TWI878725B - Plating system and method thereof - Google Patents

Abstract

A plating system and a method thereof are provided. The Mth plating layer is plated in the Nth stage to form on electrolyzation layer sequentially at drilling of substrate with the Mth current density during the Mth plating time, wherein N is a positive integer greater than or equal to 3, M is a positive integer from 1 to N. Therefore, the improving efficiency of filling rate at fixed total thickness of plating layer compared with prior art of plating filling may be achieved.

Description

Electroplating system and method thereof

An electroplating system and method thereof, in particular, an electroplating system and method thereof for performing multi-stage hole filling by using different current densities.

In order to meet the electronics industry's pursuit of faster components and smaller packaging volume, three-dimensional integrated circuits (3D IC) and high-density interconnection (HDI) technology on multi-layer printed circuit boards (PCB) have received great attention in the electronics industry in recent years. Using electroplating technology to fill holes (drilling filling) to form vertical lines that penetrate each conductor layer is a key step.

Due to the special shape of the hole (approximately U-shaped), the current density at the hole mouth of the electroplating hole filling process will be higher than that at the bottom area. Therefore, the electroplated layer electroplated in the hole is likely to be concave and uneven (i.e., the hole filling rate is reduced). The flatness of the electroplated layer will affect the yield of subsequent processes (such as stacking holes).

In order to overcome the above problems, the existing technology intentionally prolongs the electroplating time to improve the flatness of the electroplated layer (i.e., improve the hole filling rate). However, as the electroplating time is prolonged, the total thickness of the electroplated layer will be greatly increased (greater than 15μm), making it impossible to meet the current product specifications of high-density interconnect boards (HDI-PCB) (about 12μm). Therefore, an etching process is required to reduce the total thickness of the electroplated layer.

However, using the etching process to reduce the total thickness of the electroplated layer will also produce many pin holes on the surface of the electroplated layer. The generation of pin holes will cause the line impedance to increase and destroy the mechanical properties of the line. In extreme cases, if many pin holes are generated on the same line at the same time, it will cause the thin line to be broken.

In summary, it can be seen that the previous technology has long had the problem that the thickness of the electroplated layer is too thick due to the consideration of the hole filling rate, and the etching process causes pinholes on the surface of the electroplated layer, resulting in an increase in line impedance and damage to the mechanical properties of the line. Therefore, it is necessary to propose improved technical means to solve this problem.

In view of the fact that the prior art has the problem that the electroplating thickness of the electroplating layer is too thick due to the consideration of the hole filling rate, and the etching process causes pinholes to be generated on the surface of the electroplating layer, resulting in an increase in line impedance and damage to the mechanical properties of the line, the present invention discloses a plating system and method, wherein:

The electroplating system disclosed in the present invention includes: a substrate, a power supply device and an electroplating tank.

The substrate has at least one hole, and a layer to be plated is formed on the surface of the substrate. The substrate is cleaned by a pre-treatment procedure. The power supply device has a cathode and an anode. The substrate is arranged on the cathode. The power supply device provides power supply and current density adjustment during electroplating. The electroplating tank is filled with a plating solution containing metal ions, and the substrate and the anode are placed in the electroplating solution in the electroplating tank.

When the power supply device is started and set to perform the Mth stage electroplating at the Mth current density for the Mth electroplating time, an N-stage electroplating hole filling process of the Mth electroplating layer is sequentially formed on the layer to be plated in at least one hole, wherein N is a positive integer greater than or equal to 3, and M is a positive integer from 1 to N; and the power supply of the power supply device is terminated and the substrate is taken out of the electroplating solution for cleaning and drying processes.

