Electrical connection structure

Abstract

Some embodiments of the present application provide an electrical connection structure, comprising: a nickel metal layer; a copper-tin compound layer located below the nickel metal layer; a titanium layer disposed below the copper-tin compound layer; and a pad disposed below the titanium layer and electrically connected with the titanium layer, wherein a sidewall of the copper-tin compound layer is aligned with a sidewall of the nickel metal layer, a sidewall of the titanium layer is aligned with the sidewall of the copper-tin compound layer, and the nickel metal layer and the copper-tin compound layer serve as a connection layer for electrical connection. The present application effectively improves the reliability of the nickel metal layer by forming the copper-tin compound layer as an interface barrier below the nickel metal layer.

Description

Technical Field

[0001] This application relates to the field of semiconductor structure technology, and more specifically, to an electrical connection structure. Background Technology

[0002] In previous electrical interconnect structures, copper (Cu) was commonly used as the connection structure. However, while copper pillars are widely used in flip-chip and wafer-level packaging (WLP), with the increase in I / O density, the reduction in pitch (such as <40μm), and the problem of excessive growth of intermetallic compounds (IMCs), copper is prone to forming brittle intermetallic compounds with tin (typically brittle IMCs formed at room temperature or lower temperatures below 50°C), thus affecting long-term reliability. Therefore, in existing electrical interconnect structures, nickel (Ni) pillars have become popular mainly due to the higher requirements for reliability, thermal stability, and miniaturization capabilities in advanced packaging technologies. Nickel pillars effectively prevent tin from diffusing into copper through nickel as a diffusion barrier layer, thereby reducing excessive growth of intermetallic compounds, improving mechanical strength and heat resistance, and are particularly suitable for chiplet interconnects and high-power, high-frequency applications, thus becoming an advanced solution to copper pillars.

[0003] See Figure 1A and Figure 1B , Figure 1A Existing packaging structure 1 is shown and Figure 1B It shows Figure 1A An enlarged view of the area of ​​the electrical connection structure 10 in the package structure 1 shown. (See attached image.) Figure 1A and Figure 1B As shown, in the conventional packaging process of the existing electrical connection structure 10, a substrate 18 is provided with pads 16 and vias 17 formed therein. A seed layer S is formed on the pads 16 exposed by the dielectric layer 15. Typically, nickel pillars 11 and a gold (Au) layer 14 are directly electroplated on the seed layer S (titanium (Ti) layer 13 and / or copper layer 12) to prevent oxidation of the nickel pillars 11 and provide good conductivity. However, as Figure 1C As shown, in the subsequent nickel pillar 11 process, etching the seed layer S may cause the copper to have an undercut C problem, affecting the structural stability.

[0004] Specifically, see Figures 1D to 1I It shows Figure 1C The process flow for the electrical connection structure 10 shown is illustrated. See also... Figure 1D A substrate 18, on which pads 16 are formed, is provided. The substrate 18 is a silicon substrate, and vias 17 are formed therein. See also... Figure 1E A dielectric layer 15 is formed on pad 16 and substrate 18, the dielectric layer 15 having openings that expose pad 16. See also Figure 1FA seed layer S is formed on the dielectric layer 15 and the exposed pads 16. The seed layer S comprises a titanium layer 13 and a copper layer 12 located above the titanium layer. See also... Figure 1G A photoresist 2 is formed on the seed layer S, the photoresist 2 having an opening that exposes the seed layer S. See also Figure 1H Nickel pillars 11 are plated in the opening of photoresist 2, and a gold layer 14 is plated on the nickel pillars 11. Then, see... Figure 1I After removing the photoresist 2, the seed layer S is then removed, thereby forming... Figure 1C The electrical connection structure 10 shown exhibits undercut C in the seed layer S. Specifically, this undercut C phenomenon mainly occurs during the etching of the seed layer S (titanium layer 13 and / or copper layer 12). Lateral erosion of the copper layer 12 causes the bottom of the nickel pillars 11 to become thinner, thus affecting structural stability. The key reason for this undercut C phenomenon is that the vertical etching rate of copper in the copper layer 12 is approximately 0.5-2 μm / min, while the lateral etching (i.e., undercut) rate is approximately 20-50% of the vertical etching rate, i.e., 0.1-1 μm / min. Therefore, the wet etchant in the copper layer 12 causes lateral diffusion, resulting in lateral etching, i.e., the occurrence of undercut C. Therefore, a new electrical connection structure is needed to overcome the above problems. Utility Model Content

