JP5580772B2 - Manufacturing method of metal laminated structure - Google Patents

Description

  The present invention relates to a method for manufacturing a metal laminate structure.

  For example, in a semiconductor device such as an LED (Light Emitting Diode) element, it is generally performed to install a heat dissipation board (heat sink) for radiating heat generated when the semiconductor element is driven to the outside.

  For example, in Patent Document 1 (Japanese Patent No. 2860037), a Cu plate having a diameter of 200 mm and a thickness of 0.465 mm manufactured using a rolling method and a Mo plate having the same diameter as the Cu plate and a thickness of 0.090 mm are described as Cu. It describes that a Cu / Mo / Cu clad material having a thickness of 1.02 mm is produced by hot pressing in the state of being laminated in the order of a plate / Mo plate / Cu plate, and this is used as a heat dissipation substrate of a semiconductor device. (Paragraphs [0034] to [0049] of Patent Document 1).

  Patent Document 1 also describes that a highly reliable clad material can be obtained by the same manufacturing method even when W is used instead of Mo (paragraph [0033] of Patent Document 1).

Japanese Patent No. 2860037

  However, since the thickness of the heat dissipation substrate of the above-mentioned Patent Document 1 is as very large as 1.02 mm, there is a problem that it is not possible to cope with the case where the heat dissipation substrate is required to be thin.

  Moreover, about Mo board and W board, since there was a restriction | limiting in the thickness which can be rolled, there also existed a problem that it was difficult to make the whole thickness of a thermal radiation board thin.

  Furthermore, as in the hot press described above, the manufacturing method in which the Cu plate and the Mo plate are installed in the hot press device each time the clad material is manufactured, and the clad material is taken out from the hot press device after the hot press is efficient. However, there is a problem that a heat dissipation substrate cannot be manufactured.

  In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a metal laminated structure that can be made thin and can be efficiently manufactured.

  The present invention includes a first metal layer, a second metal layer, and a third metal layer, wherein the first metal layer is disposed on one surface of the second metal layer, The first metal layer includes tungsten, the second metal layer includes copper, and the third metal layer includes tungsten. A method of manufacturing a metal laminate structure including: a step of forming a first metal layer on one surface of a second metal layer by molten salt bath plating; and a second surface of the second metal layer Forming a third metal layer thereon by molten salt bath plating, and a molten salt bath used for molten salt bath plating melts a mixture containing potassium fluoride, boron oxide, and tungsten oxide. It is a manufacturing method of the metal laminated structure which was produced in this way.

  In the method for manufacturing a metal laminated structure according to the present invention, the thickness of the first metal layer relative to the sum of the thickness of the first metal layer, the thickness of the second metal layer, and the thickness of the third metal layer The sum ratio with the thickness of the third metal layer is preferably 0.2 or more and 0.8 or less.

  The metal laminate structure of the present invention includes a step of forming a fourth metal layer on the side of the first metal layer opposite to the installation side of the second metal layer, and a second layer of the third metal layer. Forming a fifth metal layer on the side opposite to the metal layer installation side, and the fourth metal layer and the fifth metal layer preferably each contain copper.

  In the method for manufacturing a metal laminated structure according to the present invention, the thickness of the first metal layer, the thickness of the second metal layer, the thickness of the third metal layer, the thickness of the fourth metal layer, and the fifth The ratio of the sum of the thickness of the first metal layer and the thickness of the third metal layer to the sum of the thickness of the metal layer is preferably 0.2 or more and 0.8 or less.

  Moreover, in the manufacturing method of the metal laminated structure of this invention, between the 1st metal layer and the 4th metal layer, and between at least one between the 3rd metal layer and the 5th metal layer. It is preferable to include a step of forming a cobalt-containing layer.

  Moreover, in the manufacturing method of the metal laminated structure of this invention, it is preferable that the thickness of a cobalt content layer is 0.05 micrometer or more and 3 micrometers or less.

  ADVANTAGE OF THE INVENTION According to this invention, thickness can be made thin and the manufacturing method of the metal laminated structure which can be manufactured efficiently can be provided.

It is typical sectional drawing of an example of the metal laminated structure of this invention. It is a typical block diagram illustrating an example of the manufacturing method of the metal laminated structure of this invention. It is a typical block diagram illustrating an example of the manufacturing method of the metal laminated structure of this invention. It is typical sectional drawing of an example of the LED element which is an example of the semiconductor device using the metal laminated structure of this invention. It is typical sectional drawing of another example of the metal laminated structure of this invention. It is a typical block diagram illustrating an example of the manufacturing method of the metal laminated structure of this invention. It is a typical block diagram illustrating an example of the manufacturing method of the metal laminated structure of this invention. It is typical sectional drawing of another example of the metal laminated structure of this invention. It is a typical block diagram of the apparatus used in Examples 1-4.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

<Metal laminate structure>
In FIG. 1, typical sectional drawing of an example of the metal laminated structure of this invention is shown. Here, the metal laminated structure 100 includes a first metal layer 1, a second metal layer 2 installed on the first metal layer 1, and a third metal installed on the second metal layer 2. It is comprised from the laminated structure with the metal layer 3. That is, in the metal laminate structure 100, the first metal layer 1 is disposed on one surface of the second metal layer 2, and the third metal layer 3 is disposed on the other surface of the second metal layer 2. is set up.

