Multilayer RDL interconnection structure and manufacturing method thereof

Abstract

The invention discloses a multilayer RDL interconnection structure and a manufacturing method thereof, and belongs to the technical field of printed circuits. The multi-layer RDL interconnection structure comprises at least one layer of RDL, a plurality of micropores used for connecting the RDL are prepared in a photosensitive dielectric material layer attached to the surface of each layer of RDL, and all the layers of RDL are interconnected through the metalized micropores. According to the structure, a copper pad structure in a conventional multilayer RDL interconnection structure is abandoned, the micropores used for interconnection are directly manufactured on the metal wires, the size of the interconnection structure is reduced, and the structure has practical value.

Description

Technical Field

[0001] The present invention belongs to the technical field of printed circuits, and in particular discloses a multi-layer RDL interconnection structure and a manufacturing method thereof. Background Art

[0002] With the development of artificial intelligence technology, high-speed, low-power interconnection in chip packaging is becoming more and more important. In the chip packaging process, RDL (Redistribution Layer) plays a role in re-layout of I / O ports. The demand for high interconnection density requires the line width and spacing of RDL metal lines to develop in a smaller direction, and also requires a multi-layer RDL structure.

[0003] The current common multi-layer RDL interconnection structure contains copper pads, and the size of the copper pads limits the development of RDL wiring density to a higher level. Poor copper pad design and manufacturing may cause distortion in signal transmission, such as signal crosstalk, delay distortion, etc., affecting the signal integrity and performance of the system.

[0004] The semi-additive method is a common method for manufacturing multi-layer RDL structures. The steps are as follows: first, a layer of dielectric material is made on the first wiring layer, and then micropores are made on the dielectric material by laser ablation. A seed layer is made on the surface of the micropores and the surface of the dielectric material. Then, photoresist is laminated on the surface of the seed layer, photolithography is patterned, copper is plated, the photoresist is stripped, and the seed layer is etched to complete the micropore metallization and the production of the second wiring layer. However, the dielectric material between RDLs commonly used in the current semi-additive process is also a factor that limits the minimization of the aperture of interconnected micropores. On the one hand, silicon dioxide fillers are often added to the dielectric material between RDLs to compensate for the need for mechanical properties, but this leads to an increase in its dielectric constant and an increase in surface roughness, which is not conducive to the production of finer and more vertical micropores; on the other hand, given the inherent characteristics of existing dielectric materials, the aspect ratio of the prepared micropores is limited. Therefore, the small-size RDL interconnects produced by the existing semi-additive process still have limitations in expanding the interconnection density.

[0005] In summary, how to achieve higher density multi-layer RDL interconnection is an urgent problem to be solved. Summary of the invention

[0006] The purpose of the present invention is to provide a multi-layer RDL interconnection structure and a manufacturing method thereof in view of the deficiencies of the above-mentioned background technology, so as to realize more sophisticated multi-layer RDL interconnection through a simple RDL interconnection manufacturing method, improve the interconnection density and reliability, and solve the technical problem that there are limitations in small-size RDL interconnection manufactured by semi-additive process.

[0007] The present invention adopts the following technical solutions to achieve the above-mentioned invention object: A multi-layer RDL interconnection structure comprises at least two layers of RDL prepared on a substrate, each layer of RDL is provided with micro-holes and grooves for preparing the previous layer of RDL, and the micro-holes prepared on each layer of RDL are metallized during the preparation process of the previous layer of RDL.

[0008] As a further optimization scheme for a multi-layer RDL interconnection structure, a first dielectric material layer and a second dielectric material layer are attached to each RDL layer, the microholes are prepared by photolithography of the first dielectric material layer, and the grooves for preparing the upper RDL layer are prepared by photolithography of the second dielectric material layer.

[0009] As a further optimization solution for the multi-layer RDL interconnection structure, the first dielectric material layer and the second dielectric material layer are photosensitive imaging dielectric material layers.

[0010] As a further optimization solution for the multi-layer RDL interconnection structure, the minimum width of the metal fine line in each layer of RDL is 2μm.

[0011] As a further optimization solution for the multi-layer RDL interconnection structure, the aperture of the microvias prepared on each layer of RDL is less than or equal to the line width of the metal fine lines in the previous layer of RDL.

