Aluminum-nickel-tin-silver bump interconnection structure based on TiW-NiV double-layer UBM
By designing a TiW-NiV dual-layer UBM structure, the problems of tin segregation and insufficient interfacial bonding force during high-temperature reflow soldering of aluminum-based bumps are solved, achieving high adhesion and strong diffusion barrier, improving the stability and reliability of the aluminum-nickel-tin-silver bump interconnect structure, and making it suitable for high-density integrated circuit packaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- 广西华芯振邦半导体有限公司
- Filing Date
- 2025-05-16
- Publication Date
- 2026-05-08
AI Technical Summary
Traditional copper-nickel-tin (Cu-Ni-Sn) bumps suffer from problems such as excessively thick intermetallic compound (IMC), insufficient electromigration performance, and complex processes. While aluminum-based bumps offer advantages in cost and density, their interface diffusion control and mechanical properties need improvement. Existing UBM layers cannot simultaneously meet the requirements of high adhesion, strong diffusion barrier, and good wettability, leading to tin segregation and insufficient interfacial bonding during high-temperature reflow soldering of bump interconnect structures, which affects the reliability of integrated circuit packaging.
The TiW-NiV double-layer UBM structure is adopted. Through the gradient composition design and thickness matching of the titanium-tungsten layer and nickel-vanadium layer, a composite layer with high adhesion and strong diffusion barrier is formed to ensure stable connection with the pad and bump layer. Combined with the optimized configuration of high-purity aluminum layer, nickel barrier layer and Sn-3.5Ag bonding layer, an optimized balance of conductivity, mechanical strength and welding performance is achieved.
It improves interfacial bonding strength, reduces thermal stress, enhances resistance to mechanical shock, and improves the stability and reliability of interconnect structures. It is suitable for high-density integrated circuit packaging, reduces costs, and simplifies the process flow.
Smart Images
Figure CN224218812U_ABST
Abstract
Description
Technical Field
[0001] This utility model specifically relates to the field of semiconductor packaging technology, and more specifically to an aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM. Background Technology
[0002] In the semiconductor packaging field, the reliability and stability of bump interconnect structures are crucial. Traditional copper-nickel-tin (Cu-Ni-Sn) bumps suffer from problems such as excessively thick intermetallic compound (IMC) layers, insufficient electromigration performance, and complex processes. While aluminum-based bumps offer cost and density advantages, their interface diffusion control and mechanical properties need improvement. Existing UBM layers (such as single metal layers) cannot simultaneously meet the requirements of high adhesion, strong diffusion barrier, and good wettability, leading to problems such as tin segregation and insufficient interfacial bonding during high-temperature reflow soldering, which seriously affects the reliability of integrated circuit packaging. As integrated circuits develop towards higher density and higher power, there is an urgent need for a new type of bump interconnect structure with optimized structure, distinct layers, and balanced performance to solve the problems of interface stability, thermomechanical matching, and material cost in existing technologies. Utility Model Content
[0003] The purpose of this invention is to provide an aluminum-nickel-tin-silver bump interconnect structure based on TIW / NiV double-layer UBM. In this device, the gradient composition design and thickness matching of the titanium-tungsten layer and the nickel-vanadium layer form a composite layer with high adhesion and strong diffusion barrier, ensuring a stable connection with the pads and bump layer, thereby solving the problems mentioned above in the background art.
[0004] To achieve the above objectives, this utility model provides the following technical solution:
[0005] An aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM includes a substrate, pads, a double-layer UBM structure, and aluminum-nickel-tin-silver bumps arranged sequentially from bottom to top. The double-layer UBM structure includes a titanium-tungsten layer tightly attached to the surface of the pads and a nickel-vanadium layer covering the surface of the titanium-tungsten layer away from the pads. The aluminum-nickel-tin-silver bumps include a high-purity aluminum layer, a nickel barrier layer, and a Sn-3.5Ag bonding layer stacked sequentially on the surface of the nickel-vanadium layer away from the titanium-tungsten layer.
