Semiconductor arrangement with a switchable semiconductor element and method for producing same
Patent Information
- Application Number
- EP2023804940
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-11-10
- Filing Date
- 2023-10-31
- Publication Date
- 2025-07-09
AI Technical Summary
The service life of semiconductor arrangements with switchable semiconductor elements is limited by the use of aluminum wire bonds, which are prone to failure in modern construction and connection technologies, especially under thermomechanical stress during copper-based bonding and welding processes.
A semiconductor arrangement with a switchable semiconductor element featuring a metallic control contacting element made of materials like silver, gold, or copper, combined with an electrically insulating layer applied via an additive process and thermal spraying, creating a larger contact area that overlaps the load contact surface to distribute forces and reduce thermomechanical stress, thereby enhancing the service life.
The solution increases the service life of semiconductor arrangements by distributing forces and minimizing thermomechanical stress, allowing for thicker bonding wires and improved adhesion, tolerance compensation, and reduced risk of damage during copper-based connections, leading to longer-lasting semiconductor modules.
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Figure 1.1
Abstract
Description
[0001] Description
[0002] SEMICONDUCTOR ARRANGEMENT WITH A SWITCHABLE
[0003] SEMICONDUCTOR ELEMENT AND METHOD FOR PRODUCING THE SAME
[0004] The invention relates to a semiconductor device with a switchable semiconductor element.
[0005] Furthermore, the invention relates to a power converter with at least one such semiconductor arrangement
[0006] Furthermore, the invention relates to a method for producing a semiconductor device with a switchable semiconductor element.
[0007] Such a semiconductor module arrangement is generally used in a power converter. A power converter can be, for example, a rectifier, an inverter, a converter or a DC-DC converter. The switchable semiconductor elements used in the semiconductor module arrangement are, for example, transistors, triacs or thyristors. The transistors are designed, for example, as insulated-gate bipolar transistors (IGBTs), field-effect transistors or bipolar transistors. Such switchable semiconductor elements usually have a control connection and load connections, each with a contacting area, for example a contact pad, wherein the contacting area of a load connection generally has a larger area than the contacting area of a control connection.
[0008] To contact the switchable semiconductor elements, wiring made of aluminum, such as aluminum wire bonds, is usually used. This can be a factor that limits or even the service life of modern packaging and connection technologies. A copper-based packaging and connection technology, for example, promises a significantly longer service life because copper, especially compared to aluminum, has better material properties such as a higher modulus of elasticity and higher electrical conductivity. The copper-based packaging and connection technology includes, among other things, copper wire bonding, pressure contacting, in particular using copper busbars or a copper leadframe, and laser welding of copper connections.However, the technologies mentioned require higher compressive forces, such as in copper wire bonding, or higher temperatures at certain points, such as in laser welding, so that the risk of damage to the semiconductor component during the manufacture of the semiconductor device is increased.
[0009] Against this background, it is an object of the present invention to provide a semiconductor device with a switchable semiconductor element which enables a longer service life.
[0010] This object is achieved according to the invention by a semiconductor arrangement with a switchable semiconductor element, which has at least one control contact with a control contact
[0011] Contact surface and at least one load contact with a load contact contact surface which is larger than the control contact contact surface, wherein an electrically insulating material is applied to a region of the load contact contact surface adjacent to the control contact contact surface by means of an additive process to form an electrically insulating layer, wherein a metallic material is applied to the control contact contact surface and the electrically insulating layer by means of a thermal spraying process to form a metallic control contacting element with a control contacting element contact surface which is larger than the control contact contact surface, wherein the control contacting element partially overlaps the load contact contact surface.
[0012] Furthermore, the object is achieved according to the invention by a power converter with at least one such semiconductor arrangement. Furthermore, the object is achieved according to the invention by a method for producing a semiconductor arrangement with a switchable semiconductor element, which has at least one control contact with a control contact contact surface and at least one load contact with a load contact contact surface which is larger than the control contact contact surface, wherein an electrically insulating material is applied to a region of the load contact contact surface adjacent to the control contact contact surface by means of an additive method to form an electrically insulating layer,wherein a metallic material is applied by means of a thermal spraying process to the control contact contact surface and the electrically insulating layer to form a metallic control contacting element with a control contacting element contact surface which is larger than the control contact contact surface, so that the control contacting element partially overlaps the load contact contact surface.
