Semiconductor device and method of manufacturing the same

Abstract

The present disclosure relates to a semiconductor device and a method for manufacturing the same, and the purpose of the present disclosure is to provide a semiconductor device and a method for manufacturing the same, in which the outermost surface of a surface electrode is modified by laser irradiation, thereby enabling low cost and improved assemblability of the semiconductor device. Comprising the surface electrode solder joint part, solder, a resin sealing material and a semiconductor element mounted under the surface electrode solder joint part. The surface electrode solder joint has a first laser-modified portion obtained by oxidizing and roughening the outermost surface, and a first solder joint region joined to the solder, and the laser-modified portion is covered with a resin sealing material.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor device and a method for manufacturing the same, and in particular to a semiconductor device suitable for use in a power converter such as an inverter and a method for manufacturing the same. Background Art

[0002] As a power semiconductor device used in an inverter or the like, a device having a structure in which the surface electrode of a semiconductor element is joined to an external electrode by solder is known. In a semiconductor device having such a structure, when subjected to thermal stress such as power cycling or thermal cycling, thermal stress is generated due to the difference in linear expansion coefficients of the materials. As a result, the material interface at the outermost periphery of the surface electrode peels off, and when the peeling progresses, problems such as cracks in the surface electrode of the semiconductor element occur.

[0003] Patent Documents 1 and 2 disclose a technique of forming a cover film made of polyimide at a material boundary portion at the outermost periphery of a surface electrode as a method for preventing cracks in a surface electrode of a semiconductor element. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent No. 6156381

[0005] Patent Document 2: Japanese Patent Application Publication No. 2019-201160 Summary of the invention Technical problem to be solved by the invention

[0006] However, when a polyimide film is formed on the surface electrode, the manufacturing process becomes complicated, resulting in an increase in manufacturing cost. In addition, there is also a problem of reduced assembly properties such as an increase in chip warpage caused by polyimide film stress and a reduction in solder bonding properties caused by polyimide curing heat treatment.

[0007] In order to solve the above problems, the present invention modifies the outermost surface of the surface electrode by laser irradiation. Therefore, its purpose is to provide a semiconductor device and a manufacturing method thereof that can achieve low cost and improved assemblability of the semiconductor device. Technical solutions to technical problems

[0008] The first method disclosed in the present invention is preferably a semiconductor device, which includes a surface electrode solder joint, solder, a resin sealing material, and a semiconductor element installed under the surface electrode solder joint. The surface electrode solder joint has a first laser modified portion after the outermost surface is oxidized and roughened, and a first solder joint area joined to the solder, and the laser modified portion is covered by the resin sealing material.

[0009] The second method of the present disclosure is preferably a method for manufacturing a semiconductor device, which has a surface electrode solder joint, solder and a resin sealing material, and the method for manufacturing the semiconductor device includes: a process of forming a laser modified portion by pulse irradiating a portion of the surface electrode solder joint with a laser; a process of performing solder joining on the surface electrode solder joint; and a process of performing resin sealing using a resin sealing material to cover the laser modified portion. Effects of the Invention

[0010] According to the aspect of the present invention, it is possible to provide a semiconductor device and a method for manufacturing the semiconductor device, which can achieve cost reduction and improved assemblability by modifying the outermost surface of a surface electrode by laser irradiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram showing a cross-sectional view of the semiconductor device according to the first embodiment. Figure 2 This is a cross-sectional view showing the semiconductor device before laser irradiation according to the first embodiment. Figure 3 1 is a cross-sectional view showing the semiconductor device after laser irradiation according to the first embodiment. Figure 4 1 is a cross-sectional view showing the semiconductor device after solder bonding according to the first embodiment. Figure 5 1 is a cross-sectional view showing the semiconductor device after resin sealing according to the first embodiment. Figure 6 This is a plan view showing the semiconductor element before laser irradiation according to the first embodiment. Figure 7 This is a plan view showing the semiconductor element after laser irradiation according to the first embodiment. Figure 8 It is a cross-sectional view showing a semiconductor device according to a fourth embodiment. Fig. 9 This is a cross-sectional view showing a semiconductor device according to a seventh embodiment. Fig.10 This is a cross-sectional view showing a semiconductor device according to an eighth embodiment. Fig.11 It is a top view showing the semiconductor element involved in the tenth embodiment. Fig.12 It is a top view showing the semiconductor element information formation region involved in the tenth embodiment. Fig.13 It is a top view showing the semiconductor element information formation region involved in the tenth embodiment. Fig.14It is a top view showing the semiconductor element involved in the eleventh embodiment. Fig.15 This is a cross-sectional view showing a semiconductor device according to the eleventh embodiment. Fig.16 It is a top view showing the semiconductor element involved in the twelfth embodiment. Fig.17 It is a top view showing the semiconductor element involved in the thirteenth embodiment. Fig.18 This is a cross-sectional view of the semiconductor device before laser irradiation according to the fourteenth embodiment. Fig.19 14 is a cross-sectional view showing a semiconductor device after resin sealing according to the fourteenth embodiment. Fig. 20 It is a top view showing the back electrode before laser irradiation according to the fourteenth embodiment. Fig.21 It is a top view showing the back electrode after laser irradiation involved in embodiment 14. Fig. 22 This is a cross-sectional view showing an end portion of a semiconductor element before resin sealing according to the fifteenth embodiment. Fig.23 It is a top view showing the semiconductor element before resin sealing involved in the fifteenth embodiment. Fig.24 It is a top view showing the semiconductor element before resin sealing involved in the sixteenth embodiment. DETAILED DESCRIPTION

