Electroplating method

Abstract

The application provides a kind of electroplating method, by periodically setting direct current output and pulsating current output in electroplating process, by setting pulsating current output, not only can ensure the thickness of metal deposition at the bottom of hole in back hole gold process is improved, also improves the electrochemical deposition efficiency, even avoid the problem that the step coverage of metal deposition at the bottom of hole in constant direct current large current electroplating is low, the electrochemical deposition efficiency is low in constant direct current small current electroplating, by setting direct current output, can ensure that the uniformity of film thickness after electrochemical deposition and the uniformity of direct current plating are basically consistent, therefore, by periodically setting direct current output and pulsating current output in electroplating process, and direct current and pulsating current are applied to the anode section interval of electroplating device, not only can ensure the thickness of metal deposition at the bottom of hole in back hole gold process is improved, also can improve the electrochemical deposition efficiency, can ensure that the uniformity of film thickness after electroplating and the uniformity of direct current plating are basically consistent.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an electroplating method. Background Technology

[0002] Existing electroplating equipment includes an electroplating tank, electroplating anodes, and a power supply module. The electroplating tank contains an electroplating solution (which acts as a resistor in the electroplating circuit). The electroplating anode is positioned within the tank, and the workpiece (such as a wafer) is positioned opposite the anode. During electroplating, the workpiece acts as the cathode, which is connected to the negative terminal of the power supply module. The electroplating anode is connected to the positive terminal of the power supply module. When the anode and cathode are connected to the power supply module, an electroplating electric field is formed between them, achieving electroplating on the workpiece. To overcome the limitation of not being able to precisely control the thickness of the electroplated layer, existing technologies typically employ segmented anode electroplating equipment to obtain a uniform electroplated layer thickness.

[0003] Back-hole gold deposition is a process that deposits metals such as Au (gold) or Ag (silver) inside holes on the back of a chip, typically used to improve the chip's heat dissipation and mechanical stability. Through Silicon Via (TSV) technology combines the vertical electrical interconnect characteristics of TSV technology with the heat dissipation and stability advantages of back-hole gold deposition. It achieves efficient vertical electrical interconnection within or between chips, effectively dissipating heat generated by the chip, reducing its operating temperature, and improving its reliability and lifespan. The back-hole gold layer also enhances the adhesion between the chip and the packaging substrate, improving the chip's resistance to shock and vibration, and ensuring stable operation in complex environments.

[0004] However, with increasing integration and miniaturization of devices, the diameter of back holes in back-hole plating processes also decreases. When using segmented anode plating equipment, plating within high aspect ratio back holes becomes more difficult. High-current-density DC plating results in low step coverage of the metal deposit at the bottom of the hole, while low-current-density DC plating is too inefficient. Pulse plating or periodic pulsed plating (i.e., periodic plating with alternating high and low currents) can improve step coverage of the metal deposit at the bottom of the hole while maintaining production efficiency. However, during the plating process, the electric field force... The interaction between the electric field and the flow field determines the migration and deposition behavior of electroplating ions. The electric field provides the driving force and direction for the migration of electroplating ions, while the flow field affects the distribution and deposition process of electroplating ions through transport, stirring, and scouring. During the electroplating process, it is necessary to reasonably control the parameters of the electric field and the flow field to obtain a high-quality coating. When the flow field remains constant, different current densities will produce different electric fields, thus affecting the uniformity of the coating thickness. Therefore, compared with constant DC electroplating, the uniformity control of pulsating electroplating with alternating large and small current densities is more difficult. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide an electroplating method to solve the problems in the prior art when using segmented anode electroplating equipment to electroplat wafers with holes, such as increased difficulty in electroplating inside holes with high aspect ratios, low step coverage of metal deposition at the bottom of holes when using high current density DC electroplating, low production efficiency when using low current density DC electroplating, and poor uniformity of film thickness after using pulsating current electroplating.