[0013] The advantages and preferred embodiments listed below with regard to the semiconductor device can be transferred analogously to the power converter and the method.
[0014] The invention is based on the idea of increasing the service life of a semiconductor device by means of a metallic control contact-making element or a buffer layer for contacting a control contact of a switchable semiconductor element. The metallic control contact-making element is made from a metallic material, for example silver, gold, copper, zinc, molybdenum or one of their alloys, and is connected to the control contact of the switchable semiconductor element and to an electrically insulating layer, the electrically insulating layer being made from an electrically insulating material, for example a polymer, and being applied to a region of a load contact contact surface of the semiconductor element adjacent to the control contact contact surface.The control contact-making element is thus connected to the load contact surface of the semiconductor element via the electrically insulating layer and is arranged so as to be electrically insulated from this. Furthermore, the control contact-making element partially overlaps the load contact surface in an adjacent region. The control contact-making element has a control contact element contact surface which has a larger area than the control contact surface of the control contact. The electrically insulating material is applied by means of an additive process, for example in liquid form, to form the electrically insulating layer, for example with a thickness in the range of 0.1 pm to 100 pm, while the metallic material is applied by means of a thermal spraying process, e.g. by means of plasma spraying.The metallic layer applied by means of the thermal spraying process can have a layer thickness in the range of 1 pm to 250 pm, in particular 5 pm to 100 pm.
[0015] Such a buffer layer distributes forces occurring during contact, minimizing, for example, thermomechanical stress that occurs during copper wire bonding, which has a positive effect on the service life of the semiconductor device. The larger contact area enables contact to be made with thicker and therefore more stable bond wires. In addition to the improved force distribution, the buffer layer, which is larger and thicker than the control contact, compensates for tolerances, so that pressure contact, particularly using copper busbars, has an improved service life. In addition, the buffer layer, which is larger and thicker than the control contact, enables melt regions in the metal, so that contacting copper connections using laser welding leads to an improved service life of the semiconductor device.A further embodiment provides that the electrically insulating material contains a polymer with a glass transition temperature of > 150°C, in particular > 250°C. Such polymers can be, among others, polyimides, polyamides, and polyamide-imides. An electrically insulating layer containing such a polymer is robust and is not damaged during coating by means of the thermal spraying process. Furthermore, the semiconductor device with such an electrically insulating layer has an improved service life, particularly under large temperature fluctuations.
[0016] A further embodiment provides that the electrically insulating material contains a polymer with thermoplastic properties. The metal particles sprayed onto the surface using the thermal spraying process bond, particularly adhesively, to the electrically insulating layer due to the thermoplastic properties of the polymer. Such bonding improves the adhesion of the buffer layer, which leads to an improved service life of the semiconductor device.
[0017] Another embodiment provides for the electrically insulating material to be applied by jetting, dispensing, or screen printing. Such additive processes allow the electrically insulating material to be applied in liquid form, allowing the electrically insulating material to flow onto the chip surface and thus preventing vertical angles from being generated. This promotes good adhesion to the chip and thus high long-term strength.
[0018] A further embodiment provides for the electrically insulating material to be thixotropic or to exhibit thixotropic properties. Thixotropy refers, in particular, to the fact that the viscosity behavior of the electrically insulating material is influenced in such a way that, for example, it does not flow up to a certain shear stress and then flows. Thixotropy also reduces the expansion coefficient, which is beneficial for the coating process.
[0019] A further embodiment provides for the electrically insulating material to contain a fumed silica. An example of such fumed silica is Aerosil, which provides suitable thixotropy.
