Conductive thin film and forming method thereof, and preparation method of semiconductor structure

Abstract

The embodiment of the invention provides a conductive thin film and a forming method thereof, and a preparation method of a semiconductor structure, and the conductive thin film comprises a thin film substrate; the net-shaped conductive circuit is positioned on the thin film substrate; and the plurality of conductive salient points are distributed on each cross point of the net-shaped conductive circuit.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and relates to but is not limited to a conductive film and a method for forming the same, and a method for preparing a semiconductor structure. Background Art

[0002] Gold finger is a common structure on the substrate. The chip structure on the substrate is connected to the gold finger on the substrate through gold wire. In order to ensure the stability and reliability of the connection between the gold wire and the gold finger, the gold finger needs to be electroplated with nickel (Ni) or gold (Au) surface treatment.

[0003] Electroplating is the process of plating a thin layer of other metals or alloys on certain metal surfaces using the principle of electrolysis. Since an external electric field is required to electroplate the gold fingers on the substrate, each gold finger on the substrate needs to be connected to the cathode or anode of the electroplating equipment. Usually, it is necessary to make electroplating auxiliary lines on the surface of the substrate to connect all the gold fingers together so that current can flow for electroplating. After the electroplating is completed, the electroplating auxiliary lines on the substrate need to be removed or cut off. The entire process is complicated and has high labor and time costs. Summary of the invention

[0004] In view of this, embodiments of the present disclosure provide a conductive film and a method for forming the same, and a method for preparing a semiconductor structure.

[0005] In a first aspect, an embodiment of the present disclosure provides a conductive film, including:

[0006] film substrate;

[0007] A mesh-shaped conductive circuit is located on the film substrate;

[0008] A plurality of conductive bumps are distributed on each intersection of the mesh conductive circuit.

[0009] In some embodiments, the conductive film further comprises:

[0010] A first insulating layer, located on the surface of the mesh conductive circuit and between the mesh conductive circuits;

[0011] The conductive bumps protrude from the first insulating layer.

[0012] In some embodiments, the conductive film is used to form a plating layer on the first pad on the front side of the substrate; the position of the conductive bump corresponds to the position of the second pad on the back side of the substrate.

[0013] In some embodiments, the material of the film substrate includes a flexible material.

[0014] In some embodiments, the material of the film substrate includes a graphite film or a fiber film.

[0015] In a second aspect, an embodiment of the present disclosure provides a method for forming a conductive film, comprising:

[0016] providing a film substrate;

[0017] forming a conductive material layer on the film substrate;

[0018] forming a plurality of conductive bumps on the surface of the conductive material layer;

[0019] The conductive material layer is patterned to form a mesh-shaped conductive circuit, wherein a plurality of the conductive bumps are distributed at each intersection of the mesh-shaped conductive circuit.

[0020] In some embodiments, the method for forming the conductive film further comprises:

[0021] A first insulating layer is formed covering the mesh-shaped conductive circuits and located between the mesh-shaped conductive circuits.

[0022] In some embodiments, forming a plurality of conductive bumps on the surface of the conductive material layer includes:

[0023] forming a second insulating layer on the conductive material layer, wherein the second insulating layer exposes a portion of the conductive material layer;

[0024] The conductive bumps are formed on the exposed surface of the conductive material layer.

[0025] In a third aspect, an embodiment of the present disclosure provides a method for preparing a semiconductor structure, comprising:

[0026] A conductive film and a substrate as described in the first aspect are provided; a first pad and a second pad are formed on the front and back of the substrate respectively; the first pad is electrically connected to the second pad;

[0027] The conductive film is laminated to the substrate by heat pressing so that the conductive bumps on the conductive film are connected to the second pads;

[0028] Performing an electroplating process to form a plating layer on the surface of the first pad;

[0029] The conductive film is removed.

[0030] In some embodiments, the substrate further includes a solder resist layer located on the back side; the solder resist layer is located between the second pads; a first dimension of the solder resist layer in a thickness direction of the substrate is larger than a second dimension of the second pad in the thickness direction of the substrate.

[0031] In some embodiments, a third dimension of the conductive bump protruding from the first insulating layer in the thickness direction of the conductive film is greater than or equal to a difference between the first dimension and the second dimension.

[0032] In some embodiments, the conductive film and the substrate are thermally pressed together, comprising:

[0033] forming a bonding layer on the back side of the substrate; the bonding layer comprises a conductive material;

[0034] At a preset temperature, a hot pressing process is performed on the substrate and the conductive film, wherein in the hot pressing process, the preset temperature is first increased so that the adhesive layer changes from a solid state to a liquid state, and then gradually decreased so that the adhesive layer changes from a liquid state to a solid state.

[0035] In some embodiments, performing an electroplating process to form a plating layer on the surface of the first pad includes:

[0036] electrically connecting the conductive film to a cathode contact of an electroplating device;

[0037] The substrate and the conductive film are placed in an electroplating solution for electroplating to form a plating layer on the surface of the first pad.

[0038] In some embodiments, removing the conductive film includes:

[0039] Heating the adhesive layer so that the adhesive layer changes from a solid state to a liquid state;

[0040] The conductive film is peeled off from the back surface of the substrate.

[0041] In some embodiments, after removing the conductive film, the method further comprises:

[0042] forming at least one semiconductor chip on the front surface of the substrate;

[0043] The at least one semiconductor chip is connected to the first pad by wire bonding.

