CN217507266U

CN217507266U - Joint structure

Info

Publication number: CN217507266U
Application number: CN202221228654.6U
Authority: CN
Inventors: 陈昭丞; 张皇贤; 周泽川
Original assignee: Advanced Semiconductor Engineering Inc
Current assignee: Advanced Semiconductor Engineering Inc
Priority date: 2022-05-19
Filing date: 2022-05-19
Publication date: 2022-09-27
Anticipated expiration: 2032-05-19

Abstract

The present application relates to a joining structure. The joining structure includes a first joining unit including: a first metal pad; a first insulating layer covering the outer side of the top surface of the first metal pad and defining a first opening on the top side of the first metal pad; and a first metal layer covering a top surface of the first metal pad and located in the first opening, and forming a non-compound interface with the first metal pad. The joint structure is beneficial to improving the definition of the edge of the metal layer, and further improving the alignment precision when the metal layers are butted.

Description

Joint structure

Technical Field

The application relates to the technical field of semiconductor packaging, in particular to a bonding structure.

Background

Copper-to-copper interfacing is a technique for three-dimensional chip (3D-IC) packaging, and the challenge is that the copper surface is easily oxidized, and the copper oxide will inhibit copper diffusion, thereby increasing the bonding temperature (e.g., > 250 ℃) and easily creating voids on the bonding surface. The foregoing problem can be overcome by performing silver replacement on the surface of the copper pad, but negative charges are easily accumulated at the edge of the copper pad due to the point discharge effect, so that silver ions are concentrated at the edge of the copper pad to form silver burrs (with a size of 0.2 micrometers to 2 micrometers), which makes it difficult to distinguish the edge of the copper pad during the butting process and make alignment difficult.

Therefore, a new technical solution is needed to solve at least one of the above technical problems.

SUMMERY OF THE UTILITY MODEL

The present application provides a joining structure.

The present application provides a joining structure including a first joining unit including:

a first metal pad;

a first insulating layer covering the outer side of the top surface of the first metal pad and defining a first opening on the top side of the first metal pad; and

and the first metal layer covers the top surface of the first metal pad, is positioned in the first opening and forms a non-compound interface with the first metal pad.

In some optional embodiments, the second bonding unit further comprises a second metal pad, and the second metal pad is directly or indirectly bonded to the first metal layer.

In some optional embodiments, the second bonding unit further includes a second insulating layer and a second metal layer;

the second insulating layer is positioned outside the top surface of the second metal pad and defines a second opening positioned on the top side of the second metal pad;

the second metal layer covers the top surface of the second metal pad and is located in the second opening, and is bonded to the first metal layer.

In some alternative embodiments, an interface is formed between the first insulating layer and the second insulating layer.

In some optional embodiments, the first insulating layer and the second insulating layer are bifurcated.

In some optional embodiments, the first metal layer and the outer side of the second metal layer are located between the first insulating layer and the second insulating layer.

In some alternative embodiments, the thickness of the first metal layer is greater than or equal to the thickness of the first insulating layer.

In some optional embodiments, the top surface of the first metal pad is a concave surface, and the first insulating layer is recessed from an outer edge of the first metal pad toward a center of the first metal pad.

In some optional embodiments, the first bonding unit further includes a first protective layer surrounding the first metal pad.

In some optional embodiments, the first insulating layer covers the first protective layer and the first metal pad.

In some optional embodiments, the first bonding unit further includes a barrier layer between the first metal pad and the first protective layer.