  Here, the first metal layer 1 is a metal layer made of a metal containing at least one of tungsten and molybdenum. In particular, the thickness of the metal multilayer structure 100 is reduced to make the metal multilayer structure 100 efficient. From the viewpoint of manufacturing, the first metal layer 1 is preferably a tungsten layer or a molybdenum layer formed by plating.

  Further, the second metal layer 2 is a metal layer made of a metal containing copper, and in particular, from the viewpoint of efficiently manufacturing the metal multilayer structure 100 by reducing the thickness of the metal multilayer structure 100, The second metal layer 2 is preferably a copper thin plate such as a copper foil.

  The third metal layer 3 is a metal layer made of a metal containing at least one of tungsten and molybdenum. In particular, the metal multilayer structure 100 is efficiently manufactured by reducing the thickness of the metal multilayer structure 100. From this point of view, the third metal layer 3 is preferably a tungsten layer or a molybdenum layer formed by plating.

  Moreover, it is preferable that the total thickness h of the metal laminated structure 100 is 20 μm or more and 400 μm or less. When the thickness h of the metal multilayer structure 100 is 20 μm or more and 400 μm or less, the tendency that the metal multilayer structure 100 can be efficiently manufactured by reducing the thickness of the metal multilayer structure 100 increases.

Further, the sum of the metal laminated structure 100, a first thickness h ₁ and the second thickness h ₃ of the thick h ₂ and the third metal layer 3 a metal layer and second metal layer 1 (h ₁ + ratio of the sum (h ₁ + h ₃₎ and h ₂ + h ₃ first thickness of the metal layer 1 with respect to) h ₁ and the thickness h ₃ of the third metal layer _{3 [(h 1 + h 3} ) / (h ₁ + h ₂ + h ₃ )] is preferably 0.2 or more and 0.8 or less. When the above ratio is 0.2 or more and 0.8 or less, the linear expansion of the metal laminated structure 100 does not become too large and the thermal conductivity does not become too small. When 100 is affixed to a semiconductor substrate of a semiconductor device, the heat dissipation function of the metal multilayer structure 100 can be sufficiently exhibited without causing a large difference in thermal expansion between the metal multilayer structure 100 and the semiconductor substrate. There is a tendency to be able to.

  Further, in order to suppress the warp of the metal multilayer structure 100, the central portion in the thickness direction of the metal multilayer structure 100 (in this example, a portion that is ½ of the total thickness h of the metal multilayer structure 100). It is preferable that the upper part and the lower part from the central part in the thickness direction of the laminated structure are symmetrical with respect to the central part in the thickness direction of the laminated structure. In the present invention, “symmetry” means that the material and thickness of a layer that appears when the metal layered structure 100 proceeds from the center in the thickness direction to the upper end surface in the vertical direction are the same. It is a concept that includes not only the case where it is completely the same as the case where it proceeds downward from the center in the thickness direction to the lower end surface, but also the case where it is equivalent.

<Method for producing metal laminate structure>
Hereinafter, although an example of the manufacturing method of the metal laminated structure 100 shown in FIG. 1 is demonstrated, it cannot be overemphasized that the manufacturing method of the metal laminated structure of this invention is not limited to this.

  First, as shown in the schematic configuration diagram of FIG. 2, a molten salt bath 8 containing at least one of tungsten and molybdenum is accommodated in a container 7. The molten salt bath 8 is not particularly limited as long as at least one of tungsten and molybdenum can be deposited by electrolysis of the molten salt bath 8. A preferred configuration of the molten salt bath 8 will be described later.

  Next, for example, the copper foil as the second metal layer 2 and the counter electrode 6 are immersed in the molten salt bath 8 accommodated in the container 7. Here, the counter electrode 6 can be used without particular limitation as long as it is a conductive electrode. For example, a metal electrode or the like can be used.

  Next, the copper foil as the second metal layer 2 is used as a cathode, the counter electrode 6 is used as an anode, and a voltage is applied between the copper foil as the second metal layer 2 and the counter electrode 6 to melt. By electrolyzing the salt bath 8, tungsten and / or molybdenum in the molten salt bath 8 is deposited on both sides of the copper foil as the second metal layer 2, respectively, and the first metal layer 1 and A third metal layer 3 is formed.

  Thereafter, the copper foil as the second metal layer 2 after the formation of the first metal layer 1 and the third metal layer 3 is taken out from the molten salt bath 8, and the first metal layer 1 and The molten salt bath 8 adhering to the third metal layer 3 is washed and removed. Then, for example, by washing with a predetermined acid, the oxide films formed on the surfaces of the first metal layer 1 and the third metal layer 3 are removed. Thus, the metal laminated structure 100 shown in FIG. 1 can be manufactured.

  Moreover, the metal laminated structure 100 shown in FIG. 1 can also be manufactured as follows, for example.

  First, as shown in the schematic configuration diagram of FIG. 3, the copper as the second metal layer 2 so that the copper foil as the second metal layer 2 passes through the molten salt bath 8 accommodated in the container 7. The foil is stretched between the first roll 31a and the second roll 31b.

  Next, the copper foil as the second metal layer 2 is fed out from the first roll 31a, and the molten salt bath 8 is electrolyzed while the copper foil is continuously immersed in the molten salt bath 8 accommodated in the container 7. Thus, tungsten and / or molybdenum is deposited on both sides of the copper foil, and the metal laminated structure 100 is formed by molten salt bath plating.