[0012] Implementation Method 1 Figure 1 1 is a cross-sectional view showing a semiconductor device according to Embodiment 1. The semiconductor device 100 includes a semiconductor element 2. The semiconductor element 2 has a back electrode 4 on the back surface. The back electrode 4 is formed of a metal film and is connected to a substrate 3 having a heat dissipation function using a conductive bonding material 5 such as solder. The substrate 3 is formed of a metal such as copper (Cu) and is connected to an insulating layer 1.

[0013] In addition, the semiconductor element 2 has a surface electrode solder joint 6 on the surface. The surface electrode solder joint 6 is formed of a metal film. In addition, the surface electrode solder joint 6 is an electrode for conducting the main current of the semiconductor element 2. The surface electrode solder joint 6 uses a conductive bonding material 5 of solder and is connected to an external electrode 10 formed of a metal such as copper (Cu).

[0014] In addition, the semiconductor element 2 has a surface electrode lead pad portion 8 on the surface. The surface electrode lead pad portion 8 is formed of a metal film. In addition, the surface electrode lead pad portion 8 is used for driving and controlling the semiconductor element 2. The surface electrode lead pad portion 8 is connected to an external electrode 14 electrically isolated from the surface electrode solder joint portion 6 using a conductive wiring material 12 such as an aluminum lead.

[0015] The entire semiconductor device 100 is sealed with a sealing material 16 in order to ensure electrical insulation, environmental resistance, etc. The sealing material 16 is formed of an insulating material such as epoxy resin.

[0016] In a semiconductor device having the above structure, when subjected to thermal stress such as power cycling or thermal cycling, thermal stress caused by the difference in linear expansion coefficients of the materials is generated at the end of the surface electrode solder joint 6 of the semiconductor element. As a result, interface peeling of the surface electrode, the conductive bonding material and the sealing material occurs. When the interface peeling progresses due to repeated thermal stress, cracks will occur in the metal film forming the surface electrode of the semiconductor element. In order to prevent the metal film from cracking, patent documents 1 and 2 disclose a technology for forming a covering film composed of polyimide at the end of the surface electrode of the semiconductor element. Thus, the metal film cracks are suppressed by forming a stress relief layer or improving the adhesion to the metal film of the substrate.

[0017] However, when a polyimide film is formed, problems arise from the viewpoints of manufacturing cost and assembly. Therefore, in the semiconductor device 100 involved in this embodiment, the outermost surface of the surface electrode is irradiated with laser instead of forming a polyimide film. Thus, by forming the laser modified portion 18, the adhesion between the surface electrode and the sealing material interface is improved, and the peeling of the interfaces of the materials is suppressed.

[0018] A manufacturing process of the semiconductor device 100 will be described. Figure 2 2 is a cross-sectional view showing a semiconductor device before laser irradiation according to Embodiment 1. The surface electrode solder joint portion 6 of the semiconductor element has a first metal film 20. The first metal film 20 contains aluminum (Al) and functions as an adhesive film. A second metal film 22 is formed on the first metal film 20. The second metal film 22 contains nickel (Ni) and functions as a bonding film. A third metal film 24 is formed on the second metal film 22. The third metal film 24 contains gold (Au) and functions as an anti-oxidation film.

[0019] The laser irradiation portion 25 indicates the area where the laser 26 is irradiated on the outermost layer of the surface electrode solder joint portion 6. The processing area 27 indicates the circular area that can be processed by a single pulse irradiation of the laser 26. In addition, a cover film 28 is formed on the first metal film 20 at a position in contact with the ends of the second metal film 22 and the third metal film 24.