The application provides a joint structure to non-conducting material that can not react with metal ion covers the metal pad edge as the insulating layer, shelters from the place that charge density is higher, makes metal ion can not receive the negative charge attraction of accumulation at the metal pad edge and form the burr when the replacement, is favorable to improving the definition at metal level edge, and then improves the counterpoint precision when the metal level docks.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:

FIG. 1A is a cross-sectional view of a prior art bonding structure prior to bonding;

FIG. 1B is a cross-sectional view of a prior art bonding structure after bonding;

FIG. 1C is a cross-sectional view of a prior art bonding structure with a silver layer;

FIG. 1D is a schematic top view of a prior art bonding structure with a silver layer;

FIG. 2 is a schematic cross-sectional view of a first embodiment of a bonding structure according to the present application;

FIG. 3 is a schematic top view of a first embodiment of a bonding structure according to the present application;

FIG. 4 is a schematic cross-sectional view of a second embodiment of a joining structure according to the present application;

FIG. 5 is a partial enlarged view of a second embodiment of a joining structure according to the present application;

FIG. 6 is a partial enlarged view of a second embodiment of a joining structure according to the present application;

FIG. 7 is a schematic cross-sectional view of a third embodiment of a bonding structure according to the present application;

FIG. 8 is a schematic cross-sectional view of a fourth embodiment of a bonding structure according to the present application;

fig. 9 and 10 are schematic views of a manufacturing process of a bonding structure according to the present application.

Description of the symbols:

11. a substrate; 12. a copper pad; 13. a dielectric material; 14. a void; 15. an oxide; 16. a silver layer; 17. silver pricks; 110. a substrate; 120. a chip; 210. a first metal pad; 220. a second metal pad; 310. a first protective layer; 320. a second protective layer; 410. a first metal layer; 420. a second metal layer; 510. a first insulating layer; 511. a first opening; 520. a second insulating layer; 600. a barrier layer; 900. a seed layer.

Detailed Description

The following description of the embodiments of the present application will be provided in conjunction with the accompanying drawings and examples, and those skilled in the art can easily understand the technical problems and effects that the present application solves and provides by the contents of the present specification. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and are not to be construed as limiting the invention. In addition, for convenience of description, only portions related to the related utility model are shown in the drawings.

It should be noted that the structures, proportions, sizes, and other elements shown in the drawings are only used for understanding and reading the contents of the specification, and are not used for limiting the conditions under which the present application can be implemented, so they do not have the technical significance, and any structural modifications, changes in proportion, or adjustments of sizes, which do not affect the efficacy and achievement of the purposes of the present application, shall still fall within the scope of the technical content disclosed in the present application. In addition, the terms "above", "first", "second" and "a" used in the present specification are used for the sake of clarity only, and are not intended to limit the scope of the present application, and changes and modifications of the relative relationship thereof are also considered to be the scope of the present application without substantial technical changes.

It should be further noted that, in the embodiments of the present application, the corresponding longitudinal section may be a front view direction section, the transverse section may be a right view direction section, and the horizontal section may be a top view direction section.

It should be readily understood that the meaning of "in.. on," "over,", and "above" in this application should be interpreted in the broadest sense such that "in.. on" not only means "directly on something," but also means "on something" including an intermediate member or layer between the two.

Furthermore, spatially relative terms, such as "below," "lower," "over," "upper," and the like, may be used herein for ease of description to describe one element or component's relationship to another element or component as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 or at other orientations) and the spatially relative descriptors used in this application interpreted accordingly as such.

In addition, the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

Fig. 1A is a cross-sectional view of a bonding structure in the prior art before bonding. As shown in fig. 1A, the surfaces of the upper substrate 11 and the lower substrate 11 are each provided with a copper pad 12. A dielectric material 13 is provided around the copper pad 12. The upper copper pad 12 and the lower copper pad 12 are located opposite to each other. Before bonding, there is a gap (i.e., a blank in fig. 1) between the upper copper pad 12 and the lower copper pad 12.

Fig. 1B is a cross-sectional view of a bonding structure in the prior art after bonding. As shown in fig. 1B, since the surface of copper is easily oxidized, an oxide 15 is easily formed between the upper copper pad 12 and the lower copper pad 12 after bonding. The oxide 15 on the one hand increases the temperature required for the bonding and on the other hand causes voids 14 (incidence greater than 5%) to appear at the bonding surface, which affects the bonding strength and the electrical conductivity of the bonded structure.

