Alumina sintered body and electrostatic chuck

Abstract

To provide a technique for suppressing the generation of particles in an alumina sintered compact.SOLUTION: The alumina sintered body contains Y in an amount of 90ppm or more and 265ppm or less and Ca in an amount of 100ppm or less, and has an average alumina grain size of 6 μm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an alumina sintered body and an electrostatic chuck. [Background technology]

[0002] As semiconductors become more miniaturized, there is a growing demand for ceramic components to suppress particle generation. Many particles from ceramics are caused by particle shedding, so particle shedding prevention is required. To prevent this, there is a method of adding grain boundary strengthening elements (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4744855 [Patent Document 2] Patent Publication No. 2021-093488 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if a phase with a different composition from the base material exists in the ceramic, the plasma Due to the difference in etching rate during irradiation, only that layer becomes convex, and it is removed from the base material. When desorbed, there is a possibility that it will become particles.

[0005] The present invention has been made to solve the above-mentioned problems, and provides an alumina sintered body. The object of the present invention is to provide a technology for suppressing particle generation. [Means for solving the problem]

[0006] The present invention has been made to solve at least one of the above problems, and provides the following: It can be realized in the form.

[0007] (1) According to one aspect of the present invention, there is provided an alumina sintered body containing Al2O3 as a main component. This alumina sintered body contains yttrium (Y) in an amount of 90 ppm or more and 265 ppm or less, Contains calcium (Ca) at 100 ppm or less, and the average particle size of alumina crystal grains is 6 μm or less is.

[0008] According to this type of alumina sintered body, since yttrium is added, alumina The grain boundaries can be strengthened. In addition, the calcium concentration of the alumina sintered body is low, so the calcium It is possible to suppress the precipitation of secondary phases containing calcium and yttrium. The average grain size of the nanocrystalline particles is controlled to 6 μm or less, which suppresses the precipitation of secondary phases. As a result, the alumina sintered body of this type can prevent particle generation. It can be suppressed.

[0009] (2) In the alumina sintered body of the above-mentioned form, the alumina sintered body is In the measurement results, it is not necessary to have a peak corresponding to a lattice spacing of 2.6 Å to 2.9 Å. According to this type of alumina sintered body, YAG (Y3Al5O 12 : Yttrium aluminum Since almost no titanium garnet precipitates at the grain boundary triple junctions, particle generation is suppressed. It can be suppressed.

[0010] (3) In the alumina sintered body of the above form, the surface of the alumina sintered body is examined using a scanning electron microscope. 1.2mm in the mirror 2 When checking the area of ​​calcium (Ca) and yttrium (Y), Covered area 10μm 2The above phases may be present in one or less places. According to the results, no phases containing calcium (Ca) and yttrium (Y) were detected, and the precipitation of secondary phases was not observed. Since the emission is suppressed, the generation of particles can be suppressed.

[0011] (4) In the above-mentioned alumina sintered body, the density is 3.96 g / cm 3 Even if it is more than This reduces the number of pores, which helps to suppress particle generation. This can be done.

[0012] (5) According to another aspect of the present invention, there is provided an electrostatic chuck for holding an object. The electric chuck has a first surface on which the object is placed and a second surface that is the backside of the first surface. a plate-shaped first layer disposed on the second surface side of the first layer, and a chuck electrode disposed therein; and a plate-shaped second layer formed on the first surface of the first layer, It is made of an alumina sintered body.

[0013] According to the electrostatic chuck of this embodiment, at least a part of the first surface on which the object is placed is Since the alumina sintered body has a shape similar to that of a sintered alumina, at least a part of the first surface has a secondary phase precipitated thereon. Therefore, when the first surface of the electrostatic chuck is irradiated with plasma, particles are generated. The occurrence of bubbles can be suppressed.