  Thereafter, the metal laminated structure 100 formed by depositing tungsten and / or molybdenum on both surfaces of the copper foil is wound around the second roll 31b and collected.

  As described above, when the metal multilayer structure 100 is continuously formed by continuously depositing tungsten and / or molybdenum on the surface of the second metal layer 2, the metal multilayer structure 100 is more efficient. Can be manufactured automatically.

<Semiconductor device>
FIG. 4 shows a schematic cross-sectional view of an example of an LED element which is an example of a semiconductor device using the metal laminated structure of the present invention. Here, the LED element shown in FIG. 4 includes the metal laminate structure 100 shown in FIG. 1 and the LED structure 10 installed on the metal laminate structure 100, and the metal laminate structure 100 and the LED structure. The body 10 is joined by a joining layer 21.

  Here, the LED structure 10 is disposed on the semiconductor substrate 14, the n-type semiconductor layer 13 disposed on the semiconductor substrate 14, the active layer 12 disposed on the n-type semiconductor layer 13, and the active layer 12. P-type semiconductor layer 11, semi-transparent electrode 17 provided on p-type semiconductor layer 11, p-electrode 15 provided on semi-transparent electrode 17, and n provided on n-type semiconductor layer 13 And an electrode 16.

  The LED structure 10 includes a p-type semiconductor layer 11, an n-type semiconductor layer 13, and an active layer 12, and the active layer 12 is disposed between the p-type semiconductor layer 11 and the n-type semiconductor layer 13. In addition, any structure that emits light from the active layer 12 by current injection can be used without particular limitation. For example, a conventionally known LED structure can be used.

  As the LED structure 10, among them, the p-type semiconductor layer 11, the active layer 12 and the n-type semiconductor layer 13 are each a group III element (at least one selected from the group consisting of Al, In and Ga) and a group V. It is preferable to use a group III-V nitride semiconductor which is a compound with an element (nitrogen). In this case, blue light can be emitted from the active layer 12.

  As an example of the LED structure 10 capable of emitting blue light from the active layer 12, for example, a GaN substrate or a sapphire substrate is used as the semiconductor substrate 14 shown in FIG. 4, and p-type GaN is used as the p-type semiconductor layer 11. An LED structure using an undoped InGaN layer as the active layer 12 and an n-type GaN layer as the n-type semiconductor layer 13 can be used.

  Moreover, the metal laminated structure of the present invention is not limited to an LED element, and can be applied to a semiconductor device other than an LED element such as a semiconductor laser element or a field effect transistor. Here, as the semiconductor substrate 14 used in the semiconductor device other than the LED structure 10 capable of emitting blue light from the active layer 12, for example, a silicon substrate, a silicon carbide substrate, a gallium arsenide substrate, or the like is used. Can do.

  The p-type semiconductor layer 11 is a semiconductor layer having a p-type conductivity type doped with a p-type impurity, and the n-type semiconductor layer 13 is an n-type conductivity type doped with an n-type impurity. Needless to say, this is a semiconductor layer. The active layer 12 may have either a p-type or n-type conductivity type, and is an undoped semiconductor layer in which neither p-type impurity nor n-type impurity is doped. Also good.

  Further, between the semiconductor substrate 14 and the n-type semiconductor layer 13, between the n-type semiconductor layer 13 and the active layer 12, between the active layer 12 and the p-type semiconductor layer 11, and between the p-type semiconductor layer 11 and the translucent electrode. Other layers may be included between at least one of the layers 17, between the translucent electrode 17 and the p-electrode 15, and between the n-type semiconductor layer 13 and the n-electrode 16.

  Further, as the bonding layer 21, for example, a layer made of a conductive material having a higher thermal conductivity than eutectic solder can be used. As the bonding layer 21, it is particularly preferable to use a metal that has low electrical resistance, high thermal conductivity, and is difficult to oxidize, and in particular, at least one selected from the group consisting of gold, silver, copper, and nickel It is more preferable to use a layer containing.

  The n-electrode 16 of the LED element having the above configuration is used as a cathode, the p-electrode 15 is used as an anode, and a voltage is applied between these electrodes, whereby the p-electrode 15 to the n-electrode 16 are formed inside the LED structure 10. Current is passed toward Thereby, light can be generated in the active layer 12 between the p-type semiconductor layer 11 and the n-type semiconductor layer 13 of the LED structure 10.

  In addition, the LED element of the structure shown in FIG. 4 can be manufactured as follows, for example.

  First, after setting the semiconductor substrate 14 in, for example, a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, the n-type semiconductor layer 13 and the active layer are formed on the surface of the semiconductor substrate 14 as shown in the schematic sectional view of FIG. Layer 12 and p-type semiconductor layer 11 are formed by epitaxial growth in this order, for example, by MOCVD.

  Next, after removing a part of the n-type semiconductor layer 13, the active layer 12, and the p-type semiconductor layer 11 by, for example, photoetching, a semi-transparent electrode is formed on the p-type semiconductor layer 11 by using, for example, a lift-off method. 17 and p electrode 15 are formed, and n electrode 16 is formed on n type semiconductor layer 13.

  Next, the metal laminated structure 100 is bonded to the back surface of the semiconductor substrate 14 after the formation of the p electrode 15 and the n electrode 16 by the bonding layer 21.

  Then, the semiconductor substrate 14 after the formation of the bonding layer 21 is cut by, for example, a circular rotary blade or the like to divide into individual LED elements having a schematic cross section shown in FIG. As described above, the LED element having the configuration shown in FIG. 4 can be obtained.

