 1. ・Evaluation A: The maximum in-plane temperature difference was less than 0.5°C. ・Evaluation B: The maximum in-plane temperature difference was 0.5°C or more and 6.0°C or less. ・Evaluation C: The maximum in-plane temperature difference was greater than 6.0°C.

[0041] <Corrosion Resistance> The surface of the ceramic plate 13 was polished to a mirror finish, and a corrosion resistance test was conducted using an ICP plasma corrosion resistance test apparatus. ICP: 800W, Bias: 450W, Introduced gas: NF ３ / O ２The test was conducted under the following conditions: Ar = 75 / 35 / 100 sccm, pressure: 0.05 Torr (6.67 Pa), exposure time: 5 hours, and sample temperature: 650°C. This test was performed by masking a portion of the polished surface of the ceramic plate 13 to create a masked surface, and then etching this masked surface against the unmasked exposed surface. The etching rate of each ceramic plate 13 was calculated by dividing the step difference between the masked surface and the exposed surface, measured by a step meter, by the test time, and was graded according to the following criteria. The results are shown in Table 1. - Evaluation A: Etching rate was less than 300 nm / h. - Evaluation B: Etching rate was 300 nm / h or more and 1000 nm / h or less. - Evaluation C: Etching rate was greater than 1000 nm / h.

[0042] <XRD> The second ceramic material constituting the ceramic plate 13 was crushed in a mortar and pestle, and X-ray diffraction (XRD) was performed using a sealed-tube X-ray diffractometer (Bruker AXS, D8 ADVANCE) under the conditions of X-ray used: CuKα, voltage: 40kV, current: 40mA, and 2θ = 5 to 70°. As a result, numerous peaks suggesting the yttrium-aluminum oxynitride phase were clearly detected as the main crystal structure. From these results, it was determined that the second ceramic material contains the yttrium-aluminum oxynitride phase.

[0043] Example 9 (Reference) A ceramic heater was fabricated and evaluated in the same manner as in Examples 1 to 8, except that a disc-shaped sintered body (first ceramic material) (diameter: 350 mm, thickness: 15 mm) (with heater electrodes 14 and internal electrodes 18 embedded inside) containing a magnesium-aluminum oxynitride phase as the main phase was fabricated and used as follows. The results are shown in Table 1 and Figure 4. As shown in Table 1, the ceramic plate 13 in this example had excellent corrosion resistance to halogen-based gases. On the other hand, as shown in Figure 4, the ceramic heater 11 in this example had a large unevenness in the temperature distribution on the surface, with a maximum in-plane temperature difference of 6.6°C, indicating poor heat uniformity.

[0044] (Preparation of ceramic plate) The ceramic plate 13 in which the heater electrode 14 and internal electrode 18 described above are embedded was prepared by the following procedure. First, MgO raw material, Al ２ O ３ Raw materials and AlN raw materials, MgO:Al ２ O ３ The ingredients were weighed and mixed to a ratio of :AlN = 10:20:70 (by weight), and wet-mixed for 4 hours using isopropyl alcohol as a solvent, a nylon pot, and alumina pebbles with a diameter of 5 mm. The resulting slurry was dried at 110°C in a nitrogen stream, and then passed through a 30-mesh sieve to obtain the formulated powder. Thus, MgO, Al ２ O ３ And AlN-containing powder was obtained. Next, MgO, Al ２ O ３ The AlN-containing powder was press-molded to obtain a first compact. On the obtained first compact, MgO and Al ２ O ３ A second compact was obtained in which the heater electrode 14 was embedded inside by pressing and molding the AlN-containing powder together with the heater electrode 14 arranged according to a predetermined circuit pattern. ２ O ３ And by placing the AlN-containing powder and the internal electrode 18 and press molding, a third compacted powder was obtained in which the internal electrode 18 was further embedded inside. Thus, as shown in Figure 2, the heater electrode 14 and the internal electrode 18 were embedded in MgO, Al ２ O ３ A press-molded body was obtained consisting of a compacted powder containing AlN. The obtained press-molded body (laminated body) was subjected to a nitrogen atmosphere at a maximum temperature of 1810°C for 5 hours at a rate of 90 kg / cm³. ２ By hot-press firing under pressure, a ceramic plate 13 was obtained in which a heater electrode 14 and an internal electrode 18 were embedded inside.