The electroplating method disclosed in the present invention comprises the following steps:

First, the substrate has at least one hole, and a layer to be plated is formed on the surface of the substrate; then, the substrate is cleaned by a pre-treatment procedure; then, a power supply device has a cathode and an anode, the substrate is arranged on the cathode, the power supply device provides power supply during electroplating, and the power supply device provides adjustment of current density; then, a plating solution containing metal ions is placed in the electroplating tank, and the substrate and the anode are placed in the electroplating tank. liquid; then, the power supply device is started and set to perform the Mth stage electroplating at the Mth current density for the Mth electroplating time so that the Nth stage electroplating hole filling process of the Mth electroplating layer is sequentially formed on the layer to be plated in at least one hole, wherein N is a positive integer greater than or equal to 3, and M is a positive integer from 1 to N; finally, the power supply of the power supply device is terminated and the substrate is taken out of the electroplating solution for cleaning and drying processes.

The system and method disclosed in the present invention are as described above, and the difference between them and the prior art is that the hole of the substrate is subjected to an N-stage electroplating hole filling process in which the M-stage electroplating is performed on the layer to be plated by sequentially forming the M-stage electroplating layer on the layer to be plated at the M-stage current density for the M-stage electroplating time, wherein N is a positive integer greater than or equal to 3, and M is a positive integer from 1 to N.

Through the above-mentioned technical means, the present invention can achieve the technical effect of improving the hole filling rate compared to the conventional electroplating hole filling technology when the total thickness of the electroplated layer is fixed.

The following will be used in conjunction with drawings and embodiments to explain the implementation of the present invention in detail, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. In order to clearly illustrate various technical features of the present invention, the technical features shown in the drawings will be presented in a more exaggerated manner.

The following first describes the electroplating system disclosed in the present invention, and please refer to "Figure 1" and "Figure 2". "Figure 1" is a schematic diagram of the structure of the electroplating system of the present invention; "Figure 2" is a cross-sectional view of the substrate of the present invention.

The electroplating system disclosed in the present invention includes a substrate 10, a power supply device 20 and an electroplating tank 30.

The thickness D of the substrate 10 may be, but not limited to, 0.2 to 3 millimeters (mm). The substrate 10 may be a BT substrate, a FR4 substrate, a copper substrate or an ABF substrate. The material of the substrate 10 may be, but not limited to, one or a mixture of glass fiber, epoxy resin, polyphenylene oxide resin (Polyphenylene Oxide, PPO), polyimide (Polyimide, PI), polypropylene (Polypropylene, PP). It is worth noting that the substrate 10 may be, but not limited to, a printed circuit board. At least one hole 11 is formed in the substrate 10 by a laser hole process or a mechanical hole process (only a single hole is used as an illustration in the figure, and the scope of application of the present invention is not limited thereto). The number and position of the hole 11 can be adjusted according to actual needs. When the hole 11 is a circular hole (i.e., its top view is circular), its pore size (diameter) can be 50 μm to 200 μm, and the AR value (i.e., the aspect ratio, the ratio of the thickness of the substrate 10 to the pore size) can be 0.5 to 4.0. This is only used as an example to illustrate, and the scope of application of the present invention is not limited thereto.

The substrate 10 can form a layer 12 to be plated on both surfaces, but this embodiment is not intended to limit the present invention and can be adjusted according to actual needs. For example, the substrate 10 can form a layer 12 to be plated only on the surface having the hole 11. Since the substrate 10 is a non-conductor, it is necessary to perform an electroless plating process, a physical vapor deposition process or a chemical vapor deposition process on its surface so that the surface of the substrate 10 has a conductive layer (i.e., the layer 12 to be plated). Among them, the material of the layer 12 to be plated can be selected from the group consisting of silver, gold, nickel, cobalt, palladium and copper, and can be adjusted according to actual needs.

The substrate 10 is cleaned by a pre-treatment process. The pre-treatment process may include: sequentially cleaning the substrate 10 and the layer 12 to be deposited formed by the hole 11 with water, a cleaning agent and an acid cleaning solution. More specifically, the pre-treatment process can remove the stains on the layer 12 to be deposited and remove the oxide layer on its surface, and avoid bubbles remaining on the layer 12 to be deposited during the cleaning process. The water may be, but is not limited to, deionized water. It should be noted that, since electroplating is performed subsequently, when the acid cleaning solution used for pickling does not contain ions contained in the electroplating solution, in order to avoid affecting the quality of the subsequent electroplated metal, it may be cleaned again with water.

