JP2016033992A - Semiconductor device manufacturing method, bonding material and bonding material formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method, a bonding material and a bonding material formation method, which can bond metal materials by using a bonding material having an intended solidus temperature.SOLUTION: A semiconductor device manufacturing method comprises the steps of: firstly placing a sheet metal 23 on a porous layer 22b formed on a surface of a surface side metal layer 12 of an insulating substrate 1, in which the sheet metal 23 is composed of a second eutectic alloy which is composed of a second metal forming all proportional solid solution alloy with a first metal, and a third metal forming a first eutectic alloy by eutectic reaction with the first metal at a first eutectic point, and has a second eutectic point lower than the first eutectic point; subsequently placing a semiconductor chip 2 on the sheet metal 23; subsequently melting the sheet metal 23 by a heat treatment at a first temperature higher than the second eutectic point and lower than the first eutectic point to impregnate a porous layer 22b; and subsequently melting the porous layer 22b by a heat treatment at a second temperature higher than the first temperature and causing dispersion of the first metal to a fused material of the sheet metal 23 thereby to form a bonding layer of a ternary alloy of first through third metals.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a semiconductor device manufacturing method, a bonding material, and a bonding material forming method.

  Conventionally, a semiconductor device having a package structure in which a semiconductor chip is bonded onto a circuit pattern provided on an insulating substrate is known. As a method for joining the metal material constituting the circuit pattern to the back electrode of the semiconductor chip, there is a joining method using a joining material such as a solder alloy. Specifically, first, a bonding material made of, for example, a plate-like or paste-like solder alloy is sandwiched between two metal parts having a flat part. Then, by heating the periphery or the whole of the bonding material by heat treatment at a temperature equal to or higher than the solidus temperature of the solder alloy to melt the bonding material and cooling to room temperature, the two metal materials are bonded to each other through the bonding material. Is done.

  When it is necessary to perform the joining process two or more times because there are a plurality of joining parts of the metal material, for example, the joining process with the highest solidus temperature in the first joining process is used. Then, a bonding material having a lower solidus temperature than that of the previous bonding step is used. Thus, by selecting the bonding material used in each bonding step, two or more bonding steps can be performed without melting the bonding layer formed in the previous bonding step.

  Low melting point Au-Ge system in which 50 ppm to 300 ppm of one or two of Pd (palladium) and Pt (platinum) is added to an Au-Ge (gold-germanium) eutectic alloy as a bonding material used for bonding metal materials A brazing material has been proposed (see, for example, Patent Document 1 below).

Japanese Patent No. 3150743

  However, the solidus temperature of a bonding material such as a solder alloy is determined for each metal used as a material, and it is possible to select a bonding material having a desired solidus temperature depending on the semiconductor chip to be mounted and the package structure. difficult. The bonding material having a desired solidus temperature is, for example, a bonding material having a solidus temperature that is an optimum heat treatment temperature for each bonding process when performing the bonding process twice or more as described above. Further, the bonding material having a desired solidus temperature is, for example, a heat resistance temperature required from the viewpoint of ensuring reliability according to the rated temperature (junction (bonding) temperature) of a semiconductor element formed on a semiconductor chip. It is a bonding material with a solidus temperature. The prior art does not disclose a bonding material having such a desired solidus temperature. For this reason, for example, when the joining process is performed twice or more, the already formed joining layer is melted, the metal material is displaced, the terminal is dropped, and the reliability may be lowered. In addition, there is a demand for the development of a bonding technique that can withstand high-temperature heat treatment for producing a high-heat-resistant semiconductor element that can be used in a high-temperature environment made of, for example, a silicon carbide (SiC) semiconductor.

  In order to eliminate the above-described problems caused by the conventional technology, the present invention provides a method for manufacturing a semiconductor device, a bonding material, and a bonding material capable of bonding metal materials using a bonding material having a desired solidus temperature. An object is to provide a forming method.

  In order to solve the above-described problems and achieve the object of the present invention, a manufacturing method of a semiconductor device according to the present invention includes a first metal material and a second metal bonded to the first metal material via a bonding layer. A method for manufacturing a semiconductor device including a material has the following characteristics. First, a first step of forming a porous layer made of a first metal on the surface of the first metal material is performed. Next, the second metal that forms a solid solution alloy with the first metal, and the third metal that forms a first eutectic alloy by eutectic reaction with the first metal at a first eutectic point. A second step of placing a metal thin plate of a second eutectic alloy having a second eutectic point lower than the first eutectic point on the surface of the porous layer is performed. Next, a third step of placing the second metal material on the metal thin plate is performed. Next, the metal thin plate is melted by heat treatment at a first temperature higher than the second eutectic point and lower than the first eutectic point, and the melt of the metal thin plate penetrates into the porous layer. Perform the fourth step. Next, the porous layer is melted by a heat treatment at a second temperature that is higher than the first temperature and lower than the first eutectic point, and the first metal is diffused into the melt of the metal thin plate. Thus, the fifth step of forming the bonding layer having the solidus temperature at the second temperature between the first metal material and the second metal material is performed.

  In the semiconductor device manufacturing method according to the present invention, in the above-described invention, in the first step, a part of the porous layer remains in the bonding layer in a state before the fifth step. In addition, the porous layer is formed.

