JP2005183650A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint material for semiconductor device that is low in environmental load, inexpensive and superior in heat resistance, and to provide a semiconductor device using it, and its manufacturing method. <P>SOLUTION: The semiconductor device has a structure wherein a semiconductor element and a copper member are joined. The semiconductor element and the copper member are joined with each other at a melting point of 250°C or higher by a first bonding member made mainly of zinc (Zn), and the bonding member is formed in an area near to a boundary surface with the semiconductor element in a manner that nickel (Ni) may be inclined and spread. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bonding member for a semiconductor device, a semiconductor device using the same, and a method for manufacturing the same, and more particularly to a high voltage semiconductor device.

  Currently, high-melting-point, high-Pb solder is used for component internal connections and high heat resistance connections. In particular, in the case of a semiconductor device for high withstand voltage, a heat resistant temperature of 200 ° C. is required in the manufacturing process. Therefore, a high Pb solder having a solid phase line near 300 ° C., for example, 95Pb5Sn (solid phase line) 300 ° C liquid phase line 314 ° C), 98Pb2Sn (solid phase line 316 ° C liquid phase line 322 ° C), 98Pb2Ag (solid phase line 304 ° C liquid phase line 305 ° C), 97.5Pb1.5Ag1Sn (solid phase line 309 ° C liquid phase Solder with high Pb content such as wire (309 ° C.) is used for connection.

  Examples of such high voltage semiconductor devices include power semiconductor elements such as IGBTs, diodes, GTOs, and transistors, and power semiconductor modules using these (hereinafter collectively referred to as semiconductor devices).

JP-A-10-125856

JP-A-7-161877 JP 2002-142424 A JP 2002-261210 A JP 2002-359328 A

  However, in recent years, from the viewpoint of environmental protection, there has been a demand for semiconductor devices and other connection structures using other alternative connection materials by eliminating Pb which has a large environmental load.

  There are various requirements for the connection structure and the connection material used therefor, but in the case of a connection material used for a high voltage semiconductor device, a heat resistance temperature of about 200 ° C. is required in the manufacturing process.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a bonding material for a semiconductor device that has a low environmental load and is low in cost and excellent in heat resistance, a semiconductor device using the same, and a method for manufacturing the same.

  In order to achieve the above object, according to the present invention, in a semiconductor device having a configuration in which a semiconductor element and a copper member are joined, the semiconductor element and the copper member have a melting point of 250 ° C. or higher and contain zinc (Zn) as a main component. In this case, nickel (Ni) is inclined and diffused in a region close to the interface with the semiconductor element.

  In order to achieve the above object, according to the present invention, in a semiconductor device having a structure in which a semiconductor element is metal-bonded to a member, the semiconductor element and the member are made of zinc (Zn) as a main component and aluminum (Al). It joined by the 1st joining member containing 8 weight% or less, and the 1st joining member was set as the structure which has a nickel (Ni) diffused layer in the area | region close | similar to the interface with a semiconductor element.

  In order to achieve the above object, according to the present invention, one surface of the semiconductor element is bonded to the first member by the first bonding member, and the second member is bonded to the other surface by the second bonding member. In the semiconductor device having the above-described configuration, the first bonding member and the second bonding member are metals containing aluminum (Al) whose main component is zinc or zinc (Zn). In the configuration, a diffusion layer of nickel (Ni) is formed in the vicinity of the interface between each of the two bonding members and the semiconductor element.

  In order to achieve the above object, according to the present invention, a copper (Cu) member is bonded to one surface of a semiconductor element having a nickel (Ni) film formed on both surfaces by a first bonding member, and the other surface is bonded to the other surface. In a semiconductor device having a configuration in which a lead electrode is joined by a second joining member, the first joining member and the second joining member are metals having zinc (Zn) as a main component and different aluminum (Al) contents. The second bonding member is made of a material having a melting point higher than that of the first bonding member.

  According to the present invention, by using a bonding material containing Zn as a main component, it is possible to obtain a high voltage semiconductor device having a small environmental load and a heat resistance of 250 ° C. or higher.

  Since the heat-resistant temperature required for semiconductor devices, particularly high-voltage semiconductor devices, is 200 ° C., the melting point of the material that contributes to the connection between members in the material structure of the connecting portion is 250 ° C. or higher. is required. That is, as the structure of the connection portion, if at least the structure that contributes to the connection between the members does not melt, the connection is maintained even if the other part melts. Furthermore, the temperature at which the semiconductor element is connected with the bonding material needs to be connected at 600 ° C. or lower from the viewpoint of protecting the semiconductor element. Accordingly, the melting point of the metal element that is the main component of the bonding material needs to be 250 ° C. or higher and 600 ° C. or lower.

