JP2004253786A - Joint structure of ceramics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint structure in which a crack hardly occurs during a heat cycle. <P>SOLUTION: The joint structure comprises a ceramic member 1, a metal joined member 4, a metal fixed member 3 which is fixed on the ceramic member 1 and has an exposed surface 3b which is exposed to a joint surface 1d of the ceramic member, and a joint layer 7 provided between the ceramic member 1, the exposed surface 3b and the joined member 4. The joint layer 7 comprises a thick portion 7a and thin portions 7b. Alternatively, the maximum thickness of the joint layer 7 is 0.15 mm or larger. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a joint structure between a ceramic member and a metal member to be joined.

At present, electrostatic chucks are used to adsorb and hold semiconductor wafers in processes such as transporting semiconductor wafers, film forming processes such as exposure, CVD, and sputtering, fine processing, cleaning, etching, and dicing. . Dense ceramics have attracted attention as a base material of such an electrostatic chuck. Particularly, in a semiconductor manufacturing apparatus, a halogen-based corrosive gas such as ClF _{3 is} frequently used as an etching gas or a cleaning gas. In addition, in order to rapidly heat and cool the semiconductor wafer while holding it, it is desired that the base material of the electrostatic chuck has high thermal conductivity. It is also desired that the material has a thermal shock resistance that does not cause breakage due to a rapid temperature change. Dense aluminum nitride and alumina have high corrosion resistance to the above-mentioned halogen-based corrosive gases.

  In the field of semiconductor manufacturing equipment, a susceptor having a built-in high-frequency electrode for generating plasma has been put to practical use. The metal electrode is buried. Furthermore, in the field of semiconductor manufacturing equipment, ceramic heaters in which a metal resistor is embedded in an aluminum nitride or alumina base material to control the temperature of a wafer during each process have been put to practical use.

  In each of these devices, it is necessary to embed a metal electrode in a ceramic substrate such as aluminum nitride and electrically connect the metal electrode to an external power supply connector. However, these joints are subjected to very high and low temperature thermal cycles in an oxidizing atmosphere and even in a corrosive gas atmosphere. It is desired to maintain high bonding strength and good electrical connection for a long time even under such bad conditions.

In addition, the present applicant has disclosed in Patent Document 1 that in a connection structure between a connector and a metal electrode, a low thermal expansion conductor is inserted between a metal member and a ceramic member to reduce residual stress. Further, in Patent Document 2, the present applicant has improved the joining structure described in Patent Document 1 and improved the oxidation resistance of the brazing material by using a soft alloy brazing material containing gold, platinum, and palladium. And further alleviate the residual stress.
JP-A-10-209255 JP-A-11-12053

  However, in the process of mass-producing a heater or an electrostatic chuck having the above-described joints, the following problem may occur. That is, when manufacturing the joining structure, a metal brazing material, for example, a gold alloy brazing material is installed between the low thermal expansion conductor and the surface of the ceramic member, and the brazing material is heated and melted, and the ceramic member and the low thermal expansion. Wet each surface with the conductor and join it by brazing. However, at this time, the thickness of the bonding layer tended to vary. This is because the surface of the ceramic member is relatively hard to wet, so that the brazing material after melting tends not to remain in the bonding layer. When the molten brazing material leaks out of the joining portion, it is difficult to accurately control the amount of the molten brazing material remaining at the joining portion. As a result, the thickness of the bonding layer varied, and for example, the thickness was reduced to 0.05 mm or less. If the thickness of the bonding layer is small, a large stress is applied at the bonding interface between the bonding layer and the ceramic member when a thermal cycle is applied, and cracks are generated in the ceramic member and the bonding layer, resulting in defective products. There was something.

  An object of the present invention is to provide a ceramic member, a metal member, a metal fixing member having an exposed surface fixed to the ceramic member and having an exposed surface exposed to a bonding surface of the ceramic member, and a bonding structure including a bonding layer. An object of the present invention is to provide a structure in which cracks are less likely to occur.

  The present invention relates to a ceramic member, a metal member to be joined, a metal fixing member fixed to the ceramic member and having an exposed surface exposed at the joining surface of the ceramic member, and a ceramic member and a member joined to the exposed surface. It is provided with a joining layer provided between members, and the joining layer is provided with a thick part and a thin part.

