Miniature adjustable liquid mixing device and process method for cleaning verdigris generated after copper is polished by alkaline polishing liquid

Abstract

The invention discloses a process method for cleaning verdigris generated after chemical and mechanical polishing of copper by alkaline polishing liquid, and relates to a miniature adjustable liquid mixing device. The process method and the miniature adjustable liquid mixing device are used for cleaning verdigris generated after chemical and mechanical polishing of copper by using the alkaline polishing liquid, so that the aim of cleaning by using an acidic cleaning agent (citric acid) after finishing copper polishing by using the alkaline polishing liquid can be achieved; the influence of by-products (such as verdigris) generated when the alkaline polishing solution is used for polishing copper on subsequent wafer polishing is effectively reduced, meanwhile, the service life of the polishing pad is prolonged, the production efficiency is improved, and the maintenance cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and particularly to a process method for cleaning copper oxide formed after polishing copper with an alkaline polishing solution by using a micro adjustable liquid mixing device. Background Art

[0002] With the reduction of the feature size of integrated circuit devices and the continuous increase of the wafer size, semiconductor manufacturing processes have become increasingly complex and sophisticated. To improve the reliability and service life of devices, the chip metal interconnection has shifted from aluminum interconnection to copper interconnection. Both aluminum interconnection and copper interconnection layers need to be planarized, and chemical mechanical polishing (CMP) technology is currently the only practical and core technology that can achieve global planarization of chips. For chemical mechanical polishing of copper, acidic polishing solutions are commonly used internationally. However, with the development of integrated circuits, various corrosion inhibitors contained in acidic copper polishing solutions, such as toxic benzotriazole (BTA), etc., are likely to remain on the surface of copper wiring and can only be removed under strong mechanical action, which is extremely likely to cause problems such as scratches, organic contamination, and film peeling. Therefore, to solve the contradiction between the low mechanical pressure requirement in practical applications and the problem of easy residue of acidic copper polishing solutions, alkaline polishing solutions are reapplied to the chemical mechanical polishing process of copper. However, copper is prone to generating oxides and hydroxides under alkaline conditions, and these by-products (referred to as copper oxide) are not easily soluble. As the number of processed wafers increases, the by-products continuously accumulate on the polishing pad, which will further affect the polishing rate of copper and the life of the polishing pad, seriously affecting the polishing effect and production efficiency.

[0003] Currently, for the by-products (copper oxide) remaining on the polishing pad, the polishing pad is usually cleaned with a citric acid solution after polishing. However, since the pH values of the citric acid solution (acidic) and the alkaline copper polishing solution are different, after using it to clean the copper oxide, it may inhibit the polishing rate of the next wafer. At the same time, a cleaning agent with too high a concentration will also affect the performance of the polishing solution.

[0004] Therefore, to solve the above problems, while adjusting the flow rate and concentration of the cleaning agent by using a micro adjustable mixing device, the present invention develops a cleaning process for copper oxide formed after polishing copper with an alkaline polishing solution, so as to reduce the impact of the different pH values of the cleaning agent and the polishing solution on the process and meet the requirements for cleaning the by-products of alkaline polishing solutions. Summary of the Invention

[0005] To overcome the above technical problems, the present invention provides a process method for cleaning copper oxide formed after chemical mechanical polishing of copper with an alkaline polishing solution based on a micro adjustable liquid mixing device, which can clean the by-products formed after polishing with an alkaline polishing solution while reducing the impact of the cleaning agent on the polishing rate of the wafers to be processed subsequently, meeting the actual requirements of the CMP process.

[0006] The present invention discloses a micro adjustable liquid mixing device, comprising: a programmable controller, a micro mixer, flow controller 1, flow controller 2 and flow controller 3; the programmable controller is respectively connected to flow controller 1, flow controller 2 and flow controller 3, and the programmable controller is used to set the flow rate and concentration values of the inflow and outflow of flow controller 1, flow controller 2 and flow controller 3.

[0007] Further, it is set that the flow rate value of flow controller 1 is equal to the sum of the flow rate values of flow controller 2 and flow controller 3, and the concentration value is equal to the ratio of the concentration value of flow controller 2 to the set value of flow controller 1.

[0008] The present invention also discloses a method for cleaning copper oxide after chemical mechanical polishing of copper with an alkaline polishing solution by using the above-mentioned micro adjustable liquid mixing device, comprising:

[0009] S1. The programmable controller sets the micro mixer to adjust the first flow rate and the first concentration of the cleaning solution flowing out.

[0010] S2. After polishing with the alkaline copper polishing solution, the wafer is removed from the polishing pad and transferred to the next process.

[0011] S3. The polishing pad is rotated at a first speed, and the cleaning solution flows out from the outlet of the polishing machine platform at the first flow rate.

