JP2010109278A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device for achieving the suppression of thermal resistance and the suppression of large size in the case of integrally bonding a structure including a semiconductor element to its support, and for suitably achieving the suppression of stress immanent in the structure and the support after the completion of junction. <P>SOLUTION: In such configurations that a reactive film 21 set to characteristics for securing a reaction temperature and a thermal conductivity with which melting brazing materials 20 is possible in an opposite relation between the reaction temperature and the thermal conductivity is interposed by the brazing materials 20, the brazing materials 20, the reaction film 21, the brazing materials 20 and the structure are sequentially laminated on a cooling unit 13. In this status, reaction conditions inducing the reaction are applied to the reactive film 21 to melt the brazing materials 20, and the structure including a semiconductor 10 is joined to the cooling unit 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a semiconductor device in which a structure including a semiconductor element used for power conversion, various power control, and the like is integrally joined to a support that supports the semiconductor element. The present invention relates to an improvement in a method for joining a structure including a substrate to a support.

  As such a semiconductor device, for example, an inverter device that is used in a hybrid vehicle, an electric vehicle, or the like and converts DC power supplied from a vehicle-mounted battery into three-phase AC or the like and performs power conversion for driving a motor is known. In such a semiconductor device, the structure including the semiconductor element (power semiconductor element) is usually integrally joined to the cooler as described above. That is, the semiconductor element is bonded and fixed to the cooler having a heat exchanging function by screwing the structure, which is mounted on the insulating substrate or the heat radiating plate, with silicon grease or the like. Heat generation during device operation is mitigated. However, when adopting such a joint structure with a cooler, the thermal conductivity of the silicon grease itself is low, so deterioration of thermal resistance is unavoidable, and in order to fasten the screws, In addition to an increase in the number of parts, it is necessary to separately provide a fastening structure for the structure and the cooler itself, which disadvantageously increases the size of the semiconductor device itself.

Therefore, conventionally, as a manufacturing method of such a semiconductor device, that is, a method of joining the structure to the cooler, a method of joining the structure to the cooler by brazing is often employed. According to such brazing, an increase in the number of parts and an increase in size as a semiconductor device are suppressed, and the brazing material itself has a low thermal resistance, so that the cooling efficiency as the semiconductor device is naturally increased. .
JP 2007-88468 A

  As described above, by adopting brazing as a method of joining the structure to the cooler, the completed semiconductor device is surely a desirable effect such as suppressing the increase in size and improving the cooling efficiency. Can be obtained. However, when such brazing is adopted, the following inconveniences in the manufacturing process, that is, the process of joining the structure to the cooler cannot be ignored.

  That is, the material used for the insulating substrate and the heat radiating plate constituting the structure and the material used for the cooler generally have different linear expansion coefficients, and the brazing itself has a high temperature due to the melting of the brazing material. In this joining method, heat application must be performed for a relatively long time. Therefore, in the natural cooling period after brazing, that is, the period until the brazing material is first cooled and the upper and lower members are fixed when each expanded member returns to the original shape by cooling, the above linear expansion coefficient There is a concern that the stress due to the difference is inherent, the cooler is warped, and the insulating substrate is cracked. Such warpage and cracks are not limited to the time when the structure is bonded to the cooler, that is, at the time of manufacturing. This tendency can also be caused by a heat cycle based on repeated operation of the semiconductor element, and this tendency becomes more remarkable as the amount of heat generated by the semiconductor element itself increases. Further, if the melting temperature of the brazing material is higher than the melting temperature of the solder and the time required for applying the heat is prolonged, the soldered portion of the structure is remelted. It can also be a thing.

  Conventionally, as seen in, for example, Patent Document 1, a high-resistance metal conductor is laid on the surface of the bonding surface (substrate), and bonding is performed using Joule heat generated by passing a current through the metal wiring. A method of bonding an object (polymer material) to a bonding surface (substrate) instantaneously (instantaneously) is also known. However, even with this method, since Joule heat is used, it takes a certain amount of time to complete the bonding, even though instantaneously (instantaneously), and it is uniform over the entire bonding area. It is also difficult to generate heat. That is, even if it is suitable for local heat generation, its application is difficult when the semiconductor element structure is bonded to the above-described cooler.

  Further, not only the cooler, but also a semiconductor device configured by integrally bonding a structure including the semiconductor element (power semiconductor element) to some support that supports the semiconductor element, and further a bonding material Even if, for example, solder or the like is used in addition to the brazing material, the above-described problems relating to the joining method are generally common.

