Semiconductor module having a first substrate, a second substrate, and spacers separating the substrates from each other

Abstract

A semiconductor module includes a first substrate (10), a second substrate (101), and a spacer (40, 40') separating the substrates (10, 10') from each other, wherein the spacer (40, 40') is formed by at least one elastic shaped metal body (40, 40'). A semiconductor (20) can be arranged between the first substrate (10) and the second substrate (10'), wherein the semiconductor (20) is firmly bonded to one of the first substrate (10) or the second substrate (10'), and the shaped metal body (40, 40') can electrically connect the semiconductor (20) to the other of the substrates (10, 10'). The first substrate (10) and / or the second substrate (10') can be a DCB substrate or can include a lead frame. The shaped metal body (40, 40') can be made elastic so that applying pressure in a first direction causes expansion in a second direction, wherein a plurality of shaped metal bodies (40, 40') can be oriented in different directions relative to each other. A shaped metal body (40, 40') can be arranged in a planar manner on the semiconductor (20) in the plane between the substrates (10, 10'). The shaped metal body (40, 40') can be bent, folded and / or configured to have a wavy cross-section and can be slotted, in particular transversely to the bent, folded or wavy configuration. The shaped metal body (40, 40') can be a film. The spacer can be formed by at least two elastic shaped metal bodies (40, 40'), which are arranged in the plane between the substrates (10, 10') and connected to each other transversely to this plane. The connection between the semiconductor (20) and one of the first substrate (10) or the second substrate (10′) and the connection between (one or more) shaped metal bodies (40, 40′) and the semiconductor (20) and the other substrate (10, 10′) can be made by sintering or nanowires, or one shaped metal body (40, 40′) can be connected to the semiconductor (20) by sintering and the other shaped metal body (40, 40′) can be connected to the other substrate (10, 10′) by nanowires. The conductive elastic spacer (40, 40') can destroy the oxidized surface via elastic compensating movement, thereby providing an electrical connection between the two substrates (10, 10'), in particular when assembling a second (upper) substrate (101) and a first (lower) substrate (10) equipped with a semiconductor (20), the wave shape of the spacer (40, 40') can be deformed both vertically and laterally, wherein the tip of the "wave crest" then slides over the surface to be contacted and performs a cleaning action, thereby making it possible to destroy the oxide layer of the aluminum semiconductor metallization, thereby obtaining a highly electrically and thermally conductive connection with the semiconductor (20), without the semiconductor necessarily having to be coated with a precious metal surface.

Description

[0001] The present invention relates to a semiconductor module having a first substrate, a second substrate, and spacers separating the substrates from each other.

[0002] When sandwich structures are used to produce semiconductor modules, spacers, often called "spacers," are installed. These spacers provide a voltage-carrying surface for a predetermined minimum distance between the substrates, particularly when using DCB substrates. These spacers are typically soldered, so the thermomechanical stresses generated during connection to the semiconductors are minimal.

[0003] The disadvantage of this method is that the reliability of the stack connection is limited to that of the solder connection. If pressure sintering technology is used instead of soldering, the rigid sintered connection generates high thermomechanical forces that can crack the semiconductor.

[0004] Between the upper substrate and the chip substrate, there is a gap of approximately 0.5 mm to 4 mm (depending on the voltage level) that needs to be filled. If such a bulk copper body is sintered onto a semiconductor, it has been observed that conchoidal cracks can form in the semiconductor body. Experience has shown that it is not possible to make the Cu layer (sintered directly onto the chip) significantly thicker than approximately 60 μm to 75 μm.

[0005] It is therefore an object of the present invention to provide a semiconductor module having higher durability and reliability than conventionally manufactured semiconductor modules.

[0006] According to the invention, this object is achieved by a semiconductor module having the features of claim 1. The object is also achieved by a method having the features of claim 24. The dependent claims each present advantageous embodiments of the invention.

[0007] The basic idea of ​​the invention is to configure the spacer as an electrically conductive spring element which can, via an elastic compensating movement, simultaneously destroy the oxidized surface and thus provide an electrical connection between two substrates, which can also be made of a base metal.

[0008] According to the present invention, a semiconductor module is therefore provided, comprising a first substrate, a second substrate and a spacer separating the substrates from one another, wherein the spacer is made of at least one elastically formed metal body.

[0009] The semiconductor is preferably arranged between the first substrate and the second substrate, particularly preferably the semiconductor is firmly bonded to one substrate and most preferably is in electrical contact with the other substrate via a shaped metal body.