[0014] The present invention can be realized in various aspects, for example, as a semiconductor manufacturing device. Parts, semiconductor manufacturing equipment, holding device, electrostatic chuck, and device including these, and semiconductor The present invention can be realized in the form of a method for manufacturing a component for a conductor manufacturing device, or the like. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a process diagram showing a method for producing an alumina sintered body. FIG. [Figure 2] FIG. 10 is a diagram showing the evaluation results of the examples. [Figure 3] FIG. 1 is a diagram showing an example of the presence or absence of a Ca—Y phase in a sample. [Figure 4] FIG. 1 is a diagram showing the difference in precipitation of secondary phases depending on the firing time. [Figure 5] FIG. 1 is an explanatory diagram conceptually illustrating the mechanism of secondary phase precipitation. [Figure 6] FIG. 10 is a diagram showing an example of an SEM image of a sample after plasma irradiation. [Figure 7] FIG. 10 is a perspective view schematically illustrating the external configuration of an electrostatic chuck according to a second embodiment. [Figure 8] FIG. 2 is an explanatory view schematically showing an XZ cross-sectional configuration of the electrostatic chuck. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment The alumina sintered body according to the first embodiment of the present invention is made of alumina (Al2O3) as the main component. It contains yttrium (Y) in an amount of 90 ppm or more and 265 ppm or less, and calcium (Ca) The average particle size of alumina crystal grains is 6 μm or less. The lower limit of the average particle size of the alumina crystal grains is not particularly limited, but it is preferably 0.5 μm or more. The sintered body preferably does not contain calcium. However, calcium may be mixed in as an impurity. In the alumina sintered body of this embodiment, as described above, the concentration is set to 100 ppm or less. It's being suppressed.

[0017] The yttrium and calcium contents can be determined as follows: For the sintered carbon material, ICP (Inductively Coupled Plasma Elemental analysis was performed using high-frequency inductively coupled plasma (ICP) emission spectrometry to determine the concentration of yttrium and calcium. The amount of sodium is quantified. Since there is sampling variation in the measurement, the number of measurements is 5 or more. Use the average value.

[0018] Adding yttrium to alumina sintered bodies strengthens the alumina grain boundaries. This means that the bonding between the alumina crystal particles becomes stronger (the bonding strength is improved). ), which can suppress grain shedding. Gadolinium (Gd) is also effective in strengthening grain boundaries. However, the addition of yttrium results in a higher yield than the addition of gadolinium. This is preferable because it increases the withstand voltage.

[0019] In addition, when calcium is contained in an alumina sintered body, calcium and yttrium Since calcium and yttrium are elements that are resistant to plasma, Therefore, the etching rate of the precipitated secondary phase during plasma exposure is different from that of alumina crystal particles. The secondary phase (Ca-Y phase) remains as a convex part, which is likely to become a particle. If calcium is added during the production of Lumina sintered body, it will promote the grain growth of alumina crystal grains. On the other hand, the alumina sintered body of this embodiment is prone to formation of secondary phases. The content is low at 100 ppm or less, which suppresses the precipitation of secondary phases with different compositions from the base material. This makes it possible to suppress the generation of particles.

[0020] The particle size of the alumina crystal grains in the alumina sintered body is measured by the intercept method. Specifically, the fracture surface of the alumina sintered body is observed by SEM (Scanning Electron Microscopy). The secondary electrons obtained were observed using a scanning electron microscope (SEM). When a line of length L is drawn on the image, the number of particles n that the line crosses is measured. The particles with both ends of the line inside are counted as 0.5. Then, by the following formula (1), The average particle size D (μm) is calculated. D = 1.5 × L / n (1) In this embodiment, the number of particles n is 100 or more, and an arbitrary number of lines intersecting the number of particles n are drawn in parallel. The average particle size D was calculated.

[0021] When the alumina crystal grains grow abnormally, a secondary phase of YAG precipitates. By setting the average particle size to 6 μm or less, the generation of secondary phases can be suppressed, and convex particles can be formed when exposed to plasma. This can prevent the formation of small particles, thereby suppressing the generation of particles. Cut.

[0022] The alumina sintered body of this embodiment has a lattice spacing of 2 It is preferable that there is no peak corresponding to 0.6 Å to 2.9 Å. The maximum YAG peak is not detected by X-ray diffraction of the sintered body. The maximum peak is at (3,1,1), and the peak corresponds to the lattice spacing of 2.6Å to 2.9Å. In such alumina sintered bodies, YAG is hardly precipitated, so the power This can suppress the occurrence of defects.

