Interface enhancement structure for Fan-out WLP and manufacturing method thereof

Abstract

The invention discloses an interface enhancement structure for Fan-out WLP and a manufacturing method thereof, and belongs to the technical field of semiconductor packaging, the interface enhancement structure comprises a plurality of polyimide layers and a copper rewiring layer, the copper rewiring layer in a virtual area is provided with a plurality of slotted holes, the slotted holes divide the copper rewiring layer into a plurality of isolated units, and the plurality of isolated units are communicated with the polyimide layers. And the polyimide filled in the slotted holes forms a guide pillar through hot-pressing curing, and the two ends of the guide pillar are fused with the polyimide layers on the upper side and the lower side of the copper rewiring layer into a whole to form an I-shaped composite structure, so that the bonding strength of the polyimide layers and a sputtering titanium interface is enhanced. Through the I-type composite structure, the interface contact area and the mechanical anchoring effect are increased, and the layering phenomenon is remarkably inhibited; stress accumulation during large-area metal electroplating is reduced through the design of the groove holes, and wafer-level electroplating consistency is improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor packaging technology, and specifically relates to an interface structure design for multilayer dielectric layers and metal redistribution layers (RDL) in fan-out wafer-level packaging (Fan-outWLP), aiming to solve the delamination problem of multilayer polyimide (PI) and sputtered titanium (Sputter Ti) interfaces in thermal processing and reliability testing. Background Technology

[0002] In existing Fan-out WLP processes, a structure of alternating stacks of multilayer polyimide (PI) and copper redistribution layers (Cu RDL) is widely used. However, as... Figure 1 Region A is a virtual region (dummy region) without any actual circuit function. The copper redistribution layer is viewed from above in this virtual region as follows: Figure 2 As shown, these are typically designed as large, continuous metal blocks, lacking clear design specifications. During thermal processes (such as annealing and reflow soldering) and reliability testing (such as temperature cycling), this design is prone to delamination at the interface between the PI and sputtered titanium due to the mismatch in thermal expansion coefficients between the metal and the dielectric material. This affects the mechanical integrity and long-term reliability of the package structure.

[0003] While existing technologies attempt to improve interfacial adhesion by optimizing materials or adding process steps, these methods often extend production cycles or increase costs, with limited effectiveness. Therefore, there is an urgent need for a structural design that can effectively enhance the interfacial adhesion strength between PI and sputtered titanium without increasing process complexity. Summary of the Invention

[0004] The purpose of this invention is to provide an interface enhancement structure for Fan-out WLP and its fabrication method, which improves interface strength without significantly altering existing processes by optimizing the graphic design of the Dummy region Cu RDL.

[0005] The objective of this invention is achieved through the following technical solution: An interface enhancement structure for Fan-out WLP includes a multilayer polyimide (PI) layer and a copper redistribution layer (Cu RDL). Multiple slots are formed on the copper redistribution layer in the dummy region, dividing the copper redistribution layer into multiple isolated units. The polyimide filling the slots is thermo-pressed and cured to form guide pillars. The two ends of the guide pillars are fused with the polyimide layers on the upper and lower sides of the copper redistribution layer to form a type I composite structure, thereby enhancing the bonding strength between the polyimide and sputtered titanium (Sputter Ti) interface.

[0006] As a further improvement of one embodiment of the present invention, the type I composite structure suppresses interface delamination during thermal processing and reliability testing through mechanical interlocking effect.

[0007] As a further improvement to one embodiment of the present invention, the slot pad has a size of 30μm×30μm and is defined by a mask pattern to optimize stress distribution. A method for creating the above-mentioned interface enhancement structure includes the following steps: S1. Define an array of slots on the Cu RDL mask in the dummy region to complete the mask design; the slot size is preferably 30μm×30μm, and the overall stress concentration in the metal region is reduced by geometric segmentation; S2. Titanium is sputtered onto the surface of the polyimide layer as an adhesion layer; then photoresist is uniformly coated, and exposure and development are performed through a mask with a slot pattern to form a Cu RDL pattern; S3. Electroplated copper fills the pattern area. After removing the photoresist, excess sputtered titanium is removed by etching to form segmented Cu RDL units. S4. The polyimide filling the slot is cured by hot pressing to form a guide post. The two ends of the guide post are fused with the polyimide layers on the upper and lower sides of the copper redistribution layer to form a whole, forming a type I composite structure with a "PI-Cu RDL-PI" structure. The interface bonding force is enhanced by the mechanical interlocking effect.

[0008] S5. Repeat the stacking and curing steps to complete the packaging structure fabrication without increasing the process cycle or adding extra steps.

[0009] As a further improvement of one embodiment of the present invention, the slot pattern is directly integrated into the existing photolithography process through a mask, avoiding modification of equipment or process.

[0010] The above technical solution has the following beneficial effects: Enhanced interface strength: The I-type composite structure increases the interface contact area and mechanical anchoring effect, significantly suppressing delamination.

[0011] Process efficiency: This design can be directly integrated into existing photolithography and electroplating processes without additional steps or equipment adjustments; it can be achieved simply by modifying the mask pattern.

[0012] Improved plating uniformity: The slot design reduces stress accumulation during large-area metal plating, improving wafer-level plating consistency. Attached Figure Description

[0013] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0014] The structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0015] Figure 1 This is a schematic diagram of a chip packaging structure provided by the present invention.

[0016] Figure 2 For the existing Figure 1 Plan view of the copper redistribution layer in the Dummy area of ​​region A.