  The present invention has been made in view of such circumstances, and the purpose thereof is to complete the bonding in addition to the suppression of thermal resistance and the increase in size when the structure including the semiconductor element is integrally bonded to the support. It is another object of the present invention to provide a method for manufacturing a semiconductor device capable of suitably suppressing the stress inherent in the structure and the support later.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
According to the first aspect of the present invention, a structure including a semiconductor element of a semiconductor device configured by integrally bonding a structure including a semiconductor element to a support that supports the structure is provided via a bonding material having a low thermal resistance. In the method of manufacturing a semiconductor device to be bonded to the support, it is possible to achieve both the reaction temperature and the thermal conductivity ensuring that the bonding material can be melted in a conflicting relationship between the reaction temperature and the thermal conductivity. The bonding material, the reactive film, the bonding material, and the structure are sequentially laminated on the support in such a manner that the reactive film set in the characteristic is sandwiched by the bonding material, and in this state, the reactive film is placed on the reactive film. The gist is to melt the bonding material by applying reaction conditions that induce a reaction, and bond the structure to the support.

  According to such a manufacturing method, based on the self-propagating reaction by the reactive film sandwiched between the bonding materials, the bonding materials are instantaneously and uniformly melted so that the structure is welded to the support. Become. At this time, as described above, the reactive film itself can satisfy both of the reaction temperature and the thermal conductivity ensuring the melting of the bonding material in the conflicting relationship between the reaction temperature and the thermal conductivity. The properties, that is, the properties that can maintain the high thermal conductivity corresponding to the reaction temperature, which is necessary and sufficient to melt the bonding material, are set so that the bonding material instantly reacts with the reactive film. After melting and solidifying, the thermal resistance as a bonding material does not increase. In the above manufacturing method, since the joining can be completed before excessive stress is inherent in the structure and the support, the stress inherent in the structure and the support is accurately suppressed after joining. Will be able to. Further, regarding the joining structure, the thermal resistance as a joining material can be kept low, and since the joining structure by so-called welding is maintained, the semiconductor device is not increased in size. In addition, as reaction conditions provided to the said reactive film, there exists application of a spark etc., for example.

  According to a second aspect of the present invention, in the method for manufacturing a semiconductor device according to the first aspect, as the reactive film, a first metal thin film made of a metal thin film having a low reaction temperature and a high thermal conductivity and a reaction temperature. The second metal thin film made of a metal thin film having a high thermal conductivity and a low thermal conductivity is used, and a plurality of layers are alternately laminated. The gist of the present invention is to set the characteristics that can achieve both the reaction temperature enabling the melting of the bonding material and the securing of thermal conductivity through film thickness adjustment with the film thickness of the metal thin film.

  According to such a manufacturing method, the reaction temperature and the thermal conductivity as a reactive film conflict with each other, and among them, the reaction temperature and the thermal conductivity that enable melting of the bonding material are ensured. It is also easy to set compatible characteristics.

  According to a third aspect of the present invention, in the method of manufacturing a semiconductor device according to the second aspect, an aluminum thin film is used as the first metal thin film constituting the reactive film, and a nickel thin film is used as the second metal thin film. The gist is to use.

  According to this manufacturing method, as the first and second metal thin films constituting the reactive film having the above characteristics, an aluminum thin film and a nickel thin film are effective, respectively. Realization and practical use as a conductive film are also easy.

  According to a fourth aspect of the present invention, in the method for manufacturing a semiconductor device according to the third aspect, an aluminum brazing material is used as the bonding material, and the reaction temperature of the reactive film is 600 ° C. The gist is that the film thickness of each of the thin film and the nickel thin film is adjusted.

  It is known that the aluminum brazing material as a bonding material has a minimum temperature of about 600 ° C. for melting. Therefore, if the reaction temperature as the reactive film is set to 600 ° C. by adjusting the film thicknesses of the aluminum thin film and the nickel thin film as in the manufacturing method, the structure is heated excessively. It is possible to promote the smooth melting of only the bonding material without any problem, and the thermal conductivity as the reactive film as a multilayer film of aluminum thin film and nickel thin film can be selected from the combination. Value.

  According to a fifth aspect of the present invention, in the method for manufacturing a semiconductor device according to any one of the first to fourth aspects, the bonding material is applied in advance to each bonding surface of the structure and the support. In addition, the gist is that the reactive film is formed in advance on the surface of any one of the structure and the support to which the bonding material is applied.

According to such a manufacturing method, handling of the structure and the support including the bonding material and the reactive film at the time of bonding can be made extremely easy.
According to a sixth aspect of the present invention, in the method for manufacturing a semiconductor device according to any one of the first to fifth aspects, the semiconductor element is formed on an insulating substrate having an aluminum plate bonded to both sides as the structure. The gist is to use what is mounted by soldering.

  This manufacturing method is particularly effective when applied to a semiconductor element structure in which a semiconductor element is mounted by soldering on an insulating substrate having aluminum plates bonded to both sides, as in the invention according to claim 6. By applying the manufacturing method, the stress inherent in the insulating substrate or the like after joining with the support can be accurately suppressed.

  A seventh aspect of the present invention is the method of manufacturing a semiconductor device according to any one of the first to fifth aspects, wherein the semiconductor element is formed on a heat radiating plate made of metal or an aluminum plate on both sides as the structure. The gist is to use a bonded insulating substrate including one mounted by soldering.