  The inventor of the present invention has examined the reason for the generation of cracks in the bonding layer and the ceramic member described above, and has found that the region where the thickness of the bonding layer is small is the main cause. Based on this finding, the present inventors have conceived of ensuring a thick portion in the bonding layer by adopting a design in which a thick portion and a thin portion coexist in the bonding layer in advance. That is, with such a design, even when the molten brazing material is a material that does not easily accumulate on the surface of the ceramic member, a thick portion having a predetermined thickness can be secured in the bonding layer. Thereby, it is possible to relieve the excessive stress to the joint part due to the thermal cycle mainly in the thick part, and it is possible to provide a structure in which a crack is hardly generated when the thermal cycle is applied.

  Further, the present invention provides a ceramic member, a metal member to be joined, a metal fixing member fixed to the ceramic member and having an exposed surface exposed at the joining surface of the ceramic member, and a ceramic member and the exposed surface and the metal member. A bonding layer provided between the bonding member and the bonding member is provided, and the maximum thickness of the bonding layer is 0.15 mm or more.

  The present inventor has studied the maximum thickness of the bonding layer to suppress the generation of cracks in the bonding portion when applying a thermal cycle, based on the above findings. As a result, it has been found that by setting the maximum thickness of the bonding layer to 0.15 mm or more, it is possible to remarkably suppress the generation of cracks at the bonding portion when applying a heat cycle.

  Hereinafter, the present invention will be described in more detail with reference to the drawings as appropriate. FIG. 1 is a sectional view showing a joint structure according to an embodiment of the present invention. For example, an electrode 2 is embedded inside a substantially disk-shaped ceramic member 1. The electrode 2 is formed of, for example, a wire mesh or a mesh.

  On the back surface 1a side of the member 2, a concave portion 1b is provided. A reticulated electrode 2 is embedded in the member 1 and a fixing member 3 made of molybdenum or a molybdenum alloy is embedded therein. One surface 3b of the fixing member 3 is exposed at the bottom surface 1d of the hole 1b, and the other surface 3a of the fixing member 3 is in contact with the metal electrode 2. 1c is a side surface of the concave portion 1b.

  In the recess 1b, for example, a member 4 to be joined having a disk shape is accommodated and installed. The bottom surface 4c of the member 4 to be joined faces the joining surface 1d of the ceramic member 1 and the joining surface 3b of the fixed member 3. In this example, a ring-shaped projection 4d is formed on the peripheral edge of the bottom surface of the member 4 to be joined, and a ring-shaped bottom surface 4c is formed on the tip end surface of the ring-shaped projection 4d. A circular recess 4b is formed inside the ring-shaped projection 4d. A bonding layer 7 is provided between the member 4 to be bonded and the ceramic member 1 and the fixed member 3. The bonding material forming the bonding layer 7 is interposed between the bottom surface 4c and the ceramic member 2 and is filled in the recess 4b. As a result, the bonding layer 7 has a circular thick portion 7a having a relatively large thickness and a ring-shaped thin portion 7b having a relatively small thickness.

  The power supply member 5 includes a main body portion 5c outside the ceramic member 1, a flange portion 5d, and a tip portion 5b inside the concave portion 1b. The end face 5a of the tip portion 5b and the end face 4a of the member 4 to be joined are joined by a conductive joining layer 10 preferably made of a brazing material.

In the example of FIG. 2, a ring-shaped projection 4d is formed on the peripheral edge of the member 4A to be joined, and a circular recess 4b is formed inside the ring-shaped projection 4d. At the same time, a ring-shaped recess or step 4e is formed outside the ring-shaped projection 4d.

  Further, a bonding layer 7A is provided between the member to be bonded 4A, the ceramic member 2 and the fixing member 3. The bonding layer 7A includes a circular thick portion 7a, a ring-shaped thin portion 7b surrounding the thick portion 7a, and a ring-shaped thick portion 7c surrounding the thin portion 7b.

  In the example of FIG. 3, a cylindrical atmosphere protection body 11 is further provided in the joining structure of FIG. That is, the distal end portion 5b of the fixing member 4 and the power supply member 5 is housed inside the cylindrical atmosphere protection body 11. The end of the atmosphere protector 11 contacts the bonding layer 7d and is bonded to the ceramic member 2.

  In the present invention, the bonding layers 7 and 7A have thick portions 7a and 7c and thin portions 7b. At this time, the thickness tC of the thick portion is preferably 0.15 mm or more, more preferably 0.2 mm or more, and more preferably 0.5 mm or more, from the viewpoint of preventing cracks at the joining portion. Is more preferred. Although there is no particular upper limit on the thickness tC of the thick portion, it is preferably 1.0 mm or less from the viewpoint of bonding strength.

