Method of manufacturing a semiconductor device and corresponding semiconductor device

Abstract

The present disclosure relates to methods of manufacturing semiconductor devices and corresponding semiconductor devices. A semiconductor device semiconductor chip mounted to a leadframe, the leadframe including a conductive pad. A conductive clip is arranged in a bridging position between the semiconductor chip and the conductive pad. The conductive clip is soldered to the semiconductor chip and the conductive pad via a solder material applied at coupling surfaces facing the semiconductor chip and the conductive pad. The device further includes a pair of complementary positioning structures formed by a cavity in the conductive clip and a protrusion formed in the conductive pad, such as a cylindrical bump or a stack of cylindrical bumps. The complementary positioning structures mutually engage to hold the conductive clip in the bridging position to avoid displacement during soldering.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Italian Patent Application No. 102022000001646, filed on February 1, 2022, the contents of which are incorporated herein by reference in their entirety to the fullest extent permitted by law. Technical Field

[0003] This specification relates to semiconductor devices. One or more embodiments can be advantageously applied to power semiconductor devices. Background Technology

[0004] Various types of semiconductor devices having plastic encapsulation include: a substrate (lead frame) on which one or more semiconductor integrated circuit chips or dies are disposed; a conductive structure (wire, strip, clip) for coupling the semiconductor chip(s) to leads (external pads) in the substrate; and an insulating encapsulation (e.g., resin) molded onto the thus formed assembly to complete the plastic body of the device.

[0005] In power semiconductor devices, the current flowing from the high-power section to the output pads of the device can be significant, and strips or clips are used instead of wires for this purpose. Wires can still be used to provide electrical coupling to the low-power section of the device (e.g., the controller). Strips are essentially placed using a wire bonding process. Clips are placed using clip attachment equipment, and solder paste is used to attach the clips to the pads and the die. Solder is applied and cured in an oven to provide a strong connection between the clips and the pads and the die.

[0006] Traditional clip attachment equipment helps achieve sufficient accuracy in chip placement because clips are applied to the die and pads, after which the assembly is transferred to an oven for solder curing. During this processing and curing, the clips can shift from the desired correct position. This can lead to defects in the final product. Solder thickness and the tendency of the clips to "float" on the solder in a fluid state can also be due to undesirable excessive clip tilting.

[0007] There is a need in this field to help fully address the aforementioned problems. Summary of the Invention

[0008] One or more embodiments may relate to a method.

[0009] One or more embodiments may relate to corresponding semiconductor devices.

[0010] One or more embodiments may provide one or more of the following advantages: facilitate accurate clip positioning by effectively counteracting unwanted movement (e.g., rotation) throughout the assembly process; and allow for appropriate control of solder thickness.

[0011] In one embodiment, a method includes: arranging at least one semiconductor chip on a die pad in a substrate, the substrate including at least one conductive pad adjacent to the die pad; positioning at least one conductive clamp in a bridge-like position between the at least one semiconductor chip and the at least one conductive pad, wherein in the bridge-like position, the at least one conductive clamp has a coupling surface facing the at least one semiconductor chip and the at least one conductive pad; and soldering the at least one conductive clamp in the bridge-like position to the at least one semiconductor chip and the at least one conductive pad to provide electrical coupling therebetween, wherein the soldering is performed via solder material at the coupling surface. The method further includes, prior to positioning the at least one conductive clamp in the bridge-like position between the at least one semiconductor chip and the at least one conductive pad, providing at least one pair of complementary positioning structures, the at least one pair of complementary positioning structures including a cavity in the at least one conductive clamp and a protrusion in at least one of the at least one semiconductor chip and the at least one conductive pad, wherein as the at least one conductive clamp is in the bridge-like position, during the soldering, the complementary positioning structures engage with each other and hold the at least one conductive clamp in the bridge-like position.

