Joint structure

Abstract

Some embodiments of the present application provide a bonding structure, including: a pad; a plurality of lines disposed on the pad; and a bonding layer between the pad and the plurality of lines and including a plurality of bonding portions, where each of the plurality of bonding portions has a tapered shape in a direction toward the pad, and where there is a bonding interface between the lines and the bonding portions. The joint structure provided by the utility model can provide better joint.

Description

Technical Field

[0001] An embodiment of the present application relates to a bonding structure. Background Art

[0002] In previous bonding structures, there are components in the bonding structure that will cause bonding problems when bonding the chip to the substrate due to the mismatch of CTE (coefficient of thermal expansion) between the die end and the substrate end at high temperatures; the current copper (Cu) to copper bonding using nanowires as the bonding interface can have the benefit of low-temperature bonding, because the mutual bonding of nanowires can be performed at a lower bonding temperature (room temperature to 200°C). However, since the process of nanowires is an electroplating process, for pads without a seed layer, it is impossible to directly electroplate nanowires on the metal points to be bonded (such as pads), and directly forming nanowires on pads will face the problem of thicker templates and easy delamination between the substrate.

[0003] Specifically, see Figure 1A , a thicker aluminum template 13 (whose thickness needs to be greater than 10 μm, which is not suitable for a manufacturing process with a maximum thickness of no more than 5 μm) is formed by sputtering aluminum on the pad 11 disposed on the substrate 14, such as Figure 1A As shown, pad 11 is formed on seed layer 16 and connected to metal trace 14T in substrate 14; Figure 1B , the aluminum template 13 is soaked in a strong acid (pH < 3) to perform anodization to form fine pores O corresponding to the nanowires 12 in the aluminum template 13. Soaking the aluminum template 13 in a strong acid requires checking the usability of other components in the strong acid. In the bonding structure 10, since the nanowires 12 are formed by soaking the aluminum template 13 in a strong acid to form fine pores, the strong acid easily destroys the substrate 14 at the same time. Next, see Figure 1C , coating / aligning the photoresist 15 is performed, that is, forming the photoresist 15 on the aluminum template 10 where the nanowires 12 are not formed. It can be seen that in the existing process, the process steps are increased and more complicated. Figure 1D , the nanowires 12 are formed in the pores O by electroplating. In some processes, electroplating is performed in a copper (Cu) / gallium (Ga) solution, thereby plating the nanowires 12 of copper (Cu) / gallium (Ga) in the pores O. Then, see Figure 1E After the nanowires 12 are electroplated, the aluminum template 13 needs to be removed using a strong acid. In this step, Figure 1D The structure shown is immersed in a strong acid (pH < 3) to remove the aluminum template 13 and the seed layer (not specifically shown), and the usability of other components in the strong acid needs to be checked. In this step, the strong acid may also damage the nanowires 12. It can be seen that directly forming the nanowires 12 on the pads 11 will face the problem of thick aluminum templates 13 and substrates 14 being easily delaminated. Finally, see Figure 1F, the nanowire 12 is bonded to the corresponding nanowire 12' of other bonding structures 10', and this bonding requires the use of an alignment machine for alignment.

[0004] In summary, the nanowires 12 in the bonding structure 10 and the nanowires 12' in the bonding structure 10' can be bonded at a relatively low bonding temperature (RT (normal temperature) to 20° C.), but in the above method, specifically, see Figure 1G Since the manufacturing process of the nanowire 12 is to electroplate on the corresponding pad 11 where a seed layer (not shown) needs to be formed through an electroplating process, if a corresponding pad of a test chip (test piece) with the seed layer removed is encountered, the nanowire 12 cannot be directly electroplated on the metal point (such as the pad) to be joined (because the seed layer does not exist), that is, most of the current processes for the nanowire 12 are copper electroplating, so a seed layer is also required for a long wire process, making the mass production of the nanowire 12 process more difficult. Utility Model Content

[0005] In order to solve the above problems, the present application provides a bonding structure with better bonding performance.

[0006] Some embodiments of the present application provide a bonding structure, comprising: a pad; a plurality of wires arranged on the pad; and a bonding layer located between the pad and the plurality of wires and comprising a plurality of bonding portions, wherein each of the plurality of bonding portions has a tapered shape in a direction toward the pad, and wherein a bonding interface exists between the wires and the bonding portions.

