Wafer-level wrapped bump packaging structure and forming process thereof
By enclosing the inner bumps of nonferrous metals through a fully wrapped precious metal layer, the problems of reduced reliability and high cost of CuNiAu structure due to oxidation are solved, and a more stable low-cost bump packaging is achieved.
Patent Information
- Application Number
- CN202411340920.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-25
- Publication Date
- 2024-12-27
AI Technical Summary
The exposed structure of the existing CuNiAu non-ferrous metals has reduced contact reliability due to Cu oxidation, which affects service life and increases the cost of renewal.
The top and sides of the inner convex points of the non-ferrous metal are fully wrapped and enclosed. The precious metal layer is fixed through seed layer and electroplating or electroplating process, with a thickness greater than or equal to 1.5 microns, extending the service life of the inner convex points of the non-ferrous metal.
It effectively avoids the oxidation of the convex points in non-ferrous metals, improves the reliability and stability of the contacts, reduces the production cost, and solves the problems of structural differences and etching effects.
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Figure CN119208281A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of chip packaging, and in particular relates to a wafer-level packaged bump packaging structure and a forming process thereof. Background Art
[0002] In the field of driver chip packaging, due to the high-frequency input and output environment of the driver chip, the input and output contacts of the chip are extremely high. At present, the input and output contacts of the mainstream driver chips on the market are pure Au gold bumps, such as Figure 1 shown.
[0003] However, as the price of gold continues to rise and competition in the display driver market becomes fierce, more and more customers need to change the original Au structure while meeting the basic needs of contacts and develop diversified and low-cost structures. Low-cost composite structures of non-ferrous metals such as CuNi have emerged.
[0004] At present, there is a kind of IC package bump that uses copper-nickel-gold combination to replace pure gold, which can effectively reduce the cost. Its structure includes a carrier, a conductive layer, an insulating layer, a titanium layer, a first copper layer, a second copper layer, a nickel layer and a gold layer arranged in sequence from bottom to top, such as Figure 2 shown.
[0005] With market verification, the exposed structure of CuNiAu non-ferrous metals has also revealed its shortcomings due to the exposure of the Cu non-ferrous metal underneath. The most critical problem is that the oxidation of the non-ferrous metal Cu leads to reduced reliability of the contacts, which affects the service life of the contacts and requires frequent replacement, greatly increasing the cost of upgrades. Summary of the invention
[0006] In response to the above-mentioned technical problems, the present technical solution provides a wafer-level wrapped bump packaging structure and a formation process thereof, which fully wraps and seals the top and side surfaces of the non-ferrous metal inner bumps in all directions through a fully wrapped precious metal layer, thereby fixing and protecting the non-ferrous metal inner bumps, avoiding oxidation of the non-ferrous metal inner bumps, and increasing the service life of the non-ferrous metal inner bumps; it can effectively solve the above-mentioned problems.
[0007] The present invention is achieved through the following technical solutions:
[0008] A wafer-level packaged bump packaging structure comprises a bare wafer structure, wherein a plurality of pad bases are embedded and fixed on the top surface of the bare wafer structure; a seed layer and non-ferrous metal inner bumps are arranged on the upper side of the pad base, and a fully wrapped noble metal layer is fixed on the outer side of the non-ferrous metal inner bumps; the seed layer comprises a seed layer 1 connected to the bottom layer of the non-ferrous metal bumps and a seed layer 2 fixed to the top layer of the pad base, and the seed layer 1 and the seed layer 2 are fixed to the upper layer of the pad base by sputtering.
[0009] Furthermore, the thickness of the fully wrapped precious metal layer is greater than or equal to 1.5 microns.
[0010] Furthermore, the fully wrapped precious metal layer uses gold Au element and is fixed to the outer surface layer including the side surface of the non-ferrous metal inner bump through an electroplating or chemical plating process.
[0011] Furthermore, the seed layer is made of titanium Ti, copper Cu, tungsten Tiw, gold Au or a variety of alloy metals.