[0006] As a further technical solution of this utility model, the thickness of the titanium-tungsten layer is 0.15-0.25μm, and its composition changes in a gradient from the pad side to the nickel-vanadium layer side. The Ti atomic percentage on the pad side is 20-30 at.%, and the W atomic percentage on the nickel-vanadium layer side is 80-90 at.%. The thickness of the nickel-vanadium layer is 0.8-1.5μm, and it is composed of 88-92% Ni and 8-12% V by mass percentage.
[0007] As a further technical solution of this utility model, the thickness of the high-purity aluminum layer is 2-3 μm and the purity is not less than 99.9%, the thickness of the nickel barrier layer is 0.8-1 μm, and the thickness of the Sn-3.5Ag bonding layer is 4-6 μm.
[0008] As a further technical solution of this utility model, the substrate is an 8-12 inch silicon wafer, the pad is disposed on the surface of the silicon wafer, and the pad is an aluminum pad with a thickness of 1-2 μm or a copper pad with a thickness of 3-5 μm; when the pad is a copper pad, an aluminum transition layer with a thickness of 1 μm is disposed between the copper pad and the titanium tungsten layer, the aluminum transition layer is tightly attached to the surface of the copper pad, and the titanium tungsten layer covers the side of the aluminum transition layer away from the copper pad.
[0009] As a further technical solution of this utility model, the surface of the titanium-tungsten layer near the pad is completely bonded to the surface of the aluminum transition layer to form a continuous barrier layer; the nickel-vanadium layer completely covers the surface of the titanium-tungsten layer away from the pad, and a tight metallurgical bonding interface is formed between the nickel-vanadium layer and the titanium-tungsten layer; the high-purity aluminum layer completely covers the surface of the nickel-vanadium layer away from the titanium-tungsten layer, the nickel barrier layer completely covers the surface of the high-purity aluminum layer away from the nickel-vanadium layer, and the Sn-3.5Ag bonding layer completely covers the surface of the nickel barrier layer away from the high-purity aluminum layer, forming a five-layer bump structure stacked sequentially from bottom to top;
[0010] As a further technical solution of this utility model, the nickel barrier layer is an alloy layer composed of Ni and V, wherein the mass percentage of V is 5%, the nickel barrier layer has a nanocrystalline structure, and the grain size is uniformly distributed; a flat interface is formed between the high-purity aluminum layer, the nickel barrier layer and the Sn-3.5Ag bonding layer, the lateral dimensions of the three layers are consistent, and they all match the lateral dimensions of the underlying nickel-vanadium layer; the upper surface of the Sn-3.5Ag bonding layer forms a hemispherical surface for welding;
[0011] As a further technical solution of this utility model, the titanium-tungsten layer, nickel-vanadium layer, high-purity aluminum layer, nickel barrier layer and Sn-3.5Ag bonding layer are all continuous thin film layers, with no gaps between each layer and tightly bonded; the lateral dimension of the double-layer UBM structure is consistent with the lateral dimension of the pad, and the lateral dimension of the aluminum-nickel-tin-silver bump is consistent with the lateral dimension of the double-layer UBM structure, forming a stacked structure aligned vertically, and the central axes of the substrate, pad, double-layer UBM structure and aluminum-nickel-tin-silver bump coincide;
[0012] Compared with the prior art, the beneficial effects of this utility model are:
[0013] 1. In this utility model, the gradient composition design and thickness matching of the titanium-tungsten layer and the nickel-vanadium layer form a composite layer with high adhesion and strong diffusion barrier, ensuring a stable connection with the pads and bump layers;
[0014] 2. In this utility model, the material selection and thickness configuration of the three-layer structure achieve an optimized balance of conductivity, mechanical strength and weldability;
[0015] 3. In this invention, the lateral dimensions of each layer are consistent and the centers are aligned, ensuring the stability and reliability of the interconnection structure, and making it suitable for high-density integrated circuit packaging. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the aluminum-nickel-tin-silver bump structure of this utility model.