[0010] The first substrate and / or the second substrate are preferably DCB substrates. Alternatively, the first substrate and / or the second substrate may include a lead frame.

[0011] The shaped metal body is in particular configured such that, upon application of a pressure force acting in a first direction, an expansion of the shaped metal body in a second direction occurs.

[0012] Furthermore, it is preferred that the semiconductor module has a plurality of shaped metal bodies oriented in different directions relative to one another.

[0013] The shaped metal body is preferably configured to yield laterally when a pressure force from the substrate, applied in the direction of the semiconductor, acts substantially vertically on the semiconductor.

[0014] According to a further preferred embodiment, the shaped metal body is arranged in a planar manner on the semiconductor in a plane between the substrates.

[0015] The shaped metal body can be preferably bent. In particular, the shaped metal body can be folded. Specifically, the cross section of the shaped metal body can be wavy.

[0016] Furthermore, the shaped metal body can be slotted, wherein the slots introduced into the shaped metal body are particularly symmetrically arranged. The slots introduced into the shaped metal body are particularly preferably arranged transversely to the bends, folds, or undulating configurations thereof. This embodiment allows elastic deformation not only in the direction of the crests and troughs of the elastically configured spacer, but also transversely to the bends, folds, or undulating configurations.

[0017] The flexures of the bent, braided, or folded shaped metal body are configured to make electrical contact with a semiconductor and another substrate.

[0018] Furthermore, the shaped metal body is preferably configured as a film.

[0019] The shaped metal body is connected to the semiconductor and the further substrate, in particular by sintering.

[0020] Alternatively, the shaped metal body is connected to the semiconductor and another substrate, in particular by using nanowires. In this technology, nanowires can be grown from one or more surfaces to be connected, and then these surfaces are bonded together. The bonding is carried out under compression and possibly at an elevated temperature. However, this technology is very suitable for the present invention because it can be successfully used at relatively low pressures, so that the connection of components can be achieved using the shaped metal body without damaging the elastic properties of the shaped metal body. The pressure used for bonding may be as high as 70MPa, but in some cases may be as low as 1MPa. Nanowires can typically include copper or gold, nickel, silver, platinum or other suitable metals. They can typically have a diameter between 30nm and 2μm and a length between 500nm and 50μm.

[0021] According to a further preferred embodiment, the spacer consists of at least two elastic shaped metal bodies which are in contact with each other in the plane between the substrates transversely to this plane.

[0022] Both are preferably constructed identically, with one shaped metal body being connected to the semiconductor, most preferably by sintering, and the other shaped metal body being connected to the other substrate by sintering.

[0023] The distance between the surface of the first substrate and the surface of the second substrate is preferably in the range of 0.8 mm to 2 mm.

[0024] A particularly advantageous embodiment is obtained when the semiconductor is at least partially made of silicon carbide (SiC).

[0025] Finally, a method for producing a semiconductor module is proposed, comprising the following steps:

[0026] - placing a semiconductor between two substrates,

[0027] - arranging an elastically shaped metal body between the substrates to produce a predefined distance between the substrates, and

[0028] - connecting the substrate, the shaped metal body and the semiconductor to one another.

[0029] According to a preferred embodiment of the process, a direct first electrical connection is formed between the semiconductor and one substrate, and a second electrical connection mediated by the elastically formed metal body is formed between the other substrate and the semiconductor.

[0030] In an alternative embodiment of the process, the connections may be made through nanowires as described above.

[0031] The invention is explained in more detail below with reference to particularly preferred embodiments shown in the accompanying drawings, in which:

[0032] Figure 1 shows a side view of a preferred example embodiment of the present invention;

[0033] Figure 2 shows a top view of two examples of particularly preferred spacers;

[0034] Figure 3 shows a side view of a preferred second exemplary embodiment of the present invention;

[0035] Figure 4 A flow chart of the method of the present invention is shown;

[0036] Figure 5 It is an icon Figure 2 Figures showing additional details of the embodiment shown in ; and

[0037] Figure 6 It is an icon Figure 2 FIGURES 1 and 2 show additional details of an alternative implementation of the embodiment shown in FIG.

[0038] Figure 1 A side view of a preferred exemplary embodiment of the present invention is shown.

