CN114959814A - Method for quickly electroplating high-conductivity and high-heat-conductivity copper layer - Google Patents

Abstract

The invention relates to a copper electroplating process, in particular to a method for rapidly electroplating a copper layer with high electrical conductivity and high thermal conductivity, which is used to solve the problem of low production capacity and high cost of copper layer preparation due to the slow deposition rate of the existing pulse electroplating copper layer method. deficiencies. The method for rapidly electroplating a copper layer with high electrical conductivity and high thermal conductivity adopts bipolar pulse electroplating, and divides the electroplating process into three stages. The third stage adopts the copper particle accumulation layer and dense filling layer formed on the adhesion dense layer with high current density; the invention can realize the rapid deposition of the copper layer, and the electrical properties of the deposited copper layer are close to pure copper, and the copper layer is improved. The production capacity is reduced, and the production cost is reduced.

Description

A method for rapid electroplating of copper layer with high electrical conductivity and high thermal conductivity

technical field

The invention relates to a copper electroplating process, in particular to a method for rapidly electroplating a copper layer with high electrical conductivity and high thermal conductivity.

Background technique

Electroplated copper layer is widely used in semiconductor devices and photovoltaic products as a material with high electrical conductivity and high thermal conductivity, and has a high cost performance. The common method of electroplating copper layer is pulse electroplating. The principle is to use the relaxation of current (or voltage) pulse to increase the activation polarization of the cathode and reduce the concentration polarization of the cathode; are deposited; when the current is turned off, the discharge ions around the cathode return to the initial concentration; such a cycle of continuous and repeated pulse current is mainly used for the reduction of metal ions, thereby improving the physical and chemical properties of the coating. During the electroplating process, with the increase of the current density, the resistivity of the copper layer will first decrease sharply and then slowly increase. This is because the copper electrocrystallization nucleates instantaneously at low current density, the number of surface nucleation is small, and the grains are relatively nucleated. As the current density increases, the number of crystal nuclei increases, but the crystal grain diameter is small, which is not conducive to interconnection. Therefore, the current pulse plating method usually adopts a current density of 2-4A/dm ² , but at this current density The lower deposition rate of the copper layer results in lower productivity and higher cost of electroplated copper layers.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the shortcomings of the existing pulse electroplating copper layer method due to the slow deposition rate resulting in low copper layer production capacity and high cost, and to provide a rapid electroplating method for high electrical conductivity and high thermal conductivity copper layer.

In order to solve the deficiencies existing in the above-mentioned prior art, the present invention provides the following technical solutions:

A method for rapidly electroplating a copper layer with high electrical conductivity and high thermal conductivity is special in that it includes the following steps:

Step 1, prepare a composite electroplating solution;

The composite electroplating solution includes metal copper ions and metal copper particles, and the metal copper particles are uniformly suspended in the composite electroplating solution; the composite electroplating solution is acidic;

Step 2, electroplating copper layer;

Using bipolar pulse electroplating, the positive electrode of the constant current power supply is electrically connected to the metal copper, and the negative electrode is electrically connected to the precursor to be plated, and the precursor to be plated is plated with a seed layer; the metal copper and the precursor to be plated are placed on the in the composite electroplating solution prepared in step 1;

The temperature of the composite electroplating solution is controlled to be 25°C to 80°C, and the composite electroplating solution is stirred;

Set constant current power supply parameters, quickly electroplating copper layer with high electrical conductivity and high thermal conductivity;

The electroplating process is divided into three stages, and the constant current power supply parameters of the three stages are:

In the first stage, the current density is 0.5～2A/dm ² , the forward current pulse duty ratio is 30%～70%, the reverse current pulse duty ratio is 0%～20%, and the electroplating time is 60s;

In the second stage, the current density is set to 2～5A/dm ² , the forward current pulse duty ratio is 30%～70%, the reverse current pulse duty ratio is 0%～20%, and the electroplating time is 120s;

In the third stage, the current density is set to 17-20A/dm ² , the forward current pulse duty ratio is 30%-70%, the reverse current pulse duty ratio is 0%-20%, and the electroplating time is 200s-600s.

