[0031] Preferred Embodiments of the Invention

[0032] The present invention will be described further, referring to the attached drawings.

[0033] FIG. 1 is a drawing schematically showing a joined article 25 according to one embodiment of the invention. The joined article 25 is composed of an electrostatic chuck 10 , a cooling flange 12 and a joining layer 14 . The chuck 10 has an electrode 18 for electrostatic chuck embedded therein. A terminal 20 is connected with the electrode 18 . The electrostatic chuck 10 has an adsorption face for supporting and adsorbing a semiconductor wafer 16 . In the example, a through hole 24 is provided through the cooling flange 12 and chuck 10 . A back side gas, such as argon gas or nitrogen gas, may be supplied through the through hole 24 as an arrow 22 . Further, through holes (not shown) may be provided in the cooling flange 12 and chuck 10 for inserting lift pins for lifting the semiconductor wafer from the adsorption face.

[0034] A process for producing a joined article 25 such as that shown in FIG. 1 will be described, referring to FIGS. 2 and 3 . In FIGS. 2 and 3 , the detailed structure of the electrostatic chuck or cooling flange shown in FIG. 1 are omitted for the purpose of providing a general explanation of the process according to the invention.

[0035] The first member 10 and second member 12 are joined with each other as shown in FIGS. 2 ( a ), ( b ) and 3 . The first member 10 contains at least a ceramics. The whole of the first member 10 may be made of a ceramics. Alternatively, the first member 10 has a main body having a joining face 10 b to be joined and a ceramics covering the joining face 10 b . In the latter case, the main body of the first member may be made of a metal, a metal composite or ceramic composite.

[0036] The first member may be made of a ceramic material including an oxide ceramics such as alumina, calcium titanate, barium titanate and a nitride ceramics. Silicon nitride and sialon are preferred among nitride ceramics for further improving the resistance of the first member against thermal stress. Aluminum nitride is preferred for improving the anti-corrosion property against a fluorine-based corrosive gas and thermal conductivity of the first member.

[0037] The kind of the first member is not particularly limited. For example, the first member may be used in a system for producing semiconductors, and may preferably be a susceptor for mounting semiconductors. Such susceptor may have any and various functions as long as it may work as a susceptor for setting a semiconductor wafer. For example, when an electrode for electrostatic chuck is provided inside of the substrate of the member, such member may be used as an electrostatic chuck system. Alternatively, when a resistance heating element is provided inside of the substrate, the supporting member may be used as a ceramic heater. Further, when an electrode for generating plasma is provided inside of the substrate, the supporting member may be used as an electrode device for generating plasma. In a particularly preferred embodiment, the supporting member is an electrostatic chuck.

[0038] The second member 12 contains at least a metal or metal composite. The whole of the second member 12 may be made of a metal or metal composite. Alternatively, the second member 12 has a main body having a joining face 12 a be joined and a metal or metal composite film covering the joining face 12 a . In the latter case, the main body of the second member may be made of a ceramics or ceramic composite.

[0039] The second member may be made of a metal not particularly limited. The metal may be aluminum, copper, stainless steel, nickel or the alloys thereof, when the second member is to be exposed against a halogen based corrosive gas.

[0040] The second member may be made of a metal composite not particularly limited. The metal composite may be composed of a metal component including aluminum alloy or copper alloy and a ceramic component including SiC, AlN or alumina.

[0041] The application or function of the second member is not particularly limited. In a preferred embodiment, the second member is a cooling system having a cooling mechanism. A refrigerant used for the cooling mechanism may be a liquid such as water and silicone oil and a gas such as air and an inert gas.

[0042] As shown in FIGS. 2 ( a ) and ( b ), an adhesive 2 and materials 1 A and 1 B are provided between the first member 10 and second member 12 to provide a laminate 13 , according to the present invention. The adhesive 2 is made of a metal containing at least indium. The materials 1 A and 1 B contain at least a component capable of reducing the melting point of indium. The laminate 13 is then heated at a temperature in solid-liquid phase coexisting temperature of an alloy of indium and the component.

[0043] The metal adhesive 2 is pure indium metal or the alloy of indium. The pure indium metal may contain inevitable impurities. The alloy of indium may contain gold, silver, tin, lead, titanium, magnesium or the alloys thereof. The amount of the metal or metals other than indium in the alloy may preferably be not larger than 10 weight percent.