  The thickness tD of the thin portion 7b is preferably 0.01 mm or more from the viewpoint of increasing the bonding strength. There is no particular upper limit on the thickness tD of the thin portion 7b, and it is sufficient that the thickness tD be smaller than the thickness of the thick portion. However, the thickness tD of the thin portion is limited by the ease of wetting of the ceramic member 1 by the bonding material, and thus it is difficult to increase the thickness tD to a certain degree or more. For this reason, tD is usually 1.0 mm or less, and in many cases, 0.5 mm or less.

  tC-tD is preferably 0.15 mm or more, more preferably 0.2 mm or more, and even more preferably 0.5 mm or more, from the viewpoint of preventing cracks at the joint. Although there is no particular upper limit for tC-tD, it is preferably 1.0 mm or less from the viewpoint of bonding strength.

  In the present invention, the maximum thickness of the bonding layers 7 and 7A can be set to 0.15 mm or more. In this case, the maximum thickness is more preferably 0.2 mm or more, and even more preferably 0.5 mm or more.

  In a preferred embodiment, as shown in FIG. 2, a thick portion 7c is provided on the peripheral edge of the joining surface of the member 7A to be joined. Since stress is likely to concentrate on the corner portion of the joining portion, the stress applied to the corner portion can be reduced by providing the thick portion 7c on the periphery of the joining surface of the member 7A to be joined.

  From the viewpoint of the present invention, the ratio B / A of the width B of the thick portion to the width A of the bonding layer is preferably 0.6 or more, and more preferably 0.7 or more. Further, B / A is less than 1.0, but is more preferably 0.95 or less from the viewpoint of the present invention.

The method for forming the thick part and the thin part is not particularly limited. In a preferred embodiment, a projection 4d is provided on the joining surface side of the member 4 to be joined, or a projection is provided on the joining surface 3b of the fixing member 3, so that a thin portion is provided on the projection, and a lateral portion of the projection is provided. Can be provided with a thick portion. Particularly preferably, a projection is provided on the joining surface side of the member 4 to be joined. In this case, the projection 4d is preferably integrated with the member 4 to be joined, but may be a separate spacer. Further, the material of the projection 4d and the material of the member to be joined 4 are preferably the same, but may be different. When the projection 4d is separate from the member to be joined, the material is required to have a melting point higher than the joining temperature by 100 ° C. or more, not to be significantly dissolved in the molten brazing material, and to have low thermal expansion. The following materials can be exemplified.
That is, a metal-based material is Fe-Ni alloy, Fe-Ni-Co alloy, Mo, W, and the like, and a ceramic-based material is alumina, aluminum nitride, silicon carbide, boron nitride, and the like.

  As the ceramic member, a heater in which a resistance heating element is embedded in a ceramic substrate, an electrostatic chuck in which an electrode for electrostatic chuck is embedded in a ceramic substrate, and a resistance heating element and an electrode for electrostatic chuck are embedded in a ceramic substrate. Examples thereof include a heater with an electrostatic chuck, a high-frequency generation electrode device in which a plasma generation electrode is embedded in a ceramic substrate, and a high-frequency generation electrode device in which a plasma generation electrode and a resistance heating element are embedded in a ceramic substrate. In these ceramic members, a power supply member 5 for supplying power to the electrodes inside the ceramic member is required.

  The material of the fixing member 3 is not limited, but is preferably formed of a high melting point metal. Examples of such a high melting point metal include tantalum, tungsten, molybdenum, platinum, rhenium, hafnium and alloys thereof.

  The joining material forming the joining layer is not limited. However, from the viewpoint of relaxing the stress in the bonding layer, it is preferable that the main component of the bonding layer is at least one metal selected from the group consisting of gold, platinum, and palladium. This metal accounts for 50% by weight or more of the constituent metal of the bonding layer, preferably 70% by weight or more, more preferably 80% by weight or more, and preferably 90% by weight or more. Is more preferable. Among them, gold is most preferable in terms of oxidation resistance.

  The bonding layer preferably contains at least one active metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, and magnesium, thereby increasing the adhesion of the bonding layer to ceramics and the bonding strength. be able to. This ratio is preferably at most 5% by weight.

  In addition, alloy components such as nickel, iron, and cobalt can be contained in the bonding layer. In this case, the proportion of the alloy component is preferably 50% by weight or less, particularly preferably 20% by weight or less, and further preferably 10% by weight or less.

  One or more third components selected from the group consisting of Si, Al, Cu and In can be contained in the bonding layer.

  In a preferred embodiment, a metal electrode and a terminal (fixing member) 3 made of molybdenum or a molybdenum alloy are embedded in a ceramic member, and an exposed portion 3b of the terminal 3 is exposed on a joint surface of the ceramic member. .

