CN118272879A - An accelerator for chip packaging electroplated copper filling process and electroplated copper electrolyte - Google Patents

Abstract

The present invention belongs to the field of chip packaging technology, and discloses an accelerator and an electroplated copper electrolyte for a chip packaging electroplated copper filling process. The electroplated copper electrolyte provided by the present invention contains an accelerator, and the accelerator is centered on a disulfide bond, and a benzothiazole structure is introduced symmetrically in space, and a sulfonic acid group is introduced at both ends of the molecular chain to obtain a structure having a sulfonic acid group, a disulfide bond, and a benzothiazole structure. While ensuring good water solubility, N+, S atoms, and thiazole rings in the accelerator can be used as active sites to adsorb the accelerator on the copper surface, and the sulfonic acid groups at both ends of the molecule can better cooperate with chloride ions to accelerate the deposition of copper ions. Compared with traditional accelerators, the accelerator of the present invention does not contain sodium ions, and avoids the influence of subsequent sealing and testing processes on the transmission of electrical signals. The electroplating solution configured with the accelerator provided by the present invention can meet the filling of through holes with a depth-to-width ratio exceeding 1, meet the requirements of advanced packaging, and have broad application prospects.

Description

An accelerator and copper electrodeposition electrolyte for chip packaging copper electrodeposition filling process

Technical Field

The invention relates to the technical field of chip packaging, and relates to a novel electroplating copper additive and application thereof, and in particular to an accelerator and an electroplating copper electrolyte for a chip packaging electroplating copper filling process.

Background technique

Integrated circuits (ICs) were developed in the 1960s. As the size of transistors continued to shrink, they evolved from small-scale integrated circuits (SSI), medium-scale integrated circuits (MSI), large-scale integrated circuits (LSI), to ultra-large-scale integrated circuits (ULSI). Whether it is a single transistor or an integrated circuit, it must be packaged to function. Packaging is the basis of system integration.

In the electronic circuit and electronic component manufacturing industry chain, electroplated copper plays a key role in modern electronic industry applications due to its high reliability, productivity and low cost advantages, while meeting the transmission characteristics of electricity and heat. Therefore, gap filling using electroplated copper has become an indispensable technology, widely used in the metallization of high-density interconnections in integrated circuits, as well as the filling of microvias in printed circuit boards and silicon through-holes in chip packaging. Additives are an important component of the electroplating solution and play an irreplaceable role in the electroplating process. Additives can effectively improve the current distribution during the electroplating process, improve the all-plating ability of the plating solution, affect the transportation and electrocrystallization process of copper ions from the solution body to the reaction interface, and thus change the electrochemical deposition rate of the micro-concave and micro-convex parts of the board surface.

Electroplating copper additives generally include accelerators, inhibitors and levelers. According to the convection-dependent adsorption (CDA) mechanism, the most widely used accelerators are sodium polydisulfide propane sulfonate (SPS) and 3-mercapto-1-propane sulfonate (MPS), which can enhance the copper deposition rate at the bottom of the hole. Inhibitors are mainly macromolecules with polyethers, such as polyethylene glycol (PEG), polypropylene glycol (PPG) or triblock copolymers of PEG and PPG. Inhibitors can usually inhibit the deposition of copper at the pore mouth in the presence of chloride ions. Levelers in copper electrodeposition are usually small molecule nitrogen-containing heterocyclic compounds, quaternary ammonium salts or polymers, and the most commonly used is Janus Green B (JGB).

At present, the acid sulfate copper plating system is selected for chip copper interconnection, and the key to acid sulfate copper plating is the selection and use of additives. The existing accelerators are mainly sodium salts containing sulfonic acid groups. Studies have shown that the thiol group (-SH) at the front end of the SPS molecule and the sulfonate ion (SO ₃ ^- ) at the end are two key functional groups for acceleration in the presence of chloride ions (Cl ^- ), and the interaction between the sulfonate ion and the chloride ion can accelerate the reduction of copper ions. However, the above accelerators still have shortcomings: first, the acceleration effect is not obvious, and the amount of accelerator added is large; second, the existing accelerators contain sodium ions. During the chip processing process, sodium ions have strong penetration ability and are very easy to penetrate into the chip, affecting the chip's electrical signal transmission and causing poor chip performance.

