High-resistance and highly corrosion-resistant ceramic materials and wafer carriers

Abstract

The present invention relates to a high-resistance and highly corrosion-resistant ceramic material and a wafer carrier. The problem to be solved is to have sufficient corrosion resistance at high temperatures and to increase the volume resistivity at high temperatures. The high-resistance and highly corrosion-resistant ceramic material of the present invention contains magnesium-aluminum oxynitride, and the carbon content is 0.005 to 0.275% by mass.

Description

Technical Field

[0001] The present invention relates to a high-resistance and highly corrosion-resistant ceramic material and a wafer mounting table. Background Art

[0002] In semiconductor manufacturing apparatuses used in dry processes, plasma coating, etc. in semiconductor manufacturing, halogen-based plasmas such as F and Cl with high reactivity are used for etching and cleaning. Therefore, high corrosion resistance is required for components assembled in such semiconductor manufacturing apparatuses. As a material having high corrosion resistance, as shown in Patent Document 1, a ceramic material having a magnesium-aluminum oxynitride phase as a main phase is known. This ceramic material can withstand highly reactive halogen-based plasmas used in semiconductor manufacturing processes for a long time.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 5680645 Gazette Summary of the Invention

[0006] In recent years, in order to form high-quality films, the process temperature has been increased to a high temperature (500°C or higher). Therefore, not only sufficient corrosion resistance at high temperatures is required, but also the ability to electrostatically adsorb wafers at high temperatures.

[0007] The present invention has been proposed to solve such problems, and the main object is to have sufficient corrosion resistance at high temperatures and to increase the volume resistivity at high temperatures.

[0008] The high-resistance and highly corrosion-resistant ceramic material of the present invention is a ceramic material containing magnesium-aluminum oxynitride, and the carbon content is 0.005 to 0.275% by mass.

[0009] According to this ceramic material, since carbon is contained in an appropriate range, it has sufficient corrosion resistance at high temperatures and can increase the volume resistivity at high temperatures.

[0010] The wafer mounting table of the present invention includes: a ceramic substrate formed of the above ceramic material and capable of mounting a wafer on its upper surface; and an electrode disposed inside the ceramic substrate.

[0011] Alternatively, the wafer mounting table of the present invention includes: a ceramic substrate formed of the above ceramic material and capable of mounting a wafer on its upper surface; a high heat conduction substrate provided on the lower surface of the ceramic substrate and having a higher heat conductivity than the ceramic substrate; an electrode disposed inside the ceramic substrate, inside the high heat conduction substrate, or between the ceramic substrate and the high heat conduction substrate; and a resistance heating element disposed inside the high heat conduction substrate and below the electrode.

[0012] According to such a wafer stage, since the ceramic substrate is formed of the above-described ceramic material, it has sufficient corrosion resistance at high temperatures and can increase the volume resistivity at high temperatures. Here, the "electrode" can be, for example, an electrostatic electrode, a heater electrode (resistance heating element), or a high-frequency (RF) electrode for plasma generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a longitudinal sectional view of the wafer stage 10.

[0014] Figure 2 is a longitudinal sectional view of the wafer stage 20.

[0015] Figure 3 is a longitudinal sectional view of the wafer stage 30.

[0016] Figure 4 is a longitudinal sectional view of the wafer stage 40.

[0017] Figure 5 is the XRD chart of Experimental Example 3.

[0018] Figure 6 is the XRD chart of Experimental Example 5.

[0019] Figure 7 is a graph showing the relationship between the C content and the volume resistivity at 500°C.

[0020] SYMBOL EXPLANATION

[0021] 10 wafer stage, 12 ceramic substrate, 12a wafer placement surface, 14 electrostatic electrode, 16 resistance heating element, 18 shaft, 20 wafer stage, 22 ceramic substrate, 22a wafer placement surface, 23 high heat conduction substrate, 24 electrostatic electrode, 26 resistance heating element, 28 shaft, 30, 40 wafer stage. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Figures 1 to 4 are longitudinal sectional views of the wafer stages 10 to 40. It should be noted that in this specification, "up" and "down" do not represent an absolute positional relationship, but a relative positional relationship. Therefore, depending on the orientation of the wafer stages 10 to 40, "up" and "down" become "down" and "up", or become "left" and "right", or become "front" and "back". In addition, in this specification, "~" indicating a numerical range is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value.

