Joint structure

Abstract

The utility model provides a joint structure. The joint structure comprises a lower welding pad, an upper welding pad in contact with the lower welding pad, and a dielectric layer wrapping the lower welding pad and the upper welding pad, a plurality of holes are formed in the lower welding pad and / or the upper welding pad; the interior of at least one hole close to the joint face of the lower welding pad and the upper welding pad is not provided with a dielectric material used for forming the dielectric layer. In the bonding structure, the hole close to the bonding surface of the lower bonding pad and the upper bonding pad is hollow, and no dielectric material exists, so that the bonding yield can be improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor packaging technology, and more specifically to a bonding structure. Background Technology

[0002] Existing hybrid bonding technologies, such as polyimide hybrid bonding, require a very high degree of flatness on the metal (e.g., copper) surface. If the depth of the depression on the metal surface is greater than 10 nm, copper-to-copper bonding may not be able to be successfully completed.

[0003] refer to Figure 1 The bonding structure shown typically involves electroplating or chemically plating a softer, more compressible metal 12, such as nanoporous copper (NP-Cu), onto the surface of the metal pad 11 to aid bonding. Currently, nanoporous copper plating is a one-step process, meaning that nanoporous copper with different porosities is directly electroplated. (Reference) Figure 6 , Figure 6 An electron microscope image of directly electroplated nanoporous copper is shown.

[0004] However, after the nanoporous copper is formed, when the dielectric layer 13 is coated, the dielectric material (such as polyimide, abbreviated as PI) constituting the dielectric layer 13 will penetrate into the pores 14 of the nanoporous copper and cannot be removed, which will affect the bonding. As a result, the yield will be affected after metal bonding because the internal pores 14 are covered with dielectric material. Utility Model Content

[0005] This application proposes a bonding structure for improving bonding yield.

[0006] The present application discloses a bonding structure comprising: a lower solder pad, an upper solder pad contacting the lower solder pad, and a dielectric layer covering the lower solder pad and the upper solder pad; the lower solder pad and / or the upper solder pad having a plurality of holes inside; wherein at least one of the holes near the bonding surface of the lower solder pad and the upper solder pad does not contain dielectric material for constituting the dielectric layer.

[0007] In some alternative embodiments, the interior of at least one of the holes near the dielectric layer contains a dielectric material.

[0008] In some alternative embodiments, at least one of the holes has a metal filler material of a different material than the lower and upper solder pads.

[0009] In some alternative embodiments, the metal filler material is zinc.

[0010] In some alternative embodiments, the interior is free of the dielectric material and has at least one of the holes filled with the metal material, away from the mating surface.

[0011] In some alternative embodiments, the plurality of holes are of different sizes, with the holes farther from the mating surface being larger than the holes closer to the mating surface.

[0012] In some optional embodiments, the lower solder pad includes a lower solder pad body and a first flexible connection portion that is bonded to the lower solder pad body; the upper solder pad includes an upper solder pad body and a second flexible connection portion that is bonded to the upper solder pad body; the first flexible connection portion contacts the second flexible connection portion, and the holes are distributed within the first flexible connection portion and the second flexible connection portion.

[0013] In some alternative embodiments, the first flexible connector and the second flexible connector are deformable under pressure.

[0014] In some alternative implementations, the horizontal width of the first flexible connection is smaller than that of the lower solder pad body, and the horizontal width of the second flexible connection is smaller than that of the upper solder pad body.

[0015] In some alternative embodiments, the first flexible connector and the second flexible connector are copper with the holes, and the first flexible connector and the second flexible connector are directly bonded copper to copper.

[0016] In some alternative embodiments, the lower pad body has a plurality of first flexible connections, and the upper pad body has a plurality of second flexible connections.

[0017] In some alternative embodiments, the dielectric layer is provided within the intervals between the plurality of first flexible connections and the intervals between the plurality of second flexible connections.