In order to overcome the above problem, silver substitution may be performed on the surface of the copper pad 12. Fig. 1C is a cross-sectional view of a prior art bonding structure with a silver layer 16. As shown in fig. 1C, a silver layer 16 may be formed on the surface of the copper pad 12 by silver displacement. Since silver is not easily oxidized, the above-described problem with the oxide 15 (see fig. 1B) can be avoided. However, due to the point discharge effect, negative charges are easily accumulated at the edge of the copper pad 12, and thus silver ions are concentrated at the edge of the copper pad 12 to form the silver burrs 17.

Fig. 1D is a schematic top view of a prior art bonding structure with a silver layer 16. As shown in fig. 1D, the existence of the silver burrs 17 reduces the definition of the edges of the copper pads 12 (i.e., the dotted lines in fig. 1D), which makes it difficult to determine the positions of the copper pads 12 during the bonding process, and affects the alignment precision, so that the alignment failure rate during the bonding process is more than 80%.

Fig. 2 is a schematic cross-sectional view of a first embodiment of a bonding structure according to the present application. As shown in fig. 2, the bonding structure includes a first bonding unit including a first metal pad 210, a first insulating layer 510, a first metal layer 410, a first protective layer 310, and a barrier layer 600.

The first metal pad 210 is disposed on the surface of the substrate 110.

The first insulating layer 510 covers the top surface of the first metal pad 210, and defines a first opening 511 (see fig. 10) on the top side of the first metal pad 210. The first insulating layer 510 covers at least a portion of the first protection layer 310 and a portion of the first metal pad 210.

The first metal layer 410 covers the top surface of the first metal pad 210 and is located in the first opening 511 (see fig. 10).

A first passivation layer 310 disposed on the surface of the substrate 110 and surrounding the first metal pad 210.

And a barrier layer 600 between the first metal pad 210 and the first protection layer 310. Note that the bonding structures in the embodiments of the present application each include the barrier layer 600, but they are only illustrated in fig. 2 and omitted in other drawings.

In some embodiments, the first metal layer 410 is formed by metal replacement, so that a non-Compound interface is formed between the first metal layer 410 and the first metal pad 210, and no Intermetallic Compound (IMC) is present.

In some embodiments, the top surface of the first metal pad 210 is subjected to a Chemical Mechanical Polishing (CMP) process, so that the top surface of the first metal pad 210 is concave. Accordingly, the first insulating layer 510 is recessed from the outer edge of the first metal pad 210 toward the center of the first metal pad 210.

In some embodiments, the material of the first metal pad 210 is, for example, copper (Cu). The first metal layer 410 may use a material that is less reactive than copper and less susceptible to oxidation and has good conductivity so as to prevent the first metal pad 210 from being oxidized. Preferably, the first metal layer 410 may use a silver (Ag) material so that the void occurrence rate is less than 2%.

The first insulating layer 510 may be made of a non-conductive material, and may have a thickness of 0.02 to 0.04 micrometers. In some embodiments, the first insulating layer 510 may be an organic material such as PI (Polyimide), PBO (p-phenylene-2, 6-benzoxazole), BCB (Benzocyclobutene), or an inorganic material such as silicon oxide (SiOx), silicon nitride (SiNx), silicon carbon nitride (SiCN). The BCB material has a better electromigration resistance, and can cover the first metal pad 210 together with the barrier layer 600 during the butt joint process, so as to prevent the first metal pad 210 from generating a cavity.

In some embodiments, barrier layer 600 is, for example, a titanium (Ti) layer.

In some embodiments, the material of the first protection layer 310 is, for example, PI, PBO, or other organic materials, or SiOx, SiNx, or other inorganic materials.

In some embodiments, the thickness of the first metal layer 410 is greater than or equal to the thickness of the first insulating layer 510, so as to successfully achieve the intermetallic bonding. Wherein the thickness of the first metal layer 410 may be greater than 0.05 microns and less than 0.5 microns.

