Semiconductor device with switchable semiconductor element and method for manufacturing same

Abstract

The present invention relates to a semiconductor device (2) comprising a switchable semiconductor element (4) having at least one control contact (6) with a control contact contact surface (12) and at least one load contact (8) with a load contact contact surface (14) larger than the control contact contact surface (12). To achieve an increased service life of the semiconductor device (2), it is proposed that an electrically insulating material be applied by an additive process to a region (34) of the load contact surface (14) adjacent to the control contact contact surface (12) to form an electrically insulating layer (26), and that a metallic material be applied by a thermal spray process to the control contact surface (12) and the electrically insulating layer (26) to form a metallic control contact element (22) with a control contact element contact surface (24) larger than the control contact surface (12), the control contact element (22) partially overlapping the load contact surface (14).

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device having a switchable semiconductor element.

[0002] Furthermore, the invention relates to a power converter comprising at least one such semiconductor device.

[0003] Furthermore, the present invention relates to a method for manufacturing a semiconductor device comprising a switchable semiconductor element. [Background technology]

[0004] Such semiconductor module devices are typically used in power converters. A power converter is understood to mean, for example, a rectifier, an inverter, a converter, or a DC-DC converter. The switchable semiconductor elements used in the semiconductor module devices are, for example, transistors, triacs, or thyristors. The transistors are, for example, designed as insulated gate bipolar transistors (IGBTs), field-effect transistors, or bipolar transistors. Such switchable semiconductor elements typically have control terminals and load terminals, each having a contact area, for example a contact pad, with the contact area of ​​the load terminal generally having a larger planar surface than the contact area of ​​the control terminal. Summary of the Invention [Problem to be solved by the invention]

[0005] Aluminum wiring materials, such as aluminum wire bonds, are typically used to connect switchable semiconductor elements, which is one of the factors limiting the service life of modern assembly and connection technologies. For example, copper-based assembly and connection technologies are expected to have a significantly longer service life because copper has better material properties, such as a higher elastic modulus and higher electrical conductivity, especially compared to aluminum. Copper-based assembly and connection technologies include, among others, copper wire bonding, pressure contact using copper bus bars or copper lead frames, and laser welding of copper terminals. However, these technologies require relatively high compressive forces, as in the case of copper wire bonding, or relatively high temperatures at certain locations, as in the case of laser welding, which increases the risk of damage to semiconductor components during the manufacture of semiconductor devices.

[0006] Against this background, the object of the present invention is to describe a semiconductor device with a switchable semiconductor element which allows for a longer service life. [Means for solving the problem]

[0007] According to the present invention, this problem is solved by a semiconductor device comprising a switchable semiconductor element having at least one control contact having a control contact surface and at least one load contact having a load contact surface larger than the control contact surface, wherein an electrical insulating layer is applied by an additive method to the region of the load contact surface adjacent to the control contact surface to form the electrical insulating layer, and a metallic material is applied by a thermal spraying method to the control contact surface and to the electrical insulating layer to form a metallic control contact element having a control contact element contact surface larger than the control contact surface, and the control contact element partially overlaps the load contact surface.

[0008] Furthermore, this object is achieved according to the invention by a power converter comprising at least one such semiconductor device.

[0009] Furthermore, according to the present invention, this problem is solved by a method for manufacturing a semiconductor device comprising a switchable semiconductor element having at least one control contact having a control contact surface and at least one load contact having a load contact surface larger than the control contact surface, wherein an electrical insulating layer is applied by an additive method to an area of ​​the load contact surface adjacent to the control contact surface to form the electrical insulating layer, and a metallic material is applied by a thermal spraying method to the control contact surface and the electrical insulating layer to form a metallic control contact element having a control contact element contact surface larger than the control contact surface, so that the control contact element partially overlaps the load contact surface.

[0010] The advantages and preferred configurations listed below with respect to the semiconductor device may be correspondingly applied to the power converter and method.