[0005] To address the aforementioned issues, this application utilizes a high-hardness intermetallic compound (IMC) (such as CuSn compound Cu6Sn5) formed at the interface between the seed layer and the nickel (Ni) metal layer to serve as an interface barrier, thereby effectively improving the reliability of the nickel metal layer.

[0006] Some embodiments of this application provide an electrical connection structure, including: a nickel metal layer; a copper-tin compound layer located below the nickel metal layer; a titanium layer disposed below the copper-tin compound layer; and a pad disposed below the titanium layer and electrically connected to the titanium layer, wherein the sidewalls of the copper-tin compound layer are aligned with the sidewalls of the nickel metal layer, the sidewalls of the titanium layer are aligned with the sidewalls of the copper-tin compound layer, and the nickel metal layer and the copper-tin compound layer serve as connection layers for electrical connection.

[0007] In some embodiments, the copper-tin compound layer is a Cu6Sn5 layer.

[0008] In some embodiments, the electrical connection structure further includes a tin layer disposed above the nickel metal layer.

[0009] In some embodiments, the electrical connection structure further includes a gold layer disposed on the nickel metal layer.

[0010] In some embodiments, the gold layer is disposed between the nickel metal layer and the tin layer attached to the nickel metal layer.

[0011] In some embodiments, the electrical connection structure further includes a dielectric layer disposed between the titanium layer and the pad, wherein a portion of the titanium layer extending through the dielectric layer directly contacts the pad.

[0012] In some embodiments, the dielectric layer covers the portion of the pad that is not in direct contact with the titanium layer and further extends along the sidewall of the pad.

[0013] In some embodiments, the electrical connection structure further includes: a substrate disposed below the pad; and a through-hole extending through the substrate and connected to the pad.

[0014] In some embodiments, the copper-tin compound layer and the titanium layer are conformally disposed and together serve as a seed layer for the nickel metal layer.

[0015] In some embodiments, the copper-tin compound layer and the titanium layer surround the bottom portion of the nickel metal layer.

[0016] In some embodiments, the sidewalls of the gold layer are aligned with the sidewalls of the nickel metal layer.

[0017] In some embodiments, the dielectric layer further extends on the substrate.

[0018] In some embodiments, the through-hole is disposed within the lateral range of the pad.

[0019] In some embodiments, the portion of the dielectric layer disposed between the titanium layer and the pad is in direct contact with the titanium layer and the pad.

[0020] In some embodiments, the bottom portion of the nickel metal layer is disposed directly above the pad.

[0021] Other embodiments of this application provide an electrical connection structure, including: a gold layer; a nickel metal layer disposed below the gold layer; and a copper-tin compound layer disposed below the nickel metal layer, wherein the copper-tin compound layer is a Cu6Sn5 layer and shares an end with the nickel metal layer.

[0022] In some embodiments, the electrical connection structure further includes a titanium layer disposed beneath the copper-tin compound layer, wherein the titanium layer is conformally disposed with the copper-tin compound layer.

[0023] In some embodiments, the electrical connection structure further includes: a pad disposed below and electrically connected to the titanium layer; and a dielectric layer disposed between the titanium layer and the pad, wherein a portion of the titanium layer extending through the dielectric layer directly contacts the pad.