  Further, in the present invention, since the metal laminated structure 100 having a thickness that is significantly thinner than the conventional one can be used as a heat sink of the semiconductor device, the material cost of the metal laminated structure 100 can be reduced, Since the metal laminated structure 100 can be easily cut when divided into elements, workability is improved. Furthermore, since the thickness of the metal laminated structure 100 can be reduced, the thickness of the semiconductor device itself can also be reduced.

<Other forms>
In FIG. 5, typical sectional drawing of another example of the metal laminated structure of this invention is shown. Here, the metal laminated structure 200 includes a fourth metal layer 4 installed on the opposite side of the first metal layer 1 to the installation side of the second metal layer 2, and the third metal layer 3 of the third metal layer 3. The fifth metal layer 5 is provided on the side opposite to the installation side of the second metal layer 2.

  Here, as the 4th metal layer 4 and the 5th metal layer 5, the metal layer which consists of a metal containing copper, for example can be used, respectively.

  Also here, the total thickness h of the metal laminated structure 200 is preferably not less than 20 μm and not more than 400 μm. When the thickness h of the metal multilayer structure 200 is 20 μm or more and 400 μm or less, the tendency that the metal multilayer structure 200 can be efficiently manufactured by reducing the thickness of the metal multilayer structure 200 increases.

Further, in the metal laminate structure 200, the first metal layer 1 of thickness h ₁ and the second thickness h ₂ of the metal layer 2 and the third thickness h ₃ of the metal layer 3 fourth metal layer 4 of the thickness h ₄ and the thickness h ₁ of the sum _{(h 1 + h 2 + h} 3 + h 4 + h 5) the first metal layer to 1 between the thickness h ₅ of the fifth metal layer 5 third metal the ratio of the sum of the thickness h ₃ of the layer _{3 (h 1 + h 3)} [(h 1 + h 3) / (h 1 + h 2 + h 3 + h 4 + h 5)] is 0.2 to 0.8 It is preferable. When the above ratio is 0.2 or more and 0.8 or less, the linear expansion of the metal laminated structure 200 does not become too large and the thermal conductivity does not become too small. When 200 is attached to a semiconductor substrate of a semiconductor device, the heat dissipation function of the metal multilayer structure 200 can be sufficiently exhibited without causing a large difference in thermal expansion between the metal multilayer structure 200 and the semiconductor substrate. There is a tendency to be able to.

  Further, in order to suppress the warp of the metal multilayer structure 200, the central portion in the thickness direction of the metal multilayer structure 200 (in this example, a portion that is ½ of the total thickness h of the metal multilayer structure 200). It is preferable that the upper part and the lower part from the central part in the thickness direction of the laminated structure are symmetrical with respect to the central part in the thickness direction of the laminated structure.

  The metal laminated structure 200 shown in FIG. 5 can be manufactured as follows, for example.

  First, by the method shown in FIG. 2 described above, tungsten and / or molybdenum in the molten salt bath 8 is deposited on both surfaces of the second metal layer 2 such as a copper foil, respectively, and the first metal is obtained by molten salt bath plating. Layer 1 and third metal layer 3 are formed.

  Next, the second metal layer 2 after the formation of the first metal layer 1 and the third metal layer 3 is taken out from the molten salt bath 8, and the first metal layer 1 and the third metal layer 1 are removed with, for example, ion exchange water. The molten salt bath 8 adhering to the metal layer 3 is washed and removed. Then, for example, by washing with a predetermined acid, the oxide films formed on the surfaces of the first metal layer 1 and the third metal layer 3 are removed.

  Thereafter, as shown in the schematic configuration diagram of FIG. 6, the second metal layer 2 after the formation of the first metal layer 1 and the third metal layer 3 in the electroplating solution 9 accommodated in the container 7. The counter electrode 6 is immersed.

  Here, the electroplating solution 9 includes metal atoms that constitute the fourth metal layer 4 and the fifth metal layer 5, and the metal that constitutes the fourth metal layer 4 and the fifth metal layer 5. Is not particularly limited as long as it can be deposited by electrolysis of the electroplating solution 9. For example, when the fourth metal layer 4 and the fifth metal layer 5 are each made of copper, the electroplating solution 9 For example, a commercially available copper sulfate plating solution can be used.

  Next, the electroplating solution 9 is electrolyzed by applying a voltage between the second metal layer 2 and the counter electrode 6 using the second metal layer 2 as a cathode and the counter electrode 6 as an anode. Thereby, copper in the electroplating solution 9 is deposited on the surface of the first metal layer 1 and the surface of the third metal layer 3 to form the fourth metal layer 4 and the fifth metal layer 5. The metal laminated structure 200 is produced.

  Then, the metal laminated structure 200 after the formation of the fourth metal layer 4 and the fifth metal layer 5 is taken out from the electroplating solution 9, and the fourth metal layer 4 and the fifth metal, for example, with ion exchange water or the like. The electroplating solution 9 adhering to the layer 5 is removed by washing, and then the oxidation formed on the respective surfaces of the fourth metal layer 4 and the fifth metal layer 5 by washing with a predetermined acid, for example. The film can be removed. As described above, the metal laminated structure 200 shown in FIG. 5 can be manufactured.

  Moreover, the metal laminated structure 200 shown in FIG. 5 can also be manufactured as follows, for example.