  In the method of manufacturing a semiconductor device according to the present invention, in the above-described invention, in the first step, first, a paste containing the first metal particles is applied to the surface of the first metal material to form a paste layer. A coating process to be formed is performed. Next, a sintering process is performed in which the paste layer is sintered to be changed into the porous layer.

  Also, in the semiconductor device manufacturing method according to the present invention, in the above-described invention, in the first step, the first metal material is vibrated after the coating step and before the sintering step, and the paste The step of planarizing the surface of the layer is further performed.

  In the semiconductor device manufacturing method according to the present invention, in the above-described invention, in the first step, as the porous layer, a sheet-like metal fiber layer formed by intertwining the metal fibers of the first metal is formed. It is characterized by doing.

  In the semiconductor device manufacturing method according to the present invention as set forth in the invention described above, the first metal is silver or copper.

  In the method for manufacturing a semiconductor device according to the present invention, the second metal is gold in the above-described invention.

  In the semiconductor device manufacturing method according to the present invention as set forth in the invention described above, the third metal is germanium or silicon.

  In addition, in order to solve the above-described problems and achieve the object of the present invention, a method for forming a bonding material according to the present invention has the following characteristics. First, the 1st process of forming the porous layer which consists of 1st metals on the surface of a work board is performed. Next, the second metal that forms a solid solution alloy with the first metal, and the third metal that forms a first eutectic alloy by eutectic reaction with the first metal at a first eutectic point. A second step of placing a metal thin plate of a second eutectic alloy having a second eutectic point lower than the first eutectic point on the surface of the porous layer is performed. Next, the metal thin plate is melted by heat treatment at a first temperature higher than the second eutectic point and lower than the first eutectic point, and the melt of the metal thin plate penetrates into the porous layer. Thus, a third step of forming a plate-like bonding material made of the first metal, the second metal, and the third metal is performed. Next, a fourth step of peeling the plate-shaped bonding material from the surface of the work plate is performed.

  In the above-described invention, the method for forming a bonding material according to the present invention uses the work plate made of a material capable of suppressing a reaction with the first metal, the second metal, and the third metal. And

  In addition, the method for forming a bonding material according to the present invention is the above-described invention, wherein in the first step, the plate is subjected to heat treatment at a second temperature that is higher than the first temperature and lower than the first eutectic point in the first step. The porous layer is formed so that a part of the porous layer remains in the state-like bonding material before the heat treatment at the second temperature.

  In the method for forming a bonding material according to the present invention, in the above-described invention, in the first step, first, a paste containing the first metal particles is applied to the surface of the work plate to form a paste layer. A coating process is performed. Next, a sintering process is performed in which the paste layer is sintered to be changed into the porous layer.

  In addition, in the method for forming a bonding material according to the present invention, in the above-described invention, in the first step, as the porous layer, a sheet-like metal fiber layer formed by intertwining the metal fibers of the first metal is formed. It is characterized by doing.

  Moreover, in the above-described invention, the method for forming the bonding material according to the present invention is the thin film of the first metal, the second metal, or the third metal on the surface of the plate-shaped bonding material after the fourth step. The method further includes a fifth step of forming the film.

  Moreover, the method for forming a bonding material according to the present invention is characterized in that, in the above-described invention, the first metal is silver or copper.

  Moreover, the method for forming a bonding material according to the present invention is characterized in that, in the above-described invention, the second metal is gold.

  In the invention described above, the method for forming a bonding material according to the present invention is characterized in that the third metal is germanium or silicon.

  In order to solve the above-described problems and achieve the object of the present invention, a bonding material according to the present invention includes first metal particles, second metal particles, and third metal particles. . The particles of the second metal form a solid solution alloy with the first metal. The particles of the third metal eutectic react with the first metal at a first eutectic point to form a first eutectic alloy, and the second metal and a second eutectic point lower than the first eutectic point. A eutectic reaction occurs at a crystal point to form a second eutectic alloy.

  Further, in order to solve the above-described problems and achieve the object of the present invention, a bonding material according to the present invention is formed by melting particles of a first metal, melting a second eutectic alloy composed of a second metal and a third metal. It is a mixture of the first metal, the second metal, and the third metal, which is solidified by mixing with an object and formed into a predetermined shape. The second metal forms a complete solid solution alloy with the first metal. The third metal forms a first eutectic alloy by eutectic reaction with the first metal at a first eutectic point. The second eutectic alloy has a second eutectic point lower than the first eutectic point.

  Further, the bonding material according to the present invention is the above-described invention, wherein the melt of the second eutectic alloy is heat-treated at a temperature higher than the second eutectic point and lower than the first eutectic point. It is characterized by being melted by a liquid phase.

  In the above-described invention, the bonding material according to the present invention is characterized in that the first metal is silver or copper.

  In the above-described invention, the bonding material according to the present invention is characterized in that the second metal is gold.

  In the above-described invention, the bonding material according to the present invention is characterized in that the third metal is germanium or silicon.

  According to the above-described invention, the first to third metals having different solidus temperatures and eutectic points are used as the joining material, and the joining layer for joining the metal materials is formed by the two-stage heat treatment at the first and second temperatures. By doing so, the solidus temperature (second temperature) of the bonding layer can be arbitrarily set.