[0044] The shape of the adhesive is not particularly limited. According to the present invention, however, the melting process takes place from the interface of the adhesive 2 and material 1 A or 1 B at a temperature lower than the melting point of indium. After the melting process, a joining layer containing an indium alloy is generated between the first member 10 and second member 12 . For facilitating the reaction of generating the alloy, the thickness of the adhesive 2 may preferably be not larger than 500 micrometer, and more preferably be not larger than 300 micrometer. On the similar viewpoint, the adhesive 2 may preferably be a metal foil.

[0045] When the thickness of the adhesive 2 is too thin, the state of the adhesive may be deviated. For further improving the air-tightness of the joining interface, the thickness of the adhesive 2 may preferably be not smaller than 20 micrometer.

[0046] The shape of the material 1 A or 1 B for reducing the melting point is not particularly limited. For improving the reaction of indium and the component for generating the alloy over the whole of the adhesive uniformly, the material may preferably have a shape of a foil or film.

[0047] When the thickness of the material for reducing the melting point is too large, the reaction of the material and indium might be insufficient. On this viewpoint, the thickness of the material for reducing the melting point may preferably be not larger than 50 micrometer, and more preferably be not larger than 30 micrometer. On the other hand, when the material for reducing the melting point is too thin, the state of the adhesive layer may be deviated. For further improving the air-tightness of the joining interface, thickness of the material for reducing the melting point may preferably be not smaller than 1 micrometer and more preferably be not smaller than 3 micrometer.

[0048] The material for reducing the melting point may be provided between the adhesive 2 and first member 10 , and/or between the adhesive 2 and second member 12 . In a preferred embodiment, the material for reducing the melting point is provided at least between the adhesive 2 and first member 10 . It is effective to provide the material on the side of the first member 10 for wetting the surface of the ceramics (first member) 10 having a low wettability with the adhesive.

[0049] According to the present invention, the adhesive composed of a metal containing at least indium and the material containing at least a component capable of reducing the melting point of indium is provided between the first and second members to provide a laminate. The laminate is then heated at a temperature in solid-liquid coexisting range of an alloy comprising indium and the component. The alloy is mainly composed of indium and the component. The solid-liquid phase coexisting temperature means a solid-liquid phase coexisting temperature corresponding with the composition of the alloy. The solid-liquid coexisting temperature is changed depending on the composition of indium alloy and may be judged from a phase diagram.

[0050] The component of the alloy is not particularly limited, as long as the component functions to reduce the melting point of indium. The component may preferably be a metal selected from the group consisting of tin and silver and the alloys thereof.

[0051] More preferably, the component is pure tin, or an alloy of tin and silver, lead, titanium or magnesium. Inevitable impurities may be contained in pure tin. The tin alloy may preferably contain 3 weight percent or less of the metal component other than tin.

[0052] The heat treatment may preferably be performed at a temperature of not lower than 90° C. and not higher than 155° C. It is possible to further reduce the air-tightness of the joining interface by the heat treatment at a temperature not lower than 90° C. On this viewpoint, the temperature may preferably be not lower than 95° C. and more preferably be not lower than 100° C.

[0053] When the component is tin or the alloy of tin, the temperature for the heat treatment may preferably be not lower than 120° C. so as to proceed the melting process of the adhesive and material for reducing the melting point.

[0054] In a preferred embodiment, the laminate is heated while the laminate is subjected to isostatic pressurizing. It is thus possible to maintain the air-tightness of the joining interface and to prevent the deterioration of the flatness of the supporting face of a semiconductor mounting member after the joining process.

[0055] Further, for example in an electrostatic chuck, it is necessary to provide various holes such as a hole for supplying a gas, holes for lift pins, and holes for inserting terminals. In this case, it is needed to provide a hole in a cooling flange communicating with each of the above holes formed in the chuck. When the holes are provided in the first and second members, respectively, and communicated with each other, it is indispensable to further improve the air-tightness along the joining interface of the first and second members. It is also necessary to prevent the flow of the adhesive into the holes and the extrusion of the adhesive.