[0011] The present invention is based on the idea of ​​increasing the service life of semiconductor devices by using metallic control contact elements or buffer layers for contacting the control contacts of switchable semiconductor elements. The metallic control contact elements are made of a metallic material, such as silver, gold, copper, zinc, molybdenum, or an alloy thereof, and are connected to the control contacts of the switchable semiconductor elements and an electrically insulating layer, which is made of an electrically insulating material, such as a polymer, and is applied to the area of ​​the load contact surface of the semiconductor element adjacent to the control contact surface. Thus, the control contact elements are connected to the load contact surface of the semiconductor element via the electrically insulating layer and are electrically insulated from the load contact surface. Furthermore, the control contact elements partially overlap the load contact surface in the adjacent area. The control contact elements have a control contact element contact surface with a larger plane than the control contact surface of the control contact. The electrically insulating material is applied by an additive method, for example in liquid form, to form an electrically insulating layer having a thickness in the range of, for example, 0.1 μm to 100 μm, while the metallic material is applied by a thermal spraying method, for example by a plasma spraying method. The metallic layer applied by a thermal spraying method may have a layer thickness in the range of 1 μm to 250 μm, in particular 5 μm to 100 μm.

[0012] Such a buffer layer distributes the forces that occur during contact, thereby minimizing thermomechanical stresses that occur, for example, during copper wire bonding, which favorably affects the service life of the semiconductor device. The increased contact surface allows for a thicker and therefore more stable contact with the bond wire. In addition to improved force distribution, the larger, thicker buffer layer compared to the control contact ensures a balance of tolerances, so that pressure contact, especially with copper bus bars, is improved in terms of its service life. Furthermore, the larger, thicker buffer layer compared to the control contact allows for a melting area in the metal, which leads to improved service life of the semiconductor device when the copper terminal is contacted by laser welding.

[0013] In a further embodiment, the electrically insulating material is intended to contain a polymer having a glass transition temperature above 150°C, particularly above 250°C. Such polymers may be polyimides, polyamides, or polyamideimides, among others. Electrically insulating layers containing such polymers are robust and not damaged when coated by thermal spraying. Furthermore, semiconductor devices having such electrically insulating layers exhibit improved service life, especially in the event of large temperature fluctuations.

[0014] In a further embodiment, the electrically insulating material may contain a polymer having thermoplastic properties. The metal particles sprayed by the thermal spraying method connect to the electrically insulating layer by the thermoplastic properties of the polymer, particularly by adhesion. Such bonding improves the adhesion of the buffer layer, thereby improving the service life of the semiconductor device.

[0015] In a further embodiment, it is contemplated that the electrically insulating material is applied by spraying, dispensing, or screen printing. Such application methods allow the electrically insulating material to be applied in liquid form, which allows it to flow out onto the chip surface and therefore does not create perpendicular angles. This promotes good adhesion on the chip and therefore high long-term strength.

[0016] In a further embodiment, the electrically insulating material is assumed to be thixotropized or to have thixotropic properties. Thixotropization is understood to mean, in particular, that the viscosity behavior of the electrically insulating material is affected so that it does not flow up to a certain shear stress and then flows. Furthermore, thixotropization also reduces the coefficient of expansion, which facilitates the coating process.

[0017] In a further embodiment, it is envisaged that the electrically insulating material contains pyrogenic silica, such as Aerosil, which allows for suitable thixotropy to be achieved.

[0018] In a further embodiment, a metallic material is applied to the load contact surface by a thermal spraying method to form a metallic load contact element having a load contact element contact surface, the load contact element being electrically insulated from the control contact element. The thermally sprayed metal layer, like the control contact element, can have a layer thickness in the range of 1 μm to 250 μm, particularly 5 μm to 100 μm. Such a buffer layer on the load contact surface distributes the forces generated during contact, thereby minimizing thermomechanical stresses that occur, for example, during copper wire bonding, which favorably affects the service life of the semiconductor device. In addition to improved force distribution, a thicker buffer layer compared to the load contact ensures a balance of tolerances, thereby improving the service life of pressure contacts, especially with copper busbars. Furthermore, a thicker buffer layer compared to the load contact allows for a melted area in the metal, thereby improving the service life of semiconductor devices when connecting copper terminals by laser welding.