[0023] The high-resistance and highly corrosion-resistant ceramic material of this embodiment contains magnesium-aluminum oxynitride, and the carbon content is 0.005 to 0.275% by mass. If the carbon content rate is within this range, it can have sufficient corrosion resistance at high temperatures and can increase the volume resistivity at high temperatures. For example, when this ceramic material is used for a ceramic substrate with a wafer placement surface and an electrostatic electrode built in, it can electrostatically adsorb the wafer at high temperatures or inhibit leakage current from flowing between the wafer and the electrode when processing the wafer at high temperatures. In addition, when this ceramic material is used for a ceramic substrate with a heater electrode (resistance heating element) or an RF electrode built in, it can inhibit leakage current from flowing between the wafer and the electrode when processing the wafer at high temperatures. When the carbon content rate is less than 0.005% by mass or exceeds 0.275% by mass, the volume resistivity at 500 °C becomes low. The carbon content rate is preferably 0.005 to 0.21% by mass. The ceramic material of this embodiment preferably contains magnesium-aluminum oxynitride as the main phase. Here, the main phase refers to the phase that contains the most in the overall phase.

[0024] The ceramic material of this embodiment preferably has a volume resistivity of 1×10 9 Ωcm or more at 500 °C. If the volume resistivity at 500 °C is 1×10 9 Ωcm or more, when this ceramic material is used as a ceramic substrate with a wafer placement surface and an electrode built in, it can sufficiently inhibit leakage current from flowing between the wafer and the electrode when processing the wafer at high temperatures. In addition, when this ceramic material is used for an electrostatic chuck, it can reliably electrostatically adsorb the wafer at high temperatures using the Johnson-Rabl force. In addition, the volume resistivity at 500 °C is preferably 5×10 11 Ωcm or less. Thus, when this ceramic material is used for an electrostatic chuck, the adsorption and desorption responsiveness of the wafer can be made good.

[0025] The ceramic material of this embodiment may contain titanium. By containing titanium, the color of the ceramic material can be made black. Therefore, the color unevenness of the ceramic material can be made less obvious. The content rate of titanium is set so that the corrosion resistance is not reduced and the volume resistivity at 500 °C does not deviate from the above range. For example, it can be set in the range of 0.1 to 1% by mass in terms of oxide conversion.

[0026] The ceramic material of the present embodiment preferably has a magnesium-aluminum oxynitride phase as the main phase, where the XRD peak when using CuKα radiation appears at least at 2θ = 47 to 50° (preferably 47 to 49°). Such a ceramic material has corrosion resistance to halogen plasmas equal to or higher than that of spinel, and is thus preferred. This main phase preferably coincides with the peak of the magnesium-aluminum oxynitride described in Patent Document 1 (Japanese Patent No. 5680645). It should be noted that the peak of the magnesium-aluminum oxynitride described in Patent Document 1 does not coincide with the peaks of MgAlON (or magnesium aluminum oxynitride) shown in Reference 1 (J. Am. Ceram. Soc., 93[2] 322-325 (2010)) and Reference 2 (Japanese Unexamined Patent Application Publication No. 2008-115065), for example. Generally, it is known that these MgAlON are substances in which an N component is solid-solved in spinel, and it is considered that they have a crystal structure different from that of the magnesium-aluminum oxynitride described in Patent Document 1.