[0012] Furthermore, the non-ferrous metal bumps and the seed layer 1 are made of the same metal material.
[0013] Furthermore, the bare wafer structure includes a substrate arranged at the bottom layer, and a plurality of pad bases are fixed at designated positions on the top surface of the substrate; a protective layer is arranged on the top surface of the substrate between the pad bases, and the protective layer extends to the edge of the pad base to form a pad base embedded structure.
[0014] A process for forming a wafer-level package type bump packaging structure is used to manufacture the above-mentioned wafer-level package type bump packaging structure. The specific process flow includes:
[0015] Step 1: Sputtering is performed on the surface of the wafer to obtain a seed layer covering the surface of the wafer;
[0016] Step 2: Apply a layer of resin glue that can be opened by exposure on the upper side of the seed layer on the surface of the wafer, and the thickness of the resin glue coating is greater than the planned height of the non-ferrous metal inner bump;
[0017] Step 3: After coating, exposure and development are performed to obtain a PR opening consistent with the size of the inner bump;
[0018] Step 4: Inside the PR opening, a non-ferrous metal inner bump is obtained by electroplating or chemical transfer;
[0019] Step 5: removing the resin glue to obtain the exposed seed layer and the non-ferrous metal inner bump structure;
[0020] Step 6: Perform a second coating to coat a photoresist layer between the non-ferrous metal inner bumps on the surface of the wafer, wherein the thickness of the photoresist layer is greater than the height of the non-ferrous metal inner bumps;
[0021] Step 7: Perform a second exposure and development to obtain a PR opening consistent with the planned outer size of the bump, forming a gap between the metal bump and the photoresist layer;
[0022] Step 8: electroplating a precious metal layer in the gap to form a fully wrapped precious metal layer;
[0023] Step 9: Perform a second debonding to remove the resin glue on the upper side of the seed layer on the surface of the wafer and around the bumps to obtain an exposed seed layer and a bump structure with a fully wrapped precious metal layer;
[0024] Step 10: Perform etching operation to remove the seed layer between the bumps on the upper side of the wafer surface, obtain the exposed wafer surface and the bumps with a fully wrapped precious metal layer, and complete the production of the wrapped bump packaging structure.
[0025] Furthermore, when performing the operation of step 8, if the capillary effect occurs, resulting in the electroplating solution being unable to enter the narrow space for electroplating, a pre-gold plating pretreatment operation of descum or PLASMA plasma cleaning is required.
[0026] Beneficial Effects
[0027] The wafer-level package type bump packaging structure and its forming process proposed by the present invention have the following beneficial effects compared with the prior art:
[0028] (1) The present invention uses a fully wrapped precious metal layer to fully wrap and seal the top and side surfaces of the non-ferrous metal inner bumps, thereby fixing and protecting the non-ferrous metal inner bumps, avoiding oxidation of the non-ferrous metal inner bumps, and increasing the service life of the non-ferrous metal inner bumps; at the same time, it also solves the problem in the prior art that when the upper and lower structure packaging is subsequently etched, the exposed parts of the side surfaces of the bumps made of non-ferrous metals Cu and Ni are affected by etching and holes appear, resulting in unstable morphology and pressure difference stability. The present invention not only obtains a low-cost bump packaging structure, but also improves the reliability and stability of the low-cost bump packaging.
[0029] (2) The present invention uses non-ferrous metal Cu to make non-ferrous metal inner bumps, which reduces the use of precious metal Au, reduces the production cost of bumps, and solves the problem of high bump packaging cost in the prior art. The non-ferrous metal inner bumps are fixed on the surface of the non-ferrous metal inner bumps by electroplating or chemical plating, and the non-ferrous metal inner bumps are wrapped and fixed to improve the stability of the bumps, which can effectively solve the problem of structural differences between the gold cap and the underlying metal in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 The schematic diagram of the input and output contacts in the background technology is pure Au gold bumps.