[0017] In the figure: 104-titanium-tungsten layer, 105-nickel-vanadium layer, 106-high-purity aluminum layer, 107-nickel barrier layer, 108-Sn-3.5Ag bonding layer. Detailed Implementation
[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0019] Please see Figure 1 In this embodiment of the invention, an aluminum-nickel-tin-silver bump interconnect structure based on a TiW / NiV double-layer UBM includes a substrate, pads, a double-layer UBM structure, and aluminum-nickel-tin-silver bumps arranged sequentially from bottom to top. The double-layer UBM structure includes a titanium-tungsten layer 104 tightly attached to the surface of the pads and a nickel-vanadium layer 105 covering the surface of the titanium-tungsten layer 104 away from the pads. The titanium-tungsten layer 104 has a thickness of 0.15-0.25 μm, and its composition changes in a gradient from the pad side to the nickel-vanadium layer 105 side. The Ti atom content on the pad side is 20-30 at.%, and the W atom content on the nickel-vanadium layer 105 side is... The ratio is 80-90 at.%; the nickel-vanadium layer 105 has a thickness of 0.8-1.5 μm and is composed of 88-92% Ni and 8-12% V by mass; the aluminum-nickel-tin-silver bump includes a high-purity aluminum layer 106, a nickel barrier layer 107 and a Sn-3.5Ag bonding layer 108 stacked sequentially on the surface of the nickel-vanadium layer 105 away from the titanium-tungsten layer 104, the high-purity aluminum layer 106 has a thickness of 2-3 μm and a purity of not less than 99.9%, the nickel barrier layer 107 has a thickness of 0.8-1 μm, and the Sn-3.5Ag bonding layer 108 has a thickness of 4-6 μm;
[0020] The substrate is an 8-12 inch silicon wafer, and the pads are disposed on the surface of the silicon wafer. The pads are aluminum pads with a thickness of 1-2 μm or copper pads with a thickness of 3-5 μm. When the pads are copper pads, an aluminum transition layer with a thickness of 1 μm is disposed between the copper pads and the titanium-tungsten layer 104. The aluminum transition layer is tightly attached to the surface of the copper pads, and the titanium-tungsten layer 104 covers the side of the aluminum transition layer away from the copper pads.
[0021] By adopting the above technical solution, the gradient composition design and thickness matching of the titanium-tungsten layer 104 and the nickel-vanadium layer 105 form a composite layer with high adhesion and strong diffusion barrier, ensuring a stable connection with the pads and bump layers.
[0022] In this embodiment, the surface of the titanium-tungsten layer 104 near the pad is completely bonded to the surface of the aluminum transition layer, forming a continuous barrier layer; the nickel-vanadium layer 105 completely covers the surface of the titanium-tungsten layer 104 away from the pad, and a tight metallurgical bonding interface is formed between the nickel-vanadium layer 105 and the titanium-tungsten layer 104; the high-purity aluminum layer 106 completely covers the surface of the nickel-vanadium layer 105 away from the titanium-tungsten layer 104; the nickel barrier layer 107 completely covers the surface of the high-purity aluminum layer away from the nickel-vanadium layer 105; and the Sn-3.5Ag bonding layer 108 completely covers the surface of the nickel barrier layer 107 away from the high-purity aluminum layer 106, forming a five-layer bump structure stacked sequentially from bottom to top.
[0023] In this embodiment, the nickel barrier layer 107 is an alloy layer composed of Ni and V, wherein the mass percentage of V is 5%. The nickel barrier layer 107 has a nanocrystalline structure with uniformly distributed grain size. A flat interface is formed between the high-purity aluminum layer 106, the nickel barrier layer 107, and the Sn-3.5Ag bonding layer 108. The lateral dimensions of the three layers are consistent and match the lateral dimensions of the underlying nickel-vanadium layer 105. The upper surface of the Sn-3.5Ag bonding layer 108 forms a hemispherical surface for welding.
[0024] By adopting the above technical solution, the material selection and thickness configuration of the three-layer structure achieve an optimized balance of conductivity, mechanical strength and weldability;
[0025] Furthermore, the titanium-tungsten layer 104, nickel-vanadium layer 105, high-purity aluminum layer 106, nickel barrier layer 107, and Sn-3.5Ag bonding layer 108 are all continuous thin film layers, with no gaps between them and tightly bonded together; the lateral dimension of the double-layer UBM structure is consistent with the lateral dimension of the pad, and the lateral dimension of the aluminum-nickel-tin-silver bump is consistent with the lateral dimension of the double-layer UBM structure, forming a stacked structure aligned vertically; the central axes of the substrate, pad, double-layer UBM structure, and aluminum-nickel-tin-silver bump coincide.