[0024] This application utilizes a copper-tin compound layer formed beneath a nickel metal layer as a barrier. This copper-tin compound layer has higher hardness, strength, and ductility than Cu, which can improve the reliability test performance (TCT) and also increase the stability of the electrical connection structure. Attached Figure Description

[0025] The various aspects of this utility model can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard industrial practice, the various components are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various components may be arbitrarily increased or decreased.

[0026] Figures 1A to 1I The electrical connection structure of the prior art is shown.

[0027] Figures 2A to 2B Electrical connection structures according to some embodiments of this application are shown.

[0028] Figures 3 to 9 The process for forming an electrical connection structure according to some embodiments of this application is illustrated. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art are within the scope of protection of this application. In addition, when using terms such as "approximately," "about," "substantial," or "basically" to describe numerical values ​​or numerical ranges, unless otherwise stated, the term is intended to cover values ​​within ±10% of the described value. For example, the term "about 5nm" covers a size range from 4.5nm to 5.5nm.

[0030] This application pre-adds a tin (Sn) layer on the copper (Cu) layer of the seed layer, and reduces the rate of lateral etching by first forming a high-hardness intermetallic compound, such as CuSn compound (e.g., Cu6Sn5), through heating.

[0031] See Figure 2ASome embodiments of this application provide an electrical connection structure 100, which includes a nickel metal layer 101 and a copper-tin compound layer 102 located below the nickel metal layer 101. The sidewalls 102s of the copper-tin compound layer 102 are aligned with the sidewalls 101s of the nickel metal layer 101, and the nickel metal layer 101 and the copper-tin compound layer 102 serve as a connecting layer for electrical connection, such as connecting a lower component downwards. In some embodiments, the copper-tin compound layer 102 is a Cu6Sn5 layer. This application uses a copper-tin compound layer 102, which is a Cu6Sn5 layer, below the nickel metal layer 101, which effectively prevents lateral etching below the nickel metal layer 101 and improves the structural stability of the electrical connection structure 100. Therefore, this application effectively improves the reliability of the nickel metal layer 101 by forming a Cu6Sn5 intermetallic compound (IMC) at the interface between the seed layer S' and the nickel metal layer 101 as an interface barrier. This is because the lateral etching rate of pure copper is 0.1-1 μm / min, while the lateral etching rate of the copper-tin compound layer 102 of Cu6Sn5 is <0.05 μm / min, which is much lower than the etching rate of pure copper. Therefore, by using this Cu6Sn5 layer as a barrier, the lateral etching is slowed down during the subsequent etching of the seed layer S'. Furthermore, the intermetallic compound (IMC) of Cu6Sn5 has higher hardness, strength and ductility than Cu, which can increase the reliability (TCT) test performance. In addition, it also increases the etching process window.

[0032] exist Figure 2A In the illustrated electrical connection structure 100, the electrical connection structure 100 further includes a gold layer 104 disposed on a nickel metal layer 101 to protect the nickel metal layer 101 from oxidation. In some embodiments, the sidewalls 104s of the gold layer 104 are aligned with the sidewalls 101s of the nickel metal layer 101. In some embodiments, the nickel metal layer 101 with the gold layer 104 disposed may be connected to an external tin layer; therefore, in this case, the gold layer 104 is disposed between the nickel metal layer 101 and the tin layer attached to the nickel metal layer 101. Further, the electrical connection structure 100 also includes a titanium layer 103 disposed below a copper-tin compound layer 102. In a further embodiment, the sidewalls 103s of the titanium layer 103 are aligned with the sidewalls 102s of the copper-tin compound layer 102, and further aligned with the sidewalls 101s of the nickel metal layer 101. In some embodiments, the titanium layer 103 and the copper-tin compound layer 102 are conformally disposed and together serve as a seed layer S' of the nickel metal layer 101. In some embodiments, a copper-tin compound layer 102 and a titanium layer 103 surround the bottom portion of a nickel metal layer 101.