[0031] Figure 2 It is a schematic diagram of an IC package bump in which a copper-nickel-gold combination replaces pure gold in the background technology.
[0032] Figure 3 This is a schematic diagram of the actual object of Example 1 taken by a microscope lens.
[0033] Figure 4 This is a schematic diagram of the overall structure of Example 1.
[0034] Figure 5 This is a schematic diagram of the overall structure of Example 3.
[0035] Figure 6 for Figure 5 Enlarged schematic diagram of part A.
[0036] Figure 7 This is a schematic diagram of the structure of Example 3.
[0037] Figure 8 This is the operating principle diagram of step 1 in Example 4.
[0038] Fig. 9 This is the result diagram obtained after the operation of step 1 in Example 4.
[0039] Fig.10 This is the operating principle diagram of step 2 in Example 4.
[0040] Fig.11 This is the result diagram obtained after the operation of step 2 in Example 4.
[0041] Fig.12 This is a schematic diagram of the operation process of step 3 in Example 4.
[0042] Fig.13 This is the operating principle diagram of step 3 in Example 4.
[0043] Fig.14 This is the result diagram obtained after the operation of step 3 in Example 4.
[0044] Fig.15 This is the operating principle diagram of step 4 in Example 4.
[0045] Fig.16 This is the result diagram obtained after the operation of step 4 in Example 4.
[0046] Fig.17 This is the result diagram obtained after the operation of step 5 in Example 4.
[0047] Fig.18 This is the result diagram obtained after the operation of step 6 in Example 4.
[0048] Fig.19 For attachment Fig.18 Physical picture.
[0049] Fig. 20 This is the result diagram obtained after the operation of step 8 in Example 4.
[0050] Fig.21 This is the result diagram obtained after the operation of step 9 in Example 4.
[0051] Fig. 22 Schematic diagram of the state before and after the operation of step P2 in Example 4.
[0052] Fig.23 It is a scatter plot of the volume ratio of gold saved and the package electroplating of the present invention.
[0053] Fig.24 This is a test data diagram of the relationship between the thickness and hardness of different wrapped metal layers of the present invention.
[0054] Fig.25 It is a scatter plot of the conversion hardness and package electroplating of the present invention.
[0055] Fig.26 It is a scatter plot of the reliability test of the present invention.
[0056] Fig. 27 This is a data graph of the stability test of the present invention.
[0057] Fig.28 It is a scatter plot of the stability test of the present invention.
[0058] Numbers in the attached drawings: 1-bare wafer structure, 11-substrate, 12-pad base, 13-protective layer, 2-non-ferrous metal inner bump, 3-fully wrapped precious metal layer, 4-seed layer, 41-seed layer one, 42-seed layer two, DETAILED DESCRIPTION
[0059] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Under the premise of not departing from the design concept of the present invention, various modifications and improvements made by ordinary persons in the art to the technical solutions of the present invention should all fall within the protection scope of the present invention.
[0060] Embodiment 1:
[0061] like Figure 3 to Figure 4 As shown, a wafer-level packaged bump packaging structure includes a bare wafer structure, the bare wafer structure includes a substrate arranged at the bottom layer, and a plurality of pad bases are fixed at designated positions on the top surface of the substrate; a protective layer is arranged on the top surface of the substrate between the pad bases, and the protective layer extends to the edge of the pad base to form a pad base embedded structure.
[0062] A non-ferrous metal inner convex point is arranged on the upper side of the pad base, and a fully wrapped precious metal layer is fixed on the outer side of the non-ferrous metal inner convex point.
[0063] In this embodiment, the non-ferrous metal inner bump is formed by precipitating and depositing non-ferrous metal Cu atoms into the openings of the photoresist through an electrochemical reaction. The copper ions gradually grow in the PR openings and form an organic whole with the top layer of the seed layer through the electroplating solution and the positive and negative electrodes of the power supply to obtain the non-ferrous metal inner bump.