[0020] A further embodiment provides that the metallic material is applied to the load contact surface by means of the thermal spraying process to form a metallic load contacting element with a load contacting element contact surface, wherein the load contacting element is arranged electrically insulated from the control contacting element. The metallic layer applied by means of the thermal spraying process can, like the control contacting element, have a layer thickness in the range from 1 pm to 250 pm, in particular 5 pm to 100 pm. Such a buffer layer on the load contact surface distributes forces occurring during contact, as a result of which, for example, thermomechanical stress that arises during copper wire bonding is minimized, which has a positive effect on the service life of the semiconductor device.In addition to improved force distribution, the buffer layer, which is thicker than the load contact, also compensates for tolerances, thus improving the service life of pressure contact, particularly with copper busbars. Furthermore, the buffer layer, which is thicker than the load contact, enables melting regions in the metal, so that contacting copper terminals using laser welding leads to an improved service life of the semiconductor device.
[0021] Another embodiment provides for the metallic material to be applied in such a way that the control contact element contact surface and the load contact element contact surface are flush. This flush finish simplifies the subsequent contacting process and ensures uniform contacting, which has a positive effect on the service life of the semiconductor device.
[0022] A further embodiment provides 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 has a tolerance-compensating effect, particularly in the case of pressure connection. Particularly during subsequent operation of the semiconductor element, for example when switching a power semiconductor on and off, the different expansion coefficients of the semiconductor and the metals used in the metallic contact element can be compensated by the porosity, which has a positive effect on the service life of the semiconductor device.
[0023] Another embodiment provides for the thermal spraying process to guide metallic particles of varying sizes into a plasma jet. For example, the metallic particles are melted by the plasma jet, and their surface is partially vaporized. The properties of the deposited layer can be specifically adjusted by the type and size of the particles, plasma parameters such as temperature, plasma pressure, etc., but also by external conditions such as deposition rate, heating temperature, atmosphere, etc. In this way, a high long-term strength of the applied layer can be achieved.
[0024] In the following, the invention is described and explained in more detail with reference to the exemplary embodiments shown in the figures.
[0025] Shown are: FIG 1 a schematic representation of a first embodiment of a semiconductor device in a cross-sectional view,
[0026] FIG 2 shows a schematic representation of a second embodiment of a semiconductor device in a cross-sectional view,
[0027] FIG 3 is a schematic representation of a first method for producing a semiconductor device,
[0028] FIG 4 is a schematic representation of a second method for producing a semiconductor device,
[0029] FIG 5 is a schematic representation of a third embodiment of a semiconductor device in a cross-sectional view,
[0030] FIG 6 is a schematic diagram of a power converter.
[0031] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another. These also further develop the invention independently of one another and are thus to be regarded as components of the invention, either individually or in a combination other than that shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.
[0032] The same reference symbols have the same meaning in the different figures.
[0033] FIG 1 shows a schematic representation of a first embodiment of a semiconductor arrangement 2 in a cross-sectional representation, which has a, in particular vertical, switchable semiconductor element 4. By way of example, the switchable semiconductor element 4 is designed as an insulated gate bipolar transistor (IGBT). Further examples of switchable semiconductor elements 4 are triacs, thyristors or other transistor types such as field effect transistors and bipolar transistors. The switchable semiconductor element 4 comprises 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.On a side of the semiconductor arrangement 2 opposite the control contact 6 and the load contact 8, a further load contact 10 is arranged, which is connected internally to the collector terminal C of the vertical semiconductor element 4 and is designed as a collector contact. Since FIG. 1 is an example of a vertical semiconductor, load contacts 8, 10 are arranged on opposite sides.
[0034] The control contact 6 and the load contacts 8, 10 each comprise a metallic contact pad which is configured for connecting at least one wiring means, e.g. a bonding wire. Furthermore, the control contact 6 has a control contact contact area 12 and the load contact 8 has a load contact contact area 14, wherein the control contact contact area 12 is significantly smaller than the load contact contact area 14. Furthermore, the control contact contact area 12 and the load contact contact area 14 are rectangular or square and arranged flush with a semiconductor surface 16.