[0007] In some embodiments, the engagement portions are disposed in a one-to-one correspondence with the wires.

[0008] In some embodiments, a central region of the engagement portion extends along a side wall of the corresponding line and has a tapered shape in a direction extending toward the corresponding line.

[0009] In some embodiments, the central region includes a first end portion in contact with the corresponding line.

[0010] In some embodiments, the joining structure further includes: a second end portion surrounding the central area and disposed at an outer edge of the joining portion, wherein a height of the first end portion is lower than a maximum height of the second end portion.

[0011] In some embodiments, a portion of one or more of the plurality of bonding portions is located on a sidewall of the pad.

[0012] In some embodiments, there is a recessed space between the first end and the second end.

[0013] In some embodiments, the recessed space has a concave surface between the first end and the second end.

[0014] In some embodiments, in a cross-sectional view passing through the corresponding line, heights of the second end portions located at opposite sides of the corresponding line are different.

[0015] In some embodiments, the wires are nanowires.

[0016] In some embodiments, there are gaps between adjacent ones of the plurality of engagement portions.

[0017] In some embodiments, adjacent joining portions among the plurality of joining portions are discontinuous.

[0018] In some embodiments, adjacent ones of the plurality of engagement portions are in contact and continuous.

[0019] In some embodiments, the plurality of lines are spaced apart from each other.

[0020] In some embodiments, the pad includes a lower portion and an upper portion located above the bottom portion, the upper portions are spaced apart from each other, and the plurality of lines are respectively disposed on the corresponding upper portions.

[0021] In some embodiments, there is a gap between the bonding portion and the pad.

[0022] In some embodiments, a base of each of the plurality of wires is embedded within a corresponding one of the engagement portions.

[0023] Other embodiments of the present application provide a bonding structure, comprising: a pad; a bonding layer, located on the pad and comprising a plurality of bonding portions; and a plurality of wires, corresponding to the plurality of bonding portions and connected to the pad through corresponding bonding portions, wherein a bonding interface exists between the wires and the corresponding bonding portions, and the corresponding bonding portions have a tapered shape in a direction toward the pad.

[0024] In some embodiments, a central region of the engagement portion extends along a side wall of the corresponding line, and a top portion of the central region in contact with the corresponding line has a tapered shape in a direction extending toward the corresponding line.

[0025] In some embodiments, the central area includes a first end in contact with the corresponding line, and the joining structure also includes: a second end surrounding the central area and arranged at the outer edge of the joining portion, wherein the height of the first end is lower than the maximum height of the second end.

[0026] The bonding structure provided by the present application can provide better bonding. In addition, the bonding structure provided by the present application can reduce the difficulty of mass production of (nano) wire processes, and for structures with removed seed layers, (nano) wires can also be transferred to corresponding pads (metal contacts). The nanowire transfer method is applicable to any product with metal (such as copper), because its basic process is to deposit metal (such as copper) on the surface of metal (such as copper). The CMP (chemical mechanical planarization) process is not required, and the flexibility of nanowires is used to reduce the requirements for high uniformity of test chips, and the problem of surface unevenness is filled after pressing.

[0027] Furthermore, in the bonding structure provided in the present application, the above-mentioned problems caused by directly depositing the nanowires on the substrate pads can be effectively solved by first forming the nanowires on the outside and then bonding the nanowires to the substrate pads. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] When read in conjunction with the accompanying drawings, various aspects of the present invention can be best understood from the following detailed description. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, for the sake of clarity of discussion, the size of the various components can be arbitrarily increased or reduced.

[0029] Figures 1A to 1G A bonding structure in the prior art is shown.

[0030] FIG. 2A to FIG. 2F A bonding structure according to some embodiments of the present application is shown.

[0031] FIG. 3A to FIG. 3C A scanning electron microscope image of a bonding structure according to some embodiments of the present application is shown.