  According to the semiconductor device manufacturing method, the bonding material, and the bonding material forming method according to the present invention, the metal materials are bonded to each other using a bonding material having a desired solidus temperature corresponding to the semiconductor chip to be mounted and the package structure. The effect that it can join is produced.

3 is a cross-sectional view showing an example of the structure of a semiconductor device having a package structure assembled by the method for manufacturing a semiconductor device according to the first embodiment; FIG. FIG. 6 is a cross-sectional view showing a state in the middle of manufacturing the semiconductor device according to the first embodiment; FIG. 6 is a cross-sectional view showing a state in the middle of manufacturing the semiconductor device according to the first embodiment; It is a phase diagram which shows the composition of the equilibrium state of the ternary alloy of Au-Ge-Ag. FIG. 6 is a cross-sectional view illustrating an example of a structure of a semiconductor device having a package structure assembled by a method for manufacturing a semiconductor device according to a second embodiment; FIG. 10 is a cross-sectional view showing a state in the middle of formation of a plate-like bonding material used in a method for manufacturing a semiconductor device according to a fourth embodiment. FIG. 10 is a cross-sectional view showing a state in the middle of manufacturing a semiconductor device according to a fifth embodiment; FIG. 10 is a cross-sectional view showing a state in the middle of manufacturing a semiconductor device according to a fifth embodiment;

  Exemplary embodiments of a method for manufacturing a semiconductor device, a bonding material, and a method for forming a bonding material according to the present invention will be explained below in detail with reference to the accompanying drawings. Note that, in the following description of the embodiments and the accompanying drawings, the same reference numerals are given to the same components, and duplicate descriptions are omitted.

(Embodiment 1)
An example of the structure of a semiconductor device having a package structure assembled by the semiconductor device manufacturing method according to the first embodiment will be described. FIG. 1 is a cross-sectional view illustrating an example of the structure of a semiconductor device having a package structure assembled by the method for manufacturing a semiconductor device according to the first embodiment. FIG. 1 shows a completed package structure in which, for example, one power semiconductor chip 2 is mounted on an insulating substrate 1. As shown in FIG. 1, the insulating substrate 1 has a front surface side metal layer (first metal material) 12 made of, for example, copper (Cu) foil constituting a circuit pattern on the front surface side of the insulating layer 11. The back side metal layer 13 is provided on the back side. The insulating layer 11 is made of an insulator such as ceramic.

  The semiconductor chip 2 has a front metal electrode (not shown) on the front surface and a back metal electrode (second metal material) 3 on the back surface. The back metal electrode 3 of the semiconductor chip 2 is bonded to the front metal layer 12 of the insulating substrate 1 through the bonding layer 21. The surface state (bonding surface) of the back surface metal electrode 3 and the front surface side metal layer 12 can be modified to a suitable condition for realizing bonding with the bonding layer 21 as necessary. Metal plating (not shown) may be formed. As metal plating formed on the surface of the back surface metal electrode 3 and the front surface side metal layer 12, for example, nickel (Ni) plating and flash gold (Au) plating (thin gold plating) are sequentially laminated. A plating film may be formed.

  The bonding layer 21 is a solder layer made of a ternary alloy of first to third metals. The second metal forms a complete solid solution alloy with the first metal. The third metal reacts with the first metal at the first eutectic point to form a first eutectic alloy, and the third metal reacts with the second metal at the second eutectic point to react with the second eutectic alloy. Eggplant. The second eutectic point is lower than the first eutectic point. Specifically, the first metal may be, for example, silver (Ag) or copper (Cu). The second metal may be gold (Au), for example. The third metal may be, for example, germanium (Ge) or silicon (Si).

  The bonding layer 21 is formed using a bonding material including first metal particles, second metal particles, and third metal particles. Specifically, the bonding layer 21 is formed using, for example, a paste containing particles of the first metal and a metal thin plate of the second eutectic alloy made of the second and third metals, as will be described later. . When the first to third metals are Ag, Au, and Ge, for example, the first eutectic alloy is an Ag—Ge eutectic alloy, and the second eutectic alloy is an Au—Ge eutectic alloy. . The first eutectic point is, for example, about 652 ° C. The second eutectic point is, for example, about 356 ° C. The joining layer 21 is a solder layer made of a ternary alloy of Au—Ge—Ag formed by joining the first metal particles and the second eutectic alloy.

  FIG. 1 shows a structure in which one semiconductor chip 2 is mounted on an insulating substrate 1, but the mounting structure can be variously changed according to design conditions. For example, two or more semiconductor chips may be mounted on the insulating substrate 1, and an electric device including a resistor, a capacitor, a metal lump, and the like (not shown) may be mounted. A general element structure such as a transistor or a diode is formed on the semiconductor chip. The surface (planar portion) of each part mounted on the insulating substrate 1 is bonded to the front surface side metal layer 12 of the insulating substrate 1 through the bonding layer 21 in the same manner as the semiconductor chip 2 described above.

  Next, as a method for manufacturing the semiconductor device according to the first embodiment, a method for mounting the semiconductor chip 2 will be described with reference to FIGS. 2 and 3 are cross-sectional views illustrating a state in the process of manufacturing the semiconductor device according to the first embodiment. As shown in FIG. 2, a paste layer 22a is formed by applying a paste containing particles of the first metal on the surface of the front metal layer 12 of the insulating substrate 1 by screen printing. The paste layer 22a is mainly composed of particles of the first metal and organic substances such as flux (pine and ni). After the formation of the paste layer 22a, the surface of the paste layer 22a is unevenly formed (thickness distribution) by applying vibration to the entire paste layer 22a so that the screen plate (stencil) is separated from the insulating substrate 1 during screen printing. You may let them.