  In the present invention, the cylindrical atmosphere protection body 11 is inserted into the concave portion 1b of the ceramic member, and the member 4 to be joined is inserted inside the cylindrical atmosphere protection body 11.

The member to be joined 4 may be a power supply member, but is preferably a low thermal expansion conductor. The low thermal expansion conductor is a conductor made of a material having a coefficient of thermal expansion of at least 400 ° C. and 8.0 × 10 ⁻⁶ / ° C. or less. Specifically, the material of the low thermal expansion conductor is preferably molybdenum, tungsten, a molybdenum-tungsten alloy, a tungsten-copper-nickel alloy, or Kovar. The material of the atmosphere protector is preferably pure nickel, a nickel-base heat-resistant alloy, gold, platinum, silver, or an alloy thereof.

  The material of the power supply member is preferably a metal having high corrosion resistance to the atmosphere, and specifically, pure nickel, a nickel-based heat-resistant alloy, gold, platinum, silver, and alloys thereof are preferable.

  4 and 5 are cross-sectional views showing another modification of the present invention. In the example of FIG. 4, the heating element 2 is wound in a coil spring shape. The fixing member 3A is provided with a projection 3c, and the end 2a of the heating element 2 is wound around the side peripheral surface 3d of the projection 3c. And are electrically connected. Of course, the method of electrically connecting the heating element 2 and the fixing member is not limited.

  In the example of FIG. 5 as well, the protrusion 3c is provided on the fixing member 3B, and the end 2a of the heating element 2 is wound around the side peripheral surface 3d of the protrusion 3c. In addition, a recess 3e is formed on the joint surface 3b side of the fixing member 3. At a position corresponding to the concave portion 3e, a projection 4g is provided on the joining surface side of the member 4B to be joined. In this example, the tip of the projection 4g is inserted into the recess 3e of the fixing member 3. A bonding layer 7e is formed between the protrusion 4g and the wall surface of the recess 3e.

  In this manner, the protrusion 4g on the member to be bonded 4 is inserted into the recess 3e of the fixing member 3, and the bonding layer is provided between the outer wall surface of the protrusion 4g and the inner wall surface of the recess 3e. The area can be increased, and the bonding strength can be further improved.

(Manufacture of joint structure)
The bonding structure shown in FIG. 3 was formed. Specifically, a disc-shaped compact was manufactured by uniaxial pressing of aluminum nitride powder. As the wire mesh 2, a wire mesh obtained by knitting molybdenum wires having a diameter of 0.12 mm at a density of 50 wires per inch was used. The wire mesh 2 was embedded in a preform of aluminum nitride. At the same time, a cylindrical molybdenum terminal 3 having a diameter of 3 mm and a height of 1.5 mm was embedded in the aluminum nitride preform. This preform was placed in a mold, sealed in a carbon foil, and fired by a hot press method at a temperature of 1950 ° C., a pressure of 200 kg / cm ² and a holding time of 2 hours to obtain a sintered body. . The relative density of this sintered body was 98.0% or more. As shown in FIG. 1, a recess 1b was formed by a machining center from the back side of the obtained sintered body, and a test piece of a ceramic member was produced. However, the outer shape of this test piece was a rectangular parallelepiped, and the dimensions were 20 mm × 20 mm × 17 mm in thickness.

  The terminal 3 was ground to remove oxides and carbides on the surface, washed and dried. Next, a gold foil (diameter φ5.6 mm, thickness 0.2 mm) and an Au-18% Ni foil (diameter φ5.6 mm, thickness 0.1 mm) were placed on the terminal 3. Atmosphere protector 11 was set around this. In addition, a Kovar plate having a diameter of 4.7 mm and a thickness of 2.2 mm was installed as a low thermal expansion conductor 4 on the metal foil. An Au-18 wt% Ni alloy foil (diameter φ4.7 mm, thickness 0.2 mm) was placed on the low thermal expansion conductor 4, and a nickel rod-shaped power supply member 5 was placed thereon.

  The assembly thus obtained was heated in a vacuum at 1000 ° C. for 10 minutes while a load of 500 g was applied thereto, thereby producing a joint structure shown in FIG.

  Here, in Example 1, the depth (tC-tD) of the recess 4d was 0.2 mm, and in Example 2, (tC-tD) was 0.5 mm. In Example 3, tC was set to 0.2 mm, and a titanium foil (diameter φ5.6 mm, thickness 0.01 mm) was provided between the terminal 3 and the gold foil. In Comparative Example 1, the bottom surface of the low-thermal-expansion conductor 4 was flat, and the recess 4d was not provided.

