AlN bond

Abstract

To provide an AlN joint that is well bonded and free from cracks.SOLUTION: An AIN joint 10 includes a first AIN member 11 and a second AIN member 12, the two members being joined together. The yttria content of the first AlN member 11 is equal to or lower than the detection limit. The second AlN member 12 contains yttria.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an AlN joined body.

Background Art

[0002] Conventionally, a ceramic heater is known that includes an AlN plate having a wafer mounting surface on which a wafer is placed and incorporating a resistive heating element, and a cylindrical shaft made of AlN joined to the back surface of the plate opposite to the wafer mounting surface (see Patent Document 1).

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above-described ceramic heater is manufactured, for example, by joining an AlN plate containing 5% by mass of yttria and a cylindrical shaft made of AlN containing 5% by mass of yttria with a flux applied. In recent years, in order to measure the outer peripheral temperature of the plate with a thermocouple, a groove for a thermocouple may be provided in the plate. Also, as a countermeasure when forming a film on the wafer, a groove for gas purge may be provided in the plate. Therefore, joining a cylindrical shaft to a plate in which such grooves are formed has been considered. As a result, it has been found that cracks starting from the grooves occur in the conventional joining method. The occurrence of cracks is due to the high pressing pressure during joining.

[0005] The present invention has been made to solve such problems, and the main object is to provide an AlN joined body that is well joined and has no cracks.

Means for Solving the Problems

[0006] One aspect of the AlN joined body of the present invention is An AlN joint formed by joining a first AlN member and a second AlN member, The yttria content of the first AlN member is below the detection limit. The second AlN member contains yttria, It is.

[0007] Another embodiment of the AlN bond of the present invention is An AlN joint formed by joining a first AlN member and a second AlN member, The first AlN member has a first diffusion layer formed by bonding, The second AlN member has a second diffusion layer formed by bonding, The yttria content of the portion of the first AlN member excluding the first diffusion layer is below the detection limit. The portion of the second AlN member excluding the second diffusion layer contains yttria. It is. [Brief explanation of the drawing]

[0008] [Figure 1] Front view of the AlN joint 10. [Figure 2] Front view of the AlN joint 20. [Figure 3] Front view of AlN joint 30. [Figure 4] Front view of AlN joint 40. [Figure 5] A vertical cross-sectional view of the ceramic heater 50. [Figure 6] Manufacturing process diagram for ceramic heater 50. [Figure 7] A vertical cross-sectional view of the ceramic heater 60. [Modes for carrying out the invention]

[0009] Preferred embodiments of the present invention will be described below with reference to the drawings. Figures 1 to 4 are front views of AlN joints 10 to 40, and Figure 5 is a longitudinal cross-sectional view of a ceramic heater (a cross-sectional view when cut along a plane including the central axis). In the following description, up and down, left and right, and front and back are as shown in Figure 1. Note that up and down, left and right, and front and back are merely relative positional relationships. In this specification, the "~" indicating a numerical range is used to mean that the numbers written before and after it are included as the lower and upper limits, respectively.

[0010] The AlN joint 10 shown in Figure 1 is formed by joining a first AlN member 11 and a second AlN member 12 using a flux (joining paste). As the flux, for example, one containing calcia (CaO), alumina (Al2O3), and yttria (Y2O3) can be used. The first AlN member 11 and the second AlN member 12 are disc members of the same size. The yttria content of the first AlN member 11 is below the detection limit, and the second AlN member 12 contains yttria. The yttria content of the second AlN member 12 is preferably 0.07% by mass or more. The first AlN member 11 preferably contains at least one oxide selected from the group consisting of rare earth metal oxides other than yttria, magnesia (MgO), and titania (TiO2). The total amount of oxide added can be, for example, 0.1 to 3% by mass. Examples of rare earth oxides include ceria (CeO2) and samaria (Sm2O3). The first AlN member 11 preferably contains rare earth metal oxides other than yttria, or magnesia and titania, and more preferably contains magnesia and titania.

