Semiconductor packaging structure and preparation method thereof

Abstract

The invention discloses a semiconductor packaging structure and a preparation method thereof. The semiconductor packaging structure comprises a copper-containing bump, the copper-containing bump comprises a copper layer and a metal layer which are arranged in a stacked mode, and the preparation method comprises the steps that a protective film layer is formed on the surface of the copper-containing bump of the semiconductor packaging structure, and the protective film layer is a Cu-N compound film layer. The Cu-N compound film layer is formed on the surface of the copper-containing bump to serve as the protective film layer, on one hand, Cu in the copper layer is prevented from being in contact with oxygen in air to be oxidized, the surface of the copper layer in the copper-containing bump is prevented from being oxidized and discolored, on the other hand, Cu atoms in the copper layer can be effectively prevented from being migrated and diffused to the surface of the metal layer, and the service life of the copper-containing bump is prolonged. According to the semiconductor packaging structure and the manufacturing method thereof, color change caused by generation of black or dark compounds such as CuO and CuS on the surface of the metal layer is prevented, so that electrical performance degradation of the semiconductor packaging structure is prevented, cavities or defects are prevented from being formed in the copper-containing bump, and uneven current distribution, generation of local hot spots and reduction of the overall mechanical strength of the copper-containing bump are prevented.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to a semiconductor packaging structure and its fabrication method. Background Technology

[0002] In semiconductor packaging, the electrical interconnect between the chip and the substrate typically uses metal bumps. Common metal bumps include copper-containing bumps and gold bumps. Among them, copper-containing bumps, which use copper as the main material, have low resistance and high thermal conductivity, and are often used in high-density interconnect applications.

[0003] Copper bumps consist of stacked copper and metal layers. As the conductive substrate, the copper layer is prone to oxidation and discoloration of Cu atoms on its surface. Furthermore, Cu atoms in the copper layer are susceptible to thermal migration under humid and hot conditions (such as post-reflow annealing in semiconductor packaging) and electromigration under electrical current. This causes Cu atoms to migrate and diffuse to the metal layer surface. O or S adsorbed on the metal layer surface combines with the diffused Cu atoms to form black or dark-colored compounds such as CuO and CuS, resulting in discoloration of the metal layer surface. Since the conductivity of these compounds is much lower than that of Cu, discoloration of the copper and metal layers means that the conductive path is occupied by high-resistivity materials, leading to increased interconnect resistance, increased signal delay, increased power consumption, and deterioration of the electrical performance of the semiconductor packaging structure. Moreover, Cu migration from the copper layer may form voids or defects inside the copper bump, causing uneven current distribution, localized hot spots, and weakening the overall mechanical strength of the copper bump. Summary of the Invention

[0004] The purpose of this application is to provide a semiconductor packaging structure and a method for fabricating the same.

[0005] To achieve at least one of the above-mentioned objectives, one embodiment of this application provides a method for fabricating a semiconductor package structure, the semiconductor package structure including copper bumps, the copper bumps including a copper layer and a metal layer stacked together, the fabrication method including:

[0006] A protective film layer is formed on the surface of copper-containing bumps in a semiconductor package structure. The protective film layer is a Cu-N composite film layer.

[0007] As a further improvement to one embodiment of this application, the preparation method includes: A reagent is prepared, wherein the chemical components of the reagent include benzotriazole, a dispersant, and water; The copper-containing bumps of the semiconductor package structure are immersed in the reagent and reacted at room temperature for 5 to 30 minutes to form the protective film layer on the surface of the copper-containing bumps.

[0008] As a further improvement of one embodiment of this application, the chemical components of the reagent include, by mass percentage: 0.5-5% benzotriazole, 1-5% dispersant, and the remainder being water.

[0009] As a further improvement of one embodiment of this application, the dispersant is selected from at least one of formaldehyde, ethanol, and acetone.

[0010] As a further improvement of one embodiment of this application, the thickness of the Cu-N composite film is 8~15nm.

[0011] As a further improvement of one embodiment of this application, the copper-containing bump is one of copper-nickel-gold bump, copper-nickel bump, copper-tin bump, and copper-nickel-tin bump.

[0012] To achieve at least one of the above-mentioned objectives, one embodiment of this application also provides a semiconductor packaging structure, which is prepared using the semiconductor packaging structure preparation method described above.

[0013] To achieve at least one of the above-mentioned objectives, one embodiment of this application also provides a semiconductor packaging structure, the semiconductor packaging structure including copper bumps and a protective film layer, the protective film layer being attached to the surface of the copper bumps, and the protective film layer being a Cu-N composite film layer.