[0039] Figure 1 In particular, a semiconductor module 100 is shown having a first substrate 10, a second substrate 10' and a spacer 40, which is designed as an elastically shaped metal body, all of which are separated from each other by the substrates 10, 10' and at the same time electrically contact the substrates 10, 10'. The corrugated spacer 40 has a thickness of approximately 0.8 mm to approximately 2 mm.

[0040] The wave shape of the spacer 40 resembles a meander in cross section, providing increased elastic behavior in at least one axis. The geometrical undulations can be achieved by further structural measures in another axis parallel to the surface of the semiconductor 20 disposed between the substrates 10, 10'. Thus, a "spacer" is obtained which, due to its elastic properties in the lateral plane, transmits only small thermomechanical stresses to the semiconductor despite its considerable thickness of approximately 0.8 mm to 2 mm (inclusive).

[0041] If the spacer 40 is elastically deformable in one direction within the plane of the semiconductor 20 , a plurality of spacers 40 may be provided in the semiconductor module 100 , the spacers being aligned in the same direction with respect to elastic deformation.

[0042] However, if Figure 2 As shown, it is particularly preferred that the spacer 40 is slotted transversely to the course of the wave-shaped structure. This configuration allows not only elastic deformation in the direction of the crests and troughs of the elastically designed spacer, but also elastic wave-forming transversely to the wave direction.

[0043] If the distance between the upper substrate 10' and the surface of the semiconductor 20 is too large, as shown in FIG. Figure 3 As shown in FIG, two spacers 40, 40' can also be used.

[0044] When lower and upper substrates 10, 10', equipped with semiconductor 20, are assembled, the wave pattern of spacer 50 deforms both vertically and laterally. The tips of the "wave crests" then slide over the surfaces to be contacted, performing a cleaning action. Most importantly, this can break down the oxide layer of the aluminum semiconductor metallization. This results in a highly electrically and thermally conductive connection to semiconductor 20, without the semiconductor having to be coated with a precious metal surface.

[0045] These wavy metal bodies, used as spacers 40, can be simply placed in a wet sintering paste 50 applied to the semiconductor surface during a rapid assembly process. During the upstream hydrostatic sintering process, the semiconductor is already firmly and reliably connected to the substrate 10 (or lead frame) via the connecting layer 30. The upper substrate 10' (or lead frame) also carries the silver paste deposit 50. The upper substrate 10' is then aligned with the lower substrate 10 and merged. Consequently, despite the significant distance of 0.8 mm to 2 mm, the contact with the spacers 40 is intimate.

[0046] This technology is particularly advantageous for fast-switching SiC modules, as these modules can utilize highly reliable sintered connections in a sandwich structure.

[0047] Alternatively, conductive nanowires can be used to connect the semiconductor 20 and the spacer 40. Such nanowires are grown from one or more surfaces to be connected and then bonded together. The bonding is carried out under compression and possibly at elevated temperatures. However, this technology is very suitable for the present invention because it can be successfully used at relatively low pressures, making it possible to use the spacer 40 to connect the components without damaging the elastic properties of the spacer 40. The pressure used for bonding may be as high as 70 MPa, but in some cases may be as low as 1 MPa. Nanowires can typically include copper or gold, nickel, silver, platinum or other suitable metals. They can typically have a diameter between 30 nm and 2 μm and a length between 500 nm and 50 μm. A potential huge advantage of using nanowires is that the joints formed are flexible, so the stress around the items being bonded, such as semiconductor chips or substrates, is reduced. This in turn greatly improves reliability and module life.

[0048] Figure 4 A flow chart of a method 200 of the present invention for manufacturing a semiconductor module is shown. The method 200 comprises the following steps:

[0049] - a semiconductor 201 is provided between the two substrates,

[0050] - arranging 202 an elastically formed metal body between the substrates to create a predefined distance between the substrates, and

[0051] - Connecting the substrate, the shaped metal body and the semiconductor to one another 203 .

[0052] Figure 5 It is an icon Figure 2 FIG. 4 is a diagram showing further details of the embodiment shown in a top (plan) view of FIG. 4 . In this orthogonal view, a spacer 40 can be seen, which comprises a shaped metal body having a wave-shaped cross section. The spacer 40 is connected to the upper surface of the semiconductor 20.

[0053] Figure 6 It is an icon Figure 2 FIGURE 4 is a diagram showing further details of an alternative embodiment of the embodiment shown in a top (plan) view. In this orthogonal view, a spacer 40 can be seen, which comprises a shaped metal body having a wave-shaped cross section. The spacer 40 is connected to the upper surface of the semiconductor 20. In this embodiment, the spacer 40 comprises a plurality of semiconductor elements 20, each of which is connected to the upper surface of the semiconductor 20. Figure 5 Such orthogonal sections increase the flexibility of the spacer 40 in the orthogonal direction.