  This manufacturing method is applied to a semiconductor element structure in which a semiconductor element or an insulating substrate bonded with an aluminum plate on both sides is mounted on a heat sink made of metal by soldering, as in the invention according to claim 7. This is also effective, and the application of the manufacturing method makes it possible to accurately suppress the stress inherent in the heat radiating plate, the insulating substrate and the like after joining with the support.

  According to an eighth aspect of the present invention, in the method for manufacturing a semiconductor device according to any one of the first to seventh aspects, a liquid-cooled or air-cooled cooler is used as a support that supports the structure. This is the gist.

  This manufacturing method is also particularly effective when applied to a support using a liquid-cooled or air-cooled cooler as the support, as in the invention according to claim 8. By applying the manufacturing method, The stress inherent in the cooler after joining with the structure can be accurately suppressed.

(First embodiment)
A semiconductor device manufacturing method according to a first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic cross-sectional structure of a semiconductor device manufacturing method according to this embodiment immediately before a bonding process of a semiconductor device to be applied.

  As shown in FIG. 1, the semiconductor device includes a structure including a semiconductor element 10 and an insulating substrate 12 on which the semiconductor element 10 is mounted, and a cooler 13 that supports the structure as a support of the structure. Consists of.

  Here, the semiconductor element 10 is a power semiconductor element that generates relatively high-temperature heat during operation of, for example, an IGBT (insulated gate bipolar transistor), and the insulating substrate 12 has a DBA (direct brazing diode). Aluminum plates 11a and 11b are bonded and fixed to both surfaces of the ceramic substrate 11 by brazing. The aluminum plate 11a is surface-treated so that the wettability of the solder 14 is obtained, and the semiconductor element 10 is mounted on the upper surface by soldering. On the other hand, the cooler 13 is for cooling the heat generated by the operation of the semiconductor element 10 by heat exchange. In the present embodiment, for example, a water-cooled cooler made of aluminum is used. Is used.

  Further, as shown in FIG. 1, a brazing material that is made of an aluminum-based material as a bonding material for bonding the semiconductor element 10 and the insulating substrate 12 and the cooler 13 together. 20 is interposed. Thus, according to the method of joining the cooler 13 and the structure using the brazing material 20, since the thermal resistance of the brazing material 20 itself is low, the transfer of heat transmitted from the semiconductor element 10 to the cooler 13. Efficiency, that is, cooling efficiency of the semiconductor device can be increased. On the other hand, as described above, in the joining method using the brazing material, it is necessary to apply heat for a relatively long period in order to melt the brazing material, and the cooler 13 and the insulating substrate 12 have different linear expansion coefficients. Due to this, there is a possibility that stress is inherent and warpage and cracks occur in the cooler 13 and the insulating substrate 12.

  Therefore, in the present embodiment, prior to the joining step by brazing, the reactive film 21 capable of melting the brazing material 20 instantaneously and uniformly is laminated in such a manner as to be sandwiched by the brazing material 20. Then, by using the reaction heat (generation enthalpy) generated during the reaction of the reactive film 21 as melting heat for melting the brazing material 20, heat that causes warping and cracks in the cooler 13 and the insulating substrate 12. Before the stress is inherent, the bonding between the cooler 13 and the insulating substrate 12 is completed. FIG. 2 shows an enlarged cross-sectional structure of the reactive film 21 employed in the present embodiment.

In general, it is a necessary condition for such a reactive film to continuously induce a chemical reaction between adjacent atoms by using a reaction heat generated by a chemical reaction between different metal atoms as a trigger. And in order for the reaction heat by a chemical reaction to exceed the cooling by heat dissipation, what is necessary is just to increase calorific value compared with a heat dissipation area. The simplest method is to stack different metals thinly and in multiple layers. In this embodiment, as shown in FIG. 2, as the reactive film 21, an aluminum (Al) thin film 21a and nickel (Ni) are used. The film structure is formed by alternately laminating a plurality of thin films 21b. Here, the aluminum thin film 21a and the nickel thin film 21b forming the reactive film 21 have characteristics in which the reaction temperature and the thermal conductivity are opposite to each other. That is, the aluminum thin film 21a has a characteristic of low reaction temperature and high thermal conductivity, and conversely, the nickel thin film 21b has a characteristic of high reaction temperature and low thermal conductivity. Therefore, in the present embodiment, by adjusting the film thickness based on these characteristics of the aluminum thin film 21a and the nickel thin film 21b, the reaction temperature of the reactive film 21 can be used to melt the aluminum-based brazing material 20. The temperature is set to a minimum required temperature (“600 ° C.”), and the thermal conductivity after reaction (after solidification) of the reactive film 21 is set to a maximum value. That is, the film thickness β of the nickel thin film 21b mainly having a function of ensuring the reaction temperature of the reactive film 21 is set to a necessary minimum thickness capable of ensuring the above reaction temperature “600 ° C.”. The film thickness α of the aluminum thin film 21a mainly having the function of ensuring the thermal conductivity of the film 21 is maximized among the same number of layers and the same combination (α> β). As a result, it is possible to ensure both the minimum reaction temperature (“600 ° C.”) necessary for melting the brazing material 20 and the thermal conductivity as the bonding material.