[0020] Moreover, the semiconductor substrate 30 is arrange|positioned under the surface electrode solder joint part 6. The semiconductor substrate 30 has the trench 32 which embeds the polysilicon (PolySi).

[0021] Figure 3 2 is a cross-sectional view showing the semiconductor device after laser irradiation according to Embodiment 1. Here, the state after the outermost layer of the third metal film 24 is irradiated with the laser 26 is shown.

[0022] The laser modified portion 36 indicates a region irradiated with the laser 26. In the laser modified portion 36, solid diffusion of gold (Au) and nickel (Ni) occurs due to the thermal energy from the laser 26. That is, Au contained in the third metal film 24 diffuses into the second metal film 22, thereby forming a nickel (Ni) oxide layer on the surface.

[0023] Figure 4 1 is a cross-sectional view of a semiconductor device after solder bonding according to Embodiment 1. In the range where solder 38 wets and spreads, an intermetallic compound layer 40 is formed by reaction with third metal film 24. On the other hand, laser modified portion 36 has a nickel (Ni) oxide layer formed on the surface, so solder wetting is hindered.

[0024] In addition, in the laser modified portion 36, the surface layer is shaved into concentric circles by the pulse irradiation of the laser 26. The area processed by the pulse irradiation once is the above-mentioned processing area 27. This process is repeated until the entire laser modified portion 36 is processed. As a result, the surface is roughened. By this roughening process, the contact area between the solder and the surface electrode increases, and the surface tension of the interface between the solder and the surface electrode increases. Therefore, solder wetting is further hindered.

[0025] During laser processing, the type of laser is selected in consideration of the characteristics of the material irradiated with the laser. In the present disclosure, a type of laser suitable for processing gold (Au) is used. In this case, the size that can be processed by one pulse irradiation is about tens of μm in diameter (φ) according to the relationship between the laser wavelength. However, in the case where the area of ​​the nickel oxide layer formed by laser irradiation is small, if a solder material or solder bonding process with a high reduction power of nickel oxide is used, the nickel oxide layer is reduced. As a result, the solder may wet and spread.

[0026] In this embodiment, the processing area 27 is formed into a multiple ring shape to surround the outermost periphery of the surface electrode. As a result, the area of ​​the nickel oxide layer can be ensured to be above a certain level, thereby increasing the margin of the nickel oxide layer to the reduction effect. As a result, in the solder joining process, the solder does not wet and spread to the laser modified portion 36. Moreover, even after solder joining, a certain level of nickel oxide layer will remain in the laser modified portion 36 in an exposed state.

[0027] Figure 5 4 is a cross-sectional view showing a semiconductor device after resin sealing according to Embodiment 1. When resin sealing is performed, the surface layer of the laser modified portion 36 is covered with the resin sealing material 42. That is, a region consisting of the laser modified surface and the sealing material interface is formed. As described above, the surface of the laser modified portion 36 is roughened. Therefore, the bonding strength of the interface between the laser modified portion 36 and the resin sealing material 42 is improved by the anchoring effect.

[0028] Figure 6 1 is a plan view showing a semiconductor element before laser irradiation according to Embodiment 1. The semiconductor element 2 includes a surface electrode solder joint portion 6 and a surface electrode lead pad portion 8 on the surface layer. The processing region 27 indicates a region that can be processed by a single pulse irradiation of the laser 26 .

[0029] Figure 7 1 is a top view showing a semiconductor element after laser irradiation according to Embodiment 1. The laser modified portion 36 indicates the area irradiated with the laser 26. In one pulse irradiation of the laser 26, only the range of the processing area 27 can be processed. By repeating this, the range of the laser modified portion 36 is processed. In addition, in the surface electrode solder joint portion 6, the area other than the laser modified portion 36 is used as the solder joint area 37.

[0030] As described above, according to the present embodiment, cracks of the metal film can be prevented without forming a polyimide film. Thus, the manufacturing processes such as photoengraving, distribution coating, and heat treatment required for forming the polyimide film in the past can be omitted. As a result, the manufacturing cost of the semiconductor device can be reduced. In addition, since the stress generated by the polyimide film or the polyimide film curing heat treatment is not required, it can be expected that the chip warpage amount will be reduced or the solder wettability will be improved. As a result, it can be expected that the assembly performance will be improved and the quality will be improved. Moreover, the surface roughness and processing width of the laser modified portion 36 can be adjusted under the laser irradiation conditions. That is, the solder wetting prevention effect and the bonding strength with the sealing material can be intentionally controlled, so the design freedom of the semiconductor device is also improved.

