Disclosure of Invention
The main purpose of the present application is to provide a novel acid copper leveling agent, which is used as a component in an electroplating additive to solve the problem of poor thermal, mechanical and electrical reliability of chip packaging caused by the formation of kirkendall holes when tin-silver or pure tin is electroplated on a copper layer obtained by copper electroplating in the chip packaging process in the prior art.
In order to achieve the above object, according to a first aspect of the present application, there is provided a copper acid leveler.
The molecular structural formula of the copper acid leveler according to the present application is:
wherein X is Cl, Br, I; a. the1,A2,A3,A4Is one or more of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aralkyl and substituted or unsubstituted heteroaralkyl; b is1,B2,B3,B4Is one or two of H, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aralkyl, substituted or unsubstituted heteroaralkyl, substituted or unsubstituted five-membered ring, substituted or unsubstituted five-membered heterocycle, substituted or unsubstituted six-membered ring and substituted or unsubstituted six-membered heterocycle; r is O or S; n is 1-10000.
Further, the molecular structural formula of the copper acid leveling agent is as follows:
in order to achieve the above object, according to a second aspect of the present application, there is provided a use of the above-mentioned acid copper leveler for electrolytic copper plating to suppress formation of kokedahl pores when tin-silver or pure tin is electroplated on a copper layer obtained by the electrolytic copper plating.
Further, the acid copper leveler is used to plate copper pillars, redistribution layers, or under bump metallization layers in semiconductor advanced packaging.
In order to achieve the above object, according to a third aspect of the present application, there is provided a copper electroplating solution comprising a base plating solution and an electroplating additive, the electroplating additive comprising the above-mentioned acid copper leveler.
Further, the basic electroplating solution is a mixed solution prepared by mixing copper sulfate, sulfuric acid and hydrochloric acid, wherein the dosage of the copper sulfate in the basic electroplating solution is 200g/L, the dosage of the sulfuric acid is 100g/L, and the dosage of the hydrochloric acid is 70 ppm.
Further, the electroplating additive comprises an acid copper accelerator, an acid copper inhibitor and an acid copper leveling agent, wherein in the copper electroplating solution, the concentration of the acid copper accelerator is 3-10 mL/L, the concentration of the acid copper inhibitor is 5-15 mL/L, and the concentration of the acid copper leveling agent is 2-50 mL/L.
Further, the acid copper accelerator is sodium polydithio-dipropyl sulfonate.
Further, the acid copper inhibitor is polyethylene glycol.
In order to achieve the above object, according to a fourth aspect of the present application, there is provided a method of preparing the above copper electroplating solution, comprising the steps of: preparing a basic electroplating solution; weighing the acid copper accelerator, the acid copper inhibitor and the acid copper leveling agent, diluting with deionized water respectively, and fixing the volume to obtain an acid copper accelerator solution, an acid copper inhibitor solution and an acid copper leveling agent solution; and adding the acid copper accelerator solution, the acid copper inhibitor solution and the acid copper leveling agent solution into the prepared basic electroplating solution, and fully stirring and mixing to obtain the copper electroplating solution.
The application has the following beneficial effects:
on the basis of being different from the traditional acid copper leveling agent, the novel acid copper leveling agent molecule which has better water solubility, is colorless, nontoxic and environment-friendly is designed and developed, has the structural characteristic of polyquaternary ammonium salt and is used as a component in an electroplating additive in the process of copper electroplating, so that the formation of a Korkinje hole is inhibited when tin-silver or pure tin is electroplated on a copper layer obtained by the copper electroplating, and the thermal, mechanical and electrical reliability of chip packaging is improved.
Detailed Description
In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It should be noted that the term "comprises/comprising" when used in this specification and claims and in the above-described drawings is intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. It should also be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The embodiment of the application provides a copper acid leveling agent, the molecular structural formula of which is shown in figure 1,
wherein X is Cl, Br, I; a. the1,A2,A3,A4Is one or more of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aralkyl and substituted or unsubstituted heteroaralkyl; b is1,B2,B3,B4Is one or two of H, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aralkyl, substituted or unsubstituted heteroaralkyl, substituted or unsubstituted five-membered ring, substituted or unsubstituted five-membered heterocycle, substituted or unsubstituted six-membered ring and substituted or unsubstituted six-membered heterocycle; r is O or S; n is 1-10000.
Preferably, the present application provides a copper acid leveler K according to a preferred embodiment of the above copper acid leveler, wherein the molecular structural formula of the copper acid leveler K is shown in fig. 2:
the present embodiments also provide a copper electroplating solution including a base electroplating solution and an electroplating additive including a copper acid leveler as shown in fig. 1 or fig. 2. Specific examples of copper electroplating solutions are given below.
Example 1
A copper electroplating solution includes a base electroplating solution and an electroplating additive.
The basic electroplating solution is a mixed solution prepared by mixing copper sulfate, sulfuric acid and hydrochloric acid, wherein the dosage of the copper sulfate in the basic electroplating solution is 200g/L, the dosage of the sulfuric acid is 100g/L, and the dosage of the hydrochloric acid is 70 ppm.