Fig. 3 is a schematic top view of a first embodiment of a bonding structure according to the present application. As shown in fig. 3, in a top view of the bonding structure, the first metal layer 410, the first insulating layer 510 and the first protection layer 310 are sequentially arranged from inside to outside. The edge of the first metal layer 410 is defined by the first insulating layer 510. During metal replacement, the first insulating layer 510 covers the edge of the first metal pad 210 (see fig. 2) and shields the place with higher charge density, so that metal ions are not attracted by negative charges accumulated on the edge of the first metal pad 210 (see fig. 2) to form burrs during replacement, which is beneficial to improving the definition of the edge of the first metal layer 410, further improving the alignment accuracy during the alignment of the first metal pad 210 (see fig. 2), and reducing the alignment failure rate during bonding to less than 5%.

Fig. 4 is a schematic cross-sectional view of a second embodiment of a bonding structure according to the present application. As shown in fig. 4, the joining structure includes a first joining unit and a second joining unit that are oppositely disposed. The second bonding unit includes the chip 120, the second metal pad 220, the second insulating layer 520, the second metal layer 420, and the second protective layer 320. The structure of the second joining unit is similar to that of the first joining unit, and reference may be made specifically to the description of the first joining unit above.

The second metal layer 420 and the first metal layer 410 are disposed on the surfaces of the second metal pad 220 and the first metal pad 210, respectively. The second metal layer 420 is directly bonded to the first metal layer 410, thereby achieving physical bonding and electrical connection of the second metal pad 220 to the first metal pad 210.

Fig. 5 is a partially enlarged view of a second embodiment of a bonding structure according to the present application, which corresponds to the structure within the dashed-line box in fig. 4. As shown in fig. 5, since the first insulating layer 510 is recessed from the outer edge of the first metal pad 210 toward the center of the first metal pad 210, and the second insulating layer 520 is recessed from the outer edge of the second metal pad 220 toward the center of the second metal pad 220, the first insulating layer 510 and the second insulating layer 520 are bifurcated on the inner side. The outer sides of the first metal layer 410 and the second metal layer 420 extend into the fork-shaped gap and are located between the first insulating layer 510 and the second insulating layer 520.

Fig. 6 is another enlarged partial view of a second embodiment of a joining structure according to the present application, showing a variation of the structure in fig. 5. As shown in fig. 6, since the first bonding unit and the second bonding unit have a certain alignment error, the first bonding unit and the second bonding unit are not in a directly facing state (for example, the first bonding unit is offset leftward with respect to the second bonding unit), and further, the inner end of the first insulating layer 510 and the inner end of the second insulating layer 520 are not in a flush state (for example, the inner end of the first insulating layer 510 is offset leftward with respect to the inner end of the second insulating layer 520).

Fig. 7 is a schematic cross-sectional view of a third embodiment of a bonding structure according to the present application, showing a variation of the bonding structure of fig. 4. In fig. 4, a surface of the first metal pad 210 is provided with a first metal layer 410 and a first insulating layer 510, and a surface of the second metal pad 220 is provided with a second metal layer 420 and a second insulating layer 520. In fig. 7, the first metal layer 410 and the first insulating layer 510 are disposed only on the surface of the first metal pad 210, and the corresponding structure is not disposed on the surface of the second metal pad 220.

As shown in fig. 7, the first metal layer 410 is directly bonded to the second metal pad 220. The first insulating layer 510 is directly bonded to the second passivation layer 320 and the second metal pad 220. The present embodiment can save the use of materials by omitting the arrangement of the second metal layer 420 and the second insulating layer 520 (see fig. 4), and can also bond the first bonding unit and the second bonding unit.

Fig. 8 is a schematic cross-sectional view of a fourth embodiment of a bonding structure according to the present application, showing a variation of the bonding structure of fig. 4. In fig. 4, the first insulating layer 510 and the second insulating layer 520 are the same material. While in fig. 8, the first insulating layer 510 and the second insulating layer 520 are different in material (shown in different cross-sectional patterns). Due to the difference in material, an interface is formed between the first insulating layer 510 and the second insulating layer 520 in fig. 8 (see a solid black line between the first insulating layer 510 and the second insulating layer 520 in fig. 8).