Further, in step 2, the electroplating process is divided into three stages, and the constant current power supply parameters of the three stages are:

In the first stage, the current density is 2A/dm ² , the forward current pulse duty cycle is 70%, the reverse current pulse duty cycle is 0%, and the electroplating time is 60s;

In the second stage, the current density is set to 5A/dm ² , the forward current pulse duty cycle is 70%, the reverse current pulse duty cycle is 20%, and the plating time is 120s;

In the third stage, the current density was set to 17.7 A/dm ² , the duty cycle of the forward current pulse was 70%, the duty cycle of the reverse current pulse was 20%, and the electroplating time was 200s.

Further, in step 1, the composite electroplating solution includes copper sulfate pentahydrate (CuSO4·5H2O), and the mass ratio between copper sulfate pentahydrate and metal copper particles is 5:1.

Further, in step 1, the diameter of the metal copper particles is 0.1-20 μm; the smaller diameter of the metal copper particles will increase the cost, and the excessively large diameter of the metal copper particles will weaken the adsorption force.

Further, in step 1, the composite electroplating solution further includes sodium hypophosphite, sodium citrate, disodium EDTA, and thiourea, and the pH of the composite electroplating solution is 5.

Further, in step 2, the seed layer is prepared by a physical vacuum method or an electroless plating method, the seed layer is a copper layer or a nickel layer or a chromium layer or a nickel-chromium alloy layer, and the thickness of the seed layer is 0.1-10 μm; Electroplating provides a conductive layer.

Further, in step 2, the precursor to be plated is a heterojunction cell or a silicon matrix cell provided with a transparent conductive layer.

Compared with the prior art, the beneficial effects of the present invention are:

The present invention is a method for rapidly electroplating a copper layer with high electrical conductivity and high thermal conductivity, which adopts bipolar pulse electroplating, and divides the electroplating process into three stages, wherein the first stage and the second stage are formed on the surface of the seed layer by using low current density In the third stage, a copper particle accumulation layer and a dense filling layer formed on the adhesion dense layer with high current density are used; the invention can realize the rapid deposition of the copper layer, and the electrical properties of the deposited copper layer are close to pure copper , the production capacity of the copper layer is improved, and the production cost is reduced.

Detailed ways

The present invention will be further described below in conjunction with exemplary embodiments.

Example 1

A method for rapidly electroplating a copper layer with high electrical conductivity and high thermal conductivity, comprising the following steps:

Step 1, prepare a composite electroplating solution;

Take 500g of copper sulfate pentahydrate (CuSO ₄ ·5H ₂ O), 50g of sodium hypophosphite, 50g of sodium citrate, 10g of disodium EDTA, 25g of thiourea and then add in deionized water and stir to dissolve; add sulfuric acid Adjust the pH to 5; then add 100 g of metal copper particles with an average diameter of 5 μm, and stir the weak acid solution to remove impurities on the surface of the copper powder to obtain a composite electroplating solution;

Step 2, electroplating copper layer;

Using bipolar pulse electroplating, the positive electrode of the constant current power supply is electrically connected to the metal copper, and the negative electrode is electrically connected to the precursor to be plated, and the precursor to be plated is plated with a seed layer, and the thickness of the seed layer is 0.1-10 μm;

placing the metallic copper and the precursor to be plated in the composite electroplating solution prepared in step 1;

Control the temperature of the composite electroplating solution to 50°C;

A stirring device is arranged in the composite electroplating solution, and the rotating speed is set to 600r/min, which can keep the concentration of metal copper ions in the electrolyte of the cathode accessories in the electroplating process normal, reduce the concentration polarization and improve the cathode current density, and accelerate the deposition speed;

Set constant current power supply parameters to quickly electroplate high electrical conductivity and high thermal conductivity copper layer;

The electroplating process is divided into three stages, and the constant current power supply parameters of the three stages are:

In the first stage, the current density is 2A/dm ² , the forward current pulse duty cycle is 70%, the reverse current pulse duty cycle is 0%, and the electroplating time is 60s;

In the second stage, the current density is set to 5A/dm ² , the forward current pulse duty cycle is 70%, the reverse current pulse duty cycle is 20%, and the plating time is 120s;

In the third stage, the current density is set to 17.7A/dm ² , the duty cycle of the forward current pulse is 70%, the duty cycle of the reverse current pulse is 20%, and the electroplating time is 200s;

After the third stage, a copper layer is obtained, and the copper layer includes the adhesion dense layer formed by the low current density adopted in the first and second stages, and the copper particle accumulation layer and dense filling layer formed by the high current density adopted in the third stage, The total thickness of the copper layer is 10.25 μm, the square resistance is 0.00185Ω/□, and the volume resistivity is 1.85 μΩ·cm.