[0032] Figures 4 to 8 , FIG. 8A to FIG. 8B as well as Figures 9 to 13 The forming process of the bonding structure according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0033] The following disclosure provides many different embodiments or examples for realizing different features of the present invention. Specific examples of components and arrangements are described below to simplify the present invention. Of course, these are merely examples and are not intended to limit the present invention. In addition, when "approximately", "about", "substantially", etc. are used to describe a numerical value or a numerical range, unless otherwise specified, the term is intended to cover a numerical value within ±10% of the described numerical value. For example, the term "about 5nm" covers a size range from 4.5nm to 5.5nm.

[0034] Some embodiments of the present application provide a bonding structure, which forms a bonding layer including multiple bonding parts between the corresponding nanowires and pads, each of the multiple bonding parts has a tapered shape in a direction toward the pad, which can increase the bonding strength between the nanowires and the pad.

[0035] Specifically, see Figure 2A and Figure 2B , Figure 2A shows a bonding structure 100 according to some embodiments of the present application, and Figure 2B Shows Figure 2A An enlarged view of region A of the bonding structure 100 is shown. Figure 2A As can be seen from the figure, the bonding structure 100 includes: a pad 101; a plurality of wires 102 disposed on the pad 101; and a bonding layer 105 located between the pad 101 and the plurality of wires 102. Figure 2B It can be seen from the enlarged view of that the bonding layer 105 includes a plurality of bonding portions 1051, 1052, ... In a further embodiment, each of the plurality of bonding portions 1051, 1052, ... has a tapered shape in a direction toward the pad 101, and wherein a distinguishable bonding interface L exists between the wire 102 and the corresponding bonding portions 1051 / 1052, ... of the bonding portions 1051, 1052, ... Figure 2A and Figure 2B It can be seen that the plurality of wires 102 are spaced apart from each other, that is, adjacent wires 102 in the plurality of wires 102 are spaced apart from each other. In an embodiment, the wires 102 are nanowires. In a further detailed embodiment, the wires 102 are nanowires made of a metal such as copper. In the present application, Figure 2A As shown, the pad 101 includes a lower portion 101B and an upper portion 101A located above the bottom portion 101B, the upper portions 101A are spaced apart from each other, and a plurality of wires 102 are respectively arranged on the corresponding upper portions 101A. In some embodiments, the pad 101 is made of metal, including but not limited to copper (Cu). In addition, the bonding layer 105 can also be made of a metal such as copper. In the above-mentioned bonding structure 100, the bonding structure 100 also includes a substrate 104, which can be a silicon substrate or a carrier substrate such as glass.

[0036] In addition, further, when forming, the bonding portions 1051, 1052... are formed using chemical plating, while the wire 102 is formed using electroplating. Even if the same material is used, the grain size of the bonding portions 1051, 1052... and the wire 102 is different. In an embodiment using copper, the grain size of the corresponding wire 102 is larger than the grain size of the corresponding bonding portions 1051 / 1052... of the bonding portions 1051, 1052...

[0037] Further from Figure 2B It can be seen that in the joint structure 100 provided in the present application, the corresponding joint portions 1051 / 1052... are arranged in a one-to-one correspondence with the wires 102, that is, one of the wires 102 corresponds to a corresponding one of the joint portions 1051, 1052... . Further, Figure 2C Shows Figure 2B A magnified view of area B from Figure 2C It can be seen that the joint portion 1051 / 1052 ... includes a central region C and a peripheral region P surrounding the central region C, and the central region C of the joint portion 1051 / 1052 ... extends along the side wall 102s of the corresponding line 102 and has a tapered shape in the direction E extending toward the corresponding line 102, such as Figure 2C In addition, further Figure 2C As shown, the central region C includes a first end 105ce in contact with the corresponding line 102 (such as the side wall 102s of the corresponding line 102). Further, the joint structure 100 also includes a second end 105pe surrounding the central region C and disposed at the outer edge 105s of the joint portion 1051 / 1052..., and the height of the first end 105ce is lower than the maximum height of the second end 105pe. In some embodiments, the height of the first end 105ce may also be higher than the maximum height of the second end 105pe. It should be understood that Figure 2C Only the first end 105ce and the second end 105pe are schematically shown. This is because the corresponding joint portion 1051 / 1052... will be formed into a "mushroom head" shape around the corresponding wire 102 (see Figure 2E The corresponding bonding portions 1051 / 1052 ... of the bonding layer 105 between the wire 102 and the pad 101 are formed into a "mushroom head" shape, which can increase the bonding strength between the wire 102 and the pad 101, and further increase the strength of fixing the corresponding wire 102 and the pad 101 with the bottom filler or the like in the subsequent process.