  First, as a material satisfying such conditions, a bonding material that replaces a conventional solder mainly composed of lead (Pb) will be examined below.

  As metal elements satisfying the above conditions, Bi (271.4 ° C.), Po (254 ° C.), Cd (321.1 ° C.), Tl (302.5 ° C.), Zn (419.6 ° C.), Te (449. 8 ° C), At (300 ° C), Pb (327.5 ° C). Of these metal elements, Zn is optimal when it is a material that satisfies the safety of environmental load reduction, non-toxicity, and softness as a bonding material, and is also suitable for connecting with a single metal element. ing. The bonding material may be a material that generates a eutectic component having a melting point of 250 ° C. or higher and 600 ° C. or lower in addition to a single metal element. However, in the case of using a two-component material system instead of a single metal material, in consideration of the compositional non-uniformity of the solder connection portion, at least a component having a melting point of 250 ° C. or less in the component of the bonding material supplied to the connection portion It is preferable that there is no. This is because, in a structure in which a component having a melting point of 250 ° C. or less remains as it is after connection using a bonding material, it melts and the reliability of connection decreases.

Therefore, it is preferable that all the components in the bonding material supplied for connection have a melting point of 250 ° C. or higher. In fact, in the case of the above-mentioned high Pb solder, Sn containing Sn may melt at a melting point of 232 ° C. due to the non-uniform composition, and reliability at a heat resistant temperature of 250 ° C. may not be obtained. However, this problem does not occur with Ag containing 961 ° C. of melting point.
In addition, although the eutectic composition material system is a two-phase mixture below the melting point of the eutectic composition, a composition that accounts for more than half of the two phases and contributes to the connection from the viewpoint of reducing the stress at the connection part is a hard metal. It is necessary that the material is not an intermetallic compound but a soft material, for example, a metal in which a single metal or a very small amount of different metals are dissolved. As the two-component material system satisfying such conditions, there are a ZnAl system, a ZnCd system, a ZnMg system, a ZnBi system, a ZnSb system, etc., but Bi and Mg systems are hard, and Cd and Sb systems are toxic. Of these systems, the ZnAl system is most preferable, and soft Zn is suitable as the metal occupying the majority.

  The above also applies to a material system having three or more components, and Zn is suitable as the metal occupying most of the material. That is, in a material system of two or more components, Zn is the main component, and as an element to be added, any element can be used as long as the structure occupies most of Zn at a melting point of 250 ° C. or higher and a temperature below the eutectic. However, for example, Al, Cd, Mg, Bi, Mn, Fe, Ni, Cu, Ag, Sb, and the like may be appropriately selected to form a two-component, three-component material system. In the ZnAl system, since the Al oxide film is strong even in a reducing atmosphere, if it is difficult to wet, it may be removed by pressurization or scrubbing so that the oxide film is mechanically broken. Further, as shown in the ZnAl-based binary alloy phase diagram shown in FIG. 10, in order to obtain a desired melting point, the weight percentage of Al may be changed as appropriate. When obtaining a lower melting point than Zn, Al may be about 8% by weight or less.

  As described above, the material of the bonding member when the heat-resistant temperature is 250 ° C. or more and 600 ° C. or less is as follows: Zn alone and a two or more component system containing Zn as a main component (hereinafter, Zn (It is referred to as a joining material of the system). Note that the bonding material composed of Zn alone is not limited to pure Zn, but also refers to a bonding material substantially made of Zn, and may contain a minute amount within a range that does not significantly affect the characteristics.

  Next, the joining of the joining member with the semiconductor element and other members will be described.

  Zn reacts with most metal elements, but does not substantially react with Si which is a semiconductor element material, and it is very difficult to directly connect Si and Zn. Therefore, for example, a pretreatment process is required in which a Ni film is formed on the Si surface and then heat-treated, and further a Ni film is formed thereon. Thereby, the wettability of Zn at the time of connection is ensured, and as a result, a good connection between Si and Zn is obtained. However, in the case where Si and Cu having a Ni film formed on the surface are connected by a Zn-based bonding member, the difference in thermal expansion coefficient between Si and Cu is large, so that a NiZn compound layer is formed. Problems such as cracks occur due to inability to withstand this thermal stress. Therefore, it is necessary to control the Ni film thickness, connection temperature, and the like so that the NiZn compound layer is not formed.