[0064] The thickness of the fully wrapped precious metal layer is greater than or equal to 1.5 microns. The fully wrapped precious metal layer uses gold Au element and is fixed to the outer surface layer including the side of the non-ferrous metal inner bump through an electroplating or chemical plating process.
[0065] In this embodiment, the fully wrapped precious metal layer is obtained by precipitating and depositing non-ferrous metal Au atoms into the gap formed by the non-ferrous metal inner bump and the photoresist through an electrochemical reaction. The gold ions gradually grow in the gap and form an organic whole with the surface layer of the non-ferrous metal inner bump through the electroplating solution and the positive and negative electrodes of the power supply to obtain a fully wrapped precious metal layer.
[0066] The top and side surfaces of the non-ferrous metal inner bumps are fully wrapped and sealed by the fully wrapped precious metal layer, which plays a role in fixing and protecting the non-ferrous metal inner bumps, avoiding oxidation of the non-ferrous metal inner bumps, and increasing the service life of the non-ferrous metal inner bumps; at the same time, it also solves the problem in the prior art that when the upper and lower structure packaging is subsequently etched, the exposed parts of the side of the bumps made of non-ferrous metals Cu and Ni are affected by etching and holes appear, resulting in unstable morphology and pressure difference stability. This embodiment not only obtains a low-cost bump packaging structure, but also improves the reliability and stability of the low-cost bump packaging.
[0067] Embodiment 2:
[0068] Based on Example 1, a seed layer may be provided between the pad base and the nonferrous metal inner bump. The seed layer may be made of any metal such as titanium Ti, copper Cu, tungsten Tiw, or gold Au, or may be an alloy metal formed by two or more metals.
[0069] The setting of the seed layer can effectively increase the bonding force between the pad base and the non-ferrous metal inner bumps.
[0070] Embodiment 3:
[0071] like Figures 5 and 6 As shown, based on Example 2, the seed layer is further refined, and the seed layer includes a seed layer 1 connected to the bottom layer of the non-ferrous metal bump and a seed layer 2 fixed to the top layer of the pad base, and the seed layer 1 and the seed layer 2 are fixed to the upper layer of the pad base by sputtering.
[0072] Seed layer 1 and seed layer 2 can be selected from any metal such as titanium Ti or copper Cu or tungsten Tiw or gold Au, or can also be an alloy metal formed by two or more metals. However, it is best to use the same metal material as the non-ferrous metal bumps for seed layer 1, such as Figure 7 shown. Figure 7 The color of the middle seed layer 1 is consistent with that of the inner bump, indicating that the two parts are made of the same metal material.
[0073] When the seed layer 1 and the non-ferrous metal bumps are made of the same metal material, the bonding force between the seed layer and the non-ferrous metal inner bumps can be further increased.
[0074] Embodiment 4:
[0075] A process for forming a wafer-level package type bump package structure is used to manufacture a wafer-level package type bump package structure of the above-mentioned embodiments 1 to 3. The specific process flow includes:
[0076] Step 1: Sputtering is performed on the surface of the wafer to obtain a seed layer covering the surface of the wafer; the specific operation method is as follows:
[0077] like Figure 8 As shown, in a vacuum environment, targets of different metals (according to needs) are placed in the cavity, and the object to be plated (wafer) is placed in the vacuum cavity, corresponding to different positive and negative electrodes respectively. Under the action of high voltage, inert gas is rushed in at the same time, and plasma is generated under the action of high pressure, which continuously bombards the target material so that the atoms in the target material gain energy and collide and fly out. The target material atoms fly toward the object to be plated and fall down to start the nucleation and film formation process and continue to form the second seed layer.
[0078] Then, a second raw material of the seed layer thickness is sputtered to obtain a seed layer 1. The raw material can be selected from various alloy metals such as Ti, Cu, TiW, Au, etc., and Cu is selected in this embodiment. According to different sputtering requirements of the seed layer, the corresponding sputtering time is controlled.