[0027] Next, a manufacturing example of the ceramic material of the present embodiment will be described. The ceramic material of the present embodiment can be manufactured by molding a mixed powder of magnesium oxide, aluminum oxide, aluminum nitride, and a carbon source and then firing it. For example, it can be weighed such that magnesium oxide is 5 mass% or more and 60 mass% or less, aluminum oxide is 60 mass% or less, and aluminum nitride is 90 mass% or less, and then a carbon source is added thereto for mixing. After the obtained powder is molded, it is fired. As the carbon source, an organic binder, an organic dispersant, or carbon powder can be added. The addition amount of the carbon source is set such that the carbon content in the fired ceramic material is 0.005 to 0.2 mass%. Alternatively, it can also be adjusted such that the carbon content in the fired ceramic material is 0.005 to 0.2 mass% by degreasing at a stage before firing. In this case, the carbon content can be adjusted by the degreasing temperature. The degreasing temperature is preferably set in the range of 300 to 600°C, for example. For molding, for example, after granulating the slurry of the mixed powder to form granules, the granules can be powder-pressed, or a green sheet can be formed from the slurry of the mixed powder using a doctor blade method. The pressure during molding is not particularly limited, and it can be appropriately set to a pressure capable of maintaining the shape. The firing temperature is preferably 1750°C or higher, more preferably 1800 to 1950°C. In addition, hot press firing is preferably used for firing, and the pressing pressure during hot press firing is preferably set to 50 to 300 kgf / cm 2 . The atmosphere during firing is preferably an atmosphere that does not affect the firing of the oxide raw material. For example, an inert atmosphere such as a nitrogen atmosphere, an argon atmosphere, or a helium atmosphere is preferred. The pressure during molding is not particularly limited, and it can be appropriately set to a pressure capable of maintaining the shape.

[0028] Next, with reference to the drawings, the wafer mounting tables 10 to 40 will be described.

[0029] As shown Figure 1 in FIG. 1, the wafer stage 10 is an electrostatic chuck heater, and includes: an electrostatic electrode 14 disposed inside a ceramic substrate 12; and a resistance heating element 16 disposed inside the ceramic substrate 12 and below the electrostatic electrode 14.

[0030] The ceramic substrate 12 is obtained by forming the above ceramic material into a disc shape, and has a wafer placement surface 12a on which a wafer can be placed on the upper surface.

[0031] The electrostatic electrode 14 is a disc-shaped metal plate or metal mesh, and is disposed parallel to the wafer placement surface 12a. In addition to the disc-shaped metal plate and mesh, the electrostatic electrode 14 can also adopt forms such as foil, perforated metal, and printed electrode. It should be noted that for "parallel", in addition to the case of complete parallelism, even if it is not completely parallel but within the allowable error (such as tolerance), it is regarded as parallel. The portion of the ceramic substrate 12 above the electrostatic electrode 14 functions as a dielectric layer. When a DC voltage is applied to the electrostatic electrode 14, the wafer placed on the wafer placement surface 12a is adsorbed to the wafer placement surface 12a due to the Johnson-Raabe force (electrostatic force). Examples of the material for the electrostatic electrode 14 include W, Mo, W-Mo alloy, or their carbides.

[0032] When observing the ceramic substrate 12 from above, the resistance heating element 16 is wired from one end to the other end throughout the whole in one stroke, and generates heat by passing an electric current between one end and the other end. The resistance heating element 16 can use, for example, a component obtained by bending a linear conductor and processing it into a wound body. The wire diameter of the resistance heating element 16 is preferably about 0.3 mm to 0.5 mm. In the case of a coil shape, the coil diameter is preferably about 2 mm to 4 mm, and the pitch is preferably about 1 mm to 7 mm. Here, the "coil diameter" refers to the inner diameter of the coil constituting the resistance heating element 16. As the shape of the resistance heating element 16, in addition to the coil shape, various forms such as strip shape, mesh shape, helical spring shape, sheet shape, and printed electrode can also be adopted. Examples of the material for the resistance heating element 16 include W, Mo, W-Mo alloy, or their carbides.

[0033] A cylindrical shaft 18 is joined to the lower surface of the wafer stage 10. The joining can be performed by sintering, for example, or can be performed using an adhesive (such as an inorganic adhesive). The shaft 18 preferably uses a component having the same or similar linear thermal expansion coefficient as that of the ceramic substrate 12. As the material of the shaft 18, AlN-YAG is preferably used. YAG is yttrium aluminum garnet (Y 3 Al 5 O 12) is the abbreviation of. AlN-YAG may contain titanium, and its content rate can be, for example, 0.1 to 1 mass% in terms of oxide conversion. When titanium is added, the color of AlN-YAG turns black, so that the color unevenness of AlN-YAG can be made less obvious.