[0012] A method for manufacturing a multi-layer RDL interconnection structure, comprising the steps of: Step 1, attaching a dielectric material onto the first RDL layer to form a first dielectric material layer; Step 2, photolithography a first dielectric material layer attached to the first RDL layer to form micro-holes; Step 3, attaching a dielectric material to the surface of the substrate with the micropores formed in step 2 to form a second dielectric material layer; Step 4: photolithography the second dielectric material layer to form a groove for preparing the upper RDL layer, and the microhole prepared on the first dielectric material layer is connected to at least one groove to form a blind hole; Step 5, on the surface of the patterned second dielectric material layer, a seed layer is formed to cover the blind holes and the grooves and the top of the second dielectric material layer remaining after photolithography; Step 6: electroplating copper on the seed layer produced in step 5 to complete microporous metallization and production of the second layer RDL; Step 7, removing excess copper and seed layer on the top of the second dielectric material layer remaining after photolithography; Step eight, repeat steps one to seven to prepare microvias on the current RDL layer and the previous RDL layer.

[0013] As a further optimization scheme for the manufacturing method of a multi-layer RDL interconnection structure, the dielectric material is a photosensitive imaging dielectric material, which is a photosensitive dielectric film in the form of a liquid or a dry film; the photosensitive imaging dielectric material used is in a dry film state, a photosensitive dielectric film, step one is to attach the photosensitive imaging dielectric material to the first layer of RDL by lamination, step three is to attach the photosensitive imaging dielectric material to the surface of the substrate with micropores formed in step two by lamination, and the thickness of the formed first photosensitive imaging dielectric material layer and the second photosensitive imaging dielectric material layer is 5μm.

[0014] As a further optimization scheme for the manufacturing method of a multi-layer RDL interconnect structure, step five uses physical vapor deposition to form a seed layer covering the blind holes and grooves and the top of the second photosensitive imaging dielectric material layer remaining after lithography, and the seed layer material is one of Cu and Ti.

[0015] As a further optimization scheme for the manufacturing method of a multi-layer RDL interconnect structure, in addition to copper sulfate, polyethylene glycol, polydipropylene disulfide sulfonate, and polyethyleneimine are added to the copper plating solution in step six as additive components.

[0016] As a further optimization scheme for the manufacturing method of a multi-layer RDL interconnect structure, in step seven, wet etching is performed to remove excess copper and seed layer on the top of the second photosensitive imaging dielectric material layer remaining after photolithography. The etching solution used is a CuCl2 solution with a concentration of 2.3 mol / L.

[0017] The present invention adopts the above technical solution and has the following beneficial effects: (1) Compared with the common multi-layer RDL interconnection structure made by the semi-additive method, the multi-layer RDL interconnection structure proposed in the present invention forms micropores and grooves for preparing the upper layer RDL by photolithography of the dielectric material attached to the RDL, and then metallizes the micropores at the same time in the process of preparing the upper layer RDL, thereby reducing the aperture of the micropores and having higher calibration accuracy, thereby realizing a structure in which the interconnected micropores are directly connected to the metal fine wires of the multi-layer RDL, thereby reducing the size of the interconnection structure.

[0018] (2) Compared with the common multi-layer RDL interconnection structure produced by the semi-additive method, the multi-layer RDL interconnection structure proposed in the present invention uses photosensitive imaging dielectric material as the dielectric material, which can produce finer and more vertical interconnection micropores and improve the electrical performance of the interconnection. The thinner dielectric material layer formed by the photosensitive imaging dielectric material can produce micropores with lower aspect ratios, thereby obtaining micropores with higher thermomechanical reliability.

[0019] (3) Compared with the common multi-layer RDL interconnection structure produced by the semi-additive method, the multi-layer RDL interconnection structure proposed in the present invention abandons the copper pad structure and realizes direct interconnection of multi-layer RDL through microvias, thereby increasing the interconnection bandwidth in terms of electrical performance.

[0020] (4) Compared with the common multi-layer RDL interconnection structure produced by the semi-additive method, the multi-layer RDL interconnection structure proposed in the present invention has fewer micro-hole defects obtained by electroplating and better electrical performance.