[0035] The control contact 6 borders an electrically insulating guard ring 18, which, for example, projects beyond the semiconductor surface 16 and thus the control contact contact surface 12 and the load contact contact surface 14. Furthermore, an electrically insulating intermediate layer 20 is arranged between the control contact 6 and the load contact 8, which, for example, also projects beyond the semiconductor surface 16. For example, the electrically insulating guard ring 18 and the electrically insulating intermediate layer 20 comprise a dielectric material, in particular polyimide.
[0036] A metallic control contact-making element 22 is connected flatly to the control contact contact surface 12 of the control contact 6, wherein the metallic control contact-making element 22 has a control contact element contact surface 24 arranged on a side facing away from the control contact contact surface 12, which control contact element contact surface 24 is larger than the control contact contact surface 12. For example, the control contact element contact surface 24 is at least four times, in particular at least eight times, as large as the control contact contact surface 12. The metallic control contact-making element 22 is made from at least one metallic material. At least in the region of the control contact element contact surface 24, the metallic control contact-making element 22 contains aluminum, silver, gold, copper, zinc, molybdenum or one of their alloys.
[0037] In addition, the metallic control contact-making element 22 partially overlaps the load contact surface 14 of the load contact 8, wherein an electrically insulating layer 26 is arranged in the region of the overlap between the metallic control contact-making element 22 and the load contact surface 14 of the load contact 8. The electrically insulating layer 26 is made of an electrically insulating material, in particular a dielectric material. The electrically insulating material can contain, among other things, a polymer which has a glass transition temperature point of > 150 ° C, in particular > 250 ° C, as is the case with polyimide, polyamides and polyamide-imides, for example. The electrically insulating material is applied, for example, in liquid form via a film or photostructuring.Application is carried out by means of an additive process, for example by jetting, in particular inkjetting, dispensing, or screen printing. The polymer can flow out onto the load contact surface 14, thus preventing vertical angles from being generated, which promotes good adhesion and thus high long-term strength. The electrically insulating material can be thixotropic or have thixotropic properties. For example, pyrogenic silica, in particular Aerosil, is added to the liquid polymer.
[0038] After the electrically insulating layer 26 has been applied and dried, the metallic material is applied to the control contact contact surface 12 and the electrically insulating layer 26 by means of a thermal spraying process, e.g. by means of plasma spraying, to form the metallic control contact element 22, such that the metallic control contact element 22 is materially connected to the control contact contact surface 12 and the electrically insulating layer 26. For example, in the thermal spraying process, metallic particles, in particular copper and / or molybdenum particles, of different particle sizes are guided into a plasma jet, the particles being melted and their surface partially evaporated. The metallic control contact element 22 produced by means of the thermal spraying process has a porosity in the range from 1% to 50%, in particular 1% to 5%.The polymer may have thermoplastic properties to form an adhesive bond with the sprayed metallic particles.
[0039] Such a coating enables, for example, gate-side contacting with wiring means, in particular bonding wires, which have a larger diameter. Furthermore, the coating enables a copper-based assembly and connection technology such as, for example, copper wire bonding, pressure contacting, in particular by means of copper busbars or by means of a copper leadframe, or laser welding of copper connections, as a result of which a longer service life can be achieved. The risk of damage to the semiconductor component 4, for example due to higher compressive forces, as in copper wire bonding, or locally higher temperatures, as in laser welding, is minimized by the described coating.
[0040] FIG 2 shows a schematic representation of a second embodiment of a semiconductor arrangement 2 in a cross-sectional view. The metallic material is additionally applied to the load contact contact surface 14 by means of the thermal spraying process to form a metallic load contacting element 28 with a load contacting element contact surface 30, wherein the load contacting element 28 is arranged electrically insulated from the control contacting element 22 and wherein the control contacting element contact surface 24 and the load contacting element contact surface 30 are flush, in particular flush. In particular, in the thermal spraying process, in particular plasma spraying, structuring is carried out by means of a stencil between the semiconductor element 4 and a spraying device, in particular a plasma spray nozzle. The further embodiment of the semiconductor arrangement 2 in FIG 2 corresponds to that in FIG 1.