[0012] In one embodiment, a device includes: at least one semiconductor chip on a die pad in a substrate, the substrate including at least one conductive pad adjacent to the die pad; at least one conductive clamp positioned in a bridge-like location between the at least one semiconductor chip and the at least one conductive pad, the at least one conductive clamp having a coupling surface facing the at least one semiconductor chip and the at least one conductive pad; solder material applied to the coupling surface of the at least one conductive clamp in the bridge-like location, the solder material electrically coupling the at least one conductive clamp to the at least one semiconductor chip and electrically coupling to the at least one conductive pad; and at least one pair of complementary positioning structures including cavities in the at least one conductive clamp and protrusions in at least one of the at least one semiconductor chip and the at least one conductive pad, the complementary positioning structures engaging with each other. Attached Figure Description

[0013] One or more embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

[0014] Figure 1 This is a perspective view of a power semiconductor device;

[0015] Figure 2 It is along Figure 1 The cross-sectional view of line II-II involves conventional power semiconductor devices;

[0016] Figure 3 It is along Figure 1The cross-sectional view of line II-II relates to a power semiconductor device according to an embodiment of this specification;

[0017] Figure 4 It is indicated by arrow IV. Figure 3 A partial view, reproduced at an enlarged scale;

[0018] Figure 5 It corresponds to Figure 4 The view illustrates possible advantageous developments of embodiments of this specification; and

[0019] Figure 6 This is a plan view of a power semiconductor device according to an embodiment of this specification. Detailed Implementation

[0020] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to the corresponding parts.

[0021] The accompanying drawings are provided to clearly illustrate relevant aspects of the embodiments and are not necessarily drawn to scale.

[0022] The edges of features drawn in the accompanying drawings do not necessarily indicate the end of the feature range.

[0023] One or more specific details are shown in the following description to provide a thorough understanding of examples of embodiments described herein. Embodiments may be obtained without one or more specific details, or by utilizing other methods, components, materials, etc. In other instances, known structures, materials, or operations have not been shown or described in detail so as not to obscure certain aspects of the embodiments.

[0024] References to “embodiment” or “an embodiment” within the framework of this specification are intended to indicate that a particular configuration, structure, or feature described with respect to that embodiment is included in at least one embodiment. Therefore, phrases such as “in an embodiment” or “in one embodiment” that may appear at one or more points in this specification do not necessarily refer to one and the same embodiment.

[0025] Furthermore, in one or more embodiments, specific conformations, structures, or properties can be combined in any suitable manner.

[0026] The headings / references used herein are provided for convenience only and therefore do not limit the scope of protection or the scope of the embodiments.

[0027] For simplicity and ease of explanation, the same reference numerals are used to indicate the same parts or elements in the various figures throughout the specification, and the corresponding descriptions will not be repeated for each figure.

[0028] In current semiconductor device manufacturing processes, multiple devices are manufactured simultaneously so that they can be separated into individual devices in a final dicing process. For simplicity and ease of explanation, the following description will focus on the fabrication of individual devices.

[0029] Figure 1 This is an example of a power semiconductor device 10 with a plastic package.

[0030] As is common in the art, device 10 includes a substrate (lead frame) 12 on which one or more semiconductor integrated circuit chips or dies are disposed. The terms chip / multiple chips and die / multiple dies are considered synonymous as used herein.

[0031] The accompanying drawings illustrate an example of a semiconductor power device 10, which includes a low-power portion (e.g., a controller integrated circuit die 141) attached to a first die pad 121A in a lead frame 12 and a high-power portion (e.g., one or more power integrated circuit dies 142) attached to one or more die pads 122A in the lead frame 12, wherein an array of leads 12B surrounds the die pads 121A, 122A and has dies 141 and 142 mounted thereon.

[0032] The term “lead frame” (or “lead frame”) is currently used (for example, see the USPC Combined Glossary) to refer to a metal frame that provides support for an integrated circuit chip or die, and electrical leads that interconnect the integrated circuit in the die or chip to other components or contacts.

[0033] Essentially, the leadframe comprises an array of conductive structures (or leads, such as 12B) extending inward from the outline location along the direction of the semiconductor chip or die (such as 141, 142), thereby forming an array of conductive structures by die pads (such as 121A, 122A), the die pads being configured to have at least one semiconductor chip or die attached thereto. This can be achieved via conventional means such as die attachment adhesive 1420 (e.g., die attachment film (DAF)).