[0018] In some alternative embodiments, the upper pad body and the lower pad body are spaced apart from each other.

[0019] To address the issue of dielectric material seeping into the pores of nanoporous copper in hybrid bonding technology, thus affecting bonding and reducing yield, this application proposes a bonding structure. In this structure, the pores near the bonding surfaces of the lower and upper solder pads are hollow and contain no dielectric material, thereby improving bonding yield. The solder pads in this bonding structure are formed through a two-step process: first, an alloy is electroplated, then etched. Specifically, after electroplating the alloy, a dielectric layer is coated, and then the electroplated alloy is etched to form pores. This creates lower / upper solder pads with pores that do not contain dielectric material. When these upper and lower solder pads are bonded, the hollow pores maintain good compressibility, resulting in a good bond and solving the technical problem of dielectric material seeping into the solder pad pores and affecting bonding, thus reducing yield. Attached Figure Description

[0020] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0021] Figure 1 This is a schematic diagram of a partial longitudinal cross-section of an existing joint structure;

[0022] Figure 2 This is a schematic diagram of the longitudinal cross-sectional structure of an embodiment 20 of the joining structure according to this application;

[0023] Figure 3 yes Figure 2 A magnified view of the structure of the area within the dashed box;

[0024] Figure 4-5 This is a schematic diagram of the manufacturing steps of one embodiment of the joining structure of this application;

[0025] Figure 6 This is an electron microscope image of nanoporous copper directly electroplated in an existing bonding structure.

[0026] Figure 7 This is an electron microscope image of the first flexible connector in one embodiment of the bonding structure of this application.

[0027] Explanation of reference numerals / symbols in the attached diagram:

[0028] 11-Metallic solder pad; 12-Soft metal; 13-Dielectric layer; 14-Void;

[0029] 21-Lower solder pad; 210-Lower solder pad body; 211-First flexible connection; 22-Upper solder pad; 220-Upper solder pad body; 221-Second flexible connection; 23-Dielectric layer; 24-Vacuum; 25-Joint surface; 26-Gas; 27-Dielectric material; 28-Metal filler material;

[0030] 31-First element; 32-Second element; 33-Photoresist; 34-Alloy material. Detailed Implementation

[0031] The specific embodiments of this application will be described below with reference to the accompanying drawings and examples. Those skilled in the art can easily understand the technical problems solved by this application and the resulting technical effects through the content described herein. It is understood that the specific embodiments described herein are merely illustrative of the relevant invention and are not intended to limit the invention. Furthermore, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0032] It should be readily understood that the meanings of “on,” “above,” and “on top of” in this application should be interpreted in the broadest sense, such that “on” means not only “directly on something,” but also “on something” including intermediate components or layers existing between the two.

[0033] Furthermore, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” and “upper” may be used herein to describe the relationship of one element or component to another element or component shown in the accompanying drawings. In addition to the orientations described in the figures, spatial relative terms are also intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90° or otherwise), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0034] As used herein, the term "layer" refers to a portion of material comprising a region of a certain thickness. A layer may extend over the entirety of an underlying or upper layer structure, or may have a extent smaller than that of the underlying or upper layer structure. Furthermore, a layer may be a region of a homogeneous or heterogeneous continuous structure, with a thickness less than that of the continuous structure. For example, a layer may be located between the top and bottom surfaces of a continuous structure, or between any pair of horizontal planes therebetween. A layer may extend horizontally, vertically, and / or along a tapered surface. A substrate may be a single layer, which may include one or more layers, and / or may have one or more layers on, above, and / or below it. A single layer may include multiple layers. For example, a semiconductor layer may include one or more doped or undoped semiconductor layers, and may have the same or different materials.

[0035] As used herein, the term "substrate" refers to the material on which subsequent material layers are added. The substrate itself may be patterned. The material added on top of the substrate may be patterned or may remain unpatterned. Furthermore, the substrate may comprise a wide variety of semiconductor materials, such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, indium phosphide, etc. Alternatively, the substrate may be made of a non-conductive material, such as glass, plastic, or sapphire wafers. Further alternatively, the substrate may have semiconductor devices or circuits formed therein.

