Metal redistribution layer structure and packaging method

Abstract

The invention provides a metal redistribution layer structure, which can effectively reduce the stress of a redistribution layer in an excessive necking area between a bonding pad and a circuit, thereby reducing the risk of fracture of the redistribution layer. The device comprises a substrate; an organic passivation layer; a metal redistribution layer; and welding spots or metal bumps; the substrate is provided with a device or a mechanism which needs to be connected with the welding spots or the metal bumps, the positions of the welding spots or the metal bumps and the device or the mechanism are not in the same plane domain position, the periphery of the device or the mechanism is covered with an organic passivation layer, and the organic passivation layer is provided with a gap corresponding to the connection position of the device or the mechanism. The diameter of the welding spots or the metal bumps is larger than the width of a connecting line of the metal rewiring layer, the position, corresponding to the welding spots or the metal bumps, of the metal rewiring layer is provided with bonding pads, and transition necking sections and necking connection positions are preset at the positions of the bonding pads and the connecting line; and the organic passivation layer is provided with a strip-shaped opening corresponding to the necking joint position.

Description

Technical Field

[0001] This invention relates to the technical field of semiconductor chip packaging, specifically to a metal redistribution layer structure, and also provides a packaging method for the metal redistribution layer. Background Technology

[0002] With the development of high-performance and miniaturized integrated circuits, advanced packaging technologies, such as fan-out packaging and 2.5D / 3D integration, have become key paths to overcome the limitations of Moore's Law. These technologies generally rely on metal redistribution layers (RDLs) to achieve electrical interconnection and signal redistribution between the chip and the substrate. RDLs form high-density wiring on the dielectric layer through micron-sized metal wires (usually copper) to meet the needs of multi-chip integration and I / O port expansion.

[0003] However, during the service life of packaged devices, the RDL structure faces significant mechanical stress challenges, especially stress concentration caused by solder joints. When devices undergo temperature cycling, mechanical shock, or power load changes, due to the mismatch in the coefficients of thermal expansion (CTE) of materials such as the chip, molding compound, and substrate, periodic thermomechanical stresses are generated at the solder joints. This stress is transmitted upwards to the RDL layer through bumps or copper pillars, causing the metal conductors (especially in the necking region) to be subjected to alternating shear and tensile loads. Under long-term stress accumulation, the RDL is prone to fatigue crack initiation and propagation, eventually leading to conductor breakage and causing open-circuit failure of the device.

[0004] While this problem has been mitigated by optimizing the toughness of dielectric materials and using stress buffer layers, the structural fragility of RDLs is becoming increasingly prominent as package thickness continues to decrease and linewidth / spacing shrinks to the submicron level. How to effectively prevent RDL breakage has become one of the core bottlenecks in improving the reliability of advanced packaging. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a metal redistribution layer structure that can effectively reduce the stress in the excessive necking area between the pads and the lines of the redistribution layer, thereby reducing the risk of redistribution layer breakage.

[0006] A metallic redistribution layer structure, characterized in that it comprises: Base; Organic passivation layer; Metal redistribution layer; Solder joints or metal bumps; The substrate is provided with devices or mechanisms that need to be connected to solder joints or metal bumps. The positions of the solder joints or metal bumps and the devices or mechanisms are not in the same plane region. The outer periphery of the devices or mechanisms is covered with an organic passivation layer. The organic passivation layer has a notch corresponding to the connection point of the devices or mechanisms. The diameter of the solder joints or metal bumps is larger than the width of the connecting line of the metal redistribution layer. The metal redistribution layer has pads corresponding to the positions of the solder joints or metal bumps. The pads and connecting lines are pre-set with transition necking sections and necking connection positions. The width of the transition necking end gradually decreases from the pad position to the end of the connecting line. The necking connection position includes the necking end, the end of the connecting line, and a transition position with obtuse angles on both sides. The organic passivation layer has a strip-shaped opening corresponding to the necking connection position. The width of the strip-shaped opening is larger than the width of the connecting line. During the arrangement of the metal redistribution layer, the area of ​​the strip-shaped opening is filled, so that the metal at the necking connection position and the metal at the lower strip-shaped opening position form an integral structure.

[0007] Its further features are: The strip opening is rectangular in shape, and the width of the strip opening is not less than the diameter of the preset pad, and its length L is 10μm to 50μm. The strip opening is arc-shaped, and the width formed by the distance between the two ends of the arc is not less than the diameter of the preset pad, and the radial distance L of the arc is 10μm to 50μm.