[0079] Parameters: The parameters mainly control the Ar gas flow rate, power and time. In this embodiment, the Ar gas flow rate is controlled to be about 80 sccm. It is adjusted according to different machine performances. The control parameters of Ti and Cu are as follows:
[0080] Step Target Time(sec) Power(W) Ar(sccm) 1 Ti1 75 6800 80.0 2 Cu1 56 8600 80.0
[0081] The thickness of the seed layer can be selected according to different process conditions. In this embodiment, Ti0.1um and Cu0.3um are selected; Fig. 9 The effect shown.
[0082] Step 2: Apply a layer of resin glue that can be opened by exposure on the upper side of the seed layer on the surface of the wafer. The thickness of the resin glue coating is greater than the planned height of the non-ferrous metal inner bump. The specific operation steps are:
[0083] like Fig.10 As shown, a layer of photoresist is coated on the surface of the seed layer of the wafer, and then soft-baked to evaporate and remove the residual solvent in the PR component to relieve stress; finally, cooled to release the stress of the wafer that has expanded after soft baking and return to its original state.
[0084] The photoresist can be resin glue, positive glue or negative glue. In this embodiment, resin glue is used. Since the resin glue contains photosensitizer, a suitable opening can be opened under different lighting conditions. The removable resin glue is applied on the wafer to open different openings under subsequent lighting conditions.
[0085] Environment: Normal temperature environment; Parameters: Mainly use the ratio of rotation speed and time to determine the thickness.
[0086] Stop Range 200 RPM Step Time(sec) Rot Spd(rpm) 1 4.0 10 2 5.0 10 3 30.0 200 4 10.0 500 5 10.0 1000 6 20.0 3150
[0087] Final thickness of resin glue: Generally, the PR thickness can be 1 to 300um; this design can adjust the PR thickness according to different chip sizes. The PR thickness of this embodiment is 20um. Fig.11 status.
[0088] Step 3: After coating, exposure and development are performed to obtain a PR opening consistent with the size of the inner bump; the specific operation method is:
[0089] The penetration ability of light of different wavelengths directly or indirectly breaks the photosensitive agent bonds in the photoresist, resulting in different acid and alkali resistances in the exposed and non-exposed areas. The mask pattern can be transferred to the photoresist through alkaline developers, such as Fig.12 and Fig.13 shown.
[0090] In different areas of the chip, the resin glue is opened at the specified position according to the requirements to form a set shape. The properties of different photosensitive agents in the resin glue are used to interrupt and form exposed and non-exposed areas. The acid and alkali resistance of the two are different. The mask pattern can be transferred to the photoresist through an alkaline developer to obtain Fig.14 The opening shown in this embodiment is an opening of 10*10um.
[0091] Raw materials: prepared according to the exposure conditions required in the existing technology; Necessary environment: different necessary environmental conditions are adopted according to different PR properties; the necessary parameters are shown in the following table:
[0092] Step focal length Energy (mj) 1 -1 1246
[0093] After exposure, it can enter the developer to dissolve, and finally form openings of different sizes, such as Fig.14 The opening area shown is a 10*10 opening.
[0094] Step 4: Electroplating or chemical transfer is used to obtain non-ferrous metal inner bumps inside the PR opening; the specific operation method is:
[0095] After the opening is completed in step 3, the bump material is produced. In the current process flow, electroplating and chemical plating methods can generally be used. Depending on the actual use environment, display drivers generally use electroplating to ensure thickness and stability. The principle of electroplating is mainly to deposit atoms into the photoresist opening through electrochemical reactions to form inner metal bumps. The inner metal bumps grown by the seed layer on the wafer surface and the electroplating solution in the opening, as well as the positive and negative electrodes of the power supply, form an organic whole, such as Fig.15 shown.
[0096] Under the overall action of the wafer, copper plating solution, and anode and cathode, copper ions gradually grow in the PR opening, and the corresponding height is controlled by controlling the time and current density given by the machine.