  For each of the joint structures thus obtained, the tensile breaking load (tensile strength) after joining was measured, and the results are shown in Table 1.

  Further, a heat cycle between 100 ° C. and 700 ° C. was applied 100 times for each joint structure. However, the heating rate was about 20 ° C./min, and the cooling rate was about 5 ° C./min. Thereafter, the tensile rupture load was measured and is shown in Table 1 as the tensile rupture load after the heat cycle.

  When the tensile strength is measured after the heat cycle test, the strength is deteriorated in Comparative Example 1, whereas no decrease is observed in Examples 1, 2, and 3. Further, in Example 3, the active material foil (titanium foil) was also used, so that the brazing material was firmly joined to the ceramic member 1, so that the breaking load was further improved.

  FIG. 6 is an optical microscope photograph showing the joint structure of Example 1. In FIG. 6, it can be seen that a thick portion having a uniform thickness is generated.

  As described above, according to the present invention, a ceramic member, a metal member, a metal fixing member fixed to the ceramic member and having an exposed surface exposed to a bonding surface of the ceramic member, and a bonding including a bonding layer In the structure, it is possible to provide a structure in which cracks are less likely to occur when a heat cycle is applied.

FIG. 2 is a cross-sectional view schematically illustrating a bonding structure according to an embodiment of the present invention, in which a bonding layer 7 is provided with a thick portion 7a and a thin portion 7b. It is sectional drawing which shows roughly the joining structure concerning other embodiment of this invention, and the thick part 7a, 7c and the thin part 7b are provided in 7 A of joining layers. It is sectional drawing which shows schematically the joining structure which concerns on still another embodiment of this invention, and the cylindrical atmosphere protection body 11 is installed around the to-be-joined member 4. As shown in FIG. This is an example of an embodiment of the present invention, in which the heating element has a coil spring shape and is wound around the fixing member 3A. This is an example of the embodiment of the present invention, in which the fixing member 3B has a concave portion 3e, and a projection 4g is provided at the center of the member to be joined correspondingly, and a joining layer 7e is provided between the two. Is provided. It is an optical microscope photograph of the joined structure concerning the example of the present invention.

Explanation of reference numerals

  Reference Signs List 1 ceramic member 1a bottom surface of ceramic member 1 2 heating element 3 fixing member 3A, 3B 3b exposed surface of fixing member 3 4, 4A, 4B joined member 4b concave portion 4c bottom surface 4d protrusion 5 power supply member (external member) 7 , 7A, 7B joining layer 7a, 7c thick part 7b thin part 11 cylindrical atmosphere protection body A joining layer width B thick part width tC thick part thickness tD thin part thickness

Claims (11)

  A ceramic member, a metal member to be joined, a metal fixing member fixed to the ceramic member and having an exposed surface exposed at the joint surface of the ceramic member, and the metal member to be joined to the ceramic member and the exposed surface. A bonding structure for ceramics, comprising: a bonding layer provided between members; and the bonding layer includes a thick portion and a thin portion.   The joining structure according to claim 1, wherein the thickness of the thick portion is 0.15 mm or more.   The joining structure according to claim 1, wherein the thick portion is provided at a peripheral portion of a joining surface of the member to be joined.   The joint structure according to any one of claims 1 to 3, wherein a protrusion is provided on a joint surface of the member to be joined.   A ceramic member, a metal member to be joined, a metal fixing member fixed to the ceramic member and having an exposed surface exposed at the joint surface of the ceramic member, and the metal member to be joined to the ceramic member and the exposed surface. A bonding structure for ceramics, comprising: a bonding layer provided between members; and a maximum thickness of the bonding layer is 0.15 mm or more.   The joining structure according to any one of claims 1 to 5, further comprising an external member to which the member to be joined is joined.   The joining structure according to any one of claims 1 to 6, wherein a main component of the joining layer is at least one metal selected from the group consisting of gold, platinum and palladium.   The bonding layer, wherein one or more active metals selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, and magnesium are contained, any one of claims 1 to 7, The joining structure according to claim.   The joint structure according to any one of claims 1 to 8, wherein a concave portion is provided in the ceramic member, and the member to be bonded is accommodated in the concave portion.   The joining structure according to claim 9, wherein a cylindrical atmosphere protection body is inserted into the recess, and the member to be bonded is housed inside the cylindrical atmosphere protection body.   The joining structure according to claim 1, wherein a conductive member electrically connected to the fixing member is provided on the ceramic member.

Images