[0023] The surface of the alumina sintered body of this embodiment was observed with a scanning electron microscope at a depth of 1.2 mm. 2 Check the area of When calcium (Ca) and yttrium (Y) were added, the area was 10 μm 2 The above phases are 1 In such an alumina sintered body, calcium (Ca) The precipitation of secondary phases containing yttrium (Y) is suppressed, reducing particle generation. It can be suppressed.

[0024] The density of the alumina sintered body of this embodiment is not particularly limited, but is preferably 3.96 g / cm 3 End Such an alumina sintered body has few pores, so it is preferable that the The density of the alumina sintered body is measured by the Archimedes method. The density of the alumina sintered body can be measured by the method of (JIS R 1634). Lumina's theoretical density is 4.0 g / cm 3 It is preferable that it is close to .

[0025] 1 is a process diagram showing a method for producing an alumina sintered body according to this embodiment. The manufacturing process for the granules consists of the blending and spray drying process P1, the degreasing process P2, and the hot pressing process P3. First, in the blending and spray drying process P1, inorganic compounds are mixed in a solvent. The inorganic component is alumina (Al 2O3) with the addition of auxiliary materials such as yttria (Y2O3) and spinel (MgAl2O4). Spinel is added to suppress the grain growth of alumina. The lees are spray dried to produce granules.

[0026] In the debinding process P2, the granules obtained in the blending and spray drying process P1 are uniaxially pressed. Mold (about 10 MPa) · CIP (Cold Isostatic Pressing) The pressed body, which has been subjected to isostatic pressing (approximately 150 MPa), is degreased at 500 to 800°C.

[0027] In the hot pressing process P3, the degreased body obtained in the degreasing process P2 is heated in an inert atmosphere (Ar The mixture is then hot pressed at 1300°C to 1625°C in a vacuum or other suitable atmosphere. This results in alumina sintering. Hot pressing produces a body by applying pressure during firing, which is different from air firing. This allows the particles to be crushed during firing, which promotes densification and makes it easier to reduce pores at the grain boundaries. In addition, the contact area between particles is increased, so the sintering process itself takes less time than air sintering. You can finish it.

[0028] The alumina sintered body of this embodiment can be used as a component for semiconductor manufacturing equipment, a semiconductor manufacturing equipment, a holding device, etc. , electrostatic chucks, and devices equipped with them. [Example]

[0029] The present invention will be explained in more detail with reference to examples. 2 shows the evaluation results of samples 1 to 18. Using the sintered samples 1 to 18, the sintered density, average particle size, calcium content, and Ca-Y The presence or absence of the YAG phase was evaluated.

[0030] 1. Sample Preparation Samples 1 to 18 were manufactured by the manufacturing method of the above embodiment. indicates the amount of yttria and spinel added in the blending and spray drying process P1, the amount of dispersant The presence or absence of addition, and the firing temperature and firing time in the hot pressing step P3 were varied. It is being done.

[0031] The amount of Y added (ppm) in Figure 2 is the amount of yttrium added minus the amount of yttria added. The yttrium content (ppm) in the alumina sintered body is calculated as follows: The yttrium content is approximately equal to the amount of yttrium added (ppm) in the alumina sintered body. It can be determined by elemental analysis using P emission spectrometry. Since the variation is about ±20%, it is recommended to measure 5 or more samples and use the average value. Therefore, the yttrium content (determined by ICP emission spectrometry) is Converge to the addition.

[0032] In the debinding process P2, debinding was performed in air at 500°C. Samples 1 to 15, 17, and 18 were hot-pressed at a pressure of 20 MPa. The topless pressure was 60 MPa. The firing temperature and firing time will be described later.

[0033] Manufacturing conditions for sample 4 (Y addition amount 174 ppm / firing temperature 1550 ° C / firing time 4 hours ) as the standard condition, the amount of yttrium added, the firing temperature, the firing time, and the effectiveness of the addition of dispersant were investigated. The dispersant added here contains calcium, and the calcium is converted into alumina. In the examples, samples 13 and 14 were added with a dispersant. The remaining samples had no dispersant added. In Samples 1 to 18, the dispersant has the effect of suppressing aggregation of inorganic components in the solvent. When a dispersant is added, water is used as the solvent. When no dispersant is added, water is used as the solvent. An organic solvent (here, ethanol) is used to suppress aggregation. Alternatively, a dispersant containing no calcium may be used and the solvent may be water. Various known organic solvents other than those mentioned above can also be used.