[0036] It should be noted that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading of the contents described in the specification. They are not intended to limit the scope of this application and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives of this application, should still fall within the scope of the technical content disclosed in this application. Furthermore, terms such as "above," "first," "second," and "a" used in this specification are merely for clarity of description and are not intended to limit the scope of this application. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this application's implementation.

[0037] It should also be noted that the longitudinal section corresponding to the embodiment of this application can be the section corresponding to the front view direction, the transverse section can be the section corresponding to the right view direction, and the horizontal section can be the section corresponding to the top view direction.

[0038] Furthermore, where there is no conflict, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] refer to Figure 2-3 , Figure 2 This is a schematic diagram of the longitudinal cross-section of an embodiment 20 of the joining structure according to this application. Figure 3 yes Figure 2 A magnified view of the structure of the area within the dashed box.

[0040] like Figure 2-3 As shown, the bonding structure 20 of this application includes: a lower solder pad 21, an upper solder pad 22 contacting the lower solder pad 21, and a dielectric layer 23 covering the lower solder pad 21 and the upper solder pad 22; the lower solder pad 21 and / or the upper solder pad 22 have a plurality of holes 24 inside; wherein, at least one hole 24 near the bonding surface 25 of the lower solder pad 21 and the upper solder pad 22 does not contain dielectric material 27 for constituting the dielectric layer 23 inside.

[0041] Here, the lower pad 21 can be a pad on the first component 31, and the upper pad 22 can be a pad on the second component 32. The first component 31 and the second component 32 are, but are not limited to, electronic components such as substrates, wafers, chips, and dies. For example, the material of the first component 31 and the second component 32 may include silicon (Si).

[0042] Here, the dielectric material of dielectric layer 23 includes, but is not limited to, polyimide (PI).

[0043] Here, the first element 31 and the second element 32 can be bonded by a hybrid bonding (or hybrid bonding) technique, wherein the dielectric layer 23 on the first element 31 and the second element 32 is directly physically bonded, and the lower pad 21 and the upper pad 22 are directly electrically bonded.

[0044] Here, when bonding, the lower pad 21 and / or the upper pad 22 have better compressibility because they have multiple holes 24, and at least one hole 24 near the bonding surface 25 is hollow and has no dielectric material 27 inside. This avoids the problem of bonding being affected by the presence of dielectric material inside the holes 24, and can improve the bonding yield.

[0045] refer to Figure 3 The multiple holes 24 in the lower solder pad 21 and / or upper solder pad 22 may include, for example, three types:

[0046] The first type is at least one hole 24 (which may be referred to as the first hole) near the bonding surface 25, which may be hollow inside, or rather, filled with gas 26 (e.g., air) and without dielectric material 27 for constituting dielectric layer 23.

[0047] The second type is at least one hole 24 (which may be referred to as the second hole) near the dielectric layer 23, which may have dielectric material 27 for constituting the dielectric layer 23 inside;

[0048] The third type is at least one hole 24 (which may be referred to as the third hole) located away from the bonding surface 25 (relative to the first hole which is hollow inside and has no dielectric material 27), which has no dielectric material 27 inside and may have a metal filler material 28 of a different material than the lower solder pad 21 and the upper solder pad 22.

[0049] For example, the lower solder pad 21 and the upper solder pad 22 can be made of copper (Cu), and the metal filler material 28 can be made of zinc (Zn).