[0021] (5) The present invention provides a method for manufacturing a multi-layer RDL interconnection structure. A photosensitive imaging dielectric material is attached to the surface of a first wiring layer by photolithography to form microholes for interconnection on the surface of the first wiring layer. A seed layer is prepared to cover the microholes and the top of the photosensitive imaging dielectric material remaining after photolithography, and then copper is plated to form copper metal layers on different planes. Only the excess copper on the top of the remaining photosensitive imaging dielectric material needs to be removed, and the copper formed in the microholes is completely retained to obtain a structure in which the multi-layer wiring layers are interconnected through the microholes on the wiring. Experimental measurements have shown that the multi-layer interconnection structure provided by the present invention can be applied to metal fine wires with a minimum line width of 2 μm. The minimum pore size of the interconnection microholes formed is 2 μm. There is no copper pad structure, which breaks through the constraints of the minimum interconnection structure of the semi-additive method. It has the technical advantages of simple process and the ability to produce interconnection through holes with lower aspect ratios. It can achieve smaller size and higher density multi-layer RDL interconnection without changing the electrical performance of the interconnection, and has the advantage of more economical and simple processing technology.

[0022] Other beneficial effects of the present invention will be given in the following description, and those skilled in the art can understand these beneficial effects through the following description or by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a structural diagram of the first wiring layer of the multi-layer RDL interconnection structure proposed by the present invention after laminating PID material.

[0024] Figure 2 This is a structural diagram of the multi-layer RDL interconnection structure proposed in the present invention after micro-holes are formed by photolithography of PID material.

[0025] Figure 3 This is a structural diagram of the multi-layer RDL interconnection structure proposed in the present invention after the PID material is laminated again.

[0026] Figure 4 This is a structural diagram of the multi-layer RDL interconnection structure proposed in the present invention after PID material is photolithographically patterned.

[0027] Figure 5 This is a structural diagram of making a seed layer on the surface of the patterned PID material for the multi-layer RDL interconnect structure proposed in the present invention.

[0028] Figure 6 A structural diagram of the multi-layer RDL interconnect structure proposed in the present invention, in which copper is electroplated and filled on a seed layer.

[0029] Figure 7 This is a structural diagram of the multi-layer RDL interconnection structure proposed in the present invention after the excess copper and seed layer on the top of the PID material are removed by wet etching.

[0030] Figure 8 It is a top cross-sectional view of the multi-layer RDL interconnection structure provided by the present invention.

[0031] Fig. 9 FIG. 4 is a flow chart of manufacturing the multi-layer RDL interconnection structure proposed in the present invention.

[0032] Explanation of the numbers in the figure: 1. substrate, 2. first layer RDL, 3. PID material, 4. microvia, 5. groove, 6. seed layer, 7. copper, 8. metallized microvia, 9. second layer RDL. DETAILED DESCRIPTION

[0033] The technical solution of the invention is described in detail below with reference to the accompanying drawings.

[0034] In view of the fact that it is difficult to achieve a smaller interconnection size when making a multi-layer RDL interconnection structure by a semi-additive process, the present invention proposes a multi-layer RDL interconnection structure and a manufacturing method thereof. First, a PID material attached to the surface of the first layer RDL is photolithographically formed to form micropores for interconnection on the surface of the first layer RDL, a layer of PID material is laminated again, and photolithographic patterning is performed to expose the micropores for interconnection and form grooves for making the second layer RDL, a seed layer covering the micropores and the top of the PID material remaining from the photolithography is made, an additive is added to the plating solution to reduce defects such as cavities generated by electroplating copper filling, and excess copper on the top of the PID material remaining from the photolithography is removed by wet etching with a CuCl2 solution, so as to obtain a multi-layer RDL structure directly interconnected by micropores on the wiring, the minimum pore size of the interconnected micropores formed reaches 2μm, and there is no copper pad structure, which breaks through the minimum interconnection structure restriction of the semi-additive method, has the technical advantages of simple process and the ability to make interconnection through holes with lower aspect ratios, and realizes smaller and higher density multi-layer RDL interconnection without changing the electrical properties of the interconnection.

[0035] The multi-layer RDL interconnection structure proposed in the present invention includes at least two layers of RDL. The bottom RDL is prepared on a substrate. Each layer of RDL is prepared with microholes and grooves for preparing the upper RDL layer. The microholes prepared on each layer of RDL are metallized during the preparation process of the upper RDL layer.