[0006] To achieve the above and other related objectives, the present invention provides an electroplating method. The electroplating method uses an electroplating apparatus to electroplat a wafer. The electroplating apparatus includes an electroplating anode, which comprises two or more non-conductive anode segments coaxially nested in sequence. The central anode segment has a cylindrical structure, while the other anode segments have an annular structure. Each anode segment is divided into a first anode segment and a second anode segment, and the first anode segment and the second anode segment are alternately coaxially nested. The electroplating method includes the following steps:

[0007] S1, perform a first-stage electroplating on the wafer: apply a direct current to the first anode section and apply a pulsating current to the second anode section;

[0008] S2, perform a second-stage electroplating on the wafer: apply a pulsating current to the first anode segment and apply a direct current to the second anode segment;

[0009] S3. Repeat steps S1 to S2 until electroplating is complete.

[0010] Optionally, during the first stage of electroplating, the DC current applied to different first anode segments has different values, and the pulsating current applied to different second anode segments has different values; during the second stage of electroplating, the pulsating current applied to different first anode segments has different values, and the DC current applied to different second anode segments has different values; during both the first and second stage of electroplating, the DC current applied to the same anode segment is equal to the larger of the applied pulsating current values.

[0011] Optionally, the electroplating time in the first stage is 1 min to 10 min, and the electroplating time in the second stage is 1 min to 10 min.

[0012] Furthermore, the electroplating time in the first stage is 1 min to 5 min, and the electroplating time in the second stage is 1 min to 5 min.

[0013] Optionally, the anode segment located at the center is the first anode segment or the anode segment located at the center is the second anode segment.

[0014] Furthermore, the electroplating anode includes five non-conductive anode segments that are coaxially nested in sequence.

[0015] Optionally, the ratio of the larger current value to the smaller current value in the pulsating current is (2~3):1.

[0016] Optionally, the ratio of the duration of the alternating output of the larger current and the smaller current in the pulsating current is (3-5):1.

[0017] Optionally, the electroplating method of the electroplating apparatus is horizontal cup electroplating.

[0018] Optionally, the material electroplated by the electroplating method is Au.

[0019] As described above, the electroplating method of the present invention has the following beneficial effects: By periodically setting DC current output and pulsed current output during the electroplating process, the electroplating method of the present invention can not only ensure the increase of metal deposition thickness at the bottom of the hole during the back hole gold process, but also improve the electrochemical deposition efficiency. It reduces or even avoids the problems of low step coverage of metal deposition at the bottom of the hole during constant DC high current electroplating and low electrochemical deposition efficiency during constant DC low current electroplating. By setting DC current output, it can ensure that the uniformity of film thickness after electrochemical deposition is basically the same as that of DC electroplating. Therefore, by periodically setting DC current output and pulsed current output during the electroplating process, and applying DC current and pulsed current intermittently to the anode section of the electroplating device, it can not only ensure the increase of metal deposition thickness at the bottom of the hole during the back hole gold process, but also improve the electrochemical deposition efficiency. At the same time, it can ensure that the uniformity of film thickness after electroplating is basically the same as that of DC electroplating. Furthermore, by periodically setting the DC current output and the pulsating current output, the electric field distribution can be dynamically adjusted, thereby optimizing the electrochemical deposition process. This helps to avoid local overheating or uneven electric field, and improves the uniformity and efficiency of electrochemical deposition across the entire anode wafer. Attached Figure Description

[0020] Figure 1 The diagram shown is a top view of the electroplating anode in a prior art electroplating apparatus.

[0021] Figure 2 The diagram shows the current setting of the electroplating method of the present invention.

[0022] Figure 3 The diagram shown is a schematic flow chart of the electroplating method of the present invention.