[0050] In some optional embodiments, the lower solder pad 21 and upper solder pad 22 in this application embodiment can be formed by a two-step process: first, electroplating an alloy, then etching. That is, first, an alloy (e.g., a copper-zinc alloy) is electroplated, then a dielectric layer 23 is coated, and finally, the electroplated alloy is etched away to remove one of the metals (e.g., zinc) to form a hole 24, thereby obtaining a lower solder pad 21 / upper solder pad 22 with an internal hole 24. The metal removed by etching (e.g., zinc) can be called metal filler material 28. Here, compared to the conventional process of directly electroplating nanoporous copper in one step, a non-porous alloy material 34 is plated during electroplating, resulting in higher electroplating efficiency. Here, if the metal filler material 28 (e.g., zinc) is not completely removed during the etching step, some of the metal filler material 28 will fill some of the holes 24 that should have been formed. These holes 24 are usually far away from the bonding surface 25 of the lower solder pad 21 and the upper solder pad 22.

[0051] Here, the diameter (or width) of the formed pore 24 can be at the nanometer level, for example, from several nanometers to tens of nanometers or even hundreds of nanometers. The first flexible connection 211 and the second flexible connection 221 with nanometer-sized pores 24 can be referred to as nanopores.

[0052] In some alternative implementations, refer to Figure 3 The sizes of the multiple holes 24 can be different. For example, the holes 24 farther away from the mating surface 25 can be larger than the holes 24 closer to the mating surface 25.

[0053] In some alternative implementations, refer to Figure 2-3 The lower solder pad 21 may include a lower solder pad body 210 and a first flexible connection portion 211 raised on the lower solder pad body 210; the upper solder pad 22 may include an upper solder pad body 220 and a second flexible connection portion 221 raised on the upper solder pad body 220; when bonding is performed, the first flexible connection portion 211 contacts and electrically connects to the second flexible connection portion 221; here, the holes 24 may be distributed in the first flexible connection portion 211 and the second flexible connection portion 221, while the lower solder pad body 210 and the upper solder pad body 220 do not have holes 24.

[0054] Because the first flexible connector 211 and the second flexible connector 221 have holes 24 inside, and at least one hole 24 near the mating surface 25 is hollow and does not contain dielectric material 27, the first flexible connector 211 and the second flexible connector 221 can maintain relatively soft and compressible characteristics. When mating, the first flexible connector 211 and the second flexible connector 221 come into contact with each other and can deform under pressure, thus enabling them to be mated as tightly as possible and improving the mating yield.

[0055] In some alternative implementations, refer to Figure 2-3 The horizontal width of the first flexible connection portion 211 is smaller than that of the lower solder pad body 210, and the horizontal width of the second flexible connection portion 221 is smaller than that of the upper solder pad body 220. In terms of manufacturing process, the first flexible connection portion 211 can be fabricated on the existing lower solder pad body 210, and the second flexible connection portion 221 can be fabricated on the existing upper solder pad body 220, thus easily achieving the above-mentioned structural features.

[0056] In some alternative embodiments, both the lower pad body 210 and the upper pad body 220 are made of copper and can be dense electroplated copper (optionally, sputtered copper as a seed layer may also be included).

[0057] In some alternative implementations, refer to Figure 2-3 The first flexible connector 211 and the second flexible connector 221 are made of copper with holes 24, and the first flexible connector 211 and the second flexible connector 221 are directly joined copper to copper.

[0058] In some alternative implementations, refer to Figure 2 The lower solder pad body 210 may have one or more first flexible connection portions 211, and the upper solder pad body 220 may have one or more second flexible connection portions 221 respectively. The multiple first flexible connection portions 211 and the multiple second flexible connection portions 221 are respectively connected in a one-to-one correspondence.

[0059] In some alternative implementations, refer to Figure 2 A dielectric layer 23 is provided in the intervals between the plurality of first flexible connectors 211 and in the intervals between the plurality of second flexible connectors 221.

[0060] In some alternative implementations, refer to Figure 2-3 The lower solder pad body 210 and the upper solder pad body 220 are spaced apart from each other, that is, they do not contact each other, but are joined together by the first flexible connection part 211 and the second flexible connection part 221.