In addition, in such a reactive film, it is usually possible to laminate thin films as many as possible in order to improve the self-heating propagation property, and to shorten the reaction time and enable uniform bonding even in a large area. . In the reactive film 21 used here, the brazing material 20 is formed by laminating a layer of aluminum thin film 21a or nickel thin film 21b of 10 nm to 500 nm in a total of 5 μm to 200 μm. The ratio of the film thickness of the aluminum thin film 21a to the film thickness of the nickel thin film 21b can be determined by the ratio of the film thickness α of the aluminum thin film 21a: the film thickness β of the nickel thin film 21b = 3: 2.
When the ratio of the number of atoms becomes “1: 1”, the heat of reaction becomes the highest. In the present embodiment, in view of such a relationship between the aluminum thin film 21a and the nickel thin film 21b, each of the above-described film thicknesses α, including the number n of layers, such that the reaction temperature becomes “600 ° C.” β is determined.

  Next, the transition of the reaction temperature of the reactive film 21 required for melting the brazing material 20 and the transition of the temperature of the heat source by the conventional high frequency induction heating method will be compared with reference to FIG. These temperature transition examples were obtained through experiments and the like.

  First, in FIG. 3, a curve L0 indicated by a two-dot chain line shows a transition of the temperature of the heat source by the conventional high frequency induction heating method. Curves L1 to L4 by solid lines indicate the ratio Pn1 of the nickel thin film 21b when the number of stacked reactive films 21 is n and the total amount of the aluminum thin films 21a and the nickel thin films 21b constituting the reactive film 21 is Q. The transition of the reaction temperature of the reactive film 21 correlated with ~ Pn4 is shown respectively. At this time, the ratios Pn1 to Pn4 of the nickel thin film 21b are as shown in the following relational expression (A).

Pn1>Pn2>Pn3> Pn4 (B)
That is, as shown by curves L1 to L4 in FIG. 3, as the proportion of the nickel thin film 21b constituting the reactive film 21 increases, the reaction temperature of the reactive film 21 increases and the reaction time decreases. As the proportion of the nickel thin film 21b constituting the reactive film 21 decreases, the reaction temperature of the reactive film 21 decreases and the reaction time increases. The inventor has confirmed that the time during which reaction heat is generated by the self-propagating reaction of the reactive film 21 is actually several microseconds to several tens of microseconds.

On the other hand, in the conventional high frequency induction heating method, as shown as a curve L0 in FIG. 3, and as is well known, the time for generating heat from the heat source by this method is several seconds. For this reason, when the same method is adopted to melt the brazing material 20, excessive heat is applied not only to the brazing material 20 but also to the insulating substrate 12 and the cooler 13 to be joined, After the brazing material 20 is solidified, excessive stress due to the difference in the coefficient of linear expansion is inherent in the objects to be joined.

  Therefore, as described above, in this embodiment, by using the reactive film 21 that enables the generation of instantaneous reaction heat in this way for melting the brazing material 20, excessive stress is inherent in the joining target. The joining of the joining object is completed previously.

  The melting temperature of the aluminum brazing material 20 used in the present embodiment is also “600 ° C.” as described above. For this reason, the ratio of the nickel thin film 21b forming the reactive film 21 is represented by a curve L2 in FIG. 3 so that the reaction temperature of the reactive film 21 is “600 ° C.”. The ratio Pn2, which is the ratio to be taken, is set. Accordingly, it is possible to suppress the generation of excessive reaction heat exceeding the melting temperature of the brazing material 20 and promote smooth and instantaneous melting of only the brazing material 20.

  Next, the relationship between the reaction temperature of the reactive film 21 and the thermal conductivity and the method of setting the ratio (film thickness) of the aluminum thin film 21a and the nickel thin film 21b constituting the reactive film 21 are illustrated. 4 and FIG. 4 and 5, the number of stacked reactive films 21 is n, and the total amount of the aluminum thin film 21a and the nickel thin film 21b constituting the reactive film 21 is the same as in FIG. It was obtained through experiments and the like based on the ratio adjustment of the aluminum thin film 21a and the nickel thin film 21b when Q is assumed.

  First, as shown in FIG. 4, the reaction temperature of the reactive film 21 increases as the ratio of the nickel thin film 21b to the reactive film 21 increases, that is, as the amount of nickel (Ni) mainly securing the reaction temperature increases. It becomes higher in proportion to this.

  On the other hand, as shown in FIG. 5, the thermal conductivity of the reactive film 21 is increased as the ratio of the nickel thin film 21b to the reactive film 21 increases, that is, the amount of aluminum (Al) that mainly ensures the thermal conductivity. As the amount of nickel (Ni) having a low thermal conductivity decreases and decreases, the amount decreases in inverse proportion to this.