[0019] In a further embodiment, it is envisaged that the metal material is applied in such a way that the control contact element contact surface and the load contact element contact surface are flush-ended, which simplifies the further contacting process and ensures uniform contact, which has a beneficial effect on the service life of the semiconductor device.

[0020] In a further embodiment, it is envisaged that the metallic control contact element and / or the metallic load contact element have a porosity in the range of 1% to 50%, in particular 1% to 5%. The increased porosity acts to balance tolerances, particularly in pressure connections. In particular, during subsequent operation of the semiconductor component, for example when switching a power semiconductor on and off, different expansion coefficients of the semiconductor and the metals used in the metallic contact elements can be compensated for by the porosity, which has a beneficial effect on the service life of the semiconductor device.

[0021] In a further embodiment, it is envisioned that metal particles of different particle sizes are introduced into the plasma jet during the thermal spraying process. For example, the metal particles are melted by the plasma jet, and their surfaces are partially vaporized. The properties of the deposited layer can be selectively adjusted not only by the type and size of the particles, plasma parameters such as temperature and plasma pressure, but also by external conditions such as deposition rate, heating temperature, atmosphere, etc. In this way, high long-term strength of the applied layer can be achieved.

[0022] In the following, the invention will be described and explained in more detail on the basis of examples shown in the drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 shows a schematic diagram of a first embodiment of a semiconductor device in cross section. [Figure 2] 1 shows a schematic diagram of a second embodiment of a semiconductor device in cross section. [Figure 3] 1 shows a schematic diagram of a first method for manufacturing a semiconductor device. [Figure 4] 1 shows a schematic diagram of a second method for manufacturing a semiconductor device. [Figure 5] 1 shows a schematic diagram of a third embodiment of a semiconductor device in cross section. [Figure 6] 1 shows a schematic diagram of a power converter. DETAILED DESCRIPTION OF THE INVENTION

[0024] The examples described below are preferred embodiments of the present invention. In the examples, the described components of the embodiments each represent individual features of the present invention that should be considered independently of each other, and these features also further shape the present invention independently of each other, and therefore should be considered as components of the present invention individually or in combinations other than those shown. Furthermore, the described embodiments can also be supplemented by additional features of the present invention that have already been described.

[0025] The same reference symbols have the same meaning in the different figures.

[0026] FIG. 1 shows a schematic diagram of a first embodiment of a semiconductor device 2, which includes a vertical switchable semiconductor element 4. For example, the switchable semiconductor element 4 is designed as an insulated gate bipolar transistor (IGBT). Further examples of the switchable semiconductor element 4 are triacs, thyristors, or other transistor types, such as field-effect transistors and bipolar transistors. The switchable semiconductor element 4 includes a gate terminal G, a collector terminal C, and an emitter terminal E. The gate terminal G is connected internally to a control contact 6, which is designed as a gate contact, while the emitter terminal E is connected internally to a load contact 8, which is designed as an emitter contact. Opposite the control contact 6 and the load contact 8 of the semiconductor device 2, a further load contact 10 is arranged. This further load contact 10 is connected internally to the collector terminal C of the vertical semiconductor element 4, which is designed as a collector contact. Since this is a vertical semiconductor element in FIG. 1, the load contacts 8 and 10 are arranged on opposite sides.

[0027] The control contact 6 and the load contacts 8, 10 each comprise a metallic contact pad configured for connecting at least one wiring means, such as a bond wire. Furthermore, the control contact 6 has a control contact surface 12, and the load contact 8 has a load contact surface 14, the control contact surface 12 being substantially smaller than the load contact surface 14. Furthermore, the control contact surface 12 and the load contact surface 14 are designed as rectangular or square and are arranged flush with the semiconductor surface 16.

[0028] The control contact 6 is adjacent to an electrically insulating guard ring 18, which for example protrudes from the semiconductor surface 16 and thus from the control contact surface 12 and the load contact surface 14. Furthermore, an electrically insulating intermediate layer 20 is arranged between the control contact 6 and the load contact 8, which likewise protrudes from the semiconductor surface 16, for example. For example, the electrically insulating guard ring 18 and the electrically insulating intermediate layer 20 comprise a dielectric material, in particular polyimide.