[0014] As a further improvement of one embodiment of this application, the ratio of Cu to N atoms in the Cu-N composite film is 3:1.

[0015] As a further improvement of one embodiment of this application, the semiconductor packaging structure further includes a substrate, the copper bump includes a copper layer and a metal layer stacked together, one end of the copper layer is embedded in the substrate, the metal layer is disposed at the end of the copper layer away from the substrate, and the protective film layer is attached to the outer surface of the copper layer.

[0016] Compared with the prior art, the semiconductor packaging structure and its preparation method provided in this application form a Cu-N composite film layer as a protective film layer on the surface of the copper-containing bumps of the semiconductor packaging structure. The Cu-N composite film layer has excellent chemical stability and density. On the one hand, it prevents Cu in the copper layer from contacting oxygen in the air and oxidizing, thus avoiding oxidation and discoloration of the copper layer surface in the copper-containing bumps. On the other hand, it can effectively prevent Cu atoms in the copper layer from migrating and diffusing to the surface of the metal layer, thereby preventing the formation of black or dark-colored compounds such as CuO and CuS on the surface of the metal layer and causing discoloration. This prevents the electrical performance of the semiconductor packaging structure from deteriorating, avoids the formation of voids or defects inside the copper-containing bumps, and prevents uneven current distribution, the generation of local hot spots, and the reduction of the overall mechanical strength of the copper-containing bumps. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a semiconductor packaging structure according to an embodiment of this application; Figure 2 This is a photograph of a semiconductor packaging structure according to one embodiment of this application; Figure 3 This is a TEM image of a semiconductor packaging structure according to an embodiment of this application; Figure 4 It is along Figure 3 A partial cross-sectional view of the copper-containing bump after being cut along the x-direction; Figure 5 yes Figure 4 Enlarged view of a portion of the image; Figure 6 yes Figure 4 Energy spectrum scanning sample image; Figures 7 to 9 They are Figure 6 The surface scans of the energy spectrum show the surface distribution of different elements; Figure 10 yes Figure 6 The intensity change curves of each element on the scan line are obtained after performing a line scan on the area where the protective film layer is located. Figure 11 This is a TEM image of the semiconductor packaging structure in comparison to that in this application; Figure 12 This is a photograph of a semiconductor packaging structure that is a comparative example of this application; Figure 13 It is along Figure 11 A partial cross-sectional view of the copper-containing bump after being cut along the x-direction; Figure 14 yes Figure 13 Enlarged view of a portion of the image; Figure 15 yes Figure 13 Energy dispersive spectral surface scan of the sample in the central region; Figures 16 to 18 They are Figure 15 The energy spectrum surface scans show the surface distribution of different elements. Detailed Implementation

[0018] The present application will now be described in detail with reference to the specific embodiments shown in the accompanying drawings.

[0019] In the various figures of this application, for ease of illustration, certain dimensions of structures or parts are enlarged relative to other structures or parts; therefore, they are only used to illustrate the basic structure of the subject matter of this application.

[0020] One embodiment of this application provides a method for fabricating a semiconductor package structure 100, and a semiconductor package structure 100 fabricated using this method, such as... Figure 1 As shown.

[0021] See Figure 1 The semiconductor package structure 100 includes copper bumps 10.

[0022] The copper-containing bump 10 includes a copper layer 11 and a metal layer 12 stacked together.

[0023] The method for fabricating the semiconductor package structure 100 is described in detail below.

[0024] The method for fabricating the semiconductor package structure 100 includes: A protective film layer 20 is formed on the surface of the copper-containing bump 10 of the semiconductor package structure 100, wherein the protective film layer 20 is a Cu-N composite film layer.

[0025] By forming a Cu-N composite film as a protective film layer 20 on the surface of the copper bump 10 of the semiconductor package structure 100, the Cu-N composite film has excellent chemical stability and density. On the one hand, it prevents the Cu in the copper layer 11 from contacting oxygen in the air and oxidizing, thus avoiding oxidation and discoloration of the surface of the copper layer 11 in the copper bump 10. On the other hand, it can effectively prevent the migration and diffusion of Cu atoms in the copper layer 11 to the surface of the metal layer 12, thereby preventing the formation of black or dark-colored compounds such as CuO and CuS on the surface of the metal layer 12 and causing discoloration. This prevents the electrical performance of the semiconductor package structure 100 from deteriorating, avoids the formation of voids or defects inside the copper bump 10, prevents uneven current distribution, the generation of local hot spots, and the reduction of the overall mechanical strength of the copper bump 10.