Example 2

In step 2 of this embodiment, the temperature of the composite electroplating solution is controlled to be 25°C;

The electroplating process is divided into three stages, and the constant current power supply parameters of the three stages are:

In the first stage, the current density is 1A/dm ² , the forward current pulse duty cycle is 40%, the reverse current pulse duty cycle is 10%, and the plating time is 60s;

In the second stage, the current density is set to 3A/dm ² , the forward current pulse duty cycle is 40%, the reverse current pulse duty cycle is 10%, and the electroplating time is 120s;

In the third stage, the current density is set to 18.5A/dm ² , the forward current pulse duty cycle is 40%, the reverse current pulse duty cycle is 10%, and the plating time is 300s;

After the third stage, a copper layer was obtained. The total thickness of the copper layer was 15.74 μm, the square resistance was 0.00128Ω/□, and the volume resistivity was 1.92 μΩ·cm.

The rest of the settings in this embodiment are the same as those in Embodiment 1.

Example 3

In step 2 of this embodiment, the temperature of the composite electroplating solution is controlled to be 80°C;

The electroplating process is divided into three stages, and the constant current power supply parameters of the three stages are:

In the first stage, the current density is 2A/dm ² , the forward current pulse duty cycle is 50%, the reverse current pulse duty cycle is 15%, and the electroplating time is 60s;

In the second stage, the current density is set to 4A/dm ² , the duty cycle of the forward current pulse is 50%, the duty cycle of the reverse current pulse is 15%, and the electroplating time is 120s;

In the third stage, the current density is set to 18.8A/dm ² , the forward current pulse duty cycle is 50%, the reverse current pulse duty cycle is 15%, and the plating time is 400s;

After the third stage, a copper layer is obtained. The total thickness of the copper layer is 20.63 μm, the square resistance is 0.00093Ω/□, and the volume resistivity is 1.86 μΩ·cm.

The rest of the settings in this embodiment are the same as those in Embodiment 1.

Example 4

In step 2 of this embodiment, the temperature of the composite electroplating solution is controlled to be 80°C;

The electroplating process is divided into three stages, and the constant current power supply parameters of the three stages are:

In the first stage, the current density is 0.5A/dm ² , the forward current pulse duty cycle is 30%, the reverse current pulse duty cycle is 0%, and the electroplating time is 60s;

In the second stage, the current density is set to 2A/dm ² , the forward current pulse duty cycle is 30%, the reverse current pulse duty cycle is 0%, and the electroplating time is 120s;

In the third stage, the current density is set to 19.1A/dm ² , the forward current pulse duty cycle is 30%, the reverse current pulse duty cycle is 0%, and the plating time is 500s;

After the third stage, a copper layer was obtained. The total thickness of the copper layer was 25.19 μm, the square resistance was 0.000784Ω/□, and the volume resistivity was 1.96 μΩ·cm.

The rest of the settings in this embodiment are the same as those in Embodiment 1.

Example 5

In step 2 of this embodiment, the temperature of the composite electroplating solution is controlled to be 80°C;

The electroplating process is divided into three stages, and the constant current power supply parameters of the three stages are:

In the first stage, the current density is 2A/dm ² , the forward current pulse duty cycle is 70%, the reverse current pulse duty cycle is 20%, and the electroplating time is 60s;

In the second stage, the current density is set to 5A/dm ² , the forward current pulse duty cycle is 70%, the reverse current pulse duty cycle is 20%, and the plating time is 120s;

In the third stage, the current density is set to 18.6A/dm ² , the forward current pulse duty cycle is 70%, the reverse current pulse duty cycle is 20%, and the plating time is 600s;

After the third stage, a copper layer was obtained. The total thickness of the copper layer was 30.38 μm, the square resistance was 0.000676Ω/□, and the volume resistivity was 2.03 μΩ·cm.

The rest of the settings in this embodiment are the same as those in Embodiment 1.