[0017] Figure 3 Provided by the present invention Figure 1 Plan view of the copper redistribution layer in the Dummy area of ​​region A.

[0018] Figure 4 This is a schematic diagram of the Type I composite structure provided by the present invention.

[0019] Figure 5 This is a schematic diagram of the process provided by the present invention.

[0020] In the picture: 1. Slots; 2. Polyimide layer; 3. Copper redistribution layer; 4. Titanium sputtering interface. Detailed Implementation

[0021] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0022] Combination Figure 3 , Figure 4As shown, an interface reinforcement structure for Fan-out WLP includes a multilayer polyimide (PI) layer 2 and a copper redistribution layer (Cu RDL) 3. Innovatively, multiple slots 1 are formed on the copper redistribution layer 3 in the dummy region. These slots are not randomly placed; their dimensions are precisely set at 30μm × 30μm and are precisely defined through a mask pattern. This design optimizes stress distribution and ensures the stability of the structure under different operating conditions.

[0023] The presence of slot 1 divides the copper redistribution layer into multiple isolated units. In the subsequent thermosetting curing process, the polyimide filling slot 1 forms guide pillars. The two ends of these guide pillars fuse with the polyimide layers on the upper and lower sides of the copper redistribution layer, respectively, thus forming a type I composite structure. This type I composite structure significantly enhances the bonding strength between the polyimide and sputtered titanium (Sputter Ti) interface 4.

[0024] In this solution, the shape of the slot 1 is not limited to a circle, square, ellipse or other regular or irregular shapes. As long as it can meet the requirement of reasonably dividing the copper redistribution layer 3 and forming an effective type I composite structure, it is within the scope of implementation.

[0025] In practical applications, the Type I composite structure effectively suppresses interface delamination problems that occur during thermal processing and reliability testing through mechanical interlocking effects, greatly improving the stability and reliability of the Fan-out WLP structure.

[0026] Combination Figure 5 As shown, a method for creating the above-mentioned interface enhancement structure includes the following steps: S1. On the Cu RDL mask in the dummy region, precisely define the array of slot pads to complete the mask design. The slot pad size is preferably 30μm×30μm. This size, through geometric division, can effectively reduce the overall stress concentration in the metal region. From the perspective of equivalent mechanical structures, the slot pad size can also be adjusted within a certain range, such as the length and width in the range of 25-35μm, as long as a similar stress dispersion effect can be achieved.

[0027] S2. Titanium is sputtered onto the surface of the polyimide layer as an adhesion layer; then photoresist is uniformly coated, and exposure and development are performed through a mask with a slot pattern to form a Cu RDL pattern; S3. The pattern area is filled by electroplating copper. After the filling is completed, the photoresist is removed. Then, excess sputtered titanium is removed by etching, and finally, segmented Cu RDL units are formed.

[0028] S4. The polyimide filling the slot is cured by hot pressing to form a guide post. The two ends of the guide post are fused with the polyimide layers on the upper and lower sides of the copper redistribution layer to form a whole, forming a type I composite structure with a "PI-Cu RDL-PI" structure. The interface bonding force is enhanced by the mechanical interlocking effect.

[0029] S5. Repeat the lamination and curing steps until the encapsulation structure is complete. This process does not increase the manufacturing cycle or add extra steps, effectively ensuring production efficiency.

[0030] Furthermore, the slot 1 pattern can be directly integrated into the existing photolithography process through a photomask. In this way, no modifications to the equipment or process are required, which reduces production costs while improving the compatibility and stability of the production process.

[0031] This invention employs the aforementioned technical solution, increasing the interface contact area and mechanical anchoring effect through a type I composite structure, resulting in a tighter bond between polyimide and sputtered titanium, effectively suppressing delamination. This design can be directly integrated into existing photolithography and electroplating processes without additional steps or equipment adjustments; only the mask pattern needs modification, significantly saving time and cost. Simultaneously, the clever slot design reduces stress accumulation during large-area metal electroplating, significantly improving wafer-level plating consistency and ensuring product quality stability.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An interface enhancement structure for Fan-out WLP, comprising multiple polyimide layers and a copper redistribution layer, characterized in that, Multiple slots are provided on the copper redistribution layer in the virtual area. The slots divide the copper redistribution layer into multiple isolated units. The polyimide filling the slots is formed into guide pillars by hot pressing and curing. The two ends of the guide pillars are fused with the polyimide layers on the upper and lower sides of the copper redistribution layer to form a whole, forming a type I composite structure.

2. The interface enhancement structure according to claim 1, characterized in that, The slots are defined using a mask pattern to optimize stress distribution.

3. A method for fabricating the interface enhancement structure as described in claim 1, characterized in that... Includes the following steps: S1. Define an array of slots on the Cu RDL mask in the virtual region to complete the mask design; S2. Titanium is sputtered onto the surface of the polyimide layer as an adhesion layer; Subsequently, photoresist is uniformly coated, and the image is exposed and developed through a mask with a slot pattern to form a Cu RDL pattern. S3. Electroplated copper fills the pattern area. After removing the photoresist, excess sputtered titanium is removed by etching to form segmented CuRDL units. S4. The polyimide filling the slot is cured by hot pressing to form a guide post. The two ends of the guide post are fused with the polyimide layers on the upper and lower sides of the copper redistribution layer to form a whole to form a type I composite structure. S5. Repeat the stacking and curing steps to complete the encapsulation structure fabrication.

4. The method according to claim 3, characterized in that, The slot pattern is directly integrated into the existing photolithography process through a mask, avoiding modifications to equipment or processes.

Images