[0026] By adopting the above technical solution, the lateral dimensions of each layer are consistent and the center is aligned, ensuring the stability and reliability of the interconnect structure, which is suitable for high-density integrated circuit packaging;
[0027] The working principle of this utility model is as follows: The structure constructs a low-loss conductive path through a layered material design: The bottom layer is a high-purity aluminum layer 106 with a purity ≥99.9% and a thickness of 2-3 μm, serving as the main conductive layer. Utilizing the low resistivity of aluminum (2.5-3.0 μΩ・cm) and the controlled gradient Ni / Sn content, Joule heat loss is reduced, adapting to high-frequency signal transmission; the middle nickel barrier layer 107 contains a nanocrystalline structure with 5 wt.% V and a thickness of 0.8-1 μm, physically isolating Sn and Al to prevent the formation of high-resistivity brittle phases such as Al3Sn, maintaining the stability of the conductive channel; the top Sn-3.5Ag bonding layer 108, with a thickness of 4-6 μm, achieves reliable connection with the external circuit through low-temperature welding at a melting point of 228℃, with Ag enhancing creep resistance; in the double-layer UBM, the titanium-tungsten layer 104 has a gradient composition of 20-30 at.% Ti on the pad side and the nickel-vanadium layer 105 has 80-90 at.% W on the side, balancing pad adhesion and conductive continuity. 88-92wt.%Ni + 8-12wt.%V improves conductivity through grain refinement <100nm, and can withstand high current densities >2×10 6 A / cm² and inhibit electromigration;
[0028] Thermal stress is reduced through gradient composition and structural design: a CTE gradient silicon wafer is formed from the substrate to the top bump layer (≈3ppm / °C → Al layer ≈23ppm / °C → Nickel barrier layer ≈14ppm / °C → Sn-Ag layer ≈30ppm / °C), which reduces the difference in thermal expansion between adjacent layers and lowers thermal stress by 30-40%. The low elastic modulus of aluminum (69GPa) absorbs the stress generated by temperature cycling from -55 to 150°C through plastic deformation. Combined with laser-assisted annealing at 250°C in an N2 atmosphere, residual stress is released in 10 seconds, achieving a thermal cycle life of 3000 cycles, which is 100% better than traditional structures. At the interface, the titanium-tungsten layer (104) with a high W content of 80-90 at.% blocks the diffusion of Al atoms, with a diffusion coefficient <10⁻¹. 7 m² / s, the V element in the nickel-vanadium layer 105 optimizes the interfacial reaction kinetics, inhibits the excessive growth of intermetallic compounds (IMC), increases the interfacial shear strength from 50 MPa to 70 MPa, and enhances the mechanical impact resistance by 40%;
[0029] Material selection and process parameters work together to improve structural performance: The aluminum-based bumps utilize the density of the natural Al2O3 oxide layer, eliminating the need for nickel / gold plating, reducing costs by 40% and simplifying the process; the copper pads are pre-plated with a 1μm aluminum transition layer to isolate intermetallic diffusion reactions and prevent the formation of brittle IMC; in the fabrication process, the titanium-tungsten layer 104 forms a compositional gradient through magnetron sputtering power gradients: Ti target 80W→20W, W target 20W→80W, balancing pad adhesion shear strength ≥120MPa and diffusion blocking; the nickel barrier layer 107 uses pulse electroplating at 50℃, 3-5mA / cm², and 100Hz pulses to generate a nanocrystalline structure, improving barrier efficiency by 2 times compared to pure Ni; the Sn-3.5Ag bonding layer 108 achieves eutectic composition control through low-temperature electroplating at 25℃ and 4mA / cm², ensuring welding reliability; the overall structure has consistent lateral dimensions and center alignment across all layers, avoiding stress concentration and meeting the uniform stress requirements of high-density packaging.