  First, as shown in the schematic configuration diagram of FIG. 7, the copper foil as the second metal layer 2 passes through the molten salt bath 8 accommodated in the container 7 and the electroplating solution 9 accommodated in the container 7, respectively. As described above, the copper foil is stretched between the first roll 31a and the second roll 31b.

  Next, the copper foil is fed out from the first roll 31a and electrolyzed in the molten salt bath 8 while continuously immersing the copper foil in the molten salt bath 8 accommodated in the container 7, respectively. Tungsten and / or molybdenum is deposited, and the first metal layer 1 and the third metal layer 3 are respectively formed on both sides of the copper foil by molten salt bath plating.

  Subsequently, the copper foil after forming the first metal layer 1 and the third metal layer 3 in the electroplating solution 9 accommodated in the container 7 is replaced with the copper foil in the electroplating solution 9 accommodated in the container 7. The electroplating solution 9 is electrolyzed while being continuously immersed. As a result, copper is deposited on the surfaces of the first metal layer 1 and the third metal layer 3, respectively, and the fourth metal is deposited on the surfaces of the first metal layer 1 and the third metal layer 3 by electroplating. The layer 4 and the fifth metal layer 5 are formed to form a metal laminated structure 200.

Thereafter, the metal laminated structure 200 is wound around the second roll 31b and collected.
Moreover, in the above, the 4th metal layer 4 and the 5th metal layer 5 were each formed using the electroplating liquid 9, but the formation method of the 4th metal layer 4 and the 5th metal layer 5 is these. Needless to say, it is not limited to.

  For example, the metal laminated structure 200 can also be formed by forming the fourth metal layer 4 and the fifth metal layer 5 by a conventionally known vapor phase method such as sputtering.

  Moreover, the 4th metal layer 4 and the 5th metal layer 5 may be formed combining the formation by electrolysis of said electroplating liquid, and formation by vapor phase methods, such as a sputtering method, for example.

  Further, the metal laminated structure is not limited to the above-described three-layer or five-layer structure, and the first metal layer 1, the second metal layer 2, and the third metal layer 3 are the same. It may be included in the order.

  For example, as shown in the schematic cross-sectional view of FIG. 8, a metal layer made of nickel or the like is formed on the surface of the fourth metal layer 4 of the metal multilayer structure 200 opposite to the installation side of the first metal layer 1. 41 may be provided.

  Further, cobalt containing cobalt is included between the first metal layer 1 and the fourth metal layer 4 and / or between the third metal layer 3 and the fifth metal layer 5 of the metal laminated structure 200. Layers may be installed.

  The metal multilayer structure 200 including the cobalt-containing layer can be manufactured, for example, as follows.

  First, by immersing the first metal layer 1 and the third metal layer 3 respectively formed on both surfaces of the surface of the second metal layer 2 in an alkaline solution, the surface of the first metal layer 1 and the third metal layer 3 are immersed. The surface of the metal layer 3 is degreased.

  Next, the first metal layer 1 and the third metal layer 3 are immersed in an alkaline aqueous solution as an anode and electrolysis is performed, so that the surface of the first metal layer 1 and the surface of the third metal layer 3 are removed. Each oxide film is removed.

  Next, the first metal layer 1 and the third metal layer 3 after the removal of the oxide film are immersed in a cobalt plating solution made of a cobalt sulfate aqueous solution or the like as a cathode, and electrolysis is performed. Cobalt is deposited on the surface of the layer 1 and the surface of the third metal layer 3 to form a cobalt-containing layer.

  Thereafter, the cobalt layer formed above is immersed in a copper sulfate plating solution as a cathode and electrolysis is performed, thereby depositing copper on the surface of the cobalt layer, and the fourth metal layer 4 and the fifth metal layer 5 made of copper. Each metal layer 5 is formed.

  As described above, the cobalt-containing layers are formed between the first metal layer 1 and the fourth metal layer 4 and between the third metal layer 3 and the fifth metal layer 5 of the metal multilayer structure 200, respectively. be able to.

<Preferred configuration of molten salt bath>
As the molten salt bath 8 used in the present invention, for example, potassium fluoride (KF), boron oxide (B ₂ O ₃ ), and tungsten oxide (WO ₃ ) are mixed at a molar ratio of, for example, 67: 26: 7. A molten salt bath produced by melting the mixture can be used.

When the first metal layer 1 and the third metal layer 3 are each made of molybdenum, as the molten salt bath 8, for example, KF, K ₂ MoO _4, and B ₂ O ₃ are used, for example, 81: 9. For example, a molten salt bath prepared by melting a mixture mixed at a molar ratio of 10 at a temperature of about 850 ° C. can be used.

When the first metal layer 1 and the third metal layer 3 are made of tungsten and molybdenum, respectively, the molten salt bath 8 may be, for example, KF, WO ₃ , K ₂ MoO ₄ , B ₂ O ₃ , It is also possible to use a molten salt bath or the like prepared by melting a mixture prepared by mixing at a molar ratio of, for example, 80: 4: 5: 10 at a temperature of about 850 ° C., for example.

<Preparation of Heat Sink of Example 1>
After 319 g of KF powder and 133 g of WO ₃ powder were sealed in a pressure vessel, the pressure vessel was held at 500 ° C., and the inside of the pressure vessel was evacuated for 2 days or more to dry the KF powder and WO ₃ powder, respectively. .