Therefore, it is urgent to develop an accelerator for the chip packaging electroplating copper filling process that will not affect the electrical signal transmission of the chip.

Summary of the invention

The present invention aims to provide an accelerator and an electrolytic copper deposition electrolyte for a chip packaging electrolytic copper filling process, so as to solve the technical problem that the accelerator used in the prior art for the chip packaging electrolytic copper filling process easily penetrates into the chip due to the presence of sodium ions, thus affecting the electrical signal transmission of the chip and causing poor chip performance.

In order to achieve the above object, the present invention provides the following technical solutions:

The present invention provides an accelerator for a chip packaging electroplated copper filling process, and the structural formula of the accelerator is as follows:

Furthermore, the accelerator is specifically obtained by introducing a benzothiazole structure with spatial symmetry around a disulfide bond and introducing sulfonic acid groups at both ends of the molecular chain. The molecular weight of the accelerator is 520.

Principle of the technical solution: Since the above-mentioned accelerator has sulfonic acid group, disulfide bond and benzothiazole structure at the same time, while ensuring good water solubility, the N+, S atoms and thiazole ring in the accelerator can be used as active sites to make the above-mentioned accelerator adsorbed on the copper surface, and the benzene heterocyclic structure can significantly reduce the internal stress between the molecules of the coating, thereby enabling the sulfonic acid groups at both ends of the accelerator molecules to better cooperate with chloride ions to accelerate the deposition of copper ions, significantly improving the copper deposition rate.

The present invention also provides an electroplated copper electrolyte for a chip packaging electroplated copper filling process. The electroplated copper electrolyte comprises an additive, and the additive comprises the accelerator in claim 1 or claim 2.

Furthermore, the addition amount of the accelerator is 5 to 50 ppm.

Furthermore, the additives also include inhibitors and levelers.

Furthermore, the inhibitor is polyethylene glycol, and the molecular weight of the inhibitor is 5000-10000.

Furthermore, the leveling agent is thiamine or thiourea.

Furthermore, the added amount of the inhibitor is 50 to 200 ppm.

Furthermore, the added amount of the leveling agent is 0.1 to 1 ppm.

Furthermore, the copper electrodeposition electrolyte also includes CuSO ₄ , H ₂ SO ₄ and chloride ions; the addition amount of the CuSO ₄ is 180-240 g/L, the addition amount of the H ₂ SO ₄ is 45-80 g/L, and the addition amount of the chloride ions is 50-70 ppm.

In summary, the present invention has the following beneficial effects:

1. The copper deposition accelerator provided by the present invention is centered on a disulfide bond, spatially symmetrically introduces a benzothiazole structure, and introduces sulfonic acid groups at both ends of the molecular chain, so it has a sulfonic acid group, a disulfide bond and a benzothiazole structure at the same time; while ensuring good water solubility, the N+, S atoms and thiazole rings in the accelerator can be used as active sites to make the accelerator adsorbed on the copper surface, and the benzene heterocyclic structure can significantly reduce the internal stress between the molecules of the coating, thereby enabling the sulfonic acid groups at both ends of the accelerator molecules to better cooperate with chloride ions to accelerate the deposition of copper ions.

2. The experimental results of the test experiments of the present invention show that the electroplating solution configured with the accelerator provided by the present invention can meet the filling of through holes with an aspect ratio exceeding 1, which meets the requirements of advanced packaging; secondly, since the electroplating solution prepared by the present invention does not contain sodium ions, during the chip processing process, sodium ions can be prevented from penetrating the chip, affecting the transmission of electrical signals of the chip, causing poor chip performance and other problems. Therefore, the electroplating solution provided by the present invention has broad application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a metallographic microscope image of wafer electroplated microholes in Example 1 of the present invention;

FIG2 is a FE SEM morphology of copper deposited on the surface of wafer micropores in Example 1 of the present invention;

FIG3 is a metallographic microscope image of wafer electroplated microholes in Example 2 of the present invention;

FIG4 is a metallographic microscope image of wafer electroplated microholes in Example 3 of the present invention;

FIG5 is a metallographic microscope image of the electroplated microholes of the wafer in Comparative Example 1 of the present invention;

FIG. 6 is a metallographic microscope image of the electroplated microholes of the wafer in Comparative Example 2 of the present invention.