  As described above, the reactive film 21 composed of the aluminum thin film 21a and the nickel thin film 21b is in a relationship in which the reaction temperature and the thermal conductivity are in conflict, and therefore, the reactive film 21 is actively used by using such a relationship. It is possible to have the characteristics that the reaction temperature and the thermal conductivity are compatible with each other. Therefore, in the present embodiment, the target reaction temperature of the reactive film 21 is set to “600 ° C.” that is the lowest temperature for melting the brazing material 20 based on the relationship shown in FIG. 4 and FIG. The ratio Pn2 of the nickel thin film 21b to the reactive film 21 and the ratio Pa2 of the aluminum thin film 21a (= (Q−Q · Pn2) / Q) are calculated. And these each film thickness (alpha) and (beta) are adjusted in the aspect with which the film thickness (alpha) of the aluminum thin film 21a, and the film thickness (beta) of the nickel thin film 21b satisfy | fill the following relational expression (b).

Pa2: Pn2 = α: β (= n · α: n · β) (B)
Pa2: Ratio of the aluminum thin film 21a to the reactive film 21
Pn2: Ratio of the nickel thin film 21b to the reactive film 21
α: film thickness of the aluminum thin film 21a
β: film thickness of the nickel thin film 21b
n: Number of stacked layers In other words, by forming the reactive film 21 in a manner that satisfies such a relational expression (b), it is possible to secure the minimum reaction temperature “600 ° C.” necessary for melting the brazing material 20 and In securing the reaction temperature “600 ° C.”, it is possible to achieve both the securing of the maximum thermal conductivity λx.

  Next, an example of the manufacturing process of the semiconductor device manufacturing method according to the present embodiment in which the insulating substrate 12 and the cooler 13 are bonded using the reactive film 21 will be described with reference to FIGS. However, it will be explained.

6A, first, on an insulating substrate (DBA) 12 in which aluminum (Al) plates 11a and 11b are bonded to both surfaces of a ceramic substrate 11 such as aluminum nitride (AlN), for example. For example, the semiconductor element 10 made of IGBT is mounted by soldering. As a result, a structure including the semiconductor element 10 and the insulating substrate 12 using the solder 14 as a bonding medium is formed. The material of the ceramic substrate 11 may be any material as long as it can ensure insulation. In addition to the above aluminum nitride (AlN), nitrogen silicon (Si ₃ N ₄₎ , aluminum oxide (Al ₂ O ₃ ), etc. The aluminum nitride (AlN) is preferable from the viewpoints of thermal conductivity, thermal expansion coefficient, and the like.

  When the formation of the structure including the semiconductor element 10 and the insulating substrate 12 is completed in this way, as shown in FIG. 6B, for example, aluminum is formed on the lower surface of the lower aluminum plate 11b constituting the insulating substrate 12. A brazing material 20 made of a system is applied. Then, as shown in FIG. 6C, the surface (lower surface) of the brazing material 20 is subjected to a film forming process using a multilayer film sputtering method or the like, and the aluminum as illustrated in FIG. A reactive film 21 in which thin films 21a and nickel thin films 21b are alternately stacked is formed. Here, depending on the ratio (film thickness) between the aluminum thin film 21a and the nickel thin film 21b, the characteristic as the reactive film 21 is the minimum reaction temperature “600 ° C.” necessary for melting the brazing material 20. As described above, it is set to a characteristic capable of satisfying both the securing of heat conductivity and the securing of thermal conductivity after solidifying the brazing material. Subsequently, as shown in FIG. 6D, in a mode facing the brazing material 20 covered with the reactive film 21 on the structure side on the cooler 13 that cools the semiconductor element 10 during operation. The other brazing material 20 is applied.

  When the application and deposition of the brazing material 20 and the reactive film 21 are completed in this manner, the brazing material 20 formed on the cooler 13 and the insulating substrate 12 are then formed as shown in FIG. A structure composed of the semiconductor element 10 and the insulating substrate 12 is laminated on the cooler 13 in such a manner that the brazing material 20 and the reactive film 21 formed on the lower aluminum plate 11b are opposed to and in contact with each other. That is, as a result, the brazing material 20 is laminated between the cooler 13 and the structure composed of the semiconductor element 10 and the insulating substrate 12 so as to sandwich the reactive film 21. In this state, reaction conditions are applied to the reactive film 21 in order to join the structure to the cooler 13. Examples of the application of the reaction conditions include application of a spark and energization of an overcurrent. When the reaction conditions are given to the reactive film 21 in this way, as shown in FIG. 3, the reaction heat of about “600 ° C.” accompanying the self-propagation reaction of the reactive film 21 is several μs to several tens μs. Occurs for a degree. As a result, the heat of about “600 ° C.”, which is the melting temperature, is applied to the brazing material 20 that is laminated in such a manner as to sandwich the reactive film 21, and the brazing material 20 is instantaneously melted. Thus, the time for which the reaction heat is applied to the brazing material 20 in response to the reaction of the reactive film 21 is an extremely short time of about several μ to several tens of μ. For this reason, before the excessive stress is inherent in the structure composed of the cooler 13, the semiconductor element 10, and the insulating substrate 12 to be bonded, the bonding is performed.