[0097] Raw materials: copper plating solution, additives, sulfuric acid, etc.; proportion: copper ion control of copper plating solution is 45g / L, sulfuric acid content is 130g / L; parameters: different electroplating times are used according to different electroplating heights. The environmental parameters are generally that the general current density of metal electroplating is 10-15ASD. According to different electroplating solution systems, the temperature is controlled at about 26 degrees. Finally, the non-ferrous metal layer grows in the PR opening with the sputtered seed layer, such as Fig.16 shown.
[0098] Step 5: Remove the resin glue to obtain the exposed seed layer and the non-ferrous metal inner bump structure; the specific operation method is:
[0099] After the internal metal bumps are completed, it is necessary to proceed to the next step of the wrapping layer metal production. In addition to removing the resin glue between the internal metal bumps, it is necessary to prepare for the next step of large-size opening removal. The main raw materials are: 13% H202 hydrogen peroxide, the operating parameters are: temperature, 70±3℃, time 340s; the final formation is as follows Fig.17 The exposed structure of the internal metal bumps is shown.
[0100] Step 6: Perform a second coating, apply a photoresist layer between the non-ferrous metal inner bumps on the surface of the wafer, the thickness of the photoresist layer is greater than the height of the non-ferrous metal inner bumps; the specific operation method is the same as that of step 2, and the glue is applied again.
[0101] Step 7: Perform a second exposure and development to obtain a PR opening consistent with the planned outer size of the bump, forming a gap between the metal bump and the photoresist layer; the specific operation method is the same as that of step 3, except that the necessary parameters are modified to obtain an opening of 14*14um; the necessary parameters of this step are the necessary parameters:
[0102] Step focal length Energy (mj) 1 -2 1476
[0103] Finally, a gap of 2um is obtained between the metal bump and the photoresist layer, such as Fig.18 and Fig.19 shown.
[0104] Step 8: Electroplating a precious metal layer in the gap to form a fully wrapped precious metal layer; if direct Au electroplating is not possible, directly proceed to step P2. The specific operation method is:
[0105] The outer wrapping precious metal layer is electroplated again by electroplating or chemical plating. The precious metal used in this embodiment is gold Au.
[0106] Under the overall action of the wafer, gold plating solution (or other precious metals, inert metals), and the cathode and anode, metal ions gradually grow in the PR opening, and the height of the metal layer is controlled by controlling the time and current density given by the machine. Raw materials: copper plating solution, additives, sulfuric acid, etc.; Proportion: The gold ion control of the gold plating solution is 5g / L, PH (6.0) 5.5-6.5; Parameters: Different electroplating times are used according to different electroplating heights / thicknesses. The environmental parameters are generally that the general current density of metal electroplating is 0.1-1ASD. According to different electroplating solution systems, the temperature is controlled to be around 45 degrees. Finally, a fully enclosed precious metal layer grows in the PR opening and gap with the sputtered seed layer and the surface of the inner metal bump, such as Fig. 20 shown.
[0107] Step 9: Perform a second debonding to remove the resin glue on the upper side of the seed layer on the wafer surface and around the bumps to obtain an exposed seed layer and a bump structure with a fully wrapped precious metal layer, such as Fig.21 The specific operation method of this step is consistent with that of step 5.
[0108] Step 10: Perform etching to remove the seed layer between the bumps on the upper side of the wafer surface to obtain Figure 7 The exposed wafer surface and the bumps with a fully wrapped precious metal layer shown complete the production of a wrapped bump packaging structure.
[0109] The etching step is because after step 9 is completed, in addition to the bump position, the seed layer in the first step also exists in the rest of the wafer surface, and metal removal is required to achieve the independence of a single chip. Using metal etching technology, the peripheral metal can be effectively removed to obtain the final form of the wrapped bump.
[0110] The raw materials used are metal etching liquid + H2O2; parameters: mainly control the etching temperature and time to control the etching efficiency, where the temperature and time are 23±3℃ and 1800s respectively. The specific time can be adjusted according to the different thickness of the seed layer.