Detailed ways

The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

In the electroplating process described in the following examples, the electroplating copper electrolyte uses an additive containing an accelerator. The accelerator is obtained by introducing a benzothiazole structure with a disulfide bond as the center, spatially symmetrically, and introducing sulfonic acid groups at both ends of the molecular chain. The molecular weight is 520. The chemical structure of the accelerator is as follows:

Embodiment 1:

The copper electroplating process of this embodiment includes the following steps:

Step S1, preparing a copper sulfate pentahydrate aqueous solution, adding sulfuric acid, adding chloride ions and additives (leveling agent (thiamine), inhibitor PEG (molecular weight of 5000) and accelerator) to obtain an electroplating solution;

The specific process is as follows: 220 g of copper sulfate pentahydrate is dissolved in 1 L of deionized water, 30.5 ml of sulfuric acid is slowly added, chloride ions, thiamine and an accelerator are added, so that the concentration of chloride ions is 55 ppm, the concentration of thiamine is 1 ppm, the concentration of the inhibitor PEG is 100 ppm and the concentration of the accelerator is 30 ppm, and an electroplating solution is obtained;

Step S2, ethanol pretreated wafer slices (2*2 cm) to obtain ethanol pretreated test plates;

The specific process is: soak the wafer slices in ethanol for 3-5 minutes to remove the contaminants on the slices, and then rinse with deionized water to ensure that the contaminants are rinsed clean to obtain ethanol pretreated slices;

Step S3, soaking the pre-treated wafer slices in the electroplating solution prepared in step S1 for 10 minutes.

Step S4, using the pre-treated wafer slice as a cathode and the phosphorus-containing copper plate as an anode to complete electroplating in an electroplating solution;

The specific process is: pour the electroplating solution prepared in step S1 into a beaker, then put the pretreated wafer slice in step S2 into the electrolytic cell as the cathode, and the phosphorus copper plate as the anode, and stir stably in a magnetic stirrer at a speed of 400r/min, and pass direct current to the cathode and the anode, first use 1AS electroplating for 60s to pre-plate a copper seed layer, then use 5ASD to plate for 300s, and finally use 10ASD to plate for 40min. The metallographic image of the micropore section of the electroplated wafer is shown in Figure 1, and the FE-SEM morphology of the electroplated wafer surface is shown in Figure 2.

Embodiment 2:

The copper electroplating process of this embodiment includes the following steps:

Step S1, preparing a copper sulfate pentahydrate aqueous solution, adding sulfuric acid, adding chloride ions and additives (leveling agent (thiourea), inhibitor PEG (molecular weight of 10000) and accelerator) to obtain an electroplating solution;

The specific process is: dissolve 180g of copper sulfate pentahydrate in 1L of deionized water, slowly add 26ml of sulfuric acid, add chloride ions, thiourea and accelerator, so that the concentration of chloride ions is 50ppm, the concentration of thiourea is 0.2ppm, the concentration of inhibitor PEG is 200ppm and the concentration of accelerator is 10ppm, and the electroplating solution is obtained.

Step S2, ethanol pretreated wafer slices (2*2 cm) to obtain ethanol pretreated test plates;

The specific process is: soak the wafer slices in ethanol for 3-5 minutes to remove contaminants from the slices, then rinse with deionized water to ensure that the contaminants are rinsed clean to obtain ethanol pretreated slices.

Step S3, soaking the pre-treated wafer slices in the electroplating solution obtained in step S1 for 10 minutes.

Step S4, using the pre-treated wafer slice as a cathode and the phosphorus-containing copper plate as an anode to complete electroplating in an electroplating solution;

The specific process is as follows: pour the electroplating solution into a beaker, place the pretreated wafer slices into the electrolytic cell as the cathode, and the phosphorus copper plate as the anode. The magnetic stirring speed is 400r/min, and stable stirring is performed. Direct current is applied to the cathode and anode. First, a copper seed layer is pre-plated with 1ASD electroplating for 60s, followed by 5ASD electroplating for 300s, and then 10ASD electroplating for 40min. The metallographic image of the electroplated wafer micropore section is shown in 3.