[0044] The embodiments of the present disclosure provide a conductive film and a method for forming the same, and a method for preparing a semiconductor structure, wherein the conductive film includes: a film substrate; a mesh-shaped conductive circuit located on the film substrate; and a plurality of conductive bumps distributed at each intersection of the mesh-shaped conductive circuit. The conductive film in the embodiments of the present disclosure has a plurality of conductive bumps distributed at each intersection of the mesh-shaped conductive circuit. Therefore, for a complex substrate surface with a recessed conductive structure, the conductive bumps can achieve close contact with the recessed conductive structure, thereby achieving good electrical connection between the conductive film and the substrate, reducing the contact resistance between the conductive film and the substrate, and reducing the power consumption of the device finally formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In the accompanying drawings (which are not necessarily drawn to scale), like reference numerals may describe similar components in different views. Like reference numerals with different letter suffixes may represent different examples of similar components. The accompanying drawings generally illustrate various embodiments discussed herein by way of example and not limitation.

[0046] Figure 1 and Figure 2 A schematic diagram of the structure of a conductive film provided in an embodiment of the present disclosure, wherein Figure 2 For along Figure 1 A-A' cross-sectional view;

[0047] Figure 3 A flow chart of a method for forming a conductive film provided in an embodiment of the present disclosure;

[0048] Figures 4 to 7 A schematic diagram of the structure of a conductive film during the formation process provided by an embodiment of the present disclosure;

[0049] Figure 8 and Fig. 9 It is a schematic diagram of the structure of a semiconductor structure in the preparation process in the related art;

[0050] Fig.10 A flow chart of a method for preparing a semiconductor structure provided in an embodiment of the present disclosure;

[0051] Figures 11 to 14 A schematic diagram of the structure of a semiconductor structure during the preparation process provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0052] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the specific embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0053] In the following description, a large number of details are given to provide a more thorough understanding of the present disclosure. However, it is obvious to those skilled in the art that the present disclosure can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present disclosure, some technical features known in the art are not described; that is, all features of actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0054] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0055] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on other elements or layers, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part discussed, it does not mean that the present disclosure necessarily has the first element, component, region, layer or part.

[0056] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present disclosure. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0057] When electroplating the gold fingers on the substrate, each gold finger on the substrate needs to be connected to the cathode or anode of the electroplating equipment. Usually, it is necessary to make electroplating auxiliary lines on the surface of the substrate to connect all the gold fingers together, and then splice many substrates into a large board (Strip). During the specific electroplating, the substrates are connected to each other through the criss-crossing electroplating lines on the large board. There will be exposed metal pads on the large board and connected to the contacts of the electroplating equipment so that current can flow for electroplating. After the electroplating is completed, the electroplating auxiliary lines on the substrate need to be removed or cut off, which is a complex process with high labor and time costs. In addition, making electroplating auxiliary lines on the substrate may have an adverse effect on the power structure on the substrate on the one hand, and on the other hand, since the electroplating auxiliary lines are difficult to be completely removed, the residual electroplating auxiliary lines will have an adverse effect on the performance of semiconductor devices.

[0058] Based on this, the embodiments of the present disclosure provide a conductive film and a method for forming the same, and a method for preparing a semiconductor structure. The conductive film in the embodiments of the present disclosure has multiple conductive bumps distributed at each intersection of the mesh conductive circuit. Therefore, for a complex substrate surface with a recessed conductive structure, close contact with the recessed conductive structure can be achieved through the conductive bumps, thereby achieving good electrical connection between the conductive film and the substrate, reducing the contact resistance between the conductive film and the substrate, and reducing the power consumption of the device finally formed.

[0059] The conductive film and its forming method, and the method for preparing the semiconductor structure in the embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0060] An embodiment of the present disclosure provides a conductive film. Figure 1 and Figure 2 , Figure 1 and Figure 2 The schematic diagram of the structure of the conductive film 10 provided in the embodiment of the present disclosure is shown. Figure 2 For along Figure 1 A-A' cross-section diagram. Figure 1 and Figure 2 As shown, the conductive film 10 comprises:

[0061] Film substrate 101;

[0062] A mesh conductive circuit 102 is located on the film substrate 101;

[0063] A plurality of conductive bumps 103 are distributed at each intersection of the mesh conductive circuit 102 .

[0064] In the conductive film 10 of the embodiment of the present disclosure, since a plurality of conductive bumps 103 are distributed on each intersection of the mesh conductive lines 102, for a complex substrate surface having a recessed conductive structure, close contact with the recessed conductive structure can be achieved through the conductive bumps 103, thereby achieving good electrical connection between the conductive film 10 and the substrate, reducing the contact resistance between the conductive film 10 and the substrate, and reducing the power consumption of the ultimately formed device.

[0065] It should be noted that the mesh conductive circuit 102 in the embodiment of the present disclosure is used to realize the electrical connection between the plurality of conductive bumps 103, and the network structure of the mesh conductive circuit 102 can be determined by the distribution position of the conductive bumps 103, and the distribution position of the conductive bumps 103 can be determined by the distribution position of the recessed conductive structure on the surface of the substrate that needs to be connected to the conductive film 10. That is, the network structure of the mesh conductive circuit 102 can be set according to the actual situation, so that the conductive film 10 has a wide applicability.

[0066] In some embodiments, the material of the film substrate 101 includes a flexible material.

[0067] In the embodiment of the present disclosure, the material of the film substrate 101 includes a flexible material, which can achieve a better combination with the mesh conductive wire on the one hand, and on the other hand, enables the formed conductive film 10 to have better bendability, deformability, etc., so that it can achieve a better combination with a rigid substrate or a substrate with a more complex surface structure.