[0034] According to the wafer stage 10 described above, the ceramic substrate 12 is formed of the above-mentioned ceramic material, and thus has the same effects as the above-mentioned ceramic material. For example, it has sufficient corrosion resistance at high temperatures and can increase the volume resistivity at high temperatures. In addition, it can electrostatically adsorb the wafer at high temperatures or suppress the leakage current flowing between the wafer and the electrostatic electrode 14 when processing the wafer at high temperatures. Furthermore, it can suppress the leakage current flowing between the wafer and the resistance heating element 16 when processing the wafer at high temperatures.

[0035] Figure 2 The wafer stage 20 shown is an electrostatic chuck heater formed by joining a high heat conduction substrate 23 with a resistance heating element 26 built-in to the lower surface of a ceramic substrate 22 with an electrostatic electrode 24 built-in. The joining can be performed by sintering, for example, or can be performed using a joining agent (such as an inorganic joining agent).

[0036] The ceramic substrate 22 is obtained by forming the above-mentioned ceramic material into a disk shape and has a wafer placement surface 22a on which the wafer can be placed on the upper surface. The electrostatic electrode 24 is the same as the above-mentioned electrostatic electrode 14, so the description is omitted.

[0037] The high heat conduction substrate 23 uses a component with a higher thermal conductivity than the ceramic substrate 22 and a linear thermal expansion coefficient the same as or close to that of the ceramic substrate 12. AlN-YAG may contain titanium, and its content rate can be, for example, 0.1 to 1 mass% in terms of oxide conversion. When titanium is added, the color of AlN-YAG turns black, so that the color unevenness of AlN-YAG can be made less obvious.

[0038] The resistance heating element 26 is the same as the above-mentioned resistance heating element 16, so the description is omitted.

[0039] A cylindrical shaft 28 is joined to the lower surface of the wafer stage 20. The shaft 28 is the same as the above-mentioned shaft 18, so the description is omitted.

[0040] According to the wafer stage 20 described above, the ceramic substrate 22 is formed of the above-mentioned ceramic material, and thus has the same effects as the above-mentioned ceramic material. For example, it has sufficient corrosion resistance at high temperatures and can increase the volume resistivity at high temperatures. In addition, it can electrostatically adsorb the wafer at high temperatures or suppress the leakage current flowing between the wafer and the electrostatic electrode 14 when processing the wafer at high temperatures.

[0041] In addition, in the wafer stage 20, a high heat conduction substrate 23 is joined to the lower surface of the ceramic substrate 22. Therefore, compared with the wafer stage 10, it is easier to make the temperature of the wafer placed on the wafer placement surface 22a uniform.

[0042] Furthermore, the coefficient of thermal expansion of the high heat conduction substrate 23 is the same as or close to that of the ceramic substrate 22. Therefore, even if heating and cooling are repeated, it is difficult to peel off from the ceramic substrate 22.

[0043] Except for disposing the electrostatic electrode 24 at the interface between the ceramic substrate 22 and the high heat conduction substrate 23, Figure 3 the wafer stage 30 shown is the same as the wafer stage 20. The wafer stage 30 can also obtain the same effect as the wafer stage 20.

[0044] Except for disposing the electrostatic electrode 24 inside the high heat conduction substrate 23 instead of the ceramic substrate 22, Figure 4 the wafer stage 40 shown is the same as the wafer stage 20. The resistance heating element 26 is disposed at a position lower than the electrostatic electrode 24. The wafer stage 40 can also obtain the same effect as the wafer stage 20. However, in the wafer stage 40, the dielectric layer (the part above the electrostatic electrode 24) is composed of the ceramic substrate 22 and the high heat conduction substrate 23. Therefore, it is easier to adjust the adsorption force of the wafer in the wafer stages 10 to 30 in which the dielectric layer is composed only of the ceramic substrate 22.

[0045] It should be noted that the present invention is not limited to the above-described embodiments, and of course, can be implemented in various ways as long as it belongs to the technical scope of the present invention.