[0033] Furthermore, the electrical connection structure 100 also includes a pad 106 disposed below and electrically connected to the titanium layer 103. In some embodiments, the bottom portion of the nickel metal layer 101 is disposed directly above the pad 106. In some embodiments, in the electrical connection structure 100, a dielectric layer 105 is disposed between the titanium layer 103 and the pad 106, and as shown... Figure 2A As shown, the portion of the titanium layer 103 extending through the dielectric layer 105 directly contacts the pad 106, and the portion of the dielectric layer 105 disposed between the titanium layer 103 and the pad 106 directly contacts both the titanium layer 103 and the pad 106; that is, the dielectric layer 105 exposes the connection between the titanium layer 103 and the pad 106. Figure 2A In the illustrated embodiment, the dielectric layer 105 covers the portion of the pad 106 that is not in direct contact with the titanium layer 103 and further extends along the sidewall 106s of the pad 106. In a further embodiment, the electrical connection structure 100 further includes: a substrate 108 disposed beneath the pad 106; and a via 107 extending through the substrate 108 to connect to the pad 106. In embodiments of this application, the dielectric layer 105 further extends on the substrate 108. In some specific embodiments, the substrate 108 is made of silicon. Figure 2A As shown, via 107 is disposed within the lateral range of pad 106. In some embodiments, pad 106 and via 107 are, but not limited to, copper, and may also be other suitable metals. In some embodiments, dielectric layer 105 includes, but is not limited to, polyimide, etc.

[0034] Figure 2B An electrical connection structure 100-1 is shown, which is similar to the electrical connection structure 100, except that... Figure 2B The electrical connection structure 100-1 shown further includes a tin layer 109 disposed above the nickel metal layer 101 for external electrical connection.

[0035] Return to reference Figure 2ASome embodiments of this application provide an electrical connection structure 100, including: a gold layer 104; a nickel metal layer 101 disposed below the gold layer 104; and a copper-tin compound layer 102 disposed below the nickel metal layer 101, wherein the copper-tin compound layer 102 is a Cu6Sn5 layer and shares an end with the nickel metal layer 101, that is, the sidewalls 102s of the copper-tin compound layer 102 are aligned with the sidewalls 101s of the nickel metal layer 101. In some embodiments, the electrical connection structure 100 further includes: a titanium layer 103 disposed below the copper-tin compound layer 102, wherein the titanium layer 103 is conformally disposed with the copper-tin compound layer 102. In some embodiments, the electrical connection structure 100 further includes: a pad 106 disposed below the titanium layer 103 and electrically connected to the titanium layer 103; and a dielectric layer 105 disposed between the titanium layer 103 and the pad 106, wherein a portion of the titanium layer 103 extending through the dielectric layer 105 directly contacts the pad 106.

[0036] Next, see Figures 3 to 9 To describe Figure 2A The forming process of the electrical connection structure 100 shown.

[0037] First, see Figure 3 A substrate 108 is provided on which pads 106 are formed, wherein the substrate 108 is a silicon substrate and vias 107 are formed therein. In this embodiment, the pads 106 and vias 107 are made of copper. See also Figure 4 A dielectric layer 105 is formed on pads 106 and substrate 108. The dielectric layer 105 comprises polyimide and has openings exposing the pads 106, covering only the edges of the pads 106. See also... Figure 5 A titanium layer 103 is formed on the dielectric layer 105 and the exposed pads 106, and a copper layer 102' is formed on the titanium layer 103, such as by a physical vapor deposition (PVD) process. See then... Figure 6 A photoresist layer 1001 is formed on the copper layer 102' using methods commonly used in the art, and as follows: Figure 6 As shown, the photoresist 1001 has an opening 1001O that exposes the copper layer 102'. In some embodiments, the opening 1001O is located directly above the pad 106.