  From the above viewpoint, the Ni film thickness is 10 μm or less, preferably 5 μm or less. When the thickness of the Ni layer is reduced in this way, since the amount of Ni supplied into the Zn-based bonding member is small when the Zn-based bonding member is connected, the Ni component is a shallow region close to the interface of the Zn-based bonding member. Although it diffuses in, it does not lead to the formation of a ZnNi compound layer, and as a result, good connection strength can be obtained between Si and a Zn-based bonding member. The Zn-based bonding member layer at the interface is connected under such a condition that Ni is diffused (gradient diffusion) in a state where the density gradually decreases from the interface, and the NiZn alloy layer is not substantially formed.

  Note that the Ni layer may be left between Si and the Zn-based bonding member containing the diffused Ni component by adjusting the connection temperature. Alternatively, a Ti film layer may be formed as a reaction stopper layer to form a structure of Si / Ni / Ti / Ni, and the thickness of the Ni film layer that reacts with the Zn-based bonding material may be controlled. Furthermore, Au and Ag plating may be performed on the Ni surface to ensure wettability of Zn.

  In any case, the NiZn compound may be diffused in the Zn-based bonding member. However, if the NiZn compound is not left as an interface layer, the Si-Zn-based bonding member and Can get a good connection.

  On the other hand, it is the connectivity between Zn and the Cu member, but Zn easily reacts with Cu to form a compound and a strong connection is obtained, and the ZnCu compound has a sufficiently high interfacial bonding strength between Zn and Cu. A Zn-based bonding member may be directly connected to the Cu member. Further, a Ni film may be applied to the surface to ensure wettability, but it is better to take measures such as setting the thickness of the Ni film to 10 μm or less, preferably 5 μm or less in consideration of the above points.

Further, as described above, the thermal expansion coefficients of Si and Cu of the semiconductor element are greatly different from Si of 2.6 × 10 ⁻⁶ / ° C. and Cu of 17 × 10 ⁻⁶ / ° C., respectively. Therefore, when a semiconductor element is directly connected to a thick Cu member, a stress based on the difference in thermal expansion coefficient is generated, and when the stress is larger than the Si strength of the semiconductor element, a crack is generated in Si. In order to reduce such thermal stress, a stress relaxation member having a coefficient of thermal expansion between Si and Cu may be interposed between the semiconductor element and the Cu member. The stress relaxation member has a three-layer structure in which a low thermal expansion material Invar or 42 alloy is sandwiched between Cu, and the overall thermal expansion coefficient can be controlled by changing the thickness ratio between the low thermal expansion material and Cu. Such a thermal expansion coefficient difference buffer material can be easily connected to Zn because the front and back surfaces are Cu. Further, Ni plating may be performed to ensure wettability. The stress buffer member is not limited to one layer having the above structure, and a plurality of layers may be provided as appropriate.

  Furthermore, as a condition for connecting with a Zn-based joining member, a neutral or reducing atmosphere is suitable, and a reducing atmosphere in which hydrogen is added to nitrogen is preferable. In addition, it is possible to connect without flux in a neutral or reducing atmosphere, but when using flux, it is being connected so that carbides do not remain and impede wettability and decrease bonding strength. A flux that completely scatters may be used.

Next, as the characteristics of Zn after melting and cooling, the tensile strength is about 50 MPa equivalent to that of the high Pb solder, and the thermal conductivity is 0.269 cal · cm ⁻¹ · s ⁻¹ · deg ⁻¹ (96.8 Kcal · m ⁻¹ · h ⁻¹ · deg ⁻¹ ) and the specific resistance is 5.9 × 10 ⁻⁶ Ωcm. These are good compared with 0.0838 cal · cm ⁻¹ · s ⁻¹ · deg ⁻¹ (30.2 Kcal · m ⁻¹ · h ⁻¹ · deg ⁻¹ ) and 2.08 × 10 ⁻⁶ Ωcm of Pb. From this, it can be seen that the connection portion using high Pb solder can be easily replaced with a Zn-based bonding material, and that the Zn-based bonding material is superior in terms of heat dissipation.

  On the other hand, the thickness of the compound layer between Zn and Cu is 1 to 3 μm in the case of high Pb solder, whereas it is 420 ° C. near the melting point of Zn in the case of a Zn-based bonding material. When connected in the range of ˜460 ° C., it becomes several tens μm or more, and the thickness of the remaining portion of the Zn-based bonding material is reduced. The compound layer is harder than the Cu or Zn-based bonding material and hardly absorbs the difference in thermal expansion coefficient between the upper and lower layers, so that as much Zn-based bonding material as possible remains to ensure the strength at the connection portion. It is necessary to adjust the thickness of the feed material. For example, when a semiconductor element and a Cu member having a thickness of 2 mm or more are directly connected using a Zn-based bonding member having a thickness of about 1 mm, the Zn portion remains in the bonding portion, and the stress on the semiconductor element is the strength of the semiconductor element. Therefore, cracks do not occur in the semiconductor element, and the bonding strength does not decrease.