[0046] For example, as the wafer stages 10 to 40, the case where the electrostatic electrodes 14 and 24 are built in is exemplified, but the electrostatic electrodes 14 and 24 may not be built in. In this case, it is also possible to suppress the leakage current flowing between the wafer and the resistance heating elements 16 and 26. In addition, an RF electrode may be built in instead of the electrostatic electrodes 14 and 24, or an RF electrode may be built in addition to the electrostatic electrodes 14 and 24, or the electrostatic electrodes 14 and 24 may be used as the RF electrode.

[0047] In addition, the outer periphery (upper surface, side surface, lower surface) of the high heat conduction substrate 23 can be wrapped with the above-described ceramic material. Thereby, the corrosion resistance of the side surface and the bottom surface can be improved.

[0048] Examples

[0049] Hereinafter, examples of the present invention will be described. Experimental examples 2 to 6, 9 to 11, 13 to 15, and 17 to 19 correspond to the examples of the present invention. It should be noted that the following examples do not limit the present invention.

[0050] [Experimental Examples 1 to 7]

[0051] ·Mixing

[0052] In Experimental Example 1, the MgO raw material, Al 2 O 3 raw material, and the AlN raw material were weighed to achieve the mass % shown in Table 1, and using isopropyl alcohol as a solvent, wet mixing was performed for 4 hours using a nylon pot and alumina balls with a diameter of 5 mm. After mixing, the slurry was taken out and dried at 110°C in a nitrogen stream. Then, it was passed through a 30-mesh sieve to obtain a blended powder.

[0053] In Experimental Example 2, the MgO raw material, Al 2 O 3 raw material, and the AlN raw material were weighed to achieve the mass % shown in Table 1, and using isopropyl alcohol as a solvent, 1.0 mass % of an acrylic binder and 0.1 mass % of a polycarboxylic dispersant were added, and wet mixing was performed for 4 hours using alumina balls in a drum sieve to prepare a raw material slurry. The obtained raw material slurry was spray-dried using a spray dryer to produce granules. Furthermore, the obtained granules were heated at 500°C in the atmosphere for 24 hours to produce partially degreased granules.

[0054] In Experimental Example 3, partial degreasing was performed by heating at 500°C in the atmosphere for 5 hours, and granules were produced in the same manner as in Experimental Example 2 except for this.

[0055] In Experimental Example 4, 1.5 mass % of an acrylic binder and 0.5 mass % of a polycarboxylic dispersant were added and partial degreasing was performed by heating at 450°C in the atmosphere for 5 hours, and granules were produced in the same manner as in Experimental Example 2 except for this.

[0056] In Experimental Example 5, degreasing was not performed, and granules were produced in the same manner as in Experimental Example 4 except for this.

[0057] In Experimental Example 6, the MgO raw material, Al 2 O 3 raw material, and the AlN raw material were weighed to achieve the mass % shown in Table 1, and using isopropyl alcohol as a solvent, 0.3 mass % of carbon powder was added, and wet mixing was performed for 4 hours using a nylon pot and alumina balls with a diameter of 5 mm. After mixing, the slurry was taken out and dried at 110°C in a nitrogen stream. Then, it was passed through a 30-mesh sieve to obtain a blended powder.

[0058] In Experimental Example 7, 0.42 mass % of carbon powder was added, and granules were produced in the same manner as in Experimental Example 6 except for this.

[0059] ·Molding

[0060] At 100 kgf / cm 2Under pressure, the blended powder or granules were uniaxially press-molded to produce a disk-shaped compact with a diameter of about 35 mm and a thickness of about 10 mm, which was then placed in a graphite mold for firing.

[0061] ·Firing

[0062] A ceramic substrate was obtained by hot-press firing the disk-shaped compact. In the hot-press firing, the pressing pressure was set at 200 kgf / cm 2 , and firing was carried out at the firing temperature (maximum temperature) shown in Table 1. The atmosphere was set to N 2 atmosphere until the end of firing. The holding time at the firing temperature was set at 4 hours.