[0023] Component designation explanation

[0024] 1. First anode body

[0025] 2. Second anode body

[0026] 3. Third anode body

[0027] 4. Fourth anode body

[0028] 5. Fifth anode body

[0029] Steps S1 to S3 Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] Please see Figures 1 to 3 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0032] This embodiment provides an electroplating method, such as Figures 1 to 3 As shown, the electroplating method uses an electroplating apparatus to electroplat a wafer. The electroplating apparatus includes an electroplating anode, which comprises two or more non-conductive anode segments coaxially nested in sequence. The central anode segment has a cylindrical structure, while the other anode segments have an annular structure. Each anode segment is divided into a first anode segment and a second anode segment, and the first anode segment and the second anode segment are alternately coaxially nested. The electroplating method includes the following steps:

[0033] S1, perform a first-stage electroplating on the wafer: apply a direct current to the first anode section and apply a pulsating current to the second anode section;

[0034] S2, perform a second-stage electroplating on the wafer: apply a pulsating current to the first anode segment and apply a direct current to the second anode segment;

[0035] S3. Repeat steps S1 to S2 until electroplating is complete.

[0036] The electroplating method in this embodiment periodically sets DC current output and pulsed current output during the electroplating process. Setting the pulsed current output not only ensures increased metal deposition thickness at the bottom of the hole during the back-hole gold plating process but also improves electrochemical deposition efficiency. It even avoids the problems of low step coverage at the bottom of the hole during constant DC high-current electroplating and low electrochemical deposition efficiency during constant DC low-current electroplating. Setting the DC current output ensures that the uniformity of the film thickness after electrochemical deposition is essentially the same as that of DC electroplating. Therefore, by periodically setting DC current output and pulsed current output during the electroplating process and applying DC current and pulsed current intermittently to the anode section of the electroplating device, it is possible to not only increase the metal deposition thickness at the bottom of the hole during the back-hole gold plating process but also improve electrochemical deposition efficiency, while ensuring that the uniformity of the film thickness after electroplating is essentially the same as that of DC electroplating. Furthermore, periodically setting the DC current output and pulsed current output allows for dynamic adjustment of the electric field distribution, thereby optimizing the electrochemical deposition process, helping to avoid localized overheating or electric field inhomogeneity, and improving the electrochemical deposition uniformity and deposition efficiency of the entire anode wafer.

[0037] During the electroplating process, the electroplating anode of the electroplating apparatus and the wafer are arranged relatively parallel. As an example, when performing horizontal electroplating, the electroplating anode of the electroplating apparatus is positioned below the wafer; when performing vertical electroplating, the electroplating anode of the electroplating apparatus is positioned to the left or right of the wafer. The shape and size of the electroplating anode of the electroplating apparatus are the same as the shape and size of the wafer. This embodiment uses the commonly used horizontal cup electroplating method of the electroplating apparatus as an example for explanation. In the horizontal cup electroplating method, the electroplating solution of the electroplating apparatus is stored in a tank, and the wafer is placed horizontally and immersed in the electroplating solution. The horizontal cup electroplating method can ensure that the wafer is better covered by the electroplating solution and improve the electroplating uniformity. The electroplating method of the electroplating apparatus is not excessively limited here.

[0038] The number of anode segments in the electroplating anode can be set according to the size of the wafer. For example, the wafer is generally 3 inches, 4 inches, 6 inches, 8 inches, and 12 inches, etc., and the number of electroplating anodes can be 2 to 20 segments. The shape of the anode segments is not specifically limited, and their projection surface can be annular, polygonal, etc. In this embodiment, the electroplating anode includes 5 non-conductive anode segments that are coaxially nested in sequence. Specifically, as shown... Figure 1 As shown, the anode segments of the electroplating anode are respectively the first anode body 1, the second anode body 2, the third anode body 3, the fourth anode body 4, and the fifth anode body 5 in the radial direction from the center.

[0039] The positions of the first anode segment and the second anode segment are not overly limited. As an example, the anode segment located at the center can be considered the first anode segment or the anode segment located at the center can be considered the second anode segment. Figure 1 In this configuration, the first anode segment can be configured as the first anode body 1, the third anode body 3, and the fifth anode body 5, and the second anode segment can be configured as the second anode body 2 and the fourth anode body 4; alternatively, the second anode segment can be configured as the first anode body 1, the third anode body 3, and the fifth anode body 5, and the first anode segment can be configured as the second anode body 2 and the fourth anode body 4. The specific configuration can be determined according to actual needs, and no excessive limitations are imposed here.