  By the step of flattening the surface of the paste layer 22a, the concentration distribution of the first metal in the horizontal direction of the bonding layer 21, which is the final solid state of the paste layer 22a, can be made uniform. The horizontal direction is a direction parallel to the front surface of the insulating substrate 1. Furthermore, a fillet (not shown) can be formed at the end of the paste layer 22a by the step of flattening the surface of the paste layer 22a. The fillet is a portion of the paste layer 22a that protrudes outward from between the front metal layer 12 and the semiconductor chip 2 based on the wettability of the paste layer 22a. It is a part that covers the part.

  The fillet shape at the end of the paste layer 22a is determined depending on the condition for applying vibration to the paste layer 22a. The fillet is also formed at the end of the bonding layer 21, which is the final solid phase state of the paste layer 22a. The shape of the fillet at the end of the bonding layer 21 is approximately the same as the shape of the fillet at the end of the paste layer 22a. Since the fillet is formed at the end of the bonding layer 21, the contact area between the semiconductor chip 2 (or the semiconductor chip 2 and the insulating substrate 1) and the bonding layer 21 increases, and therefore stress concentration at the end of the bonding layer 21 is reduced. Can be relaxed.

  Next, as shown in FIG. 3, the organic material contained in the paste layer 22a is volatilized (vaporized) by heat treatment, and the particles of the first metal in the paste layer 22a are sintered, so that the paste layer 22a becomes the first metal. The porous layer 22b is made of In the formation of the porous layer 22b, after a heat treatment for forming the bonding layer 21 described later, an amount of paste is used so that a part of the porous layer 22b remains in the bonding layer 21 without being melted. The porous layer 22b may be formed. Since the porous layer 22b that is not melted remains in the bonding layer 21, the thickness of the paste layer 22a and the thickness of the metal thin plate 23 to be described later are not changed, and the bonding layer 21 is fixed only at the second temperature level. This is because the phase wire temperature can be controlled. In addition, the porous layer 22b that is not melted remains in the bonding layer 21, so that the first metal can be sufficiently supplied and the solidus temperature can be raised to the heat treatment temperature.

  Next, the metal thin plate 23 made of the second eutectic alloy of the second and third metals (for example, an eutectic alloy of Au—Ge) is placed on the porous layer 22b. Next, the semiconductor chip 2 is placed on the thin metal plate 23 with the back metal electrode 3 facing down (the thin metal plate 23 side), and the entire insulating substrate 1 on which the semiconductor chip 2 is placed is placed in a reflow furnace in a vacuum atmosphere, for example. Heat treatment. That is, the bonding layer 21 is formed using the porous layer 22b and the metal thin plate 23 as bonding materials. Specifically, first, the temperature in the reflow furnace is once maintained at the first temperature to melt the metal thin plate 23, and the melt of the second eutectic alloy is infiltrated into the entire porous layer 22b. That is, before the first metal is dissolved in the melt of the second eutectic alloy, the melt of the second eutectic alloy penetrates into every corner of the porous layer 22b due to the capillary phenomenon of the porous layer 22b. Let

  Next, the temperature in the reflow furnace is raised to the second temperature and maintained, the porous layer 22b is melted, and the first metal is diffused into the melt of the metal thin plate 23 (second eutectic alloy). . As a result, almost the entire melt of the second eutectic alloy becomes a solid phase of the ternary alloy of the first to third metals (for example, Au—Ge—Ag), and the bonding made of the ternary alloy of the first to third metals Layer 21 is formed. A part of the porous layer 22b may not dissolve in the melt of the metal thin plate 23 during the heat treatment at the second temperature, and some unmelted first metal may remain in the bonding layer 21 ( Not shown). The solidus temperature of the bonding layer 21 (ternary alloy) is a second temperature that is a heat treatment temperature when the bonding layer 21 is formed. The second temperature rises in proportion to the concentration of the first metal diffused in the melt of the second eutectic alloy. For this reason, the solidus temperature of the bonding layer 21 can be arbitrarily controlled by appropriately setting the amount of the first metal diffused into the melt of the second eutectic alloy.

  The first temperature is higher than the second eutectic point (for example, 356 ° C.) and lower than the first eutectic point (for example, about 652 ° C.). Specifically, when the metal thin plate 23 is made of an eutectic alloy of Au—Ge, the first temperature may be, for example, about 360 ° C. higher than the second eutectic point by about 0 ° C. or more and 10 ° C. or less. . The second temperature is higher than the first temperature and lower than the first eutectic point. Specifically, the second temperature may be about 450 ° C., for example. Thereafter, the inside of the reflow furnace is cooled to room temperature (for example, about 25 ° C.). As described above, the bonding layer 21 forming the ternary alloy of the first to third metals is formed by the steps so far, and is insulated from the back surface metal electrode 3 of the semiconductor chip 2 through the bonding layer 21. The front surface side metal layer 12 of the substrate 1 is bonded. Thereafter, wiring, sealing (molding), and the like are performed by a general method, whereby a semiconductor device having a package structure is completed.

