Method for forming electrically conductive structure between two substrates

Abstract

A method for forming an electrically conductive structure between two substrates is disclosed. The method includes forming a first patterned base layer and a second patterned base layer on respective front surfaces of a first substrate and a second substrate; forming a first metal contact structure in the through hole of the first patterned base layer and forming a second metal contact structure in the through hole of the second patterned base layer; forming a first patterned polymer layer and a second patterned polymer layer on respective front surfaces of the first patterned base layer and the second patterned base layer; passivating front surfaces of the first metal contact structure and the second metal contact structure; bonding the front surfaces of the first metal contact structure and the second metal contact structure to each other; and after the front surfaces of the first metal contact structure and the second metal contact structure are bonded to each other, bonding the front surfaces of the first patterned polymer layer and the second patterned polymer layer to each other.

Description

Technical Field

[0001] The present application relates generally to semiconductor technology and, more particularly, to methods for forming a conductive structure between two substrates. Background Art

[0002] Hybrid bonding is a chip-level interconnect technology that can increase the density of integrated chip packages, thereby achieving high performance, small size and low power consumption of integrated chip packages. Before the bonding process used to form hybrid bonding, a chemical mechanical polishing (CMP) process is usually required to flatten the surface of the integrated chip package or other substrate. However, metal dishing or oxide erosion may occur after the CMP process, which may affect the quality of hybrid bonding.

[0003] Therefore, further improvements in hybrid bonding technology are needed. Summary of the invention

[0004] An object of the present application is to provide a hybrid bonding technique for forming a conductive structure between two substrates.

[0005] According to one aspect of the present application, a method for forming a conductive structure between two substrates is disclosed. The method comprises: forming a first patterned base layer and a second patterned base layer on the respective front surfaces of a first substrate and a second substrate, wherein the first patterned base layer and the second patterned base layer include through holes partially exposing the respective front surfaces of the first substrate and the second substrate; forming a first metal contact structure in the through hole of the first patterned base layer and forming a second metal contact structure in the through hole of the second patterned base layer, wherein both the first metal contact structure and the second metal contact structure have a front surface that is higher than the respective front surfaces of the first patterned base layer and the second patterned base layer; forming a first metal contact structure in the through hole of the first patterned base layer and a second metal contact structure in the through hole of ... A first patterned polymer layer and a second patterned polymer layer are formed on a surface, wherein the first metal contact structure and the second metal contact structure are exposed from the corresponding front surfaces of the first patterned polymer layer and the second patterned polymer layer and are higher than the corresponding front surfaces of the first patterned polymer layer and the second patterned polymer layer; the front surfaces of the first metal contact structure and the second metal contact structure are passivated; the front surfaces of the first metal contact structure and the second metal contact structure are bonded to each other; and after the front surfaces of the first metal contact structure and the second metal contact structure are bonded to each other, the front surfaces of the first patterned polymer layer and the second patterned polymer layer are bonded to each other.

[0006] According to another embodiment of the present application, a method for forming a conductive structure between two substrates is disclosed. The method includes: forming a first patterned base layer and a second patterned base layer on the respective front surfaces of a first substrate and a second substrate, wherein the first patterned base layer and the second patterned base layer include through holes partially exposing the respective front surfaces of the first substrate and the second substrate; forming a first metal contact structure in the through hole of the first patterned base layer and forming a second metal contact structure in the through hole of the second patterned base layer, wherein both the first metal contact structure and the second metal contact structure have front surfaces that are higher than the respective front surfaces of the first patterned base layer and the second patterned base layer; forming a first patterned base layer on the respective front surfaces of the first patterned base layer and the second patterned base layer; A method of bonding a first patterned polymer layer and a second patterned polymer layer, wherein the first metal contact structure and the second metal contact structure are exposed from the corresponding front surfaces of the first patterned polymer layer and the second patterned polymer layer and are lower than the corresponding front surfaces of the first patterned polymer layer and the second patterned polymer layer; forming a solder material on the corresponding front surfaces of the first metal contact structure and the second metal contact structure; bonding the front surfaces of the first patterned polymer layer and the second patterned polymer layer to each other; and after the front surfaces of the first patterned polymer layer and the second patterned polymer layer are bonded to each other, bonding the first metal contact structure and the second metal contact structure to each other through the solder material thereon.