[0029] The metallic control contact element 22 is connected to the control contact surface 12 of the control contact 6 in a planar manner, and has a control contact element contact surface 24 arranged on a side remote from the control contact surface 12 and larger than the control contact surface 12. For example, the control contact element contact surface 24 is at least four times, in particular at least eight times, larger than the control contact surface 12. The metallic control contact element 22 is made of at least one metallic material. At least in the region of the control contact element contact surface 24, the metallic control contact element 22 contains aluminum, silver, gold, copper, zinc, molybdenum, or an alloy thereof.

[0030] Furthermore, the metallic control contact element 22 partially overlaps the load contact surface 14 of the load contact 8, and an electrical insulating layer 26 is arranged in the overlapping area between the metallic control contact element 22 and the load contact surface 14 of the load contact 8. The electrical insulating layer 26 is made of an electrically insulating material, particularly a dielectric material. The electrically insulating material may contain a polymer with a glass transition temperature above 150°C, particularly above 250°C, such as polyimide, polyamide, and polyamideimide, among others. The electrically insulating material is applied in liquid form, for example, by film or photostructuring. Application is carried out by additive methods, for example, by jetting, particularly ink jetting, dispensing, or screen printing. The polymer can flow onto the load contact surface 14, thus avoiding perpendicular angles, which promotes good adhesion and therefore high long-term strength. The electrically insulating material may be thixotropic or have thixotropic properties. For example, pyrogenic silica, especially Aerosil, is added to the liquid polymer.

[0031] After the electrical insulation layer 26 is applied and dried, a metallic material is applied to the control contact surface 12 and the electrical insulation layer 26 by a thermal spraying method, e.g., plasma spraying, to form the metallic control contact element 22, so that the metallic control contact element 22 is materially connected to the control contact surface 12 and the electrical insulation layer 26. For example, in a thermal spraying method, metal particles of different particle sizes, particularly copper and / or molybdenum particles, are introduced into a plasma jet, where the particles melt and their surfaces partially vaporize. The metallic control contact element 22 manufactured by a thermal spraying method has a porosity ranging from 1% to 50%, particularly from 1% to 5%. The polymer may have thermoplastic properties to form an adhesive connection with the sprayed metal particles.

[0032] Such a coating allows, for example, contact on the gate side with wiring means having a larger diameter, in particular bond wires. Furthermore, the coating allows copper-based assembly and connection techniques, such as copper wire bonding, in particular pressure contact with copper bus bars or copper lead frames, or laser welding of copper terminals, thereby achieving a longer service life. The risk of damage to the semiconductor component 4 due to relatively high compressive forces, as in the case of copper wire bonding, or relatively high temperatures at certain points, as in the case of laser welding, is minimized by the described coating.

[0033] FIG. 2 shows a schematic cross-sectional view of a second embodiment of a semiconductor device 2. Furthermore, a metallic material is applied to the load contact surface 14 by a thermal spraying method to form a metallic load contact element 28 having a load contact element contact surface 30, which is arranged electrically insulated from the control contact element 22, and the control contact element contact surface 24 and the load contact element contact surface 30 end up flush, in particular flush in a planar manner. In particular, in a thermal spraying method, in particular plasma spraying, the structuring is carried out by a mold between the semiconductor element 4 and a spraying device, in particular a plasma spray nozzle. The further configuration of the semiconductor device 2 of FIG. 2 corresponds to the configuration of FIG. 1.

[0034] 3 shows a schematic diagram of a first method for manufacturing a semiconductor device 2, in particular including a vertical switchable semiconductor element 4. The steps of the manufacturing method are shown in a top view on the left and in a cross-sectional view on the right in FIG. 3. The semiconductor element 4 comprises a control contact 6 having a control contact surface 12 and a load contact 8 having a load contact surface 14 that is several times larger than the control contact surface 12. The control contact 6 of the semiconductor element 4 is integrated into a corner 32 of the rectangular or square load contact surface 14 and is spaced apart from the load contact 8 via an electrically insulating intermediate layer 20, thus providing electrical insulation.