Further, 148 g of B ₂ O ₃ powder was sealed in a pressure vessel different from the above, and then the pressure vessel was kept at 380 ° C., and the inside of the pressure vessel was evacuated for 2 days or more to dry the B ₂ O ₃ powder. I let you.

Then, using the apparatus shown in the schematic diagram in FIG. 9, was prepared molten salt bath from KF powder, B ₂ O ₃ powder and WO ₃ powder after drying the above.

Specifically, first, the KF powder, the B ₂ O ₃ powder and the WO ₃ powder after drying are put into an SiC crucible 111 which has been dried at 500 ° C. for 2 days or more, respectively. The crucible 111 was sealed in a quartz vacuum-resistant container 110.

  Next, the crucible 111 was held at 500 ° C. with the cover 118 made of SUS316L in the opening at the top of the vacuum resistant container 110, and the inside of the vacuum resistant container 110 was evacuated for one day or more.

  Then, high-purity argon gas is introduced into the vacuum-proof container 110 from the gas inlet 117, and the high-pressure argon gas is filled into the vacuum-proof container 110, and the crucible 111 is held at 850 ° C. The molten salt bath precursor 112 was produced by melting.

Next, a rod-shaped electrode including a tungsten plate 113 (surface: 20 cm ² ) serving as an anode and a rod-shaped electrode including a nickel plate 114 (surface: 20 cm ² ) serving as a cathode are respectively inserted from openings provided in the lid 118. Then, the tungsten plate 113 and the nickel plate 114 were respectively immersed in the molten salt bath precursor 112 in the crucible 111.

  Here, in the above rod-shaped electrode, lead wires 115 are connected to the tungsten plate 113 and the nickel plate 114, respectively, and a tungsten wire is used as the lead wire 115 inside the vacuum resistant vessel 110. A copper wire was used as the external lead wire 115. Further, at least a part of the lead wire 115 was covered with a coating material 116 made of alumina.

  In addition, when inserting the rod-shaped electrode, high purity argon gas was introduced from the gas introduction port 117 into the vacuum resistant container 110 so that the atmosphere was not mixed into the vacuum resistant container 110.

  In order to prevent impurities from being mixed into the molten salt bath precursor 112 due to the progress of oxidation of the tungsten plate 113 and the nickel plate 114, as shown in FIG. It was immersed in the molten salt bath precursor 112.

  Then, the molten salt bath precursor 112 was electrolyzed to precipitate impurities on the nickel plate 114, thereby removing the impurities from the molten salt bath precursor 112 to prepare a molten salt bath.

Next, after replacing the nickel plate 114 on which the impurities were deposited with a copper foil having a thickness of 40 μm, a current having a current density of 3 A / dm ² was passed between the tungsten plate 113 and the copper foil for 17 minutes. Then, constant current electrolysis of the molten salt bath was performed, and tungsten was deposited on both sides of the copper foil to form a tungsten layer having a thickness of 5 μm. Then, the copper foil after forming the tungsten layer is taken out from the apparatus shown in FIG. 9, and the surface of the tungsten layer is removed by washing the molten salt bath adhering to the tungsten layer with ion exchange water, and then washed with an acid. The heat sink of Example 1 was produced by removing the oxide film formed on the surface of the tungsten layer.

  And about the heat sink of Example 1, the linear expansion coefficient (ppm / degreeC) to a horizontal direction was measured. The results are shown in Table 1. The linear expansion coefficient (ppm / ° C.) was measured by a thermomechanical analyzer (TMA), measured from room temperature to 150 ° C., and the average value was calculated.

<Preparation of Heat Sink of Example 2>
Using a copper foil having a thickness of 20 μm, a constant current electrolysis of the molten salt bath is performed by flowing a current having a current density of 3 A / dm ² for 136 minutes between the copper foil and the tungsten plate 113 of the apparatus shown in FIG. Thus, a heat sink of Example 2 was produced in the same manner as Example 1 except that tungsten was deposited on both surfaces of the copper foil to form a 40 μm thick tungsten layer.

  And also about the heat sink of Example 2, it carried out similarly to Example 1, and measured the linear expansion coefficient (ppm / degreeC) to a horizontal direction. The results are shown in Table 1.

<Preparation of Heat Sink of Example 3>
A heat sink of Example 3 was produced in the same manner as Example 1 except that a copper foil having a thickness of 10 μm was used. And also about the heat sink of Example 3, it carried out similarly to Example 1, and measured the linear expansion coefficient (ppm / degreeC) to a horizontal direction. The results are shown in Table 1.

<Preparation of Heat Sink of Example 4>
First, a constant current electrolysis of a molten salt bath was performed except that a current density of 3 A / dm ² was passed between the copper foil having a thickness of 100 μm and the tungsten plate 113 of the apparatus shown in FIG. 9 for 340 minutes. In the same manner as in Example 1, tungsten was deposited on both sides of the copper foil to form a tungsten layer having a thickness of 100 μm.

  Next, the copper foil after the tungsten layer is formed is taken out from the apparatus shown in FIG. 9, and the surface of the tungsten layer is removed by washing the molten salt bath adhering to the tungsten layer with ion exchange water, and then washed with an acid. As a result, the oxide film formed on the surface of the tungsten layer was removed.

  Next, the surface of the tungsten layer after the removal of the oxide film was washed by immersing it in an alkali degreasing solution (A screen A220 manufactured by Okuno Pharmaceutical Co., Ltd.) at 50 ° C. for 20 minutes.