[0034] Figure 1 The device shown is intended to be mounted on a substrate such as a printed circuit board (PCB – not visible in the figure) using, for example, solder materials.

[0035] A conductive structure is provided to electrically couple (multiple) semiconductor chips 141, 142 to selected leads (external pads) 12B in lead frame 12.

[0036] As shown, these conductive structures include wire bonding patterns 16 that couple low-power portions (chip 141) to selected leads 12B and high-power portions (one or more chips 142). These wire bonding patterns 16 are coupled to die pads 1410 provided on the front or top surfaces of chips 141 and 142.

[0037] Instead, the so-called clip 18 is used to couple the high-power portion (one or more chips 142) to a selected lead 12B that serves as the (power) output pad for device 10.

[0038] The use of clip 18 instead of the leads included in the lead bonding pattern 16 (for providing electrical coupling to the low-power section (e.g., controller 141)) takes into account the fact that the current transferred from the high-power section 142 to the output pads in the power semiconductor device can be quite large. As mentioned above, wires such as wire 16 are still used to provide electrical coupling to the low-power section (e.g., controller) in the device.

[0039] An insulating encapsulation 20 (e.g., epoxy resin) is molded onto the thus formed component to complete the plastic body of the device 10.

[0040] Although the device 10 shown includes two clips 18, some devices may include only one clip or more than two clips.

[0041] As explained herein, this device structure is conventional in the art, which makes it unnecessary to provide a more detailed description herein.

[0042] In summary, for the purposes of this document, manufacturing the device 10 as discussed herein includes: arranging at least one semiconductor chip 142 on a die pad 12A in a substrate 12, the substrate 12 including at least one conductive pad 12B (i.e., adjacent to or side-by-side with the die pad 12A); and positioning at least one conductive clamp 18 in a bridge-like position between the at least one semiconductor chip 142 and the at least one conductive pad 12B.

[0043] In this bridge-like position, the conductive clamp 18 has a coupling surface facing the semiconductor chip 142 and the conductive pad 12B.

[0044] The conductive clamp 18 located in the bridge-shaped position is soldered to the semiconductor chip 142 and the conductive pad 12B to provide electrical coupling therebetween.

[0045] As shown, welding is achieved via welding material 22 (in a manner known to those skilled in the art) distributed at the coupling surfaces. The welding material 22 is cured (in a manner known to those skilled in the art themselves), for example via heat treatment in an oven.

[0046] As discussed, clips such as clip 18 are placed using clip attachment equipment, and solder paste 22 is used to attach the clips to the pads and the die. Solder cured in the oven is applied to provide a strong connection between the clip 18 and the pads (e.g., 12B) and the die (e.g., 142).

[0047] Conventional clip attachment equipment helps to achieve sufficient precision in chip placement because clips 18 are applied in a bridge-like manner between a bare die such as die 142 and a corresponding pad / lead such as pad / lead 12A: this is considered simple; in some devices, a single clip 18 can be coupled to, for example, multiple pads / leads.

[0048] After the clips are placed, the assembly is transferred to an oven for solder curing. During this processing and curing, the clips may shift from their intended correct position, which could result in a defective final product.

[0049] The thickness of solder 22 and the tendency of the clips to "float" on solder 22 in a fluid state may also be based on undesirable excessive clip tilting.

[0050] Undesirable clip movement (displacement) can be counteracted by adding fixing features to the clip and lead frame design.

[0051] Smoothing can also help achieve very precise clamp centering during clamp placement.

[0052] Alternatively, you can consider choosing a solder paste material that can counteract the unwanted clip floating characteristics.

[0053] For various reasons, none of these solutions seem entirely satisfactory.

[0054] For example, certain features added to the clip / leadframe design may be space-consuming, which may suggest reducing the pad size and / or using a larger package size to gain space, neither of which is attractive / desirable.

[0055] The handling of the components involved is already a fairly mild process, and further improvements in these areas are unimaginable.

[0056] Choosing a solder paste material that differs from conventionally used materials may have negative effects on thermal and electrical properties.

[0057] The examples considered in this article utilize the current availability of equipment (e.g., wire bonding equipment) configured to form so-called column bumps in semiconductor device manufacturing processes.