[0007] It should be understood that the above general description and the following detailed description are only exemplary and illustrative, rather than limiting the present invention. In addition, the accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate embodiments of the present invention and are used together with this specification to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The drawings cited herein constitute a part of the specification. The features shown in the drawings only illustrate some embodiments of the present application, rather than all embodiments of the present application, and unless the detailed description explicitly states otherwise, readers of the specification should not make contrary suggestions.

[0009] Figures 1A to 1M A method for forming a conductive structure between two substrates according to one embodiment of the present application is presented.

[0010] Figures 2A to 2C Some steps of a method for forming a conductive structure between two substrates according to another embodiment of the present application are shown.

[0011] The same reference numbers will be used throughout the drawings to refer to the same or like parts. DETAILED DESCRIPTION

[0012] The following detailed description of exemplary embodiments of the present application refers to the accompanying drawings that form a part of the specification. The drawings illustrate specific exemplary embodiments in which the present application can be practiced. The detailed description including the drawings describes these embodiments in sufficient detail to enable a person skilled in the art to practice the present application. A person skilled in the art may further utilize other embodiments of the present application and make logical, mechanical and other changes without departing from the spirit or scope of the present application. Therefore, the reader of the following detailed description should not interpret the description in a limiting sense, and only the appended claims define the scope of the embodiments of the present application.

[0013] In this application, unless otherwise specifically stated, the use of the singular includes the plural. In this application, the use of "or" means "and / or" unless otherwise stated. In addition, the use of the term "including" is not limiting. In addition, unless otherwise explicitly stated, terms such as "element" or "component" cover elements and components that include one unit, as well as elements and components that include more than one subunit. In addition, the section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described.

[0014] As used herein, spatially relative terms such as "below," "below," "above," "on," "upper," "lower," "left," "right," "vertical," "horizontal," "side," etc. are used for ease of description to describe the relationship of one element or feature to another element or feature as shown in the accompanying drawings. In addition to the orientation depicted in the accompanying drawings, spatially relative terms are also intended to cover different orientations of the device when in use or in operation. The device can be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein can likewise be interpreted accordingly. It should be understood that when an element is referred to as being "connected to" or "coupled to" another element, it can be directly connected to or coupled to the other element, or there can be intermediate elements.

[0015] Conventional hybrid bonding processes require chemical mechanical planarization (CMP) and chemical vapor deposition (CVD) processes, which may introduce undesirable defects to the surfaces of the substrates to be bonded together. The inventors of the present application have proposed a new hybrid bonding process that does not require surface planarization using a CMP process, which can form a more conductive structure between two substrates at a relatively low cost. In addition, hybrid bonding can be achieved by utilizing the different thermal expansion characteristics of the materials at the bonding surfaces (i.e., the conductive material and the insulating material).

[0016] Figures 1A to 1M A method for forming a conductive structure between two substrates according to one embodiment of the present application is presented. It should be understood that it is desirable that the two substrates be bonded together by hybrid bonding, and thus similar or identical preparation steps of the method are performed on both substrates. For illustrative purposes, some steps are presented with reference to only one of the substrates, but it should be understood that the other substrates can be processed similarly.

[0017] like Figure 1A As shown, a first substrate 102 is provided. The first substrate 102 may include a device substrate, wherein a conductive pattern (not shown) is formed on its front surface, or an interconnect substrate including, for example, a redistribution layer (RDL) substrate, or an interposer substrate, wherein a conductive pattern (not shown) is also formed on its front surface. The device substrate may include a semiconductor chip or a similar device. It is desirable that the conductive pattern of the first substrate 102 is electrically coupled to the conductive pattern of the second substrate so that certain structures, elements or devices of the two substrates can be electrically coupled together. Similarly, the second substrate may be a device substrate or an interconnect substrate. In some embodiments, the first substrate and the second substrate may include a printed circuit board (PCB), a carrier substrate, a semiconductor substrate with electrical interconnection, or a ceramic substrate. In some other instances, the substrate may include a laminated interposer, a strip interposer, a lead frame or other suitable substrate. In some embodiments, the substrate may include a plurality of interconnect structures, which may provide connectivity to electronic components mounted on the substrate. The interconnect structure may include one or more of Cu, Al, Sn, Ni, Au, Ag or any other suitable conductive material. In some instances, the interconnect structure may include a redistribution structure. The redistribution structure may include one or more dielectric layers and one or more conductive layers between and through the dielectric layers. The conductive layers may define pads, traces, and plugs through which electrical signals or voltages may be distributed horizontally and vertically across the redistribution structure.