The power supply device 20 has a cathode 21 and an anode 22. The substrate 10 with the layer 12 to be plated needs to be arranged at the position of the cathode 21, and the position of the anode 22 can be configured with a soluble anode (i.e., used to replenish the metal ions consumed in the plating solution) or an insoluble anode (for example: titanium mesh, iridium/titanium oxide composite anode...etc., which is only used as an example here and does not limit the scope of application of the present invention). In this embodiment, the material of the anode 22 can be but is not limited to an iridium/titanium oxide composite insoluble anode.

The power supply device 20 is used to supply power and adjust the current density when the substrate 10 is subjected to the electroplating hole filling process. The electroplating solution 31 containing metal ions is contained in the electroplating tank 30. The substrate 10 and the anode 22 of the power supply device 20 are placed in the electroplating solution 31 in the electroplating tank 30. When the power supply device 20 provides power, the current density is adjusted. When the source is supplied, the substrate 10 is subjected to an electroplating hole filling process. The aforementioned metal ions are other metal ions other than copper ions, such as silver ions, gold ions, nickel ions, cobalt ions, and palladium ions, etc. This is only used as an example to illustrate the invention, and the scope of application of the invention is not limited thereto. The method can be adjusted according to the material of the Mth electroplating layer to be generated.

Please refer to "FIG. 3", which is a schematic diagram of the multi-stage formation of multiple electroplating layers of the present invention. Although three electroplating layers (i.e., a three-stage electroplating hole filling process) are used as an illustration in the figure, the illustration in the figure does not limit the scope of application of the present invention.

When the power supply device 20 is started and set to perform the Mth stage plating at the Mth current density for the Mth plating time, the Nth stage plating hole filling process of the Mth plating layer is sequentially formed on the layer to be plated 12 in the hole 11, wherein N is a positive integer greater than or equal to 3, and M is a positive integer from 1 to N. The following will describe an embodiment in which N is 3 and M is 1 to 3. This is only an example for illustration and is not intended to limit the scope of application of the present invention.

The power supply device 20 adjusts the current density to the first current density for the first electroplating time to perform the first stage electroplating hole filling process on the to-be-plated layer 12 of the substrate 10, so as to form a first electroplating layer 131 on the to-be-plated layer 12 in the hole 11.

Next, the power supply device 20 adjusts the current density to the second current density and continues the second electroplating time to continue the second stage electroplating hole filling process on the first electroplating layer 131, so as to form the second electroplating layer 132 on the first electroplating layer 131 in the hole 11.

Next, the power supply device 20 adjusts the current density to a third current density for a third plating time to continue the third stage of the plating hole filling process on the second plating layer 132, so as to form a third plating layer 133 on the second plating layer 132 in the hole 11.

The present invention first sets the Mth current density and the Mth electroplating thickness THK of the corresponding Mth electroplating layer, and calculates the Mth electroplating time required for the electroplating hole filling process at the corresponding stage at the Mth current density by using Faraday's law. The Faraday's law formula is as follows:

Where, t is the Mth electroplating time (unit: minute), is the electroplating thickness of the Mth electroplating layer (unit: μm), j is the Mth current density (unit: A/ ^dm2 or ASD).

It is worth noting that the current density used in each stage of the electroplating hole filling process (i.e., the first current density, the second current density, and the third current density) is between 0.5 and 100 ASD, and the current density used in each stage of the electroplating hole filling process is the same or different.

In the embodiment where N is 3 and M is 1 to 3, the second current density set in the second stage electroplating is the first current density set in the first stage electroplating increased by The third current density set in the third stage of electroplating is equal to the second current density set in the second stage of electroplating. Specifically, assuming that the first current density of the first stage electroplating is set to 1ASD, the second current density of the second stage electroplating can be set to a range of 1.9 to 2.1ASD; assuming that the second current density of the second stage electroplating is set to 2ASD, the third current density of the third stage electroplating can be set to a range of 0.4 to 0.6 ASD. This is only used as an example to illustrate this, and the scope of application of the present invention is not limited thereto.