[0111] Step P2: When performing the operation in step 8, if the capillary effect occurs, which makes it impossible for the plating solution to enter the narrow space for electroplating, a pre-gold plating pretreatment operation of descum or PLASMA plasma cleaning is required.
[0112] According to the actual verification results, since the gap formed in step 7 is relatively narrow, the capillary effect causes the plating solution to be unable to enter the narrow gap space for electroplating, so pretreatment is required, such as Fig. 22 As shown. Pretreatment is referred to as descum or PLASMA plasma cleaning (also known as plasma). The principle adopted is plasma bombardment cleaning. After processing the existing circuit board small holes, dense holes, blind vias and other products, there are often residual smears or surface burrs. This operation is required to make it smooth and hydrophilic. Therefore, the dry process of plasma cleaning has attracted attention: it is now widely used in the cleaning process inside the hole after drilling the circuit board. For the internal metal layer, in order to ensure the stability and non-oxidizability, it is necessary to avoid the use of oxygen for plasma cleaning, and argon or nitrogen is required. The main control parameters are: bottom pressure (250mtorr), working pressure (300-350mtorr), power (6-8kw), time (10-15min), gas flow and ratio (6:2:1).
[0113] In order to verify the superiority and effectiveness of this solution, the inventors conducted the following experiments and data verification, specifically:
[0114] Cost verification:
[0115] Calculated based on a material size of 10 in length*10 in width*10 in height, the volume of gold used is 10^3. If an exposed type is used, the top metal thickness is generally around 1um. However, this has extremely low reliability issues and is not recommended.
[0116] If the wrapping type is used, the specific data is shown in Table 1. According to the data in Table 1, the following can be obtained: Fig.23 The following conclusions can be drawn from the curve graph shown:
[0117] If the wrapping type is used, with a thickness of 0.1um, the cost can be saved by 94.11% compared with full gold bumps;
[0118] If the wrapping type is used, with a thickness of 0.2um, the cost can be saved by 88.4% compared with full gold bumps;
[0119] If the wrapping type is used, with a thickness of 0.3um, the cost can be saved by 83.0% compared with full gold bumps;
[0120] If the wrapping type is used, with a thickness of 0.4um, the cost can be saved by 77.85% compared with full gold bumps;
[0121] If the package type is used, the cost saving is 72.9% compared with full gold bumps when the thickness is 1um;
[0122] If the wrapping type is used with a thickness of 2um, the cost saving is 21.6% compared to full gold bumps.
[0123]
[0124] Table 1
[0125] According to the volume formula, the thinner the package thickness, the more gold is saved, but the limitations of the actual application end must also be considered as follows:
[0126] ① Standard size: The size can be controlled by controlling the thickness. As long as the actual size meets the standard, it will not affect the actual thickness.
[0127] ②Hardness compliance: In the back-end packaging, there are a variety of packaging types, which basically need to be pressed together. This requires the chip surface to have a corresponding hardness, which limits the thickness to not be too thin (too thin to control the hardness and press).
[0128] Hardness test:
[0129] Use the needle to press in. If it is too hard, the indentation is small. If it is too soft, the indentation is large. Fig.24 The data shown and Fig.25 The curve table shown. It can be concluded that the thickness of the fully wrapped precious metal layer is generally required to be above 1.5um with high stability.
[0130] Reliability test:
[0131] Compared with the traditional chip bump structure, it has the following advantages: the same reliability and stability; no difference in reliability, the data chart summary performance is as follows Fig.26 As shown, the data is basically the same; there is no difference after reliability, and the data performance is shown in the following table:
[0132]
[0133]
[0134] Stability test:
[0135] Compared with the upper and lower structure bumps (bump sidewalls exposed), it has better stability against sidewall etching and avoids the instability caused by sidewall etching. The specific data is as follows: Fig. 27 As shown, the matrix diagram is as follows Fig.28 According to data analysis, the sidewall exposed bump structure of the traditional chip bump or the upper and lower structures is basically a negative depression, while the wrapped bump basically maintains an outward expansion state, which protects the overall chip state very well.