[0036] Compared with the existing dielectric material layer, the dielectric material layer formed by PID (Photosensitive Imaging Dielectric) material is thinner and can be used to make micro-holes with a lower aspect ratio, which is beneficial to improving the thermomechanical reliability of the micro-holes and increasing the interconnection density. Preferably, in this embodiment, PID material is selected to form the dielectric layer, and a first PID material layer and a second PID material layer are attached to each layer of RDL, micro-holes are prepared on the first PID material layer, and grooves are prepared on the second PID material layer, and the micro-holes are connected to at least one groove.

[0037] A multi-layer RDL interconnect structure including two layers of RDL is shown in FIG. Figure 7 As shown, Figure 8 As shown, it includes: a first layer RDL2, metallized microvias 8, and a second layer RDL9. The first layer RDL2 is interconnected with the second layer RDL9 through the metallized microvias 8, and the aperture of the metallized microvias 8 is less than or equal to the line width of the second layer RDL9.

[0038] like Figure 7 The method for manufacturing the multi-layer RDL interconnection structure includes: Fig. 9 The seven steps from step one to step seven are shown.

[0039] Step 1: Laminate the PID material onto the first RDL layer like Figure 1 As shown, the PID material 3 is laminated on the first layer RDL2 to form a first PID material layer, and the first layer RDL2 is prepared on the substrate 1. In this embodiment, a 5-micron ultra-thin photosensitive dry film dielectric polymer IF4605 material produced by TOK Company is selected, and its dielectric constant is 3.8. It is laminated to the first layer RDL2 by a vacuum laminator, and its temperature is 90°C and the time is 30s.

[0040] Step 2: Photolithography of the first PID material layer attached to the first RDL layer like Figure 2 As shown, the first PID material layer attached to the first layer RDL2 is photolithographically formed to form micro-holes 4 for interconnection. In this embodiment, the specific method of photolithography of the PID material is: using a projection photolithography machine UX-44101 for photolithography, and the setting parameters are 600mj / cm 2 ; Place the substrate after photolithography of PID material in a 90°C oven for 20 minutes; For the baked substrate, immersion development is performed with PGMEA material for 90 seconds; The developed substrate is placed in a 200°C oven for curing for 60 minutes.

[0041] Step 3: Laminate another layer of PID material like Figure 3As shown, after the micropores are formed by photolithography of the PID material in step 2, a layer of PID material of the same specification is laminated again on the surface of the substrate to form a second PID material layer.

[0042] Step 4: Photolithography the second PID material layer to pattern it to form grooves for making the second layer of RDL like Figure 4 As shown, the second PID material layer is photolithographically formed to form a groove 5 for making the second layer RDL, and the microhole 4 is connected / through at least one groove 5 to form a blind hole structure. In this embodiment, the specific method of photolithography of the second PID material layer is: using a projection lithography machine UX-44101 for photolithography, and the setting parameters are 600mj / cm 2 ; Place the substrate after photolithography of PID material in a 90°C oven for 20 minutes; For the baked substrate, immersion development is performed with PGMEA material for 90 seconds; The developed substrate is placed in a 200°C oven for curing for 60 minutes.

[0043] Step 5: Making a seed layer on the surface of the patterned second PID material layer like Figure 5 As shown, on the surface of the patterned second PID material layer, a seed layer 6 is formed to cover the blind holes and the grooves 5 and the top of the second PID material layer remaining after photolithography. In this embodiment, a Cu seed layer with a thickness of 200 nm is formed by physical vapor deposition.

[0044] Step 6: Electroplating and filling copper on the seed layer made in step 5 like Figure 6 As shown, copper 7 is electroplated and filled in the seed layer using a copper sulfate solution containing additives such as polyethylene glycol (PEG), poly (disulfide propane sulfonate) (SPS), and polyethyleneimine (PEI).

[0045] Step 7: Use wet etching to remove the excess copper and seed layer on the top of the second PID material layer remaining after photolithography. like Figure 7 As shown, a 2.3 mol / L copper chloride solution is used to wet etch and remove the excess copper and seed layer on the top of the second PID material remaining after photolithography, and the second layer RDL 9 is prepared while metallizing the microvias and blind holes on the first layer RDL to form metallized microvias 8 and a flat and smooth surface. Wet etching of excess copper and seed layers has the advantage of no plastic strain.