Next, COMSOL-Multiphysics (version: 6.0) will be used to perform electroplating simulation of the electroplating hole filling process. Please refer to "Figure 4" and "Figure 5A" to "Figure 5E". "Figure 4" is a schematic diagram of the hole filling rate of the present invention; "Figure 5A" to "Figure 5E" are simulation results of a single-stage electroplating hole filling process using different current densities.

The filling rate of the present invention is the distance b from the lowest position of the electroplated layer surface to the bottom of the hole divided by the distance a from the highest position of the electroplated layer surface to the bottom of the hole multiplied by 100%, that is, the filling rate = As shown in "Figure 4", it is worth noting that since the actual thickness of the layer 12 to be deposited is not high, the calculation process of distance a and distance b can be ignored, and distance a and distance b can also include the thickness of the layer 12 to be deposited.

In Figure 5A, a single-stage electroplating hole filling process with a fixed electroplating layer thickness of 15μm is performed using a single current density of 0.5ASD. The electroplating time simulation result of the electroplating hole filling process with a current density of 0.5ASD is 136.36 minutes and the hole filling rate simulation result is 66.8%. The hole filling rate of 66.8% is due to Calculated.

In Figure 5B, a single-stage electroplating hole filling process with a fixed electroplating layer thickness of 15μm is performed using a single current density of 1ASD. The electroplating time simulation result of the electroplating hole filling process with a current density of 1ASD is 68.18 minutes and the hole filling rate simulation result is 66.7%. The hole filling rate of 66.7% is due to Calculated.

In Figure 5C, a single-stage electroplating via filling process with a fixed electroplating layer thickness of 15μm is performed using a single current density of 2ASD. The electroplating time simulation result of the electroplating via filling process with a current density of 2ASD is 34.09 minutes and the via filling rate simulation result is 66.5%. The via filling rate of 66.5% is obtained by Calculated.

In Figure 5D, a single-stage electroplating via filling process with a fixed electroplating layer thickness of 15μm is performed using a single current density of 5ASD. The simulation result of the electroplating time of the via filling process with a current density of 5ASD is 13.63 minutes and the simulation result of the via filling rate is 66%. The via filling rate of 66% is obtained by Calculated.

In Figure 5E, a single-stage electroplating via filling process with a fixed electroplating layer thickness of 15μm is performed using a single current density of 10ASD. The electroplating time simulation result of the electroplating via filling process with a current density of 10ASD is 6.81 minutes and the via filling rate simulation result is 64.5%. The via filling rate of 64.5% is obtained by Calculated.

From the above simulation results, it can be concluded that the electroplating time required to form a fixed electroplating layer with an electroplating thickness of 15μm using a high current density (e.g. 10ASD) is much shorter than that using a low current density (e.g. 1ASD) for the electroplating hole filling process. However, the filling rate of the hole filling process using a high current density (e.g. 10ASD) is much lower than that using a low current density (e.g. 1ASD) for the electroplating hole filling process to form a fixed electroplating layer with an electroplating thickness of 15μm. Therefore, using a high current density (e.g. 5ASD, 10ASD, etc.) will not be conducive to the improvement of the hole filling rate.

Please refer to "Figure 6A" and "Figure 6B", "Figure 6A" shows the simulation result of a single-stage electroplating hole filling process using a single current density; "Figure 6B" shows the simulation result of the present invention using different current densities to perform the hole filling process and the electroplating thickness of each stage of the electroplating layer is the same.

In FIG. 6A , a single-stage electroplating hole filling process with a fixed electroplating layer thickness of 8 μm is performed using a single current density of 2ASD. The simulation result of the electroplating time for the electroplating hole filling process with a current density of 2ASD is 18.2 minutes and the simulation result of the hole filling rate is 51%.