[0031] Implementation Method 2 Embodiment 2 is different from Embodiment 1 in that the processing regions 27 are arranged at regular intervals. In the semiconductor device according to Embodiment 1, when the processing regions 27 are arranged arbitrarily, a portion of the laser modified portion 36 becomes an unirradiated portion. In the unirradiated portion, the surface of the third metal film 24 remains exposed. Therefore, when the resin sealing material 42 is used for sealing, an interface between the third metal film 24 and the resin sealing material 42 is formed in a portion of the region, and the bonding strength is reduced.

[0032] Therefore, in this embodiment, the processing regions 27 are arranged to overlap at a certain interval to prevent the generation of unirradiated portions. As a result, the interface between the laser modified portion 36 and the resin sealing material 42 is uniformly formed, so the bonding strength is improved, and the reliability of the semiconductor device can be improved.

[0033] Implementation 3 In the third embodiment, the width of the laser modified portion 36 is at least 100 μm, which is different from the previous embodiments. In the semiconductor device according to the first embodiment, the nickel oxide layer on the surface of the laser modified portion 36 is sometimes reduced during the solder bonding process. In this case, the solder wets and spreads to the laser modified portion 36, and the width of the laser modified portion 36 becomes narrower. If the width is narrowed by more than a certain amount, after being sealed with the resin sealing material 42, the area where the laser modified portion 36 and the resin sealing material 42 are in contact becomes narrower, which becomes a major cause of reduced bonding strength.

[0034] Generally, when the reducing power of nickel oxide in the solder bonding process is strong, the following phenomenon is confirmed: nickel oxide is reduced in the area of ​​tens of μm of the laser modified part through the main solder bonding part of the surface electrode, and the solder wets and spreads. Therefore, the width of the laser modified part is formed to be at least 100 μm. As a result, since the area where the laser modified part and the sealing material are connected can be stably ensured, the bonding strength can be improved and the reliability of the semiconductor device can be achieved.

[0035] Implementation 4 Figure 8 1 is a cross-sectional view showing a semiconductor device according to Embodiment 4. Embodiment 4 is different from the previous embodiments in that the energy density supplied to the laser modification portion 36 is changed for each region.

[0036] In the semiconductor device according to Embodiment 1, in order to enhance the laser modification effect, it is necessary to increase the energy of the irradiated laser. Then, the influence of the energy spreads to the non-laser irradiated area, and as a result of the precipitation of the second metal film 22, its surface is oxidized, and solder wettability may be reduced.

[0037] Therefore, in the present embodiment, the energy density of the irradiated laser is reduced only in the area connected to the surface electrode solder joint 6. That is, the energy density of the laser irradiated to the laser modified portion 36a is smaller than that of the laser modified portion 36b. In this way, the influence of the reduced wettability of the solder in the non-laser irradiated area can be kept to a minimum. Even if the energy density is reduced, the surface of the laser modified portion 36a becomes a nickel oxide layer. Therefore, in the solder joining process, the solder will not wet and extend to the laser modified portion 36a. In addition, by maintaining the energy density of the laser irradiated to the laser modified portion 36b, the adhesion of the interface between the laser modified portion 36b and the resin sealing material 42 will not be damaged.

[0038] Implementation method 5 Embodiment 5 is different from the previous embodiments in that the laser absorption rate of each metal film is changed separately. In the semiconductor device according to Embodiment 1, it is considered that the laser irradiation energy is too high, or the laser absorption rate of the first metal film 20 or the second metal film 22 is higher than that of the third metal film 24. In this case, the heat generated by the laser irradiation causes the metal film to melt inside the semiconductor substrate, so that the electrical characteristics of the semiconductor element become abnormal.

[0039] Therefore, in this embodiment, the surface electrode is formed in such a manner that the laser absorption rate of the third metal film 24 is higher than that of the first metal film 20 and the second metal film 22. As a result, when the outermost surface of the third metal film 24 is irradiated with laser, the heat generated by the first metal film 20 and the second metal film 22 as the lower layer is reduced. As a result, the risk of the metal film melting due to the heat of laser irradiation can be reduced, so that the damage to the semiconductor element can be reduced.

[0040] Implementation 6 Embodiment 6 is different from the previous embodiments in that the total thickness of the first metal film 20 and the second metal film 22 is at least 1 μm or more, and the thickness of the third metal film 24 is 0.2 μm or less.