[0063] [Evaluation]

[0064] (1) Crystal phase evaluation

[0065] The ceramic substrates obtained in Experimental Examples 1 to 7 were crushed in a mortar, and the crystal phase was identified using an X-ray diffractometer. The measurement conditions were CuKα, 40 kV, 40 mA, 2θ 5 - 70°, and an enclosed tube type X-ray diffractometer (D8 ADVANCE manufactured by Bruker AXS) was used. As a result, in any of Experimental Examples 1 to 7, the main phase was magnesium-aluminum oxynitride (peaks were present at 2θ = 47 - 49°). This main phase was consistent with the peaks of the magnesium-aluminum oxynitride identified in Patent Document 1. Figure 5 And Figure 6 The XRD patterns of representative examples (Experimental Examples 3 and 5) are shown.

[0066] (2) Carbon (C) content

[0067] The C content was measured according to the method for measuring the total carbon content described in JIS R1616:2007. Specifically, in an oxygen stream, the sample was burned together with a combustion aid by high-frequency heating, and the generated carbon dioxide (and carbon monoxide) was sent together with oxygen into an infrared analyzer to measure the change in the infrared absorption amount, and the C content was determined. The C contents of the ceramic substrates obtained in Experimental Examples 1 to 7 are shown in Table 1. The C contents in Experimental Examples 1 and 7 were 0.002 mass% and 0.30 mass%, respectively, while in Experimental Examples 2 to 6, they were 0.005 - 0.21 mass%. Experimental Example 1 was an implementation product of Patent Document 1, and the C content of Experimental Example 1 was the value when no carbon source was actively added (the C content contained as an impurity).

[0068] (3) Volume resistivity (500 °C)

[0069] The volume resistivity was measured at 500 °C in the atmosphere by a method based on JIS-C2141. The test piece had a shape of diameter 50 mm × (0.5 - 1 mm), and each electrode was formed of silver such that the diameter of the main electrode was 20 mm, the inner diameter of the guard electrode was 30 mm and the outer diameter was 40 mm, and the diameter of the applied electrode was 40 mm. The applied voltage was 500 V / mm, the current value at 3 minutes after the application of the voltage was read, and the room temperature volume resistivity was calculated from this current value. The volume resistivities of the ceramic substrates obtained in Experimental Examples 1 to 7 are shown in Table 2. In the volume resistivity in Table 2, [E8] represents 10 8 , and [E10] represents 10 10 . Regarding the volume resistivity at 500 °C, it was 1 × 10 9 Ω·cm or more in Experimental Examples 2 to 6, but was a lower value in Experimental Examples 1 and 7. A graph showing the relationship between the C content rate and the volume resistivity at 500 °C is shown in Figure 7 . From the Figure 7 curve graph, the C content rate at which the volume resistivity at 500 °C is 1 × 10 9 Ω·cm or more is 0.005 - 0.275 mass%. In addition, if it is 0.011 - 0.19 mass%, it reaches 5 × 10 9 Ω·cm or more, which is better.

[0070] (4) Thermal conductivity (room temperature)

[0071] The thermal conductivity was measured by the laser flash method. The thermal conductivities at room temperature of the ceramic substrates obtained in Experimental Examples 2, 3, 5, and 6 are shown in Table 2.

[0072] (5) Average linear thermal expansion coefficient (40 - 1000 °C)

[0073] The average linear thermal expansion coefficient at 1000 °C was measured using a dilatometer (manufactured by Bruker AXS) in a nitrogen atmosphere at 40 - 1000 °C. The average linear thermal expansion coefficients at room temperature of the ceramic substrates obtained in Experimental Examples 2, 3, 5, and 6 are shown in Table 2.

[0074] (6) Etching rate

[0075] The etching rates of the ceramic substrates obtained in Experimental Examples 1, 3, 5, and 6 are shown in Table 2. Specifically, the surface of each material was mirror-polished, and a corrosion resistance test was performed under the following conditions using an ICP plasma corrosion resistance test device. Then, the step difference between the mask surface and the exposed surface measured by a step gauge was divided by the test time to calculate the etching rate of each material. As a result, it was found that Experimental Examples 3, 5, and 6 had the same or higher corrosion resistance compared to Experimental Example 1 (the product of Patent Document 1 having the same or higher corrosion resistance as spinel).