  However, in consideration of the heat dissipation of the semiconductor device, in order to improve the heat transfer characteristics between the semiconductor element and the Cu member, it is preferable to make the layer of the joining member interposed between them as thin as possible within a range in which the joining strength can be secured. good. Therefore, when the thickness of the Zn-based bonding material is 0.2 mm or less, the thickness of the Cu member to be connected is set to be equal to or less than the thickness of the semiconductor element, or a stress relaxation member is inserted to the semiconductor element. What is necessary is just to make it the structure which reduces the thermal stress of. Since the CuZn compound layer is softer than the NiZn compound layer and easily absorbs thermal stress, the compound layer may be formed. However, the NiZn compound layer is not formed as a layer as described above. Is good. Moreover, in order to suppress the thickness of the reaction layer to be formed, the temperature at the time of connection is preferably in the temperature range of the melting point to the melting point + 50 ° C.

  The bonding strength between the semiconductor element and the 2 mm thick Cu plate when using Zn alone as the bonding member is tensile when the diameter of the semiconductor element is 6 mm and the thickness of the Zn element is 0.2 to 1 mm. The strength is about 320 N, and when a stress relaxation member for reducing stress is inserted between the semiconductor element and the Cu plate, a tensile strength of 400 N or more can be obtained. In addition, when eutectic Zn5Al is used as a Zn-based bonding material instead of Zn alone, a strength of about 250 N is obtained in the case of a semiconductor element and a Cu plate, and 320 N or more is obtained when a stress relaxation member is inserted. . In addition, when a stress relaxation member is inserted using the above Zn simple substance or Zn5Al as a bonding member, the strength is 80% or more of the initial tensile strength even after a thermal cycle test (-40 to 200 ° C., 400 cycles). Was confirmed to be secured.

  Furthermore, by covering at least the portion connected by the Zn-based bonding member with a resin satisfying heat resistance of 250 ° C., such as polyimide resin, the environment resistance of the Zn-based connecting portion is improved and the semiconductor element and the member The bonding strength with the material is also improved.

  Based on the above examination, an example in which the Zn-based bonding member is applied to a high voltage semiconductor device will be described.

  As a first embodiment, several embodiments will be described with reference to the drawings in the case where the present invention is applied to a high voltage semiconductor device used in an in-vehicle AC generator.

  FIG. 1 shows a first embodiment of Example 1 of a semiconductor device according to the present invention. A semiconductor element 1, a support electrode body 3 that supports the semiconductor element 1 via a stress relaxation member 5, a semiconductor element, and an electric circuit. Connected lead electrode 7, bonding members 2, 4, 6 made of Zn-based bonding material for connecting each of them, and sealing material 8 filling the inside of support electrode body 3. Yes. In the case of the first embodiment, Zn-based bonding members 2 and 4 are bonded in contact with the surface of the semiconductor element 1, and no other layer exists between them. Thereby, the semiconductor device excellent in heat resistance, heat stress resistance, and heat dissipation can be provided. Here, the semiconductor element 1 is a rectifying element such as a Zener diode.

  In this embodiment, both surfaces of the semiconductor element 1 and the stress relaxation member 5 and the connection surfaces of the support electrode body 3 and the lead electrode 7 are previously plated with a nickel (Ni) film in order to improve the wettability of the bonding member. Joined by the joining members 2, 4, 6 in a thinly formed state, but in the state after joining shown in FIG. 1, Ni diffuses into the joining members 2, 4, 6 and the Ni film disappears doing.

  Note that the bonding members 2, 4, and 6 do not need to use Zn-based bonding materials having the same composition, but use Zn-based bonding materials having different compositions from the viewpoint of the temperature hierarchy, stress hierarchy, and the like described in detail below. May be. In addition, the bonding material is preferably provided with a thin film thickness of about 0.1 to 0.3 mm in consideration of improvement in heat dissipation characteristics of the entire semiconductor device. As the stress relaxation member 5, a three-layer structure in which Invar or 42 alloy is sandwiched between Cu may be used. In FIG. 1, only one layer of the stress relaxation member 5 is provided, but a plurality of layers may be provided to further reduce thermal stress. For the support electrode body 3 and the lead electrode 7, a Cu member having a high thermal conductivity may be used. As the sealing material 8, a heat-resistant resin or silicone rubber may be used.