[0018] Still reference Figure 1A , a base layer 104 may be formed on the front surface of the first substrate 102. The base layer 104 may be formed of an insulating material (e.g., a polymer material) that may provide insulation between substrates to be bonded together and between conductive structures to be formed within the base layer 104. In some embodiments, the base layer 104 may be formed of a photosensitive polymer so that it may be directly patterned using photolithography. In some other embodiments, a photoresist layer may be formed on the base layer 104 to pattern the base layer 104, and may be removed after the base layer 104 is patterned. Figure 1AAs shown, a via 106 can be formed in the patterned base layer 104, which can partially expose the front surface of the first substrate 102, such as at the topmost conductive pattern of the first substrate 102. The via 106 can be formed when the base layer 104 is patterned.

[0019] Next, if Figure 1B As shown, a seed layer 108 may be formed on the first substrate 102, the seed layer covering the front surface of the base layer 104 and the front surface of the first substrate 102 exposed through the through hole 106. The seed layer 108 may help to subsequently form a conductive material in the through hole 106. In some embodiments, the seed layer 108 may be formed of a combination of titanium and copper, and may be formed on the first substrate 102 using a physical vapor process such as sputtering.

[0020] Afterwards, if Figure 1C As shown, a patterned photoresist layer 110 may be formed on the first substrate 102 to cover a portion of the seed layer 108 on the front surface of the base layer 104 but expose other portions of the seed layer 108 within the through hole 106. Figure 1D As shown, a metal material (such as copper) can be filled in the through hole 106 to form a corresponding metal contact structure 112 therein. In some embodiments, electroplating can be used to fill the metal material in the through hole. Since the seed layer 108 is partially covered by the patterned photoresist layer 110, the metal material can be formed only in the through hole 106, but not on the photoresist layer 110. In some alternative embodiments, sputtering can be used to fill the metal material, and thus cover both the patterned photoresist layer 110 and the exposed seed layer 108.

[0021] Next, if Figure 1E As shown, the patterned photoresist layer can be removed from the first substrate 102, thereby leaving the seed layer 108 and the metal contact structure 112 on the first substrate 102. In some embodiments where the metal material is also formed on the patterned photoresist layer, the metal material outside the via can be lifted off along with the removed photoresist layer.

[0022] Afterwards, if Figure 1FAs shown, the seed layer 108 on the front surface of the base layer 104 can be etched away to expose the base layer 104. If the seed layer 108 is not etched away from the front surface of the base layer 104, the residue of the seed layer 108 may form an undesirable horizontal conductive structure, which may damage the insulation performance of the base layer 104. Since the thickness of the seed layer 108 is much smaller than the thickness of the metal conductive structure 112, the metal conductive structure 112 can maintain a generally complete structure after the seed layer 108 is etched away. It should be understood that the portion of the seed layer 108 filled in the through hole and located below the metal conductive structure 112 may not be removed.

[0023] Next, if Figure 1G As shown, a polymer layer 114 may be formed on the first substrate 102 to cover the respective front surfaces of the patterned base layer 104 and the metal contact structure 112. In some embodiments, the polymer layer 114 may be formed of a photosensitive polymer so that it may be directly patterned using photolithography. In some other embodiments, a photoresist layer may be formed on the polymer layer 114 to pattern the polymer layer 114, and the photoresist layer may be removed after the polymer layer 114 is patterned.

[0024] Next, if Figure 1H As shown, polymer layer 114 may be patterned, for example using photolithography, to expose metal contact structure 112. In some embodiments, since polymer layer 114 previously covered metal contact structure 112, the front surface of patterned polymer layer 114 is higher than the front surface of metal contact structure 112.

[0025] Next, if Fig. 1I As shown, the patterned polymer layer 114 can be descummed to remove undesirable contaminants or residues at the top of the polymer layer 114. Specifically, the descum treatment can be polymer-specific, so that except for the metal oxide 116 that may be formed on the front surface of the metal contact structure 112, the metal contact structure 112 is generally intact and unaffected by the descum treatment. In addition, the descum treatment can remove a portion of the patterned polymer layer 114, so that the front surface of the patterned polymer layer 114 may be lowered to, for example, a level below the front surface of the metal contact structure 112. In some embodiments, the descum treatment can be performed in an oxygen atmosphere, or in a mixed atmosphere of oxygen and nitrogen. Some polymer materials of the polymer layer 114 can be etched by oxygen and thus removed from the substrate. In some preferred embodiments, a mixed atmosphere of oxygen and nitrogen is preferred because the mixed gas of oxygen and nitrogen has a higher etching rate than oxygen for polymer materials.