[0011] The AlN joint 20 shown in Figure 2 is formed by joining a third AlN member 13 to the surface of the first AlN member 11 of the AlN joint 10 that is opposite to the surface joined to the second AlN member 12, using a flux. As the flux, for example, one containing calcia, alumina, and yttria can be used. The third AlN member 13 is a disc member of the same size as the first and second AlN members 11 and 12. The third AlN member 13 contains yttria. Preferably, the yttria content of the third AlN member 13 is 0.07% by mass or more.

[0012] The AlN joint 30 shown in Figure 3 is formed by joining a first AlN member 31 and a second AlN member 32 using a flux. The flux can, for example, contain calcia (CaO), alumina (Al2O3), and yttria (Y2O3). The first AlN member 31 and the second AlN member 32 are disc members of the same size. The first AlN member 31 has a first diffusion layer 31a formed by the joining process. The second AlN member 32 has a second diffusion layer 32a formed by the joining process. The first and second diffusion layers 31a and 32a are layers into which the flux components have diffused. The yttria content of the portion of the first AlN member 31 excluding the first diffusion layer 31a is below the detection limit, and the portion of the second AlN member 32 excluding the second diffusion layer 32a contains yttria. The yttria content of the second AlN member 32, excluding the second diffusion layer 32a, is preferably 0.07% by mass or more. The first AlN member 31 preferably contains at least one oxide selected from the group consisting of rare earth metal oxides other than yttria, magnesia (MgO), and titania (TiO2). The total amount of oxide added can be, for example, 0.1 to 3% by mass. Examples of rare earth oxides include ceria (CeO2) and samaria (Sm2O3). The first AlN member 31 preferably contains rare earth metal oxides other than yttria, or magnesia and titania, and more preferably contains magnesia and titania.

[0013] The AlN assembly 40 shown in Fig. 4 is formed by joining a third AlN member 33 to the surface of the first AlN member 31 of the AlN assembly 30 that is opposite to the joint surface with the second AlN member 32 using a flux. As the flux, for example, a flux containing calcium, alumina, and yttria can be used. The third AlN member 33 is a disc member having the same size as the first and second AlN members 31 and 32. The first AlN member 31 has another first diffusion layer 31a formed by the joining with the third AlN member 33. The third AlN member 33 has a third diffusion layer 33a formed by the joining. The third diffusion layer 33a is a layer in which the flux components have diffused. The yttria content of the portion of the first AlN member 31 excluding the two first diffusion layers 31a is below the detection limit. The portion of the third AlN member 33 excluding the third diffusion layer 33a contains yttria. The yttria content of the portion of the third AlN member 33 excluding the third diffusion layer 33a is preferably 0.07 mass% or more.

[0014] The ceramic heater 50 shown in Fig. 5 includes a circular plate 52 having a wafer placement surface 52a with a resistance heating element 52b embedded therein, a cylindrical shaft 53 having a smaller diameter than the circular plate 52, and an intermediate ring 51 sandwiched between the circular plate 52 and the cylindrical shaft 53. The circular plate 52 has a thermocouple groove 52c provided along the radial direction inside. The cylindrical shaft 53 has a flange 53a on the side facing the circular plate 52. The intermediate ring 51 and the circular plate 52 are joined using a flux, and the intermediate ring 51 and the cylindrical shaft 53 are also joined using a flux. As the flux, for example, a flux containing calcium, alumina, and yttria can be used. As shown in Fig. 6, the joining method is as follows: First, place the circular plate 52 on the workbench with the wafer placement surface 52a facing down, apply the flux P in a ring shape on the surface opposite to the wafer placement surface 52a, place the intermediate ring 51 thereon, apply the flux P on the upper surface of the intermediate ring 51, and place the cylindrical shaft 53 thereon with the flange 53a facing down. In this state, apply a load (e.g., 10 - 40 kg / cm from above to the flange 53a 2) is added and the process is carried out at a predetermined bonding temperature (for example, 1600 to 1700°C). In Figure 5, the circular plate 52 corresponds to the second AlN members 12 and 32 described above, the cylindrical shaft 53 corresponds to the third AlN members 13 and 33 described above, and the intermediate ring 51 corresponds to the first AlN members 11 and 31 described above. In addition to or instead of the thermocouple groove 52c, a groove for gas purging may be provided in the circular plate 52 as a measure when forming a film on the wafer.