[0038] In addition, there is a recessed space R between the first end 105ce and the second end 105pe. In some embodiments, the recessed space R has a concave surface Rs between the first end 105ce and the second end 105pe. Figure 2C In the cross-sectional view shown, the heights of the second ends 105pe located at opposite sides of the corresponding line 102 are different, which can be further seen in FIG. Figure 3CThe heights D1 and D2 shown are from Figure 3C It can be clearly seen from the structure shown that the height D1 is smaller than the height D2 , that is, the heights D1 and D2 are different.

[0039] In some other embodiments, FIG. 2A to FIG. 2C In the illustrated bonding structure 100, a portion of one or more bonding portions 1051, 1052, ... among the plurality of bonding portions 1051, 1052, ... is located on the sidewall 101s of the pad 101. In other words, a portion of one or more bonding portions 1051, 1052, ... is located at the edge 101e of the pad 101. Figure 2C As shown, there is a gap V between the bonding portion 1051 / 1052 ... and the pad 101. Figure 2C In the illustrated embodiment, the bottom 102d of each of the plurality of wires 102 is embedded in the corresponding bonding portion 1051 / 1052..., which may further enhance the bonding.

[0040] Back to reference Figure 2B , there is a gap G between adjacent bonding portions (such as bonding portions 1051, 1052) among the plurality of bonding portions 1051, 1052, ... and the adjacent bonding portions (such as bonding portions 1051, 1052) are not continuous. In some other embodiments, possibly affected by the distance between the wires 102 and the process of forming the plurality of bonding portions 1051, 1052, the adjacent bonding portions (such as bonding portions 1051, 1052) among the plurality of bonding portions 1051, 1052, ... may be in contact and continuous.

[0041] In addition, in the bonding structure 100 provided in the present application, see Figure 2D The problem of depositing the nanowire 12 directly on the pad 11 of the substrate 14 (such as by attaching the nanowire 12 to a carrier 1000 such as silicon via an adhesive layer 1000') can be effectively solved by first forming the nanowire 102 externally (such as by attaching the nanowire 102 to a carrier 1000 such as silicon via an adhesive layer 1000') and then transferring and bonding the nanowire 102 to the pad 101 of the substrate 104. Figure 1G In addition, the method provided by the present application can be used to bond the nanowire 102 to any interface S, such as Figure 2F As shown in the scanning electron microscope image, the difficulty of mass production of nanowires is reduced.

[0042] Further, FIG. 3A to FIG. 3C Shows Figure 2A The SEM image of a portion of the bonding structure 100 is shown. FIG. 3A to FIG. 3C It can be seen from the figure that the bonding structure 100 has corresponding bonding portions 1051 / 1052 . . . in a “mushroom head” shape formed under each nanowire 102 . . .

[0043] Continue to refer to Figure 2A Some embodiments of the present application further provide a bonding structure 100, the bonding structure 100 comprising: a pad 101; a bonding layer 105, located on the pad 101 and comprising a plurality of bonding portions 1051, 1052, ...; and a plurality of wires 102, corresponding to the plurality of bonding portions 1051, 1052, ... and connected to the pad 101 through the corresponding bonding portions 1051 / 1052, ..., wherein a bonding interface L exists between the wires 102 and the corresponding bonding portions 1051 / 1052, ..., and the corresponding bonding portions 1051 / 1052 have a tapered shape in a direction D toward the pad 101. In a further embodiment, referring to Figure 2C , a central region C of the joining portion 1051 / 1052 . . . extends along the side wall 102s of the corresponding line 102 , and a top of the central region C in contact with the corresponding line 102 has a tapered shape in a direction E extending toward the corresponding line 102 .

[0044] Similarly, see Figure 2C The central area C includes a first end 105ce in contact with the corresponding line 102, and the joining structure 100 also includes: a second end 105pe surrounding the central area C and arranged at the outer edge 105s of the joining portion 1051 / 1052..., wherein the height of the first end 105ce is lower than the maximum height of the second end 105pe.