[0034] 2.Measurement method The density of the alumina sintered body was measured by the Archimedes method (JIS R 1634). .

[0035] The average grain size of the alumina crystal grains in the alumina sintered body was determined by the intercept method as described above. The particle diameters were calculated using the particle diameters measured by the

[0036] The calcium content was determined by ICP emission spectrometry. The presence or absence of the Ca-Y phase was determined by the fracture of each sample. SEM images of the cross section and mirror-polished surface were confirmed, and EDS (energy dispersive scanning electron microscope) The presence of the YAG phase was determined by identifying the elements contained therein using X-ray spectroscopy. The absence or presence of ions was determined by XRD (X-ray diffraction).

[0037] 3.Measurement results FIG. 3 shows an example of the presence or absence of the Ca-Y phase in the sample. The SEM images of samples 4, 13, and 15 are shown in Fig. 3(A), and the EDS image of sample 13 is shown in Fig. 3(B). The results are shown in Figure 3(D). The spectrum is shown on the left side, and the quantitative results are shown on the right side. Figure 5 shows the difference in secondary phase precipitation depending on the firing time. 6 is a conceptual explanatory diagram showing an example of an SEM image of a sample after plasma irradiation. Figure.

[0038] Sample 4 (alumina sintered body 100) manufactured under standard conditions was found to have the following properties (1) to (6): The requirements are met (Figure 2). [1] Contains yttrium (Y) in an amount of 90 ppm or more and 265 ppm or less. [2] Contains calcium (Ca) at 100 ppm or less. [3] The average particle size of the alumina crystal particles is 6 μm or less. [4] The results of X-ray diffraction measurements of alumina sintered bodies show that the lattice spacing is 2.6 Å to There is no peak corresponding to 2.9 Å, i.e., no YAG phase. [5] The surface of the alumina sintered body was examined with a scanning electron microscope at 1.2 mm 2 When checking the area of It contains calcium (Ca) and yttrium (Y) and has an area of ​​10 μm 2 The above phases are present in one or more places. In other words, there is no Ca-Y phase. [6] The density of sintered alumina is 3.96 g / cm 3 That's all.

[0039] Figure 3(A) is an SEM image of the surface (mirror polished) of Sample 4. As shown in the figure, In the SEM image of pull 4, no secondary phase precipitation was observed.

[0040] Samples 3, 5-7, 17, and 18 were manufactured by changing only the firing temperature compared to sample 4. Samples 3, 17, and 18 were lower than sample 4, at 1525°C, respectively. Samples 5 to 7 were manufactured at firing temperatures of 1450°C, 1490°C, and 1460°C, respectively. The sintering temperatures were 1575℃, 1600℃, and 1625℃, respectively. Sample 3 has the same sintered density as Sample 4, but the average grain size is smaller than Sample 4. Samples 5 and 6 have a lower sintered density than Sample 4, and a larger average grain size than Sample 4. Sample 7 has a higher sintering density and average grain size than Sample 4. Samples 17 and 18 have a higher sintering density and average grain size than Sample 4. The degree and average particle size are smaller than those of sample 4. Samples 3, 5 to 7, 17, and 18 also have the same properties as those of [1] above. The requirements of [6] are met. That is, Ca-Y phase and YAG phase (secondary phase) are formed. In addition, the results for samples 3 to 7, 17, and 18 show that the higher the firing temperature, the greater the average It can be seen that the particle size increases.

[0041] Sample 2 contains less Mg (added as spinel) than Sample 4, and The other conditions were the same as those of Sample 4. Sample 2 had a higher sintered density than Sample 4. The average particle size is the same as that of Sample 4. Sample 2 also satisfies the above requirements [1] to [6]. In other words, the Ca-Y phase and the YAG phase (secondary phase) are not formed.

[0042] Sample 1 has a lower amount of yttrium added than Sample 4, at 87 ppm. Other conditions were the same as those of Sample 4. Sample 1 had the same sintered density as Sample 4. Sample 1 also satisfies the above requirements (1) to (6). That is, the Ca-Y phase and the YAG phase (secondary phase) are not formed.