Embodiment 3:

The copper electroplating process of this embodiment includes the following steps:

Step S1, preparing a copper sulfate pentahydrate aqueous solution, adding sulfuric acid, adding chloride ions and additives (leveling agent (thiamine), inhibitor PEG (molecular weight 8000) and accelerator) to obtain an electroplating solution;

The specific process is: dissolve 240g of copper sulfate pentahydrate in 1L of deionized water, slowly add 42ml of sulfuric acid, add chloride ions, thiamine and accelerator, so that the concentration of chloride ions is 70ppm, the concentration of thiamine is 0.5ppm, the concentration of inhibitor PEG is 60ppm and the concentration of accelerator is 50ppm, and the electroplating solution is obtained.

Step S2, ethanol pretreated wafer slices (2*2 cm) to obtain ethanol pretreated test plates;

The specific process is: soak the wafer slices in ethanol for 3-5 minutes to remove contaminants from the slices, then rinse with deionized water to ensure that the contaminants are rinsed clean to obtain ethanol pretreated slices.

Step S3, soaking the pre-treated wafer slices in the electroplating solution obtained in step S1 for 10 minutes.

Step S4, using the pre-treated wafer slice as a cathode and the phosphorus-containing copper plate as an anode to complete electroplating in an electroplating solution;

The specific process is: pour the plating solution into a beaker, put the pretreated wafer slices into the electrolytic cell as the cathode, and the phosphorus copper plate as the anode. The magnetic stirring speed is 400r/min, and stable stirring is performed. Direct current is applied to the cathode and anode. First, 1ASD electroplating is performed for 60s to pre-plate a copper seed layer, followed by 5ASD plating for 300s, and then 10ASD plating for 40min. The metallographic image of the electroplated wafer micropore section is shown in Figure 4.

As can be seen from Figures 1 to 4, by using the accelerator and copper electroplating process provided by the present invention, blind hole copper electroplating filling without gaps or voids can be obtained, and the surface of the coating is bright and smooth, which can be widely used in the metallization of high-density interconnection of integrated circuits and micro-hole filling of printed circuit boards, and has better stability and reliability.

Comparative Example 1:

This comparative example provides a copper electroplating process using PSP as an accelerator, comprising the following steps:

Step S1, preparing a copper sulfate pentahydrate aqueous solution, adding sulfuric acid, adding chloride ions and additives (leveling agent (thiamine), inhibitor PEG (molecular weight 5000) and accelerator PSP) to obtain an electroplating solution;

The specific process is: dissolve 220g of copper sulfate pentahydrate in 1L of deionized water, slowly add 30.5ml of sulfuric acid, add chloride ions, thiamine and accelerator, so that the concentration of chloride ions is 55ppm, the concentration of thiamine is 1ppm, the concentration of inhibitor PEG is 100ppm and the concentration of accelerator PSP is 30ppm, and obtain the electroplating solution.

Step S2, ethanol pretreated wafer slices (2*2 cm) to obtain ethanol pretreated test plates;

The specific process is: soak the wafer slices in ethanol for 3-5 minutes to remove contaminants from the slices, then rinse with deionized water to ensure that the contaminants are rinsed clean to obtain ethanol pretreated slices.

Step S3, soaking the wafer slices pretreated in step S2 in the electroplating solution prepared in step S1 for 10 minutes.

Step S4, using the wafer slice pretreated in step S2 as a cathode and the phosphorus-containing copper plate as an anode to complete electroplating in an electroplating solution;

The specific process is: pour the electroplating solution prepared in step S1 into a beaker, then put the wafer slices pretreated in step S2 into an electrolytic cell as a cathode, and a phosphorus copper plate as an anode, and stir them stably in a magnetic stirrer at a speed of 400r/min, and pass direct current to the cathode and the anode, first use 1ASD to electroplate a copper seed layer for 60s, then use 5ASD to plate for 300s, and finally use 10ASD to plate for 25min. The metallographic image of the micropore section of the wafer after electroplating is shown in Figure 5. It can be seen from Figure 5 that the growth mode of the electroplated copper is super thick deposition (V-type growth).

Comparative Example 2:

This comparative example provides a copper electroplating process without adding an accelerator, comprising the following steps:

Step S1, preparing a copper sulfate pentahydrate aqueous solution, adding sulfuric acid, adding a chloride ion additive (a leveling agent (thiamine) and an inhibitor PEG) to obtain an electroplating solution;

The specific process is: dissolve 220g of copper sulfate pentahydrate in 1L of deionized water, slowly add 30.5ml of sulfuric acid, add chloride ions and thiamine, so that the concentration of chloride ions is 55ppm, the concentration of thiamine is 1ppm, and the concentration of inhibitor PEG is 100ppm to obtain an electroplating solution.