[0076] ICP: 800 W, Bias: 300 W, Introduced gas: NF 3 / Ar = 75 / 100 sccm 13 Pa, Exposure time: 5 hours, Specimen temperature: 550 °C

[0077] [Table 1]

[0078]

[0079] [Table 2]

[0080]

[0081] ※Mg-Al-O-N: Magnesium-aluminum oxynitride (XRD: Peaks exist at 2θ = 47 - 49°)

[0082] [Experimental Examples 8 - 19]

[0083] In Experimental Examples 8 - 19, the MgO raw material, Al 2 O 3 raw material, and AlN raw material were weighed in such a way as to achieve the mass % shown in Table 1. Based on Experimental Examples 1 - 7, blended powders or granules were produced, formed, and fired to obtain a ceramic substrate. The C content rate of the obtained ceramic substrate is shown in Table 1. In addition, the C content rates of Experimental Examples 8, 12, and 16 are the values when no carbon source was actively added (C content rate contained as an impurity).

[0084] [Experimental Example 20]

[0085] Experimental Example 20 is an example of a high thermal conductivity substrate made of AlN - YAG. First, the AlN raw material, Y 2 O 3 raw material, Al 2 O 3 raw material, and TiO 2 raw material were weighed in such a way as to achieve 74.5 mass %, 15 mass %, 10 mass %, and 0.5 mass %, respectively. Using isopropyl alcohol as a solvent, wet mixing was performed for 4 hours using a nylon jar and alumina balls with a diameter of 5 mm. After mixing, the slurry was taken out and dried at 110 °C in a nitrogen stream. Then, it was passed through a 30 - mesh sieve to produce a blended powder. Using this blended powder, forming and firing were performed in the same manner as in Experimental Example 1 to obtain a disk - shaped high thermal conductivity substrate. The XRD spectrum of this high thermal conductivity substrate was analyzed. As a result, the main phase was AlN - YAG. In addition, the color of the high thermal conductivity substrate was black. The volume resistivity of the obtained high thermal conductivity substrate at 500 °C was 5×10 9 Ωcm, the thermal conductivity at room temperature was 81 W / m·K, and the thermal expansion coefficient at 40 - 1000 °C was 6.1×10 -6 / K. That is, the thermal conductivity is approximately 10 times that of Experimental Examples 2, 3, 5, and 6, and the coefficient of thermal expansion is equivalent to that of Experimental Examples 2, 3, 5, and 6. Experimental Example 20 can be used as the shaft 28 of the above-mentioned wafer placement tables 10 to 40 or the high thermal conductivity substrate 23 of the wafer placement tables 20 to 40.

Claims

1. A high-resistance and highly corrosion-resistant ceramic material, which is a ceramic material containing magnesium-aluminum oxynitride, wherein, the carbon content is 0.085% by mass or more and 0.19% by mass or less, The volume resistivity at 500 °C is 5×10 9 Ω·cm or more, and the ceramic material contains titanium in an amount of 0.1 to 1% by mass.

2. The ceramic material according to claim 1, wherein, the magnesium-aluminum oxynitride phase in which the XRD peak when using CuKα radiation appears at least at 2θ = 47 to 50° is used as the main phase.

3. A wafer placement table, comprising: a ceramic substrate formed of the ceramic material according to claim 1 or 2 and capable of placing a wafer on its upper surface; and an electrode disposed inside the ceramic substrate.

4. A wafer placement table, comprising: a ceramic substrate formed of the ceramic material according to claim 1 or 2 and capable of placing a wafer on its upper surface; a high thermal conductivity substrate provided on the lower surface of the ceramic substrate and having a higher thermal conductivity than that of the ceramic substrate; an electrode disposed inside the ceramic substrate, inside the high thermal conductivity substrate, or between the ceramic substrate and the high thermal conductivity substrate; and a resistive heating element disposed inside the high thermal conductivity substrate and below the electrode.

5. The wafer placement table according to claim 4, wherein, the high thermal conductivity substrate contains AlN and YAG.

6. The wafer placement table according to claim 5, wherein, the high thermal conductivity substrate contains titanium.

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