[0043] Sample 8 was fired at a higher temperature of 1625°C than Sample 4, and the firing time was longer. The other conditions were the same as those for Sample 4. Sample 8 was The average particle size of the mina crystal grains was 7.5 μm, which was larger than that of sample 4, and the YAG phase (secondary phase Sample 8 meets requirements (3) and (4) of the above requirements (1) to (6). does not satisfy.

[0044] Sample 16 was fired at a lower temperature of 1300°C than Sample 4, and was hot pressed. The pressure is large, 60 MPa. Other conditions are the same as those of Sample 4. Sample 16 is The sintered density and average grain size are smaller than those of Sample 4. Sample 16 also satisfies the above requirements (1) to (6). In other words, Ca-Y phase and YAG phase (secondary phase) are not formed. As mentioned above, the lower the firing temperature, the smaller the average particle size of the alumina crystal particles. If the temperature is too low, the material will not harden. Therefore, in sample 16, the hot press pressure was increased. do.

[0045] Figure 4(A) shows SEM images (channeling contrast images) of Samples 7 and 8. Samples 7 and 8 differ in firing time, 4 and 8 hours, but the other conditions are the same. As shown in Figure 4(A), sample 7 had less secondary phase precipitation, and the temperature was 22. 5mm 2 Secondary phases were observed in only two locations within the field of view. On the other hand, sample 8 showed a large amount of secondary phase precipitation. 22.5mm 2 The secondary phase was confirmed in 14 places in the field of view. As the time was extended, the growth of alumina crystal grains and the increase of secondary phases were confirmed.

[0046] Figure 4(B) shows the XRD results for Samples 7 and 8. In Sample 8, YAG and The corresponding peaks were confirmed. Therefore, the secondary phase of sample 8 was determined to be YAG. The wavelength of the X-rays is 1.5418 Å (characteristic X-rays of Cu Kα).

[0047] The secondary phase is thought to precipitate as follows: As shown in the upper part of Figure 5, At the start of the hot pressing step P3), yttrium 1 is present at the alumina grain boundaries. The grain boundary area decreases with the growth of the nanocrystalline particles 10, causing the secondary phase 2 to precipitate (middle of Figure 5). Diffusion through the secondary phase causes abnormal grain growth, which further reduces the grain boundary area. A few secondary phases are clustered (bottom row of Figure 5).

[0048] As shown in FIG. 2, Samples 9 to 11 have a higher yttrium content than Sample 4. The most common were 209 ppm, 261 ppm, and 348 ppm, respectively. Sample 9 has the same sintered density as Sample 4, and the average grain size is Sample 9 meets the requirements of [1] to [6] above. The sintered density of Puru 10 is slightly higher than that of Sample 4, but the average grain size is the same as that of Sample 4. Sample 10 satisfies the above requirements (1) to (6). That is, Samples 9 and 10 In this case, secondary phases such as Ca-Y phase and YAG phase are not formed.

[0049] Sample 11 has the same sintered density as Sample 4, and the average grain size of the alumina crystal grains is The sample 11 is slightly larger than the sample 4 and has a YAG phase (secondary phase). Among the requirements [1] to [6], [4] is not met. Sample 11 contains yttrium Due to the large amount of yttrium added, some of the yttrium cannot exist at the grain boundaries of the alumina crystal grains. It is thought that this precipitated as a secondary phase.

[0050] Sample 12 has less magnesium added than Sample 4, but other The conditions were the same as those for Sample 4. Sample 12 had a slightly higher sintered density than Sample 4. The average particle size is slightly smaller than that of Sample 4. Sample 12 also meets the above requirements (1) to (6). In other words, secondary phases such as Ca-Y and YAG phases are not formed.

[0051] Samples 13 and 14 contain calcium-containing dispersants, but other The conditions were the same as for sample 4. Sample 13 had a calcium content of 103 ppm. The sintered density and average grain size are slightly larger than those of sample 4, and Ca-Y phase (secondary phase) is formed. In the SEM image of the sample surface shown on the left side of Figure 3(B), the circled area A secondary phase was confirmed in the sample. In addition, calcium precipitation was confirmed from the EDS results of sample 13. (Fig. 3(D)). Sample 13 met the requirements of [2] and [5] above. I don't.