The electroplating additive comprises sodium polydithio-dipropyl sulfonate (SPS), polyethylene glycol (PEG) and a copper acid leveling agent K, wherein the concentration of the SPS in the copper electroplating solution is 3mL/L, the concentration of the PEG is 5mL/L, and the concentration of the copper acid leveling agent K is 2 mL/L.
Example 2
A copper electroplating solution includes a base electroplating solution and an electroplating additive.
The basic electroplating solution is a mixed solution prepared by mixing copper sulfate, sulfuric acid and hydrochloric acid, wherein the dosage of the copper sulfate in the basic electroplating solution is 200g/L, the dosage of the sulfuric acid is 100g/L, and the dosage of the hydrochloric acid is 70 ppm.
The plating additive comprises sodium polydithio-dipropyl sulfonate (SPS), polyethylene glycol (PEG) and a copper acid leveling agent K, wherein the concentration of the SPS in the copper plating solution is 10mL/L, the concentration of the PEG is 15mL/L, and the concentration of the copper acid leveling agent K is 50 mL/L.
Example 3
A copper electroplating solution includes a base electroplating solution and an electroplating additive.
The basic electroplating solution is a mixed solution prepared by mixing copper sulfate, sulfuric acid and hydrochloric acid, wherein the dosage of the copper sulfate in the basic electroplating solution is 200g/L, the dosage of the sulfuric acid is 100g/L, and the dosage of the hydrochloric acid is 70 ppm.
The electroplating additive comprises sodium polydithio-dipropyl sulfonate (SPS), polyethylene glycol (PEG) and a copper acid leveling agent K, wherein the concentration of the SPS in the copper electroplating solution is 4mL/L, the concentration of the PEG is 10mL/L, and the concentration of the copper acid leveling agent K is 4 mL/L.
The method for preparing a copper plating solution according to embodiments 1 to 3, comprising the steps of:
(1) diluting the copper sulfate solution with the calculated amount of 280g/L by using ionized water, slowly adding the sulfuric acid and the hydrochloric acid with the calculated amount into the copper sulfate solution, stirring the mixture until the volume is 1L, and taking 500mL of the mixture to a beaker for later use;
(2) weighing SPS, PEG and a copper sulfate leveling agent K, diluting with deionized water respectively, and fixing the volume in a 50mL volumetric flask to obtain an SPS solution, a PEG solution and a copper sulfate leveling agent K solution for later use;
(3) and (3) adding the calculated amounts of the SPS solution, the PEG solution and the acid copper leveling agent K solution into the beaker in the step (1), and fully stirring for 30min at the rotating speed of 350rpm to obtain the copper electroplating solution.
According to the method, through a large number of experiments, on the basis of being different from the traditional copper acid leveling agent, a novel copper acid leveling agent molecule which is good in water solubility, colorless, non-toxic and environment-friendly is designed and developed, and through the matched use of the copper acid leveling agent and a copper acid accelerator and a copper acid inhibitor, the good electroplating performances of a copper column, a redistribution layer (RDL), a under bump metallization layer (UBM) and the like in the advanced packaging of a semiconductor are realized. The effect of the copper acid leveler provided in the present application will be demonstrated by the following experimental examples in conjunction with the accompanying drawings.
Experimental example: experiment of using effect of acid copper leveling agent K on wafer electroplated copper column
Firstly, electroplating equipment: a direct current power supply.
II, experimental grouping:
the wafer is plated with copper posts using a copper plating solution.
1. Experimental groups: the copper plating solution of example 3 was used
2. Control group: the copper electroplating solution of example 3 wherein a 4mL/L concentration of the copper acid leveler K was replaced with a 20mL/L concentration of the commercially available leveler.
Thirdly, setting electroplating parameters:
1. anode: a phosphor copper anode plate;
2. cathode: a wafer (2X 2cm 2);
3. current density and current magnitude: 10ASD, 45.68 mA;
4. electroplating time: 15min
5. Stirring speed: 350rpm
Fourth, experimental results
The results of the copper pillar plating on the wafer in this example are shown in table 1.
TABLE 1 wafer copper pillar electroplating experimental results
Grouping
|
Diameter of copper cylinder (mum)
|
Plating height (μm)
|
Morphology of copper pillar
|
Experimental group
|
30
|
41.6
|
Flat 0.4 μm
|
Control group
|
30
|
34.9
|
Concave 2.2 mu m |
FIG. 3a shows a 3D laser microimaging of copper pillars on an experimental set of plated wafers, and FIG. 3b shows a profile view of 3 a; accordingly, fig. 4a shows a 3D laser microimaging of copper pillars on control plated wafers, and fig. 4b is a profile view of fig. 4 a.
As can be seen from the experimental results shown in table 1, fig. 3a, fig. 3b, fig. 4a, and fig. 4b, the use of the copper leveling agent provided in the present application can significantly improve the flatness of the copper pillar surface.
Further, FIG. 3c shows FIB pictures of pure tin electroplated on the electroplated copper columns of the experimental group after heat treatment at 175 ℃/1000 h; accordingly, FIG. 4c shows a FIB picture of pure tin electroplated on the electroplated copper column of the control group after heat treatment at 175 ℃/1000 h.
As can be seen from FIGS. 3c and 4c, the formation of Cokendall pores in the Cu-Sn interfacial layer can be significantly suppressed by using the Cu-acid leveler provided herein.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.