[0040] To dynamically adjust the electric field distribution and improve the uniformity and efficiency of electrochemical deposition across the entire wafer, for example, in the first stage of electroplating, the applied DC current value can be set to be different for different first anode segments, and the applied pulsating current value can be set to be different for different second anode segments; in the second stage of electroplating, the applied pulsating current value can be set to be different for different first anode segments, and the applied DC current value can be different for different second anode segments; in both the first and second stage of electroplating, the applied DC current value and the larger applied pulsating current value of the same anode segment are equal. For example, Figure 1 Taking the electroplating anode structure as an example, the explanation is as follows: Figure 1 and Figure 2As shown, in the first stage of electroplating, the DC current values ​​applied to the first anode body 1, the third anode body 3, and the fifth anode body 5 can be set to be different, and the pulsating current values ​​applied to the second anode body 2 and the fourth anode body 4 can be set to be different; in the second stage of electroplating, the pulsating current values ​​applied to the first anode body 1, the third anode body 3, and the fifth anode body 5 are different, and the DC current values ​​applied to the second anode body 2 and the fourth anode body 4 are different; in the first stage of electroplating and the fifth anode body 5... In the two-stage electroplating process, the DC current applied to the first anode body 1 is equal to the larger current value among the applied pulsating currents; the larger current value among the pulsating currents applied to the second anode body 2 is equal to the applied DC current; the DC current applied to the third anode body 3 is equal to the larger current value among the applied pulsating currents; the larger current value among the pulsating currents applied to the fourth anode body 4 is equal to the applied DC current; and the DC current applied to the fifth anode body 5 is equal to the larger current value among the applied pulsating currents. In actual electroplating processes, the DC current values ​​and the larger current value among the pulsating currents for each anode segment during the first and second stages of electroplating can be adaptively adjusted according to the actual electrochemical deposition conditions, the state of the wafer serving as the cathode, and the characteristics of the electroplating material to achieve the best electrochemical deposition effect. No excessive limitations are imposed here.

[0041] Furthermore, as an example, during the first stage of electroplating, the sum of the current values ​​of all DC currents applied to all first anode segments and the larger current value among the pulsating currents applied to all second anode segments can be set as the constant DC current value used when the electroplating apparatus achieves optimal uniformity of the electroplated film using constant DC electroplating; during the second stage of electroplating, the sum of the current values ​​of all DC currents applied to all second anode segments and the larger current value among the pulsating currents applied to all first anode segments can be set as the constant DC current value used when the electroplating apparatus achieves optimal uniformity of the electroplated film using constant DC electroplating, thereby obtaining a better electric field distribution and improving the electrochemical deposition uniformity of the entire wafer. For example, using... Figure 1 Taking the electroplating anode structure as an example, the explanation is as follows: Figure 1 and Figure 2As shown, in the first stage of electroplating, the sum of the current values ​​of all DC currents applied to the first anode body 1, the third anode body 3, and the fifth anode body 5, and the larger current value among the pulsating currents applied to the second anode body 2 and the fourth anode body 4, can be set as the constant DC current value used when the electroplating device achieves optimal uniformity of the electroplated film layer using constant DC electroplating; in the second stage of electroplating, the sum of the current values ​​of all DC currents applied to the second anode body 2 and the fourth anode body 4, and the larger current value among the pulsating currents applied to the first anode body 1, the third anode body 3, and the fifth anode body 5, can be set as the constant DC current value used when the electroplating device achieves optimal uniformity of the electroplated film layer using constant DC electroplating.

[0042] As a specific example, such as Figure 1 As shown, in this embodiment, the first anode segment is defined as the first anode body 1, the third anode body 3, and the fifth anode body 5, and the second anode segment is defined as the second anode body 2 and the fourth anode body 4. The electroplating method includes:

[0043] First, step S1 is performed to conduct a first-stage electroplating on the wafer: a direct current is applied to the first anode body 1, the third anode body 3, and the fifth anode body 5, and a pulsating current is applied to the second anode segment, which consists of the second anode body 2 and the fourth anode body 4; as a specific example, such as Figure 2 As shown, the ratio of the DC current applied to the first anode body 1 to the larger current in the pulsating current applied to the second anode body 2, the DC current applied to the third anode body 3, the larger current in the pulsating current applied to the fourth anode body 4, and the DC current applied to the fifth anode body 5 can be set to 25:20:20:18:17. In actual electroplating processes, this ratio can be adjusted adaptively according to the actual electrochemical deposition conditions to achieve the best electrochemical deposition effect. No excessive restrictions are imposed here.