[0015] The ceramic heater 60 shown in Figure 7 comprises a second circular plate 62 having a wafer mounting surface 62a and an embedded resistance heating element (heater) 62b, a third circular plate 63 joined to a cylindrical shaft 64, and a first circular plate 61 sandwiched between the second circular plate 62 and the third circular plate 63. The first to third circular plates 61 to 63 are joined to each other using a flux to form a laminated plate 65. As the flux, for example, one containing calcia, alumina, and yttria can be used. The laminated plate 65 has thermocouple grooves 66 provided radially inside. The thermocouple grooves 66 are composed of a straight groove 61c formed in the first circular plate 61 and a through hole 63c that penetrates the third circular plate 63 in the vertical direction. The cylindrical shaft 64 has a flange 64a on the side facing the third circular plate 63, and the flange 64a is joined to the third circular plate 63. The joining can be performed according to Figure 6. In Figure 7, the second circular plate 62 corresponds to the second AlN members 12 and 32 described above, the third circular plate 63 corresponds to the third AlN members 13 and 33 described above, and the first circular plate 61 corresponds to the first AlN members 11 and 31 described above. In addition to or instead of the thermocouple groove 66, a gas purging groove may be provided in the laminated plate 65 as a measure when forming a film on the wafer.

[0016] According to the AlN joints 10 to 40 and the ceramic heaters 50 and 60 of the embodiments described above in detail, each member can be joined with a low load. Therefore, they can be joined well, and cracks are less likely to occur in each member. Also, the amount of bleeding of the flux used for joining is reduced, and the amount of particles generated during use is also reduced. Furthermore, the deformation of each member is reduced.

[0017] Note that the present invention is not limited to the above-described embodiments at all, and it is needless to say that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

[0018] For example, in the above-described embodiments, the first to third AlN members 11 to 13 are exemplified as disk members of the same size, but the present invention is not limited to this. For example, the first to third AlN members 11 to 13 may have different shapes and different sizes. The same applies to the first to third AlN members 31 to 33.

[0019] In the above-described embodiments, a flux (paste for joining) is used, but a sheet for joining may be used instead of the flux.

[0020] Also, thick AlN plates containing yttria may be sandwiched via a thin AlN plate not containing yttria (below the detection limit) and fired to obtain a laminated AlN plate having a high thermal conductivity. The higher the yttria content of the AlN plate, the higher the thermal conductivity. Since the obtained laminated AlN plate has a large proportion of plates containing yttria, the thermal conductivity is improved.

[0021] When providing a thermocouple groove, a gas groove, etc. in the plate by joining the plates, firing can be performed at a lower pressure, deformation can be prevented, and a plate having a good thermal conductivity can be created.

[0022] Aluminum nitride containing yttria and aluminum nitride with yttria below the detection limit can be alternately stacked to form three or more layers.

Example

[0023] Examples of the present invention will be described below. Note that the following examples do not limit the present invention in any way.

[0024] [Example 1] 1. Fabrication of a circular plate AlN raw material powder was mixed with Y2O3 powder using a ball mill to form a mixed powder, which was then granulated by spray drying. The Y2O3 powder was added to a total of 5% by mass. Next, a disc-shaped molded body was made using the obtained granules. Then, a circular plate made of AlN sintered body was produced by hot pressing this molded body. In the hot pressing process, the maximum temperature during firing (firing temperature) was set to 1650-1850°C, the holding time at the firing temperature was 2 hours, the press pressure was 20 MPa, and the atmosphere was a nitrogen atmosphere.