[0012] S4. The Disk (polishing pad dressing disk) is pressed on the polishing pad with a first pressure, and at the same time, the Disk rotates at a second speed and swings back and forth from the center of the polishing pad to the outside at a third speed.

[0013] S5. Maintain this state to clean for a first period of time.

[0014] S6. Close the cleaning solution, open the high-pressure nozzle to rinse with ultrapure water at a second flow rate, and under other conditions such as S4, clean for a second period of time.

[0015] S7. Raise the Disk and stop its rotation, fix it to the edge of the polishing pad, and at the same time increase the rotation speed of the polishing pad to a fourth speed, and the high-pressure nozzle rinses with ultrapure water at a third flow rate, and maintain this state for a third period of time.

[0016] S8. Perform polishing of the next wafer.

[0017] Preferably, in S1, the cleaning solution is a citric acid solution, the first flow rate is 500 ml / min, the first concentration is a citric acid solution with a mass percentage concentration of 10%, and the concentration after 10-fold dilution.

[0018] Preferably, in S3, the first speed of the polishing pad rotation is 101 revolutions per minute. The inflow or outflow of the cleaning solution is controlled by the chemical mechanical polishing system;

[0019] Preferably, in S4, the first pressure of the Disk (polishing pad dressing disk) is 5 lbf (pound-force), the second rotational speed is 108 revolutions per minute, the third swinging speed is 19 swps / min, and the swing amplitude ranges from 2 inches to 14.7 inches from the radius of the polishing pad.

[0020] Preferably, in S5, the first time is set to 5 s.

[0021] Preferably, in S6, the second holding time is set to 10 s. The second flow rate and the switch of the high-pressure nozzle are controlled by the chemical mechanical polishing system, and the second flow rate is 5 L / min.

[0022] Preferably, in S7, the third flow rate of the high-pressure nozzle is 5 L / min. The Disk is lifted above the polishing pad and fixed at 14.7 inches from the radius of the polishing pad. The third holding time is set to 5 s, and the fourth speed is 108 revolutions per minute.

[0023] Preferably, in S1 - S7, the concentration and flow rate of the citric acid solution, the rotational speed of the polishing pad, the pressure / rotational speed / swinging speed and amplitude of the disk, and the duration of the process steps can be adjusted according to the requirements of wafer processing to meet the requirements of different processes.

[0024] Preferably, in the micro adjustable liquid mixing device, the ultrapure water and citric acid inlets are respectively connected to the micro mixer through 1 / 4-inch pipelines via flow controllers 1 and 2. The two are mixed in the micro mixer to form a citric acid solution, which is then connected to the liquid outlet through a 3 / 8-inch pipeline via an automatic flow controller 3.

[0025] Through this process step and related devices, the purpose of cleaning with an acidic cleaning agent (citric acid) after copper polishing with an alkaline polishing solution can be achieved, effectively reducing the impact of by-products (such as copper green) generated during copper polishing with the alkaline polishing solution on subsequent wafer polishing. At the same time, the life of the polishing pad is increased, the production efficiency is improved, and the maintenance cost is reduced. Description of the Drawings

[0026] Figure 1 Process step diagram for cleaning copper green generated after chemical mechanical polishing of copper with an alkaline polishing solution

[0027] Figure 2 Schematic diagram of the micro adjustable liquid mixing device

[0028] Figure 3 Comparison diagram of the polishing pad before and after cleaning

[0029] Figure 4 Graph of the change in the copper polishing rate of the alkaline polishing solution Detailed Description of the Invention

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms "a", "the", and "said" used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0032] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it may be a mechanical connection or an electrical connection, or it may be the communication inside two components. It may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0033] Copper is prone to generate oxides and hydroxides during polishing under alkaline conditions. These by-products (abbreviated as verdigris) are not easily soluble, and as the number of processed wafers increases, the by-products continuously accumulate on the polishing pad, which will further affect the polishing rate of copper and the life of the polishing pad, seriously affecting the polishing effect and production efficiency. Currently, for the by-products (verdigris) remaining on the polishing pad, the polishing pad is usually cleaned with a citric acid solution after polishing. However, since the pH values of the citric acid solution (acidic) and the alkaline copper polishing solution are different, after using it to clean the verdigris, it may inhibit the polishing rate of the next wafer. At the same time, a cleaning agent with too high a concentration will also affect the performance of the polishing solution.