[0044] Next, step S2 is performed on the wafer for a second stage of electroplating: a pulsating current is applied to the first anode body 1, the third anode body 3, and the fifth anode body 5, and a direct current is applied to the second anode segment, which consists of the second anode body 2 and the fourth anode body 4; as a specific example, such as Figure 2As shown, the ratio of the larger current value in the pulsating current applied to the first anode body 1: the current value of the DC current applied to the second anode body 2: the larger current value in the pulsating current applied to the third anode body 3: the current value of the DC current applied to the fourth anode body 4: the larger current value in the pulsating current applied to the fifth anode body 5 can be set to 25:20:20:18:17. In actual electroplating processes, this ratio can be adjusted adaptively according to the actual electrochemical deposition conditions to achieve the best electrochemical deposition effect. No excessive restrictions are imposed here.

[0045] Next, proceed to step S3, and repeat steps S1 to S2 until electroplating is complete.

[0046] like Figure 2 As shown, the first and second stages of electroplating involve periodically applying direct current and pulsating current to dynamically adjust the electric field distribution. For example, the first stage of electroplating takes 1 to 10 minutes, and the second stage of electroplating takes 1 to 10 minutes. In this embodiment, it is preferable to set the first stage of electroplating to 1 to 5 minutes and the second stage of electroplating to 1 to 5 minutes to avoid local overheating or uneven electric field, improve the uniformity of electrochemical deposition, and achieve a better electrochemical deposition effect. The time settings for the first and second stages of electroplating can be adaptively adjusted according to the actual electrochemical deposition situation, the state of the wafer used as the cathode, and the characteristics of the electroplating material to achieve the best electrochemical deposition effect. No excessive restrictions are imposed here.

[0047] By setting alternating smaller current values ​​in the pulsating current, the metal deposition thickness at the bottom of the hole during the through-hole gold plating process is increased. Conversely, setting alternating larger current values ​​improves electrochemical deposition efficiency, reducing or even eliminating the problem of low step coverage at the bottom of the hole and low electrochemical deposition efficiency during constant DC low-current plating. For example, the ratio of alternating larger to smaller current values ​​in the pulsating current is set to (2-3):1, thereby dynamically adjusting the electric field distribution and optimizing the electrochemical deposition process to avoid electric field inhomogeneity and achieve better electrochemical deposition results. In actual processes, the ratio of alternating larger to smaller current values ​​in the pulsating current can be adaptively adjusted according to the actual electrochemical deposition conditions, the state of the wafer serving as the cathode, and the characteristics of the plating material to achieve the best electrochemical deposition effect; no excessive restrictions are imposed here.

[0048] As an example, the ratio of the duration of the alternating output of the larger and smaller current values ​​in the pulsating current is set to (3-5):1. For example, it can be set to 75ms:25ms, 50ms:17ms, or 30ms:10ms, etc., so as to dynamically adjust the electric field distribution, optimize the electrochemical deposition process, avoid electric field inhomogeneity, and achieve better electrochemical deposition effect. In actual process, the ratio of the duration of the alternating output of the larger and smaller current values ​​in the pulsating current can be adaptively adjusted according to the actual electrochemical deposition situation, the state of the wafer as the cathode, and the characteristics of the electroplating material to achieve the best electrochemical deposition effect. No excessive restrictions are imposed here.