[0026] In one embodiment, the method for fabricating the semiconductor package structure 100 includes: A reagent is prepared, wherein the chemical components of the reagent include benzotriazole (BTA), a dispersant, and water; The copper-containing bump 10 of the semiconductor package structure 100 is immersed in the reagent and reacted at room temperature for 5-30 minutes to form the protective film layer 20 on the surface of the copper-containing bump 10. The protective film layer 20 is a Cu-N composite layer.

[0027] By immersing the copper-containing bumps 10 of the semiconductor package structure 100 in the reagent, benzotriazole chemically adsorbs and coordinates with the copper on the surface of the copper layer 11 of the copper-containing bumps 10 under the action of a dispersant, forming a stable and dense Cu-N composite film. This not only prevents the Cu in the copper layer 11 from contacting oxygen in the air and oxidizing, but also effectively prevents the migration and diffusion of Cu atoms in the copper layer 11 to the surface of the metal layer 12, thereby preventing the formation of black or dark-colored compounds such as CuO and CuS on the surface of the metal layer 12 and causing discoloration. Moreover, this method is simple, requires no high temperature or complex equipment, and is suitable for large-scale production.

[0028] Immersing the copper-containing bumps 10 of the semiconductor package structure 100 into the reagent means immersing at least a portion of the copper-containing bumps 10 of the semiconductor package structure 100 into the reagent. That is, only the copper-containing bumps 10 can be immersed in the reagent, or the copper-containing bumps 10 and the rest of the semiconductor package structure 100 can also be immersed in the reagent.

[0029] In one embodiment, the chemical components of the reagent, by mass percentage, include: 0.5-5% benzotriazole, 1-5% dispersant, and the remainder being water. By controlling the ratio of benzotriazole to dispersant, not only can the reaction between benzotriazole and the copper on the surface of copper layer 11 be fully ensured to form a sufficiently stable and dense Cu-N composite film, thus improving the protective effect, but the amount of benzotriazole and dispersant can also be controlled to manage costs.

[0030] The dispersant is selected from at least one of formaldehyde, ethanol, and acetone. These dispersants have good solubility and volatility, which helps to uniformly disperse benzotriazole and ensure sufficient contact with the surface of the copper layer 11, thereby improving the film quality.

[0031] In other words, one embodiment of this application also provides a semiconductor packaging structure 100. The semiconductor packaging structure 100 includes copper bumps 10 and a protective film layer 20, the protective film layer 20 being attached to the surface of the copper bumps 10. The protective film layer 20 is a Cu-N composite film layer. The copper bumps 10 include a copper layer 11 and a metal layer 12 stacked together.

[0032] The ratio of Cu to N atoms in the Cu-N composite film is 3:1.

[0033] The semiconductor packaging structure 100 further includes a substrate 30, one end of the copper layer 11 is embedded in the substrate 30, and the metal layer 12 is disposed at the end of the copper layer 11 away from the substrate 30.

[0034] The protective film layer 20 is attached to the outer surface of the copper layer 11. That is, the Cu-N composite film layer is attached to the outer surface of the copper layer 11.

[0035] The thickness of the Cu-N composite film is 8~15 nm. In this way, the Cu-N composite film can provide sufficient protection without affecting the dimensional accuracy and electrical performance of the copper bump 10, while maintaining good process controllability.

[0036] The copper-containing bump 10 is one of copper-nickel-gold bump, copper-nickel bump, copper-tin bump, and copper-nickel-tin bump. Correspondingly, the metal layer 12 is one of nickel layer, nickel-gold layer, tin layer, and nickel-tin layer.

[0037] For example, if the copper bump 10 is a copper-nickel-gold bump, then the metal layer 12 is a nickel-gold layer. Specifically, the metal layer 12 includes a nickel layer 121 and a gold layer 122 stacked together. The copper layer 11, the nickel layer 121, and the gold layer 122 are stacked sequentially. The end of the copper layer 11 away from the nickel layer 121 is embedded in the substrate 30, and the protective film layer 20 is attached to the outer surface of the copper layer 11.

[0038] For example, if the copper bump 10 is a copper-nickel bump, then the metal layer 12 is a nickel layer, the copper layer 11 and the nickel layer are stacked, one end of the copper layer 11 is embedded in the substrate 30, the nickel layer is disposed at the end of the copper layer 11 away from the substrate 30, and the protective film layer 20 is attached to the outer surface of the copper layer 11.

[0039] For example, if the copper bump 10 is a copper-tin bump, then the metal layer 12 is a tin layer, the copper layer 11 and the tin layer are stacked, one end of the copper layer 11 is embedded in the substrate 30, the tin layer is disposed at the end of the copper layer 11 away from the substrate 30, and the protective film layer 20 is attached to the outer surface of the copper layer 11.