[0068] In some embodiments, the material of the film substrate 101 may include a graphite film or a fiber film. Since the graphite film is made of a highly oriented graphite polymer film, it has good reprocessability and can be compounded or coated with other film materials such as polyethylene terephthalate (PET) according to the purpose. The graphite film is elastic and can be cut and punched into any shape and can be bent multiple times. Therefore, the graphite film is suitable for converting point heat sources into surface heat sources for rapid heat conduction, and it has high thermal conductivity. In this way, the use of graphite film as the material of the film substrate 101 in the embodiment of the present disclosure can make the final conductive film 10 more flexible and more applicable.

[0069] In some embodiments, the material of the film substrate 101 may include a flexible thin layer of conductive metal foil, such as copper foil, aluminum foil, tin foil, and indium foil. On the one hand, the conductive metal foil can achieve better bonding with the mesh conductive wires. On the other hand, the formed conductive film 10 has better bendability, deformability, etc., so that it can achieve better bonding with a rigid substrate or a substrate with a more complex surface structure.

[0070] In some embodiments, if the surface structure of the base or substrate to be electroplated is simple and flat, the material of the film substrate 101 may include hard conductive metal or other hard non-metallic materials, which is not limited here.

[0071] In some embodiments, the material of the mesh conductive line 102 and the conductive bump 103 can be any material with good conductivity, such as any one or more of titanium, titanium nitride, tungsten nitride, tungsten, cobalt, platinum, palladium, ruthenium, copper, and polysilicon. The materials of the mesh conductive line 102 and the conductive bump 103 can be different or the same.

[0072] In some embodiments, the mesh conductive circuit 102 and the conductive bumps 103 are made of the same material, such as copper, because copper has excellent conductivity, good corrosion resistance and long service life.

[0073] In the embodiment of the present disclosure, the mesh-shaped conductive circuit 102 and the conductive bumps 103 are made of the same material, which can reduce the contact resistance between the two and improve the performance of the conductive film 10 .

[0074] In some embodiments, please refer to Figure 2 The conductive film 10 further includes: a first insulating layer 104 located on the surface of the mesh conductive circuit 102 and between the mesh conductive circuits 102 ; and conductive bumps 103 protruding from the first insulating layer 104 .

[0075] In the embodiment of the present disclosure, the first insulating layer 104 can provide protection for the mesh-shaped conductive circuit 102 , and can also enhance the adhesion between the mesh-shaped conductive circuit 102 and the film substrate 101 .

[0076] In some embodiments, the material of the first insulating layer 104 may include but is not limited to polyimide (PI).

[0077] In some embodiments, the conductive film 10 is used to form a plating layer on the first pad on the front side of the substrate; the position of the conductive bump 103 corresponds to the position of the second pad on the back side of the substrate.

[0078] Specifically, the conductive film 10 in the embodiment of the present disclosure can cover the back of the substrate and be connected to the second pads on the back of the substrate through the conductive bumps 103, so that all the second pads are connected together. Since the first pads on the front of the substrate are electrically connected to the second pads on the back, the first pads on the front of the substrate can be connected together through the conductive film 10, so that the first pads on the front of the substrate can be electroplated to form a plated layer.

[0079] Another embodiment of the present disclosure further provides a method for forming a conductive film. Figure 3 A flowchart of a method for forming a conductive film provided in an embodiment of the present disclosure, Figures 4 to 7 The schematic diagram of the structure of the conductive film during the formation process provided by the embodiment of the present disclosure. Figures 3 to 7 The method for forming the conductive film 10 provided in the embodiment of the present disclosure is described in detail.

[0080] like Figures 3 to 7 As shown, the method for forming the conductive film 10 includes steps 101 to 104:

[0081] First, please refer to Figure 4 , execute step 101 to provide a film substrate 101.

[0082] Here, the material of the film substrate 101 may include a flexible material, such as a graphite film or a fiber film.

[0083] The material of the film substrate 101 includes flexible material, which can achieve better bonding with the mesh conductive wires on the one hand, and on the other hand, enable the subsequently formed conductive film 10 to have better bendability and deformability, etc., so as to achieve better bonding with a rigid substrate or a substrate with a more complex surface structure.

[0084] In addition, when the material of the film substrate 101 includes a graphite film or a fiber film, the processing technology for forming the film substrate 101 can be simplified, and the conductive film 10 formed subsequently can have better flexibility and wider applicability.

[0085] In some embodiments, the material of the film substrate 101 may include a flexible thin layer of conductive metal foil, such as copper foil, aluminum foil, tin foil, and indium foil. On the one hand, the conductive metal foil can achieve better bonding with the mesh conductive wires. On the other hand, the formed conductive film 10 has better bendability, deformability, etc., so that it can achieve better bonding with a rigid substrate or a substrate with a more complex surface structure.

[0086] In some embodiments, if the surface structure of the base or substrate to be electroplated is simple and flat, the material of the film substrate 101 may include hard conductive metal or other hard non-metallic materials, which is not limited here.

[0087] Next, please continue to refer to Figure 4 , perform step 102 to form a conductive material layer 105 on the film substrate 101.

[0088] In some embodiments, the conductive material layer 105 can be formed by one or more deposition processes including physical vapor deposition, chemical vapor deposition, or atomic layer deposition, wherein the material of the conductive material layer 105 can be any material with good conductivity, such as any one or more combinations of titanium, titanium nitride, tungsten nitride, tungsten, cobalt, platinum, palladium, ruthenium, copper, and polysilicon.

[0089] In some embodiments, the formed conductive material layer 105 and the film substrate 101 may be pressed together through an adhesive layer based on a pressing process, so that the conductive material layer 105 and the film substrate 101 are fully combined to form a complete initial conductive film.

[0090] In some embodiments, the conductive material layer 105 includes, but is not limited to, copper foil, because copper has excellent conductivity and good corrosion resistance, and the copper foil has good bonding with the film substrate 101. The adhesive layer includes, but is not limited to, epoxy resin.