  When the reaction of the reactive film 21 is completed in this manner, as shown in FIG. 7B, the semiconductor element 10 and the insulating substrate are brought into the cooler 13 by the bonding layer 23 in which the brazing material 20 and the reactive film 21 are melted and mixed. The structure consisting of 12 is joined, and the manufacture is completed as a semiconductor device in which these are integrated.

As described above, according to the manufacturing method of the semiconductor device according to the present embodiment, the following effects can be obtained.
(1) The brazing material 20 is instantaneously and uniformly melted by reaction heat based on the self-propagating reaction of the reactive film 21 sandwiched by the brazing material 20, so that the cooler 13 includes the semiconductor element 10 and the insulating substrate 12. The structure was welded. Accordingly, the bonding can be completed before excessive stress is inherent in the structure composed of the cooler 13, the semiconductor element 10, and the insulating substrate 12, and the stress inherent in the structure and the cooler 13 after the bonding. Can be accurately suppressed.

  (2) The reactive film 21 is formed by alternately laminating aluminum thin films 21a and nickel thin films 21b, and the ratio of the aluminum thin films 21a and the nickel thin films 21b is set to a temperature necessary and sufficient for melting the brazing material 20 (" 600 ° C. ”). As a result, when the cooler 13 and the structure including the semiconductor element 10 and the insulating substrate 12 are bonded, it is possible to promote melting of only the brazing material 20 without applying excessive heat to these bonding targets. become.

  (3) Since the ratio of the aluminum thin film 21a and the nickel thin film 21b is set so that the reaction temperature of the reactive film 21 becomes a temperature necessary and sufficient for melting the brazing material 20 (“600 ° C.”), the reactivity It also becomes possible to make the thermal conductivity that is in a relation with the reaction temperature as the film 21 opposite to the maximum value. For this reason, the thermal resistance as a bonding material can be kept low.

  (4) Since these bondings can be completed at a stage where the influence of thermal stress on the structure composed of the cooler 13, the semiconductor element 10, and the insulating substrate 12 is extremely small, the linear expansion coefficients of the bonding objects are different. Anyway, the effect can be almost ignored. In other words, this makes it possible to expand the degree of freedom in selecting the materials to be joined.

(5) Further, as described above, the heat application time is extremely short when the cooler 13 is bonded to the structure including the semiconductor element 10 and the insulating substrate 12, and the structure is particularly heated excessively. By suppressing this, it is possible to complete the formation of the structure, that is, the mounting of the semiconductor element 10 on the insulating substrate 12 by soldering in the previous step of joining the structure to the cooler 13. . As a result, the soldering itself can be facilitated, and the semiconductor device can be produced by a more ideal procedure. That is, the soldering process of the semiconductor element 10 can be performed in a pre-process of bonding between the cooler 13 and the structure including the semiconductor element 10 and the insulating substrate 12, so that the semiconductor element 10 can be formed in advance prior to the bonding. It becomes possible to inspect electric characteristics and the like, and if there is a defect or the like, that fact can be detected before joining with the cooler 13.
(Second Embodiment)
The second embodiment of the present invention will be described below with reference to FIG. In the second embodiment, a structure that further includes a heat dissipation plate 30 for treating the heat generation of the semiconductor element 10 is an object to be bonded (manufactured), and the basic manufacturing method is as described above. This is common with the first embodiment.

  FIG. 8 shows a schematic cross-sectional structure immediately before the bonding step of the semiconductor device to be manufactured in the second embodiment as a diagram corresponding to FIG. In FIG. 8, elements that are the same as those shown in FIG. 1 are given the same reference numerals, and redundant descriptions of these elements are omitted.

That is, as shown in FIG. 8, in this embodiment, a heat radiating plate 30 is further bonded and fixed to the insulating substrate (DBA) 12 on which the semiconductor element 10 is mounted by soldering, and the heat radiating plate 30 is provided. This structure is an object to be joined to the cooler 13. The heat sink 30 is made of molybdenum (Mo), copper-molybdenum (Cu-Mo) alloy, aluminum-silicon carbide (Al-SiC) alloy, copper (Cu), aluminum (Al), or the like. Among these, molybdenum (Mo) having high thermal conductivity and a thermal expansion coefficient close to that of a power semiconductor element is particularly preferable. Further, here, as shown in FIG. 8, wiring by wire bonding is applied to the emitter terminal and the gate terminal provided on the surface of the semiconductor element 10 made of, for example, the above-described IGBT or the like, and these wires 31a. And the electrical characteristics of the semiconductor element 10 wired via 31b are inspected beforehand. Only the structure on which the semiconductor element 10 exhibiting normal electrical characteristics is mounted is to be joined to the cooler 13.