  Next, a second embodiment of Example 1 of the semiconductor device of the present invention will be described with reference to FIG. The semiconductor device according to the second embodiment includes a semiconductor element 1, a support electrode body 3 that supports the semiconductor element 1, a lead electrode 7 that is electrically connected to the semiconductor element, and a Zn-based bonding material that connects each of them. And the sealing member 8 filling the inside of the support electrode body 3. In the case of the present embodiment, since the stress relaxation member 5 is not provided, the film thickness of the bonding member 4 between the semiconductor element 1 and the support electrode body 3 is slightly thicker about 0.3 to 0.6 mm as a measure against thermal stress. Is preferably provided.

  Also in this embodiment, as in the first embodiment described above, the surfaces of the semiconductor element 1 and the connection surfaces of the support electrode body 3 and the lead electrode 7 are previously Ni-coated in order to improve the wettability of the bonding member. In the state where the film is thinly formed by plating, it is joined by the joining members 2, 4, 6; however, Ni is diffused into the joining members 2, 4, 6 in the state after joining shown in FIG. The membrane has disappeared.

  Next, a third embodiment of Example 1 of the semiconductor device of the present invention will be described with reference to FIG. The semiconductor device according to the third embodiment includes a semiconductor element 1, a support electrode body 3 that supports the semiconductor element 1 via a stress relaxation member 5, and a lead electrode 7 that is electrically connected to the semiconductor element. It has joining members 2, 4, 6 made of a Zn-based joining material to be connected, a Ni layer 9 provided at the interface thereof, and a sealing material 8 filling the inside of the support electrode body 3. The difference from the first embodiment described above is that, in the first embodiment, as shown in FIG. 1, the Ni film disappears after joining with the Zn-based joining members 2, 4, 6. On the other hand, in the case of the present embodiment, the Ni film remains between the respective layers even after bonding with the Zn-based bonding members 2, 4, 6. Since bonding is performed with the Zn-based bonding members 2, 4, 6 in a state where the Ni film is placed between the respective layers, the wettability at the time of manufacture is improved and good connection is obtained. In the case of this embodiment, since the Ni film is formed between the respective layers, the wettability at the time of manufacture is improved and a good connection is obtained. For example, the Ni layer 9 is bonded in contact with the surface of the semiconductor element 1, and the Zn-based bonding members 2 and 4 are bonded in contact with the surface of the Ni layer 9. Also in this case, it is necessary to prevent the NiZn alloy layer from being formed between the Ni layer 9 and the Zn-based joining members 2 and 4 for the reason described above. In the semiconductor device shown in FIG. 3, the Ni layer 9 is provided between the respective layers. However, the present invention is not limited to this, and a structure in which the Ni layer 9 is not provided between arbitrary layers may be employed.

  Next, a fourth embodiment of Example 1 of the semiconductor device of the present invention will be described with reference to FIG. The semiconductor device of the fourth embodiment includes a semiconductor element 1, a support electrode body 3 that supports the semiconductor element 1, a lead electrode 7 that is electrically connected to the semiconductor element, and a Zn-based bonding material that connects each of them. And the Ni layer 9 provided at the interface thereof, and the sealing material 8 filling the inside of the support electrode body 3. The third embodiment is almost the same as the third embodiment except that the stress relaxation member 5 is not provided. Accordingly, as a measure against thermal stress, the thickness of the bonding member 4 between the semiconductor element 1 and the support electrode body 3 is slightly increased. The Ni layer 9 provided on both surfaces of the bonding member 4 is preferably thinner than the other Ni layers. Note that, similarly to the third embodiment, a structure in which the Ni layer 9 is not appropriately provided between arbitrary layers may be employed.

  Next, a first method for manufacturing a semiconductor device according to the present embodiment will be described with reference to FIG. 5, taking the semiconductor device shown in FIG. 1 as an example.

  First, the Ni film 9 is formed on the front surface and the back surface of the semiconductor element 1 (step 601), and then one surface of the semiconductor element 1 and the lead electrode 7 are bonded to each other by a Zn-based bonding member 2 in a reducing atmosphere (step). 602). Here, the Ni film 9 may be formed by plating, but the film thickness may be 10 μm or less, preferably 5 μm or less so as not to form the NiZn alloy layer after bonding. As a result, as shown in FIG. 1, a Zn (Zn in which Ni component is diffused) layer can be formed immediately above the semiconductor element 1, and a NiZn alloy layer is not formed, so that a good connection can be obtained. In the case of manufacturing the semiconductor device of FIG. 3 with the Ni layer 9 left, it is not necessary to be restricted by the Ni film thickness, but the bonding environment and temperature should be adjusted so as not to form the NiZn alloy layer. That's fine.