[0041] In the semiconductor device according to the first embodiment, as described above, the heat generated by laser irradiation causes abnormalities in the electrical characteristics of the semiconductor element. Therefore, in the present embodiment, the total thickness of the first metal film 20 and the second metal film 22 is set to at least 1 μm, and the thickness of the third metal film 24 is set to 0.2 μm or less. As a result, the laser processing target film becomes thinner and the laser processing non-target film becomes thicker, so that the nickel oxide layer can be formed at low power. As a result, damage to the semiconductor element caused by heat during laser processing can be reduced.

[0042] Implementation 7 Fig. 92 is a cross-sectional view showing a semiconductor device according to Embodiment 7. Embodiment 7 is different from the previous embodiments in that an ineffective cell region 44 is formed immediately below the laser modified portion 36 .

[0043] In the semiconductor device according to the first embodiment, as described above, the heat generated by laser irradiation causes abnormalities in the electrical characteristics of the semiconductor element. Therefore, in the present embodiment, the area directly below the laser modified portion 36 is set as an invalid cell region 44. The trench 32 and the oxide film 34 required for the function of the semiconductor element are not installed in the invalid cell region 44. As a result, the number of trenches 32 and oxide films 34 affected by the heat during laser processing is reduced, so that the damage to the semiconductor element function of the entire semiconductor device can be reduced.

[0044] Implementation 8 Fig.10 1 is a cross-sectional view showing a semiconductor device according to Embodiment 8. Embodiment 8 is different from the previous embodiments in that a barrier metal layer 46 is provided at the boundary between the first metal film 20 and the oxide film 34 .

[0045] In the semiconductor device according to Embodiment 1, as described above, the heat generated by laser irradiation causes abnormalities in the electrical characteristics of the semiconductor element. Therefore, in this embodiment, a barrier metal layer 46 is provided at the boundary between the first metal film 20 and the oxide film 34. Thus, it is possible to prevent the aluminum (Al) forming the first metal film 20 from being diffused solid to the semiconductor substrate interface, thereby reducing the damage to the semiconductor element caused by the heat during laser processing.

[0046] Implementation method 9 Embodiment 9 is different from the previous embodiments in that the cover film 28 is formed so as to increase the reflectivity of the laser light 26. In the semiconductor device according to Embodiment 1, the cover film 28 is arranged at the outermost periphery of the surface electrode solder joint 6. An oxide film or an insulating film may be arranged below the cover film 28. In this case, the irradiation of the laser light 26 may damage the surface of the oxide film or the insulating film.

[0047] Therefore, in this embodiment, the cover film 28 is formed so as to increase the reflectivity of the laser light 26. A polyimide film with a low refractive index can be exemplified as a film with a high reflectivity of the laser light 26. Thus, damage to the oxide film or the insulating film by the laser light 26 can be minimized, and thus, it is expected that the quality of the semiconductor device can be improved.

[0048] Embodiment 10 Fig.111 is a plan view showing a semiconductor element according to Embodiment 10. Embodiment 10 is different from the previous embodiments in that a semiconductor element information forming region 48 is provided in a part of the laser modified portion 36 .

[0049] In the semiconductor device according to the first embodiment, since the laser 26 is irradiated to the entire area of ​​the laser modified portion 36, there is a problem that the laser irradiation time becomes long. Therefore, in the present embodiment, a semiconductor element information forming region 48 is provided to a part of the laser modified portion 36. The semiconductor element information forming region 48 is different from the laser modified portion 36, and only the portion where the semiconductor element information is printed is irradiated with the laser. Thus, since the number of laser irradiation pulses is reduced, the laser irradiation time can be shortened.

[0050] Fig.12 and Fig.13 It is a top view showing the semiconductor element information formation region involved in the tenth embodiment. Fig.12 1 shows a case where a two-dimensional code is presented by the laser modified portion 36. That is, a two-dimensional code is presented by the laser modified portion 36 shown in black and the third metal film 24 shown in white. Fig.13 The figure shows a case where a two-dimensional code is presented in a region not irradiated by laser. That is, a two-dimensional code is presented by the laser modified portion 36 shown in white and the third metal film 24 shown in black. In any case, by printing semiconductor element information by laser irradiation, the traceability of semiconductor elements can be improved.

[0051] In addition to the semiconductor element information, for example, a mark indicating the position information of the semiconductor element may be printed in advance. In this case, during the semiconductor device assembly process, the position information of the semiconductor element can be identified on the device side, so the visibility of the semiconductor element is improved, and it can be expected that the assemblability of the semiconductor device will be improved.

[0052] Implementation 11 Fig.14 1 is a plan view showing a semiconductor element according to Embodiment 11. Embodiment 11 is different from the previous embodiments in that laser irradiation is performed in a stripe shape.