[0136] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the present invention.
Claims
1. A wafer-level package type bump packaging structure, comprising a bare wafer structure, wherein a plurality of pad bases are embedded and fixed on the top surface of the bare wafer structure; characterized in that: A seed layer and a non-ferrous metal inner bump are provided on the upper side of the pad base, and a fully wrapped precious metal layer is fixed on the outer side of the non-ferrous metal inner bump; the seed layer includes a seed layer 1 connected to the bottom layer of the non-ferrous metal bump and a seed layer 2 fixed to the top layer of the pad base, and the seed layer 1 and the seed layer 2 are fixed to the upper layer of the pad base by sputtering.
2. The wafer-level package bump packaging structure according to claim 1, characterized in that: The thickness of the fully wrapped precious metal layer is greater than or equal to 1.5 microns.
3. A wafer-level package bump packaging structure according to claim 1 or 2, characterized in that: The fully wrapped noble metal layer adopts gold Au element and is fixed to the outer surface layer including the side surface of the non-ferrous metal inner convex point through the process of electroplating or chemical plating.
4. The wafer-level package bump packaging structure according to claim 1, characterized in that: The seed layer is made of titanium Ti, copper Cu, tungsten Tiw, gold Au or a variety of alloy metals.
5. The wafer-level package bump packaging structure according to claim 1, characterized in that: The non-ferrous metal convex point and the seed layer 1 are made of the same metal material.
6. The wafer-level package bump packaging structure according to claim 1, characterized in that: The bare wafer structure includes a substrate arranged at the bottom layer, and a plurality of pad bases are fixed at designated positions on the top surface of the substrate; a protective layer is arranged between the pad bases on the top surface of the substrate, and the protective layer extends to the edge of the pad base to form a pad base embedded structure.
7. A process for forming a wafer-level package type bump package structure, used for manufacturing a wafer-level package type bump package structure according to any one of claims 1 to 6, characterized in that: The specific process includes: Step 1: Sputtering is performed on the surface of the wafer to obtain a seed layer covering the surface of the wafer; Step 2: Apply a layer of resin glue that can be opened by exposure on the upper side of the seed layer on the surface of the wafer, and the thickness of the resin glue coating is greater than the planned height of the non-ferrous metal inner bump; Step 3: After coating, exposure and development are performed to obtain a PR opening consistent with the size of the inner bump; Step 4: Inside the PR opening, a non-ferrous metal inner bump is obtained by electroplating or chemical transfer; Step 5: removing the resin glue to obtain the exposed seed layer and the non-ferrous metal inner bump structure; Step 6: Perform a second coating to coat a photoresist layer between the non-ferrous metal inner bumps on the surface of the wafer, wherein the thickness of the photoresist layer is greater than the height of the non-ferrous metal inner bumps; Step 7: Perform a second exposure and development to obtain a PR opening consistent with the planned outer size of the bump, forming a gap between the metal bump and the photoresist layer; Step 8: electroplating a precious metal layer in the gap to form a fully wrapped precious metal layer; Step 9: Perform a second debonding to remove the resin glue on the upper side of the seed layer on the surface of the wafer and around the bumps to obtain an exposed seed layer and a bump structure with a fully wrapped precious metal layer; Step 10: Perform etching to remove the seed layer between the bumps on the upper side of the wafer surface, obtain the exposed wafer surface and the bumps with a fully wrapped precious metal layer, and complete the production of the wrapped bump packaging structure.
8. The process for forming a wafer-level package bump package structure according to claim 7, characterized in that: When performing step 8, if the capillary effect occurs, which prevents the plating solution from entering a narrow space for electroplating, a pre-gold plating pretreatment operation such as descum or PLASMA plasma cleaning is required.