[0061] refer to Figure 4-5 , Figure 4-5 This is a schematic diagram illustrating the manufacturing steps of one embodiment of the joining structure 20 of this application. Figure 4-5 As shown, the manufacturing steps of the joining structure 20 of this application may include:

[0062] Step S1: Provide a first component 31, which has a lower pad body 210. In this step, a photoresist 33 covering the lower pad body 210 is applied to the first component 31 by means of, for example, coating, and photolithography is performed on the photoresist 33.

[0063] Step S2: By developing the photoresist 33 after photolithography, the photoresist 33 is patterned, exposing the upper surface of the lower pad body 210. Next, an alloy material 34 is electroplated onto the exposed lower pad body 210. The alloy material 34 can be, for example, a copper-zinc alloy (Cu-Zn Alloy). Compared to the conventional method of directly electroplating nanoporous copper in one step, this method uses a non-porous alloy material 34, resulting in higher electroplating efficiency.

[0064] Step S3: Remove photoresist 33. Here, the alloy material 34 electroplated in the previous step serves as the first flexible connection portion 211, which together with the lower solder pad body 210 constitutes the lower solder pad 21. Optionally, there may be one or more first flexible connection portions 211 on the lower solder pad body 210.

[0065] Step S4: In this step, a dielectric layer 23 is formed on the first component 31 by a process such as coating or lamination, and the dielectric layer 23 covers the lower solder pad 21.

[0066] Step S5: For example, the dielectric layer 23 is thinned by a process such as grinding, so that the upper surface of the lower pad 21 (i.e. the upper surface of the first flexible connection portion 211) is exposed in the thinned dielectric layer 23.

[0067] Step S6: For example, dealloying is performed by etching, that is, one material, such as zinc, is removed from the alloy material 34 constituting the first flexible connection 211, while retaining another material, such as copper. In this way, as the zinc is removed, pores 24 are formed in the remaining copper, thereby forming the first flexible connection 211 with multiple pores 24. Here, compared with directly electroplating nanoporous copper in one step, the pores 24 formed by etching the alloy have higher distribution uniformity and size uniformity, resulting in a more flexible and compressible first flexible connection 211.

[0068] Here, in the portion of the first flexible connection 211 that is farther from the upper surface and closer to the lower solder pad body 210, the zinc inside is more difficult to etch because it is far from the etching solution, so some zinc may remain. In other words, the locations where the zinc remains can also be considered as holes 24, only filled with zinc. This zinc filling the holes 24 can be called metal filler material 28 (see...). Figure 3 ).

[0069] Here, the portion of the first flexible connection 211 closer to the upper surface is closer to the etching solution, allowing the zinc inside to be cleanly etched away, thus forming completely hollow holes 24. In other words, these holes 24 are filled with gas 26, such as air (see [reference]). Figure 3 ).

[0070] refer to Figure 7 , Figure 7 An electron microscope image of the first flexible connection 211 formed after dealloying is shown.

[0071] Step S7: Provide a second component 32 having an upper solder pad 22. The upper solder pad 22 includes an upper solder pad body 220 and a second flexible connection portion 221 with multiple holes, and the upper solder pad 22 is surrounded by a dielectric layer 23. The fabrication steps of the upper solder pad 22 on the second component 32 can be referred to the aforementioned steps S1-S6, and will not be repeated here. In this step, the first component 31 and the second component 32 are mixed and bonded, wherein their respective dielectric layers 23 are directly bonded, and the lower solder pad 21 and the upper solder pad 22 are directly bonded.

[0072] In step S8, after the hybrid bonding is completed, the lower solder pad 21 and the upper solder pad 22 are bonded together by direct copper-to-copper bonding and are covered by a dielectric layer 23 bonded together by adhesive bonding. During the bonding process, the first flexible connection portion 211 and the second flexible connection portion 221 have relatively soft and compressible characteristics due to having at least one hollow hole 24 inside, which can deform under pressure, thus enabling them to bond as tightly as possible and improving the bonding yield. Optionally, due to the pressure during the bonding process, a portion of the hole 24 near the dielectric layer 23 may be filled with dielectric material 27 (see...). Figure 3 ).