[0041] FIG 3 shows a schematic representation of a first method for producing a semiconductor arrangement 2, which comprises a, in particular vertical, switchable semiconductor element 4. The respective steps of the production method are shown in FIG 3 on the left in a plan view and on the right in a cross-sectional view. The semiconductor element 4 has a control contact 6 with a control contact contact area 12 and a load contact 8 with a load contact area 14, which is many times larger than the control contact area 12. The control contact 6 of the semiconductor element 4 is integrated into a corner 32 of the rectangular or square load contact area 14 and is spaced from the load contact 8 by an electrically insulating intermediate layer 20 and is thus arranged in an electrically insulated manner.
[0042] An electrically insulating material is applied A to a region 34 of the load contact contact surface 14 and the electrically insulating intermediate layer 20 adjacent to the control contact contact surface 12 by means of an additive process to form an electrically insulating layer 26. The electrically insulating material can contain, among other things, a polymer and is applied, for example, in liquid form via a film or photostructuring. The additive process can include jetting, in particular inkjetting, dispensing, or screen printing.
[0043] After the electrically insulating layer 26 has dried, a further step involves applying B a metallic material by means of a thermal spraying process to the control contact contact surface 12 and the electrically insulating layer 26 to form a metallic control contact element 22, as well as to the load contact contact surface 14 to form a metallic load contact element 28. The load contact element 28 is arranged so as to be electrically insulated from the control contact element 22. The thermal spraying process can, for example, include plasma spraying. For example, in the thermal spraying process, metallic particles, in particular copper and / or molybdenum particles, of different particle sizes are guided into a plasma jet, the particles being melted and their surface partially evaporating.The control contact-making element contact surface 24 of the control contact-making element 22 and the load contact-making element contact surface 30 of the load contact-making element 28 are flush. The further embodiment of the semiconductor arrangement 2 in FIG. 3 corresponds to that in FIG. 2. FIG. 4 shows a schematic representation of a second method for producing a semiconductor arrangement 2, wherein the control contact 6 of the semiconductor element 4 is arranged substantially centrally within the rectangular or square load contact contact surface 14, which is many times larger than the control contact contact surface 12. The control contact 6 is spaced from the load contact 8 by an electrically insulating intermediate layer 20 surrounding the control contact 6 and is thus arranged in an electrically insulated manner.
[0044] The application A of the electrically insulating material takes place on an area 34 of the load contact contact surface 14 and the electrically insulating intermediate layer 20 adjacent to the control contact contact surface 12 towards an edge center 36 of the rectangular or square load contact contact surface 14.
[0045] The application B of the metallic material by means of the thermal spraying process onto the control contact
[0046] Contact surface 12 and the electrically insulating layer 26 are formed by forming a metallic control contact element 22, which borders the edge center 36 of the load contact surface 14, wherein a path 38 is formed by means of the thermal spraying process, which electrically connects the control contact 6 to the control contact element 22. The further embodiment of the manufacturing process in FIG. 4 corresponds to that in FIG. 3.
[0047] FIG. 5 shows a schematic representation of a third embodiment of a semiconductor device 2 in a cross-sectional view, wherein a connecting element 40 is connected, in particular materially, to the control contacting element contact surface 24. The liquid, electrically insulating material is applied in a thixotropic manner, running down the chip edge 42 in a controlled manner and solidifying, so that a chip corner insulation 44 is formed.
[0048] The electrically insulating material has, for example, a dielectric strength of > 150 kV / mm. In particular, when a saw edge of the semiconductor element 4 is at a lower potential of the further load contact 10, the risk of a flashover, e.g., to the connecting element 40, is minimized by such chip corner insulation 44. The further embodiment of the semiconductor device 2 in FIG. 5 corresponds to that in FIG. 4.
[0049] FIG 6 shows a schematic representation of a power converter 46, which comprises, for example, a semiconductor arrangement 2.