[0026] Thereafter, the metal oxide on the front surface of the metal contact structure 112 may be etched away, for example using a plasma treatment, such as Figure 1J As shown. In one example, during the plasma treatment, Ar ions may bombard the front surface of the metal contact structure 112, so that metal oxides and some other contaminants can be removed, thereby leaving a clean surface for subsequent bonding processes. It can be seen that the planarization of the metal contact structure 112 and the patterned polymer layer 114 can be performed using electroplating, etching and descumming processes instead of using a relatively costly CMP process.

[0027] Next, if Figure 1K As shown, the front surface of the metal contact structure 112 can be passivated, for example, using another plasma treatment. In some embodiments, nitrogen can be used to passivate the front surface of the metal contact structure 112. After the treatment, a nitride 118, such as Cu4N, can be formed on the front surface of the metal contact structure 112, which can prevent the formation of metal oxides but does not affect the subsequent bonding process.

[0028] As mentioned above, Figures 1A to 1K The above steps shown in can be performed similarly with another substrate (such as a second substrate to be bonded to the first substrate 102). Next, as Figure 1L As shown, two substrates 102 (i.e., a first substrate and a second substrate) can be moved close to each other, wherein their front surfaces face each other. Specifically, the metal contact structures 112 on the two substrates 102 can be aligned with each other. Then, the front surfaces of the metal contact structures 112 on the two substrates 102 can contact each other, and the metal contact structures 112 can be subjected to a bonding process. For example, the metal contact structures 112 can be pressed against each other at a first temperature. The first temperature for bonding the metal contact structures 112 can vary according to the characteristics and materials of the metal contact structures 112. In some instances where the metal contact structures 112 are formed of copper, the first temperature can be approximately 250 to 300 degrees Celsius. At such temperatures, copper nitride can be decomposed and copper-copper direct bonding can be implemented at the same time.

[0029] In addition, since the front surface of the metal contact structure 112 is generally higher than the front surface of the corresponding patterned polymer layer 114, the patterned polymer layers 114 on the two substrates 102 may not contact each other during the bonding process of the metal contact structure 112. In this case, a separate bonding process may be performed on the patterned polymer layer 114. Figure 1MAs shown, after the front surfaces of the first and second metal contact structures 112 are bonded to each other, the front surfaces of the patterned polymer layers on the two substrates 102 can be bonded to each other at a second temperature. The second temperature is different from the first temperature. In some embodiments, the second temperature can be higher than the first temperature. For example, the polymer material can be polyimide or polybenzobisoxazole (benzobisoxazole, PBO), which can be photosensitive. The polymer material can have a higher thermal expansion coefficient than copper or similar metal materials, so that when heated to a high temperature, the expansion degree of the patterned polymer layer 114 can be greater than the expansion degree of the metal contact structure 112. The polymer material of the patterned polymer layer 114 can expand at the second temperature to the extent that the patterned polymer layer 114 can contact each other and fully solidify. In some examples, the second temperature can be 300 to 350 degrees Celsius. It should be understood that the expansion of the patterned polymer layer 114 at the second temperature may not damage the bonding surface of the metal contact structure 112, but can produce a firm interface between the patterned polymer layers 114. In this way, hybrid bonding of two substrates 102 may be performed, with an electrically conductive structure extending between the two.

[0030] It should be understood that Figures 1A to 1M In the method shown, due to the descum treatment shown in FIG. 1 that reduces the significant thickness of the patterned polymer layer 114, the front surface of the patterned polymer layer 114 is lower than the front surface of the metal contact structure 112. However, the large expansion of the patterned polymer layer 114 ensures that the opposing patterned polymer layers 114 can be combined and bonded after bonding of the metal contact structure 112. Nevertheless, it is desirable that the two materials (i.e., the polymer material and the metal material) are bonded at two different temperatures to allow each of the two materials to bond better.

[0031] Can Figures 1A to 1M The method shown makes some modifications. Figures 2A to 2C Some steps of a method for forming a conductive structure between two substrates according to another embodiment of the present application are shown. Most of the steps in the method can be Figures 1A to 1M The steps shown in the method are similar. For example, Figure 2A The steps shown can be found in Figure 1H The steps shown are then performed, wherein a patterned polymer layer and exposed metal contact structures can be formed. In this embodiment, the polymer material is bonded before the metal material between the two substrates is bonded.