Claims

1. A semiconductor module comprising a first substrate, a second substrate, a spacer provided in a plane separating the substrates from each other, and a semiconductor provided between the first substrate and the second substrate, It is characterized by: The spacer is made of at least a first elastically formed metal body and a second elastically formed metal body, and the first elastically formed metal body and the second elastically formed metal body are stacked in a direction transverse to the plane, wherein one of the first elastically formed metal body and the second elastically formed metal body is connected to the semiconductor and the other is connected to one of the first substrate and the second substrate, The first elastic formed metal body and the second elastic formed metal body are bent or folded, or the cross-sections of the first elastic formed metal body and the second elastic formed metal body are wavy, and the first elastic formed metal body and the second elastic formed metal body are slotted transversely to the bent, folded or wavy structure.

2. The semiconductor module according to claim 1, wherein The semiconductor is firmly bonded to one of the first substrate or the second substrate.

3. The semiconductor module according to claim 2, wherein: The first elastically formed metal body and the second elastically formed metal body electrically connect the semiconductor to another of the substrates.

4. The semiconductor module according to any one of claims 1 to 3, characterized in that The first substrate and / or the second substrate is a DCB substrate.

5. The semiconductor module according to any one of claims 1 to 3, characterized in that The first elastically formed metal body and the second elastically formed metal body are made elastic so that application of pressure in a first direction causes expansion in a second direction.

6. The semiconductor module according to claim 5, characterized in that The first and second resiliently formed metal bodies are oriented in different directions relative to each other.

7. The semiconductor module according to claim 2, wherein: The first and second resiliently formed metal bodies are configured to yield laterally when pressure from a substrate acting in the direction of the semiconductor is applied substantially vertically to the semiconductor.

8. The semiconductor module according to claim 3, wherein The flexures of the first and second resiliently formed metal bodies are brought into electrical contact with the other substrate.

9. The semiconductor module according to any one of claims 1 to 3, characterized in that The first elastically formed metal body and the second elastically formed metal body are films.

10. The semiconductor module according to claim 3, wherein The first elastically formed metal body and the second elastically formed metal body are connected to the semiconductor and the other substrate by sintering.

11. The semiconductor module according to claim 1, wherein The first elastically formed metal body and the second elastically formed metal body have the same design.

12. The semiconductor module according to claim 3, wherein One of the first and second elastically formed metal bodies is connected to the semiconductor by sintering, while the other elastically formed metal body is connected to the other substrate by sintering.

13. The semiconductor module according to claim 3, wherein One of the first elastically shaped metal body and the second elastically shaped metal body is connected to the semiconductor by sintering, and the other elastically shaped metal body is connected to the other substrate through nanowires.

14. The semiconductor module according to any one of claims 1 to 3, characterized in that A distance between a surface of the first substrate and a surface of the second substrate is in a range of 0.8 mm to 2 mm.

15. The semiconductor module according to claim 1, wherein The semiconductor is at least partially made of silicon carbide.

16. A method for producing a semiconductor module, characterized by the following steps: - placing a semiconductor between two substrates, - a first elastically formed metal body and a second elastically formed metal body are arranged in a plane between the substrates to produce a predefined distance between the substrates, and the first elastically formed metal body and the second elastically formed metal body are stacked in a direction transverse to the plane, and the first elastically formed metal body and the second elastically formed metal body are bent or folded or the cross-section of the first elastically formed metal body and the second elastically formed metal body are wavy, and the first elastically formed metal body and the second elastically formed metal body are slotted transversely to the bent, folded or wavy configuration, and - connecting the substrates, the first elastically formed metal body, the second elastically formed metal body and the semiconductor (30) to one another, wherein one of the first elastically formed metal body and the second elastically formed metal body is connected to the semiconductor and the other is connected to one of the two substrates.

17. The method of claim 16, wherein a first direct electrical connection is established between one substrate and the semiconductor, and a second electrical connection between the semiconductor and another substrate is conveyed through the first elastically formed metal body and the second elastically formed metal body.

18. The method according to any one of claims 16 and 17, characterized in that The connection is made by sintering.

19. The method according to any one of claims 16 and 17, characterized in that The connection is made via nanowires.

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