[0091] Next, please refer to Figure 5 and Figure 6 , perform step 103 to form a plurality of conductive bumps 103 on the surface of the conductive material layer 105 .

[0092] In some embodiments, step 103 may be implemented by the following steps:

[0093] Please continue to refer to Figure 5, forming a second insulating layer 106 on the conductive material layer 105 , wherein the second insulating layer 106 exposes a portion of the conductive material layer 105 ;

[0094] In some embodiments, the second insulating layer 106 may be formed by a coating process, wherein the material of the second insulating layer 106 may include but is not limited to polyimide. Exemplarily, firstly, polyimide resin powder is mixed with a solvent to form a resin slurry, and then the resin slurry is evenly coated on the position to be covered on the conductive material layer 105, and the second insulating layer 106 is formed after film formation.

[0095] Please continue to refer to Figure 6 , forming conductive bumps 103 on the surface of the exposed conductive material layer 105 .

[0096] In some embodiments, the conductive bump 103 may be formed by one or more deposition processes of physical vapor deposition, chemical vapor deposition or atomic layer deposition, wherein the conductive bump 103 may be any material with good conductivity, such as any one or more of titanium, titanium nitride, tungsten nitride, tungsten, cobalt, platinum, palladium, ruthenium, copper, and polysilicon. The materials of the conductive bump 103 and the conductive material layer 105 may be different or the same.

[0097] In some embodiments, the conductive bumps 103 and the conductive material layer 105 are made of the same material, for example, copper, because copper has excellent conductivity, good corrosion resistance and long service life.

[0098] In the disclosed embodiment, the conductive material layer 105 and the conductive bumps 103 are made of the same material, which can reduce the contact resistance between the subsequently formed mesh conductive circuit 102 and the conductive bumps 103 and improve the performance of the conductive film 10 .

[0099] Finally, execute step 104, please refer to Figure 7 and Figure 1 , patterning the conductive material layer 105 to form a mesh conductive circuit 102 ; wherein a plurality of conductive bumps 103 are distributed at each intersection of the mesh conductive circuit 102 .

[0100] In some embodiments, step 104 may be implemented by:

[0101] First, please refer to Figure 7 , removing the second insulating layer 106;

[0102] In some embodiments, a wet process may be used to remove the second insulating layer 106. For example, when the material of the second insulating layer 106 includes PI, a PI film stripping solution is used to remove the second insulating layer 106.

[0103] Next, the conductive material layer 105 is patterned based on the patterned photoresist layer to form Figure 1 The mesh-shaped conductive circuit 102 is shown.

[0104] In some embodiments, a dry etching process, such as plasma etching, may be used to pattern the conductive material layer 105 .

[0105] In some embodiments, the method for forming the conductive film 10 further includes: forming a conductive film covering the mesh conductive lines 102 and located between the mesh conductive lines 102. Figure 2 A first insulating layer 104 is shown.

[0106] In the embodiment of the present disclosure, the first insulating layer 104 can not only provide protection for the mesh-shaped conductive circuit 102 , but also enhance the adhesion between the mesh-shaped conductive circuit 102 and the film substrate 101 .

[0107] In some embodiments, the first insulating layer 104 may be formed by a coating process, wherein the material of the first insulating layer 104 may include but is not limited to polyimide. The process of forming the first insulating layer 104 can be understood by referring to the process of forming the second insulating layer 106, which will not be repeated here.

[0108] Since the conductive film 10 in the embodiment of the present disclosure has multiple conductive bumps 103 distributed on each intersection of the mesh conductive lines 102, for a complex substrate surface with a recessed conductive structure, close contact with the recessed conductive structure can be achieved through the conductive bumps 103, thereby achieving good electrical connection between the conductive film 10 and the substrate, reducing the contact resistance between the conductive film 10 and the substrate, and reducing the power consumption of the device finally formed.

[0109] In another embodiment of the present disclosure, the method for forming the conductive film further includes the following steps 1 to 4:

[0110] Step 1: Evenly apply a layer of adhesive (corresponding to the above-mentioned adhesive layer) on the graphite film (corresponding to the above-mentioned film substrate 101), attach a complete conductor copper (corresponding to the above-mentioned conductive material layer 105), and press together to allow the graphite film and the conductor copper to be fully combined to form a conductor film (corresponding to the above-mentioned initial conductive film).

[0111] Step 2: Brush a layer of PI film (corresponding to the above-mentioned second insulating layer 106) on the conductor film, expose the conductor copper in the corresponding area of ​​the ball pad (corresponding to the above-mentioned second pad 312), and there is a layer of insulating layer PI in other areas. Copper is deposited in the ball pad area so that micro bumps (corresponding to the above-mentioned conductive bumps 103) grow in the corresponding area of ​​the ball pad.

[0112] Step 3: Remove the first insulating layer PI with liquid medicine, then apply photosensitive coating (Photoresist, PR) and remove the excess conductor copper through exposure, development and etching to form the required circuit connection (corresponding to the mesh conductive line 102 mentioned above).

[0113] Step 4: Brush the second insulating layer PI (corresponding to the first insulating layer 104 mentioned above) to protect the metal on the conductive film, and expose the micro bumps in the area corresponding to the ball pad.

[0114] During the design of the Low Power Double Data Rate (LPDDR) substrate, the chip (die) and the substrate are connected by gold wires for electrical signals. The solder joint (solder joint 1) at one end of the gold wire is on the chip connection pad (die pad), and the solder joint (solder joint 2) at the other end of the gold wire is on the gold finger of the substrate. In order to ensure the stability and reliability of the connection between the gold wire and the gold finger, the gold finger needs to be surface treated by electroplating nickel (Ni) and gold (Au).