[0045] Below Figures 4 to 13 The formation of the corresponding bonding structure 100 and the related bonding are explained.

[0046] Reference Figure 4 , by sputtering to form the nanowires 102 (such as Figure 2A The polymer film 1001 (shown in FIG. 1 ) has holes 1001O corresponding to the nanowires 102 to be formed later. In some embodiments, the polymer film 1001 may be a polyimide film, a polyethylene film, etc., as long as it can withstand strong alkali (such as a strong alkali with a pH of about 13). Figure 5 , a seed layer 1002 such as copper is sputtered at the bottom of the polymer film 1001. In some other embodiments, the seed layer 1002 can be any suitable metal layer, such as a titanium layer.

[0047] Next, see Figure 6 , the polymer film 1001 formed with the seed layer 1002 is attached to the carrier 1004, such as by the adhesive layer 1003. In some embodiments, the carrier 1004 may be a silicon carrier for support, and the adhesive layer 1003 may be a glue layer, an adhesive layer, etc.

[0048] See also Figure 7 , nanowires are plated in the holes 1001O of the polymer film 1001 by electroplating. In this embodiment, the nanowires are copper nanowires. It should be noted that Figure 7 The structure shown is a structure ready for mass transfer. Figure 7 The structure shown is subsequently used to form the joining structure 100 .

[0049] Figure 8 Shows the removal Figure 7 The polymer film 1001 in the structure shown is removed by lift-off or other methods. After the polymer film 1001 is removed, the corresponding nanowires 102 (which are copper nanowires) are formed. Fig. 8A and Figure 8B FIG. 1 shows a scanning electron microscope image of the formed nanowire 102 (specifically, a copper nanowire). Fig. 8A and Figure 8B As can be seen in FIG. 1 , the nanowires 102 formed by electroplating have a uniform and dense structure.

[0050] Next, see Fig. 9 ,Will Figure 7 The structure shown is flipped over and attached to a carrier 1006, such as by an adhesive layer 1005. In some embodiments, the carrier 1006 may be a glass carrier for support, and the adhesive layer 1005 may be a glue layer, an adhesive layer, etc. Then the seed layer 1002 is removed, such as by dry etching or wet etching. It should be noted that after the seed layer 1002 is removed, the bottom 102d of the nanowire 102 protrudes from the corresponding polymer film 1001. Afterwards, see Fig.10 , a bonding layer 105 is formed by using copper through a chemical plating process to bond the nanowire 102 to the upper portion 101A of the pad 101 (in the present embodiment, the pad 101 is a copper pad). In the chemical plating process, a microfluidic system may or may not be used (this may be determined according to actual conditions), wherein the direction of flow of the plating solution in the plating process is shown as F, and in the plating process, the pH value of the plating solution is maintained at about 13. Since the electrons gather near the nanowire 102 and the electrons at the edge of the nanowire 102 are more concentrated, copper is deposited faster, while the portion of the nanowire 102 in contact with the pad 101 is a surface with fewer electrons, and copper is deposited slower. Therefore, the copper near the edge of the nanowire 102 is thicker, thereby forming a corresponding bonding portion 1051 / 1052 in the shape of a "mushroom head" under each nanowire 102..., as shown in FIG. FIG. 3A to FIG. 3C As shown in the scanning electron microscope image of FIG. 1 , a bonding layer 105 is formed to bond the nanowire 102 to the pad 101, see Fig.11By forming the bonding layer 105 through chemical copper plating, the nanowires 102 can be bonded to the surface of any structure without forming a seed layer. Fig.12 , removing the polymer film 1001, such as by peeling, thereby obtaining Fig.12 The bonding structure 100 corresponds to FIG. 2 .

[0051] Finally, see Fig.13 , at room temperature (about 20°C) Fig.12 The bonding structure 100 shown is bonded to another bonding structure 100 ′ formed by the method of the present application, such as bonding the nanowire 102 to the nanowire 102 ′ by using a metal-to-metal direct bonding method commonly used in the art.