  On the other hand, a Zn-based bonding member 6 is supplied to the support electrode body 3 having a Ni film formed on the surface (step 603), and the support electrode body 3 and the stress relaxation member 5 are bonded by the Zn-based bonding member 6 by reflow. (Step 604). Thereafter, a connection structure formed by bonding the semiconductor element 1 and the lead electrode 7 and a connection structure formed by bonding the support electrode body 3 and the stress relaxation member 5 are bonded by a Zn-based bonding member 4. Then, the inside of the support electrode body 3 to which the semiconductor element 1 is bonded is molded with a heat-resistant resin or silicone rubber or the like (step 606). In addition, as a supply method of a Zn-based bonding material, a plate shape, a foil shape, plating, a paste, or the like can be considered, and may be appropriately selected as necessary.

  In the case of this manufacturing method, there is a possibility that the Zn-based bonding members 2 and 6 that have already been bonded at the time of bonding by the Zn-based bonding member 4 may be remelted. A Zn-based bonding material having a composition having a higher melting point than that of the bonding member 4 may be used and a temperature hierarchy may be provided. Specifically, for example, Zn alone may be used for the Zn-based bonding members 2 and 6, and Zn 5 Al-based bonding material may be used for the Zn-based bonding member 4.

  Next, a second manufacturing method of the semiconductor device of the present invention will be described with reference to FIG. First, the Zn-based bonding member 6 is supplied to the support electrode body 3 having a Ni film formed on the surface (step 701), and the stress relaxation member 5 is bonded to the support electrode body 3 with the Zn-based bonding member 6 in a reducing atmosphere. (Step 702). Next, the Zn-based bonding member 4 is supplied onto the stress relaxation member 5 (step 703), and the semiconductor element 1 having the Ni film formed on both surfaces and the stress relaxation member 5 are joined with the Zn-based bonding member 4. Joining (step 704). Next, a Zn-based bonding member 2 is supplied onto the semiconductor element 1 (step 705), and the semiconductor element 1 and the lead electrode 7 having a Ni film formed on the surface are bonded by the Zn-based bonding member 2. (Step 706). Finally, the inside of the support electrode body 3 to which the semiconductor element 1 is bonded is molded to complete (step 707).

  In the case of this manufacturing method, since the Zn-based joining members 6, 4, 2 are sequentially joined, it is necessary to provide three temperature layers. For example, in the case of joining in the above order, Zn may be used, the bonding material 4 may be a Zn3Al-based bonding material, and the bonding member 6 may be a Zn5Al-based bonding material.

  Next, a third manufacturing method of the semiconductor device in this example will be described with reference to FIG.

  First, a Zn-based bonding member 6 is supplied to the support electrode body 3 whose surface is Ni-plated (step 801), and a stress relaxation member 5 is supplied on the Zn-based bonding member 6 (step 802). A Zn-based bonding member 4 is supplied on the stress relaxation member 5 (step 803). Further, the semiconductor element 1 having Ni films formed on both surfaces thereof is supplied on the Zn-based bonding member 4 (step 804), and the Zn-based bonding member 2 is supplied on the semiconductor element 1 (step 805). The lead electrode 7 is supplied onto the Zn-based bonding member 2 (step 806). Next, by reflow treatment, the electrode support 3 and the stress relaxation member 5 are bonded with a Zn-based bonding member 6, the stress relaxation member 5 and the semiconductor element 1 are bonded with a Zn-based bonding member 4, and the semiconductor element and the lead electrode 7. Are joined together with the Zn-based joining member 2 (step 807). Finally, the inside of the support electrode body 3 to which the semiconductor element 1 is bonded is molded to complete (step 808).

  In the case of this manufacturing method, since the Zn-based bonding members 2, 4, 6 are collectively bonded, all members having the same composition may be used, and no temperature hierarchy is provided unlike the first and second manufacturing methods. May be. Therefore, in the case of this manufacturing method, layers may be provided in an optimum combination from the viewpoints of the softness of each composition of the Zn-based bonding material, thermal resistivity, thermal conductivity, and the like.

  As described above, several methods for manufacturing a semiconductor device according to the present embodiment have been described. However, the present invention is not limited to the above-described embodiment, and the bonding order may be appropriately changed, and an optimal bonding material may be selected accordingly.

  In the above embodiment, an example of a Zener diode has been described as the semiconductor element 1, but a rectifier element or a thyristor element for high power may be used.

  Next, as Example 2, the case where the present invention is applied to an IGBT module assembled using an IGBT (Insulated Gate Bipolar Transistor) element will be described.