[0030] The structure achieves a lightweight design with a density of 2.7 g / cm³, only 30% of that of copper-based materials, and low-temperature bonding at 230°C with laser assistance, making it compatible with mobile devices and sensitive components. Furthermore, through material substitution and process simplification, it balances performance and cost, providing a highly reliable and low-cost interconnect solution for 2.5D / 3D integrated circuit packaging.
[0031] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0032] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. An aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM, characterized in that: The structure includes a substrate, pads, a double-layer UBM structure, and aluminum-nickel-tin-silver bumps arranged sequentially from bottom to top. The double-layer UBM structure includes a titanium-tungsten layer (104) tightly attached to the surface of the pads and a nickel-vanadium layer (105) covering the surface of the titanium-tungsten layer (104) away from the pads. The aluminum-nickel-tin-silver bumps include a high-purity aluminum layer (106), a nickel barrier layer (107), and a Sn-3.5Ag bonding layer (108) stacked sequentially on the surface of the nickel-vanadium layer (105) away from the titanium-tungsten layer (104).
2. The aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM according to claim 1, characterized in that: The high-purity aluminum layer (106) has a thickness of 2-3 μm and a purity of not less than 99.9%, the nickel barrier layer (107) has a thickness of 0.8-1 μm, and the Sn-3.5Ag bonding layer (108) has a thickness of 4-6 μm.
3. The aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM according to claim 1, characterized in that: The substrate is an 8-12 inch silicon wafer, and the pads are disposed on the surface of the silicon wafer. The pads are aluminum pads with a thickness of 1-2 μm or copper pads with a thickness of 3-5 μm. When the pads are copper pads, an aluminum transition layer with a thickness of 1 μm is disposed between the copper pads and the titanium tungsten layer (104). The aluminum transition layer is tightly attached to the surface of the copper pads, and the titanium tungsten layer (104) covers the side of the aluminum transition layer away from the copper pads.
4. The aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM according to claim 1, characterized in that: The surface of the titanium-tungsten layer (104) near the pad is completely bonded to the surface of the aluminum transition layer, forming a continuous barrier layer; the nickel-vanadium layer (105) completely covers the surface of the titanium-tungsten layer (104) away from the pad, and a tight metallurgical bonding interface is formed between the nickel-vanadium layer (105) and the titanium-tungsten layer (104); the high-purity aluminum layer (106) completely covers the surface of the nickel-vanadium layer (105) away from the titanium-tungsten layer (104); the nickel barrier layer (107) completely covers the surface of the high-purity aluminum layer away from the nickel-vanadium layer (105); and the Sn-3.5Ag bonding layer (108) completely covers the surface of the nickel barrier layer (107) away from the high-purity aluminum layer (106), forming a five-layer bump structure stacked sequentially from bottom to top.
5. The aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM according to claim 4, characterized in that: The nickel barrier layer (107) has a nanocrystalline structure with uniformly distributed grain size; a flat interface is formed between the high-purity aluminum layer (106), the nickel barrier layer (107) and the Sn-3.5Ag bonding layer (108), the three layers have the same lateral dimensions, and all of them match the lateral dimensions of the nickel-vanadium layer (105) below. The upper surface of the Sn-3.5Ag bonding layer (108) forms a hemispherical surface for welding.
6. The aluminum-nickel-tin-silver bump interconnect structure based on TiW-NiV double-layer UBM according to claim 5, characterized in that: The titanium-tungsten layer (104), nickel-vanadium layer (105), high-purity aluminum layer (106), nickel barrier layer (107), and Sn-3.5Ag bonding layer (108) are all continuous thin film layers with no gaps between them and are tightly bonded. The lateral dimension of the double-layer UBM structure is consistent with the lateral dimension of the pad, and the lateral dimension of the aluminum-nickel-tin-silver bump is consistent with the lateral dimension of the double-layer UBM structure, forming a stacked structure with the top and bottom aligned. The central axes of the substrate, pad, double-layer UBM structure, and aluminum-nickel-tin-silver bump coincide.