[0115] It should be noted that electroplating is the process of plating a thin layer of other metals or alloys on certain metal surfaces using the principle of electrolysis. It is a process that uses electrolysis to attach a layer of metal film to the surface of metal or other material parts. Since electroplating requires an external electric field, each gold finger on the substrate needs to be connected to the cathode or anode of the electroplating equipment. In related technologies, the back of the substrate is etched (Etch back) and a layer of metal is added to the substrate. Figure 8 The electroplating lead 20 shown is used to connect all the gold finger signals on the substrate. Since there is a conductor connection between the gold fingers and the pads 21 of the same circuit network on the substrate, all the gold fingers are electrically connected together through the electroplating lead 20 to perform the electroplating process on the gold fingers.

[0116] In some embodiments, since the size of a single substrate (Unit) is too small, during production and processing, many substrates will be spliced ​​into a large board (Strip), and the size of the large board can be, for example, 240 mm x 77.5 mm. During electroplating, the substrates are connected to each other through the criss-crossing electroplating lines on the large board. There will be exposed metal pads on the large board that are connected to the contacts of the electroplating equipment. The cathode contact is connected to the metal pad of the strip, and the electroplating solution is connected to the anode.

[0117] In some embodiments, after the electroplating is completed, the electroplating lead 20 needs to be etched. For example, the electroplating lead 20 can be disconnected by using an etching solution (such as Fig. 9 As shown), forming Fig. 9The open window area (SR open) 22 is shown. This ensures that there is no risk of short circuit between different electrical signals. However, the method of etching the back of the substrate to add the electroplating lead 20 and disconnecting the electroplating lead 20 after the electroplating is completed has the following three disadvantages from an electrical perspective: First, since the etching cannot completely etch the electroplating lead 20, the electroplating lead 20 remains (such as Fig. 9 Second, the stub may have an uncertain state in the conversion between logic 0 and logic 1, which will affect the integrity and distortion of high-speed signals. Second, the excess stub may have an antenna effect during signal transmission, causing external signal radiation to interfere with other signals. Third, when etching the back side of the substrate, it needs to be isolated from the power plane or ground plane. A large amount of etch back on the substrate will challenge the power integrity.

[0118] Based on this, another embodiment of the present disclosure also provides a method for preparing a semiconductor structure. In the embodiment of the present disclosure, the conductive film is hot-pressed and bonded to the substrate, and the second pads on the back of the substrate are connected together through the conductive bumps on the conductive film. Since the first pad on the front of the substrate is electrically connected to the second pad, the first pad can be connected together through the conductive film to perform an electroplating process on the first pad, and after the electroplating is completed, the conductive film is removed. Therefore, compared with the related art, the embodiment of the present disclosure does not make any changes to the structure of the substrate itself, and no electroplating lead residue will be generated, thereby ensuring the integrity of the high-speed signal, and at the same time, no antenna effect will be generated, and the electromagnetic interference effect can be reduced. In addition, since it is no longer necessary to etch the surface of the substrate to form the electroplating lead, the power supply current is guaranteed, the voltage drop is reduced, and it is beneficial to the integrity of the power supply.

[0119] Fig.10 A flowchart of a method for preparing a semiconductor structure provided in an embodiment of the present disclosure is provided. Figures 11 to 14 The schematic diagram of the structure of the semiconductor structure provided in the embodiment of the present disclosure during the preparation process. Figures 10 to 14 The method for preparing the semiconductor structure provided in the embodiment of the present disclosure is described in detail.

[0120] like Fig.11 As shown, the method for preparing a semiconductor structure includes steps 101 to 104:

[0121] First, please refer to Fig.11 , perform step 101, provide a substrate 30 and the above-mentioned embodiment Figure 2 The conductive film 10 shown in the figure has a first pad 311 and a second pad 312 formed on the front side 301 and the back side 302 of the substrate 30 respectively; the first pad 311 is electrically connected to the second pad 312.

[0122] In the disclosed embodiment, the first pad 311 may be a gold finger formed on the front side 301 of the substrate 30 , and the second pad 312 may be a solder pad formed on the back side 302 of the substrate 30 .

[0123] In some embodiments, the material of the first pad 311 may include but is not limited to metal copper, and the second pad 312 may be a copper (Cu) pad, or other conductive metal pads, such as an aluminum (Al) pad, a gold (Au) pad, a tungsten (W) pad, etc.

[0124] In some embodiments, please refer to Fig.11 The substrate 30 also includes a conductive column 303 formed therein, the first pad 311 and the conductive column 303 are connected through the first wiring layer 304, and the second pad 312 and the conductive column 303 are connected through the second wiring layer 305, so that the electrical connection between the first pad 311 and the second pad 312 can be achieved. Among them, the conductive column 303, the first wiring layer 304 and the second wiring layer 305 can be composed of any one or more conductive metal materials, such as tungsten, cobalt (Co), copper, aluminum and other metals or alloys. The materials of the conductive column 303, the first wiring layer 304 and the second wiring layer 305 can be different or the same.

[0125] In some embodiments, the conductive pillars 303 , the first wiring layer 304 and the second wiring layer 305 are made of the same material, for example, copper, because copper has excellent conductivity, good corrosion resistance and long service life.

[0126] In the embodiment of the present disclosure, the conductive pillars 303 , the first wiring layer 304 , and the second wiring layer 305 are made of the same material, which can reduce contact resistance and improve device performance.

[0127] In some embodiments, please refer to Fig.11 The substrate 30 also includes a solder resist layer 306 formed on the back side 302 ; the solder resist layer 306 is located between the second pads 312 ; a first dimension d1 of the solder resist layer 306 in the thickness direction of the substrate 30 is greater than a second dimension d2 of the second pads 312 in the thickness direction of the substrate 30 .