[0058] In a conventional wire bonding (e.g., as used to provide the previously discussed wire bonding pattern 16), a ball is formed at the end of the lead metal material such as, for example, aluminum (Al), copper (Cu), and gold (Au), which is bonded to the die pad. The wire then extends toward the lead forming the second wire bonding.

[0059] If the lead terminates after the first bonding, a "bump" is formed only on the die pad. Such a bump can be used to interconnect to dies flip-chipped onto a substrate, for example, using thermoacoustic or thermocompression processes.

[0060] In the example considered herein, one or more cylindrical protrusions 100 are formed on pads / leads 12B to which the clip 18 is to be coupled. One or more corresponding recesses or cavities 102 are formed, for example, cylindrical (blind) holes in the surface of the clip 18 facing the pads / leads 12B, such that one or more protrusions 100 can penetrate into these recesses or cavities 102. The protrusion 100 / cavity 102 pairs can, for example, be positioned in... Figure 1 The area shown is 180 locations.

[0061] Therefore, each pair of protrusions 100 / cavities 102 can provide a centering feature that counteracts the undesirable mutual displacement of the clips 18 relative to the pads 12B (and relative to the substrate 12 and the chip or multiple chips 142).

[0062] Therefore, the method shown herein includes providing at least one pair of complementary positioning structures, such as the cavity 102 in the conductive clamp 18 and the protrusion 100 in the conductive pad 12B, prior to soldering.

[0063] The complementary positioning structures 100 and 102 engage with each other in response to the conductive clamp 18 being positioned in the desired bridge-like position.

[0064] Therefore, the complementary positioning structures 100, 102 hold the clip 18 in this bridge-like position during the welding process (e.g., via solder paste delivered and solidified by heat curing in an oven) to counteract unwanted displacement and "floating" onto the molten solder paste.

[0065] Provide at least two pairs of protrusions 100 / cavities 102 in the clips or each clip (e.g., see...). Figure 6 This advantageously counteracts the mutual rotation of the clip 18 relative to the pad 12B, the substrate 12, and the (multiple) chips 142.

[0066] Other conventional wire bonding techniques using materials such as gold or (less expensive) copper can be used to create and bond cylindrical bumps such as cylindrical bumps 100 on pad 12B.

[0067] The recesses or cavities 120 on the clip 18 can be created during the production of the clip, for example during clip stamping (of a metallic material, such as, for example, copper) to provide the desired shape thereon.

[0068] like Figure 4 and 5 As can be seen, multiple stacked columnar protrusions 100 can be generated to provide anchoring “pillars”, which are configured to extend a certain length into the corresponding recesses 102 (e.g., until the end surface of the recess 102).

[0069] like Figure 5 As shown, one or more “spaced” cylindrical protrusions 100’ can be formed without recessed mating in the clip 18 to keep the clip 18 (slightly) away from the pad 12B, thereby providing a controlled width gap between the clip 18 and the pad 12A.

[0070] This gap can be penetrated by solder material 22. This arrangement has been found to be beneficial in controlling (minimum) solder thickness and resisting undesirable clip tilting.

[0071] The examples presented in this article help keep the clips precisely "centered" during the assembly process, thus offsetting unwanted displacement (translation, rotation, tilt). Solder thickness can be appropriately controlled.

[0072] In the example presented herein, the positioning structure 100 (e.g., columnar protrusion) is formed to protrude from the pad / lead 12B in the lead frame 12 and engage the corresponding cavity 102 (e.g., blind via) in the clip 18.

[0073] At least in principle, this positioning structure 100 can also be formed at or only at a die pad, such as a die pad 1410 provided on the front or top surface of the chip or die 142 (as is common in the art).

[0074] Alternatively, spaced cylindrical protrusions, such as those shown in the figure, may be provided on the surface of the clip 18 (or only).

[0075] It should be noted that the presence of (multiple) anchoring structures 100 protruding from the pads / leads and engaging with the corresponding cavities 102 (e.g., blind vias) in the clip 18 will also be noticeable in the final device, even after solder material 22 is provided between the clip 18 and the pads 12B to which the clip is soldered.