[0008] A strip-shaped opening is provided at the necking joint of the organic passivation layer. The redistribution layer thickness is increased at this location, which can reduce the stress at this location and reduce the risk of breakage. Moreover, compared with directly increasing the redistribution layer thickness to reduce the risk of breakage, this structure does not require increasing the overall redistribution layer thickness. The redistribution layer thickness is increased only at the necking joint in the high-risk area, and the area of ​​the redistribution layer relative to the inner layer is larger than that of the redistribution layer at the necking joint, thereby reducing the overall package thickness.

[0009] A packaging method for a metal redistribution layer structure, characterized by comprising the following steps: S1. A first organic passivation layer and a first metal redistribution layer are formed on the substrate, and the two are combined to form a wiring layer; S2. A new second organic passivation layer is formed on the wiring layer. The second organic passivation layer has a notch at the connection position of the first metal redistribution layer, and the second organic passivation layer forms a strip opening at the necking connection position of the preset pad. The notch and the strip opening are both obtained by photolithography. S3. The electroplating process forms a second metal redistribution layer, fills the strip openings and gaps of the second metal redistribution layer, and then forms a solder resist layer or an organic passivation layer. The reflow process forms solder joints.

[0010] Its further features are: The solder joint can also be formed by combining a bump metal pillar and an upper solder joint; The strip opening is rectangular or arc-shaped.

[0011] By adopting this invention, a strip-shaped opening is provided at the necking joint of the organic passivation layer. The redistribution layer thickness at this location is increased, which can reduce the stress at this location and reduce the risk of breakage. Moreover, compared with directly increasing the redistribution layer thickness to reduce the risk of breakage, this structure does not require increasing the overall redistribution layer thickness. The redistribution layer thickness is increased only at the necking joint in the high-risk area, and the area of ​​the redistribution layer relative to the inner layer is larger than that of the redistribution layer at the necking joint, thereby reducing the overall package thickness. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the front view sectional structure of the present invention; Figure 2 This is a top view of a specific embodiment of the present invention; Figure 3 This is a top view of a specific embodiment two of the present invention; Figure 4 This is a simplified schematic diagram of step S1 of the packaging method of the present invention; Figure 5 This is a simplified schematic diagram of step S2 of the packaging method of the present invention; Figure 6 This is a simplified schematic diagram of step S3 of the packaging method of the present invention; Figure 7 This is another schematic diagram of step S3 of the packaging method of the present invention. Detailed Implementation

[0013] A metal redistribution layer structure, see Figures 1-3A first metallic redistribution layer 103, which needs to be connected to solder joints 109, is disposed on a substrate 101. The location of solder joints 109 and the connection point of the first metallic redistribution layer 103 are not in the same plane region. The outer periphery of the first metallic redistribution layer 103 is covered with a first organic passivation layer 104. A notch 1 is provided in a second organic passivation layer 105 corresponding to the connection point of the first metallic redistribution layer 103. The diameter of solder joints 109 is larger than the width of the connecting line 2 of the second metallic redistribution layer 107. A pad 3 is provided in the second metallic redistribution layer 107 corresponding to the location of solder joints 109. The pad 3 and the connecting line 2 are located at... The system includes a transition necking section 4 and a necking connection position 5. The width of the transition necking section 4 gradually decreases from the pad 3 to the end of the connector 2. The necking connection position 5 includes a necking end 51, a connector end 52, and a transition position with obtuse angles on both sides. The second organic passivation layer 105 has a strip opening 106 corresponding to the necking connection position 5. The width of the strip opening 106 is greater than the width of the connector 2. During the arrangement of the second metal redistribution layer 107, the area of ​​the strip opening 106 is filled, so that the metal of the necking connection position 5 and the metal of the lower strip opening 106 form an integral structure.

[0014] Specific Implementation Example 1, see Figure 2 The strip opening 106 is rectangular in shape. At this time, the width of the strip opening 106 is not less than the diameter of the preset pad 3, and its length L is 10μm to 50μm. See Specific Implementation Example 2 Figure 3 The shape of the strip opening 106 is arc-shaped. At this time, the width formed by the distance between the two ends of the arc of the strip opening 106 is not less than the diameter of the preset pad 3, and the radial distance L of the arc is 10μm to 50μm.