[0052] Sample 14 has a calcium content of 175 ppm and a sintered density lower than Sample 4. The average particle size is 7.2 μm, which is slightly larger than that of Sample 4. In the case of Sample 1, both the Ca-Y phase and the YAG phase were formed as secondary phases. 3 does not meet the requirements of [2] to [5] above.

[0053] Sample 15 has four times more yttrium added than Sample 4, and the firing temperature The temperature was also high at 1600°C, and the other conditions were the same as those of Sample 4. Although the sintered density is the same as Sample 4, the average grain size is larger than Sample 4 at 6.2 μm. The YAG phase (secondary phase) is formed on the sample surface shown on the left side of Figure 3(C). In the SEM image, a secondary phase was confirmed in the circled area. Sample 15 is the same as above (3) and and (4) does not meet the requirements.

[0054] The example shown in Figure 6 is an SEM image of a sample after plasma irradiation under the following conditions: be. Plasma irradiation Method: ICP Gas: CF4+O2 Source RF: 1000W Bias RF: 300W Irradiation time: 5 minutes

[0055] As described above, in sample 4 shown in FIG. 6(A), secondary phases (YAG phase, Ca-Y phase) were formed. On the other hand, no protrusions were formed on the surface after plasma irradiation. As mentioned above, the secondary phase (YAG phase) was formed in Sample 15, and after plasma irradiation, Secondary phase 2 (YAG phase) remains in a convex shape on the surface.

[0056] As explained above, samples 1 to 7, 9, 10, 12, and 16 to 18 are the same as those in the above [1] to [ 6] and is an example of the alumina sintered body 100 according to the above embodiment. These samples do not form secondary phases and therefore do not undergo photocatalytic degradation when exposed to plasma. This can suppress the occurrence of defects.

[0057] Second Embodiment FIG. 7 is a schematic diagram showing the external configuration of an electrostatic chuck 1000 according to a second embodiment of the present invention. 8 is a perspective view showing the XZ cross-sectional structure of the electrostatic chuck 1000. In Figures 7 and 8, mutually orthogonal X, Y and Z axes are shown to identify the direction. In FIG. 8, the positive Y-axis direction is the direction toward the back side of the paper. The positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction. 000 may actually be installed in a different orientation than that.

[0058] The electrostatic chuck 1000 attracts and holds an object (for example, a wafer W) by electrostatic attraction. It is a device used to fix a wafer W in a vacuum chamber of a semiconductor manufacturing device, for example. The electrostatic chuck 1000 is made up of a first layer 1 arranged in the vertical direction (Z-axis direction). 10, the second layer 200, the cooling section 300, and a cooling element disposed between the second layer 200 and the cooling section 300. and a joining section 400 that joins the second layer 200 and the cooling section 300 together.

[0059] The first layer 110 has a first surface S1 having a circular flat shape and a second surface S2 which is a rear surface of the first surface S1 and is also a circular flat surface. In this embodiment, the first layer 110 is a plate-shaped member having a first surface S1 and a second surface S2. The first layer 110 functions as a mounting surface on which the wafer W is mounted. It is made of a mineral sintered body 100. The porosity of the first layer 110 is 1% or less.

[0060] The second layer 200 is a plate-like member having a third surface S3 and a fourth surface S4, which is the back surface of the third surface S3. Specifically, the second layer 200 is a plate-like member having a third surface S3 that is substantially circular and flat. a second layer body 210 (FIG. 1) and a flange 220 (FIG. 1) protruding from the second layer body 210; , and the diameter expands stepwise downwards (towards the negative Z-axis direction) as a whole. As shown in the figure, the third surface S3 has substantially the same planar shape as the second surface S2, The fourth surface S4 has a larger diameter than the third surface S3.

[0061] The second layer 200 is made of ceramics known as fine ceramics or new ceramics. However, the porosity of the second layer 200 is 1 / 2 that of the first layer 110. The porosity is larger than that of the ceramics, and is 1% to 5%. 2O3), aluminum nitride (AlN), zirconia (ZrO2), silicon carbide (SiC) , zircon (ZrO2·SiO2), mullite (3Al2O3·2SiO2), silicon nitride ( The main component of the second layer 200 can be selected from various ceramics such as silicon nitride (Si3N4). If the main component of the first layer 110 is alumina, the thermal expansion coefficient of the first layer 110 and the second layer 200 is This is preferable because it allows the difference in numbers to be kept small.