[0076] Without departing from the basic principles, details and embodiments may be changed, even significantly changed, relative to what has been described by way of example only, without departing from the scope of protection.

[0077] The claims form an integral part of the technical teachings of the embodiments provided herein.

[0078] The scope of protection is determined by the appended claims.

Claims

1. A method for manufacturing a semiconductor device, comprising: Semiconductor integrated circuit chips are arranged on die pads of a substrate, the substrate including conductive pads adjacent to the die pads; A pair of complementary positioning structures are provided, the complementary positioning structures including cavities in conductive fixtures and protrusions in at least one of the semiconductor integrated circuit chip or the conductive pads; The at least one conductive clamp is positioned in a bridge-like location between the semiconductor integrated circuit chip and the conductive pad, wherein the complementary positioning structures are engaged with each other. The conductive clamp has a coupling surface facing the semiconductor integrated circuit chip and the conductive pad in the bridge-shaped position; as well as The conductive fixture in the bridge-shaped position is welded to the semiconductor integrated circuit chip and the conductive pad to provide electrical coupling between the semiconductor integrated circuit chip and the conductive pad, wherein the welding is performed via welding material at the coupling surface.

2. The method of claim 1, wherein providing the pair of complementary positioning structures comprises: At least two pairs of complementary positioning structures are provided, wherein the at least two pairs of complementary positioning structures counteract the rotation of the at least one conductive clamp relative to the bridge-shaped position during the welding.

3. The method of claim 1, wherein providing the pair of complementary positioning structures comprises: The cavity is formed in the conductive fixture and the protrusion is formed in the conductive pad.

4. The method according to claim 1, wherein the cavity includes a blind hole.

5. The method of claim 1, wherein the protrusion comprises a cylindrical protrusion.

6. The method of claim 1, wherein the protrusion comprises a stack of a plurality of cylindrical protrusions.

7. The method of claim 1, further comprising: Prior to the soldering, a spacer structure is provided on at least one of the semiconductor integrated circuit chip and the conductive pad at a location spaced apart from the pair of complementary positioning structures, wherein the spacer structure is configured to keep the conductive jig at a distance from one or more of the semiconductor integrated circuit chip and the conductive pad during the soldering.

8. The method of claim 7, wherein the spacer structure comprises a columnar protrusion.

9. A semiconductor device, comprising: Substrate, the substrate including conductive pads adjacent to die pads; A semiconductor integrated circuit chip is mounted to the bare die pad of the substrate; A conductive clamp is located in a bridge-like position between a semiconductor integrated circuit chip and the conductive pad, the conductive clamp having a coupling surface facing the semiconductor integrated circuit chip and the conductive pad; Solder material is applied to the coupling surface of the conductive clamp in the bridge-shaped position, the solder material electrically coupling the conductive clamp to the semiconductor integrated circuit chip and to the conductive pad; and A pair of complementary positioning structures, including cavities in the conductive fixture and protrusions in at least one of the semiconductor integrated circuit chip and the conductive pad, wherein the complementary positioning structures are engaged with each other.

10. The device according to claim 9, further comprising another pair of complementary positioning structures.

11. The device of claim 9, wherein the pair of complementary positioning structures comprises the cavity in the conductive clamp and the protrusion in the conductive pad.

12. The device of claim 9, wherein the cavity includes a blind hole.

13. The device of claim 9, wherein the protrusion comprises a cylindrical protrusion.

14. The device of claim 9, wherein the protrusion comprises a stack of a plurality of cylindrical protrusions.

15. The device of claim 9, further comprising a spacing structure on at least one of the semiconductor integrated circuit chip and the conductive pad, at a position spaced apart from the pair of complementary positioning structures, wherein the spacing structure is configured to hold the conductive clamp at a distance from the semiconductor integrated circuit chip and the conductive pad.

16. The device of claim 15, wherein the spacer structure is a cylindrical protrusion.

17. The device of claim 9, wherein the semiconductor integrated circuit chip is a power semiconductor integrated circuit, and wherein the size and dimensions of the conductive clamp are configured to carry the current generated by the power semiconductor integrated circuit.

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