[0050] In summary, the invention relates to a semiconductor device 2 with a switchable semiconductor element 4, which has at least one control contact 6 with a control contact
[0051] contact area 12 and at least one load contact 8 with a load contact contact area 14 which is larger than the control contact contact area 12. In order to achieve a longer service life of the semiconductor arrangement 2, it is proposed that an electrically insulating material is applied to a region 34 of the load contact contact area 14 adjacent to the control contact contact area 12 by means of an additive method to form an electrically insulating layer 26, wherein a metallic material is applied to the control contact contact area 12 and the electrically insulating layer 26 by means of a thermal spraying method to form a metallic control contact-making element 22 with a control contact-making element contact area 24 which is larger than the control contact contact area 12, wherein the control contact-making element 22 partially overlaps the load contact contact area 14.
Claims
Patent claims 1. A semiconductor arrangement (2) comprising a switchable semiconductor element (4) which has at least one control contact (6) with a control contact contact area (12) and at least one load contact (8) with a load contact area (14) which is larger than the control contact area (12), wherein an electrically insulating material is applied to a region (34) of the load contact area (14) adjacent to the control contact area (12) by means of an additive process to form an electrically insulating layer (26), wherein a metallic material is applied to the control contact area (12) and the electrically insulating layer (26) by means of a thermal spraying process to form a metallic control contact element (22) with a control contact element contact area (24) which is larger than the control contact area (12),wherein the control contact element (22) partially overlaps the load contact surface (14)., 2. Semiconductor device (2) according to claim 1, wherein the electrically insulating material contains a polymer having a glass transition temperature point > 150°C, in particular > 250°C.
3. Semiconductor device (2) according to one of claims 1 or 2, wherein the electrically insulating material contains a polymer with thermoplastic properties.
4. Semiconductor device (2) according to one of the preceding claims, wherein the electrically insulating material is applied by jetting, dispensing or screen printing.
5. Semiconductor arrangement (2) according to one of the preceding claims, wherein the electrically insulating material is thixotropic or has thixotropic properties.
6. Semiconductor device (2) according to claim 5, wherein the electrically insulating material contains a pyrogenic silica.
7. Semiconductor arrangement (2) according to one of the preceding claims, wherein the metallic material is applied to the load contact contact surface (14) by means of the thermal spraying process to form a metallic load contacting element (28) with a load contacting element contact surface (30), wherein the load contacting element (28) is arranged electrically insulated from the control contacting element (22).
8. Semiconductor arrangement (2) according to claim 7, wherein the metallic material is applied such that the control contacting element contact surface (24) and the load contacting element contact surface (30) are flush.
9. Semiconductor arrangement (2) according to one of claims 7 or 8, wherein the metallic control contacting element (22) and / or the metallic load contacting element (28) have a porosity in the range of 1% to 50%, in particular 1% to 5%.
10. Power converter (46) with at least one semiconductor arrangement (2) according to one of the preceding claims.
11. A method for producing a semiconductor device (2) with a switchable semiconductor element (4) which has 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) which is larger than the control contact contact surface (12), wherein an electrically insulating material is applied to a region (34) of the load contact contact surface (14) adjacent to the control contact contact surface (12) by means of an additive method to form an electrically insulating layer (26), wherein a metallic material is applied to the control contact contact surface (12) and the electrically insulating layer (26) by means of a thermal spraying method to form a metallic control contacting element (22) with a control contacting element contact surface (24) which is larger than the control contact contact surface (12),so that the control contact element (22) partially overlaps the load contact surface (14)., 12. The method according to claim 11, wherein the electrically insulating material is applied by jetting, dispensing or screen printing.
13. A process according to any one of claims 11 or 12, wherein a polymer having a glass transition temperature point > 150°C, in particular > 250°C, to form the electrically insulating layer (26).
14. The method according to any one of claims 11 to 13, wherein the metallic material is applied to the load contact contact surface (14) by means of the thermal spraying process to form a metallic load contacting element (28) having a load contacting element contact surface (30), wherein the load contacting element (28) is arranged electrically insulated from the control contacting element (22).
15. The method according to any one of claims 11 to 14, wherein in the thermal spraying process metallic particles of different particle sizes are guided into a plasma jet.