  FIG. 8 is a diagram showing a partial structure of an IGBT module assembled using an IGBT element. In the figure, 1001-1 and 2 are IGBT elements, 1002 is an insulating substrate, 1003-1 and 1003-2 are copper wiring patterns formed on the insulating substrate 1002, 1004 is a copper plate, 1005 is an aluminum wire, and 1006 is an internal The wiring, 1007 is a case, 1008 is a lid, and 1009 is a terminal. The IGBT element 1001-1 and the copper wiring patterns 1003-1 and 1003-2 are made of a Zn-based bonding material 1010, and the insulating substrate 1002 and the copper plate 1004. Are Zn-based bonding members 1011 connected to each other. As the Zn-based bonding member 1010 and the Zn-based bonding member 1011, the same as described in Example 1, Zn alone, Zn—Al alloy, or other metal component added to Zn—Al 3 Use an alloy of the original system or higher. Further, the inside of the case 1007 is filled with a sealing material 1012 such as silicon gel.

  Also in this embodiment, the Ni film has a thickness of 10 μm or less in advance on the surfaces where the IGBT elements 1001-1 and 1001-2 and the copper wiring patterns 1003-1 and 1003-2 are bonded by the respective Zn-based bonding members 1010. The thickness is preferably 5 μm or less, and the surface on which the Ni film is formed is joined by a Zn-based joining member 1010. Also in this embodiment, in the Zn-based bonding member layer at the interface between the Zn-based bonding member 1010 and the IGBT elements 1001-1 and 1001-2 and the wiring pattern, Ni diffuses in a state where the density gradually decreases from the interface. (Inclined diffusion) and the NiZn alloy layers are connected under such a condition that they are not substantially formed.

  In addition, a Ni film is formed to a thickness of 10 μm or less, preferably 5 μm or less, on the surfaces where the insulating substrate 1002 and the copper plate 1004 are joined by the respective Zn-based joining members 1011. The formed surface is joined by a Zn-based joining member 1011. In this case, similarly to the above, Ni is inclined and diffused in the Zn-based bonding material layer at the interface between the Zn-based bonding member 1010 and the insulating substrate 1002 and the copper plate 1004, and the NiZn alloy layer is They are connected under such conditions that they are not substantially formed. Thereby, the IGBT module excellent in heat resistance, heat stress resistance, and heat dissipation can be provided.

  Here, when the connection of the insulating substrate 1002 on the copper plate 1004 and the connection of the wiring patterns 1003-1 and 1003-2 and the IGBT elements 1001-1 and 1001-2 on the insulating substrate 1002 are performed separately, Zn The bonding member 1010 based on the system and the bonding member 1011 based on the Zn may have different melting points by changing the composition ratio. For example, as a combination of the Zn-based bonding members 1010 and 1011, Zn alone may be used for 1010, Zn3Al or Zn5Al may be used for 1011, and when Zn3Al is used for 1010, Zu5Al may be used for 1011. Good.

  On the other hand, when the connection of the insulating substrate 1002 on the copper plate 1004 and the connection of the wiring patterns 1003-1 and 1003-2 and the IGBT elements 1001-1 and 1001-2 on the insulating substrate 1002 are performed simultaneously, The bonding member 1011 and the Zn-based bonding member 1011 may have the same composition.

  Next, as Example 3, a semiconductor device will be described with reference to FIG. The semiconductor device according to the third embodiment includes a semiconductor element 1 having a circuit formed on the surface, a Cu-based lead frame 10 that supports the semiconductor element 1, an external lead 11 portion of the Cu-based lead frame 10, and the semiconductor element 1. Are electrically connected to each other, and at least a sealing material 8 for sealing the semiconductor element 1. In this embodiment, the Zn-based bonding member 2 is bonded to the back surface of the semiconductor element 1 and the Cu-based lead frame 10 with a Ni film having a thickness of 10 μm or less, preferably 5 μm or less formed thereon. . In the same manner as in the first and second embodiments described above, an inclined Ni diffusion layer is formed on the back surface of the semiconductor element 1 of the Zn-based bonding member layer and the interface with the Cu-based lead frame 10. The NiZn alloy layer is not substantially formed. That is, as described above, the NiZn compound layer is not formed, but in the bonding step, a Ni film is provided on the back surface of the semiconductor element 1 and then bonded to the Zn-based bonding member 2. The joining member 2 is in a state where the Ni component or NiZn compound is diffused. Thereby, the semiconductor device excellent in heat resistance, heat stress resistance, and heat dissipation can be provided. As the sealing material 8, a heat-resistant resin or silicone rubber may be used.

  As mentioned above, although the invention made | formed by this inventor was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, various changes are possible.