[0035] The application A of the electrically insulating material to the load contact surface 14 and to the region 34 of the electrically insulating intermediate layer 20 adjacent to the control contact surface 12 is carried out by an additive method to form the electrically insulating layer 26. The electrically insulating material may contain, inter alia, a polymer and is applied in liquid form, for example, by film or photostructuring. The additive method may include jetting, in particular ink jetting, dispensing, or screen printing.

[0036] After the electrical insulation layer 26 has dried, a further step involves applying a metallic material B by thermal spraying to the control contact contact surface 12 and the electrical insulation layer 26 to form the metallic control contact element 22 and to the load contact contact surface 14 to form the metallic load contact element 28. The load contact element 28 is electrically insulated from the control contact element 22. Thermal spraying techniques include, for example, plasma spraying. For example, in thermal spraying, metal particles of different particle sizes, particularly copper and / or molybdenum particles, are introduced into a plasma jet, melting the particles and partially vaporizing their surfaces. The control contact element contact surface 24 of the control contact element 22 and the load contact element contact surface 30 of the load contact element 28 end up flush with each other. The further configuration of the semiconductor device 2 in FIG. 3 corresponds to the configuration in FIG. 2.

[0037] 4 shows a schematic diagram of a second method for manufacturing a semiconductor device 2, in which the control contacts 6 of the semiconductor element 4 are arranged substantially centrally within a rectangular or square load contact surface 14 that is many times larger than the control contact surface 12. The control contacts 6 are arranged spaced apart from, and therefore electrically isolated from, the load contacts 8 via an electrically insulating intermediate layer 20 that surrounds them.

[0038] Application A of electrical insulating material is applied to the area 34 of the load contact surface 14 and the electrically insulating interlayer 20 adjacent to the control contact surface 12, toward the edge center 36 of the rectangular or square load contact surface 14.

[0039] A metallic material is applied B to the control contact contact surface 12 and the electrical insulating layer 26 by thermal spraying to form the metallic control contact element 22 adjacent the edge center 36 of the load contact contact surface 14, and a via 38 is formed by thermal spraying to conductively connect the control contact 6 to the control contact element 22. A further configuration of the manufacturing method of Figure 4 corresponds to the manufacturing method of Figure 3.

[0040] FIG. 5 shows a schematic cross-sectional view of a third embodiment of a semiconductor device 2, in which a connecting element 40 is connected to the contact surface 24 of the control contact element, particularly by material bonding. A liquid electrically insulating material is applied in a thixotropic state, which flows down the chip edge 42 in a controlled manner and solidifies, thereby forming a chip corner isolation 44. For example, the electrically insulating material has a dielectric strength of more than 150 kV / mm. Such a chip corner isolation 44 minimizes the risk of sparkover to the connecting element 40, for example, when the saw edge of the semiconductor element 4 is at a lower potential than the additional load contact 10. The further configuration of the semiconductor device 2 in FIG. 5 corresponds to the configuration in FIG. 4.

[0041] FIG. 6 shows a schematic diagram of a power converter 46, which exemplarily comprises the semiconductor device 2.

[0042] In summary, the present invention relates to a semiconductor device 2 comprising a switchable semiconductor element 4 having at least one control contact 6 with a control contact surface 12 and at least one load contact 8 with a load contact surface 14 larger than the control contact surface 12. To achieve an increased service life of the semiconductor device 2, it is proposed that an electrically insulating material is applied by an additive method to a region 34 of the load contact surface 14 adjacent to the control contact surface 12 to form an electrically insulating layer 26, and that a metallic material is applied by a thermal spray method to the control contact surface 12 and to the electrically insulating layer 26 to form a metallic control contact element 22 with a control contact element contact surface 24 larger than the control contact surface 12, the control contact element 22 partially overlapping the load contact surface 14. [Explanation of symbols]