[0034] Therefore, to solve the above problems, in one embodiment of the present invention, a process method for cleaning the verdigris generated after chemically mechanical polishing of copper with an alkaline polishing solution based on a micro adjustable mixing device is provided. Figure 1 It is a process step diagram for cleaning the verdigris generated after chemically mechanical polishing of copper with an alkaline polishing solution in the invention. Figure 2 It is a schematic diagram of the micro adjustable mixing device in the invention. As Figure 1-2 , a process method for cleaning the verdigris generated after chemically mechanical polishing of copper with an alkaline polishing solution based on a micro adjustable mixing device is shown. Figure 2The shown micro adjustable liquid mixing device includes a programmable controller, flow controller 1, flow controller 2, flow controller 3, and a micro mixer. The programmable controller is also connected to a computer. As Figure 1 The process steps for cleaning the copper oxide generated after chemically mechanical polishing of copper with an alkaline polishing solution using this device include:

[0035] S1. Set the micro adjustable liquid mixer through the computer to adjust the flow rate and concentration of the cleaning solution (citric acid solution) flowing out.

[0036] S2. After polishing with the alkaline copper polishing solution, the wafer is removed from the polishing pad by the polishing head and transferred to the next process.

[0037] S3. Rotate the polishing pad at a certain speed through the chemical mechanical polishing system, and let the cleaning solution flow out at the set flow rate.

[0038] S4. Press the Disk (polishing pad dresser) onto the polishing pad with a certain pressure. At the same time, rotate the Disk at a certain speed and swing back and forth from the center of the polishing pad to the outside at a certain speed.

[0039] S5. Maintain this state for a certain cleaning time.

[0040] S6. Close the cleaning solution, open the high-pressure nozzle to rinse with ultrapure water at a large flow rate, and keep other settings unchanged. Maintain for a certain time.

[0041] S7. Raise the Disk and stop its rotation, fix it to the edge of the polishing pad, and at the same time increase the rotation speed of the polishing pad, with other settings unchanged. Maintain this state for a certain time.

[0042] S8. Polish the next wafer.

[0043] Furthermore, as Figure 2 shown, the three flow controllers are all connected to the programmable controller, and the programmable controller is connected to the computer. The programmable controller can be set through the computer, and then the set values of the three flow controllers can be adjusted. Set the flow value of flow controller 3 to be equal to the sum of the flow values of flow controller 1 and flow controller 2, and set the concentration value of flow controller 3 to be equal to the ratio of the concentration value of flow controller 2 to the concentration value of flow controller 1.

[0044] Furthermore, as Figure 2 shown, the ultrapure water and citric acid inlets are respectively connected to the micro mixer through 1 / 4-inch pipelines via flow controller 2 and 1. The two are mixed in the micro mixer to form a citric acid solution, and then connected to the liquid outlet through a 3 / 8-inch pipeline via automatic flow controller 3.

[0045] Furthermore, as Figure 1As shown, among S1 - S7, the concentration and flow rate of the citric acid solution, the rotation speed of the polishing pad, the disk pressure / rotation speed / oscillation speed and amplitude, and the duration of the process steps can be adjusted according to the requirements of wafer processing to meet the requirements of different processes.

[0046] Further, as a preferred embodiment, in S1, the cleaning solution is a citric acid solution with a mass percentage concentration of 10%, the flow rate is 500 ml / min, and the adjusted outflow concentration is the concentration after diluting the cleaning solution by 10 times.

[0047] Further, as a preferred embodiment, in S3, the rotation speed of the polishing pad is set to 101 revolutions per minute. The inflow or outflow of the cleaning solution is controlled by the chemical mechanical polishing system and completed by the chemical mechanical machine.

[0048] Further, as a preferred embodiment, in S4, the disk pressure is 5 lbf, the rotation speed is 108 revolutions per minute, the oscillation speed is 19 swps / min, and the oscillation amplitude ranges from 2 inches to 14.7 inches at the radius of the polishing pad.

[0049] Further, as a preferred embodiment, in S5, the holding time is set to 5 s.

[0050] Further, as a preferred embodiment, in S6, the holding time is set to 10 s. The flow rate and switch of the high - pressure nozzle are controlled by the chemical mechanical polishing system, and the flow rate is 5 L / min.

[0051] Further, as a preferred embodiment, in S7, the flow rate of the high - pressure nozzle is 5 L / min, the Disk is lifted above the polishing pad and fixed at 14.7 inches at the radius of the polishing pad, the holding time is set to 5 s, and the rotation speed of the polishing pad is increased to 108 revolutions per minute.

[0052] In this embodiment, wafer polishing and cleaning of copper rust on the polishing pad are both carried out in the chemical mechanical polishing machine, and the parameters involved can be set and adjusted through the chemical mechanical polishing machine.

[0053] In this embodiment, wafer polishing, copper rust cleaning, and polishing of the next wafer are a continuous process, and the mechanical actions required in the process steps can all be realized by the chemical mechanical polishing machine.