  Even in such a semiconductor device, the structure can be joined to the cooler 13 in accordance with the first embodiment. That is, after the process shown in FIG. 6A is performed, the heat sink 30 is soldered to form a structure, and after the wiring described above, the inspection of the electrical characteristics of the semiconductor element 10 is completed. The manufacturing (joining) can be completed by the procedure according to FIGS. 6 (a) to 6 (d) and FIGS. 7 (a) and 7 (b).

  As described above, the semiconductor device manufacturing method according to the second embodiment can obtain the effects according to the effects (1) to (5) according to the first embodiment, and further. The following effects can be obtained.

(6) After the structure is formed and before it is joined to the cooler 13, wiring by wire bonding is performed to inspect the electrical characteristics of the semiconductor element 10. As a result, it is possible to select the quality of the semiconductor element 10 before joining the cooler 13 and the structure, and the yield and productivity of the semiconductor device can be improved.
(Other embodiments)
In addition, each said embodiment can also be implemented with the following aspects.

  In the first embodiment, for convenience of explanation, the reference to the inspection of the electrical characteristics of the semiconductor element 10 is omitted. However, in the first embodiment, as in the second embodiment, the inspection is performed in advance. The wiring and electrical characteristics may be inspected.

  As the above structure, in addition to the previous examples, as shown in FIG. 9 as a diagram corresponding to FIG. 1, for example, a reactive film 21 sandwiched between brazing members 20 is placed on the cooler 13. In addition, a structure in which the metal plate 40, the insulating resin 41, the heat radiating plate 42, and the semiconductor element 10 are sequentially laminated may be employed. Even in such a structure, stress is applied to the structure and the cooler 13 by applying reaction conditions to the reactive film 21 at the time of joining to the cooler 13 in a manner similar to the above embodiments. It is possible to manufacture a semiconductor device that is difficult to exist.

  Similarly, as shown in FIG. 10 as a diagram corresponding to FIG. 1, for example, housings 50a and 50b are formed around the structure, and are further electrically connected to the wires 31a and 31b therein. The manufacturing method of the present invention can also be applied to a semiconductor device in which the bus bars 51a and 51b are formed. Further, as shown in FIG. 11 as a diagram corresponding to FIG. 1, for example, the housings 50a and 50b and the wires 31a and 31b are provided in the semiconductor device manufactured in the second embodiment illustrated in FIG. The manufacturing method of the present invention is also applicable to a structure in which a structure as illustrated in FIG. 9 is sealed with a mold package 52 as shown in FIG. The same applies.

In each of the above-described embodiments, the example in which the reactive film 21 is formed by the multilayer film sputtering method has been described. Alternatively, for example, the reactive film 21 may be formed by a PVD method, a CVD method, or the like.
In each of the above embodiments, the reactive film 21 is formed on the brazing material 20 applied to the lower surface of the structure. However, the present invention is not limited to this, and the brazing material 20 applied on the cooler 13 is not limited to this. A reactive film 21 may be formed thereon. Alternatively, the reactive film 21 may be formed in a separate process and laminated in such a manner that the reactive film 21 is sandwiched between the brazing materials 20.

  In each of the above embodiments, the aluminum-based brazing material 20 is used as the bonding material. However, the present invention is not limited to this, and silver brazing, phosphorous copper brazing, copper brazing, copper alloy brazing, paste brazing, powder brazing, aluminum A brazing material such as alloy brazing or nickel brazing may be used, and the thickness of the aluminum thin film 21a and the nickel thin film 21b may be adjusted in accordance with the melting temperature thereof. The bonding material only needs to have a low thermal resistance, and for example, solder or the like may be used instead of the brazing material 20.

  In each of the above embodiments, the aluminum thin film 21a and the nickel thin film 21b are used as the metal thin film constituting the reactive film 21. However, the bonding material can be melted in the contradictory relationship between the reaction temperature and the thermal conductivity. As long as the reaction temperature and the thermal conductivity are set to be compatible with each other, when the aluminum thin film 21a is the first metal thin film, the second metal thin film is alternately laminated. In addition to the nickel thin film, for example, a titanium (Ti) thin film or a tantalum (Ta) thin film can be employed.

  In each of the above embodiments, the reactive film 21 is formed by alternately laminating two kinds of metal thin films, ie, the first metal thin film and the second metal thin film. The reactive film 21 may be formed by laminating three or more kinds of metal thin films.

  In the above embodiment, after the semiconductor element 10 is soldered on the insulating substrate 12, the structure and the cooler 13 are joined. Not limited to this, the semiconductor element 10 may be soldered onto the insulating substrate 12 after the structure and the cooler 13 are joined.