  Further, the contents of the semiconductor device and the manufacturing method thereof described separately for each of the above embodiments are not limited to only the respective embodiments, but may be applied as appropriate to other embodiments.

It is sectional drawing of the semiconductor device in 1st Embodiment of Example 1 of this invention. It is sectional drawing of the semiconductor device in 2nd Embodiment of Example 1 of this invention. It is sectional drawing of the semiconductor device in 3rd Embodiment of Example 1 of this invention. It is sectional drawing of the semiconductor device in 4th Embodiment of Example 1 of this invention. It is a flowchart about the 1st manufacturing method of the semiconductor device in Example 1 of this invention. It is a flowchart about the 2nd manufacturing method of the semiconductor device in Example 1 of this invention. It is a flowchart about the 3rd manufacturing method of the semiconductor device in Example 1 of this invention. It is sectional drawing of the IGBT module in Example 2 of this invention. It is sectional drawing of the semiconductor device in Example 3 of this invention. It is a phase diagram of a ZnAl-type alloy.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor element 2,4,6,1001-1,1001-2 ... Zn-type joining member 3 ... Support electrode body 5 ... Stress relaxation material 7 ... Lead electrode 8 ··· Sealing material 9 ··· Ni layer 10 ··· Cu-based lead frame 11 ··· External lead 12 · · · Wire 1001-1, 1001-2 · · · IGBT elements 1003-1 and 1003-2 · · ..Copper wiring pattern 1002-1, 1002-2 ... Insulating substrate 1004 ... Copper plate

Claims (14)

  A semiconductor device having a configuration in which a semiconductor element and a copper member are joined, wherein the semiconductor element and the copper member are first joining members having a melting point of 250 ° C. or more and mainly containing zinc (Zn). A semiconductor device characterized in that nickel (Ni) is inclined and diffused in a region close to the interface with the semiconductor element.   The semiconductor device according to claim 1, wherein the copper member is bonded to the support member by a second bonding member mainly composed of zinc (Zn).   2. The semiconductor device according to claim 1, wherein the copper member is a member constituting a buffer material for buffering a difference in coefficient of thermal expansion between the semiconductor element and the support member.   2. The semiconductor device according to claim 1, wherein the first bonding member and the second bonding member containing zinc as a main component contain 8% by weight or less of aluminum (Al).   The semiconductor device according to claim 1, wherein the first bonding member mainly containing zinc and the second bonding member have different melting points.   A semiconductor device having a configuration in which a semiconductor element is metal-bonded to a member, wherein the semiconductor element and the member include zinc (Zn) as a main component and aluminum (Al) in an amount of 8% by weight or less. The semiconductor device is bonded by a member, and the first bonding member has a nickel (Ni) diffusion layer in a region close to the interface with the semiconductor element.   8. The nickel (Ni) diffusion layer is formed by diffusing a nickel (Ni) film formed on a surface of the semiconductor element into the first bonding member. The semiconductor device described.   The member is further metal-connected to a support member by a second bonding member containing zinc (Zn) as a main component and containing aluminum (Al) in an amount of 8% by weight or less, and the first bonding member and the second bonding member The semiconductor device according to claim 7, wherein the melting point is different from that of the bonding member.   The semiconductor device according to claim 1, wherein the semiconductor element is either a rectifying element or an IGBT element.   A semiconductor device having a configuration in which one surface of a semiconductor element is bonded to a first member by a first bonding member and a second member is bonded to the other surface by a second bonding member. The joining member and the second joining member are metals containing aluminum (Al) mainly composed of zinc or zinc (Zn), and each of the first joining member and the second joining member A semiconductor device, wherein a nickel (Ni) diffusion layer is formed in the vicinity of an interface with a semiconductor element.   Each of the nickel (Ni) diffusion layers of the first bonding member and the second bonding member is inclined and diffused such that the nickel (Ni) density is higher as it is closer to the interface with the semiconductor element. The semiconductor device according to claim 10, wherein:   A copper (Cu) member is bonded to one surface of a semiconductor element having nickel (Ni) films formed on both surfaces by a first bonding member, and a lead electrode is bonded to the other surface by a second bonding member. In the semiconductor device, the first bonding member and the second bonding member are metals mainly composed of zinc (Zn) having different aluminum (Al) content, and the second bonding member A semiconductor device having a melting point higher than that of the first bonding member.   A region in which nickel of a nickel film formed on a surface of the semiconductor element diffuses is provided in the vicinity of the interface between the first bonding member and the second bonding member with the semiconductor element. Item 13. A semiconductor device according to Item 12. The semiconductor device according to claim 10, wherein the semiconductor element is a rectifying element.

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