[0053] In the semiconductor device involved in the first embodiment, since the surface electrode solder joint portion 6 is continuous, there is a problem of thermal stress generated at the interface of the solder joint. Therefore, in this embodiment, the interface of the solder joint is divided into a plurality of parts by laser irradiation in a stripe shape, as in the laser modified portion 36c. Thus, the thermal stress generated at the interface of the solder joint can be dispersed during the power cycle test.

[0054] Fig.152 is a cross-sectional view showing a semiconductor device according to Embodiment 11. By forming the laser modified portion 36c into a stripe shape, a void 50 is formed below the surface electrode solder joint portion 6. That is, since the solder joint interface is divided into a plurality of portions, the thermal stress generated during the power cycle test can be dispersed.

[0055] Implementation 12 Fig.16 1 is a plan view showing a semiconductor element according to Embodiment 12. Embodiment 12 is different from the previous embodiments in that laser irradiation is performed in a grid pattern.

[0056] In the semiconductor device according to the first embodiment, since the surface electrode solder joint portion 6 is continuous, there is a problem of thermal stress generated at the interface of the solder joint. Therefore, in this embodiment, the interface of the solder joint is divided into a plurality of parts by laser irradiation in a grid shape, as in the laser modified portion 36d. Thus, the thermal stress generated at the interface of the solder joint can be dispersed during the power cycle test.

[0057] Implementation 13 Fig.17 1 is a plan view showing a semiconductor element according to Embodiment 13. Embodiment 13 is different from the previous embodiments in that laser irradiation is also performed on the surface electrode lead pad portion 8 .

[0058] In the semiconductor device according to the first embodiment, when solder bonding is performed in the assembly process of the semiconductor element 2, solder may scatter to the surface electrode lead pad portion 8. Then, when bonding is performed with aluminum wire or the like, a problem of aluminum wire bonding failure occurs.

[0059] Therefore, in this embodiment, the surface of the surface electrode lead pad portion 8 is irradiated with laser to form the laser modified portion 36e. This can suppress solder wetting of the surface electrode lead pad portion 8 when solder scatters, and thus improve the yield in the assembly process.

[0060] Implementation 14 Fig.18 1 is a cross-sectional view showing a semiconductor device before laser irradiation according to Embodiment 14. Embodiment 14 is different from the previous embodiments in that laser irradiation is also performed on the back electrode.

[0061] The semiconductor element involved in the embodiment 14 includes a back electrode 52. The back electrode 52 has a fourth metal film 54 and a fifth metal film 56. The back electrode 52 is joined to a heat sink formed of a conductive material such as copper by solder in the assembly process. As a result, a solder joint area is formed along the shape of the back electrode 52.

[0062] Consider the case where a thermal cycle test is performed on the semiconductor device described above to apply thermal stress. In this case, due to the difference in linear expansion coefficients of the materials, thermal stress is concentrated on the back electrode and the solder joint area, and the corner of the solder joint area peels off. As a result, the following problem arises: the semiconductor device deteriorates due to cracks in the solder. Therefore, in this embodiment, laser irradiation is also performed on the back electrode 52.

[0063] Fig.19 1 is a cross-sectional view showing a semiconductor device after resin sealing according to Embodiment 14. Here, the semiconductor device after solder bonding and resin sealing are performed on the front electrode side and the back electrode side is shown.

[0064] When laser irradiation is applied to a portion of the back electrode side, a laser modified portion 36f is formed on the surface layer of the fourth metal film 54. Then, solder bonding is performed, but the solder 38 does not wet and spread on the laser modified portion 36f. On the other hand, solder bonding is performed on the portion other than the laser modified portion 36f because the solder 38 wets and spreads. At this time, an intermetallic compound layer 58 is formed. Then, when resin sealing is performed, the laser modified portion 36f is covered with the resin sealing material 42.

[0065] Fig. 20 It is a top view showing the back electrode before laser irradiation according to the fourteenth embodiment. Fig.21 3 is a top view showing the back electrode after laser irradiation according to Embodiment 14. When forming the laser modified portion 36f, laser irradiation is performed in such a way that the corners of the unirradiated portion are rounded. The unirradiated portion becomes the solder joint region 55. Thus, the stress applied to the corners of the solder joint region can be dispersed, and peeling of the corners can be prevented.

[0066] In addition, although the embodiment in which the laser irradiation is performed on the back electrode in such a manner that the corners of the unirradiated portion are rounded is shown here, the laser irradiation may be performed on other regions in such a manner that the corners of the unirradiated portion are rounded.