[0128] In the embodiment of the present disclosure, the first dimension of the solder resist layer 306 in the thickness direction of the substrate 30 is greater than the second dimension of the second pad 312 in the thickness direction of the substrate 30, so that the solder resist layer 306 has a better isolation effect on the second pad 312 and facilitates the positioning between the subsequently formed solder ball and the second pad 312.

[0129] It should be noted that, due to the ball surface of the substrate (corresponding to the above-mentioned back side 302), the ball pad (corresponding to the above-mentioned second pad 312) is surrounded by green oil SR (corresponding to the above-mentioned solder mask layer 306), and there is a height difference between the ball pad and the SR (SR protrudes from the ball pad). Therefore, the contact point of the electroplated film (corresponding to the above-mentioned conductive film 10) needs to have a little protrusion, which must be a micro-bump (corresponding to the above-mentioned conductive bump 103). If the electroplated film adopts a large-area metal plate, there is a certain limitation on the bending degree. Because the substrate itself has a certain degree of warping during the production process, the electroplated film is required to have a certain degree of bending to ensure that the contact point and the substrate ball pad are in more reliable contact. During electroplating, large-area metal plates or metal foils will greatly increase the risk of the plating solution being contaminated by other metal ions.

[0130] In some embodiments, please refer to Fig.11 The third dimension d3 of the conductive bump 103 protruding from the first insulating layer 104 in the thickness direction of the conductive film 10 is greater than or equal to the difference between the first dimension d1 and the second dimension d2.

[0131] In the embodiment of the present disclosure, the third dimension of the conductive bump 103 protruding from the first insulating layer 104 in the thickness direction of the conductive film 10 is greater than or equal to the difference between the first dimension and the second dimension, which can ensure close contact between the conductive bump 103 and the second pad 312, thereby improving the reliability and stability of the electrical connection between the conductive film 10 and the substrate 30.

[0132] Next, please refer to Fig.12 , perform step 102 to thermally press-bond the conductive film 10 and the substrate 30 so that the conductive bump 103 on the conductive film 10 is connected to the second pad 312 .

[0133] In some embodiments, step 102 may be implemented by:

[0134] forming a bonding layer (not shown) on the back side 302 of the substrate 30;

[0135] In some embodiments, the adhesive layer may include a conductive material; in this way, the adhesive layer can be prevented from having an adverse effect on the electrical connection between the conductive bump 103 and the second pad 312 , which is beneficial for reducing the contact resistance between the conductive bump 103 and the second pad 312 .

[0136] In other embodiments, the adhesive layer may not include conductive material, and the conductive film 10 and the substrate 30 are electrically connected through the close contact between the conductive bump 103 and the second pad 312 .

[0137] In some embodiments, the bonding layer may be formed by coating, and the bonding layer includes a heat-sensitive material, so that the bonding effect of the bonding layer decreases with increasing temperature. The material of the bonding layer may include, for example, a thermoplastic resin, which may become liquid at high temperature, and has low viscosity, so that it is easy to be coated on the back side 302 of the substrate 30. In the process of gradually decreasing the temperature, the thermoplastic resin may change from liquid to solid, so as to facilitate the execution of subsequent processes.

[0138] At a preset temperature, a hot pressing process is performed on the substrate 30 and the conductive film 10, wherein in the hot pressing process, the preset temperature is first increased to change the adhesive layer from a solid state to a liquid state, and then gradually decreased to change the adhesive layer from a liquid state to a solid state.

[0139] In some embodiments, the temperature of the hot pressing process is greater than the melting point of the material of the bonding layer, so that the bonding layer can be first changed from solid to liquid during the hot pressing process. The hot pressing pressure and time can be set according to actual needs, for example, based on the material and thickness of the bonding layer and the temperature of the hot pressing process, etc., and no specific limitation is made here.

[0140] In the embodiment of the present disclosure, when performing the hot pressing process, first, the temperature is increased to change the adhesive layer from a solid state to a liquid state. At this time, the adhesive layer has a lower viscosity and better fluidity; next, under a set pressure, pressing is performed for a set time to form a close contact between the conductive bump 103 on the conductive film 10 and the second pad 312 on the back side 302 of the substrate 30, and at the same time, the adhesive layer fully fills the gap between the substrate 30 and the conductive film 10; next, the temperature is gradually lowered while continuing to maintain the set pressure for pressing until the adhesive layer changes from a liquid state to a solid state. At this time, the adhesive layer has a better viscosity, thereby achieving a close and stable combination between the substrate 30 and the conductive film 10.

[0141] Next, please refer to Fig.12 , perform step 103 , perform an electroplating process to form a plating layer 31 on the surface of the first pad 311 .

[0142] In some embodiments, step 103 may be implemented by the following steps:

[0143] electrically connecting the conductive film 10 to a cathode contact of an electroplating device;

[0144] In the disclosed embodiment, the conductive film 10 is electrically connected to the cathode contact of the electroplating equipment, that is, all the first pads 311 are electrically connected to the cathode contact of the electroplating equipment, thereby facilitating the execution of subsequent electroplating processes.

[0145] The substrate 30 and the conductive film 10 are placed in an electroplating solution for electroplating to form a plating layer 31 on the surface of the first pad 311 .

[0146] In some embodiments, the electroplating may be performed using a rack plating process.