[0046] This embodiment exemplarily illustrates the multi-layer RDL structure and the manufacturing method thereof of the present invention. Based on the inventive concept of the present invention, those skilled in the art can also perform Fig. 9In step eight, interconnected microvias and a new layer of RDL are prepared on the second RDL through the same preparation process to achieve high-density interconnection of more layers of RDL.

[0047] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above specific embodiments. The descriptions in the above specific embodiments and the specification are only for further illustrating the principles and preparation effects of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements. For example, the RDL process of the present invention may be implemented with a glass substrate or an organic substrate. These changes and improvements fall within the scope of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A multi-layer RDL interconnection structure, characterized in that: The invention comprises at least two layers of RDL prepared on a substrate, each layer of RDL is provided with micro-holes and grooves for preparing the upper layer of RDL, and the micro-holes prepared on each layer of RDL are metallized during the preparation process of the upper layer of RDL.

2. A multi-layer RDL interconnection structure according to claim 1, characterized in that: A first dielectric material layer and a second dielectric material layer are attached to each RDL layer, the microholes are prepared by photolithography of the first dielectric material layer, and the grooves used to prepare the upper RDL layer are prepared by photolithography of the second dielectric material layer.

3. A multi-layer RDL interconnection structure according to claim 2, characterized in that: The first dielectric material layer and the second dielectric material layer are photosensitive imaging dielectric material layers.

4. A multi-layer RDL interconnection structure according to claim 3, characterized in that: In each RDL layer, the minimum width of the metal fine line is 2 μm.

5. A multi-layer RDL interconnection structure according to claim 4, characterized in that: The aperture of the micro-holes prepared on each layer of RDL is less than or equal to the line width of the metal fine lines in the previous layer of RDL.

6. The method for manufacturing a multi-layer RDL interconnection structure according to claim 1, characterized in that: The steps include: Step 1, attaching a dielectric material onto the first RDL layer to form a first dielectric material layer; Step 2, photolithography a first dielectric material layer attached to the first RDL layer to form micro-holes; Step 3, attaching a dielectric material to the surface of the substrate with the micropores formed in step 2 to form a second dielectric material layer; Step 4: photolithography the second dielectric material layer to form a groove for preparing an upper RDL layer, wherein the microhole prepared on the first dielectric material layer is connected to at least one groove to form a blind hole; Step 5, on the surface of the patterned second dielectric material layer, a seed layer is formed to cover the blind holes and the grooves and the top of the second dielectric material layer remaining after photolithography; Step 6: electroplating copper on the seed layer produced in step 5 to complete microporous metallization and production of the second layer RDL; Step 7, removing excess copper and seed layer on the top of the second dielectric material layer remaining after photolithography; Step eight, repeat steps one to seven to prepare microvias on the current RDL layer and the previous RDL layer.

7. The method for manufacturing a multi-layer RDL interconnection structure according to claim 6, characterized in that: The dielectric material is a photosensitive imaging dielectric material, which is a photosensitive dielectric film in a dry film state. In step one, the photosensitive imaging dielectric material is attached to the first layer RDL by lamination to form a first photosensitive imaging dielectric material layer. In step three, the photosensitive imaging dielectric material is attached to the surface of the substrate with micropores formed in step two by lamination to form a second photosensitive imaging dielectric material layer.

8. The method for manufacturing a multi-layer RDL interconnection structure according to claim 7, characterized in that: In the step five, a physical vapor deposition method is used to form a seed layer covering the blind holes and the grooves as well as the top of the second photosensitive imaging dielectric material layer remaining after photolithography.

9. The method for manufacturing a multi-layer RDL interconnection structure according to claim 8, characterized in that: Step 6: When electroplating copper on the seed layer produced in step 5, polyethylene glycol, poly(dipropylene glycol disulfide) sulfonate and polyethyleneimine are added to the copper plating solution as additive components.

10. The method for manufacturing a multi-layer RDL interconnection structure according to claim 9, characterized in that: In step seven, the excess copper and seed layer on the top of the second photosensitive imaging dielectric material layer remaining after photolithography are removed by a wet etching process, and the etching solution is a cupric chloride solution with a concentration of 2.3 mol / L.

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