[0025] 2. Fabrication of a cylindrical shaft AlN raw material powder Y 2 O 3 powder The mixture was mixed using a ball mill to obtain a mixed powder, which was then granulated by spray drying. The Y2O3 powder was added so that its content in the sintered body was 5% by mass. Next, a molded body was made using the obtained granules. Then, an AlN sintered body (cylindrical shaft) was produced by firing this molded body at atmospheric pressure. The maximum firing temperature (firing temperature) was set at 1750-1900°C, the holding time at the firing temperature was 1-5 hours, and the atmosphere was a nitrogen atmosphere.

[0026] 3. Fabrication of the intermediate ring AlN raw material powder was mixed with MgO powder and TiO2 powder using a ball mill to obtain a mixed powder, which was then granulated by spray drying. The MgO powder was added so that it contained 1% by mass and the TiO2 powder contained 0.5% by mass in the sintered body. Next, a molded body was made using the obtained granules. Then, an AlN sintered body was produced by hot pressing this molded body. In the hot pressing, the maximum temperature during firing (firing temperature) was set to 1750-1850°C, the holding time at the firing temperature was 1-5 hours, the press pressure was 20 MPa, and the atmosphere was a nitrogen atmosphere. After firing, the center of the plate was hollowed out by machining to create an intermediate ring with a thickness of 3 mm. Note that the intermediate ring may also be fired after being formed into a ring shape.

[0027] 4. Fabrication of the joint The flux (bonding paste) was prepared as follows: The paste was prepared by (a) heat-treating a mixed powder of CaO, Al2O3, and Y2O3 in a mass ratio of 35-40:42-47:17-22 so that the total amount was 100, at 1330-1390°C to obtain a synthetic powder; (b) mixing the synthetic powder with AlN powder in a mass ratio of 100:60-70, then grinding it to obtain a pulverized powder with an average particle size of 30 μm or less; and (c) kneading the mixture with ethanol as a solvent. The bonded body (plate with shaft) was prepared using a circular plate, a cylindrical shaft, an intermediate ring, and the flux as follows: As shown in Figure 6, the circular plate, paste, intermediate ring, paste, and cylindrical shaft were stacked from bottom to top. Bonding was performed at a maximum temperature of 1600-1700°C and a load of 10-40 kg / cm². 2 The process was carried out under a nitrogen atmosphere. Alternatively, a bonding sheet may be used instead of the flux.

[0028] 5. Rating The resulting bonded structure was inspected for defects at the joint surface using an ultrasonic flaw detection device, and no defects were found. Furthermore, SEM images of the joint surface showed no defects, confirming good bonding properties. Examination of the joint's appearance revealed that the circular plate and cylindrical shaft were white, while the intermediate ring was gray (likely due to the influence of TiO2). A diffusion layer of flux components was observed near the joint surface with the circular plate and the joint surface with the cylindrical shaft in the intermediate ring. The Y2O3 content in the areas outside these diffusion layers was analyzed using inductively coupled plasma emission spectrometry (ICP-AES). ) Measurements showed levels below the detection limit (5 ppm by mass or less). A diffusion layer was observed near the joint surface with the intermediate ring in the circular plate, but the Y2O3 content in the area other than this diffusion layer was measured in the same manner and found to be 5% by mass. A diffusion layer was also observed near the joint surface with the intermediate ring in the cylindrical shaft, but the Y2O3 content in the area other than this diffusion layer was measured in the same manner and found to be 5% by mass. Furthermore, the joint strength was measured using the four-point bending method in accordance with JIS 1601 and found to be 370 MPa.

[0029] [Comparative Example 1] A joint was fabricated using the same circular plate and cylindrical shaft as in Example 1, as follows: The same flux as in Example 1 was applied between the circular plate and the cylindrical shaft, and the two were joined. The joining was performed at a maximum temperature of 1630°C and under a load of 80 kg / cm². 2 The process was carried out in a nitrogen atmosphere. Upon visual inspection of the resulting bonded structure, cracks were found in the circular plate.