The first insulating layer 510 and the second insulating layer 520 may be made of different materials having good butt joint capability to ensure the joint effect.

When the first protection layer 310 needs to be made of a specific material (e.g., a low-k/high-k material) according to a specific requirement, but the bonding capability of the selected material is just poor, the first insulation layer 510 (or the first insulation layer 510 and the second insulation layer 520) with better bonding capability can be used to ensure the bonding effect.

Fig. 9 and 10 are schematic views of a manufacturing process of a bonding structure according to the present application. As shown in fig. 9 and 10, the manufacturing process includes the steps of:

first, a first protective layer 310 is formed on the substrate 110.

In the second step, a barrier layer 600 and a seed layer 900 are sequentially sputtered (Sputter) on the surface of the first passivation layer 310. The material of the barrier layer 600 is, for example, titanium (Ti), and the material of the seed layer 900 is, for example, copper (Cu).

Third, Plating (Plating) is performed on the surface of the seed layer 900 to form the first metal pad 210. The material of the first metal pad 210 is, for example, copper (Cu).

Fourth, the surfaces of the first metal pad 210 and the barrier layer 600 are chemically and mechanically polished.

In the fifth step, a PI material is disposed on the surfaces of the first protection layer 310 and the first metal pad 210, and photolithography (Litho) is performed to form a first insulation layer 510 and a first opening 511.

In the sixth step, a first metal layer 410 is formed in the first opening 511 by a metal replacement (silver replacement). The first joining unit and the second joining unit are formed by the foregoing steps.

Seventh, the first bonding unit and the second bonding unit are aligned and thermocompression bonded (Thermal compression bond), resulting in the bonding structure shown in fig. 4. Wherein the thermal compression bonding can be heated at a temperature of 150 ℃ to 200 ℃ for 0.5 hour to 1 hour.

The specific details and technical effects of the above manufacturing process can be found in the foregoing description of the joint structure, and are not repeated herein.

While the present application has been described and illustrated with reference to particular embodiments thereof, such description and illustration are not intended to limit the present application. It will be clearly understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof within the embodiments without departing from the true spirit and scope of the present application as defined by the appended claims. The illustrations may not be drawn to scale. There may be a difference between the technical reproduction in the present application and the actual device due to variables in the manufacturing process and the like. There may be other embodiments of the application that are not specifically illustrated. The specification and drawings are to be regarded in an illustrative rather than a restrictive sense. Modifications may be made to adapt a particular situation, material, composition of matter, method, or process to the objective, spirit and scope of the present application. All such modifications are intended to fall within the scope of the claims appended hereto. Although the methods disclosed herein have been described with reference to particular operations performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form equivalent methods without departing from the teachings of the present application. Accordingly, unless specifically indicated herein, the order and grouping of the operations is not a limitation of the present application.

Claims

1. A joining structure characterized by comprising a first joining unit that includes:

a first metal pad;

2. The bonding structure of claim 1, further comprising a second bonding unit comprising a second metal pad bonded directly or indirectly to the first metal layer.

3. The bonding structure according to claim 2, wherein the second bonding unit further comprises a second insulating layer and a second metal layer;

the second metal layer covers the top surface of the second metal pad, is located in the second opening and is connected with the first metal layer.

4. The bonding structure according to claim 3, wherein an interface is formed between the first insulating layer and the second insulating layer.

5. The bonding structure according to claim 3, wherein the first insulating layer and the second insulating layer are bifurcated.

6. The bonding structure of claim 3, wherein the outer sides of the first and second metal layers are located between the first and second insulating layers.

7. The bonding structure of claim 1, wherein a thickness of the first metal layer is greater than or equal to a thickness of the first insulating layer.

8. The bonding structure of claim 1, wherein the top surface of the first metal pad is concave, and the first insulating layer is recessed from an outer edge of the first metal pad toward a center of the first metal pad.

9. The bonding structure of claim 1, wherein the first bonding unit further comprises a first protective layer surrounding the first metal pad.

10. The bonding structure of claim 9, wherein the first insulating layer covers the first protective layer and the first metal pad.