[0062] The inside of the second layer 200 is made of a conductive material (for example, tungsten, molybdenum, etc.). The chuck electrode 230 (FIG. 8) is arranged as shown in FIG. The shape of the chuck electrode 230 is, for example, circular. A voltage is applied to the chuck electrode 230 from a power source (not shown). When the wafer W is applied, an electrostatic attraction force is generated, and the wafer W is attracted to the first surface of the first layer 110 by the electrostatic attraction force. It is fixed by suction to S1.

[0063] In addition, inside the second layer 200, there is a lower side (negative side of the Z axis) than the chuck electrode 230. A spiral heater 240 (FIG. 8) is disposed as viewed in the Z-axis direction. The heater 240 is a metallized layer made of tungsten, molybdenum, or the like. The shape of the heater 240 is not limited to that of this embodiment, and may be, for example, a disk shape. In other embodiments, the second layer 200 may not include a heater 240 .

[0064] In this embodiment, the first layer 110 and the second layer 200 are bonded by diffusion bonding. In other embodiments, the same material (so-called base material) as the first layer 110 or the second layer 200 is used. In this case, the first layer 110 and the second layer 200 may be bonded together. By bonding the first layer 110 and the cooling section without using an adhesive mainly composed of an organic material, 300, the decrease in heat transfer between the

[0065] The cooling section 300 is a circular, flat, plate-like member having a diameter larger than that of the fourth surface S4 of the second layer 200. The cooling unit 300 is made of a metal with high thermal conductivity. For example, aluminum It is possible to use aluminum, titanium, molybdenum, or alloys containing each of these as the main component. The diameter of the cooling section 300 is, for example, about 220 mm to 550 mm (usually 220 mm to 3 50 mm), and the thickness of the cooling part 300 is, for example, about 20 mm to 40 mm.

[0066] A coolant flow path 310 (FIG. 8) is formed inside the cooling unit 300. When the wafer W held on the first layer 110 of 00 is processed using plasma, the wafer W Heat is input from the plasma to the cooling unit 300, causing the temperature of the wafer W to rise. When a coolant (for example, a fluorine-based inert liquid or water) flows through the coolant flow path 310, the cooling unit 30 The second layer 200 and the cooling portion 300 via the joint 400 and the first layer 11 are cooled. 0, the first layer 110 is cooled, and the first surface S1 of the first layer 110 is held The wafer W is cooled. This allows the temperature of the wafer W to be controlled. Alternatively, the cooling unit may not have a refrigerant flow path formed therein, and may be cooled from the outside.

[0067] The joint 400 is a circular, flat plate-like member having a diameter equal to that of the first surface S1. The bonding part 400 is made of an adhesive whose main component is an organic material. The organic material is, for example, silicone, acrylic, polyimide, etc. You can be there.

[0068] According to the electrostatic chuck 1000 of this embodiment, the mounting surface (first surface S) on which the wafer W is mounted 1) is formed by the alumina sintered body 100 of the first embodiment. When the wafer W held at 000 is processed using plasma, the first layer 110 is The second layer 200 is exposed to more plasma than the cooling portion 300. In the example shown in FIG. 1, the alumina sintered body 100 of the first embodiment is used in a portion more exposed to plasma. The alumina sintered body 100 is placed in a position where particles are generated when exposed to plasma. Therefore, when the electrostatic chuck 1000 of this embodiment is used, the wafer W This can suppress the generation of particles when performing plasma processing on the substrate.

[0069] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and any modifications may be made without departing from the spirit and scope of the present invention. It can be implemented in various modes, and for example, the following modifications are also possible.

[0070] The method for producing the alumina sintered body is not limited to the above embodiment. By appropriately changing the amount of added, firing method, firing atmosphere, firing temperature, hot press pressure, etc. Therefore, it contains yttrium (Y) in an amount of 90 ppm or more and 265 ppm or less, and calcium (Ca) alumina sintered body containing 100 ppm or less of alumina and having an average particle size of 6 μm or less It is also possible to produce a solidified body by other known methods such as gel casting. Good too.

[0071] In the above embodiment, impurities other than yttrium, calcium, and magnesium are contained. However, it is better to use a material that does not contain other impurities, as this can suppress the precipitation of secondary phases. Therefore, it is preferable.