[0147] During implementation, the substrate 30 to be plated is connected to the cathode line of the electroplating equipment and suspended in the electroplating solution; the anode block is connected to the anode line of the electroplating equipment and suspended in the electroplating solution; under the action of the external electric field, an oxidation-reduction reaction occurs, the anode block is continuously dissolved, and the metal ions or their complex ions in the electroplating solution are reduced and deposited on the surface of the first pad 311 of the substrate 30 to form a metal layer.

[0148] It should be noted that before performing the electroplating process, the area on the front side 301 of the substrate 30 except the first pad 311 is covered, for example, with green paint, so that only the surface of the first pad 311 is exposed, so that the metal ions or their complex ions in the electroplating solution can be reduced and deposited into a metal layer on the surface of the first pad 311.

[0149] In some embodiments, the first pad 311 includes metal copper, and the plating layer 31 includes a nickel layer and a gold layer sequentially covering the metal copper.

[0150] In the embodiment of the present disclosure, since the plating layer 31 is formed on the surface of the first pad 311 , the stability and reliability of the connection between the gold wire formed in the subsequent process and the first pad 311 can be guaranteed.

[0151] Finally, please refer to Fig.13 , perform step 104 to remove the conductive film 10 .

[0152] In the embodiment of the present disclosure, after the electroplating is completed, the conductive film 10 is removed. Therefore, compared with the related art, the structure of the substrate 30 itself is not changed, and no electroplating lead residue is generated, thereby ensuring the integrity of the high-speed signal, and at the same time, no antenna effect is generated, which can reduce the electromagnetic interference effect. In addition, since it is no longer necessary to etch the surface of the substrate 30 to form the electroplating lead, the power supply current is guaranteed, the voltage drop is reduced, and it is beneficial to the integrity of the power supply.

[0153] In some embodiments, step 104 may be implemented by:

[0154] Heating the adhesive layer so that the adhesive layer changes from a solid state to a liquid state;

[0155] In some embodiments, the temperature at which the adhesive layer is heated is greater than the melting point of the material of the adhesive layer, so that the adhesive layer changes from a solid state to a liquid state, and at this time, the adhesive layer has a lower viscosity.

[0156] The conductive film 10 is peeled off from the back surface 302 of the substrate 30 .

[0157] In the embodiment of the present disclosure, when the adhesive layer is in liquid state, the adhesive layer has low viscosity, and the bonding force between the substrate 30 and the conductive film 10 is small, so the conductive film 10 can be easily peeled off from the back side 302 of the substrate 30. Specifically, for example, a vacuum suction cup can be used to easily separate the substrate 30 and the conductive film 10.

[0158] In the disclosed embodiment, after the electroplating is completed, the conductive film 10 can be easily peeled off from the back side 302 of the substrate 30 without any influence on the structure of the substrate 30 itself, and the peeled conductive film 10 can be used multiple times.

[0159] In some embodiments, please refer to Fig.14 After removing the conductive film 10 , the method for preparing the semiconductor structure further includes: forming at least one semiconductor chip 32 on the front side 301 of the substrate 30 ; and connecting the at least one semiconductor chip 32 to the first pad 311 through wire bonding 33 .

[0160] In the disclosed embodiment, the semiconductor chip 32 may be a dynamic random access memory (DRAM) chip, a static random access memory (SRAM) chip, a phase-change memory (PCM) chip, a NAND flash memory chip or a Nor Flash chip.

[0161] In some embodiments, the lead wire 33 may be a metal wire or alloy wire such as gold wire, silver wire, copper wire, aluminum wire, etc. The semiconductor chip 32 is connected to the first pad 311 by bonding the lead wire 33, so that the electrical signal connection between the semiconductor chip 32 and the substrate 30 can be achieved.

[0162] It should be noted that if Fig.14 As shown, in the above embodiment, four semiconductor chips 32 are formed on the front surface 301 of the substrate 30 as an example. In other embodiments, the number of semiconductor chips 32 may be one, two, three, or five or more. The semiconductor chip 32 located at the bottom layer may be connected to the front surface 301 of the substrate 30 through a die attach film 34 (DAF) 34, and adjacent semiconductor chips 32 may be connected through a film over wire (FOW) 35.

[0163] In the embodiment of the present disclosure, the conductive film 10 and the substrate 30 are heat-pressed and bonded, and the second pad 312 on the back side 302 of the substrate 30 is connected together through the conductive bump 103 on the conductive film 10. Since the first pad 311 on the front side 301 of the substrate 30 is electrically connected to the second pad 312, the first pad 311 can be connected together through the conductive film 10 to perform an electroplating process on the first pad 311, and after the electroplating is completed, the conductive film 10 is removed. Therefore, compared with the related art, the embodiment of the present disclosure does not make any changes to the structure of the substrate 30 itself, and no electroplating lead residue will be generated, thereby ensuring the integrity of the high-speed signal, and at the same time, no antenna effect will be generated, which can reduce the electromagnetic interference effect. In addition, since it is no longer necessary to etch the surface of the substrate 30 to form the electroplating lead, the power supply current is guaranteed, the voltage drop is reduced, and it is beneficial to the integrity of the power supply.

[0164] Another embodiment of the present disclosure provides a method for preparing a semiconductor structure, which specifically includes the following steps 1 to 4:

[0165] Step 1: Provide an electroplated film (corresponding to the conductive film 10 mentioned above), with the film (corresponding to the film substrate 101 mentioned above) as a carrier, and a mesh copper conductor (corresponding to the mesh conductive line 102 mentioned above) attached to the film surface. According to the distribution of the ball pad (corresponding to the second pad 312 mentioned above) on the substrate (corresponding to the substrate 30 mentioned above), there are copper micro-bumps (corresponding to the conductive bumps 103 mentioned above) at the corresponding positions of the film.