[0067] Implementation 15 Embodiment 15 is different from the previous embodiments in that the laser is irradiated to the outermost periphery of the semiconductor substrate 30. In the semiconductor device according to Embodiment 1, when thermal stress such as thermal cycle is applied, shear stress from the resin sealing material 42 is applied to the outermost periphery of the semiconductor element 2. As a result, the problem of interface peeling between the resin sealing material 42 and the semiconductor element 2 occurs.

[0068] Therefore, in the present embodiment, laser light is irradiated onto the outermost peripheral portion of the semiconductor substrate 30. This can improve the interfacial bonding strength between the resin sealing material 42 and the semiconductor substrate 30, thereby achieving high reliability of the semiconductor device.

[0069] Fig. 22 1 is a cross-sectional view showing an end of a semiconductor element before resin sealing according to Embodiment 15. An oxide film 34 is formed on a semiconductor substrate 30. The oxide film 34 is covered with an overcoat film 60. The overcoat film 60 is covered with a cover film 28.

[0070] The outermost peripheral portion of the semiconductor substrate 30 is formed with a laser modified portion 36g by laser irradiation. The cover film 28 does not cover the outermost peripheral portion of the semiconductor element 2. Therefore, in the subsequent resin sealing step, the interface bonding strength between the resin sealing material 42 and the semiconductor substrate 30 is improved due to the effect of the laser modified portion 36g.

[0071] Fig.23 3 is a plan view showing a semiconductor element before resin sealing according to Embodiment 15. The laser modified portion 36g is formed on all outermost peripheral portions of the semiconductor element 2. This can improve the interfacial bonding strength between the resin sealing material 42 and the semiconductor substrate 30.

[0072] Implementation 16 Fig.24 16 is a top view of a semiconductor element before resin sealing according to Embodiment 16. Embodiment 16 is different from the previous embodiments in that the corners of the semiconductor substrate 30 are irradiated with laser. The shear stress described in Embodiment 15 is concentrated at the corners of the semiconductor element. Therefore, in this embodiment, the corners of the semiconductor substrate 30 are irradiated with laser. That is, a laser modified portion 36h is formed at the corners of the semiconductor substrate 30. Thus, by locally improving the interface bonding strength between the resin sealing material 42 and the semiconductor substrate 30, it is possible to achieve high reliability of the semiconductor device.

[0073] Implementation 17 Embodiment 17 is different from the previous embodiments in that the semiconductor substrate 30 is formed of silicon carbide.

[0074] As a material for semiconductor substrates, silicon is currently the most popular. Compared with silicon substrates, silicon carbide has a longitudinal elastic coefficient 2.6 times larger and a linear expansion coefficient 1.5 times larger, and its bonding strength with resin sealing materials is less than 2 / 3. Therefore, in existing semiconductor devices, if a silicon carbide substrate is used for power cycle testing, interface peeling between the sealing material and the surface of the semiconductor element is likely to occur. In other words, the reliability of the semiconductor device is reduced.

[0075] However, in the semiconductor device according to the present disclosure, the adhesion between the sealing material and the semiconductor element surface is expected to be improved by the roughening process using laser modification. Therefore, even when a silicon carbide substrate is used, the reliability of the semiconductor device can be expected to be improved.

[0076] In existing semiconductor devices, a cover film such as a polyimide film is used as a stress buffer layer. Therefore, it is necessary to determine the width of the stress buffer layer in consideration of not only the characteristics caused by the material such as viscosity and photosensitivity, but also the accuracy deviation caused by the coating device such as the coating position, air pressure, and coating amount.

[0077] However, in the semiconductor device involved in the first embodiment, if only the processing accuracy of the laser is considered, the size of the processing area can be determined. That is, the processing deviation can be reduced compared with the existing semiconductor device. Therefore, by using expensive silicon carbide for the semiconductor substrate of the present disclosure, it is expected that the cost of the semiconductor device can be reduced compared with the past.

[0078] In addition, although the semiconductor substrate is formed of silicon carbide in this embodiment, it can also be formed of a wide bandgap semiconductor having a large bandgap like silicon carbide. Examples of the wide bandgap semiconductor include gallium nitride-based materials and diamond. Description of symbols

[0079] 2 Semiconductor components 4 Back electrode 6 Surface electrode solder joint 8 Surface electrode lead pad 16 Sealing material 18 Laser modification department 26 Laser 27 Processing Area 28 Covering film 34 Oxide film 36 Laser modification department 36a Laser modification department 36b Laser modification department 36c Laser modification department 36d Laser modification department 36e Laser Modification Department 36f Laser modification department 36g Laser modification department 36h Laser modification department 37 Solder joint area 42. Resin sealing material 44 Invalid cell area 46 Barrier Metal Layer 48Semiconductor device information formation area 52 Back electrode 55 Solder joint area 100 semiconductor devices.