[0045] (XRD and EPMA) In addition, X-ray diffraction (XRD) and EPMA measurements were performed as follows to identify the first ceramic material in this example. The second ceramic material constituting the ceramic plate 13 was crushed in a mortar and pestle, and X-ray diffraction was performed using a sealed-tube X-ray diffractometer (Bruker AXS, D8 ADVANCE) under the conditions of X-ray used: CuKα, voltage: 40kV, current: 40mA, and 2θ = 5 to 70°. Furthermore, EPMA was used to detect and identify the constituent elements of the first ceramic material and to analyze the concentration of each constituent element. As a result, the XRD analysis chart of the first ceramic material consisted of multiple unidentifiable peaks and a peak of MgO-AlN solid solution, in which aluminum nitride is dissolved in magnesium oxide. The unidentifiable peak had a peak at 2θ = 47–49° (47–50°) that did not match magnesia, spinel, or aluminum nitride, and was presumed to be magnesium-aluminum oxynitride. Furthermore, the XRD peaks of the (111), (200), and (220) planes of the MgO-AlN solid solution appeared at 2θ = 36.9–39°, 42.9–44.8°, and 62.3–65.2°, which are between the peaks of the cubic phase of magnesium oxide and the peaks of the cubic phase of aluminum nitride. In addition, elemental mapping images obtained by EPMA confirmed that the first ceramic material is composed of two phases: magnesium-aluminum oxynitride and MgO-AlN solid solution, with the former being the main phase. Here, the main phase refers to the component that accounts for 50% or more by volume, and the secondary phase refers to the phase other than the main phase in which an XRD peak was identified. Since the area ratio in cross-sectional observation is thought to reflect the volume ratio, the main phase is defined as the region with an area of ​​50% or more in the EPMA elemental mapping image, and the secondary phase is defined as the region other than the main phase. From the EPMA elemental mapping image, the area ratio of magnesium-aluminum oxynitride was found to be approximately 66%, indicating that magnesium-aluminum oxynitride is the main phase.

[0046]

[0047] Table 1 shows the following: First, the second ceramic materials in Examples 2-6 (reference examples), which were prepared with a yttrium oxide content of 10-30 parts by weight per 100 parts by weight of aluminum nitride, exhibit excellent thermal conductivity and consequently excellent uniformity of heat, although their corrosion resistance is inferior. On the other hand, the highly corrosion-resistant material (first ceramic material) in Example 9 (reference example), which mainly consists of magnesium-aluminum oxynitride, exhibits excellent corrosion resistance but poor uniformity of heat. Furthermore, since the difference in the coefficient of linear expansion between the second ceramic materials in Examples 2-6 (reference examples) and the first ceramic material in Example 9 (reference example) is either negligible or extremely small, it can be said that when joined to the highly corrosion-resistant material (first ceramic material) to form a joint, damage due to differences in thermal expansion is less likely to occur compared to Examples 1, 7, and 8 (comparative examples), where the difference in the coefficient of linear expansion is large. These results suggest that by constructing a ceramic plate joint in which the lower ceramic plate is made of the second ceramic material from Examples 2-6, which is a high thermal conductivity material, and the upper ceramic plate is made of the first ceramic material from Example 9, which is a high corrosion resistance material, it is possible to provide a ceramic heater that can achieve both corrosion resistance and uniform heat distribution. This will be further verified in Example 7 below.

[0048] Example 10 The following shows an example of a two-layer ceramic plate joint formed according to the present invention.

[0049] (1) Fabrication of the ceramic heater A ceramic heater 10 having the structure shown in Figure 1 was fabricated using the components shown below, following a known procedure. <Components and their specifications> ・Ceramic plate joint 12: Joint of upper ceramic plate 12a and lower ceramic plate 12b ・Upper ceramic plate 12a: Disc-shaped sintered body (diameter: 360 mm, thickness: 5 mm) with the same composition as the ceramic plate (first ceramic material) fabricated in Example 9 (reference example) (neither the heater electrode 14 nor the internal electrode 18 is embedded) ・Lower ceramic plate 12b: Disc-shaped sintered body (diameter: 360 mm, thickness: 12 mm) with the same composition as the ceramic plate (second ceramic material) fabricated in Example 4 (reference example) (heater electrode 14 and internal electrode 18 are embedded inside) - Heater electrode 14: A coil-shaped resistance heating element embedded in a predetermined circuit pattern at a depth of 6.5 mm from the first surface 12d of the ceramic plate assembly 12 (inside the lower ceramic plate 12b). - Heater rod 16: Two nickel terminal rods connected to the heater electrode 14. - Internal electrode 18 (RF / ESC electrode): A molybdenum electrode layer embedded at a depth of 1.0 mm from the first surface 12d of the ceramic plate assembly 12 (inside the lower ceramic plate 12b). - Terminal rod 20 (RF / ESC rod): A single nickel terminal rod. - Ceramic shaft 24: A cylindrical aluminum nitride sintered body (height: 170 mm, maximum outer diameter: 90 mm, minimum outer diameter: 60 mm, inner diameter: 50 mm).

[0050] (Fabrication of the ceramic plate assembly) The ceramic plate assembly 12, in which the heater electrode 14 and internal electrode 18 described above are embedded, was fabricated by the following procedure.

[0051] (i) Preparation of the upper ceramic plate First, the raw material powder for the upper ceramic plate 12a (first ceramic material) is the same MgO and Al used in Example 9 (reference example). ２ O ３ And an AlN-containing powder was prepared. MgO, Al ２ O ３The AlN-containing powder was then press-molded. The resulting press-molded body was subjected to a nitrogen atmosphere at a maximum temperature of 1950°C for 3 hours at a rate of 200 kg / cm². ２ By hot-press firing under pressure, a single upper ceramic plate 12a was obtained.

