Package structure and method of forming the same

Abstract

The application discloses a packaging structure and a forming method thereof. The packaging structure comprises a substrate, a redistribution layer and a connecting layer. The substrate has a first pad. The redistribution layer has a second pad. The connecting layer connects the substrate and the redistribution layer. The connecting layer connects the first pad and the second pad. The heat absorption coefficient of the connecting layer is greater than that of the first pad or the second pad. The technical scheme can reduce the size of the connecting via, thereby meeting the requirements of high-order products.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to a packaging structure and a method for forming the same. Background Technology

[0002] With the maturation of wafer packaging technology and increased competition, wafers are becoming smaller and smaller, and their functions are becoming more and more numerous. The industry trend is gradually evolving towards SiP (System-in-a-Package) and 3D packaging, which not only increases the number of I / Os but also makes the pitch smaller and smaller.

[0003] As the number of substrate layers increases, yield decreases and costs rise significantly. One current approach uses a Redistribution Layer (RDL) to create fine lines, bonding it to the substrate via an adhesion layer to reduce costs. However, this typically requires laser-drilled vias to penetrate the RDL and substrate. Besides the high cost, laser-drilled vias also have pitch limitations; considering subsequent reliability testing, the minimum permissible size is 60μm, and smaller sizes raise concerns about reliability. Even direct Cu-Cu butt bonding has limitations due to the minimum Ni-Cu-SnAg plating width of approximately 50μm, making it unsuitable for RDLs of 25μm. Summary of the Invention

[0004] To address the connection problem of RDL 25um in related technologies, this invention proposes a packaging structure and its formation method, which can reduce the size of the connection via, thereby meeting the requirements of high-end products.

[0005] The technical solution of this invention is implemented as follows:

[0006] According to one aspect of the present invention, a packaging structure is provided, comprising: a substrate having a first pad; a redistribution layer having a second pad; and a bonding layer for bonding the substrate to the redistribution layer. The bonding layer connects the first pad and the second pad, and the thermal absorption coefficient of the bonding layer is greater than that of either the first pad or the second pad.

[0007] According to an embodiment of the present invention, the material of the connecting layer includes Ta, Fe, Ni, or a combination thereof.

[0008] According to an embodiment of the present invention, the packaging structure further includes an underfill material that fills between the substrate and the redistribution layer and surrounds the first pad, the second pad, and the connection layer between the first pad and the second pad.

[0009] According to an embodiment of the present invention, the region adjacent to the interconnect layer of the first pad is a doped region. The lattice of the doped region is larger than the lattice of other regions of the first pad.

[0010] According to an embodiment of the present invention, the region adjacent to the interconnect layer of the second pad is a doped region. The lattice of the doped region is larger than the lattice of other regions of the second pad.

[0011] According to an embodiment of the present invention, the redistribution layer further has a via connected above the second pad. The maximum width of the via is no greater than 25 μm.

[0012] According to an embodiment of the present invention, the material of the first pad or the second pad is Cu.

[0013] According to another aspect of the present invention, a method for forming a package structure is provided, comprising: forming a high thermal absorption coefficient material over a first pad of a substrate; stacking a redistribution layer having a second pad over the substrate, wherein the second pad is bonded to the high thermal absorption coefficient material, the thermal absorption coefficient of the high thermal absorption coefficient material being greater than the thermal absorption coefficient of the first pad or the second pad; and performing microwave heating to diffuse the high thermal absorption coefficient material into the first pad or the second pad.

[0014] According to an embodiment of the present invention, forming a material with a high heat absorption coefficient includes: applying the material with a high heat absorption coefficient using slit coating.

[0015] According to an embodiment of the present invention, microwave heating includes performing microwave heating at a temperature of 200°C.

[0016] According to an embodiment of the present invention, after microwave heating, the region of the first pad adjacent to the material with a high thermal absorption coefficient is formed as a doped region.

[0017] According to an embodiment of the present invention, the lattice of the doped region is larger than the lattice of other regions of the first pad.

[0018] According to an embodiment of the present invention, after microwave heating, the region of the second pad adjacent to the material with a high thermal absorption coefficient is formed as a doped region.

[0019] According to an embodiment of the present invention, the lattice of the doped region is larger than the lattice of other regions of the second pad.