In "Figure 6B", the first current density of 0.5ASD is used to perform the first stage electroplating hole filling process with a first electroplating layer thickness of 2.6μm, and then the second current density of 2ASD is used to perform the second stage electroplating hole filling process with a second electroplating layer thickness of 2.6μm, and then the third current density of 1ASD is used to perform the third stage electroplating hole filling process with a third electroplating layer thickness of 2.6μm. After the three-stage electroplating hole filling process, the electroplating time simulation result is 42.42 minutes and the hole filling time is 42.42 minutes. The rate simulation result is 51.97%. It is worth noting that the plating thickness of the first plating layer, the plating thickness of the second plating layer and the plating thickness of the third plating layer are the same. This is only used as an example to illustrate, and the application scope of the present invention is not limited to this. In fact, the plating thickness of the first plating layer, the plating thickness of the second plating layer and the plating thickness of the third plating layer may also be different, and the plating thickness of the first plating layer, the plating thickness of the second plating layer and the plating thickness of the third plating layer may also be partially the same and partially different.

Please refer to "Figure 7A" and "Figure 7B", "Figure 7A" shows the simulation result of a single-stage electroplating hole filling process using a single current density; "Figure 7B" shows the simulation result of the present invention using different current densities to perform the hole filling process and the electroplating thickness of each stage of the electroplating layer is the same.

In FIG. 7A , a single-stage electroplating via filling process with a fixed electroplating layer thickness of 20 μm is performed using a single current density of 2ASD. The simulation result of the electroplating time for the electroplating via filling process with a current density of 2ASD is 45.45 minutes and the simulation result of the via filling rate is 74%.

In "Figure 7B", the first current density of 0.5ASD is used to perform the first stage electroplating hole filling process with a first electroplating layer thickness of 6.7μm, and then the second current density of 2ASD is used to perform the second stage electroplating hole filling process with a second electroplating layer thickness of 6.7μm, and then the third current density of 1ASD is used to perform the third stage electroplating hole filling process with a third electroplating layer thickness of 6.7μm. After the three-stage electroplating hole filling process, the plating time simulation result is 106.1 minutes and the hole filling time is 106.1 minutes. The rate simulation result is 77.07%. It is worth noting that the plating thickness of the first plating layer, the plating thickness of the second plating layer and the plating thickness of the third plating layer are the same. This is only used as an example to illustrate, and the application scope of the present invention is not limited to this. In fact, the plating thickness of the first plating layer, the plating thickness of the second plating layer and the plating thickness of the third plating layer may also be different, and the plating thickness of the first plating layer, the plating thickness of the second plating layer and the plating thickness of the third plating layer may also be partially the same and partially different.

Next, the electroplating method of the present invention will be described below, and please refer to "Figure 8" at the same time, which is a method flow chart of the electroplating method of the present invention.

The electroplating method of the present invention comprises the following steps:

First, a substrate has at least one hole, and a layer to be plated is formed on the surface of the substrate (step 101). Next, a power supply device has a cathode and an anode, and the substrate is disposed on the cathode. The power supply device provides power supply during electroplating, and the power supply device provides adjustment of current density (step 102). Next, a plating solution containing metal ions is placed in a plating tank, and the substrate and the anode are placed in the plating solution in the plating tank (step 10 3); then, the power supply device is started and set to perform the Mth stage electroplating with the Mth current density for the Mth electroplating time so that the Mth electroplating layer is sequentially formed on the layer to be plated in at least one hole, wherein N is a positive integer greater than or equal to 3, and M is a positive integer from 1 to N (step 104); finally, the power supply of the power supply device is terminated and the substrate is taken out of the electroplating solution for cleaning and drying processes (step 105).

In summary, the difference between the present invention and the prior art is that the hole of the substrate is subjected to an N-stage electroplating hole filling process in which the M-th electroplating layer is sequentially formed on the layer to be plated by performing the M-th stage electroplating at the M-th current density for the M-th electroplating time, wherein N is a positive integer greater than or equal to 3, and M is a positive integer from 1 to N.

This technical means can be used to solve the problem of the previous technology that the electroplating thickness of the electroplated layer is too thick due to the consideration of the filling rate, and the etching process causes pinholes on the surface of the electroplated layer, resulting in an increase in line impedance and damage to the mechanical properties of the line. In addition, the technical effect of improving the filling rate compared to the conventional electroplating filling technology can be achieved when the total thickness of the electroplated layer is fixed.