[0052] In the present application, the bonding layer 105 is formed by a chemical copper plating method, and the nanowire 102 is formed by an electrolytic copper plating method. This is because the bonding layer 105 formed by the chemical copper plating method has a relatively loose structure and a small grain size, while the nanowire 102 formed by the electrolytic copper plating method has a dense structure and high strength, and a large grain size, so that the grain size of the corresponding wire 102 is larger than the grain size of the corresponding bonding part 1051, 1052... of the bonding part 1051 / 1052... Therefore, after the nanowire 102 is formed, the bonding layer 105 is formed by a chemical copper plating method to transfer the nanowire 102, which can ensure that the nanowire 102 is well bonded to the corresponding pad 101, regardless of whether a seed layer is formed on the pad 101. Bonding the nanowire 102 by this method has the following advantages:

[0053] 1) The difficulty of mass production of the nanowire 102 is reduced, and the nanowire can be transferred to the pad 101 (ie, metal contact) even for a structure where the seed layer has been removed.

[0054] 2) The transfer method is applicable to any product that uses metal (such as copper) bonding, because its basic process is to electrolessly plate metal (such as copper) on the metal (such as copper) surface.

[0055] 3) The process of chemical mechanical planarization (CMP) may not be required, and the nano-flexibility may be utilized to reduce the requirement of high uniformity of the bonding structure 100 , and the problem of surface unevenness may be filled by lamination.

[0056] 4) The bonding structure 100 provided in the present application can further improve the bonding strength of the corresponding bonding structure.

[0057] In summary, the formation method of the bonding structure 100 of the present application is solder-free bonding, which can provide nanowire processes on different surfaces and can be mass-produced. In addition, based on the polymer film 1001, the manufacturer can customize the product, so the produced nanowires 102 can also be customized, for example: the density, height, diameter, shape, etc. of the nanowires can be changed.

[0058] In addition, the method provided in the present application is a material transfer method, which can be performed without a circuit, and any pattern can be joined by a chemical plating method (i.e., can be plated). Specifically, a polymer template is used to make a high-density nanohole (i.e., the hole 1001O corresponding to the nanowire 102), the electroplated metal is filled in the hole, and then the polymer template is removed to form the nanowire. It should be noted that the joints between the chemically plated metal (such as copper) and the electroplated nanowire (such as copper nanowire) are in the shape of a "mushroom head".

[0059] The features of several embodiments are summarized above so that those skilled in the art can better understand aspects of the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis to design or modify other processes and structures for implementing the same purpose and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also appreciate that such equivalent constructions do not deviate from the spirit and scope of the present invention, and that they can make various changes, substitutions, and modifications herein without departing from the spirit and scope of the present invention.

Claims

1. A joining structure, characterized in that: include: Solder pads; A plurality of wires are disposed on the pad; as well as a bonding layer located between the pad and the plurality of wires and including a plurality of bonding portions, wherein each of the plurality of bonding portions has a tapered shape in a direction toward the pad, and wherein a bonding interface exists between the wire and the bonding portion.

2. The joining structure according to claim 1, characterized in that: A central area of ​​the engagement portion extends along a side wall of the corresponding line and has a tapered shape in a direction extending toward the corresponding line.

3. The joining structure according to claim 2, characterized in that: The central region includes a first end portion in contact with the corresponding line.

4. The joining structure according to claim 3, characterized in that: Also includes: a second end portion surrounding the central area and disposed at an outer side edge of the engaging portion, Wherein, the height of the first end is lower than the maximum height of the second end.

5. The joining structure according to claim 1, characterized in that: A portion of one or more of the plurality of bonding portions is located on a sidewall of the pad.

6. The joining structure according to claim 4, characterized in that: There is a recessed space between the first end and the second end.

7. The joining structure according to claim 6, characterized in that: The recessed space has a concave surface between the first end and the second end.

8. The joining structure according to claim 4, characterized in that: In a cross-sectional view passing through the corresponding line, heights of the second end portions located at opposite sides of the corresponding line are different.

9. The joining structure according to claim 1, characterized in that: The pad includes a lower portion and an upper portion located above the bottom portion, the upper portions are spaced apart from each other, and the plurality of lines are respectively disposed on the corresponding upper portions.

10. The joining structure according to claim 1, characterized in that: A bottom portion of each of the plurality of wires is embedded in the corresponding engagement portion.

Images