[0054] In this embodiment, the computer contains an operable interface to control the flow rate and concentration of the citric acid solution.

[0055] In this embodiment, a hard polishing pad is used, and a diamond polishing disc is used for the Disk (polishing pad dressing disc). The radius of the polishing pad is 15.2 inches, and the radius of the disk is about 2.125 inches.

[0056] In this embodiment, Figure 3 It is a comparison diagram of the residual by-products on the polishing pad before and after cleaning using this process. It can be clearly seen that the verdigris has significantly decreased, and the content of by-products (verdigris) in each part of the groove is zero, indicating a remarkable cleaning effect.

[0057] In this embodiment, Figure 4 It is a graph showing the change of the copper polishing rate of the alkaline polishing solution with the number of wafers processed after using this process. The polishing rate is relatively stable, indicating that this process method can effectively reduce the influence of the cleaning agent on the polishing rate of the alkaline polishing solution and improve production efficiency.

[0058] It should be noted that the embodiments of the present invention have good implementability and are not any form of limitation to the present invention. Any person skilled in the art may use the disclosed technical content to modify or transform it into equivalent effective embodiments. However, as long as it does not depart from the technical content of the present invention, any modification, equivalent change or modification made to the above embodiments based on the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A micro adjustable liquid mixing device, characterized in that, Including: A programmable logic controller, a micro mixer, flow controllers (1), (2) and (3); the programmable logic controller is respectively connected to flow controllers (1), (2) and (3), and the programmable logic controller is used to set the flow rates and concentration values of the inflow and outflow of flow controllers (1), (2) and (3).

2. The micro adjustable liquid mixing device according to claim 1, characterized in that, Set the flow rate value of flow controller (3) to be equal to the sum of the flow rate values of flow controller (1) and flow controller (2), and set the concentration value of flow controller (3) to be equal to the ratio of the concentration value of flow controller (2) to the concentration value of flow controller (1).

3. A process for cleaning copper patina after chemically mechanical polishing of copper with the alkaline polishing solution by using the micro adjustable liquid mixing device described in claims 1-2, characterized in that, Including: S1. The programmable logic controller sets the micro mixer to adjust the first flow rate and the first concentration of the cleaning liquid flowing out; S2. After polishing with the alkaline copper polishing liquid, the wafer is removed from the polishing pad and transferred to the next process; S3. Rotate the polishing pad at the first speed and let the cleaning liquid flow out at the first flow rate; S4. Press Disk (polishing pad dressing disk) on the polishing pad with the first pressure, while Disk rotates at the second speed and swings back and forth from the center of the polishing pad to the outside at the third speed; S5. Maintain this state for the first cleaning time; S6. Close the cleaning liquid, open the high-pressure nozzle of the polishing machine to rinse with ultrapure water at the second flow rate, and keep other conditions as in S4 for the second cleaning time; S7. Raise Disk and stop its rotation, fix it to the edge of the polishing pad, while increase the rotation speed of the polishing pad to the fourth speed, and the high-pressure nozzle rinses with ultrapure water at the third flow rate, and maintain this state for the third time; S8. Perform the polishing of the next wafer.

4. The method for cleaning verdigris according to claim 3, wherein In S1, the cleaning liquid is a citric acid solution, the first flow rate is 500 ml / min, the first concentration is a citric acid solution with a mass percentage concentration of 10%, and the concentration after 10-fold dilution.

5. The method for cleaning verdigris according to claim 3, characterized in that, In S3, the first speed of the rotation of the polishing pad is 101 revolutions per minute.

6. The method for cleaning verdigris according to claim 3, wherein In S4, the first pressure of Disk is 5 lbf (pound-force), the second speed is 108 revolutions per minute, the third speed is 19 swps / min, and the swing amplitude is from 2 inches to 14.7 inches of the radius of the polishing pad.

7. The copper green cleaning method according to claim 3, wherein In S5, the first time is 5 s.

8. The copper green cleaning method according to claim 3, wherein, In S6, the second time is 10 s, and the second flow rate is 5 L / min.

9. The copper green cleaning method according to claim 3, characterized in that, In S7, the third flow rate is 5 L / min, the fourth speed is 108 revolutions per minute, Disk is lifted above the polishing pad and fixed at 14.7 inches of the radius of the polishing pad, and the third time is 5 s.

10. The copper green cleaning method according to claim 3, wherein, In the micro adjustable liquid mixing device, the ultrapure water and citric acid inlets are respectively connected to the micro mixer through flow controllers (1) and (2) by 1 / 4-inch pipelines. The two are mixed in the micro mixer to form a diluted citric acid solution, and then connected to the liquid outlet through a 3 / 8-inch pipeline via an automatic flow controller (3).

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