Although the implementation methods disclosed in the present invention are as above, the above contents are not used to directly limit the scope of patent protection of the present invention. Any person with ordinary knowledge in the technical field to which the present invention belongs can make some changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention. The scope of patent protection of the present invention shall still be defined by the scope of the attached patent application.

10: substrate 11: hole 12: layer to be plated 131: first electroplating layer 132: second electroplating layer 133: third electroplating layer 20: power supply device 21: cathode 22: anode 30: electroplating tank 31: electroplating solution a: distance b: distance D: thickness THK: electroplating thickness Step 101: the substrate has at least one hole, and the layer to be plated is formed on the surface of the substrate Step 102: the power supply device has a cathode and an anode, the substrate is arranged on the cathode, the power supply device provides power supply during electroplating, and the power supply device provides adjustment of current density Step 103: Plating solution containing metal ions is placed in the plating tank, and the substrate and the anode are placed in the plating solution in the plating tank. Step 104: The power supply device is started and set to perform the Mth stage plating at the Mth current density for the Mth plating time so that the Mth plating layer is sequentially formed on the layer to be plated in at least one hole, wherein N is a positive integer greater than or equal to 3, and M is a positive integer from 1 to N. Step 105: Terminate the power supply of the power supply device and take the substrate out of the plating solution for cleaning and drying processes.

FIG. 1 is a schematic diagram of the structure of the electroplating system of the present invention. FIG. 2 is a cross-sectional view of the substrate of the present invention. FIG. 3 is a schematic diagram of the multi-stage electroplating layer formed in the present invention. FIG. 4 is a schematic diagram of the hole filling rate of the present invention. FIG. 5A to FIG. 5E are simulation results of a single-stage electroplating hole filling process using different current densities. FIG. 6A is a simulation result of a single-stage electroplating hole filling process using a single current density. FIG. 6B is a simulation result of a hole filling process using different current densities and the electroplating thickness of the electroplating layer in each stage is the same. FIG. 7A shows the simulation result of a single-stage electroplating hole filling process using a single current density. FIG. 7B shows the simulation result of the present invention using different current densities to perform the hole filling process and the electroplating thickness of each stage of the electroplating layer is the same. FIG. 8 shows a method flow chart of the electroplating method of the present invention.

10: Substrate

11: Holes

12: Waiting for coating

20: Power supply device

21: cathode

22: Yang pole

30: Electroplating tank

31: Plating solution

Claims (4)

A plating method comprises the following steps: a substrate having at least one hole, a layer to be plated is formed on the surface of the substrate; a power supply device having a cathode and an anode, the substrate being arranged on the cathode, the power supply device providing power supply during plating, and the power supply device providing adjustment of current density; a plating solution containing metal ions is placed in a plating tank, the substrate and the anode are placed in the plating solution in the plating tank; the power supply device is started and set to perform an Mth stage of plating with an Mth current density for an Mth plating time so that the layer to be plated in the at least one hole is sequentially plated. The Mth electroplating layer is formed, and the Mth electroplating time is calculated by dividing the set electroplating thickness of the Mth electroplating layer by (0.22 multiplied by the Mth current density), wherein N is a positive integer greater than or equal to 3, M is a positive integer from 1 to N, the second current density set for the second stage electroplating is 100±10% higher than the first current density set for the first stage electroplating, and the third current density set for the third stage electroplating is 25±5% of the second current density set for the second stage electroplating; and the power supply of the power supply device is terminated and the substrate is taken out of the electroplating solution for cleaning and drying processes. The electroplating method as claimed in claim 1, wherein the current density of each stage of the electroplating via filling process is between 0.5 and 100 A/dm ² (ASD), and the current density of each stage of the electroplating via filling process is different. The electroplating method as described in claim 1, wherein the electroplating thickness of each electroplating layer is the same or different. The electroplating method as described in claim 1, wherein the metal ions are other metal ions other than copper ions.

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