[0166] Step 2: Before electroplating, the electroplating film and the ball pad surface of the substrate are hot-pressed so that the surface of the ball pad of the substrate is tightly attached to the electroplating film, and the micro-bumps on the film are tightly combined with the ball pads on the substrate. Then, all the ball pads on the substrate are short-circuited together through the mesh copper conductor on the electroplating film. Since there is a conductor connection between the finger (corresponding to the first pad 311 mentioned above) and the ball pad of the same circuit network on the substrate itself, all the fingers are short-circuited together. Specifically, first, a layer of adhesive (corresponding to the above-mentioned adhesive layer) is brushed on the substrate, and then the electroplating film and the substrate are pressed together with a hot press, so that the adhesive is first liquefied and then solidified, and the electroplating film and the substrate are perfectly combined.

[0167] Step 3: Electroplating. After the electroplating is completed, the substrate and the electroplated film can be separated by shedding. The electroplated film can be used multiple times. Specifically, after the electroplating is completed, the substrate is heated and the adhesive becomes liquid. Since the adhesive effect of this adhesive decreases with the increase of temperature, after heating, the substrate and the electroplated film can be easily separated by a vacuum suction cup. The electroplated film can be used multiple times.

[0168] The embodiments of the present disclosure have the following two beneficial effects:

[0169] First, since the present invention does not make any changes to the substrate itself, compared with the traditional method, there is no redundant residue (corresponding to the above-mentioned electroplated lead residue), which ensures the integrity of the high-speed signal. At the same time, it does not produce an antenna effect, reducing the electromagnetic interference effect.

[0170] Second, the ball pad layer has no Etch back to divide the power supply, which ensures the power current, reduces the voltage drop, and is beneficial to the power integrity.

[0171] In the several embodiments provided in the present disclosure, it should be understood that the disclosed structures and methods can be implemented in a non-targeted manner. The structural embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the components shown or discussed are coupled or directly coupled to each other.

[0172] The features disclosed in several method or structural embodiments provided in the present disclosure may be arbitrarily combined without conflict to obtain new method embodiments or structural embodiments.

[0173] The above are only some embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A conductive film, characterized in that: include: film substrate; A mesh-shaped conductive circuit is located on the film substrate; A plurality of conductive bumps are distributed on each intersection of the mesh conductive circuit.

2. The conductive film according to claim 1, characterized in that: Also includes: A first insulating layer, located on the surface of the mesh conductive circuit and between the mesh conductive circuits; The conductive bumps protrude from the first insulating layer.

3. The conductive film according to claim 2, characterized in that: The conductive film is used to form a plating layer on the first pad on the front side of the substrate; The position of the conductive bump corresponds to the position of the second pad on the back side of the substrate.

4. The conductive film according to any one of claims 1 to 3, characterized in that: The material of the film substrate includes a flexible material.

5. The conductive film according to claim 4, characterized in that: The material of the film substrate includes graphite film or fiber film.

6. A method for forming a conductive film, characterized in that: providing a film substrate; forming a conductive material layer on the film substrate; forming a plurality of conductive bumps on the surface of the conductive material layer; The conductive material layer is patterned to form a mesh-shaped conductive circuit, wherein a plurality of the conductive bumps are distributed at each intersection of the mesh-shaped conductive circuit.

7. The method according to claim 6, characterized in that Also includes: A first insulating layer is formed covering the mesh-shaped conductive circuits and located between the mesh-shaped conductive circuits.

8. The method according to claim 6 or 7, characterized in that: Forming a plurality of conductive bumps on the surface of the conductive material layer includes: forming a second insulating layer on the conductive material layer, wherein the second insulating layer exposes a portion of the conductive material layer; The conductive bumps are formed on the exposed surface of the conductive material layer.

9. A method for preparing a semiconductor structure, characterized in that: include: A conductive film and a substrate as claimed in claim 3 are provided; a first pad and a second pad are formed on the front and back of the substrate respectively; the first pad is electrically connected to the second pad; The conductive film is laminated to the substrate by heat pressing so that the conductive bumps on the conductive film are connected to the second pads; Performing an electroplating process to form a plating layer on the surface of the first pad; The conductive film is removed.

10. The method according to claim 9, characterized in that The substrate further comprises a solder resist layer located on the back side; the solder resist layer is located between the second pads; A first dimension of the solder resist layer in a thickness direction of the substrate is greater than a second dimension of the second pad in the thickness direction of the substrate.

11. The method according to claim 10, characterized in that A third dimension of the conductive bump protruding from the first insulating layer in the thickness direction of the conductive film is greater than or equal to a difference between the first dimension and the second dimension.

12. The method according to claim 9, characterized in that The conductive film and the substrate are thermally pressed together, comprising: forming a bonding layer on the back side of the substrate; the bonding layer comprises a conductive material; At a preset temperature, a hot pressing process is performed on the substrate and the conductive film, wherein in the hot pressing process, the preset temperature is first increased so that the adhesive layer changes from a solid state to a liquid state, and then gradually decreased so that the adhesive layer changes from a liquid state to a solid state.

13. The method according to claim 9, characterized in that Performing an electroplating process to form a plating layer on the surface of the first pad includes: electrically connecting the conductive film to a cathode contact of an electroplating device; The substrate and the conductive film are placed in an electroplating solution for electroplating to form a plating layer on the surface of the first pad.

14. The method according to claim 12, characterized in that Removing the conductive film comprises: Heating the adhesive layer so that the adhesive layer changes from a solid state to a liquid state; The conductive film is peeled off from the back surface of the substrate.

15. The method according to claim 9, characterized in that After removing the conductive film, the method further comprises: forming at least one semiconductor chip on the front surface of the substrate; The at least one semiconductor chip is connected to the first pad by wire bonding.

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