Examples 1 to 5, the parameter settings of the constant current power supply in the third stage and the performance of the prepared copper layer are shown in Table 1:

Table 1

It can be concluded from Table 1 that in the third stage, with the increase of the plating time, the thickness of the plating layer increases linearly, and the volume resistivity of the copper plating layer is close to that of pure copper ( 1.76 μΩ·cm), from this point of view, the electrical properties of the copper layer prepared by the present invention have the electrical properties of pure copper.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them. For those skilled in the art, the specific technical solutions recorded in the foregoing embodiments can be modified, or some of the technical solutions can be modified. The features are equivalently replaced, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the present invention.

Claims (7)

1. A method for quickly electroplating a high-conductivity high-thermal-conductivity copper layer is characterized by comprising the following steps:

step 1, preparing a composite electroplating solution;

the composite electroplating solution comprises metal copper ions and metal copper particles, and the metal copper particles are uniformly suspended in the composite electroplating solution; the composite electroplating solution is acidic;

step 2, electroplating a copper layer;

adopting bipolar pulse electroplating to electrically connect the anode of a constant current power supply with metal copper, electrically connecting the cathode of the constant current power supply with a precursor to be plated, and plating a seed layer on the precursor to be plated; placing the metal copper and the precursor to be plated in the composite electroplating solution prepared in the step 1;

controlling the temperature of the composite electroplating solution to be 25-80 ℃, and stirring the composite electroplating solution;

setting constant current power supply parameters, and quickly electroplating a high-conductivity and high-heat-conductivity copper layer;

the electroplating process is divided into three stages, and the parameters of the constant current power supply in the three stages are respectively as follows:

the current density of the first stage is 0.5-2A/dm ² The duty ratio of the forward current pulse is 30-70%, the duty ratio of the reverse current pulse is 0-20%, and the electroplating time is 60 s;

the current density of the second stage is set to be 2-5A/dm ² The duty ratio of the forward current pulse is 30-70%, the duty ratio of the reverse current pulse is 0-20%, and the electroplating time is 120 s;

the current density of the third stage is set to be 17-20A/dm ² The duty ratio of the forward current pulse is 30-70%, the duty ratio of the reverse current pulse is 0-20%, and the electroplating time is 200-600 s.

2. The method for rapidly electroplating the copper layer with high electric conductivity and high thermal conductivity according to claim 1, wherein the method comprises the following steps: in the step 2, the electroplating process is divided into three stages, and the parameters of the constant current power supply in the three stages are respectively as follows:

the current density of the first stage is 2A/dm ² The duty ratio of the forward current pulse is 70%, the duty ratio of the reverse current pulse is 0%, and the electroplating time is 60 s;

the current density in the second stage was set to 5A/dm ² The duty ratio of the forward current pulse is 70%, the duty ratio of the reverse current pulse is 20%, and the electroplating time is 120 s;

the current density of the third stage was set to 17.7A/dm ² The duty ratio of the forward current pulse is 70%, the duty ratio of the reverse current pulse is 20%, and the plating time is 200 s.

3. The method for rapidly electroplating the copper layer with high electric conductivity and high thermal conductivity according to claim 1 or 2, wherein: in the step 1, the composite plating solution comprises copper sulfate pentahydrate, and the mass ratio of the copper sulfate pentahydrate to the metal copper particles is 5: 1.

4. The method for rapidly electroplating the copper layer with high electric conductivity and high thermal conductivity according to claim 3, wherein the method comprises the following steps: in the step 1, the diameter of the metal copper particles is 0.1-20 μm.

5. The method for rapidly electroplating the copper layer with high electrical conductivity and high thermal conductivity according to claim 4, wherein the method comprises the following steps: in the step 1, the composite electroplating solution further comprises sodium hypophosphite, sodium citrate, disodium ethylene diamine tetraacetate and thiourea, and the pH value of the composite electroplating solution is 5.

6. The method for rapidly electroplating the copper layer with high electrical conductivity and high thermal conductivity according to claim 5, wherein: in the step 2, the seed layer is prepared by a physical vacuum method or a chemical plating method, the seed layer is a copper layer or a nickel layer or a chromium layer or a nickel-chromium alloy layer, and the thickness of the seed layer is 0.1-10 μm.

7. The method as claimed in claim 6, wherein the copper layer with high conductivity and high thermal conductivity is plated rapidly by the following steps: in the step 2, the precursor to be plated is a heterojunction cell or a silicon substrate cell provided with a transparent conducting layer.