[0049] The materials electroplated using the described electroplating method are set according to actual needs, and no excessive restrictions are imposed here. This embodiment is particularly suitable for Au materials with a slow deposition rate. When Au ions are electrochemically deposited in the holes of the wafer, after the Au ions in the holes are consumed, the Au ions outside the holes cannot be replenished in time, resulting in a decrease in the electroplating efficiency inside the holes. However, when Au is deposited slowly during low-current electroplating, there is time to replenish the Au ions in the holes. This embodiment ensures an increase in the metal deposition thickness at the bottom of the holes during the back-hole gold process by setting alternating small current values ​​in the pulsating current output.

[0050] In summary, the electroplating method of the present invention, by periodically setting DC current output and pulsed current output during the electroplating process, not only ensures an increase in the metal deposition thickness at the bottom of the hole during the back-hole gold plating process, but also improves the electrochemical deposition efficiency. This reduces or even avoids the problems of low step coverage of the metal deposition at the bottom of the hole during constant DC high-current electroplating and low electrochemical deposition efficiency during constant DC low-current electroplating. Setting the DC current output ensures that the uniformity of the film thickness after electrochemical deposition is essentially the same as that of DC electroplating. Therefore, by periodically setting DC current output and pulsed current output during the electroplating process, and applying DC current and pulsed current intermittently to the anode section of the electroplating device, not only can the metal deposition thickness at the bottom of the hole be increased during the back-hole gold plating process, but the electrochemical deposition efficiency can also be improved. Simultaneously, it ensures that the uniformity of the film thickness after electroplating is essentially the same as that of DC electroplating. Furthermore, by periodically setting the DC current output and pulsed current output, the electric field distribution can be dynamically adjusted, thereby optimizing the electrochemical deposition process, helping to avoid local overheating or electric field inhomogeneity, and improving the electrochemical deposition uniformity and deposition efficiency of the entire anode wafer. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0051] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An electroplating method, wherein the electroplating method uses an electroplating apparatus to electroplat a wafer, characterized in that, The electroplating apparatus includes an electroplating anode, which comprises two or more anode segments that are non-conductive and coaxially nested in sequence. The anode segment located at the center has a cylindrical structure, while the other anode segments have an annular structure. Each anode segment is divided into a first anode segment and a second anode segment, and the first anode segment and the second anode segment are alternately coaxially nested. The electroplating method includes the following steps: S1, perform a first-stage electroplating on the wafer: apply a direct current to the first anode section and apply a pulsating current to the second anode section; S2, perform a second-stage electroplating on the wafer: apply a pulsating current to the first anode segment and apply a direct current to the second anode segment; S3. Repeat steps S1 to S2 until electroplating is complete.

2. The electroplating method according to claim 1, characterized in that: During the first stage of electroplating, the DC current applied to different first anode sections has different values, and the pulsating current applied to different second anode sections has different values. During the second stage of electroplating, the values ​​of the pulsating current applied to different first anode sections are different, and the values ​​of the direct current applied to different second anode sections are different. During the first and second stages of electroplating, the current value of the DC current applied to the same anode segment is equal to the larger current value in the applied pulsating current.

3. The electroplating method according to claim 1, characterized in that: The electroplating time for the first stage is 1 min to 10 min, and the electroplating time for the second stage is 1 min to 10 min.

4. The electroplating method according to claim 3, characterized in that: The electroplating time for the first stage is 1 min to 5 min, and the electroplating time for the second stage is 1 min to 5 min.

5. The electroplating method according to claim 1, characterized in that: The anode segment located at the center is either the first anode segment or the anode segment located at the center is the second anode segment.

6. The electroplating method according to claim 5, characterized in that: The electroplating anode comprises five non-conductive anode segments that are coaxially nested in sequence.

7. The electroplating method according to claim 1, characterized in that: The ratio of the larger current value to the smaller current value in the alternating output of the pulsating current is (2~3):

1.

8. The electroplating method according to claim 1, characterized in that: The ratio of the duration of the alternating output of the larger current and the smaller current in the pulsating current is (3~5):

1.

9. The electroplating method according to claim 1, characterized in that: The electroplating method of the electroplating device is horizontal cup electroplating.

10. The electroplating method according to claim 1, characterized in that: The material electroplated using the electroplating method is Au.

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