  Next, the oxide layer was removed from the surface of the tungsten layer by immersing it in an alkaline aqueous solution using the washed tungsten layer as an anode and performing electrolysis (alkali anode electrolysis).

  Next, an anode made of one cobalt plate and a copper foil after the above alkaline anodic electrolysis were immersed in a cobalt plating solution made of an aqueous cobalt sulfate solution as opposed to the anode. Here, as the cobalt plating solution, a cobalt sulfate aqueous solution in which 200 g of cobalt sulfate and 100 g of sulfuric acid were dissolved in water per liter of the cobalt plating solution was used.

Then, with the cobalt plating solution kept at 80 ° C., a current density of 15 A / dm ² was passed between the anode and the cathode for 3 minutes.

  By performing electrolysis of the cobalt plating solution under such conditions, cobalt is deposited on each surface of the tungsten layer of the copper foil after the formation of the tungsten layer as the cathode, so that each of the tungsten layers on both sides of the copper foil is deposited. A cobalt layer having a thickness of 0.5 μm was formed on the surface.

  Thereafter, the copper foil after the formation of the cobalt layer is taken out of the cobalt plating solution, and the cobalt plating solution adhering to the tungsten layer is washed and removed with ion exchange water, and then washed with an acid on the surface of the tungsten layer. The formed oxide film was removed.

  Next, the copper after forming the cobalt layer together with a counter electrode made of phosphorus-containing copper in a copper sulfate plating solution (Rebco EX manufactured by Uemura Kogyo Co., Ltd.) contained in a Pyrex (registered trademark) beaker. The foil was immersed so as to face the counter electrode.

Then, with the temperature of the copper sulfate plating solution maintained at 30 ° C., a current of 20 mA (milliampere) per 1 cm ² of the surface of the copper foil after formation of the counter electrode as the anode and the cobalt layer as the cathode (current density 20 mA / cm ² ) A current was passed between the anode and the cathode so as to flow for 1470 minutes.

  By electrolyzing the copper sulfate plating solution under such conditions, copper was deposited on the respective surfaces of the cobalt layer on both sides of the copper foil after the formation of the cobalt layer as the cathode, thereby forming a 49 μm thick copper layer. Formed.

  Next, after removing the copper sulfate plating solution adhering to the copper layer with ion-exchange water after removing the copper layer surface of the copper foil after the copper layer is formed, the surface of the copper layer is washed with an acid. The formed oxide film was removed, and the heat sink of Example 4 was produced.

  And also about the heat sink of Example 4, it carried out similarly to Example 1, and measured the linear expansion coefficient (ppm / degreeC) to a horizontal direction. The results are shown in Table 1.

  It was confirmed that the heat sinks of Examples 1 to 4 manufactured as described above can be manufactured as thin as 100 μm or less as a whole, and can be efficiently manufactured by electroplating using a plating solution. It was.

  Moreover, as shown in Table 1, in the heat sinks of Examples 1 to 4, the tungsten layer was added to the sum of the total thickness of the copper layers (including the thickness of the copper foil) and the total thickness of the tungsten layers. Since the ratio of the total thickness was 0.2 or more and 0.8 or less, it was confirmed that the heat sink was an excellent heat sink in which linear expansion did not become too large and thermal conductivity did not become too small.

<Preparation of Heat Sink of Example 5>
First, a mixture is prepared by mixing potassium fluoride (KF) powder, boron oxide (B ₂ O ₃ ) powder, and tungsten oxide (WO ₃ ) powder in a molar ratio of 67: 26: 7, and the mixture is made of SiC. In a crucible (manufactured by As One Co., Ltd.).

Here, potassium fluoride (KF) powder, boron oxide (B ₂ O ₃ ) powder and tungsten oxide (WO ₃ ) powder are each weighed in a glove box in an Ar (argon) atmosphere, and SiC contained in the same glove box. It was put into a made crucible.

  Next, the SiC crucible charged with the above mixture was heated to 850 ° C. using a mantle heater to melt the above mixture to prepare a molten salt bath.

  Next, in the above glove box, a copper foil (cathode) having a thickness of 40 μm was immersed in the molten salt bath together with the counter electrode (anode) made of a tungsten plate so as to face the counter electrode.

  Here, a nickel wire is welded to each of the anode and the cathode, and a current can be supplied from the nickel wire between the anode and the cathode.

In the state where the temperature of the molten salt bath is maintained at 850 ° C., a current of 30 mA (milliampere) per 1 cm ^{2 of the} anode surface (current density 30 mA / cm ² ) flows while swinging the anode and the cathode. A current was passed between the anode and the cathode for 150 minutes.

  By performing electrolysis of the molten salt bath under such conditions, tungsten was deposited on the surface of the copper foil serving as the cathode to form a tungsten layer made of tungsten precipitates with a thickness of 30 μm.

  Next, outside the glove box, the copper foil after the formation of the tungsten layer is taken out from the molten salt bath, and the molten salt bath adhering to the tungsten layer is removed by washing with ion exchange water, and then the acid is removed. The oxide film formed on the surface of the tungsten layer was removed by washing with. Thus, the heat sink of Example 5 was produced.

  It was confirmed that the heat sink of Example 5 manufactured as described above can be manufactured as thin as 100 μm as a whole, and can be manufactured efficiently by molten salt bath plating.