[0043] 2...semiconductor device, 4...semiconductor element, 6...control contact portion, 8...load contact portion, 10...load contact portion, 12...control contact portion contact surface, 14...load contact portion contact surface, 16...semiconductor surface, 18...electrically insulating protective ring, 20...electrically insulating intermediate layer, 22...metallic control contact element, 24...control contact element contact surface, 26...electrically insulating layer, 28...metallic load contact element, 30...load contact element contact surface, 32...corner, 34...area, 36...edge center, 38...path, 40...connection element, 42...chip edge, 44...chip corner insulator, 46...power converter, C...collector terminal, E...emitter terminal, G...gate terminal

Claims

1. A semiconductor device (2) comprising a switchable semiconductor element (4) having at least one control contact (6) with a control contact contact surface (12) and at least one load contact (8) with a load contact contact surface (14) larger than the control contact contact surface (12), an electrically insulating material is applied by an additive process to a region (34) of the load contact surface (14) adjacent to the control contact surface (12) to form an electrically insulating layer (26); a metallic material is applied to the control contact contact surface (12) and the electrical insulating layer (26) by a thermal spraying process to form a metallic control contact element (22) having a control contact element contact surface (24) larger than the control contact contact surface (12); The control contact element (22) partially overlaps the load contact surface (14). Semiconductor device (2).

2. 2. The semiconductor device (2) according to claim 1, wherein the electrically insulating material contains a polymer having a glass transition temperature point above 150°C, in particular above 250°C.

3. 3. The semiconductor device (2) according to claim 1 or 2, wherein the electrically insulating material comprises a polymer with thermoplastic properties.

4. 4. The semiconductor device (2) according to any one of claims 1 to 3, wherein the electrically insulating material is applied by spraying, dispensing or screen printing.

5. 5. The semiconductor device (2) according to any one of claims 1 to 4, wherein the electrically insulating material is thixotropized or has thixotropic properties.

6. 6. The semiconductor device (2) of claim 5, wherein said electrically insulating material comprises pyrogenic silica.

7. the metallic material is applied to the load contact surface (14) by the thermal spray process to form a metallic load contact element (28) having a load contact element contact surface (30); The load contact element (28) is arranged electrically insulated from the control contact element (22). A semiconductor device (2) according to any one of claims 1 to 6.

8. 8. The semiconductor device (2) of claim 7, wherein the metallic material is applied so that the control contact element contact surface (24) and the load contact element contact surface (30) end in the same plane.

9. 9. The semiconductor device (2) according to claim 7 or 8, wherein the metallic control contact element (22) and / or the metallic load contact element (28) have a porosity in the range of 1% to 50%, in particular 1% to 5%.

10. A power converter (46) comprising at least one semiconductor device (2) according to any one of claims 1 to 9.

11. A method for manufacturing a semiconductor device (2) comprising a switchable semiconductor element (4) having at least one control contact (6) with a control contact contact surface (12) and at least one load contact (8) with a load contact contact surface (14) larger than the control contact contact surface (12), comprising: applying an electrically insulating material to an area (34) of the load contact surface (14) adjacent to the control contact surface (12) by an additive method to form an electrically insulating layer (26); applying a metallic material to the control contact contact surface (12) and the electrical insulating layer (26) by a thermal spraying process to form a metallic control contact element (22) having a control contact element contact surface (24) larger than the control contact contact surface (12); Therefore, the control contact element (22) partially overlaps the load contact surface (14). method.

12. The method of claim 11 , wherein the electrically insulating material is applied by spraying, dispensing, or screen printing.

13. 13. The method according to claim 11 or 12, wherein a polymer having a glass transition temperature point above 150°C, in particular above 250°C, is applied to form the electrically insulating layer (26).

14. applying the metallic material to the load contact surface (14) by the thermal spraying process to form a metallic load contact element (28) having a load contact element contact surface (30); The load contact element (28) is arranged to be electrically insulated from the control contact element (22).

14. The method according to any one of claims 11 to 13.

15. 15. The method of any one of claims 11 to 14, wherein metal particles of different particle sizes are introduced into the plasma jet during the thermal spraying process.

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