  In the embodiment described above, the water-cooled cooler 13 is used as a support for supporting the structure, but an air-cooled cooler may be used instead. Moreover, you may make it use not only a cooler but a heat sink (block), a metal plate (block), etc. as the support body.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a cross-sectional structure of a semiconductor device manufacturing method according to the present invention immediately before joining a semiconductor device to be applied; Sectional drawing which shows the expanded sectional structure of the reactive film employ | adopted as the embodiment. The graph which compares and shows the transition example of the reaction temperature of the reactive film in the same embodiment, and the transition example of the temperature of the heat source by the high frequency induction heating method conventionally used for melting of the brazing material. The graph which shows the relationship between the ratio of the nickel thin film (aluminum thin film) which comprises the reactive film in the same embodiment, and the reaction temperature of a reactive film. The graph which shows the relationship between the ratio of the nickel thin film (aluminum thin film) which comprises the reactive film in the embodiment, and the thermal conductivity of a reactive film. (A)-(d) is a schematic sectional drawing which mainly shows the lamination process about the manufacturing method of the semiconductor device in the embodiment. (A), (b) is a schematic sectional drawing which mainly shows the joining process about the manufacturing method of the semiconductor device in the embodiment. The schematic sectional drawing which shows the cross-section immediately before joining of the semiconductor device made into application object about 2nd Embodiment of the manufacturing method of the semiconductor device concerning this invention. The schematic sectional drawing which shows the cross-section immediately before joining of the semiconductor device made into application object about the modification with respect to said each embodiment of the manufacturing method of the semiconductor device concerning this invention. The schematic sectional drawing which shows the cross-section immediately before joining of the semiconductor device made into application object about the modification with respect to said each embodiment of the manufacturing method of the semiconductor device concerning this invention. The schematic sectional drawing which shows the cross-section immediately before joining of the semiconductor device made into application object about the modification with respect to said each embodiment of the manufacturing method of the semiconductor device concerning this invention. The schematic sectional drawing which shows the cross-section immediately before joining of the semiconductor device made into application object about the modification with respect to said each embodiment of the manufacturing method of the semiconductor device concerning this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Semiconductor element, 11 ... Ceramic substrate, 11a, 11b ... Aluminum plate, 12 ... Insulating substrate (DBA), 13 ... Cooler, 14 ... Solder, 20 ... Brazing material, 21 ... Reactive film | membrane, 21a ... Aluminum thin film, 21b ... nickel thin film, 23 ... bonding layer, 30 ... heat sink, 31a, 31b ... wire, 40 ... metal plate, 41 ... insulating resin, 42 ... heat sink, 50a, 50b ... housing, 51a, 51b ... bus bar, 52 ... Mold package.

Claims (8)

A semiconductor device in which a structure including a semiconductor element is integrally bonded to a support that supports the structure, and the structure including the semiconductor element is bonded to the support via a bonding material having a low thermal resistance. In the manufacturing method of
A reactive film having a characteristic that can achieve both a reaction temperature that enables melting of the bonding material and securing of thermal conductivity in a conflicting relationship between the reaction temperature and thermal conductivity is sandwiched by the bonding material. In this embodiment, the bonding material, the reactive film, the bonding material, and the structure are sequentially laminated on the support, and in this state, the reactive film is given reaction conditions that induce the reaction. A method for manufacturing a semiconductor device, comprising: melting a substrate and bonding the structure to the support. As the reactive film, a plurality of first metal thin films made of a metal thin film having a low reaction temperature and high thermal conductivity and a second metal thin film made of a metal thin film having a high reaction temperature and low thermal conductivity, Using the alternately stacked films, the bonding material can be melted by adjusting the film thicknesses of the first metal thin film and the second metal thin film within a specific number of layers. The method for manufacturing a semiconductor device according to claim 1, wherein the characteristics are set such that the reaction temperature and the thermal conductivity can be ensured. The method of manufacturing a semiconductor device according to claim 2, wherein an aluminum thin film is used as the first metal thin film constituting the reactive film, and a nickel thin film is used as the second metal thin film. 4. The semiconductor device according to claim 3, wherein an aluminum-based brazing material is used as the bonding material, and the aluminum thin film and the nickel thin film are each adjusted to have a reaction temperature of 600 ° C. 4. Production method. The bonding material is previously applied to each bonding surface of the structure and the support, and the reactive film is applied to the surface of one of the structure and the support to which the bonding material is applied. The method for manufacturing a semiconductor device according to claim 1, wherein a film is formed in advance. The semiconductor device according to any one of claims 1 to 5, wherein the structure includes a structure in which the semiconductor element is mounted by soldering on an insulating substrate having an aluminum plate bonded on both sides. Method. The structure according to any one of claims 1 to 5, wherein the structure includes a semiconductor radiator or an insulating substrate having an aluminum plate bonded to both sides thereof mounted by soldering on a heat sink made of metal. The manufacturing method of the semiconductor device of description. The method for manufacturing a semiconductor device according to claim 1, wherein a liquid-cooled or air-cooled cooler is used as a support that supports the structure.

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