Step S2, ethanol pretreated wafer slices (2*2 cm) to obtain ethanol pretreated test plates;

The specific process is: soak the wafer slices in ethanol for 3-5 minutes to remove contaminants from the slices, then rinse with deionized water to ensure that the contaminants are rinsed clean to obtain ethanol pretreated slices.

Step S3, soaking the wafer slices pretreated in step S2 in the electroplating solution prepared in step S1 for 10 minutes.

Step S4, using the wafer slice obtained after pretreatment in step S2 as a cathode and the phosphorus-containing copper plate as an anode to complete electroplating in an electroplating solution;

The specific process is: pour the electroplating solution prepared in step S1 into a beaker, put the wafer slices pretreated in step S2 into an electrolytic cell as a cathode, and a phosphorus copper plate as an anode, and stir them stably in a magnetic stirrer at a speed of 400r/min, and pass direct current to the cathode and the anode, first use 1ASD to electroplate a copper seed layer for 60s, then use 5ASD to plate for 300s, and finally use 10ASD to plate for 40min. The blind hole metallographic image of the electroplated test board is shown in Figure 6. It can be seen from Figure 6 that the micropore filling effect of the wafer of the test board electroplated in the electroplating solution without adding an accelerator is not good, the surface is protruding and there are defects.

In summary, the electroplating solution prepared by the accelerator provided by the present invention is applied to the copper electroplating process to obtain blind hole copper plating filling without gaps and voids, and the surface of the plated layer is bright and smooth; it can be widely used in the metallization of high-density interconnection of integrated circuits and micro-hole filling of printed circuit boards, and has better stability and reliability than the prior art.

The above is only an embodiment of the present invention, and the common knowledge such as the specific technical scheme or characteristics known in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical scheme of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims (10)

1. An accelerator for chip packaging electroplated copper filling process, characterized in that the structural formula of the accelerator is as follows: 2. An accelerator for chip packaging electroplated copper filling process according to claim 1, characterized in that the accelerator is obtained by introducing a benzothiazole structure with spatial symmetry around a disulfide bond and introducing sulfonic acid groups at both ends of the molecular chain, and the molecular weight of the accelerator is 520. 3. An electrolytic copper deposition electrolyte for a chip packaging electrolytic copper filling process, characterized in that the electrolytic copper deposition electrolyte comprises an additive, and the additive comprises the accelerator described in claim 1 or claim 2. 4. The copper electrodeposition electrolyte for the copper electrodeposition filling process of chip packaging according to claim 3, characterized in that the addition amount of the accelerator is 5 to 50 ppm. 5. The copper electrodeposition electrolyte for the copper electrodeposition filling process of chip packaging according to claim 4, characterized in that the additive further comprises an inhibitor and a leveler. 6. The copper electrodeposition electrolyte for the copper electrodeposition filling process of chip packaging according to claim 5, characterized in that the inhibitor is polyethylene glycol, and the molecular weight of the inhibitor is 5000-10000. 7. The copper electrodeposition electrolyte for the copper electrodeposition filling process of chip packaging according to claim 5, characterized in that the leveling agent is thiamine or thiourea. 8. The copper electrodeposition electrolyte for the copper electrodeposition filling process of chip packaging according to claim 5 or 6, characterized in that the added amount of the inhibitor is 50-200 ppm. 9. The copper electrodeposition electrolyte for the copper electrodeposition filling process of chip packaging according to claim 5, 6 or 7, characterized in that the added amount of the leveling agent is 0.1-1 ppm. 10. An electrolytic copper deposition electrolyte for a chip packaging electrolytic copper filling process according to claim 3, 4, 6 or 7, characterized in that the electrolytic copper deposition electrolyte further comprises CuSO ₄ , H ₂ SO ₄ and chloride ions; The addition amount of the CuSO ₄ is 180-240 g/L, the addition amount of the H ₂ SO ₄ is 45-80 g/L, and the addition amount of the chloride ion is 50-70 ppm.