[0038] Next, see Figure 7 A tin layer 1002, a nickel metal layer 101, and a gold layer 104 are sequentially formed in the opening 1001O using a plating process such as electroplating or electroless plating. The sidewalls of the tin layer 1002 are aligned with the sidewalls 101s of the nickel metal layer 101 and the sidewalls 104s of the gold layer 104. In some embodiments, the thickness ratio of the copper layer 102' to the tin layer 1002 is approximately 6:5. See also... Figure 8After forming the tin layer 1002, the nickel metal layer 101, and the gold layer 104, the photoresist layer 1001 is removed by any suitable process, such as stripping. See then... Figure 9 Through heat treatment such as heating (e.g., above approximately 170°C, such as 217°C), a Cu6Sn5 copper-tin compound layer 102 (intermetallic compound) is formed between the tin layer 1002 and the underlying copper layer 102'. This copper-tin compound layer 102, together with the underlying titanium layer 103, forms a seed layer S'. Finally, the titanium layer 103 and copper layer 102' not covered by the tin metal layer 101 are removed, thereby forming... Figure 2A The electrical connection structure 100 shown is shown.

[0039] In the above-described formation process, an extremely thin tin layer 1002 is electroplated and then preheated or subjected to a short-time heat treatment, causing the tin layer 1002 to react with the copper layer 102' to form a preliminary Cu6Sn5 copper-tin compound layer 102 (intermetallic compound). This application utilizes this pre-formed Cu6Sn5 layer (copper-tin compound layer 102) as a barrier to slow down the lateral etching of copper during the subsequent etching process of the seed layer S'. Furthermore, this copper-tin compound layer 102 has higher hardness, strength, and ductility than Cu, thus increasing the reliability (TCT) performance.

[0040] In summary, this application effectively improves the reliability of the nickel metal layer 101 by forming a high-hardness intermetallic compound (IMC) (such as CuSn compound 102 of Cu6Sn5) at the interface between the seed layer S' and the nickel metal layer 101 as an interface barrier.

[0041] The features of several embodiments have been summarized above to enable those skilled in the art to better understand aspects of the present invention. Those skilled in the art should understand that they can readily use the present invention as a basis to design or modify other processes and structures for implementing the same purposes and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the present invention, and that various changes, substitutions, and alterations can be made therein without departing from the spirit and scope of the present invention.

Claims

1. An electrical connection structure, characterized in that, include: Nickel metal layer; A copper-tin compound layer is located below the nickel metal layer; A titanium layer is disposed beneath the copper-tin compound layer; as well as The pads are located beneath the titanium layer and are electrically connected to the titanium layer. The sidewalls of the copper-tin compound layer are aligned with the sidewalls of the nickel metal layer, the sidewalls of the titanium layer are aligned with the sidewalls of the copper-tin compound layer, and the nickel metal layer and the copper-tin compound layer serve as connecting layers for electrical connection.

2. The electrical connection structure according to claim 1, characterized in that, The copper-tin compound layer is a Cu6Sn5 layer.

3. The electrical connection structure according to claim 1, characterized in that, Also includes: A tin layer is disposed above the nickel metal layer.

4. The electrical connection structure according to claim 1, characterized in that, Also includes: A gold layer is disposed on the nickel metal layer.

5. The electrical connection structure according to claim 4, characterized in that, The gold layer is disposed between the nickel metal layer and the tin layer attached to the nickel metal layer.

6. The electrical connection structure according to claim 1, characterized in that, Also includes: A dielectric layer is disposed between the titanium layer and the pad. The portion of the titanium layer that extends through the dielectric layer directly contacts the pad.

7. The electrical connection structure according to claim 6, characterized in that, The dielectric layer covers the portion of the pad that is not in direct contact with the titanium layer and extends further along the sidewall of the pad.

8. The electrical connection structure according to claim 6, characterized in that, Also includes: The substrate is disposed below the pads; as well as Through-holes extend through the substrate and connect to the pads.

9. The electrical connection structure according to claim 1, characterized in that, The copper-tin compound layer and the titanium layer are conformally disposed and together serve as a seed layer for the nickel metal layer.

10. The electrical connection structure according to claim 9, characterized in that, The copper-tin compound layer and the titanium layer surround the bottom portion of the nickel metal layer.

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