  Next, with respect to the principle that the solidus temperature of the bonding layer 21 is increased by adding the first metal (Ag) to the second eutectic alloy (Au—Ge eutectic alloy), the Au—Ge—Ag 3 A case where the bonding layer 21 made of the original alloy is formed will be described as an example. FIG. 4 is a state diagram showing an equilibrium composition of an Au—Ge—Ag ternary alloy. Each axis in FIG. 4 indicates the molar concentration (mol%) of each component of the ternary alloy of Au—Ge—Ag, and the contour lines indicate the solidus temperature. The second eutectic point (eutectic point) of the second eutectic alloy is a portion indicated by a black dot (● mark) in the figure. The composition ratio of the second eutectic alloy at the second eutectic point is Au: Ge = 73 mol%: 27 mol%.

  As shown in FIG. 4, the solidus temperature of the second eutectic alloy (namely, Au: Ge: Ag = 73 mol%: 27 mol%: 0 mol%) is 356 ° C. The first metal is dissolved in the second eutectic alloy, that is, the molar concentration of the first metal is increased along the arrow shown in the figure, and the alloy component is changed to an Au—Ge—Ag ternary alloy. In this case, it can be seen that the solidus temperature increases as the molar concentration of the first metal increases. Therefore, the porous layer 22b made of the first metal is adjusted by appropriately adjusting the amount of the paste made of the first metal for forming the porous layer 22b (that is, changing the concentration of the first metal in the bonding layer 21). It can be seen that the bonding layer 21 having a desired solidus temperature can be formed using the metal thin plate 23 made of the second eutectic alloy. In addition to the method of adjusting the amount of the paste made of the first metal, the bonding layer 21 having a desired solidus temperature can be formed by sufficiently supplying the first metal and adjusting the heat treatment temperature. Is possible.

  As described above, according to the first embodiment, the first to third metals having different solidus temperatures and eutectic points are used as the bonding materials, and the first and second temperatures are sequentially heat-treated. By forming a bonding layer made of a ternary alloy of three metals, the solidus temperature (second temperature) of the bonding layer can be arbitrarily set based on the concentration of the first metal contained in the bonding layer. . Therefore, by applying the present invention, a semiconductor device having desired heat resistance can be manufactured. Specifically, for example, a high heat-resistant semiconductor device that can withstand a high temperature environment such as a semiconductor element made of a silicon carbide (SiC) semiconductor can be manufactured.

(Embodiment 2)
Next, a method for manufacturing the semiconductor device according to the second embodiment will be described. FIG. 5 is a cross-sectional view illustrating an example of the structure of a semiconductor device having a package structure assembled by the semiconductor device manufacturing method according to the second embodiment. FIG. 5 shows a completed semiconductor module in which the back-side metal layer 13 of the insulating substrate 1 on which one semiconductor chip 2 is mounted is bonded to a metal base (for example, Cu base) or a metal fin (hereinafter referred to as a metal base 4). The main part of is shown. The manufacturing method of the semiconductor device according to the second embodiment is a modification in which the manufacturing method of the semiconductor device according to the first embodiment is applied in performing the bonding step of bonding metal materials through the bonding layer twice or more. is there.

  As shown in FIG. 5, in the semiconductor device having a package structure assembled by the method for manufacturing a semiconductor device according to the second embodiment, the back surface metal electrode 3 of the semiconductor chip 2 has a bonding layer (like the first embodiment). In the second embodiment, the insulating substrate 1 is bonded to the front surface side metal layer 12 via the first bonding layer 21 hereinafter. The rear surface side metal layer 13 of the insulating substrate 1 is bonded to the front surface of the metal base 4 via the second bonding layer 24. The solidus temperature of the second bonding layer 24 is lower than the solidus temperature of the first bonding layer 21.

  Specifically, first, as in the first embodiment, first bonding made of a ternary alloy of first to third metals by heat treatment at a first temperature (for example, about 360 ° C.) and a second temperature (about 450 ° C.). Layer 21 is formed. That is, similarly to the first embodiment, the back surface metal electrode 3 of the semiconductor chip 2 and the front surface side metal layer 12 of the insulating substrate 1 are bonded via the first bonding layer 21. Next, the second bonding layer 24 is formed by a heat treatment at a third temperature (for example, 400 ° C.) higher than the first temperature and lower than the second temperature, and the insulating substrate 1 of the insulating substrate 1 is interposed via the second bonding layer 24. The back side metal layer 13 and the metal base 4 are joined. Then, a semiconductor module is completed by performing wiring, sealing (molding), etc. by a general method.

  As described above, the second bonding layer 24 is formed by heat treatment at a temperature lower than the solidus temperature of the first bonding layer 21 formed in the first bonding step. For this reason, the first bonding layer 21 formed in the first bonding step is not melted in the second bonding step for forming the second bonding layer 24. Even when the bonding process is performed three times or more, the bonding process may be performed by a heat treatment at a temperature lower than the solidus temperature of the bonding layer formed by the previous bonding process. Therefore, the present invention can be applied even in the case where it is necessary to perform a joining process two or more times when manufacturing (manufacturing) one semiconductor module.