[0032] like Figure 2AAs shown, solder material 220 (eg, lead-free solder) may be electroplated on the front surface of the exposed metal contact structure 212. Solder material 220 may not cover the front surface of patterned polymer layer 214. In some embodiments, patterned polymer layer 214 may include a benzocyclobutene-based (BCB-based) polymer.

[0033] Next, if Figure 2B As shown, two substrates (each substrate having Figure 2A The surface structures shown in the figure) can be moved close to each other, wherein their front surfaces face each other. The front surfaces of the patterned polymer layer 214 can then contact each other, and the bonding process can be performed on the patterned polymer layer 214. For example, the patterned polymer layer 214 can be pressed against each other at a first temperature. The first temperature for bonding the patterned polymer layer 214 can vary depending on the characteristics and material of the patterned polymer layer 214. In this embodiment, the patterned polymer layer 214 can be a BCB-type polymer that bonds at room temperature or another temperature that may be significantly lower than the reflow temperature of the solder material 220.

[0034] Next, if Figure 2C As shown, after the patterned polymer layer 214 is bonded together and cured, the metal contact structures 212 on the two substrates 202 may contact each other due to the shrinkage of the polymer layer 214 at a higher temperature, and the bonding process can be performed on the metal contact structure 212 at a second temperature. For example, the second temperature can be about 250 to 300 degrees Celsius, and the solder material 220 at the top of the metal contact structure 212 can be reflowed at the temperature, thereby enhancing the bonding of the metal contact structure 212. In this way, the two substrates 202 can be bonded together, with the conductive structure extending between the two.

[0035] It should be understood that when the substrate warps and the metal contact structures cannot be directly bonded to each other, Figures 2A to 2C Since the polymer material can be bonded at room temperature or another relatively lower temperature, the solder material between the metal contact structures may not reflow. In this way, solder bridges may not be formed between adjacent metal contact structures.

[0036] Although the method for forming a conductive structure between two substrates of the present application has been described in conjunction with the corresponding drawings, those skilled in the art will appreciate that modifications and adjustments may be made to the method without departing from the scope of the present invention.

[0037] The discussion herein includes a number of illustrative drawings that illustrate various portions of a method for forming a conductive structure between two substrates. For clarity of description, such drawings do not illustrate all aspects of each example semiconductor package. Any example optical sensor package provided herein may share any or all characteristics with any or all other optical sensor packages provided herein.

[0038] Various embodiments have been described herein with reference to the accompanying drawings. However, it will be apparent that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broad scope of the invention as set forth in the appended claims. In addition, other embodiments will be apparent to those skilled in the art by considering the specification and practice of one or more embodiments of the invention disclosed herein. Therefore, the present application and the embodiments herein are intended to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following list of exemplary claims.

Claims

1. A method for forming a conductive structure between two substrates, characterized in that The method comprises: forming a first patterned base layer and a second patterned base layer on respective front surfaces of a first substrate and a second substrate, wherein the first patterned base layer and the second patterned base layer include through holes partially exposing the respective front surfaces of the first substrate and the second substrate; forming a first metal contact structure in the through hole of the first patterned base layer and forming a second metal contact structure in the through hole of the second patterned base layer, wherein both the first metal contact structure and the second metal contact structure have front surfaces that are higher than respective front surfaces of the first patterned base layer and the second patterned base layer; forming a first patterned polymer layer and a second patterned polymer layer on the respective front surfaces of the first patterned base layer and the second patterned base layer, wherein the first metal contact structure and the second metal contact structure are exposed from the respective front surfaces of the first patterned polymer layer and the second patterned polymer layer and are higher than the respective front surfaces of the first patterned polymer layer and the second patterned polymer layer; passivating the front surfaces of the first metal contact structure and the second metal contact structure; bonding the front surfaces of the first metal contact structure and the second metal contact structure to each other; and After the front surfaces of the first metal contact structure and the second metal contact structure are bonded to each other, the front surfaces of the first patterned polymer layer and the second patterned polymer layer are bonded to each other.

2. The method according to claim 1, characterized in that Forming a first metal contact structure in the through hole of the first patterned base layer and forming a second metal contact structure in the through hole of the second patterned base layer includes: forming respective seed layers on the front surfaces of the first and second patterned base layers and the exposed front surfaces of the first and second substrates; forming corresponding patterned photoresist layers on the front surfaces of the first patterned base layer and the second patterned base layer; depositing a metal material within the through holes of the first patterned base layer and the second patterned base layer to form the first metal contact structure and the second metal contact structure; and The patterned photoresist layer and the seed layer thereunder are removed from the first patterned base layer and the second patterned base layer, respectively.