[0056] In the above embodiment, a first hole is provided in the first member, a second hole is provided in the second member, and the both holes are communicated with each other. In this embodiment, it is preferred to provide an air-tight sealing member between the first and second holes and the adhesive so that the air-tight sealing member is directly contacted with the first and second members for sealing, when the first and second members are laminated. The holes are thereby sealed with the air-tight sealing member and further sealed with the joining layer according to the present invention, so that the air-tightness may be further improved. At the same time, it is possible to prevent the extrusion of the adhesive into the holes. As a result, when mass production is to be performed, it is possible to improve the production yield of products having desired air-tightness.

[0057] The kind or material of the air-tight sealing member is not particularly limited. It is preferred to apply a sealing member capable of exhibiting excellent air-tightness when a pressure is applied from the first and second members, such as an O-ring or gasket. A rubber O-ring commonly used for a vacuum system may be applied. Preferably, an O-ring is made of a material for reducing particle generation used for a semiconductor production system.

[0058] Preferred embodiments will be described further in detail below. As shown is FIG. 2 ( a ), a material 1 A for reducing melting point is provided on a joining face 10 b of a first member 10 , and a material 1 B for reducing melting point is provided on a joining face 12 a of a second member 12 . The materials 1 A and 1 B are foils or films. Such film may be formed by means of any processes including ion plating, chemical vapor deposition, physical vapor deposition, organic metal chemical vapor deposition, vapor deposition, sputtering and plating methods.

[0059] The thus obtained assembly 13 is heated while it is subjected to isostatic pressing. The actual methods applied for performing the heating and isostatic pressing of the assembly 13 are not particularly limited. Preferably, as shown in FIG. 2 ( b ), the assembly 13 is vacuum packaged in a packaging film 3 and then contained in a sealed container filled with an inert gas. The vacuum packaged assembly is subjected to isostatic pressing with the inert gas in the sealed container. Alternatively, the assembly may be subjected to isostatic pressing with a liquid.

[0060] The material of the film 3 is not particularly limited, as long as it has elasticity and thermal resistance at a temperature applied for heating the assembly. The inert gas may be nitrogen, argon or a mixed gas of nitrogen and argon. The pressure of the inert gas in the sealed container is not limited as long as it is effective for producing a joined article having a sufficiently high air-tightness. The pressure of the gas may preferably be not lower than 5 atm for further improving the air-tightness of the joined article. The upper limit of the gas pressure is not particularly set on the viewpoint of the invention. The pressure may preferably be not higher than 100 atm and more preferably not higher than 20 atm from the practical point of view. The heating temperature was described above.

[0061] The sealed container is not particularly limited and preferably an autoclave.

[0062] In a preferred embodiment, as shown in FIG. 3, a vacuum packaged assembly 13 is contained in an autoclave 4 , and then heated and pressed. A gas source 6 is connected through a gas passage 5 in the autoclave 4 . A heater 7 is also contained in the autoclave 4 and the calorific power of the heater is controlled with a power controller 8 . A fan 9 is provided in the front of the heater 7 for reducing the temperature deviation in the autoclave.

[0063] It is not needed that the material for reducing melting point be provided on the both sides of the adhesive as described above. For example, as shown in FIGS. 4 ( a ) and 4 ( b ), the material 1 A may be provided between the adhesive 2 and first member 10 .

[0064] In a preferred embodiment, the assembly is subjected to isostatic pressing while heating the assembly at the maximum temperature. That is, as shown in FIG. 5 , the pressure is adjusted at a specified value “P1” during the maximum temperature “T1” (from the time points “t2” to “t3”.)

[0065] In a preferred embodiment, the isostatic pressing is continued during the temperature reduction period after “t3” (the end of maximum temperature period). In a particularly preferred embodiment, the isostatic pressing is continued to “t4” (the end of the temperature reduction period to room temperature T 4 ). It is found that the continued isostatic pressing may be effective for further improving the flatness of the supporting face of the supporting member after the joining process.

[0066] In the joined article of the present invention, the flatness of the supporting face of the supporting member may preferably be not larger than 30 μm and more preferably be not larger than 10 μm.

[0067] A joined body 15 A is thus obtained as schematically shown in FIG. 6 ( a ). The joined body 15 A has a first member 10 , second member 12 and a joining layer 14 joining the members. The joining layer 14 has inhomogeneous microstructure containing indium alloy phase. A through hole 21 is provided in the joined body 15 B shown in FIG. 6 ( b ).