Claims

1. A semiconductor device, The semiconductor device comprises a surface electrode solder joint portion, solder, a resin sealing material, and a semiconductor element mounted under the surface electrode solder joint portion, wherein: The surface electrode solder joint portion has: A first laser modified portion after oxidizing and roughening the outermost surface; and a first solder joint region to be joined with the solder, The laser modified portion is covered with the resin sealing material.

2. The semiconductor device according to claim 1, wherein The first laser modified portion is formed by pulse irradiation of laser light.

3. The semiconductor device according to claim 2, wherein: The first laser modified portion is formed by arranging a plurality of processing regions, which are regions that can be processed by one pulse irradiation, so as to surround the outer periphery of the surface electrode solder joint portion.

4. The semiconductor device according to claim 3, wherein: The processing areas are arranged at certain intervals so that adjacent areas overlap each other.

5. The semiconductor device according to claim 1, wherein: The first laser modified portion has a width of 100 μm or more.

6. The semiconductor device according to claim 1, wherein: In the first laser modified portion, the degree of oxidation and roughening is smaller in a region away from the outermost peripheral portion of the surface electrode solder joint portion than in a region close to the outermost peripheral portion of the surface electrode solder joint portion.

7. The semiconductor device according to claim 1, wherein The semiconductor element includes an effective cell region having functionality and an ineffective cell region having no functionality. The ineffective cell region is located directly below the first laser modified portion.

8. The semiconductor device according to claim 1, wherein The semiconductor element has an oxide film on the surface. A barrier metal layer is formed at a boundary between the oxide film and the surface electrode solder joint portion.

9. The semiconductor device according to claim 2, wherein: including a cover film covering the outer edge of the surface electrode solder joint portion, The cover film is formed of a material having a higher reflectivity of the laser light than that of the surface electrode solder joint portion.

10. The semiconductor device according to claim 1, wherein The first laser modified portion has a semiconductor device information forming region in which a desired code is embedded.

11. The semiconductor device according to claim 1, wherein The first solder bonding region is divided into a plurality of regions.

12. The semiconductor device according to claim 11, wherein The first laser modified portion is formed in a stripe shape on the surface layer of the surface electrode solder joint portion.

13. The semiconductor device according to claim 11, wherein The first laser modified portion is formed in a grid shape on the surface layer of the surface electrode solder joint portion.

14. The semiconductor device according to claim 1, wherein: Also includes a surface electrode lead pad portion, The surface electrode lead pad portion has a second laser modified portion in which the outermost surface is oxidized and roughened.

15. The semiconductor device according to claim 1, wherein Also includes a back electrode, The back electrode has: a third laser modified portion after oxidizing and roughening the outermost surface; as well as a second solder bonding region bonded to the solder, Processing is performed to round the corners of the solder joint area.

16. The semiconductor device according to claim 1, wherein The semiconductor element has a fourth laser modified portion in the outermost peripheral portion, in which the outermost surface is oxidized and roughened.

17. The semiconductor device according to claim 1, wherein: The semiconductor element has a fifth laser modified portion at a corner of the outermost peripheral portion, in which the outermost surface is oxidized and roughened.

18. The semiconductor device according to claim 1, wherein The semiconductor element is formed of a wide bandgap semiconductor.

19. The semiconductor device according to claim 18, wherein: The wide bandgap semiconductor is silicon carbide, gallium nitride-based material or diamond.

20. A method for manufacturing a semiconductor device, A method for manufacturing a semiconductor device including a surface electrode solder joint, solder, and a sealing resin material, characterized in that: include: a step of forming a laser modified portion by irradiating a portion of the surface electrode solder joint portion with a laser pulse; a step of performing solder joining on the surface electrode solder joining portion; and and performing resin sealing using the resin sealing material so as to cover the laser modified portion.

21. The method for manufacturing a semiconductor device according to claim 20, wherein: The surface electrode solder joint portion comprises an upper metal film and a lower metal film, The lower metal film has a higher laser absorption rate than the upper metal film.

22. The method for manufacturing a semiconductor device according to claim 20, wherein: The surface electrode solder joint portion comprises an upper metal film and a lower metal film, The thickness of the lower metal film is 1 μm or more. The thickness of the upper metal film is less than 0.2 μm.

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