[0020] According to an embodiment of the present invention, the lattice size of the material with high thermal absorption coefficient increases after microwave heating.

[0021] According to an embodiment of the present invention, the method of forming a package structure further includes: forming an underfill between a substrate and a redistribution layer, the underfill surrounding a first pad, a second pad, and a high thermal absorption coefficient material between the first pad and the second pad.

[0022] According to embodiments of the present invention, the high thermal absorption coefficient material includes Ta, Fe, Ni, or a combination thereof.

[0023] According to an embodiment of the present invention, the material of the first pad or the second pad is Cu. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figures 1A to 1E This is a schematic diagram of the various intermediate stages of a method for forming an encapsulation structure according to an embodiment of the present invention.

[0026] Figure 2A and Figure 2B This is a schematic diagram of the crystal structure of a high thermal absorption coefficient material in its original state and after microwave heating treatment.

[0027] Figure 3A and Figure 3B This is a schematic diagram of a material with a high thermal absorption coefficient after conventional heat treatment and microwave heat treatment. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0029] Figures 1A to 1E These are schematic diagrams illustrating the various intermediate stages of a method for forming a packaging structure according to embodiments of the present invention. Figure 1A As shown, a receiving substrate 10 is provided. A first pad 12 is provided on the surface of the substrate 10. The first pad 12 can be connected to a line 16 in the substrate 10, for example, via a through-hole 14.

[0030] like Figure 1B As shown, a high thermal absorption coefficient material 15 is formed above the first pad 12 of the substrate 10. In some embodiments, the high thermal absorption coefficient material 15 can be coated on the substrate 10 using a slot coating process. The layer formed by the high thermal absorption coefficient material 15 may be referred to below as the bonding layer 15.

[0031] like Figure 1CAs shown, a redistribution layer 20 having a second pad 22 is stacked above a substrate 10, wherein the second pad 22 is bonded to a high thermal absorption coefficient material 15. The thermal absorption coefficient of the high thermal absorption coefficient material 15 is greater than that of the first pad 12 or the second pad 22. In some embodiments, the material of the first pad 12 or the second pad 22 may be Cu. The high thermal absorption coefficient material 15 includes, for example, Ta, Fe, Ni, or combinations thereof. In some embodiments, the high thermal absorption coefficient material 15 may be Fe-Ni, Fe-Cu, etc.

[0032] The selection of high heat absorption coefficient material 15 can be referred to Table 1 below.

[0033] Table 1 Selection of materials with high heat absorption coefficient

[0034]

[0035] like Figure 1D As shown, microwave heating is performed. The microwave heating process diffuses a material with a high thermal absorption coefficient into the first pad 12 or the second pad 22. In some embodiments, the microwave heating temperature is below 200°C. Figure 2A and Figure 2B As shown, after microwave heating, Cu melts into iron, creating gaps that allow highly absorbent materials (such as Fe) to diffuse into Cu. Therefore, the electrical properties are improved after microwave heating.

[0036] After microwave heating, the region adjacent to the high thermal absorption coefficient material 15 of the first pad 12 is formed as a doped region 122. The lattice of the doped region 122 is larger than the lattice of other regions of the first pad 12.

[0037] Similarly, after microwave heating, the region adjacent to the high thermal absorption coefficient material 15 of the second pad 22 is formed as a doped region 222. The lattice of the doped region 222 is larger than the lattice of other regions of the second pad 22.

[0038] In other words, after microwave heating, the lattice size of the high thermal absorption coefficient material 15 increases. Microwave heating technology can achieve better process efficiency, increasing mechanical and electrical properties. It also offers high selectivity; rapid and short-time heating allows for different temperatures in different regions of the process. After microwave heating and sintering, the average particle size of the connecting region becomes more uniform and is half the size of the original sintered particle size. (Reference) Figure 3A and Figure 3B As shown. Moreover, the lattice size after calcination is twice as large as that after traditional heating, thus resulting in better electrical properties.