3. The method according to claim 1, characterized in that Forming a first patterned polymer layer and a second patterned polymer layer on the respective front surfaces of the first patterned base layer and the second patterned base layer comprises: forming a first polymer layer and a second polymer layer on the respective front surfaces of the first patterned base layer and the second patterned base layer and on the respective front surfaces of the first metal contact structure and the second metal contact structure; patterning the first polymer layer and the second polymer layer to form the first patterned polymer layer and the second patterned polymer layer exposing the respective front surfaces of the first metal contact structure and the second metal contact structure; descumming the first patterned polymer layer and the second patterned polymer layer; and Metal oxide is etched on the front surfaces of the first and second metal contact structures.

4. The method according to claim 3, characterized in that The first polymer layer and the second polymer layer are photosensitive polymer layers.

5. The method according to claim 1, characterized in that Passivating the front surfaces of the first metal contact structure and the second metal contact structure includes: The front surfaces of the first and second metal contact structures are passivated using a plasma treatment.

6. The method according to claim 1, characterized in that The bonding of the front surfaces of the first and second metal contact structures is performed at a first temperature, and the bonding of the front surfaces of the first and second patterned polymer layers is performed at a second temperature, which is higher than the first temperature.

7. A method for forming a conductive structure between two substrates, characterized in that The method comprises: forming a first patterned base layer and a second patterned base layer on respective front surfaces of a first substrate and a second substrate, wherein the first patterned base layer and the second patterned base layer include through holes partially exposing the respective front surfaces of the first substrate and the second substrate; forming a first metal contact structure in the through hole of the first patterned base layer and forming a second metal contact structure in the through hole of the second patterned base layer, wherein both the first metal contact structure and the second metal contact structure have front surfaces that are higher than respective front surfaces of the first patterned base layer and the second patterned base layer; forming a first patterned polymer layer and a second patterned polymer layer on the respective front surfaces of the first patterned base layer and the second patterned base layer, wherein the first metal contact structure and the second metal contact structure are exposed from and are lower than the respective front surfaces of the first patterned polymer layer and the second patterned polymer layer; forming a solder material on the respective front surfaces of the first metal contact structure and the second metal contact structure; bonding the front surfaces of the first patterned polymer layer and the second patterned polymer layer to each other; and After the front surfaces of the first patterned polymer layer and the second patterned polymer layer are bonded to each other, the first metal contact structure and the second metal contact structure are bonded to each other through the solder material thereon.

8. The method according to claim 7, characterized in that Forming a first metal contact structure in the through hole of the first patterned base layer and forming a second metal contact structure in the through hole of the second patterned base layer includes: forming respective seed layers on the front surfaces of the first and second patterned base layers and the exposed front surfaces of the first and second substrates; forming corresponding patterned photoresist layers on the front surfaces of the first patterned base layer and the second patterned base layer; depositing a metal material within the through holes of the first patterned base layer and the second patterned base layer to form the first metal contact structure and the second metal contact structure; and The patterned photoresist layer and the seed layer thereunder are removed from the first patterned base layer and the second patterned base layer, respectively.

9. The method according to claim 7, characterized in that: Forming a first patterned polymer layer and a second patterned polymer layer on the respective front surfaces of the first patterned base layer and the second patterned base layer comprises: forming a first polymer layer and a second polymer layer on the respective front surfaces of the first and second patterned base layers and on the respective front surfaces of the first and second metal contact structures; and The first polymer layer and the second polymer layer are patterned to form the first patterned polymer layer and the second patterned polymer layer exposing the respective front surfaces of the first metal contact structure and the second metal contact structure.

10. The method according to claim 7, characterized in that The first polymer layer and the second polymer layer include benzocyclobutene-based polymers.

11. The method according to claim 7, characterized in that After forming the solder material, the first metal contact structure and the second metal contact structure are respectively lower than the first patterned polymer layer and the second patterned polymer layer.

12. The method according to claim 7, characterized in that The bonding of the first patterned polymer layer to the front surface of the second patterned polymer layer is performed at a first temperature, and the bonding of the first metal contact structure to the second metal contact structure is performed at a second temperature, the second temperature being higher than the first temperature.

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