  In the heat sink of Example 5, the ratio of the total thickness of the tungsten layer to the sum of the total thickness of the copper layer (including the thickness of the copper foil) and the total thickness of the tungsten layer is 0. 6 and in the range of 0.2 or more and 0.8 or less, it was confirmed that this was an excellent heat sink in which linear expansion did not become too large and thermal conductivity did not become too small.

<Production of LED elements of Examples 1 to 5>
Next, five wafers having LED structures formed on one surface of the sapphire substrate were produced.

  Here, the five wafers were manufactured as follows. First, an n-type GaN layer, an undoped InGaN active layer, and a p-type GaN layer are epitaxially grown in this order by MOCVD on the surface of a sapphire substrate having a circular surface with a diameter of 100 mm and a thickness of 100 μm. It was.

  Next, part of each of the n-type GaN layer, the undoped InGaN active layer, and the p-type GaN layer was removed by photoetching until a part of the surface of the n-type GaN layer was exposed.

  Thereafter, the above-described wafers were produced by forming an n-electrode on the n-type GaN layer, a semi-transparent electrode on the p-type GaN layer, and a p-electrode on the semi-transparent electrode by lift-off.

  Then, each of the heat sinks of Examples 1 to 5 produced above was joined to the back surface of the wafer produced above on the side opposite to the LED structure formation side by eutectic solder, and 10 mm × 10 mm with a circular rotary blade. The LED elements of Examples 1 to 5 were obtained by dividing into LED elements of a size having a square surface.

<Evaluation of LED elements of Examples 1 to 5>
A copper plate and a tungsten plate are joined by pressure welding, and a heat sink composed of a laminated structure of copper (20 μm) / tungsten (60 μm) / copper (20 μm) having a total thickness of 1 mm and the LED structure are bonded by the above eutectic solder. A comparative LED element was produced in the same manner as described above except that the LED element was formed by bonding.

  And when the light emission characteristic of the LED element of Examples 1-5 produced above and the LED element of said comparative example was compared, the light emission characteristic was equivalent.

  However, since the thickness of the heat sink of the LED elements of Examples 1 to 5 is 100 μm or less and the thickness of the heat sink of the LED element of the comparative example is 1 mm, the LED elements of Examples 1 to 5 are the LEDs of the comparative example. It was confirmed that the material cost of the heat sink can be reduced as compared with the element, and the workability is improved because the wafer can be easily cut with a circular rotary blade.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The metal laminate structure manufacturing method of the present invention may be used for a heat sink of a semiconductor device, for example.

  DESCRIPTION OF SYMBOLS 1 1st metal layer, 2nd 2nd metal layer, 3rd metal layer, 4th 4th metal layer, 5th 5th metal layer, 6 counter electrode, 7 container, 8 molten salt, 9 electroplating liquid DESCRIPTION OF SYMBOLS 10 LED structure, 11 p-type semiconductor layer, 12 active layer, 13 n-type semiconductor layer, 14 semiconductor substrate, 15 p electrode, 16 n electrode, 17 translucent electrode, 31a 1st roll, 31b 2nd roll , 41 Bonding layer, 100, 200 Metal laminated structure, 110 Vacuum resistant container, 111 crucible, 112 Molten salt precursor, 113 Tungsten plate, 114 Nickel plate, 115 Lead wire, 116 Coating material, 117 Gas inlet, 118 lid.

Claims (6)

A first metal layer, a second metal layer, and a third metal layer;
The first metal layer is disposed on one surface of the second metal layer;
The third metal layer is disposed on the other surface of the second metal layer;
The first metal layer includes tungsten;
The second metal layer includes copper;
The third metal layer is a method of manufacturing a metal laminated structure containing tungsten,
Forming the first metal layer on one surface of the second metal layer by molten salt bath plating;
Forming the third metal layer on the other surface of the second metal layer by molten salt bath plating,
Molten salt bath used in the molten salt bath plating, and potassium fluoride, and boron oxide state, and are not produced by melting a mixture containing tungsten oxide,
The metal total thickness of the multilayer structure is Ru der than 400μm or less 20 [mu] m, method for producing a metal laminated structure.   The sum of the thickness of the first metal layer and the thickness of the third metal layer with respect to the sum of the thickness of the first metal layer, the thickness of the second metal layer, and the thickness of the third metal layer The manufacturing method of the metal laminated structure of Claim 1 whose ratio is 0.2-0.8. Forming a fourth metal layer on the opposite side of the first metal layer from the installation side of the second metal layer;
Forming a fifth metal layer on the opposite side of the third metal layer from the installation side of the second metal layer,
The method for manufacturing a metal laminated structure according to claim 1, wherein each of the fourth metal layer and the fifth metal layer contains copper.   The thickness of the first metal layer, the thickness of the second metal layer, the thickness of the third metal layer, the thickness of the fourth metal layer, and the thickness of the fifth metal layer with respect to the sum. The manufacturing method of the metal laminated structure of Claim 3 whose ratio of the sum of the thickness of 1 metal layer and the thickness of the said 3rd metal layer is 0.2 or more and 0.8 or less.   Forming a cobalt-containing layer between the first metal layer and the fourth metal layer and between at least one of the third metal layer and the fifth metal layer; The manufacturing method of the metal laminated structure of Claim 3 or 4.   The manufacturing method of the metal laminated structure of Claim 5 whose thickness of the said cobalt content layer is 0.05 micrometer or more and 3 micrometers or less.

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