  As described above, according to the second embodiment, the same effect as in the first embodiment can be obtained. Further, according to the second embodiment, for example, when it is necessary to perform the joining process twice or more, such as assembling a high heat resistant power module, first, the first joining process is performed at a relatively high temperature by applying the present invention. Next, the second and subsequent joining steps can be performed at a lower temperature than the previous joining step using the same joining material. Thereby, two or more joining processes can be performed without remelting the already formed joining layer. Therefore, it is possible to prevent a decrease in reliability.

(Embodiment 3)
Next, a method for manufacturing the semiconductor device according to the third embodiment will be described with reference to FIG. The semiconductor device manufacturing method according to the third embodiment is different from the semiconductor device manufacturing method according to the first embodiment in that metal fibers made of the first metal are used as a bonding material instead of the paste containing the first metal particles. It is a point to use as.

  Specifically, first, metal fibers having a fine diameter (for example, about 10 μm) are entangled and rolled by a press or the like so as to be thicker than the diameter of the metal fibers (for example, about 30 μm), and then formed into a sheet shape in advance. Then, this sheet-like metal fiber is placed on the front surface side metal layer 12 of the insulating substrate 1 to form a metal fiber layer. Then, the metal thin plate 23 made of the second eutectic alloy is placed on the metal fiber layer, and the semiconductor chip 2 is placed on the metal thin plate 23 with the back metal electrode 3 facing down. That is, the metal fiber layer is formed at the position of the porous layer (the layer indicated by reference numeral 22b in FIG. 3) in the first embodiment. The configuration of the metal thin plate 23 is the same as that of the first embodiment. Thereafter, similarly to the first embodiment, the entire insulating substrate 1 on which the semiconductor chip 2 is mounted is sequentially subjected to the heat treatment in the reflow furnace, thereby completing the packaged semiconductor device.

  As described above, according to the third embodiment, the same effect as in the first embodiment can be obtained. In addition, according to the third embodiment, it is useful when the joining surface of the metal material has large undulations that cannot be handled by the porous layer formed by screen printing and heat treatment.

(Embodiment 4)
Next, a method for manufacturing the semiconductor device according to the fourth embodiment will be described. FIG. 6 is a cross-sectional view illustrating a state in the middle of forming a plate-like bonding material used in the method for manufacturing a semiconductor device according to the fourth embodiment. The manufacturing method of the semiconductor device according to the fourth embodiment applies the manufacturing method of the semiconductor device according to the first embodiment, and is a plate shape made of a ternary alloy of first to third metals in advance on the work plate 5 or the like. It is a modification which forms a joining material. The plate-like bonding material is a porous body made of the first metal infiltrated with the second eutectic alloy of the second and third metals.

  In Embodiment 4, for example, after sandwiching a plate-shaped bonding material between two metal materials, the porous layer constituting the plate-shaped bonding material may be melted by heat treatment at a second temperature. As a result, the plate-like bonding material becomes a bonding layer made of a ternary alloy of the first to third metals as in the first embodiment, and the metal materials are bonded to each other through this bonding layer. Thereafter, wiring, sealing (molding), and the like are performed by a general method, whereby a semiconductor device having a package structure is completed.

  Next, a method for forming the plate-like bonding material will be described. First, a porous layer (not shown) made of the first metal is formed on the work plate 5, and a metal thin plate of the second eutectic alloy is placed on the porous layer. Next, the metal thin plate is melted at the first temperature, the second eutectic alloy melt is infiltrated into the entire porous layer, and then cooled to room temperature. As a result, a ternary alloy precursor 25 in which the second eutectic alloy of the second and third metals is infiltrated into the porous body made of the first metal is formed. That is, on the work plate 5, as in the first embodiment, by performing the steps from the formation of the paste layer containing the first metal particles to the heat treatment at the first temperature, the ternary that becomes the plate-like bonding material An alloy precursor 25 is formed. The work plate 5 is made of a material which can easily peel the ternary alloy precursor 25 and does not react with the ternary alloy precursor 25. Specifically, as the work plate 5, for example, plate glass may be used, or a metal plate subjected to general surface treatment may be used. Thereafter, the precursor 25 is peeled off from the work plate 5, and the ternary alloy precursor 25 is rolled as necessary, and processed into a desired dimension, thereby completing the plate-like bonding material.

  Moreover, it is also possible to improve the wettability with respect to the metal material used as joining object by coat | covering the surface of a plate-shaped joining material with the thin film in any one of the 1st-3rd metal. Further, the flat portions of the two plate-like bonding materials may be bonded together. Alternatively, the third embodiment may be applied to the fourth embodiment, and the precursor 25 of the ternary alloy may be formed using a fine metal fiber layer instead of the porous layer.

  As described above, according to the fourth embodiment, the same effect as in the first embodiment can be obtained. Further, according to the fourth embodiment, after the plate-like bonding material is sandwiched between two metal materials, heat treatment is performed at a second temperature that is higher than the first temperature and lower than the first eutectic point. Metal materials can be joined together. For this reason, the manufacturing process can be simplified.