[0015] A strip-shaped opening is provided at the necking joint of the organic passivation layer. The redistribution layer thickness is increased at this location, which can reduce the stress at this location and reduce the risk of breakage. Moreover, compared with directly increasing the redistribution layer thickness to reduce the risk of breakage, this structure does not require increasing the overall redistribution layer thickness. The redistribution layer thickness is increased only at the necking joint in the high-risk area, and the area of ​​the redistribution layer relative to the inner layer is larger than that of the redistribution layer at the necking joint, thereby reducing the overall package thickness.

[0016] A packaging method for a metal redistribution layer structure, see Figures 4-7 It includes the following steps: S1. A first organic passivation layer 102 and a first metal redistribution layer 103 are formed on the substrate 101, and the two are combined to form a wiring layer 104. S2. A new second organic passivation layer 105 is formed on the wiring layer 104. The second organic passivation layer 105 has a notch 1 at the connection position of the first metal redistribution layer 103, and the necking connection position 5 of the second organic passivation layer 105 at the preset pad 3 position forms a strip opening 106. The notch 1 and the strip opening 106 are both obtained by photolithography. S3. The electroplating process forms a second metal redistribution layer 107, fills the strip openings and gaps below the second metal redistribution layer 107, and then forms a solder resist layer or an organic passivation layer 108. The reflow process forms solder joints 109.

[0017] In another embodiment, solder joint 109 may also be formed by combining bump metal pillar 110 and upper solder joint 111. The strip opening 106 is rectangular or arc-shaped.

[0018] The principle is as follows: A strip-shaped opening is set at the necking joint of the organic passivation layer. The redistribution layer thickness at this location is increased, which can reduce the stress at this location and reduce the risk of breakage. Moreover, compared with directly increasing the redistribution layer thickness to reduce the risk of breakage, this structure does not require increasing the overall redistribution layer thickness. The redistribution layer thickness is increased only at the necking joint in the high-risk area, and the area of ​​the redistribution layer relative to the inner layer is larger than that of the redistribution layer at the necking joint, thereby reducing the overall package thickness.

[0019] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0020] 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. A metal redistribution layer structure, characterized in that, It includes: Base; Organic passivation layer; Metal redistribution layer; Solder joints or metal bumps; The substrate is provided with devices or mechanisms that need to be connected to solder joints or metal bumps. The positions of the solder joints or metal bumps and the devices or mechanisms are not in the same plane region. The outer periphery of the devices or mechanisms is covered with an organic passivation layer. The organic passivation layer has a notch corresponding to the connection point of the devices or mechanisms. The diameter of the solder joints or metal bumps is larger than the width of the connecting line of the metal redistribution layer. The metal redistribution layer has pads corresponding to the positions of the solder joints or metal bumps. The pads and connecting lines are pre-set with transition necking sections and necking connection positions. The width of the transition necking end gradually decreases from the pad position to the end of the connecting line. The necking connection position includes the necking end, the end of the connecting line, and a transition position with obtuse angles on both sides. The organic passivation layer has a strip-shaped opening corresponding to the necking connection position. The width of the strip-shaped opening is larger than the width of the connecting line. During the arrangement of the metal redistribution layer, the area of ​​the strip-shaped opening is filled, so that the metal at the necking connection position and the metal at the lower strip-shaped opening position form an integral structure.

2. The metal redistribution layer structure according to claim 1, characterized in that: The strip opening is rectangular in shape, and its width is not less than the diameter of the preset pad, and its length L is 10μm to 50μm.

3. The metal redistribution layer structure according to claim 1, characterized in that: The strip opening is arc-shaped, and the width formed by the distance between the two ends of the arc is not less than the diameter of the preset pad, and the radial distance L of the arc is 10μm to 50μm.

4. A packaging method for a metal redistribution layer structure, used to fabricate the metal redistribution layer structure as described in claims 1-3, characterized in that, Includes the following steps: S1. A first organic passivation layer and a first metal redistribution layer are formed on the substrate, and the two are combined to form a wiring layer; S2. A new second organic passivation layer is formed on the wiring layer. The second organic passivation layer has a notch at the connection position of the first metal redistribution layer, and the second organic passivation layer forms a strip opening at the necking connection position of the preset pad. The notch and the strip opening are both obtained by photolithography. S3. The electroplating process forms a second metal redistribution layer, fills the strip openings and gaps of the second metal redistribution layer, and then forms a solder resist layer or an organic passivation layer. The reflow process forms solder joints.

5. The packaging method for a metal redistribution layer structure according to claim 4, characterized in that: The solder joint is formed by a combination of a bump metal pillar and an upper solder joint.

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