[0039] like Figure 1EAs shown, an underfill 30 is formed between the substrate 10 and the redistribution layer 20. The underfill 30 surrounds the first pad 12, the second pad 22, and the high thermal absorption coefficient material 15 between the first pad 12 and the second pad 22. During the... Figure 1E Following the steps shown, a semiconductor structure 100 is formed. A bonding layer 15 bonds the substrate 10 to the redistribution layer 20, and the bonding layer 15 connects the first pad 12 and the second pad 22. As described above, the thermal absorption coefficient of the bonding layer 15 is greater than the thermal absorption coefficient of either the first pad 12 or the second pad 22.

[0040] Due to the microwave heating treatment performed on the interconnect layer 15, the region adjacent to the interconnect layer 15 of the first pad 12 can be formed as a doped region. The lattice of the doped region of the first pad 12 is larger than the lattice of other regions of the first pad 12. Similarly, due to the microwave heating treatment performed on the interconnect layer 15, the region adjacent to the interconnect layer 15 of the second pad 22 is a doped region. The lattice of the doped region of the second pad 22 is larger than the lattice of other regions of the second pad 22.

[0041] In the semiconductor structure 100, the redistribution layer 20 also has a via connected to the second pad 22. Because the interconnect layer 15, after microwave heating treatment, has better electrical properties, the size of the via can be reduced. In some embodiments, the maximum width of the via is no greater than 25 μm.

[0042] The technical solution of this invention uses microwave heating to process the high absorption coefficient material of the bonding layer, and performs heating and sintering at the required depth and location, so that the high absorption coefficient material is sintered with the redistribution layer and the substrate, thereby connecting the signal of the redistribution layer and the substrate. The structural approach of this invention can reduce the size of the bonding vias (e.g., no larger than 25 μm), thereby meeting the requirements for applications in high-end products.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A packaging structure, characterized in that, include: The substrate has a first pad; The redistribution layer has a second pad and a via connected above the second pad; as well as A bonding layer, which is a coating located between the first pad and the second pad, is provided to bond the substrate to the redistribution layer. The connection layer connects the first pad and the second pad. The thermal absorption coefficient of the connection layer is greater than that of either the first pad or the second pad. The region adjacent to the connection layer of the first pad is a doped region, and the region adjacent to the connection layer of the second pad is a doped region. The material of the bonding layer includes Fe, and the lattice of the doped region of the first pad is larger than the lattice of other regions of the first pad, or the lattice of the doped region of the second pad is larger than the lattice of other regions of the second pad. The maximum width of the through hole is no greater than 25 μm.

2. The packaging structure according to claim 1, characterized in that, The material of the connecting layer also includes Ni.

3. The packaging structure according to claim 1, characterized in that, Also includes: The bottom filler fills the space between the substrate and the redistribution layer, and surrounds the first pad, the second pad, and the connection layer between the first pad and the second pad.

4. A method for forming an encapsulation structure, characterized in that, include: A material with a high heat absorption coefficient is coated above the first pad of the substrate; A redistribution layer having a second pad is stacked on top of the substrate, wherein the second pad is bonded to the high thermal absorption coefficient material, and a through-hole is connected to the side of the second pad facing away from the high thermal absorption coefficient material, the thermal absorption coefficient of the high thermal absorption coefficient material being greater than the thermal absorption coefficient of the first pad or the second pad; and Microwave heating is performed to diffuse the material with a high thermal absorption coefficient into the first pad or the second pad. The high thermal absorption coefficient material includes Fe, and after microwave heating, the lattice size of the high thermal absorption coefficient material increases. The region adjacent to the high thermal absorption coefficient material on the first pad is a doped region, and the region adjacent to the high thermal absorption coefficient material on the second pad is also a doped region. The lattice size of the doped region on the first pad is larger than the lattice size of other regions on the first pad, or vice versa. The maximum width of the through hole is no greater than 25 μm.

5. The method for forming an encapsulation structure according to claim 4, characterized in that, The high heat absorption coefficient material being coated includes: The high heat absorption coefficient material is coated using slot coating.

6. The method for forming an encapsulation structure according to claim 4, characterized in that, Microwave heating includes: The microwave heating is performed at a temperature of 200°C.

7. The method for forming an encapsulation structure according to claim 4, characterized in that, Also includes: An underfill is formed between the substrate and the redistribution layer, the underfill surrounding the first pad, the second pad, and the high thermal absorption coefficient material between the first pad and the second pad.

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