[0072] In the second embodiment, the entire first surface S1 of the first layer 110 is made of aluminum as in the first embodiment. Although an example in which the first layer 110 is formed of the carbonaceous sintered body 100 has been shown, at least one of the first surfaces S1 of the first layer 110 It is sufficient that the part is formed of the alumina sintered body 100 of the first embodiment. When a wafer W is placed on the first surface S1, a part including a part that is not covered by the wafer W and is exposed is It may be formed by the alumina sintered body 100 of the first embodiment. This can suppress the occurrence of defects.

[0073] In the second embodiment, the electrostatic chuck 1000 has a first surface S 1, a flow path for flowing a gas such as helium (He) gas may be provided between the first and second electrodes.

[0074] The present invention has been described above based on the embodiments, examples, and modifications. The above embodiments are provided to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the claims. The present invention also includes the equivalents thereof. If not described as essential, it may be omitted where appropriate.

[0075] The present invention can also be realized as the following application examples. [Application example 1] An alumina sintered body mainly composed of Al2O3, Contains yttrium (Y) in an amount of 90 ppm or more and 265 ppm or less, Contains calcium (Ca) at 100 ppm or less, The average particle size of the alumina crystal particles is 6 μm or less. Alumina sintered body. [Application example 2] The alumina sintered body according to Application Example 1, The alumina sintered body was measured by X-ray diffraction and found to have a lattice spacing of 2.6 Å to 2 characterized by the absence of a peak corresponding to 0.9 Å. Alumina sintered body. [Application example 3] The alumina sintered body according to Application Example 1 or Application Example 2, The surface of the alumina sintered body was examined by a scanning electron microscope at 1.2 mm 2 When checking the area of , containing calcium (Ca) and yttrium (Y) and having an area of ​​10 μm 2 The above phases are present in one place or less characterized in that Alumina sintered body. [Application example 4] The alumina sintered body according to any one of Application Examples 1 to 3, Density is 3.96g / cm 3 The above is characterized by the above. Alumina sintered body. [Application example 5] An electrostatic chuck for holding an object, A plate-shaped first surface having a first surface on which the object is placed and a second surface that is the reverse side of the first surface. 1 layer and a plate-shaped second layer disposed on the two surfaces of the first layer and having a chuck electrode disposed therein; , Equipped with At least a part of the first surface of the first layer is The alumina sintered body is characterized by being formed from the above-described alumina sintered body. Electrostatic chuck. [Explanation of symbols]

[0076] 1. Yttrium 2…Second phase 10...Alumina crystal particles 100...Alumina sintered body 110…1st layer 200…Second layer 210...2nd layer main body 220…Flange 300...Cooling section 400…Joint part 1000...Electrostatic chuck S1...Side 1 S2...Side 2 S3...Side 3 S4...Side 4

Claims

1. Al 2 O 3 An alumina sintered body having as its main component: Contains yttrium (Y) in an amount of 90 ppm or more and 265 ppm or less, Contains calcium (Ca) at 100 ppm or less, The average particle size of the alumina crystal particles is 6 μm or less. Alumina sintered body.

2. The alumina sintered body according to claim 1, The alumina sintered body was measured by X-ray diffraction and found to have a lattice spacing of 2.6 Å to 2 .9 Å, characterized by the absence of a peak corresponding to Alumina sintered body.

3. The alumina sintered body according to claim 1, The surface of the alumina sintered body was examined by a scanning electron microscope at 1.2 mm 2 When checking the area of , containing calcium (Ca) and yttrium (Y) and having an area of ​​10 μm 2 The above phases are present in one place or less characterized in that Alumina sintered body.

4. The alumina sintered body according to claim 1, Density is 3.96 g / cm 3 The above is characterized by the above. Alumina sintered body.

5. An electrostatic chuck for holding an object, A plate-shaped first surface having a first surface on which the object is placed and a second surface that is the reverse side of the first surface. One layer and a plate-shaped second layer disposed on the second surface side of the first layer and having a chuck electrode disposed therein; and, Equipped with At least a portion of the first surface of the first layer is formed of the material according to any one of claims 1 to 4. The alumina sintered body is characterized by being formed from the above-described alumina sintered body. Electrostatic chuck.

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