[0040] For example, if the copper bump 10 is a copper-nickel-tin bump, then the metal layer 12 is a nickel-tin layer. Specifically, the metal layer 12 includes a nickel layer and a tin layer stacked together, and the copper layer 11, the nickel layer, and the tin layer are stacked sequentially. The end of the copper layer 11 away from the nickel layer is embedded in the substrate 30, and the protective film layer 20 is attached to the outer surface of the copper layer 11.

[0041] See Figure 1 The substrate 30 includes a base 31, a metal pad 32, a UBM layer 33, and a passivation layer 34. The base 31 has a first surface 310 facing the copper bump 10 and a second surface 320 facing away from the copper bump 10.

[0042] Both the metal pad 32 and the passivation layer 34 are disposed on the first surface 310. The metal pad 32 covers a portion of the first surface 310, and the passivation layer 34 covers the remaining portion of the first surface 310 and a portion of the metal pad 32.

[0043] The UBM layer 33 is disposed on the surface of the metal pad 32 facing the copper bump 10, and the UBM layer 33 covers the remaining portion of the metal pad 32 and part of the passivation layer 34. The copper bump 10 is embedded in the UBM layer 33.

[0044] The orthographic projection of the UBM layer 33 on the horizontal plane falls within the orthographic projection of the copper-containing bump 10 on the horizontal plane. The UBM layer 33 includes a seed layer 331 and a barrier layer 332 stacked together, with the seed layer 331 disposed on the side of the barrier layer 332 facing the copper-containing bump 10.

[0045] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application, and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.

[0046] The beneficial effects of this application will be further illustrated below through examples and comparative examples. Of course, these examples are only a part of the many variations contained in this application, and not all of them.

[0047] Example This embodiment provides a method for preparing a semiconductor package structure 100 and the semiconductor package structure 100 prepared by the method.

[0048] The method for fabricating the semiconductor package structure 100 includes: (1) Preparation of reagent, wherein the chemical components of the reagent include, by mass percentage: 0.5-5% benzotriazole, 1-5% ethanol, and the remainder being water.

[0049] (2) Immerse the copper-containing bump 10 of the semiconductor package structure 100 in the reagent and react at room temperature for 10 minutes. See also... Figure 1 The semiconductor package structure 100 includes a substrate 30 and copper bumps 10. The copper bumps 10 are copper-nickel-gold bumps, that is, copper layer 11, nickel layer 121 and gold layer 122 are stacked in sequence, and the end of copper layer 11 away from nickel layer 121 is embedded in the substrate 30.

[0050] The prepared semiconductor package structure 100 was observed and photographed, as shown in the following figures. Figure 2 shown, since Figure 2It can be seen that the discoloration of the metal layer 12 containing copper bumps 10 is not obvious.

[0051] See Figure 3 According to TEM testing requirements, the copper-containing bump 10 was cut along the x-direction, sampled, and then embedded and cured with resin to prepare the test sample. The x-direction is the direction from the gold layer 122 to the copper layer 11. The prepared sample was observed using TEM, and the results are as follows: Figure 4 and Figure 5 As shown in the figure, it can be clearly observed that there is a continuous film layer with a thickness of about 10 nm on the surface of the copper layer 11, which is the protective film layer 20 described in this application.

[0052] See Figure 6 The prepared sample was subjected to energy dispersive spectroscopy (EDS) and the elemental distribution of the protective film 20 was analyzed. The results are as follows: Figures 7 to 9 As shown in the figure, the enrichment signals of Cu and N elements are clearly displayed. Figure 7 Since Cu is represented by purple and N by blue, the area where Cu and N overlap appears bright blue. This area is the location of the protective film 20, and the signal profile of this area matches the morphology of the protective film 20, which confirms that the protective film 20 is a Cu-N composite film.

[0053] Energy dispersive spectroscopy (EDS) was performed on the region containing the protective film layer 20, and the intensity variation curves of each element on the scan lines were analyzed, such as... Figure 10 As shown, the Cu and N signals appear synchronously and overlap. By calculating the intensity ratio of Cu to N in the overlapping region, the ratio of Cu to N atoms in the Cu-N composite film is found to be 3:1.

[0054] Comparative Example See Figure 11 This comparative example provides a semiconductor package structure 100a, which includes a substrate 30a and copper-containing bumps 10a. The copper-containing bumps 10a are copper-nickel-gold bumps, that is, copper layers, nickel layers, and gold layers are stacked sequentially, with the end of the copper layer away from the nickel layer embedded in the substrate 30a. Unlike the embodiments, the copper-containing bumps 10a in this comparative example have not undergone the reagent treatment of the embodiments.