[0073] The present application proposes a bonding structure 20 and its manufacturing steps. Through a two-step process, an alloy material 34 is first electroplated, then a dielectric layer 23 is coated, and finally the electroplated alloy material 34 is etched to form a hole 24, thereby forming a lower solder pad 21 / upper solder pad 22 with a hole 24 inside. Therefore, the hole 24 near the bonding surface 25 of the lower solder pad 21 and the upper solder pad 22 in this structure is hollow and has no dielectric material 27. In this way, the bonding yield can be improved and the technical problem of dielectric material 27 penetrating into the hole of the solder pad and affecting the bonding, resulting in a decrease in yield, can be solved.

[0074] Compared with existing joint structures, the joint structure 20 of this application can also achieve the following technical effects: ① lower joint pressure, which can be reduced from the existing 10MPa or more to below 5MPa; ② lower joint temperature, which can be reduced from the existing 300℃ or more to below 250℃; thus making it more suitable for industrial applications.

[0075] Although this application has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not limiting of this application. It will be readily understood by those skilled in the art that various changes can be made and equivalent elements can be substituted within embodiments without departing from the true spirit and scope of this application as defined by the appended claims. Illustrations may not be drawn to scale. Differences may exist between the technical representation in this application and actual implementation due to variables in the manufacturing process, etc. Other embodiments of this application may exist that are not specifically described. The description and illustrations should be considered illustrative rather than restrictive. Modifications can be made to adapt particular circumstances, materials, composition, methods, or processes to the objectives, spirit, and scope of this application. All such modifications fall within the scope of the appended claims. While the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations can be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of this application. Therefore, unless specifically indicated herein, the order and grouping of operations do not limit this application.

Claims

1. A joining structure, characterized in that, include: The lower solder pad, the upper solder pad that contacts the lower solder pad, and the dielectric layer covering the lower solder pad and the upper solder pad; the lower solder pad and / or the upper solder pad have a plurality of holes inside; wherein, at least one of the holes near the mating surfaces of the lower solder pad and the upper solder pad does not contain dielectric material for forming the dielectric layer.

2. The joining structure according to claim 1, characterized in that, The interior of at least one of the holes near the dielectric layer contains dielectric material.

3. The joining structure according to claim 1, characterized in that, At least one of the holes has a metal filler material of a different material than the lower and upper solder pads.

4. The joining structure according to claim 3, characterized in that, The cavity contains no dielectric material and has at least one of the holes filled with the metal material, located away from the mating surface.

5. The joining structure according to claim 1, characterized in that, The multiple holes are of different sizes, with the holes farther away from the mating surface being larger than the holes closer to the mating surface.

6. The joining structure according to claim 1, characterized in that, The lower solder pad includes a lower solder pad body and a first flexible connecting portion protruding from the lower solder pad body; The upper solder pad includes an upper solder pad body and a second flexible connecting portion protruding from the upper solder pad body; The first flexible connector contacts the second flexible connector, and the holes are distributed within the first flexible connector and the second flexible connector.

7. The joining structure according to claim 6, characterized in that, The horizontal width of the first flexible connection portion is smaller than that of the lower solder pad body, and the horizontal width of the second flexible connection portion is smaller than that of the upper solder pad body.

8. The joining structure according to claim 6, characterized in that, The first flexible connector and the second flexible connector are made of copper with the holes, and the first flexible connector and the second flexible connector are directly joined copper to copper.

9. The joining structure according to claim 6, characterized in that, The lower solder pad body has a plurality of first flexible connection portions, and the upper solder pad body has a plurality of second flexible connection portions.

10. The joining structure according to claim 9, characterized in that, The dielectric layer is provided within the intervals between the plurality of first flexible connections and the intervals between the plurality of second flexible connections.

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