[0030] [Comparative Example 2] A joint was fabricated using the same circular plate and cylindrical shaft as in Example 1, as follows: The same flux as in Example 1 was applied between the circular plate and the cylindrical shaft, and the two were joined. The joining was performed at a maximum temperature of 1630°C and a load of 40 kg / cm². 2 The experiment was conducted in a nitrogen atmosphere. The resulting bonded material had low bonding strength, and SEM observation confirmed that the flux was agglomerating at the bonding interface.

[0031] In the above Example 1, a circular plate containing 5% by mass of yttria and a cylindrical shaft containing 5% by mass of yttria were joined with an intermediate ring containing a low concentration of yttria in between. However, a circular plate containing 5% by mass of yttria and a cylindrical shaft containing a low concentration of yttria may be joined without an intermediate ring.

[0032] Alternatively, a circular plate containing several mass percent of yttria and a cylindrical shaft containing a lower concentration of yttria than the circular plate may be joined together with an intermediate ring containing a lower concentration of yttria than the circular plate and cylindrical shaft. In this case, by using an intermediate ring with yttria below the detection limit, a stronger joint can be obtained. [Explanation of Symbols]

[0033] 10,20,30,40 AlN bonded body, 11,31 first AlN member, 12,32 second AlN member, 13,33 third AlN member, 31a first diffusion layer, 32a second diffusion layer, 33a third diffusion layer, 50 ceramic heater, 51 intermediate ring, 52 circular plate, 52a wafer mounting surface, 52b resistance heating element, 52c thermocouple groove, 53 cylindrical shaft, 53a flange, 60 ceramic heater, 61 first circular plate, 61c straight groove, 62 second circular plate, 62a wafer mounting surface, 62b resistance heating element, 63 third circular plate, 63c through hole, 64 cylindrical shaft, 64a flange portion, 65 laminated plate, 66 thermocouple groove.

Claims

1. An AlN joint formed by joining a first AlN member and a second AlN member, The first AlN member has a first diffusion layer formed by bonding, The second AlN member has a second diffusion layer formed by bonding, The yttria content of the portion of the first AlN member excluding the first diffusion layer is 5 ppm by mass or less, as measured by high-frequency inductively coupled plasma emission spectrometry. The first AlN member contains magnesia and titania as oxides, and the total amount of the oxides added is 0.1 to 3% by mass. The portion of the second AlN member excluding the second diffusion layer contains yttria as a sintering aid. The first diffusion layer and the second diffusion layer contain calcia, alumina, and yttria. AlN composite.

2. The yttria content of the portion of the second AlN member excluding the second diffusion layer is 0.07% by mass or more. The AlN bond according to claim 1.

3. An AlN bond according to claim 1 or 2, A third AlN member is bonded to the surface of the first AlN member opposite to the bonding surface with the second AlN member, and has a third diffusion layer formed by the bonding. Equipped with, The first AlN member has another first diffusion layer formed by bonding with the third AlN member, The yttria content of the portion of the first AlN member excluding the two first diffusion layers is 5 ppm by mass or less, as measured by high-frequency inductively coupled plasma emission spectrometry. The portion of the third AlN member excluding the third diffusion layer contains yttria as a sintering aid. The aforementioned first diffusion layer and the third diffusion layer contain calcia, alumina, and yttria. AlN composite.

4. The yttria content of the portion of the third AlN member excluding the third diffusion layer is 0.07% by mass or more. The AlN bond according to claim 3.

5. The second AlN member is a circular plate having a wafer mounting surface, The third AlN member is a cylindrical shaft with a smaller diameter than the circular plate. The first AlN member is a ring sandwiched between the circular plate and the cylindrical shaft. The AlN bond according to claim 3 or 4.

6. The second AlN member is a second circular plate having a wafer mounting surface in which a heater is embedded, The third AlN member is a third circular plate joined to a cylindrical shaft, The first AlN member is a first circular plate sandwiched between the second circular plate and the third circular plate. The AlN bond according to claim 3 or 4.

7. The circular plate has a groove, The AlN bond according to claim 5.

8. The laminated plate formed by stacking the first to third circular plates has grooves. The AlN bond according to claim 6.

Images