[0055] The semiconductor package structure 100a was observed and photographed, as shown in the following figures. Figure 12 shown, since Figure 12 It can be seen that the surface of the metal layer 12a containing the copper bump 10a has undergone severe discoloration.

[0056] See Figure 11According to TEM testing requirements, the copper-containing bump 10a was also sectioned along the x-direction for sampling. The sample was then prepared using resin embedding and curing processes to obtain a test sample, where the x-direction is the direction from the gold layer to the copper layer. The prepared sample was observed using TEM, and the results are as follows: Figure 13 and Figure 14 As shown in the figure, a continuous film layer 40 with a thickness of about 15 nm can be clearly observed on the surface of the copper layer 11a.

[0057] See Figure 15 The prepared sample was subjected to energy dispersive spectroscopy (EDS) and the elemental distribution of the continuous film layer 40 was analyzed. The results are as follows: Figures 16 to 18 As shown in the figure, the enrichment signals of Cu and O elements are clearly displayed. Figure 16 In the diagram, since Cu is represented by purple and O by green, the area where Cu and O overlap appears as light gray. This area is where the continuous film layer 40 is located, and the signal profile of this area matches the morphology of the continuous film layer 40, which confirms that the continuous film layer 40 is a Cu-O compound film layer.

[0058] Comparing the embodiments and comparative examples, it can be seen that, compared with the comparative examples, the semiconductor packaging structure 100 and its preparation method of this application form a Cu-N composite film layer as a protective film layer 20 on the surface of the copper-containing bump 10 of the semiconductor packaging structure 100. On the one hand, it prevents the Cu in the copper layer 11 from contacting with oxygen in the air and oxidizing, thus avoiding oxidation and discoloration of the surface of the copper layer 11 in the copper-containing bump 10. On the other hand, it can effectively prevent the migration and diffusion of Cu atoms in the copper layer 11 to the surface of the metal layer 12, thereby preventing the formation of black or dark-colored compounds such as CuO and CuS on the surface of the metal layer 12 and causing discoloration.

[0059] The structure, features and effects of this application have been described in detail above with reference to the embodiments shown in the accompanying drawings. The above description is only a preferred embodiment of this application, but this application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments with equivalent changes, that do not exceed the spirit covered by the specification and drawings, should be within the protection scope of this application.

Claims

1. A method for fabricating a semiconductor package structure, the semiconductor package structure comprising copper bumps, the copper bumps comprising stacked copper layers and metal layers, characterized in that, The preparation method includes: A protective film layer is formed on the surface of copper-containing bumps in a semiconductor package structure. The protective film layer is a Cu-N composite film layer.

2. The method for fabricating the semiconductor packaging structure according to claim 1, characterized in that, The preparation method includes: A reagent is prepared, wherein the chemical components of the reagent include benzotriazole, a dispersant, and water; The copper-containing bumps of the semiconductor package structure are immersed in the reagent and reacted at room temperature for 5 to 30 minutes to form the protective film layer on the surface of the copper-containing bumps.

3. The method for preparing a semiconductor packaging structure according to claim 2, characterized in that, The chemical composition of the reagent, by mass percentage, includes: 0.5-5% benzotriazole, 1-5% dispersant, and the remainder is water.

4. The method for preparing a semiconductor packaging structure according to claim 2, characterized in that, The dispersant is selected from at least one of formaldehyde, ethanol, and acetone.

5. The method for fabricating a semiconductor packaging structure according to claim 1, characterized in that, The thickness of the Cu-N composite film is 8~15 nm.

6. The method for preparing a semiconductor packaging structure according to claim 1, characterized in that, The copper-containing bump is one of the following: copper-nickel-gold bump, copper-nickel bump, copper-tin bump, and copper-nickel-tin bump.

7. A semiconductor packaging structure, characterized in that, The semiconductor packaging structure is prepared by the method for preparing a semiconductor packaging structure as described in any one of claims 1 to 6.

8. A semiconductor packaging structure, characterized in that, The semiconductor packaging structure includes copper bumps and a protective film layer. The protective film layer is attached to the surface of the copper bumps and is a Cu-N composite film layer.

9. The semiconductor packaging structure according to claim 8, characterized in that, The ratio of Cu to N atoms in the Cu-N composite film is 3:

1.

10. The semiconductor packaging structure according to claim 8, characterized in that, The semiconductor packaging structure further includes a substrate, and the copper bump includes a copper layer and a metal layer stacked together. One end of the copper layer is embedded in the substrate, and the metal layer is disposed at the end of the copper layer away from the substrate. The protective film layer is attached to the outer surface of the copper layer.

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