[0052] (ii) Preparation of the lower ceramic plate Next, as the raw material powder for the lower ceramic plate 12b (second ceramic material), the same yttrium oxide-containing aluminum nitride powder prepared in Example 4 (reference example) (mixing ratio of yttrium oxide powder to 100 parts by weight of aluminum nitride powder: 20 parts by weight) was prepared. The yttrium oxide-containing aluminum nitride powder was placed on the upper ceramic plate 12a prepared in (i) above and press-molded to obtain a first compact on the lower ceramic plate 12b. On the obtained first compact, the internal electrode 18 was placed together with the yttrium oxide-containing aluminum nitride powder according to a predetermined circuit pattern and press-molded to obtain a second compact with the internal electrode 18 embedded inside. On the obtained second compact, the yttrium oxide-containing aluminum nitride powder and the heater electrode 14 were placed and press-molded to obtain a third compact with the heater electrode 14 further embedded inside. Thus, as shown in Figure 1, a laminate was obtained consisting of a lower ceramic plate 12b and a compacted aluminum nitride powder containing yttrium oxide in which the heater electrode 14 and internal electrode 18 were embedded. The obtained laminate was subjected to a nitrogen atmosphere at a maximum temperature of 1770°C for 2 hours at a rate of 200 kg / cm³. ２ By hot-press firing under pressure, a ceramic plate assembly 12 was obtained in which an upper ceramic plate 12a and a lower ceramic plate 12b, in which a heater electrode 14 and an internal electrode 18 are embedded, are joined to each other at a joint surface 12c.

[0053] (2) The ceramic heater obtained was evaluated for uniform heat distribution in the same manner as in Example 1. As shown in Figure 5, the ceramic heater 10 of this example had a uniform temperature distribution on its surface, a low maximum in-plane temperature difference of 0.5°C, and excellent uniform heat distribution. Furthermore, as can be inferred from the results of Example 9 (comparative example), the first ceramic material constituting the upper ceramic plate 12a (the same highly corrosion-resistant material as in Example 9) exhibits excellent corrosion resistance. Therefore, it can be said that the ceramic heater of this embodiment exhibits improved uniform heat distribution while ensuring corrosion resistance to corrosive gases such as halogen-based gases.

[0054] 10, 11 Ceramic heater 12 Ceramic plate assembly 12a Upper ceramic plate 12b Lower ceramic plate 12c Joint surface 12d, 13a First surface 12e Second surface 13 Ceramic plate 14 Heater electrode 16 Heater rod 18 Internal electrode 20 Terminal rod 22 Temperature sensing hole 24 Ceramic shaft S Internal space

Claims

1. A ceramic heater comprising: an upper ceramic plate and a lower ceramic plate joined together at a joint surface, the upper ceramic plate having a first surface opposite to the joint surface and the lower ceramic plate having a second surface opposite to the joint surface; and a heater electrode embedded only in the lower ceramic plate, wherein the upper ceramic plate comprises a first ceramic material mainly composed of magnesium, aluminum, oxygen, and nitrogen, the first ceramic material mainly comprises a magnesium-aluminum oxynitride phase in which a peak is observed at least at 2θ = 47 to 50° in the XRD profile obtained by XRD using CuKα rays, and the lower ceramic plate comprises a second ceramic material containing yttrium, aluminum, oxygen, and nitrogen in a ratio of 10 to 30 parts by weight of yttrium oxide to 100 parts by weight of aluminum nitride.

2. The ceramic heater according to claim 1, wherein the ratio of yttrium oxide to 100 parts by weight of aluminum nitride in the lower ceramic plate is 10 to 25 parts by weight.

3. The second ceramic material is a composite material of yttrium oxide and aluminum nitride, and a Y material in which aluminum nitride is solid-dissolved in magnesium oxide. ２ O ３ - A ceramic heater according to claim 1 or 2, comprising an AlN solid solution and / or yttrium-aluminum oxynitride.

4. The ceramic heater according to claim 1 or 2, wherein the second ceramic material comprises a yttrium-aluminum oxynitride phase.

5. The ceramic heater according to claim 1 or 2, wherein the lower ceramic plate has a linear expansion coefficient of 5.9 to 6.7 ppm / K.

6. The ceramic heater according to claim 1 or 2, wherein the lower ceramic plate has a thermal conductivity of 50 to 140 W / m·K.

7. The ceramic heater according to claim 1 or 2, wherein the first ceramic material includes as a secondary phase a crystalline phase of an MgO-AlN solid solution in which aluminum nitride is solid-dissolved in magnesium oxide.

8. The ceramic heater according to claim 1 or 2, wherein the first ceramic material does not contain an AlN crystalline phase.

9. The ceramic heater according to claim 1 or 2, further comprising internal electrodes which are ESC electrodes and / or RF electrodes embedded in the upper ceramic plate and / or the lower ceramic plate.

10. The ceramic heater according to claim 1 or 2, wherein the average particle size of the ceramic particles constituting the upper ceramic plate is 1.1 times or more the average particle size of the ceramic particles constituting the lower ceramic plate.

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