(Embodiment 5)
Next, the structure of the semiconductor device according to the fifth embodiment will be described. 7 and 8 are cross-sectional views illustrating a state during the manufacture of the semiconductor device according to the fifth embodiment. The manufacturing method of the semiconductor device according to the fifth embodiment differs from the manufacturing method of the semiconductor device according to the first embodiment in that the paste containing the first metal particles and the second eutectic system of the second and third metals. Instead of a metal thin plate made of an alloy, an alloy paste is used as a bonding material. Specifically, for example, as an alloy paste, an alloy paste in which the first metal particles and the second eutectic alloy particles of the second and third metals are protected and mixed using a suitable organic solvent is joined. Used as a material.

  Specifically, as shown in FIG. 7, first, an alloy paste layer 26a is formed on the surface of the front metal layer 12 of the insulating substrate 1 by screen printing. The alloy paste layer 26a includes particles of a first metal (for example, Ag), particles of a second eutectic alloy of a second and third metal (for example, an eutectic alloy of Au-Ge), and an organic substance such as a flux (pine pine). And the main component. Similar to the first embodiment, the unevenness of the surface of the alloy paste layer 26a may be flattened by applying vibration to the alloy paste layer 26a. Next, the semiconductor chip 2 is placed on the alloy paste layer 26a with the back metal electrode 3 facing down, and the entire insulating substrate 1 on which the semiconductor chip 2 is placed is heat-treated in a reflow furnace in a vacuum atmosphere, for example.

  Specifically, the particles of the second eutectic alloy contained in the alloy paste layer 26a are maintained at the first temperature while the organic paste contained in the alloy paste layer 26a is vaporized during the heat treatment. Melt. As a result, the alloy paste layer 26a is in a state where the particles of the first metal are dispersed in the melt of the second eutectic alloy. Next, the temperature in the reflow furnace is raised to and maintained at a second temperature higher than the first temperature, and the first metal particles contained in the alloy paste layer 26a are melted. As a result, the melt of the first metal is melted into the melt of the second eutectic alloy of the second and third metals, and the joining composed of the ternary alloy layers of the first to third metals as in the first embodiment. A layer 26b is formed, and the metal materials are bonded to each other through the bonding layer 26b as shown in FIG. The first and second temperatures are the same as in the first embodiment. As in the first embodiment, some unalloyed first metal particles may remain in the bonding layer 26b. Thereafter, wiring, sealing (molding), and the like are performed by a general method, whereby a semiconductor device having a package structure is completed.

  Further, the joining process may be performed twice or more by applying the fifth embodiment to the second embodiment. Further, the plate-like bonding material may be formed by applying the fifth embodiment to the fourth embodiment.

  As described above, according to the fifth embodiment, the same effects as in the first and fourth embodiments can be obtained.

(Embodiment 6)
Next, a method for manufacturing the semiconductor device according to the sixth embodiment will be described. The semiconductor device manufacturing method according to the sixth embodiment differs from the semiconductor device manufacturing method according to the fifth embodiment in that plate-like solder is used as a bonding material instead of paste-like solder. The plate-like solder is obtained by mixing the first metal particles in the second eutectic alloy of the second and third metals.

  In the sixth embodiment, after the plate-like solder is sandwiched between two metal materials, the first metal particles contained in the plate-like solder may be melted by heat treatment at a second temperature. Thus, the plate-like solder becomes a joining layer made of a ternary alloy of the first to third metals as in the fifth embodiment, and the metal materials are joined through the joining layer. Thereafter, wiring, sealing (molding), and the like are performed by a general method, whereby a semiconductor device having a package structure is completed.

  Next, a method for forming plate solder will be described. First, the solder of the second eutectic alloy is prepared at a temperature higher than the solidus temperature (second eutectic point). Next, the solder of the second eutectic alloy is held at a first temperature slightly higher than the solidus temperature. Here, after the first metal particles are uniformly mixed in the melt of the second eutectic alloy, it is immediately cooled to room temperature. The mixture of the first metal particles and the second eutectic alloy of the second and third metals formed in this way is rolled as necessary, and processed into a desired size to obtain a plate-like bonding material. Complete.

  Further, the joining process may be performed twice or more by applying the sixth embodiment to the second embodiment.

  As described above, according to the sixth embodiment, the same effects as in the first, fourth, and fifth embodiments can be obtained.

  As described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, a case where the back surface metal electrode of the semiconductor chip and the front surface side metal material of the insulating substrate are joined is described as an example. If it exists, it can join by applying this invention. Further, as a semiconductor material of the semiconductor chip, for example, a silicon (Si) semiconductor may be used, or various semiconductor materials such as a silicon carbide (SiC) semiconductor having a wider band gap than the silicon semiconductor may be used.

  As described above, the method for manufacturing a semiconductor device, the bonding material, and the method for forming the bonding material according to the present invention are useful for bonding metal materials constituting a semiconductor device used in a high temperature environment.

DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Semiconductor chip 3 Back surface metal electrode of semiconductor chip 4 Metal base or metal fin of semiconductor module 5 Work plate 11 Insulating layer of insulating substrate 12 Front surface side metal layer of insulating substrate 13 Back surface side metal layer of insulating substrate 21, 26b Junction layer (solder layer) made of a ternary alloy of first to third metals
22a Paste layer containing particles of the first metal 22b Porous layer made of the first metal 23 Metal thin plate of the second eutectic alloy 24 Second bonding layer 25 In the porous body made of the first metal, the second and third metals Precursor of ternary alloy layer infiltrated with second eutectic alloy of No. 26a Alloy paste layer comprising first metal particles and second eutectic alloy particles of second and third metals

Claims (23)

A method for manufacturing a semiconductor device, comprising: a first metal material; and a second metal material joined to the first metal material via a joining layer,
A first step of forming a porous layer made of a first metal on a surface of the first metal material;
A second metal that forms a solid solution alloy with the first metal, and a third metal that forms a first eutectic alloy by eutectic reaction with the first metal at a first eutectic point. A second step of placing a metal sheet of a second eutectic alloy having a second eutectic point lower than one eutectic point on the surface of the porous layer;
A third step of placing the second metal material on the metal sheet;
Fourth step of melting the metal thin plate by a heat treatment at a first temperature higher than the second eutectic point and lower than the first eutectic point, and allowing the melt of the metal thin plate to penetrate into the porous layer. When,
Melting the porous layer by a heat treatment at a second temperature higher than the first temperature and lower than the first eutectic point, and diffusing the first metal in the melt of the metal sheet, A fifth step of forming the bonding layer having a solidus temperature of the second metal material between the first metal material and the second metal material;
A method for manufacturing a semiconductor device, comprising:   In the first step, the porous layer is formed so that a part of the porous layer remains in the bonding layer in a state before the fifth step. The manufacturing method of the semiconductor device of description. The first step includes
An application step of applying a paste containing particles of the first metal on the surface of the first metal material to form a paste layer;
The method for manufacturing a semiconductor device according to claim 1, further comprising: a sintering step in which the paste layer is sintered to be changed into the porous layer. The first step includes
The semiconductor device according to claim 3, further comprising a step of planarizing a surface of the paste layer by vibrating the first metal material after the coating step and before the sintering step. Manufacturing method.   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the first step, a sheet-like metal fiber layer formed by entanglement of the metal fibers of the first metal is formed as the porous layer.   The method of manufacturing a semiconductor device according to claim 1, wherein the first metal is silver or copper.   The method for manufacturing a semiconductor device according to claim 1, wherein the second metal is gold.   The method for manufacturing a semiconductor device according to claim 1, wherein the third metal is germanium or silicon. A first step of forming a porous layer made of a first metal on the surface of the work plate;
A second metal that forms a solid solution alloy with the first metal, and a third metal that forms a first eutectic alloy by eutectic reaction with the first metal at a first eutectic point. A second step of placing a metal sheet of a second eutectic alloy having a second eutectic point lower than one eutectic point on the surface of the porous layer;
By melting the thin metal sheet by a heat treatment at a first temperature higher than the second eutectic point and lower than the first eutectic point, and impregnating the melt of the thin metal sheet into the porous layer, A third step of forming a plate-like bonding material comprising the first metal, the second metal, and the third metal;
A fourth step of peeling the plate-like bonding material from the surface of the work plate;
A method for forming a bonding material, comprising:   The method for forming a bonding material according to claim 9, wherein the work plate made of a material capable of suppressing a reaction with the first metal, the second metal, and the third metal is used.   In the first step, after the heat treatment at a second temperature that is higher than the first temperature and lower than the first eutectic point, the porous bonding is performed in the plate-like bonding material in a state before the heat treatment at the second temperature. The method for forming a bonding material according to claim 9 or 10, wherein the porous layer is formed so that a part of the porous layer remains. The first step includes
An application step of applying a paste containing the first metal particles on the surface of the work plate to form a paste layer;
The method for forming a bonding material according to claim 9, further comprising: a sintering step in which the paste layer is sintered to be changed into the porous layer.   The said 1st process WHEREIN: The sheet-like metal fiber layer formed by intertwining the metal fiber of the said 1st metal as said porous layer is formed, The formation of the joining material of Claim 9 or 10 characterized by the above-mentioned. Method.   9. The method according to claim 9, further comprising a fifth step of forming a thin film of the first metal, the second metal, or the third metal on the surface of the plate-like bonding material after the fourth step. 14. The method for forming a bonding material according to any one of 13 above.   The method for forming a bonding material according to claim 9, wherein the first metal is silver or copper.   The said 2nd metal is gold | metal | money, The formation method of the bonding | jointing material as described in any one of Claims 9-15 characterized by the above-mentioned.   The method for forming a bonding material according to any one of claims 9 to 16, wherein the third metal is germanium or silicon. A first metal particle;
Particles of a second metal forming a total solid solution alloy with the first metal;
A first eutectic point reacts with the first metal to form a first eutectic alloy and a second eutectic point lower than the first eutectic point with the second metal. Particles of a third metal forming a bieutectic alloy;
A bonding material comprising:   The first metal particles, a second metal that forms a solid solution alloy with the first metal, and a third metal that forms a first eutectic alloy by eutectic reaction with the first metal at the first eutectic point. The first metal, the first metal, which is mixed and solidified with a melt of a second eutectic alloy having a second eutectic point lower than the first eutectic point and formed into a predetermined shape. A bonding material comprising a mixture of two metals and the third metal.   The melt of the second eutectic alloy is melted by a heat treatment at a temperature higher than the second eutectic point and lower than the first eutectic point to form a liquid phase. The bonding material described in 1.   The bonding material according to claim 18, wherein the first metal is silver or copper.   The bonding material according to claim 18, wherein the second metal is gold.   The bonding material according to any one of claims 18 to 22, wherein the third metal is germanium or silicon.

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